Desorption Characteristics of Aromatic Compounds in Aqueous Solution on Solid Adsorbents

Abstract

Adsorption and desorption equilibria of 11 kinds of aromatic compounds were measured in their aqueous solution on an activated carbon and synthetic adsorbents. In the adsorption of aromatic compounds substituted by electron-donating groups in aqueous solution, the hysteresis between adsorption and desorption, which suggested the appearance of irreversible adsorption, was observed on activated carbon. Desorption isotherms coincided with adsorption isotherms on synthetic adsorbents. The electronic state of adsorbents and adsorbates was determined by the semiempirical molecular orbital calculation. It was found that irreversible adsorption appeared when the energy difference between HOMO of adsorbate and LUMO of adsorbent was small. An influence of acidic surface oxides of activated carbon was experimentally studied on the desorption characteristics of aromatic compounds. Although the amount adsorbed decreased by the wet oxidation of the carbon, the desorption characteristics were improved and the hysteresis disappeared. The results were supposed to be attributed to the change of the LUMO energy of carbon by wet oxidation.