Investigation on Abrasion versus Fragmentation of the Si-rich Passivation Layer for Enhanced Carbon Mineralization via CO2 Partial Pressure Swing

One of the most permanent methods of carbon storage is fixing CO2 into a solid matrix of carbonate minerals. The most recent reports by the U.S. National Academies and the Mission Innovation presented that carbon mineralization is a CO2 utilization technology with a great carbon storage potential and a large market size. While the mineral carbonation reaction is thermodynamically favored, its kinetics has been considered to be too slow without engineered enhancements. Particularly, the formation of the Si-rich passivation layer on mineral particles limits the overall reaction rate by creating a significant diffusion barrier. In this study, a unique internal grinding system was designed by directly incorporating grinding media into the carbon mineralization reactor based on a P-CO2 (partial pressure of CO2) swing. The effect of physical properties (e.g., sizes and densities) of grinding media on the dissolution behaviors of heat-treated Mg-silicate minerals (i.e., serpentine, Mg3Si2O5(OH)(4)) was investigated. The stress intensity, which is proportional to the energy transferred from grinding media to the heat-treated serpentine particles during a stress event, was used to describe the effect of the reaction parameters on the extent of the physical activation and the enhancements in mineral dissolution. The existence of the optimum stress intensity was identified where the minimum particle size was obtained. It was found that two attrition modes, abrasion and fragmentation/pulverization, were dominant depending on the stress intensity and that the fragmentation/pulverization mode was more effective in removing the Si-rich passivation layer and promoting Mg extraction during the dissolution step. The internal grinding system resulted in greater Mg leaching compared to the conventional ex situ grinding because the in situ approach allowed the synergistic effect of continuous removal of the Si-rich layer and surface dissolution reaction leading to the improved overall energy efficiency of the developed CO2 utilization and storage technology.