Incineration of acidic aqueous solutions of dopamine by electrochemical advanced oxidation processes with Pt and BDD anodes

The degradation of 1.04 mM of the drug dopamine hydrochloride (100 mg L-1 of dissolved organic carbon (DOC)) solutions of pH 3.0 has been comparatively studied by electrochemical advanced oxidation processes (EAOPs) like anodic oxidation (AO) with a Pt anode and AO, electro-Fenton (EF) and photoelectro-Fenton (PEF) with a boron-doped diamond (BDD) anode. The AO processes were performed with a stainless steel cathode, whereas EF and PEF used an air-diffusion cathode that produced H2O2 center dot AO with a Pt anode led to very poor mineralization because of the low oxidizing ability of (OH)-O-center dot formed at the Pt surface. The use of a BDD anode in AO yielded faster incineration due to the much greater oxidation of (OH)-O-center dot generated by BDD. The production of (OH)-O-center dot in the bulk from Fenton's reaction enhanced largely the mineralization process in EF, which was upgraded in PEF by the photodecomposition of some intermediates by UVA light. Almost total mineralization with 97% DOC removal was found after 360 min of EF and 240 min of the most powerful PEF at 100 mA cm(-2). The rise in current density from 16.7 to 100 mA cm(-2) caused increasing DOC reduction for all EAOPs. The change in mineralization current efficiency and specific energy consumption per unit DOC mass was also discussed. Generated short-linear carboxylic acids like maleic, tartronic, glycolic, acetic, oxalic, oxamic and formic were identified by ion-exclusion HPLC These acids were quickly removed in EF and more rapidly in PEF due to the photolysis of their Fe(III) complexes. Ion chromatography revealed the pre-eminent generation of NH4+ ion along with a lower proportion of ion. This technique also confirmed the oxidation of the starting CI- ion at both Pt and BDD anodes with high CIO4- production using BDD. (C) 2016 Elsevier B.V. All rights reserved.