“…The positive values of Δ H 0 indicate an endothermic adsorption process, which is in accordance with the fact that the adsorption is facilitated at high temperature, this corresponds to the result in Figure 12 . A probable interpretation for the positive enthalpy comes from the breakthrough of the hydration sheath and the ionic atmosphere around U(VI) before adsorption [ 1 ]. The energy needed for this process exceeds the energy released when the ions are attached to the solid surface, thus a high temperature is favored.…”
Section: Resultsmentioning
confidence: 99%
“…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. [ 1 , 2 ]. Among them, 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.…”
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.
“…The positive values of Δ H 0 indicate an endothermic adsorption process, which is in accordance with the fact that the adsorption is facilitated at high temperature, this corresponds to the result in Figure 12 . A probable interpretation for the positive enthalpy comes from the breakthrough of the hydration sheath and the ionic atmosphere around U(VI) before adsorption [ 1 ]. The energy needed for this process exceeds the energy released when the ions are attached to the solid surface, thus a high temperature is favored.…”
Section: Resultsmentioning
confidence: 99%
“…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. [ 1 , 2 ]. Among them, 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.…”
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.
“…This was due to [UO 2 (CO 3 ) 2 ] 2− and [UO 2 (CO 3 ) 3 ] 4− etc . predominating in the presence of CO 2 , leading to a reduction in adsorption efficiency 51 .Figure 5Effect of initial pH on the adsorption capacity (T = 298 K, V = 20 mL, m = 0.01 g, C 0 = 100 mg L −1 ).…”
Section: Resultsmentioning
confidence: 99%
“…9a,b, the C@Ni-Al LDH HSS composite exhibited better selectivity for U(VI) adsorption than Ni-Al LDH HSS, maintaining a removal rate of up to 90% in the existence of competing ions. Table 3 listed the distribution coefficients (K d ) of each ions 51 . The values of K U d-C@Ni-Al LDH HSS (14866 mL g −1 ) and K U d-Ni-Al LDH HSS (7268 mL g −1 ) were markedly higher than the K M d values of the other metal ions (M = Zn, Ba, Ca, Mg, Ni, Sr, Co, Fe, Na, V and K).…”
In this paper, a double hollow spherical shell composite modified with layered double hydroxide (C@Ni-Al LDH HSS) was fabricated for uranium(VI) (U(VI)) adsorption. Various batch experiments were carried out to investigate the influence of pH, concentration, time and coexistence ion on extraction. The results showed that the adsorption processes of U(VI) onto C@Ni-Al LDH HSS were spontaneous and endothermic and closely followed pseudo-second-order and Langmuir isotherm models. The equilibrium time and maximum adsorption capacity of C@Ni-Al LDH HSS was 360 min and 545.9 mg g
−1
. FT-IR and XPS analyses proved that the adsorption behavior was primarily attributed to the strong interaction between oxygen-containing functional groups and U(VI). Moreover, the extraction of trace U(VI) (μg L
−1
) in artificial and natural seawater was also studied. The results showed that C@Ni-Al LDH HSS provided a promising application for the efficient extraction of U(VI) from seawater.
“…Previous studies indicated that amidoximation 21,77,[108][109][110][111][112][113][114][115][116] 33-43 of PAN led to uranyl uptake that was dependent on pH, and additional gains in U extraction efficiency were achieved using high surface area to volume nanomaterials 117,118 and electrospun fibers. 21,119,120 Here, high , and spectra are similar to previous literature reports.…”
Section: A31 Characterization Of and Uranyl Uptake On Pan And Ao-pamentioning
Uranium contamination in drinking water sources, such as ground or surface water, poses a potential health risk. In areas, such as the Navajo Nation, uranium levels can be found at concentrations ~300 times higher than the maximum concentration limit (MCL) set by the Environmental Protection Agency (EPA) of 30 µg/L. Exposure to these contaminated waters can result in elevated uranium concentrations within the body even after several months of eliminating the source. Inside the body uranium is a nephrotoxin (damages the kidney) and has been linked to cancer among other health problems. Reducing these health risks towards individuals requires methods for cleaning uranium from aqueous systems and sensing it within water and body fluids for biomonitoring. The objective of this work was to synthesize, characterize, and test electrospun polymer nanofiber mats capable of extracting uranium from water with applications in sensing and/or point of use (POU) treatments devices. Materials were synthesized with a suite of functional groups capable of extracting uranium from aqueous systems such as amidoxime, phosphonic acids, and quaternary ammonium salts (QAS) then characterized to evaluate materials physical and chemical traits. Batch uptake studies evaluated materials uptake rates, efficiency at varying pH's, and ability to remove uranium over a range of initial concentrations. Flow through studies assessed materials abilities to be used as a POU treatment technology for removing uranium from drinking water.
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