Gas-particle two-phase adsorption of toluene and ultrafine particles on activated carbon studied by molecular simulation.

Adsorption is regarded as the most reliable technology for gaseous pollutant removal. Activated carbon is a widely used adsorbent due to its good adsorption capacity and low price. However, substantial ultrafine particles (UFPs) in the air cannot be effectively removed even if a high-efficiency particulate air filter is located before the adsorption stage. The adhesion of UFPs to the porous surface of activated carbon affects the removal of gaseous pollutants and shortens its service life. So, we adopted molecular simulation to explore the gas-particle two-phase adsorption and analyze the effects of the properties of UFPs such as concentration, shape, size and chemical composition on the toluene adsorption. The parameters of equilibrium capacity, diffusion coefficient, adsorption site, radial distribution function, adsorption heat and energy distribution were used to evaluate the gas adsorption performance. The results showed that the equilibrium capacity of toluene was decreased by 16.51 % compared to that of only toluene adsorption at the toluene concentration of 1 ppb and UFPs concentration of 1.81 × 10-5/cm3. Compared with cubic and cylindrical particles, the particles in spheres were more likely to hinder the pore channels from reducing gas capacity. Larger UFPs in the selected particle size range (1-3 nm) had a greater impact. Carbon black UFPs themselves could adsorb toluene, so the amount of toluene adsorbed was not significantly decreased.