Double‐functional characteristics of a surface molecular imprinted adsorbent with immobilization of nano‐TiO2

A new chitosan molecular imprinted adsorbent obtained by immobilization of nano‐TiO₂ on the adsorbent surface (surface‐imprinted adsorbent with nano‐TiO₂) was prepared. Based on photocatalytic reaction and the surface molecular imprinting technology, this new kind of surface‐imprinted adsorbent with immobilization of nano‐TiO₂ can not only adsorb template metal ions but can also degrade organic pollutants. The results showed that, after the nano‐TiO₂ was immobilized on the adsorbent surface, the adsorption ability for the imprinted ion (Ni²⁺) of this new imprinted adsorbent immobilized with nano‐TiO₂ was not affected, but the degradation ability for p‐nitrophenol (PNP) of the surface‐imprinted adsorbent with nano‐TiO₂ increased three‐fold compared with that of the surface‐imprinted adsorbent without nano‐TiO₂, from 23.8 to 76.1% (at an initial PNP concentration of 20 mg·dm^?3). The optimal TiO₂ concentration in the adsorbent preparation was 0.025 g·TiO₂ g^?1 adsorbent. The removal capacity for PNP reached 60.25 mg·g^?1 (at 400 mg·dm^?3 initial PNP concentration) under UV irradiation. The surface‐imprinted adsorbent with nano‐TiO₂ can be reused for at least five cycles without decreasing the removal ability for PNP and the imprinted ion (Ni²⁺). Copyright © 2006 Society of Chemical Industry     

Removal of organic contaminants in paper pulp effluents by AOPs: an economic study

The degradation of the organic content of a bleaching Kraft mill effluent was carried out using Advanced Oxidation Processes (AOPs). The study was focused on the identification of the AOP, or combination of AOPs, that showed the highest efficiency together with the lowest cost. Direct UV photolysis (UV), TiO₂ assisted‐photocatalysis (TiO₂/UV), Fenton, Fenton‐like, and photo‐Fenton reactions (Fe(II)/H₂O/UV), UV‐assisted ozonation (O₃/UV) and addition of Fe²⁺ and/or H₂O₂ to the TiO₂/UV and the O₃/UV systems, were used for the degradation of a conventional cellulose bleaching effluent. The effluent was characterized by the general parameters TOC, COD and color, and analyzed for chlorinated low molecular weight compounds using GC–MS. The costs of the systems per unit of TOC reduction were compared. Fenton, Fenton‐like and photo‐Fenton reactions achieved better levels of TOC degradation than photocatalysis and with lower cost's than photocatalytic treatments. Ozonation is an effective but rather expensive process. The use of UVA light, however, increased the effectiveness of ozonation with a significant decrease (>25%) in the operational cost. © 2002 Society of Chemical Industry     

Mineralisation of the antibiotic amoxicillin in pure and surface waters by artificial UVA‐ and sunlight‐induced Fenton oxidation

BACKGROUND: The degradation and mineralisation of the antibiotic amoxicillin by photo‐Fenton reactions, mediated by artificial UVA or solar irradiation, were investigated. Experiments were conducted with 30 mg L^?1 amoxicillin solutions prepared with deionised or surface water at Fe²⁺ and H₂O₂ concentrations in the range 0.0179–0.0895 and 1–10 mmol L^?1, respectively. Black‐light irradiation at 365 nm was provided by a 13 W m^?2 lamp, while samples were exposed to sunlight at 20 W m^?2 for solar experiments. RESULTS: In all cases, quantitative amoxicillin degradation occurred within 5 min and this was accompanied by lower mineralisation rates. Mineralisation followed first‐order kinetics with respect to organic carbon content and it was not affected by the water matrix with either type of illumination. Solar‐induced reactions were only marginally faster than artificial irradiation. Increasing the H₂O₂ to Fe²⁺ concentration ratio increases the extent of mineralisation up to a point beyond which degradation is impeded due to radical scavenging associated with the high concentrations of the Fenton reagents. CONCLUSION: Amoxicillin is readily degradable by homogeneous photocatalysis, being converted to more stable intermediates as indicated by lower mineralisation rates. The process can be driven by solar irradiation, thus providing a sustainable treatment technology. Copyright © 2009 Society of Chemical Industry     

