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

ABSTRACT: 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, curve fitting the time-dependent data into different kinetics mechanisms showed a satisfactory correlation with the pseudo-second-order model. Binary system results show a decrease in Sc adsorption capacity of the absorbent in the presence of secondary ions because of 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. Data from experiments on synthetic electrolytes with Y/Sc ratio of 5 found in actual mining copper leach solution were used for extracting scandium by circulating mine-leach solution through a resin column. The results demonstrate a preferential 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 mgL-1 Sc rich solution or 60:1 concentration ratio over the original copper leach solution.