Microwave–sintered Sr0.5Zr2(PO4)3–CePO4 composite ceramic materials derived from uranium tailings for immobilizing strontium and cerium radionuclides

Uranium (U) tailings, generated as byproducts of U mining and milling, pose significant disposal challenges owing to their large volume, radiotoxicity, and chemically heterogeneous mineral composition. Herein, we report a microwave–assisted route for preparing (1– x )Sr 0.5 Zr 2 (PO 4 ) 3 – x CePO 4 ( x = 0, 0.2, 0.4, 0.6, 0.8, 1) [strontium zirconium phosphate(SZP)–cerium phosphate(CP)] composite ceramics while incorporating real U tailings as a Si/Al–rich secondary waste component. The raw–batch U–tailing loading was 39.7–47.0 wt% for the designed compositions and 45.4 wt% for the optimized SZP–CP–0.8 batch. Compared with reagent–derived SZP–CP systems, the present work focuses on the practical utilization and stabilization of actual U tailings during ceramic waste−form preparation. The phase assemblage, microstructure, density, Vickers hardness, Ce surface valence, and 42–day PCT chemical durability were evaluated. The optimized SZP–CP–0.8 ceramic exhibited a density of 4.32 g ·cm –3 , a porosity of 0.12%, and low normalized leaching rates after 42 days, with Sr, P, and Si of approximately 10 −4 g ·m −2 ·d −1 , Ce of approximately 10 –7 g ·m –2 ·d –1 , and Zr of approximately 10 –8 g ·m –2 ·d –1 , supporting the feasibility of microwave–sintered SZP−CP composites for treatment and disposal of U tailings and simulated divalent/tetravalent radionuclides. Quantitative phase refinement, statistically representative grain–size analysis, replicate–vessel leaching uncertainty, and radionuclide–specific leaching of native trace elements from tailings are identified as future work rather than over interpreted from the present dataset.