Efficient Removal of Cationic and Anionic Radioactive Pollutants from

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Efficient Removal of Cationic and Anionic Radioactive Pollutants from Water Using Hydrotalcite-Based Getters Arixin Bo,† Sarina Sarina,*,† Hongwei Liu,‡ Zhanfeng Zheng,§ Qi Xiao,† Yuantong Gu,† Godwin A. Ayoko,† and Huaiyong Zhu† †

School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, Brisbane, Queensland 4001, Australia ‡ Australian Centre for Microscopy and Microanalysis, The University of Sydney, Sydney, New South Wales 2006, Australia § Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan, Shanxi 030001, China S Supporting Information *

ABSTRACT: Hydrotalcite (HT)-based materials are usually applied to capture anionic pollutants in aqueous solutions. Generally considered anion exchangers, their ability to capture radioactive cations is rarely exploited. In the present work, we explored the ability of pristine and calcined HT getters to effectively capture radioactive cations (Sr2+ and Ba2+) which can be securely stabilized at the getter surface. It is found that calcined HT outperforms its pristine counterpart in cation removal ability. Meanwhile, a novel anion removal mechanism targeting radioactive I− is demonstrated. This approach involves HT surface modification with silver species, namely, Ag2CO3 nanoparticles, which can attach firmly on HT surface by forming coherent interface. This HT-based anion getter can be further used to capture I− in aqueous solution. The observed I− uptake mechanism is distinctly different from the widely reported ion exchange mechanism of HT and much more efficient. As a result of the high local concentrations of precipitants on the getters, radioactive ions in water can be readily immobilized onto the getter surface by forming precipitates. The secured ionic pollutants can be subsequently removed from water by filtration or sedimentation for safe disposal. Overall, these stable, inexpensive getters are the materials of choice for removal of trace ionic pollutants from bulk radioactive liquids, especially during episodic environmental crisis. KEYWORDS: hydrotalcite, radioactive waste, cation removal, anion removal, water cleaning

1. INTRODUCTION Radioactive wastes are the byproducts generated in nuclear power stations, nuclear weapon tests, mining industries, and medical research.1−6 Exposure to radioactive surroundings can lead to serious consequences on both human health and the environment.7 The U.S. Environmental Protection Agency has documented 90Sr (half-life: 28.9 years) as the most frequently detected radioactive isotope in the ecosystem and groundwater around nuclear facilities.8 Its traits such as high fission yield (5− 6% from slow-neutron fission of 235U), propensity for generation of penetrating ionizing radiation (β and γ), and tendency to act as Ca2+ substitute in the bone structure are of severe concern.9 Reports also suggest 140Ba2+ as another radioactive hazard10 whose biochemical behavior is similar to that of strontium,11 and its ionic diameter resembles that of 226 2+ 12 Ra . For anion pollutants, radioactive iodine with half-life time of around 8 days (131I) to 1.6 × 107 years (129I) can cause serious damage to the human thyroid because the organ collects iodides nonselectively.13 Therefore, timely removal of these radioactive ions from contaminated waters is extremely crucial. Ion exchange is an effective process for the removal of ionic wastes.14−17 Nevertheless, the ion exchange process requires © XXXX American Chemical Society

diffusion of the ions in the ion-exchangeable materials, which takes a considerable amount of time and may limit their application in water treatments. In addition, ion exchange is generally a reversible process, which means the toxic ions could be released from the solid materials to aqueous solutions and cause secondary pollution. Alternatively, precipitation is an effective process that is widely used for separating target ions from liquids. It has the merits of simplicity, speed, and low operation cost; however, it requires a high concentration of at least one component of the precipitates. It is thus regarded as an unviable approach for trace ions removal from water.7 Most importantly, the recovery issue exists when the precipitates are fine nanoparticles (particles size ≪ 100 nm) since it is extremely difficult to separate them from a large quantity of water. Consequently, more efficient radioactive hazard getters are needed especially during and after emergency pollutant leakage. Hydrotalcite (with a formula of [Mg6Al2(OH)16]CO3· mH2O) is a layered double hydroxide (LDH) that possesses Received: April 18, 2016 Accepted: June 9, 2016

A

DOI: 10.1021/acsami.6b04632 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX

