Catalyst-free UV/H2O2 oxidation of high-concentration organic pollutants: Degradation kinetics and molecular reactivity

Catalyst-free UV/H 2 O 2 oxidation avoids catalyst recovery and metal leaching, but its application to high-strength organic wastewater is often limited by inefficient oxidant utilization and incomplete mineralization. Herein, the degradation of structurally distinct organic pollutants at high initial concentrations was investigated under ambient conditions. RhB at 100–250 mg/L was almost completely degraded within 120 min, with TOC removal reaching approximately 70%, while Rh-6G, metronidazole, and phenol achieved 95–100% removal at 100 mg/L. Comparative analyses of pollutant degradation, H 2 O 2 conversion, and TOC removal revealed that pollutant elimination and mineralization were governed by molecular structure and transformation behavior rather than H 2 O 2 consumption alone. Radical-quenching experiments confirmed ·OH as the dominant reactive species. Spectroscopic and chromatographic analyses indicated the destruction of parent pollutants and subsequent oxidation of transformation products, while DFT calculations predicted the preferential sites for ·OH attack and provided molecular-level insight into structure-dependent oxidation behavior. The results establish a structure–reactivity–mineralization relationship and demonstrate the potential of catalyst-free UV/H 2 O 2 oxidation for treating high-strength organic wastewater.