Application of Fe-doped biochar in Cr(VI) removal from washing wastewater and residual Cr(VI) immobilization in contaminated soil

Abstract

High-content Cr(VI)-contaminated soils are challenging to remediate using a single remediation technique. This study combined soil washing and immobilization to remediate high-content (3440 mg kg−1) Cr(VI)-contaminated soil, which investigated the effects of operating time, temperature, and liquid-solid ratio (LSR) on the Cr(VI) removal efficiency of soil washing and evaluated the potential of Fe-doped biochar (FeBC) in soluble Cr(VI) removal from the washing wastewater and residual Cr(VI) immobilization in the washed soil. The Cr(VI) removal efficiency of soil washing increased with the operating time, temperature, and LSR, but still cannot remove Cr(VI) to achieve the safety content (<100 mg kg−1). FeBC showed satisfactory potential in both Cr(VI) removal and immobilization from wastewater and soil, in which the main mechanisms involve ion exchange, redox, and coprecipitation. These results demonstrate applying soil washing & immobilization to remediate high-content Cr(VI)-contaminated soil is a promising alternative method.