Search

As the presence of antibiotics in environmental waters enhances antimicrobial resistance, photolysis and heterogeneous photocatalysis of chloramphenicol (CAP) were evaluated in deionized water (DW) and in sewage treatment plant (STP) effluent under black light and solar irradiation. Processes were compared in terms of CAP degradation, reaction kinetics, and electrical energy per order, as well as regarding theoretical toxicity, biodegradability, carcinogenicity, and mutagenicity of transformation products (TPs). Rate constants obtained under photolysis (0.008 min

The degradation of a pharmaceutical mixture (gemfibrozil, hydrochlorothiazide and naproxen) by TiO2/UV-A in different aqueous matrices was evaluated. The matrix components affected the operational conditions, rate constants, and removal efficiency of the pharmaceuticals, as well as toxicity. For sewage treatment plant effluent, a TiO2 concentration three-fold higher (450 mg L−1) and an irradiation time 1.5-3 times longer were required to reach the same efficiency of degradation as the pharmaceuticals in deionized water and surface water matrices. An improvement in the rate constants and the removal efficiency of the pharmaceuticals was achieved by adding 6 mg L−1 of H2O2 and 150 mg L−1 of TiO2 in deionized water and surface water, but not in the sewage treatment plant effluent, due to the coupling of 450 mg L−1 of TiO2 and 50-200 mg L−1 of H2O2. Overall, TiO2/UV-A efficiently degraded all compounds, but an additional step is needed for the removal of residual toxicity.

Antibiotics are known to be refractory to natural biological degradation and conventional water treatments. Their presence in the effluent of sewage treatment plants and surface waters may harm aquatic environments, making it important to evaluate new technologies and to assess their degradation potential at near-neutral conditions. This study thus describes the degradation of the antibiotic chloramphenicol in both surface water and a tertiary effluent from a municipal wastewater treatment plant by the photo-Fenton process under black-light and solar irradiation conditions. The best results in surface water at an initial pH of 5.8 (natural of this matrix) were obtained using 48 μmol L−1 FeOx and 44 μmol L−1 H2O2, with a 144 μmol L−1 oxalate added at 10 min, reaching 88% degradation after 15 min of black-light irradiation. However, in a previous step where the pH was adjusted from 7.7 to 6.0, high FeOx (192 µmol L−1) and H2O2 (1500 µmol L−1) concentrations were needed to achieve 79% chloramphenicol degradation in the tertiary effluent after 20 min of black-light irradiation. Using the same experimental conditions for each matrix, the best results, in terms of chloramphenicol degradation rate as by-products of low toxicity, were obtained under solar irradiation, as confirmed by the blank experiments using the matrices in the absence of chloramphenicol. These results show the viability and effectiveness of FeOx as a photocatalyst for the treatment of wastewaters containing this pollutant at near-neutral conditions under solar irradiation, as well as the added savings in energy costs associated with the photo-Fenton treatment.

Biodiesel effluent demands treatment to enhance their organoleptic properties and to reduce the levels of organic load and toxicity. A step of coagulation-flocculation using 0.50 mmol L−1 Fe(NO3)3 was applied at the natural pH of the effluent (pH 2.9) removing its turbidity and apparent color. A solar/photo-Fenton process was employed to minimize the chemical oxygen demand – COD, when multiple additions of oxalate were done at intervals of 50 kJ m−2 of accumulated UVA radiation, during the photocatalytic reaction. The best results were achieved using 1.0 mmol L−1 of ferrioxalate, allowing reducing in 72% the COD and in 76% the biochemical oxygen demand of the treated effluent, after 602 kJ m−2 of accumulated dose of UVA radiation. Concomitantly, the acute toxicity to Vibrio fischeri was reduced from 70% to 6%. In view of this, this modality of treatment can be a good alternative for decontamination and detoxification of this kind of wastewater, mainly considering that no further step of neutralization is need once that during the treatment the pH increase up to close 7, and that solar energy can be employed, reducing costs related to energy consumption.

