Carbon dioxide intercalation in Na-fluorohectorite clay at near-ambient conditions

A molecular dynamics study by Cygan et al.[1] shows the possibility of intercalation and retention of CO$_{2}$ in smectite clays at 37 $^{o}$C and 200 bar, which suggests that clay minerals may prove suitable for carbon capture and carbon dioxide sequestration. In this work we show from x-ray diffraction measurements that gaseous CO$_{2}$ intercalates into the interlayer space of the synthetic smectite clay Na-fluorohectorite. The mean interlayer distance of the clay when CO$_{2}$ is intercalated is 12.5 {\AA} at {\-}20 \r{ }C and 15 bar. The magnitude of the expansion of the interlayer upon intercalation is indistinguishable from that of the dehydrated-monohydrated intercalation of H$_{2}$O, but this possibility is ruled out by careful repeating the measurements exposing the clay to nitrogen gas. The dynamics of the CO$_{2}$ intercalation process displays a higher intercalation rate at increased pressure, and the rate is several orders of magnitude slower than that of water or vapor at ambient pressure and temperature.\\[4pt] [1] Cygan, R. T.; Romanov, V. N.; Myshakin, E. M. \textit{Natural materials for carbon capture}; Techincal report SAND2010-7217; Sandia National Laboratories: Albuquerque, New Mexico, November, 2010.