DOPO-Modied Cellulose Microsphere: Preparation and Application for Selective Adsorption U(VI) under Acidic Solutions

29 Effective radioactive wastewater disposal is of great significance to the wide use of nuclear 31 dimethyneimino)] diphenol (t-DOPO) was used to modify microcrystalline cellulose microsphere (t- 32 DOPOR) to further enhance it affinity toward U(VI) through radiation method. The t-DOPOR were 33 characterized for structural, morphological, and thermal properties by FTIR, SEM and TGA, which prove 34 that t-DOPO is successfully modified on cellulose. Combination the advantage of cellulose and t-DOPO, 35 t-DOPOR possessed abundant functional group (-OH, -NH and P=O), and exhibited extremely strong 36 affinity toward U(VI) with a maximum adsorption capacity of 51.51 mg/g at pH 3. Particularly, A large 37 distribution, K dU , up to 2.54×10 4 mL g −1 is found, implying extremely strong affinity toward U(VI) than 38 Ln(III) (La(III), Eu(III), Dy(III), Yb(III)) at the binary system. Dynamic column experiment confirmed 39 that t-DOPOR could separate selectively U(VI) in column experiment. In addition, even in the simulated 40 groundwater trace amount of U(VI) was also eliminated efficiently by t-DOPOR. Lastly, the adsorption 41 mechanism elaborated by XPS analysis was inner-sphere surface complexation between U(VI) and -OH, 42 -NH and P=O groups of t-DOPOR. Overall, the synthesized t-DOPOR may be utilized as a promising 43 adsorbent for separation and remediation of U(VI) from wastewater. U(VI) from 103 contaminated groundwater was also carried out. The adsorption mechanism of U(VI) on t-DOPOR was 104 highlighted by XPS. This work is expected to look for a powerful and high selective adsorbent for 105 removal of U(VI) from radioactive wastewater.


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With the development of nuclear technology, an increasing number of radioactive wastes have been 57 released into the environment (Ding et al. 2015). Uranium, a major resource of nuclear fuel, is inevitably 58 discharged with the release of radioactive wastes, which can pose serious health risks to human beings 59 due to its biological toxicity and high radioactivity (Yuan et al. 2017). Therefore, from the standpoints of 60 environmental protection, it is crucial to eliminate the uranium from wastewater.

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Various techniques, such as ion exchange, liquid-liquid extraction, chemical precipitation, filtration,  to prepare phosphate-based adsorbents, which showed excellent ability in chelating metals.

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The structural, morphological, and thermal properties of t-DOPOR was investigated through various 99 characteristic methods like FTIR, SEM and TGA, and the adsorption performance of t-DOPOR toward 100 U(VI) were systematically investigated under different environmental factors (solution pH, contact time, 101 ionic strength, competitive metal ions, and so on). In addition, the investigation of dynamic column 102 experiment from simulated radioactive wastewater and the removal of the trace amount of U(VI) from 103 contaminated groundwater was also carried out. The adsorption mechanism of U(VI) on t-DOPOR was 104 highlighted by XPS. This work is expected to look for a powerful and high selective adsorbent for 105 removal of U(VI) from radioactive wastewater.

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The TG analysis was performed within 0-800 °C at a heating rate of 10 °C/min under air atmosphere.

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The XPS was conducted by using monochromatic Al Ka radiation and low energy electron flooding for

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The adsorption amount of U(VI) (qe, mg/g) and removal efficiency (E, %) by t-DOPOR were 144 calculated by the initial (Co, mg/L) and equilibrium concentration of U(VI) (Ce, mg/L) as following Eq.

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Where V and m was the volume of U(VI) solution and the weight of t-DOPOR, respectively.

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The distribution coefficient (Kd, mL/g) and separation factor (SF) for the adsorbent were calculated 163 Nd(III)) was prepared and used as feed solution. The velocity of space (SV) was regulated at 19.32 h −1 .

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The effluent sample was collected at regular intervals and analyzed for metal ions using ICP.   The effect of the contact time on t-DOPOR toward adsorption U(VI) at pH 5.0 is depicted in Fig.   242 3b. The adsorption efficiency of U(VI) increased rapidly at 6 h and then gradually reached the maximum 243 at 10 h. To investigate the controlling mechanism of the adsorption process, pseudo-first-order and 244 pseudo-second-order were used to evaluate the experimental data. As shown in table S1, the highest

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The separation of actinides from lanthanides is an important challenge for the processing of 311 radioactive water. Herein, the effect of lanthanides ions on t-DOPOR for U(VI) adsorption in the binary 312 system was investigated at various pH. Among the experiment, La 3+ was the representative of light 313 lanthanides, Eu 3+ , Dy 3+ were the representatives of middle lanthanides, and Yb 3+ was the representatives 314 of heavy lanthanides. As shown in Fig. 5, t-DOPOR could efficiently adsorb U(VI) ions and rarely adsorb 315 other lanthanide ions (La(III), Eu(III), Dy(III), Yb(III)) when pH < 3. As shown in Fig. 5a, at pH=3 (Table 2).

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In summary, t-DOPOR can yield good separation of U(VI) from other lanthanides ions, suggesting 329 that t-DOPOR could be used as potential adsorbent in separation of actinides ions from lanthanides ions 330 in the practical industrial.

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The XPS analysis was adopted to further investigate the adsorption mechanism between t-DOPOR 370 and U(VI). After the adsorption of U(VI), a strong double U 4f peaks was appeared in the spectrum of t-371 DOPOR (Fig. 7a), indicating the U(VI) adsorbed by t-DOPOR. The U 4f peak could be resolved into 372 two peaks at 392.82 eV (U 4f 5/2) and 381.93 eV (U 4f 7/2) (Fig. S3).

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The fitting of P 2p and O 1s, N 1s spectra could deduce the specific functional group that coordinated 374 with U(VI). The high-resolution P 2p spectrum (Fig. 7b) was decomposed into two peaks at 133.04, 375 132.20 eV, which are assigned to P 2p 1/2 and P 2p 3/2, respectively. The peaks of P 2p 1/2 and P 2p 3/2 were 376 shifted to a higher energy after U(VI) uptake, suggesting that the P-related functional group plays a