Solid–aqueous solution interface phenomena at the molecular level

There are plenty of experimental observations showing that the macroscopic phenomena are governed by interactions at molecular and atomic levels and are related to the nature and structure of the first produced layer. The understanding of the mechanisms of interaction of the first molecules with solid surfaces is, therefore, the fundamental requirement for making possible the prediction, control and modification of the macroscopic phenomena taking place in nature and for designing efficient technologies. For this purpose, we have developed an infrared external reflection technique, supported by computer modelling, that has a very unique ability to study interface phenomena at a molecular level for heterogeneous substrates. The variety, precision and reliability of information about interface phenomena delivered by this technique are superior to other single techniques. The experiments are fast and non-destructive. High sensitivity (starting from 20% of monolayer), in situ collected information in a multiphase system even in the region of a strong absorption of substrate makes this technique a very valuable experimental tool. The complexity of recorded reflection spectra, their sensitivity to any variations of the optical properties of all investigated phases in the system and their spatial distribution, are in fact the major strength of the technique. In this paper, the most interesting examples of application of the technique for monitoring and understanding surface modifications of sulphide and semi-soluble minerals in aqueous solutions by adsorption of surfactants will be discussed in detail. The developed techniques have been exploited intensively for the description of natural geochemical phenomena and a few industrial applications. To cite this article: E. Mielczarski, J.A. Mielczarski, C. R. Geoscience 334 (2002) 703–715.