Chemosphere (v.61, #4)

A novel strain (PYJ-1) of Rhodococcus pyridinovorans that was isolated from a biofilter was able to degrade styrene at a maximum rate of 0.16 mg (mg protein)−1 h−1 in batch culture at 97 mg l−1 of initial styrene gas concentration. The optimum pH and temperature for styrene degradation were 7 and 32 °C, respectively. The degradation kinetic constants were obtained using substrate inhibition kinetics. In a perlite-packed biofilter the maximum styrene removal rate by the strain was 279 g m−3  h−1. Styrene removal in the biofilter was more sensitive to the temperature than in the batch culture.
Keywords: Styrene; Degradation; Rhodococcus pyridinovorans PYJ-1; Biofiltration;

Heterogeneous photocatalysed reaction of three selected pesticide derivatives such as propham (1), propachlor (2) and tebuthiuron (3) has been investigated in aqueous suspensions of titanium dioxide by monitoring the change in substrate concentration employing UV Spectroscopic analysis and depletion in Total Organic Carbon (TOC) content as a function of irradiation time. The degradation kinetics was studied under different conditions such as pH, catalyst concentration, substrate concentration, different types of TiO2 and in the presence of electron acceptors such as hydrogen peroxide (H2O2), potassium bromate (KBrO3) and ammonium persulphate (NH4)2S2O8 besides molecular oxygen. The degradation rates were found to be strongly influenced by all the above parameters. The photocatalyst Degussa P25 was found to be more efficient as compared with other photocatalysts. The pesticide derivative propham (1) was found to degrade faster as compared to propachlor (2) and tebuthiuron (3). An attempt has also been made to identify the products formed during the photooxidation process through GC/MS analysis technique. All the model pollutants showed the formation of several intermediate products, which were identified on the basis of molecular ion and mass spectrometric fragmentation pattern. A probable mechanism for the formation of the products has been proposed.
Keywords: Photocatalysis; Propham; Propachlor; Tebuthiuron; Semiconductor;

The kinetic of the catalytic decomposition of methyl isobutyl ketone over a Pt/γ-Al2O3 catalyst by Ting-Ke Tseng; Hsin Chu; Tzu-Hsing Ko; Lung-Kai Chaung (469-477).
Environmental catalysis also can refer to catalytic technologies for reducing emission of environmentally unacceptable compounds. Catalytic decomposition also is one of the cost-effective technologies to solve the troublesome volatile organic compounds. This study treated methyl isobutyl ketone (MIBK) by a commercial catalyst, Pt/γ-Al2O3, in an isothermal fixed bed differential reactor. The effects of O2 and MIBK content in carrier gas on the catalysis’s reaction rate are also observed. Three kinetic models, i.e. the Mars and van Krevelen model, Langmuir–Hinshelwood model and power-rate law were applied to best fit the experimental results. The results indicate that the kinetic behavior of MIBK oxidation with catalysis can be accounted for by using the rate expression of the Mars and van Krevelen model and Langmuir–Hinshelwood model. Kinetic parameters are also determined on the basis of the differential reactor data. The experimental results are compared with those of the model predicted.
Keywords: Catalytic decomposition; Pt/γ-Al2O3; Kinetic; Methyl isobutyl ketone; Model prediction;

Adsorption of arsenic(V) by activated carbon prepared from oat hulls by C.L. Chuang; M. Fan; M. Xu; R.C. Brown; S. Sung; B. Saha; C.P. Huang (478-483).
The efficiency of self-manufactured activated carbon (AC) produced from oat hulls in adsorbing arsenic(V) was tested in a batch reactor. The results indicated that the adsorptive capacity of AC was affected by initial pH value, with adsorption capacity decreasing from 3.09 to 1.57 mg As g−1 AC when the initial pH values increased from 5 to 8. A modified linear driving force model conjugated with a Langmuir isotherm was created to describe the study’s kinetics. The test results show that rapid adsorption and slow adsorption exist simultaneously when AC is used to remove arsenic(V).
Keywords: Arsenic; Activated carbon; Adsorption; Oat hulls;

