Solvent extraction test work to evaluate a Versatic 10/Nicksyn synergistic system for nickel-calcium separation

Tati Nickel is currently operating a hydrometallurgical demonstration plant in Botswana, using the Activoxi?½ process developed by LionOre Technology to produce nickel cathode and a cobalt salt from a sulphide concentrate. Cobalt is extracted using Cyanex 272. This reagent also extracts all the iron, aluminium, copper, zinc, and manganese from the nickel stream. Versatic 10 carboxylic acid is then used as extractant to recover nickel from the stream, separating it from calcium and magnesium, and upgrading it to provide a suitable advance electrolyte for nickel electrowinning. However, the selectivity of Versatic 10 for nickel over calcium is limited, and gypsum formation in the extraction circuit is a problem when attempts are made to maximize the recovery of nickel. Mintek has developed a synergistic system with Versatic 10 for improved separation of nickel from calcium and magnesium. Laboratory testwork was conducted on the raffinate of the cobalt solvent extraction circuit to optimize the Versatic 10/Nicksyni?½ (Mintek synergist) system to be employed. Extraction and stripping parameters suitable for this stream were optimized in the laboratory and then applied on the demonstration plant. A commercial batch (0.5 tons) of Nicksyni?½ reagent was produced for the demonstration plant. The laboratory testwork results and the demonstration plant performance are discussed in detail in this paper.