Peracetic acid‐enhanced photocatalytic and sonophotocatalytic inactivation of E. coli in aqueous suspensions

BACKGROUND: Although chlorination is an effective and widely employed method of water disinfection, it suffers serious drawbacks such as the formation of toxic chlorinated by‐products. Therefore, other disinfection technologies have been researched and developed, including advanced oxidation. RESULTS: The efficacy of heterogeneous photocatalysis and sonophotocatalysis induced by UV‐A irradiation and low frequency (24–80 kHz) ultrasound irradiation in the presence of TiO₂ as the photocatalyst and peracetic acid (PAA) as an additional disinfectant to inactivate E. coli in sterile water was evaluated. PAA‐assisted UV‐A/TiO₂ photocatalysis generally leads to nearly complete E. coli inactivation in 10–20 min of contact time with the extent of inactivation depending on the photocatalyst type and loading (in the range 100–500 mg L^?1) and PAA concentration (in the range 0.5–2 mg L^?1). The simultaneous application of ultrasound and UV‐A irradiation in the presence of TiO₂ and PAA prompted further E. coli inactivation. CONCLUSIONS: The proposed advanced disinfection technology offers complete E. coli inactivation at short treatment times and low PAA doses. Copyright © 2010 Society of Chemical Industry     

Performance of a photo‐impinging streams reactor for the phenol degradation process

BACKGROUND: Photocatalysis is one of the advanced oxidation processes that has gained in importance over recent years owing to its ability to decompose a wide range of organic and inorganic pollutants at ambient temperature and pressure. However, there are two essential issues regarding photocatalytic processes, i.e. limitations on photon transfer and on mass transfer. In the present study, a novel photo‐impinging streams reactor, which can minimize such limitations, has been utilized in the photocatalytic degradation of phenol. The design and operating parameters such as type of nozzle, flow rate, catalyst loading, pH, initial phenol concentration and light intensity were found to have the expected impact on the efficiency of the process. The effects of two different co‐oxidants, H₂O₂ and Na₂S₂O₈ on the photocatalysis were also examined. RESULTS: Results indicated that 100 mg L^?1 of phenol in a 750 cm³ solution was completely degraded within 2.5 h reaction time in the presence of TiO₂ without a co‐oxidant present; and within 1 h in the presence of a co‐oxidant. CONCLUSION: A comparison between the current data and those available in the literature revealed higher efficiency and increased performance of the present reactor relative to conventional apparatus. Copyright © 2010 Society of Chemical Industry     

Highly stable Fe/γ‐Al2O3 catalyst for catalytic wet peroxide oxidation

BACKGROUND: A highly stable Fe/γ‐Al₂O₃ catalyst for catalytic wet peroxide oxidation has been studied using phenol as target pollutant. The catalyst was prepared by incipient wetness impregnation of γ‐Al₂O₃ with an aqueous solution of Fe(NO₃)₃· 9H₂O. The influence of pH, temperature, catalyst and H₂O₂ doses, as well as the initial phenol concentration has been analyzed. RESULTS: The reaction temperature and initial pH significantly affect both phenol conversion and total organic carbon removal. Working at 50 °C, an initial pH of 3, 100 mg L^?1 of phenol, a dose of H₂O₂ corresponding to the stoichiometric amount and 1250 mg L^?1 of catalyst, complete phenol conversion and a total organic carbon removal efficiency close to 80% were achieved. When the initial phenol concentration was increased to 1500 mg L^?1, a decreased efficiency in total organic carbon removal was observed with increased leaching of iron that can be related to a higher concentration of oxalic acid, as by‐product from catalytic wet peroxide oxidation of phenol. CONCLUSION: A laboratory synthesized γ‐Al₂O₃ supported Fe has shown potential application in catalytic wet peroxide oxidation of phenolic wastewaters. The catalyst showed remarkable stability in long‐term continuous experiments with limited Fe leaching, < 3% of the initial loading. Copyright © 2010 Society of Chemical Industry     

