Influence of the anode materials on the electrochemical oxidation efficiency. Application to oxidative degradation of the pharmaceutical amoxicillin

In this study, the electro-oxidation capacities of several electrode materials such as carbon-felt, carbon-fiber, carbon-graphite, platinum, lead dioxide, dimensionally stable anode (DSA), (Ti/RuO2-IrO2), and BDD (Boron-Doped Diamond) were tested for the destruction of the antibiotic amoxicillin (AMX) in aqueous medium. BDD anode was more efficient than DSA to oxidize and mineralize totally AMX in water. Moreover, for BDD electrode we obtained very high electrolysis efficiency for the initial stage of the process even for high current densities, which is an indirect indicator that mediated oxidation is involved in the whole degradation of AMX. Considering the oxidation reactions under mass transfer control, the apparent rate constants for oxidation of AMX by hydroxyl radicals were determined for all anode materials tested. The data obtained shows that in all cases, the oxidation rate constants depended mainly on applied current densities for each material. Platinum showed a relatively good oxidation behavior compared to carbon-fiber and carbon-graphite. DSA was found to be the less efficient electrode for oxidation of AMX. BDD was evidenced as the best anode material at high current densities due to the formation of large amounts of hydroxyl radicals and of other different oxidants such as hydrogen peroxide, ozone and persulfates that contribute to the enhancement of oxidation and mineralization of AMX via mediated oxidation.