Comparison of three methods to predict adsorption isotherms for organic vapors from similar polarity and nonsimilar polarity reference vapors

Abstract The Polanyi-Dubinin equation was used to predict adsorption isotherms for eight organic vapors at 25°C and for two organic vapors at 25°C, 40°C and 60°C on activated carbon in this analysis. The theoretical affinity coefficient, β, is calculated by three methods (molar volume, molecular parachor, and electronic polarization) based on nonpolar and polar reference vapors. The corresponding experimental isotherm data were measured by gravimetric method. Comparison between calculated and experimental isotherm data showed that 1. (1) for optimum isotherm prediction, the reference vapor should have similar polarity to the vapor whose adsorption is being predicted, 2. (2) after choosing an appropriate reference vapor, there is essentially no difference in the accuracy of the isotherm predictions by the three methods, and 3. (3) the molar volume method is more applicable for predicting isotherms at different temperatures.