The contribution of oxygen-containing functional groups to the gas-phase adsorption of volatile organic compounds with different polarities onto lignin-derived activated carbon fibers

Abstract

Lignin-based activated carbon fibers (LCFK) were prepared by electrospinning method and evaluated in adsorption of volatile organic compounds (VOCs). Batch adsorption experiments for various component were carried out in a fixed-bed reactor. The molecular polarity of VOCs plays a pivotal role in the monocomponent dynamic adsorption. As a result, the adsorption capacity of toluene was larger than that of methanol or acetone. In the various multicomponent atmospheres (without water), the components interact with each other and competitive adsorption phenomenon occurs, resulting in the adsorption capacity of each component decreased significantly. Also, the samples before and after adsorption were characterized via Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), and Boehm titration. The results reveal that methanol and acetone, controlled by physical adsorption, prefer to be adsorbed on polar groups on the surface of LCFK through the dipole–dipole interactions (i.e., van der Waals' forces). Differently, the adsorption of toluene onto LCFK was controlled by physical and chemical processes, and the lactone groups have a positive contribution to the adsorption of toluene. It was also observed that water vapor can enhance the negative effect on the adsorption of VOCs, especially for toluene. The results from this study will be valuable for explaining the mechanisms of competitive adsorption among each component in the various multicomponent atmospheres and understanding the contribution of chemical functional groups on the surface of LCFK in the adsorption process.

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