Enhanced plasma-photocatalysis degradation of coumarin using modified fountain dielectric barrier discharge and WO₃/ZnO nanoparticles

Coumarin is widely used in cosmetic and pharmaceutical formulations, and as a hydroxyl radical (•OH) probe, yet it is increasingly recognized as an emerging contaminant because of its persistence, bioaccumulation potential, and toxic transformation products. Plasma-based advanced oxidation processes are promising for refractory pollutants but are limited by high energy demand, incomplete mineralization, and poor mechanistic understanding of plasma–catalyst interactions under comparable conditions. Here, a modified fountain dielectric barrier discharge (MF-DBD) reactor was evaluated for aqueous coumarin degradation: alone and with WO₃, ZnO, and WO₃–ZnO catalysts. Degradation kinetics, reactive species roles, mineralization via total organic carbon (TOC) removal, and catalyst reusability were assessed. Plasma alone showed concentration-dependent biphasic first-order kinetics dominated by •OH, achieving 95.0 ± 1.7% removal at 16 mg L −1 . Coupling with WO₃ enhanced reactive oxygen species generation, increasing the fast-phase rate constant from 0.088 to 0.208 min −1 and enabling complete degradation with improved mineralization (84.2 ± 0.2% TOC). ZnO mainly stabilized the solution pH but showed limited mineralization, whereas WO₃–ZnO composites exhibited composition-dependent coupling; the 70:30 composite reached 99.2 ± 0.1% degradation and 81.3 ± 0.03% TOC removal. Reusability tests showed negligible activity loss, indicating good stability of the catalysts. These results demonstrate that MF-DBD plasma–catalyst coupling, particularly with WO₃, is an energy-efficient and mechanistically robust approach for mineralizing recalcitrant organic pollutants in water, though identification of intermediates and toxicity assessment remain necessary. • MF-DBD plasma effectively degrades coumarin in water. • Plasma+WO₃ achieves ≤100% coumarin degradation and 84% TOC removal • Coupling plasma+WO₃ enhances fast-phase kinetic constant from 0.088 to 0.208 min −1 • Plasma+WO3 present superior energy yield 307.4 ± 5.3 mg kWh −1 for pollutant mineralization.