New rare earth langbeinite phosphosilicates KBaREEZrP2SiO12 (REE: La, Nd, Sm, Eu, Gd, Dy) for lanthanide comprising nuclear waste storage

• Published in: Journal of alloys and compounds Vol. 657; pp. 422 - 429
• Main Authors: Kumar, Sathasivam Pratheep, Gopal, Buvaneswari
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 05.02.2016
• Subjects: Chemical durability; Infrared spectra; Langbeinite phosphosilicate; Thermal analysis; X-ray diffraction; X-ray diffraction; Langbeinite phosphosilicate; Infrared spectra; Thermal analysis; Chemical durability
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2015.10.088

In contrast to the existing cubic langbeinite phosphates and sulphates, orthorhombic langbeinite phosphosilicates of the chemical formula KBaYMP2SiO12 (M: Zr, Sn), KBaREEZrP2SiO12 (REE: La, Nd, Sm, Eu, Gd, Dy) and the wasteform KBaY0.6La0.1Nd0.1Sm0.1Eu0.1ZrP2SiO12 have been synthesized by solution method. Powder X-ray diffraction analysis affirmed that the compounds were phase pure and crystallized in an orthorhombic structure with P212121 space group. Spectral analysis of the wasteform revealed the phase stability, thermal stability and chemical durability of the langbeinite structure. Chemical durability of the powder wasteform has been studied by a dynamic Soxhlet test. Elemental analysis of the leachates showed that the normalized mass losses of barium, zirconium and silicon were in the order of 10−3–10−2 g/m2, 10−5–10−4 g/m2 and 10−2–10−1 g/m2 respectively. Normalized mass losses of lanthanides, potassium and phosphorous were found to be below the instrumental detection limits. [Display omitted] •A series of new langbeinite phosphosilicates have been synthesized.•New langbeinite wasteform has been fabricated and characterized.•Synthesized phosphosilicates were crystallized in orthorhombic structure.•Dissolution study of the wasteform revealed negligible leaching of lanthanides.