Adsorption of Scandium and Yttrium from Aqueous Solutions by Purolite C100Na Resin: Equilibrium and Kinetic Modeling

Adsorption of Sc from single and bi-component Sc-Y solutions by Purolite C100Na was studied experimentally and kinetic and thermodynamic characteristics are described. The extended Freundlich isotherm was found to be successful in validating the experimental results. Moreover, the curve fitting the time-dependent data into different kinetics mechanisms showed a satisfactory correlation with the pseudo-second-order model. Binary system resultsshow a decrease in Sc adsorption capacity of the absorbent in presence of secondary ions due to competition for adsorption sites. Furthermore, thermodynamic parameters indicate similarity of reaction mechanisms for both single and binary systems, with Sc absorption adversely affected by temperature. Results from synthetic solutions with an actual Y/Sc ratio of 5 were used for extracting scandium from actual mining copper leach solution by circulating it through a resin column. The results demonstrate a satisfactory collection of Sc ions despite the fivefold concentration of Y over Sc. The elusion studies showed that the yttrium desorption peak occurs before that of Sc which corroborates the adsorption isotherm findings. This results in a 180 mg/L Sc rich solution or 60:1 concentration ratio over the original copper leach solution.