Molecular simulation to analyze the effect of ultrafine particles on indoor organic gaseous pollutants removal by activated carbon

Abstract

Activated carbons are usually used to control the gas phase pollutants in the indoor environment. Actually, there are substantial ultrafine particles (UFPs) in air that have an impact on the gas pollutants removal by activated carbons in the actual implementation. In this paper, the influence of UFPs on the adsorption performance of activated carbon was analyzed by molecular simulation. The nanoporous carbon model was developed to describe the activated carbon. The adsorption of low concentration toluene with/without NaCl UFPs in the activated carbon was simulated and evaluated from the perspectives of adsorption capacity, diffusion coefficient, adsorption site, radial distribution function, adsorption heat and energy distribution. The results showed that the toluene adsorption was decreased by 21~29% since the existence of NaCl UFPs blocked the pores to some extent and occupied a portion of adsorption sites of toluene. The morphology of toluene molecules adsorbed in the activated carbon was double-layer. The optimal adsorption sites were at a distance of 4.4 Å from the activated carbon skeleton. As the concentration of toluene was increased, the toluene molecules were adsorbed on the active sites that released more energy and gradually moved to the common sites that released less energy. The existence of NaCl UFPs neither affected the optimal adsorption distance of toluene in the activated carbon, nor the energy distribution and adsorption heat. This study revealed the mechanism of gas-solid coupling mass transfer in the porous materials and would help master the actual adsorption performance of adsorbent