Effect of pre‐treatments based on UV photocatalysis and photo‐oxidation on toluene biofiltration performance

BACKGROUND: The integration of UV photocatalysis and biofiltration seems to be a promising combination of technologies for the removal of hydrophobic and poorly biodegradable air pollutants. The influence of pre‐treatments based on UV_{254 nm} photocatalysis and photo‐oxidation on the biofiltration of toluene as a target compound was evaluated in a controlled long‐term experimental study using different system configurations: a standalone biofilter, a combined UV photocatalytic reactor‐biofilter, and a combined UV photo‐oxidation reactor (without catalyst)‐biofilter. RESULTS: Under the operational conditions used (residence time of 2.7 s and toluene concentrations 600–1200 mg C m^?3), relatively low removal efficiencies (6–3%) were reached in the photocatalytic reactor and no degradation of toluene was found when the photo‐oxidation reactor was operated without catalyst. A noticeable improvement in the performance of the biofilter combined with a photocatalytic reactor was observed, and the elimination capacity of the biological process increased by more than 12 g C h^?1 m^?3 at the inlet loads studied of 50–100 g C h^?1 m^?3. No positive effect on toluene removal was observed for the combination of UV photoreactor and biofilter. CONCLUSIONS: Biofilter pre‐treatment based on UV_{254 nm} photocatalysis showed promising results for the removal of hydrophobic and recalcitrant air pollutants, providing synergistic improvement in the removal of toluene. Copyright © 2011 Society of Chemical Industry     

Immobilized titanium dioxide/powdered activated carbon system for the photocatalytic adsorptive removal of phenol

Titanium dioxide (TiO₂) and powdered activated carbon (PAC) were fabricated via a layer by layer arrangement on a glass plate using a dip-coating technique for the photocatalytic-adsorptive removal of phenol. Thinner TiO₂ layer coated on PAC sub-layer has larger surface area and better phenol removal than the thicker TiO₂ layer. The system obeyed the Langmuir isotherm model, which exhibited a homogeneous and monolayer adsorption with a maximum capacity of 27.8 mg g^-1. The intra-particle diffusion was the rate-limiting step as the linear plot crossed the origin, while the adsorption was unfavorable at elevated temperature. Under light irradiation, the TiO₂/PAC system removed phenol two-times more effectively than the TiO₂ monolayer due to the synergistic effect of photocatalysis by TiO₂ top layer and adsorption by PAC sub-layer. The COD removal of phenol was rapid for 10mg L^-1 of concentration and under solar light irradiation. It was shown that the PAC sub-layer plays a significant role in the total removal of phenol by providing the adsorption sites and slowing down the recombination rate of charge carriers to improve the TiO₂ photocatalytic oxidation performance.     

Degradation and Transformation of Organic Compounds in Songhua River Water by Catalytic Ozonation in the Presence of TiO2/Zeolite

This paper presents experimental results of the catalytic ozonation of Songhua River water in the presence of nano-TiO₂ supported on Zeolite. The removal efficiency of TOC and UV₂₅₄, the variation of AOC and molecular weight distribution of organics was studied. Results showed that TOC and UV₂₅₄ removal efficiency by ozone was improved in the presence of TiO₂/Zeolite, and increased by 20% and 25%, respectively. The part of organic compounds less than 1000 Da increased in ozonation, but decreased in catalytic ozonation. The AOC of water increased in catalytic ozonation, and the increase of AOC was particularly obvious when ozone dose increased from 28.8 mg·L^?1 to 46.6 mg·L^?1. The degradation and transformation of organic compounds was analyzed by means of GC-MS. The total number of organic compounds was reduced from 50 in the untreated water to 36 and 20, respectively, in ozonation and catalytic ozonation. The removal efficiency of the total organic compounds peak area in ozonation and catalytic ozonation were 23.5% and 62.5%, respectively. Most of the hydrocarbons could be removed easily in ozonation and catalytic ozonation. The organic compounds having hydroxyl, carboxyl or carbonyl groups were hard to be removed in ozonation, but could be removed efficiently in the presence of TiO₂/Zeolite.     