Impact of microbial activity on copper, lead and nickel mobilization during the bioremediation of soil PAHs by Myriam A. Amezcua-Allieri; Jamie R. Lead; Refugio Rodrı́guez-Vázquez (484-491).
A fungal bioremediation method using P. frequentans removed up to 75% of phenanthrene with the addition of water and nutrients over a period of 30 d. During the bioremediation process, changes in metal behavior were monitored by an in situ technique (diffusive gradients in thin-films, DGT) and by soil solution chemistry. DGT provided absolute data on fluxes from the solid phase to the DGT device and relative trends of concentrations of the most labile metal species. DGT response indicated that bioremediation increases metal mobilization from the solid phase. Filtration provided data on the concentrations of solution phase (<0.45 μm) metal. In all case, metal fluxes and concentrations significantly increased after the bioremediation process began. Fluxes increased from <0.1 pg cm−2  s−1 before bioremediation to between 0.2 and 0.5 pg cm−2  s−1 after bioremediation. Metal concentrations in the soils solution (filtration at 0.45 μm) increased from 2 to 10 μg l−1 (Cu), 1–4 μg l−1 (Pb) and from 40 to 140 μg l−1 (Ni) after bioremediation. Although over a short time period, these data strongly indicated that there was remobilization of metal from solid to solution (and thus to the DGT device) directly due to the bioremediation process. Although the mechanism was not unambiguously identified, it was shown not to be related to small changes in bulk pH over time and was attributed to the microbial action on the surface of the soil solid phase, releasing metal into solution. Additionally, differences in metal concentration and flux were observed in sterilized and non-sterilized soils and in the absence or presence of phenanthrene. The results indicated that the bioremediation of soil by P. frequentans increased the flux, lability and mobility of trace metal species and therefore the likely metal bioavailability to plants.
Keywords: Metals; Penicillium frequentans; Flux; Phenanthrene;

Removal of congo red from aqueous solution by bagasse fly ash and activated carbon: Kinetic study and equilibrium isotherm analyses by Indra Deo Mall; Vimal Chandra Srivastava; Nitin Kumar Agarwal; Indra Mani Mishra (492-501).
Present investigation deals with the utilisation of bagasse fly ash (BFA) (generated as a waste material from bagasse fired boilers) and the use of activated carbons—commercial grade (ACC) and laboratory grade (ACL), as adsorbents for the removal of congo red (CR) from aqueous solutions. Batch studies were conducted to evaluate the adsorption capacity of BFA, ACC and ACL and the effects of initial pH (pH0), contact time and initial dye concentration on adsorption. The pH0 of the dye solution strongly affected the chemistry of both the dye molecules and BFA in an aqueous solution. The effective pH0 was 7.0 for adsorption on BFA. Kinetic studies showed that the adsorption of CR on all the adsorbents was a gradual process. Equilibrium reached in about 4 h contact time. Optimum BFA, ACC and ACL dosages were found to be 1, 20 and 2 g l−1, respectively. CR uptake by the adsorbents followed pseudo-second-order kinetics. Equilibrium isotherms for the adsorption of CR on BFA, ACC and ACL were analysed by the Freundlich, Langmuir, Redlich–Peterson, and Temkin isotherm equations. Error analysis showed that the R–P isotherm best-fits the CR adsorption isotherm data on all adsorbents. The Freundlich isotherm also shows comparable fit. Thermodynamics showed that the adsorption of CR on BFA was most favourable in comparison to activated carbons.
Keywords: Dye removal; Bagasse fly ash; BFA; Congo red; CR; Adsorption kinetics; Isotherms; Error analyses;

