Magnetically separable Fe₃O₄-SiO₂/Pt catalyst and its application for uranium reduction

Magnetically separable Fe₃O₄-SiO₂/Pt catalysts with ~ 2% Pt loading have been developed for the generation of U(IV) in HNO₃-N₂H₄ medium, used in the nuclear spent fuel reprocessing. Pt was impregnated in the catalysts via reductive heat treatment. The catalysts were characterized by x-ray diffraction, magnetization measurement, field emission scanning electron microscope and high-resolution transmission electron microscope studies. Catalysts reduced at 200 °C and above temperatures were found to be sufficient for the complete reduction of Pt to its Pt(0) state and were highly efficient for the U(IV) generation via hydrogenation. The U(IV) produced during the experiment was analyzed via the titrimetric and spectroscopic methods. Among all the catalysts prepared under the scope of the study, the highest saturation magnetization was measured for the Fe₃O₄-10SiO₂/Pt catalysts prepared at 200 °C (Fe₃O₄-10SiO₂/Pt(200)). However, the catalyst was least effective towards U(VI) reduction compare to the catalysts prepare at 250 °C (Fe₃O₄-10SiO₂/Pt(250)) and 300 °C (Fe₃O₄-10SiO₂/Pt(300)). The saturation magnetization of Fe₃O₄-10SiO₂/Pt(300) was found to be higher than that of Fe₃O₄-10SiO₂/Pt(250). Finally, Fe₃O₄-10SiO₂/Pt(300) was considered a model catalyst for the detailed characterization, benchmarking and recycling of the catalyst material. Samples with higher silica content were also prepared at 300 °C and assessed for their catalytic activity.