Journal of Hazardous Materials (v.191, #1-3)
Fast kinetic and efficient removal of As(V) from aqueous solution using anion exchange resins
by Ahmed M. Donia; Asem A. Atia; Dalia H. Mabrouk (pp. 1-7).
Glycidyl methacrylate/methelenebisacrylamide resin with immobilized tetraethylenepentamine ligand was prepared. This pentamine containing resin was transformed to two anion exchange resins through treatment by glycidyl trimethylammonium chloride to give (RI) or hydrochloric acid giving (RII). The resins were used to adsorb As(V) at different experimental conditions using batch and column methods. Kinetics and thermodynamic properties as well as the mechanism of interaction between As(V) and resin active sites were discussed. The maximum adsorption capacities of As(V) on RI and RII were found to be 1.83 and 1.12mmol/g, respectively. The regeneration and the durability of the loaded resin towards the successive reuse were also investigated.
Keywords: Adsorption; Kinetics; Anion exchange resins; Arsenic; Water treatment
Vent sizing: Analysis of the blowdown of a hybrid non tempered system
by Luc Véchot; Wilfried Minko; Jean-Pierre Bigot; Marc Kazmierczak; Patricia Vicot (pp. 8-18).
The runaway and blowdown of a non tempered hybrid chemical system (30% cumene hydroperoxide) exposed to an external heat input was investigated using a 0.1l scale tool.The maximum temperature and the maximum temperature rise rate were showed to be sensitive to the vent size. An Antoine type correlation between the maximum temperatures and pressures was observed. These resulted from the presence of vapour, mainly generated by the reaction products. Increasing the initial filling ratio resulted in an earlier vent opening but did not have a significant influence on the blow-down. Three types of mass venting behaviour were observed, when changing the vent area to volume ratio ( A/ V):•for large A/ V, two-phase venting occurred from the vent opening until the end of the second pressure peak;•for medium A/ V, two-phase venting occurred before and after the turnaround. The data seem to indicate that gas only venting occurred at turn-around;•for low A/ V, two-phase venting was observed only after the second pressure peak.Two-phase venting after the second pressure peak probably results from the boiling of the hot reaction products at low pressure.
Keywords: Safety vent sizing; Run-away; Blowdown; Non tempered system; Cumene hydroperoxide
Feasibility study on an oxidant-injected permeable reactive barrier to treat BTEX contamination: Adsorptive and catalytic characteristics of waste-reclaimed adsorbent
by Si-Hyun Do; Yong-Jae Kwon; Sung-Ho Kong (pp. 19-25).
The adsorptive and catalytic characteristics of waste-reclaimed adsorbent (WR), which is a calcined mixture of bottom-ash and dredged-soil, was investigated for its application to treating BTEX contamination. BTEX adsorption in WR was 54%, 64%, 62%, and 65%, respectively, for a 72h reaction time. Moreover, the catalytic characteristics of WR were observed when three types of oxidation systems (i.e., H2O2, persulfate (PS), and H2O2/Fe(III)/oxalate) were tested, and these catalytic roles of WR could be due to iron oxide on its surface. In PS/WR system, large amounts of metal ions from WR were released because of large drops of solution pH, and the surface area of WR was also greatly reduced. Moreover, the BTEX that was removed per consumed oxidant (Δ Crem/ΔOx) increased with increasing PS. In H2O2/Fe(III)/oxalate with WR system, the highest BTEX degradation rate constants ( kdeg) were calculated as 0.338, 0.365, 0.500 and 0.716h−1, respectively, when 500mM of H2O2 was used, and the sorbed BTEX on the surface of WR was also degraded, which suggests the regeneration of WR. Therefore, the oxidant-injected permeable reactive barrier filled in WR could be an alternative to treating BTEX with both adsorption and catalytic degradation.
Keywords: BTEX; Waste-reclaimed adsorbent; The catalytic degradation; Modified Fenton; Persulfate; PRB
Simultaneous determination of ultratrace lead and cadmium by square wave stripping voltammetry with in situ depositing bismuth at Nafion-medical stone doped disposable electrode
by Hongbo Li; Jing Li; Zhanjun Yang; Qin Xu; Chuantao Hou; Jinyun Peng; Xiaoya Hu (pp. 26-31).
An ultrasensitive electrochemical method for simultaneous determination of lead and cadmium was first developed using the novel bismuth–Nafion-medical stone doped disposable electrode (an improved wax-impregnated graphite electrode). Through the synergistic sensitization effect of the resulting composite material, the disposable electrode showed remarkable electrochemical responses to lead and cadmium. The oxidation of the two metals produced two well-defined and separated square wave peaks at about −0.62V for Pb2+ and −0.85V for Cd2+, respectively. The effects of the amount of medical stone, concentration of Nafion, thickness of bismuth, pH of buffer solution, deposition potential, accumulation time, voltammetric measurement and possible interferences were investigated in detail. Under the optimal conditions, the fabricated electrode exhibited linear ranges from 2.0 to 12.0μgL−1 with detection limit of 0.07μgL−1 for lead and 2.0–12.0μgL−1 with detection limit of 0.47μgL−1 for cadmium. The assay results of heavy metals in wastewater with the proposed method were in acceptable agreement with the atomic absorption spectroscopy method.
Keywords: Bismuth; Nafion; Medical stone; Stripping voltammetry; Heavy metal ions
Molecular mechanism of hippocampal apoptosis of mice following exposure to titanium dioxide nanoparticles
by Renping Hu; Lei Zheng; Ting Zhang; Guodong Gao; Yaling Cui; Zhe Cheng; Jie Cheng; Mengmeng Hong; Meng Tang; Fashui Hong (pp. 32-40).
Previous studies demonstrate that the exposure to titanium dioxide nanoparticles (TiO2 NPs) damages the central nervous system of mice; however, very little is known about the effects of TiO2 NPs on hippocampal apoptosis or its molecular mechanism. The present study investigated the molecular mechanism associated with hippocampal apoptosis in mice induced by intragastric administration of TiO2 NPs for consecutive 60 days. Our findings indicate that TiO2 NPs accumulate in the mouse hippocampus, and this accumulation, in turn, led to hippocampal apoptosis and impairment in spatial recognition memory in mice. In addition, TiO2 NPs significantly activated caspase-3 and -9, inhibited Bcl-2, and promoted the levels of Bax and cytochrome c. Furthermore, TiO2 NPs induced accumulation of reactive oxygen species in the mouse hippocampus. These findings suggest that TiO2 NP-induced apoptosis in the mouse hippocampus may result from an intrinsic pathway, and workers and consumers should take great caution when handling nanomaterials.
Keywords: Titanium dioxide nanoparticles; Mice; Hippocampus; Apoptotic pathway
Efficiency of green waste compost and biochar soil amendments for reducing lead and copper mobility and uptake to ryegrass
by Nadia Karami; Rafael Clemente; Eduardo Moreno-Jiménez; Nicholas W. Lepp; Luke Beesley (pp. 41-48).
Green waste compost and biochar amendments were assessed for their assistance in regulating the mobility of copper (Cu) and lead (Pb) and the resultant uptake of these metals into vegetation. The amendments were mixed with a heavily Cu and Pb contaminated soil (600 and 21,000mgkg−1, respectively) from a former copper mine in Cheshire (UK), on a volume basis both singly and in combination in greenhouse pot trials. Ryegrass ( Lolium perenne L. var. Cadix) was grown for the following 4 months during which biomass, metals in soil pore water and plant uptake were measured in three consecutive harvests. Very high Pb concentrations in pore water from untreated soil (>80mgl−1) were reduced furthest by compost amendment (<5mgl−1) whereas biochar was the more effective treatment at reducing pore water Cu concentrations. Duly, ryegrass shoot Cu levels were reduced and large, significant reductions in shoot Pb levels were observed after biochar and compost amendments, respectively during successive harvests. However, because green waste compost singly and in combination with biochar vividly enhanced biomass yields, harvestable amounts of Pb were only significantly reduced by the compost amendment which had reduced shoot Pb levels furthest. The low biomass of ryegrass with biochar amendment meant that this was the only amendment which did not significantly increase harvestable amounts of Cu. Therefore the two amendments have opposing metal specific suitability for treating this contaminated soil regarding whether it is a maximum reduction in plant tissue metal concentration or a maximum reduction in harvestable amount of metal that is required.
Keywords: Heavy metals; Compost; Biochar; Ryegrass; Pore water; Remediation
The efficiency of CO2 sequestration via carbonate mineralization with simulated wastewaters of high salinity
by S. Mignardi; C. De Vito; V. Ferrini; R.F. Martin (pp. 49-55).
Salinity generally strongly affects the solubility of carbon dioxide in aqueous solution. This would seem to involve a reduction of the efficiency of the carbonate mineralization process with the objective to sequester this greenhouse gas. On the contrary, we demonstrate here that with a more concentrated solution of magnesium chloride, the residence time of CO2 is enhanced in the aqueous medium because of a reduced tendency to produce CO2(g). Experiments intended to simulate more closely the Mg-rich wastewaters that are industrially available have been carried out using solutions differing in Mg concentration (7, 16, 32gL−1 Mg). A comparison of the efficiency of the CO2 mineralization process among sets of experiments shows that the reduction of the efficiency, to about 65%, was lower than that expected, as the low degree of CO2 degassing results in the enhanced availability of carbonic ions to react with Mg ions to form stable carbonate minerals over a longer time.
Keywords: Solubility of CO; 2; Carbonate mineralization; Nesquehonite; Carbon dioxide sequestration; Discharge of saline wastewater
Comparative in vitro cytotoxicity study of carbon nanotubes and titania nanostructures on human lung epithelial cells
by S. Wadhwa; C. Rea; P. O’Hare; A. Mathur; S.S. Roy; P.S.M. Dunlop; J.A. Byrne; G. Burke; B. Meenan; J.A. McLaughlin (pp. 56-61).
