Assessing the Potential of Sepiolite-Palygorskite Group Minerals as Materials for CO2 Capture and Storage Applications

Abstract:

The carbonation of magnesium silicate minerals within ultramafic rocks is one of the most promising routes to CO₂ sequestration involving chemical reaction with natural materials. However, in practice the rate of magnesium silicate carbonation is very slow at ambient temperature. Although using smaller magnesium silicate grains with greater reactive surface area can enhance reaction rates, the coherency of ultramafic rock makes crushing the material an energy-consuming task in its own right. Instead of relying on a mineral forming reaction to capture carbon, it has been hypothesized that naturally occuring nanoporous materials may be used to capture and store carbon dioxide. Sepiolite-palygorskite clays are of interest because in addition to being common minerals in marine and lacustrine sediments, they are natural weathering products of ultramafic rocks, and are already used extensively in industrial scale applications. Due to the presence of nanoscopic channel structures in sepiolite-palygorskite clays these materials exhibit extremely high surface areas. However, in the native structure the channels are filled with water. In order for these minerals to act as efficient CO₂ storage materials channel water must be displaced and replaced with CO₂. Herein we present preliminary findings using molecular dynamics simulations to quantify the thermodynamic driving force for displacing channel bound water with CO₂ and assess the feasibility of sepiolite-palygorskite clays to act as CO₂ storage materials.