Letter www.acsami.org
POM Constructed from Super-Sodalite Cage with Extra-Large 24Membered Channels: Effective Sorbent for Uranium Adsorption Yayu Dong,†,‡ Zhimin Dong,†,§ Zhibin Zhang,§ Yunhai Liu,§ Weiwei Cheng,‡ Hao Miao,⊥ Xingxiang He,‡ and Yan Xu*,‡,⊥ ‡
College of Chemistry and Chemical Engineering, State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University, Nanjing 210009, P. R. China § State Key Laboratory Breeding Base of Nuclear Resources and Environment, East China University of Technology, Nanchang 330013, P.R. China ⊥ Coordination Chemistry Institute, State Key Laboratory of Coordination Chemistry, Nanjing University, Nanjing 210093, P. R. China S Supporting Information *
ABSTRACT: A POMs-based sorbent functionalized by phosphate groups: H33Na14MoV24MoVI2(PO4)11O73 has been successfully isolated under hydrothermal conditions. The cooperative assembly of the ring-shaped polyoxometalate structural building unit {P4Mo6} and MoO4 tetrahedra linkers gives rise to an unprecedented supersodalite cage containing approximately spherical cavities with a 8.76 Å diameter. As POMs-based inorganic material, compound 1 was first applied as sorbent to adsorb U(VI) from aqueous solution, exhibiting good stability, high efficiency, and selectivity. The maximum sorption capacity reaches 325.9 mg g−1, which may capture radionuclides through cooperative binding of the phosphate groups. The adsorbed U(VI) could be nearly drastically eluted when using 0.1 M Na2CO3 and the sorption capacity for U(VI) slightly decreased 10.16% through five successive sorption/desorption cycles. This work represents first application of POMs-based inorganic materials as sorbent to adsorb uranium from aqueous solution and provides a feasible approach for the entrapment and recovery of radionuclides. KEYWORDS: POMs, super-sodalite cage, phosphate groups, adsorption, U(VI)
N
nonlinear optics,9 medical,10 magnetic,11 materials science.12 It is mainly because high-nuclearity metal oxides clusters can be interconnected by electrophilic linkers or electrostatic interactions.13 The utilization of these materials so far has largely hinged on nonspecific binding interactions to host molecular guests.14 In 2010, Cronin’s groups utilized POMs-based materials to uptake of Cu cations from solution into the network channels and cavities,15 manifesting that POMs-based materials as solid-phase sorbents will provide a potential avenue for effective entrapment of heavy metal ion or radionuclides. Additionally, some new sorbents such as MOFs functionalized by phosphate groups have been reported.16 These works highlight that the introduction of phosphoric acid groups could be greatly enhanced the affinity of sorbent and U(VI)17 and materials functionalized by phosphate groups will be good candidates for disposing radioisotopes, such as U(VI).18 Therefore, we speculate that the incorporation of phosphate groups and POMs may be a feasible tactic to construct sorbents
uclear power, as the emerging industry, has grown into a mature and significant technology capable of meeting growing energy demand.1 Meanwhile, it also causes serious environmental consequences, in which large amounts of volatile radionuclides such as uranium have been generated, posing a serious threat to the environment and organisms.2 Therefore, the entrapment and recycle of uranium from radioactive wastewater are of great significance considering the view of sustainable utilization of uranium resources and environmental protection.3 Among a variety of technologies,4 adsorption is proved a most economic and practical technology, because of low cost, high efficiency, and flexibility in operation. Consequently, compared with the traditional type of sorbents,5 a major challenge has been the design and construction of novel sorbents. The design and syntheses of functionalized polyoxometalates (POMs)-based materials have triggered widespread attention in the domain of materials science since nanoscale clusters.6 The novel functionalized materials built from inorganic building units POMs molecular precursors not only exert aesthetically fantastic structures and inimitable properties7 but importantly show promise for diverse applications including catalysis,8 © XXXX American Chemical Society