► The in-vitro cytotoxic effects of CNTs and titania nanostructures were compared. ► The cytotoxicity was correlated with the physico-chemical properties of materials. ► CNTs were found to be relatively more toxic than titania nanostructures. ► Titania nanostructures were found to enhance cell proliferation.The aim of this study is to assess in vitro cytotoxic effects of titania nanostructures and carbon nanotubes (CNTs) by exposing A549 lung epithelial cell line to these materials. Titania nanotubes (TiNTs) were grown by hydrothermal treatment of TiO2 nanoparticles, followed by annealing them at 400°C. The titania nanostructures obtained on annealing (mixture of nanotubes and nanorods) were hollow and open ended, containing 3–5 layers of titania sheets, with an internal diameter ∼3–5nm and external diameter ∼8–10nm, and a specific surface area of 265m2/g. As-supplied single walled (SWCNTs) and microwave plasma enhanced chemical vapour deposition (MPCVD) grown multi walled carbon nanotubes (MWCNTs) were used in this study. The lengths and diameters of the SWCNTs were 5–10nm and 0.5–3nm respectively. The lengths and diameters of the MWCNTs were 25–30μm and 10–30nm respectively. The cell viability was evaluated using the MTT (3-(4,-dimethylthiazol-2-yl)-2, 5-diphenyl-tetrazolium) assay. No significant cytotoxic effects of titania nanostructures were observed over a period of a week of testing time, while the presence of CNTs in some cases demonstrated significant cytotoxic effects. Finally, possible reason of cytotoxicity is discussed in the light of microstructures of materials.
Keywords: Titania; Cytotoxicity; Carbon nanotube; Epithelial cell; Hydrothermal treatment
Degradation of pyridine by one Rhodococcus strain in the presence of chromium (VI) or phenol
by Ji-Quan Sun; Lian Xu; Yue-Qin Tang; Fu-Ming Chen; Wei-Qiang Liu; Xiao-Lei Wu (pp. 62-68).
► A Rhodococcus strain could use pyridine as the sole carbon and nitrogen source. ► It could degrade pyridine at low concentrations of phenol and Cr (VI). ► Phenol at low concentration could stimulate the strain to degrade pyridine. ► It is the first Rhodococcus strain reported to have these abilities.A Rhodococcus strain, Chr-9, which has the ability to degrade pyridine and phenol and reduce chromium (VI) (Cr (VI)) was isolated. The strain could grow with pyridine as the sole carbon and nitrogen source, and its pyridine-degradation capability was enhanced by 100mgl−1 phenol; however, the degradation of pyridine was inhibited when the phenol concentration was greater than 400mgl−1. The hydroxylation of pyridine suggested that the stimulation and inhibition of phenol to the pyridine degradation may be attributed to competition of phenol and pyridine for the hydroxylase gene. Strain Chr-9 was also able to reduce Cr (VI) when glucose and LB was used as the carbon source; however, the Cr (VI) reduction did not occur when pyridine was the sole carbon and energy source. In addition, strain Chr-9 could reduce Cr (VI) and simultaneously degrade pyridine in the presence of glucose. To the best of our knowledge, strain Chr-9 is the first Rhodococcus strain reported to degrade pyridine in the presence of Cr (VI), and the first strain with the pyridine degradation being stimulated by low concentrations of phenol.
Keywords: Pyridine; Phenol; Cr (VI); Biodegradation; Co-contamination; Rhodococcus; sp.
Investigations of Human and Organizational Factors in hazardous vapor accidents
by Yan Fu Wang; Shahrzad Faghih Roohi; Xiu Ming Hu; Min Xie (pp. 69-82).
► HFACS provides a systematic guideline in accident investigations. The hierarchal structure of HFACS forces investigators to seek out latent HOFs. ► Bayesian Network enhances the ability of the HFACS by allowing experts to quantify the degree of relationships among the HOFs. ► The fuzzy AHP helps to reduce the subjective biases by avoiding the need to give explicit probability values for the variables’ states.This paper presents a model to assess the contribution of Human and Organizational Factor (HOF) to accidents. The proposed model is made up of two phases. The first phase is the qualitative analysis of HOF responsible for accidents, which utilizes Human Factors Analysis and Classification System (HFACS) to seek out latent HOFs. The hierarchy of HOFs identified in the first phase provides inputs for the analysis in the second phase, which is a quantitative analysis using Bayesian Network (BN). BN enhances the ability of HFACS by allowing investigators or domain experts to measure the degree of relationships among the HOFs. In order to estimate the conditional probabilities of BN, fuzzy analytical hierarchy process and decomposition method are applied in the model. Case studies show that the model is capable of seeking out critical latent human and organizational errors and carrying out quantitative analysis of accidents. Thereafter, corresponding safety prevention measures are derived.
Keywords: Bayesian Network; Fuzzy analytical hierarchy process; Human and Organizational Factor; Human Factors Analysis and Classification System
Identification of fireproofing zones in Oil&Gas facilities by a risk-based procedure
by Annamaria Di Padova; Alessandro Tugnoli; Valerio Cozzani; Tiziana Barbaresi; Fabrizio Tallone (pp. 83-93).
► A new risk-based method providing criteria for fireproofing application was developed. ► Criteria for improved protection from fire damage and escalation are provided. ► Jet-fire and pool fire damage potentials are considered by the new method. ► Comparison with existing methods evidenced the importance of protection from jet-fires. ► A case-study confirmed the potentialities of the new method.Fire is among the more dangerous accident scenarios that may affect the process and chemical industry. Beside the immediate and direct harm to workers and population, fire may also cause damages to structures, which may trigger escalation resulting in severe secondary scenarios. Fireproofing is usually applied to improve the capacity of structures to maintain their integrity during a fire. Past accidents evidenced that the available standards for fireproofing application in onshore chemical and process plants do not consider all the fire scenarios that may cause structural damage. In the present study a methodology was developed for the identification of the zones where fireproofing should be applied. The effect of both pool fires and jet fires was accounted. Simplified criteria, based on radiative heat intensity, were provided for the identification of the fire protection zones. A risk-based procedure was proposed for the selection of significant reference release scenarios to be used in the evaluation of worst credible fire consequences.
Keywords: Major accident hazard; Fire protection; Fire hazard; Fireproofing; Quantitative risk analysis
Enhancement effect of relative humidity on the formation and regional respiratory deposition of secondary organic aerosol
by Kuo-Pin Yu; Chi-Chi Lin; Shang-Chun Yang; Ping Zhao (pp. 94-102).
► We examine the effect of humidity on the formation of secondary organic aerosol (SOA). ► We found the increase of humidity could enhance the SOA mass and number. ► These changes did not alter the pattern of regional respiratory deposition of SOA.In this study, we investigated the effect of relative humidity (RH) on the formation of secondary organic aerosol (SOA) generated from the ozonolysis of d-limonene in an environmental chamber. The mass yield and the number concentration of SOA increased seven and eight times, respectively, when the RH increased from 18% to 82%. The measured total loss rates (apparent loss rates) of the number and mass concentration of SOA in the chamber ranged from 1.70 to 1.77h−1 and from 2.51 to 2.61h−1, respectively, at a controlled ventilation rate of 0.72±0.04h−1. The wall-deposition-loss-rate coefficient observed (1.00±0.02h−1) was approximate to the estimated value based on Zhao and Wu's model which includes the factors of turbulence, Brownian diffusion, turbophoresis and surface roughness. According to the ICRP (International Commission on Radiological Protection) model, the inhaled SOA particles are deposited primarily in the alveoli of the lung. The integrated alveolar deposited dose of the mass (surface area) of SOA over 3h accounted for 74.0–74.8% (74.3–74.9%) of the total deposited dose at the investigated RH. Raising the RH resulted in the growth of SOA particle sizes and increment of the deposition dose but did not cause significant changes in the ratio of regional to the total respiratory deposition of SOA.
Keywords: Nanoparticles; Environmental chamber; d; -Limonene; Ozone; Wall loss
Sorption and biodegradation of tetracycline by nitrifying granules and the toxicity of tetracycline on granules
by Yi-Jing Shi; Xin-Hua Wang; Zhen Qi; Mu-He Diao; Ming-Ming Gao; Su-Fang Xing; Shu-Guang Wang; Xing-Chen Zhao (pp. 103-109).
This paper examines the simultaneous sorption and biodegradation performance of tetracycline (TC) by the nitrifying granular sludge as well as the short-term exposure toxicity of TC. The removal of TC was characterized by a quick sorption and a slow process of biodegradation. The adsorption process fits pseudo-second-order kinetic model, with a complex mechanism of surface adsorption and intra-particle diffusion. Both temperature and mixed liquor suspended solid (MLSS) influenced TC sorption to the granules. TC biodegradation was enhanced with the increase of COD and NH4+–N concentrations, with except of the NH4+–N concentrations higher than 150mg/L. With the ATU addition, TC degradation was weakened remarkably, indicating a synergistic effect of multiple microbes. Results of the short-term exposure (12h) effects showed that the respirometric activities of the microbes decreased greatly. The addition of TC also decreased the rate of NH4+–N utilization considerably, with the half saturation constant ( Ks) increasing from 297.7 to 347.2mg/L.
Keywords: Tetracycline; Nitrifying granular sludge; Sorption; Biodegradation; Toxicity
Sorption behaviour of Co(II) and Cu(II) on chitosan in presence of nitrilotriacetic acid
by Abdul Nishad Padala; Anupkumar Bhaskarapillai; Sankaralingam Velmurugan; Sevilimedu V. Narasimhan (pp. 110-117).
