Our research relates to the characterization and valorisation of industrially obtained mineral wastes and by-products such as:
Depending on the raw material studied and the intended application, this may include studies on:
Current Projects
Coal fly ash as inorganic filler
The most significant and large-scale application of coal fly ash is in its partial replacement for Portland cement in the cement and concrete industry. The use of fly ash as an engineering material primarily originates from its pozzolanic nature, spherical shape, and relative uniformity. Inorganic fillers are generally used in polymers to reduce production costs and improve certain physical characteristics. Surface treatment is usually performed on mineral fillers to enhance workability, improve compatibility and facilitate interaction between the polymer and filler.
Extraction of aluminium from coal fly ash
The potential for extracting major elements from coal fly ash and various types of mine tailings are pursued. In most of these studies, we make use of a preceding thermochemical treatment step to increase the reactivity and dissolution behaviour of the elements of interest. Subsequent aqueous leaching of the thermochemically activated products instead of the conventionally acid-leaching procedures used in most hydrometallurgical processes is preferred. An example of a process flow diagram for the multi-stage extraction process studies, and FESEM images of thermochemically activated coal fly ash is shown below:
Utilisation of mine waste products such as tailings and slimes as secondary metal and mineral resources
South Africa's energy and mining sectors represent an important part of the country’s economy, but they are also major contributors to solid mine residues and other waste streams such as acid mine drainage. Mine residues are becoming increasingly problematic due to the large volumes generated; the ongoing financial burden associated with their long-term management, and in some instances their acid-generating potential. There is therefore a constant need to create innovative and sustainable solutions, which can include the development of valorisation technologies for metal or mineral recovery.
These projects focus on the reactivity and dissolution behaviour of minerals contained in mine tailings and slimes for elemental extraction. Elemental extraction is achieved via a thermochemical solid-solid treatment using ammonium sulphate ((NH4)2SO4), a widely available, low-cost, recyclable extracting agent to recover and synthesise added-value products from mine tailings and slimes. This extraction process offers the significant advantage of recovering major elements or individual mineral phases from tailings in a readily available soluble form, which could be subsequently converted to value-added products, which may assist in minimizing their disposal and in making treatment processes more viable economically.
Left: Process flow diagram for the multi-stage extraction process using ammonium sulphate,
Right: FESEM images illustrating morphological changes due to thermochemical treatment
The analytical techniques that are mostly applied include Thermogravimetric analysis (TGA and TGA-FTIR), Differential Scanning Calorimetry (DSC), Surface area determinations (BET), X-ray powder diffraction (XRD), X-ray fluorescence (XRF), Field Emission Scanning Electron Microscopy (FESEM), Transmission Electron Microscopy (TEM), Raman and Fourier-transform infrared (FTIR) spectroscopies, Particle size distribution (PSD) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS).
Prof Liezel van der Merwe Room 3-39, Nat Science Building 1 Tel: 012 420 5379
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Mrs Barbara Castleman Room 3-46, Nat Science Building 1 Tel: 012 420 2043
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Ms Sameera Mohamed PhD Student Topic: Chemical reactivity of Bushveld Igneous Complex mine residues for mineral beneficiation |
Mrs Barbara Castleman PhD Student Topic: Beneficiation of diamond mine residues for the synthesis of Mg-containing compounds |
Mr Dennis Moyo PhD Student Topic: Insecticide filled polyethylene films for malaria vector control |
Mr Sydney Ngetu MSc Student Topic: Calcined kaolinitic clay in highly substituted pozzolanic cements |
Ms Rachel McCondochie MSc Student Topic: Extraction of Al and Si from coal fly ash for the production of catalyst supports |
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List of graduates |
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