Novel polysaccharide based on modified D-mannose/silica composite for selective and efficient uranium sorption;...

The extraction of uranium from aqueous solutions is a pressing environmental concern because of its radioactive and toxic nature. In this regard, we investigated the efficacy of a novel polysaccharide-base sorbent from D-mannose after modification with silica (SiO₂-CAH-HA) for uranium extraction from simulated and natural leachate solutions (uranium-containing liquor). Characterization methods including; infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM)/Energy-dispersive X-ray spectroscopy (EDX), N₂ adsorption/desorption isotherms, thermogravimetry (TGA), elemental analysis, and titration (for pH_pzc), were applied for verifying modification, and binding mechanisms. Series of sorption studies (including, pH effect, uptake kinetics, isotherms, and selectivity) were used to investigate the physical and chemical properties of the sorbent, beside the sorption efficiency. The findings revealed that pH 5 was the optimum pH for sorption, the sorption kinetics indicated rapid uranium uptake (equilibrium achieved within 35-40 min), with the PFORE model. Furthermore, the sorption isotherms highlighted the sorption capacities equivalent to 230 mg U g^-1, with a better fit for the Sips equation. The sorbent had remarkable limited lose in capacity (4.4 %) after five cycles of sorption-desorption with relative stability under high acidic condition. The selectivity of the sorbent was evaluated, demonstrating significantly higher selectivity for uranium against other metal ions in equimolar solutions. While in the acidic ore leachate, it showing promising results even when uranium present in a trace amount with complex polymetallic ions. These findings offer insights into designing and optimizing hydrazinyl derivative-based biosorbents for uranium adsorption applications, with implications for environmental protection and nuclear waste management.