Clay- and olivine-based strategies for CO2 mitigation

Capturing CO2 from the air and storing it or converting it into useful products is arguably the biggest challenges of mankind for the decades to come. In this work, we present two approaches based on the interaction of CO2 with two earth-abundant minerals. In the first approach, we investigate the sorption of CO2 onto and into nanoparticles of montmorillonite clay. We show that the sorption capacity of the clay can be tuned by exchanging the cations in the interlayer space between the aluminosilicate layers of the clay. For the optimum cations (Cs+), almost 1.5mmol CO2/g clay can be sorbed. The capacity is largely controlled by the minimum interlayer spacing required to fit a cation along with competition with other contaminants such as H2O. Kinetic studies show that CO2 sorption into clays is highly reversible. To achieve permanent CO2 storage, we explored the fixation using olivine. While 1t of olivine has the potential fix approximately 1t of CO2, the conversion of olivine to MgCO3 and SiO2 is kinetically severely hindered by the formation of passivation layers. We developed strategies to monitor the dissolution of olivine and to follow in situ the formation of passivation layers using confocal Raman microscopy.