This paper describes the degradation of the antibiotic chloramphenicol by a photo-Fenton process under artificial and solar irradiation. Using artificial radiation, the role of different sources and concentrations of iron (salts of Fe2+ and Fe3+ and the iron complexes citrate (FeCit) and oxalate (FeOx)), initial pH, concentration of H2O2 and addition of oxalate at initial pH 6.0 were evaluated. The concentration of chloramphenicol was reduced to below the quantification limit of the equipment (

Pharmaceutical compounds are known to be persistent. Their presence after conventional treatments in sewage treatment plants may harm aquatic environments. The simultaneous degradation of the pharmaceuticals gemfibrozil, hydrochlorothiazide and naproxen involving photo-Fenton processes was evaluated using different sources and concentrations of iron (Fe2+, Fe3+ and the iron complexes of oxalate – FeOx), initial pH (2.6, 5.0 and 7.0) and concentrations of H2O2. The classic photo-Fenton reaction (at initial pH 2.6, using Fe2+and Fe3+) showed a limited efficiency in promoting gemfibrozil degradation, which, based on evidence provided by LC–MS measurements, is related to the formation of associations between this compound and iron ions. The simultaneous degradation of gemfibrozil and the other compounds was improved using FeOx (1.0 mg L−1 in iron) at an initial pH of 2.6 and 2.0 mg L−1H2O2. In addition, using this catalyst it was possible to efficiently degrade the pharmaceuticals at an initial pH of 5.0, reaching complete degradation of these compounds with a treatment time varying between 20 and 60 min and generating a low toxicity effluent. These results highlight the potential applicability of ferrioxalate as a photocatalyst in the photo-Fenton process as an alternative method to degrade this kind of pollutant at a pH near neutrality.

The feasibility of biodiesel effluent treatment combining coagulation-flocculation with a photolytic process was evaluated, being the photolytic process involving the irradiation of the effluent by UV-C, or by UV-C irradiation with simultaneous addition of H2O2 (H2O2/UV-C). The coagulation-flocculation was performed at the natural pH of the effluent (pH 2.9) using different Fe3+ salts (chloride, nitrate and sulfate) at different concentrations (0.25, 0.50 and 1.0 mmol L-1) of the counterions. The best results were achieved using 0.50 mmol L-1 Fe(NO3)3. Following, the degradation of the organic load and toxicity reduction of the pre-treated effluent by UV-C irradiation was evaluated. The H2O2/UV-C process showed to be advantageous, mainly when multiple additions of H2O2 were used during the course of the reaction. Additionally, the influence of the initial pH on the degradation was also evaluated. A high level of mineralization (94%) was achieved after 6 h of irradiation concomitantly with multiple additions of 2,000 mg L-1 H2O2, and with the effluent at the natural pH. Thus, using coagulation-flocculation followed by the H2O2/UV-C process, it was possible to achieve a favourable condition for reuse of the pre-treated effluent, since, in addition to the significant reduction of the organic load, the final DBO5 (

Microplastics have become a hot topic in the scientific community as they promote adverse effects to living beings. Various analytical tools must be used simultaneously for identification and characterization of microplastics and their transformation products in environmental compartments. Despite limitations associated to the reproduction of real conditions of microplastics occurrence in environmental matrices (composition, size, concentration), increased toxicity has been observed as a consequence of their interaction with contaminants of emerging concern and/or heavy metals. Yet, some factors (i.e., pH, particle age and size of microplastic, among others) may affect this phenomenon. Membrane filtration and coagulation-flocculation-settling treatments are non-destructive, needing an additional step to degrade microplastics. Biological treatment has been demonstrated as unsatisfactory (

