Studies of the Hydrous Zirconium(IV) Oxide Ion Exchanger. I. Ion-Exchange Properties and Effect of Heat Treatment

Abstract

A satisfactory method was established for synthesizing a hydrous zirconium(IV) oxide ion exchanger; also, its ion-exchange properties and thermal stability were studied. The exchanger was synthesized reproducibly by hydrolyzing a ZrOCl2 solution at pH 9.3 with the addition of NH3 aq. This material was an amphoteric ion exchanger possessing an isoelectric point close to pH 6.5. The order of affinity for the cations was, transition metal> alkaline earth metal>alkali metal. Transition metal ions form a coordinate bond with OH groups in the exchanger. The OH groups, which were easily condensed by a heat treatment, were not restored even when the samples subjected to thermal treatment were immersed in water: Thirty percent of the initial ion-exchange capacity was lost when the exchanger was heat-treated at a temperature as low as 70 °C, and the exchange sites were completely destroyed between 400 and 550 °C.