Biosorption of uranium and thorium

TLDR

Selected samples of waste microbial biomass from various industrial fermentation processes and biological treatment plants were screened for biosorption of uranium and thorium in aqueous solutions. Biosorption isotherms were used to evaluate uptake capacity of the biomass, compared to activated carbon and ion exchange resin used in uranium production. The biosorption isotherms were concentration‑independent, with optimal uptake at pH 4–5; Rhizopus arrhizus achieved >180 mg g⁻¹, removing 2.5–3.3× more uranium and 20× more thorium than ion‑exchange resin and 2.3× more than activated carbon, outperforming all other biomass types.

Abstract

Abstract Selected samples of waste microbial biomass originating from various industrial fermentation processes and biological treatment plants have been screened for biosorbent properties in conjunction with uranium and thorium in aqueous solutions. Biosorption isotherms have been used for the evaluation of biosorptive uptake capacity of the biomass which was also compared to an activated carbon and the ion exchange resin currently used in uranium production processes. Determined uranium and thorium biosorption isotherms were independent of the initial U or Th solution concentration. Solution pH affected the exhibited uptake. In general, lower biosorptive uptake was exhibited at pH 2 than at pH 4. No discernible difference in uptake was observed between pH 4 and pH 5 where the optimum pH for biosorption lies. The biomass of Rhizopus arrhizus at pH 4 exhibited the highest uranium and thorium biosorptive uptake capacity (g) in excess of 180 mg/g. At an equilibrium uranium concentration of 30 mg/liter, R. arrhizus removed approximately 2.5 and 3.3 times more uranium than the ion exchange resin and activated carbon, respectively. Under the same conditions, R. arrhizus removed 20 times more thorium than the ion exchange resin and 2.3 times more than the activated carbon. R. arrhizus also exhibited higher uptake and a generally more favorable isotherm for both uranium and thorium than all other biomass types examined.