Scandium adsorption from sulfuric-chloride solutions with activated carbons

Abstract

The study covers scandium adsorption in batch conditions by VSK, DAS and PFT activated carbon grades (Russia) of different origin (сoconut shell, аnthracite, thermoset waste, respectively) from sulfuric acid-chloride solutions (pH = 2) simulating the composition of the underground leaching solutions of polymetallic ores. It was found that scandium adsorption by DAS and VSK carbons proceeds with the highest distribution coefficients (133 and 45.8 cm3/g, respectively). Isotherms of scandium adsorption with these carbons are linear and described by the Henry equation with constants 133 ± 21 and 46 ± 7 cm3/g, respectively. A limited solution volume method was used to obtain the integral kinetic curves of scandium adsorption. Their linearization according to the kinetic models of the pseudo-first, pseudo-second order, the Elovich model and the Weber–Morris intra-particle diffusion model indicates that the kinetics of scandium adsorption with VSK carbon having a higher correlation coefficient (0.999) is described using the pseudo-second order model. Description of the kinetic data obtained during the adsorption of scandium with DAS carbon showed that for all the models used the correlation coefficient is low (<0.939), while the highest value is observed when using the intra-particle diffusion model. It was suggested that the scandium adsorption process occurs in the mixed diffusion region. The possibility of scandium elution from VSK and DAS carbons with sodium carbonate solution (10 %) was studied in batch conditions, where the degree of scandium desorption in two stages of elution was 84.0 and 90.4 %, respectively.