Performance of the hydrolyzation film bed and biological aerated filter (HFB–BAF) combined system for the treatment of low‐concentration domestic sewage in south China

The performance of the hydrolyzation film bed and biological aerated filter (HFB–BAF) combined system in pilot scale (with a daily treatment quantity of 600–1300 m³ d^?1), operated for 234 days, for low‐strength domestic sewage was assessed using different amounts of aeration, reflux ratios and hydraulic loading rates (HLR). In steady state it was found that the average removal efficiency of chemical oxygen demand (COD) and biological oxygen demand at 5 days (BOD₅) were 82.0% and 82.2% and the average effluent concentrations were 15.8 mg L^?1 and 9.4 mg L^?1 respectively as the HFB was running at an HLR of 1.25–1.77 m³ m^?2 h^?1 and the BAF was running at an HLR of 1.56–2.21 m³ m^?2 h^?1. In general, the removal efficiency of total nitrogen (TN) fluctuated with the HLR, gas–water ratio and reflux ratio, so the ratio of gas to water should be controlled from 2:1 to 3:1 and the reflux ratio should be as high as possible. The effluent concentration of TN was 10.4 mg L^?1 and the TN removal averaged 34.3% when the gas–water ratio was greater than 3:1 and the reflux ratio was 0.5. The effluent concentration and removal efficiency of NH₄⁺‐N averaged respectively 2.3 mg L^?1 and 78.5%. The overall reduction of total phosphorus (TP) was 30% and the average effluent concentration was 0.95 mg L^?1. The removal efficiency of linear alkylbenzene sulfonates (LAS) reached 83.8% and the average effluent concentration was almost 0.9 mg L^?1. The effluent concentration and removal efficiency of polychlorinated biphenyls (PCBs) were 0.0654 µ g L^?1 and 37.05% respectively when the influent concentration was 0.1039 µ g L^?1. The excess sludge containing water (volume 15 m³) was discharged once every 3 months. The power consumption of aeration was 0.06–0.09 kWh of sewage treated. The results show that the HFB–BAF combined technology is suitable for the treatment of low‐concentration municipal sewage in south China. Copyright © 2005 Society of Chemical Industry     

生物活性滤池饮用水除氨氮的影响因素

以实际沉淀池出水进行配水,通过模型实验,探讨了生物活性滤池（BAF）除氨氮的影响因素及作用机理。结果表明,滤前水中有机物含量和滤料粒径对BAF除氨氮能力影响较大。当采用沉淀池出水中自身携带的有机物时,BAF-1除氨氮效率为97%;当沉淀池出水中另配入2 mg·L^-1牛肉膏+2 mg·L^-1蛋白胨+2 mg·L^-1葡萄糖时,由于受到异养菌对溶解氧和生存空间竞争的限制,其除氨氮效率下降至51.0%。活性炭粒径采用0.8～1.2 mm的BAF-1氨氮去除率比采用1.0～2.0 mm的BAF-2高1.5%～16.7%。当滤前水氨氮浓度低于1.60 mg·L^-1时,BAF-1的氨氮去除率接近100%;当氨氮浓度逐渐升高时,由于受到溶解氧的限制,去除率逐渐下降。对滤前水进行预曝气充氧,能提高BAF-1的除氨氮效率。滤速对BAF-1除氨氮影响不显著。反冲洗可适当提高BAF-1的除氨氮效率。     

Photocatalytic oxidation of treated municipal wastewaters for the removal of phenolic compounds: optimization and modeling using response surface methodology (RSM) and artificial neural networks (ANNs)

