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

S. Das; C. Tsouris; C. Zhang; J. Kim; S. Brown; Y. Oyola; C. J. Janke; R. T. Mayes; L. J. Kuo; J. R. Wood; G. A. Gill; S. Dai

doi:10.1021/acs.iecr.5b02735

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

S. Das, C. Tsouris, C. Zhang, J. Kim, S. Brown, Y. Oyola, C. J. Janke, R. T. Mayes, L. J. Kuo, J. R. Wood, G. A. Gill, S. Dai

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Abstract

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.

Original language	English
Pages (from-to)	4294-4302
Number of pages	9
Journal	Industrial and Engineering Chemistry Research
Volume	55
Issue number	15
DOIs	https://doi.org/10.1021/acs.iecr.5b02735
State	Published - May 4 2016

Funding

This research was conducted at the Oak Ridge National Laboratory (ORNL) and at the Marine Sciences Laboratory, a part of the Pacific Northwest National Laboratory (PNNL) located in Sequim, WA. Work at ORNL was supported by the U.S. DOE Office of Nuclear Energy, under Contract DE-AC05-00OR22725 with ORNL, managed by UT-Battelle, LLC. The PNNL effort was also supported by the U.S. DOE Office of Nuclear Energy, under Contract DE-AC05-76RL01830 to PNNL.

Funders	Funder number
DOE Office of Nuclear Energy	DE-AC05-00OR22725
Oak Ridge National Laboratory
Pacific Northwest National Laboratory
UT-Battelle	DE-AC05-76RL01830

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10.1021/acs.iecr.5b02735

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Das, S., Tsouris, C., Zhang, C., Kim, J., Brown, S., Oyola, Y., Janke, C. J., Mayes, R. T., Kuo, L. J., Wood, J. R., Gill, G. A., & Dai, S. (2016). Enhancing Uranium Uptake by Amidoxime Adsorbent in Seawater: An Investigation for Optimum Alkaline Conditioning Parameters. Industrial and Engineering Chemistry Research, 55(15), 4294-4302. https://doi.org/10.1021/acs.iecr.5b02735

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

abstract = "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.",

author = "S. Das and C. Tsouris and C. Zhang and J. Kim and S. Brown and Y. Oyola and Janke, {C. J.} and Mayes, {R. T.} and Kuo, {L. J.} and Wood, {J. R.} and Gill, {G. A.} and S. Dai",

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AU - Tsouris, C.

AU - Zhang, C.

AU - Kim, J.

AU - Brown, S.

AU - Oyola, Y.

AU - Janke, C. J.

AU - Mayes, R. T.

AU - Kuo, L. J.

AU - Wood, J. R.

AU - Gill, G. A.

AU - Dai, S.

PY - 2016/5/4

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

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