Solvent extraction separate of zinc and cadmium from magnesium and calcium in sulfuric acid medium by mixing extractants

摘要

Synergistic extraction has been proven to enhance extractability and selectivity for the separation of cadmium and zinc from magnesium and calcium in the sulfuric acid medium with Mextral V10 and Mextral 622H (aromatic hydroxamic) mixtures diluted in DT100. Mixtures of Mextral V10 and 622H are highly selective for Zn and Cd over Mg and Ca compared with the single Mextral V10, resulting in larger synergistic shifts for zinc and cadmium with the ΔpH50 (Zn–Ca) values increasing substantially from 0.83 to 1.73 pH units and ΔpH50 (Cd–Ca) values increasing from 0.63 to 2.13 pH units. The aqueous to organic ratio (A/O ratio), the saponification ratio of Mextral V10 and extracting agent concentration were studied on the effect of metal ions extraction, which helped to increase the organic capacity of metal extraction. The McCabe-Thiele plot for Cd and Zn extraction with 5% (volume fraction) Mextral V10 and 5% Mextral 622H extractants mixture indicate the necessity of only one theoretical stages at an A/O ratio of 1.5:1. One stage extraction simulation test conducted at pH 6.50 shows that Cd and Zn reach the extraction of 99.6% and 97.9%,respectively, and only low levels of magnesium and calcium are extracted in the organic phase. The extracted Zn2+ or Cd2+-organic species are Zn(A1)(A2) or Cd(A1)(A2) with the mixture system by slope analysis.