This study proposes a set of isotherm equations that comprehensively describes water vapor adsorption, desorption, and competitive adsorption with CO2. The Freundlich-Gaussian (F-G) equation is used to predict the water vapor adsorption isotherm, and two expressions derived from the F-G adsorption equation is used to describe the desorption isotherm. Equations for H2O/CO2 binary adsorption isotherms are developed by combining the F-G equation for water vapor and the Freundlich equation for CO2. Results show that the proposed equations properly describe water vapor equilibriums on alumina F-200. (C) 2014 Elsevier B.V. All rights reserved.