Journal of Hazardous Materials (v.166, #2-3)
Behaviour of antimony during thermal treatment of Sb-rich halogenated waste
by J. Klein; S. Dorge; G. Trouvé; D. Venditti; S. Durécu (pp. 585-593).
Antimony compounds have a wide range of industrial applications, particularly as additives in flame retardants. To ensure environmentally friendly waste incineration of Sb-rich wastes, it is essential to strengthen the knowledge about the fate of antimony and the potential formation of harmful species. Investigations should be conducted particularly in relation with the main operational parameters controlling the process, chiefly temperature, residence time and air supply in the oven and in the post-combustion zone, prior final adapted cleaning of the flue-gas stream. Experimental studies focusing on antimony behaviour were undertaken through laboratory-scale thermal treatment at 850°C and 1100°C of a Sb-rich halogenated waste, originating from the sector of flame retardants formulation. The configuration of our laboratory experimental device allowed to achieve only low oxidative conditions in the waste bed, but high oxidative strength coupled with high temperature and sufficient gas residence time in the post-combustion zone, as prescribed during the incineration of hazardous wastes. Atomic absorption spectroscopy was used to assess the partition of antimony in the different compartments of the process. The oxidation degree of antimony in the gas-phase was determined by the use of electrochemical techniques, namely polarography coupled with anodic stripping voltamperometry. The partition of antimony between the residual ash and the gas-phase under moderate oxidative conditions in the waste bed was constant, whatever the temperature: the volatilization rate for antimony was ∼64%, while a ∼36% fraction remained in the residual bottom ashes. But interestingly, while at 850°C, antimony was mainly present in the gas-phase at a +III oxidation degree, an increase in temperature of 250°C favoured the presence of antimony to its highest oxidation degree +V in the flue-gas stream, a valence known to be involved in less toxic species.
Keywords: Antimony; Oxidation degree; Thermal treatment; Flame retardant
Oxidation by Fenton's reagent combined with biological treatment applied to a creosote-comtaminated soil
by C. Valderrama; R. Alessandri; T. Aunola; J.L. Cortina; X. Gamisans; T. Tuhkanen (pp. 594-602).
In this study, we investigated the feasibility of using Fenton oxidation to remove sorbed polycyclic aromatic hydrocarbons (PAHs) in aged soil samples with creosote oil from a wood preserving site. The optimal dosage of reagents was determined by a statistical method, the central composite rotatable experimental design. The maximum PAH removal was 80% with a molar ratio of oxidant/catalyst equal to 90:1. In general low molecular weight PAHs (3 rings) were degraded more efficiently than higher molecular weight PAHs (4 and 5 rings). The hydrogen peroxide decomposition kinetic was studied in the presence of KH2PO4 as stabilizer. The kinetic data were fitted to a simple model, the pseudo-first-order which describes the hydrogen peroxide decomposition. The PAH kinetic degradation was also studied, and demonstrated that non-stabilized hydrogen peroxide was consumed in less than 30min, whilst PAH removal continued for up to 24h. In a second part of the work, a combined chemical and biological treatment of the soil was carried out and shown to be dependent on the pre-oxidation step. Different reagent doses (H2O2:Fe) were used (10, 20, 40, 60:1) in the pre-treatment step. An excess of hydrogen peroxide resulted in a poor biological removal, thus the optimal molar ratio of H2O2:Fe for the combined process was 20:1. The combined treatment resulted in a maximum total PAH removal of 75% with a 30% increase in removal due to the biodegradation step. The sample with highest PAH removal in the pre-oxidation step led to no further increase in removal by biological treatment. This suggests that the more aggressive chemical pre-oxidation does not favour biological treatment. The physico-chemical properties of the pollutants were an important factor in the PAH removal as they influenced chemical, biological and combined treatments.
Keywords: Creosote; Soil; PAHs; Oxidation; Fenton reaction; Biological treatment
Effects of alcohol-partitioning type and airflow on cosolvent flooding to benzene-LNAPL saturated porous media
by Seung-Woo Jeong; Byung-Kyu Ju; Byung-Jin Lee (pp. 603-611).
This study fundamentally investigated the swelling and distribution of benzene-light nonaqueous phase liquid (LNAPL) in porous media while cosolvent was flushed to the benzene-partially saturated system. Furthermore, the effects of simultaneous injection of cosolvent and air on the LNAPL behavior were visualized and thus quantified within a two-dimensional transparent porous medium. Partitioning types of alcohols affected dissolution of benzene entrapped in porous media. Tert-butanol (TBA) and 1-propanol floods apparently increased the LNAPL area, while a 70% ethanol flood reduced the LNAPL area by dissolution. Airflow facilitates mobilization of the swollen LNAPL by TBA and 1-propanol, while it facilitates dissolution of non-swollen LNAPL by ethanol. Therefore, LNAPL behavior during cosolvent flooding would be determined by partitioning type of alcohols and the presence of airflow.
Keywords: Light nonaqueous phase liquid (LNAPL); Cosolvent; Porous media; Dissolution; Mobilization
Gold(III) biosorption and bioreduction with the brown alga Fucus vesiculosus
by Y.N. Mata; E. Torres; M.L. Blázquez; A. Ballester; F. González; J.A. Muñoz (pp. 612-618).
In this paper, the bioreduction of Au(III) to Au(0) using biomass of the brown alga Fucus vesiculosus was investigated. The recovery and reduction process took place in two stages with an optimum pH range of 4–9 with a maximum uptake obtained at pH 7. In the first stage, an induction period previous to gold reduction, the variation of pH, redox potential and gold concentration in solution was practically negligible and no color change was observed. In the second stage, the gold reduction was followed by a sharp decrease of gold concentration, pH and redox potential of solution and a color change from yellow to reddish purple. Hydroxyl groups present in the algal polysaccharides were involved in the gold bioreduction. Metallic gold was detected as microprecipitates on the biomass surface and in colloidal form as nanoparticles in the solution. Bioreduction with F. vesiculosus could be an alternative and environmentally friendly process that can be used for recovering gold from dilute hydrometallurgical solutions and leachates of electronic scraps, and for the synthesis of gold nanoparticles of different size and shape.
Keywords: Biosorption; Bioreduction; Gold; Fucus vesiculosus; Nanoparticles
Continuous elimination of Pb2+, Cu2+, Zn2+, H+ and NH4+ from acidic waters by ionic exchange on natural zeolites
by Benjamin Calvo; Laureano Canoira; Fernando Morante; José M. Martínez-Bedia; Carlos Vinagre; Jerónimo-Emilio García-González; Jan Elsen; Ramon Alcantara (pp. 619-627).
A study of breakthrough curves for cations usually found in acid mine drainage (Pb2+, Cu2+, Zn2+ and H+) and municipal wastewater (NH4+) have been conducted on some natural zeolitic tuffs. The zeolitic tuffs used in this study are: three zeolitic tuffs from Cayo Formation, Guayaquil (Ecuador), characterized by X-ray diffraction as clinoptilolite (sample CLI-1) and heulandite (samples HEU-1 and HEU-2)-rich tuffs, and two zeolitic tuffs from Parnaiba Basin, Belem do Pará (Brazil), characterized as stilbite-rich tuffs (samples STI-1 and STI-2). The clinoptilolite sample CLI-1 shows an exceedingly good exchange capacities for Pb2+ and NH4+ as received, and also a very high exchange capacity for Cu2+ and Zn2+ when conditioned with 2M sodium chloride, with much higher values than those reported in the literature for other clinioptilolite ores. A general order of effective cation exchange capacity could be inferred from breakthrough curves on these zeolitic tuffs:CLI-1>HEU-2>HEU-1>STI-2Since it is true for most of the cations studied.
Keywords: Natural zeolites; Breakthrough curves; Acid mine drainage; Wastewater
Agricultural soil monitoring of PCDD/Fs in the vicinity of a municipal solid waste incinerator in Eastern China: Temporal variations and possible sources
by Meng-xia Xu; Jian-hua Yan; Sheng-yong Lu; Xiao-dong Li; Tong Chen; Ming-jiang Ni; Hui-fen Dai; Fei Wang; Ke-fa Cen (pp. 628-634).
The temporal variations of polychlorinated dibenzo- p-dioxins and dibenzofurans (PCDD/Fs) in 33 agricultural soil samples in the vicinity of a municipal solid waste incinerator (MSWI) in Eastern China were determined one year after the initial investigation in 2006. The soil PCDD/F concentrations in 2007 ranged from 73.6 to 377ngkg−1 (0.60–6.38ngI-TEQkg−1). During 2006–2007, the overall soil PCDD/F levels increased significantly, i.e., 33% and 39% for total concentration and I-TEQ (median value), respectively. Moreover, soils in the study area are proved to be almost free from previously suspected PCDD/F sources, i.e., pentachlorophenol/sodium penta-chlorophenate (PCP/PCP-Na) and 1,3,5-trichloro-2-(4-nitrophenoxy) benzene (CNP) contaminations. Furthermore, the results from a congener-specific factor analysis between soils (collected in two investigations) and dioxin emission sources suggest that diffuse sources including open burning of wastes, traffic and hot water boilers are major contributors that are responsible for the accumulation of PCDD/Fs in soils. By contrast, the impact of the presumably major PCDD/F source identified in our previous study, i.e., the MSWI, seems to be limited.
Keywords: Polychlorinated-; p; -dioxins and dibenzofurans; Agricultural soil; MSWI; Open burning; Hot water boiler
Adsorption of organic compounds from aqueous solution onto the synthesized zeolite
by Wen-Tien Tsai; Kuo-Jong Hsien; Hsin-Chieh Hsu (pp. 635-641).
A novel zeolite was synthesized, characterized and employed for the adsorption of methylene blue (cationic dye) and bisphenol-A in aqueous solution. The pore properties of the synthesized zeolite have been determined using N2 adsorption–desorption isotherms, indicating that it is a supermicroporous adsorbent with BET surface area of over 400m2g−1. Based on the XRD image, it was indicative of the probable formation of zeolite-P2 in the hydrothermal synthesis. The metal content and zeta-potential of the zeolite were also measured to examine the hydrophilicity and the effect of pH on the surface charge, respectively. It was found that the synthesized zeolite exhibited significantly higher adsorption capacity for methylene blue than that for bisphenol-A due to the difference in molecular properties. Kinetic studies at 25°C indicated that the adsorption of methylene blue well followed the pseudo-second-order model and could be elucidated by considering the pore property and surface charge of the synthesized zeolite. The kinetic parameters thus obtained from the fittings of the model were dependent on initial dye concentration, pH, and adsorbent mass.
Keywords: Liquid-phase adsorption; Synthesized zeolite; Methylene blue; Bisphenol-A; Kinetic modeling
Adsorption of Cr(VI) onto cationic surfactant-modified activated carbon
by Hyun-Doc Choi; Woo-Sung Jung; Jung-Min Cho; Byung-Gon Ryu; Jung-Seok Yang; Kitae Baek (pp. 642-646).
Highly toxic oxyanions, such as hexavalent chromium (Cr(VI)), have caused adverse effects on human health. This study evaluated the feasibility of using cationic surfactant-modified activated carbon (AC) to remove Cr(VI). To modify activated carbon using a cationic surfactant, AC was mixed with a surfactant solution of 0.5 critical micelle concentration (CMC), at which concentration the surfactant molecules exist as mono-molecules. Adsorption kinetics and an isotherm model were used to study the adsorption characteristics of Cr(VI) onto MAC. The adsorption capacity of MAC for Cr(V) was enhanced compared to that of AC. MAC modified by hexadecyltrimethylammonium had a higher adsorption capacity for the removal of Cr(VI) than that modified by cetylpyridinium. The modification of AC by a cationic surfactant enhanced both its Cr(VI) adsorption rate and its Cr(VI) adsorption capacity. The breakthrough point of MAC for Cr(VI) was 100 times greater than for the raw AC. As a result, MAC is a promising adsorbent to treat Cr(VI) in an aqueous stream.
Keywords: Cr(VI); Hexadecyltrimethylammonium bromide; Cetylpyridinium chloride; Surface-modification; Surfactant
Feasibility analysis of color removal from textile dyeing wastewater in a fixed-bed column system by surfactant-modified zeolite (SMZ)
by Ozgur Ozdemir; Mustafa Turan; Abdullah Zahid Turan; Aysegul Faki; Ahmet Baki Engin (pp. 647-654).
In this study, the ability of surfactant-modified zeolite (SMZ) to remove color from real textile wastewater was investigated. Tests were performed in a fixed-bed column reactor and the surface of natural zeolite was modified with a quaternary amine surfactant hexadecyltrimethylammonium bromide (HTAB). The zeolite bed that was modified at 1gL−1 HTAB concentration and HTAB flow rate of 0.015Lmin−1 showed good performance in removing color. Effects of wastewater color intensity, flow rates and bed heights were also studied. Wastewater was diluted several times in the ratios of 25%, 50% and 75% in order to assess the influence of wastewater strength. The breakthrough curves of the original and diluted wastewaters are dispersed due to the fact that breakthrough came late at lower color intensities and saturation of the bed appeared faster at higher color intensities. The column had a 3-cm diameter and four different bed heights of 12.5, 25, 37.5 and 50cm, which treated 5.25, 19.50, 35.25 and 51L original textile wastewater, respectively, at the breakthrough time at a flow rate of 0.025Lmin−1. The theoretical service times evaluated from bed depth service time (BDST) approach for different column variables. The calculated and theoretical values of the exchange zone height were found with a difference of 27%. The various design parameters obtained from fixed-bed experimental studies showed good correlation with corresponding theoretical values, under different bed heights. The regeneration of the SMZ was also evaluated using a solution consisting of 30gL−1 NaCl and 1.5gL−1 NaOH at pH 12 and temperature 30°C. Twice-regenerated SMZ showed the best performance compared with the others while first- and thrice-regenerated perform lower than the original SMZ.
Keywords: Surfactant-modified zeolite (SMZ); Color removal; Textile wastewater; Column study; BDST model
Pharmaceutical residues in wastewater treatment works effluents and their impact on receiving river water
by J.L. Zhou; Z.L. Zhang; E. Banks; D. Grover; J.Q. Jiang (pp. 655-661).
Various pharmaceutical residues are being discharged from wastewater treatment works (WTW) effluents, the impact of which on river water quality is of high relevance to environmental risk assessment. The concentrations of eleven pharmaceutical compounds were determined in three WTWs in England, and the river Ouse receiving effluents from Scaynes Hill WTW. Results show that five compounds propranolol, sulfamethoxazole, carbamazepine, indomethacine and diclofenac were detected in all wastewater and river water samples, with carbamazepine showing the highest concentrations (up to 2336ngL−1) in WTW influent. Different compounds were removed to different extent in the WTWs, varying from 43 to 92%, with the highest performance obtained by the WTW with tertiary treatment (sand filtration). The pharmaceutical residues from Scaynes Hill WTW were eventually discharged into the river Ouse, causing an elevation in their concentrations downstream of the outfall. This was confirmed by the good agreement between measured concentrations and those predicted by a simple dilution model.
Keywords: Pharmaceuticals; Wastewater; Liquid chromatography–tandem mass spectrometry; River; Dilution
Evaluation of arsenic and other physico-chemical parameters of surface and ground water of Jamshoro, Pakistan
by Jameel Ahmed Baig; Tasneem Gul Kazi; Muhammad Balal Arain; Hassan Imran Afridi; Ghulam Abbas Kandhro; Raja Adil Sarfraz; Muhammad Khan Jamal; Abdul Qadir Shah (pp. 662-669).
Arsenic contamination in water has caused severe health problems around the world. The purpose of this study was to evaluate the geological and anthropogenic aspects of As pollution in surface and groundwater resources of Jamshoro Sindh, Pakistan. Hydride generator atomic absorption spectrophotometry (HG-AAS) is employed for the determination of arsenic in water samples, with detection limit of 0.02μgl−1. Arsenic concentrations in surface and underground water range from 3.0 to 50.0, and 13 to 106μgl−1, respectively. In most of the water samples As levels exceeded the WHO provisional guideline values 10μgl−1. The high level of As in under study area may be due to widespread water logging from Indus river irrigation system which causes high saturation of salts in this semi-arid region and lead to enrichment of As in shallow groundwater. Among the physico-chemical parameters, electrical conductivity, Na+, K+, and SO42− were found to be higher in surface and ground water, while elevated levels of Ca2+ and Cl− were detected only in ground water than WHO permissible limit. The high level of iron was observed in ground water, which is a possible source of As enrichment in the study area. The multivariate technique (cluster analysis) was used for the elucidation of high, medium and low As contaminated areas. It may be concluded that As originate from coal combustion at brick factories and power generation plants, and it was mobilized promotionally by the alkaline nature of the understudy groundwater samples.
Keywords: Arsenic; Cluster analysis; Ground water; Physico-chemical parameters; Surface water
Evaluation of environmental compatibility of EAFD using different leaching standards
by M.G. Sebag; C. Korzenowski; A.M. Bernardes; A.C. Vilela (pp. 670-675).
A study on laboratory scale to evaluate the environmental compatibility of electric arc furnace dust (EAFD) is reported in this article. EAFD, a waste by-product of the steel-making process, was generated on a steel plant located in Brazil. Different leaching tests, NBR10005 (Brazilian), AFNORX31-210 (French), JST-13 (Japanese), DIN38414-S4 (German), TCLP (American), and NEN 7343 (Netherland) were conducted. These leaching procedures are batch tests and are columns conducted in a way that an equilibrium condition should be achieved. The pH of the medium showed a crucial parameter governing the release of metals from the solid phase into solution. As the pH of the medium varies with the leachant used, this determines the dissolution of the elements. Zn, Pb, Mn, Cd, and Cu presented high leachability at NBR10005 procedures (acid pH). Except Pb and Cr, the leachability of all others metals in leaching tests with alkaline pH decreases with the increase of the pH. NBR10005 classifies the EAFD as a hazardous waste due to high concentration of Pb and Cd in leachate. The column tests are presented in the following order of leaching: Pb>Cr>Zn>Mn>Cu>Cd.
Keywords: Leaching; Metals; EAF dust; Hazardous waste
Assessing hazardous risks of human exposure to temple airborne polycyclic aromatic hydrocarbons
by Kuo-Chih Chiang; Chia-Pin Chio; Yu-Hui Chiang; Chung-Min Liao (pp. 676-685).
We proposed an integrated probabilistic risk assessment framework based on reported data to quantify human health risks of temple goers/workers to airborne polycyclic aromatic hydrocarbons (PAHs) from incense burning in typical Taiwanese temples. The framework probabilistically integrates exposure, human respiratory tract, and incremental lifetime cancer risk (ILCR) models to quantitatively estimate size-dependent PAHs exposure in human lung regions and cancer risks for temple goers (moderate and high exposures) and temple workers (extreme exposure). Our results show that the ILCRs are greater than the acceptable level of 10−6 for extreme and high exposure groups through inhalation route. The result also indicates that the higher ILCRs (10−6 to 10−4) are found in ingestion and dermal contact routes for temple goers/workers. For personal extreme exposure to carcinogenic PAH in the temple, 95% probability total ILCR (TILCR) (9.87×10−4 to 1.13×10−3) is much greater than the range of 10−6 to 10−4, indicating high potential health risk to temple workers. For temple goers with high and moderate exposure groups, however, the 95% probability TILCRs were estimated from 6.44×10−5 to 7.50×10−5 and 5.75×10−6 to 6.99×10−6, respectively. This study successfully offers a scientific basis for risk analysis due to incense burning to enhance broad risk management strategies for temple indoor air quality.
Keywords: Incense burning; Polycyclic aromatic hydrocarbons; Risk assessment; Indoor air quality; Temple
Catalysis of oxidation of carbon monoxide on supported gold nanoparticle
by Chao-Heng Tseng; Thomas C.K. Yang; Hsin-En Wu; Hsu-Cheng Chiang (pp. 686-694).
Gold used to be considered to have no catalytic activity. In the 1980s, however, Masatake Haruta found that nano-sized gold particles supported by metal oxides can catalyze the oxidation of carbon monoxide. This work examines the oxidation of carbon monoxide (CO) and the adsorption/desorption behaviors on nano-sized gold catalyst at room temperature by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Carbonate, bicarbonate and carboxylate were observed. The effects of various factors (relative humidity, CO gas concentration, and total surface area) on the CO conversion efficiency were studied using the response surface designs in the Experiment Design Method. The results indicate that the conversion efficiency of CO was high when the ratio of CO and O2 was close to 1:1. The gas concentration is the most important factor, followed by the weight of gold catalyst, followed by relative humidity. An appropriate humidity enhances the catalytic reaction in the long-term.
Keywords: Nanoparticle; Gold; Catalyst; Carbon monoxide; Experiment design
Copper removal from oil-field brine by coprecipitation
by Jafar Khosravi; Abdolmohammad Alamdari (pp. 695-700).
The present study aims at investigation of copper removal from oil-field brine by coprecipitation process. The produced brine containing heavy metals is usually returned to the reservoir for water flooding or is discarded to the surroundings. Therefore, surface waters or underground waters may be polluted due to probable contact to these discarded waters. Removal experiments were carried out at room temperature in a bench-scale crystallizer equipped with a draft tube. In order to gain an insight into the influence of soluble compounds in the industrial natural brine on the precipitation process, some comparative experiments were performed both on a sample of natural brine and on a synthetic simulated brine in the absence of natural impurities. A metal removal practice by coprecipitation of copper through CaCO3 precipitates induced by reaction of Na2CO3 and CaCl2 reduced the copper concentration (Cu2+) from 0.27ppm in the synthetic brine to 0.06ppm. This removal of 78% required only 1g of precipitate per 0.15mg copper metal. Analysis of the experimental results suggested that about 5% of the copper removal from the synthetic brine was through the mechanism of incorporation into the crystal lattice, and around 95% was through the adsorption on the crystal faces.
Keywords: Heavy metal; Copper removal; Coprecipitation; Reactive crystallization; Calcium carbonate
A new induction period based reaction rate method for determination trace amounts of phenylhydrazine in water samples
by M. Arab Chamjangali; G. Bagherian; S. Ameri (pp. 701-705).
A simple, selective, and sensitive kinetic spectrophotometric method is described for the determination of trace amounts of phenylhydrazine, which is based on its inhibition effect on the reaction between meta cresol purple (MCP) and periodate in the presence of bromide ions. The reaction was monitored spectrophotometrically by measuring the change in absorbance of MCP at 525nm. The calibration graph was linear in the range of 1.0–10.0μM. The detection limit (3 σ) was 0.020μM. The relative standard deviations for 10 replicate measurements of 3.0, 5.0 and 7.0μM of phenylhydrazine were 2.0%, 1.4%, and 0.90%, respectively. The potential interfering substances were studied in the presence of phenylhydrazine. The proposed method was applied to the analysis of water samples.
Keywords: Meta cresol purple (MCP); Kinetic; Spectrophotometric; Induction period; Phenylhydrazine
Characterization and activity studies of highly heavy metal resistant sulphate-reducing bacteria to be used in acid mine drainage decontamination
by Mónica Martins; M. Leonor Faleiro; Raúl J. Barros; A. Raquel Veríssimo; M. Alexandra Barreiros; M. Clara Costa (pp. 706-713).
Biological treatment with sulphate-reducing bacteria (SRB) has been considered as the most promising alternative for acid mine drainage (AMD) decontamination. Normally, these wastewaters contain high concentrations of sulphate and heavy metals, so the search for SRB highly resistant to metals is extremely important for the development of a bioremediation technology. A SRB consortium resistant to high concentrations of heavy metals (Fe, Cu and Zn), similar to those typically present in AMD, was obtained among several environmental samples, from a wastewater treatment plant. The phylogenetic analysis of the dsr gene sequence revealed that this consortium contains species of SRB affiliated to Desulfovibrio desulfuricans and Desulfobulbus rhabdoformis. The results show that the presence of usually lethal concentrations of Fe (400mg/L), Zn (150mg/L) and Cu (80mg/L) is not toxic for the sulphate-reducing bacteria present in this sample. As a consequence, a very good efficiency in terms of sulphate reduction and metals removal was obtained. Both ethanol and lactate can be used by this inoculum as carbon source. With the other samples tested sulphate reduction was inhibited by the presence of copper and zinc. This highly metal resistant consortium will be used to inoculate a bioreactor to carry out AMD decontamination.