Received: May 31, 2017 Accepted: June 26, 2017 Published: June 26, 2017 A
DOI: 10.1021/acsami.7b07573 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
Letter
ACS Applied Materials & Interfaces
the SOD, the supersodalite cage in this work consists of six 10membered and four 9-membered rings. Strikingly, the symmetry (Oh) of SOD is the same as that of supersodalite cage. The connection of {P4Mo6} units and MoO4 tetrahedra creates six 10-membered ring windows of about 11.66 Å × 4.63 Å instead of the hexagonal or 12-membered ring windows (Figure 2). These “large” windows may provide the feasible
based on POMs. To the best of our knowledge, such materials as sorbent represents the first example of treatment of radionuclide uranium. Taking these factors into account, a POMs-based inorganic framework material functionalized with phosphate group was synthesized by the hydrothermal method. The combination of {P4Mo6} anionic with MoO4 tetrahedra constructs supersodalite cage architecture containing approximately spherical cavities. Strikingly, each cavity captures a phosphate group fixed by the Na cations. Therefore, to explore the functionality of this material, we present detailed studies that compound 1 was used as sorbent to adsorb U(VI) at the batch adsorption tests. As adsorbent based on POMs, compound 1 exhibits high efficient in adsorbing U(VI) ion with a biggish sorption capacity of 325.9 mg g−1 in comparison to other traditional adsorbents, such as graphene oxide nanosheets, carbonaceous nanofiber, HTC-btg, MOF-76, phosphonate-functionalized mesoporous silica, etc. (detailed in Table S6). Moreover, the adsorbed U(VI) could be nearly drastically eluted when using 0.1 M Na2CO3 and compound 1 presents higher selectivity for U(VI) in comparison to other competing metal ions. The results manifest the promise of POMs-based inorganic material for practical treatment of radionuclides uranium. Single-crystal X-ray diffraction revealed asymmetry structure of compound 1 crystallized in Pn3̅m space group, which can be conceptualized as a supersodalite cage containing molybdenum and phosphorus. The assembly process of the cage is illustrated in Figure 1. Six edge-sharing MoO6 octahedra construct a ring
Figure 2. SOD (left); The simplify structure of supersodalite cage (right). Mo atoms are in blue, and phosphorus atoms are in yellow.
channels for the entrapment and recovery of radionuclides from solution into the cavities. Markedly, each “empty” cage possesses approximately spherical cavity with an internal diameter of 8.76 Å. This cavity may be free of radionuclides and the alkali-metal cations Na+ are padded in the cavity as counter cations to counteract the charges of polyoxoanion and further reinforce the structure. Importantly, the other remarkable feature is that a phosphate group occupies the heart of supersodalite cage fixed by Na atoms. The oxygen atom (O9) linked to two Mo atoms from MoO4 tetrahedra give rise to {Mo-O9-Mo} coordination bonds (Figures S3 and S4), bridging two adjacent cages. Therefore, a 3D inorganic supersodalite framework is generated by means of such connection modes, which are arranged in parallel 24-ring channels. The size of cannels is about 9 × 9 Å and may be conducive to the desorption of U(VI) from framework (Figure S5). The size is comparable with NTHU-1 (10.4 Å).23 Especially, phosphate groups not only direct the structure of the resulting framework but impart significant adsorption U(VI) property to the material on account of the special constructional features of compound 1. The pH−zeta potential curves of before and after adsorptions are presented in Figure 3a. With the pH increases, the zeta potential gradually declines, attributing to the mechanisms of the variable charge generation, whereas, the surface negative charges increase because of possessing pHdependent functional groups in compound 1, such as free phosphate group. Phosphate groups are likely protonated in
Figure 1. Assembly process of the cluster. (a) Structure of the cluster {P4Mo6} units; (b) view of the cage containing a 8.76 Å cavity; Mo, blue; P, yellow; MoO6, red.
