Degradation of clofibric acid in acidic aqueous medium by electro-Fenton and photoelectro-Fenton

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• 作者：Ignasi Siré ; s ; Conchita Arias ; Pere Lluí ; s Cabot ; Francesc Centellas ; José ; Antonio Garrido ; Rosa Marí ; a Rodrí ; guez ; Enric Brillas
• 关键词：Drug mineralization ; Electro-Fenton ; Photoelectro-Fenton ; Catalysis ; Water treatment
• 刊名：Chemosphere
• 出版年：2007
• 期刊代码：15_00456535
• 类别：env
• 出版时间：January 2007
• 卷：66
• 期：9
• 页码：1660-1669
• 文件大小：335 K

摘要

Acidic aqueous solutions of clofibric acid (2-(4-chlorophenoxy)-2-methylpropionic acid), the bioactive metabolite of various lipid-regulating drugs, have been degraded by indirect electrooxidation methods such as electro-Fenton and photoelectro-Fenton with Fe²⁺ as catalyst using an undivided electrolytic cell with a Pt anode and an O₂-diffusion cathode able to electrogenerate H₂O₂. At pH 3.0 about 80%of mineralization is achieved with the electro-Fenton method due to the efficient production of oxidant hydroxyl radical from Fenton’s reaction between Fe²⁺ and H₂O₂, but stable Fe³⁺ complexes are formed. The photoelectro-Fenton method favors the photodecomposition of these species under UVA irradiation, reaching more than 96%of decontamination. The mineralization current efficiency increases with rising metabolite concentration up to saturation and with decreasing current density. The photoelectro-Fenton method is then viable for treating acidic wastewaters containing this pollutant. Comparative degradation by anodic oxidation (without Fe²⁺) yields poor decontamination. Chloride ion is released during all degradation processes. The decay kinetics of clofibric acid always follows a pseudo-first-order reaction, with a similar rate constant in electro-Fenton and photoelectro-Fenton that increases with rising current density, but decreases at greater metabolite concentration. 4-Chlorophenol, 4-chlorocatechol, 4-chlororesorcinol, hydroquinone, p-benzoquinone and 1,2,4-benzenetriol, along with carboxylic acids such as 2-hydroxyisobutyric, tartronic, maleic, fumaric, formic and oxalic, are detected as intermediates. The ultimate product is oxalic acid, which forms very stable Fe³⁺-oxalato complexes under electro-Fenton conditions. These complexes are efficiently photodecarboxylated in photoelectro-Fenton under the action of UVA light.