In this work it was studied the degradation of the insecticide fipronil (FIP) by heterogeneous photocatalysis induced by TiO2 P25. Using chemometric methods (Factorial Design and Response Surface Methodology), it was possible to evaluate the role of interaction between pH of the reaction medium, the reaction time and concentration of TiO2, optimizing the conditions for degradation using artificial radiation. Under the optimized conditions (79.4 mg L−1 TiO2 and 66.3 min of reaction time for 1.1 mg L−1 of FIP, at pH 5.6–5.8 (natural pH of the irradiated suspension)), 90.9% of FIP degradation was achieved at a degradation rate of 1.54 × 10−2 m2 kJ−1 in terms of accumulated UVA radiation, corresponding to a pseudo-first order rate constant of 1.34 × 10−2 min−1 and a half-life of 51.7 min. Under the same conditions, these assays were extended to the use of solar radiation, when the degradation rate was 14% higher, with half-life of 45 min, suggesting that in both cases FIP degradation was successful. Four by-products of FIP photocatalytic degradation could be separated, identified, and their formation and consumption followed by UHPLC-Q-TOF. Although the same intermediates have been obtained using both irradiation sources, a faster degradation of the transformation products (TPs) was observed under solar irradiation due to its expressive photonic flux covering the UVA and UVB. It is noteworthy that both the untreated effluent and the identified compounds have low toxicity with respect to V. fischeri, suggesting that the heterogeneous photocatalysis may be a good alternative for treatment of wastewaters containing FIP and its TPs, mainly when solar radiation is the source of radiation, since under this condition the power consumption during the treatment can be significantly reduced.

The conditions for treatment of a biodiesel effluent, combining coagulation-flocculation and membrane filtration with Fenton/photo-Fenton reactions, in order to ensure the reuse of water, are presented in this work. Coagulation-flocculation and membrane filtration were applied as a first stage to remove the turbidity, suspended solids, apparent color and oil & fats. In the second stage, Fenton/photo-Fenton reactions were used to reduce the organic load. Under the best condition achieved for this stage (3500 mg L−1 H2O2, 25 mg L−1 Fe2+ and pH between 2.5 and 2.9), 90% of the dissolved organic carbon and the same percentage of chemical oxygen demand were removed after 24 of irradiation. In addition, the same acute ecotoxicity to Vibrio fischeri was obtained, when compared to the effluent treated in the first stage and diluted to 20% v/v. These results demonstrate the effectiveness of coupling physical processes with photo-Fenton reactions to promote the treatment of biodiesel effluent.

The role of different operational parameters related to Fenton reactions (pH, concentration of Fe2+ and H2O2, and reaction time) and of Cl− and SO 4 − was investigated in the degradation of the azo dye Direct Red 81, expressed in terms of its decolorization. The factorial design and Pareto’s charts showed that only Fe2+ concentration and pH influence the decolorization under the conditions evaluated. So, only these parameters were optimized using the response surface model. Under the best experimental conditions (initial pH 2.5, 11 mg L−1 Fe2+, 78 mg L−1 H2O2, and 20 min of reaction), 94 % of decolorization was achieved. However, even under the these conditions, but in the presence of Cl− and SO 4 − , a striking loss of efficiency was observed as the concentration of these ions was increased, due the formation of chloride- and sulfate-iron complexes and less reactive inorganic radicals (Cl2 •– and SO4 •–). The results show that the presence of Cl− is more deleterious, since sulfate-iron complexes are more reactive towards H2O2, and the SO4 •– turns out to favor the degradation. On the other hand, the negative effect of Cl− can be compensated by increasing the chloride concentration up to 300 mmol L−1. In addition, although a high degradation level has been obtained by monitoring the dye absorbance and by HPLC-UV, a low mineralization occurred, being generated degradation products of higher ecotoxicity to Vibrio fischeri, showing the need of subsequent studies to identify these compounds as well as the application of additional treatments aiming the complete mineralization of the dye.

This study presents the degradation of fipronil in sewage treatment plant (STP) effluent by photo-Fenton at near neutral pH (pH 6.0) using Fe3+/Citrate complex. 83% of fipronil degradation was reached using a molar iron/citrate ratio of 1:3 (192 μmol L−1 of Fe3+/576 μmol L−1 of citrate). Photo-Fenton reduced the toxicity of treated solutions as according to the survival of Drosophila melanogaster exposed to non-treated and treated samples. Control experiments performed in distilled water using 32 μmol L−1 of Fe3+/96 μmol L−1 of citrate achieved 98% of fipronil degradation within 100 kJ m−2 (UV-A radiation, k = 30 × 10−3 kJ−1 m2 and t1/2 = 23 kJ m−2), thus indicating that fipronil degradation is impaired by natural organic matter and inorganic ions present in STP effluent. Degradation was faster under solar radiation, as the same efficiency (98%) was obtained after 75 kJ m−2 (k = 63 × 10−3 kJ−1 m2 and t1/2 = 11 kJ m−2). In addition, pathways of fipronil degradation using Fe3+/Citrate under solar and UV-A radiation were investigated and transformation products proposed. Results revealed that the HO• attack occurred preferentially in the pyrazole ring. Eight transformation products were identified by UHPLC-Q-TOF-MS and four are unprecedented in the literature. Control experiments in distilled water demonstrated that toxicity reduction is related to fipronil degradation and that transformation products are less toxic than fipronil. Furthermore, toxicity of STP fortified with fipronil was reduced after photo-Fenton. These results demonstrate the feasibility of applying this process using Fe3+/Citrate complex for fipronil degradation in a real matrix.

