Synthesis and characterization of uranium(IV) phosphate-hydrogenphosphate hydrate and cerium(IV) phosphate-hydrogenphosphate hydrate

A new uranium (IV) phosphate of proposed formula U-2(PO4)(2)(HPO4H2O)-H-., i.e. uranium phosphate-hydrogen phosphate hydrate (UPHPH), was synthesized in autoclave and/or in polytetrafluoroethylene closed containers at 150 degrees C by three ways: from uranium (IV) hydrochloric Solution and phosphoric acid, from uranium dioxide and phosphoric acid and by transformation Of the uranium hydrogenphosphate hydrate U(HPO4)(2)(.)nH(2)O. The new product appears similar to the previously published thorium phosphate-hydrogenphosphate hydrate Th-2(PO4)(2)(HPO4H2O)-H-. (TPHPH). From preliminary studies, it was found that UPHPH crystallizes in monoclinic system (a = 2.1148(7) nm, b = 0.6611(2) nm, c = 0.6990(3) nm, beta = 91.67(3)degrees and V = 0.9768(10) nm(3)). Heated under inert atmosphere, this compound is decomposed above 400 degrees C into uranium phosphate-triphosphate U-2(PO4)P3O10, uranium diphosphate alpha-UP2O7 and diuranium oxide phosphate U2O(PO4)(2). Crystallized cerium (IV) phosphate-hydrogenphosphate hydrate Ce-2(PO4)(2)(HPO4H2O)-H-. (CePHPH) was also synthesized from (NH4)(2)Ce(NO3)(6) and phosphoric acid Solutions by the same method (inonoclinic system: a = 2.1045(5) nm, b = 0.6561(2) nm, c = 0.6949(2) nm, beta = 91.98(1)degrees and V = 0.9588(9) nm(3)). When heating above 600 degrees C. cerium (IV) is reduced into Ce (III) and forms a mixture of CePO4 (monazite structure) and CeP3O9. (c) 2005 Elsevier Inc. All rights reserved.