Combined extraction of metals and production of Mg(OH)2 for CO2 sequestration from nickel mine ore and overburden

• Mg, Ni, Cu and Fe were extracted from nickel ore using ammonium sulphate (AS) and bisulphate (ABS).
• Circa 1/3 of Ni was extracted together with 80% of Mg, 75% of Cu and 40% of Fe with ABS at 450 °C.
• ABS and smaller particle size improve the extraction rate. Water presence is not always beneficial.

Carbon storage by mineralisation (CSM) is an option for CO2 emissions mitigation that has been under intensive study at Åbo Akademi (ÅA), Finland. Magnesium from silicate rocks is extracted with recoverable ammonium salts at 250–500 °C. The extracted elements are separated by selective precipitation and Mg is subsequently carbonated in a pressurised fluidised bed. This work studies the applicability of the process for co-extraction of Ni, Cu, Fe and Mg from nickel ore and nickel mine waste rock (overburden). The rock samples were collected from the Hitura Nickel mine, Finland. The results show that it is possible to co-extract the listed elements and integrate CSM (by the ÅA process) with steelmaking and Ni production industries.