Search

[Display omitted] • Underwater plasma bubbles were used to degrade cefixime in water. • Complete cefixime degradation with high-energy yield of 1.5 g/kWh. • Degradation of cefixime was conducted by reactive species, especially short-lived OH radicals. • Degradation pathways of cefixime were proposed by intermediates identified by LCMS. • Plasma treatment leads to the loss of antibacterial activity and cytotoxicity of cefixime. Excessive use and indiscriminate discharge of antibiotics inevitably lead to their accumulation in the environment, posing significant ecological and physiological risks. Non-thermal plasma (NTP) is receiving increasing attention as a sustainable technology for the efficient breakdown of these antibiotics as well as other contaminants. However, implementation of NTP technology still faces several hurdles, particularly the maximization of the reactive plasma effects and the practical scaling approaches. In this study, we generated NTP inside forming bubbles with enlarged gas-liquid interfacial areas for efficient delivery of reactive plasma species to target cefixime antibiotic molecules in aqueous solution. The degradation of cefixime was largely dependent on the different number of microholes, air flow rate, discharge power, plasma exposure time and solution properties. Results show that a high-performance degradation was achieved in the 10-microhole reactor with an energy yield of 1.5 g/kWh, after 30 min of plasma treatment. Based on LC-MS analysis, an NTP-initiated cefixime degradation pathway was proposed. Cytotoxicity studies demonstrated that the antibiotic activity of cefixime was effectively and wholly deactivated by the plasma process, and that no toxic effects of the 30 min-treated water were observed toward human cell lines. Furthermore, considering that air was employed as the inducer gas, which results in the formation of reactive nitrogen species in the water, the treated water was able to enhance seedling growth, further contributing to the societal and economic benefits of this plasma-based antibiotic degradation strategy. [ABSTRACT FROM AUTHOR]

[Display omitted] • Underwater plasma bubbles were used to degrade cefixime in water. • Complete cefixime degradation with high-energy yield of 1.5 g/kWh. • Degradation of cefixime was conducted by reactive species, especially short-lived OH radicals. • Degradation pathways of cefixime were proposed by intermediates identified by LCMS. • Plasma treatment leads to the loss of antibacterial activity and cytotoxicity of cefixime. Excessive use and indiscriminate discharge of antibiotics inevitably lead to their accumulation in the environment, posing significant ecological and physiological risks. Non-thermal plasma (NTP) is receiving increasing attention as a sustainable technology for the efficient breakdown of these antibiotics as well as other contaminants. However, implementation of NTP technology still faces several hurdles, particularly the maximization of the reactive plasma effects and the practical scaling approaches. In this study, we generated NTP inside forming bubbles with enlarged gas-liquid interfacial areas for efficient delivery of reactive plasma species to target cefixime antibiotic molecules in aqueous solution. The degradation of cefixime was largely dependent on the different number of microholes, air flow rate, discharge power, plasma exposure time and solution properties. Results show that a high-performance degradation was achieved in the 10-microhole reactor with an energy yield of 1.5 g/kWh, after 30 min of plasma treatment. Based on LC-MS analysis, an NTP-initiated cefixime degradation pathway was proposed. Cytotoxicity studies demonstrated that the antibiotic activity of cefixime was effectively and wholly deactivated by the plasma process, and that no toxic effects of the 30 min-treated water were observed toward human cell lines. Furthermore, considering that air was employed as the inducer gas, which results in the formation of reactive nitrogen species in the water, the treated water was able to enhance seedling growth, further contributing to the societal and economic benefits of this plasma-based antibiotic degradation strategy. [ABSTRACT FROM AUTHOR]

• Underwater plasma bubbles facilitated mass transfer of highly reactive species. • Plasma catalytic bubbles using CeO 2 enhanced the AP removal efficiency. • Catalytic performance and durability of CeO 2 were improved by plasma activation. • Degradation mechanisms of AP were proposed by intermediates identified by LCMS. Interactions between effects generated by non-thermal plasma (NTP) and catalysts are increasingly investigated, ranging from energy conversion and material synthesis to pollutant degradation (e.g. volatile organic compounds, VOCs) and water purification. To make the water ecosystem more environmentally and economically sustainable, green and efficient wastewater treatment technologies are urgently required. In this study, a plasmacatalytic bubble column reactor was designed to generate underwater plasma bubbles (PBs) for efficient delivery of plasma-produced gaseous reactive oxidative species to the liquid phase for subsequent applications. This system shows great potential for degrading a stubborn water contaminant azophloxine (AP), which was further enhanced with an addition of CeO 2 catalysts, resulting in the catalytic oxidation of the azo dyes. Moreover, the performances and durability of CeO 2 were further improved via plasma pre-activation. The plasma-treated CeO 2 (CeO 2 -P) displayed a combination of favourable properties, such as a higher concentration of oxygen vacancies and Ce3+ (observed by XPS), a narrowed energy bandgap, and an increased specific surface area (by 41.39%). Compared with the sole PBs and PBs/CeO 2 systems, the highest removal efficiency and kinetic constant up to 99.5% and 0.907 min−1, respectively, were achieved in the PBs/CeO 2 -P system. Reactive species trapping corroborated that ·OH and ·O 2 – played an integral part in AP degradation. Finally, intermediates in the process of AP degradation were identified and a degradation pathway was proposed. This research would offer a promising remediation methodology for water purification via the integration of underwater plasma bubbles and CeO 2 catalysts. [ABSTRACT FROM AUTHOR]