Heap leaching kinetics are proportional to the irrigation rate divided by heap height

Zinc sulphide ore was leached in columns of various heights and under various irrigation rates. This study aimed to investigate the relationship between heap leaching kinetics and irrigation rates in bioleaching processes. Experimental columns were constructed with heights ranging from 1 m to 8 m and were irrigated at different rates. The findings indicated that sphalerite and pyrite bioleaching kinetics were well modeled by the colonization shrinking core model, where an initial colonization phase is succeeded by a steady rate phase. It was observed that colonization rate constants for both minerals increased linearly with the inverse of column height while shrinking core rate constants were also inversely related to heap height. Notably, when adjustments were made to the irrigation rate to account for varying heights, the leaching curves for all columns remained consistent. This indicated that the kinetics of sphalerite and pyrite heap bioleaching are proportional to the ratio of irrigation rate to heap height. Furthermore, sphalerite bioleaching was observed to be favored over pyrite at lower ratios, whereas higher ratios promoted greater sulfur oxidation. The study provides critical insights into optimizing bioleaching processes in zinc extraction.