Aromatics adsorption properties onto oxidized activated carbon from aqueous solution

Abstract

Adsorption of various aromatics onto activated carbons oxidized by nitric acid in aqueous solution was examined comparing with non-oxidized counterparts. The aromatics used were aniline, benzoic acid, nitrobenzene, phenol and bisphenol A. All aromatics exhibited two-step adsorption isotherms for oxidized activated carbons with the rise in concentration of adsorbates, whereas only one-step adsorption isotherms were observed for non-oxidized carbons. The amount of aromatics adsorption was also decreased by oxidation except bisphenol A. The aromatics adsorption sites on the oxidized activated carbon were consid-ered to be different from those on the non-oxidized carbon. Adsorption mechanism was investigated by a brief numerical analysis for the experimental data of two-step adsorption isotherms principally assuming a two-layer adsorption model and a mono-layer reorientation model. Based on the analysis for the two-step isotherms observed on the oxidized activated carbon, a reorientation model switching from flat-on to end-on molecular position is probable as well as a two-layer model.