Selective removal of uranyl ions using ion-imprinted amino-phenolic functionalized chitosan

The recovery of uranium from aqueous effluents is very important for both the environment and the future of nuclear power. However, issues of sluggish rates and poor selectivity persist in achieving high-efficiency uranium extraction. In this study, uranyl (UO₂²⁺) ions were imprinted on an amino-phenolic chitosan derivative using an ion-imprinting method. First, 3-hydroxy-4-nitrobenzoic acid (HNB) units were joined to chitosan via amide bonding, followed by reducing the -NO₂ residues into -NH₂. The amino-phenolic chitosan polymer ligand (APCS) was coordinated with UO₂²⁺ ions, then cross-linked with epichlorohydrin (ECH), and finally the UO₂²⁺ ions were taken away. When compared to non-imprinted sorbent, the resulting UO₂²⁺ imprinted sorbent material (U-APCS) recognized the target ions preferentially, allowing for much higher adsorption capacities (q_m = 309 ± 1 mg/g) and improved adsorption selectivity for UO₂²⁺. The FTIR and XPS analyses supported the pseudo-second-order model's suggestion that chemisorption or coordination is the primary adsorption mechanism by fitting the data well in terms of kinetics. Also, the Langmuir model adequately explained the isotherms, suggesting UO₂²⁺ adsorption in the form of monolayers. The pH_ZPC value was estimated at around 5.7; thus, the optimum uptake pH was achieved between pHs 5 and 6. The thermodynamic properties support the endothermic and spontaneous nature of UO₂²⁺ adsorption.