Microstructure evolution of low-grade chalcopyrite ores in chloride leaching - A synchrotron-based X-ray CT approach combined with a data-constrained modelling (DCM)

Abstract

The dissolution of metal sulfides, especially chalcopyrite and the development of porosity in samples of two different low-grade ores during chloride leaching have been studied by synchrotron-based micro-CT. Quantitative analysis of the changes was achieved by using a data-constrained modelling (DCM) approach. The result indicated that void spaces developed from the surface gradually into the core of a sample, which increased from 0.08% to as much as 11.1% in the Chilean ore, and from 0.05% to 0.93% in the Mongolian ore. Combining the results of DCM modelling and CsCl distribution test, no pore structure stretching into the core of the samples was found. As a result, the leaching of metal sulfide mostly happened in the out rim of both samples, where the mineral is directly exposed to the solution. For the Chilean ore, the volume fraction of metal sulfide decreased from 4.45% to 4.06% in 17 h in the sample as a whole, and from 1.23% to 1.2% in the core. For the Mongolian ore, the volume fraction of metal sulfide decreased from 0.23% to 0.21% in the same time span. This study provides clear evidence that contact of the target mineral with leaching solution is the primary premise for metal dissolution to happen. It also demonstrates that the combination of synchrotron CT and DCM is a useful approach for mineral micro-structure analysis.