Enhanced degradation kinetics of antibiotic-containing medical wastewater via microbubble-enhanced plasma: mechanistic insights and systematic evaluation

The pervasive contamination of aquatic environments by pharmaceutical residues, particularly antibiotics, necessitates the development of efficient and sustainable advanced oxidation technologies. Here, an integrated plasma-microbubble system was developed by coupling atmospheric-pressure dielectric barrier discharge (DBD) with a Venturi-based microbubble generator. With intensified gas-liquid interfacial interactions, the integrated system achieved 99.5% degradation of tetracycline (TC) (100 mg/L) within 10 min, corresponding to a 47.4% enhancement relative to DBD plasma alone. The introduction of microbubbles elevated the degradation performance of air discharge to a level approaching that of pure oxygen plasma, underscoring the efficacy of microbubble integration. Combined analysis of discharge products and scavenger experiments substantiated the enhanced interfacial mass transfer and highlighted O₂⁻ and ·OH as the key reactive species governing degradation. Density functional theory (DFT) calculations combined with liquid chromatograph mass spectrometer (LC-MS) analysis elucidated transformation pathways at the molecular level. Furthermore, antibacterial assays and quantitative structure - activity relationship (QSAR) modeling confirmed a substantial reduction in biological activity and ecotoxicological risk following treatment. By integrating interfacial regulation with systematic mechanistic and toxicity assessment, this work advances the rational design of energy-efficient multiphase plasma reactors.