Adsorption Properties of Chalk: Contributions from Calcite and Clays

Water and ethanol vapour adsorption measurements were used to estimate the contribution from calcite and clay (kaolinite) on the adsorption behaviour of outcrop chalk. Both sets of measurements indicate that adsorption isotherms of chalk can be closely mimicked by a linear combination of clay and calcite adsorption isotherms. The values of the isosteric heat of adsorption for all investigated surfaces were determined in the temperature range 273 – 293 K. Pure calcite adsorbs water and ethanol vapour with energies typical of chemisorption, while chalk and kaolinite show adsorption energies more typical for physisorption and form multilayers of adsorbed water and ethanol on their surfaces.