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

• Typical rare earth (La, Gd) co-doped PbO2 electrode was prepared.
• Rare earth La and Gd offered a synergistic effect to enhance PbO2 anode activity.
• Electrochemical method is proved to be a useful way for the treatment of levodopa.
• Levodopa electrochemical degradation mechanism was analyzed.
• A possible levodopa degradation pathway was proposed.

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.