The effect of phosphonates on lanthanide separation for surface-grafted porous zirconia

Abstract

The effect of phosphonate groups on selective lanthanide sorption for a series of inorganic–organic hybrid materials was investigated. Four functional ligands with an increasing number of aminomethylenephosphonate groups were attached to the porous zirconia matrix via the post-synthetic grafting method. Successful surface grafting was confirmed by FTIR and ³¹P MAS-NMR spectroscopies. All the synthesized hybrids showed a lanthanide uptake of about 100 μmol g⁻¹ at pH 3. The sorption studies revealed that the hybrids of ligands with a larger number of phosphonate groups possess higher selectivity, as one with the largest number showed a separation factor of over 80 for La³⁺ and Lu³⁺. Fixed-bed column experiments also demonstrated the materials’ favored uptake of Lu³⁺ over La³⁺ at pH 3, in addition to the reusability and applicability to the actual separation settings. These results propose strategies for the selection of organic ligands for hybrid sorbent synthesis.