Carbon dioxide adsorption behaviors of aluminum-pillared montmorillonite-supported alkaline earth metals

The Al-pillared montmorillonite-supported alkaline earth metal 5M/Al-PILC (PILC = pillared clay, M = Mg, Ca, Sr, and Ba) and xMg/Al-PILC (x = 1, 3, 5, and 7 wt.%) samples were prepared using an impregnation method. Physical properties of the materials were determined by means of X-ray diffraction (XRD) and N₂ adsorption-desorption, and their CO₂ adsorption behaviors were investigated using the thermogravimetric analyzer (TG), CO₂ temperature-programmed desorption (CO₂-TPD), and in situ diffuse reflectance infrared transform spectroscopy (in situ-DRIFTS) techniques. It is shown that 5Mg/Al-PILC possessed the highest CO₂ adsorption capacity (2.559 mmol/g). The characterization results indicate that Al-pillaring increased the specific surface area of montmorillonite, which was beneficial for the adsorption of CO₂. The CO₂ adsorption process on the sample was mainly chemical adsorption, and alkalinity was the main factor influencing its adsorption capacity. The alkalinity of the sample was enhanced by loading an appropriate amount of alkaline earth metal, and the adsorbed CO₂ was present in the form of bicarbonate and carbonate. In addition, the 5Mg/Al-PILC sample exhibited an excellent regeneration efficiency. We believe that the outcome of this research would provide a good option for developing highly effective CO₂ adsorption materials.