While South Africa’s energy and mining sectors represent an important part of the country’s economy, they are also major contributors to toxic waste streams such as acid mine drainage and large volumes of solid mine residues. These waste streams represent an ongoing financial burden to the country since they require high-cost treatment and/or long-term management. Lasting sustainable solutions that can be implemented by the South African government and the private sector alike need to be found. The aim of this project is to synthesise CaAl2O4 mineral nanopowders using plagioclase-rich Bushveld mine tailings as starting materials. CaAl2O4 nanopowders can be used as mineral additives for accelerated strength development of concrete and/or geopolymers. The technological process under development involves a two-step approach. The first step extracts Al and Ca from plagioclase-rich tailings to solution. The second step involves solution combustion of the leachates to form CaAl2O4 nanopowders. Key to the process will be the ability to control the chemical and mineralogical composition, as well as the size and shape of the prepared CaAl2O4 nanoparticles to suit the targeted applications.

Mine tailings from the Bushveld Igneous Complex contain a substantial amount of aluminium- (Al), chromium- (Cr), iron- (Fe), calcium- (Ca) and magnesium- (Mg) bearing silicates which have the potential to serve as secondary mineral sources for the synthesis of nanomaterials such as Fe2O3/Fe3O4, FeCr2O4, MgO/MgAl2O4 or Fe-Cr-Al alloy nanopowders. Specific applications that will be targeted include nanoparticles as plant fertilisers for drought stress management and nanomaterials for toxic metal removal from water and acid mine drainage.