Insights into the degradation and detoxication mechanisms of aqueous capecitabine in electrochemical oxidation process

Abstract

Electrocatalytic oxidation and detoxication of capecitabine (CAP) in aqueous solution were investigated with Ti/SnO₂-Sb/Ce-PbO₂ anode. The relative contributions of generated free radicals showed an increase in the pseudo zero order tare constants in the following order: OH (9.4%) < SO₄^- (24.2%) < O₂^- (53.3%). The operating parameters and solution matrixes, i.e. applied current densities, initial CAP concentrations, initial Cl^- and NO₃^- concentrations, influencing the CAP degradation efficiency were evaluated. The kinetic rate constant of 0.1404 min^-1 was found within 7 min at current density of 10 mA cm^-2 and initial CAP concentration of 20 mg L^-1, while the mineralization efficiency of 59.5%, mineralization current efficiency of 2.06%, detoxication rate to Escherichia coli of 55.5% were achieved at reaction time 90 min. The major degradation pathways of CAP were oxidation, defluorination and bond cleavage, following with the formation of carboxylic acids, NO₃^-, NO₂^-, NH₄⁺ and F^-. Electrochemical oxidation process based on Ti/SnO₂-Sb/Ce-PbO₂ anode is proved to be effective for elimination, mineralization and detoxication of aqueous CAP.

Keywords: Capecitabine; Degradation mechanism; Detoxication; Electrocatalytic oxidation; Micropollutants.