Adsorption of pure vapours of ethanol and n-heptane and their liquid mixtures on activated carbon

Abstract

Physical characterization of the adsorbent has been made by means of the adsorption of nitrogen at 77 K and of pure ethanol and pure n-heptane at 298 K. Analysis of these isotherms by the B.E.T. method and the α_s-plot of the nitrogen isotherm reveals the existence of narrow pores of different width including ultramicropores in which the accessibility of ethanol and n-heptane is restricted.

The adsorption isotherm from the liquid mixture ethanol(1)–n-heptane(2) on activated carbon has been determined at 298 K. To analyse this isotherm the results obtained from the adsorption of the pure component vapours have been used. There is a lack of consistency with a monolayer model for the liquid/solid interface in which all segments of the chain molecules lie parallel to the surface. Assuming this orientation, an adsorbed phase of at least three layers must be considered. The monolayer model requires that the adsorbed molecules are perpendicular to the surface.