On the mechanism of ion exchange in crystalline zirconium phosphates — VIII Na+/K+ exchange on α-zirconium phosphate
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The isotherms for Na+/K+ exchange on crystalline α-zirconium phosphate have been determined at several pH values. When the pH is below significant and variable amounts of hydrogen ion are exchanged. At pH 11 little or no hydrogen ion is exchanged. When K+ replaces sodium ion, a solid solution of the two ions in the exchanger is obtained. However, when the solubility limit of K+ is exceeded, a new potassium rich phase forms along with the solid solution. Further potassium uptake then takes place at constant solution composition until only the new potassium rich phase is obtained. Then a single phase region is observed until at still higher K+ loading the solubility limit is exceeded and another two phase region is obtained. The second phase consists of a small amount of Na+ in solid solution in potassium zirconium phosphate. This solid solution then persists up to 100 per cent loading of potassium ion. In the reverse exchange reactions the same phases are observed but their composition limits are different. This produces a small hysterisis loop in the isotherm. The isotherm at pH 9 exhibits a more pronounced hysterisis and this is attributed to the uptake of some hydrogen ion by the exchanger. © 1973.
author list (cited authors)
Clearfield, A., & Medina, A. S.