Clean separation and purification for strategic metals of molybdenum and rhenium from minerals and waste alloy scraps–A review

•Worldwide Mo and Re resources characteristics and consumption are summarized.•Diverse processes for pre- and deep separation of Mo and Re are reviewed.•Technical principles of the pyro-, hydro- methods are outlined.•Differences of Mo and Re ionic forms in the solution are critical for separation.•Ammonia-modified reagents can realize the selective adsorption of Mo and Re.•Molybdate mainly reacts with -OH/H while rhenate chiefly combines with the N atom. Molybdenum (Mo) and rhenium (Re) are strategic key metals for the development of modernization. In nature, 99 wt.% of Re is associated with molybdenite minerals via the form of isomorphism, and the element abundance of Mo (about 1.1–1.5 ppm) and Re (about 0.0004–0.0026 ppm) is tremendous in the continental crust. These congenital characteristics make it difficult to separate Mo and Re. In this work, the Mo and Re resource features and products consumption are briefly summarized, and the pre-separation of Mo and Re from minerals or secondary alloy scraps, and the deep separation of the dissolved Mo and Re from solutions are systematically reviewed. Pyrometallurgy approaches are suitable for the treatment of high-grade Mo concentrates, however it lacks vast energy consumption and SO2 emission. Hydrometallurgical process is appropriate to deal with low-grade Mo concentrates, but leaching efficiency of Mo is low and numerous expensive oxidants are consumed. As for deep separation of Mo and Re from the solutions, selective chemical precipitation, ion exchange, and solvent extraction are commonly used in industry to separate Mo and Re. Due to separation efficiency, Mo and Re mixture solutions with low concentrations generally lower than 0.5 g/L are concomitantly generated after ion exchange and solvent extraction. Selective adsorption is a prospective method to separate Mo and Re from ultra-low concentration solutions, while the existing preparation technologies of high-selectivity adsorbents are characterized as complex and expensive. Developing facile and low-cost preparation of adsorbents is a promising research orientation for clean and deep separation of Mo and Re from solutions. [Display omitted]