The adsorption isotherms of benzoic acid and benzaldehyde from aqueous solution onto the silanized active carbon have been measured at 25℃ and 35℃. The changes of standard free energy ΔGⅲ, enthalpy ΔHⅲ and entropy ΔSⅲ in adsorption processes have been calculated from the Langmuir parameter. The experimental data have been treated with Hillde Boer equation. The results show that, (1)with the lapse of the silanized time, the adsorption amounts (mol.m^-^2) of benzoic acid and benzaldehyde increase greatly; -ΔGⅲ, -ΔHⅲ increase slightly, and ΔSⅲ shows to be positive. (2)the interaction between adsorbed molecules is weak, and the interaction between adsorbed molecule and the surface of the active carbon increase with silanization. (3)the benzene ring of the benzoid compounds is adsorbed on the surface of the active carbon.

Key words: ACTIVE CARBON, SILANIZATION, ADSORPTION, THERMODYNAMICS, BENZALDEHYDE, BENZENECARBOXYLIC ACID, ADSORPTION PROCESS