Electrochemical degradation of DCF by boron-doped diamond anode: degradation mechanism, pathways and influencing factors

Abstract

Nonsteroidal anti-inflammatory drugs (NAIDS) have been widely detected in wastewater and surface water, which indicates the removal of NAIDS by wastewater treatment plants was not efficiency. Electrochemical advanced oxidation technology is considered to be an effective process. This study presents an investigation of the kinetics, mechanism and influencing factors of Diclofenac (DCF) degradation by an electrochemical process with the boron doped diamond anodes. Relative operating parameters and water quality parameters are examined. It appears that the degradation follows the pseudo-first-order degradation kinetics. DCF degradation was accelerated with the increase of pH from 6 to 10. The degradation was promoted by the addition of electrolyte concentrations and current density. HA and HCO3− significantly inhibited the degradation, whereas Cl− accelerated it. According to the inhibition tests, hydroxyl radicals (•OH) and sulfate radicals (SO4•–) contributed 76.5% and 6.5%, respectively, to the degradation. Sodium sulphate remains a more effective electrolyte, compared to sodium nitrate and sodium phosphate, suggesting the quenching effect of nitrate and phosphate on •OH. Major DCF transformation products were identified. According to the degradation products detected by liquid chromatography-mass spectrometry, hydroxylation and decarboxylation are the main pathways to DCF degradation; meanwhile, dechlorination, chlorination and nitro substitution are also included.