Cyclic Imide Dioximes: Formation and Hydrolytic Stability

Kang, Sung Ok; Vukovic, Sinisa; Custelcean, Radu; Hay, Benjamin P.

doi:10.1021/ie300492z

Cited by 84 publications

(122 citation statements)

References 43 publications

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“…The formation of carboxylate from amidoxime during KOH conditioning was previously demonstrated on small molecule model compounds. 21 Similar conversion can also be observed using solid-state NMR after treatment of the AF160-2 fiber with KOH at 80°C for 3 h (Figure 7). The signals at 149 ppm and a shoulder centered at 157 ppm ( Figure 7a) are ascribed to cyclic imidedioxime and open-chain amidoxime, respectively.…”

Section: Industrial and Engineering Chemistry Researchsupporting

confidence: 70%

Enhancing Uranium Uptake by Amidoxime Adsorbent in Seawater: An Investigation for Optimum Alkaline Conditioning Parameters

Das

Tsouris

Zhang

et al. 2015

Ind. Eng. Chem. Res.

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A high-surface-area polyethylene-fiber adsorbent (AF160-2) has been developed at the Oak Ridge National Laboratory by radiation-induced graft polymerization of acrylonitrile and itaconic acid. The grafted nitriles were converted to amidoxime groups by treating with hydroxylamine. The amidoximated adsorbents were then conditioned with potassium hydroxide (KOH) by varying different reaction parameters such as KOH concentration (0.2, 0.44, and 0.6 M), duration (1, 2, and 3 h), and temperature (60, 70, and 80°C). Adsorbent screening was then performed with simulated seawater solutions containing sodium chloride and sodium bicarbonate, at concentrations found in seawater, and uranium nitrate at a uranium concentration of ∼7−8 ppm and pH 8. Fourier transform infrared spectroscopy and solid-state NMR analyses indicated that a fraction of amidoxime groups was hydrolyzed to carboxylate during KOH conditioning. The uranium adsorption capacity in the simulated seawater screening solution gradually increased with conditioning time and temperature for all KOH concentrations. It was also observed that the adsorption capacity increased with an increase in concentration of KOH for all the conditioning times and temperatures. AF160-2 adsorbent samples were also tested with natural seawater using flow-through experiments to determine uranium adsorption capacity with varying KOH conditioning time and temperature. Based on uranium loading capacity values of several AF160-2 samples, it was observed that changing KOH conditioning time from 3 to 1 h at 60, 70, and 80°C resulted in an increase of the uranium loading capacity in seawater, which did not follow the trend found in laboratory screening with stimulated solutions. Longer KOH conditioning times lead to significantly higher uptake of divalent metal ions, such as calcium and magnesium, which is a result of amidoxime conversion into less selective carboxylate. Scanning electron microscopy showed that long conditioning times may also lead to adsorbent degradation. ■ INTRODUCTIONCapturing uranium from seawater is a challenging task that requires consideration of chemical, transport, and process design aspects. The concentration of uranium in seawater is on the order of 1.4 × 10 −8 mol L −1 (3.3 ppb) and is the anionic triscarbonato-uranate (VI) [UO 2 (CO 3 ) 3 ] 4− species under the prevailing conditions. 1 The major problems pertaining to the development of a suitable uranium recovery system from seawater are due to the low concentration, the stability of triscarbonato uranate (VI), and the large excess of competing ions. 1−3 Triscarbonato uranate (VI) has a high stability constant that limits the choice of functional groups for uranium recovery from seawater. Poly(acrylamidoxime) (pAO) has been found to be chemically suitable for uranium recovery from seawater. 1−20 However, the major challenge for making uranium recovery economically viable is developing an adsorbent that has a high uranium sorption rate and a high uptake capacity.For this current study, pAO adsorbents have been ...

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Section: Industrial and Engineering Chemistry Researchsupporting

confidence: 70%

Enhancing Uranium Uptake by Amidoxime Adsorbent in Seawater: An Investigation for Optimum Alkaline Conditioning Parameters

Das

Tsouris

Zhang

et al. 2015

Ind. Eng. Chem. Res.

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“…Since NOM such as humic substances can be dissolved in alkaline condition, the observation provides a line of evidence of NOM adsorption on adsorbents in real seawater exposure. According to the NMR results reported by Hay et al., amidoxime molecules are stable in 1 M NaOD (deuterated NaOH) solution for several months at room temperature. An amidoxime‐based polymeric braid adsorbent from ORNL was used for adsorption of uranium from fresh seawater pumped from the Sequim Bay, Washington in a recirculating flume system.…”

Section: Resultsmentioning

confidence: 96%

Bicarbonate Elution of Uranium from Amidoxime‐Based Polymer Adsorbents for Sequestering Uranium from Seawater

et al. 2017

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Uranium adsorbed on amidoxime‐based polyethylene fibers in simulated seawater can be quantitatively eluted using 3 M KHCO3 at 40 °C. Thermodynamic calculations are in agreement with the experimental observation that at high bicarbonate concentrations (3 M) uranyl ions bound to amidoxime molecules are converted to uranyl tris‐carbonato complex in the aqueous solution. The elution process is basically the reverse reaction of the uranium adsorption process which occurs at a very low bicarbonate concentration (∼10−3 M) in seawater. In real seawater experiments, the bicarbonate elution is followed by a NaOH treatment to remove natural organic matter adsorbed on the polymer adsorbent. Using the sequential bicarbonate and NaOH elution, the adsorbent is reusable after rinsing with deionized water and the recycled adsorbent shows no loss of uranium loading capacity based on real seawater experiments.

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“…Interestingly, though the concentration of vanadium (1.9 μg kg –1 , 37 nM)8 is approximately three times the uranium concentration in seawater, it occupies nearly twenty times as many sorption sites as uranium, essentially limiting the sorption capacity for uranium. Moreover, the stripping conditions required to elute the sorbed V( v ) from the sorbent for reuse are much harsher than those used to elute uranium and other cations and ultimately destroy the sorbent 9,10. These factors indicate that vanadium is a particularly problematic element that affects the economic viability of extraction of uranium from seawater using poly(amidoxime) sorbents.…”

Section: Introductionmentioning

confidence: 99%

Structural and spectroscopic studies of a rare non-oxido V(v) complex crystallized from aqueous solution

et al. 2016

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Cyclic Imide Dioximes: Formation and Hydrolytic Stability

Cited by 84 publications

References 43 publications

Enhancing Uranium Uptake by Amidoxime Adsorbent in Seawater: An Investigation for Optimum Alkaline Conditioning Parameters

Enhancing Uranium Uptake by Amidoxime Adsorbent in Seawater: An Investigation for Optimum Alkaline Conditioning Parameters

Bicarbonate Elution of Uranium from Amidoxime‐Based Polymer Adsorbents for Sequestering Uranium from Seawater

Structural and spectroscopic studies of a rare non-oxido V(v) complex crystallized from aqueous solution

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