Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
9617602 | Microporous and Mesoporous Materials | 2005 | 8 Pages |
Abstract
The kinetics of binary ion exchange of Ca2+ and Mg2+ for Na+ in quasi-crystalline and crystalline zeolite A has been investigated. Diffusion of either divalent cation into crystalline zeolite NaA is relatively fast, while the exchanges are slower in the quasi-crystalline precursor materials. The diffusion coefficient for Mg2+ exchange (D(Mg)) into crystalline zeolite A is an order of magnitude lower than that of Ca2+ (D(Ca)), due to the larger hydration sphere of the Mg2+ ion. However, the ratio (D(Ca):D(Mg)) was found to scale with the degree of crystallinity of the sample. Calcium and magnesium ions diffuse into the quasi-crystalline materials at comparable rates; this phenomenon is ascribed to the presence of larger pores in the quasi-crystalline structure, as compared to the crystalline material. Low impact mechanical treatment of quasi-crystalline zeolite precursors further decreases the difference between D(Ca) and D(Mg), while the crystallinity of the material is not noticeably decreased.
Related Topics
Physical Sciences and Engineering
Chemical Engineering
Catalysis
Authors
Eric N. Coker, Lovat V.C. Rees,