Abstract
The research work in the present paper determined the conditions at which nickel and cobalt can be recovered, as easily filterable precipitates, from leach liquors, which are produced by sulphuric acid leaching of nickel oxide ores at atmospheric pressure. Nickel and cobalt were precipitated as hydroxides at pH = 8·7, using CaO pulp as a neutralising agent, by 99·9 and 99·8% respectively. At this pH value manganese and magnesium, which were contained in the leach liquor, were precipitated, having a concentration of about 2·6 and 4·7% respectively in the final mixed precipitate. Statistical design and analysis of experiments were used in order to determine the main effects and interactions of the precipitation factors, which were the pH value at equilibrium and temperature. The characterisation of the produced mixed precipitate was carried out by X-ray diffraction, thermogravimetric/differential thermal analysis (TG/DTA), scanning electron microscopy and particle size distribution analyser. The main mineralogical phases of the precipitate after drying at 110°C were nickel hydroxide and bassanite (CaSO4.0·5H2O).
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