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 investigated. Adsorption experiments at controlled solution pH conditions confirmed that both electrostatic and dispersive adsorbate/adsorbent interactions can have a significant influence on the equilibrium uptakes of ionic and nonionic adsorbate species. For aniline (a weak electrolyte), maximum uptakes were found on oxidized carbon surfaces at solution pH near the adsorbate's point of zero charge (pH(PZC)). In contrast, nondissociating nitrobenzene uptakes were enhanced on heat-treated surfaces with graphene layers unperturbed by electron-withdrawing Functional groups, particularly at solution pH similar to pH(PZC). A theoretical model that can successfully account for the observed trends is hereby proposed as a much needed predictor of the experimental conditions and adsorbent surface chemical properties that will maximize the uptake of aromatic compounds by activated carbons. (C) 1997 Elsevier Science Ltd.