Synthetic Sulfide Concentrate Dissolution Kinetics in HNO 3 Media.

The nature of tennantite (Cu 12 As 4 S 13 ), chalcopyrite (CuFeS 2 ) and sphalerite (ZnS) particles' mixture dissolution in nitric acid (HNO 3 ) media was investigated in this study. The effects of temperature (323-368 K), HNO 3 (1-8 mol/L) and Fe 3+ (0.009-0.036 mol/L) concentrations, reaction time (0-60 min) and pyrite (FeS 2 ) additive (0.5/1-2/1; FeS 2 /sulf.conc.) on the conversion of the minerals were evaluated. It has been experimentally shown that the dissolution of the mixture under optimal conditions (>353 K; 6 mol/L HNO 3 ; FeS 2 /synt. conc = 1/1) allows Cu 12 As 4 S 13 , CuFeS 2 and ZnS conversion to exceed 90%. The shrinking core model (SCM) was applied for describing the kinetics of the conversion processes. The values of E a were calculated as 28.8, 33.7 and 53.7 kJ/mol, respectively, for Cu 12 As 4 S 13 , CuFeS 2 and ZnS. Orders of the reactions with respect to each reactant were calculated and the kinetic equations were derived to describe the dissolution rate of the minerals. It was found that the interaction between HNO 3 solution and Cu 12 As 4 S 13 , CuFeS 2 and ZnS under the conditions investigated in this are of a diffusion-controlled nature. Additionally, the roles of Fe(III) in the initial solution and FeS 2 in the initial pulp as catalysts were studied. The results indicated that the increase in Fe 3+ concentration significantly accelerates the dissolution of the mixture, while the addition of FeS 2 forms a galvanic coupling between FeS 2 , and Cu 12 As 4 S 13 and CuFeS 2 , which also accelerates the reaction rate. The results of the study are considered useful in developing a hydrometallurgical process for polymetallic sulfide raw materials treatment.