Siberian Federal University (Krasnoyarsk, Russia)

N. V. Belousova, Head of the Department of Metallurgy of Non-Ferrous Metals1, Doctor of Chemical Sciences, Professor, netmamba@mail.ru

Siberian Federal University (Krasnoyarsk, Russia)¹ ; Institute of Chemistry and Chemical Technology of the Siberian Branch of the Russian Academy of Sciences (ICCT SB RAS) (Krasnoyarsk, Russia)²
O. V. Belousov, Leading Researcher of Laboratory of Hydrometallurgical Processes², Professor of the Department of Metallurgy of Non-Ferrous Metals¹, Doctor of Chemical Sciences, Associate Professor, ov_bel@icct.ru

R. V. Borisov, Senior Researcher of the Laboratory of Hydrometallurgical Processes², Associate Professor of the Department of Mineral Processing¹, Candidate of Chemical Sciences, Associate Professor, roma_boris@list.ru

Institute of Chemistry and Chemical Technology of the Siberian Branch of the Russian Academy of Sciences (ICCT SB RAS) (Krasnoyarsk, Russia)
A. A. Akimenko, Junior Researcher of the Laboratory of hydrometallurgical processes2, Candidate of Chemical Sciences, akim_aa@mail.ru

The characteristics of single-stage dissolution of metallic platinum with varying particle sizes under hydrothermal autoclave conditions in hydrochloric acid solutions using hydrogen peroxide as an oxidizing agent were investigated. The study utilized annealed platinum powders with an average particle size of approximately 1 μm, along with two highly dispersed samples with average particle sizes of 35 and 72 nm. The structure of the platinum was characterized using transmission and scanning electron microscopy, X-ray diffraction analysis, and specific surface area adsorption measurements. The kinetic characteristics of their dissolution were investigated over a temperature range of 50–160 °C. It was established that the dissolution process of metallic platinum, regardless of particle size and temperature range, follows first-order kinetics. The experimental data are satisfactorily described by the shrinking core model, indicating that the platinum dissolution process proceeds in the kinetic control regime. Based on the temperature dependence of the rate constants, the apparent activation energies for the dissolution of platinum fractions with varying particle sizes in the HCl – H₂O₂ system were calculated. A significant effect of hydrochloric acid concentration on the dissolution kinetics of annealed metallic platinum, accompanied by the formation of chloride complexes, was established. It is shown that the predominant species of platinum in the leaching solutions is the hexachloroplatinate (IV) ion, [PtCl₆]^2–. The obtained results substantiate the feasibility of applying the developed process in refining operations, the synthesis of platinum-containing precursors, and analytical sample preparation. An environmentally friendly method for dissolving platinum-containing materials, serving as an alternative to chlorine- and nitrate-based processes, is proposed. The use of hydrogen peroxide as an oxidizing agent enables a high degree of metal recovery at moderate temperatures, completely eliminating the need for traditional nitrate-chloride systems and preventing the formation of toxic gaseous emissions.
The study was supported by the Russian Science Foundation, Project No. 25-29-00159.

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