Electrochemical degradation of levodopa with modified PbO2 electrode: Parameter optimization and degradation mechanism

Electrochemical degradation of levodopa in aqueous solution was investigated over PbO2 electrode, La-PbO2 electrode, Gd-PbO2 electrode and La-Gd-PbO2 electrode. The degradation efficiencies of these four electrodes were investigated and it was found that the catalytic effect decreased in the following order: La-Gd-PbO2 electrode > La-PbO2 electrode > Gd-PbO2 electrode > PbO2 electrode. The main influencing factors on electrochemical decomposition of levodopa over La-Gd-PbO2 electrode were evaluated as a function of electrolyte concentration, initial levodopa concentration and current density. The results indicated that the maximum removal of levodopa, COD and TOC reached 100%, 79.20% and 65.31% respectively, after 120 min electrolysis at an initial 100 mg L-1 levodopa concentration at constant current density of 50 mA cm(-2) with a 0.1 mol L-1 Na2SO4 supporting electrolyte solution. The degradation mechanism of levodopa in electrochemical oxidation system is analyzed and a possible degradation pathway for the anodic oxidation of levodopa is proposed based on the intermediates identified. (C) 2014 Published by Elsevier B.V.