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ACS Applied Materials & Interfaces positively charged layers of mixed hydroxides (Mg2+ and Al3+) with carbonate anions on the surface and between the layers.18,19 Generally, LDH materials are applied for removal of anion pollutants from aqueous solution by its anion exchange ability.20−23 The ability of HT to capture certain heavy metal cations is reported in literature but research on cation removal by HT is not comprehensive and the results vary greatly by 10 to 100 order of magnitudes.24,25 In the present work, we explored the ability of both HT and calcined HT to capture radioactive cation species (Sr2+ and Ba2+) and found that HT material after calcination outperformed pristine HT in cation removal ability. For the removal of Sr2+, HTbased getters have higher uptake capacity (2.84 mmol g−1) compared with the heatedly investigated cation exchangers such as titanate ( 8), Ba2+ and Sr2+ cannot exist as free ionic state, and the resulting fine precipitates are extremely hard to recover. In contrast, in a low pH environment (pH < 4), HT species become unstable as Al and Mg are dissolved into the solution, causing HT structural deformation.33 Therefore, HTbased getters are suitable candidates for radioactive cation removal in slightly acidic to neutral solutions. It is noted that 90 2+ Sr cations are the major activities of the acidic waste generated during the recovery of 99Mo from the dissolution of irradiated, weakly enriched UO2 targets.34 The anion removal performance of the HT-Ag anion getter is compared with that of pristine HT. It can be seen from Figure 1E that the I− ion removal ability of silver species loaded HT is distinctively different from that of HT. Evidently, the loaded silver species can effectively remove I− ions from aqueous solutions, and the maximum I− uptake amount is 495 mg g−1 (3.89 mmol g−1). Confirming the amount of Ag (5.14 mmol g−1, as summarized in Table S2) on the HT-Ag getter, its I− capturing efficiency is around 76%. In comparison, I− removal by anion exchange with the interlayer CO32− ions on HT is negligible. The bar chart in Figure 1F shows the corresponding I− ion removal percentage under different concentrations where nearly 300 mg/L of I− is completely removed from the solution using HT-Ag. In contrast, it is difficult for the monovalent I− ions to replace bivalent CO32− ions within the HT getter. The EDS elemental analysis of a HT-Ag getter particle after I− removal clearly shows the presence of both Ag and I at the surface of HT-Ag (Figure 1H). X-ray diffraction (XRD) patterns of the samples (Figure 2) show that calcined HT lost the layered structure and has a poor crystalline structure as indicated by the broad peaks. Water molecules are removed from HT during calcination, turning it to a mixture of aluminum and magnesium oxide.23 The resulting calcined HT presents smaller particle size since the calcination eliminated the carbonate anions and water molecules inside and outside the HT layers, causing dehydration of the HT layers. It can also be seen from the XRD patterns that the calcined HT restored the layered structure after being dispersed in aqueous solutions due to the

Figure 2. XRD patterns of HT, calcined HT, and HT-Ag getters before and after their usage for removal of ionic pollutants (Sr2+, Ba2+ and I−). Panel A shows the XRD patterns of the samples before and after they were used for Sr2+ and Ba2+ cations removal. The characteristic peaks of carbonates are indicated by ▲, BaCO3, and ■, SrCO3. HT-Ag getter and HT-Ag used for I− removal (HT-AgI) is shown in panel B. The characteristic peaks are marked inside the graph by stars, Ag2CO3, and ▼, AgI.

