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Hydrometallurgical Processing of Rare Earth Elements from Ion Adsorption Clays

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posted on 2023-08-31, 12:29 authored by Eddy MiiroEddy Miiro, Jochen PetersenJochen Petersen



The  surface mining and heap leaching of China’s ion-adsorption rare-earth  resources have caused severe environmental damage, there is a need to better  understand Rare Earth leaching from Clay ore with the use of agglomerates that  improve the permeability of the ore during heap leaching operation. The  practice of in-situ leaching has also revealed serious environmental problems  including underground contamination, mine collapses, and landslides. 

The  performance of lixiviants in extracting Rare Earth has been compared in many  studies however still this has been carried out in agitated systems and the  heap leach scenario is different from agitated systems. This limits the  understanding of poor heap permeability and post-closure stability whereas  un-agitated leaching of Rare Earth from Clay agglomerates gives a better  understanding of diffusion, heap permeability, and material balance to mimic  the heap leach scenario. A comprehensive understanding of the leaching  mechanism is crucial for achieving high extraction efficiency with low cost  and less environmental impact. 

A  series of inorganic salts with different concentrations were employed to leach  the Ion-adsorption rare earth agglomerates, and the relationship between the  leaching efficiency of rare earth and reagent type was investigated in  unagitated systems. This study showed that ammonium sulfate extracts less  aluminum content than magnesium chloride. Even when magnesium sulfate  (hydrate) extracts less aluminum (impurity in Pregnant Leach Solution) content  than the other lixiviants used in the study, magnesium sulfate extracts less Rare  Earth Elements (REE) compared to the other lixiviants in the same leaching  time, this was mainly attributed to it being a heptahydrate and magnesium  sulfate without the hydrate was much more expensive compared to the prices of  the other leaching reagents. Therefore the lixiviant of preference in terms of  REE extraction from ion adsorption clays in un-agitated systems is in the  order (NH4)2SO4 > MgCl2.6H2O  > NaCl > MgSO4.7H2O.



Chemical Engineering