Abstract
Achievements of carbon neutrality and transition to global clean energy need accelerated CO2 mineralization and enhanced supply of critical metals. Comprehensive utilization of ultramafic tailings is a promising way since it contains abundant suitable minerals for CO2 mineralization and residual critical metals for further recovery. This work presents the accelerated CO2 mineralization and simultaneous critical metal recovery from ultramafic tailings in a single step under elevated temperature and CO2 pressure. Olivine ((Mg,Fe,Ni,Co)2SiO4) is found as the main reactive mineral during the accelerated CO2 mineralization process and as the important source of nickel and cobalt for recovery. Usage of an aqueous solution containing sodium bicarbonate and a suitable ligand (e.g. trisodium nitrilotriacetate(NTA)) can simultaneously achieve CO2 permanent storage and nickel and cobalt extraction from olivine-based mine tailings. The selectively extracted nickel and cobalt in aqueous solution can be recovered through sulfide precipitation as high-value nickel sulfide concentrates. The usage of NTA can also significantly accelerate the coupled CO2 mineralization and metal leaching process and minimize the effects of iron content in olivine on the reaction kinetics. The important findings can make important contributions to utilize ultramafic tailings for enhanced CO2 storage and global supply of critical metals towards carbon neutrality and sustainable developments.