The nature of Schwertmannite and Jarosite mediated by two strains of Acidithiobacillus ferrooxidans with different ferrous oxidation ability

► Jarosite and Schwertmannite biosynthesized by two strains of A. ferrooxidans. ► The materials are varied in color, shape, surface area and crystallinity. ► The Cr(VI) adsorption capacity of Schwertmannite was higher than Jarosite. ► Adsorption capacity of the materials varies inversely with their crystallinity. ► Adsorption capacity is related to the ferrous oxidation ability of the bacteria.