Abstract
Calcium exchanged A type zeolite is extensively used as an adsorbent in petroleum and gas purification application. The precursor of calcium and silver-exchanged zeolite was prepared in a hydrothermal process, followed by an exchange process. In this study, LTA zeolite was synthesized. Calcium-ex- changed and silver-exchanged molecular sieves were prepared and characterized by a series of techniques, such as scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, etc. Physical properties of Ca- and Ag-exchanged zeolite A, such as surface structure, crystal structure, cation exchange capacity, and the ion-exchange properties were measured. Water adsorption studies using thermogravimetric method indicated that water molecules are more strongly bound in the Ca-A zeolite compared to Ag-A zeolite. XPS studies confirmed the presence of highly dispersed cationic silver species at exchange sites. The results of this study indicated that sodium was successfully exchanged with the calcium and silver in both Ca- and Ag-ex- changed zeolite frameworks. High cation exchange capacity, tailored aperture size, high porosity and specific surface area, as well as high thermal stability make cation-exchanged A type zeolite a successful candidate for adsorption, ion exchange, and catalysis applications.
Highlights
High porosity synthetic zeolites have been popular materials since their advent in late 1940s for catalysis, separation and purification applications, among others
The results of this study indicated that sodium was successfully exchanged with the calcium and silver in both Ca- and Ag-exchanged zeolite frameworks
The color change observed upon heating of Ag-A under vacuum has been attributed to the formation of AAAAnxnx+ clusters inside sodalite cavities of zeolite A
Summary
High porosity synthetic zeolites have been popular materials since their advent in late 1940s for catalysis, separation and purification applications, among others. Minerals and Materials Characterization and Engineering physiochemical properties such as adsorption, cation exchange, molecular sieving, and catalysis. They function on the basis of physisorption. The main driving force of the adsorption is the highly polar internal surface of the zeolite [1] [2] [3] [4]. This unique property distinguishes zeolites from other adsorbents and enables them to have an extremely high adsorption capacity. Maintaining a charged and large internal surface area, having a defined aperture size, presence of pores and cavities in the order of molecular dimensions (0.3 - 1.0 nm) plays a significant role in separation process, allowing or prohibiting the entrance of molecules to the pore system, leading to high separation factors [5] [6] [7]
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