REVERSE HEMIMICELLE FORMATION OF 1-DECANOL FROM HEPTANE AT THE SOLUTION GRAPHITE INTERFACE

Based on a two-step adsorption mode (i.e., in the first step the amphiphiles are adsorbed through van der Waals attraction between the amphiphiles and the solid, e.g., carbon black; then, in the second step, the so called reverse hemimicelles form through hydrogen bonding and/or other polar interactions between the adsorbed amphiphiles) and the mass-action law, an isotherm equation is derived for adsorption of amphiphiles on solids from nonpolar solvents. The result has been quantitatively supported by the adsorption data of 1 -decanol from heptane at the solution/graphite interface reported by Findenegg et al. The average aggregation number of the reverse hemimicelles, evaluated from the general adsorption isotherm equation, is in the range of 3-6, in the temperature range of 15-35°C, and decreases with increasing temperature. The calculation of the thermodynamics of surface aggregation shows that both the values of ΔHrhmo and ΔSrhmo of the reverse hemimicelle formation are negative. The reverse hemimicelle concentrations (r.h.m.c.) have also been reported. © 1990.