EXPERIMENTAL STUDY AND THERMODYNAMIC MODELING OF SUPERGENE PROCESSES IN TAILINGS OF COPPER-NICKEL ORES
The results studies the mineral oxidation were obtained by us during the methods of physico-chemical analyses and thermody-namic modeling of sulfides in tailings of copper-nickel wastes in Kola peninsula. Sulphide minerals begin to oxidize already at the stage of stockpiling and initial stages of storing. The proportion of non-ferrous metals and magnesium oxide increases with time, calci-um partially precipitating in the form of gypsum. Comparison of heavy metal contents in pore solutions in current and stale copper-nickel ore concentration tailings has revealed a significant differ-ence in practically all the parameters. The lower metal contents in current tailing pore solutions (by 5-30 times) are probably due to the presence of float reagent residues blocking oxidation. Much lower concentrations of magnesium and calcium can be accounted for by the difference in kinetics: the rate of sulphide oxidation at this stage is much higher than that of solution interaction with non-metallic minerals as the result of which the solid phase - solution equilibri-um is not achieved. The direct determination of the total and silicate Ni contents in the tailings from current production and in storage tailings has shown that both sulfide and silicate Ni forms occur in tailings. The average silicate Ni content accounts for 10% of the bulk Ni content in the current tailings and it increases to 40% in the storage tailings. Thus, the storage tailings are marked not only by sulfide oxidation and the removal of water-soluble sulfates, but also by the interaction of sulfates with the silicate matrix. Although complete equilibrium is not achieved even within 30 yr under polar-region conditions, the major part of the Ni in fine-grained fractions passes into silicate form. The migration of Ni as sulfates and its pre-cipitation by chemically active silicates distorts the distribution of this component in the coarse- and fine-grained fractions that are typical of tailings from the current production of copper-nickel ores. On the one hand, the variation of the mode of Ni occurrence in stor-age tailings lowers the value of technogenic raw materials as a source of this metal.