Sol–gel synthesis of Zr(HPO₄)₂·H₂O

Abstract

Inorganic ion exchangers such as α-Zr(HPO4)2·H2O are usually synthesized from aqueous solution. Amorphous precipitates are then obtained, which crystallize very slowly upon ageing at ca. 90 °C in their mother liquor. Crystallization could be much faster if alkoxide precursors are used. The sol–gel synthesis of α-Zr(HPO4)2·H2O from both inorganic and metallo-organic precursors has been followed by solid-state 31P MAS NMR and X-ray diffraction. Condensation mechanisms leading to the formation of a solid phase are discussed. Compared to ZrOCl2 in aqueous solution, zirconium n-propoxide allows shorter reaction times and lower crystallization temperatures. This results in a material with smaller grains which should exhibit enhanced exchange properties.