New lixiviant liberates light REEs from insoluble hydroxide mixture

combination image of diagram of chemical compound and a bar chart showing precision leaching of REEs from caustically cracked RE(PO4)3 (RE(OH)3) after 26 h at RT. Top, pH 8.6: The new lixiviant acyclopa enables selective dissolution of large REEs from the hydroxide mixture, whereas the conventional chelator EDTA fails to demonstrate any selectivity.
Precision leaching of REEs from caustically cracked RE(PO4)3 (RE(OH)3) after 26 h at RT. Top, pH 8.6: The new lixiviant acyclopa enables selective dissolution of large REEs from the hydroxide mixture, whereas the conventional chelator EDTA fails to demonstrate any selectivity.

CMI researchers at Oak Ridge National Laboratory conducted the research for this highlight

Innovation 
Develop chelators that can selectively recognize and leach large over small rare earth elements (REEs) from mineral sources.

Achievement

  • Selective leaching of light, large REEs from caustically cracked synthetic REE phosphate (REE hydroxide) by a new size-selective lixiviant, acyclopa.
  • Single-pass separation factor (SF) of 295 between La and Y, large and small REEs, respectively, that are abundant in monazite and xenotime minerals.

Significance and Impact

  • Paves the way towards extracting individual REEs selectively from RE minerals, eliminating the use of non-selective brute-force leaching methods (e.g., strong mineral acid dissolution) and reducing reliance on downstream energy-intensive solvent extraction for REE separation.
  • Next step: optimize leaching conditions to further increase SFs; develop 2nd generation derivatives with higher leaching capacity.

Hub Target Addressed 
Unlocking unconventional resources; highly selective separation from complex sources; intra-REE separation.

bar chart showing Bottom, pH 9.2: Increasing the solid loading in each sample significantly increases separative leaching of La from Y by acyclopa, resulting in higher La/Y separation factors (SFs) approaching 300!
pH 9.2: Increasing the solid loading in each sample significantly increases separative leaching of La from Y by acyclopa, resulting in higher La/Y separation factors (SFs) approaching 300!