Ball Milling Effect on the CO2 Uptake of Mafic and Ultramafic Rocks: A Review

Abstract

Mineral carbonation is considered to be the most stable mechanism for the sequestration of CO₂. This study comprises a comparative review of the effect of ball milling on the CO₂ uptake of ultramafic/mafic lithologies, which are the most promising rocks for the mineralization of CO₂. Samples of dunite, pyroxenite, olivine basalt and of a dolerite quarry waste material were previously subjected to ball milling to produce ultrafine powders with enhanced CO₂ uptake. The optimum milling conditions were determined through selective CO₂ chemisorption followed by temperature-programmed desorption (TPD) experiments, revealing that the CO₂ uptake of the studied lithologies can be substantially enhanced via mechanical activation. Here, all these data are compared, demonstrating that the behavior of each rock under the effect of ball milling is predominantly controlled by the mineralogical composition of the starting rock materials. The ball-milled rock with the highest CO₂ uptake is the dunite, followed by the olivine basalt, the pyroxenite and the dolerite. The increased CO₂ uptake after ball milling is mainly attributed to the reduction of particle size to the nanoscale range, thus creating more adsorption sites per gram basis, as well as to the structural disordering of the constituent silicate minerals.