Selective Removal of Radioactive Cesium from Nuclear Waste by

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Selective Removal of Radioactive Cesium from Nuclear Waste by Zeolites: On the Origin of Cesium Selectivity Revealed by Systematic Crystallographic Studies Ha Young Lee, Hu Sik Kim, Hae-Kwon Jeong, Man Park, DongYong Chung, Keun-Young Lee, Eil-Hee Lee, and Woo Taik Lim J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/acs.jpcc.7b02432 • Publication Date (Web): 18 Apr 2017 Downloaded from http://pubs.acs.org on April 25, 2017

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The Journal of Physical Chemistry

Selective Removal of Radioactive Cesium from Nuclear Waste by Zeolites: On the Origin of Cesium Selectivity Revealed by Systematic Crystallographic Studies

Ha Young Lee,a Hu Sik Kim,a Hae-Kwon Jeong,b,c,* Man Park,d Dong-Yong Chung,e Keun-Young Lee,e Eil-Hee Lee,e and Woo Taik Lim a,*

a b

Department of Applied Chemistry, Andong National University, Andong 36729, Korea

Artie McFerrin Department of Chemical Engineering and cDepartment of Materials Science and Engineering, Texas A&M University, College Station, TX 77843-3122, USA d

Soil Science Lab. College of Agriculture and Life Sciences, Kyungpook National University, Daegu 41566, Korea e

Decontamination & Decommissioning Research Division, Korea Atomic Energy Research Institute, Taejon 34057, Korea

ACS Paragon Plus Environment

The Journal of Physical Chemistry 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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(abstract) Selective ion-exchange with zeolites has been considered as one of the most promising means to remove a radioactive isotope of cesium,

137

Cs, present in low concentration in seawater.

However, there has been no report on the fundamental structure-property relation of zeolite-based Cs ion-exchangers.

In this study, we investigate the origin of the selectivity of the radioactive

cesium isotope in zeolite frameworks using zeolite A (LTA) as a model system. We prepared seven single crystals of fully dehydrated and partially cesium exchanged Zeolite A (LTA) with different Cs+/Na+ ratios.

Their single-crystal synchrotron X-ray diffraction experiments revealed

the significant differences in the degree of exchange and the site selectivity of Cs+ ions depending on the initial Cs+ concentrations in given ion exchange solutions.

The degree of Cs+-ion

exchange increases from 15.8 to 44.2% as the initial Cs+ concentration increases and the Na+ content decreases.

In addition, it was found that Cs+ ions are energetically preferred and

occluded in the center of 8-oxygen rings.

With this finding, we tested the Cs adsorption capacity

of pure zeolite Rho which has much more 8-oxygen rings than zeolite A along with commercial faujasite-type zeolite and titanosilicate from deionized water and seawater.

Zeolite Rho showed

significantly better performance on the Cs removal in the presence of high salt contents (i.e., seawater) than faujasite-type zeolite and titanosilicate.


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■ INTRODUCTION

The Chernobyl and Fukushima nuclear disasters in 1986 and 2011, respectively, have caused significant damage to the environments.

Furthermore, nuclear defense activities over the

past several decades have produced a large amount of nuclear wastes, leading to substantial risks to the environments.1 A radioactive isotope of cesium,

137

Cs, in particular has attracted a great

deal of attentions because it is one of the most common heavy fission products by the nuclear fission of 235U and other fissionable materials in nuclear reactors and nuclear weapons.2 Besides, 137

Cs is considered most harmful among the fission product nuclides since it has an intermediate

half-life time (30.17 years), decays by high-energy pathways, and possesses high solubility, and chemical reactivity.2 One of the most effective strategies to minimize the nuclear waste volumes is the selective separation of

137

Cs from waste seawater prior to the final disposal.3

quite challenging to separate

137

It is, however,

Cs from waste seawater because of its low concentrations of 10-3

~ 10-5 M present along with many other ionic species that are in high concentrations (e.g., Na+ content up to 6 M).1 Many researchers have suggested that inorganic ion-exchangers such as potassium cobalt hexacyanoferrate(II),4 molybdenum phosphates,5 ammonium phosphomolybdate,6 antimony silicate,7 titanosilicate,8 and zeolites9-12 are useful for the selective removal of

137

Cs from nuclear

wastes due to their high radiation stability and extreme selectivity.13-15 Most hexacyanoferrate complexes have been known as the highly selective ion exchangers for cesium so that many researches have been conducted for their usage of the selective separation of cesium from nuclear waste solution.4

For example, Lehto et al.4

synthesized potassium cobalt hexacyanoferrate(II) and reported that its effective capacity for cesium was 0.35 meq/g, corresponding to 6% of the theoretical capacity and cesium was only



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adsorbed as a monolayer on the external surface of the crystallites. Moller et al.5 synthesized three different structures of microporous layered molybdenum phosphates.

They investigated

the ability of removal of the radionuclides commonly found in nuclear waste solutions such as 85

Sr,

134

Cs,

57

Co,

65

Zn,

59

Fe,

54

Mn,

51

Cr,

110

Ag,

236

Pu, and

241

Am.

They reported that the

hydrothermally prepared NH4MoPO was very selective for cesium with a distribution coefficient (KD) of 23,400 mL/g in 0.1 M HNO3, about half of that of well-known ammonium 12molybdophosphate (AMP) (44,000 mL/g).

