Biosorption of uranium by immobilized Saccharomyces cerevisiae

A novel biosorbent was prepared and applied for the removal of uranium from aqueous solution. A new immobilization method was studied and used to embed living yeast cells of Saccharomyces cerevisiae (2% w/v) by sodium sulfate (0.5 mol/L) based on saturated boric acid-alginate calcium cross-linking method. The swelling ratio, hydraulic and chemical stability and bioactivity of immobilized microbial cells were examined. Their ultra-microstructure and property were observed by SEM, TEM and FTIR techniques. The influencing factors, such as contact time, initial uranium concentration, and initial pH were investigated. The adsorption capacity of biosorbent increased from 0.75 to 113.4 μmol/g when the equilibrium concentration of U was 0.9, and 43.9 μmol/L, respectively. U adsorption followed pseudo first-order kinetic model. SEM-EDS and TEM-EDS observation indicated that uranium was adsorbed both on the surface and the inner parts of the biosorbent. FTIR and the XPS results confirmed the role of oxygen in capturing uranium from aqueous solution. XPS analysis showed that the mixture of U (VI) and U (IV) existed on the surface of biosorbent, which evidenced that uranium was microbiologically reduced.