Langmuir and Dubinin-Radushkevich analyses on equilibrium adsorption of activated carbon fabrics in aqueous solutions

The present study investigated the adsorption of phenol, iodine and tannic acid onto activated carbon fabrics in aqueous solutions. The carbon fabrics were made of polyacrylonitrile with different extents of activation in ste am. The increasing extent of activation is accompanied by increasing carbon porosity as well as liquid-phase adsorption capacity. Langmuir and Dubinin -Radushkevich (D-R) models were employed to analyze the equilibrium adsorpt ion data. The fractional filling of carbon micropores and the mean free ene rgy for adsorption were estimated according to these models. It is suggeste d on the basis of the present work that the mesopore fraction of the fabric s, the extent of carbon activation, and the adsorbate size are important as well as competitive factors determining the adsorption capacity. Both the equilibrium constant and free energy for adsorption increase with the mesop ore fraction, indicating that the mesopores promote the adsorption onto hig h energy sites, whereas the fraction filling micropores decreases with the extent of carbon activation and the size of the adsorbates. (C) 2000 Societ y of Chemical Industry.