Keywords: Acid mine drainage; Bioremediation; Metals; Sulphate-reducing bacteria; Toxicity
Preparation of a new sorbent with hydrated lime and blast furnace slag for phosphorus removal from aqueous solution
by Guozhuo Gong; Shufeng Ye; Yajun Tian; Qi Wang; Jiandi Ni; Yunfa Chen (pp. 714-719).
The removal of dissolvable inorganic phosphate (H2PO4−) by sorbents prepared from hydrated lime (HL) and blast furnace slag (BFS) was fundamentally studied by an orthogonal experiment design. Based on statistic analysis, it is revealed that the weight ratio of BFS/HL is the most significant variable, and an optimized preparation condition is figured out. With the increase of HL content, the adsorption capacity increases, suggesting that the HL plays the important role in the removal process in the gross. However, in the lower HL content, it is interesting that the adsorption capacity of as-prepared sorbents exceed the sum of the capacities of the same ratio of BFS and HL. The further analysis indicate the excess capacities linearly depend on the specific surface area of sorbents, suggesting that the removal of H2PO4− is closely related with the microstructure of sorbents in the lower HL content, according to the characterization with SEM, XRD and pore analysis. Additionally, an adsorption model and kinetic are discussed in this paper.
Keywords: Phosphate removal; Blast furnace slag; Hydrated lime
Separation of copper from aqueous sulfate solutions by mixtures of Cyanex 301 and LIX® 984N
by E.A. Fouad (pp. 720-727).
The extraction equilibria of copper(II) with Cyanex 301, LIX® 984N, and their mixtures have been investigated. Extraction was studied as a function of organic phase composition, sulfuric acid concentration, pH, temperature, initial copper concentration, mixing speed, and aqueous/organic volume ratio. Considerable synergistic enhancement has been observed in the extraction of Cu2+ with mixtures of Cyanex 301 and LIX® 984N. The results demonstrate that copper ion is extracted as CuRL2H with synergistic mixture. The thermodynamic parameter, enthalpy change (Δ H) of Cyanex 301, LIX® 984N, and their mixtures have been determined and the endothermic process has been found. The synergistic enhancement factor of copper(II) with mixtures is higher at more acidic solutions, which suggests that it is a promising synergistic extraction system for the separation of copper(II) from more acidic medium. HCl was found to be more efficient for copper stripping from loaded synergistic mixtures.
Keywords: Copper; Cyanex 301; LIX; ®; 984N; Synergistic mixture; Extraction
Rapid photocatalytic degradation of PCP–Na over NaBiO3 driven by visible light irradiation
by Xiaofeng Chang; Guangbin Ji; Qian Sui; Jun Huang; Gang Yu (pp. 728-733).
The photocatalytic performance of sodium pentachlorophenate (PCP–Na) over NaBiO3 under visible light irradiation was first investigated systematically. After 1h of photocatalytic reaction, the degradation rate of PCP–Na could reach to 90.5% in appropriate conditions.OH is the dominant photooxidant rather than O2− based on the experiment results and density of states (DOS) analysis. The PCP–Na solution became basic (pH value increased to ∼9) with the progress of photocatalytic reaction which may be attributed to the PCP− oxidized to the pentachlorophenoxy radical by an attack on PCP− byOH. The photocatalyic reaction over NaBiO3 follows the rule of first-order reaction according to the Langmuir–Hinshelwood model. The initial concentration of the PCP–Na, the initial pH value of PCP–Na aqueous solution and the amount of NaBiO3 used have great influences on the photocatalytic performance. Three kinds of photocatalytic systems (P25, Bi2O3 and P25–Bi2O3 heterojunction) exhibited relative lower photocatalytic activity compared to NaBiO3 powder.
Keywords: NaBiO; 3; Photocatalysis; Sodium pentachlorophenate (PCP–Na)
Metal removal by bed filter materials used in domestic wastewater treatment
by Agnieszka Renman; Gunno Renman; Jon Petter Gustafsson; Lars Hylander (pp. 734-739).
Bed filters using reactive materials are an emerging technology for on-site wastewater treatment. Used materials, which are enriched with phosphorus, can be used as a fertiliser or soil amendment. However the materials can also be enriched with metals from the wastewater. Six materials (opoka, sand, Polonite®, limestone, two types of blast furnace slag) exposed to long-term wastewater loading in columns and in a compact filter well filled with Polonite were investigated for metal removal and accumulation. Wastewater applied to the columns had low heavy metal concentrations in the order Zn>Cu>Mn>Ni>Cr. All columns were able to remove 53%–83% of Zn except those filled with sand. Polonite demonstrated a high removal capacity of Mn (>98%), while only the slag materials were able to remove Ni. All materials showed increased Cu, Cr(III), Mn, Pb and Zn content after filtration. Speciation calculations showed that high concentrations of dissolved organic matter might have prevented efficient metal removal, particularly in the case of Cu. The low content of toxic heavy metals in the studied filter materials studied would probably not restrict their use as a fertiliser or soil amendment.
Keywords: Column experiment; Contamination; Blast furnace slag; Soil amendment; Polonite; ®
Post-treatment of banknote printing wastewater using polysilicate ferro-aluminum sulfate (PSFA)
by Zu-min Qiu; Wen-tian Jiang; Zong-jian He (pp. 740-745).
In this paper, a new kind of inorganic polymeric flocculant (IPF)—polysilicate ferro-aluminum sulfate (PSFA) was adopted to treat banknote printing wastewater. Effects of flocculants dosage on the colour and Chemical Oxygen Demand (COD) removal were examined. Experiments revealed that maximal colour removal efficiency of 98% and COD removal efficiency of 85% could be achieved at the optimal dosage of 30.33g/L. And the colour and COD removal results treated by the PSFA flocculant were compared with those treated by aluminum sulfate. Experimental results showed that the most attracting parts of PSFA as compared with that of Al2(SO4)3 were: (i) lower COD and colour contained effluents; (ii) less quantity and volume sludge; (iii) better dewatering behaviour and solid–liquid separation flocs; (iv) providing a possibility to eliminate the high labour intensity plate-frame pressure procedure and replace it by ordinary filtration. Therefore, the using of PSFA generally offered a lower cost of operation and maintenance choice to treat banknote printing wastewater as compared to that of Al2(SO4)3.
Keywords: Polysilicate ferro-aluminum sulfate (PSFA); Banknote printing wastewater; Ultrafiltration (UF); Al; 2; (SO; 4; ); 3; Wastewater treatment
Enhancement of leaching copper by electro-oxidation from metal powders of waste printed circuit board
by Zhu Ping; Fan ZeYun; Lin Jie; Liu Qiang; Qian GuangRen; Zhou Ming (pp. 746-750).
Oxidation leaching copper from metal powders of waste printed circuit boards (PCBs) was conducted at room temperature in sulfuric acid solution. The result showed that the copper in metal powders was oxidized by Cu2+ to form CuCl2− in the presence of chloride ion without electrochemical oxidation. Then, CuCl2− was oxidized into CuSO4 by oxygen derived from the air insufflated into leaching solution. The leaching rate of copper reached 100%. The whole reaction took 5.5h because it was limited by the low solubility of the air in water. In the electro-oxidation conditions, the chloride ion was electro-oxidized into ClO−, which oxidized CuCl2− into CuSO4 and ClO− was reduced into Cl− itself again at the same time. Since Cl− was recycled in the solution not only as a complexing agent but also as an oxidant, which made the reaction speed up to 3.5h to reach 100% leaching rate. Leaching solution was concentrated to crystallize CuSO4·5H2O, and crystal liquor was reused to leach copper from metal powders.
Keywords: Copper; Waste PCBs; Leaching; Electro-oxidization
Re-use of fluoride contaminated bone char sludge in concrete
by Sudhakar M. Rao; B.V. Venkatarama Reddy; S. Lakshmikanth; N.S. Ambika (pp. 751-756).
Managing sludge generated by treating groundwater contaminated with geogenic contaminants (fluoride, arsenic, and iron) is a major issue in developing nations. Their re-use in civil engineering applications is a possible pathway for reducing the impact on the geo-environment. This paper examines the re-use of one such sludge material, namely, fluoride contaminated bone char sludge, as partial replacement for fine aggregate (river-sand) in the manufacture of dense concrete specimens. Bone char sludge is being produced by defluoridation of contaminated groundwater in Nalagonda District, Andhra Pradesh, India. The impact of admixing 1.5–9% sludge contents on the compression strength and fluoride leaching potential of the sludge admixed concrete (SAC) specimens are examined. The compression strengths of the SAC specimens are examined with respect to strength criteria for manufacture of dense, load-bearing concrete blocks. The fluoride release potential of the SAC specimens is examined with respect to standards specific to disposal of treated leachate into inland surface water.
Keywords: Concrete; Groundwater; Fluoride; Re-cycle; Sludge
Adsorption of 2,4,6-trinitrotoluene on a novel adsorption material PEI/SiO2
by Fuqiang An; Baojiao Gao; Xiaoqin Feng (pp. 757-761).
In this paper, functional macromolecule polyethyleneimine (PEI) was grafted onto the surface of silica gel particles in order to produce the novel adsorption material, PEI/SiO2. Then this novel material's adsorption properties for TNT were investigated through static methods, and the experimental results showed that PEI/SiO2 possessed strong adsorption ability for TNT. In fact, the saturated adsorption amount could reach 14.47mgg−1. The empirical Freundlich isotherm was also found to describe well the equilibrium adsorption data. In addition, the pH and temperature were found to have great influence on the adsorption amount. Finally, PEI/SiO2 was observed to possess excellent reusability properties as well.
Keywords: Polyethyleneimine; Silica gel; Adsorption; 2,4,6-Trinitrotoluene (TNT)
Simple correlation for predicting detonation velocity of ideal and non-ideal explosives
by Mohammad Hossein Keshavarz (pp. 762-769).
This paper describes a simple method for prediction of detonation velocity of ideal and non-ideal explosives. A non-ideal aluminized and nitrated explosive can have Chapman–Jouguet detonation velocity significantly different from that expected from existing thermodynamic computer codes for equilibrium and steady-state calculations. Detonation velocity of explosives with general formula C aH bN cO dAl e can be predicted only from values of a, b, c, d, e and a specific structural parameter without using any assumed detonation products, heat of formation and experimental data. Predicted detonation velocities by this procedure for ideal and non-ideal explosives show good agreement with respect to experimental values as compared to computed results of BKWR and BKWS equations of state.
Keywords: Detonation velocity; Ideal explosive; Non-ideal explosive; Elemental composition; Loading density
Simultaneous spectrophotometric determination of binary mixtures of surfactants using continuous wavelet transformation
by Abbas Afkhami; Davood Nematollahi; Tayyebeh Madrakian; Maryam Abbasi-Tarighat; Mitra Hajihadi (pp. 770-775).
This work presents a simple, rapid, and novel method for simultaneous determination of binary mixtures of some surfactants using continuous wavelet transformation. The method is based on the difference in the effect of surfactants Cetyltrimethylammoniumbromide (CTAB), dodecyl trimethylammonium bromide (DTAB), cetylpyridinium bromide (CPB) and TritonX-100 (TX-100) on the absorption spectra of complex of Beryllium with Chrome Azurol S (CAS) at pH 5.4. Binary mixtures of CTAB–DTAB, DTAB–CPB and CTAB–TX-100 were analyzed without prior separation steps. Different mother wavelets from the family of continuous wavelet transforms were selected and applied under the optimal conditions for simultaneous determinations. The proposed methods, under the working conditions, were successfully applied to simultaneous determination of surfactants in hair conditioner and mouthwash samples.
Keywords: Cationic surfactants; TX-100; Simultaneous determination; Wavelet transformation; Hygienic products
The performance of iodine on the removal of elemental mercury from the simulated coal-fired flue gas
by Yao Chi; Naiqiang Yan; Zan Qu; Shaohua Qiao; Jinping Jia (pp. 776-781).
In order to facilitate the removal of elemental mercury (Hg0) in flue gas, iodine was used as the oxidant to convert Hg0 to the oxidized or particulate-bound form. The removal of Hg0 by the homogenous gas phase reaction and the heterogeneous particle-involved reactions was investigated under various conditions, and a method to test the particle-involved reaction kinetics was developed. Iodine was found to be efficient in Hg0 oxidation, with a 2nd-order rate constant of about 7.4(±0.2)×10−17cm3molecules−1s−1 at 393K. Nitric oxide showed significant inhibition in the homogenous gas reaction of Hg0 oxidation. The oxidation of Hg0 with iodine can be greatly accelerated in the presence of fly-ash or powder activated carbon. SO2 slightly reduced Hg0 removal efficiency in the particle-involved reaction. It was estimated that Hg0 removal efficiency was as high as 70% by adding 0.3ppmv iodine into the flue gas with 20g/m3 of fly-ash. In addition, the predicted removal efficiency of Hg0 was as high as 90% if 10mg/m3 of activated carbon and 0.3ppmv iodine were injected into the flue gas with fly-ash. The results suggest that the combination of iodine with fly-ash and/or activated carbon can efficiently enhance the removal of Hg0 in coal-fired flue gas.
Keywords: Elemental mercury; Coal-fired flue gas; Iodine; Removal efficiency
Treatment of combined acid mine drainage (AMD)—Flotation circuit effluents from copper mine via Fenton's process
by Ayse Mahiroglu; Esra Tarlan-Yel; Mehmet Faik Sevimli (pp. 782-787).
The treatability of a copper mine wastewater, including heavy metals, AMD, as well as flotation chemicals, with Fenton process was investigated. Fenton process seems advantageous for this treatment, because of Fe2+ content and low pH of AMD. First, optimum Fe2+ condition under constant H2O2 was determined, and initial Fe2+ content of AMD was found sufficient (120mg/L for removal of chemical oxygen demand (COD) of 6125mg/L). In the second step, without any additional Fe2+, optimum H2O2 dosage was determined as 40mg/L. Fe2+/H2O2 molar ratio of 1.8 was enough to achieve the best treatment performance. In all trials, initial pH of AMD was 4.8 and pH adjustment was not performed. Utilization of existing pH and Fe2+, low H2O2 requirements, and up to 98% treatment performances in COD, turbidity, color, Cu2+, Zn2+ made the proposed treatment system promising. Since the reaction occurs stepwise, a two-step kinetic model was applied and calculated theoretical maximum removal rate was consistent to experimental one, which validates the applied model. For the optimum molar ratio (1.8), 140mL/L sludge of high density (1.094g/mL), high settling velocity (0.16cm/s) with low specific resistance (3.15×108m/kg) was obtained. High reaction rates and easily dewaterable sludge characteristics also made the proposed method advantageous.
Keywords: Acid mine drainage; Copper mine; Fenton process; Oxidation
Removal of oxyanions from synthetic wastewater via carbonation process of calcium hydroxide: Applied and fundamental aspects
by G. Montes-Hernandez; N. Concha-Lozano; F. Renard; E. Quirico (pp. 788-795).
Removal of oxyanions (selenite, selenate, arsenate, phosphate and nitrate) during calcite formation was experimentally studied using aqueous carbonation of calcium hydroxide under moderate pressure (PCO2≅20bar) and temperature (30°C). The effects of Ca(OH)2 dose (10 and 20g), Ca(OH)2 source (commercial pure material or alkaline paper mill waste) and oxyanion initial concentration (from 0 to 70mgatom/L) were investigated for this anisobaric gas–liquid–solid system.The Ca(OH)2 carbonation reaction allowed successfully the removal of selenite (>90%), arsenate (>78%) and phosphate (≅100%) from synthetic solutions. Conversely, nitrate and selenate had not any physicochemical affinity/effect during calcite formation.The rate of CO2 transfer during calcite formation in presence of oxyanions was equal or slower than for an oxyanion-free system, allowing to define a retarding kinetic factor RF that can vary between 0 (no retarding effect) to 1 (total inhibition). For selenite and phosphate RF was quite high, close to 0.3. A small retarding effect was detected for arsenate ( RF≈0.05) and no retarding effect was detected for selenate and nitrate ( RF≈0). In general, RF depends on the oxyanion initial concentration, oxyanion nature and Ca(OH)2 dose.The presence of oxyanions could also influence the crystal morphology and aggregation/agglomeration process. For example, a c-axis elongation of calcite crystals was clearly observed at the equilibrium, for calcite formation in presence of selenite and phosphate.The oxyanions removal process proposed herein was inspired on the common physicochemical treatment of wastewater using calcium hydroxide (Ca(OH)2). The particularity, for this novel method is the simultaneous calcium hydroxide carbonation with compressed carbon dioxide in order to stabilise the solid matter. This economical and ecological method could allow the removal of various oxyanions as well as the ex situ mineral sequestration of CO2; particularly, when the Ca(OH)2 source comes from alkaline solid waste.
Keywords: Oxyanions; Aqueous carbonation; Calcium hydroxide; Water treatment; Mineralization of CO; 2
Determination of arsenic removal efficiency by ferric ions using response surface methodology
by Meltem Bilici Baskan; Aysegul Pala (pp. 796-801).
Arsenic contamination of drinking water is a serious problem in many parts of the world. The precipitation/coprecipitation method was used for arsenic removal from drinking water by ferric chloride, ferric sulfate and ferrous sulfate as coagulant. A Box–Behnken statistical experiment design method was used to investigate the effects of major operating variables such as initial arsenate concentration (10–1000μgL−1), coagulant dose (0.5–60mgL−1) and pH (4–9) were investigated. Experimental data were used for determination of the response functions coefficients. Predicted values of arsenate removal obtained using the response functions were in good agreement with the experimental data. Fe(III) ions were more effective and economic than Fe(II) ion due to required lower coagulant dose and pH. In the low initial arsenate concentrations, the highest arsenate removal efficiency was required high ferric chloride and ferric sulfate dose of 50 and 40mgL−1, while in the high initial arsenate concentrations, the highest arsenate removal efficiency was provided at low ferric chloride and ferric sulfate dose of 37 and 32mgL−1, respectively. This study showed that Box–Behnken design and response surface methodology was reliable and effective in determining the optimum conditions for arsenic removal by coagulation and flocculation.
Keywords: Arsenic removal; Iron salts; Coagulation; Box–Behnken design
Comparative sorption of benzo[α]phrene to different humic acids and humin in sediments
by Jinghuan Zhang; Mengchang He; Yehong Shi (pp. 802-809).
Sediment/soil organic matter (SOM) is the predominant sorbents for hydrophobic organic compounds (HOCs). The identification and comparison of sorption characterization of HOCs by different organic matter fractions are essential to predict the fate and transport of HOCs in soils and sediments. The objectives of this paper are to compare the sorption of benzo[α]phrene (BaP) to the humic acid (HA) and humin (HM) extracted from different sediments. The HA and HM were extracted with 0.1M NaOH from five sediments in different areas in China, and their sorption isotherms for BaP were determined. All sorption isotherms were nonlinear and nonlinearity increased in the order HAKoc values of BaP than HA. This implied the importance of both aliphatic and aromatic groups in BaP sorption. HM contributed to 54–92% of the total sorption depending on initial concentrations, clearly indicating the dominance of HM in BaP sorption by the sediments.
Keywords: Benzo[α]phrene (BaP); Sorption; Humic acids; Humin; Sediment
Gamma-ray induced degradation of diazinon and atrazine in natural groundwaters
by K.A. Mohamed; A.A. Basfar; A.A. Al-Shahrani (pp. 810-814).
Degradation of diazinon and atrazine pesticides present in natural groundwaters was investigated on a laboratory scale upon γ-irradiation from a60Co source. The effects of pesticide type, initial concentration, characteristics of natural groundwater, potential radical scavengers and absorbed dose on efficiency of pesticide degradation were investigated using GC–MS. γ-Irradiation experiments were carried out for three concentrations (i.e. 0.329, 1.643 and 3.286μM/diazinon and 0.464, 2.318 and 4.636μM/atrazine) with irradiation doses over the range 0.5–5.6kGy for diazinon and 0.2–21kGy for atrazine. γ-Radiolysis showed that diazinon was much easier to degrade by ionizing radiation compared to atrazine in all natural groundwater samples. This was observed at the three initial concentrations over the range irradiation doses. The irradiation doses required for degradation of 50 and 90% diazinon (distilled water) and atrazine (humic aqueous solution) at the three concentrations were not sufficient to degrade the same concentrations in different natural groundwater samples. Moreover, the presence of naturally occurring inorganic scavengers in solutions of diazinon and atrazine decreased significantly the efficiency of radiolytic degradation of pesticides, especially at higher concentrations.
Keywords: Radiolytic degradation; Diazinon; Atrazine; Natural groundwaters; Decontamination
Study on the adsorption of cadmium(II) from aqueous solution by D152 resin
by C.H. Xiong; C.P. Yao (pp. 815-820).
The feasibility of using D152 resin as an adsorbent for cadmium(II) was examined. The adsorption capacity of D152 resin for cadmium(II) ions was studied as a function of solution pH, temperature and contact time. The optimal pH for the adsorption of cadmium(II) ions was found to be 5.95 in the HAc–NaAc system. The maximum uptake capacity of cadmium(II) was estimated to 378mg/g D152 resin at 298K, at an initial pH value of 5.95. The results obtained from equilibrium adsorption studies were conformed to the Langmuir and Freundlich and the correlation coefficients have been evaluated. The apparent adsorption rate constant was k298K=4.01×10−5s−1, and the apparent activation energy was 2.78kJ/mol. Thermodynamic parameters, Δ S was 108J/(molK), heat of adsorption (Δ H) value of 12.8kJ/mol indicated the endothermic nature of the adsorption process, and a decrease of Gibbs free energy (Δ G) with increasing temperature also indicated the spontaneous nature of the process, respectively. The elution tests were carried out using various mixed reagents. The maximum elution percent of cadmium(II) ions were obtained when the reagent 0.5mol/L HCl was used.
Keywords: D152 resin; Cadmium(II); Adsorption; Kinetics; Thermodynamic
Montmorillonite-supported magnetite nanoparticles for the removal of hexavalent chromium [Cr(VI)] from aqueous solutions
by Peng Yuan; Mingde Fan; Dan Yang; Hongping He; Dong Liu; Aihua Yuan; JianXi Zhu; TianHu Chen (pp. 821-829).
Montmorillonite-supported magnetite nanoparticles were prepared by co-precipitation and hydrosol method. The obtained materials were characterized by X-ray diffraction, nitrogen adsorption, elemental analysis, differential scanning calorimetry, transmission electron microscopy and X-ray photoelectron spectroscopy. The average sizes of the magnetite nanoparticles without and with montmorillonite support are around 25 and 15nm, respectively. The montmorillonite-supported magnetite nanoparticles exist on the surface or inside the interparticle pores of clays, with better dispersing and less coaggregation than the ones without montmorillonite support. Batch tests were carried out to investigate the removal mechanism of hexavalent chromium [Cr(VI)] by these synthesized magnetite nanoparticles. The Cr(VI) uptake was mainly governed by a physico-chemical process, which included an electrostatic attraction followed by a redox process in which Cr(VI) was reduced into trivalent chromium. The adsorption of Cr(VI) was highly pH-dependent and the kinetics of the adsorption followed the Pseudo-second-order model. The adsorption data of unsupported and clay-supported magnetite nanoparticles fit well with the Langmuir and Freundlich isotherm equations. The montmorillonite-supported magnetite nanoparticles showed a much better adsorption capacity per unit mass of magnetite (15.3mg/g) than unsupported magnetite (10.6mg/g), and were more thermally stable than their unsupported counterparts. These fundamental results demonstrate that the montmorillonite-supported magnetite nanoparticles are readily prepared, enabling promising applications for the removal of Cr(VI) from aqueous solution.
Keywords: Magnetite; Montmorillonite; Chromium; Adsorption; Transmission electron microscopy
Removal of basic dye using raw and acid activated bentonite samples
by E. Eren; B. Afsin (pp. 830-835).
