Ion Exchange of Alkali Metals on Crystalline α-Hafnium Phosphate

Abstract

Sodium ion exchange behavior was investigated in forward and backward directions on a-hafnium phosphate which had been prepared by the direct precipitation method. pH-Titration curves and X-ray powder diffraction patterns for the exchanged solid indicate that the ion exchange proceeds in two steps, involving formation of an intermediate monosodium salt with large interlayer distance of 11.9 Å. α-Hafnium phosphate was reproduced toward the end of the backward exchange, in contrast to the case of α-zirconium phosphate, where much more hydrated θ-zirconium phosphate formed. Preliminary experiments of ternary H⁺-Na⁺-Cs⁺ ion exchange system were also attempted, as well as caesium ion exchange on monosodium form of a-hafnium phosphate.