Lehto et al.6 studied potassium cobalt hexacyano-

ferrate(II), potassium copper cobalt hexacyanoferrate(II), and ammonium phosphomolybdate for the separation of cesium from nuclear power plant low-level waste solutions.

They determined

the distribution coefficient and the ion exchange rate of cesium as a function of pH, sodium and potassium ion concentrations, and grain sizes at three different temperature (i.e., 293, 310, and 330 K).

Moller et al.7 prepared two antimony silicates, one crystalline and the other amorphous,

using two different procedures in order to improve the selectivity for some radionuclides such as 85

Sr, 57Co, 59Fe, 63Ni, and 134Cs.

They reported that two antimony silicates, crystalline SbSi and

amorphous KSbSi adsorbed strontium ions extremely well in a wide range of pH and performed better than many of the commercially available inorganic ion exchangers such as zeolites, sodium titanates, and silicotitanates. 59

These materials had also a high or reasonable selectivity for 57Co,

Fe, and 63Ni, but the selectivity for

134

Cs was low.

The selectivity for

134

Cs was improved by

doping the antimony silicates with Ti4+, Nb5+, Mo6+ or W6+. Celestian et al.8 investigated the mechanism of ion-exchange selectivity for cesium for a crystalline titanosilicate using timeresolved X-ray and neutron scattering coupled with theoretical calculations.

They suggested that

the cesium exchange of a proton-exchanged titanosilicate proceeded via a two-step process mediated by conformational changes in the framework of the titanosilicate rather than a simple ion-for-ion displacement reaction into favorable sites.

The two-step process mechanism

involves repulsive forces between Cs+ and H2O dipole that cause extra-framework H2O to rotate


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in order to rehydrate Cs+, explaining the remarkable ion selectivity of the crystalline titanosilicate for Cs. On the other hands, zeolites, crystalline microporous aluminosilicate materials, are very promising as ion exchangers.

This is due to their anionic tetrahedral framework structures

enclosing cavities occupied by charge-balancing cations and water molecules, both of which have enough freedom of movement to permit cation exchange and reversible dehydration.16 Harjula et al.9,10 studied three synthetic zeolites: Zeolon 900, Linde AW-500, and mordenite for the selective separation of cesium from low-active waste solutions which often contain a large amount of sodium ions and in some cases potassium ions.

Gualtieri et al.11

interpreted different cesium ion selectivity of both sedimentary and synthetic phillipsite by Rietveld structural analysis.

They suggested that phillipsite might be utilized as a selective

cation exchanger for the removal of cesium radionuclide in nuclear waste.

Despite all of these

promising studies mentioned above, as insisted by Yoshida et al.,12 there are still open questions on the physical and chemical origins of selective ion-exchange abilities of different cations and in particular detailed atomic structures of exchanged cations inside the nanoscale channels and cavities of zeolites at the atomic level. In this work, for the first time, we performed systematic crystallographic investigations on the origin of Cs selectivity in the zeolite framework.

Zeolite A (LTA) was chosen as a model

system due to its small pores and high ion-exchange capacities.

Zeolite A has two types of

polyhedrals; a simple cubic arrangement of 8 tetrahedral, double 4-oxygen rings (D4R) and a truncated octahedron of 24 tetrahedra (β-cage).17

A large cavity (α–cage) of zeolite A is

generated by placing the cubic D4R units and β-cages in the centers of the edges of a cube of 12.3 Å and corners of the cube, respectively.

The center of the unit cell of zeolite A is a large

cavity which has 6 8-oxygen rings, 8 6-oxygen rings, and 12 4-oxygen rings. cation generally prefers sites near 6-, 8- , and 4-oxygen rings.


Exchangeable

The systematic crystallographic


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studies enabled us to attribute the selectivity of Cs ions to the energetically favorable Cs adsorption in the 8-oxygen rings of zeolite A. Based on this finding, we proposed and verified zeolite Rho possessing relatively high numbers of 8-oxygen rings as a highly selective Cs adsorbent.

■ MATERIALS AND METHODS

Synthesis of Large Single Crystals of Zeolite A. Clear, colorless, transparent, large single crystals of sodium zeolite A, stoichiometry |Na12|[Si12Al12O48]-LTA, were prepared following the previously reported procedure by Lim et al. using the Charnell’s method18 from gels of composition 1Na2O : 1Al2O3 : 2SiO2 : xH2O.

A gel was prepared by mixing sodium

metasilicate nonahydrate (technical, Wako), sodium aluminate (technical, Wako), and triethanolamine (TEA, 99+%, Acros) in distilled water (resistivity > 14.8 MΩcm). In a typical synthesis, 10 g of sodium metasilicate nonahydrate was dissolved in 70 mL of distilled water in a 250-mL PTFE beaker.

10 mL of triethanolamine was added to this silica

solution, and the mixture was stirred until complete dissolution.

To prepare a solution an

aluminum source, 4 g of sodium aluminate was dissolved in 70 mL of distilled water, and then 10 mL of triethanolamine was added to the aluminum source solution.

Both of the solutions were

filtered twice using a 0.2-µm membrane filter (PTFE syringe, Whatman).

Finally, the latter

solution (aluminum source) was added into the silica solution in a 250 mL HDPE bottle; the mixture became a very viscous gel.

