I. V. Tananaev Institute of Chemistry and Technology of Rare Elements and Mineral Raw Materials of the Russian Academy of Sciences Kola Science Center, Apatity, Russia:

A. G. Kasikov, Head of Laboratory, Candidate of Chemical Sciences, Associate Professor, e-mail: kasikov@chemy.kolasc.net.ru
L. V. Diakova, Senior Researcher, Candidate of Technical Sciences, Associate Professor
E. G. Bagrova, Engineer

Kola Mining and Metallurgical Company JSC, Monchegorsk, Russia:
О. А. Khomchenko, Chief Specialist of Science and Technology Development Department, Engineering Center, Candidate of Technical Sciences, Associate Professor

The process that is currently adopted by Kola MMC for processing cobalt concentrate involves the use of hydrochlorides. The resultant product includes strong solutions of nickel-cobalt chlorides. Through liquid extraction, cobalt is then extracted from the above solutions with the help of tertiary amines in an inert diluent mixed with aliphatic alcohols. The latter act as a modifier and hinder the formation of the second organic phase. During the process introduction period, a number of issues arose that required process optimization. One of the factors affecting the extraction performance includes high viscosity of organic mixtures. It leads to slower diffusion at the phase boundary, increased creaming time, and the cobalt extract bleeding into the aqueous phase. The paper analyses and compares aliphatic high-molecular alcohols and ketones when they are used as modifiers of tertiary amine-based extraction mixtures. It was established that the currently used alcohols lead to increased viscosity of extraction mixtures and cobalt extracts. Moreover, they inhibit cobalt extraction due to stable solvates being formed. Unlike alcohols, aliphatic ketones not only have the capacity to significantly decrease the extract viscosity, but they also enhance cobalt extraction from chloride solutions and raise the capacity of extraction mixtures in application to cobalt. Thus, under comparable conditions the concentration of cobalt in the extract containing 30% trioctylamine and a portion of 2-undecanone was 13.1 g/dm³, whereas for the mixture of trialkylamine and alcohols it was only 9.9 g/dm³. Accounting for low solubility and high flash point, it is recommended that 2-undecanone should be used as a modifier in Kola MMC’s cobalt extraction process.

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