Synthesis of exopolysaccharide-based organo-montmorillonite with improved affinity towards carbon dioxide and hydrophilic character

Abstract

Grafting of a bio-sourced exopolysaccharide (EPS) using a disulfide ethyl moiety with two ammonium ends as interface on Na$^{+}$-exchanged montmorillonite (NaMt) turned out to be a “green” route to produce an OH-enriched organoclay with improved affinity towards CO$_{2}$ and moisture. Characterization through X-ray diffraction, infrared spectroscopy and thermogravimetric analysis revealed an organized structure with an increased basal spacing that facilitates the diffusion of CO$_{2}$ and water molecules and thermal stability up to 190 °C. Measurements through thermal programmed desorption (TPD) showed that at least 16 CO$_{2}$ molecules are adsorbed per OH group incorporated via HO:CO$_{2}$ interactions between CO$_{2}$ molecules and both EPS, and adsorbed water molecules. Adsorbed CO$_{2}$ can be completely released below 190 °C. This opens promising prospects for designing respiratory devices that support vegetal-derived moieties that can capture non-stoichiometric amounts of CO$_{2}$ in CO$_{2}$-rich gas mixtures and enclosures with non-thermal regeneration.

Keywords

• Montmorillonite
• Exopolyssacharide
• Chemical grafting
• CO$_{2}$ capture
• Surface basicity
• Thermal programmed desorption