In the present study, a hydrophilic bifunctional polymeric resin (LS-2) with sulfonic groups was synthesized, and the adsorption performance of three aniline compounds, aniline, 4-methylaniline, and 4-nitroaniline onto LS-2 was compared with that on the commercial Amberlite XAD-4. The uptake of the aniline compounds on LS-2 is a procedure of coexistence of physisorption and chemisorption and obeys the pseudo-second order rate equation, while the uptake of the compounds on XAD-4 is merely a physical adsorption and follows the pseudo-first order rate equation. All the isothermal data fit well with the Freundlich model, and the values of K F of the compounds adsorbing on LS-2 are much higher than those on XAD-4 suggesting the higher adsorbing capacities on LS-2 than those on XAD-4, which may be attributed to the microporous structure and the polar groups on the network of LS-2 resin. Dynamic adsorption and desorption studies for aniline on LS-2 show that the breakthrough adsorption capacity and the total adsorption capacity are 0.96 and 1.24 mmol per milliliter resin, respectively. Nearly 100% regeneration efficiency for the adsorbent was achieved by 5% hydrochloric acid.
Keywords: Adsorption; Bifunctional polymeric adsorbent; Aniline; Kinetics; Coexistence;

The potential of loofa sponge discs to immobilize fungal biomass of Phanerochaete chrysosporium (a known biosorbent) was investigated as a low cost biosorbent for the removal of Cd(II) ions from aqueous solution. A comparison of the biosorption of Cd(II) by immobilized and free fungal biomass from 10 to 500 mg l−1 aqueous solutions showed an increase in uptake of over 19% when the biomass is immobilized (maximum biosorption capacity of 89 and 74 mg Cd(II) g−1 biomass for immobilized and free biomass respectively at a solution pH of 6). Equilibrium was established within 1 h and biosorption was well defined by the Langmuir isotherm model. The immobilized biomass could be regenerated using 50 mM HCl, with up to 99% metal recovery and reused in ten biosorption–desorption cycles without significant loss of capacity. This study suggests that such an immobilized biosorbent system has the potential to be used in the industrial removal/recovery of cadmium and other pollutant metal ions from aqueous solution.
Keywords: Immobilization; Biosorption; Cadmium; Loofa sponge; Phanerochaete chrysosporium; Fixed-bed bioreactor;

Electrokinetic remediation of a Cu–Zn contaminated red soil by controlling the voltage and conditioning catholyte pH by Dong-Mei Zhou; Chang-Fen Deng; Long Cang; Akram N. Alshawabkeh (519-527).
Electrokinetics is an innovative technique for treating heavy metals contaminated soil, especially low pH soils such as the Chinese red soil (Udic Ferrisols). In this paper, a Cu–Zn contaminated red soil is treated by electrokinetics. When the Cu–Zn contaminated red soil was treated without control of catholyte pH during the electrokinetic treatment, the soil pH in the soil sections near cathode after the experiment was high above 6, which resulted in accumulation of large amounts of Cu and Zn in the soil sections with such high pH values. Compared to soil Cu, soil Zn was more efficiently removed from the soil by a controlled electrokinetic method. Application of lactic acid as catholyte pH conditioning solution caused an efficient removal of Cu and Zn from the soil. Increasing the electrolyte strength (salt concentration) of the conditioning solution further increased Cu removal, but did not cause a significant improvement for soil Zn. Soil Cu and Zn fractions after the electrokinetic treatments were analyzed using sequential extraction method, which indicated that Cu and Zn precipitation in the soil section closest to the cathode in the treatments without catholyte pH control limited their removal from the soil column. When the catholyte pH was controlled by lactic acid and CaCl2, the soil Cu and Zn removal percentage after 554 h running reached 63% and 65%, respectively. Moreover, both the residual soil Cu and Zn concentrations were lower than 100 mg kg−1, which is adequate and meets the requirement of the Chinese soil environmental quality standards.
Keywords: Red soil; Electrokinetic remediation; Cu; Zn; Lactic acid; Enhancing reagents;

Anaerobic degradation of hexachlorocyclohexane isomers in liquid and soil slurry systems by Juan Carlos Quintero; Maria Teresa Moreira; Gumersindo Feijoo; Juan M. Lema (528-536).
Gamma-hexachlorocyclohexane (γ-HCH or lindane), one of the most commonly used insecticides, has been mainly used in agriculture. Organochloride compounds are known to be highly toxic and persistent, causing serious water and soil pollution. The objective of the present study is the evaluation of the anaerobic degradation of α-, β-, γ-, δ-HCH in liquid and slurry cultures. The slurry system with anaerobic sludge appears as an effective alternative in the detoxification of polluted soils with HCH, as total degradation of the four isomers was attained. While α- and γ-HCH disappeared after 20–40 d, the most recalcitrant isomers: β- and δ-HCH were only degraded after 102 d. Intermediate metabolites of HCH degradation as pentachlorocyclohexane (PCCH), tetrachlorocyclohexene (TCCH), tri-, di- and mono-chlorobenzenes were observed during degradation time.
Keywords: HCH; Anaerobic sludge; Biodegradation metabolic pathway; Soil slurry treatment;