The resulting bottle containing the mixture gel was placed

in a convection oven at 368 K for 3 weeks.

Afterwards the product was filtered, washed with

distilled water 10 times, and dried at 353 K for 1 day. Ion Exchange and Dehydration. Hydrated Cs,Na-A crystals were first prepared by the static ion-exchange of hydrated Na-A with various aqueous mixtures of CsNO3 (Aldrich, 99.999%,


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Ca 1.4 ppm, K 0.3 ppm, Mg 0.2 ppm, Mn < 1.2 ppm, Na 0.3 ppm, Ni 1.6 ppm) and NaNO3 (Aldrich, 99.995%, Ca 9.2 ppm, B 3.7 ppm, K 0.7 ppm, Mg 0.3 ppm, Al 0.2 ppm, Zn 0.2 ppm, Ga FAU > Titanosilicate (see Figure 10B). In order to investigate the effects of high salt concentrations on the Cs adsorption in the three adsorbents, the seawater-based adsorption experiments were conducted under the conditions identical to the previous experiments.

All three samples showed their Cs removal efficiencies

decreased in seawater condition as compared to in deionized water, indicating that the competitive adsorption of other cations, mainly Na ions, in the adsorbents (see Figure 11A).

Even under this

competitive adsorption in seawater, zeolite Rho showed the best performance in the Cs removal. Besides, for zeolite Rho, the adsorption yields of Cs varied within 20% of decrease and the distribution coefficients remained near 103 in all m/V conditions.

In contrast, the other zeolites

exhibited significant decreases in both adsorption yields and distribution coefficients.

Based on

the Cs adsorption results in deionized water and seawater (see Figure 10B and 11B), the ratios



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between the adsorbed Cs amount in deionized water and that in seawater (qDW/qSW) of zeolite Rho, titanosilicate and zeolite FAU were around 1.4, 3.7, and 31.1, respectively.

This result suggests

that the Cs adsorption by zeolite Rho was affected by the presence of the high salt contents much less than the other adsorbents.

This impressive Cs selectivity of zeolite Rho in the presence of

high salt contents can be attributed to the presence of the abundant 8-oxygen rings present in zeolite Rho, energetically favored Cs adsorption sites.

Titanosilicate performs better than zeolite

FAU in the presence of high salt contents, supporting the aforementioned Cs selectivity of 8oxygen rings in zeolites, because titanosilicate has the 8-oxygen rings (not as many as in zeolite Rho) whereas zeolite FAU has no 8-oxygen ring. Finally, the Cs removal performance of zeolite Rho (this work) was compared with other previously reported zeolite-based Cs removers such as titanosilicate, chabazite, clinoptilolite, and mordenite.35,36

It should be noted that the comparison might not be fair since the experimental

conditions are not the same.

Nonetheless in the presence of high salt contents (i.e., seawater),

the specific Cs removal capacity of zeolite Rho after 2 hrs of adsorption time estimated to be higher than other zeolite sorbents (see Table 9)35,36

In addition, in the initial 2 hrs of adsorption

time, zeolite Rho removed Cs+ ions more rapidly under seawater condition than the other zeolite Cs+ sorbents.

■ Conclusion

For the first time, we have performed systematic crystallographic investigations on the origin of Cs+ selectivity in the zeolite framework using zeolite A (LTA) as a model system.

We

have prepared the seven single crystals of fully dehydrated and partially Cs+ exchanged zeolite A with different Cs+/Na+ ratios.

The locations of Cs+ and Na+ in partially Cs+ exchanged zeolite A

were determined by single-crystal X-ray diffraction techniques.


Relatively large Cs+ ion is

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energetically preferred in the 8-oxygen ring sites, thereby occupying this site first.

Once Cs+

ions nearly fill the 8-oxygen rings, the remaining ions go to 6-oxygen rings. With increasing the initial Cs+ concentration, the degree of Cs+ ion exchange increased from 15.8 to 44.2%.

Based

on this finding, zeolite Rho with abundant 8-oxygen rings was suggested as an effective Cs+ selective adsorbent.

It was found that zeolite Rho showed much better performance for Cs

removal from both deionized water and seawater as compared to other zeolites such as titanosilicate and zeolite FAU.

This result strongly suggests the importance of 8-oxygen rings in

zeolites for efficient and selective for Cs removal, paving ways to the future directions.

Indeed,

we are currently investigating zeolites with even more 8-oxygen rings than zeolite Rho.

■ ASSOCIATED CONTENT Supporting Information Characterization data for titanosilicate and observed and calculated structure factors squared with esds for seven crystal structures of Cs,Na-A.

This is available free of charge via the Internet at

http:// http://pubs.acs.org. .

■ AUTHOR INFORMATION Corresponding Authors *Phone: +1 979 862 4850; fax: +1 979 845 6446; e-mail: [email protected] *Phone: +82 54 820 5454; fax: +82 54 822 5452; e-mail: [email protected]

■ ACKNOWLEDGEMENTS The authors wish to thank the staff at Beamline 2D SMC at the Pohang Light Source, Korea, for assistance during data collection.

This work was supported by the National Research

Foundation of Korea (NRF) Grant funded by the Korea Government (MSIP) (No. NRF-



2012M2A8A5025658).


