MnO₂-loaded microorganism-derived carbon for U(VI) adsorption from aqueous solution

A low-cost industrial microorganism, Saccharomyces cerevisiae, was employed as a precursor to synthesize carbon/MnO₂ composites (MMCs) via an oxidation-reduction reaction and one-step carbonization method for U(VI) adsorption. Scanning electron microscopy and nitrogen adsorption measurement indicated that the microorganism's carbonization could form surface porous structure and increase the specific surface area. Batch experiments showed that the maximum U(VI) adsorption capacity of MMCs reached 207 mg g⁻¹ at [U(VI)]_initial = 25 mg L⁻¹ and pH_initial = 4.5. The obtained thermodynamic and kinetic parameters suggested that the process is endothermic, spontaneous, and chemisorption. FTIR and X-ray photoelectron spectroscopy demonstrated that the surface hydroxyl groups of composites might be the reactive adsorption sites for U(VI). Additionally, 0.5 mol L⁻¹ HNO₃ solution could desorb ~ 95% uranium from U(VI)-loaded MMCs, and materials exhibited good regenerated availability. This study suggests that MMCs can be a potential adsorbent for U(VI) preconcentration and removal from radioactive wastewater.