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The work presents studies on the application of hydrometallurgical recovery of cobalt(II) from solutions after leaching spent industrial catalysts used in process of hydrodesulfurization. A four-stage process was proposed, which consists of: leaching, precipitation of metal hydroxides accompanying Co(II), extraction of Co(II) with bis(2,4,4-trimethylpentyl)phosphinic acid and Co(II) stripping from the organic phase. The results indicate that by using the proposed method it is possible to leach Co(II) and Mo(VI) from spent catalyst, and remove main impurities such as Al(III), Fe(III) in hydroxide precipitation step and separate Co(II) from Mo(VI) by extraction and stripping.

The paper presents basic studies on the precipitation of platinum, palladium, rhodium, and ruthenium nanoparticles from model acidic solutions using sodium borohydride, ascorbic acid, and sodium formate as reducing agents and polyvinylpyrrolidone as a stabilizing agent. The size of the obtained PGM particles after precipitation with NaBH4 solution does not exceed 55 nm. NaBH4 is an efficient reducer; the precipitation yields for Pt, Pd, Ru, Rh are 75, 90, 65 and 85%, respectively. By precipitation with ascorbic acid, it is possible to efficiently separate Pt, Rh, and Ru from Pd from the two-component mixtures. The obtained Pt, Pd, and Rh precipitates have the catalytic ability of the catalytic reaction of p-nitrophenol to p-aminophenol. The morphological characteristic of the PGM precipitates was analyzed by AFM, SEM-EDS, and TEM.

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