Decolorization of Acid Blue 161 (AB161) by solid peroxides such as CaO2 and Na2O2 catalyzed by iron in aqueous solution was investigated. The effect of initial pH, concentration of H2O2, Fe2+, and AB161 on the decolorization kinetics was investigated and compared with the results by liquid H2O2. The experimental results show that decolorization of AB161 follows the second-order kinetic. The second decolorization rate constants and oxidation efficiency at different initial pH, Fe2+, H2O2, and AB161 concentration were correlated with dimensionless ratios such as H2O2/Fe2+ or H2O2/AB161. About two dozens of correlation equations are developed in this paper to quantify the effect of the variables on the decolorization rate constants of AB161. Among solid peroxides such as CaO2 and Na2O2 and liquid H2O2, the optimal pH and [Fe2+] are 2.5 and 5.0 × 10−4 mol L−1, while the concentration of CaO2, Na2O2, and H2O2 is 0.30, 0.25 g L−1 and 3.1 × 10−3 mol L−1, respectively. Our experimental results show that d...

Degradation kinetics of azo dye, Acid Blue 161 (AB161), by Fenton and photo-Fenton processes in aqueous solution was investigated. At pH 3.5, the effects of H2O2, Fe2+, and H2O2/Fe2+ molar ratios, on the AB161 decolorization kinetic rates, were evaluated. Experimental results confirmed that the optimal H2O2/Fe2+ molar ratio of 12 is close to the theoretical value of 11 as predicted by previously developed model. The influence of azo bond loading (L azo bond), from 0.25 to 1.0, and pH values from 2.5 to 4.0 were evaluated on AB161 decolorization kinetic rates. A correlation between the natural logarithm of the decolorization rates and L azo bond was established at the different pH values. The decolorization rate increased linearly with decreasing L azo bond, in the order of pH: 3.5 > 3.0 > 2.5 > 4.0. UV radiation of Fenton processes increases degradation of AB161 more than 40 % due to the regeneration of Fe2+ through photo-catalytic reactions. This phenomenon was confirmed by measuring H2O2 concentration during the photo-Fenton processes. The results suggest that Fenton processes can effectively decolorize or degrade wastewater containing azo dye, AB161. Photo-Fenton processes may further increase the degradation efficiency of AB161 by 40 %.

This study reports a protocol for the treatment of a sanitary landfill leachate through integration between a stage of coagulation-flocculation, a step of filtration of the resulting suspension, and application of the photo-Fenton process using a ferrioxalate complex and solar irradiation. The best results for turbidity removal by coagulation-flocculation were reached using Al3+ as nitrate salt mainly using concentrations up close 4.4 mmol L-1, at the natural pH of the effluent (pH 7.9), when the removal of 66% of the turbidity was achieved. By using a ferrioxalate complex after adjusting the pH of the effluent to 5, it was possible to circumvent the classical limitations of the Fenton process (related to the pH of the medium limited to between 2.5 and 3.0), performing a removal of 68% of the remaining dissolved organic carbon. The global dissolved organic carbon removal in this process was of 86% after a membrane filtration step before the photo-Fenton process.