so-called “memory effect”.23 Diffraction peaks of SrCO3 (Powder Diffraction File (PDF) No. 04-006-5442, Joint Committee on Powder Diffraction Standards (JCPDS), 2005) and BaCO3 (PDF No. 04-015-3221, JCPDS, 2011) are observed from the patterns on both HT and calcined HT after their usage for removing Sr2+ and Ba2+ cations respectively (Figure 2A). When dispersed in water, calcined HT regains OH− anions on its surface where it is able to precipitate the metal ions forming metal hydroxide. Thereafter, solid Sr(OH)2 and Ba(OH)2 can convert to carbonates by reacting with CO2 in air. For HT-Ag getter, the silver species are confirmed to be Ag2CO3 nanocrystals as shown in the XRD pattern in Figure 2B. Two Ag2CO 3 crystal phases exist: hexagonal and monoclinic. The identified Ag2CO3 phase in the HT-Ag getter is a uniformly hexagonal structure. After the HT-Ag was used as I− getter, characteristic peaks of AgI crystalline structure were detected, confirming the stabilization of I− pollutant on HT-Ag. A crucial issue for the process of radioactive ion removal by precipitation is that the formed fine precipitate has to firmly attach to the larger getter particles. In this regard, highresolution transmission electron microscope (HRTEM) analysis in Figure 3 indicates that the formed SrCO3 crystals are not randomly orientated on HT substrate but stay with a defined crystallographic alignment with respect to HT crystal structure (crystalline structure characterization shown in Figure S2). In Figure 3A, the morphology of a HT nanoparticle after Sr2+ uptake is shown to have irregular shape and nonuniform thickness. HT prepared in the present study are thin, sheetlike particles that aggregate in much larger particles (most of them >200 nm). In this regard, the fine precipitate particles can be readily separated from water by filtration or sedimentation if they attach to the larger HT particles. From the view of thermodynamics, the fine particles have reduced surface energy when attached to HT. From HRTEM images shown in Figure 3B and inset, lattice fringes of the crystals (marked in the red rectangular box) and their fast Fourier transformation (FFT) image can be extracted. The lattice information was measured, which identifies two highlighted lattice fringes of planes (12̅1) and (200) of SrCO3 (Figure 3C,D). It is observed that HT crystals have large exposed planes of (112̅0) as shown in the red rectangle box of Figure 3E, whose FFT image is shown in the inset and indexed in Figure 3F. The SrCO3 crystals formed on (112̅0) plane of HT have a specific orientation where the [010] zone axis of SrCO3 crystals is parallel to the HT (112̅0) D


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Figure 4. Panel A is a bright-field image showing Ag 2 CO 3 nanoparticles on HT substrates. Panel B shows a high-resolution TEM image (HRTEM) of Ag2CO3 nanoparticle. FFT image corresponding to the red square area is shown in the inset. Panel C gives the indexed results of the panel B inset FFT image. Panel D is a TEM micrograph of the sample HT-AgI. Bright-field image E shows AgI nanoparticles on HT substrates. The inset shows the FFT image of panel E and the indexed result. Inverse FFT image F for AgI shows lattice fringes of planes (21̅1̅0) (d-spacing 0.23 nm) and (1̅21̅2) (dspacing 0.19 nm).

Figure 3. TEM characterizations of Sr2+ grafted HT. Image A shows a low-magnification bright-field image of Sr species attached HT having irregular morphology and nonuniform thickness. Panel B is a highresolution TEM image of the well-developed crystalline state of SrCO3 nanopartices. Inset of B is fast Fourier transformation image (FFT), which is indexed in panel D with zone axis of [01̅2]SrCO3. Panel C is an inverse FFT image corresponding to panel D, highlighting two lattice fringes of plane (12̅1) and (200) of SrCO3. Panel E is a high-resolution TEM image of the well-developed crystalline state of HT and SrCO3 nanocrystals. Inset is FFT image, which is indexed in panel F with zone axis of [11̅00]HT//[010]SrCO3. Panel G highlights two lattice fringes of plane (002) and (200) of SrCO3 and the plane (0006) of HT, which has a discrepancy angle of 21° with the plane (002) of SrCO3..

between the two interfaces as shown in Figure 4B and inset. The indexed results (Figure 4C) show that plane (110̅ 10) of HT is parallel to (42̅2̅1) of Ag2CO3. This indicates that there is a plane registration between the above two phases, which can join together to form a well-matched coherent interface. Hence, the Ag2CO3 nanoparticles can attach firmly to the HT particles owing to the similarity in the interfaces shared between Ag2CO3 and HT.26 After the HT-Ag getter is used for I− removal, particles of AgI can be observed on HT (Figure 4D). As a result of the coherent interface between Ag2CO3 and HT surface, the newly deposited AgI can firmly attach to the HTAg getter, which can be further removed from the solution. Indexed results of images taken from the AgI particle indicate that the FFT image could be assigned to zone axis [0223̅ ]̅ of AgI (Figure 4E). The inverse FFT image for AgI nanoparticle (Figure 4F) clearly shows lattice fringes of planes (21̅1̅0) (dspacing 0.23 nm) and (1̅21̅2) (d-spacing 0.19 nm). It is identified as AgI hexagonal phase with lattice parameters a = 0.46 nm and c = 0.75 nm, which is in good agreement with the XRD results. Rapid removal of the all the radioactive pollutants were observed on both HT and calcined HT getters. The kinetic curves of their cation removal ability show that the getters reached the uptake saturation capacity within 30 min (Figure 5A and inset). Similarly, I− removal by HT-Ag is also measured to be instantaneous as shown in Figure 5B. Both I− removal by HT-Ag and cation removal by HT and calcined HT getters are based on a precipitation process that is considerably faster than ion exchange. Precipitation takes place promptly at the moment of interaction between the pollutants and getters, which practically guarantees efficient removal of radioactive contaminants. As an efficient purification method, a controllable fixed-bed column is widely applied in both research and industrial applications.36 When contaminated water passes through the column that was internally built with the getter particles, ideally the contaminants are completely removed or their concen-