The adsorption behavior of crystal violet (CV+) from aqueous solution onto raw (RB) and acid activated (AAB) bentonite samples was investigated as a function of parameters such as initial CV+ concentration, contact time and temperature. The Langmuir and Freundlich adsorption models were applied to describe the equilibrium isotherms. The adsorption rate was fast and more than half of the adsorbed-CV+ was removed in the first 55min for RB and 25min for 0.2-AAB at the room temperature ( C0=1.2mmol/g). The pseudo-first order, and pseudo-second order kinetic models were used to describe the kinetic data and rate constants were evaluated. The results best fit the pseudo-second order kinetic model with the rate constant, k2, in the range of 13.52×10−2 to 5.53×10−2g/mmol and 52.70×10−2 to 6.69×10−2mmol/g min for RB and 0.2-AAB sample, respectively ( C0=0.1–1.2mmol/g).
Keywords: Dye adsorption; Activation thermodynamic; Kinetic; Acid activation; X-ray diffraction
Development and application of an auto-normalization program for optimal treatment of numerous metal-containing hazardous sludges
by Kun-Sen Chang; Yu-Chien Lin; Tao-Shin Liu (pp. 836-841).
Precise control of all pollutant concentrations during co-treating numerous hazardous materials is difficult because of the variety of pollutants and concentrations. An Auto-Nor program for normalizing various concentrations of numerous hazardous materials had been developed, and the normalization theory, processes, and a practical case of 20 metal-containing sludges was presented. Metal concentrations ( C ij) of each sludge, including Cd, Cr, Cu, Pb and Zn, were divided by toxicity characteristic leaching procedure (TCLP) regulatory limit to be relative concentrations ( R ij). Computations at a systematic threshold of normalization ( U) by the Auto-Nor program would automatically sort out optimal co-treatment groups. In the 20-sludge case, three optimal co-treatment groups, comprising 14, 3 and 3 sludges, were sorted out and the application results show that all random samples passed the TCLP test. The Auto-Nor program can be further applied to the treatment or remediation of hazardous fly ashes and contaminated soils, improving and benefiting their concentration control, dosage management and cost reduction.
Keywords: Normalization; Program; Optimal; Metal; Hazardous sludge
Concentration-dependence of the explosion characteristics of chlorine dioxide gas
by Ri-ya Jin; Shuang-qi Hu; Yin-ghao Zhang; Tao Bo (pp. 842-847).
The explosion characteristics of chlorine dioxide gas have been studied for the first time in a cylindrical exploder with a shell capacity of 20L. The experimental results have indicated that the lower concentration limit for the explosive decomposition of chlorine dioxide gas is 9.5% ([ClO2]/[air]), whereas there is no corresponding upper concentration limit. Under the experimental conditions, and within the explosion limits, the pressure of explosion increases with increasing concentration of chlorine dioxide gas; the maximum pressure of explosion relative to the initial pressure was measured as 0.024MPa at 10% ClO2 and 0.641MPa at 90% ClO2. The induction time (the time from the moment of sparking to explosion) has also been found to depend on the concentration of chlorine dioxide gas; thus, at 10% ClO2 the induction time was 2195ms, but at 90% ClO2 the induction time was just 8ms. The explosion reaction mechanism of ClO2 is of a degenerate chain-branching type involving the formation of a stable intermediate (Cl2O3), from which the chain-branching occurs. Chain initiation takes place at the point of ignition and termination takes place at the inner walls of the exploder.
Keywords: Chlorine dioxide gas; Explosive decomposition; Pressure of explosion; Explosion limit
Degradation of gas-phase trichloroethylene over thin-film TiO2 photocatalyst in multi-modules reactor
by Sang Bum Kim; Jun Yub Lee; Gyung Soo Kim; Sung Chang Hong (pp. 848-852).
The present paper examined the photocatalytic degradation (PCD) of gas-phase trichloroethylene (TCE) over thin-film TiO2. A large-scale treatment of TCE was carried out using scale-up continuous flow photo-reactor in which nine reactors were arranged in parallel and series. The parallel or serial arrangement is a significant factor to determine the special arrangement of whole reactor module as well as to compact the multi-modules in a continuous flow reactor. The conversion of TCE according to the space time was nearly same for parallel and serial connection of the reactors.
Keywords: Photocatalytic degradation; Trichloroethylene; Photocatalysis; Thin-film TiO; 2; Continuous flow system
Investigation of different linear and nonlinear chemometric methods for modeling of retention index of essential oil components: Concerns to support vector machine
by Siavash Riahi; Eslam Pourbasheer; Mohammad Reza Ganjali; Parviz Norouzi (pp. 853-859).
The quantitative structure-retention relationship (QSRR) of the essential oil components against the gas chromatography retention index (RI) was studied. The genetic algorithm (GA) was employed to select the variables that resulted in the best-fitted models. After the variables were selected, the linear multivariate regressions [e.g. the multiple linear regression (MLR), the partial least squares (PLS)] as well as the nonlinear regressions [e.g. the polynomial PLS (poly-PLS), the support vector machine (SVM)] were utilized to construct the linear and nonlinear QSRR models. The obtained results using SVM were compared with those of MLR, PLS and poly-PLS, exhibiting that the SVM model demonstrated a better performance than that of the other models. The relative standard error SE (%) of the training set and the test set for the SVM model was 1.96 and 4.25, and the square correlation coefficients were 0.987 and 0.962 respectively, while the square correlation coefficient of the cross validation ( Q2) on the SVM model was 0.963, revealing the reliability of this model. The resulting data indicated that SVM could be used as a powerful modeling tool for the QSRR studies. This is the first research on the QSRR of the essential oil compounds against the retention index using the SVM.
Keywords: Chemometrics; QSRR; Genetic algorithms; Support vector machine; Essential oils
Environmentally friendly efficient coupling of n-heptane by sulfated tri-component metal oxides in slurry bubble column reactor
by Hongzhu Ma; Jing Xiao; Bo Wang (pp. 860-865).
SO42−/M xO y is of the greatest interest in solid catalysts and green catalysts. Slurry bubble column reactors are of considerable interest in industrial processes and various biochemical processes. The cetane number (CN) has widely used diesel fuel quality parameter related to the ignition delay time (and combustion quality) of a fuel. CN improvement of diesel fuels is a difficult task that refiners will face in the near future. For that purpose, the tests were designed in which n-heptane is used as the reactant in the air or ozone atmosphere at room temperature (RT) and local atmospheric pressure (LAP) using different catalysts of sulfated tri-component metal oxides SO42−/Fe2O3-TiO2-SnO2 (SFTSn) and SO42−/MnO2-TiO2-SnO2 (SMTSn) in slurry bubble column reactor. The products distribution was analyzed by gas chromatography–mass spectrometry (GC–MS) method and the results show that the relative selectivity of long linear alkane (C12–C28) reaches the maximum (87.330%) when SMTSn is used as catalyst in flow air at 60min. Diesel fuel components with higher cetane numbers can be easily obtained from this study.
Keywords: Sulfated metal oxides; Slurry bubble column reactors; Cetane number; n; -heptane; Long linear alkane
Enhanced mercury ion adsorption by amine-modified activated carbon
by Jianzhong Zhu; John Yang; Baolin Deng (pp. 866-872).
Mercury (Hg) is one of the most toxic metals found in water and sediments. In an effort to develop an effective adsorbent for aqueous Hg removal, activated carbon (AC) was modified with an amino-terminated organosilicon (3-aminopropyltriethoxysilane, APTES). Surface properties of the APTES-modified AC (MAC) were characterized by the scanning electron microscopy in conjunction with the energy-dispersive spectroscopy (SEM-EDS), the Fourier transform infrared spectroscopy (FT-IR), and potentiometry. The impacts of solvent, APTES concentration, reactive time and temperature on the surface modification were evaluated. The aqueous Hg adsorptive kinetics and capacity were also determined. Results demonstrated that the strong Hg-binding amine ligands were effectively introduced onto the AC surfaces through the silanol reaction between carbon surface functional groups (–COOH, –COH) and APTES molecules. The modification lowered the pH at the point of zero charge (pHpzc) to 4.54 from 9.6, favoring cation adsorption. MAC presented a faster rate of the Hg (II) adsorption and more than double adsorptive capacity as compared with AC.
Keywords: Activated carbon; APTES; Surface modification; Mercury adsorption
Measurement and receptor modeling of atmospheric polycyclic aromatic hydrocarbons in urban Kaohsiung, Taiwan
by K.S. Chen; H.C. Li; H.K. Wang; W.C. Wang; C.H. Lai (pp. 873-879).
The concentrations of 21 individual polycyclic aromatic hydrocarbons (PAHs) and total suspended particles (TSPs) were measured using high-volume air samplers at Tzuo-Yin and Hsiung-Kong sites in Kaohsiung City, Taiwan, for four seasons from 2005 to 2006. The gaseous and particulate phases of individual PAHs were identified using a gas chromatograph with a flame-ionization detector (GC/FID). Measurements show that the concentrations of total (gas+particulate) PAHs generally followed the seasonal variations of the concentrations of TSP (107.2–117.1μgm−3), being the highest in winter (143.9–182.9ngm−3) and lowest in summer (81.4–95.2ngm−3) at both sites. Most PAH species were low-weight PAHs (approximately 80.8–82.0%), followed by high-weight PAHs (10.5–14.6%) and medium-weight PAHs (6.5–6.8%). The fractions of gaseous PAHs decreased with molecular weight or ring number. The particle phase (60.2(73.5%) dominated the high-weight PAHs. Results of receptor model show that industrial combustions (49.1–63.7%) contributed most to ambient PAHs, followed by restaurant emissions (18.4–39.7%) and mobile sources (11.3–22.8%) at the Tzuo-Yin site. At the Hsiung-Kong, mobile sources (49.5–63.3%) contributed most to ambient PAHs, followed by restaurant emissions (19.8–36.6%) and industrial combustions (13.7–27.1%). The differences in the results at the two sites are mainly attributed to the different industries at each site.
Keywords: PAHs; Total suspended particles; Receptor modeling; Chemical mass balance
Nitrogen dilution effect on the flammability limits for hydrocarbons
by Chan-Cheng Chen; Tzu-Chi Wang; Horng-Jang Liaw; Hui-Chu Chen (pp. 880-890).
Theoretical models to predict the upper/lower flammability limits of hydrocarbons diluted with inert nitrogen gas are proposed in this study. It is found that there are linear relations between the reciprocal of the upper/lower flammability limits and the reciprocal of the molar fraction of hydrocarbon in the hydrocarbon/inert nitrogen mixture. Such linearity is examined by experimental data reported in the literature, which include the cases of methane, propane, ethylene and propylene. The R-squared values ( R2) of the regression lines of the cases explored are all greater than 0.989 for upper flammability limit (UFL). The theoretical slope of the predictive line for lower flammability limit (LFL) is found to be very close to zero for all explored cases; and this result successfully explains the experimental fact that adding inert nitrogen to a flammable material has very limited effect on LFL. Because limit oxygen concentration (LOC) could be taken as the intersectional point of the UFL curve and LFL curve, a LOC-based method is proposed to predict the slope of the UFL curve when experimental data of UFL are not available. This LOC-based method predicts the UFL with average error ranging from 2.17% to 5.84% and maximum error ranging from 8.58% to 12.18% for the cases explored. The predictive models for inert gas of nitrogen are also extended to the case of inert gas other than nitrogen. Through the extended models, it was found that the inert ability of an inert gas depends on its mean molar heat capacity at the adiabatic flame temperature. Theoretical calculation shows that the inert abilities of carbon dioxide, steam, nitrogen and helium are in the following order: carbon dioxide>steam>nitrogen>helium; and this sequence conforms to the existing experimental data reported in the literature.
Keywords: Upper flammability limit; Lower flammability limit; Inerting; Fire safety
Removal of phosphate from secondary effluent with Fe2+ enhanced by H2O2 at nature pH/neutral pH
by Chunjuan Li; Jun Ma; Jimin Shen; Peng Wang (pp. 891-896).
Removal of phosphate in secondary effluents was investigated in presence of Fe2+/H2O2. The effect of H2O2-dose, Fe-dose and initial phosphate concentration were assessed. The results indicated that Fe2+/H2O2 could greatly increase the removal of phosphate compared with those achieved by Fe2+ alone. For initial phosphate concentration of 0.97–3.75mg P/L, phosphate removal rates of 50–60% were observed at 1:1 molar addition of Fe(II). However, a 125% excess of Fe-dose was necessary for complete phosphate removal. The experimental data demonstrated that removal of phosphate with Fe2+/H2O2 was higher than that observed with ferric coagulation alone. This fact suggested that in situ formed Fe(III) having much affinity for ligand phosphate. Chemical co-precipitation was considered as the dominant mechanism about phosphate removal in presence of Fe2+/H2O2. The electron paramagnetic resonance (EPR) spectra tests in secondary effluents showed that Fe2+/H2O2 could produce an increasing hydroxyl radical concentration with a decrease in both H2O2 dosage and phosphate concentration. Fe2+/H2O2 had the potential to be utilized for removal of phosphate due to the lower cost and the higher phosphate removal capability.
Keywords: Phosphate; Co-precipitation; In situ formed Fe; 3+; Secondary effluent; Hydroxyl radical
Establishment of activity indicator of TiO2 photocatalytic reaction—Hydroxyl radical trapping method
by Chen-Yu Chang; Yung-Hsu Hsieh; Ling-Ling Hsieh; Kuo-Shan Yao; Ta-Chih Cheng (pp. 897-903).
In this study, a new, low cost and easy method, hydroxyl radical trapping method, was employed to investigate the photo-activity of UV/TiO2 photocatalytic reaction. The Taguchi method was utilized to optimize the preparation of titanium dioxide (TiO2) thin-film reactor through the modified chemical vapor deposition (CVD) method. The optimal yield of hydroxyl radicals was then evaluated by calculating the conversion ratio of salicylic acid under the optimal conditions. In the experiments, salicylic acid was used as the free-radical scavenger and the formation of three different intermediates were examined to shed light on the trend and kinetics of reaction of hydroxyl radical with organic substance under different operation conditions. The results indicated that the yield of hydroxyl radicals increased with increasing irradiation intensity and dissolved oxygen level. The optimal experimental conditions obtained in this study were irradiation with intensity of 2.9mWcm−2 on salicylic acid at concentration of 250mgL−1 by both agitation and aeration processes (dissolved oxygen level=8.2mgO2L−1) at pH 5. Such conditions could achieve the optimal hydroxyl radical yield of 5.1×10−17M.
Keywords: Chemical vapor deposition method; Titanium dioxide; Salicylic acid; Hydroxyl radical; Activity indicator
Rapid decolorization of azo dye methyl orange in aqueous solution by nanoscale zerovalent iron particles
by Jing Fan; Yanhui Guo; Jianji Wang; Maohong Fan (pp. 904-910).
Azo dyes are recalcitrant and refractory pollutants that constitute a significant burden on the environment. The report here is focused on the decolorization treatment of water soluble azo dye methyl orange (MO) by chemically synthesized nanoscale zerovalent iron (NZVI) particles. Experimental variables such as initial dye concentration, iron dosage, solution pH and temperature were studied systematically. Batch experiments suggest that the decolorization efficiency was enhanced with the increase of NZVI dosage and reaction temperature, but decreased with increasing initial dye concentration and initial solution pH. Further studies indicated that existence of inorganic salt (Na2SO4) could inhibit the decolorization of MO. Kinetic analyses based on the experimental data elucidated that the decolorization process followed a first order exponential decay kinetics model. The activation energy was determined to be 35.9kJ/mol.
Keywords: Nanoscale zerovalent iron; Azo dye; Decolorization; Methyl orange
Pretreatment of ammonium removal from landfill leachate by chemical precipitation
by Tao Zhang; Lili Ding; Hongqiang Ren (pp. 911-915).
Chemical precipitation is a useful technology to remove ammonium (NH4+) from landfill leachate. In this paper, the removal of ammonium from landfill leachate was studied. The objective of this study was to investigate optimum pH, optimum molar ratio, and different kinds of chemicals combinations for magnesium ammonium phosphate (MAP) precipitation. Furthermore, the kinetics of MAP formation and surface characterization were analyzed. The results indicated that ammonium in landfill leachate could be removed with the optimum pH of 9.5. The Mg2+:NH4+:PO43− molar ratio was practically controlled at 1.15:1:1 to remove ammonium effectively and avoid higher concentration of PO43− in the effluent. Highest salt concentration was generated by using MgCl2·6H2O plus Na2HPO4·12H2O. Compare to MgCl2·6H2O and Na2HPO4·12H2O, adding MgO and 85% H3PO4 could significantly minimize the salt concentration, although ammonium removal ratio was 9 percents lower. The lowest ammonium removal ratio was generated by adding Ca(H2PO4)2·H2O and MgSO4·7H2O. Moreover, the kinetics experiment shown that the rate of reaction was closer to the first-order kinetic model. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analysis indicated that MAP was the main composition of the precipitates. Scanning electron microscopy with energy dispersive X-ray (SEM–EDX) analysis indicated that the unshaped crystal was coarse and its size was irregular, the surface composition of the precipitates contains a great deal of O, P, Mg and trace of C, K, Na, Cl.
Keywords: Landfill leachate; Ammonium (NH; 4; +; ); Magnesium ammonium phosphate (MAP); Pretreatment
Ability of the Fire Propagation Apparatus to characterise the heat release rate of energetic materials
by H. Biteau; A. Fuentes; G. Marlair; S. Brohez; J.L. Torero (pp. 916-924).
Energetic materials encompass a wide range of chemical compounds. They react very rapidly releasing large amounts of energy. One of their peculiarities is that they carry an oxidizer and do not require oxygen from the air as their primary reaction partner. The aim of this paper is to present an analysis of the ability to estimate the heat release rate of a sample energetic material using two calorimetric methodologies. The methods are based on Oxygen Consumption and Carbon Dioxide Generation principles. Data have been obtained from experiments carried out with the Fire Propagation Apparatus. First, results from smoke powder combustion tests reveal significant discrepancies between the two approaches. Results from a sensitivity analysis realised in a previous work underlined that the most likely parameters to alter the heat release rate estimation are the energy constants and the concentration of oxygen. Correction procedures have been developed; one based on the estimation of the amount of oxygen supplied by the oxidizer, and a second one based on the calculation of new energy constants accounting for the chemical decomposition of the tested materials. Results are presented in this study.
Keywords: Energetic materials; Heat release rate; Fire propagation apparatus; Oxygen consumption calorimetry; Carbon dioxide generation calorimetry
Rapid removal of cobalt ion from aqueous solutions by almond green hull
by A. Ahmadpour; M. Tahmasbi; T. Rohani Bastami; J. Amel Besharati (pp. 925-930).
Almond green hull, an agriculture solid waste, was chemically treated and used for the adsorption of Co (II) from aqueous solutions. The efficiency of this new adsorbent was studied using batch adsorption technique under different experimental conditions such as sorbent amount, initial metal-ion concentration, contact time, adsorbent particle size, and chemical treatment. Optimum dose of sorbent for maximum metal-ion adsorption were 0.25g for 51.5mgl−1 and 0.4g for 110mgl−1 solutions, respectively. High removal efficiencies of Co (II) were occurred in the first 1min of sorbent contact time. The adsorption of Co (II) on almond green hull was also observed to follow the pseudo second-order kinetics. Adsorption isotherms were expressed by Langmuir and Freundlich adsorption models. The Langmuir adsorption model fits the experimental data reasonably well compared to the Freundlich model. The maximum adsorption capacity of this new sorbent was found to be 45.5mgg−1. The present study revealed that such a low cost material could be used as an efficient sorbent for the removal of cobalt from wastewater streams.
Keywords: Almond green hull; Agricultural waste; Sorbent; Cobalt; Langmuir
Theoretical studies on polynitro-1,3-bishomopentaprismanes as potential high energy density compounds
by Limei Qiu; Xuedong Gong; Jian Zheng; Heming Xiao (pp. 931-938).
Based on the fully optimized molecular geometric structures at the DFT-B3LYP/6-31G* level, the densities ( ρ), detonation velocities ( D) and pressures ( P) for a series of polynitro-1,3-bishomopentaprismanes (PNBPPs), as well as their thermal stabilities, were investigated to look for high energy density compounds (HEDCs). The studied PNBPPs have high values of heats of formation (HOFs) and the magnitude is correlative with the number ( n) and the space distance of nitro groups. D and P for PNBPPs were estimated by using modified Kamlet–Jacobs equations based on the calculated HOFs and ρ. It is found that ρ, D and P all increase with n and satisfy the group additivity rule. The calculations on the bond dissociation energies of CNO2 and CC bonds indicate that both bonds are possible to be the trigger bond in the pyrolysis process, and this interesting phenomenon is related with the molecular structure, especially the strain energy of the skeleton. In conjunction with the energetic performances and thermal stabilities, PNBPPs with n=8–12 are recommended as the preferred candidates of HEDCs. These results would provide basic information for the further studies of PNBPPs.
Keywords: Density functional theory; Heat of formation; Density; Detonation properties; Bond dissociation energy
Enhanced photocatalytic activity of S-doped TiO2–ZrO2 nanoparticles under visible-light irradiation
by Guohui Tian; Kai Pan; Honggang Fu; Liqiang Jing; Wei Zhou (pp. 939-944).
Porous nanocrystalline S-doped TiO2–ZrO2 visible-light photocatalysts were prepared through a one-step method. The resulting materials were characterized by X-ray diffraction (XRD), N2 adsorption–desorption measurements, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectra (DRS), Fourier transform infrared spectra (FT-IR) and electron paramagnetic resonance (ESR). It was found that modification by ZrO2 could effectively inhibit phase transformation, enhance visible-light absorption, and possess more surface hydroxyl groups. The photocatalytic activity of S-doped TiO2–ZrO2 was higher than that of unmodified S-doped TiO2 and Degussa P25. The enhanced photocatalytic activity could be attributed to the higher specific area, smaller crystal size, porous structure and more surface hydroxyl groups in the catalyst.
Keywords: S-doped TiO; 2; Visible-light absorption; Photocatalysis; Hydroxyl radical
Evaluation of laboratory and industrial meat and bone meal combustion residue as cadmium immobilizing material for remediation of polluted aqueous solutions: “Chemical and ecotoxicological studies”
by M. Coutand; E. Deydier; M. Cyr; F. Mouchet; L. Gauthier; R. Guilet; L. Bernues Savaete; S. Cren; P. Clastres (pp. 945-953).
Meat and Bone Meals (MBM) combustion residues (ashes) are calcium and phosphate-rich materials. The aim of this work is to evaluate ashes efficiency for remediation of cadmium-contaminated aqueous solutions, and to assess the bioavailability of cadmium on Xenopus laevis larvae. In this study both industrial (MBM-BA) and laboratory (MBM-LA) ashes are compared regarding their efficiency. Kinetic investigations reveal that cadmium ions are quickly immobilized, with a maximum cadmium uptake at 57mg Cd2+/g of ashes for MBM-LA, two times higher than metal uptake quantity of MBM-BA, in our experimental conditions. Chemical and X-ray diffraction analysis (XRD) reveal that Cd2+ is mainly immobilized as Ca10− xCd x(PO4)6(OH)2 by both ashes, whereas otavite, Cd(CO3), is also involved for MBM-LA in cadmium uptake. Otavite formation could be explained by the presence of carbonates in MBM-LA, as observed by IR. Genotoxicity of cadmium solution on Xenopus larvae is observed at 0.02, 0.2 and 2mg Cd2+/L. However addition of only 0.1g/L MBM-LA inhibits these effects for the above concentration values whereas Cd2+ bioaccumulation in larvae's liver is similar for both experiments, with and without ashes.
Keywords: Meat and bone meal; Incineration; Cadmium; Toxicity; Xenopus; larvae
Kinetics and mechanism of photolysis and TiO2 photocatalysis of triclosan
by Hyun-Seok Son; Gwangpyo Ko; Kyung-Duk Zoh (pp. 954-960).