In this study the coagulation-flocculation process was evaluated as an alternative for treatment of biodiesel wastewater. The role of two coagulants, Al3+ and Fe3+, as well as its dosage, pH, treatment time, stirring and aeration were evaluated. It was observed that in the treatment using Al3+ the pH of the effluent (9.7) does not need to be adjusted, while for Fe3+ a previous adjustment to pH 5.0 was necessary. On the other hand, a high concentration of Al3+ (243 mg L-1) and a relatively long treatment time (70 min) were required to reach more than 96% of turbidity removal, when compared to the processing using Fe3+ (56 mg L-1 and 53 min), attributed to the formation of different mole fractions of hydrolyzed cationic species. Under the optimized conditions, more than 96% of turbidity, apparent color and suspended solids, and 82% of oil and fats were removed.

The Fenton process is evaluated as a treatment method to reduce the total organic carbon (TOC) and increase biodegradability of the organic substrate in a mature landfill leachate. Biodegradability was quantified in terms of the ratios between biochemical oxygen demand after 5 days (BOD5) to chemical oxygen demand (COD) (after different Fenton reaction times), and BOD5 (after different Fenton reaction times) to initial BOD5 (original leachate sample), termed as BOD5,0, respectively. An increased TOC removal and improved BOD5/COD ratios were observed following the pH sequence of 3.5 > 6.0 > 2.0. The maximum TOC removal of 61 % and the highest BOD5/COD ratio from 0.11 to 0.37 were observed at pH 3.5. To quantify biodegradability enhancement at different COD loading factors (LCOD) by the Fenton process, the H2O2/Fe2+ ratio was fixed at 1.8 (w/w) and LCOD ranged from 0.22 to 1.19. Experimental results showed that higher TOC removal and biodegradability enhancement were obtained at lower LCOD. Quantitatively, two linear regression equations between LCOD and biodegradability (in terms of BOD5/COD and BOD5/BOD5,0) were established, as: BOD5/COD = 0.57–0.38 LCOD and BOD5/BOD5,0 = 1.40–0.40 LCOD with correlation coefficients (R 2 ) of 0.87 and 0.51, respectively. The experimental work described here, demonstrated that the Fenton process can be used as an effective pre-treatment strategy to increase leachate biodegradability within a short reaction time from 1 to 5 min.

In this study we evaluated the feasibility of application of photo-Fenton process in the treatment of aqueous solution contaminated by chloramphenicol (CAP). The results suggest that the concentration of H 2 O 2 and the concentration of Fe 2+ influence the degradation efficiency of this antibiotic. The best efficiency at lab-scale was achieved when the concentration of H 2 O 2 was equal to 400 mg L −1 , while only a small improvement was observed when the concentration of H 2 O 2 increased from 400 to 500 mg L −1 . A concentration of 750 mg L −1 was necessary in the process mediated by solar radiation, probably due to thermal decomposition of H 2 O 2 . The concentration of Fe 2+ influences positively the rate of CAP and COD removal. A significant increase was observed between 5 and 10 mg L −1 , remaining constant from 10 to 15 mg L −1 . On the other hand, the mode of addition of H 2 O 2 (single or multiple additions) did not influence the rate of CAP removal. Thus, the option was for simple addition. Finally, the results suggest that the degradation of CAP by photo-Fenton process can be performed on a large scale, yielding oxidized by-products of low toxicity and without antimicrobial activity. The use of solar radiation was feasible in the treatment of waters containing this kind of pollutant, which is extremely advantageous, since the energy costs of the process can be reduced.

