Sorption of Scandium from Sulfuric–Chloride Solutions by Activated Carbons

Abstract

Sorption of scandium by activated carbons of VSK, DAS, and PFT brands of different origin (coconut shell, anthracite, and thermosetting-plastic waste, respectively) from sulfuric–chloride solutions (pH 2) simulating the composition of solutions for the underground leaching of complex ores is studied in batch conditions. It is established that the sorption of scandium by carbons of DAS and VSK brands proceeds with the highest distribution coefficients (133 and 45.8 cm³/g, respectively). Herewith, the sorption of scandium by DAS carbon is also characterized by a large volume coefficient (116 \({{{\text{cm}}_{{{\text{sln}}}}^{{\text{3}}}} \mathord{\left/ {\vphantom {{{\text{cm}}_{{{\text{sln}}}}^{{\text{3}}}} {{\text{cm}}_{{{\text{carb}}}}^{{\text{3}}}}}} \right. \kern-0em} {{\text{cm}}_{{{\text{carb}}}}^{{\text{3}}}}}\)). Sorption isotherms of scandium by these carbons are linear and described by the Henry equation with constants 133 ± 21 and 46 ± 7 cm³/g, respectively. The integral kinetic curves of sorption of scandium are found by the method of the limited volume of the solution, and their linearization according to the kinetic models of the pseudo-first and pseudo-second order, the Elovich model, and the Weber–Morris intraparticle diffusion model evidences that the sorption kinetics of scandium by VSK carbon with a higher correlation coefficient (0.999) is described using the pseudo-second-order model. Processing the kinetic data on the sorption of scandium by DAS carbon showed that, when using all models, the correlation coefficient is low (<0.939) and the highest value is observed when applying the intraparticle diffusion model. It is assumed that the sorption of scandium occurs in the mixed diffusion region. The possibility of eluting scandium from VSK and DAS carbons by the sodium carbonate solution (10%) is studied under the batch conditions and the degree of desorption of scandium for two elution steps is 84.0 and 90.4%, respectively.