乳化纳米铁(EZVI)强化地下水氯代烃还原脱氯

对氯代烃污染地下水进行厌氧微生物还原脱氯时,存在微生物驯化时间长、pH值持续降低、有毒中间产物累积等限制修复效率的问题,为解决上述问题,本课题组制备了一种乳化油(EVO)包覆纳米零价铁(NZVI)的修复试剂,即乳化纳米铁(EZVI),其可以抑制NZVI钝化,增强反应速率并促进厌氧微生物脱氯反应.通过静态批实验探究了EZVI与三氯乙烯的反应动力学及EZVI对四氯乙烯(PCE)还原脱氯的中间代谢产物,并阐明了该过程机理.结果表明EZVI可以有效延缓NZVI钝化、提高反应活性,反应符合一级反应动力学,k_obs=0.182d^-1;EZVI还原PCE可以减少中间产物二氯乙烯的积累,10天内去除PCE达到97.2%,比EVO还原体系提高了68.9%;反应过程中pH值保持在6.5~7.5,ORP值在-50~10mV,提供了良好的还原环境,有效促进了厌氧微生物脱氯反应进行.

Enhanced reductive dechlorination of chlorinated hydrocarbons in groundwater by emulsified zero-valentiron

The biological reduction is an alternative for the remediation of chlorinated hydrocarbons polluted groundwater. However, some issues limit its effectiveness, such as long start up time for microbial acclimatization, continuous pH reduction and the accumulation of toxic by-products. Aiming at the limits, emulsified zero-valent iron (EZVI) was prepared by nano-zero-valent iron (NZVI) coated with emulsified oil (EVO) to retard NZVI passivation and continuously provide carbon source for anaerobic microbial dechlorination. The static batch experiments were conducted to study the kinetics of TCE reduction by EZVI and the intermediate metabolites of tetrachloroethylene (PCE) reduction by EZVI. The results showed that EZVI could effectively retard the passivation of NZVI and enhance the reaction activity.The removal process of TCE by EZVI was a first-order reaction and the reaction rate constant k_obs=0.182d^-1. Reduction of PCE by EZVI can inhibit the accumulation of DCE. On the 10th day, 97.2% PCE was removed by EZVI, which was 68.9% higher than that by adding EVO. In the reaction process, pH and ORP maintained at 6.5-7.5 and -50-10mV, respectively, which provided a beneficial reduction environment for the effective enhancement of the anaerobic biological dechlorination reaction.