Investigation of the extraction of samarium and gadolinium from leaching solutions of phosphorus-containing raw materials using solid extractants

Abstract

In accordance with the State Program of the Russian Federation «Development of Industry and Its Competitiveness», as well as the absence of balance deposits of rare earth metals on the territory of the Russian Federation, it is urgent to study methods for the extraction and separation of rare earth metals from technological solutions obtained during the processing of apatite concentrates. The article is devoted to the study of the kinetic features of solid-phase extraction of samarium (III) and gadolinium (III) from simulated industrial phosphoric acid solutions. Levextrel resine (co-polymerization product of styrene and divinylbenzene) containing Di-2-ethylhexylphosphoric acid (D2EHPA) – was used as a solid-phase extraction agent. Significant dependence of samarium (III) and gadolinium (III) extraction rate constant on the stirring rate was revealed using the formal first-order kinetic equation. Based on the linear dependences of the logarithm of the reaction rate constant on the reciprocal temperature, the activation energies for the extraction of Gd and Sm from phosphate model solutions were established, which, respectively, were 42.47 and 28.48 kJ/mol. The obtained values of the activation energies indicate that the limiting stage of the extraction process on a solid extractant can be considered a chemical reaction between ions of rare-earth metals and functional groups of the extractant. Separation of elements at the extraction stage is possible at temperature of 333 K under non-equilibrium conditions with separation coefficient up to 1.8 in 5 min.