Packed-bed plasma coupled with microbubbles for the efficient degradation of antibiotics in water: Performance and mechanism

In this study, atmospheric packed-bed dielectric barrier discharge (PB-DBD) plasma was combined with microbubble technology for the efficient degradation of contaminants in water. The antibiotic norfloxacin (NOR) was selected as the target pollutant to systematically investigate plasma-generated reactive oxygen species (ROS) production and microbubble-enhanced mass transfer. Key parameters, such as discharge voltage, frequency, gas flow rate, packing bead diameter, and gas composition were optimized. Experimental results revealed that the packed-bed configuration amplified the local electric field strength by over 10-fold (up to 4.06 × 10⁷ V/m) as compared to empty reactors, significantly enhancing ozone production (150 g/kWh) and hydroxyl radical generation. Microbubbles further improved gas-liquid interfacial contact within the system, achieving 98 % NOR degradation within 3 min under optimal conditions, representing a 142 % improvement over systems without microbubbles. The energy efficiency of the system outperformed that of comparable low-temperature plasma devices, such as plate-water DBD and microwave plasma, due to the dual benefits of improved ROS utilization and reduced energy consumption. This study provides comprehensive technical insights into the generation of plasma-activated gas using PD-DBD and its potential application for antibiotic degradation, establishing a theoretical groundwork for the large-scale implementation of PD-DBD technologies.