ADSORPTION FROM SOLUTIONS IX. THERMODYNAMICS OF ADSORPTION OF BENZENE, NAPHTHALENE, ANTHRACENE AND PHENANTHRENE AT THE SILICACYCLOHEXANE INTERFACE

Adsorption isotherms for benzene, naphthalene, anthracene and phenanthrene on silica surface from oyclohexane have been measured at 10, 20 and 30℃. The order of adsorption is phenanthrene≥anthracenenaphthalenebenzene. The ratio of adsorbed amount of benzene, naphthalene, anthracene (or phenanthrene) is approximately 1:2:3 at low concentration. By using the model of exchange equilibrium between bulk and surface phase, the calculation shows that standard surface free energe change △G° for benzene, naphthalene, anthraoene and phenanthrene is approximately constant. This result suggests a flat-wise orientation of the adsorbed aromatic compounds on silica surface.