► Chitosan as a sorbent under strong complexing conditions. ► pH dependent cobalt, copper, and NTA sorption. ► Reversal of selectivity in favor of cobalt in NTA medium.Separation and isolation of radioactive cobalt (60Co), one of the main contributors towards the activity build up in nuclear reactors, is essential for radioactive waste volume reduction during nuclear reactor decontamination procedures. In this context, sorption of free and complexed Co(II), Cu(II) and nitrilotriacetic acid (NTA) on the biosorbent, chitosan was studied. A detailed investigation on the role of pH on sorption of Co(II), Cu(II) and NTA was done. Uptake capacities of the metal ions and NTA were measured within pH range of 2.0–7.0. At pH above 5, the NTA uptake capacities were found to be higher in presence of the metal ions than in their absence. Effect of NTA was found to be more pronounced on copper uptake than on cobalt uptake. Significant change in selectivity of chitosan towards metal ion uptake from NTA medium was observed with respect to change in pH. At pH 2.9, the uptake of cobalt was found to be more than that of copper, while the selectivity was reversed at pH 6.0. The respective selectivity coefficient ( kCo/Cu) values were found to be 2.06 and 0.072.
Keywords: Chitosan; Biosorption; Radioactive cobalt; Copper; NTA
Sequencing Batch Reactor (SBR) for the removal of Hg2+ and Cd2+ from synthetic petrochemical factory wastewater
by Amirhossein Malakahmad; Amirhesam Hasani; Mahdieh Eisakhani; Mohamed Hasnain Isa (pp. 118-125).
► We assessed SBR performances to treat synthetic wastewater containing Hg2+ and Cd2+. ► SBR was able to remove 76–90% of Hg2+ and 96–98% of Cd2+. ► COD removal efficiency and MLVSS was affected by Hg2+ and Cd2+ concentrations. ► Removal was not only biological process but also by biosorption process of sludge.Petrochemical factories which manufacture vinyl chloride monomer and poly vinyl chloride (PVC) are among the largest industries which produce wastewater contains mercury and cadmium. The objective of this research is to evaluate the performance of a lab-scale Sequencing Batch Reactor (SBR) to treat a synthetic petrochemical wastewater containing mercury and cadmium. After acclimatization of the system which lasted 60 days, the SBR was introduced to mercury and cadmium in low concentrations which then was increased gradually to 9.03±0.02mg/L Hg and 15.52±0.02mg/L Cd until day 110. The SBR performance was assessed by measuring Chemical Oxygen Demand, Total and Volatile Suspended Solids as well as Sludge Volume Index. At maximum concentrations of the heavy metals, the SBR was able to remove 76–90% of Hg2+ and 96–98% of Cd2+. The COD removal efficiency and MLVSS (microorganism population) in the SBR was affected by mercury and cadmium concentrations in influent. Different species of microorganisms such as Rhodospirilium-like bacteria, Gomphonema-like algae, and sulfate reducing-like bacteria were identified in the system. While COD removal efficiency and MLVSS concentration declined during addition of heavy metals, the appreciable performance of SBR in removal of Hg2+ and Cd2+ implies that the removal in SBR was not only a biological process, but also by the biosorption process of the sludge.
Keywords: Sequencing Batch Reactor; Mercury; Cadmium; Petrochemical factory wastewater
Enhancing atrazine biodegradation by Pseudomonas sp. strain ADP adsorption to Layered Double Hydroxide bionanocomposites
by Tatiana Alekseeva; Vanessa Prevot; Martine Sancelme; Claude Forano; Pascale Besse-Hoggan (pp. 126-135).
► Effect of Pseudomonas sp. strain ADP adsorption by LDH and humic acid modified LDH on atrazine biodegradation was demonstrated. ► Cell adsorption increases with LDH anion exchange capacity and decreases with humic substances loading at LDH surface. ► Adsorption of Pseudomonas sp. strain ADP cell occurs by a preferential and progressive coverage of the clay mineral surface. ► Direct interactions of LDH and bacteria have a strong boosting effect on the biodegradation kinetics.To mimic the role of hydroxide minerals and their humic complex derivatives on the biodegradability of pesticides in soils, synthetic Mg RAl Layered Double Hydroxides (LDH) and Mg RAl modified by Humic substances (LDH–HA) were prepared for various R values (2, 3 and 4) and fully characterized. Adsorption properties of LDH and LDH–HA toward Pseudomonas sp. strain ADP were evaluated. The adsorption kinetics were very fast (<5min to reach equilibrium). The adsorption capacities were greater than previously reported (13.5×1011, 41×1011 and 45.5×1011cells/gLDH for Mg2Al, Mg3Al and Mg4Al, respectively) and varied with both surface charge and textural properties. Surface modification by HA reduced the adsorption capacities of cells by 2–6-fold. Biodegradation kinetics of atrazine by Pseudomonas sp. adsorbed on both LDHs and LDH–HA complexes were measured for various solid/liquid ratios and adsorbed cell amounts. Biodegradation activity of bacterial cells was strongly boosted after adsorption on LDHs, the effect depending on the quantity and properties of the LDH matrix. The maximum biodegradation rate was obtained in the case of a 100mg/mL Mg2Al LDH suspension (26 times higher than that obtained with cells alone).
Keywords: Layered Double Hydroxides; Humic acid–LDH complexes; Pseudomonas; sp. strain ADP; Bacteria adsorption; Atrazine; Biodegradation rate
Heterogeneous photocatalytic degradation of phenanthrene in surfactant solution containing TiO2 particles
by Yanlin Zhang; J.W.C. Wong; Peihong Liu; Min Yuan (pp. 136-143).
► Degradation of phenanthrene in surfactant solution and the role of surfactant have been elucidated. ► Possible pathway of phenanthrene degradation in surfactant solution is proposed. ► The degradation of phenanthrene follows pseudo-second-order kinetics. ► It is proved that applying the surfactants as solubilizing agents to remove contaminants from soils followed by photocatalytic degradation is a promising strategy for soil remediation.Photocatalytic degradation of phenanthrene (PHE) over TiO2 in aqueous solution containing nonionic surfactant micelles was investigated. All photocatalytic experiments were conducted using a 253.7nm mercury monochromatic ultraviolet lamp in a photocatalytic reactor. The surfactant micelles could provide a nonaqueous “cage” to result in a higher degradation rate of PHE than in an aqueous solution, but the higher Triton X-100 concentration (more than 2g/L) lowered the degradation ratio of PHE because the additional surfactant micelles hindered the movement of micelles containing PHE so as to reduce their adsorption onto titania. Pseudo-second-order kinetics was observed for the photocatalytic degradation of PHE. Alkaline solution environment was beneficial to the photocatalytic degradation of PHE. PHE degradation could mainly be attributed to the formation of hydroxyl radicals as evident from the comparison of degradation efficiencies when O2, H2O2 and tert-butyl alcohol (TBA) were applied as oxidants or hydroxyl radical scavenger. Based on the GC/MS analysis of the intermediates, the possible pathways of the photocatalytic degradation of PHE were proposed.
Keywords: Phenanthrene; Photocatalytic degradation; Surfactant; Degradation pathway
Desorption of cadmium from a natural Shanghai clay using citric acid industrial wastewater
by Ying-Ying Gu; Albert T. Yeung (pp. 144-149).
► CAIW is very effective in desorbing cadmium from soil particle surfaces at soil mixture pHs of lower than 5. ► The cadmium desorption efficiency of CAIW also depends on the initial sorbed concentration of cadmium on soil particle surfaces. ► Complexions of cadmium with citric acid and acetic acid are the dominant mechanisms for cadmium desorption in the soil mixture pH range of 4–8. ► CAIW may be a promising enhancement agent for the remediation of heavy metal-contaminated soils.The sorption/desorption characteristics of heavy metals onto/from soil particle surfaces are the primary factors controlling the success of the remediation of heavy-metal contaminated soils. These characteristics are pH-dependent, chemical-specific, and reversible; and can be modified by enhancement agents such as chelates and surfactants. In this study, batch experiments were conducted to evaluate the feasibility of using citric acid industrial wastewater (CAIW) to desorb cadmium from a natural clay from Shanghai, China at different soil mixture pHs. It can be observed from the results that the proportion of cadmium desorbed from the soil using synthesized CAIW is generally satisfactory, i.e., >60%, when the soil mixture pH is lower than 6. However, the proportion of desorbed cadmium decreases significantly with increase in soil mixture pH. The dominant cadmium desorption mechanism using CAIW is the complexion of cadmium with citric acid and acetic acid in CAIW. It is concluded that CAIW can be a promising enhancement agent for the remediation of cadmium-contaminated natural soils when the environmental conditions are favorable. As a result, CAIW, a waste product itself, can be put into productive use in soil remediation.
Keywords: Electrokinetic remediation; Sorption; Desorption; Citric acid industrial wastewater (CAIW); MINTEQA2; Soil remediation
Detoxification of a carcinogenic paint preservative by Blumea malcolmii Hook cell cultures
by Vinayak S. Adki; Utkarsha U. Shedbalkar; Umesh B. Jagtap; Jyoti P. Jadhav; Vishwas A. Bapat (pp. 150-157).
Phytoremediation is considered as an effective viable alternative to remediate the contaminated sites, industrially hazardous chemicals and other toxic pollutants. This bioremediation option offers a safe, cheap and eco friendly alternative to existing physical and chemical remediation technologies as well as other biological sources. The wall paint preservatives consist of several harmful and carcinogenic compounds causing serious environmental concerns. In the present study, an actively growing Blumea malcolmii Hook cell suspensions were established successfully on MS+CM (20%) +2,4-D (5mgl−1)+Gln (100mgl−1)+sucrose (3%) and were used to detoxify a paint preservative Troysan S 89 (a mixture of carbendazim, diuron and ochthilinone). FTIR and UV spectral analytical studies revealed the phytotransformation of Troysan S 89 by Blumea cell suspension cultures. The non-toxic nature of the products formed after phytotransformation was confirmed by phytotoxicity, cytogenotoxicity while non-carcinogenic nature by Ames tests. The novelty of the present study is effective communal degradation of a mixture of three toxicants in Troysan S 89 by cell suspension cultures of Blumea. This work suggested that Blumea cell suspensions might be able to contribute to the wider and safer application of phytoremediation.
