Factors determining ion exchange selectivity—I high temperature phases formed by α-zirconium phosphate and its sodium and potassium exchanged forms
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The phases formed at elevated temperatures by α-zirconium phosphate (α-ZrP) and its partially exchanged sodium and potassium ion phases have been determined by a combination of thermal and X-ray methods. α-ZrP converts to ζ-ZrP without water loss at 105-115°C. At somewhat higher temperatures one mole of water is lost followed by conversion of ζ-ZrP to ν-ZrP at ca. 230°C. Starting at 400-450° phosphate groups condense by split out of another mole of water. In the process a largely amorphous solid results. This in turn is converted to α-ZrP2O7 at still higher temperatures. Two new partially sodium and potassium exchanged phases were discovered to form at elevated temperatures. The phases have the approximate compositions ZrNa0·20H1·80(PO4)2 and ZrNa0·80H1·20(PO4)2 and ZrK0·16 H1·84(PO4)2 and ZrK0·64H1·36(PO4)2 in the sodium and potassium ion systems, respectively. The spontaneous disproportionation at room temperature of partially exchanged sodium and potassium ion phases into phases of lower and higher Na+ or K+ content indicates that ions can diffuse very readily throughout the crystal lattice. In the same context a new phase, λ-ZrP, was prepared by reaction of gaseous HCl with the cation exchanged zirconium phosphate phases. © 1975.
author list (cited authors)
Clearfield, A., & Pack, S. P.