Electrochemical Advanced Oxidation of Carbamazepine: Mechanism and optimal operating conditions

Abstract

Effective electrochemical degradation of carbamazepine (CBZ) in water was accomplished with minimal energy and chemical requirements, showing that electrochemical Advanced Oxidation Processes (eAOPs) with a Boron-Doped Diamond (BDD) anode are a promising method for the in situ degradation of contaminants of emerging concern (CECs). The influence of several operating parameters (i.e., pH, temperature and initial anolyte and pollutant concentrations) was determined through the Taguchi optimization method. Optimal conditions corresponded to 1 μM CBZ, pH 2, 30 °C, 10 mM Na2SO4 and 50 A m−2, resulting in complete CBZ removal in less than 5 min. Complementary scenarios with different ion species, energy sources and current densities further corroborated the suitability of the optimum. Moreover, they revealed that the optimal conditions were driven by the presence of both SO42− and NO3− ions in solution. Hence, the optimal degradation results were also attained when replacing HNO3 by NaNO3, which allowed to operate without prior pH adjustments. The contribution of •OH and SO4•− radicals was studied through scavenging tests and it was for the first time tentatively ascribed to the Oxygen Evolution Reaction (OER), since the selection of the operating potential influences the type of oxidative species present. Finally, the primary transformation products formed during CBZ degradation under optimal conditions were investigated.