BACKGROUND: TiO₂ heterogeneous photocatalysis should be optimized before application for the removal of pollutants in treated wastewaters. The response surface methodology (RSM) and artificial neural networks (ANNs) were applied to model and optimize the photocatalytic degradation of total phenolic (TPh) compounds in real secondary and tertiary treated municipal wastewaters. RESULTS: RSM was developed by considering a central composite design (CCD) with three input variables, i.e. TiO₂ mass, initial concentration of TPh and irradiation intensity. At the same time a feed‐forward multilayered perceptron ANN trained using back propagation algorithms was used and compared with RSM. Under the optimum conditions established in experiments ([TPh]₀ = 3 mg L^?1; [TiO₂] = 300 mg L^?1; I = 600 W m^?2) the degradation for both TPh and total organic carbon (TOC) followed pseudo‐first‐order kinetic model. Complete degradation of TPh took place in 180 min and reduction of TOC reached 80%. A significant abatement of the overall toxicity was accomplished as revealed by Microtox bioassay. CONCLUSIONS: It was found that the variables considered have important effects on TPh removal efficiency. The results demonstrated that the use of experimental design strategy is indispensable for successful investigation and adequate modeling of the process and that ANNs gave better modelling capability than RSM. Copyright © 2012 Society of Chemical Industry     

Regression model,artificial intelligence,and cost estimation for phosphate adsorption using encapsulated nanoscale zero-valent iron

This study investigated the adsorption of PO₄^3? onto encapsulated nanoscale zero-valent iron (nZVI). At initial PO₄^3–: 10 mg · L^?1, the optimum condition was initial pH: 6.5, nZVI dosage: 20 g · L^?1, stirring-rate: 100 rpm, and time: 30 min, achieving PO₄^3? removal of 42%. The effect of pH and time on the PO₄^3? removal efficiency was quadratic-linear concave up, whereas the curve of nZVI dosage was quadratic-convex. Artificial neural network with a structure of 5?7?1 adequately predicted PO₄^3? removal (R²: 97.6%), and the sensitivity analysis demonstrated that pH was the most influential input. The cost of the adsorption unit was 3.15 $USD · m^?3.     

Removal of 4‐chlorophenol from contaminated water using coconut shell waste pretreated with chemical agents

BACKGROUND: At concentrations higher than 1 mg L^?1, 4‐chlorophenol (4‐CP) is very toxic to living organisms, and if ingested beyond the permitted concentration it causes health disorders such as cancer and mutation. This laboratory study investigates treatment of contaminated water laden with 4‐CP using coconut shell charcoal (CSC) waste. Batch studies were conducted to study the effects of dose, pH, and equilibrium time on 4‐CP removal. To improve 4‐CP removal, surface modification of the adsorbent with TiO₂, HNO₃, and/or NaOH was undertaken. RESULTS: At an initial 4‐CP concentration of 25 mg L^?1 under optimized conditions (dose 13.5 g L^?1, pH 2.0; agitation speed 150 rpm and 50 min equilibrium time), the NaOH‐treated CSC demonstrated a greater removal of 4‐CP (71%) than those oxidized with HNO₃ (40%) and/or coated with TiO₂ (52%). The adsorption capacity of the NaOH‐treated CSC (54.65 mg g^?1) was higher than those treated with HNO₃ (23.13 mg g^?1) or coated with TiO₂ (48.42 mg g^?1). CONCLUSION: Although treatment results using the NaOH‐treated CSC alone were promising, the treated effluents were still unable to meet the required limit of less than 1 mg L^?1. Therefore, subsequent treatments are still required to complement the removal of 4‐CP from the wastewater. Copyright © 2010 Society of Chemical Industry     

Photo‐reduction and adsorption in aqueous Cr(VI) solution by titanium dioxide,carbon nanotubes and their composite

