Achieving highly efficient olivine carbonation: The critical roles of grinding method and elevated CO2 partial pressure

Mineral carbonation, which transforms CO 2 into stable carbonates via reaction with Ca- and Mg-silicates, offers a permanent and secure carbon sequestration pathway. Olivine is a highly reactive feedstock, and its carbonation kinetics are known to depend on particle size, CO 2 partial pressure ( \({P_{{\rm CO}_2}}\) ), temperature, and additives. However, two key gaps persist in the current understanding. First, the time-dependent influence of \({P_{{\rm CO}_2}}\) throughout the carbonation process remains unclear. Furthermore, the effect of the grinding method (wet vs. dry) is frequently oversimplified as reducing particle size, neglecting its concurrent alteration of other physicochemical properties. This study systematically addresses these gaps by investigating the carbonation of fine-grained olivine under varied \({P_{{\rm CO}_2}}\) (5–14 MPa) at 185 °C. Reaction progress was tracked in real time using a flush-sampling batch reactor. Our results reveal that the wet-ground olivine, possessing a higher specific surface area (SSA), achieved significantly greater carbonation efficiency compared to the dry-ground sample. Kinetic analysis based on the shrinking core model (SCM) indicates that the formed porous carbonate layer does not act as a diffusion barrier but facilitates the reaction. Increasing \({P_{{\rm CO}_2}}\) significantly enhanced the carbonation rate and final efficiency, with the maximum conversion reaching 98.45% at 14 MPa after 8 h. Furthermore, we identified that the reaction was most sensitive to \({P_{{\rm CO}_2}}\) during the initial stage, with the most pronounced effect observed within the first hour. The primary mechanistic insight is that initial carbonation is predominantly controlled by \({P_{{\rm CO}_2}}\) -driven dissolution, whereas at later stages, the available reactive surface area becomes the limiting factor. This work demonstrates that optimizing both the grinding method (preferring wet grinding for ex-situ applications) and employing elevated \({P_{{\rm CO}_2}}\) (⩾ 8 MPa for in-situ scenarios) are critical strategies for enhancing the efficiency and practical viability of olivine-based CO 2 sequestration.