Influence of Surface Oxides on Ethanol Regeneration of Spent Carbonaceous Adsorbents

Activated carbon (AC) and activated carbon fiber (ACF) that adsorbed aromatic compounds were regenerated by ethanol. The influence of their acidic surface oxides on ethanol regeneration was studied based on the frontier orbital theory. It is found that the regeneration efficiency can be correlated by the energy difference between HOMO of aromatic compounds and LUMO of adsorbents |EH - EL|. The regeneration efficiency is improved by oxidizing AC or ACF because the adsorptive interaction becomes weak as the energy difference |EH - EL| increases. The influence of the oxides on repeating ethanol regeneration of the carbons that adsorbed p-cresol was then experimentally elucidated. Although the regeneration efficiency of oxidized AC or ACF is kept higher than that of original AC or ACF even after the 16th regeneration, the oxidation has no practical use because the adsorption capacity is decreased by the oxidation. Copyright 1997 Academic Press. Copyright 1997Academic Press