Roman V. Borisov

Behavior of platinum metal concentrates under autoclave conditions

Dressing processes of platinum metal concentrates (CP-1 and CP-2) in acid and alkaline media under autoclave conditions were studied. The optimal recovery conditions (time-, temperature-, and concentration-related) of impurity elements were found for the temperature range under study. It was demonstrated that the predominant changes occur during the first 30–60 min. Use of reducing agents can preclude transfer of noble metals into solution in leaching of impurity elements.

Refining of platinum–palladium concentrate under hydrothermal conditions

The possibility of refining platinum–palladium concentrates in alkaline and acid media by hydrothermal treatment under autoclave conditions was determined. The recovery parameters of impurity elements were found. Autoclave processing of platinum–palladium concentrate in alkaline media with sodium formate leads to recovery of the stable palladium oxide modification, which significantly improves opening of the concentrate in hydrochlorination.

Thermostimulated transformations of highly disperse powders of platinum group metals in an argon atmosphere

The behavior of palladium, rhodium, iridium, and platinum powders during their heating in an argon atmosphere was studied by differential scanning calorimetry (DSC). The DSC curves showed the exothermal peaks corresponding to the enlargement of the platinum group metal powders under study. Electron microscopy and XRD studies revealed that the particle size of highly disperse powders changed during the heating. Chemisorbed oxygen was removed from the powder surface above 800 K. During the heating of the mechanical mixture of highly disperse platinum and palladium powders, a solid solution formed with an exothermal effect.

Carbon-Supported Palladium–Gold Bimetallic Disperse Systems Formed in Aqueous Solutions at 110°С

Various palladium–carbon composites have been manufactured by autoclaving at 170°С to be used as precursors for manufacturing bimetallic particles. The morphology of the manufactured items was comprehensively studied by scanning electron microscopy; the ultrafine metal palladium was found to have particles sizes lying in the range 30–120 nm. The specifics of hydrothermal reduction of gold(III) chloro complexes by palladium–carbon composites at 110°С have been studied. An appreciable increase in gold(III) reduction rate was observed with the use of a palladium–carbon composite relative to the rate observed for ultrafine metallic palladium. Gold is reduced on a palladium–carbon composite to an individual metallic phase.

Autoclave Processing of Concentrates Containing Stable Form of Palladium Oxide

Stable modification of palladium oxide and a material modeling the palladium-containing platinum–palladium concentrate poorly soluble in acids were synthesized. It was found that silica is dissolved in alkaline solutions of sodium formate, and palladium oxide is quantitatively reduced under autoclave conditions, which improves the parameters of the subsequent hydrochlorination of the concentrate. Raising the temperature results in that the separation of the palladium phase from alkaline solution is improved and enables separation via decantation.

Redox potentials of gold-palladium powders in aqueous solutions of H2PdCl4

The redox potential of fine-dispersed and compact bimetallic powders of the palladium-gold system in hydrochloric acid solutions of H2PdCl4 at a temperature of 60°C was studied. It was found that the redox potential increases with gold enrichment of the solid solution in accordance with the Nernst equation. The effect of gold-palladium particle size on this redox potential is shown. The morphology, sizes, and composition of bimetallic particles are determined via transmission electron microscopy and X-ray diffraction analysis.