Electrokinetics coupling with microbially-induced calcite precipitation that strengthens the chromate removal in the bio-electrochemical system

Hexavalent chromium (Cr(VI)) is a well-known carcinogen, which must be completely removed from the contaminated water or reduced to a less toxic state. In this work, a bio-electrochemical platform combining electrokinetics (EK) and microbially induced calcite precipitation (MICP) was assembled to enhance Cr(VI) removal from the stocking solution. The chromate was removed mainly by the chemical precipitation of CaCrO 4 and further immobilized by CaCO 3 produced from the microbial bio-mineralization in the bioremediation. The coupling method was proved to be more effective in increasing the removal efficiencies of Cr(VI) and enhancing the immobilization of Cr(VI) compared with using bioremediation or electrokinetics alone. The maximum efficiency of 97.63% was achieved in the bio-electrochemical experiments. The exchangeable fraction of Cr(VI) was significantly reduced from 40.12% to 22.34% in the precipitation obtained from the bio- electrochemical system. A relatively high voltage was preferred in the coupling system. Generally, the combination of EK and MICP not only strengthened the removal of Cr(VI) from the solution and also significantly reduced the potential re-release of Cr(VI) in the final precipitation.