A microcalorimetric study of the interaction between water and poly(hexamethylene guanidine)-modified kaolinite surface

The isotherms and differential heats of water vapor adsorption on kaolinite modified with poly(hexamethylene guanidine) hydrochloride are measured. Modification efficiency is, to a high extent, determined by the compliance (complementarity) between the structure of the modifying agent and the chemical nature of the kaolinite surface. It is shown that the individual stages of the interaction between water and the modified sorbent comprise sorption of four or five molecules on triads of amino groups of the modifying layer, conformational changes in the layer, the formation of additional adsorption sites, partial rupture of the modifying layer, and the dispersion of kaolinite particles induced by adsorbed water. Alternative opinions are presented on the reason for the appearance of the additional adsorption sites. It is proven that not only the adsorbate, but also the adsorbent, undergoes efficient changes during the adsorption.