Keywords: Blumea; Cell suspensions; Paint; Phytoremediation; Troysan S 89
Underestimation of language issues in frequently used accident investigation methods
by P. Lindhout; C. van Gulijk; B.J.M. Ale (pp. 158-162).
► Language issues are identified as an underestimated danger. ► Language issues are related to up to 10 percent of accidents in Seveso II companies. ► Language issues related causal factors are underrepresented in accident investigation methods taxonomy. ► Learning from language issues related accidents in order to initiate prevention activities is jeopardised.A wide variety of methods exist in the field of accident investigation. The challenge to find the cause for each and every accident has perpetuated a complicated and fundamental debate. In spite of the different paradigms, the many branch specific investigation methods, decades of accumulated and documented accident investigation experience, the diversity in taxonomy of causal factors, and an increasing depth of general systematic analysis tools, there are still causal factors missing out. A recent study identifies language issues as an underestimated danger. Dutch Labour Inspectorate records identify procedures and communication as an important causal factor area for major accidents. Accident investigation method taxonomies that are frequently used in The Netherlands, were investigated on the content related to language issues. Language issues are found to be either present less than proportional with observed accident rates or not present at all in frequently applied accident investigation classification systems. Hence a new taxonomy problem was found in Dutch accident data. Language issues need more attention in accident investigation methods.
Keywords: Taxonomy; Accident investigation, Language issues; Diversity; Industrial safety; SEVESO
Prussian-blue-modified iron oxide magnetic nanoparticles as effective peroxidase-like catalysts to degrade methylene blue with H2O2
by Hui Wang; Yuming Huang (pp. 163-169).
► Prussian-blue (PB)-modified iron oxide magnetic nanoparticles (PBMNPs) were synthesized. ► The removal of methylene blue (MB) using PBMNPs as a catalyst and H2O2 as an oxidant was examined. ► PBMNPs showed high peroxidase-like activity for MB removal and mineralization over a wide pH range. ► PBMNPs promised high magnetization, temperature tolerance, and good stability.Prussian-blue (PB)-modified γ-Fe2O3 magnetic nanoparticles (PBMNPs) were successfully synthesized based on electric interactions between negatively charged [Fe(CN)6]4− and positively charged γ-Fe2O3 nanoparticles. The in situ PB coating was generated by the coordinating reaction between the adsorbed [Fe(CN)6]4− and the ferric ions on the surface of γ-Fe2O3 NPs. The as-prepared PBMNPs were characterized by FT-IR, XRD, TEM, and used to remove organic pollutants from aqueous solution, namely, using methylene blue (MB) as model compound. The experimental results showed that the target compound could be removed efficiently from solution over a wide pH range from 3 to 10 in the presence of PBMNPs as peroxidase-like catalyst and H2O2 as oxidant. Under optimal conditions, MB could be removed completely after 120min of reaction at 298K; the chemical oxygen demand (COD) removal efficiency and the total organic carbon (TOC) abatement efficiency were 53.6% and 35%, respectively. Furthermore, the PBMNPs catalysts showed high magnetization, temperature tolerance, long-term storage and operational stability, and they could be readily separated from solution by applying an external magnetic field. Finally, a possible reaction mechanism for MB degradation was also discussed.
Keywords: Prussian-blue-modified γ-Fe; 2; O; 3; Magnetic nanoparticles; Peroxidase-like catalyst; Methylene blue; Hydrogen peroxide
Effect of illite and birnessite on thallium retention and bioavailability in contaminated soils
by Aleš Vaněk; Michael Komárek; Petra Vokurková; Martin Mihaljevič; Ondřej Šebek; Gabriela Panušková; Vladislav Chrastný; Ondřej Drábek (pp. 170-176).
► The application of birnessite (δ-MnO2) to the contaminated soils can effectively transform Tl from the labile (easily mobilizable) fraction to its reducible form, thus reducing Tl bioavailability. ► Birnessite added to the soils reduced substantially Tl uptake; Tl levels in plants decreased by up to 50%, compared to the non-amended soil. ► The use of birnessite like soil additive might be an efficient and environment-friendly solution for soil systems contaminated with Tl. ► The general applicability of illite for Tl stabilization in soils seems to be limited and strongly dependent on soil composition.The influence of illite and birnessite (δ-MnO2) amendments on the retention and bioavailability of Tl in contaminated soils was investigated. The efficiency of both phases was evaluated using Tl uptake by white mustard ( Sinapis alba L.), sequential extraction and sorption experiments. The obtained data demonstrate that the application of birnessite can effectively transform Tl from the labile (easily mobilizable) fraction to its reducible form, thus lowering Tl bioavailability in soil and subsequent accumulation by plants. The Mn oxide added to the soils reduced substantially Tl uptake; Tl levels in the plants decreased by up to 50%, compared to the non-amended soil. The effect of illite on the immobilization and uptake of Tl was less pronounced, and in the carbonate-rich Leptosol has not been proved at all, suggesting the importance of bulk soil mineralogy and nature of the soil sorption complex on the behavior of this amendment. Therefore, the general applicability of illite for Tl stabilization in soils seems to be limited and strongly dependent on soil composition. In contrast, the use of birnessite like soil additive might be an efficient and environment-friendly solution for soil systems contaminated with Tl.
Keywords: Thallium; Amendment; Soil; Uptake; Mustard
Synthesis of core–shell magnetic molecularly imprinted polymers and detection of sildenafil and vardenafil in herbal dietary supplements
by Meijuan Ding; Xiaoli Wu; Lihua Yuan; Shu Wang; Yun Li; Ruoyu Wang; Tingting Wen; Shuhu Du; Xuemin Zhou (pp. 177-183).
An analytical procedure for selective extraction of sildenafil and vardenafil in herbal dietary supplements (HDSs) has been set up by using the magnetic molecularly imprinted polymers (MMIPs) as the extraction and clean-up materials, followed by high performance liquid chromatography-ultraviolet (HPLC-UV). The MMIPs were prepared by a surface molecular imprinting technique, using Fe3O4 magnetite as a magnetically susceptible component, sildenafil as template molecule, 2-(trifluoromethyl) acrylic acid (TFMAA) as functional monomer, ethylene glycol dimethacrylate (EGDMA) as polymeric matrix components. The MMIPs were characterized by transmission electron microscope (TEM), Fourier transform infrared spectrometer (FT-IR), X-ray diffraction (XRD) and vibrating sample magnetometer (VSM), respectively. The heterogeneity of the MMIPs was modeled with the Freundlich isotherm equation. The resulting MMIPs had high recognition ability and fast binding kinetics for sildenafil. The MMIPs were used as dispersive solid-phase extraction (DSPE) materials to selectively extract sildenafil and vardenafil from HDSs, the contents of sildenafil and vardenafil were found to be 8.05 and 3.86μgg−1, respectively, and the average recoveries in spiked HDSs were 70.91–91.75% with a relative standard deviation (R.S.D.) below 7%. The MMIPs were successfully used to selectively enrich and determine sildenafil and vardenafil from HDSs.
Keywords: Magnetic molecularly imprinted polymers; PDE-5 inhibitors; Sildenafil; Herbal dietary supplements; HPLC-UV
Regeneration of hexamminecobalt(II) catalyzed by activated carbon treated with KOH solutions
by Jing-yi Cheng; Lin Yang; Li Dong; Xiang-li Long; Wei-kang Yuan (pp. 184-189).
► The catalytic performance of the coconut activated carbon can be improved by modified with KOH solution. ► Modification by KOH solution increases the surface area of the carbon and the micropore area on the surface of the carbon. The physical characteristics are important factors determining the catalytic capacity of the carbon. ► The modified coconut activated carbon can obtain a much higher NO removal efficiency than the original coconut activated carbon in the simultaneous removal of SO2 and NO with Co(NH3)62+ ammonia solution.The combined elimination of NO and SO2 can be realized by hexamminecobalt(II) solution which is formed by adding soluble cobalt(II) salt into the aqueous ammonia solution. Activated carbon is used as a catalyst to regenerate hexamminecobalt(II), Co(NH3)62+, so that NO removal efficiency can be maintained at a high level for a long time. In this study, KOH solution has been explored to modify coconut activated carbon to meliorate its catalytic performance in the reduction of hexamminecobalt(III), Co(NH3)63+. The experiments have been performed in a batch stirred cell to investigate the effects of KOH concentration, impregnation duration, activation temperature and activation duration on the performance of activated carbon. The results show that the best KOH concentration for the improvement of activated carbon is 0.5moll−1. The optimal impregnation duration is 9h. High temperature is favorable to ameliorating the catalytic performance of activated carbon. The optimum activation duration is 4h.
Keywords: Activated carbon; Catalysis; Hexamminecobalt; Modification; Reduction
Treatment of substituted phenol mixtures in single phase and two-phase solid–liquid partitioning bioreactors
by M. Concetta Tomei; Sara Rita; Domenica Mosca Angelucci; M. Cristina Annesini; Andrew J. Daugulis (pp. 190-195).
► We investigate the biodegradation of a phenolic mixture (2,4-dimethylphenol and 4-nitrophenol). ► We identify an effective polymer to absorb these substrates. ► We utilize the polymer in a Two Phase Partitioning Bioreactor (TPPB) to overcome cytotoxicity. ► The polymer-based TPPB significantly out-performs a single phase system. ► The re-release of the substrates at differing rates (based on the partition coefficients) affects the process kinetics.The biological treatment of phenolics is constrained by the inherent cytotoxicity of these compounds. One method to alleviate such toxicity is to add a sequestering phase to absorb, and subsequently release, the substrate(s) to the micro-organisms; such a system is termed a Two Phase Partitioning Bioreactor. Here we have compared the performance of a TPPB, relative to single phase operation, in which a small volume (5%, v/v) of beads of the polymer Hytrel 8206 was used to treat aqueous mixtures of 2,4-dimethylphenol and 4-nitrophenol. Hytrel 8206 was selected from a range of polymers that were tested for their partition coefficients (PCs) for the target molecules, with the more hydrophobic compound (2,4-dimethylphenol) having a higher PC value (201) than 4-nitrophenol (143). Significantly increased removal rates for both substrates were demonstrated in TPPB mode relative to single phase operation. Additionally, the differential release of the compounds to the aqueous phase and their distinct PC values changed the kinetic pattern of the biotreatment system, smoothing out the cellular oxygen demand. Release of the substrates by the polymer over 60 operating cycles was virtually complete (>97%) demonstrating the reusability and robustness of the use of polymers in overcoming cytotoxicity of phenolic substrates.
