Zinc extraction from sulfate–chloride solutions with mixtures of a trialkyl amine and organic acids

Abstract

In this work, for the first time, zinc extraction from sulfate–chloride solutions containing iron using mixtures of a С7–С9 fraction trialkyl amine (TAA) with a p-alkyl phenol (HP) and monocarboxylic acids (HAs) was studied. P-tertbutyl phenol was used as the alkyl phenol, while caprylic acid and the С11–С19 higher fractions of iso-acids (HIAs) were used as the monocarboxylic acids. The main process parameters that provided for high zinc recovery (~98.5–99%) and its separation from iron (βZn/Fe=15–25) were determined.Two extraction flowsheets for zinc recovery from sulfate–chloride solutions as zinc chloride followed by its conversion to zinc sulfate are proposed. The first one includes zinc extraction with the TAA and alkyl phenol mixture, washing of the extract from impurities and zinc stripping with water. The subsequent zinc concentration and its conversion to the sulfate solution are carried out by extraction with di(2-ethylhexyl)phosphoric acid (D2EHPA). The second flowsheet includes zinc extraction with the TAA and HIA mixture, washing of the extract with water to remove impurities, chloride ion stripping with an alkaline solution, and zinc stripping with a sulfuric acid solution, resulting in the extractant regeneration.The data obtained for synthetic solutions were confirmed for leach liquors of a sulfide concentrate from the Zimneye deposit (Russia). Zinc extraction was carried out from solutions containing (g/L) 10–12 Zn, 2–4 Cu, 12–15 Fe(III), 40–50 Fe(II), 0.7–0.8 Pb, 80–85 Cl, and 20–80 H2SO4. The composition of the zinc sulfate obtained by both technologies was of the best quality in accordance with the State Standard of Russia.