Promising chlorination technology for improving precious metal concentrate production

The work is devoted to obtaining rich, highly selective concentrates of platinum metals using chlorine technology. Since one of the key operations determining the performance indicators — primarily direct extraction and duration of the process cycle — is head digestion, the greatest attention is paid to the features of this process. It is shown that hydrochlorination of materials enriched with a carbon reducing agent has its own characteristics. Thus, in a wide range of process parameters (temperature, L:S, acidity), high extraction of platinum metals (PM) into solution is ensured. With an initial content of the sum of PM of 15–30% and chlorination in two stages, the residual content of platinum and palladium is at the level of 0.1–0.2%, which corresponds to an extraction of more than 95–97%. The behavior of gold differs sharply and depends on the amount and properties of the residual reducing agent, changes in its sorption properties and the completeness of oxidation during the chlorination process. The process flow includes digestion in hydrochloric acid environments, purification of solutions from impurities of base metals and platinum-associated metals (PAM), precipitation of platinum-palladium concentrate (more than 90% Pt + Pd) from the purified solution, processing of the precipitate of PAM impurities to obtain a concentrate containing more than 20% Rh, Ru, Ir, and smelting of insoluble residues to obtain a gold concentrate containing more than 40% Pt + Pd + Au. The modes for carrying out the main process operations have been tested in laboratory conditions at Gipronickel Institute and verified on large-scale installations of the precious metals refining department of the scientific and technical center of JSC Kola MMC.E. I. Trofimova, O. V. Severinova, D. M. Bogatyrev (Gipronickel Institute), A. V. Rakitin, A. V. Bratishchev, D. A. Karataev, G. V. Nevsky, A. A. Shishmanova (Kola MMC) took part in the work.