Remediation of hexavalent chromium contaminated soil by nano-FeS coated humic acid complex in combination with Cr-resistant microflora.

A novel nano-composite material (CMC-FeS@HA) combining the advantages of humic acid (HA) and FeS was synthesized to remediate hexavalent chromium (Cr(VI)) contaminated soil along with chromium (Cr) resistant microflora. The characteristic analysis confirmed the successful synthesis of the nano-composite, which provided further mechanism evidence of its detoxification effect on polluted soil. Energy Dispersive System analysis proved the adsorption of the microbe consortium (MC) for Cr. After remediation, Cr(VI) in all treatments was dramatically reduced and the leachable Cr in soil treated by CMC-FeS@HA and MC decreased 89.14% compared with control. The result of BCR sequential extraction showed that Cr was stabilized, whose form changed to oxidizable and residual from HOAC-extractable. Besides, CMC-FeS@HA, as a sustained-release acid with high biocompatibility, could continuously decrease the pH of strongly alkaline soil and created a suitable micro-ecological environment for soil microorganisms. Moreover, CMC-FeS@HA dramatically improved soil physicochemical property, soil microbial activity (dehydrogenase, hydrolase, urease, and invertase activities), and soil microecological diversity. In total, this study provided a useful technology for soil remediation, which innovatively combined chemical remediation and microbial-remediation with a positive effect on soil quality, providing a good approach for the multiple technology combination in the environmental cause.