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S UNCLASSIFIED HW-74609
LOADING AND ELUTION CHARACTERISTICS OF SOME NATURAL AND
SYNTHETIC ZEOLITES
L. L. Ames and K. C. Knoll
INTRODUCTION
The zeolites are a family of well defined, hydrated aluminosilicates closely
related to each other in chemical composition (4). Alkali or alkaline earth metal
cations are necessary to electrostatically balance (A104)-5 substitutions for (SiO4)4
tetrakedra within the zeolite crystal lattice, and are stoichiometrically exchangeable
for other cations with little or no lattice expansion or contraction.
There are at least three mechanisms responsible for the ion exchange character-
istics of zeolites. They include cation size-crystal lattice interactions, charge
distribution interactions and cation-anionic site-water interactions within the zeo-
lite crystal lattice (2). Cation size requirements were minimized as a mechanism by
choosing zeolites whose effective pore diameter allow exchange of all cations used in
this study. Often the larger cations can be excluded from exchange sites due to their
inability to diffuse through the zeolite crystal lattice and into the exchange sites.
A second mechanism of charge distribution is due to the rigid spatial distri-
bution of anionic sites on the crystal lattice. Often high field strength or highly
charged cations cannot effectively electrostatically neutralize the anionic charges.
The net result can be exclusion of the rare earth, for example, from exchange sites
even though diffusion through the zeolite crystal lattice is possible.
The third mechanism involves the electrostatic interaction of incoming cation,
internal or zeolitic water, and anionic site within the zeolite lattice. Lower field
-2-
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Ames, L. L., Jr. & Knoll, K. C. Loading and Elution Characteristics of Some Natural and Synthetic Zeolites, report, August 10, 1962; Richland, Washington. (https://digital.library.unt.edu/ark:/67531/metadc1057485/m1/5/: accessed July 16, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.