CONFORMATIONAL DYNAMICS OF 1,2-DICHLOROETHANE ON ILLITE DURING SORPTION AND DESORPTION

In situ diffuse reflectance infrared spectroscopy is used in this study to gain insight into the molecular level mechanisms by which 1,2-dichloroethane (DCA) is retained on the surfaces of an illite specimen clay. The results support the conclusions presented earlier for 1,2-dibromoethane in which sorption is described as a process of condensation to form a liquid enriched in the gauche conformer due to the presence of a dielectric field. In addition, spectral evidence suggest the presence of a “sorbed” vapor phase, different in composition to unassociated vapor phase chemical, that desorbs more rapidly than the liquid. The behavior of DCA on clay surfaces is consistent with accepted concepts used to explain characteristic isotherm behavior observed for the sorption of vapor phase chemicals on porous media. This in turn supports the importance of sorbent porosity in the retention process. © 1993 by Academic Press, Inc.