Rare earth elements (REE), originally found in various low-grade deposits in the form of different minerals, are associated with gangues that have similar physicochemical properties. However, the production of REE is attractive due to their numerous applications in advanced materials and new technologies. The presence of the radioactive elements, thorium and uranium, in the REE deposits, is a production challenge. Their separation is crucial to gaining a product with minimum radioactivity in the downstream processes, and to mitigate the environmental and safety issues. In the present study, different techniques for separation of the radioactive elements from REE are reviewed, including leaching, precipitation, solvent extraction, and ion chromatography. In addition, the waste management of the separated radioactive elements is discussed with a particular conclusion that such a waste stream can be employed as a valuable co-product.

In this study, we investigated reduction of magnetite by H₂ during microwave irradiation. This process combines the advantages of microwave irradiation and using H₂ as a reducing agent to mitigate CO₂ emissions during the ironmaking process. Weight change measurements showed that a reduction of 75% was achieved after treatment under H₂ for 60 min. For better understanding of the effective parameters in microwave chemistry, scanning electron microscopy, combined with energy-dispersive X-ray spectroscopy (SEM-EDX), was performed, which demonstrated a greater reduction of large particles (>40 μm) than small particles. This behaviour could be attributed to the higher microwave absorption capability of large particles with a higher ratio of particle size to penetration depth (d/δ). Small particles behave as transparent material and are heated via conduction and/or convection; thus, there is no contribution from the catalytic effect of microwaves to the reduction reaction. Moreover, the reduction of Fe₃O₄ to Fe_0.94O, followed by transformation to Fe, seems to proceed from the surface toward the centre of the particle despite the volumetric microwave heating. This could be due to the higher gas accessibility of iron oxide on the particle surface than in the particle centre.

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