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The purpose of this work was to determine the degradation products and pathway of chlorfenvinphos (CFVP) in water treated by photo-Fenton driven by solar irradiation, as well as to develop an analytical procedure for the degradation experiments. Degradation products and pathway were determined in a laboratory experimental setup. Routine water sample analysis was done by standard laboratory wet chemistry procedures and the use of laboratory equipment such as HPLC–UV and ionic chromatography (IC). Solid-phase extraction (SPE) was used to extract analytes from an aqueous matrix, and GC–MS was used to identify intermediate degradation products. The use of an HPLC–TOF-MS provided more results on degradation products and more insight was gained into how degradation takes place. In all experiments, strong mineralisation and degradation of CFVP was observed. CFVP and its degradation products, like 2,4-dichlorophenol, 2,4-dichlorobenzoic acid and triethylphosphate were decomposed into organic substances like acetate, formate, maleate, and inorganic ions like chloride and phosphate, within the detection limits (12.5μg/L for CFVP in the GC–MS and 40μg/L in HPLC–UV) of the equipment used. In fact, Cl− emerges in nearly stoichiometric concentrations and PO4 3 − is precipitated as FePO4. The remarkably complete absence of chlorinated aliphatic substances and chlorinated acids leads to the conclusion that chlorine is removed very quickly, and that residual DOC does not correspond to any chlorinated compound. [Copyright &y& Elsevier]

A coupled solar photo-Fenton (chemical) and biological treatment has been used to remove biorecalcitrant diuron (42mgl−1) and linuron (75mgl−1) herbicides from water at pilot plant scale. The chemical process has been carried out in a 82l solar pilot plant made up by four compound parabolic collector units, and it was followed by a biological treatment performed in a 40l sequencing batch reactor. Two Fe(II) doses (2 and 5mgl−1) and sequential additions of H2O2 (20mgl−1) have been used to chemically degrade the initially polluted effluent. Next, biodegradability at different oxidation states has been assessed by means of BOD/COD ratio. A reagent dose of Fe=5mgl−1 and H2O2 =100mgl−1 has been required to obtain a biodegradable effluent after 100min of irradiation time. Finally, the organic content of the photo-treated solution has been completely assimilated by a biomass consortium in the sequencing batch reactor using a total suspended solids concentration of 0.2gl−1 and a hydraulic retention time of 24h. Comparison between the data obtained at pilot plant scale (specially the one corresponding to the chemical step) and previously published data from a similar system performing at laboratory scale, has been carried out. [Copyright &y& Elsevier]

Abstract: A multivariate analysis using experimental design techniques was performed to determine the effect of iron, hydrogen peroxide and titanium dioxide in the solar photodegradation of dichloroacetic acid in a combined TiO2/photo-Fenton process. The study was carried out at pilot-plant scale, using TiO2 supported on silica as the heterogeneous photocatalyst to facilitate separation of the solids after the reaction, and iron concentrations of less than 3mgL−1 to avoid removal of iron from the effluent. The results show that iron is the most important factor influencing the reaction rate, which suggests that in strongly acidic solutions, the Fenton mechanism controls the process even at such low iron concentrations. Under these conditions, the expected synergism between TiO2 and iron degradation pathways seems to be negligible compared to the antagonistic effect between hydrogen peroxide and TiO2, which reduces the activity of the combined system. However, in the absence of hydrogen peroxide, the activity achieved by the combined Fe/TiO2 system is similar to that of the photo-Fenton process, with the advantage that H2O2 is replaced by a reusable TiO2-based catalytic material. Consequently, the analysis of pilot-plant operation economics took not only the degradation rate, but also the cost of chemicals into account. [Copyright &y& Elsevier]

Abstract: In recent years, there has been a tremendous amount of research and development in the area of photocatalysis, a process included in a special class of oxidation techniques defined as advanced oxidation processes (AOPs), all characterized by the same chemical feature, production of ls. This paper reviews the use of sunlight to produce the ls. The systems necessary for performing solar photocatalysis are described. The paper also summarizes most of the research related to solar photocatalytic degradation of water contaminants carried out during recent years, and how it could significantly contribute to the treatment of very persistent toxic compounds. Various solar reactors for photocatalytic water treatment based mainly on non-concentrating collectors erected during the last few years are also described in detail in this review, as well as the use of the solar photocatalytic processes to inactivate microorganisms present in water, placing special emphasis on some experimental systems erected to optimize this disinfecting technique. [Copyright &y& Elsevier]

Abstract: Alachlor, atrazine and diuron dissolved in water at 50, 25 and 30mg/L, respectively were photodegraded by Fe2+/H2O2, Fe3+/H2O2, TiO2 and TiO2/Na2S2O8 treatments driven by solar energy at pilot-plant scale using a compound parabolic collector (CPC) photoreactor. All the advanced oxidation processes (AOPs) employed mainly compared the TOC mineralisation rate to evaluate treatment effectiveness. Parent compound disappearance, anion release and oxidant consumption are discussed as a function of treatment time. The use of Fe2+ or Fe3+ showed no influence on the reaction rate under illumination and the reaction using 10 or 55mg/L of iron was quite similar. TiO2/Na2S2O8 showed a quicker reaction rate than TiO2 and a similar rate compared to photo-Fenton. The main difference found was between TiO2/Na2S2O8 and photo-Fenton, detected during atrazine degradation, where pesticide transformation into cyanuric acid was confirmed only for TiO2/Na2S2O8. [Copyright &y& Elsevier]

Abstract: In this paper, we present the photo-Fenton treatment in a solar pilot-plant scale of several EU priority hazardous substances (Alachlor, Atrazine, Chlorfenvinphos, Diuron and Isoproturon) dissolved in water. The results have been evaluated not only from the point of view of contaminant disappearance and mineralisation, but also of toxicity reduction and enhancement of biodegradability. Degradation was monitored by total organic carbon, pesticide concentration by HPLC–UV, inorganics released by ion chromatography, and biodegradability by the Zahn–Wellens (Z–W) test. The total volume of the solar photoreactor, composed of compound parabolic collectors with a total area of 4.16m2, was between 70 and 82L. The treatment was shown to be effective, mineralising all of the pesticides tested, both alone and in mixtures. In order to find out the conditions for biocompatibility using the photo-Fenton reaction as a pre-treatment step, wastewater inoculated with unacclimated municipal sludge containing pesticides after certain degradation time was evaluated by the Z–W test. Biodegradability was enhanced (70% considered biodegradable) by the photo-Fenton treatment after 12–25min. It may be concluded that the photo-Fenton treatment consistently enhances biodegradability of wastewater containing pesticides. [Copyright &y& Elsevier]