A study of the preparation and reactivity of potassium ferrate by C. Li; X.Z. Li; N. Graham (537-543).
In the context of water treatment, the ferrate ([FeO4]2−) ion has long been known for its strong oxidizing power and for producing a coagulant from its reduced form (i.e. Fe(III)). However, it has not been studied extensively owing to difficulties with its preparation and its instability in water. This paper describes an improved procedure for preparing solid phase potassium ferrate of high purity (99%) and with a high yield (50–70%). The characteristics of solid potassium ferrate were investigated and from XRD spectra it was found that samples of the solid have a tetrahedral structure with a space group of D2h (Pnma) and a  = 7.705 Å, b  = 5.863 Å, and c  = 10.36 Å. The aqueous stability of potassium ferrate at various pH values and different concentrations was investigated. It was found that potassium ferrate solution had a maximum stability at pH 9–10 and that ferrate solution at low concentration (0.25 mM) was more stable than at high concentration (0.51 mM). The aqueous reaction of ferrate with bisphenol A (BPA), a known endocrine disrupter compound, was also investigated with a molar ratio of Fe(VI):BPA in the range of 1:1–5:1. The optimal pH for BPA degradation was 9.4, and at this pH and a Fe(VI):BPA molar ratio of 5:1, approximately 90% of the BPA was degraded after 60 s.
Keywords: Bisphenol A; BPA; Endocrine disruptor; Fe(VI); Potassium ferrate; Preparation method;

This study demonstrates that both synthetic and natural endocrine disrupting chemicals (EDCs) (e.g., bisphenol A, estrone and 17β-estradiol) were found in the crude wastewaters from two wastewater treatment works (WwTWs). Conventional biological processes can lower EDCs concentrations to several tens to hundreds ng l−1. Since natural EDCs (e.g., estrone and 17β-estradiol) have biological activity and adverse impact on the environment at extremely low concentrations (several tens of ng l−1), further treatment after conventional biological processes is required. Preliminary trials with ferrate(VI) and electrochemical oxidation process demonstrated that both processes can effectively reduce EDCs to very low levels, ranging between 10 and 100 ng l−1, but the former is more effective than the latter to reduce COD concentration in wastewater for given studying conditions.
Keywords: EDCs; Wastewater treatment; Ferrate(VI); Electrochemical oxidation;

Degradation of volatile organic compounds with thermally activated persulfate oxidation by Kun-Chang Huang; Zhiqiang Zhao; George E. Hoag; Amine Dahmani; Philip A. Block (551-560).
This study investigated the extent and treatability of the degradation of 59 volatile organic compounds (VOCs) listed in the EPA SW-846 Method 8260B with thermally activated persulfate oxidation. Data on the degradation of the 59 VOCs (in mixture) reacted with sodium persulfate in concentrations of 1 g l−1 and 5 g l−1 and at temperatures of 20 °C, 30 °C, and 40 °C were obtained. The results indicate that persulfate oxidation mechanisms are effective in degrading many VOCs including chlorinated ethenes (CEs), BTEXs and trichloroethanes that are frequently detected in the subsurface at contaminated sites. Most of the targeted VOCs were rapidly degraded under the experimental conditions while some showed persistence to the persulfate oxidation. Compounds with “C=C” bonds or with benzene rings bonded to reactive functional groups were readily degraded. Saturated hydrocarbons and halogenated alkanes were much more stable and difficult to degrade. For those highly persulfate-degradable VOCs, degradation was well fitted with a pseudo first-order decay model. Activation energies of reactions of CEs and BTEXs with persulfate were determined. The degradation rates increased with increasing reaction temperature and oxidant concentration. Nevertheless, to achieve complete degradation of persulfate-degradable compounds, the systems required sufficient amounts of persulfate to sustain the degradation reaction.
Keywords: VOCs; Persulfate; Chemical oxidation; Kinetics; Trichloroethene; 1,1,1-Trichloroethane;