The degradations of triclosan (5-chloro-2-(2,4-dichlorophenoxy)-phenol), a potent broad-spectrum antimicrobial agent, were compared in TiO2-only in the dark condition, photolysis, and TiO2 photocatalysis with a UV-A lamp. TiO2 photocatalysis more effectively degraded and mineralized triclosan compared to TiO2-only and photolysis conditions. While triclosan removed only 30% by TiO2-only condition within 20min, the triclosan degradation in photolysis and photocatalysis at the same time was 75 and 82%, respectively, and TOC removal was significantly higher in photocatalysis than in photolysis. The data of kinetics showed that triclosan adsorption onto TiO2 was fitted to Langmuir isotherm, and TiO2 photocatalysis was fitted to Langmuir–Hinshelwood model ( b=27.99mM−1, Ktriclosan=9.49mM−1). The neutral range of pH was favorable to photocatalysis due to the charge effect between TiO2 and triclosan. The addition of 2-propanol, a radical scavenger, significantly reduced the degradation of triclosan both in photolysis and photocatalysis. Dioxin-type intermediates such as dibenzo-dichloro- p-dioxin (DCDD), dibenzo- p-dioxin were produced in photolysis with and without 2-propanol, and also in photocatalysis with 2-propanol, but these intermediates were not detected in photocatalysis without 2-propanol. This result indicates that the photocatalytic degradation of triclosan is mainly achieved by radicals, and these radicals can further degrade dioxin-type intermediates once they are produced in photocatalysis.
Keywords: TiO; 2; Langmuir–Hinshelwood; Radical scavenger; Dibenzo-dichloro-; p; -dioxin; Dibenzo-; p; -dioxin
Study of kinetic and fixed bed operation of removal of sulfate anions from an industrial wastewater by an anion exchange resin
by Reza Haghsheno; Ali Mohebbi; Hassan Hashemipour; Amir Sarrafi (pp. 961-966).
Sulfate anions represent very important wastewater pollutants, which appear in the effluents discharged from copper mines. In this study, for the first time, an attempt has been made on the removal of sulfate anions by an ion exchange resin. This work is focused on the removal of sulfate anions from the Sarcheshmeh copper complex (Kerman province, Southeast of Iran) wastewater by an anion exchange resin. Batch experiments of sulfate anions adsorption on Lewatit K6362 resin were carried out to determine the adsorption equilibrium data and the relation of adsorption isotherms. Isothermal data can be fitted with Freundlich adsorption isotherms better than Langmuir equation. The results show that maximum removal of sulfate anions take places in the resin dosage of 1000mg/100ml and the adsorption of sulfate anions on the resin follows reversible first-order kinetics. The overall adsorption rate constants were compared for different initial concentrations. Finally, the effects of parameters such as the flow rate, bed height and inlet adsorbate concentration on the breakthrough curve in a fixed bed column were studied in detail.
Keywords: Adsorption; Ion exchange; Kinetics; Resin; Sulfate
Suitability of nitrogen rich compounds for gun propellant formulations
by R.S. Damse; A.K. Sikder (pp. 967-971).
This paper reports the suitability of a novel nitrogen rich compound, guanidinium-5-aminotetrazolate for RDX-based high-energy gun propellant formulations in respect of flame temperature as well as the burning rate characteristics. It has been found that the partial replacement of RDX with guanidinium-5-amino tetrazolate at the rate of five parts decreases the flame temperature of the propellant by about 120K without adversely affecting the burning rate characteristics, i.e. linear rate of burning co-efficient and pressure exponent.
Keywords: Guanidinium-5-aminotetrazolate; Triaminoguanidine nitrate; Triaminoguanidine azide; Flame temperature; Force constant; Homolytic cleavage; Ring-opening mechanism
Characterization of the fly ashes from the lignite burning power plants of northern Greece based on their quantitative mineralogical composition
by G. Kostakis (pp. 972-977).
In the present work, mineralogical analysis of fly ashes produced from the brown coal burning power plants of Agios Dimitrios, Kardia, Ptolemais, LIPTOL, Amynteon, and Achlada-Meliti (Western Macedonia, Greece) was performed, with the aim of characterizing the ashes on the basis of their quantitative mineral phase composition and asses their variability at different time periods. The fly ashes from the Agios Dimitrios, Kardia, and Ptolemais power plants were found to have nearly the same mineralogical composition, consisting mainly of feldspars, lime, anhydrite, quartz, calcium silicates, and high amounts of amorphous phases. The fly ashes from Amynteon were slightly different, having lower content of lime and higher content of feldspars, whilst those from LIPTOL had a relative variable quantitative composition. The fly ashes from the Meliti-Achlada power plant consisted mainly of amorphous phases (very high amounts), mullite, feldspars, and quartz. The mineralogical composition of the ashes produced in all the power plants, except from these of LIPTOL, did not fluctuate significantly over time. An assessment of the hydraulic (cementitious) or pozzolanic character of the ashes is proposed, introducing the use of triangle diagrams A–B–C, which represent the total fraction of the phases with hydraulic or pozzolanic (A), inert (B) character, and the amorphous phases (C).
Keywords: Greek lignite power plants; Lignite fly ash mineralogical composition; Fly ash reactivity
Treatment of a synthetic solution of galvanization effluent via the conversion of sodium cyanide into an insoluble safe complex
by Ibrahim Ismail; Nabil Abdel-Monem; Seif-Eddeen Fateen; Waleed Abdelazeem (pp. 978-983).
Wastewater discharged from metal-finishing processes usually contains cyanide, a hazardous substance that is used extensively in the surface finishing industry. In the present study, a synthetic solution resembling the contaminated wastewater was chemically treated using ferrous sulfate. This simple one-step process was applied successfully to remove cyanide from metal finishing wastewater. The experiments were carried out on a synthetic solution containing ions of cyanide and zinc. The effects of mixing velocity, ratio of ferrous ions to cyanide ions, ferrous ions concentration, initial cyanide concentration, pH of solution, temperature, mixing time and zinc ions concentration were studied. The results showed that the removal efficiency of cyanide increased as the mixing velocity increased, ferrous ion molar ratio to cyanide ions increased, temperature increased and time of mixing increased at an optimum of pH 8. The reduction of cyanide concentration reached the allowable limit for wastewater discharge according to the Egyptian Environmental Law decree 44/2000, which is 0.2mg/l. The formed complexes were analyzed and the stability of each complex was studied under different pH value solutions after 7 days of contact. A typical example of electroplating wastewater from a local company in the field of metal finishing, which contains18mg/lCN− and 12mg/lZn2+, was treated according to the determined optimum conditions for the treatment process and the concentration of CN− was reduced to 0.095mg/l after 15min of agitation.
Keywords: Industrial wastewater treatment; Sodium cyanide; Ferrous sulfate
Reduction of 2,4,6-trichlorophenol with zero-valent zinc and catalyzed zinc
by Jeong-Hak Choi; Young-Hun Kim (pp. 984-991).
Reductive dechlorination of 2,4,6-trichlorophenol (2,4,6-TCP) was conducted with Zn and Zn bimetals, Pd/Zn, Ni/Zn, Cu/Zn, Pt/Zn. Zn showed relatively low reaction rate toward 2,4,6-TCP, while Pd/Zn had dramatically increased reactivity and other bimetals had higher reaction rates than that of plain zinc. Phenol and less chlorinated phenols were found as dechlorination products. Pd/Zn produced cyclohexanone which is a product of aromatic ring reduced. Surface area normalized kinetic constants and second metal contents normalized kinetic constants were calculated and compared. Two mechanisms, mainly catalytic activation and enhanced corrosion, were proposed for the reactivity enhancement.
Keywords: Reductive dechlorination; 2,4,6-trichlorophenol; Zero-valent zinc; Catalyzed zinc
Dechlorination of γ-hexachlorocyclohexane by zero-valent metallic iron
by Zhiyuan Wang; Ping’an Peng; Weilin Huang (pp. 992-997).
This study investigated the rates and pathways of γ-hexachlorocyclohexane (γ-HCH) dechlorination by granular zero-valent iron under different pH, iron dosage and temperature conditions. It was found that γ-HCH was rapidly reduced to benzene and chlorobenzene (CB) with benzene as the major product and that the dechlorination likely follows three steps of dichloroelimination to benzene, or two steps of dichloroeliminations and one step of dehydrohalogenation to CB. The calculated pseudo-first-order rate of γ-HCH degradation was 0.0125min−1 at pH 6.73, 25°C and 10gL−1 iron dosage, corresponding to 55.5min of half-life. It was also found that the rate of γ-HCH dechlorination increases as a function of reaction temperature and zero-valent iron dosage and decreases as a function of solution pH. The calculated activation energy is 33.5kJmol−1 at pH 6.73, which is much lower than that of dehydrohalogenation facilitated by hydroxyl under basic conditions. The study suggested that zero-valent iron could be used to effectively and efficiently transform γ-HCH.
Keywords: Zero-valent iron; Dechlorination; γ-HCH; Kinetics
Biosorption of lead from aqueous solution by Ficus religiosa leaves: Batch and column study
by Suleman Qaiser; Anwar Rasheed Saleemi; Muhammad Umar (pp. 998-1005).
The biosorption of lead by Ficus religiosa leaves (FRLs) in powder and immobilized form was investigated. Batch experiments were conducted to determine the biosorption capacity, equilibrium time, optimal pH and temperature. The maximum biosorption capacity of lead was 37.45mgg−1 at optimal pH of 4. The temperature change in the range of 20–40°C affected the biosorption capacity and the maximum removal was observed at 25°C. The thermodynamics parameters were determined from experimental data. The Langmuir and Freundlich models were used to explain the equilibrium data. The Langmuir model showed better fit of data with correlation coefficient of 0.97. The kinetics of biosorption followed pseudo second order model. For continuous biosorption experiments, FRLs biomass was immobilized in polysulfone matrix. Breakthrough curves were analyzed at different flow rates, pH and bed depth. Bed depth service time (BDST) and the Thomas models were used to describe the experimental data. A solution of 0.05M HNO3 did well to elute lead from biomass. The release of Ca, Mg and Na ions during lead biosorption revealed that ion exchange was the major removal mechanism.
Keywords: Biosorption; Lead; Kinetics; Equilibrium; Thermodynamics
Removal of some metal ions by activated carbon prepared from Phaseolus aureus hulls
by M. Madhava Rao; D.K. Ramana; K. Seshaiah; M.C. Wang; S.W. Chang Chien (pp. 1006-1013).
Removal of lead [Pb(II)], zinc [Zn(II)], copper [Cu(II)], and cadmium [Cd(II)] from aqueous solutions using activated carbon prepared from Phaseolus aureus hulls (ACPAH), an agricultural waste was studied. The influence of various parameters such as effect of pH, contact time, adsorbent dose, and initial concentration of metal ions on the removal was evaluated by batch method. The removal of metal ions by ACPAH was pH dependent and the optimum pH values were 7.0, 8.0, 7.0 and 6.0 for Cu(II), Cd(II), Zn(II), and Pb(II), respectively. The sorption isotherms were studied using Langmuir, Freundlich, Dubinin–Radushkevich (D–R), and Temkin isotherm models. The maximum adsorption capacity values of ACPAH for metal ions were 21.8mgg−1 for Pb(II), 21.2mgg−1 for Zn(II), 19.5mgg−1 for Cu(II), and 15.7mgg−1 for Cd(II). The experiments demonstrated that the removal of metal ions followed the pseudo-second-order kinetic model. Desorption experiments were carried out using HCl solution with a view to regenerate the spent adsorbent and to recover the adsorbed metal ions.
Keywords: Lead; Zinc; Copper; Cadmium; Phaseolus aureus; hulls
Synthesis of high capacity cation exchangers from a low-grade Chinese natural zeolite
by Yifei Wang; Feng Lin (pp. 1014-1019).
The Chinese natural zeolite, in which clinoptilolite coexists with quartz was treated hydrothermally with NaOH solutions, either with or without fusion with NaOH powder as pretreatment. Zeolite Na–P, Na–Y and analcime were identified as the reacted products, depending on the reaction conditions such as NaOH concentration, reaction time and hydrothermal temperature. The products were identified by X-ray diffraction, and characterized by Fourier transform IR and ICP. With hydrothermal treatment after fusion of natural zeolite with NaOH, high purity of zeolite Na–Y and Na–P can be selectively formed, their cation exchange capacity (CEC) are 275 and 355meq/100g respectively, which are greatly higher than that of the natural zeolite (97meq/100g). Furthermore, the ammonium removal by the synthetic zeolite Na–P in aqueous solution was also studied. The equilibrium isotherms have been got and the influence of other cations present in water upon the ammonia uptake suggested an order of preference Ca2+>K+>Mg2+.
Keywords: Natural zeolite; Hydrothermal synthesis; Cation exchange capacity; Zeolite Na–P; Ammonium uptake
Degradation of fuel oil in salt marsh soils affected by the Prestige oil spill
by Flora A. Vega; Emma F. Covelo; Manuel J. Reigosa; María Luisa Andrade (pp. 1020-1029).
We assessed natural degradation of fuel oil in three marshes from Galicia (Spain) affected by the Prestige oil spill (Baldaio, Barizo, and Muxía). Soil samples collected from polluted and unpolluted areas on four different dates were used to determine total petroleum hydrocarbon content and fuel-oil components. Natural degradation was monitored by analysing changes in the proportion of saturated hydrocarbons, aromatics, asphaltenes and resins in the soils, and also by evaluating the degree of depletion of saturated hydrocarbons on each sampling date. We additionally assessed the phytoremediation potential of Lolium perenne, L., Convolvulus arvensis L. and Raphanus raphanistrum L. All marsh soils exhibited natural degradation of saturated and aromatic hydrocarbons to between 85 and 95% in most cases. In contrast, asphaltenes and resins were degraded to a lesser extent ( viz. 64–76% in Barizo 1, Muxía and Traba; 39–44% in Baldaio; and only 12% in Barizo 2, where flooding by the river continues to introduce balls of fuel oil into the soil). Monitoring analyses revealed natural degradation to be dependent on the thickness of the pollutant layer. Field plots sown with L. perenne L. exhibited no significant differences in fuel-oil degradation from untreated plots.
Keywords: Marsh soils; Oil spill; Hydrocarbons; Degradation
Thermodynamic analysis of the selective chlorination of electric arc furnace dust
by C.A. Pickles (pp. 1030-1042).
The remelting of automobile scrap in an electric arc furnace (EAF) results in the production of a dust, which contains high concentrations of the oxides of zinc, iron, calcium and other metals. Typically, the lead and zinc are of commercial value, while the other metals are not worth recovering. At the present time, EAF dusts are treated in high temperature Waelz rotary kiln-type processes, where the lead and zinc oxides are selectively reduced and simultaneously reoxidized and a crude zinc oxide is produced. Another alternative processing route is selective chlorination, in which the non-ferrous metals are preferentially chlorinated to their gaseous chlorides and in this manner separated from the iron. In the present research, a detailed thermodynamic analysis of this chlorination process has been performed and the following factors were investigated; temperature, amount of chlorine, lime content, silica content, presence of an inert gas and the oxygen potential. High lead and zinc recoveries as gaseous chlorides could be achieved but some of the iron oxide was also chlorinated. Additionally, the calcium oxide in the dust consumes chlorine, but this can be minimized by adding silica, which results in the formation of stable calcium silicates. The optimum conditions were determined for a typical dust composition. The selectivities achieved with chlorination were lower than those for reduction, as reported in the literature, but there are other advantages such as the potential recovery of copper.
Keywords: Electric arc furnace; Dust; Thermodynamics; Selective; Chlorination
Co(II) removal by magnetic alginate beads containing Cyanex 272®
by Audrey-Flore Ngomsik; Agnès Bee; Jean-Michel Siaugue; Delphine Talbot; Valérie Cabuil; Gérard Cote (pp. 1043-1049).
In this study, a series of batch experiments is conducted to investigate the ability of magnetic alginate beads containing Cyanex 272® to remove Co(II) ions from aqueous solutions. Equilibrium sorption experiments show a Co(II) uptake capacity of 0.4mmolg−1. The data are successfully modelled with a Langmuir equation. A series of kinetics experiments is then carried out and a pseudo-second order equation is used to fit the experimental data. The effect of pH on the sorption of Co(II) ions is also investigated. Desorption experiments by elution of the loaded beads with nitric acid at pH 1 show that the magnetic alginate beads could be reused without significant losses of their initial properties even after 3 adsorption–desorption cycles.
Keywords: Magnetic separation; Nanoparticles; Heavy metals; Alginate; Maghemite; Remediation
Biosorption of arsenic from aqueous solution using agricultural residue ‘rice polish’
by D. Ranjan; M. Talat; S.H. Hasan (pp. 1050-1059).
‘Rice polish’ (an agricultural residue) was utilized successfully for the removal of arsenic from aqueous solution. Various parameters viz. pH, biosorbent dosage, initial metal ion concentration and temperature were studied. Langmuir, Freundlich and Dubinin–Radushkevich (D–R) isotherm models were used and the system followed all three isotherms, showing sorption to be monolayer on the heterogeneous surface of the biosorbent. The maximum sorption capacity calculated using Langmuir model was 138.88μg/g for As(III) at 20°C and pH 7.0 and 147.05μg/g at 20°C and pH 4.0 for As(V). The mean sorption energy ( E) calculated from D–R model indicated chemisorption nature of sorption. Study of thermodynamic parameters revealed the exothermic, spontaneous and feasible nature of sorption process in case of both As(III) and As(V). The pseudo-second-order rate equation described better the kinetics of arsenic sorption with good correlation coefficients than pseudo-first-order equation. Mass transfer, intraparticle diffusion, richenberg and elovich models were applied to the data and it was found that initially the sorption of arsenic was governed by film diffusion followed by intraparticle diffusion. Rice polish was found to be efficient in removing arsenic from aqueous solution as compared to other biosorbents already used for the removal of arsenic.
Keywords: Rice polish; Arsenic; Biosorption; Isotherms; Sorption kinetics
Cyanide uptake from wastewater by modified natrolite zeolite–iron oxyhydroxide system: Application of isotherm and kinetic models
by Meissam Noroozifar; Mozhgan Khorasani-Motlagh; Parisa Ahmadzadeh Fard (pp. 1060-1066).
A method for the removal of cyanides from wastewater is described. The method involves the adsorption of cyanides by a modified natural zeolite (natrolite) using batch technique. A new iron oxyhydroxide–natrolite system was used in this study. A combination of XRD, XRF and FTIR spectroscopies, as well as TG/DSC thermal analyses was used for characterization of zeolitic materials. Effects of parameters such as pH, amount of adsorbent and contact time on the cyanide removing yield are studied. It was observed that the yield increases by increasing dosage of adsorbent and contact time at a fixed pH 7.5. A yield of 82% was achieved at optimum conditions for removing cyanide from industrial wastewaters. The experimental data obtained for optimum conditions were selected for modeling the adsorption behavior of the materials using six isotherm equations (Freundlich, Langmuir, Langmuir–Freundlich, Dubinin–Radushkevich, Redlich–Peterson and Toth). The obtained modeling results indicated that, although the three-parameter models, taking into account the surface heterogeneity, provided the closest approach to the measurement data, the parameters estimates could be highly biased. The kinetic studies proved that the second-order kinetic was the applicable model.
Keywords: Natrolite; Modification; Iron oxyhydroxide–natrolite; Cyanide
Multi-walled carbon nanotubes as adsorbents for the removal of parts per billion levels of hexavalent chromium from aqueous solution
by K. Pillay; E.M. Cukrowska; N.J. Coville (pp. 1067-1075).
The adsorption capabilities for the removal of parts per billion levels (ppb) of hexavalent chromium by three adsorbents namely activated carbon, functionalised multi-walled carbon nanotubes (MWCNTs) and unfunctionalised multi-walled carbon nanotubes were investigated as a function of contact time, initial solution pH, initial Cr(VI) concentrations and the presence of competing anions. The unfunctionalised MWCNTs showed the highest adsorption capability with up to 98% of a 100ppb Cr(VI) solution being adsorbed. Both functionalised and non-functionalised MWCNTs showed a superior adsorption capability to that of activated carbon. The removal of Cr(VI) was higher at lower pH. Furthermore, the uptake of Cr(VI) was hindered by the presence of the competing anions, Cl− and SO42−. Both Langmuir and Freundlich isotherms have been used to describe the Cr(VI) adsorption process. The major mechanisms for Cr(VI) removal have been identified as an ion exchange mechanism, intraparticle diffusion and electrostatic interactions. The adsorbed Cr(VI) could also be desorbed readily from the MWCNTs surface at high pH.
Keywords: Adsorption; Hexavalent chromium; Multi-walled carbon nanotubes; Langmuir isotherm; Freundlich isotherm
Modeling of gadolinium recovery from nitrate medium with 8-hydroxyquinoline by emulsion liquid membrane
by M.A. Hasan; R.F. Aglan; S.A. El-Reefy (pp. 1076-1081).
The extraction equilibrium of Gd(III) from nitrate medium by 8-hydroxyquinoline (HOX) in toluene was studied. Liquid–liquid investigations were first carried out. Based on the equilibrium results, the extraction of Gd(III) from aqueous nitrate medium into an emulsion liquid membrane system (ELM) containing 8-hydroxyquinoline in toluene as extractant, HNO3 as stripping solution, Span-80 as surfactant was studied. The stability of the prepared ELM was studied in terms of the degree of membrane breakage. The different parameters affecting the permeation of gadolinium (III) were also studied.A general permeation model for the recovery of Gd(III) by the selected membrane is presented. The internal mass transfer in the water in oil (W/O) emulsion drop, the external mass transfer around the drop, the rates of formation and decomposition of the complex at the external aqueous–organic interface were considered.
Keywords: Solvent extraction; Emulsion liquid membrane; Gadolinium; Modeling
Phenols removal by immobilized horseradish peroxidase
by I. Alemzadeh; S. Nejati (pp. 1082-1086).
Application of immobilized horseradish peroxidase (HRP) in porous calcium alginate (ca-alginate) for the purpose of phenol removal is reported. The optimal conditions for immobilization of HRP in ca-alginate were identified. Gelation (encapsulation) was optimized at 1.0% (w/v) sodium alginate in the presence of 5.5% (w/v) of calcium chloride. Upon immobilization, pH profile of enzyme activity changes as it shows higher value at basic and acidic solution. Increasing initial phenol concentration results in a decrease in % conversion. The highest conversion belongs to phenol concentration of 2mM. Investigation into time course of phenol removal for both encapsulated and free enzymes showed that encapsulated enzyme had lower efficiency in comparison with the same concentration of free enzyme; however the capsules were reusable up to four cycles without any changes in their retention activity. Increasing enzyme concentration from 0.15 to 0.8units/g alginate results in gradual increase in phenol removal. The ratio of hydrogen peroxide/phenol at which highest phenol removal obtained is found to be dependent on initial phenol concentration and in the solution of 2 and 8mM phenol it was 1.15 and 0.94 respectively.
Keywords: Horseradish peroxidase (HRP); Hydrogen peroxide; Calcium alginate; Encapsulation; Phenol
The potential of compost-based biobarriers for Cr(VI) removal from contaminated groundwater: Column test
by Maria Rosaria Boni; Silvia Sbaffoni (pp. 1087-1095).
This paper presents the results of a column reactor test, aiming at evaluating the performance of a biological permeable barrier made of low-cost waste materials, for Cr(VI) removal from contaminated groundwater. A 1:1 by volume mixture of green compost and siliceous gravel was tested as reactive medium in the experimental activity. A 10mg/l Cr(VI) contaminated solution was used and the residual Cr(VI) concentration along the column height and in the outlet was determined in the water samples collected daily. Also pH, redox potential and COD were analyzed. At the end of the test, the reactive medium was characterized in terms of Cr(VI) and total chromium.The Cr(VI) removal efficiency was higher than 99% during the entire experimental activity. The influence of the biological activity on Cr(VI) removal efficiency was evaluated by varying the organic carbon and nitrogen dosages in the contaminated solution fed to the system; a removal decrease was observed when the organic carbon was not enough to sustain the microbial metabolism. The Cr(VI) removal was strictly linked to the biological activity of the native biomass of compost. No Cr(III) was detected in the outlet: the Cr(III) produced was entrapped in the solid matrix.Two main processes involved were: adsorption on the organic-based matrix and reduction into Cr(III) mediated by the anaerobic microbial metabolism of the bacteria residing in green compost. Siliceous gravel was used as the structure matrix, since its contribution to the removal was almost negligible.Thanks to the proven efficiency and to the low-cost, the reactive medium used can represent a valid alternative to conventional approaches to chromium remediation.
