Remediation of high-concentration Cr(VI)-contaminated soils with FeSO4 combined with biostimulation: Cr(VI) transformation and stabilization

Abstract

Efficient and sustainable technologies for cleaning up of hexavalent chromium (Cr(VI)) contaminated soil are under urgent demand. In this study, chemical reduction and biostimulation were combined to remediate contaminated soil with a high concentration of hexavalent Cr(VI) to compensate for the shortcomings of single-treatment technology. The Cr(VI) concentration, Cr speciation, and bacterial diversity of the contaminated soil were measured after combined remediation with ferrous sulfate (FeSO4) and different electron donors. The changes in various indexes in the soil after microbial death were also studied. The results indicated that the optimal reduction rate of Cr(VI) was as high as 95.20% when 10% FeSO4 was combined with lactic acid. The water-soluble fraction of Cr with the highest toxicity in the soil was almost completely converted into other stable fractions. Stabilization experiments proved that Cr(III) in the remediated soil did not revert to Cr(VI) after microorganism death, and had a good stabilization effect. The bacterial diversity results indicated that Acinetobacter spp. and Pseudomonas spp. were the dominant species during the biostimulation process and might be involved in the reduction of Cr(VI).