Abstract
The β-cyclodextrin-graft-(maleic anhydride-co-acrylonitrule) copolymer (β-CD-g-(MAH-co-AN)) synthesized through radical polymerization reactions of β-cyclodextrin (β-CD) with maleic anhydride (MAH) and acrylonitrule (AN) in the special monomer proportion, chemically modify with amidoxime groups to obtained the new adsorbent, which was terms as amidoxime-functionalized β-cyclodextrin-graft-(maleic anhydride-co-acrylonitrule) copolymer (β-CD-g-(MAH-co-AO)). Based on the characteristic results of Fourier transform infrared spectra (FTIR), scanning electron microscopy (SEM), X-ray Diffraction (XRD), and thermalgravity analysis (TGA) techniques, the grafted nitrile groups were successfully converted to amidoxime groups by reaction with hydroxylamine. In this report, the influence of different factors such as pH value and ionic strength, solid-liquid ratio, contact time, initial U(VI) concentration, and temperature on adsorption was investigated by a batch adsorption experiment. The adsorption process fitting results show that the adsorption followed the Langmuir isotherm model and the maximum adsorption capacity was 0.747 g/g at pH 4.0. In addition, the regeneration performance was investigated by varying the concentration of eluent, temperature, and contact time. Under the desorption condition of 0.10 M HNO3, the adsorbents can be reused 12 times in the case that the adsorption capacity was not significantly reduced. The functionalized copolymer exhibits high selectivity under circumstance of other co-existing ions is present in the solution.
Highlights
In recent years, the adsorption method has been widely discussed in the extraction of uranium from seawater on account of it be “cost-effectively” and “environmentally friendly”
The synthesis of adsorbents consists of two steps: (1) Figure 1 shows a schematic illustration for the preparation of β-CD-g-(MAH-co-AN). β-CD
FT-IR analysis was conducted as follows: A characteristic bands of the glucopyranose unit at 947 cm−1, the width peak at the wave number of 3365 cm−1 is assigned to the O–H in β-cyclodextrin [23]
Summary
The adsorption method has been widely discussed in the extraction of uranium from seawater on account of it be “cost-effectively” and “environmentally friendly”. Various adsorbents have been investigated extensively in order to minimize or avoiding the use of other expensive and complex treatment technologies, such as chemical precipitation, ion exchange, membrane filtration, etc. Organic and inorganic solid adsorbents which with the functional group of phosphoric acid, salicylic acid, aminocarboxylic acids, amino-phosphoric acids and hydroxyquinolines, have been attracted the attention of the scientists, by the reason of their affinity toward uranium species. There is a large amount of uranium in seawater, but the low concentration, the high salinity and the interference of the coexistence ion make it extremely challenging to adsorption. A retraction notice was published on 25 November 2020 in Polymers 2020, 12, 2782; doi:10.3390/polym12122782
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