Phase transformations of mechanically activated bornite in autoclave oxidative leaching

Abstract

Bornite is one of the common sulfides in the pyrrhotite concentrate separated from the sulfide ore of the Norilsk and Talnakh fields and processed by hydrometallurgical autoclave technology in the Nadezhdinsk Metallurgical Plant of the Norilsk Hydrometallurgical Combine [i]. The relative rates of nickel, copper, and iron sulfide oxidation in autoclave leaching for 3 h at 373 • 2~ and 0.45 MPa oxygen pressure were studied in [2]. The sulfuric acid content in the original pulp was 5 g/liter and the solid to liquid ratio was 1:40. Under these conditions the degree of copper extraction into solution, which was taken as the criterion of bornite decomposition, was 50-55% and the relative sequence of the minerals in terms of their leaching rate was troilite, pyrrhotite, pentlandite, bornite, chalcopyrite, cubanite, talnakhite, and pyrite.It was shown earlier [3] that CusFeS ~ oxidation accelerates appreciable in the bacterial leaching process after its preliminary mechanical activation.The purpose of this work was to clarify the effect of bornite treatment in a planetary mill on the mechanism of its autoclave oxidative leaching (AOL).It has been proved in recent years that similar treatment of pyrrhotite, pyrrhotite concentrate, and pentalandite alters their physicochemical proeprties markedly [4,5] and renders their autoclave leaching more effective [6,7]. The x-ray structural and thermal characteristics of bornite after its activation in an M-3 planetary mill (designed by S. I. Golosov) and the kinetics of its oxidation upon heating are also altered markedly [8,9].The bornite isolated from the ore contained (%): copper 50.4, sulfur 24.7, iron 14.0, nickel 6.5. A 25 g sample was activated in an M-3 mill in aqueous medium for 0.5-30 min. The steel grinding bodies weighed 500 g and the water volume in the mill was 125 ml. The x-ray phase analysis ~PA) of the solid leaching residues was performed on a DRON-2.0 diffractometer (radiation: ferromonochromatic with a graphite single crystal, 25 kV, i0 mA, BSV-II tube). The diffration patterns were photographed and calculated by N. T. Mandrikova and A. I. Mikolaenko.Volume of leaching autoclave 1.0 dm 3, bornite sample weight 14 g, volume of 0.3% sulfuric acid solution 700 ml. After loading of the autoclave the experiments were started simultaneously with the oxygen supply into it. The oxygen concentration in the gas phase was kept constant by supplying it continuously through a reducing valve and by evacuation of the gas phase through a needle valve.The experiments were carried out at 381 and 403~ and at 0.2, 0.5, and 1.0 MPa partial oxygen pressures.Three experiments were performed by bubbling the pulp with oxygen at 363~The duration of each experiment was 2 h. The samples of the liquid phase were taken for copper and nickel analysis and for measuring the pH and eH at intervals of 5, i0, 15, 30, 45, 60, 90, and 120 min of oxygen supply.The solid phase was studied by XPA. Results.Mechanical activation alters the physicochemical properties of bornite markedly. The intensity of ...