Simulated monazite crystalline wasteform La0.4Nd0.1Y0.1Gd0.1Sm0.1Ce0.1Ca0.1(P0.9Mo0.1O4): Synthesis, phase stability and chemical durability study

• Published in: Journal of nuclear materials Vol. 458; pp. 224 - 232
• Main Authors: Pratheep Kumar, Sathasivam, Gopal, Buvaneswari
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.03.2015
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/j.jnucmat.2014.12.081

•Hexavalent molybdenum and selected lanthanides were immobilized into monazite structure at low temperature.•The wasteform has been characterized by powder XRD, FTIR, SEM-EDX and XPS analysis.•Immobilization of molybdenum was proved by energy dispersive X-ray analysis.•Chemical durability of the wasteform was studied by dynamic Soxhlet test.•Polymer–ceramic composite approach reduced the leaching of molybdenum from monazite lattice. In this work, incorporation of hexavalent molybdenum and selected trivalent lanthanides using divalent calcium as charge compensator into the monazite structure were studied. Rare earth substituted phosphomolybdates of the formula REE0.9Ca0.1P0.9Mo0.1O4 (REE=Ce, Nd, Sm, Gd) and the wasteform La0.4Nd0.1Y0.1Gd0.1Sm0.1Ce0.1Ca0.1P0.9Mo0.1O4 were synthesized by simple solution route. The prepared compounds were characterized by powder X-ray diffraction, Fourier transformed infrared spectra, thermogravimetric analysis, energy dispersive X-ray analysis and scanning electron microscopic techniques. Chemical durability of the wasteform was studied by dynamic MCC-5 test for a period of one month. Normalized elemental mass loss and leach rate of molybdenum was found to be in the order of 103g/m2 and 103–101g/m2/d respectively. Polymer-monazite composite wasteform was prepared to control the leaching of molybdenum. The composite approach reduced molybdenum leach rate order from 101 to 10−4g/m2/d.