The extraction process begins with high-grade ore, mined in the Kalahari. The ore is milled to a powder and then it is reduced to a soluble form in rotary kilns. The reduced ore is dissolved in acid solution, followed by purification (precipitation of impurities and filtration). Sulphur dioxide, and not selenium dioxide, is added to the purified solution before electrolysis can take place. The solution is then fed into the electrolytic cells, where electric current causes the manganese to plate on the cathodes. Pure manganese metal is plated on the cathodes, while sulphuric acid, formed at the anodes, is re-cycled back to the dissolution process. The plated manganese is stripped from the cathodes, washed, dried and degassed. This metal is manganese in its purest, cleanest form. Depending individual customer requirements, the metal is then processed further and packaged for shipment. The solid waste remaining after dissolving the manganese is filtered to recover manganese- and ammonium sulphates to obtain a dry cake for disposal. MMC holds permits to operate a hazardous landfill facility at Kingston Vale. The Kingston Vale landfill design includes liners with leakage detection and filter trenches to collect all rain run-off. After collection the liquid is passed through MMC’s evaporation plant.
Liquid effluents are treated to ensure that no contaminated water leaves the MMC site. Rainwater is also collected and passed through the same treatment plant, where dissolved metals are precipitated and filtered out, then stripped of ammonia.
MMC’s total process flow is designed to produce a high purity, selenium-free product while limiting the impact on the environment and protecting the health of its employees.