Keywords: Phenolic mixtures degradation; Solid–liquid TPPBs; 2,4-Dimethylphenol; 4-Nitrophenol; Polymers
Solar photocatalitycal treatment of carbofuran at lab and pilot scale: Effect of classical parameters, evaluation of the toxicity and analysis of organic by-products
by Blady Lopez-Alvarez; Ricardo A. Torres-Palma; Gustavo Peñuela (pp. 196-203).
► TiO2 photocatalytical degradation of pesticide carbofuran in water, at lab and pilot scale, was studied. ► Effect of carbofuran, TiO2 concentration and pH were evaluated and optimized using the surface response methodology. ► Analysis of five by-products and evaluation of the treatment in presence of isopropanol or acetonitrile suggest that the degradation is carried out byOH radical attack. ► Pilot test indicated that solar TiO2 photocatalysis is able to completely degrade the pesticide and considerably reduce the toxicity of the solution.In this work the TiO2 solar-photocatalytical degradation of the pesticide carbofuran (CBF) in water, at lab and pilot scale, was studied. At lab scale the evaluation of CBF concentration (14–282μmolL−1) showed that the system followed a Langmuir–Hinshelwood kinetics type. TiO2 concentration (0.05–2gL−1) and initial pH (3–9) were also evaluated and optimized using the surface response methodology and the Pareto diagram. In the range of variables studied, initial pH 7.60 and 1.43gL−1 of TiO2 favoured the efficiency of the process. Under optimal conditions the evolution of substrate, chemical oxygen demand, dissolved organic carbon, toxicity and organics by-products were evaluated. In the pilot scale tests, using direct sunlight, 55mgL−1 of CBF in a commercial formulation was eliminated after 420min; while after 900min of treatment 80% of toxicity (1/ E50 on Vibrium Fischeri), 80% of chemical oxygen demand and 60% of dissolved organic carbon were removed. The analysis and evolution of five CBF by-products, as well the evaluation of the treatment in the presence of isopropanol or using acetonitrile as a solvent suggest that the degradation is mainly carried out byOH radical attack. Finally, a schema depicting the main degradation pathway is proposed.
Keywords: Carbofuran; Furadan; TiO; 2; photocatalysis; Advanced oxidation processes; Pesticide; Water treatment
Inhibition of hydrogen sulfide generation from disposed gypsum drywall using chemical inhibitors
by Qiyong Xu; Timothy Townsend; Gabriel Bitton (pp. 204-211).
Disposal of gypsum drywall in landfills has been demonstrated to elevate hydrogen sulfide (H2S) concentrations in landfill gas, a problem with respect to odor, worker safety, and deleterious effect on gas-to-energy systems. Since H2S production in landfills results from biological activity, the concept of inhibiting H2S production through the application of chemical agents to drywall during disposal was studied. Three possible inhibition agents – sodium molybdate (Na2MoO4), ferric chloride (FeCl3), and hydrated lime (Ca(OH)2) – were evaluated using flask and column experiments. All three agents inhibited H2S generation, with Na2MoO4 reducing H2S generation by interrupting the biological sulfate reduction process and Ca(OH)2 providing an unfavorable pH for biological growth. Although FeCl3 was intended to provide an electron acceptor for a competing group of bacteria, the mechanism found responsible for inhibiting H2S production in the column experiment was a reduction in pH. Application of both Na2MoO4 and FeCl3 inhibited H2S generation over a long period (over 180 days), but the impact of Ca(OH)2 decreased with time as the alkalinity it contributed was neutralized by the generated H2S. Practical application and potential environmental implications need additional exploration.
Keywords: Hydrogen sulfide; Gypsum drywall; Landfill; Molybdenum; Lime; Ferric chloride
Facilitation of phosphorus adsorption onto sediment by aquatic plant debris
by S.T. Du; J.L. Shentu; B.F. Luo; I.H. Shamsi; X.Y. Lin; Y.S. Zhang; C.W. Jin (pp. 212-218).
► Aquatic plant debris effects on P flux in water-sediment systems. ► Aquatic plant debris facilitates decrease of soluble reactive P in overlying water. ► Plant components have effect similar to the aquatic plant debris. ► The effect of aquatic plant debris on P flux requires the microbial activity.Aquatic plant debris in lakes or rivers may affect phosphorus flux in water–sediment systems. In this study, either aquatic plant debris or typical plant components (cellulose or glucose), were added into a system of sediment (50g) and overlying water (2L) with different initial SRP (soluble reactive phosphorus) concentrations to investigate the impact. After 18 days of treatment with 4g of plant debris, the SRP in the overlying water for 0.5 and 2mgL−1 initial SRP tests at 30°C decreased by 41 and 53%, respectively, compared to the treatments without plant debris. Cellulose and glucose treatments gave similar results as plant debris treatment. When the water–sediment system was sterilized, the cellulose- or glucose-facilitated decrease in SRP vanished. Additionally, in the non-sterilized system, the glucose treatment significantly increased both the microbial biomass carbon and the microbial biomass phosphorous in the sediment. Although total phosphorous in the sediment increased with glucose treatment, its water soluble and iron associated inorganic fractions, two labile phosphorus fractions, were clearly reduced. Our results suggest that the short-term retention of plant debris in water systems facilitates a decrease in overlying water SRP through microbe-mediated mechanisms of phosphorus adsorption and stabilization in sediment.
Keywords: Cellulose; Glucose; Microorganism; Sediment; Phosphorus; Plant debris
Mineralogy and leachability of gasified sewage sludge solid residues
by Ana Belén Hernandez; Jean-Henry Ferrasse; Perrine Chaurand; Hans Saveyn; Daniel Borschneck; Nicolas Roche (pp. 219-227).
► Study of the solid residue's characterization, solids resulting from sewage sludge gasification. ► Multi-technique approach is used to study the evolution of the mineralogy including innovative methods. ► Sewage sludge mineralogy undergoes significant transformations during thermal treatment, influenced mainly by temperature and heating atmosphere. ► Heavy metals are differently stabilized and located. ► Steam gasification is an attractive route for sewage sludge disposal in view of the mobility of heavy metals retained in the residues.Gasification of sewage sludge produces combustible gases as well as tar and a solid residue as by-products. This must be taken into account when determining the optimal thermal conditions for the gasification process. In this study, the influence of temperature, heating atmosphere and residence time on the characteristics of the gasified sewage sludge residues is investigated. ICP-AES analyses reveal that the major chemical elements in the char residues are phosphorus, calcium, iron and silicon. Heavy metals such as copper, zinc, chromium, nickel and lead are also present at relatively high levels – from 50 to more than 1000mg/kg of dry matter. The major mineral phases’ identification – before and after heating – as well as their morphology and approximate chemistry (XRD and SEM-EDX) demonstrate that a number of transformations take place during gasification. These are influenced by the reactor's temperature and the oxidative degree of its internal atmosphere. The copper-, zinc- and chromium-bearing phases are studied using chemometric tools, showing that the distribution of those metals among the mineral phases is considerably different. Finally, batch-leaching tests reveal that metals retained in the residue are significantly stabilized after thermal treatment to a higher or lower extent, depending on the thermal conditions applied.
Keywords: Waste management; Ash; Micro-XRF; Pollutants; SIMPLISMA
Can a breathing biocover system enhance methane emission reduction from landfill?
by Wen-Jing Lu; Zi-Fang Chi; Zi-Shen Mou; Yu-Yang Long; Hong-Tao Wang; Yong Zhu (pp. 228-233).
Based on the aerothermodynamic principles, a kind of breathing biocover system was designed to enhance O2 supply efficiency and methane (CH4) oxidation capacity. The research showed that O2 concentration (v/v) considerably increased throughout whole profiles of the microcosm (1m) equipped with passive air venting system (MPAVS). When the simulated landfill gas SLFG flow was 771gm−3d−1 and 1028gm−3d−1, the O2 concentration in MPAVS increased gradually and tended to be stable at the atmospheric level after 10 days. The CH4 oxidation rate was 100% when the SLFG flow rate was no more than 1285gm−3d−1, which also was confirmed by the mass balance calculations. The breathing biocover system with in situ self-oxygen supply can address the problem of O2 insufficient in conventional landfill covers and/or biocovers. The proposed system presents high potential for improving CH4 emission reduction in landfills.
Keywords: Passive air venting; Biocover; Landfill; Methane oxidation; Aerothermodynamic
Removal of dimethyl sulfide utilizing activated carbon fiber-supported photocatalyst in continuous-flow system
by W.K. Jo; S.H. Shin; E.S. Hwang (pp. 234-239).
The present study investigated the adsorptional photocatalytic decomposition (APD) efficiency of activated carbon fiber-supported TiO2 (ACF/TiO2) in a continuous-flow reactor for the removal of dimethyl sulfide (DMS). The SEM analysis identified that the ACF/TiO2 exhibited the same tridimensional shape as uncovered ACF and that a TiO2 photocatalyst could be embedded in the surface of the ACF. In the absence of UV light, the time-series removal efficiencies by ACF and the ACF/TiO2 units exhibited a similar pattern, which decreased gradually as it reached close to zero. However, the APD efficiency determined via the ACF/TiO2 with UV light remained at nearly 60% during the remaining courses of the 13-h period, after decreasing from a maximum APD of 80%. The APD efficiencies depended upon the weights of the TiO2 embedded into the ACFs, the UV sources, the relative humidity, and DMS input concentrations. During a long-term (219-h) APD test, the APD efficiencies dropped from 80% to ca 60% within 1h after the initiation of the APD process and then fluctuated between 52% and 60%. No byproducts were measurable or observable in the effluent gas or on the ACF/TiO2 surface. Consequently, the continuous-flow ACF/TiO2 system could effectively be applied to control DMS without any significant functional deterioration.
