Correlation between the hydrophilic character and affinity towards carbon dioxide of montmorillonite-supported polyalcohols

Polyalcohol incorporation was found to enhance the hydrophilic character of montmorillonite and its affinity towards carbon dioxide. CO2 adsorption occurred in both dry and humid conditions, but higher amounts were retained in the presence of moisture. This suggests two adsorption pathways: 1. direct OH-CO2 interaction and 2. more predominantly via indirect ternary OH-H2O-CO2 interactions. The retained amounts of water and CO2 increased almost proportionally with the number of OH groups incorporated, thus providing clear evidence that these groups act as adsorption sites. The improvement of the CO2 retention capacity (CRC) appears to be also due to the enhancement of the hydrophilic character of the adsorbent. The CRC value was found to strongly depend on the operating conditions. The major part of the retained CO2 was desorbed at 60-70°C from hydrated matrices, but at 20-50°C from dry adsorbents. CO2 can be easily released even at room temperature through forced convection under a gas stream, or under static conditions in dry and CO2-free media, e.g. in the presence of KOH pellets. It results that the CO2 retention also involves physical interactions. These results open new prospects for the reversible capture of other gases on low-cost hybrid adsorbents without thermal regeneration.