Environ. Sci. Technol. 2002, 36, 3030-3035
Degradation of Herbicide 4-Chlorophenoxyacetic Acid by Advanced Electrochemical Oxidation Methods BIRAME BOYE,† MOMAR M. DIENG,‡ AND E N R I C B R I L L A S * ,† Laboratori de Cie`ncia i Tecnologia Electroquı´mica de Materials, Departament de Quı´mica Fı´sica, Facultat de Quı´mica, Universitat de Barcelona, Martı´ i Franque`s 1-11, 08028 Barcelona, Spain, and Laboratoire de Chimie Physique Organique et d’Analysis Instrumental, De´partement de Chimie, Faculte´ de Sciences et Techniques, Universite´ Cheikh Anta Diop, Dakar, Senegal
groundwaters, respectively. Research efforts are underway to develop powerful oxidation methods for achieving their overall mineralization (i.e., conversion into CO2 and inorganic ions). Most papers related to the treatment of chlorophenoxy herbicides in aqueous medium describe the degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) by advanced oxidation processes (AOPs) involving chemical (1), photochemical (1-3), or photocatalytic (4) production of hydroxyl radicals (OH•), which act as nonselective, strong oxidants of organics yielding dehydrogenated or hydroxylated derivatives. Pignatello (1) reported complete mineralization of 0.1 mM solutions of 2,4-D and 4-CPA at pH ca. 3 via oxalic acid, using H2O2 with Fe2+ (Fenton’s reagent) or H2O2/Fe3+/UV. In both cases, OH• is generated in the solution by the wellknown Fenton’s reaction between ferrous ion and hydrogen peroxide:
Fe2+ + H2O2 f Fe(OH)2+ + OH•
The herbicide 4-chlorophenoxyacetic acid (4-CPA) has been degraded in aqueous medium by advanced electrochemical oxidation processes such as electroFenton and photoelectro-Fenton with UV light, using an undivided cell containing a Pt anode. In these environmentally clean methods, the main oxidant is the hydroxyl radical produced from Fenton’s reaction between Fe2+ added to the medium and H2O2 electrogenerated from an O2-diffusion cathode. Solutions of a 4-CPA concentration