Keywords: Adsorptional photocatalytic; Adsorption efficiency; SEM analysis; Titanium dioxide; Byproduct
Sorption characteristics of fluoride on to magnesium oxide-rich phases calcined at different temperatures
by Keiko Sasaki; Naoyuki Fukumoto; Sayo Moriyama; Tsuyoshi Hirajima (pp. 240-248).
► Higher calcination temperatures produced more crystalline MgO with smaller specific surface area and provided larger values of the total basicity per unit surface area. ► Larger total basicity per unit surface area made the reactivity with F- ions in aqueous phase more feasible, resulting in a greater degree of F- sorption. ► This is the first paper which describes the relationship between the solid base characteristics obtained by CO2-TPD for MgO with different calcination temperature as a function of the reactivity of F- sorption in the aqueous phase.The effect of calcination temperature during production of magnesium oxide-rich phases from MgCO3 on the sorption of F− ions in the aqueous phase has been investigated. Magnesium oxide-rich phases were formed by calcination at over 873K for 1h. Higher calcination temperatures produced more crystalline MgO with smaller specific surface area and provided larger values of the total basicity per unit surface area. The higher calcination temperatures lead to slower F− removal rate, and lower equilibrium F− concentrations, when the equilibrium F− concentrations are less than 1mmoldm−3. Larger total basicity per unit surface area made the reactivity with F− ions in aqueous phase more feasible, resulting in a greater degree of F− sorption. For equilibrium F− concentrations more than 1mmoldm−3, lower calcination temperatures favored the co-precipitation of F− with Mg(OH)2, probably leading to the formation of Mg(OH)2− xF x, and the achievement of larger sorption density. This is the first paper which describes the relationship between the solid base characteristics obtained by CO2-TPD for MgO with different calcination temperatures as a function of the reactivity of F− sorption in the aqueous phase.
Keywords: Magnesium oxides; Fluoride; Calcinations; Sorption isotherm; Temperature programmed desorption of CO; 2
Enhanced remedial amendment delivery to subsurface using shear thinning fluid and aqueous foam
by Lirong Zhong; Jim Szecsody; Mart Oostrom; Mike Truex; Xin Shen; Xiqing Li (pp. 249-257).
A major issue with in situ subsurface remediation is the ability to achieve an even spatial distribution of remedial amendments to the contamination zones in an aquifer or vadose zone. Amendment delivery to the aquifer using shear thinning fluid and to the vadose zone using aqueous foam has the potential to enhance the distribution. 2-D saturated flow cell experiments were conducted to evaluate the enhanced fluid sweeping over heterogeneous system, improved contaminant removal, and extended amendment presence in low-permeability zones achieved by shear thinning fluid delivery. Unsaturated column and flow cell experiments were conducted to investigate the improvement on contaminant mobilization mitigation, amendment distribution, and lateral delivery implemented by foam delivery. It was demonstrated that the shear thinning fluid injection enhanced the fluid sweeping and increased the delivery of remedial amendment into low-perm zones. The presence of amendment distributed by the shear thinning fluid in the low-permeability zones was increased. Foam delivery was shown to mitigate the mobilization of highly mobile contaminant from sediments. It also achieved more uniform amendment distribution in a heterogeneous unsaturated system, and demonstrated remarkable increasing in lateral distribution of the injected liquid compared to direct liquid injection.
Keywords: Subsurface remediation; Delivery; Remedial amendment; Heterogeneity; Shear thinning fluid; Foam; Vadose zone
Environmental life-cycle comparisons of two polychlorinated biphenyl remediation technologies: Incineration and base catalyzed decomposition
by Xintao Hu; Jianxin Zhu; Qiong Ding (pp. 258-268).
► We study the environmental impacts of two kinds of remediation technologies including Infrared High Temperature Incineration(IHTI) and Base Catalyzed Decomposition(BCD). ► Combined midpoint/damage approaches were calculated for two technologies. ► The results showed that major environmental impacts arose from energy consumption. ► BCD has a lower environmental impact than IHTI in the view of single score.Remediation action is critical for the management of polychlorinated biphenyl (PCB) contaminated sites. Dozens of remediation technologies developed internationally could be divided in two general categories incineration and non-incineration. In this paper, life cycle assessment (LCA) was carried out to study the environmental impacts of these two kinds of remediation technologies in selected PCB contaminated sites, where Infrared High Temperature Incineration (IHTI) and Base Catalyzed Decomposition (BCD) were selected as representatives of incineration and non-incineration. A combined midpoint/damage approach was adopted by using SimaPro 7.2 and IMPACTA2002+ to assess the human toxicity, ecotoxicity, climate change impact, and resource consumption from the five subsystems of IHTI and BCD technologies, respectively. It was found that the major environmental impacts through the whole lifecycle arose from energy consumption in both IHTI and BCD processes. For IHTI, primary and secondary combustion subsystem contributes more than 50% of midpoint impacts concerning with carcinogens, respiratory inorganics, respiratory organics, terrestrial ecotoxity, terrestrial acidification/eutrophication and global warming. In BCD process, the rotary kiln reactor subsystem presents the highest contribution to almost all the midpoint impacts including global warming, non-renewable energy, non-carcinogens, terrestrial ecotoxity and respiratory inorganics. In the view of midpoint impacts, the characterization values for global warming from IHTI and BCD were about 432.35 and 38.5kg CO2-eq per ton PCB-containing soils, respectively. LCA results showed that the single score of BCD environmental impact was 1468.97 Pt while IHTI's score is 2785.15 Pt, which indicates BCD potentially has a lower environmental impact than IHTI technology in the PCB contaminated soil remediation process.
Keywords: Remediation technologies; PCB contaminated sites; Life cycle assessment; Environmental management
Physico-chemical and radioactive characterization of TiO2 undissolved mud for its valorization
by M.J. Gázquez; J. Mantero; J.P. Bolívar; R. García-Tenorio; F. Vaca; R.L. Lozano (pp. 269-276).
In order to find a potential valorization of a waste generated in the industrial process devoted to the production of TiO2 pigments, and as an essential and basic step, this waste must firstly be physically and chemically characterized. Moreover, the content of radioactivity is taken in to account due to it comes from a NORM (Naturally Occurring Radioactive Material) industry. With this end, microscopic studies were performed by applying scanning electron microscopy with X-ray microanalysis (SEM–XRMA), while the mineralogical compositions were carried out by means of the X-ray diffraction (XRD) technique. The concentrations of its major elements were determined by X-ray fluorescence (XRF), while heavy metals and other trace elements were ascertained through Inductively Coupled Plasma Mass Spectrometry (ICP-MS).The results obtained for this waste have revealed several lines of research into potential applications. Firstly, with the refractory properties of mineral phases observed leading to a possible use in the ceramics industry or in thermal isolators. And secondly, attending to the characteristic particle-size spectra can be used as an additive in the manufacture of cement and finally, its high concentration of titanium may be used as a bactericide in brick production.
Keywords: NORM industry; Titanium dioxide; Characterization waste; Ilmenite undisolved muds
Removal of heavy metals using different polymer matrixes as support for bacterial immobilisation
by Carlos Pires; Ana P.G.C. Marques; António Guerreiro; Naresh Magan; Paula M.L. Castro (pp. 277-286).
Great attention is focused on the microbial treatment of metal contaminated environments. Three bacterial strains, 1C2, 1ZP4 and EC30, belonging to genera Cupriavidus, Sphingobacterium and Alcaligenes, respectively, showing high tolerance to Zn and Cd, up to concentrations of 1000ppm, were isolated from a contaminated area in Northern Portugal. Their contribution to Zn and Cd removal from aqueous streams using immobilised alginate, pectate and a synthetic cross-linked polymer was assessed. In most cases, matrices with immobilised bacteria showed better metal removal than the non-inoculated material alone. For the immobilisation with all the polymers, 1C2 was the strain that increased the removal of Zn the most, whereas EC30 was the most promising for Cd removal, especially when combined with the synthetic polymer with up to a ca. 11-fold increase in metal removal when compared to the polymer alone. Removal of individual metals from binary mixtures showed that there was differential immobilisation. There was greater removal of Cd than Zn (removals up to 40% higher than those showed for Zn). The results show that metal contaminated environments constitute a reservoir of microorganisms resistant/tolerant to heavy metals that have the capacity to be exploited in bioremediation strategies.Capsule immobilisation of bacteria in the naturally occurring alginate and pectate and in a synthetic cross-linked polymer increased the Zn and Cd removal abilities from single and binary contaminated waters; the applications with the synthetic polymer were the most promising for Cd and Zn removal in single and binary mixtures.
Keywords: Heavy metals; Bacterial immobilisation; Synthetic polymer; Acetate; Pectate; Binary mixtures
In-situ remediation of acid mine drainage using a permeable reactive barrier in Aznalcóllar (Sw Spain)
by Oriol Gibert; Tobias Rötting; José Luis Cortina; Joan de Pablo; Carlos Ayora; Jesús Carrera; José Bolzicco (pp. 287-295).
