Abstract
The globally growing demand in nickel production necessitates the development of sustainable extraction strategies from low-grade mineral resources while achieving carbon neutrality. This study investigated the selective recovery of nickel from a low-grade silicate sample with an integrated focus on carbon dioxide sequestration through mineral carbonation. The nickel (0.3wt%) in the sample was present in mixed form of both sulfide and silicate minerals, occupying approximately 35% and 65%, respectively. Atmospheric and high-pressure leaching approaches are systematically investigated using nitrilotriacetic salt (NTA) as a complexing agent to enhance nickel dissolution while realizing CO2 mineralization as stable mineral carbonates. It is found that the atmospheric nickel extraction with carbon mineralization was effective for nickel in sulfide minerals. Within half an hour, the nickel from sulfide minerals, mainly pyrrhotite and pyrite, can be completely and selectively leached into aqueous solution under ambient temperature and pressure, together with the simultaneously direct CO2 mineralization at approximately 40 kg CO2/t ore resources. The pressure nickel leaching with carbon mineralization under elevated temperature and CO2 overpressure was effective for nickel in silicate minerals, mainly serpentine and olivine. Within two hours, all the nickel from silicate minerals can be selectively extracted together with the simultaneous carbon mineralization at 72 kg CO2/t ore resources, although a heat pre-treatment can further enhance the carbon mineralization efficiency. The integration of atmospheric and pressure leaching approaches can effectively and selectively extract nickel existed in mixed forms of sulfide and silicates of low-grade resources while achieving carbon mineralization from both air and CO2 resources. This integrated approach presents a promising pathway for the sustainable processing of sulfide- and silicate-mixed nickel resources, offering reduced environmental impact and contributing to the development of low-carbon nickel production aligned with global clean energy and critical minerals objectives.