decorated by four PO4 tetrahedra. Three decorate the ring and the other situates the midpoint. The central PO4 tetrahedron provides three μ3-O bridging the six molybdenums, whereas three other peripheral PO4 groups (the P atoms each with half site-occupancy disorder) connect two Mo by two oxygen atoms. It results in the formation of classics building block {P4Mo6}19 as shown in Figure 1a. Interestingly, each MoO4 tetrahedron (Mo and O atoms with half site-occupancy disorder) serves as a bridge to link three adjacent {P4Mo6} units by three μ2-O atoms, constructing a supersodalite cage (Figure 1b). Notably, it is different from 3D 8-connected pure inorganic framework in the reported literature, which was constructed from four {P4Mo6} units by four {ZnO4} linkers.20 And POMs units in most of porous polyoxometalate -based MOF materials21 are connected by organic ligands. Whereas supersodalite cage in this work is pure inorganic framework. Additionally, no complex organic synthesis is required so that synthesis is flexibility in operation and cost is also low. The simple sodalite (SOD)22 crystallized in the Im3m space group, comprising six 4-rings and eight 6-rings. Compared with
Figure 3. (a) Zeta potentials of before and after adsorption; (b) effect of solution pH on the U(VI) adsorption on compound 1 (m. 0.01 g; V, 50 mL; t, 5 h; C0, 100 mg L−1; T, 298.15 K). B
DOI: 10.1021/acsami.7b07573 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
Letter
ACS Applied Materials & Interfaces acidic conditions, protonated products included HPO42−, H2PO4−, resulting in the augmentation of negative charge cites in compound.24 The zeta potentials of after adsorption decrease from +10.2 to −7.92 mV within the range of 2.5 to 8.0, which are relatively high in comparison with before adsorption complex with range of −8.92 to −37.06 mV. The results illustrate an increase in positive-charge groups in compound 1 after adsorption, demonstrating that the uranium ions were successfully adsorbed onto compound 1. The pH of the solution was an important factor for adsorbing metal ions. Therefore, the stability of compound 1 was first checked at pH value of 3.0−6.0. As shown in Figure S7, PXRD patterns of samples treated at different pH adjusted by HNO3 for 5 h are in agreement with that of the simulated, attesting the skeleton could be reserved under experiment conditions. Figure 3b reveals that the process of U(VI) adsorption strongly depends on pH value: the U(VI) adsorption capacity increase initially then declined as pH value augment. The maximum sorption capacity was about 325.9 mg g−1 at pH 4.5. This tendency is other from the majority of U(VI) adsorbents.25 The higher adsorption capacity is likely attributed to ample phosphate groups and the porosity structure of compound 1, which has a higher affinity for U(VI). The decrease in adsorption at pH > 4.5 could rationalized due to the hydrolysis of uranium into colloidal or oligomeric species ((UO2)2(OH)22+, (UO2)3(OH)5+) as well as the pH-induced changes of the adsorbent surface charge.2 pH 4.5 was the optimum value for subsequent sorption experiments. Hitherto, the adsorption rate becomes a critical role in evaluating the practical applications value of adsorbents. As shown in Figure 4a, the initial sorption rate of the adsorbents
enhance the interaction between the adsorbate and the adsorbent with the increasing U(VI) concentrations.27 The adsorption isotherm was carried out to figure maximum sorption capacity (Supporting Information section S8). According to the linear correlation coefficients in Table S2 and Figure 5a, the sorption of U(VI) onto compound 1
Figure 5. Sorption isotherms of compound 1: (a) fitting curves of Langmuir and Freundlich adsorption isotherms; (b) fitting curves of D-R isotherm.
effectively correlated well with the Langmuir isotherm model (R2 > 0.99), showing that U(VI) sorption onto compound 1 was primarily a monolayer process rather than multilayers. Figure 5b also supports the above results. The value of RL (Table S3) demonstrates that the U(VI) that adsorbed on compound 1 was favorable and irreversible. Moreover, sorption was promoted at lower concentration due to the higher RL value. The experimental data of compound 1 was also described by the D-R adsorption isotherm model (Figure 5b), with a high correlation coefficient of R2 = 0.98, from which the EDR (12.5 kJ mol−1) was within the range of 8−16 kJ mol−1, indicating a chemical adsorption, which are consistent with the kinetic studies.28 The effect of temperature on uranium sorption onto compound 1 was measured at different temperatures. The results are shown in Figure 6. It is clear that the value of
Figure 4. (a) Effect of contact time on U(VI) sorption onto compound 1; (b) pseudo-second-order model (m, 0.01 g; V, 50 mL; C0, 100 mg L−1; pH 4.5; T, 298.15 K).
Figure 6. (a) Effect of temperature on U(VI) sorption onto compound 1; (b) The thermodynamics for U(VI) sorption onto compound 1 (m, 0.01 g; V, 50 mL; C0, 100 mg L−1; pH 4.5).
