AN EXPERIMENTAL AND THEORETICAL-STUDY OF THE ADSORPTION OF AROMATICS POSSESSING ELECTRON-WITHDRAWING AND ELECTRON-DONATING FUNCTIONAL-GROUPS BY CHEMICALLY-MODIFIED ACTIVATED CARBONS

The adsorption of model aromatic compounds (aniline and nitrobenzene) on chemically tailored activated carbons has been systematically inves tigated. Adsorption experiments at controlled solution pH conditions c onfirmed that both electrostatic and dispersive adsorbate/adsorbent in teractions can have a significant influence on the equilibrium uptakes of ionic and nonionic adsorbate species. For aniline (a weak electrol yte), maximum uptakes were found on oxidized carbon surfaces at soluti on pH near the adsorbate's point of zero charge (pH(PZC)). In contrast , nondissociating nitrobenzene uptakes were enhanced on heat-treated s urfaces with graphene layers unperturbed by electron-withdrawing Funct ional groups, particularly at solution pH similar to pH(PZC). A theore tical model that can successfully account for the observed trends is h ereby proposed as a much needed predictor of the experimental conditio ns and adsorbent surface chemical properties that will maximize the up take of aromatic compounds by activated carbons. (C) 1997 Elsevier Sci ence Ltd.