Keywords: Biological barriers; Compost; Contaminated groundwater; Hexavalent chromium; In situ; treatment
Leaching of aluminum and iron from boiler slag generated from a typical Chinese Steel Plant
by Jinping Li; Jinhua Gan; Xianwang Li (pp. 1096-1101).
This paper presents a new way of recycling aluminum and iron in boiler slag derived from coal combustion plants, which integrates efficient extraction and reuse of the leached pellets together. The boiler slag was pelletised together with washed coal and lime prior to sintering and then was sintered at 800–1200°C for different periods to produce sintered pellets for the leaching test. An elemental analysis of aqueous solutions leached by sulfuric acid was determined by EDTA–Na2–ZnCl2 titration method. The components and microstructures of the samples, sintered pellets and leached residue were examined by means of XRF, XRD and SEM. XRD analysis indicates that predominate minerals such as kaolinite, quartz, calcium silicide, hematate and metakoalin exist in the boiler slag. An aluminum extraction efficiency of 86.50% was achieved. The maximum extraction efficiency of Fe was 94.60% in the same conditions of that for the maximum extraction efficiency of Al. The extraction efficiencies of Al and Fe increased with an increase in temperature, leaching time and acidity. High Al extraction efficiency was obtained for pellets with high CaO content. The final product of alumina would be used directly for the production of metallic aluminum.
Keywords: Boiler slag; Sintering; Extraction efficiency; Leaching
Biogas – Municipal solid waste incinerator bottom ash interactions: Sulphur compounds removal
by Gaëlle Ducom; Daniela Radu-Tirnoveanu; Christophe Pascual; Belkacem Benadda; Patrick Germain (pp. 1102-1108).
This study focuses on a new way of reusing municipal solid waste incinerator bottom ash: landfill gas purification before energetic valorisation. A pilot plant was designed and operated on a landfill site located in France (Loire). One kilogram bottom ash is able to sequestrate more than 3.0g of hydrogen sulphide, 44mg of methyl mercaptan, and 86mg of dimethyl sulphide. Hydrogen sulphide retention is probably due to acid-basic reactions conducting to sulphur mineralisation under the form of low solubility metal sulphides. The reaction medium is hydration water. The retention mechanism for methyl mercaptan is probably similar but dimethyl sulphide is most likely retained by physical adsorption. As methane is not retained by bottom ash, the landfill gas energetic content will not be lowered. There seems to be no appreciable difference in these results whether bottom ash is fresh or carbonated. These results are encouraging in the perspective of a field scale application of this biogas treatment process.
Keywords: MSWI bottom ash reuse; Landfill gas purification; Hydrogen sulphide; Methyl mercaptan; Dimethyl sulphide
Translocation and toxicity assessment of heavy metals from circulated fluidized-bed combustion of oil shale in Huadian, China
by Jingde Luan; Aimin Li; Tong Su; Xuan Li (pp. 1109-1114).
Oil shale and fly ash collected from two thermal power plants located in Huadian, the northeast city of China were subjected to fraction distribution, translocation regularity and toxicity assessment to provide preliminary assessment of suitability for land application. By Tessier sequential extraction, the results showed that Ni, Cr, Pb and Zn were mostly bounded with iron–manganese and organic bound in oil shale, but Cu and Cd were mostly associated with iron–manganese bound and residue fraction. Through circulated fluidized-bed combustion, high concentration of heavy metals (Cu, Cd, Ni, Cr, Pb, and Zn) was found in iron–manganese bound and residue fraction in fly ash. There was accumulation of all studied metals except Ni and Cr in fly ash and translocation mass of metals were as follows: Pb>Zn>Cu>Cd during circulated fluidized-bed combustion. Fly ash was contaminated with Cd higher than the pollution concentration limits listed in GB15168-1995, China. This work demonstrated that it was unadvisable way to carry out landfill without any treatment. By means of STI model, toxicity assessment of heavy metals was carried out to show that there was notable increase in toxicity from oil shale to fly ash.
Keywords: Oil shale; Heavy metal; Fly ash; Translocation; STI model
A simple approach for predicting impact sensitivity of polynitroheteroarenes
by Mohammad Hossein Keshavarz; Abbas Zali; Arash Shokrolahi (pp. 1115-1119).
A new method has been introduced to predict impact sensitivity of different types of polynitroheteroarenes which can include nitropyridine, nitroimidazole, nitropyrazole, nitrofurazane, nitrooxadiazole, nitro-1,2,4-triazole, nitro-1,2,3-trazole and nitropyrimidine explosives. The model is based on the number of carbons and hydrogens as well as specific structural parameters that can increase or decrease impact sensitivity. The new method has been applied to 67 polynitroheteroarenes which have different structural parameters. The predicted results are compared with outputs of recent calculated results of complex neural network. The root mean squares (rms) of deviations of different polynitroheteroarenes are 36 and 66cm for the new and neural network methods, respectively. The novel model also predicts good results for some miscellaneous nitroheterocyclic explosives and several new synthesized polynitroheteroarenes compared to experimental data.
Keywords: Impact sensitivity; Correlation; Polynitroheteroarene; Safety
Molecular based equation of state for shocked liquid nitromethane
by Nicolas Desbiens; Emeric Bourasseau; Jean-Bernard Maillet; Laurent Soulard (pp. 1120-1126).
An approach is proposed to obtain the equation of state of unreactive shocked liquid nitromethane. Unlike previous major works, this equation of state is not based on extended integration schemes [P.C. Lysne, D.R. Hardesty, Fundamental equation of state of liquid nitromethane to 100kbar, J. Chem. Phys. 59 (1973) 6512]. It does not follow the way proposed by Winey et al. [J.M. Winey, G.E. Duvall, M.D. Knudson, Y.M. Gupta, Equation of state and temperature measurements for shocked nitromethane, J. Chem. Phys. 113 (2000) 7492] where the specific heatCv, the isothermal bulk modulusBT and the coefficient of thermal pressure(∂P/∂T)V are modeled as functions of temperature and volume using experimental data. In this work, we compute the complete equation of state by microscopic calculations. Indeed, by means of Monte Carlo molecular simulations, we have proposed a new force field for nitromethane that lead to a good description of shock properties [N. Desbiens, E. Bourasseau, J.-B. Maillet, Potential optimization for the calculation of shocked liquid nitromethane properties, Mol. Sim. 33 (2007) 1061; A. Hervouët, N. Desbiens, E. Bourasseau, J.-B. Maillet, Microscopic approaches to liquid nitromethane detonation properties, J. Phys. Chem. B 112 (2008) 5070]. Particularly, it has been shown that shock temperatures and second shock temperatures are accurately reproduced which is significative of the quality of the potential. Here, thermodynamic derivative properties are computed: specific heats, Grüneisen parameter, sound velocity among others, along the Hugoniot curve. This work constitutes to our knowledge the first determination of the equation of state of an unreactive shocked explosive by molecular simulations.
Keywords: Monte Carlo molecular simulation; Equation of state; Nitromethane; Hugoniot; Derivative properties
Degradation of azo and anthraquinone dyes by a low-cost Fe0/air process
by Shih-Hsien Chang; Kai-Sung Wang; Shu-Ju Chao; Tzu-Huan Peng; Lung-Chiu Huang (pp. 1127-1133).
Degradation of two different kinds of dyes, anthraquinone Reactive Blue 4 (RB4) and azo Reactive Black 5 (RB5), by low-cost zero valent iron (Fe0) in a N2 bubbling system (Fe0/N2 process) and air bubbling system (Fe0/air process) was investigated. The operating parameters, including initial solution pH, dye concentration and Fe0 dose, were also evaluated. The Fe0/air process shows a higher decolorization rate compared to the Fe0/N2 process. Both RB4 and RB5 solutions at 100mgL−1 were rapidly decolorized by Fe0/air process within 9 and 3min, respectively, at initial solution pH 3, Fe dose of 50gL−1 and air flow rate of 5Lmin−1. The optimal initial solution pH was 3. The Fe0/N2 process removed only <17% of COD. However, significant COD removals were achieved for RB 4 (87%) and RB5 (43%) by the Fe0/air process after 9min of treatment. Spectra analysis results indicated that the Fe0/N2 process destroyed only the anthraquinone group (A594) for the RB4 solution and decreased the azo (A596) and naphthalene group (A310) for the RB5 solution. However, the Fe0/air process rapidly removed A594, A370, A296 (anthraquinone group) and A256 (aromatic and dichlorotriazine group) for RB4, and A597 and A310 (naphthalene group) for RB5. The results indicated that the low-cost Fe0/air process is a potential technique for rapid degradation of RB4 and RB5 solutions.
Keywords: Azo dye; Anthraquinone dye; Zero valent iron; Decolorization
Performance of UV and UV/H2O2 processes for the removal of pharmaceuticals detected in secondary effluent of a sewage treatment plant in Japan
by Ilho Kim; Naoyuki Yamashita; Hiroaki Tanaka (pp. 1134-1140).
The effectiveness of UV-based processes (UV and UV/H2O2) for the removal of pharmaceuticals in real wastewater using bench-scale experiment setup with a treatment capacity of 10m3/day was investigated. Forty-one kinds of pharmaceuticals including 12 antibiotics and 10 analgesics were detected in secondary effluent used for tested water. For UV process a good removal seems to be expected for just a few pharmaceuticals such as ketoprofen, diclofenac and antipyrine. Especially, the removal efficiencies of macrolide antibiotics such as clarithromycin, erythromycin and azithromycin for UV alone process were found to be very low even by the introduction of considerable UV dose of 2768mJ/cm2. For UV/H2O2 process, a 90% removal efficiency could be accomplished in 39 pharmaceuticals at UV dose of 923mJ/cm2, indicating that it will be possible to reduce UV energy required for the effective pharmaceuticals removal by the combination of H2O2 with UV process.
Keywords: Pharmaceuticals; UV; UV/H; 2; O; 2; AOPs; LC/MS/MS
Dechlorination of 1,2,3- and 1,2,4-trichlorobenzene by the white-rot fungus Trametes versicolor
by Ernest Marco-Urrea; Miriam Pérez-Trujillo; Gloria Caminal; Teresa Vicent (pp. 1141-1147).
The degradation of 1,2,3-, 1,3,5- and 1,2,4-trichlorobenzene (TCB) by the white-rot fungus Trametes versicolor was studied. Time course experiments showed a degradation rate of 2.27 and 2.49nmold−1mg−1 dry weight of biomass during the first 4d of incubation in cultures spiked with 6mgL−1 of 1,2,3- and 1,2,4-TCB, respectively. A high percent of degradation of 91.1% (1,2,3-TCB) and 79.6 (1,2,4-TCB) was obtained after 7d. However, T. versicolor was not able to degrade 1,3,5-TCB under the conditions tested. For a range of concentrations of 1,2,4-TCB between 6.5 and 23mgL−1, a complete dechlorination of the molecule was observed. Cytochrome P450 monooxygenase appears to be involve in the first step of 1,2,4-TCB degradation, as evidenced by marked inhibition of both dechlorination and degradation of 1,2,4-TCB in the presence of the known cyt P450 inhibitors 1-aminobenzotriazole and piperonyl butoxide. Four intermediates formed from 1,2,4-TCB degradation were detected the second day of incubation, which did not appear the seventh day: 2,3,5-trichloromuconate, its corresponding carboxymethylenebutenolide, 2- or 5-chloro-4-oxo-2-hexendioic acid and 2- or 5-chloro-5-hydroxy-4-oxo-2-pentenoic acid. Based on these results, a degradation pathway of 1,2,4-TCB through cyt P450 monooxygenase and epoxide hydrolase was proposed.
Keywords: Trametes versicolor; Trichlorobenzene; Biodegradation; Cytochrome P450; White-rot fungi
Removal of radioactive caesium from low level radioactive waste (LLW) streams using cobalt ferrocyanide impregnated organic anion exchanger
by T.P. Valsala; S.C. Roy; J.G.Shah; J. Gabriel; Kanwar Raj; V. Venugopal (pp. 1148-1153).
The volumes of low level waste (LLW) generated during the operation of nuclear reactor are very high and require a concentration step before suitable matrix fixation. The volume reduction (concentration) is achieved either by co-precipitating technique or by the use of highly selective sorbents and ion exchange materials. The present study details the preparation of cobalt ferrocyanide impregnated into anion exchange resin and its evaluation with respect to removal of Cs in LLW streams both in column mode and batch mode operations. The Kd values of the prepared exchanger materials were found to be very good in actual reactor LLW solutions also. It was observed that the exchanger performed very well in the pH range of 3–9. A batch size of 6gl−1 of the exchanger was enough to give satisfactory decontamination for Cs in actual reactor LLW streams. The lab scale and pilot plant scale performance of the exchanger material in both batch mode and column mode operations was very good.
Keywords: Anion exchanger; Cobalt ferrocyaide; Chemical treatment; Decontamination factor; Radioactivity; Spike solution; Low level waste
Improvement of plant growth and nickel uptake by nickel resistant-plant-growth promoting bacteria
by Ying Ma; Mani Rajkumar; Helena Freitas (pp. 1154-1161).
In this study, among a collection of Ni-resistant bacterial strains isolated from the rhizosphere of Alyssum serpyllifolium and Phleum phleoides grown on serpentine soil, five plant growth-promoting bacteria (PGPB) were selected based on their ability to utilize 1-aminocyclopropane-1-carboxylate (ACC) as the sole N source and promote seedling growth. All of the strains tested positive for indole-3-acetic acid (IAA) production and phosphate solubilization. In addition, four of the strains exhibited significant levels of siderophores production. Further, the efficiency of PGPB in enhancing Ni solubilization in soils was analyzed. Compared with control treatment, inoculation of PGPB strains significantly increased the concentrations of bioavailable Ni. Furthermore, a pot experiment was conducted to elucidate the effects of inoculating Ni-resistant PGPB on the plant growth and the uptake of Ni by Brassica juncea and B. oxyrrhina in soil contaminated with 450mgkg−1 Ni. Psychrobacter sp. SRA2 significantly increased the fresh (351%) and dry biomass (285%) of the B. juncea test plants ( p<0.05), whereas Psychrobacter sp. SRA1 and Bacillus cereus SRA10 significantly increased the accumulation of Ni in the root and shoot tissues of B. juncea compared with non-inoculated controls. This result indicates that the strains SRA1 and SRA10 facilitated the release of Ni from the non-soluble phases in the soil, thus enhancing the availability of Ni to plants. A significant increase, greater than that of the control, was also noted for growth parameters of the B. oxyrrhina test plants when the seeds were treated with strain SRA2. This effect can be attributed to the utilization of ACC, solubilization of phosphate and production of IAA. The results of the study revealed that the inoculation of Ni mobilizing strains Psychrobacter sp. SRA1 and B. cereus SRA10 increases the efficiency of phytoextraction directly by enhancing the metal accumulation in plant tissues and the efficient PGPB, Psychrobacter sp. SRA2 increases indirectly by promoting the growth of B. juncea and B. oxyrrhina.
Keywords: PGPB; Nickel; Siderophores; IAA; Phytoremediation
Toxic effects of two acid sulfate soils from the Dabaoshan Mine on Corymbia citriodora var.variegata and Daphnia carinata
by Y. Liu; C. Lin; Y. Ma; W. Lu; Y. Wu; S. Huang; L. Zhu; J. Li; A. Chen (pp. 1162-1168).
Acidic, metal-stressed conditions encountered in the acid sulfate soils significantly inhibited the growth of Corymbia citriodora var.variegata, possibly due to the reduced rate of photosynthesis and plant root activity. However, the plant's self-protection mechanism to counteract stress-induced cellular damage by reactive oxygen species still functioned well even at a soil pH as low as 2.81. This may explain the high tolerance of this plant species to the extremely acidic environments. The observed phytotoxicity symptoms were not accompanied by elevated concentrations of heavy metals in the plant tissues, suggesting that heavy metal levels in plant tissue alone are not valid indications of phytotoxicity to the tested plant species. Leachates from the acid sulfate soils had strong toxicity to Daphnia carinata. Median lethal dilution factor (LDF50) was much higher for the leachate from the highly acidic acid sulfate soils (ASS) than that from the mildly acidic ASS. Although the concentration of various metals markedly decreased with increasing number of leaching cycle, leachate toxicity to Daphnia carinata did not decrease accordingly. This suggests that levels of heavy metals and Al in the leachate are not good indicators of the mine water biotoxicity.
Keywords: Acid sulfate soil; Acid mine drainage; Ecotoxicity; Corymbia; Daphnia
Studies on the interaction of olive cake and its hydrophylic extracts with polyvalent metal ions (Cu(II), Eu(III)) in aqueous solutions
by Maria Konstantinou; Konstantina Kolokassidou; Ioannis Pashalidis (pp. 1169-1173).
The paper presents and discusses the chemical affinity of two different forms of natural organic matter (e.g. in solid (SOM) and soluble form (DOM)) for Cu2+ and Eu3+ ions. In the this study SOM is represented by olive cake and DOM by its hydrophilic extracts. The investigations were performed in aqueous 0.1M NaClO4 solutions at pH 6, 23°C and under atmospheric conditions by means of potentiometry using a copper ion selective electrode and competitions reactions between the two metal ions. The experimental data were evaluated according to an “operational” approach, which is based on the charge neutralization model and the Scatchard approach. Evaluation of the data resulted in the determination of conditional formation constants (β*), which are a measure for the chemical affinity of natural organic matter for a metal ion. For the olive cake metal ion binding the values of logβ* for Cu(II) and Eu(III) were evaluated to be 5.1±0.3 and 5.4±0.5, respectively, whereas for the hydrophilic extracts the corresponding values for the Cu(II) and Eu(III) complexes were evaluated to be 5.3±0.3 and 6.3±0.5, respectively. The β* values show that natural organic matter in the two different forms presents almost similar affinity for the Cu2+ ion, whereas the affinity of DOM for the Eu3+ ion is significantly higher than the corresponding affinity of SOM. This is ascribed to the higher flexibility of DOM, which allows better coordination of its active sites around the Eu3+ ion.
Keywords: Natural organic matter; Copper; Europium; Complexation; Stability
Sorption of arsenate and dichromate on polymerin, Fe(OH) x–polymerin complex and ferrihydrite
by F. Sannino; A. De Martino; M. Pigna; A. Violante; P. Di Leo; E. Mesto; R. Capasso (pp. 1174-1179).
Dihydrogenarsenate [H2AsO4−, As(V)] or dichromate [Cr2O72−, Cr(VI)] at pH=4.0 showed to be sorbed on a Fe(OH) x–polymerin complex and ferrihydrite to a greater extent than on polymerin, the organic polymeric fraction of olive oil mill wastewater (OMW). In particular, the maximum amount ( xm) of arsenate sorbed on Fe(OH) x–polymerin complex was similar to that on ferrihydrite (880.26 and 743.02mmolkg−1, respectively), and was much greater than that sorbed on polymerin (384.25mmolkg−1). The sorption of dichromate was to a comparable extent on Fe(OH) x–polymerin complex and ferrihydrite (205.90 and 254.88mmolkg−1, respectively). Cr(III), a less toxic chromium form, mainly, and Cr(V) were indeed the effective forms sorbed on polymerin (200mmolkg−1), as a consequence of the redox reaction of the strongly toxic Cr(VI) with the CH2OH groups of the polysaccharide moiety of this bio-sorbent, according to the data deriving from XPS and DRIFT analyses. The potential exploitation of the selected sorbents for the removal of As(V) or Cr(VI) from aqueous effluents is briefly discussed.
Keywords: Olive oil mill wastewater; Polymerin; Fe(OH); x; –polymerin complex; Ferrihydrite; Dihydrogenarsenate; Dichromate; Sorption
Adsorption of p-nitroaniline from aqueous solutions onto activated carbon fiber prepared from cotton stalk
by Kunquan Li; Zheng Zheng; Jingwei Feng; Jibiao Zhang; Xingzhang Luo; Guohua Zhao; Xingfa Huang (pp. 1180-1185).
Activated carbon fiber prepared from cotton stalk was used as an adsorbent for the removal of p-nitroaniline (PNA) from aqueous solutions. Liquid phase adsorption experiments were conducted and the maximum adsorptive capacity was determined. The effect of experimental parameters such as pH, salinity and temperature on the adsorption was studied. The obtained experimental data were then fitted with the Langmuir, Freundlich and Redlich-Peterson models to describe the equilibrium isotherms. The kinetics rates were modeled by using the pseudo-first-order and pseudo-second-order equations. The results indicated that cotton stalk activated carbon fiber (CS-ACF) is an effective adsorbent for the removal of PNA from aqueous solutions. The maximum adsorption capacity of 406mgg−1 was achieved at the initial PNA concentration of 200mgL−1. The optimum pH for the removal of PNA was found to be 7.6. The presence of ammonium chloride proved to be favorable for the process of adsorption. The adsorption amount decreased with increasing temperature. The Redlich-Peterson model was found to best represent the equilibrium data. The kinetic data followed closely the pseudo-second-order equation. Thermodynamic study showed the adsorption was a spontaneous exothermic physical process.
Keywords: Activated carbon fiber; p; -Nitroaniline; Adsorption isotherm; Kinetics
Distribution and speciation of heavy metals in sediments from the mainstream, tributaries, and lakes of the Yangtze River catchment of Wuhan, China
by Zhifeng Yang; Ying Wang; Zhenyao Shen; Junfeng Niu; Zhenwu Tang (pp. 1186-1194).
A comparative study of the heavy metal (As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn) concentrations in sediments collected from the mainstream, tributaries, and lakes of the Yangtze River catchment of Wuhan, China, was conducted. Compared with the maximum background values in Wuhan Province soils, Cd was the metal with the highest contamination level, especially in the mainstream, followed by Zn and Cu. In a few samples from tributaries and lakes, the Hg concentration was very high compared to background levels. The concentrations of As and Ni in all sites fluctuated close to background levels. Partitioning of speciation of each heavy metal in sediments was similar for samples taken from the mainstream, tributaries, and lakes. Compared to the other metals studied, Cd, Cu, Zn, and Pb had higher bioavailability in the three zones, which means they pose a higher ecological risk. Significant correlations among group a (Zn, Cu, and Pb, r>0.9) and group b (Cr and Ni, r=0.978) in the mainstream; Hg, Cu, Cd, and Pb in lakes ( r>0.9); and Cu and Pb ( r>0.9) in tributaries were observed using Cluster and correlation analysis. However, a low correlation between As and the other elements in the three zones was shown. Overall, 63.6% of samples from the mainstream, 75.0% from tributaries, and 88.9% from lakes exhibited low and moderate ecological risk of heavy metals, and the potential ecological risks in the mainstream and tributaries were higher than those in lakes.
Keywords: Speciation; Concentration; Comparative risk assessment; Heavy metal; Sediments; Yangtze River
Coupling process between solid–liquid extraction of amino acids by calixarenes and photocatalytic degradation
by L. Elsellami; V. Chartron; F. Vocanson; P. Conchon; C. Felix; C. Guillard; L. Retailleau; A. Houas (pp. 1195-1200).
The removal of biological or pharmaceutical compounds through the wastewater treatment becomes relevant. These compounds are present as traces in sewage. In this work, we propose a coupling process which combines the pre-concentration of the pollutant by selective extraction and then degradation of these pollutants by photocatalysis in presence of TiO2. This process is efficient at room temperature by activation of a photocatalyst (TiO2) under UV light. Aromatic amino acids were chosen as model of pharmaceutical pollutants. Their extraction from water, ensured by calixarene derivatives, and their photocatalytic degradation were investigated. It was shown that photodegradation follows a first-order kinetic and that the rate constant enhances with amino acid concentration. The effect of the pH on the rate constant will be discussed.
