Microbial granules: a novel biomaterial for U(VI) removal

The study seeks to examine whether self-immobilised microbial aggregates could be used as novel biosorbents for heavy metals/radionuclides. Aerobic microbial granules were cultivated in a laboratory sequencing batch reactor using acetate as carbon source. Batch experiments were carried out at different initial U(VI) concentrations to determine the kinetics and maximum U(VI) removal capability of the granules. The granules were able to remove U(VI) from aqueous solution in the pH range 1.0 to 8.0. Removal of uranium by granules was rapid in acidic pH as compared to that at neutral or basic pH. The maximum U(VI) removal capacity of granular biomass was found to be 218 mg g-1 granular biomass. Physical integrity of the microbial granules remained intact in the tested pH range. Up to 80% of the sorbed uranium could be desorbed from the granules using low pH(1.0) aqueous solution or 1 M HNO3. The granules, after exposure to the uranium solution, were analyzed using x-ray photoelectron spectroscopy, The study suggests that microbial granules could be used as effective biosorbent material for recovering uranium from nuclear wastes. (author)