Roles of acid-base interactions in hydrogen chloride removal by activated carbon fibers

In this study, atmospheric pressure plasma (APP) treatments with N ₂, O₂, or CO₂ on activated carbon fibers (ACFs) were carried out to introduce hydrophilic functional groups onto the carbon surfaces in order to increase the hydrogen chloride (HCl) gas-removal-capacity of the ACF surfaces. The surface properties of these ACFs were determined using XPS and SEM techniques. The N₂/77 K adsorption isotherms were investigated using the BET and t-plot methods. The gas-removal-capacity on the ACFs was confirmed using a gas chromatography technique. All APP-treated ACFs showed a decrease in the specific surface area and total pore volume, but the HCl removal ability of the ACFs increased. The N₂-plasma-treated sample showed the highest gas-removal-capacity. This result indicates that N₂-plasma treatment led to the formation of basic functional groups on the carbon surfaces, resulting in the predominant increase in the interaction between the ACFs' functional groups and acidic HCl gas.