Effect of ageing on the oxygen surface complexes of an oxidized activated carbon

An activated carbon prepared by CO2 activation from a demineralized Spanish lignite char was oxidized by treatment with H2O2. This oxidized activated carbon was heat treated in an He flow at different temperatures up to 1273 K, and the samples so obtained were exposed to ambient air for two years. The oxygen surface complexes of these aged samples were analysed by temperature-programmed desorption and titrations with bases of different strength and with HCl. Results were compared with those obtained from fresh samples (i.e. samples prepared just before carrying out the temperature-programmed desorption). Results indicate that there is a memory effect which tends, by ageing, to restore the situation of the original oxidized activated carbon.