Ion Exchange of Alkali Metals on Crystalline α-Hafnium Phosphate

Abstract

Sodium ion exchange behavior was investigated in forward and backward directions on α-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 11.9Å. 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 α-hafnium phosphate.