plane, expressed as [010]SrCO3∥[11̅00]HT (Figure 3E,F). It is observed that plane (002)SrCO3 has a discrepancy angle of ∼21° to the plane (0006)HT (Figure 3G). Measurement also shows that HT has a hexagonal structure with lattice parameters a = 0.3054 nm and c = 2.281 nm and that SrCO3 crystal has orthogonal structure where a = 0.51 nm, b = 0.84 nm, and c = 0.60 nm. According to the invariant line theory analysis35 and the above parameters, the system of HT and SrCO3 is calculated to be stable when the oriented attachment has a discrepancy angle of 19.52°, which is very close to the observed angle of 21°. This indicates that the coherent interface between SrCO3 precipitate and HT substrate has low surface energy that makes the system stable. Hence, the captured SrCO3 is bonded firmly on the HT surface. In addition to precipitation on the getter surface, substitution of the bivalent Mg in the positively charged layers of HT is also considered. The leached Mg2+ ions were detected after removal of the bivalent cations, and the amount is given in Table S3. After mixing the HT-based getters for 24 h in the solution with an excess amount of cations, Mg2+ amounts in the solution are detected that are significantly lower than that of the removed cation. When it comes to capturing bivalent cations, the ion exchange of hydrotalcite is far less significant. Therefore, Mg2+ cation exchange cannot efficiently trap and dispose cation pollutants. This is also observed in XRD spectra as no peak shift occurs referring changes of the sublayer (brucite-like layer) within HT. It further confirms that the predicted capability of HT materials to capture cations is very different from its anion capturing mechanism. The stability of the silver species on HT substrate was also investigated using HRTEM. Shown as the darker particles in Figure 4A, the sizes of Ag2CO3 nanoparticles are in the range of 5−35 nm, and they are closely attached to the HT surface. HRTEM and FFT images reveal the structural alignment E


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Figure 5. Kinetic removal of Sr2+ and Ba2+ is shown in A and inset. Kinetic removal I− on HT-Ag is solely shown in graph B. All the ionic pollutants are designed to be removed from aqueous solutions under room temperature.

Figure 6. Sr2+ removal ability of HT-embedded column is depicted in graph A. It shows the cation concentrations at the outlet of column against removal time at different flow rates (0.25, 0.5, and 1.0 mL min−1). Graph B shows the I− concentrations at the outlet of the column against time using HT-Ag as getter. The flow rates are controlled at 0.3, 0.5, and 1.0 mL min−1, respectively.

Cl− anions was 100 times higher than that of I− anion although Ag2CO3 and Cl− could form solid AgCl precipitate. This selective removal of I− can be explained by the Gibbs energies of the reaction between Ag species and I− or Cl−. The Gibbs free energy is −32 kJ mol−1 for the reaction of Ag2CO3 with I− and +41 kJ mol−1 for that with Cl−. This implies that the reaction with I− ions is more thermodynamically favorable than that with Cl− ions, and the precipitation reaction is considered as the driving mechanism for I− uptake on Ag anchored getters.16,39 Lastly, the ionic pollutants are captured by irreversible precipitation process, the formed precipitate on the getter surface cannot convert to the mobile ionic form to cause secondary pollution unless treated with strong acids.

