Surface chemistry of activated carbons: Combining the results of temperature-programmed desorption, boehm, and potentiometric titrations

Three samples of activated carbon were used for this study: two of wood and one of coal origin. The samples were further oxidized to study the effect of oxidation on the surface chemistry. The surface chemistry was characterized by using Boehm and potentiometric titrations, temperature-programmed desorption (TPD), and DRFTS. The results showed that oxidation introduces a variety of functional groups to the surface, making it more heterogeneous. Titration methods provide comparable results, whereas TPD detects more oxygen-containing groups. Discrepancies in the obtained results are due to limitations of the titration methods where only acidic and basic sites of certain strength can be detected. On the other hand, TPD can assess all functional groups but with less quantitative information. Moreover, comparison of TPD and titration methods leads to the detection of functional groups containing atoms other than oxygen and carbon as, for instance nitro groups, introduced to the carbon matrix via the nitration mechanism during oxidation with HNO3. (C) 2001 Academic Press.