Studies on the structure of activated carbon fibers activated by phosphoric acid

By solid-state C-13- and P-31-NMR, XPS, and FTIR, the chemical structure of activated carbon fiber-P (ACF-P) and its reaction with phosphoric acid were studied. Even when activated at low temperatures, these fibers developed a graphitelike carbon structure with a certain amount of phenol groups as well as acetal (or methylenedioxy) carbon. As expected, the oxygen-containing groups were greatly reduced at high activation temperatures. Different from the ACF-W, metaphosphoric acid (or polyphosphates) and a small amount of phosphorus exist on ACF-P. The original ACF-P activated at low temperature contained a lot of phosphoric acid, so it had to be washed with water to expose the large surface area. The washing process can be omitted for ACF-P activated at high temperature because most phosphorus compounds in fiber have volatilized. The ACF-P activated at lower temperature possessed a large amount of oxygen-containing surface groups and had enhanced adsorption ability for polar adsorbates. The remaining of metaphosphoric acid enhanced the adsorption of silver ion. The experimental results showed that the peaks of P-31-NMR, P-2p-XPS, and FTIR at 1620 cm(-1) shifted with the increase of activated temperature. (C) 2003 Wiley Periodicals, Inc.