ABSTRACT
Surface modification of mineral substances with adsorbed organic layers is widely used in various industrial processes, ranging from the polymer industry, where it facilitates filler incorporation in polymer composites [1], to ore flotation, where it permits selectivity between the ore and the matrix [2]. New promising applications, such as thin coating for sensors or optical devices, have also been reviewed recently by Swalen etai. [3]. The surface properties induced by adsorbed organic layers are usually investigated on flat surfaces with contact angle or surface force measurements. However, in the case of powders, these methods are inappropriate. Wettability of finely divided solids is then assessed by contact angle measurements on pellets, or by the capillary rise technique [4, 5]. In this paper, we develop
an alternative approach based on the exploitation of high-resolution adsorption isotherms. This technique, primarily applicable to high surface area powders, is illustrated by using a calcium carbonate sample coated with increasing amounts of water-repellent molecules. By combining various experimental techniques, results obtained at the solid-liquid interface, wetting index and immersion enthalpy, are related to those derived from an analysis of nitrogen, argon, and water vapor adsorption at the solid-gas interface.
