Modeling of Benzene Adsorption in the Gas Phase on Single-Walled Carbon Nanotubes for Reducing Air Pollution

Air Pollution has always been a major problem in metropolises. Volatile organic compounds are one of the major pollutants that are caused by incomplete combustion of fuels in vehicles and gasoline evaporation, especially in fueling stations. Removing these pollutants through traditional methods has always been considered. The paper investigates and studies chemical adsorption behavior of benzene on single-walled carbon nanotubes (9, 9) and (7, 7) in the gas phase by the Gaussian 09 program and using quantum chemical calculations and density functional theory method (DFT). First, carbon nanotubes were generated by a nanotube modeler, and then benzene was passed through the inside and outside of the nanotubes. After that, the absorption energies were calculated using the B3LYP calculation method and 6-31G basic set at different time intervals. Next, the amount of structure energy for carbon nanotube and benzene was separately calculated by the Gaussian 09 program. Using the existing equations, the absorption energy at different time intervals was obtained as follows: For 0.5, 1, 1.5, and 2 angstrom outside the nanotube (7, 7), 14.25, 11.22, 3.32, and 0.78 electron volts (eV); for the nanotube (9, 9), -776.34, -807.12, -817.16, and -844.62 electron volts (eV); for the inside of the nanotube (7, 7), 14.66, 7.76, 7.30, and 7.27 electron volts (eV); and for the nanotube (9, 9), -813.69, -813.97, -816.68, and -819.33 electron volts (eV), respectively. As the results show, when the diameter of the nanotube increases, the energy absorption decreases. Therefore, the carbon nanotube (7, 7), which has a smaller diameter than the carbon nanotube (9, 9), will be more effective in absorbing and removing benzene from the air.