The development of low-cost rare earth clean production technology is a challenge for rare earth resource utilization. One of the key problems is the development of new rare earth separation system and relevant technology.

　　Solvent extraction and chemical precipitation are two of the most widely used separation technologies, which have made important contributions to the development of China's rare earth industry, but they still have shortcomings.

　　In a study published in Hydrometallurgy, a research group led by Prof. SUN Xiaoqi from Fujian Institute of Research on the Structure of Matter of the Chinese Academy of Sciences prepared a new type of phenoxycarboxylic acid extractants. The extractants can quantitatively extract low-concentration rare earth, forming solid extracting complexes, which can be stripped and recycled.

　　Researchers synthesized some alkyl phenoxy carboxylic acid derivatives by the Williamson reaction, taking into account their abilities to form solid complexes with rare earth ions from an aqueous phase, and they were used as the solid extractants.

　　An extraction-precipitation method based on this type of extractants was developed, which combines the advantages of solvent extraction and chemical precipitation. Without using organic solvent, the new separation technique is characterized by quantitatively extracting metal ions to form the precipitation of extracting complexes. The extractant can be stripped and recycled.

　　This method is different from classical methods of liquid-liquid extraction, solid-liquid extraction, chemical precipitation, flotation and adsorption in the field of hydrometallurgy. Industrial tests conducted by researchers and the collaborators showed that it has advantages including low cost, good stability, large phase ratio, fast separation, large processing capacity, good sustainability and safety.

　　The technology has good industrial application prospects in the fields of enrichment of rare earth from leaching liquor of ion-absorption minerals, leaching liquid transformation of Baotou rare earth minerals, softening of ammonia sulfate rare earth wastewater, and rare earth secondary resource recovery.

The old saying goes, touch a stone and turn it into gold. To efficiently and sustainably enrich rare earth elements, a novel extraction-precipitation method has been developed for Industrial applications. (Image by Prof. SUN's group)