Biosorption of metal ions using chitosan, chitin, and biomass of Rhizopus oryzae

The biosorptive capacity of dried biomass fungus Rhizopus oryzae Went & Prinsen-Geerlings for metal sorption was compared with commercially available sources of chitin, chitosan and chitosan cross-linked with benzoquinone. Initial pH of the metal solution significantly influenced metal uptake capacity. The optimum biomass/solution ratio for metal uptake in all systems was 1 g/L. The highest metal uptake values (137, 108, 58, and 124 mg/g, respectively, for copper, zinc, arsenic, and chromium) were achieved with chitosan (1 g/L, at pH 4) from initial metal concentrations of 400 mg/L. Decreases in mean metal concentrations from a simulated copper/zinc mine effluent were 73%, 14%, and 36% for copper, aluminum, and zinc, respectively, which corresponded to respective metal uptake values of 16, 11, and 21 mg/g. Sorption from a simulated gold mine effluent showed decreases in mean concentrations of aluminum, arsenic, and copper of 85%, 30%, and 92%, respectively, which corresponded to respective metal uptake values of 3.0, 6.0, and 1.6 mg/g. The observed decreases in copper levels to concentrations below 1 mg/L indicate potential for specific polishing applications. At low pH, R oryzae biomass was more resistant than was chitosan. Cross-linking with benzoquinone under alkaline conditions conferred stability to the chitosan biomass under low pH, but some reduction in sorption capacity was observed.