Enrichment of U(VI) on Bacillus subtilis/Fe3O4 nanocomposite

The enrichment of U(VI) on Bacillus subtilis/Fe3O4 (B. subtilis/Fe3O4) nanocomposites was investigated by batch and XPS analysis. Herein, B. subtilis/Fe3O4 nanocomposites were successfully synthesized via one-step method and characterized by SEM, XRD, zeta-potential and FT-IR analysis. The characteristic results showed uniform decoration of nano-Fe3O4 particles on B. subtilis surface by chemical bonds. The batch experiments showed that the sorption of U(VI) on B. subtilis/Fe3O4 was independent of ionic strength, indicating the formation of inner-sphere surface complexion. The sorption data of U(VI) onto B. subtilis/Fe3O4 can be satisfactorily fitted by pseudo-second-order model. The calculated thermodynamic parameters showed that U(VI) sorption on B. subtilis/Fe3O4 was a spontaneous and endothermic process. FT-IR and XPS analysis indicated that the formation of inner-sphere complexes were mainly due to the combination of U(VI) with oxygen-containing groups (i.e., carboxylate and phosphate groups) of B. subtilis/Fe3O4 surface, whereas reductive precipitation also contribute to the U(VI) sorption at low pH. The findings herein highlight the application of microbe-based composites in the removal of radionuclides in cleanup.