BACKGROUND: This study compared the removal of aqueous Cr(VI) by multi‐walled carbon nanotubes (CNTs) modified by sulfuric acid, titanium dioxide (TiO₂) and composite of CNTs and TiO₂. RESULTS: More than 360 h contact time was needed to completely adsorb 3 mg L^?1 of Cr(VI) by CNTs, indicating that the rate of adsorption by CNTs alone was slow. The reaction time approaching equilibrium depended on the Cr(VI) concentration. XPS analysis of CNTs after adsorbing Cr(VI) showed that the Cr(VI) on the surface of CNTs was partially reduced to Cr(III). A 3 mg L^?1 solution of Cr(VI) was fully photocatalyzed by commercial TiO₂ (Degussa P25) in less than 0.5 h under UV irradiation. Unlike P25, reduction by another commercial TiO₂ (Hombikat UV100) took 4 h and more than 2 h were necessary for reduction by the composite. Thus the efficiency of Cr(VI) photo‐reduction by the composite was lower than by TiO₂, but higher than that by CNTs. XPS analysis of TiO₂ and composite showed the existence of both Cr(VI) and Cr(III) on their surfaces. CONCLUSION: In contrast to TiO₂, the reduction rate of aqueous Cr(VI) using CNTs as adsorbent was slow. P25 had a markedly higher photocatalytic efficiency than the composite or UV100 alone. Using P25 to reduce aqueous Cr(VI) has a higher potential for practical application. The diameters of TiO₂ and CNTs and the ratio of TiO₂/CNTs are key problems in the preparation of TiO₂/CNTs composite. Copyright © 2011 Society of Chemical Industry     

Treatment of paper and pulp wastewater and removal of odorous compounds by a Fenton‐like process at the pilot scale

A Fenton‐like process, involving oxidation and coagulation, was evaluated for the removal of odorous compounds and treatment of a pulp and paper wastewater. The main parameters that govern the complex reactive system [pH and Fe(III) and hydrogen peroxide concentrations] were studied. Concentrations of Fe(III) between 100 and 1000 mg L^?1 and of H₂O₂ between 0 and 2000 mg L^?1 were chosen. The main mechanism for color removal was coagulation. The maximum COD, color and aromatic compound removals were 75, 98 and 95%, respectively, under optimal operating conditions ([Fe(III)] = 400 mg L^?1; [H₂O₂] = 500–1000 mg L^?1; pH = 2.5; followed by coagulation at pH 5.0). The biodegradability of the wastewater treated increased from 0.4 to 0.7 under optimal conditions and no residual hydrogen peroxide was found after treatment. However, partially or non‐oxidized compounds present in the treated wastewater presented higher acute toxicity to Artemia salina than the untreated wastewater. Based on the optimum conditions, pilot‐scale experiments were conducted and revealed a high efficiency in relation to the mineralization of organic compounds. Terpenes [(1S)‐α‐pinene, β‐pinene, (1R)‐α‐pinene and limonene] were identified in the wastewater and were completely eliminated by the Fenton‐like treatment. Copyright © 2006 Society of Chemical Industry     

The generation of hydroxyl radicals by hydrogen peroxide decomposition on FeOCl/SBA‐15 catalysts for phenol degradation

Iron oxychloride (FeOCl) supported on mesoporous silica (SBA‐15), as a Fenton‐like solid catalyst for phenol degradation, showed supreme activity for production of hydroxyl radical (HO·) by H₂O₂ decomposition, and the generation capacity was comparable to the conventional Fenton reagent (Fe²⁺+H₂O₂). The structure of FeOCl was characterized with spectroscopies. The generation of HO· species during the reaction was detected using 5,5‐dimethyl‐1‐pyrroline N‐oxide trapped electron paramagnetic resonance. Furthermore, the kinetics in detail was driven for the creation and diffusion of HO· by H₂O₂ decomposition over FeOCl, which follows a first‐order rate through a two‐step reaction. With the combination of the catalyst structure and kinetic parameters, the plausible mechanism for H₂O₂ decomposition during the oxidative degradation of phenol was rationalized. As a Fenton‐like solid catalyst, FeOCl/SBA‐15 is a promising alternative for the removal of low‐level organic contaminates from water. © 2014 American Institute of Chemical Engineers AIChE J, 61: 166–176, 2015     

Photodegradation of four fluoroquinolone compounds by titanium dioxide under simulated solar light irradiation

