Characterization of a coarse synthetic silver ore as a model ore material for heap leaching research

Abstract

Leaching and micro-focus X-Ray computed tomography (µXCT) characterization studies were performed on a synthetic silver ore prepared from cement mixtures with embedded silver grains. This was done with the aim to understand the leaching behaviour of coarse ore particles in laboratory-scale heap leaching experiments. The synthetic ore was developed to possess specific ideal properties including uniform grain dispersion and size, homogenous porosity, and even grade distribution, and the “homogenized ore” was evaluated for these characteristics. The study validated that the ore had achieved its homogenized properties; however, the inner-particle pores were not found to be continuous at the µXCT detection limit of 4.8 µm. Poor extraction from the coarse particles in the leaching investigation suggested the pore network was not well established and may exist only at the sub-micron scale. Coarse particle leaching extraction data was analysed with the diagnostic shrinking core and the extended mixed topology models, which demonstrated that a diffusion–reaction mechanism governed the dissolution extraction from the larger particles. The results showed that leaching was restricted to the near-surface regions, but did not extend to the inner core, resulting in low extraction. Coarse synthetic particle leaching under controlled conditions could be utilized as a potential deterministic technique for understanding the reaction performance in coarse particle heap leaching.