In situ infrared study of the surface oxidation of activated carbon in oxygen and carbon dioxide

Abstract

The surface oxidation of a wood-based activated carbon by heat treatment in oxygen and carbon dioxide has been studied by diffuse reflectance Fourier transform infrared spectroscopy and compared with the results of aqueous oxidation by hydrogen peroxide and nitric acid. Untreated carbon gave infrared bands due to CO, C—O and aromatic species. Gaseous oxidation generated cyclic acid anhydride groups, CO groups associated with polynuclear aromatic systems and several types of C—O species. The formation of C—O species was independent of whether oxygen or carbon dioxide was used as oxidant but CO species were less readily formed in carbon dioxide than in oxygen. Aqueous oxidation followed by drying at 393 K gave similar surface groupings to those resulting from the gas-phase treatments.