Understanding the variability of leaching kinetics is extremely challenging due to the nature of leaching processes. Common experimental setups, such as column leaching experiments, only allow for quantification of apparent leach kinetics at the macroscale (e.g. at the particle or column level), failing to capture grain-scale variability. In this paper, we study variability in leaching kinetics at the micro- and macroscale using a combination of 4D imaging and standard chemical measurements.

The impact of chloride ions on leaching performance was evaluated using column leaching experiments. Micro-computed tomography (micro-CT) was combined with SEM/EDX to isolate chalcopyrite from pyrite dissolution. Using in-house algorithms, the leaching behaviour of hundreds of thousands of grains was quantified and tracked over time. Morphological changes at the agglomerate level were assessed, coupling porosity network development and microcrack formation to leaching variability.

It was concluded that a decrease in internal macro porosity does not significantly impact macro-scale leaching performance. Grain size had an impact, although grain location does not influence mass transport resistance. Another key finding was that leaching in chloride media is more selective for copper sulphides, evidencing virtually no pyrite dissolution. This study not only provides new understanding of the factors influencing the leach behaviour of chalcopyrite ore, but also generates data that represents the process more accurately and allows for better planning.