Characterization of microstructure and surface properties of heat-treated PAN-and rayon-based activated carbon fibers

Polyacrylonitrile- and rayon-based activated carbon fibers (ACFs), subject to heat treatment over 600–1,100°C under N₂ flow, were investigated using a number of surface analytical methods, including N₂ adsorption isotherm, elemental analysis, and X-ray photoelectron spectroscopy. The adsorption capacities of benzene, carbon tetrachloride, and water vapor on as-received and heat-treated ACFs were determined. Results show that the ACFs under study were highly microporous but heat-treated ACFs contained more mesopores in the range of 20–30 Å for PAN-based and 30–45 Å for rayon-based. It can be seen that the high-resolution α_s plot provided valuable information about structure properties. The pore size distributions of ACFs gave insight into the pore development with heat treatment temperature. Besides, phenolic groups were found to be the most abundant oxygen-containing functional groups on the surface of both ACFs. The vapor adsorptions on ACFs indicated that molecular size and polarity of vapors, as well as the microstructure and chemistry of ACFs profoundly influenced the adsorption performance.