Hydrometallurgical Processing of Eudialyte Bearing Concentrates to Recover Rare Earth Elements Via Low-Temperature Dry Digestion to Prevent the Silica Gel Formation

Eudialyte belongs to the group of cyclosilicate minerals and has a significant content of valuable heavy rare earth elements. In comparison to conventional ores like bastnaesite or monazite, the content of radioactive elements like thorium and uranium is quite low; thus, it is an ideal source for the sustainable extraction of rare earth elements (REE). In this way, a further processing or a disposal, direct or after using phase, of radioactive elements could be minimized. The cyclosilicate structure facilitates the easy decomposition of eudialyte by mineral acids. On one hand, this is a positive effect to lixiviate the REEs but leads to an excess liberation of silicon in the water-based system which involves the risk of silica gel formation. Within this research project, a hydrometallurgical pre-treatment is developed to decompose the eudialyte for the extraction of REEs and to stabilize the silicon in the residue during the following leaching step.