Institute of Metallurgy of the Ural Branch of the Russian Academy of Sciences, Ekaterinburg, Russia:

B. D. Khalezov, Chief Researcher, e-mail: bd-chalezov@yandex.ru
A. S. Gavrilov, Junior Researcher, e-mail: gavrilov_208.90@mail.ru
S. A. Petrova, Senior Researcher
L. A. Ovchinnikova, Senior Researcher

About 70% of the global nickel reserves are contained in oxidized nickel ores (ONOs). This type of ores is characterized by a relatively low concentration of nickel compared with copper-nickel sulphide ores. Processing of ONOs using blast smelting in Russia doesn’t prove to be cost-effective. It is for this reason that the Ural plants of Yuzhuralnickel and Ufaleynickel closed down. However, the problem can be solved by adopting hydrometallurgical processes. Global practice features autoclave and ammonium-carbonate techniques for processing high-grade ONOs. Researchers are looking at such techniques as agitation leaching based on the use of nitrogen, hydrochloric and sulphuric acids. There is also some data on heap leaching of ONOs. However, none of the published techniques has found an industrial application. The use of the existing techniques to process leaching solutions is extremely complicated and still requires some finalization. This paper examines the process of selective deposition of nickel from the heap leaching solutions of ONOs using sodium hydrosulfide. Curves were built that show the nickel recovery at various pH levels and sodium hydrosulfide concentrations. Optimum process parameters for nickel deposition from solutions were established. A 97–98% nickel recovery was achieved. Deposits were obtained with the following average concentrations: 24%wt Ni and 1.3%wt Co. The findings show that the related impurities of Fe, Mn, Mg and Al make almost no transition from the solution to the deposit. The authors also looked at recovering nickel from the standard test solutions of nickel sulfate. The results of both chemical and X-ray phase analyses indicate that in terms of composition the resultant deposits are identical to the deposits recovered from the actual process solutions. Experiments were carried out for dissolving the nickel bearing deposits.

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