Comparison of sphalerite concentrate leaching by chemical and microbially produced ferric sulfate

Abstract

High-temperature ferric leaching is a promising method to improve the recovery of nonferrous metals from sulfide ores and concentrates. In this study, differences in the leaching kinetics of a sphalerite concentrate using chemical and biogenic ferric iron have been revealed. A comparison of leaching with a (i) biosolution containing ferric iron produced by microbial cells assigned to the strain Leptospirillum ferriphilum BUT, (ii) cell-free iron-containing L. ferriphilum culture liquid, and (iii) commercial reagent of ferric iron indicated that the latter allowed the maximum zinc and copper extraction into the solution. It is suggested that the products of the microbial cell lysis interacted with metal cations, decreasing their reactivity, and slowed down the removal of products from the reaction zone. This led to the formation of a dense layer of reaction products coating sulfide minerals. Probably, the rate of zinc and copper leaching was controlled by both the diffusion of the oxidant through a layer of the reaction products and a chemical reaction on the surface of mineral particles, indicating a mixed type of control. This pattern was independent of the chemical or biological origin of the ferric iron solution. The results provide new insights into the kinetic patterns and structural changes of sulfide minerals during ferric leaching and may contribute to the intensification of the processing of sulfide raw materials.