Keywords: Supramolecular chemistry; Amino acids; Complexation; Solid–liquid extraction; Photocatalysis; Water treatment
Adsorption characteristics of anionic nutrients onto the PP- g-AA-Am non-woven fabric prepared by photoinduced graft and subsequent chemical modification
by Hyun-Ju Park; Choon-Ki Na (pp. 1201-1209).
PP- g-AA-Am non-woven fabric, which possesses anionic exchangeable function, was prepared by chemical modification of carboxyl group in PP- g-AA non-woven fabric to amine group using diethylene triamine. Its sorption characteristics for anionic nutrients including isotherm, kinetics, effects of pH and co-anions, and regeneration efficiency were studied by batch sorption experiments. Sorption equilibriums of PO4-P on PP- g-AA-Am fabric were well described by the Langmuir isotherm model, and their sorption energies were ranged between 9.94 and 15.96kJ/mol indicating an ion exchange process as primary sorption mechanism. Sorption kinetic data fitted with pseudo-second-order kinetic model and indicated that both external and intraparticle diffusion took part in sorption processes. The uptake of PO4-P by PP- g-AA-Am fabric increased with increasing pH of solution and its optimum pH region was in pH ≥4, whereas the uptake of NO3-N and NO2-N was higher in weak and strong acidic pH region, respectively. The sorption selectivity for anions by PP- g-AA-Am fabric was increased in the order: SO4≥PO4>NO3>Cl. The PP- g-AA-Am fabric could be regenerated by a simple acid washing process without lowering the sorption capacity or physical durability.
Keywords: PP-; g; -AA-Am non-woven fabric; Anion exchange; Isotherm; Kinetics; Ion selectivity; Regeneration efficiency
Nitrogen dioxide formation in the gliding arc discharge-assisted decomposition of volatile organic compounds
by Zheng Bo; Jianhua Yan; Xiaodong Li; Yong Chi; Kefa Cen (pp. 1210-1216).
To apply gliding arc discharge (GAD) plasma processing to volatile organic compounds (VOCs) emission control, the formation of NO2 as an undesired byproduct needs to be addressed. Comparative results of effluent temperature and product concentrations between experiment and thermodynamic equilibrium calculation show that the NO2 formation in dry air GAD is totally out of thermodynamic equilibrium. Meanwhile, obvious NO (A2∑+) and N2+ (B2∑u+) are detected as the major reactive species in the dry air GAD plasma region. These results suggest that the thermal (or Zeldovich) NO x formation mechanism is not significant in GAD system, while the energy level and the density of electrons in the plasma region will severely influence the NO2 formation. The presence of 500ppm VOCs in the feed gases shows a limiting influence on the NO2 formation, which is in the order of aromatic hydrocarbon (C6H6 and C7H8)>straight-chain hydrocarbon (C4H10 and C6H14)>halogenated hydrocarbon (CCl4). The influences of VOCs chemical structure, supply voltage, feed gas humidity, and reactor geometry on NO2 formation are investigated, and the results correspond to above mechanism analysis. Based on the above, the possible pathways of the inhibition of NO2 formation in GAD-assisted VOCs decomposition process are discussed.
Keywords: Gliding arc discharge; Nitrogen dioxide; Byproduct; Volatile organic compounds; Non-thermal plasma
An attractive agro-industrial by-product in environmental cleanup: Dye biosorption potential of untreated olive pomace
by Tamer Akar; Ilknur Tosun; Zerrin Kaynak; Esra Ozkara; Onur Yeni; Esin N. Sahin; Sibel Tunali Akar (pp. 1217-1225).
This research deals with the evaluation of highly available and cost effective waste biomass of olive pomace for the removal of reactive textile dye, RR198 from aqueous medium and a real effluent. The experiments were conducted to assess the effects of process variables such as initial pH, biosorbent dosage, contact time, temperature and ionic strength. The results showed that the highest dye biosorption capacity was found at pH 2 and the needed time to reach the biosorption equilibrium was 40min with a biosorbent concentration of 3.0gL−1. The sorption kinetics of dye was best described by the pseudo-second-order kinetic model. The equilibrium biosorption data were analyzed by Langmuir, Freundlich and Dubinin–Radushkevich isotherm models and the results from the isotherm studies showed that the RR198 biosorption process occurred on a homogenous surface of the biosorbent. The waste biomass of olive oil industry displayed biosorption capacities ranging from 6.05×10−5 to 1.08×10−4molg−1 at different temperatures. The negative values of Δ G° and the positive value of Δ H° suggest that the biosorption process for RR198 was spontaneous and endothermic. Dye–biosorbent interactions were examined by FTIR and SEM analysis. Finally, high biosorption yield of olive waste for the removal of RR198 dye from real wastewater makes it possible that the olive pomace could be applied widely in wastewater treatment as biosorbent taking into account that no pretreatment on the solid residue is carried out.
Keywords: Biosorption; Olive waste; Reactive dye; Real wastewater; Isotherms
Enhancement of phenanthrene and pyrene degradation in rhizosphere of tall fescue ( Festuca arundinacea)
by Sardar Alam Cheema; Muhammad Imran Khan; Xianjin Tang; Congkai Zhang; Chaofeng Shen; Zaffar Malik; Shafaqat Ali; Jianjun Yang; Kaili Shen; Xincai Chen; Yingxu Chen (pp. 1226-1231).
A greenhouse experiment was conducted with varying concentrations of phenanthrene (11–344mgkg−1) and pyrene (15–335mgkg−1) spiked in the soil to evaluate the phytoremediation of PAHs contaminated soil using tall fescue ( Festuca arundinacea). After 65-day of tall fescue growth, plant biomass, microbial viable counts, dehydrogenase activity, water-soluble phenolic compounds, phenanthrene and pyrene residual concentrations and removal percentages were determined. The results showed that target PAHs (phenanthrene and pyrene) did not affect plant biomass at lower concentrations but a reduced biomass (only 53.5% of shoot and 29.7% of root compared to control) was observed at higher concentrations. Higher biological activities (microbial viable counts, water-soluble phenolic compounds, dehydrogenase activity) and PAHs degradation rates were detected in planted soils than unplanted controls. After harvest, 91.7–97.8% of phenanthrene and 70.8–90.0% of pyrene had been degraded in the planted soils, which were 1.88–3.19% and 8.85–20.69% larger than those in corresponding unplanted soils. This enhanced dissipation of target PAHs in planted soils might be derived from increased biological activity in the rhizosphere. The results of the present study suggest that the presence of tall fescue roots were effective in promoting the phytoremediation of PAHs contaminated soil.
Keywords: PAHs; Phenanthrene; Pyrene; Phytoremediation; Tall fescue (; Festuca arundinacea; )
Using tracer technique to study the flow behavior of surfactant foam
by Yih-Jin Tsai; Feng-Chih Chou; Shin-Jen Cheng (pp. 1232-1237).
Surfactant foam was used to remove absorbed hydrocarbons from soils. The nature and extent of the foam pathway decide the efficiency of this technology. The characteristics and behavior of foam flow are difficult to visually observe. In this study, laboratory sandbox experiments were performed to estimate the flow behavior of surfactant foam and thus elucidate the properties and flow behavior of surfactant foam. To quantitatively determine the distribution of foam and evaluate accurately the flow field of foam in the soil, this study designed a special technique, applying micro-scale iron powder as a tracer. The foam generated with 4% (w/v) mixed solution of Span 60 and sodium dodecyl sulfate (SDS) showed an excellent stability and quality, which made it particularly apt for this study. The results indicated that the foam flows through the zone above the clay planes and also flows through the zone between the clay planes. The heterogeneous sand does not inhibit the invasion of foam flow. Moreover, the results of tracer tests and photographs of the foam distributions in sandbox were identical in the behavior of foam flow. This knowledge is valuable for providing insight into the foam remediation of contaminated soil.
Keywords: Tracer technique; Surfactant foam; Sandbox test; Iron powder; Foam flow
Thermal behaviour of arsenic trioxide adsorbed on activated carbon
by Frederic Cuypers; Christopher De Dobbelaere; An Hardy; Marlies K. Van Bael; Lieve Helsen (pp. 1238-1243).
The thermal stability and desorption of arsenic trioxide (As2O3) adsorbed on activated carbon (AC) was investigated as this phenomenon is expected to influence the arsenic release during low temperature pyrolysis of chromated copper arsenate (CCA) wood waste. Firstly, a thermogravimetric (TG) experiment with arsenolite, an allotropic form of As2O3, was performed. The sample starts to sublime at temperatures lower than 200°C with a sublimation peak temperature of 271°C. Subsequently, TG experiments with samples of As2O3 adsorbed on AC revealed that only very little (max. 6±3wt%) As2O3 was volatilised at temperatures below 280°C, while still 41.6 (±5)wt% of the original arsenic concentration was retained at 440°C and 28.5 (±3)wt% at 600°C. The major arsenic volatilisation occurred between 300°C and 500°C. The kinetic parameters of desorption, activation energy of desorption ( Ed) and pre-exponential factor ( A), were determined by fitting an Arrhenius model to the experimental data, resulting in Ed=69kJ/mol, A=1.21×104s−1. It can be concluded that the adsorption of As2O3 on AC can contribute to the thermal stabilisation of As2O3. Consequently, during low temperature pyrolysis of CCA wood arsenic release may be prevented by adsorption of As2O3 on the coal-type product formed during the thermal decomposition of the wood.
Keywords: Arsenic trioxide; Activated carbon; Desorption; Thermogravimetric analysis; Thermal stability
Photocatalytic degradation of indole in a circulating upflow reactor by UV/TiO2 process—Influence of some operating parameters
by Smail Merabet; Abdelkrim Bouzaza; Dominique Wolbert (pp. 1244-1249).
The present work involves the photocatalytic degradation of indole on a recirculating reactor. The effects of various factors as initial concentration of indole, catalyst-loading, pH, agitation and flow rate of the solution on the photodegradation were examined. The experimental results indicate that the optimal pH for indole elimination is about 6–7; the effect of catalyst loading shows an optimal value (1g/L) which is necessary to degrade indole; the increase of recirculating rate leads to a decrease of degradation rate due to the reduction of the residence time; the agitation speed has a slight influence on the indole degradation by improving the mass transfer step. Finally, L–H model was used to fit experimental results concerning the influence of experimental data. L–H model constants’ were determined also.
Keywords: Photocatalysis; Indole; Circulating reactor; Langmuir–Hinshelwood; Wastewater
Elemental composition of suspended particulate matter and sediments in the coastal environment of Thermaikos Bay, Greece: Delineating the impact of inland waters and wastewaters
by C. Violintzis; A. Arditsoglou; D. Voutsa (pp. 1250-1260).
An integrate study on the occurrence of major, minor and trace elements in the coastal environment of Thermaikos Gulf, Northern Aegean Sea, was carried out. The elemental composition of marine sediments and suspended particulate matter from Thermaikos Bay as well as the composition of suspended particles from various inland water (3 rivers and 4 streams) and wastewater (4 types of municipal and industrial origin) end up to the gulf was investigated during the period 2005–2006. The elemental profiles and characteristics of particulate matter from the examined water-types were discussed. The pollution status of marine sediments was evaluated by employing enrichment factors and sediment quality guidelines (TEL/PEL, ERM/ERL). Zn, Cu, Pb, As and Ag were found to have significant contribution from anthropogenic sources. Sites located at the northern part of the bay exhibited higher pollution indices and can be considered of medium-high priority. Principal Component Analysis was employed to find out the factors affecting the composition of the sediments and suspended particulate matter and to elucidate similarities/dissimilarities in the elemental profiles between the different water-types.
Keywords: Factor analysis; Sediments; Surface waters; Suspended particulate matter; Wastewaters
Adsorption removal of phosphate in industrial wastewater by using metal-loaded skin split waste
by Xin Huang; Xuepin Liao; Bi Shi (pp. 1261-1265).
Leather industry inevitably generates a large amount of skin split waste (SSW) due to the necessary operation of splitting in leather making process. In this study, two adsorbents, SSW-Fe and SSW-Al, were prepared by loading Fe(III) and Al(III) onto SSW, and their adsorption behaviors to phosphate in industrial wastewater were investigated through batch and column adsorption experiments. The macro-adsorption kinetics data obtained from batch experiments were well fitted by the pseudo-second-order rate model and the adsorption isotherms can be well described by the Langmuir equation. The adsorption behaviors of the columns can be well described by Yoon and Nelson model and the time at breakthrough point can be accurately predicted by this model. It was found that the metal-loaded adsorbents prepared by using SSW as supporting matrix can effectively remove phosphate from industrial wastewater. The leakage of metal ions during adsorption process is neglectable. These results indicate that the metal-loaded SSW adsorbents have a good future in practical application for the removal of phosphate from industrial wastewater.
Keywords: Phosphate removal; Adsorption; Solid waste; Skin collagen; Metal-loaded adsorbent
Chromatographic separations and recovery of lead ions from a synthetic binary mixtures of some heavy metal using cation exchange resin
by N.A. Badawy; A.A. El-Bayaa; A.Y. Abdel-Aal; S.E. Garamon (pp. 1266-1271).
A simple solid phase extraction procedure on cation exchange resin Purolite C100 is presented. The procedure based on a column technique for separation and recovery of lead ions from synthetic binary mixtures. Equilibrium distribution coefficient, kd for the different metal ions such as Al(III), Fe(III), Ba(II) and Pb(II) in the presence of nitric acid and ammonium acetate solutions of variable concentrations was determined at 25°C. The values of separation factor, α were evaluated. Quantitative separation of lead ions from a synthetic binary mixtures are based on the fact that ammonium acetate is a good elute for lead ions but fails to elute the other cations.
Keywords: Ion exchange; Separation; Removal; Distribution coefficient; Chromatographic
Kinetics and thermodynamics of textile dye adsorption from aqueous solutions using babassu coconut mesocarp
by Adriana P. Vieira; Sirlane A.A. Santana; Cícero W.B. Bezerra; Hildo A.S. Silva; José A.P. Chaves; Júlio C.P. de Melo; Edson C. da Silva Filho; Claudio Airoldi (pp. 1272-1278).
Extracted babassu coconut ( Orbignya speciosa) mesocarp (BCM) was applied as a biosorbent for aqueous Blue Remazol R160 (BR 160), Rubi S2G (R S2G), Red Remazol 5R (RR 5), Violet Remazol 5R (VR 5) and Indanthrene Olive Green (IOG) dye solutions. The natural sorbent was processed batchwise while varying several system parameters such as stirring time, pH and temperature. The interactions were assayed with respect to both pseudo-first-order and second-order reaction kinetics, with the latter the more suitable kinetic model. The maximum adsorption was obtained at pH 1.0 for all dyes due to available anionic groups attached to the structures, which can be justified by pHpzc 6.7 for the biosorbent BCM. The ability of babassu coconut mesocarp to adsorb dyes gave the order R S2G>VR 5>BR 160>IOG>RR 5, which data were best fit to Freundlich model, but did not well-adjusted for all dyes. The dye/biopolymer interactions at the solid/liquid interface are all spontaneous as given by free Gibbs energy, with exothermic enthalpic values of −26.1, −15.8, −17.8, −15.8 and −23.7kJmol−1 for BR 160, R S2G, RR 5, IOG and VR 5, respectively. In spite of the negative entropic values contribution, the set of thermodynamic data is favorable for all dyes removal. However, the results pointed to the effectiveness of the mesocarp of babassu coconut as a biosorbent for removing textile dyes from aqueous solutions.
Keywords: Mesocarp; Babassu coconut; Adsorption; Dye textile
Comparative study on the degradation of I.C. Remazol Brilliant Blue R and I.C. Acid Black 1 by Fenton oxidation and Fe0/air process and toxicity evaluation
by Shih-Hsien Chang; Shun-Hsing Chuang; Heng-Ching Li; Hsiu-Hao Liang; Lung-Chiu Huang (pp. 1279-1288).
Degradation of Remazol Brilliant Blue R (anthraquinone dye) and Acid Black 1 (azo dye) by Fenton oxidation and low-cost Fe0/air process was compared. The doses of Fenton reagent needed for decolorization of Remazol Brilliant Blue R was much higher than for Acid Black 1. The Fe0/air process rapidly decolorized dyes within 5min at the Fe0 doses of 10 and 50gL−1 for Remazol Brilliant Blue R and Acid Black 1, respectively. COD removals of Remazol Brilliant Blue R and Acid Black 1 by the Fe0/air treatment were significantly higher than those by Fenton oxidation. 98% COD of Remazol Brilliant Blue R was removed by the Fe0/air process. The toxicity of Fe0/air-treated solution was significantly lower than that of Fenton-treated solution; no toxicity was detected after the treatment of Remazol Brilliant Blue R by the Fe0/air process. Fe0/air technique is a potential process for dye degradation.
Keywords: Fenton reagent; Zero-valent iron; Azo; Anthraquinone; Vibrio fischeri
Improved phenol adsorption on carbons after mild temperature steam reactivation
by B. Cabal; B. Tsyntsarski; T. Budinova; N. Petrov; J.B. Parra; C.O. Ania (pp. 1289-1295).
The purpose of this work is to explore steam reactivation at moderate temperatures of activated carbon exhausted with phenol, a highly toxic compound frequently present in industrial wastewater. The spent carbon was treated with steam at various temperatures (450, 600 and 850°C) and times (from 5 to 60min). Promising results were obtained by applying moderate temperatures and times. Whereas at low temperatures the complete regeneration of the carbon is not accomplished, an almost quantitative desorption of the pollutant was achieved at 600°C after exposure times below 30min, with minimal damages in the porous network of the carbon. Further reutilization of the regenerated carbon resulted in a superior performance towards phenol uptake. The regeneration efficiency at 850°C strongly depends on the time of reactivation, with an enhanced phenol uptake when short treatment times are applied. Prolonged duration of the regeneration treatment reduced phenol adsorption capacities, due to overreactivation of the carbon in the steam atmosphere, and to the blockage of the porous carbon network.
Keywords: Adsorption; Phenol; Steam regeneration; Moderate temperatures
Prediction of detonation performance of CHNO and CHNOAl explosives through molecular structure
by Mohammad Hossein Keshavarz (pp. 1296-1301).
A new pathway has been introduced to predict detonation pressure of CHNO and CHNOAl explosives. Although aluminized explosives can have Chapman-Jouguet detonation performance significantly different from those expected from existing thermodynamic computer codes for equilibrium and steady state calculations, new correlation can also be used here. Molecular structures of CHNO and CHNOAl explosives are the only necessary parameters that would be needed in this new scheme. There is no need to use heat of formation or any experimental data. Besides, elemental compositions of CHNO and CHNOAl explosives rather than assumed detonation products are essential input parameters. Predicted detonation pressures for CHNO explosives are compared with experimental data as well as computed results gained by complicated computer code using BKWR and BKWS equations of state so the new method shows the best results. Also, the calculated results for CHNOAl explosives indicate good agreement with the measured data as compared to estimated results of BKWS-EOS using full and partial equilibrium.
Keywords: Detonation performance; CHNO explosive; CHNOAl explosive; Elemental composition; Loading density
Colour and COD removal of disperse dye solution by a novel coagulant: Application of statistical design for the optimization and regression analysis
by Abdelkader Anouzla; Younes Abrouki; Salah Souabi; Mohammed Safi; Hicham Rhbal (pp. 1302-1306).
The investigation presented here focussed on the steel industrial wastewater (SIWW) FeCl3 rich as an original coagulant to remove the synthetic textile wastewater. Response surface methodology was used to study the cumulative effect of the various parameters namely, coagulant dosage, initial pH of dye solution, dye concentration and to optimize the process conditions for the decolourization and COD reduction of disperse blue 79 solution. For obtaining the mutual interaction between the variables and optimizing these variables, a 23 full factorial central composite rotatable design using response surface methodology was employed. The efficiencies of decolourization and COD reduction for disperse blue 79 solution were accomplished at optimum conditions as 99% and 94%, respectively.
Keywords: Optimization; Coagulation; SIWW; Dye removal; Statistical design method
Adsorption and desorption behavior of copper ions on Na-montmorillonite: Effect of rhamnolipids and pH
by Günseli Özdemir; Saadet Yapar (pp. 1307-1313).
In this work, the effects of an anionic biosurfactant, rhamnolipid (RL), and pH on the adsorption and desorption of Cu2+ ions on Na-montmorillonite were investigated. Adsorption studies were conducted through the addition of Cu2+ to the dispersions containing pristine- and/or RL-modified clay. In the case of pristine clay, RL was also added simultaneously with the Cu2+. The effect of pH was studied in the range between 1.0 and 8.0. The highest adsorption capacity was obtained at the pH of 4.7–4.8. Among the models including the Langmuir, Freundlich and Dubinin–Kaganer–Radushkevich isotherms; Langmuir isotherm gave a better fit to the experimental data. The most suitable fit for the adsorption kinetics of Cu2+ was obtained with a pseudo-second-order model. It was determined that the adsorption capacity of the pristine clay is comparable with that of the activated carbon and the modification of clay with RL causes an increase in the adsorption rate due to the distribution of clay platelets in the solution.
Keywords: Adsorption; Heavy metal ions; Sodium-montmorillonite; Activated carbon; Rhamnolipids
Activity of Cu-activated carbon fiber catalyst in wet oxidation of ammonia solution
by Chang-Mao Hung (pp. 1314-1320).
Aqueous solutions of 200–1000mg/L of ammonia were oxidized in a trickle-bed reactor using Cu-activated carbon fiber (ACF) catalysts, which were prepared by incipient wet impregnation with aqueous solutions of copper nitrate that was deposited on ACF substrates. The results reveal that the conversion of ammonia by wet oxidation in the presence of Cu-ACF catalysts was a function of the metal loading weight ratio of the catalyst. The total conversion efficiency of ammonia was 95% during wet oxidation over the catalyst at 463K at an oxygen partial pressure of 3.0MPa. Moreover, the effect of the initial concentration of ammonia and the reaction temperature on the removal of ammonia from the effluent streams was also studied at a liquid space velocity of less than 3.0h−1.
Keywords: Catalytic wet oxidation (CWO); Ammonia; Trickle-bed reactor (TBR); Cu-ACF catalyst
Experimental study on melting and flowing behavior of thermoplastics combustion based on a new setup with a T-shape trough
by Qiyuan Xie; Heping Zhang; Ruibo Ye (pp. 1321-1325).
The objective of this work is to quantitatively study the burning characteristics of thermoplastics. A new experimental setup with a T-shape trough is designed. Based on this setup, the loop mechanism between the wall fire and pool fires induced by the melting and dripping of thermoplastic can be well simulated and studied. Additionally, the flowing characteristics of pool fires can also be quantitatively analyzed. Experiments are conducted for PP and PE sheets with different thicknesses. The maximum distances of the induced flowing pool flame in the T-shape trough are recorded and analyzed. The typical fire parameters, such as heat release rates (HRRs), CO concentrations are also monitored. The results show that the softening and clinging of the thermoplastic sheets plays a considerable role for their vertical wall burning. It is illustrated that the clinging of burning thermoplastic sheet may be mainly related with the softening temperatures and the ignition temperatures of the thermoplastics, as well as their viscosity coefficients. Through comparing the maximum distances of flowing flame of induced pool fires in the T-shape trough for thermoplastic sheets with different thicknesses, it is indicated that the pool fires induced by PE materials are easier to flow away than that of PP materials. Therefore, PE materials may be more dangerous for their faster pool fire spread on the floor. These experimental results preliminarily illustrate that this new experimental setup is helpful for quantitatively studying the special burning feature of thermoplastics although further modifications is needed for this setup in the future.
Keywords: Thermoplastics; Combustion; Melting; Flowing; T-shape trough
Sensitive adsorptive stripping voltammetric method for determination of lead in water using multivariate analysis for optimization
by E. Espada-Bellido; M.D. Galindo-Riaño; M. García-Vargas (pp. 1326-1331).