trations are significantly reduced at the column outlet before the water is released to the nature. In the present study, HT-Ag and HT were respectively loaded in glass columns, and their abilities to trap hazardous ions under different flow rates were investigated. When 50 mg/L Sr2+ solution passes through the column bedded with 0.1 g of HT, no Sr2+ anions are detected in the solution at the outlet for about 2 h at a flow rate of 0.25 mL min−1. When the flow rate increases, the pollutant trapping ability of the column degrades as Sr2+ penetration is restrained for nearly 45 min. The system becomes overwhelmed when the flow rate is as high as 1.0 mL min−1 (Figure 6A). I− removal was carried out on HT-Ag getter under similar conditions. When the flow rate was 0.3 mL min−1, an I− solution of 500 mg/L shows no trace of pollutant at the outlet for as long as 2 h. When the flow rate elevates, it takes a shorter time for the getter to reach saturation. At a 1.0 mL min−1 flow rate, the HTAg getter can still maintain functionality for 20 min (Figure 6B). Herein, the industrial application of the getters in the fixed-bed column is proposed where the flow rate of the mobile phase needs to be considered accordingly. In practical applications, the coexistence of other competitive ions at various concentrations is unavoidable. Therefore, the ability to remove the target ions in the presence of competitive ions is a key criterion in the performance assessment of the getters.37 Na+ is the most commonly found competitive cation that is present in large concentrations in the wastewater system.38 An obvious advantage of HT and calcined HT getters is that high Na+ concentration (100 times higher than that of target metal cations) in the contaminated solution does not affect their performances since Na+ ion does not form precipitates. For I− ion removal, the common competitive anions are Cl− anions. No significant interference to I− anion removal was observed when the concentration of the coexistent

4. CONCLUSIONS Efficient removal of trace radioactive metal species from water can be achieved by using the HT-based getters. Hydrotalcite solids are utilized to provide high local concentrations of available precipitants, such as carbonate and hydroxyl anions on the particle surface. Importantly, HT surface can also be tailored with silver species for I− removal in a more efficient way than the traditionally applied ion exchange approach. The high local concentration of precipitants enables rapid and complete precipitation of trace radioactive ions from polluted water. The formed fine precipitate particles attach firmly to larger HT particles via coherent interfaces and thus can be readily separated from water for safe disposal. Precipitate formation is preferred for the used getters since the captured toxic ions will not be released to cause secondary pollution. Lastly, HT-based getters can be readily made at low cost, and they are also known to be stable with respect to radiation, chemical, thermal, and mechanical changes. Thus, HT-based materials are suitable candidates for the emergent treatment of F


