Modification of the Surface Chemistry of Activated Carbons

The surface chemistry of two active carbons was modified using a microwave device as a heat source. When microwave treatments are conducted in a nitrogen flow, most oxygen-containing groups are removed from the surface of the carbons. This in turn gives rise to a significant increase in the pH of the carbons. Microwave treatment is less time-consuming than conventional heating. Only a few minutes are required to transform an acidic carbon into a basic carbon with a relatively low oxygen content. On the other hand, microwave-treated carbons undergo re-oxidation, to a greater or lesser extent, upon atmospheric exposure. It was observed that atmospheric re-oxidation of microwave-treated carbons tends to restore more acidic groups when the treatment is carried out on an acidic precursor than when the carbon is of a basic character. Nevertheless, carbons exposed to the atmosphere for up to 2 months still showed higher pHs than those of the corresponding precursors.