Samarium(III) Removal by Weak Acid Exchanger Amberlite IRC-50 in (H+) and (Na+) Forms

Abstract

Adsorption of samarium(III) on a weakly macroporous cation exchanger Amberlite IRC-50 (H⁺) and (Na⁺) forms is studied as a function of the initial pH of the aqueous solution, time and temperature, initial samarium(III) ion concentration, and the amount of resin at a fixed temperature (20±1 °C).

The concentration range was between 0.1 - 5 mmol/L, the pH range was between 1.8 and 10.5; the stirring time was between 2 and 60 min; and the amount of resin was between 0.025 and 0.15 g. Both the film and particle diffusion equations are applied to explain the kinetic data. The rate constant values for samarium(III) adsorption were calculated for both film and particle diffusion processes. It is observed to follow the order (Na⁺)>(H⁺). Temperature is found to have an insignificant effect on both diffusional processes. Various thermodynamic parameters (ΔH°, ΔS°, and ΔG°) from samarium(III) exchange on the resin were calculated. The optimum conditions were found to be a concentration of 1 mmol/L, pH of 9.3, stirring time of 20 and 5 min for Amberlite IRC-50 (H⁺) and (Na⁺) forms, respectively, and 0.15 g of resin. The equilibrium extraction of samarium was 22.2 mg/g for Amberlite IRC-50 (H⁺) and 21.9 mg/g for Amberlite IRC-50 (Na⁺) at an initial concentration of 1 mmol/L. The results obtained show that the Amberlite IRC-50 weak cation-exchange resin performed well for the removal and recovery of samarium(III). The optimization procedure provides access to industrial-scale Sm(III) removal processing.