Experimental Study On Benzene Adsorption By Activated Carbon Fibers At Low Concentrations

Volatile organic compounds comprise the majority of indoor air pollution and the hazardous air pollutants emitted by industrial sources. Study on the treatment of organic gas pollution has become one of the hotspots in the field of heat and mass transfer and the field of indoor environment. The emission of waste gas containing benzene is very common, and it has great damages to environment and human health. Activated carbon adsorption is mostly adopted for the treatment of benzene. And activated carbon fiber (ACF), a new activated carbon material, is getting more and more applications in waste gas treatment due to its high efficiency adsorption and desorption properties. The use of activated carbon fiber adsorbent is a cyclic regeneration process, but the existing researches have paid much more attention on the adsorption of organic gas, whereas little research was done on desorption regeneration. Therefore, an exploratory study on desorption and cyclic adsorption/desorption were investigated in this paper. Meanwhile, the properties of activated carbon fiber and benzene adsorption were also studied carefully.The properties of the activated carbon fiber samples were analyzed by nitrogen adsorption method at 77K (ASAP2010). The nitrogen adsorption isotherms of ACF samples exhibited a type I isotherm, which is indicative of microporous materials. The surface areas of ACF samples can be measured using the Langmuir equation and the BET equation. The external surfaces area and micropore volumes were obtained by t-plot. Also the pore distributions of ACF samples were determined by H-K method, and the fractal dimensions were also calculated in this paper. The results show that micropore volumes increase with the increase of surface area, but the ACF sample with the smallest surface area had the highest fractal dimension, and the fractal dimension was consistent with pore distribution.In this paper, experiments were done on the self-built experimental platform. The benzene adsorption, desorption and cyclic adsorption/desorption were measured thermogravimetrically using a TGA/SDTA851~e. The Langmuir, Freundlich and DR equations were used to model the experimental adsorption data. The results show that the Freundlich and DR equations are in good agreement with the experimental data, and the DR equation is more suitable for the modeling of low concentration organic gas. For the desorption regeneration experiment, it can be concluded from the comparison of weight loss curves that the process of desorption can be divided into three sections: therapid phase (within 20 minutes), the slow phase (from 20 to 100 minutes) and theequilibrium phase (after 100 minutes). The cyclic adsorption/desorption experimentresults reveal that adsorption rate has a decreasing tendency and the residual rate istended to be stable.