Modeling Volatile Organic Compound Sorption in Activated Carbon. II: Multicomponent Equilibrium

A new approach is presented for modeling multicomponent volatile organic compound (VOC) sorption equilibrium in ultra- and supernanoporous activated carbons. The model uses “Dubinin–Astakhov thermal equation of equilibrium adsorption” (DA-TEEA) for single-component adsorption thermodynamics and “ideal/real adsorbed solution theories” (IAST/RAST) for the multicomponent mixing rules. Use of the Henry’s Law adsorption isotherm resolves the singularity of DA-TEEA at zero-coverage conditions. The introduced method predicts multicomponent adsorption equilibria of VOCs based on equilibrium data of only one similar component. Single and binary adsorption equilibria of acetone and benzene vapors in Kynol ACFC-5092-20 activated-carbon-fiber-cloth adsorbents are predicted with the presented models and compared with modeled and measured characterization data available in the literature. The Wilson model for nonideal binary solution mixtures is used to predict the activity coefficients needed in DA-TEEA/RAST. Modeled results are compared against measured characterization data. The selected Henry’s Law upper-bound pressure (HUBP) is found to be an important factor controlling the accuracy of the multicomponent equilibrium models. An optimum HUBP can generate highly accurate results from both DA-TEEA/IAST and DA-TEEA/RAST. The accuracy realized by applying this method to acetone–benzene mixtures is sufficient for engineering design and development purposes.