Commercial activated carbons were impregnated with 1 mol·-1 nitric acid

1 mol·-1 hydrochloric acid

and 1 mol·-1 sulphuric acid separately

denoted as AC-N

AC-1

and AC-S

respectively.Specific surface area and pore distribution analyzer

Boehm titration and Fourier transformed infrared spectroscopy (FTIR) were used to measure the physicochemical properties of the activated carbons.Fixed-bed adsorption experiments were conducted at 283 K using toluene and methanol as adsorbates.The study shows that the acid modification can remove surface basic groups and increase the amount of surface acidic oxygen-containing groups.The relationship of the adsorption capacity of acid modification activated carbons and the specific surface area

total pore volume

micropore volume

amount of total surface acidic groups is linear.The Langmuir equation describes the adsorption of toluene and methanol onto activated carbons better than the Freundlich equation.The adsorption of methanol on activated carbons is physical adsorption.The adsorption of toluene on activated carbons is dominated by physical adsorption

but the chemical bond with surface functional groups can increase the adsorption capacity of toluene.The order of micropore diffusion coefficients of toluene and methanol on activated carbons is:AC-N>AC-1>AC-S>AC-C.The micropore diffusion coefficients of methanol are larger than that of toluene.