Efficient Degradation of High-Concentration Benzotriazole Wastewater via UV/H₂O₂/O₃ Operation: Degradation Mechanism, Toxicological Evaluation, and Economic Analysis

Abstract

This work reports an efficient treatment for wastewater containing a high benzotriazole (BTZ) concentration. The treatment uses the combinational UV/H2O2/O3 system under basic condition. The traditional UV/H2O2 operation was proven to be ineffective in the treatment of such sewage, due to the generation of the color intermediates. The degradation of BTZ can be promoted by introducing O3 to the UV/H2O2 system, indicated by the higher synergistic coefficient (S = 2.73). The quenching experiments confirmed that the ·OH species played the key role in the UV/H2O2/O3 system. The reaction parameters including the H2O2 dosage, O3 concentration, initial pH, and inorganic anions were found to influence the degradation. Further, the optimal conditions were determined: H2O2 dosage of 0.09 mol/L, O3 concentration of 10.5 mg/min, and initial pH of 11.0. BTZ can be removed completely with a COD reduction of 98.60% after 270 min of treating under the best process. Using the Fukui function calculation and LC–MS measurements, the BTZ degradation mechanisms were proposed. Predictions using the TEST software showed that the biotoxicity of BTZ containing wastewater decreased after treatment. The operational cost calculated for the best conditions is 0.1813 USD/L.