Abstract
The problem of processing stale tailings is a global one, and the main task is the extraction of economically valuable metals. In Kazakhstan, the market for the extraction of nickel and cobalt from stale tailings is practically undeveloped. In addition, the need for nickel and cobalt increases annually due to the high demand for nickel-cobalt batteries for the manufacture of electric vehicles, special alloys and others. Pyrite concentrate containing nickel-cobalt from Sokolovsko-Sarbaisky mining and processing plant is a valuable source of extraction of a number of valuable non-ferrous metals such as iron, nickel, cobalt, etc. The purpose of the study is to study the optimal conditions for the extraction of nickel and cobalt from thermally decomposed pyrite concentrate of the Sokolovsko-Sarbaisky mining and processing plant using sulfuric acid solutions. Thermodynamic analysis of oxidation reactions of the main components of pyrite concentrate showed that thermal decomposition of higher sulfides of iron, nickel and cobalt produced a series of non-stoichiometric lower sulfides Fe0.877S, FeS, Fe2S3, Fe7S8; Ni3S2, Ni3S4 and CoS0.89, CoS, respectively. The Pourbaix diagrams of Ni-S-H2O, Co-S-H2O and Fe-S-H2O systems show that sulfuric acid leaching of cobalt and nickel from thermally decomposed pyrite concentrate is possible at pH 0 - 1.5 and E > - 0.5 V. Leaching of non-stoichiometric FeS-Fe7S8 low iron sulfides is possible at pH 0 - 4.0 and E > 0 V. Studies to determine the optimum conditions of leaching of thermally treated pyrite concentrates found that for the extraction of nickel and cobalt effective concentration of sulfuric acid is 100 g/dm3, the leaching time is 120 minutes and temperature of 100°C and the maximum recovery of metals is 86.71% and 93.01%, respectively. Increasing the acid concentration, duration and temperature leads to complete dissolution of iron. A combined method for processing stale pyrite tailings can be used to process similar raw materials.