Liquid–Liquid Equilibria in Multicomponent Systems Containing o-Xylene, Di-(2-ethylhexyl)phosphoric Acid, Water, Nitric Acid, and Europium (Gadolinium, Dysprosium) Nitrate at 298.15 K

Abstract

The extraction of europium­(III), dysprosium­(III), and gadolinium­(III) nitrates with di-(2-ethylhexyl) phosphoric acid (D2EHPA) in o-xylene was investigated at 298.15 K. Spectrophotometry and ICP-AES techniques were used for rare earth elements (REE) content determination. The content of nitric acid was measured by acid–base titration. The density of the equilibrium phases was determined. In the case of high content of rare earth element nitrates in the initial aqueous solutions, the third solid phase formation was observed during extraction experiments.

Separation of Rare-Earth Elements Using Supported Liquid Membrane Extraction in Pilot Scale

“…Zhang et al (2016) reported the formation of gray/white or yellow/white precipitates in REE solvent extraction systems using D2HEPA that could not dissolve in diluents but dissolved by increasing the concentration of D2HEPA . The gel is a formation of REE-extractant molecular chains (polymers) and leads to increased viscosity and phase separation problems that reduces performance and can even stop the process completely. − Gel formation can be avoided by decreasing the metal concentration and pH in the feed and increasing the carrier concentration in the membrane phase. , Yurtov and Murashova (2007) observed the formation of gel in the bulk of the organic phase for a lanthanide-D2EHPA system when the concentration ratio of D2HEPA/lanthanide corresponded to the formation of neutral and acid salts . Antico et al.…”

“…46−48 Gel formation can be avoided by decreasing the metal concentration and pH in the feed and increasing the carrier concentration in the membrane phase. 10,49 Yurtov and Murashova (2007) observed the formation of gel in the bulk of the organic phase for a lanthanide-D2EHPA system when the concentration ratio of D2HEPA/lanthanide corresponded to the formation of neutral and acid salts. 46 Antico et al (1996) studied the distribution of Y 3+ at different concentrations between acidic chloride solutions and organic solutions of D2EHPA diluted in kerosene.…”