Solvent Extraction of Calcium and Strontium into Nitrobenzene by Using Hydrogen Dicarbollylcobaltate in the Presence of Dibutyl Diethylcarbamoylmethylene Phosphonate

Abstract

Extraction of micro amounts of calcium and strontium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B⁻) in the presence of dibutyl diethylcarbamoylmethylene phosphonate (DBDECMP, L) has been investigated. The equilibrium data have been explained assuming that the complexes HL⁺, $\mathrm{HL}_{2}^{+}$, $\mathrm{ML}_{2}^{2+}$ and $\mathrm{ML}_{3}^{2+}$ (M²⁺=Ca²⁺,Sr²⁺) are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined. It was found that the stability of the complex cations $\mathrm{CaL}_{3}^{2+}$, $\mathrm{SrL}_{3}^{2+}$, $\mathrm{EuL}_{3}^{3+}$ and $\mathrm{AmL}_{3}^{3+}$, where L is DBDECMP, increases in the order Sr²⁺<Ca²⁺≪Eu³⁺≈Am³⁺.