Facilitating role of biogenetic schwertmannite in the reduction of Cr(VI) by sulfide and its mechanism

► Schwertmannite was obtained through an oxidation of FeSO4 by Acidithiobacillus ferrooxidans LX5 cell suspensions. ► Schwertmannite can markedly accelerate the removal of Cr(VI) by sulfide. ► The catalysis is ascribed to the activated Fe(III) on schwertmannite serving as a “bridge” in the transportation of electrons between sulfide and Cr(VI).