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(14) Yang, D. J.; Zheng, Z. F.; Zhu, H. Y.; Liu, H. W.; Gao, X. P. Titanate Nanofibers as Intelligent Absorbents for the Removal of Radioactive Ions from Water. Adv. Mater. 2008, 20, 2777−2781. (15) Yang, D. J.; Zheng, Z. F.; Yuan, Y.; Liu, H.; Waclawik, E. R.; Ke, X.; Xie, M.; Zhu, H. Sorption Induced Structural Deformation of Sodium Hexa-Titanate Nanofibers and Their Ability to Selectively Trap Radioactive Ra (II) Ions from Water. Phys. Chem. Chem. Phys. 2010, 12, 1271−1277. (16) Yang, D. J.; Sarina, S.; Zhu, H. Y.; Liu, H. W.; Zheng, Z. F.; Xie, M. X.; Smith, S.; Komarneni, S. Capture of Radioactive Cesium and Iodide Ions from Water by Using Titanate Nanofibers and Nanotubes. Angew. Chem., Int. Ed. 2011, 50, 10594−10598. (17) Kodama, T.; Harada, Y.; Ueda, M.; Shimizu, K.; Shuto, K.; Komarneni, S. Selective Exchange and Fixation of Strontium Ions with Ultrafine Na-4-mica. Langmuir 2001, 17, 4881−4886. (18) Barriga, C.; Gaitán, M.; Pavlovic, I.; Ulibarri, M. A.; Hermosĩn, M. C.; Cornejo, J. Hydrotalcites as Sorbent for 2, 4, 6-Trinitrophenol: Influence of the Layer Composition and Interlayer Anion. J. Mater. Chem. 2002, 12, 1027−1034. (19) Mills, S. J.; Christy, A. G.; Kampf, A. R.; Housley, R. M.; Favreau, G.; Boulliard, J. C.; Bourgoin, V. Zincalstibite-9R: The First Nine-Layer Polytype with the Layered Double Hydroxide StructureType. Mineral. Mag. 2012, 76, 1337−1345. (20) Goh, K. H.; Lim, T. T.; Dong, Z. Application of Layered Double Hydroxides for Removal of Oxyanions: A Review. Water Res. 2008, 42, 1343−1368. (21) Das, J.; Patra, B. S.; Baliarsingh, N.; Parida, K. M. Adsorption of Phosphate by Layered Double Hydroxides in Aqueous Solutions. Appl. Clay Sci. 2006, 32, 252−260. (22) Davison, A.; Howard, G.; Stevens, M.; Callan, P.; Fewtrell, L.; Deere, D.; Bartram, J. Water Safety Plans: Managing Drinking-Water Quality from Catchment to Consumer; Water Sanitation Health, World Health Organization: Geneva, Switzerland, 2005. (23) Frost, R. L.; Musumeci, A. W. Nitrate Absorption Through Hydrotalcite Reformation. J. Colloid Interface Sci. 2006, 302, 203−206. (24) Liang, X.; Zang, Y.; Xu, Y.; Tan, X.; Hou, W.; Wang, L.; Sun, Y. Sorption of Metal Cations on Layered Double Hydroxides. Colloids Surf., A 2013, 433, 122−131. (25) Ford, R. G.; Scheinost, A. C.; Sparks, D. L. Frontiers in Metal Sorption/Precipitation Mechanisms on Soil Mineral Surfaces. Adv. Agron. 2001, 74, 41−62. (26) Sarina, S.; Bo, A.; Liu, D.; Liu, H.; Yang, D.; Zhou, C.; Maes, N.; Komarneni, S.; Zhu, H. Separate or Simultaneous Removal of Radioactive Cations and Anions from Water by Layered Sodium Vanadate-Based Sorbents. Chem. Mater. 2014, 26, 4788−4795. (27) Sahai, N.; Carroll, S. A.; Roberts, S.; O’Day, P. A. X-Ray Absorption Spectroscopy of Strontium(II) Coordination. J. Colloid Interface Sci. 2000, 222, 198−212. (28) Ebner, A. D.; Ritter, J. A.; Navratil, J. D. Adsorption of Cesium, Strontium, and Cobalt Ions on Magnetite and a Magnetite-Silica Composite. Ind. Eng. Chem. Res. 2001, 40, 1615−1623. (29) Prasanna, S. V.; Kamath, P. V. Anion-Exchange Reactions of Layered Double Hydroxides: Interplay between Coulombic and HBonding Interactions. Ind. Eng. Chem. Res. 2009, 48, 6315−6320. (30) Livingood, J.; Seaborg, G. Radioactive Isotopes of Iodine. Phys. Rev. 1938, 54, 775−782. (31) Morioka, H.; Tagaya, H.; Karasu, M.; Kadokawa, J.; Chiba, K. Preparation of New Useful Materials by Surface Modification of Inorganic Layered Compound. J. Solid State Chem. 1995, 117, 337− 342. (32) Gong, J.; Liu, T.; Wang, X.; Hu, X.; Zhang, L. Efficient Removal of Heavy Metal Ions from Aqueous Systems with the Assembly of Anisotropic Layered Double Hydroxide Nanocrystals@Carbon Nanosphere. Environ. Sci. Technol. 2011, 45, 6181−6187. (33) Jobbágy, M.; Regazzoni, A. E. Dissolution of Nano-Size Mg-AlCl Hydrotalcite in Aqueous Media. Appl. Clay Sci. 2011, 51, 366−369. (34) New Developments and Improvements in Processing of ‘Problematic’ Radioactive Waste, Results of a Coordinated Research Project, 2003−

large quantity of radioactive ion contaminated liquids during and after radioactive leakages.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsami.6b04632. Thermogravimetric analysis (TGA) of the HT and calcined HT, details of HT structural characterization by HRTEM, composition density of the getter, getter surface area, unit amount of functional groups, unit uptake amount of pollutants, and leached amount of Mg2+ after mixing with the getters (PDF)

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We gratefully acknowledge financial support from the Australian Research Council (ARC DP110104990 and DP150102110). The electron microscopy work was performed through a user project supported by the Central Analytical Research Facility (CARF), Queensland University of Technology.