increased sharply, which is attributes to the coordination interaction between compound 1 and U(VI). Then sorption gradually reached equilibrium after 300 min, it could be interpreted to the limited number of surface adsorptive sites of the adsorbents and intraparticle diffusion controls the adsorption rate.26 The results indicates that phosphate groups in sorbent possesses very significant affinity toward U(VI) The higher correlation coefficient value with the qe,ca2 closer to the qe,exp suggested that the pseudo-second-order model could be used for a better description of the sorption process, see section S7, Table S1, Figure S8a and Figure 4b, implying a dominating chemisorption that could be the rate-controlling step. Figure S9 shows the effect of initial U(VI) concentration on the adsorption. The sorption capacity of compound 1 gradually raised with increasing equilibrium uranium concentrations in the range of the studied concentrations. It could be likely to manifest as an increase in the amount of uranyl ions and
sorption capacity (qe) gradually increased with the increase of temperatures, illuminating that higher temperatures are beneficial for the U(VI) sorption. It is mainly because higher temperature expedites the velocity of molecular movement following the augmentation of the mass transfer rate. Therefore, the diffuse coefficient also increases. The corresponding values of thermodynamic parameters for the sorption of U(VI) were given in section S9 and Table S4. The positive values of ΔHo indicated that the sorption was endothermic, whereas ΔSo > 0 indicated randomness and disorder at the solid and solution interface increased during the sorption process.29 However, ΔGo < 0 confirmed that sorption process was spontaneous and feasible. Moreover, the declining C
DOI: 10.1021/acsami.7b07573 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
ACS Applied Materials & Interfaces
■
value of ΔGo with increasing temperature revealed that sorption is promoted at higher temperatures. Additionally, Figure S10 shows that the sorption capacity of U(VI) on compound 1 is as high as 128.56 mg g−1 at pH 4.5, while it is very low for other metal ions. When pH 4.0, the adsorption capacity decrease about half of that at pH 4.5. The values of selectivity coefficients Kd, SU/M, and Sr are listed in Table S5. Clearly, a higher Kd value testifies stronger affinity and excellent capability of the sorbent. The SU/M values are very high, indicating sorbent possesses a desirable selectivity for U(VI). To evaluate the practical applications value of adsorbents, it is essential to research the regeneration and reuse performance of the adsorbent. Figure S11a shows elution efficiencies in different eluents. Clearly, U(VI) ions could be nearly drastically eluted when using 0.1 M Na2CO3, which easily approximated a desorption percent 98%. The sorption capacity of U(VI) slightly decreased from 325.9 to 292.8 mg g−1 through five successive sorption/desorption cycles (Figure S11b), revealing compound 1 possesses better reusability and presents a superior sorbent for environment remediation of U(VI). Figure 7 display the fundamental motifs investigated for UO22+ binding. We speculate that U(VI) sorption is facilitated
Letter
ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsami.7b07573. Synthesis, single-crystal structure analysis, characterization, supplementary structural figures, PXRD measurements, IR spectrum, crystallographic data, supplementary calculation detail, and crystal refinements (PDF) Crystallographic data for compound 1 (CIF)
■
AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. ORCID
Yan Xu: 0000-0001-6059-075X Author Contributions †
Y.D. and Z.D. contributed equally to this work.
Notes
The authors declare no competing financial interest.
■
ACKNOWLEDGMENTS This work was supported by the NSFC (Grant 21571103, 21301028, 11475044, 41461070, 21561002, 21401022), the Major Natural Science Projects of the Jiangsu Higher Education Institution (Grant 16KJA150005), the Program for Changjiang Scholars and Innovative Research Team in University (Grant IRT13054).
