Carbon Dioxide Intercalation in Sodium Fluorohectorite Clay

Abstract

Wide angle X-ray Scattering (WAXS) measurements of the layered synthetic silicatesodium fluorohectorite (NaFh) when exposed to pressurized carbon dioxideare reported. With a custom made sample holder placed on top of a coolingsystem, measurements of the NaFh were taken at diferent conditions for temperatureand pressure. The interlamellar spacing of the clay particles is observedto expand approximately 2:4Å in the 001-direction when the sample is held at -20 degrees Celsius and exposed to 15 bar of CO2 for over 9 days, indicating the intercalation of CO2. The d-spacing after intercalation is indistinguishable from the d-spacing of NaFh in the 1WL hydration state. The rate of intercalation process is reported to be dependent on the temperature and the pressure of CO2, with the decreaseof temperature and the increase of pressure beeing favorable for intercalatingCO2. Through various measurements the possibillity of water as the observedintercalated guest substance has been ruled out. Molecular models based onthe swelling free energy are proposed to explain some of the features observedin the experiment.