Oxidation of activated carbon fibers: Effect on pore size, surface chemistry, and adsorption properties

Activated carbon fibers (ACFs) were oxidized using both aqueous and nonaque ous treatments. As much as 29 wt % oxygen can be incorporated onto the pore surface in the form of phenolic hydroxyl, quinone, and carboxylic acid gro ups. The effect of oxidation on the pore size, pore volume, and the pore su rface chemistry was thoroughly examined, The average micropore size is typi cally affected very little by aqueous oxidation while the micropore volume and surface area decreases with such a treatment. In contrast, the micropor e size and micropore volume both increase with oxidation in air. Oxidation of the fibers produces surface chemistries in the pore that provide for enh anced adsorption of basic (ammonia) and polar (acetone) molecules at ambien t and nonambient temperatures. The adsorption capacity of the oxidized fibe rs for acetone is modestly better than the untreated ACFs while the adsorpt ion capacity for ammonia can increase up to 30 times compared to untreated ACFs, The pore surface chemical makeup was analyzed using elemental analysi s, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), an d X-ray photoelectron spectroscopy (XPS).