2001: Characterization of Activated Carbons Using Liquid Phase Adsorption

The pore size distribution is the most important aspect in characterization of structural heterogeneity of porous materials. Different methods have been developed and applied for the characterization of this property, and the most often used is gas adsorption [1,2], while liquid phase adsorption is seldom used [3]. A modification of the Dubinin-Radushkevich pore filling by incorporation of the repulsive contribution to the pore potential, and bulk nonideality, is proposed in this paper for characterization of three commercial activated carbons (Filtrasorb-400, Norit ROW 0.8, and Norit ROX 0.8) using liquid phase adsorption of flavor esters (ethyl propionate, ethyl butyrate, and ethyl isovalerate). The bulk-liquid phase nonideality is incorporated through the UNIFAC activity coefficient model, and the repulsive contribution to the pore potential incorporated through the Steele 10-4-3 potential model. The bimodal gamma function was utilized as the pore size distribution in the generalized adsorption isotherm. Excellent agreement between the bimodal gamma pore size distribution and DFT-cumregularization based pore size distribution is also observed, supporting the validity of the proposed model.