Non-dispersive interactions at liquid/liquid and liquid/solid interfaces

Abstract

Non-dispersive interactions developed at liquid/liquid and liquid/solid interfaces are studied by determining directly (liquid/liquid interface) or indirectly, by contact angle measurements (liquid/solid interface), the variation of the interfacial free energy, γ ij , according to the Gibbs equation. For the liquid/liquid model, the interface between octane containing small quantities of long-chain aliphatic acids or amines and water is considered. The liquid/solid interfaces are constituted of the same organic solutions in contact with fused silica or with calcite, solids having respectively acid and basic properties. From the Dupre and Gibbs equations, the non-dispersive interaction energies between the acidic or basic organic molecules and water, silica, or calcite have been obtained. If the non-dispersive interaction energy is particularly important for the acid/base couples, it is far from being negligible for the acid/acid or base/base couples. This result can be explained by the existence of polar interactions, by the presence of adsorbed water on the solids, or by an amphoteric behavior of the acidic and basic organic molecules.