Advanced Ozone Oxidation Systems for Organic Pollutant Degradation: Performance Evaluation and Mechanism Insights

Textile dyeing wastewater, rich in recalcitrant organic compounds such as azo and anthraquinone dyes, poses significant environmental concerns. This study investigates the degradation of methyl orange (MO) using two ozone (O3) oxidation systems—O3/H2O2 and O3/K2S2O8—and analyzes the degradation products and toxicity via ESR characterization. The O3/K2S2O8 system shows a higher removal rate in the initial stage (<4 min) due to rapid ·SO4- radical generation. However, O3/H2O2 produces more ·OH radicals, leading to better overall degradation performance. The O3/K2S2O8 system is more effective for pollutants with electron-rich groups, such as Congo red and sulfamethoxazole, while O3/H2O2 performs better in natural lake water. Mechanistic studies reveal that ·O2- is the dominant oxidizing species in O3/H2O2, while ·SO4- and ·O2- dominate in O3/K2S2O8. The toxicity of degradation products is assessed, showing lower bioaccumulation and developmental toxicity in most intermediate products compared to MO. This research provides valuable insights into the use of combined ozonation-peroxidation coupling technology for effective wastewater treatment.