Acta Phys. -Chim. Sin. ›› 2005, Vol. 21 ›› Issue (11): 1211-1216.doi: 10.3866/PKU.WHXB20051104

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A Model of Stoichiometric Displacement for the Adsorption of Benzoic Acid and Benzene by Silica Gel from Cyclohexane Solution

CHEN Yu-yin; LIU Fan; LIU Yong-chun   

  1. Department of Environment and Life Science, Leshan Teachers College, Leshan, Sichuan 614004
  • Received:2005-03-04 Revised:2005-05-09 Published:2005-11-15
  • Contact: CHEN Yu-yin

Abstract: Adsorption of benzoic acid and benzene from cyclohexane solution by silica gel was studied under 293~313 K. It was indicated that adsorption of benzoic acid by silica gel well fit the stoichiometric displacement mode for adsorption (SDM-A). But for benzene, when treated with SDM-A there was a turning point in its adsorption isotherm, which corresponding to the dividing point between monomolecular and multimolecular layer adsorption. Thermodynamics formulae of adsorption were also set up based on SDM-A. It was demonstrated that benzoic acid was spontaneously adsorbed by silica gel accompanied with an entropy increase process, but for benzene it was accompanied with an entropy decrease process. The free energy change for adsorption of benzoic acid was larger than that of benzene and the adsorption enthalpy change was reversed because of the stronger affinity to silica gel and the stronger solvophobic ability for benzoic acid than that for benzene.

Key words: Silica gel, Adsorption, Benzoic acid, Benzene, Cyclohexane solution, SDM-A, Adsorption thermodynamics