FeSm原位修复砷污染地下水的实验研究

In-situ remediation of arsenic contaminated groundwater by FeS_m: Experimental study

在以高砷地下水为主要饮水水源的偏远农村地区,研发一种经济高效、操作简便的砷污染处理技术对解决其饮水安全问题具有重大意义.本文通过室内柱实验,利用Fe SO_4、NaAsO_2和Na_2S交替注入方法,完成并优化了硫化亚铁型除砷材料的制备.同时,探讨了强还原条件下含水层原位搭载除砷过程与机制.研究表明,FeSO_4∶Na_2S摩尔比为5∶4,连续注入120 h为最佳原位搭载条件;搭载实验柱除砷过程中,As(Ⅲ)(1000μg·L^(-1))穿透时间(100 h)远高于示踪剂荧光素钠(1.25 h)所需时间,其阻滞因子达37,表明硫化亚铁型除砷材料具有显著的除砷效果;除砷前后硫化亚铁涂层的表征结果说明,原位搭载除砷过程中,As(Ⅲ)与硫化亚铁发生的吸附/共沉淀形成富砷草莓状黄铁矿是实现固砷的主要机理.

The occurrence of natural high arsenic groundwater in some rural areas results in the suffering of arsenic exposure for local residents,therefore,a low-cost and easy-operating remediation technique would be very helpful and useful to assure the safe drinking water supply. Accordingly,in this study,alternating injection of FeSO_4,NaAsO_2 and Na_2S were performed to synthesize a Fe-sulfide material,which was coated on quartz sand to remove As from groundwater. Column experiments were furthermore conducted to determine the optimal conditions for Fe-sulfide material preparation and the mechanism of in-situ arsenic immobilization. The results indicate that the optimal molar ratio of FeSO_4∶ Na_2Sis_5∶4（ in mmol·L^（-1））,and the corresponding coating time is 120 h. The breakthrough time of As（ Ⅲ）（ 100 h） is significantly higher than that of fluorescein sodium（ 1.25 h） which was considered as an inactive tracer,and As（ Ⅲ） retardation factor is 37,indicating the high removal capacity of coated Fe-sulfide materials for As. The results of SEM and EDS indicate that As（ Ⅲ） can be incorporated into Fe sulfides to form As-bearing framboidal pyrite during the experiment,thereby realizing arsenic immobilization.