Selective Liberation and Extraction of Energy-Critical Metals from Mafic and Ultramafic Ore Tailings with Carbon Mineralization

Sustainable recovery of energy-critical metals such as Co, Ni, and Cu from mining waste tailings represents a major opportunity for supply of these metals. Though mafic and ultramafic ore is rich in Ca, Mg, and Fe silicates which make liberation via conventional methods difficult, this also provides a unique avenue to combine innovative extraction and separation technology with carbon mineralization of those elements for the future of sustainable mining. This poster presents a framework for the design of functionalized ligands for both targeting Mg and Ca, aiding in the liberation of metals from tailings and separating them for carbonation, as well as the separation of Co and Ni for high purity recovery after liberation. The effectiveness of the ligands was compared, for a collection of input ore, across particle size, mineralogy, and composition, using low-energy<i> in-situ</i> grinding to improve liberation to allow for less acid and base usage for greater sustainability. Oxalic acid, a compound of interest from a CO₂ utilization perspective, was used in this system to leach Mg and Ca, with Mg being leached into solution at comparable rates to the standard of sulfuric acid, while selectively precipitating out calcium oxalate. The resulting leachate was evaluated in downstream separation using ligand-assisted solvent extraction and electrowinning with a target of high recovery and purity of Ni and Co. Using ligands with tuned binding constants and pH windows, we can separate metals like Ni and Co while minimizing acid use and maintaining ligand recycling. After this, the remaining Mg-rich leachate was used to form magnesium carbonate from carbon dioxide under mild conditions. With this framework, we target the recovery of high purity value metals from mine tailings while also sequestering carbon.