11 research outputs found
Identification and Exploration of Elementary School Teacher Misconception in Mathematical Learning
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 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 η<sup>2</sup> 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