Mathematical modeling of sulfuric acid leaching of pyrite cinders after preliminary chemical activation

Pyrite cinders, waste products of pyrite concentrate processing by firing to produce sulfuric acid, can serve as raw materials for the extraction of precious, ferrous, and non-ferrous metals. The paper considers the possibilities of obtaining non-ferrous metal concentrate from pyrite cinders by sulfuric acid leaching. This operation is one of the stages in the integrated technology. To increase the extraction of non-ferrous metals during leaching, the method of preliminary chemical activation was used. Chemical activation was carried out in a solution containing 40-120 g/dm3 NaНCO3 at temperatures of 90-230 ° C and a duration of 30-300 minutes. Sulfuric acid leaching of pyrite cinder after activation was carried out in H2SO4 solutions with a concentration of 5-20 % at a temperature of 60 ° C, duration of 30 minutes, and pulp density of 33 %. To determine the optimal conditions for the sulfuric acid leaching of pyrite cinders, a mathematical planning method was used, which allows to assess with a high degree of reliability the influence of the main factors (temperature, pulp density, the concentration of the solution NaHCO3 and duration) and predict an increase in the efficiency of the process by analyzing the numerical values of the regression equations. As a result of sulfuric acid leaching of pyrite cinders after preliminary chemical activation under optimal conditions determined by a mathematical model, the extraction of iron and non-ferrous metals into a solution is 10-15% higher than without activation.