Functionalized cellulose for enhanced uranium(VI) and thorium(IV) sorption: Mechanisms and performance

Overview & Synopsis

Herein, an efficient functionalized cellulose-based sorbent (F-Cel) was synthesized via chlorination followed by 1-amino-2-naphthol-4-sulfonic acid grafting. Comprehensive characterization (via CHN analysis, XRD, XPS, pHPZC, SEM-EDX) validated successful functionalization and revealed critical structure-property relationships. The sorption efficiency exhibited strong pH-dependence, peaking at pH 3.5 for Th(IV) and 4.5 for U(VI). Kinetic equilibria occurred at 90 min (Th(IV)) and 120 min (U(VI)), adhering to pseudo-first-order (Cel) and pseudo-second-order (F-Cel) kinetics, reflecting their distinct surface functionalities. The F-Cel achieved superior sorption capacities (0.716 mmol/g for Th(IV) and 0.655 mmol/g for U(VI) at 298 K) compared to Cel (0.341 mmol/g for U(VI) and 0.309 mmol/g for Th(IV) at 298 K). This represents a ∼2.1-fold and ∼2.3-fold increase in capacity for Th(IV) and U(VI), respectively. This leap stems from synergistic –SO₃H (ion-exchange) and–OH/–NH₂ (chelation) groups, contrasting Cel’s physisorption, as conclusively validated through multispectral mechanistic analysis. Thermodynamically, F-Cel exhibits spontaneous endothermic sorption for both metals, contrasting Cel's exothermic behavior. U(VI) shows > 86 % desorption efficiency in NaHCO3/HCl with stable recyclability over 7 cycles (