(41c) Comparison of the Dual-Process Langmuir and Generalized Langmuir Isotherms for Representation of Unary, Binary, and Ternary Equilibria

Mixed gas adsorption is still a very active area of research, where newly proposed models need to be compared actively to standards in the field. The generalized Langmuir (gL) isotherm, proposed by Hamid et al. to address adsorption of different size molecules on heterogeneous adsorbents without requiring evaluation of the Gibbs isotherm, [1] has thus-far been tested mainly against the adsorbed solution theory (AST). The gL isotherm was shown to be thermodynamically consistent, [2] and gave either better or similar representation than both IAST and RAST-aNRTL. [1 - 3] Here, the gL isotherm will be contrasted with the duel-process Langmuir (DPL) isotherm popularized by Ritter and his coworkers at USC. [4 - 7]. The models will be compared based on their representation of the equilibrium loading and isosteric heat of adsorption (where available) of individual components, binary, and ternary mixtures of various gaseous adsorbates on different adsorbents over a range of experimental pressures and temperatures.

Works Cited:

1. Hamid, U.; Vyawahare, P.; Tun, H.; Chen, C.-C. (2021). Generalization of Thermodynamic Langmuir Isotherm for Mixed-Gas Adsorption Equilibria. In Review.
2. Hamid, U.; Vyawahare, P.; Sees, M.D.; Chen, C.-C. (2021, November). “Generalized Langmuir Isotherm Addresses Spreading Pressure Dependency of Modified Ideal Adsorbed Solution Theory.” Paper presented at the 2021 Annual Meeting of the American Institute of Chemical Engineers, Boston, MA.
3. Hamid, U.; Vyawahare, P.; Chen, C.-C. (2021, November). “Isosteric Heat of Adsorption of Pure Component and Mixed-Gas Adsorption from Generalized Langmuir Isotherm.” Paper presented virtually at the 2021 Annual Meeting of the American Institute of Chemical Engineers, Boston, MA.
4. Ritter, J.A.; Bhadra, S.J.; and Ebner, A.D. (2011). On the Use of the Duel-Process Langmuir Model for Correlating Unary Equilibria and Predicting Mixed-Gas Adsorption Equilibria. Langmuir, 27, 4700 – 4712.
5. Bhadra, S.J.; Ebner, A.D.; Ritter, J.A. (2012). On the Use of the Duel-Process Langmuir Model for Predicting Unary and Binary Isosteric Heats of Adsorption. Langmuir, 28, 6935 – 6941.
6. Ritter, J.A.; Bumiller, K.C.; Tynan, K.J.; and Ebner, A.D. (2019). On the Use of the Duel-Process Langmuir Model for Binary Gas Mixture Components that Exhibit Single-Process or Linear Isotherms. Adsorption, 25, 1511 – 1523.
7. Tynan, K.J.; Tosso, S.; Ebner, A.D.; and Ritter, J.A. (2021). On the Use of Single, Dual, and Three-Process Langmuir Models for Binary Gas Mixtures that Exhibit Unique Combinations of These Processes. Adsorption, 27, 637 – 658.