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Removal of Co and Sr Ions from Nuclear Laundry Wastewater. J. Membr. Sci. 2013, 447, 8795. (29) Blake Vance, T.; Seff, K. Hydrated and Dehydrated Crystal Structures of Seven-twelfths Cesium-exchanged Zeolite A. J. Phys. Chem. 1975, 20, 2183-2167. (30) Handbook of chemistry and physics, 70th ed.; CRC Press.: Cleveland, OH 1989/1990; p F187. (31) Dejsupa, C.; Heo, N. H.; Seff, K.

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Complete Aqueous Exchange. Zeolites. 1989, 9, 146-151. (32) Kim, Y.; Seff, K. The Crystal Structure of Zeolite A Exchanged with Silver(1+) and Thallium (1+), Ag6.5Tl5.5-A, Evacuated at 400. Degree. C. A Partial Mechanism for the Intrazeolitic



Reduction of Silver(1+) ion to form Hexasilver. J. Phys. Chem. 1978, 82, 1307-1311. (33) Park, Y.; Shin, W. S.; Choi, S. J. Ammonium Salt of Heteropoly Acid Immobilized on Mesoporous Silica (SBA-15): An Efficient Ion Exchanger for Cesium Ion. Chem. Eng. J., 2013, 220, 204-213. (34) Ma, B.; Oh, S.; Shin, W. S.; Choi, S. J. Removal of Co2+, Sr2+ and Cs+ from Aqueous Solution by Phosphate-modified Montmorillonite (PMM). Desalination, 2011, 276, 336-346. (35) Datta, S. J.; Moon, W. K.; Choi, D. Y.; Hwang, I. C.; Yoon, K. B. A Novel Vanadosilicate with Hexadeca-coordinated Cs+ ions as A Highly Effective Cs+ Remover. Angew. Chem. Int. Ed., 2014, 53, 1-7. (36) Lee, K. Y.; Park, M.; Kim, J.; Oh, M.; Lee, E. H.; Kim, K. W.; Chung, D. Y.; Moon, J. K. Equilibrium, Kinetic and Thermodynamic Study of Cesium Adsorption on to Nanocrystalline Mordenite from High-salt Solution. Chemosphere, 2016, 150, 756-771.


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+

Table 1. Summary of experimental and crystallographic data of dehydrated Cs -exchanged zeolite A Crystal cross-section (mm) Ion exchange T (K) Ion exchange with Cs+ and Na+(mL, days) Molar ratio of Cs+ : Na+ in 0.1 M Dehydration T (K) Dehydration P (Pa) Crystal color Data collection T (K) Space group, Z X-ray source Detector Wavelength (Å) Unit cell constant, a (Å) 2θ range in data collection (deg) Total reflections harvested No. of unique reflections, m No. of reflections with Fo > 4σ(Fo) No. of variables, s Data/parameter ratio, m/s Weighting parameters, a/b Rinta Rsigmab Final error indices R1/wR2 (Fo > 4σ(Fo)) c R1/wR2 (all intensities) d Goodness-of-fite a c

Crystal 1 0.13 294 100, 2.5 1 : 11 623 -4 1 × 10 colorless 100(1) Pm 3 m, 1

Crystal 2 0.18 294 100, 2.5 1:5 623 1 × 10-4 colorless 100(1) Pm 3 m, 1

Crystal 6 0.10 294 100, 2.5 5:1 623 -4 1 × 10 colorless 100(1) Pm 3 m, 1

Crystal 7 0.15 294 100, 2.5 6:0 623 -4 1 × 10 colorless 100(1) Pm 3 m, 1

0.70000 12.2737(1) 66.94 43,486 795 715 33 24.1 0.086/3.1 0.0160 0.0160

Crystal 3 Crystal 4 Crystal 5 0.15 0.12 0.17 294 294 294 100, 2.5 100, 2.5 100, 2.5 1:2 1:1 2:1 623 623 623 -4 -4 1 × 10-4 1 × 10 1 × 10 colorless colorless colorless 100(1) 100(1) 100(1) Pm 3 m, 1 Pm 3 m, 1 Pm 3 m, 1 Pohang Light Source (PLS) (Beamline 2D SMC) ADSC Quantum210 0.70000 0.70000 0.70000 12.2551(1) 12.2643(1) 12.2505(1) 66.95 67.00 66.78 43,145 42,639 43,336 777 794 761 713 715 691 37 37 37 21.0 21.5 20.6 0.118/1.9 0.091/4.0 0.086/4.7 0.0110 0.0129 0.0501 0.0130 0.0131 0.0333

0.70000 12.2520(1) 58.99 37,708 587 579 33 17.8 0.083/4.2 0.0132 0.0134

0.70000 12.2440(1) 59.03 37,651 582 572 41 14.2 0.067/5.1 0.0073 0.0094

0.70000 12.2601(1) 66.72 43,419 787 711 37 21.3 0.084/4.1 0.0062 0.0105

0.0546/0.1523 0.0549/0.1531 1.128

0.0682/0.2497 0.1091/0.3994 1.403

0.0578/0.1846 0.0683/0.2181 1.214

0.0450/0.1275 0.0453/0.1284 1.153

0.0467/0.1455 0.0507/0.1580 1.096

0.0480/0.1492 0.0535/0.1663 1.053

0.0498/0.1927 0.0907/0.3510 1.401

Rint = Σ|Fo2-Fo2(mean)|/Σ[Fo2]; Rint is calculated from the merging of equivalent data for internal agreement for all reflections.

b

Rsigma = Σ[σ(Fo2)]/Σ[Fo2]

R1 = Σ|Fo-|Fc||/ΣFo and wR2 = [Σw(Fo2-Fc2)2/Σw(Fo2)2]1/2; R1 and wR2 are calculated using only the reflections for which Fo > 4σ(Fo).

calculated using all unique reflections measured.

e

d

R1 and wR2 are

Goodness-of-fit = [Σw(Fo2-Fc2)2/(m-s)]1/2, where m is the number of unique reflections and s is the

number of variables, respectively.


