气体扩散电极体系电化学消毒

Electrochemical Disinfection Using the Gas Diffusion Electrode System

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,主要探讨了膜电极中PTFE质量分数W(PTFE)和造孔剂含量m(NH4HCO3),外部操作条件pH值和氧气流速Q(O2)对杀菌效果的影响.结果表明,W(PTFE)为0.5时,H2O2的产量最高.适量造孔剂的添加有效地提高了杀菌效率,与酸性条件相比,效果在中性条件下更为突出.BET比表面积分析结果表明,随着造孔剂含量的增加,膜电极表面的平均孔径先大幅度减小,后缓慢增加,这有助于电极上的气体传质效果.吸附在杀菌过程中起的作用不大.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为3～10,以载铂量W(Pt)为3‰的气体扩散电极作为阴极进行电解,30 min后杀菌效率均能达到80%以上.在一定范围内增加氧气流速Q(O2)对H2O2的产生及杀菌效率的提高无太大影响.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适当缩短了处理时间,降低了设备投资.机制研究表明,开始时阳极的直接氧化与自由基的产生起了重要作用;随着反应时间的延长,阴极H2O2间接杀菌的作用迅速增强;电解30 min后阴极室和阳极室的杀菌效率基本相当,此时两者的作用接近.

Study on the electrochemical disinfection with the H2O2 produced at the gas diffusion electrode（GDE） prepared from active carbon/ poly-tetrafluoroethylene（PTFE） was performed in the non-membrane cell.The effects of PTFE mass fraction WPTFE and content of the pore-forming agent in GDE m（NH4HCO3）,operating conditions such as pH value and oxygen flow rate Q（O2） on disinfection were investigated,respectively.The experimental results showed that H2O2 reached peak production at WPTFE of 0.5 in GDE.Addition of the pore-forming agent in the appropriate amount improved the disinfection,and this phenomenon was more obvious at neutral pH than at acidic pH.BET specific area analysis indicated that the average pore size in the membrane electrode first decreased significantly with the increasing amount of pore-forming agent,and then increased moderately.This helped the mass transfer of oxygen at the GDE.Adsorption made little or no progress to kill the bacteria during the electrolysis..Drop of pH value resulted in a rapid rise of the germicidal efficacy.This system had a broad pH coverage： when total bacterial count in raw water was 10^6 CFU·mL^-1,pH 3-10,the germicidal efficacy was greater than 80% after 30 min electrolysis using the GDE with WPt of 3‰ as cathode.Increase of the oxygen flow rate Q（O2） within limits had little influence on the production of H2O2 and the succeeding disinfection.On one hand,resistance of the solution and energy consumption on the disinfection increased at high oxygen flow rate,which gave rise to an increase in the operating cost of disinfection with the GDE system;on the other hand,treatment time could be reduced reasonably at high oxygen flow rate,which leads to reduction of equipment investment.Killing mechanism study showed that the direct oxidation and formation of the free radicals at the anode played a greater role in the beginning,and then the oxidative indirect effect of the generated H2O2 at the GDE enhanced rapidly with the prolonging of the reaction time.30 min after electrolysis the germicidal efficacy in the anode compartment was almost the same as in the cathode compartment indicating that their contribution was similar at that time.