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Rare earth elements (REEs) are used in a wide range of products. The global demand for REEs is growing at a rate of 3.7-8.6% annually. Yttrium (Y), europium (Eu), cerium (Ce), lanthanum (La) and terbium (Tb) are used in the phosphors for fluorescent lamps (FLs). This article reviews the challenges and techniques associated with the recycling and recovery of REEs in phosphors from waste FLs. The recovery rate and grade of resultant products and the processing costs are the primary factors to be considered regarding trichromatic phosphors enrichment and monochrome phosphor separation. Currently, most researchers have focused on the recovery of Y and Eu from red phosphor using hydrometallurgy methods, and on the difficulties of leaching Ce, La, Tb and Eu in green and blue phosphors. The final recovery rate of Y and Eu can reach more than 80%, but a higher rate is desirable, considering the total value of the REEs in FLs. Studies on improving the leaching behavior of phosphors have been conducted; however, they present problems such as energy and agents consumption, and generation of viscous solution of silicate. Some pyrometallurgy and electrometallurgy approaches are also discussed.

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Recycling metals from wastes is essential to a resource-efficient economy, and increasing attention from researchers has been devoted to this process in recent years, with emphasis on mechanochemistry technology. The mechanochemical method can make technically feasible the recycling of metals from some specific wastes, such as cathode ray tube (CRT) funnel glass and tungsten carbide waste, while significantly improving recycling efficiency. Particle size reduction, specific surface area increase, crystalline structure decomposition and bond breakage have been identified as the main processes occurring during the mechanochemical operations in the studies. The activation energy required decreases and reaction activity increases, after these changes with activation progress. This study presents an overall review of the applications of mechanochemistry to metal recycling from wastes. The reaction mechanisms, equipment used, method procedures, and optimized operating parameters of each case, as well as methods enhancing the activation process are discussed in detail. The issues to be addressed and perspectives on the future development of mechanochemistry applied for metal recycling are also presented.

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The effective separation of aluminum (Al) foil and cathode materials is a critical issue for the recycling of spent lithium-ion batteries (LIBs). Previous studies have shown that the strong binding force provided by the organic binder polyvinylidene fluoride (PVDF) between the cathode materials and the Al foil of spent LIBs makes it difficult to peel off the cathode materials from the Al foil, reducing the effectiveness of the metal recovery process. This study reports on a low-temperature molten salt technology for melting the organic binder PVDF. The results showed that an aluminum chloride-sodium chloride (AlCl3-NaCl) systema nontoxic reaction mediumcould melt PVDF efficiently and is environmentally friendly as well, because of the phase transformation of molten salt caused by heat storage. The optimal conditions for peeling off cathode materials were a temperature of 160 °C, molten salt:cathode electrode mass ratio of 10:1, and holding time of 20 min. The highest peeling off percentage of cathode materials was 99.8 wt %. The purpose of this study was to provide an environmentally friendly, low-cost, and effective solution for the separation of cathode materials and Al foil from spent LIBs.