Synthesis of crystalline titanium(IV) phosphates by direct precipitation from Ti(III) solutions and ion exchange properties of some of the prepared phases

Abstract

Crystalline phases of titanium(IV) phosphate have been precipitated by oxidation of titanium(III) in phosphoric acid solutions. Three phases with layered structures have been prepared. Besides α-Ti(HPO4)2 · H2O and γ-Ti(HPO4)2 · 2H2O, known before, a new phase with chemical composition Ti4(HPO4)7(H2PO4)2 · 0-4H2O has also been found. The ion exchange properties of α-Ti(HPO4)2 · H2O especially are very sensitive to the degree of crystallinity. Well crystallized α-Ti(HPO4)2 · H2O can be prepared by oxidation of Ti(III) in 15 M H3PQ4 at 140 °C.