Highly efficient degradation of ofloxacin in water by plasma/persulfate/ZnO system
Treatment of antibiotics in water is of great significance for ecological safety and human health.Non-thermal plasma has been proven to be effective in degrading aqueous antibiotics,but the low energy utilization efficiency has always limited its further application.Previous studies have shown that plasma activated persulfate(PS)can improve the utilization efficiency of energy and degradation efficiency of antibiotics.However,its photons and chemical substances are still not fully utilized,and the low utilization efficiency of energy has not been truly solved.Based on this,this work proposed to use ZnO to promote PS activation in plasma system for ofloxacin(OFX)degradation in water,thereby significantly improving energy utilization efficiency of plasma and degradation efficiency of organic compounds.ZnO nanoparticles were prepared by hydrothermal method,and characterized by scanning electron microscopy and transmission electron microscopy.After adding PS into the plasma,the degradation efficiency of OFX increased.After further adding ZnO to the plasma/PS system,the degradation efficiency of OFX was further improved.The degradation efficiency of OFX by plasma,plasma/PS and plasma/PS/ZnO systems reached 53.6％,82.8％and 98.9％,respectively.Increasing the input voltage favored OFX degradation.Lower initial concentration resulted in a higher OFX degradation efficiency.The degradation of OFX was more favorable under alkaline conditions compared to acidic and neutral conditions.Electron spin resonance(ESR)results showed that the plasma/PS/ZnO system was capable of generating OH,·SO4-and 1O2.Higher input voltage improved the generation of·OH,·SO4-and 1O2.The capture agent experiments showed that OH,·SO4-,·O2-and 1O2 all played a positive role in the degradation of OFX.During the plasma discharge,the solution pH gradually decreased while the conductivity gradually increased.Plasma/PS/ZnO was able to achieve mineralization of OFX,which reached 49.6％.The biochemistry was improved and the COD removal could reach 69.5％.Degradation pathways of OFX were identified through LC-MS and DFT analysis.The toxicity analysis of intermediates using ECOSAR showed that the toxicity of OFX decreased after degradation.ZnO had more desirable reusability properties.
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