Remediation of Cr(VI)-Contaminated Soil Based on Cr(VI)-Reducing Bacterium Induced Carbonate Precipitation

Microbially induced carbonate precipitation (MICP) provides a novel idea to solve the problem of reduction and stabilization of Cr(VI) in contaminated soil. In this study, the remediation of Cr(VI) in severely polluted soil (total Cr = 5530.00 +/- 120.21 mg/kg) by MICP technology combined with the Cr(VI)-reducing bacterium Sporosarcina saromensis W5 was systematically investigated. The results indicated that in W5 and CaCl2 treatment after 35 d of remediation, the Cr in exchangeable fraction could be converted into the oxidizable fraction (F3) and the proportion was 41.49%. Compared to original Cr(VI)-contaminated soil, the content of organic matter and soil urease were enhanced after remediation, indicating the improvement of soil quality. The increase in pH also facilitated the formation and stabilization of carbonate precipitation. In addition, the characterization results showed that Cr(VI) in soil was first reduced to Cr(III), and then formed Ca10Cr6O24(CO3) coprecipitation with CaCO3. The stabilization mechanism of Cr(VI) contained bioreduction, adsorption/complexation, and coprecipitation. The results of this study proposed an efficient and reliable strategy of Cr(VI)-reducing bacterium combined with MICP technology to reduce and stabilize Cr(VI) in high concentration Cr(VI) contaminated soil.