Adsorption from Solution

Abstract

This chapter describes single decanol molecules from heptane at the solution/graphite interface. It describes the study of adsorption of higher n-alkanols from n-heptane onto graphitized carbon black by measuring the surface excess amount and enthalpy of displacement over a range of concentrations and a range of temperatures. Isotherms of the specific surface excess amount n2(n) of the system(heptane+ decanol)/g.c.b. at five experimental temperatures were analyzed on the basis of a monolayer model by assuming that the adsorbed layer is confined to a single layer of molecules oriented parallel to the solid surface. The sharp increase of the surface concentration of decanol within a narrow concentration range exhibited by the isotherms up to about 25°C suggests a phase change in the adsorbed layer. At sufficiently low temperatures, the step of the isotherm occurs at very low bulk concentration of solute. Adsorption of single decanol molecules from heptane onto graphite is energetically not favorable. The preferential adsorption of the alkanol in these systems is largely due to the strong solute–solute attractive interactions in the adsorbed monolayer.