Use of stainless-steel electrodes on the electrochemical oxidation of naproxen and its transformation products in surface water

© 2021 by the authors. Licensee MDPI, Basel, Switzerland.In this study, stainless-steel electrodes were used to effectively oxidize naproxen and its transformation products in surface water by electrochemical oxidation in short reaction times. An evaluation of the effects of current density, chloride concentrations, and pH on the electrochemical oxidation process (mechanisms, kinetics, and reaction times) was conducted. Results showed that degradation rates of naproxen were greater, and the reaction times were shorter than those reported in other studies for other compounds and electrode materials. Oxidation naproxen and its transformation products were faster at high current densities, high chloride concentrations, and low pH conditions; however, good performance of the electrochemical oxidation process was observed at 16.3 mA/cm2 and pH 5 for both the naproxen and its transformation products, which were oxidized in only 15 min for the treated effluent and 30 min in the case of sludge. At pH 3 and 5, the number of transformation products and the reaction times required for achieving complete oxidation were greater in sludge than in the treated effluent; meanwhile, at pH 7 and 9, the number of transformation products and reaction times needed for non-detection were of the same order in both the treated effluent and the sludge.