■
REFERENCES
(1) Patzek, T. W.; Croft, G. D. A global coal production forecast with multi-Hubbert cycle analysis. Energy 2010, 35, 3109−3122. (2) Zolfaghari, G.; Esmaili-Sari, A.; Anbia, M.; Younesi, H.; Amirmahmoodi, S.; Ghafari-Nazari, A. Taguchi optimization approach for Pb(II) and Hg(II) removal from aqueous solutions using modified mesoporous carbon. J. Hazard. Mater. 2011, 192, 1046−1055. (3) Liu, J.; Zhao, C. S.; Zhang, Z. B.; Liao, J. L.; Liu, Y. H.; Cao, X. H.; Yang, J. J.; Yang, Y. Y.; Liu, N. Fluorine effects on U(VI) sorption by hydroxyapatite. Chem. Eng. J. 2016, 288, 505−515. (4) Djedidi, Z.; Bouda, M.; Souissi, M. A.; Cheikh, R. B.; Mercier, G.; Tyagi, R. D.; Blais, J. F. Metals removal from soil, fly ash and sewage sludge leachates by precipitation and dewatering properties of the generated sludge. J. Hazard. Mater. 2009, 172, 1372−1382. (5) Sun, Y. B.; Yang, S. T.; Sheng, G. D.; Guo, Z. Q.; Wang, X. K. The removal of U(VI) from aqueous solution by oxidized multiwalled carbon nanotubes. J. Environ. Radioact. 2012, 105, 40−47. (6) Song, Y. F.; McMillan, N.; Long, D. L.; Thiel, J.; Ding, Y. L.; Chen, H. S.; Gadegaard, N.; Cronin, L. Design of hydrophobic polyoxometalate hybrid assemblies beyond surfactant encapsulation. Chem. - Eur. J. 2008, 14, 2349−2354. (7) Müller, A.; Rehder, D.; Haupt, E. T. K.; Merca, A.; Bögge, H.; Schmidtmann; Heinze-Brückner, M. G. Artificial cells: temperaturedependent, reversible Li+-Ion uptake/release equilibrium at metal oxide nanocontainer Pores. Angew. Chem., Int. Ed. 2004, 43, 4466− 4470. (8) Ma, L.; Abney, C.; Lin, W. B. Enantioselective catalysis with homochiral metal−organic frameworks. Chem. Soc. Rev. 2009, 38, 1248−1256. (9) Wang, C.; Zhang, T.; Lin, W. B. Rational synthesis of noncentrosymmetric metal-organic frameworks for second-order nonlinear optics. Chem. Rev. 2012, 112, 1084−1104. (10) Long, D. L.; Tsunashima, R.; Cronin, L. Polyoxometalates: building blocks for functional nanoscale systems. Angew. Chem., Int. Ed. 2010, 49, 1736−1758.
Figure 7. Simplified adsorption mechanism. UO22+ is coordinated in to the oxygen atoms of phosphate groups. Distances between oxygen range from 3.12 to 5.25 Å.
by the cooperative binding of the phosphate groups. Each cage possesses six 10-membered apertures of about 11.66 Å × 4.63 Å and suitable intersorbent distances between oxygen atoms, which is large enough to trap the linear UO22+. Additionally, IR (section S10 and Figure S12) is carried out to clarify UO22+ loaded onto compound 1. After adsorption, a new peak located at 930 cm−1 is typical of the characteristic stretching bond of UO22+, confirming that uranium ions are successfully loaded by compound 1. In summary, we have successfully isolated a POMs-based inorganic material functionalized with phosphate group, which construct from an unprecedented supersodalite cage containing approximately spherical cavities. Meaningfully, it represents the first typical application of POMs-based materials as sorbent. The maximum sorption capacity was about 325.9 mg g−1. The adsorbed U(VI) could be nearly drastically eluted when using 0.1 M Na2CO3 and the sorption capacity slightly decreased from 325.9 to 292.8 mg g−1 through five successive sorption/ desorption cycles. These results not only demonstrate the promise of POMs-based inorganic material for practical treatment of radionuclides uranium but also importantly show this might be a significant step toward the design and synthesis of new sorbent materials based on POMs. D
DOI: 10.1021/acsami.7b07573 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
Letter
