Removal of cobalt(II) and zinc(II) from sulphate solutions by means of extraction with sodium bis(2,4,4-trimethylpentyl)phosphinate (Na-Cyanex 272)

Abstract

The removal of Co(II) and Zn(II) from model and real crude nickel sulphate (CNS) solutions by extraction with sodium bis(2,4,4-trimethylpentyl)phosphinate (Na-Cyanex 272) is studied and compared with the effect of using bis(2,4,4-trimethylpentyl)phosphinic acid (Cyanex 272). The proposed novel approach to manage both hazardous metal ions from CNS with sodium salt of Cyanex 272 focuses on the following issues: (i) effect of the initial pH of feeds on the extraction efficiency, (ii) leaching of metal ions from CNS, (iii) efficiency and selectivity of metal ion extraction from real CNS, and (iv) FT-IR analysis of structure of complexes formed by the metal ions with the extractant studied. It is concluded that converting Cyanex 272 into its sodium salt greatly improves the efficiency of the extraction in comparison to the conversion into the acidic form of the extractant, regardless of the type of metal ion considered, whether Zn(II) or Co(II). These phenomena occurring in the extraction system are confirmed by the obtained FT-IR spectra of the organic phases after extraction and stripping.