The adsorption of benzene vapor, as a volatile organic component, from inert gas (N2) by activated carbon was studied experimentally in the isothermal fixed bed reactor at various operating conditions. The activated carbon used in this study had pistachio shell base with high surface area. To improve the adsorption capacity of VOC vapor, the activated carbon was chemically treated with H2SO4, HNO3, NaOH, and NH3 solutions. The saturated adsorption capacities of benzene on initial activated carbon and treated samples were measured and compared. The results showed that the activated carbon treated with nitric acid had higher adsorption capacity than others samples, 640 mg/g. In addition, a mathematical model for adsorption in a fixed bed reactor was proposed in this study. The model results had good agreement with experimental data. In order to demonstrate the effects of operating conditions on adsorption and breakthrough curve, the experimental tests and simulation runs were carried out at various gas flow rate, temperature, and benzene concentration. The results showed that with increase VOC concentration from 700 to 1000 ppm, the total time of adsorption was decreased from 25 to 21 h and breakthrough point appeared earlier.