Surface energies of some smectite clay minerals

Résumé En

The surface free energy of a clay mineral, in common with all solids, is determined (apart from their electrostatic surface potential) by two components : 1) the Lifshitz-van der Waals component, y LU, and 2) the polar or the electron donor /electron acceptor (in the Lewis acid/base concept) component, yAB. The non-additive parameters of the AB energy component are the electron donor parameter, у and the electron acceptor parameter, y * These surface tension components have been determined, using the extended form of Young's equation, for several common smectite minerals by measuring contact angles made by a group of polar and non-polar liquids of blown surface tension components. The minerals have been prepared either as self supporting alms or as films deposited on smooth glass plates. The minerals examined include hectorite (green and pink varieties), Bentolite-L, Polar Gel, Panther Creek montmorillonite, Wyoming montmorillonite, Gonzales montmorillonite, and Volclay. As would be expected from their chemistry and structure, these minerals are nearly monopolar electron donors with y evarying between approximately 15 and 45 mJ/m2 and varying between 0 and 3 mJ/m2. The similarity in structure among the minerals studied also suggests that the LW component would be relatively constant for the group of minerals and the y lw values were found to vary between 44 and 50 mJ /m2. The observed components indicate that the adsorption properties of these clays for organic materials will vary.