Competitive and Synergistic Adsorption of Mixtures of Polar and Nonpolar Gases in Carbonaceous Nanopores

Abstract

Most adsorption applications involve mixtures, yet accurate predictions of the adsorption of mixtures remain challenging, in part due to the inability to account for the interplay between adsorbate−adsorbate and adsorbate−adsorbent interactions. This study involves a comprehensive Monte Carlo simulation of the adsorption of two groups of mixtures (namely, supercritical and subcritical ones) in carbon nanopores and quantifies Henry's constants, isotherms, energetics, and density distributions in the pores. When interadsorbate interactions are negligible (e.g., in supercritical mixtures such as mixtures of nonpolar gases), adsorbates behave like ideal gases and the adsorption isotherm can be predicted with the ideal adsorbed solution theory (IAST). However, when interadsorbate interactions become significant, IAST fails. This study reveals that (1) in mixtures of polar and nonpolar gases, the stronger intermolecular interaction for the polar constituent leads to synergistic adsorption that causes the nonpolar adsorbate to desorb and (2) for mixtures of polar gases, such as ethanol and water, the adsorbate−adsorbate interactions are so dominant that the unfavorable adsorbate−adsorbent interactions are overcome, such that water adsorbs onto the hydrophobic adsorbent. The competitive and synergistic interactions highlighted here are expected to be valuable in enhancing gas separations.

Efficient Removal of Basic Fuchsin from Synthetic Medical Wastewater and Competitive Adsorption in the Mixture

“…From the isotherms in Figure 8, competitive adsorption, on the active adsorption sites on GC, was detected for the adsorption of BF in a mixture with Ph (the adsorption capacity for BF adsorption has declined from 287.0 to 147.3 mg g -1 ), while a synergetic effect of BF molecules was found on the adsorption of phenol on GC (the adsorption capacity of GC towards phenol molecules has increased from 675.4 to 711.6 mg g -1 ) [42].…”

Active learning for efficient navigation of multi-component gas adsorption landscapes in a MOF

“…This behaviour was also reported by Tan and coauthors, where they studied mixture adsorption of polar and non-polar gases in carbonaceous nanopores. 71 This feature space where CO 2 adsorption is high at low pressure, corresponds to the synergistic zone where electrostatic interaction of CO 2 with the MOF is stronger. The adsorbates with stronger inter-molecular interactions accumulate near the adsorbent surface and continue to adsorb, out-competing the other gas with weaker adsorbate-adsorbate interaction.…”