A sensitive adsorptive cathodic stripping voltammetric (AdCSV) method is presented for direct determination of Pb(II) at nanomolar levels in water based on metal complexation with 2-acetylpyridine salicyloylhydrazone (2-APSH) and subsequent adsorptive deposition onto hanging mercury drop electrode (HMDE). The instrumental and chemical factors were optimized using exploratory (Plackett–Burman) and sequential (Simplex) designs. Under optimal conditions (pH 5.6, −0.552V for deposition voltage, 0.0083V for voltage step and 0.87s for time interval for voltage step) a limit of detection of 0.17nM was obtained and the relative standard deviation of five measurements of 17.3nM was 1.20%. The voltammetric responses increased linearly with metal ion concentrations ranging from 2.4 to 145nM. The method was free from interferences of inorganic salts and trace metals usually present in seawater. The proposed method was successfully validated using certified reference estuarine water (LGC 6016) with relative error of −2.15% and applied to real seawater samples (relative errors of −4.40% and +1.84%).
Keywords: Lead; Water; Stripping voltammetry; 2-Acetylpyridine salicyloylhydrazone; Multivariate optimization
Phycoremediation of Chromium (VI) by Nitella and impact of calcium encrustation
by Pattiyage I.A. Gomes; Takashi Asaeda (pp. 1332-1338).
This article discusses the applicability of the Charophyte, Nitella pseudoflabellata in the remediation of Cr (VI) contaminated waters at different calcifying potentials . Its growth was found to be positively correlated with Ca in water (CaW), but marginally significant in the presence of Cr (VI) in water (CrW). High CaW resulted in calcite encrustation on the plant cell wall. CaW was found to be aiding Cr (VI) fixation in the long run, as this correlated positively with both CaW and CrW. However, Ca interfered with passive Cr (VI) accumulation in live plant matter at low CrW concentrations (≤0.2mg/L). Biosorption by dead plant matter seemed to be the major mechanism as the dead plant organs contained >1mg/g Cr dry weight of plant. Cr (VI) concentrations greater than 0.4mg/L were too toxic, showing maximum quantum efficiency of PSII photochemistry ( Fv/ Fm) values<0.63. The opposite was noticed ( Fv/ Fm>0.76) when Cr (VI) was less than 0.2mg/L. Elongation curve patterns based on shoot lengths showed similar scenarios. In all cases high CaW units with calcite encrustation found to be least affected by Cr (VI) toxicity. Optimum remediation was obtained using a combination of high Ca and Cr (VI) in the case of passive (short-term) operation and low Ca and Cr (VI) for active (long-term) operation. Under the passive scenario, plants accumulated above 1.2mg/g Cr dry weight whereas in the active case, accumulation was 0.8mg/g Cr dry weight. We conclude that Nitella-mediated Cr (VI) remediation is a promising technique within the range and conditions investigated.
Keywords: Calcium; Chromium; Nitella pseudoflabellata; Phycoremediation
Entrapment of iron nanoparticles in calcium alginate beads for groundwater remediation applications
by Achintya N. Bezbaruah; Sita Krajangpan; Bret J. Chisholm; Eakalak Khan; Juan J. Elorza Bermudez (pp. 1339-1343).
Zero-valent iron nanoparticles (nZVI) have been successfully entrapped in biopolymer, calcium (Ca)-alginate beads. The study has demonstrated the potential use of this technique in environmental remediation using nitrate as a model contaminant. Ca-alginate beads show promise as an entrapment medium for nZVI for possible use in groundwater remediation. Based on scanning electron microscopy images it can be inferred that the alginate gel cluster acts as a bridge that binds the nZVI particles together. Kinetic experiments with 100, 60, and 20mg NO3−-NL−1 indicate that 50–73% nitrate-N removal was achieved with entrapped nZVI as compared to 55–73% with bare nZVI over a 2-h period. The controls ran simultaneously show little NO3−-N removal. Statistical analysis indicates that there was no significant difference between the reaction rates of bare and entrapped nZVI. The authors have shown for the first time that nZVI can be effectively entrapped in Ca-alginate beads and no significant decrease in the reactivity of nZVI toward the model contaminant (nitrate here) was observed after the entrapment.
Keywords: Iron nanoparticle; Alginate beads; Entrapment; Nitrate; Groundwater remediation
Assessment of trace metal levels in some moss and lichen samples collected from near the motorway in Turkey
by Durali Mendil; Fatma Çelik; Mustafa Tuzen; Mustafa Soylak (pp. 1344-1350).
In this study, 14 different lichen and moss samples were collected from near the Sivas-Tokat motorway (5–25m), control samples were collected from uncontaminated locations (1000–3000m) during 2005. Samples were analyzed using flame and graphite furnace atomic absorption spectrometry after microwave digestion. The maximum metal concentrations were found to be as 468.1μg/g (Fe), 270.5μg/g (Mn), 67.6μg/g (Zn), 53.3μg/g (Pb), 79.6μg/g (Ni), 33.9μg/g (Cr), 29.6μg/g (Cu) and 5.7μg/g (Cd) for mosses, 455.5μg/g (Fe), 170.5μg/g (Mn), 77.6μg/g (Zn), 6.5μg/g (Pb), 10.1μg/g (Ni), 3.8μg/g (Cr), 25.6μg/g (Cu) and 1.5μg/g (Cd) μg/g for lichens. The concentration of trace metals in samples is depended on moss and lichen species. Some species is accumulated trace metals at high ratio.
Keywords: Heavy metals; Moss; Lichen; Atomic absorption spectrometry
Adsorption and desorption characteristics of monosulfuron in Chinese soils
by Zhenwu Tang; Wei Zhang; Yumin Chen (pp. 1351-1356).
Through batch equilibration experiments, the adsorption–desorption characteristics of monosulfuron, a new sulfonylurea herbicide widely used, were investigated in eight agricultural soil samples collected from China. The isotherms for monosulfuron adsorption were nonlinear ( n ranged from 0.748 to 0.943) and well described by the revised Freundlich equation. Data obtained from adsorption experiments showed that monosulfuron had weak to moderate adsorption capability in different soils and might readily result in leaching problems, which was correlated significantly with soil properties. The content and chemical characteristic of the soil organic matter (SOM) was considered to be one of the important factors leading to differences in sorption capacity. Meanwhile, the extent of monosulfuron adsorption on soil was at rather high level under low pH value conditions and decreased with increasing pH value. Besides, desorption hysteresis of monosulfuron were observed in most of tested soils, and was demonstrated to be improved with increased concentration in initial solution and depended significantly on SOM.
Keywords: Sulfonylurea herbicide; Sorption; Desorption; Hysteresis; Soils
Kinetic study on the photocatalytic degradation of salicylic acid using ZnO catalyst
by A. Nageswara Rao; B. Sivasankar; V. Sadasivam (pp. 1357-1361).
The photocatalytic degradation of salicylic acid was studied by a batch process using ZnO as the catalyst on irradiation with UV light. The effect of process parameters such as pH, catalyst loading and initial concentration of salicylic acid on the extent of degradation was investigated. The degradation of salicylic acid was found to be effective in the neutral pH range. The optimum catalyst loading was observed at 2.0g/L. The process followed first order kinetics and the apparent rate constant decreased with increase in the initial concentration of salicylic acid. The mechanism for the degradation of salicylic acid could be explained on the basis of Langmuir–Hinshelwood mechanism. The complete mineralization of salicylic acid was observed in the presence of ZnO photocatalyst. The ZnO was found to be quite stable and undergoes photocorrosion only to a negligible extent.
Keywords: Kinetics; Photocatalysis; Zinc oxide; Salicylic acid
Treatment of cyanide effluents by oxidation and adsorption in batch and column studies
by E.Y. Yazıcı; H. Deveci; İ. Alp (pp. 1362-1366).
In this study the removal of free cyanide from aqueous solutions by air oxidation and adsorption was investigated. Effects of air and pure oxygen, and catalyst on the rate and extent of the removal of cyanide were studied. It was found that the oxidative removal of cyanide by air/oxygen was very limited although it tended to improve in the presence of pure oxygen and catalyst such as activated carbon (AC) and copper sulphate. In the presence of continuous aeration, the non-oxidative removal of cyanide was correlated with a decrease in pH effected apparently by the transfer of carbon dioxide from air phase into the medium. The removal of cyanide by adsorption on activated carbon, nut shell (NS) and rice husk (RH) was also examined. Adsorption capacity of activated carbon was shown to be significantly enhanced via impregnation of activated carbons with metals such as copper (AC–Cu) and silver (AC–Ag). In the column tests, the breakthrough capacity of adsorbents was found to be in an increasing order of RH
Keywords: Cyanide removal; Air oxidation; Adsorption; Activated carbon; Environment
Removal of thiocyanate from aqueous solutions by ion exchange
by N. Dizge; E. Demirbas; M. Kobya (pp. 1367-1376).
The adsorption kinetics and equilibrium of thiocyanate in aqueous solutions onto an anion-exchange resin (Purolite A-250) were investigated in a batch-mode operation to assess the possible use of this adsorbent. The effect of various parameters such as initial thiocyanate concentration, contact time, pH, particle size, resin dosage and temperature were studied. A comparison of four kinetic models, the pseudo-first-order, second-order, Elovich and diffusion controlled kinetic models, on the thiocyanate-resin system was used to determine the rate constants and the adsorption mechanism. The kinetic results correlated well with pseudo-second-order model. The experimental parameters had also an effect on the pore and surface diffusivities. The optimum conditions for removal of thiocyanate were found to be pH 8, 2g/l of adsorbent dosage, 355–500μm of particle size and equilibrium time of 30min, respectively. The column capacity and performance by the bed depth service time model using bed depth and flow rate as variables were evaluated. The adsorption isotherm data were fitted well to Langmuir and Freundlich isotherms. The adsorption capacity was calculated as 191.20mg/g at 323K. Thermodynamics parameters such as freeΔG0,ΔH0 andΔS0 for the adsorption were evaluated. The positive value ofΔH0 indicated that the process was endothermic in nature.
Keywords: Thiocyanide ions; Anion-exchange resin; Adsorption kinetics; Adsorption equilibrium
The effect of mineral carrier composition on phosphate-accumulating bacteria immobilization
by J. Hrenovic; T. Ivankovic; D. Tibljas (pp. 1377-1382).
The goal of this study was to determine the dynamics and yield of immobilization of the phosphate-accumulating bacterium Acinetobacter junii on mineral carriers. As mineral carriers natural clinoptilolite tuff from Turkey (T) and Serbia (S) and natural bentonite (TER), in original and magnesium (Mg)-exchanged form were used. The key feature which determined the extent of immobilization of A. junii was the type of carrier; the immobilization yield decreased in order T>TER>S. The number of immobilized cells was significantly higher for the Mg-exchanged carriers when compared to their original counterparts (95 and 75×108CFUg−1 for T, 74 and 58×108CFUg−1 for TER, 19 and 6×108CFUg−1 for S). The Mg-exchanged T and S displayed a prolonged biofilm growth up to 24h, while the original counterparts reached the mature biofilm after 12h of incubation. Both forms of TER reached the mature biofilm after 24h of incubation, due to swelling property of the material. The number of immobilized cells correlated significantly negatively with particle size of the carrier, indicating that particle size is another important feature which determined the extent of immobilization. The Mg-exchange of original carriers resulted in significant increase of the zeta potential. When all of the materials were compared, the increase of the zeta potential of carriers correlated negatively with the number of immobilized cells, suggesting that the zeta potential of material is not a crucial factor which determined the immobilization of cells.
Keywords: Bentonite; Clinoptilolite; Immobilization; Phosphate-accumulating bacterium; Wastewater; Zeta potential
Application of cotton as a solid phase extraction sorbent for on-line preconcentration of copper in water samples prior to inductively coupled plasma optical emission spectrometry determination
by Mohammad Faraji; Yadollah Yamini; Shahab Shariati (pp. 1383-1388).
Copper, as a heavy metal, is toxic for many biological systems. Thus, the determination of trace amounts of copper in environmental samples is of great importance. In the present work, a new method was developed for the determination of trace amounts of copper in water samples. The method is based on the formation of ternary Cu(II)–CAS–CTAB ion-pair and adsorption of it into a mini-column packed with cotton prior applying inductively coupled plasma optical emission spectrometry (ICP-OES). The experimental parameters that affected the extraction efficiency of the method such as pH, flow rate and volume of the sample solution, concentration of chromazurol S (CAS) and cethyltrimethylammonium bromide (CTAB) as well as type and concentration of eluent were investigated and optimized. The ion-pair (Cu(II)–CAS–CTAB) was quantitatively retained on the cotton under the optimum conditions, then eluted completely using a solution of 25% (v/v) 1-propanol in 0.5molL−1 HNO3 and directly introduced into the nebulizer of the ICP-OES. The detection limit (DL) of the method for copper was 40ngL−1 ( Vsample=100mL) and the relative standard deviation (R.S.D.) for the determination of copper at 10μgL−1 level was found to be 1.3%. The method was successfully applied to determine the trace amounts of copper in tap water, deep well water, seawater and two different mineral waters, and suitable recoveries were obtained (92–106%).
Keywords: Copper; On-line solid phase extraction; ICP-OES; CAS; Water samples
Acetylene soot reaction with NO in the presence of CO
by T. Mendiara; M.U. Alzueta; A. Millera; R. Bilbao (pp. 1389-1394).
The heterogeneous reaction of soot with NO can be considered as a means of reduction of the emissions of both pollutants from combustion systems. In this paper, the influence of the presence of CO in the soot–NO reaction is studied. Soot was obtained by pyrolysis at 1373K of 5000ppmv acetylene in nitrogen. The study of the influence of CO on the soot–NO reaction was performed in experiments fixing NO concentration at 900ppmv and introducing different CO concentrations among 0 and 9900ppmv. An increase in both the carbon consumption rate and NO reduction by acetylene soot was observed as the concentration of CO increases. These results can be explained by the oxide-stripping reaction, CO+Cf(O)→CO2+Cf. The direct reaction of CO with NO catalyzed by the carbon surface, CO+NO→CO2+1/2N2 may not be considered in this case the dominant process due to the absence of mineral impurities in the acetylene soot. The influence of CO in the acetylene soot–NO reaction was also tested in the presence of oxygen (250–5000ppmv). In these conditions and for relatively high CO/O2 ratios, CO seems to also contribute to NO reduction by the previous oxide-stripping reaction.
Keywords: Acetylene soot; Reactivity; CO; NO reduction; Oxygen
Retention of copper originating from different fungicides in contrasting soil types
by Michael Komárek; Aleš Vaněk; Vladislav Chrastný; Jiřina Száková; Karolina Kubová; Petr Drahota; Jiří Balík (pp. 1395-1402).
This work described the retention of Cu from two different commonly used pesticides, the Bordeaux mixture (CuSO4+Ca(OH)2) and Cu-oxychloride (3Cu(OH)2·CuCl2), and from Cu(NO3)2 in contrasting soil types (Leptosol, Chernozem, Cambisol). Thermodynamic modeling showed that Cu speciation was similar in all fungicide solutions. However, the retention of Cu differed with the fungicide used (maximum retention from the Bordeaux mixture) which indicates that different retention processes occurred in the studied soils. The suggested mechanisms include: specific and non-specific adsorption (especially on soil organic matter), precipitation of newly formed phases, such as CuO, Cu(OH)2, Cu2(OH)3NO3, CuCO3/Cu2(OH)2CO3 and in the case of the Bordeaux mixture, precipitation of various Cu-hydroxysulfates. These phases were identified by the speciation model. The retention of fungicide-derived Cu in the studied soil types followed well the Freundlich isotherm and was directly controlled by the chemical form of Cu. This fact should be taken into account for both environmental and practical applications.
Keywords: Copper oxychloride; Bordeaux mixture; Isotherm; Sorption; Soil contamination; Pesticide
Toxicity of free and various aminocarboxylic ligands sequestered copper(II) ions to Escherichia coli
by Subburaj Selvaraj; K. Chabita Saha; Anindita Chakraborty; Sudhindra N. Bhattacharyya; Abhijit Saha (pp. 1403-1409).
Cytotoxicity of free Cu(II) ions and its complexes of EDTA, NTA or IDA in Escherichia coli (AB 4401) wild type cells were assessed by cell inactivation assay. In order to understand the toxic effects of these additives, membrane status by AFM vis-à-vis K+ ion efflux were followed in the absence and in the presence of Cu(II) ions or its complexes. This was coupled with the determinations of cellular copper concentrations by atomic absorption spectrometry. The observed results show that free copper ions are more cytotoxic and cause considerable plasma membrane damage compared to that of Cu–EDTA, Cu–NTA and Cu–IDA. Determination of cellular copper reveals that Cu2+ and Cu–NTA are able to enter inside the cells while Cu–EDTA and Cu–IDA fail to do that. This may be attributed to the electron affinity of free Cu2+ ions and Cu–NTA, which help in binding with histidine present in copper transport proteins. In addition to cytotoxicity, genotoxicity of free copper and its complexes were also assessed on E. coli isogenic DNA repair proficient and repair-deficient strains. In contrast to free Cu2+ ions, Cu–NTA does not cause any significant cytotoxicity but render greater genotoxicity.
Keywords: Abbreviations; EDTA; ethylene diamine tetra-acetate; NTA; nitrilotriacetate; IDA; iminodiacetate; AFM; atomic force microscopyToxicity; Metal complexes; Cell inactivation; E. coli; Copper ions
Influence of minerals on lead-induced alterations in liver function in rats exposed to long-term lead exposure
by D'souza Sunil Herman; Menezes Geraldine; Venkatesh T (pp. 1410-1414).
The objective of this study was to evaluate the role of minerals on lead-induced effect on the liver. Differentiation of minerals and heavy metals pose an inherent problem due to certain common properties shared by them. With this approach to the problem of heavy metal toxicity, in the present study two groups of male Wistar albino rats, one group (well-nourished) fed on mineral rich diet and other group (undernourished) fed on diet without mineral supplements were used. Both the groups of rats were subjected to long-term lead exposure. The diet of well-nourished group was supplemented with calcium (Ca); 1.2%, phosphorous (P); 0.6%, iron (Fe); 90mg/kg, zinc (Zn); 50mg/kg, magnesium (Mg); 0.08%, manganese (Mn); 70mg/kg, selenium (Se); 0.2mg/kg, copper (Cu); 5mg/kg, molybdenum (Mo); 0.8mg/kg, iodine (I); 0.6mg/kg, cobalt (Co); 3.0mg/kg. Their blood lead and parameters of liver function were monitored periodically. Results of the study showed a very high statistically significant increase ( p<0.001) in the blood lead (PbB) levels and liver function test parameters in the undernourished subjects compared to the well-nourished subjects. Nutritional management of lead poisoning is of importance since essential elements and toxic heavy metals may interact to minimize the absorption of lead.
Keywords: Toxicity; Minerals; Blood lead; Nutrition
As(V) adsorption on maghemite nanoparticles
by T. Tuutijärvi; J. Lu; M. Sillanpää; G. Chen (pp. 1415-1420).
In this study a novel adsorbent, maghemite nanoparticles (γ-Fe2O3), is used for As(V) removal. Maghemite nanoparticles are an exceptional adsorbent material due to its magnetic properties and a good adsorption capacity. The aims of the study were to investigate the suitability of maghemite nanoparticles for As(V) adsorption and to compare properties of different maghemites and their As(V) adsorption efficiency. Maghemite nanoparticles were characterized by XRD, XPS, TEM, VSM, BET and Zeta potential analyzers. Size of the particles varied from 3.8 to 18.4nm. Adsorption experiments were carried out with three different kinds of maghemite nanoparticles: (i) commercially available, (ii) homemade with mechanochemical method and (iii) homemade with sol–gel process. All three different kinds of maghemite nanoparticles were successful in removing As(V) from water, one of them reached as high adsorption capacity as 50mg/g.
Keywords: Arsenate; Adsorption isotherm; Maghemite; Magnetic nanoparticles
Decolorization and biodegradation of textile dye Navy blue HER by Trichosporon beigelii NCIM-3326
by R.G. Saratale; G.D. Saratale; J.S. Chang; S.P. Govindwar (pp. 1421-1428).
Navy blue HER was decolorized and degraded within 24h by Trichosporon beigelii NCIM-3326 under static condition. In the present study, we investigated various physicochemical parameters such as agitation, temperature, pH, cell concentration, initial dye concentration and different carbon and nitrogen sources to achieve maximum dye degradation by T. beigelii. Sequentially, decolorization and decrease in the total organic carbon (TOC) of Navy blue HER by T. beigelii were measured. Among five strains T. beigelii gave the better performance on the decolorization of Navy blue HER along with a 95% TOC reduction within 24h. A significant increase in the activities of NADH-DCIP (dichlorophenolindophenol) reductase and azoreductase in the cells obtained after complete decolorization presumably indicates involvement of these enzymes in decolorization process. UV–vis, TLC, HPLC and FTIR analysis of extracted products confirmed the biodegradation of Navy blue HER. Phytotoxicity study demonstrated no toxicity of the biodegraded products with respect to plants viz. Phaseolus mungo and Sorghum vulgare. In addition to Navy blue HER, this strain also shows ability to decolorize various industrial dyes, including Red HE7B, Golden yellow 4BD, Green HE4BD, Orange HE2R, Malachite green, Crystal violet and Methyl violet.
Keywords: Microbial dye decolorization; Navy blue HER; Phytotoxicity; TOC; Trichosporon beigelii
Physicochemical characterization of raw materials and co-products from the titanium dioxide industry
by M.J. Gázquez; J.P. Bolívar; R. García-Tenorio; F. Vaca (pp. 1429-1440).
The present study was conducted to characterize several raw materials and co-products from the titanium dioxide industry in relation to their elemental composition (major, minor and trace elements), granulometry, mineralogy, microscopic morphology and physical composition. The main objective was to gain basic information for the future potential application of these co-products in fields such as agriculture, construction, civil engineering, etc. Microscopic studies were performed by applying scanning electron microscopy with X-ray microanalysis (SEM–XRMA) while the mineralogical compositions were analysed by means of the X-ray diffraction (XRD) technique. The concentrations of major elements such as Na, Al, Si, Ca, Ti, Fe, S and K were determined by X-ray fluorescence (XRF), while heavy metals and other trace elements were determined by ICP-MS.The physicochemical characterization of the raw materials used in the titanium dioxide industry, in addition to the characterization of the co-products generated, has enabled the evaluation of the degree of fractionation of different elements and compounds between the different co-products, as well as the control of the possible variations in the physicochemical composition of the raw materials throughout the time and the study of the influence of these variations in the characteristics of the obtained co-products.As a main conclusion of our study, it is possible to indicate that the levels of the pollutant elements associated to the co-products analysed were, in general, within safe limits and, therefore, they could potentially be used in composites as fertilizers or for building materials in road construction, etc. Nevertheless, for the specific application of each of these co-products in agriculture, construction and civil engineering, additional studies need to be performed to evaluate their appropriateness for the proposed application, together with specific studies on their health and environmental impact.
Keywords: Titanium dioxide; Co-products; Red gypsum; Sulphate heptahydrate and monohydrate
Flame atomic absorption spectrometric determination of zinc, nickel, iron and lead in different matrixes after solid phase extraction on sodium dodecyl sulfate (SDS)-coated alumina as their bis (2-hydroxyacetophenone)-1, 3-propanediimine chelates
by M. Ghaedi; H. Tavallali; A. Shokrollahi; M. Zahedi; M. Montazerozohori; M. Soylak (pp. 1441-1448).
A sensitive and simple solid phase extraction method for the simultaneous determination of trace and toxic metals in food samples has been reported. The method is based on the adsorption of zinc, nickel, iron and lead on sodium dodecyl sulfate (SDS)-coated alumina, which is also chelated with bis (2-hydroxyacetophenone)-1, 3-propanediimine (BHAPN). The retained analyte ions on modified solid phase were eluted using 8mL of 4molL−1 HNO3. The analyte determinations were carried out by flame atomic absorption spectrometry. The influences of some metal ions and anions on the recoveries of understudy analyte ions were investigated. The proposed method has been successfully applied for the evaluation of these trace and toxic metals in some traditional food samples from Iran.