This study describes the influence and optimization of Fenton's reagent (concentration of Fe2+ and H2O2 ) on the efficiency of mineralization of the herbicide paraquat (PQT, 50 mg L-1) in water, after 60 min (equivalent to 642 kJ L-1 of accumulated UVA radiation) treatment by photo-Fenton process in laboratory scale, using central composite design (CCD). Under optimized conditions, kinetic experiments were done, evaluating the PQT removal, its mineralization and toxicity in laboratory scale, using artificial irradiation, and in a pilot plant under solar irradiation. The same removal efficiency and mineralization of PQT were obtained in both reactors. The toxicity of the samples, estimated in terms of mortality of Artemia salina, decreases simultaneously with the decay of concentration of PQT, suggesting the formation of intermediates of lower toxicity. In this way, the solar photo-Fenton process can be considered as a viable alternative for the treatment of wastewater containing PQT. Este trabalho descreve a influência e otimização dos reagentes de Fenton (concentração de Fe2+ e H2O2) na eficiência da mineralização do herbicida paraquat (PQT, 50 mg L-1) em água, após 60 min (equivalendo a 642 kJ L-1 de radiação UVA acumulada) de tratamento por processo foto-Fenton em escala de laboratório, usando planejamento composto central (CCD). Sob condições otimizadas, experimentos cinéticos foram feitos, avaliando a remoção do PQT, sua mineralização e toxicidade em escala de laboratório, usando irradiação artificial, e em planta piloto sob irradiação solar. A mesma eficiência de remoção e mineralização do PQT foram obtidas em ambos os reatores utilizados. A toxicidade das amostras, estimada em termos de mortalidade de Artemia salina, diminui simultaneamente com o decaimento da concentração de PQT, sugerindo a formação de intermediários de menor toxicidade. Dessa maneira, o processo foto-Fenton/solar pode ser considerado uma alternativa viável para o tratamento de águas residuais contendo PQT.

The photocatalytic performance of a composite based on the association of TiO2 and 2.5 wt.% of zinc(II) phthalocyanine (TiO2/ZnPc) was evaluated towards the mineralization of paracetamol and compared to that observed for the bare oxide in different pH and H2O2 concentrations. The results show that the photocatalytic performances were influenced by the pH, with maximum efficiency around the isoelectric point. Mineralization efficiencies between 86-91% was obtained using TiO2/ZnPc in pH 5.5-6.8, with 33 mg L-1 of H2O2, ca. 15% higher than that observed with TiO2. The mineralization efficiencies using bare TiO2 and TiO2/ZnPc were respectively 112 and 18% lower in the absence of H2O2. The better performance of TiO2/ZnPc is related to its extended light absorption and non-uniform coating of the TiO2 surface by ZnPc aggregates. Above pH 6.8, the mineralization efficiencies decrease for both photocatalysts, although the consumption of H2O2 remains above 90%, due to its decomposition in alkaline pH.

The photo-Fenton degradation of paracetamol (PCT) was evaluated using FeSO4 and the iron complex potassium ferrioxalate (FeOx) as iron source under simulated solar light. The efficiency of the degradation process was evaluated considering the decay of PCT and total organic carbon concentration and the generation of carboxylic acids, ammonium and nitrate, expressed as total nitrogen. The results showed that the degradation was favored in the presence of FeSO4 in relation to FeOx. The higher concentration of hydroxylated intermediates generated in the presence of FeSO4 in relation to FeOx probably enhanced the reduction of Fe(III) to Fe(II) improving the degradation efficiency. The degradation products were determined using liquid chromatography electrospray time-of-flight mass spectrometry. Although at different concentrations, the same intermediates were generated using either FeSO4 or FeOx, which were mainly products of hydroxylation reactions and acetamide. The toxicity of the sample for Vibrio fischeri and Daphnia magna decreased from 100% to less than 40% during photo-Fenton treatment in the presence of both iron species, except for D. magna in the presence of FeOx due to the toxicity of oxalate to this organism. The considerable decrease of the sample toxicity during photo-Fenton treatment using FeSO4 indicates a safe application of the process for the removal of this pharmaceutical.

