An integrated process for rare earth elements recovery and silica production from Turkish bauxite-related ores

The evaluation of bauxite-associated shales as a secondary source of rare earth elements (REEs) is strategically important for securing a sustainable supply of critical raw materials used in advanced technologies. In this study, shale ore associated with bauxite, unsuitable for aluminium production due to its high silica content, was investigated as a potential resource for valuable REEs. The effect of thermal activation on REE recovery was examined, and the potential use of the leach residue as a silica source was assessed. Based on acid leaching results, the optimum calcination temperature was identified as 700 degrees C. Under these conditions, high REE recoveries were achieved: 92.9% La, 89.9% Ce, 89.0% Pr, 88.7% Nd, and 73.0% Sm. After leaching, the residue was enriched in alumina and silica. To improve silica purity and recover remaining REEs and Al, a second-stage leaching process was applied. This resulted in a byproduct containing 55% SiO2 with a specific surface area of 48 m2 g-1, indicating its potential as a silica source. The results demonstrate that bauxite-associated shale can be sustainably valorised through intensive milling, calcination, and acid leaching, enabling efficient REE recovery and the production of a silica-rich byproduct. L'& eacute;valuation de schistes associ & eacute;s & agrave; la bauxite comme source secondaire d'& eacute;l & eacute;ments de terres rares (ETR) est strat & eacute;giquement importante pour garantir un approvisionnement durable en mati & egrave;res premi & egrave;res critiques utilis & eacute;es dans les technologies avanc & eacute;es. Dans cette & eacute;tude, on a examin & eacute; le minerai de schiste associ & eacute; & agrave; la bauxite, inappropri & eacute; & agrave; la production d'aluminium en raison de sa teneur & eacute;lev & eacute;e en silice, comme ressource potentielle d'ETR pr & eacute;cieux. On a examin & eacute; l'influence de l'activation thermique sur la r & eacute;cup & eacute;ration des ETR et l'on a & eacute;valu & eacute; l'utilisation potentielle du r & eacute;sidu de lixiviation comme source de silice. D'apr & egrave;s les r & eacute;sultats de la lixiviation acide, on a identifi & eacute; la temp & eacute;rature optimale de calcination & agrave; 700 degrees C. Dans ces conditions, on a obtenu des r & eacute;cup & eacute;rations d'ETR & eacute;lev & eacute;es: 92.9% de La, 89.9% de Ce, 89.0% de Pr, 88.7% de Nd et 73.0% de Sm. Apr & egrave;s la lixiviation, le r & eacute;sidu & eacute;tait enrichi en alumine et en silice. Afin d'am & eacute;liorer la puret & eacute; de la silice et de r & eacute;cup & eacute;rer les ETR et l'Al restants, on a appliqu & eacute; une deuxi & egrave;me & eacute;tape de lixiviation. Cela a engendr & eacute; un sous-produit contenant 55% de SiO2 et pr & eacute;sentant une surface sp & eacute;cifique de 48 m2/g, indiquant son potentiel en tant que source de silice. Les r & eacute;sultats d & eacute;montrent que le schiste associ & eacute; & agrave; la bauxite peut & ecirc;tre valoris & eacute; de mani & egrave;re durable par broyage intensif, calcination et lixiviation acide, permettant une r & eacute;cup & eacute;ration efficace des ETR et la production d'un sous-produit riche en silice.