The mechanism of REE ion adsorption by diglycolamic acid ligands was investigated.
Ether oxygen atoms in the ligands played a crucial role in REE ion adsorption.
Amide oxygen atoms in the ligands also participated in REE ion adsorption.
Exchange of the protons in the carboxylic acid group for REE ions also played a role.
Tridentate chelation by the diglycolamic acid ligands conferred high REE selectivity.