Reduction and Enrichment of Uranium after Biosorption on Inactivated Saccharomyces cerevisiae

Microorganisms not only have a strong biosorption capacity but also can achieve tremendous volume reduction effects for radionuclide wastes. Batch experiments were conducted to investigate the biosorption characteristics of uranium on inactivated Saccharomyces cerevisiae and the volume reduction and enrichment of uranium after biosorption were also studied in combination with the ashing method. The results revealed that inactivated S. cerevisiae biomass was able to adsorb uranium. The maximum removal efficiency and biosorption capacity for uranium were 96.8% and 31.8 mg/g, respectively. The optimum pH for U(VI) removal was 2.75 and U(VI) biosorption was well described by the Freundlich isotherm model. Thermodynamic investigations showed that biosorption of U(VI) on inactivated S. cerevisiae was a spontaneous and endothermic process. In the kinetic studies, U(VI) adsorption on inactivated S. cerevisiae reached an equilibrium in 60 min and followed a pseudo-secondorder kinetics model. The 100 mg/L of uranium was reduced to less than 0.05 mg/L after 6 rounds gradient descent adsorption, which was enough to meet the National uranium wastewater discharge standards. The ashing experiment demonstrated that ashing process resulted in a large volume and weight reduction ratio as well as enrichment for uranium in the ash. XRD results showed that the species of uranium that existed in the ash were uranium phosphate and KPUO6·3H2O. Waste volume reduction and metal enrichment can be obtained by ashing treatment of the biological absorbent. The method may be beneficial for nuclide and heavy metal disposal treatment in many fields.