The Journal of Physical Chemistry 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47

Page 26 of 53

Table 2. Steps of structure determination and refinement of dehydrated Cs+-exchanged zeolite A

Step 1b 2 3 4 5 6c 7d

Cs(1)

Cs(2)

1.5(1) 1.6(1) 1.9(1) 1.9(1) 1.9(1) 2

1b 2 3 4 5 6c 7d

2.7(1) 2.6(1) 2.6(1) 2.6(1) 2.6(1) 3

1b 2 3 4 5

3.0(1) 3.0(1) 2.9(1) 2.9(1)

Cs(3)

Occupancya at Na(1) Na(2) Na(3) Na(4) Crystal 1, |Cs2Na10|[Si12Al12O48]-LTA

4.0(1) 2.6(3) 5.6(3) 7.9(1) 8.5

5.7(3) 2.5(1) 3.5(7) 0.4(1) 1.3(3) 0.5 1 Crystal 2, |Cs3Na9|[Si12Al12O48]-LTA

7.9(1) 4.9(5) 3.0(5) 5.0(5) 3.0(5) 4.6(19) 3.5(19) 4.5 3.5 Crystal 3, |Cs3.5Na8.5|[Si12Al12O48]-LTA

0.4(1) 0.5(3) 0.5(1)

Na(5)

7.2(2) 5.2(3)


2.2(3)

0.7(2) 0.8(1) 1

R1

wR2

0.4765 0.2580 0.1219 0.0713 0.0702 0.0528 0.0546

0.8385 0.6907 0.4361 0.1953 0.1919 0.1488 0.1523

0.5048 0.2335 0.0763 0.0658 0.0637 0.0494 0.0682

0.8391 0.5849 0.2749 0.2580 0.2580 0.2223 0.2497

0.5638 0.2245 0.2116 0.0775 0.0651

0.8919 0.6798 0.6682 0.2308 0.2034

Page 27 of 53 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47


6 7c 8d

2.9(1) 2.9(1) 3

1b 2 3 4 5 6 7c 8d

2.7(1) 2.8(1) 2.8(1) 2.9(1) 2.9(1) 2.9(1) 3

1b 2 3 4 5 6 7c 8d

2.0(1) 2.7(1) 2.9(1) 2.9(1) 2.9(1) 2.9(1) 3

1b 2 3 4 5 6

2.3(1) 2.6(1) 3.0(1) 2.9(1) 2.9(1)

0.5(1) 0.5(1) 0.5

5.2(3) 2.2(3) 5.7(16) 2.1(17) 5.5 2 Crystal 4, |Cs3.5Na8.5|[Si12Al12O48]-LTA

7.5(1) 5.2(4) 2.4(4) 5.3(4) 2.3(4) 5.2(4) 2.4(4) 6.2(20) 1.5(20) 6.5 1.5 Crystal 5, |Cs3.5Na8.5|[Si12Al12O48]-LTA

0.3(1) 0.3(1) 0.4(1) 0.5

7.0(2) 7.1(1) 5.2(3) 2.1(3) 5.1(3) 2.2(3) 5.9(12) 1.8(13) 6 1.5 Crystal 6, |Cs4.5Na7.5|[Si12Al12O48]-LTA

0.6(1) 0.6(1) 0.6(1) 0.6(1) 0.5

0.8(1) 0.8(!) 0.8(1)

0.3(1) 0.3(1)

6.6(3) 6.7(2) 6.8(1) 5.2(3) 27


1.9(3)

0.6(2) 0.8(2) 1

0.0644 0.0545 0.0578

0.2012 0.1782 0.1846

0.3(1) 0.5(1) 0.5

0.5366 0.2157 0.0722 0.0630 0.0574 0.0563 0.0449 0.0480

0.8739 0.5567 0.1885 0.1705 0.1504 0.1496 0.1390 0.1492

0.3(1) 0.5(1) 0.5

0.5376 0.3425 0.0953 0.0738 0.0601 0.0597 0.0476 0.0498

0.8643 0.7351 0.2977 0.2377 0.2117 0.2105 0.1883 0.1927

0.5578 0.2395 0.1248 0.0770 0.0621 0.0486

0.8808 0.7027 0.5055 0.1992 0.1628 0.1243


7c 8d 1b 2 3 4 5 6c 7d a

2.9(1) 3

2.6(1) 2.4(1) 2.7(1) 2.9(1) 2.9(1) 3

0.8(1) 1

1.0(1) 1.4(1) 0.9(1) 0.9(1) 1

0.3(1) 0.5

1.6(1) 1.5(1) 1.5

6.2(17) 1.3(18) 6 1.5 Crystal 7, |Cs5.5Na6.5 |[Si12Al12O48]-LTA

4.8(3) 6.3(1) 6.2(1) 6.5

The occupancy is given as the number of ions per unit cell at each position.

model. They were all refined anisotropically.

