In-situ formation of Fe(II)-sulfide coatings on aquifer sediments to remediate high arsenic groundwater

摘要

A field test was conducted to evaluate a novel technology of in-situ remediation of high arsenic aquifer based on microbially-stimulated Fe(II)-sulfide coating formation under reducing conditions. After multiple supply of FeSO_4 into the aquifer for 25 days, groundwater arsenic decreased from an initial concentration of 593 μg/L to 159 μg/L, and further lowered to 136 μg/L 30 days later after field implementation. Microbial sulfate reduction produced high aqueous sulfide that reacted with Fe(II) to firstly form mackinawite on sediment surfaces. Aqueous arsenic was sequestered via surface adsorption and co-precipitation with mackinawite that could be transformed to arsenic-bearing pyrite. Furthermore, As(V) can be reduced by sulfide into As(III) to facilitate its incorporation into the newly-formed Fe(II)- sulfide phases in the environment of enhanced reducing condition.