Solvent extraction of gadolinium (III) from hydrochloric acid solutions with cationic extractants D2EHPA and Ionquest 801

Abstract

The solvent extraction of gadolinium (III) from hydrochloric acid solutions with cationic extractants D2EHPA and Ionquest 801 dissolved in Exxsol D100 was investigated. The study was carried out with concentrated solutions in order to better reproduce industrial process conditions. The following operational variables were investigated: initial concentration of gadolinium (16–40 g L⁻¹, i.e., 0·104–0·255 mol L⁻¹), initial concentration of extractant (0·5–1·5 mol L⁻¹), initial pH of the aqueous phase (1–5) and aqueous/organic volumetric ratio (0·5–2·0). Data fitting including the statistical analysis of the estimated equilibrium parameters indicated that gadolinium (III) is extracted from hydrochloric acid solutions with D2EHPA and Ionquest 801 according to the overall reaction Gd³⁺+3(HX)₂⇆GdX₃(HX)₃+3H⁺. The apparent equilibrium constant at 298±1 K was found to be 1·9±0·3 for the system Gd(III)–D2EHPA and 0·028±0·003 for the system Gd(III)–Ionquest 801.

Keywords

Solvent extraction Gadolinium D2EHPA Ionquest 801 Equilibrium

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