Surface energetics of calcium carbonates using inverse gas chromatography

Various calcium carbonate samples were characterized by inverse gas chromatography (IGC) at infinite dilution. The interactions between the samples and hydrocarbon probes, C5–C10 were related to the retention volume in gas chromatographic experiments. The surface energetics of chalk, marble and precipitated calcium carbonate (PCC) were determined in terms of the apolar component of the surface free energy γSLW and the differential enthalpy of adsorption, −ΔHA∘. These results were evaluated with respect to bulk chemical composition, BET surface area and pore structure. The results suggest that physi- and chemisorbed water bound at surface sites and within the pore structure significantly influence the surface properties of the calcium carbonates. The values of γSLW and −△HA∘ after redeposition of the water adlayer suggested reversibility of the water sorption process and the resulting changes in the energetics of the surfaces. Values of γSLW for the chalk samples in the initial state were 140–180 mJ m−2, whereas the marble and PCC were ≈55mJ m−2. Removal of bound and pore water by heating at elevated temperatures caused a progressive increase in the γSLW to ≈250 mJ m−2 for the PCC sample. The γSLW of the chalk sample also increased but to a much lesser extent. △HA∘ values for the samples followed the trend chalk>marble>PCC.