► A biological permeable reactive barrier to remediate acid mine drainage is reported. ► The PRB is successful to neutralize pH and remove heavy metals from groundwater. ► Sulfate is far from being completely reduced by sulfate-reducing bacteria (SRB). ► The poor SRB activity is due to short residence time and low substrate degradability.Following on the accident occurred in Aznalcóllar in 1998, whereby a huge amount of acid mine drainage and heavy metal-bearing pyritic sludge was released to the Agrio river valley with the subsequent contamination of groundwater, a subsurface permeable reactive barrier (PRB) was installed to mitigate the long-term impacts by the spillage. The PRB material consisted of a mixture of limestone and vegetal compost. A particular characteristic of the Agrio aquifer is its high water flow velocity (0.5–1m/d), which may pose difficulties in its remediation using PRB technology. The present study reports the 36-month performance of the PRB. Vertical differences in water velocity were observed within the PRB, with the deeper part being slower and more effective in neutralizing pH and removing heavy metals (Zn, Al, Cu). On the other hand, partial sulfate removal appeard to be restricted to the bottom of the PRB, but with no apparent influence on downgradient water quality. The results are finally compared with the other four reported existing PRBs for AMD worldwide.
Keywords: Acid mine drainage; Permeable reactive barrier; In situ remediation; Sulfate-reducing bacteria; Heavy metals
Chromium behavior during cement-production processes: A clinkerization, hydration, and leaching study
by Suthatip Sinyoung; Prayoon Songsiriritthigul; Suwimol Asavapisit; Puangrat Kajitvichyanukul (pp. 296-305).
► Behavior of chromium during cement-production processes. ► Formation of new chromium compounds in clinker with chromium oxidation states of +3, +4.6, +5, and +6. ► Addition of chromium altered the composition of the clinker phases, setting time, and compressive strength of hydrated mixes. ► Cr3+ and Cr6 were leached during leaching tests, whereas other species remained in the mortar.The behavior of chromium during the production of cement clinker, during the hydration of cement and during the leaching of cement mortars was investigated. The microstructures of clinker and mortar properties were investigated using free lime, XRD, SEM/EDS, and TG/DTA techniques. Chromium was found to be incorporated in the clinker phase. The formation of new chromium compounds such as Ca6Al4Cr2O15, Ca5Cr3O12, Ca5Cr2SiO12, and CaCr2O7, with chromium oxidation states of +3, +4.6, +5, and +6, respectively, was detected. After the hydration process, additional chromium compounds were identified in the mortar matrix, including Ca5(CrO4)3OH, CaCrO4·2H2O, and Al2(OH)4CrO4, with chromium oxidation states of +4.6, +6, and +6, respectively. Additionally, some species of chromium, such as Cr3+ from Ca6Al4Cr2O15 and Cr6+ from CaCr2O7, CaCrO4·2H2O, and Al2(OH)4CrO4, were leached during leaching tests, whereas other species remained in the mortar. The concentrations of chromium that leached from the mortar following U.S. EPA Method 1311 and EA NEN 7375:2004 leaching tests were higher than limits set by the U.S. EPA and the Environment Agency of England and Wales related to hazardous waste disposal in landfills. Thus, waste containing chromium should not be allowed to mix with raw materials in the cement manufacturing process.
Keywords: Chromium; Clinker; Hydrated cement; Leaching; Mortar
Predictive hydrogeochemical modelling of bauxite residue sand in field conditions
by Laurin Wissmeier; David A. Barry; Ian R. Phillips (pp. 306-324).
► Geochemical and hydrological model for bauxite residue sand. ► Combined hydrogeochemical simulation of bauxite residue sand under field conditions, in 2D, heterogeneous domain. ► Evaluation of management practise for the amelioration of bauxite residue sand as substrate for plant growth.The suitability of residue sand (the coarse fraction remaining from Bayer's process of bauxite refining) for constructing the surface cover of closed bauxite residue storage areas was investigated. Specifically, its properties as a medium for plant growth are of interest to ensure residue sand can support a sustainable ecosystem following site closure. The geochemical evolution of the residue sand under field conditions, its plant nutrient status and soil moisture retention were studied by integrated modelling of geochemical and hydrological processes. For the parameterization of mineral reactions, amounts and reaction kinetics of the mineral phases natron, calcite, tricalcium aluminate, sodalite, muscovite and analcime were derived from measured acid neutralization curves. The effective exchange capacity for ion adsorption was measured using three independent exchange methods. The geochemical model, which accounts for mineral reactions, cation exchange and activity corrected solution speciation, was formulated in the geochemical modelling framework PHREEQC, and partially validated in a saturated-flow column experiment. For the integration of variably saturated flow with multi-component solute transport in heterogeneous 2D domains, a coupling of PHREEQC with the multi-purpose finite-element solver COMSOL was established. The integrated hydrogeochemical model was applied to predict water availability and quality in a vertical flow lysimeter and a cover design for a storage facility using measured time series of rainfall and evaporation from southwest Western Australia. In both scenarios the sand was fertigated and gypsum-amended. Results show poor long-term retention of fertilizer ions and buffering of the pH around 10 for more than 5y of leaching. It was concluded that fertigation, gypsum amendment and rainfall leaching alone were insufficient to render the geochemical conditions of residue sand suitable for optimal plant growth within the given timeframe. The surface cover simulation demonstrates that the soil moisture status in the residue sand can be ameliorated by an appropriate design of the cover layer with respect to thickness, slope and distance between lateral drains.
Keywords: Bauxite refining residue; Geochemical modelling; IPhreeqc; COMSOL; Vadose zone; Waste management
User perception study for performance evaluation of domestic defluoridation techniques for its application in rural areas
by Sneha Lunge; Rajesh Biniwale; Nitin Labhsetwar; Sadhana S. Rayalu (pp. 325-332).
Tea bag type sachet for defluoridation.Display Omitted► Loose sorbent, bamboo column and tea bag sachet method was evaluated for defluoridation. ► Domestic defluoridation techniques were tested in the field. ► Feed back was obtained from the rural users for the performance and acceptance of the method. ► Chitosan based adsorbents were used in this technique.Fluoride concentrations in ground water have been monitored in rural areas of Dhar and Jhabua districts in Madhya Pradesh, India. A correlation of fluoride concentration with pH, TDS and conductivity has been estimated to identify surrogate monitoring parameter. Further, fluoride removal from drinking water has been achieved by using adsorbents specially developed for domestic applications. These adsorbents have been evaluated using three different methods namely; loose adsorbent, pre-packed sachet and packed bamboo column. Comparative evaluation of these methods has been demonstrated in the laboratory and field. The stringent limit of 1mg/L for fluoride concentration in drinking water has been achieved by use of specially designed adsorbents. A feedback from end-users in Tarapur and Ukala villages of Dhar districts Madhya Pradesh regarding the adsorbents and its acceptability has been collected. User's perception regarding these household treatments reveals encouraging response for defluoridation methods. According to user's perception loose adsorbent approach emerged out as most simple, clean and safe household defluoridation method.
Keywords: Fluoride removal; Domestic treatment; User's perception
Posidonia oceanica (L.) fibers as a potential low-cost adsorbent for the removal and recovery of orthophosphate
by Mohamed Ali Wahab; Rafik Ben Hassine; Salah Jellali (pp. 333-341).
Adsorption efficiency of orthophosphate from aqueous solution onto Posidonia oceanica fibers (POF) as a raw, natural and abundant material was investigated and compared with other common natural materials. A series of batch tests were undertaken to assess the effect of the system variables, i.e. initial aqueous orthophosphate concentration, contact time, adsorbent dosage, pH and temperature. Results indicate that orthophosphate uptake increased with increasing initial orthophosphate concentration, temperature and adsorbent dosage and decreased with increasing pH values. The maximum adsorption capacity ( Qm) determined from the Langmuir isotherm was calculated to be 7.45mgg−1 for the studied orthophosphates concentration range of 15–100mgL−1, pH 7; adsorbent dosage of 2gL−1 and temperature of 20±2°C. The adsorption data were very well described by the pseudo-second order model predicting a chemisorption process. The energy dispersive spectroscopy (EDS) and FTIR analysis before and after adsorption of orthophosphate onto POF showed that the main involved mechanisms are ligand exchange between orthophosphate and Cl−, SO42− and OH− and precipitation with calcium. In comparison with other natural adsorbents, raw POF could be considered as one of the most efficient natural materials for the removal of orthophosphate with the possibility of agronomic reuse.
Keywords: Orthophosphate; Removal; POF; Modeling; Adsorption mechanisms
Speciation of arsenic in rice and estimation of daily intake of different arsenic species by Brazilians through rice consumption
by Bruno L. Batista; Juliana M.O. Souza; Samuel S. De Souza; Fernando Barbosa Jr. (pp. 342-348).
► Speciation of arsenic in Brazilian rice samples is provided. ► Inorganic arsenic and DMA were the predominant forms found in all samples. ► Estimated daily intake of inorganic arsenic (the most toxic form) by Brazilians through rice consumption is 10% of the PTDI.Rice is an important source of essential elements. However, rice may also contain toxic elements such as arsenic. Therefore, in the present study, the concentration of total arsenic and five main chemical species of arsenic (As3+, As5+, DMA, MMA and AsB) were evaluated in 44 different rice samples (white, parboiled white, brown, parboiled brown, parboiled organic and organic white) from different Brazilian regions using high-performance liquid chromatography hyphenated to inductively coupled plasma mass spectrometry (HPLC–ICP-MS). The mean level of total arsenic was 222.8ngg−1 and the daily intake of inorganic arsenic (the most toxic form) from rice consumption was estimated as 10% of the Provisional Tolerable Daily Intake (PTDI) with a daily ingestion of 88g of rice. Inorganic arsenic (As3+, As5+) and dimethylarsinic acid (DMA) are the predominant forms in all samples. The percentages of species were 38.7; 39.7; 3.7 and 17.8% for DMA, As3+, MMA and As5+, respectively. Moreover, rice samples harvested in the state of Rio Grande do Sul presented more fractions of inorganic arsenic than rice in Minas Gerais or Goiás, which could lead to different risks of arsenic exposure.
Keywords: Arsenic; Rice; Speciation; Daily intake; Risk assessment
A risk analysis model for radioactive wastes
by Fatih Külahcı (pp. 349-355).
