Microorganism-derived carbon microspheres for uranium removal from aqueous solution

• Microbial cells were applied to hydrothermal carbonization.
• Hummers method was employed to oxidize microorganism-derived hydrothermal carbon.
• Functional hydrothermal carbon was obtained without chemical grafting.
• The sorbent exhibits high sorption capacity for uranium.

Saccharomyces cerevisiae, a typical industrial microorganism, was employed as a precursor to directly synthesize carbon microspheres. After a low temperature hydrothermal treatment (180 °C, 12 h), the microbial cells were successively transferred to carbon microspheres that had a diameter of 3–5 μm. The Hummers method was used to chemically modify the hydrothermal carbon materials to obtain functional materials for uranium removal. The characterizations and analysis showed that the morphology of the hydrothermal carbon was partially destroyed after functionalized activation, and abundant oxygen-containing groups were introduced onto the material surface. The results of the sorption behavior showed that the uranium (U) sorption capacity of the modified sorbent reached up to 183.4 mg g−1, which was an improvement of approximately 4.6 times relative to the raw carbon materials. The thermodynamic and kinetic parameters demonstrated the removal process to be spontaneous, endothermic and pseudo-second-order chemisorption. The selective sorption of U(VI) from the simulated nuclear effluent at different pH values suggested that the sorbent displayed a desirable selectivity for the U(VI) ions over the other 11 competitive cations.

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