Insight into the Adsorption Process of Ethanol and Water on the Pore Structure and Surface Chemistry Properties Engineered Activated Carbon Fibers

Modified activated carbon fibers (ACFs) with a large specific surface area, a relatively large pore network, and abundance of chemical functional groups were prepared by using the steam secondary activation method and tested for ethanol and water adsorption. A micro-mesopore hierarchical porous structure was successfully established on ACF-850. Also, the surface polarity and hydrophilicity were significantly improved. As a result, ACF-850 presented the highest static adsorption capacity (12.59 mmol/g), the lowest activation energy, and the lowest isosteric heats during the adsorption process of ethanol. Furthermore, the dynamic adsorption/desorption performances of ethanol on ACF-850 were carried out under both dry and humid conditions. The results showed that water has a positive effect on the adsorption of ethanol due to the capillary condensation, which can act as a new adsorption site for ethanol adsorption. The highest adsorbed amount of 1.579 mmol/g under a relative humidity of 30% can be attained, which is 1.43 times higher than that under dry conditions. More importantly, ACF-850 possessed excellent regeneration ability, and a 94% adsorption efficiency can be recovered only by purging of nitrogen at room temperature. Thus, ACF-850 would be a promising ethanol adsorbent and can be applied to control ethanol under both wet and dry conditions.