Insights into the mechanochemical interfacial interaction between calcite and serpentine: Implications for ambient CO2 capture

Mineral carbonation of readily-available serpentine is a promising solution for massive atmospheric carbon dioxide (CO2) sequestration, in which process the most significant challenge is to overcome slow carbonation kinetics under atmospheric conditions. To enhance the mineral dissolution rate and overall carbonation efficiency, activation of serpentine is required. In this study, for the first time, a facile way to obtain activated serpentine by simply co-milling with calcite was discovered, and the as-prepared materials were applied to direct CO2 capture under atmospheric conditions. A series of analytical techniques were carried out to understand the interaction mechanism between serpentine and calcite during ball-milling process, demonstrating the occurrence of interfacial reaction with the mutual diffusion and replacement of sectional ion constituents. This robust interaction between two mineral phases endowed the minerals with superior reactivity compared to single serpentine phase, and meanwhile generated a certain amount of magnesium carbonate directly. From the confirmed cadmium precipitation as carbonate (otavite phase) from solution, methodologically, with Cd removal as quantitative index, the carbonation efficiency of co-milled materials at the molar ratio of 1:1 was about 4 times as high as that of singly-milled minerals within 2 h, indicating the tremendously enhanced CO2 capture capacity of co-milled materials. These findings about the mechanochemical interfacial reaction between calcite and serpentine may provide a novel concept and an alternative way for the activation of magnesium silicates, which can be potentially applicable to solve some tough environmental issues including CO2 sequestration.