Acrylic acid functionalized silica composite resin for selective recovery of Ru from simulated high-level liquid...

The selective and efficient separation of ruthenium from high-level liquid waste (HLLW) will not only benefit the resource shortage of Ru, a member of platinum group metal, but also advancing the nuclear fuel cycle. However, the separation and recovery of Ru(III) from HLLW faces challenges due to its complex speciation in nitric acid, intense radioactivity, complex competing ions of HLLW. Herein, an acrylic acid functionalized silica composite resin (AA/SiO₂) was synthesized via in-situ polymerization for selective adsorption of Ru(III) from simulated HLLW. AA/SiO₂ achieved a maximum adsorption capacity of 94.49 mg Ru/g in 0.5 M HNO₃ at 348 K. The adsorption AA/SiO₂ towards Ru matched well with the pseudo-second-order kinetics model, Langmuir isotherm. The thermodynamic parameters, calculated based on the Van't Hoff equation and plot, showed ΔH^o (5.62 kJ/mol) > 0, ΔS^o (0.18 kJ/K·mol) > 0 and ΔG^o less than 0. It indicates the adsorption reaction is a spontaneous, endothermic, monolayer chemical adsorption. Moreover, Crucially, AA/SiO₂ exhibited high selectivity for Ru(III) in 12 coexisting ions (SF_{Ru/Other metal ions except for Pd} = 132.2, SF_Ru/Pd = 47.3). FT-IR and XPS analyses confirmed that adsorption occurred primarily through ion exchange between carboxyl groups (-COOH) and [RuNO]³⁺ cationic complexes. The resin maintained stable reusability over 5 cycles using 0.5 M NaNO₂ as eluent with only 3.77 mg Ru/g decrease in adsorption capacity. This work provides a cost-effective, high selective, and robust resin for sustainable Ru recovery from HLLW.