ACS Applied Materials & Interfaces (11) Clemente-Juan, J. M.; Coronado, E.; Gaita-Arino, A. Magnetic polyoxometalates: from molecular magnetism to molecular spintronics and quantum computing. Chem. Soc. Rev. 2012, 41, 7464−7478. (12) Fu, H.; Qin, C.; Lu, Y.; Zhang, Z. M.; Li, Y. G.; Su, Z. M.; Li, W. L.; Wang, E. B. An ionothermal synthetic approach to porous polyoxometalate-based metal−organic frameworks. Angew. Chem., Int. Ed. 2012, 51, 7985−7989. (13) Ritchie, C.; Streb, C.; Thiel, J.; Mitchell, S. G.; Miras, H. N.; Long, D. L.; Boyd, T.; Peacock, R. D.; McGlone, T.; Cronin, L. Reversible redox reactions in an extended polyoxometalate framework solid. Angew. Chem., Int. Ed. 2008, 47, 6881−6884. (14) Li, Q. W.; Zhang, W. Y.; Miljanić, O. Š.; Sue, C. H.; Zhao, Y. L.; Liu, L. H.; Knobler, C. B.; Stoddart, J. F.; Yaghi, O. M. Docking in metal-organic frameworks. Science 2009, 325, 855−859. (15) Mitchell, S. G.; Streb, C.; Miras, H. N.; Boyd, T.; Long, D. L.; Cronin, L. Face-directed self-assembly of an electronically active Archimedean polyoxometalate architecture. Nat. Chem. 2010, 2, 308− 312. (16) Carboni, M.; Abney, C. W.; Liu, S. B.; Lin, W. B. Highly porous and stable metal−organic frameworks for uranium extraction. Chem. Sci. 2013, 4, 2396−2402. (17) Knope, K. E.; Cahill, C. L. Homometallic UO22+ diphosphonates assembled under ambient and hydrothermal conditions. Dalton Trans. 2010, 39, 8319−8324. (18) Singh, A.; Catalano, J. G.; Ulrich, K. U.; Giammar, D. E. Molecular-scale structure of uranium(VI) immobilized with goethite and phosphate. Environ. Sci. Technol. 2012, 46, 6594−6603. (19) Peloux, C. D.; Mialane, P.; Dolbecq, A.; Marrot, J.; Riviere, E.; Secheresse, F. Synthesis, crystal structure and magnetic properties of new molybdenum(V) phosphates containing Mn2+ or Co2+ with three dimensional structures directed by the nature of the transition metal. J. Mater. Chem. 2001, 11, 3392−3396. (20) Du, D. Y.; Qin, J. S.; Li, Y. G.; Li, S. L.; Lan, Y. Q.; Wang, X. L.; Shao, K. Z.; Su, Z. M.; Wang, E. B. An unprecedented 3D 8-connected pure inorganic framework based on nanosized {[Na12PO16H24]⊂[P4Mo6O31H6]4}15− clusters and zinc cations. Chem. Commun. 2011, 47, 2832−2834. (21) Du, D. Y.; Qin, J. S.; Li, S. L.; Su, Z. M.; Lan, Y. Q. Recent advances in porous polyoxometalate based metal−organic framework materials. Chem. Soc. Rev. 2014, 43, 4615−4632. (22) Beitone, L.; Huguenard, C.; Gansmüller, A.; Henry, M.; Taulelle, F.; Loiseau, T.; Férey, G. Order−disorder in the supersodalite Zn3Al6(PO4)12 4tren 17H2O (MIL-74): a combined XRD− NMR assessment. J. Am. Chem. Soc. 2003, 125, 9102−9110. (23) Lin, C. H.; Wang, S. L.; Lii, K. H. [Ga2(DETA)(PO4)2]·2H2O (DETA = Diethylenetriamine): a novel porous gallium phosphate containing 24-Ring channels. J. Am. Chem. Soc. 2001, 123, 4649−4650. (24) Xu, X.; Gao, B. Y.; Tan, X.; Yue, Q. Y.; Zhong, Q. Q.; Li, Q. Characteristics of amine-crosslinked wheat straw and its adsorption mechanisms for phosphate and chromium (VI) removal from aqueous solution. Carbohydr. Polym. 2011, 84, 1054−1060. (25) Li, Z. J.; Chen, F.; Yuan, L. Y.; Liu, Y. L.; Zhao, Y. L.; Chai, Z. F.; Shi, W. Q. Uranium(VI) adsorption on graphene oxide nanosheets from aqueous solutions. Chem. Eng. J. 2012, 210, 539−546. (26) Li, B.; Ma, L. J.; Tian, Y.; Yang, X. D.; Li, J.; Bai, C. Y.; Yang, X. Y.; Zhang, S.; Li, S. J.; Jin, Y. D. A catechol-like phenolic ligandfunctionalized hydrothermal carbon: one-pot synthesis, characterization and sorption behavior toward uranium. J. Hazard. Mater. 2014, 271, 41−49. (27) Chen, S. P.; Hong, J. X.; Yang, H. X.; Yang, J. Z. Adsorption of uranium (VI) from aqueous solution using a novel graphene oxideactivated carbon felt composite. J. Environ. Radioact. 2013, 126, 253− 258. (28) Pillewan, P.; Mukherjee, S.; Roychowdhury, T.; Das, S.; Bansiwal, A.; Rayalu, S. Removal of As(III) and As(V) from water by copper oxide incorporated mesoporous alumina. J. Hazard. Mater. 2011, 186, 367−375. (29) Song, Q.; Ma, L. J.; Liu, J.; Bai, C. Y.; Geng, J. X.; Wang, H.; Li, B.; Wang, L. Y.; Li, S. J. Preparation and adsorption performance of 5-
azacytosine-functionalized hydrothermal carbon for selective solidphase extraction of uranium. J. Colloid Interface Sci. 2012, 386, 291− 299.
E
DOI: 10.1021/acsami.7b07573 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
