等离子体/过硫酸盐/ZnO体系高效降解水中的氧氟沙星

Highly efficient degradation of ofloxacin in water by plasma/persulfate/ZnO system

水中抗生素治理对生态安全及人类健康具有重要意义,低温等离子体被证实能够有效降解水中抗生素,然而其能量利用率低的问题一直限制其进一步应用.已有研究表明,等离子体激活过硫酸盐(persulfate,PS)能够提高其能量利用效率及抗生素降解效率,然而其光子及化学效应仍旧未被充分利用,能量利用率低的问题并未真正解决.基于此,本文提出采用ZnO促进等离子体激活PS降解水中氧氟沙星(ofloxacin,OFX),从而大幅度提高等离子体能量利用率及有机物的降解率.采用水热法制备了ZnO纳米颗粒,并采用扫描电镜和透射电镜对其结构进行了表征.在等离子体中加入PS后,OFX的降解率随之提高.进一步向等离子体/PS体系中加入ZnO,OFX的降解率进一步的提升.等离子体、等离子体/PS和等离子体/PS/ZnO体系对OFX的降解率分别达到53.6%、82.8%和98.9%.提高输入电压有利于OFX的降解,较低的初始浓度呈现出较高的OFX降解率.相对于酸性和中性条件,碱性条件下更有利于OFX的降解.电子自旋共振(Electron Spin Resonance,ESR)结果表明,等离子体/PS/ZnO体系能够产生·OH、·SO_(4)^(−)和^(1)O_(2),且较高的输入电压能够提高·OH、·SO_(4)^(−)和^(1)O_(2)的生成量.捕获剂实验证明,·OH、·SO_(4)^(−)、·O_(2)^(−)和^(1)O_(2)均对OFX的降解起到一定作用.等离子体放电的过程中,溶液pH逐渐降低而电导率逐渐升高.相对于去单独等离子体,等离子体/PS/ZnO体系中pH降低及电导率升高的更为明显.等离子体/PS/ZnO能够实现对OFX的矿化,矿化度可达49.6%.同时可生化性提高,COD去除率可达69.5%.通过LC-MS及DFT分析,确定了OFX的降解路径.活性物质主导的OFX的降解路径主要涉及自由基攻击吡啶环和哌嗪环.采用ECOSAR对中间产物毒性分析可知,OFX降解后其毒性降低.ZnO具有较好的重复使用性能.

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,·SO_(4)^(−)and ^(1)O_(2).Higher input voltage improved the generation of·OH,·SO_(4)^(−)and ^(1)O_(2).The capture agent experiments showed that·OH,·SO_(4)^(−),·O_(2)^(−)and ^(1)O_(2) 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.