The effects of hydrophilic structures of active carbon on the adsorption of benzene and methanol vapors

Abstract

Two kinds of commercial coconut-shell active carbons were treated by sequential washing with hydrochloric acid, hydrofluoric acid and water followed by deoxygenation at 1000°C in a H 2 atmosphere. The determination of the hydrophilic structures such as oxygen complexes and ash before and after the treatments showed that these structures covered about 10% and 6% of the surfaces of the original active carbons and decreased to one-tenth or one-fourth after the treatments. Dynamic adsorption of benzene and methanol vapors carried by nitrogen with or without moisture was performed through the beds of those active carbons and a kind of silica gel. The results showed that the removal of hydrophilic structures of the active carbons decreased the adsorption affinities for methanol and water, but not for benzene. Coexistent moisture caused a decrease in the adsorption of benzene, and the effect was greatest on silica gel and smallest on the treated active carbons. It also caused a decrease in the adsorption of methanol by silica gel, but promoted the adsorption of methanol by the active carbons. The removal of hydrophilic structures promoted the selective adsorptivity of active carbon to a hydrophobic adsorbate from a hydrophilic adsorbate.