Molecular insights into the selective action of a magnetically removable complexone-grafted adsorbent

Abstract

The binding and release of trivalent rare earth element (REE) cations (Dy(3+), Nd(3+) and La(3+)) from solutions by a new fully characterized magnetic nano adsorbent material, consisting of iminodiacetic acid ligand (H2IDA) grafted onto SiO2 covered γ-Fe2O3 nanoparticles, was investigated. The nano adsorbent revealed a slightly higher capacity towards heavier REE and appreciable selectivity, especially on desorption. It was found that the composition of the surface complex was RE(3+) : L = 1 : 1. The complexation of the molecular H2IDA with RE(3+) in this ratio under non-basic conditions was therefore investigated by X-ray crystallography to produce relevant molecular models. Unexpectedly big differences in coordination numbers and binding mode of IDA along with distinct analogies in packing of the ligand molecules in the obtained 2D-coordination polymer structures provided valuable insights into possible reasons for the observed selectivity.

Elaboration of Luminescent and Magnetic Hybrid Networks Based on Lanthanide Ions and Imidazolium Dicarboxylate Salts: Influence of the Synthesis Conditions

“…The chloride anion is present in the cavities of the network and is involved in hydrogen bonds with the coordinated water molecules (Figure 8b). [Cl] is reminiscent of that reported in other structures involving lanthanide ions (La 3+ or Dy 3+ ) and linear imino diacetic acid [37]. In the latter, a "pillared" structure was observed, the ligand linking lanthanide layers; while in the present case, due to the geometry of the 1,3-carboxymethylimidazolium ligand, a staircase linking is observed between adjacent chains.…”

Unusual seeding mechanism for enhanced performance in solid-phase magnetic extraction of Rare Earth Elements

“…As it can be observed in Table 1, the high uptake observed by EDS analysis is confirmed by complexometric titration. In the same molar ratio REE: ligand as previously reported for neutral conditions36, the observed capacity was almost three times higher, and therefore on a logical further step, the initial concentration of Nd was increased in order to check if this lead to an improved efficiency. Indeed the uptake could be more than 20 times higher than what was observed at neutral pH, where the mechanism was governed by concerted action between the terminal carboxylic groups of the ligand and the REE cations.…”

“…In our previous study36, we investigated the interaction between an iminodiacetic acid organosilane derivate attached onto the surface of core-shell magnetic nanoparticles and REE cations in solution. Our initial hypothesis was that REE cations should chelate with the organic ligand, assuming that the nitrogen atoms would be involved in the chelation via their free electron pair.…”

“…The obtained Fe 3 O 4 NPs were spherical with an average diameter of about 12 nm, according TEM analysis and a specific surface area of about 96 m 2  g −1 36.…”

“…For industrial applications, the adsorbent needs to be easily removable. This can be achieved using magnetic silica based nanoadsorbents, recently reported by our group36. It has been demonstrated that solid inorganic or hybrid nanoadsorbents were reasonably efficient for REE adsorption, being comparable to, for example, ion-exchange resins at neutral pH2428.…”