Degradation of 2,4-Dichlorophenol Solution and Toxicity Reduction by a Dual-Cathode Oxidation System

Electrochemical degradation of 2,4-dichlorophenol (2,4-DCP) in aqueous solution has been studied by a dual-cathode oxidation system (DOS), in which a gas-diffusion electrode was used to produce H2O2 in situ by oxygen reduction, a graphite cathode was employed to accelerate the reduction of Fe3+ and a Ti/SnO2-Sb2O5-IrO2 anode was used for the anodic oxidation (AO) of organics. It is shown that both electro-Fenton oxidation and AO account for the degradation of 2,4-DCP in this process. Comparative degradation showed that DOS could present a more rapid removal of 2,4-DCP compared with the single-cathode oxidation system. When −0.70 and −0.10 V were applied to the gas-diffusion cathode and the graphite cathode, respectively, the degradation of 2,4-DCP solution (100 mg/L) with 0.15 mM Fe2+ at pH 3.0 for 240 min yielded 80% total organic carbon removal and a mineralization current efficiency of 20%. The effect of DOS treatment on the toxicity reduction was evaluated by the dehydrogenase activity (DHA) of activated sludge. It was found that DHA value became greater via the treatment in contrast with the DHA value of untreated solution. This work suggests that DOS might present an alternative for the treatment or the pretreatment of effluents containing chlorophenols.