Microstructure evolution of chalcopyrite agglomerates during leaching – A synchrotron-based X-ray CT approach combined with a data-constrained modelling (DCM)

Abstract Agglomeration provides substantial advantages on heap leaching, such as creating a porous heap to improve low-permeability ore leaching efficiency, as well as building an environmentally friendly heap by reducing metal releases from waste rock and tailings. In this study, we employed synchrotron X-ray computed tomography (X-ray CT) combined with a data-constrained modelling (DCM) approach to investigate the properties and evolution of pore networks of chalcopyrite-dominant agglomerates during leaching. In particular, these agglomerates, with and without prior CaCl2 addition to produce binding reagent gypsum, were subjected to column leaching tests for a period of 37 days. The copper recovery is found to be highly dependent on interior structures of agglomerates: oxidative dissolution of sulphide minerals within agglomerates was considerably promoted by high CaCl2 addition, through more interior connected pore network structure, resulting in effective migration and diffusion of lixiviant solution. The leaching data clearly show that sufficient binding capacity is essential for the maintenance of agglomerate structure by improving its mechanical resistance. Synchrotron X-ray CT data reveals that the decomposition of agglomerate has a performance of dispersing sulphide grains within the agglomerate particle and improved intra-particle porosity. This study demonstrates that combined synchrotron X-ray CT and DCM approach is a powerful tool for understanding the characteristics and evolution of valuable minerals during leaching of agglomerates.