A review on strategies to assess the spatiotemporal heterogeneity of column leaching experiments for heap leaching upscaling

Abstract

Column leaching experiments are an essential step in the upscaling process towards a heap leaching operation. However, these experiments are often restricted to the optimisation of a reduced set of parameters. In doing so, most column leaching experiments tend to be ore-specific and to neglect key aspects such as mineralogical or structural changes over time, surface-level processes, or hydrodynamic features. The omission of these factors results in the loss of information on the spatiotemporal heterogeneity of column leaching experiments, which could provide insights leading to more environmentally or economically sustainable operations. Certain studies have focused on accessing this spatiotemporal information by using 3D imaging techniques (such as Computed Tomography − CT or Magnetic Resonance Imaging − MRI) or hydrodynamic assessment procedures (residence time distribution − RTD analysis or gravimetric liquid holdup estimation methods) to study column leaching. These studies have demonstrated that there is more information in column leaching experiments than what is acquired during conventional optimisation tests. Despite this, two essential gaps have been identified in the literature: (1) surface-level processes have received very limited attention as part of column leaching experiments and (2) chemical characterisation of the leaching solution is restricted to collection points before and after the column, providing a very low spatial resolution for these measurements. Multimodal methodologies capable of assessing several aspects of the process need to be implemented to bridge these gaps and to unlock information on the spatiotemporal heterogeneity of column leaching experiments.