Highly effective biosorption of Sr(II) from low level radioactive wastewater.

Bacillus subtilis was first used to remove Sr(II) from low-level radioactive wastewater. Influence parameters, biosorption kinetics and biosorption equilibrium were investigated. The results showed that the maximum adsorption capacity of Sr(II) at over 2,000 mg g(-1) by Bacillus subtilis was higher than for other biosorbents. At pH 6.3, Sr(II) concentration of 15 mg L(-1), biomass dosage of 0.3 g L(-1) and temperature of 20 °C, the maximum removal efficiency was as high as 96.3% at 1,440 minutes. The biosorption kinetics and the equilibrium isotherm data can be described by the pseudo-second-order equation and Freundlich isotherm equation, respectively. The negative values of ΔG and the positive values of ΔH implied that Sr(II) biosorption on Bacillus subtilis was a spontaneous and endothermic process. Fourier transform infrared spectroscopy indicated that the functional groups, hydroxyl, carboxylate and amide groups, might participate in the interaction between Sr(II) and Bacillus subtilis.