Remediation of soil pollution is one of the many current environmental challenges. Anthropogenic activity has resulted in the contamination of extended areas of land, the remediation of which is both invasive and expensive by conventional means. Phytoextraction of heavy metals from contaminated soils has the prospect of being a more economic in situ alternative. In addition, phytoextraction targets ecotoxicologically the most relevant soil fraction of these metals, i.e. the bioavailable fraction. Greenhouse experiments were carried out to evaluate the potential of four high biomass crop species in their potential for phytoextraction of heavy metals, with or without with the use of soil amendments (EDTA or EDDS). A calcareous dredged sediment derived surface soil, with high organic matter and clay content and moderate levels of heavy metal pollution, was used in the experiments. No growth depression was observed in EDTA or EDDS treated pots in comparison to untreated controls. Metal accumulation was considered to be low for phytoextraction purposes, despite the use of chelating agents. The low observed shoot concentrations of heavy metals were attributed to the low phytoavailability of heavy metals in this particular soil substrate. The mobilising effects induced by EDTA in the soil were found to be too long-lived for application as a soil amendment in phytoextraction. Although EDDS was found to be more biodegradable, higher effect half lives were observed than reported in literature or observed in previous experiments. These findings caution against the use of any amendment, biodegradable or otherwise, without proper investigation of its effects and the longevity thereof.
Keywords: Phytoextraction; Brassica rapa; Cannabis sativa; Helianthus annuus; Zea mays; Heavy metals; EDDS; EDTA;

Catalytic wet oxidation of ammonia: Why is N2 formed preferentially against NO 3 - ? by Deuk Ki Lee; Jeong Shik Cho; Wang Lai Yoon (573-578).
The role of catalyst and the reason for the preferential formation of N2 in the catalytic oxidation reaction of ammonia in water over a Ru (3 wt.%)/TiO2 catalyst were elucidated. It was verified that the catalyst in the reaction had no direct relevance to the selective formation of N2, but was responsible only for the oxidation of aqueous ammonia, NH3(aq), finally giving a molecule of nitrous acid. The preferential production of N2 was experimentally demonstrated due to the homogeneous aqueous phase reaction of the nitrous acid-dissociated NO 2 - with NH 4 + ions. Even under the highly oxidizing condition, NO 2 - was much more likely to react with NH 4 + to form N2 than being oxidized over the catalyst to NO 3 - as long as NH 4 + was available in solution.
Keywords: Reaction pathway; Preferential or selective formation of nitrogen; Ammonium and nitrite ions; Catalytic wet oxidation; Ammonia;

A poly-aluminum-chloride-sulfate (PACS) was prepared at various experimental conditions. It was found that the coagulation performance of PACS in water treatment was affected by the PACS particle size distribution and zeta potential value. The experimental results indicated that the PACS particle size distribution and zeta potential value were highly influenced by SO 4 2 - / Al 3 + molar ratio and bacicities (γ,  γ  = [OH]/[Al]) value. At a fixed γ value of 2.0, the average PACS particle size increased from 25 to 80 nm with the increase of SO 4 2 - / Al 3 + ratio from 0 to 0.1. Further increase of the SO 4 2 - / Al 3 + ratio resulted in acute increment particle size of PACS extremely, which can be attributed to its aggregation. At a fixed SO 4 2 - / Al 3 + ratio of 0.0664, the largest average size of PACS occurred at γ  = 2.0. It was also found that the zeta potential value of PACS was strongly influenced by the SO 4 2 - / Al 3 + ratio, γ value and pH of the aquatic solution. The zeta potential value of PACS increased with increasing of SO 4 2 - / Al 3 + ratio. At a fixed SO 4 2 - / Al 3 + ratio of 0.0664, PACS achieved greatest zeta potential value at γ value of around 2.0. The maximum positive zeta potential value of PACS was found at pH 5.3. At a fixed γ value of 2.0 and SO 4 2 - / Al 3 + ratio of 0.0664, the PACS achieved an optimum natural organic matter and turbidity removal efficiency.
Keywords: Particle size; Zeta potential; Coagulation; NOM and turbidity removal;