Page 28 of 53

b

0.0392 0.0450

0.1095 0.1275

0.5423 0.3113 0.2129 0.1313 0.0693 0.0442 0.0467

0.8778 0.7485 0.6689 0.5401 0.1773 0.1368 0.1455

Only the atoms of zeolite framework were included in the initial structure

c

All atoms were refined anisotropically, except Na(3) in crystal 1.

28


d

All atoms were fixed.

Page 29 of 53 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47


Table 3. Positional, thermal, and occupancy parametersa of dehydrated Cs+-exchanged zeolite A

Wyckoff atom

position

x

y

U11b or Uiso

z

Occupancyc U22

U33

U23

U13

U12 fixed

varied

Crystal 1, |Cs2Na10|[Si12Al12O48]-LTA Si,Al

24(k)

0

1834(1)

3709(1)

234(5)

168(5)

134(5)

16(3)

0

0

24d

O(1)

12(h)

0

2236(4)

5000e

495(24)

422(24)

167(15)

0

0

0

12

O(2)

12(i)

0

7075(3)

7075(3)

731(32)

281(13)

281(13)

183(16)

0

0

12

O(3)

24(m)

1122(2)

1122(2)

3395(3)

346(9)

346(9)

332(14)

-22(9)

-22(9)

104(11)

24

e

e

2

1.9(1)

Cs(1)

3(c)

0

5000

5000

649(10)

458(6)

458(6)

0

0

0

Na(1)

8(g)

1581(14)

1581(14)

1581(14)

91(49)

91(49)

91(49)

-60(56)

-60(56)

-60(56)

0.5

0.4(1)

Na(2)

8(g)

1999(2)

1999(2)

1999(2)

428(9)

428(9)

428(9)

182(11)

182(11)

182(11)

8.5

7.9(1)

Na(3)

12(J)

0

4079(49)

4079(49)

1294(266)

Si,Al

24(k)

0

1833(1)

3706(1)

208(4)

171(4)

113(3)

21(2)

0

0

24d

O(1)

12(h)

0

2238(3)

5000e

364(16)

452(19)

146(11)

0

0

0

12

O(2)

12(i)

0

2941(2)

2941(2)

691(24)

226(9)

226(9)

143(11)

0

0

12

O(3)

24(m)

1126(1)

1126(1)

3380(2)

283(6)

283(6)

277(10)

12(6)

12(6)

39(8)

24

e

e

3

2.6(1)

1.3(3) 1 + + ∑(Cs +Na )=11.5(2)

Crystal 2, |Cs3Na9|[Si12Al12O48]-LTA

Cs(1)

3(c)

0

5000

5000

393(5)

522(4)

522(4)

0

0

0

Na(2)

8(g)

2002(9)

2002(9)

2002(9)

242(46)

242(46)

242(46)

51(35)

51(35)

51(35)

4.5

4.6(19)

Na(4)

8(g)

2056(28)

2056(28)

2056(28)

452(95)

452(95)

452(95)

235(78)

235(78)

235(78)

3.5

3.5(19)

2123(24)

e

609(206)

609(206)

557(260)

0

0

-268(219)

1

0.8(1)

Na(5)

12(J)

2123(24)

5000

29



Page 30 of 53

∑(Cs++Na+)=11.5(5) Crystal 3, |Cs3.5Na8.5|[Si12Al12O48]-LTA Si,Al

24(k)

0

1832(1)

3700(1)

202(4)

174(4)

110(4)

22(2)

0

0

24d

O(1)

12(h)

0

2197(4)

5000e

348(16)

556(24)

124(11)

0

0

0

12

O(2)

12(i)

0

2957(2)

2957(2)

597(23)

227(9)

227(9)

150(11)

0

0

12

O(3)

24(m)

1126(2)

1126(2)

3359(2)

271(7)

271(7)

303(11)

16(6)

16(6)

33(8)

24

e

e

3

2.9(1)

Cs(1)

3(c)

0

5000

5000

421(5)

471(4)

471(4)

0

0

0

Cs(2)

8(g)

733(4)

733(4)

733(4)

822(37)

822(37)

822(37)

-325(26)

-325(26)

-325(26)

0.5

0.5(1)

Na(2)

8(g)

2018(4)

2018(4)

2018(4)

226(12)

226(12)

226(12)

52(10)

52(10)

52(10)

5.5

5.7(16)

Na(4)

8(g)

2184(14)

2184(14)

2184(14)

382(69)

382(69)

382(69)

216(76)

216(76)

216(76)

2

2.1(17)

2229(26)

e

541(147)

541(147)

1809(659)

0

0

-84(196)

Na(5)

12(J)

2229(26)

5000

0.8(2) 1 + + ∑(Cs +Na )=12.0(4)

Crystal 4, |Cs3.5Na8.5|[Si12Al12O48]-LTA Si,Al

24(k)

0

1833(1)

3704(1)

184(4)

152(4)

95(3)

21(2)

0

0

24d

O(1)

12(h)

0

2205(4)

5000e

322(17)

468(22)

121(12)

0

0

0

12

O(2)

12(i)

0

2952(2)

2952(2)

608(25)

207(10)

207(10)

147(12)

