Aerobic granular biomass: a novel biomaterial for efficient uranium removal.

摘要

Aerobic microbial granules, self-immobilized microbial consortia cultured in aerobically operated bioreactors, primarily consist of mixed species of bacteria ensconced in an extracellular polymeric matrix of their own creation. Such aerobically grown microbial granules have attracted considerable research interest in environmental biotechnology. In recent times, it has been demonstrated that the granules could be used for efficient degradation of recalcitrant organic compounds and for the treatment of a growing number of wastes. This study was conducted to investigate whether aerobic granules could be used as novel biomass material for biosorption of uranium from aqueous solutions. The granular biomass for biosorption experiments was cultivated in a laboratory-scale sequencing batch reactor by feeding with synthetic waste water. Biosorption of uranium (U(VI)) was studied at different initial pH values (1 to 8) and different initial uranium concentrations (6 to 750 mg litre-1). Biosorption was observed to be rapid (<1 h) in acidic pH range (1 to 6) compared to that at pH 7.0 or above. Almost complete removal of uranium was observed in the range 6-100 mg litre-1 in less than 1 h. Redlich-Peterson model gave the best fit when the experimental data were analysed using different adsorption isotherm equations. The maximum biosorption capacity of U(VI) was 218+or-2 mg g-1 dry granular biomass. Further, it was observed that cations such as Na+, K+, Mg+2, and Ca+2 were simultaneously released into the bulk solution during U(VI) biosorption, indicating the involvement of ion exchange mechanism in radionuclide uptake. Live and dead biomass did not show significant difference in U removal, indicating the involvement of a passive sorption process. The study suggests that aerobic granular biomass has the potential as an effective biosorbent material for recovering/removing uranium (and probably other radionuclides) from dilute nuclear wastes..