Efficient Degradation of High-Concentration Benzotriazole Wastewater via UV/H₂O₂/O₃Operation: Degradation Mechanism, Toxicological Evaluation, and Economic Analysis

This work reports an efficient treatment for wastewater containing a high benzotriazole (BTZ) concentration. The treatment uses the combinational UV/H₂O₂/O₃system under basic condition. The traditional UV/H₂O₂operation 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 O₃to the UV/H₂O₂system, 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/O₃system. The reaction parameters including the H₂O₂dosage, O₃concentration, initial pH, and inorganic anions were found to influence the degradation. Further, the optimal conditions were determined: H₂O₂dosage of 0.09 mol/L, O₃concentration 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.