Enhanced antibiotic degradation in micro-nanobubble-assisted dielectric barrier discharge systems: The role of gas-liquid interfaces in ROS exposure

Micro-nanobubble-assisted dielectric barrier discharge (MNB-DBD) alleviates gas-liquid mass transfer limitations and enhances interfacial reactions. In this study, we established a comparative, quantitative framework that coupled the analysis of probe-based reactive species exposure with an interfacial mass transfer-reaction model to analyze MNB effects in in situ and ex situ DBD systems under matched operating conditions. The ex situ system performed optimally at pH 11, where the degradation rate with MNBs was ∼20-fold higher than that with conventional bubbles (CBs). The in situ system operated optimally at pH 3, with MNBs resulting in only a ∼1.1-fold enhancement relative to CBs. Both systems produced ∙OH and O₂^∙-, whereas O21 was detected only in the in situ system. Probe-based kinetic model analysis indicated that the rate disparity was primarily attributed to differences in ∙OH exposure. Mechanistically, the interfacial mass transfer-reaction kinetic model indicated that the MNBs in the ex situ system increased the cross-interface flux of O₃. In contrast, the in situ system depended on locally generated, short-lived Reactive Oxygen Species and their near-interface exposure. Collectively, the probe-based kinetic model and the interfacial mass transfer-reaction kinetic model provide a mechanistic basis for optimizing MNB-DBD applications.