Study of the leaching and pore evolution in large particles of a sulfide ore

Abstract

A long-term leach investigation was undertaken on particles of a sulfide ore to determine the nature of solution transport into large particles and to identify the primary roles concentrations of acid and oxidant on controlling solution transport. Bulk leaching results showed that in the case of Fe leaching, both [Fe3+] and [H2SO4] promoted the extent of Fe extraction whereas the extent of Zn and Pb extraction was dependent only on [H2SO4]. Based on the bulk extraction of Al and Mg, it appears that [H2SO4] drives the expansion of inner particle pores by promoting the dissolution of gangue minerals. The findings indicated that the generation of cracks and/or pores to enhance solution contact with the value minerals remains the critical factor in improving value metal recovery from this type of material during heap leaching. Comparative laboratory and synchrotron X-CT studies were also undertaken on single ore particles using a novel in–situ leach cup technique. Similar to the solution results, the acid concentration was shown to be critical in creating effective porosity and pore networks through the centre of the particles for the transport of solution to value minerals and subsequent leaching and transport to the bulk solution. This occurred primarily through the dissolution of auxiliary aluminosilicate gangue minerals, which in turn created networks of porosity for effective bulk solution transport into large particles during heap leaching. This, in turn, enables local solution micro-environments where leaching occurs at the solid-liquid interface. Following the accessibility of bulk solution into the particle, the reaction is then governed by surface-mineral reactions between the sulfidic minerals.