Ural Federal University named after the first President of Russian Federation B. N. Yeltsin, Ekaterinburg, Russia:

L. G. Elfimova, Senior Lecturer, e-mail: elg-mtf@yandex.ru
K. A. Karimov, Laboratory Responsible, Engineer, e-mail: kirill_karimov07@mail.ru
A. V. Kritskii, PhD Student, Engineer, Lecturer Assistant, e-mail: alekseikritskii@gmail.com
S. S. Naboychenko, Professor, Head of the Department “Non-Ferrous Metals Metallurgy”

A complex two-stage technology for converter matte processing using sulfuric acid pressure oxidative leaching was developed. The study was carried out on a model sample of the following composition, %: 62 Ni, 7.1 Cu, 3.7 Fe, 2.2 Co, 18 S. Process was investigated in a wide range of technological parameters (t = 85–150 ^oC, PO₂ = 0.1–0.5 MPa). Optimal parameters at different temperature regimes are suggested. Selective leaching of Ni from converter matte should be performed at t = 85 ^oC, PO₂ = 0.2 MPa. This made it possible to reduce the leaching period from 4 to 8 hours in case of atmospheric leaching to 1.3 to 1.5 hours at autoclave conditions, providing extraction into the solution the following components, %: 55 Ni, <1 Cu, <1 Fe. High-temperature sulfuric acid pressure oxidative leaching should be applied for most complete extraction (98–99%) of converter matte’s valuable components at t = 140 ^оC, PO₂ = 0.4 MPa. The resulting solutions after purification from impurities are supposed to be sent to a stage of electroextraction/crystallization of nickel to produce high-quality products. Purification of leaching solutions against copper was performed using nickel sulphide, chemically precipitated by NaHS solution.The process of purification was implemented in two stages at 60 ^оC, changing excess coefficient from 1–5.6 (NiS_solid/Cu_solution) for 60 min in a lack of free acid. At mentioned conditions — 99.9% of Cu were precipitated out of the solution; the possibility of obtaining cake with a content of 44% Cu.
This research was funded by the Russian Science Foundation (Project No. 18-19-00186).

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