Institute of Chemistry and Chemical Technology Federal Research Center “Krasnoyarsk ScienceCenter” of the Siberian Branch of the Russian Academy of Sciences (SB RAS); Krasnoyarsk, Russia

N. A. Grigorieva, Senior Researcher, Candidate of Chemical Sciences, e-mail: natasha@icct.ru
I. Yu. Fleitlikh, Leading Researcher, Candidate of Chemical Sciences

Chelyabinsk Zinc Plant JSC, Chelyabinsk, Russia
S. A. Zagrebin, Deputy Head of Technical Department, Candidate of Technical Sciences
K. M. Kozlov, Deputy Head of Hydrometallurgical Department

Based on a literature and patent review and experimental data, it was concluded that the most promising extraction systems for the extraction of indium from zinc sulfate solutions are mixtures of di(2-ethylhexyl)phosphoric acid (D2EHPA, HR) with proton-donor additives, in particular, aliphatic alcohol, 2-ethylhexanol. It has been shown that in these systems not only effective extraction of indium can take place, but also its re-extraction. The introduction of alcohol into the organic phase containing D2EHPA helps to significantly improve the indium re-extraction compared to D2EHPA alone. The improvement in the indium re-extraction in a mixture of D2EHPA with 2-ethylhexanol (HA) is due to the formation of stable intermolecular associates between HR and HA, such as [HR·nHA]. The optimal parameters for indium extraction, washing the extract from impurities, and indium stripping have been determined. The optimal composition of the extractant is: 0.3 M (15.8 %) D2EHPA + 0.3 M (4.7 %) 2-ethylhexanol in a diluent (kerosene or petroleum paraffins). It is proposed to use mixtures of sulfuric acid with sodium chloride as a re-extractant; in this case, a noticeable concentration of indium in the reextract occurs (> 33.0 g/l In). Indium recovery at the extraction stage is 97.5–99.0%, and at the reextraction stage – 99%. To regenerate the extractant, it is proposed to use ammonium oxalate solutions. A technological scheme has been developed for the extraction extraction of indium from zinc sulfate solutions using mixtures of D2EHPA and 2-ethylhexanol in petroleum paraffins.
This work was conducted within the framework of the budget project (project FWES-2021-0014) for Institute of Chemistry and Chemical Technology SB RAS and an agreement with Chelyabinsk Zinc Plant JSC using the equipment of Krasnoyarsk Regional Research Equipment Center of SB RAS.

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