China is the global leader in rare earth (RE) production using hydrometallurgical processes. Advantageous extraction techniques of rare earths from Baotou mixed rare earth minerals, bastnaesite, and ion-adsorption clays of rare earth deposits have been developed in China. The separation and purification technologies have also achieved rapid development. The industrial application processes for rare earth hydrometallurgy were summarized in the present paper. With the large demands and rapid development of rare earths, the issues of resources and environment are more prominent. This review gives an overview of the main processes that were developed in the past toward greener hydrometallurgy of rare earths in China. Based on the development of the rare earth industry, comprehensive utilization and cleaner production should still be focused on in the future, to support the sustainable development.

Ion-adsorption rare earth element (REE) ores are strategic mineral resources, particularly for heavy REEs.

In most cases, wet-process phosphoric acid (WPA) contains trace amount of rare earth elements and uranium, which ultimately enter and accumulate in soil and may cause environmental damages. In order to remove and recover these elements, studies about solvent extraction of heavy rare earth elements (HREEs) and uranium (U) with D2EHPA, selective stripping of HREEs from U, and evaporation precipitation of light rare earth elements (LREEs) were investigated. Extraction efficiency of U from WPA was greatly enhanced, but HREEs extraction were significantly retarded when using the solvent mixture of di-(2-ethylhexyl) phosphoric acid (D2EHPA) and tri-butyl-phosphate (TBP) or tri-octyl-phosphine oxide (TOPO) compared with D2EHPA alone. 89.4 % and 94.2% accumulative two-stage extraction efficiencies of HREEs and U, respectively, were achieved with 1.0 M D2EHPA alone. And more than 98.1% HREEs were selectively stripped from loaded D2EHPA with 6.0 M HCl via three stages. In addition, LREEs were enriched to 1204.3 ug/g in evaporation sludge during the concentration process of phosphoric acid from 30% to 50% P 2 O 5 , and the filtration performance was greatly improved. Based on the studies, an alternative process was developed to recover and group LREEs, HREEs and U during the phosphoric acid production.