Design and synthesis of chelating diamide sorbents for the separation of lanthanides

A nanoporous sorbent designed around chelating iminodiacetamide (“IDA-Amide”) moiety was made on mesoporous silica (MCM-41) and evaluated for lanthanide separations (Ce3+, Nd3+, Eu3+, Gd3+, and Lu3+). The effects of solution pH on lanthanide binding were studied, as well as sorption kinetics, and competition from other metal ions. The IDA-Amide SAMMS® demonstrated an interesting difference in the kinetics of sorption of the lanthanide ions in the order of Lu3+ > Eu3+ > Gd3+ > Nd3+ > Ce3+. The close proximity of the ligands in the IDA-Amide SAMMS® may allow for multiple metal–ligand interactions (“macromolecular chelation”).