0

0

12

O(3)

24(m)

1125(2)

1125(2)

3370(2)

254(7)

254(7)

267(11)

6(6)

6(6)

35(9)

24

e

e

3

2.9(1)

Cs(1)

3(c)

0

5000

5000

403(5)

498(4)

498(4)

0

0

0

Cs(2)

8(g)

742(7)

742(7)

742(7)

1334(83)

1334(83)

1334(83)

-489(57)

-489(57)

-489(57)

0.5

0.4(1)

Na(2)

8(g)

2016(4)

2016(4)

2016(4)

243(11)

243(11)

243(11)

67(10)

67(10)

67(10)

6.5

6.2(20)

Na(4)

8(g)

2198(21)

2198(21)

2198(21)

484(119)

484(119)

484(119)

275(131)

275(131)

275(131)

1.5

1.5(20)

2196(24)

e

226(124)

226(124)

379(245)

0

0

-141(165)

Na(5)

12(J)

2196(24)

5000

Crystal 5, |Cs3.5Na8.5|[Si12Al12O48]-LTA 30


0.5(1) 0.5 + + ∑(Cs +Na )=11.5(4)

Page 31 of 53 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47


Si,Al

24(k)

0

1831(1)

3699(1)

192(4)

164(4)

92(4)

24(2)

0

0

24d

O(1)

12(h)

0

2186(4)

5000e

321(18)

550(26)

116(13)

0

0

0

12

O(2)

12(i)

0

2962(2)

2962(2)

579(25)

218(10)

218(10)

151(13)

0

0

12

O(3)

24(m)

1128(2)

1128(2)

3350(2)

268(7)

268(7)

268(12)

18(7)

18(7)

32(9)

24

e

e

Cs(1)

3(c)

0

5000

5000

415(5)

447(4)

447(4)

0

0

0

Cs(2)

8(g)

734(3)

734(3)

734(3)

628(28)

628(28)

628(28)

-275(20)

-275(20)

-275(20)

Na(2)

8(g)

2039(3)

2039(3)

2039(3)

225(9)

225(9)

225(9)

75(9)

75(9)

Na(4)

8(g)

2251(19)

2251(19)

2251(19)

685(105)

685(105)

685(105)

456(117)

2182(31)

e

314(197)

314(197)

1060(639)

0

Na(5)

12(J)

2182(31)

5000

3

2.9(1)

0.5

0.6(1)

75(9)

6

5.9(12)

456(117)

456(117)

2

1.8(13)

0

-225(249)

0.5

0.5(1)

+

+

∑(Cs +Na )=11.7(3) Crystal 6, |Cs4.5Na7.5|[Si12Al12O48]-LTA Si,Al

24(k)

0

1828(1)

3694(1)

172(5)

150(5)

71(4)

22(3)

0

0

24d

O(1)

12(h)

0

2162(4)

5000e

285(19)

491(26)

96(14)

0

0

0

12

O(2)

12(i)

0

2972(2)

2972(2)

516(25)

184(11)

184(11)

117(14)

0

0

12

O(3)

24(m)

1126(2)

1126(2)

3336(2)

244(8)

244(8)

218(12)

24(7)

24(7)

31(10)

24

e

e

Cs(1)

3(c)

0

5000

5000

419(6)

439(5)

439(5)

0

0

0

3

2.9(1)

Cs(2)

8(g)

774(3)

774(3)

774(3)

744(19)

744(19)

744(19)

-198(16)

-198(16)

-198(16)

1

0.8(1)

Cs(3)

8(g)

2848(7)

2848(7)

2848(7)

657(30)

657(30)

657(30)

10(37)

10(37)

10(37)

0.5

0.3(1)

Na(2)

8(g)

2044(3)

2044(3)

2044(3)

198(13)

198(13)

198(13)

57(13)

57(13)

57(13)

6

6.2(17)

Na(4)

8(g)

2263(15)

2263(15)

2263(15)

294(73)

294(73)

294(73)

125(78)

125(78)

125(78)

1.5

1.3(18) +

+

∑(Cs +Na )=11.5(4) Crystal 7, |Cs5.5Na6.5|[Si12Al12O48]-LTA Si,Al

24(k)

0

1830(1)

3701(1)

169(4)

153(4)

96(3)

17(2)

0

0

24d

O(1)

12(h)

0

2195(4)

5000e

353(17)

406(20)

124(12)

0

0

0

12

31



Page 32 of 53

O(2)

12(i)

0

2966(2)

2966(2)

471(20)

191(9)

191(9)

123(11)

0

0

12

O(3)

24(m)

1124(2)

1124(2)

3358(2)

250(7)

250(7)

260(11)

16(6)

16(6)

56(9)

24

e

e

Cs(1)

3(c)

0

5000

5000

426(5)

488(4)

488(4)

0

0

0

3

2.9(1)

Cs(2)

8(g)

849(2)

849(2)

849(2)

555(12)

555(12)

555(12)

-183(9)

-183(9)

-183(9)

1

0.9(1)

Cs(3)

8(g)

2775(1)

2775(1)

2775(1)

264(4)

264(4)

264(4)

71(4)

71(4)

71(4)

1.5

1.5(1)

Na(2)

8(g)

2045(2)

2045(2)

2045(2)

274(6)

274(6)

274(6)

87(8)

87(8)

87(8)

6.5

6.2(1) +

+

∑(Cs +Na )=11.5(1) a

4

Positional and thermal parameters X 10 are given. Numbers in parentheses are the esds in the units of the least significant figure given for the corresponding parameter.

b

The anisotropic temperature factor is exp[-2π2a-2(U11h2 + U22k2 + U33l2 + 2U23kl + 2U13hl + 2U12hk)].

cell.

d

Occupancy for (Si) = 12, occupancy for (Al) = 12.

e

Exactly 1/2 by symmetry.

