JSC Uralmekhanobr, Ekaterinburg, Russia:

S. A. Vzorodov, Leading Research Worker
A. M. Klyushnikov, Senior Research Worker, e-mail: kl-anton-mih@yandex.ru

This paper discusses the technology of processing copper waste containing precious metals, including: roasting, ash smelting, refining the resulting bronze with the release of blister copper, sulfuric acid dissolution of blister copper with separation of the precious metals concentrate into an insoluble residue. To accelerate the dissolution of the copper phase, a deep refining operation is necessary. It is founded that the refining of bronze (80–85% copper) is to be carried out in two stages, with the blowing of the melt with air. Air consumption corresponds to the stoichiometric amount for the oxidation of impurities. The first stage of refining proceeds under the flux, which consists of natural calcium borate (colemanite), the flux consumption of 18–20%. At the first stage deep refining of copper from zinc, lead, and iron proceeds. For deep refining from tin, the second stage of refining is carried out with air supply and following fluxes consumption: colemanite — 18–20%, sodium carbonate — 6–7%. As a result, blister copper with the content of the main component of 97–99% is obtained. This blister copper is recommended to be processed by dissolving in a mixture of H₂SO₄ and H₂O₂ that results in producing of slurry with precious metals content highly increased. The optimal conditions for the dissolution of blister copper are determined: the consumption of 37–38% hydrogen peroxide in an amount of about 2.0–2.3 m3/t while the temperature of the pulp reaches about 40–50 oC due to the heat of exothermic reactions. The behavior of impurity components of blister copper in the process of dissolution is investigated. It is shown that the dissolution of metal phases of lead and tin in the H₂O₂ – H₂SO₄ solution is accompanied by the formation of insoluble phases of tin oxide and lead sulfate. The proposed technology allows to obtain concentrate containing up to 48% of the amount of precious metals with end-to-end extraction not less than 99%, and a copper sulfate solution, suitable for the production of cathode copper according to GOST 546–2001. Slags of the first and second stage of refining can be disposed at zinc and tin processing plants, respectively.

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