Heterogeneity in solution adsorption: Edge carbon and oxide coverages: I. Methanol—benzene

Abstract

Adsorption from methanol—benzene system at 25° was investigated on two carbon black heterogeneity sequences. In one sequence the heterogeneity was edge carbons, the carbon atoms on the crystallite sheet edges, and in the other the heterogeneity was surface oxide groups. When edge carbons replaced basal carbon atoms adsorption changed from near total benzene preference to strong methanol preference. Covering the edge sites with oxide groups caused little change in adsorption preference except when significant amounts of surface CO 2 complexes were present. The methanol preference increased with CO 2 content and total preference is predicted for an all CO 2 monolayer. The changes in preference caused by each heterogeneity type indicate qualitatively the relative strength of interaction between a surface group and the various solution monomers and hydrogen bonded species. Simple monolayer-mass balance theory shows multilayer development in several cases although this theory failed when applied to monolayers. The results suggest that surface heterogeneity must be included as a major factor in the more involved solution adsorption theories.