Multivariate study of the dynamics of CO2 reaction with brucite-rich ultramafic mine tailings

Mineral carbonation of a nickel mine tailing (NiMT) was studied using a dual-compartment carbonation cell employing moderate CO2 partial pressures for accelerating carbon uptake and to simulate outdoor temperature conditions prevailing in mining waste disposal sites. Time-dependent X-ray powder diffraction analysis and scanning electron microscopy reveal formation of transitional, metastable porous, flaky magnesium carbonates which subsequently evolved into less porous nesquehonite layers, which are shown to be responsible for surface passivation despite availability of unreacted brucite. However, the reactive cores could be turned into easily accessible regions following ex-foliation of carbonated materials. Moreover, it was demonstrated that slow carbonate nucleation events such as during carbonation of as-received ores may be significantly accelerated by means of carbonate pre-seeding strategies.