Keywords: Heavy metal; Bis (2-hydroxyacetophenone)-1,3-propanediimine; Flame atomic absorption spectrometry; Surfactant-coated alumina; Food
Preconcentration of Zn(II) in water samples using a new hybrid SBA-15-based material
by Damián Pérez-Quintanilla; Alfredo Sánchez; Isabel del Hierro; Mariano Fajardo; Isabel Sierra (pp. 1449-1458).
A SBA-15 mesoporous silica has been chemically modified with 5-mercapto-1-methyltetrazole. The newly synthesized material (MTTZ-SBA-15) has been characterized, by powder X-ray diffraction, N2 adsorption, FT-IR,13C NMR spectroscopy and elemental analysis, and used to preconcentrate Zn(II) in water samples. The effect of some variables on the adsorption capacity has been studied using the column techniques. The adsorption capacity of the prepared material followed the order: Zn≫Cu>Cd≫Mn, and under optimized conditions the maximum adsorption value for Zn(II) was 0.96±0.01mmol/g with the adsorption efficiency of 0.76. In column experiments, adsorption was quantitative for 1000mL of 7.65×10−4mM of Zn(II) solution and adsorbed ions were eluted out by 5mL of 1M HCl (preconcentration factor of 200). Spiked tap water and mineral water were used for the preconcentration and determination of Zn(II) by flame atomic absorption spectrometry (FAAS), and a 102±2 and 98±3% recoveries were obtained. The LOD and LOQ values of the proposed method were found to be 8.0×10−6 and 1.23×10−5mM, respectively. The relative standard deviation for four preconcentration experiments was found to be ≤4% in all cases.
Keywords: Heavy metal adsorption; SBA-15; Preconcentration; Zinc; Hybrid materials
Plant absorption of trace elements in sludge amended soils and correlation with soil chemical speciation
by Silvana Torri; Raúl Lavado (pp. 1459-1465).
The aim of the present study was to investigate the relationship between Lolium perenne L. uptake of Cd, Cu, Pb, and Zn in sludge amended soils and soil availability of these elements assessed by soil sequential extraction. A greenhouse experiment was set with three representative soils of the Pampas Region, Argentina, amended with sewage sludge and sewage sludge enriched with its own incinerated ash. After the stabilization period of 60 days, half of the pots were sampled for soil analysis; the rest of the pots were sown with L. perenne and harvested 8, 12, 16 and 20 weeks after sowing, by cutting just above the soil surface. Cadmium and Pb concentrations in aerial tissues of L. perenne were below detection limits, in good agreement with the soil fractionation study. Copper and Zn concentration in the first harvest were significantly higher in the coarse textured soil compared to the fine textured soil, in contrast with soil chemical speciation. In the third harvest, there was a positive correlation between Cu and Zn concentration in aerial biomass and soil fractions usually considered of low availability. We conclude that the most available fractions obtained by soil sequential extraction did not provide the best indicator of Cu and Zn availability to L. perenne.
Keywords: Sewage sludge; Copper; Zinc; Availability; Lolium perenne; L.
Naphthalene degradation by Pseudomonas sp. HOB1: In vitro studies and assessment of naphthalene degradation efficiency in simulated microcosms
by Hilor Pathak; Datasha Kantharia; Ankita Malpani; Datta Madamwar (pp. 1466-1473).
Naphthalene, being a ubiquitous pollutant of the environment and a perilous material, its biodegradation has been receiving constant scientific consideration. Highly potential, naphthalene degrading bacteria were isolated from sediments of polluted Amlakadi canal, Gujarat, India. Among the isolates, Pseudomonas sp. HOB1, showed ability to degrade 2000ppm naphthalene within 24h. The culture exhibited potential to tolerate as high as 60,000ppm of naphthalene. Statistical approach was used to analyze the effect of physiological parameters and initial biomass concentration on naphthalene degradation. Naphthalene degradation was found to be augmented in the pH range of 7.5–8.5. Naphthalene degradation was maximum in the temperature range of 35–37°C and initial inoculum size of more than 1.8ml of 1.0A660. Simulated microcosm studies in the presence and absence of indigenous microflora confirmed its ability for naphthalene degradation and to colonize the soil. Pseudomonas sp. HOB1 was found to be highly potent in degrading higher concentrations of naphthalene under laboratory conditions as well as in simulated microcosms.
Keywords: Naphthalene degradation; Pseudomonas; sp.; Response surface methodology (RSM); Simulated microcosms; Polycyclic aromatic hydrocarbons (PAH)
4-chlorophenol degradation by pulsed high voltage discharge coupling internal electrolysis
by Xiangli Yin; Wenjuan Bian; Junwen Shi (pp. 1474-1479).
A system of pulsed high voltage discharge coupling internal electrolysis (PHVDCIE) in water has been developed to remove 4-chlorophenol (4-CP). The hydrogen peroxide formed by discharge was little utilized by 4-CP degradation in the sole discharge system, but most of the hydrogen peroxide could be utilized in the PHVDCIE system to form hydroxyl radicals for the production of Fe2+. The Fe2+ was generated in the cell reaction and was reacted with the hydrogen peroxide through the Fenton's reaction. The formation rate of hydroxyl radical was increased in the PHVDCIE system. It was 5.28×10−7molL−1s−1 with bubbling oxygen but it was 1.49×10−7molL−1s−1 in the sole discharge system. With increase in the yields of hydroxyl radical, the 4-CP removal was sped up. The removal efficiency of 4-CP was improved to more than 90% correspondingly by 36min discharge in the PHVDCIE system. With the promotion of 4-CP degradation, more intermediate products such as formic, acetic and oxalic acid were produced.
Keywords: Pulsed high voltage discharge; 4-chlorophenol; Degradation; Cast iron scrap
Removal of Pb(II) ions from aqueous solution by a waste mud from copper mine industry: Equilibrium, kinetic and thermodynamic study
by Duygu Ozdes; Ali Gundogdu; Baris Kemer; Celal Duran; Hasan Basri Senturk; Mustafa Soylak (pp. 1480-1487).
The objective of this study was to assess the adsorption potential of a waste mud (WM) for the removal of lead (Pb(II)) ions from aqueous solutions. The WM was activated with NaOH in order to increase its adsorption capacity. Adsorption studies were conducted in a batch system as a function of solution pH, contact time, initial Pb(II) concentration, activated-waste mud ( a-WM) concentration, temperature, etc. Optimum pH was specified as 4.0. The adsorption kinetic studies indicated that the overall adsorption process was best described by pseudo-second-order kinetics. The equilibrium adsorption capacity of a-WM was obtained by using Langmuir and Freundlich isotherm models and both models fitted well. Adsorption capacity for Pb(II) was found to be 24.4mgg−1 for 10gL−1 of a-WM concentration. Thermodynamic parameters including the Gibbs free energy (Δ G°), enthalpy (Δ H°), and entropy (Δ S°) indicated that the adsorption of Pb(II) ions on the a-WM was feasible, spontaneous and endothermic, at temperature range of 0–40°C. Desorption studies were carried out successfully with diluted HCl solutions. The results indicate that a-WM can be used as an effective and no-cost adsorbent for the treatment of industrial wastewaters contaminated with Pb(II) ions.
Keywords: Waste mud; Removal of lead ions; Adsorption/desorption; Equilibrium; Kinetic and thermodynamic
Competitive biosorption of Pb2+, Cu2+ and Zn2+ ions from aqueous solutions onto valonia tannin resin
by İ. Ayhan Şengil; Mahmut Özacar (pp. 1488-1494).
Competitive biosorption of Pb2+, Cu2+ and Zn2+ on valonia tannin resin (VTR) present in binary and ternary mixture were compared with the single metal solution. The effects of the presence of one metal ion on the biosorption of the other metal ion were investigated in terms of equilibrium isotherm and biosorption yield. Experimental results indicated that the uptake capacity and biosorption yield of one metal ion were reduced by the presence of the other metal ion. The extent of adsorption capacity of the binary and ternary metal ions tested on VTR was low (18–80%) as compared to single metal ions. Comparisons between biosorption of Pb2+, Cu2+ and Zn2+ ions by the biomass of VTR in the binary and ternary solution could lead to the conclusion that biosorption of Pb2+ ions was preferential to that of Cu2+ and Zn2+ ions. VTR removed the target metal ions in the selectivity order of Pb2+>Cu2+>Zn2+. The biosorption equilibrium data for the single metal solutions fitted the Langmuir model well. Results show that the pseudo-second-order equation provides the best correlation for the biosorption process in the single-ion system.
Keywords: Valonia tannin resin; Chemical modification; Metal ions; Competitive sorption
Aqueous p-chloronitrobenzene decomposition induced by contact glow discharge electrolysis
by Yongjun Liu (pp. 1495-1499).
Aqueous p-chloronitrobenzene (PCNB) decomposition induced by contact glow discharge electrolysis under various reaction conditions was investigated. Experimental results showed that, at voltage 450–550V and initial concentration 50–500mg/L, the decay of PCNB can be described by a first-order reaction kinetics of In( C0/ C t)=0.029 ( I/ V) t, where C0, I, V and C t denote the initial PCNB concentration (mg/L), applied current (A), solution volume (L) and instantaneous PCNB concentration (mg/L) at treatment time t (min). Major intermediate products such as 4-nitrophenol, 2-chloro-5-nitrophenol, oxalic and formic acids, chloride and nitrate ions were identified by LC/MS and IC, respectively. No chlorophenols present indicated that the dechlorination was easier than denitration from the aromatic ring of PCNB. Formation of hydrogen peroxide during the degradation was observed and the role of Fenton's reaction was examined. Hydroxyl radicals may be the most responsible species for PCNB degradation.
Keywords: Electrical discharge; Non-equilibrium plasma; Degradation; Water treatment
Bacillus sp. strain DJ-1, potent arsenic hypertolerant bacterium isolated from the industrial effluent of India
by Dhaval N. Joshi; S.J.S. Flora; Kiran Kalia (pp. 1500-1505).
Arsenic hypertolerant bacterial cells were isolated from the common industrial effluent treatment plant, Vapi, India. Strain DJ-1 sustaining 400mM, As (V) out of 16 bacterial strains was identified as Bacillus sp. strain DJ-1 through 16S rRNA ribotyping. The maximum arsenic accumulation of 9.8±0.5mgg−1 (dry weight) was observed during stationary phase of growth. Intracellular compartmentalization has shown 80% of arsenic accumulation in cytoplasm. The lack of arsC gene and arsenate reductase activity indicated that Bacillus sp. strain DJ-1 may lack classical ars operon and detoxification may be mediated through some novel mechanism. The arsenite binding protein was purified by affinity chromatography and characterized as DNA protection during starvation (DPS) protein by electrospray ionization mass spectrometry. The induction of DPS showed the adaptation of bacteria in arsenic stress condition and/or in detoxification mechanism, relies on its ability to bind with arsenic. These results indicate the hypertolerance with higher intracellular accumulation of arsenic by Bacillus sp. strain DJ-1, which could be mediated by DPS protein thus signifying this organism is a potential candidate for the removal of arsenic from industrial wastewater, which needs further study.
Keywords: Arsenic hypertolerance; Bacillus; sp.; Arsenic accumulation; Arsenite binding protein
Sorption behavior of Pb(II) and Cd(II) on iron ore slime and characterization of metal ion loaded sorbent
by M. Mohapatra; K. Rout; B.K. Mohapatra; S. Anand (pp. 1506-1513).
The present investigation evaluates the sorption effectiveness of Pb(II) and Cd(II) ions on iron ore slime (IOS) obtained from Jindal Steel Ltd., Vijayanagaram, India. The sorption followed pseudo-second-order kinetics for both the cations. Pb(II) and Cd(II) sorption increased with the increase in pH from 2 to 4.5. The sorption data fitted well to Freundlich model as compared to Langmuir model. Synergistic effect of Pb(II) and Cd(II) on their sorption on IOS sample showed that Pb(II) sorption increases in presence of Cd(II) whereas Cd(II) sorption decreases. Presence of chloride or sulphate resulted in increased Pb(II) sorption but adversely affected Cd(II) sorption. The XRD patterns of Pb(II) adsorbed on IOS sample showed disappearance of some silica peaks and shifting of hematite peaks corresponding to 104 and 110 plane. For Cd(II) sorbed IOS sample, only peak shift for hematite of 104 and 110 plane was observed. Shifting of IR bands indicated that the Pb(II) sorption occurred through an inner sphere mechanism where as Cd(II) sorption occurred through outer sphere mechanism. EPMA studies showed that Pb(II) form a uniform thin layer and Cd(II) concentrate only on iron oxide phase. Regeneration and stability data on metal ion loaded IOS sample has been included.
Keywords: Iron ore slime; Sorption; Isotherms; Kinetics; IR; EPMA; TCLP
Preparation and characterization of activated carbon from cotton stalk by microwave assisted chemical activation—Application in methylene blue adsorption from aqueous solution
by Hui Deng; Le Yang; Guanghui Tao; Jiulei Dai (pp. 1514-1521).
The activated carbon prepared from cotton stalk with ZnCl2 as activation was investigated under microwave radiation. Effects on the yield and adsorption capacities of activated carbon were evaluated then, such as, microwave power, microwave radiation time and the impregnation ratio of ZnCl2. It indicated that the optimum conditions were as follows: microwave power of 560W, microwave radiation time of 9min and the impregnation ratio of ZnCl2 was 1.6g/g. Iodine number, amount of methylene blue adsorption and the yield of activated carbon prepared under optimum conditions were 972.92mg/g, 193.50mg/g and 37.92%, respectively. Laboratory prepared activated carbons were characterized by pHZPC, SEM, FT-IR, SBET and pore structural parameters. Then they were used as adsorbent for the removal of methylene blue from aqueous solutions under varying conditions of initial concentration, carbon dosage and pH. It indicated that Langmuir isotherm was fitter than Freundlich isotherm and Temkin isotherm.
Keywords: Activated carbon; Cotton stalk; Microwave radiation; ZnCl; 2; Adsorption
Use of maize wastewater for the cultivation of the Pleurotus spp. mushroom and optimization of its biological efficiency
by Edenes Loss; Andrea Rafaela Royer; Marcio Barreto-Rodrigues; Ana Claudia Barana (pp. 1522-1525).
This study evaluated the Pleurotus spp. mushroom production process using an effluent from the maize agroindustrial process as a carbon and nitrogen source and as a wetting agent. A complete experimental design based on factorial planning was used to optimize the biological efficiency and evaluate the effect of the concentration of effluent, pH and species of Pleurotus. The results indicated that the effluent affects the biological efficiency for the production of both species of mushrooms at all pH values studied. The maximum biological efficiency predicted by the model (81.36%) corresponded to the point defined by the effluent contents ( X1=1), pH ( X2=−1) and fungus species ( X3=1), specifically 50%, 5.0 and P. floridae, respectively. The results demonstrated that the effluent is a good alternative for the production of Pleurotus mushrooms.
Keywords: Maize effluent; Pleurotus; Biological efficiency
Effect of impregnation of activated carbon with chelating polymer on adsorption kinetics of Pb2+
by Mohamed Kheireddine Aroua; Chun Yang Yin; F.N. Lim; W.L. Kan; Wan Mohd Ashri Wan Daud (pp. 1526-1529).
The effects of polyethyleneimine (PEI) impregnation on the Pb2+ adsorption kinetics of palm shell-activated carbon and pH profile of bulk solution were investigated. Adsorption data were fitted to four established adsorption kinetics models, namely, pseudo-first-order, pseudo-second-order, Elovich equation and intraparticle diffusion. It was found that PEI impregnation at 16.68 and 29.82wt% PEI/AC increased the Pb2+ uptake rate while the opposite was observed for PEI impregnation at 4.76 and 8.41wt% PEI/AC. The increased uptake rates were due to higher concentration of PEI molecules on the surface of clogged pores as well as varying pore volumes. The adsorption kinetics data fitted the pseudo-second-order model better than the pseudo-first-order model, implying chemisorption was the rate-controlling step. The bulk solution pH generally showed an increasing trend from the use of virgin to PEI-impregnated activated carbon.
Keywords: Pb2; +; Adsorption kinetics; Polyethyleneimine; Palm shell-activated carbon
Integrated treatment of landfill leachates including electrooxidation at pilot plant scale
by Ane Urtiaga; Ana Rueda; Ángela Anglada; Inmaculada Ortiz (pp. 1530-1534).
This paper reports the integration of advanced and conventional technologies to deal with the treatment of landfill leachates. The raw leachate, with average values of COD=4430mg/L and N–NH4+=1225mg/L, was first treated on site by an activated sludge large-scale process reducing the former parameters to 1750mg/L (av.) of COD and 750mg/L (av.) of N–NH4+. Next, 50L/h of the effluent were pumped to a pilot plant that included Fenton oxidation followed by an electrooxidation unit, provided with boron doped diamond anodes (anode area=1.05m2); almost complete removal of the organic matter and ammonium nitrogen was achieved. Comparison of the results with those obtained in the laboratory (70cm2 of anode area) was performed observing a similar performance in the kinetics of COD removal, while differences were found in the ammonium removal rates. The specific energy consumption necessary to electro-oxidize the organic load below the disposal limit (COD<160mg/L) at pilot plant scale was 35kWh/m3.
Keywords: Electrooxidation; Landfill leachate; Pilot plant
Effect of V2O5 on the properties of mullite ceramics synthesized from high-aluminum fly ash and bauxite
by Jin-Hong Li; Hong-Wen Ma; Wen-Hui Huang (pp. 1535-1539).
In this communication, high-strength mullite ceramics was prepared from bauxite and high-aluminum fly ash that is a by-product of coal combustion in thermal power plants. The effects of the doping V2O5 on the bulk density, apparent porosity, bending strength and microstructure of mullite ceramics were studied in detail. It was indicated that 5–10mol% V2O5 reduced the sintering temperature by 50°C. The apparent porosity and water absorption of the mullite ceramics decreased with increasing V2O5 content. Mullite ceramics with bending strength as high as 108MPa were obtained at 1500°C with the addition of 10mol% V2O5. X-ray diffraction analysis suggested that the prepared ceramics was mainly in phase of mullite, and scanning electron microscope images confirmed that it mostly existed in the shape of a long parallelepiped. This research may provide a new method in utilizing the vast resources of fly-ash waste from power plants in the production of low-cost mullite-based engineering materials.
Keywords: Mullite ceramics; Fly ash; V; 2; O; 5
Sulfuric acid baking and leaching of spent Co-Mo/Al2O3 catalyst
by Hong-In Kim; Kyung-Ho Park; Devabrata Mishra (pp. 1540-1544).
Dissolution of metals from a pre-oxidized refinery plant spent Co-Mo/Al2O3 catalyst have been tried through low temperature (200–450°C) sulfuric acid baking followed by mild leaching process. Direct sulfuric acid leaching of the same sample, resulted poor Al and Mo recoveries, whereas leaching after sulfuric acid baking significantly improved the recoveries of above two metals. The pre-oxidized spent catalyst, obtained from a Korean refinery plant found to contain 40% Al, 9.92% Mo, 2.28% Co, 2.5% C and trace amount of other elements such as Fe, Ni, S and P. XRD results indicated the host matrix to be poorly crystalline γ- Al2O3. The effect of various baking parameters such as catalyst-to-acid ratio, baking temperature and baking time on percentage dissolutions of metals has been studied. It was observed that, metals dissolution increases with increase in the baking temperature up to 300°C, then decreases with further increase in the baking temperature. Under optimum baking condition more than 90% Co and Mo, and 93% Al could be dissolved from the spent catalyst with the following leaching condition: H2SO4=2% (v/v), temperature=95°C, time=60min and Pulp density=5%.
Keywords: Spent catalyst; H; 2; SO; 4; baking; Molybdenum; Cobalt; Aluminum
Reactions of sulphur mustard and sarin on V1.02O2.98 nanotubes
by T.H. Mahato; G.K. Prasad; Beer Singh; A.R. Srivastava; K. Ganesan; J. Acharya; R. Vijayaraghavan (pp. 1545-1549).
Reactions of sulphur mustard and sarin were studied on the surface of V1.02O2.98 nanotubes by gas chromatography and gas chromatography–mass spectrometry techniques. The V1.02O2.98 nanotube samples were made by using hydrothermal method and characterized by scanning electron microscopy, nitrogen adsorption, X-ray diffractometry and thermogravimetry. Later, they were exposed to sulphur mustard and sarin separately at ambient temperature (30±2°C). The data explored the formation of sulphoxide of sulphur mustard, thiodiglycol for sulphur mustard and isopropyl methyl phosphonic acid for sarin on V1.02O2.98 nanotubes illustrating the role of oxidation and hydrolysis reactions in the decontamination.
Keywords: V; 1.02; O; 2.98; nanotubes; Sulphur mustard; Sarin; Decontamination
Kinetic and thermodynamic uranyl (II) adsorption process into modified Na-Magadiite and Na-Kanemite
by Denis Lima Guerra; Alane Azevedo Pinto; Janaína Azevedo de Souza; Claudio Airoldi; Rúbia Ribeiro Viana (pp. 1550-1555).
The compound 2-mercaptopyrimidine (MPY) was attached onto synthetic Na-Magadiite (M) and Na-Kanemite (K) samples by homogeneous route. The final matrices named MMPY and KMPY have been characterized through X-ray powder diffraction and scanning electron microscopy (SEM). The resulted materials were submitted to process of adsorption with uranyl solution at pH 2.0 and 298±1K. The kinetic parameters were analyzed by the Lagergren and Elovich models of adsorption and demonstrated to be good fit for all experiments. From calorimetric determinations the quantitative thermal effects for uranyl(II)/basic center interactions gave exothermic enthalpy, negative Gibbs free energy, and positive entropy. These thermodynamic data confirmed the energetically favorable condition of such interactions at the solid/liquid interface for all systems.
Keywords: Na-Magadiite; Na-Kanemite; Uranyl; Kinetic; Calorimetry
Selection of metal oxides in the preparation of rice husk ash (RHA)/CaO sorbent for simultaneous SO2 and NO removal
by Irvan Dahlan; Keat Teong Lee; Azlina Harun Kamaruddin; Abdul Rahman Mohamed (pp. 1556-1559).
In this work, the removal of SO2 and NO from simulated flue gas from combustion process was investigated in a fixed-bed reactor using rice husk ash (RHA)/CaO-based sorbent. Various metal precursors were used in order to select the best metal impregnated over RHA/CaO sorbents. The results showed that RHA/CaO sorbents impregnated with CeO2 had the highest sorption capacity among other impregnated metal oxides for the simultaneous removal of SO2 and NO. Infrared spectroscopic results indicated the formation of both sulfate (SO42−) and nitrate (NO3−) species due to the catalytic role played by CeO2. Apart from that, the catalytic activity of the RHA/CaO/CeO2 sorbent was found to be closely related to its physical properties (specific surface area, total pore volume and average pore diameter).
Keywords: Sorbent; Rice husk ash (RHA); Metal oxides; SO; 2; NO
Evaluation of blast furnace slag as basal media for eelgrass bed
by Amelia B. Hizon-Fradejas; Yoichi Nakano; Satoshi Nakai; Wataru Nishijima; Mitsumasa Okada (pp. 1560-1566).
Two types of blast furnace slag (BFS), granulated (GS) and air-cooled slag (ACS), were evaluated as basal media for eelgrass bed. Evaluation was done by comparing BFS samples with natural eelgrass sediment (NES) in terms of some physico-chemical characteristics and then, investigating growth of eelgrass both in BFS and NES. In terms of particle size, both BFS samples were within the range acceptable for growing eelgrass. However, compared with NES, low silt-clay content for ACS and lack of organic matter content for both BFS samples were found. Growth experiment showed that eelgrass can grow in both types of BFS, although growth rates in BFS samples shown by leaf elongation were slower than that in NES. The possible reasons for stunted growth in BFS were assumed to be lack of organic matter and release of some possible toxins from BFS. Reduction of sulfide content of BFS samples did not result to enhanced growth; though sulfide release was eliminated, release of Zn was greater than before treatment and concentration of that reached to alarming amounts.
Keywords: Blast furnace slag; Eelgrass; Eelgrass bed restoration; Eelgrass substrate; Zostera marina
by Gary F. Bennett (pp. 1567-1568).
by Gary F. Bennett (pp. 1568-1568).