Extraction of calcium and strontium into nitrobenzene by using a synergistic mixture of hydrogen dicarbollylcobaltate and tetraisopropyl methylene diphosphonate

Abstract

Extraction of microamounts of calcium and strontium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B⁻) in the presence of tetraisopropyl methylene diphosphonate [T(iPr)MDP, L] has been investigated. The equilibrium data have been explained assuming that the species HL⁺, ${\text{HL}}_{2}^{ + }$, ${\text{ML}}_{2}^{2 + }$ and ${\text{ML}}_{3}^{2 + }$ (M²⁺ = Ca²⁺, Sr²⁺) are extracted into the organic phase. The values of extraction and stability constants of the cationic complexes in nitrobenzene saturated with water have been determined. In the considered nitrobenzene medium, it was found that the stability constants of the ${\text{CaL}}_{n}^{2 + }$ complexes, where n = 2, 3 and L is T(iPr)MDP, are somewhat higher than those of the corresponding complex species ${\text{SrL}}_{n}^{2 + }$.