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

Electrocatalytic oxidation and detoxication of capecitabine (CAP) in aqueous solution were investigated with Ti/SnO 2 –Sb/Ce–PbO 2 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%) < SO 4 − (24.2%) < O 2 − (53.3%). The operating parameters and solution matrixes, i.e. applied current densities, initial CAP concentrations, initial Cl − and NO 3 − 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 , NO 3 − , NO 2 − , NH 4 + and F − . Electrochemical oxidation process based on Ti/SnO 2 –Sb/Ce–PbO 2 anode is proved to be effective for elimination, mineralization and detoxication of aqueous CAP.