Sorption of scandium by hypercrosslinked polystyrene impregnate containing organophosphorus acids

Abstract

We have studied the sorption of scandium from acidic sulfate-chloride solution by hypercrosslinked
polystyrene sorbents (MN-202) impregnated with di-2-ethylhexyl phosphoric acid (D2EHPA) and ethylhexyl
phosphoric acid (EHPA). The samples of impregnated resins obtained in this work contained 0.233 and 0.244
g of extractant per 1 g of impregnated resin respectively. The sorption of scandium by impregnated resins
(D2EHPA) and (EHPA) was studied depending on pH, scandium concentration in solution, temperature and
the duration. It has been found that the impregnated sorbent in acidic sulfate-chloride solutions of scandium
have relatively low static sorption capacity (≤ 0.251 mmol/g). The equilibrium of scandium sorption is rapidly
established within 20-30 min. The models of pseudo-first and pseudo-second orders and the Elovich equation
were used for processing of integrated kinetic curves of scandium sorption. The values of the rate constants
calculated from the model pseudo-second order describing the data with the best correlation coefficients
(R2
0.999) reached 14.4 g · (mmol · min)-1. Activation energy of the sorption of scandium is equal
10.0-13.4 kJ/mol. The rate is determined by the slowest stage - diffusion. The coefficients of diffusion of
scandium in impregnate have the order of 10-11-10-12 m2
/s. Solutions of sodium hydroxide are used for the
elution of scandium. Reduction of scandium capacity does not exceed 15% after 5 cycles of sorptionwashing-desorption.

Result of the study of characteristics of new hypercrosslinked polystyrene impregnates containing
D2EHPA and EHPA allow us to recommend them to extraction of scandium from acidic sulfate-chloride
solutions of different composition, including natural and waste waters from processing of polymetallic ores
and other scandium-containing raw materials.