Date of Completion
Thomas F. Morris, Chad P. Johnston
Field of Study
Master of Science
The adsorption selectivity of Cs+, K+, and Na+ cations on a ZSM-5 zeolite was studied by collecting the adsorption envelopes and analyzing the data with adsorption modeling. The adsorption of alkali metals increased on ZSM-5 with high aluminum content and the adsorption sites were mainly controlled by aluminum adsorption sites. Four adsorption sites were observed from these adsorption envelopes. The data were described using an ion-exchange model with four reaction sites. The adsorption cations had a selectivity sequence of Cs+ > K+ > Na+ for inner-sphere complexes. The adsorption strength of each cation had a strong correlation with the hydration enthalpy, indicating that the free energy of the adsorption reaction is greatly influenced by the cation’s hydration enthalpy. A shift in the adsorption strength of these cations on ZSM-5 was also observed and was described in terms of their solubility interactions inside the pore channels. The adsorption selectivity of cations was also studied on montmorillonite clay minerals in constrained and non-constrained environments. Montmorillonite clay minerals were placed in a stainless-steel container to limit the expansion of the interlayer and to create a constrained environment, or were suspended in a container for free expansion of the interlayer and to create a non-constrained environment. The dominant native cation concentrations present in the montmorillonite clay minerals were Na+ and Ca2+. The adsorption of Na+ cations increased its adsorption strength in the constrained environments, while the adsorption of the other cations decreased slightly or did not show any changes.
Oba, Maria, "Adsorption Selectivity of Cations in Constrained Environments" (2015). Master's Theses. 781.
Cristian P. Schulthess