Made available in DSpace on 2013-09-27T14:52:48Z (GMT). No. of bitstreams: 1 WOS000287054500042.pdf: 405012 bytes, checksum: 09917f2d3f44d20ab9f6416c05f66edc (MD5) Previous issue date: 2011-01-01 Made available in DSpace on 2013-09-30T19:24:22Z (GMT). No. of bitstreams: 1 WOS000287054500042.pdf: 405012 bytes, checksum: 09917f2d3f44d20ab9f6416c05f66edc (MD5) Previous issue date: 2011-01-01 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T15:34:35Z No. of bitstreams: 1 WOS000287054500042.pdf: 405012 bytes, checksum: 09917f2d3f44d20ab9f6416c05f66edc (MD5) Made available in DSpace on 2014-05-20T15:34:35Z (GMT). No. of bitstreams: 1 WOS000287054500042.pdf: 405012 bytes, checksum: 09917f2d3f44d20ab9f6416c05f66edc (MD5) Previous issue date: 2011-01-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Spanish Ministry of Education Andalusia Regional Government The influence of iron species on amoxicillin (AMX) degradation, intermediate products generated and toxicity during the photo-Fenton process using a solar simulator were evaluated in this work. The AMX degradation was favored in the presence of the potassium ferrioxalate complex (FeOx) when compared to FeSO(4). Total oxidation of AMX in the presence of FeOx was obtained after 5 min, while 15 min were necessary using FeSO4. The results obtained with Daphnia magna biossays showed that the toxicity decreased from 65 to 5% after 90 min of irradiation in the presence of FeSO(4). However, it increased again to a maximum of 100% after 150 min, what indicates the generation of more toxic intermediates than AMX, reaching 45% after 240 min. However, using FeOx, the inhibition of mobility varied between 100 and 70% during treatment, probably due to the presence of oxalate, which is toxic to the neonates. After 240 min, between 73 and 81% TOC removal was observed. Different pathways of AMX degradation were suggested including the opening of the four-membered beta-lactamic ring and further oxidations of the methyl group to aldehyde and/or hydroxylation of the benzoic ring, generating other intermediates after bound cleavage between different atoms and further oxidation to carboxylates such acetate, oxalate and propionate, besides the generation of nitrate and ammonium. (C) 2010 Elsevier Ltd. All rights reserved. UNESP Univ Estadual Paulista, Inst Quim Araraquara, BR-14801970 Araraquara, SP, Brazil Univ Almeria, Pesticide Residues Grp, Almeria 04120, Spain CIEMAT, Tabernas 04200, Almeria, Spain UNESP Univ Estadual Paulista, Inst Quim Araraquara, BR-14801970 Araraquara, SP, Brazil Spanish Ministry of Education: CSD2006-00044 Andalusia Regional Government: P06-TEP-02329

In the present work the use of a coupled process, soil washing and photo-Fenton oxidation, was investigated for remediation of a soil contaminated with p , p ′-DDT (DDT) and p , p ′-DDE (DDE), and a soil artificially contaminated with diesel. In the soil washing experiments, Triton X-100 (TX-100) aqueous solutions were used at different concentrations to obtain wastewaters with different compositions. Removal efficiencies of 66% (DDT), 80% (DDE) and 100% (diesel) were achieved for three sequential washings using a TX-100 solution strength equivalent to 12 times the effective critical micelle concentration of the surfactant (12 CMC eff ). The wastewater obtained was then treated using a solar photo-Fenton process. After 6 h irradiation, 99, 95 and 100% degradation efficiencies were achieved for DDT, DDE and diesel, respectively. In all experiments, the concentration of dissolved organic carbon decreased by at least 95%, indicating that residual concentration of contaminants and/or TX-100 in the wastewater was very low. The co-extraction of metals was also evaluated. Among the metals analyzed (Pb, Cr, Ni, Cu, Cd, Mn and Co), only Cr and Mn were detected in the wastewater at concentrations above the maximum value permitted by current Brazilian legislation. The effective removal of contaminants from soil by the TX-100 washing process, together with the high degradation efficiency of the solar photo-Fenton process, suggests that this procedure could be a useful option for soil remediation.

In this work, the photocatalytic degradation of the antibiotic sulfamethoxazole (SMX) by solar photo-Fenton at pilot plant scale was evaluated in distilled water (DW) and in seawater (SW). Degradation and mineralization of SMX were strongly hindered in SW compared to DW. The influence of H(2)O(2) and iron concentration on the efficiency of the photocatalytic process was evaluated. An increase in iron concentration from 2.6 to 10.4 mg L(-1) showed only a slight improvement in SMX degradation and mineralization. However, an increase in H(2)O(2) concentration up to 120 mg L(-1) during photo-Fenton in DW decreased SMX solution toxicity from 85% to 20%, according to results of Daphnia magna bioassays. The same behaviour was not observed after photo-Fenton treatment in SW. Despite 45% mineralization in SW, toxicity increased from 16% to 86% as shown by Vibrio fischeri bioassays, which suggests that the intermediates generated in SW are different from those in DW. A SMX degradation pathway during the photo-Fenton treatment in DW is proposed.