Improvement of the degradation of pesticide deethylatrazine by combining UV photolysis with electrochemical generation of hydrogen peroxide

An electrochemically induced UV/H2O2 (E-UV/H2O2) process was developed by combining UV254 irradiation with electrolysis. The E-UV/H2O2 process uses a carbon-based cathode to electrochemically produce H2O2 from O-2 in the sparged oxygen gas, air, or from O-2 generated from anodic side reactions such as water oxidation. The in-situ generated H2O2 then undergoes UV254 induced photolysis to yield (OH)-O-center dot, which is a powerful oxidant and can therefore significantly enhance pollutant degradation in the E-UV/H2O2 process. Results show that when pure O-2, air, or anodically-induced O-2 (without aeration) was used as the oxygen source for cathodic H2O2 production, the E-UV/H2O2 process increased the rates of deethylatrazine (DEA) degradation by similar to 205%, 148%, and 116%, respectively, compared with the mathematical sum of the individual rates of corresponding UV photolysis (k = 0.129 min(-1)) and electrolysis (k = 0.003 min(-1)) processes. Due to its faster pollutant degradation kinetics, the E-UV/H2O2 process decreased the electrical energy consumption for 90% DEA removal by similar to 49-64% compared with UV photolysis alone. These results indicate that by applying a small current to electro-generate H2O2 from O-2 during UV irradiation, the E-UV/H2O2 process can significantly improve the kinetics and energy efficiency for pollutant degradation. The E-UV/H2O2 process may thus offer a simple and effective way to improve the performance of existing UV processes for pollutant degradation in water and wastewater treatment. (C) 2016 Elsevier B.V. All rights reserved.