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REFERENCES

(1) Slovic, P.; Flynn, J. H.; Layman, M. Perceived Risk, Trust, and the Politics of Nuclear Waste. Science 1991, 254, 1603−1607. (2) Normile, D. Cooling a Hot Zone. Science 2013, 339, 1028−1029. (3) Lyman, G. H.; Lyman, C. G.; Johnson, W. Association of Leukemia with Radium Groundwater Contamination. JAMA, J. Am. Med. Assoc. 1985, 254, 621−626. (4) Komarneni, S.; Roy, R. Use of γ-zirconium Phosphate for Cs Removal from Radioactive Waste. Nature 1982, 299, 707−708. (5) Komarneni, S.; Roy, R. A Cesium-Selective Ion Sieve Made by Topotactic Leaching of Phlogopite Mica. Science 1988, 239, 1286− 1288. (6) Eckelmann, W. R.; Kulp, J. L.; Schulert, A. R. Strontium-90 in Man, II. Science 1958, 127, 266−274. (7) Fu, F.; Wang, Q. Removal of Heavy Metal Ions from Waste Waters: A Review. J. Environ. Manage. 2011, 92, 407−418. (8) Sureda, R.; Martínez-Lladó, X.; Rovira, M.; De Pablo, J.; Casas, I.; Giménez, J. Sorption of Strontium on Uranyl Peroxide: Implications for a High-Level Nuclear Waste Repository. J. Hazard. Mater. 2010, 181, 881−885. (9) Gerke, T. L.; Little, B. J.; Luxton, T. P.; Scheckel, K. G.; Maynard, J. B. Strontium Concentrations in Corrosion Products from Residential Drinking Water Distribution Systems. Environ. Sci. Technol. 2013, 47, 5171−5177. (10) Peng, Y.; Huang, H.; Liu, D.; Zhong, C. Radioactive Barium Ion Trap Based on Metal-Organic Framework for Efficient and Irreversible Removal of Barium from Nuclear Wastewater. ACS Appl. Mater. Interfaces 2016, 8, 8527−8535. (11) Anderson, E. C.; Schuch, R. L.; Fisher, W. R.; van Dilla, M. A. Barium-140 Radioactivity in Foods. Science 1958, 127, 283−284. (12) Jurado-Vargas, M.; Olguín, M. T.; Ordóñez-Regil, E.; JiménezReyes, M. Ion Exchange of Radium and Barium in Zeolites. J. Radioanal. Nucl. Chem. 1997, 218, 153−156. (13) Eisenbud, M.; Mochizuki, Y.; Goldin, A. S.; Laurer, G. R. Iodine131 Dose from Soviet Nuclear Tests. Science 1962, 136, 370−374. G


Research Article

ACS Applied Materials & Interfaces 2007; technical report no. IAEA-TECDOC-1579 prepared for International Atomic Energy Agency: Wien, Austria, 2007. (35) Liu, H.; Zheng, Z.; Yang, D.; Ke, X.; Jaatinen, E.; Zhao, J. C.; Zhu, H. Y. Coherent Interfaces between Crystals in Nanocrystal Composites. ACS Nano 2010, 4, 6219−6227. (36) Debnath, S.; Biswas, K.; Ghosh, U. C. Removal of Ni (II) and Cr (VI) with Titanium (IV) Oxide Nanoparticle Agglomerates in Fixed-Bed Columns. Ind. Eng. Chem. Res. 2010, 49, 2031−2039. (37) Koong, L. F.; Lam, K. F.; Barford, J.; McKay, G. A Comparative Study on Selective Adsorption of Metal Ions Using Aminated Adsorbents. J. Colloid Interface Sci. 2013, 395, 230−240. (38) Peters, R. W.; Shem, L. Separation of Heavy Metals: Removal from Industrial Wastewaters and Contaminated Soil, Energy Systems Div; Argonne National Lab: Lemont, IL, 1993. (39) Bo, A.; Sarina, S.; Zheng, Z.; Yang, D.; Liu, H.; Zhu, H. Removal of Radioactive Iodine from Water Using Ag2O Grafted Titanate Nanolamina as Efficient Adsorbent. J. Hazard. Mater. 2013, 246−247, 199−205.

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Efficient Removal of Cationic and Anionic Radioactive Pollutants from

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