The transformation and enrichment of rare earth sulfate in Bayan Obo ore water leaching solution by dibenzyl phosphate based extraction-precipitation method

Summary of the Research Progress on Advanced Engineering, Processes, and Process Parameters of Rare Earth Green Metallurgy

The addition of rare earth metals to aluminum alloys can effectively improve their corrosion resistance and has been widely used in the aerospace and military industries. However, the current methods for the preparation of rare earth metals involve long processing steps, high energy consumption, and high carbon emissions, which severely constrains the development of aluminum alloys. Its output is further developed. To this end, this paper reviews mainstream rare earth production processes (precipitation methods, microemulsion methods, roasting-sulfuric acid leaching methods, electrochemical methods, solvent extraction methods, and ion exchange methods) to provide basic information for the green smelting of rare earth metals and help promote the development of green rare earth smelting. Based on the advantages and disadvantages of each process as well as recent research results, the optimal process parameters and production efficiency were summarized. Studies have concluded that the precipitation method is mostly used for the recovery of rare earth elements and related valuable metals from solid waste; the microemulsion method is mostly used for the preparation of nanosized rare earth alloys by doping; the roasting-sulfuric acid leaching method is mostly used for the treatment of raw rare earth ores; and the molten salt electrolysis method is a more specific method. This is a green and environmentally friendly production process. The results of this study can provide direction for the realization of green rare earth smelting and provide a reference for improving the existing rare earth smelting process.

A review of the application of cerium and lanthanum in phosphorus removal during wastewater treatment: Characteristics, mechanism, and recovery

Owing to their strong bond with anions, rare earth elements (REEs) are prime contenders in wastewater treatment to meet the stringent phosphorus (P) effluent quality requirements. REEs outcompete traditional metals to abate phosphorus. The application of lanthanides in wastewater treatment is mainly through adsorption, where REEs are incorporated into a carrier matrix to improve the adsorption capacity. As coagulants, information on the performance of lanthanides is lacking. In this review, the performance of major water coagulants (iron and aluminum) is discussed and compared to two lanthanides: cerium and lanthanum. The use of lanthanides as adsorbents and as coagulants is elucidated during P treatment. The recovery of P and REEs is also discussed. Where details were lacking in the literature, experiments were conducted to fill these research gaps. Using REEs as adsorbents limits their P precipitation potential; as coagulants, REE capacity is 520.79 mg P/g La³⁺ and 469.96 mg P/g Ce³⁺. In addition, as coagulants, they are not affected by pH (3.0 < pH < 10.0); however, carbonates and sulfate are the major species that can reduce the performance of REEs during P treatment. REE-P precipitation is orchestrated through the formation of an REE-PO₄ bond. Unfortunately, this strong bond between lanthanides and phosphate makes phosphate recovery almost impractical. If the goal is to recover REEs and reuse P in other applications like fertilizers, REEs are not the best candidates. We recommend additional research dedicated to understanding lanthanide coagulants in typical wastewater treatment facilities and their release from phosphate precipitates under different environmental conditions.