3 research outputs found
Radiolytic Treatment of the Next-Generation Caustic-Side Solvent Extraction (NGS) Solvent and its Effect on the NGS Process
<div><p>It is shown in this work that the solvent used in the Next Generation Caustic-Side Solvent Extraction (NGS) process can withstand a radiation dose well in excess of the dose it would receive in multiple years of treating legacy salt waste at the US Department of Energy Savannah River Site. The solvent was subjected to a maximum of 50 kGy of gamma radiation while in dynamic contact with each of the aqueous phases of the current NGS process, namely SRS−15 (a highly caustic waste simulant), sodium hydroxide scrub solution (0.025 M), and boric acid strip solution (0.01 M). Bench-top testing of irradiated solvent confirmed that irradiation has inconsequential impact on the extraction, scrubbing, and stripping performance of the solvent up to 13 times the estimated 0.73 kGy/y annual absorbed dose. Stripping performance is the most sensitive step to radiation, deteriorating more due to buildup of p-sec-butylphenol (SBP) and possibly other proton-ionizable products than to degradation of the guanidine suppressor, as shown by chemical analyses.
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Urea-Functionalized M<sub>4</sub>L<sub>6</sub> Cage Receptors: Anion-Templated Self-Assembly and Selective Guest Exchange in Aqueous Solutions
We present an extensive study of a novel class of <i>de novo</i> designed tetrahedral M<sub>4</sub>L<sub>6</sub>
(M = Ni, Zn) cage
receptors, wherein internal decoration of the cage cavities with urea
anion-binding groups, via functionalization of the organic components
L, led to selective encapsulation of tetrahedral oxoanions EO<sub>4</sub><sup><i>n</i>–</sup> (E = S, Se, Cr, Mo,
W, <i>n</i> = 2; E = P, <i>n</i> = 3) from aqueous
solutions, based on shape, size, and charge recognition. External
functionalization with <i>t</i>Bu groups led to enhanced
solubility of the cages in aqueous methanol solutions, thereby allowing
for their thorough characterization by multinuclear (<sup>1</sup>H, <sup>13</sup>C, <sup>77</sup>Se) and diffusion NMR spectroscopies. Additional
experimental characterization by electrospray ionization mass spectrometry,
UV–vis spectroscopy, and single-crystal X-ray diffraction,
as well as theoretical calculations, led to a detailed understanding
of the cage structures, self-assembly, and anion encapsulation. We
found that the cage self-assembly is templated by EO<sub>4</sub><sup><i>n</i>–</sup> oxoanions (<i>n</i> ≥
2), and upon removal of the templating anion the tetrahedral M<sub>4</sub>L<sub>6</sub> cages rearrange into different coordination
assemblies. The exchange selectivity among EO<sub>4</sub><sup><i>n</i>–</sup> oxoanions has been investigated with <sup>77</sup>Se NMR spectroscopy using <sup>77</sup>SeO<sub>4</sub><sup>2–</sup> as an anionic probe, which found the following selectivity
trend: PO<sub>4</sub><sup>3–</sup> ≫ CrO<sub>4</sub><sup>2–</sup> > SO<sub>4</sub><sup>2–</sup> >
SeO<sub>4</sub><sup>2–</sup> > MoO<sub>4</sub><sup>2–</sup> > WO<sub>4</sub><sup>2–</sup>. In addition to the complementarity
and flexibility of the cage receptor, a combination of factors have
been found to contribute to the observed anion selectivity, including
the anions’ charge, size, hydration, basicity, and hydrogen-bond
acceptor abilities
Urea-Functionalized M<sub>4</sub>L<sub>6</sub> Cage Receptors: Anion-Templated Self-Assembly and Selective Guest Exchange in Aqueous Solutions
We present an extensive study of a novel class of <i>de novo</i> designed tetrahedral M<sub>4</sub>L<sub>6</sub>
(M = Ni, Zn) cage
receptors, wherein internal decoration of the cage cavities with urea
anion-binding groups, via functionalization of the organic components
L, led to selective encapsulation of tetrahedral oxoanions EO<sub>4</sub><sup><i>n</i>–</sup> (E = S, Se, Cr, Mo,
W, <i>n</i> = 2; E = P, <i>n</i> = 3) from aqueous
solutions, based on shape, size, and charge recognition. External
functionalization with <i>t</i>Bu groups led to enhanced
solubility of the cages in aqueous methanol solutions, thereby allowing
for their thorough characterization by multinuclear (<sup>1</sup>H, <sup>13</sup>C, <sup>77</sup>Se) and diffusion NMR spectroscopies. Additional
experimental characterization by electrospray ionization mass spectrometry,
UV–vis spectroscopy, and single-crystal X-ray diffraction,
as well as theoretical calculations, led to a detailed understanding
of the cage structures, self-assembly, and anion encapsulation. We
found that the cage self-assembly is templated by EO<sub>4</sub><sup><i>n</i>–</sup> oxoanions (<i>n</i> ≥
2), and upon removal of the templating anion the tetrahedral M<sub>4</sub>L<sub>6</sub> cages rearrange into different coordination
assemblies. The exchange selectivity among EO<sub>4</sub><sup><i>n</i>–</sup> oxoanions has been investigated with <sup>77</sup>Se NMR spectroscopy using <sup>77</sup>SeO<sub>4</sub><sup>2–</sup> as an anionic probe, which found the following selectivity
trend: PO<sub>4</sub><sup>3–</sup> ≫ CrO<sub>4</sub><sup>2–</sup> > SO<sub>4</sub><sup>2–</sup> >
SeO<sub>4</sub><sup>2–</sup> > MoO<sub>4</sub><sup>2–</sup> > WO<sub>4</sub><sup>2–</sup>. In addition to the complementarity
and flexibility of the cage receptor, a combination of factors have
been found to contribute to the observed anion selectivity, including
the anions’ charge, size, hydration, basicity, and hydrogen-bond
acceptor abilities