Leaching of rare earth elements

Modelling in-situ leaching of rare earth elements

As the grades of ore, containing precious metals, decline leaching can under certain circumstances present a potentially more economically viable and environmentally friendly process option compared with traditional pyro-metallurgical processes.
As experimental investigations of leaching processes are often time consuming and lack scalability, the development of models to simulate these processes has become of increasing importance. However, as the modelling of leaching systems has been approached from various perspectives, there has been an inconsistent approach to their calibration and validation. This has called into question their reliability in predicting full scale leaching operations. Further systematic modelling investigations are therefore required to address these shortcomings.
As models should always be calibrated and validated against experimental data a case study is required. With the demand for Rare Earth Elements (REEs) rising due to their increasingly ubiquitous use in technology, coupled with the fact that they have not been extensively modelled, extracting REEs using in-situ leaching was chosen as a case study.
Nicole Uys
MSc Chemical Engineering
Completed a BSc (Hons) in Chem Eng (2014), a Postgraduate Diploma in Management, specialising in Entrepreneurship (2015) and currently working towards a MSc within MtM at UCT. Passionate about renewable energy, water purification and waste minimisation and would like to identify new opportunities by exploring the lifecycles of materials from an engineering and entrepreneurship perspective

The influence of diffusion pathways on the solution potential in mineral leach systems
High grade ores resources continue to decline and therefore the mineral processing industry is compelled to process lower grade ore resources which are metallurgically more complex. The processing of lower grade ores necessitates the use of less energy intensive processes in order make extraction economically viable. Heap leaching gained popularity as it is most applicable to the leaching of lower grade ores as it only requires size reduction to relatively coarse particle size, typically in the range of 12 – 25 mm, and is resultantly less energy intensive.
However, heap leaching is still characterized by slow leaching times and low recoveries, which have been linked to using these coarser particle sizes whereby desired mineral grains may not be fully liberated. This is due to that leaching occurs on the surface of 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 n diffuse through to the mineral surface and products out to the bulk solution, resulting in concentration profiles within the pores. Therefore, a fundamental and experimental investigative study was undertaken in order to elucidate the extent to which concentration profiles within diffusion cracks/pores affect the leaching of encapsulated mineral grains.
Buhle Manana
MSc Chemical Engineering
“I am the master of my fate, I am the captain of my soul” – William Ernest Henley (Invictus)

Dry processing: Developing innovative technologies for improved sustainability in mining
Due to current technologies being exploited in the mining industry, access to high grade ores is becoming difficult due to the depths of mining shafts. As a result, most ores that are being mined currently are low grade ores or complex ores. Ore processing is an energy intensive process; energy intensity is increased when processing low grade ores or high grade complex ores in order to attain desired liberation of valuable minerals. For most ores both low grade and high grade ores, grinding is required to expose the surface area of valuable minerals. Conventional mills (tumbling mills) are energy intensive when it comes to grinding and with the global energy crisis, the use of tumbling mills is not sustainable.
The project aims to investigate the use of a high pressure grinding roll (HPGR) followed by air classifiers for the processing of kimberlite and platinum ores; the overall objective of the project is to save comminution energy, save water in comminution and use the air classifier to separate clay minerals and find the economic value of the clay minerals. Clay minerals are problematic in minerals processing as their undesirable effects are observed in comminution through to tailings dams’ construction.
Gilbert Ncube
MSc Chemical Engineering
“Courage is not something that you already have that makes you brave when the tough times start. Courage is what you earn when you’ve been through the tough times and you discover they aren’t so tough after all” – Malcom Gladwell (David and Goliath)

Minerals To Metals Symposium 2016


Dust Monitoring Equipment – providing equipment, services and training in dust fallout management to the mining industry.

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