MSc (commenced 2015)
Project Title: The influence of diffusion pathways on the solution potential in mineral leach systems
Supervisors: Prof Jochen Petersen; Dr Rahul Ram
High grade ores resources continue to decline and the mineral processing industry is therefore compelled to process lower-grade ore resources which are metallurgically more complex. This necessitates the use of less energy-intensive processes in order make extraction economically viable. Heap leaching has gained popularity as it is most applicable to the leaching of lower-grade ores, and only requires size reduction to relatively coarse particle size, typically in the range of 12 – 25 mm; consequently, it is less energy intensive. However, heap leaching is still characterized by slow leaching times and low recoveries, which have been linked to the treatment of coarse particles in which the desired mineral grains may not be fully liberated. This is because leaching occurs on surface-exposed or subsurface mineral grains exposed to the lixiviant via cracks/ pores induced during crushing. Once the cracks/pores are fully saturated with solution, dissolved reagents can diffuse to the mineral surface and products can diffuse out to the bulk solution, resulting in concentration profiles within the pores. The aim of this fundamental and experimental investigative study was to elucidate the extent to which concentration profiles within diffusion cracks/pores affect the leaching of encapsulated mineral grains. Electrochemical techniques and analyses were used to develop an integrated experimental reaction rate model for the leaching of sub-surface mineral grains.