BACKGROUND; In this study, simultaneous photocatalytic degradation of four fluoroquinolone (FQ) compounds (i.e. ofloxacin, norfloxacin, ciprofloxacin and enrofloxacin) was investigated in TiO₂ suspensions under simulated solar light irradiation. Effects of experimental variables including pH, TiO₂ dosage, initial substrate concentration and hydrogen peroxide (H₂O₂) on the degradation processes were also investigated. RESULTS: The antibiotics degradation was pH‐influenced. The photocatalytic reaction followed the pseudo‐first‐order model, with reaction rate constants (k) 0.026, 0.027, 0.022 and 0.026 min^?1 for ofloxacin, norfloxacin, ciprofloxacin and enrofloxacin, respectively. Complete elimination of four FQs was achieved in a reaction system composed of 0.5 g L^?1 of TiO₂ and 82.5 mg L^?1 of H₂O₂ at pH 6 after 90 min irradiation. Mineralization of FQs during TiO₂ photocatalysis was slower than the FQs conversion, and the antibacterial activity of the four FQs was completely removed by TiO₂ under simulated solar light irradiation. CONCLUSION: The four FQs can be simultaneously degraded and mineralized with commercially available TiO₂ under simulated solar light irradiation. Microbiological analysis showed that the antibacterial activity of the four FQs was completely removed. These results are helpful for antibiotics removal in the environment, and for exploring new technology for wastewater treatment. Copyright © 2012 Society of Chemical Industry     

2,4,6‐Trichlorophenol and phenol removal in methanogenic and partially‐aerated methanogenic conditions in a fluidized bed bioreactor

A fluidized bed bioreactor (FBBR) was operated for more than 575 days to remove 2,4,6‐trichlorophenol (TCP) and phenol (Phe) from a synthetic toxic wastewater containing 80 mg L^?1 of TCP and 20 mg L^?1 of Phe under two regimes: Methanogenic (M) and Partially‐Aerated Methanogenic (PAM). The mesophilic, laboratory‐scale FBBR consisted of a glass column (3 L capacity) loaded with 1 L of 1 mm diameter granular activated carbon colonized by an anaerobic consortium. Sucrose (1 g COD L^?1) was used as co‐substrate in the two conditions. The hydraulic residence time was kept constant at 1 day. Both conditions showed similar TCP and Phe removal (99.9 + %); nevertheless, in the Methanogenic regime, the accumulation of 4‐chlorophenol (4CP) up to 16 mg L^?1 and phenol up to 4 mg L^?1 was observed, whereas in PAM conditions 4CP and other intermediates were not detected. The specific methanogenic activity of biomass decreased from 1.01 ± 0.14 in M conditions to 0.19 ± 0.06 mmolCH₄ h^?1 gTKN^?1 in PAM conditions whereas the specific oxygen uptake rate increased from 0.039 ± 0.008 in M conditions to 0.054 ± 0.012 mmolO₂ h^?1 gTKN^?1, which suggested the co‐existence of both methanogenic archaea and aerobic bacteria in the undefined consortium. The advantage of the PAM condition over the M regime is that it provides for the thorough removal of less‐substituted chlorophenols produced by the reductive dehalogenation of TCP rather than the removal of the parent compound itself. Copyright © 2005 Society of Chemical Industry     

Removal of diazinon by various advanced oxidation processes

Diazinon is a widely used organophosphorus insecticide that is an important pollutant in aquatic environments. The chemical removal of diazinon has been studied using UV radiation, ozone, Fenton's reagent, UV radiation plus hydrogen peroxide, ozone plus hydrogen peroxide and photo‐Fenton as oxidation processes. In the photodegradation process the observed quantum yields had values ranging between 2.42 × 10^?2 and 6.36 × 10^?2 mol E^?1. Similarly, the ozonation reaction gave values for the rate constant ranging between 0.100 and 0.193 min^?1. In the combined systems UV/H₂O₂ and O₃/H₂O₂ the partial contributions to the global oxidation reaction of the direct and radical pathways were deduced. In the Fenton's reagent and photo‐Fenton systems, the mechanism of reaction has been partially discussed, and the predominant role of the radical pathway pointed out. Additionally, the rate constant for the reaction between diazinon and the hydroxyl radicals was determined, with the value 8.4 × 10⁹ L mol^?1 s^?1 obtained. A comparison of the different oxidation systems tested under the same operating conditions revealed that UV radiation alone had a moderate oxidation efficiency, which is enhanced in the case of ozone, while the most efficient oxidant is the photo‐Fenton system. Copyright © 2007 Society of Chemical Industry