Sequestration of U(VI) from Acidic, Alkaline, and High Ionic-Strength Aqueous Media by Functionalized Magnetic Mesoporous Silica Nanoparticles: Capacity and Binding Mechanisms

Uranium­(VI) exhibits little adsorption onto sediment minerals in acidic, alkaline or high ionic-strength aqueous media that often occur in U mining or contaminated sites, which makes U­(VI) very mobile and difficult to sequester. In this work, magnetic mesoporous silica nanoparticles (MMSNs) were f...

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Bibliographic Details
Published in:Environmental science & technology 2017-12, Vol.51 (24), p.14330-14341
Main Authors: Li, Dien, Egodawatte, Shani, Kaplan, Daniel I, Larsen, Sarah C, Serkiz, Steven M, Seaman, John C, Scheckel, Kirk G, Lin, Jinru, Pan, Yuanming
Format: Article
Language:English
Subjects:
Adsorption
Aqueous solutions
Binding
Carbonates
Functional groups
Groundwater
INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
Ions
Ligands
Mine wastes
Minerals
Mining
Nanoparticles
pH effects
Saline water
Salts
Sequestering
Silica
Silicon Dioxide
Sorbents
Species
Uranium
Water
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Summary:Uranium­(VI) exhibits little adsorption onto sediment minerals in acidic, alkaline or high ionic-strength aqueous media that often occur in U mining or contaminated sites, which makes U­(VI) very mobile and difficult to sequester. In this work, magnetic mesoporous silica nanoparticles (MMSNs) were functionalized with several organic ligands. The functionalized MMSNs were highly effective and had large binding capacity for U sequestration from high salt water (HSW) simulant (54 mg U/g sorbent). The functionalized MMSNs, after U exposure in HSW simulant, pH 3.5 and 9.6 artificial groundwater (AGW), were characterized by a host of spectroscopic methods. Among the key novel findings in this work was that in the HSW simulant or high pH AGW, the dominant U species bound to the functionalized MMSNs were uranyl or uranyl hydroxide, rather than uranyl carbonates as expected. The surface functional groups appear to be out-competing the carbonate ligands associated with the aqueous U species. The uranyl-like species were bound with N ligand as η2 bound motifs or phosphonate ligand as a monodentate, as well as on tetrahedral Si sites as an edge-sharing bidentate. The N and phosphonate ligand-functionalized MMSNs hold promise as effective sorbents for sequestering U from acidic, alkaline or high ionic-strength contaminated aqueous media.
ISSN:0013-936X
1520-5851
DOI:10.1021/acs.est.7b03778