Dissolution studies on TiO2 with organics by Amitava Mukherjee; Ashok M. Raichur; Jayant M. Modak (585-588).
In this work the effect of organic reducing reagents, namely, ascorbic acid, oxalic acid and l-cysteine on dissolution of commercial TiO2 has been investigated. Kinetic studies showed that a maximum of about 45% of TiO2 was dissolved by ascorbic acid in 4 h when oxide:acid molar ratio was kept at 1:2. The dissolution of TiO2 increased with increase in ascorbic acid and oxalic acid concentration up to 0.15 M in 4 h (corresponding to molar ratio of oxide to acid of 1:3) and further addition did not affect the dissolution. Nearly 45% TiO2 dissolution was obtained with ascorbic acid alone while oxalic acid yielded 40% dissolution. When oxalic acid was added along with ascorbic acid in equi-molar concentrations, dissolution of TiO2 was enhanced to 60% in 2.5 h but when cysteine was added to ascorbic acid the dissolution was about 50% in just 1 h.
Keywords: Reductant; Ascorbic acid; Oxalic acid; Cysteine;

Photocatalytic degradation of p-nitrophenol on nanometer size titanium dioxide surface modified with 5-sulfosalicylic acid by Shun-xing Li; Feng-ying Zheng; Xian-li Liu; Feng Wu; Nan-sheng Deng; Jian-hong Yang (589-594).
The surface of nanometer size TiO2 was simply and fast modified by chemical adsorption in saturated solution of 5-sulfosalicylic acid. After surface modification, a stable, yellow surface complex was formed quickly, the wavelength response range of TiO2 was expanded, it has obvious absorption in the region from 320 to 450 nm; the adsorption efficiency of p-nitrophenol (PNP) by TiO2 was enhanced from 42% to 84%. The photocatalytic activity was tested on the degradation of PNP. The influences of catalyst and its dosage, pH value, and PNP concentration on the degradation were investigated. On optimal photodegradation conditions, including initial pH 4.0, PNP 5 mg l−1, catalyst 100 mg, irradiation time 120 min with 160 W high-pressure mercury lamp, the degradation efficiency of PNP was increased from 40% to 88% after surface modification. Surface modification led not only to an increase in the light utilization, but also improved the surface coverage of PNP in comparison with the pure TiO2. Both of these factors are crucial for the photocatalytic activity of heterogeneous photocatalysis, especially for photodegradation of benzenoid pollutants.
Keywords: Titanium dioxide; Photodegradation; Surface modification; 5-sulfosalicylic acid; Nitrophenol;

Enhancement of lead uptake by alfalfa (Medicago sativa) using EDTA and a plant growth promoter by Martha L. López; Jose R. Peralta-Videa; Tenoch Benitez; Jorge L. Gardea-Torresdey (595-598).
Phytoremediation is a novel cleanup technology for the removal of contaminants from polluted waters and soils. In phytoremediation, the plant uptake capability and the availability of the pollutant in the media are important. Here we show the results of a study on the combined effects of ethylenediaminetetraacetic acid (EDTA) and the phytohormone indole-3-acetic acid (IAA) on Pb uptake by Medicago sativa (alfalfa). Plants were grown in hydroponics media containing a nutrient solution amended with Pb at 0.2 mM and different combinations of EDTA, and IAA. After 10 d of treatment, the Pb content in plant tissues was quantified using an Inductively Coupled Plasma Optical Emission Spectrometer (ICP/OES). The results showed that the combination of 100 μM IAA/0.2 mM EDTA increased the Pb accumulation in leaves by about 2800% and by about 600%, as compared to Pb content in leaves of plants exposed to Pb alone and those cultivated with Pb/EDTA, respectively. These results indicate that non-metal hyperaccumulator plants could increase their hyperaccumulating potential without genetic manipulation.
Keywords: Phytoremediation; Lead; Plant hormone; Indole acetic acid; Auxin;