Institute of Metallurgy of Ural Branch of Russian Academy of Sciences, Ekaterinburg, Russia:

D. S. Reutov, Junior Researcher, e-mail: reutov-ds@mail.ru
B. D. Khalezov, Chief Researcher
L. A. Ovchinnikova, Senior Researcher
A. S. Gavrilov, Junior Researcher

Flotation processing of copper-smelting dump slags expedites accumulation of flotation tails. According to the chemical analysis results, these tails contain about 0.5% (mass) of copper and 4% (mass) of zinc. Copper and zinc are both included into primary and secondary mineral compounds as isomorphous impurities, and form their own mineral phases, including copper (0.76% (mass)) and zinc (9.24% (mass)) ferrites. To develop technology for extraction of copper and zinc from tailings, it is necessary to determine the direction of research. To this end, zinc ferrite was synthesized according to the ceramic technology, which consists in the joint thorough grinding of the stoichiometric amount of zinc and iron oxides, followed by sintering in a muffle furnace at the temperature of 1000–1100 ^оC and holding for at least 12 hours. Tablets were compressed from synthesized ferrites on a hydraulic press under a load of 40 MPa. Tablets of 20 mm size were pasted into the holder of PTFE using epoxy glue. An experimental study was made of the rate of dissolution of zinc ferrite by the roll-disc method. A laboratory setup was used, consisting of a water bath, a stirring device with speed control, a thermometer and a pH meter. Kinetics of zinc ferrite (ZnFe₂O₄) dissolution in aqueous solution of sulfuric acid were examined under different concentrations, temperature and hydrodynamical regime. Dependences of the rate of dissolution of zinc ferrite on the concentration of sulfuric acid and the intensity of mixing were constructed. The value of the experimental (apparent) activation energy of the process was calculated according to the Arrhenius equation. A conclusion is drawn on the diffusion mode of dissolution of ZnFe₂O₄. The obtained data are the basis for the developed technology.
Our investigation was carried out with the financial support of the Russian Foundation for Basic Research, project 16-35-00169.

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