Extraction of Dysprosium Ions with DTPA Functionalized Superparamagnetic Nanoparticles Probed by Energy Dispersive X-ray Fluorescence and TEM/High-Angle Annular Dark Field Imaging

Abstract

The extraction of dysprosium (Dy3+) ions from aqueous solution was carried out successfully, using magnetite (Fe3O4) nanoparticles functionalized with diethylenetriaminepentaacetic acid (MagNP@DTPA). The process was monitored by energy dispersive X-ray fluorescence spectroscopy, as a function of concentration, proceeding according to a Langmuir isotherm with an equilibrium constant of 2.57 × 10-3 g(MagNP) L-1 and a saturation limit of 63.2 mgDy/gMagNP. The presence of paramagnetic Dy3+ ions attached to the superparamagnetic nanoparticles led to an overall decrease of magnetization. By imaging the nanoparticles surface using scanning transmission electron microscopy equipped with high resolution elemental analysis, it was possible to probe the binding of the Dy3+ ions to DTPA, and to show their distribution in a region of negative magnetic field gradients. This finding is coherent with the observed decrease of magnetization, associated with the antiferromagnetic coupling between the lanthanide ions and the Fe3O4 core.

Superparamagnetic Maghemite-Based CdTe Quantum Dots as Efficient Hybrid Nanoprobes for Water-Bath Magnetic Particle Inspection

“…It should be noted that the most common magnetic materials are based on iron oxide nanoparticles constituted by magnetite (Fe 3 O 4 ) and maghemite (γ-Fe 2 O 3 ). They exhibit strong superparamagnetic behavior in the presence of a magnetic field and their colloidal suspensions (also referred as ferrofluids) play an important role in biotechnology, medicine − as well as in the recent advances in mineral processing based on magnetic nanohydrometallurgy. − Although maghemite has a slightly smaller (∼25%) magnetic moment as compared with magnetite, it is more stable in air and has the advantage of exhibiting a much lower optical absorption in the visible region. In fact, in magnetite there are O 2– → Fe­(III) charge-transfer and Fe­(II) → Fe­(III) intervalence transitions spanning all the visible region, imparting a typical black color.…”

Green Processing of Strategic Elements Based on Magnetic Nanohydrometallurgy

“…61 An important observation is that the red spots representing the dysprosium ions are located over the yellow stain, comprising the DTPA ligand, as expected from the capture of the lanthanide ion by the complexing agent.…”

“…We have already proposed a rather simple and didactic approach, based on external weighing in the presence of a magnetic field, using an analytical balance, 61,63 and a versatile LEGO  toy setup. The typical arrangement involved a non magnetic assembly positioned on the balance plate, using a diamagnetic cantilever (nuclear magnetic resonance, NMR, or electron paramagnetic resonance, EPR, tube) to support the sample tube, as shown in Figure 5.…”

“…64 By changing the distance from the magnet, the kinetics and the relative weight at the equilibration point are strongly affected by the magnetic field as predicted by equation 13, the magnetophoretic rates decrease at longer distances from the magnet. 61 Magnetophoresis has been successfully applied 61 to the capture of Dy 3+ ions by the NP@DTPA nanoparticles ( Figure 5). …”

“…The anti-ferromagnetic coupling has also been probed and confirmed using the vibration magnetometer equipment, as reported in the literature. 61 …”