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 O₂ in the sparged oxygen gas, air, or from O₂ generated from anodic side reactions such as water oxidation. The in-situ generated H₂O₂ then undergoes UV₂₅₄ induced photolysis to yield OH, which is a powerful oxidant and can therefore significantly enhance pollutant degradation in the E-UV/H₂O₂ process. Results show that when pure O₂, air, or anodically-induced O₂ (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 ~205%, 148%, and 116%, respectively, compared with the mathematical sum of the individual rates of corresponding UV photolysis (= 0.129 min^-1) and electrolysis (= 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 ~49-64% compared with UV photolysis alone. These results indicate that by applying a small current to electro-generate H₂O₂ from O₂ 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.