Selective Uptake of Rare Earths from Aqueous Solutions by EDTA-Functionalized Magnetic and Nonmagnetic Nanoparticles

Abstract

Magnetic (Fe3O4) and nonmagnetic (SiO2 and TiO2) nanoparticles were decorated on their surface with N-[(3-trimethoxysilyl)propyl]ethylenediamine triacetic acid (TMS-EDTA). The aim was to investigate the influence of the substrate on the behavior of these immobilized metal coordinating groups. The nanoparticles functionalized with TMS-EDTA were used for the adsorption and separation of trivalent rare-earth ions from aqueous solutions. The general adsorption capacity of the nanoparticles was very high (100 to 400 mg/g) due to their large surface area. The heavy rare-earth ions are known to have a higher affinity for the coordinating groups than the light rare-earth ions but an additional difference in selectivity was observed between the different nanoparticles. The separation of pairs of rare-earth ions was found to be dependent on the substrate, namely the density of EDTA groups on the surface. The observation that sterical hindrance (or crowding) of immobilized ligands influences the selectivity could provide a new tool for the fine-tuning of the coordination ability of traditional chelating ligands.

Isothermal titration microcalorimetry to determine the thermodynamics of metal ion removal by magnetic nanoparticle sorbents

“…range of pH and water hardness) as well as shown good regenerability and reusability. Though magnetic nanoparticle sorbents have successfully been applied to remove heavy metal ions, 10,[18][19][20][21][22] hydrophobic compounds, [23][24][25] pesticides, 26,27 natural organic matter, 22,28,29 oxyanions 30,31 and emerging organic contaminants, 25,32,33 those studies focused on the synthesis and characterization of physicochemical properties of these engineered nanomaterials, as well as their environmental application. However, the key quantitative thermodynamic data (e.g.…”

On the Extraction of Rare Earth Elements from Geothermal Brines

“…A variety of sorbents show high affinities towards a variety of REEs with good capacities, rapid kinetics, and economics. Although many REE adsorbents have been studied [49][50][51][52][53][54][55][56][57][58][59][60][61], to date, there is no adsorbent material in practical use.…”

Diglycolamic Acid–Grafted Film-Type Adsorbent for Selective Recovery of Rare Earth Elements

“…Many adsorbents for REEs have been studied [7][8][9][10][11][12][13][14][15][16][17]; however, none is in practical use, and the adsorption of dilute REE ions from solutions containing high concentrations of base metal ions is particularly difficult with the adsorbents reported to date.…”