摘要:
以自制活性炭/聚四氟乙烯(PTFE)气体扩散电极在无隔膜体系发生H2O2进行电化学消毒的系统研究,探讨了膜电极中PTFE质量分数WPTFE对氧气电还原特性的影响,研究了膜电极中载铂量WPt和造孔剂含量WNH4HCO3、外部操作条件pH值、氧气流速、溶液含盐量和电流密度对杀菌效率的影响.结果表明,WPTFE对H2O2的产率有明显的影响:产H2O2的峰电流先是随着WPTFE的增加而增大,然后减小.当WPTFE=50%时,峰电流最高.杀菌效果随着载铂量的提高而改善,WPt增加到4‰,杀菌效果和WPt=3‰时的杀菌效果基本相当.适量造孔剂的添加有效地改善了杀菌效果.杀菌效率随着pH值的下降迅速提高;该体系pH值适用范围较广:当原水细菌总数为106cfu·ml-1,pH=3—10,以载铂量WPt=3‰的气体扩散电极作为阴极进行电解,30min后杀菌效率均能达到80%以上.在一定范围内增加氧气流速对H2O2的产生及杀菌效率的变化无太大影响.一方面,高的氧气流速增大了水的电阻,增加了杀菌能耗,提高了气体扩散电极体系杀菌的运行成本;另一方面,高的氧气流速在一定程度上缩短了处理时间,降低了设备投资.含盐量的增加使杀菌能耗减小,因此本电化学杀菌体系更加适合于高含盐量的水.杀菌效率随电流的升高而增加,但电流较大时,杀菌效率增加幅度较小.电流密度控制在6.6mA·cm-2较为适宜.
Abstract:
Study was performed on the electrochemical disinfection with H2O2 produced at the gas diffusion electrode(GDE)prepared from active carbon/ poly-tetrafluoroethylene(PTFE)in the non-membrane cell.The effect of PTFEmass fraction WPTFEon the reduction of oxygen at GDEwas investigated.Additionally,the effect of Pt load WPt and the pore-forming agent content in GDE,operating such as pHvalue,oxygen flow rate QO2,salt content and current density on the disinfection were also investigated.The experimental results showed that WPTFEhad a significant effect on the generation of H2O2: its peak current first increased with WPTFE,then decreased,and reached the highest at WPTFEof 50%.The disinfection improved with increasing Pt load,but its efficiency at WPt of 3% was equivalent to that at WPtof 4%.Addition of the pore-forming agent in the appropriate amount significantly improved the disinfection.lower pHvalue resulted in rapid rise of the disinfection efficiency.This system worked in abroad pHrange: the disinfection efficiency η80% after 30 min electrolysis in the pHrange of 3 to 10 using the GDEwith WPt of 3% as cathode when total bacterial count in raw water was 106cfu·ml-1.Increase of oxygen flow rate within the tested limit had little influence on the generation of H2O2 and the disinfection rate.On the one hand,oxygen flow rate caused an increase in solution's resistance and energy consumption on the disinfection,which gave rise to an increase in the operating cost of the disinfection with the GDEsystem;On the other hand,treatment time could be reduced reasonably at high oxygen flow rate,which leads to reduction of equipment investment.The increase of salt content resulted in reduction of energy consumption on the disinfection.This system,therefore,is more suitable for high salt water.The disinfection efficiency increased with current density.but leveled off at very high current density.Therefore,it is appropriate to control the current density at 6.6 mA·cm-2.
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