Comparison of direct and indirect microbubble plasma with PMS for efficient degradation of ciprofloxacin in water

In this study, the effects of direct microbubble plasma (DMBP) and indirect microbubble plasma (IMBP) on peroxymonosulfate (PMS) activation were investigated for the synergistic degradation of ciprofloxacin (CIP) and their efficiencies were compared. The effects of discharge voltage, gas flow rate, and PMS dosage on CIP degradation efficiency were systematically examined. Under optimal conditions, CIP removal in the DMBP/PMS system reached 91.74 %, which is significantly higher than that in the DMBP (by 37.38 %), IMBP/PMS (by 48.53 %), and IMBP (by 61.62 %) systems. These results highlight the superior performance of DMBP and its strong synergy with PMS. UV–vis spectroscopy and total organic carbon analyses confirmed that PMS addition enhanced both degradation and mineralization. Reactive species detection and radical scavenging experiments identified singlet oxygen, hydroxyl radicals, and sulfate radicals as key active species. Liquid chromatography–mass spectrometry revealed 11 intermediates, from which, three major degradation pathways were inferred. Toxicity evaluation indicated reduced solution toxicity after treatment. Overall, the study conducted a comparative analysis of microbubble plasma systems and proposed a plasma-based strategy for efficient CIP degradation, offering insights into antibiotic-contaminated water treatment. • The PMS activation by DMBP vs IMBP for synergistic CIP degradation was compared. • The MBP system efficiently activated PMS to enhance CIP degradation. • 1 O₂, ·OH and SO 4 − · were the key active species in CIP degradation. • 11 intermediates and 3 possible degradation pathways were proposed based on LC-MS.