New insight into the removal process of benzotriazole UV stabilizers by UV/H₂O₂: Integrating quantum chemical calculation with CFD simulation

Benzotriazole UV stabilizers (BT-UVs) are important UV absorbers. As high-production chemicals and potential hazards, their ubiquitous presence in aquatic environments is of greatly pressing concern. Herein, the removal of six typical BT-UVs by UV/H₂O₂ was comprehensively investigated by quantum chemistry calculation integrated with CFD simulation. Utilizing such a micro and macro incorporated model in treating contaminants is the first report. From the micro-view, degradation mechanisms of BT-UVs by •OH oxidation were determined, and corresponding rate constants were obtained with values of 10⁹∼10¹⁰ M⁻¹s⁻¹. In a macroscopic aspect, combining the established kinetic model and CFD simulation, the effects of UV lamp power (P), volumetric flow rate (Q_v), and H₂O₂ dosage ([H₂O₂]₀) on removal yields of BT-UVs were expounded, increasing P or [H₂O₂]₀ or decreasing Q_v are effective in improving removal yields of BT-UVs, but the enhancement was abated when P or [H₂O₂]₀ increased to a certain level. When [H₂O₂]₀ is 5 mg/L and Q_v is decreased from 0.1 to 0.05 m³/h, the removal yields of BT-UVs could achieve more than 95% (P = 150 W) and 99% (P = 250 W), respectively. This work provides a new interdisciplinary insight for investigating organic contaminant removal in potential industrial applications of UV/H₂O₂ systems.