Effect of chemical surface heterogeneity on the adsorption mechanism of dissolved aromatics on activated carbon

The effects of oxygen-containing groups, particularly carboxylic and carbonyl groups, on the adsorption of dissolved aromatics on ash-free activated carbon have been studied. Adsorption isotherms for phenol, aniline, nitrobenzene, and benzoic acid were generated in both aqueous and cyclohexane media, using carbons with different amounts of surface oxygen groups. It was found that water adsorption, dispersive/repulsive interactions, and hydrogen-bonding were the main mechanisms by which surface oxygen groups influence the adsorption capacity, while donor-acceptor interactions were found not to be significant. The adsorption mechanism was also found to be influenced by the properties of the functional group on the aromatic adsorbate, especially its ability to hydrogen-bond and through its activating/deactivating influence on the aromatic ring. (C) 2000 Elsevier Science Ltd. All rights reserved.