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The unique configuration of unpaired 4f and 5f electrons and the rich structures of their energy levels enable rare-earth metals to possess many particular physical and chemical properties, such as high electrical conductivity, large magnetic moment, and very high complexation reactivity. [1,2] Based on these properties, the rare-earth metals and compounds have been applied extensively in permanent magnets, [3] autocatalysts, [4] superconductors, [5] etc. Demand for high-purity rareearth oxides and rare-earth metals is expected to increase particularly for use in corrosion resistance, [6] heat storage and dispersal, [7] and also in environmentally friendly applications such as in pigments for paint and plastics, [8] in cement manufacture to reduce the temperature of calcination and help save energy, [9] and in refrigeration components arising from the search for chlorofluorocarbon (CFC) replacements.[10] For the nanoscale rare-earth metals, because of the significantly increased total surface area or the grain boundary area, some new features show in the crystal structures, interface, thermodynamics, and phase transitions. [11][12][13] Consequently, remarkably improved optical, electronic, magnetic, and catalysis properties can be expected. [14][15][16] However, because of the extremely high chemical reactivity and hence the considerably rigorous equipment requirements to preserve a high purity of the product, the preparation and characterization of nanostructured pure rare-earth metals are still big challenges in nanoscience and nanotechnology. Thus, many important features of nanoscale rare-earth metals, such as the physical, chemical, thermal, and mechanical characteristics have rarely been reported so far. The research corresponding to these characteristics is of great importance, however, both for the development of nanoscience and nanotechnology and for extending the applications of the rareearth metals. In this consideration, we demonstrate in the present work how to prepare nanostructured bulk materials of some typical members of the rare-earth metals, laying the foundation for characterizing the physical and chemical properties of nanoscale rare-earth metals.During the past two decades, a number of techniques have been developed to synthesize nanocrystalline bulk materials, such as inert gas condensation and consolidation, [17] electrodeposition, [18] severe plastic deformation, [19] crystallization of amorphous solids, [20] surface mechanical attrition, [21] and powder metallurgy. [22][23][24] However, it is hard to produce nanocrystalline materials with controllable grain sizes in a wide range below 100 nm. Furthermore, in powder metallurgy for the consolidation of nanoparticles, the grain size in the synthesized bulk is generally larger than the initial particle size. [22][23][24] Particularly, in conventional powder metallurgy processes, a rapid coarsening of nanoparticles occurs very often, leading to the formation of grains in the submicrometer or even micrometer range. Using a new "oxygen-free" (o...

The extensive use of selective catalytic reduction (SCR) catalysts will afford many spent SCR catalysts. The mass fraction of the titanium component is over 80% in spent SCR catalysts, but currently, it is usually thrown away without proper recycling. This work aims to develop a clean, green, and economical approach to recovering titanium and regenerating TiO2 photocatalysts from spent SCR catalysts based on the conversion of the titanium component. This titanium component is converted into metastable α-Na2TiO3 with high efficiency (>98%) using a NaOH molten salt method, and the optimal conditions were found to be a roasting temperature of 550 °C, a NaOH-to-spent-SCR-catalysts mass ratio of 1.8:1, a roasting time of 10 min, and a NaOH concentration of 60–80 wt %. And a possible chemical reaction mechanism is proposed. A subsequent hydrothermal treatment of α-Na2TiO3 regenerates TiO2 photocatalysts with high purity (>99.0%) that can satisfy commercial requirements. In addition, the present iron element contained in spent SCR catalysts is doped into regenerated TiO2 photocatalysts, resulting in providing visible-light-driven photocatalytic activities. The regenerated TiO2 photocatalysts possess superior photocatalytic degradation capacities for dye pollutants and can be used to efficiently treat wastewater. This work introduces a promising technology for the cyclical regeneration of titanium from spent SCR catalysts.

In this paper, efficiency recovery of rare earth elements from cathode ray tubes (CRT) waste. Moreover, recycled yttrium was also served as raw material to produce a low-cost Y-doped TiO2 nanosheets film with exposed {001} facets. An etching/dissolution growth mechanism was postulated by systematically investigating the influence of the reaction time. The synergistic effect of the Y dopant and the dominant {001} facets endows TiO2 nanosheets film with excellent activity in the photoremoval of Methyl Orange (MO) and Cr­(VI). A possible mechanism of photoremoval of MO and Cr­(VI) is proposed. This study not only contributes to recycling methods for CRT waste but also presents a new way to prepare low-cost sustainable photocatalytic materials using economically viable waste.