Synthetic inorganic ion-exchange materials—II: Hydrous zirconium oxide and other oxides

Abstract

The oxides ZrO 2, ThO 2, and TiO 2 behave as anion exchangers in acid and neutral solution and cation exchangers in alkaline solution, the pH at which their behaviour changes depending upon the oxide itself and possibly also upon the nature of the exchanging ion. The oxides have been prepared in granular form and their reversible reactions with ions in solution have been studied; they are monofunctional exchangers, with appreciable rates of exchange, and display the expected affinity towards ions in solution. Owing to their weakly basic nature, exchanged ions are readily removed by treatment with water. When ZrO 2 is treated with phosphoric acid it is converted into zirconium phosphate having properties qualitatively similar to the material described in Part I; the reaction cannot be solely one of anion exchange, but must involve breakdown of the oxide and introduction of further acid phosphate groups by neutralization. WO 3 is a cation exchanger in acid solution, but dissolves in alkaline solution.