Use of dead fungal biomass for the detoxification of hexavalent chromium: screening and kinetics

The removal of hexavalent chromium from aqueous solution was carried out in batch experiments using dead biomass of four fungal strains - Aspergillus niger, Rhizopus oryzae, Saccharomyces cerevisiae and Penicillium chrysogenum. All of these dead fungal biomass completely removed Cr(VI) from aqueous solutions, that of R. oryzae being the most effective. Cr(VI) was removed from aqueous solutions by the reduction to Cr(III) when it contacted with the biomass. The removal rate of Cr(VI) increased with a decrease in pH or with increases of Cr(VI) and biomass concentrations. In particular, the removal rate of Cr(VI) was proportional to total chromate concentration [Cr(VI)], and equivalent concentration of organic compounds [OC], suggesting a simple rate equation in a form of d[Cr(VI)]/dt = -k[Cr(VI)][OC]. This model fitted well with the experimental data obtained at pH 2, supporting the mechanism that Cr(VI) is removed via a redox reaction. From the practical view point, the abundant and inexpensive dead fungal biomass could be used for the conversion of toxic Cr(VI) into less toxic or nontoxic Cr(III). (c) 2005 Elsevier Ltd. All rights reserved.