Adsorption Behaviors of Azulene and Phenol on Surface-Modified Activated Carbons in Organic Solvents

Abstract

The effect of the surface acidity of activated carbons on the adsorption of organic solutes in organic solvents was examined. Several activated carbons with differentsurface acidity but with the same porosity were prepared by oxidation of commercial activated carbon with nitric acid and heat treatment in hydrogen gas. The adsorbability of azulene, as a nonpolar solute, and phenol, as a polar solute, was measured on the surface-modified activated carbons in organic solvents of different polarities.The adsorbability of azulene decreased with decreasing solvent polarities and showed the lowest value in chloroform, but then increased with further decreasing solvent polarities. Similar behavior was also observed with phenol, though the magnitude of the decrease in the adsorbability was lower, and its adsorbability showed the lowest value in 1-octanol.The adsorbability increased with increasing surface acidity for both azulene and phenol, because increase in the carbon surface acidity caused a decrease in the affinity of the solvent for the activated carbon. The influence of the carbon surface acidity on the adsorption of azulene was larger than that of phenol.