Zinc extraction from sulfate media with bis(2,4,4-trimethylpentyl)dithiophosphinic acid in the absence and in the presence of electron donor additives

The paper presents data on zinc extraction from sulfate solutions with bis(2,4,4-trimethylpentyl)dithiophosphinic acid (HR, trade mark CYANEX 301) diluted with nonane and kerosene in the absence and in the presence of electron-donor additives (L). Trialkyl amine (TAA), trialkyl phosphine oxide (TAPO), tributyl phosphate (TBP), and n-octanol were used as additives.Using the zinc distribution data and spectral methods, it was shown that, in the absence of additives, zinc extraction with CYANEX 301 proceeds by a cation exchange mechanism. The composition of the extracted compound in the organic phase was found to be ZnR2. In all cases, the introduction of additives into the organic phase results in a decrease in zinc extraction, which is probably due to a decrease in the extractant activity resulting from the interaction between HR and L. The degree of extraction decreases in the series HR without additives > HR + n-octanol > HR + TBP > HR + TAPO > HR + TAA.In the HR + TAA system, with increasing aqueous acidity, a change in the mechanism of zinc extraction from cation exchange to binary extraction takes place. In this case, the counter ion (bisulfate ion) is extracted together with the cation (zinc).The mixtures of HR with TAA could be of interest for zinc recovery from various industrial solutions, for example, in the processing of viscose rayon fibre solutions for the separation of zinc from calcium, for purification of zinc solutions from manganese, etc. Unlike the system containing only dithiophosphinic acid, both effective zinc extraction and its effective stripping with dilute solutions of sulfuric acid are possible for the HR + TAA system.

► We study zinc extraction with CYANEX 301 alone and in the presence of additives. ► The additives used were TAA, TAPO, TBP, n-octanol. ► Introduction of additives into CYANEX 301 results in a decrease in zinc extraction. ► The degree of extraction decreases when passing from n-octanol to TOA. ► The CYANEX 301/TAA system is most effective for Zn extraction and its stripping.