Characterisation of surface uptake and biosorption of cationic nuclear fission products by sulphate-reducing bacteria

Abstract

The treatment of radioactive fission products – 90Sr2+, 60Co2+ and 137Cs+ – from simulated nuclear wastewater was evaluated using locally-isolated sulphate-reducing organisms. In this study, sulphate-reducing bacteria (SRB) were used as biosorbents for removal of the cationic fission products. The cultures achieved 90%, 100%, and 80% removal of Sr2+, Co2+ and Cs+, respectively, for a 75 mg×ℓ-1 solution of each metal under a low ionic strength of 0.01 M. Increasing the ionic strength of the solution to 0.5 M resulted in a decreased metal uptake to 80%, 65% and 70% for Sr2+, Co2+ and Cs+, respectively. Approximately 68% of the adsorbed fraction on cell surfaces was exchangeable (i.e., was desorbed under acidic conditions). Using surface complexation models and equilibrium modelling analysis, reaction sites on the cell walls of the cultures were determined to belong to the –COOH and –H2PO4 groups (pKa = 4–5 and 7–8, respectively).

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