Enhancing CO2 hydrate kinetics with cost-effective calcium-based montmorillonite for carbon capture

Abstract CO 2 emission-driven climate change demands efficient CCUS technology. Montmorillonite (mmt) is an abundant, cheap, and eco-friendly terrestrial porous material, with the potential to turn from a passive geological medium to an active functional material for carbon capture. However, hydrate-based CO 2 capture, though promising for high storage density and eco-friendliness, is hindered by slow kinetics and high energy use. To address this, our study systematically explores the enhancement of CO 2 hydrate kinetics using mmt through both external optimization and intrinsic modification, by considering the effect of mmt concentration, SDS compounding, stirring rate, comparison with illite, and acid-leached modification. Results indicate that (i) mmt suspensions promote both the CO 2 hydrate nucleation and growth, particularly with low concentration, while the enhancement of mass transfer is crucial for the high concentration-mmt system. (ii) Subsequently, the addition of SDS (≥ 1000 ppm) can form micelles to enrich aqueous CO 2 locally, and the application of stirring (600 rpm) disrupted hydrate films to enable continuous CO 2 supply, which has both proved effective to promote CO 2 capture. (iii) The non-expandable illite performed worse than mmt, highlighting the expandable layers and high specific surface area for enhancing hydrate kinetics. This is further verified by acid leaching modification of mmt (m-mmt) that transforms its structure into a highly porous amorphous network. Notably, 1 wt% m-mmt achieved a CO 2 capture capacity of 93.9 mmol/mol, representing an 83.9% improvement over pristine mmt. These findings demonstrate the promising promotion effect of mmt for CO 2 hydrate, offering new insights for advancing cost-effective hydrate-based CO 2 capture. Graphical Abstract