Table 1 Al, Fe, and Th impurities and their effect on REE processing and final products1.

From: Iron, aluminum, and thorium impurity removal from a rare earth element pregnant leach solution using magnesium carbonate

Impurity

Effect on REE processing

Effect on final REE product

Al

Accumulates in solvent extraction circuits and forms emulsions.

Reduces precipitation efficiency of REE oxalates.

Impedes the formation of REE carbonate crystals.

Diminishes the saturation magnetization and anisotropy field of NdFeB magnets.

Fe

Accumulates in solvent extraction circuits and forms emulsions (as Fe(III)).

Decreases the precipitation efficiency of REE oxalates.

Causes undesired discoloration of glasses (e.g., La2O3-B2O3 lenses).

Th

Co-precipitates to some extent with REE double sulfates or oxalates.

Reduces the loading of REEs in solvent extraction.

Requires strict regulations for tailings disposal.

Contains radioactivity, with exposure usually being strictly regulated.

Forms undesirable intermetallic compounds in some magnetocaloric materials.

Back to article page