Sampling points in the research region and risk distribution of40K wastes formed according to Weibull probability distribution function. Sampling stations are the yellow points. The upper part is 2D and shows the iso-Weibull pdf risk distribution. The lower figure shows the distribution of 3D Weibull pdf.Display Omitted► A new risk analysis model is proposed for waste materials. ► Risk analysis developed in this research can be used for any waste materials. ► Risk model consists from probability distribution functions. ► The Weibull pdf explained successfully spatial distribution of K in the environment.Hazardous wastes affect natural environmental systems to a significant extend, and therefore, it is necessary to control their harm through risk analysis. Herein, an effective risk methodology is proposed by considering their uncertain behaviors on stochastic, statistical and probabilistic bases. The basic element is attachment of a convenient probability distribution function (pdf) to a given waste quality measurement sequence. In this paper,40K contaminant measurements are adapted for risk assessment application after derivation of necessary fundamental formulations. The spatial contaminant distribution of40K is presented in the forms of maps and three-dimensional surfaces.
Keywords: Potassium wastes; Risk analysis; Risk assessment; Distribution function
Comparison of morphology and photo-physiology with metal/metalloid contamination in Vallisneria neotropicalis
by C. Lafabrie; K.M. Major; C.S. Major; M.M. Miller; J. Cebrián (pp. 356-365).
► We investigate impact of metal contamination on the performance of V. neotropicalis. ► We compare morpho-physiological attributes with metal levels in plant tissues. ► An overall negative effect on plant growth was observed. ► No detrimental effects were found on plant photosynthetic physiological performance. ► This plant tolerates moderate contamination with little impact on its overall health.The overarching goal of this in situ study was to investigate the integrated impact(s) that metal/metalloid contamination might have on the overall health and performance of the ecologically important aquatic macrophyte, Vallisneria neotropicalis. Morphological (i.e., shoot growth-based endpoints) and photo-physiological (i.e., photosynthetic activity measured as chlorophyll a fluorescence and oxygen exchange) variables, along with aboveground tissue metal/metalloid concentrations, were measured in natural populations of V. neotropicalis that differed with respect to their anthropogenic pressure. With the exception of an overall negative effect on growth, our results suggest that there were no detrimental effects of low/moderate contamination of V. neotropicalis by trace elements (i.e., arsenic As and mercury Hg; 1.04–2.77μgg−1drywt. and 3.76–15.18ngg−1drywt., respectively) on the photosynthetic physiological performance of this species. V. neotropicalis appears to tolerate low/moderate levels of trace element contamination with little impact on plant health and performance.
Keywords: Submerged aquatic vegetation (SAV); Pollution; Gulf of Mexico; Effective quantum yield of photosystem II (PSII; Δ; F; /; F; m; ′); Photosynthetic performance
Assessing soil heavy metal pollution in the water-level-fluctuation zone of the Three Gorges Reservoir, China
by Chen Ye; Siyue Li; Yulong Zhang; Quanfa Zhang (pp. 366-372).
► We assess heavy metal pollution in the water level fluctuation zone of the Three Gorges Reservoir. ► There are higher concentrations of As, Cd, Pb, Cu, and Zn in the upper and low reaches. ► As and Cd are the primary pollutants originated from domestic sewage and industrial wastes before submergence. ► The major contaminants are Hg, Cd, and Pb with primary contribution from traffic exhaust and industrial effluent after submergence.The water-level-fluctuation zone (WLFZ) between the elevations of 145–175m in China's Three Gorges Reservoir has experienced a novel hydrological regime with half a year (May–September) exposed in summer and another half (October–April) submerged in winter. In September 2008 (before submergence) and June 2009 (after submergence), soil samples were collected in 12 sites in the WLFZ and heavy metals (Hg, As, Cr, Cd, Pb, Cu, Zn, Fe, and Mn) were determined. Enrichment factor (EF), factor analysis (FA), and factor analysis-multiple linear regression (FA-MLR) were employed for heavy metal pollution assessment, source identification, and source apportionment, respectively. Results demonstrate spatial variability in heavy metals before and after submergence and elements of As, Cd, Pb, Cu, and Zn are higher in the upper and low reaches. FA and FA-MLR reveal that As and Cd are the primary pollutants before submergence, and over 45% of As originates from domestic sewage and 59% of Cd from industrial wastes. After submergence, the major contaminants are Hg, Cd, and Pb, and traffic exhaust contributes approximately 81% to Hg and industrial effluent accounts about 36% and 73% for Cd and Pb, respectively. Our results suggest that increased shipping and industrial wastes have deposited large amounts of heavy metals which have been accumulated in the WLFZ during submergence period.
Keywords: Submergence; Heavy metal; Enrichment factor; Source identification; Source apportionment
Municipal solid waste compost application improves productivity, polyphenol content, and antioxidant capacity of Mesembryanthemum edule
by Abdelbasset Lakhdar; Hanen Falleh; Youssef Ouni; Samia Oueslati; Ahmed Debez; Riadh Ksouri; Chedly Abdelly (pp. 373-379).
► We used municipal waste compost 40tha−1 to improve plant antioxidant activities. ► Slow-release fertilizer effect of compost enhanced growth of Mesembryanthemum edule. ► Compost amendment positively affect polyphenol contents and antioxidant capacities. ► The levels of heavy metals (Pb, Cd, Cu, and Zn) were under allowed limits.Organic wastes were successfully used as soil amendment to improve agrosystems productivity. Yet, the effectiveness of this practice to enhance plant antioxidant capacities has received little attention. Here, we assess the effect of municipal solid waste (MSW) compost (at 40tha−1) on growth, polyphenol contents and antioxidant activities of Mesembryanthemum edule. MSW compost application significantly increased the soil contents of carbon, nitrogen, calcium, phosphorus and potassium. This was associated with higher nutrient (N, P, and K) uptake, which likely led to the significant improvement of the plant biomass and relative growth rate (RGR) (+93% on average) as compared to the control. In the same way, the fertilizing effect of the added organic matter significantly enhanced the antioxidant potential M. edule, assessed by radical scavenging activity, iron reducing power and β-carotene bleaching capacity. This was associated with significantly higher antioxidant contents, mainly total phenols and flavonoids. Heavy metal (Pb, Cd, Cu, and Zn) concentrations were slightly increased upon compost application, but remained lower than phytotoxic values. Overall, our results point out that short-term MSW compost application at 40tha−1 is efficient in enhancing the productivity together with the antioxidant potentiality of M. edule without any adverse environmental impact.
Keywords: Growth; Mesembryanthemum edule; Antioxidant activities; Phenolic compounds; Heavy metals
Consequence of chitosan treating on the adsorption of humic acid by granular activated carbon
by Sh. Maghsoodloo; B. Noroozi; A.K. Haghi; G.A. Sorial (pp. 380-387).
► We explore the equilibrium and kinetic adsorption of humic acid onto chitosan treated granular activated carbon (MGAC). ► It was shown that pre-adsorption of chitosan onto the surface of GAC improved the adsorption capacity for HA. ► Monolayer capacities for the adsorption of HA onto MGAC was more than GAC. ► Film diffusion and intra-particle diffusion were simultaneously operating during the adsorption process for MGAC. ► Chitosan provides chemical binding for the adsorption onto the GAC.In this work, equilibrium and kinetic adsorption of humic acid (HA) onto chitosan treated granular activated carbon (MGAC) has been investigated and compared to the granular activated carbon (GAC). The adsorption equilibrium data showed that adsorption behaviour of HA could be described reasonably well by Langmuir adsorption isotherm for GAC and Freundlich adsorption isotherm for MGAC. It was shown that pre-adsorption of chitosan onto the surface of GAC improved the adsorption capacity of HA changing the predominant adsorption mechanism. Monolayer capacities for the adsorption of HA onto GAC and MGAC were calculated 55.8mg/g and 71.4mg/g, respectively. Kinetic studies showed that film diffusion and intra-particle diffusion were simultaneously operating during the adsorption process for MGAC.
Keywords: Activated carbon; Adsorption; Chitosan; Humic acid; Natural organic matter (NOM)
Removal of lead compounds from polyvinylchloride in electric wires and cables using cation-exchange resin
by Masami Tsunekawa; Mayumi Ito; Yuta Sasaki; Tomoo Sakai; Naoki Hiroyoshi (pp. 388-392).
► Cable insulation PVC contains lead component as thermal stabilizer. ► Lead removal is needed to recycle PVC as insulation resin. ► Lead removal by an adsorption method using ion exchange resin was investigated. ► Low lead concentration, complying with the requirements of RoHS, was achieved.Recycling treatment of cable insulation resin generated from electric wires and cables was investigated. Conventional insulation PVC contains a lead component, tribase, as a thermal stabilizer and lead removal is necessary to recycle this PVC as insulation resin. This paper describes a solid surface adsorption method using ion exchange resin to remove the fine lead containing particles from PVC dissolved solution. Low lead concentration in the recovered PVC, complying with the requirements of RoHS, was achieved.
Keywords: Polyvinylchloride; Recycling; Lead removal; Cation-exchange resin
Novel biodegradation pathways of cyclohexane by Rhodococcus sp. EC1
by Taewoo Yi; Eun-Hee Lee; Yun Gyong Ahn; Geum-Sook Hwang; Kyung-Suk Cho (pp. 393-396).
The metabolism of cyclohexanes by Rodococcus sp. EC1 was investigated using a sequential tracking method of degradation intermediate. Evidence for the formation of cyclohexanol, cyclohexaone, 2-cyclohexen-1-one, and phenol was presented. EC1 metabolized cyclohexane to phenol by aromatization of 2-cyclohexen-1-one, and furthermore gamma-butyrolactone as an intermediate of 2-cyclohexen-1-one was formed. Aromatization by EC1 was confirmed using tetrahydrofuran. Tetrahydrofuran was metabolized through aromatization reaction, involving furan and 2,3-dihydrofuran as key intermediates. EC1 can degrade cyclohexane and tetrahydrofuran in aromatization via desaturation.
Keywords: Cyclohexane; Rhodococcus; sp.; Oxidation pathway; Aromatization