32


c

The Occupancy factor is given as the number of atoms or ions per unit

Page 33 of 53 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47


Table 4. Selected interatomic distances (Å) and angles (deg)a in dehydrated Cs+-exchanged zeolite A

(Si,Al)-O(1) (Si,Al)-O(2) (Si,Al)-O(3) Mean (Si,Al)-O

Crystal 1 1.6567(16) 1.6465(11) 1.6725(11) 1.6586

Crystal 2 1.6641(17) 1.6522(12) 1.6793(10) 1.6652

Crystal 3 1.6546(15) 1.6527(10) 1.6811(9) 1.6628

Crystal 4 1.6538(14) 1.6534(11) 1.6809(9) 1.6494

Crystal 5 1.6524(15) 1.6535(11) 1.6832(10) 1.6630

Crystal 6 1.6500(15) 1.6561(12) 1.6832(11) 1.6631

Crystal 7 1.6543(14) 1.6590(10) 1.6808(9) 1.6647

Cs(1)-O(1) Cs(1)-O(2) Cs(2)-O(3) Cs(3)-O(2) Cs(3)-O(3) Na(1)-O(3) Na(2)-O(3) Na(3)-O(1) Na(3)-O(2) Na(4)-O(3) Na(5)-O(1) Na(5)-O(3)

3.387(5) 3.596(5) 2.361(9) 2.288(3) 2.52(23) 2.00(8) -

3.391(5) 3.573(5) 2.272(4) 2.307(9) 2.67(5) 2.70(5)

3.435(5) 3.541(4) 3.289(6) 2.257(3) 2.332(6) 2.73(3) 2.77(3)

3.428(5) 3.553(4) 3.291(12) 2.268(3) 2.351(13) 2.69(3) 2.73(3)

3.448(5) 3.531(4) 3.276(6) 2.252(3) 2.366(14) 2.67(4) 2.73(4)

3.476(5) 3.511(4) 3.196(5) 3.493(8) 3.041(11) 2.243(3) 2.367(12) -

3.439(4) 3.527(4) 3.113(4) 3.4177(12) 2.950(3) 2.267(3) -

O(1)-(Si,Al)-O(2) O(1)-(Si,Al)-O(3) O(2)-(Si,Al)-O(3) O(3)-(Si,Al)-O(3)

108.39(22) 112.01(13) 106.81(14) 110.51(22)

107.26(23) 112.39(13) 106.98(13) 110.49(22)

107.74(20) 112.25(12) 107.00(11) 110.27(18)

107.89(21) 112.12(12) 107.01(11) 110.40(18)

107.85(22) 112.32(12) 106.86(12) 110.29(20)

107.95(22) 112.28(12) 107.03(12) 109.96(20)

107.19(19) 112.35(11) 107.23(11) 110.17(18)

(Si,Al)-O(1)-(Si,Al) (Si,Al)-O(2)-(Si,Al) (Si,Al)-O(3)-(Si,Al)

145.4(3) 161.4(3) 143.51(22)

145.4(3) 159.2(3) 142.69(20)

148.6(3) 156.90(3) 141.52(17)

147.9(3) 157.9(3) 142.04(17)

149.5(3) 156.2(3) 140.85(18)

151.4(4) 154.5(3) 140.27(18)

148.6(3) 155.8(3) 141.41(17)

O(1)-Cs(1)-O(1)

90 180 45 135 -

90 180 45 135 -

90 180 45 135 72.10 -

90 180 45 135 72.53 -

90 180 45 135 71.97 -

90 180 45 135 73.55 78.0(3)

90 180 45 135 76.93 82.08(9)

O(1)-Cs(1)-O(2) O(3)-Cs(2)-O(3) O(3)-Cs(3)-O(3)


-


O(3)-Na(1)-O(3) O(3)-Na(2)-O(3) O(1)-Na(3)-O(1) O(3)-Na(4)-O(3) O(1)-Na(5)-O(1) O(1)-Na(5)-O(3) O(3)-Na(5)-O(3) a

113.1(6) 118.79(5) 143(4) -

119.1(3) 116.1(7) 93.2(21) 62.6(12) 94.9(21)

118.11(10) 112.2(6) 88.4(13) 60.4(8) 92.9(14)

118.25(9) 111.8(10) 90.5(13) 61.4(7) 94.2(13)

Page 34 of 53

117.47(9) 108.9(9) 90.2(16) 61.8(9) 95.8(17)

117.11(10) 107.9(8) -

117.33(6) -

The numbers in parentheses are the estimated standard deviations in the units of the least significant digit given for the corresponding paramete

34


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Table 5. Displacements of atoms from the (111) plane at O(3)a in dehydrated Cs+-exchanged zeolite A

atom

Crystal 1

Crystal 2

Crystal 3

Crystal 4

Crystal 5

Crystal 6

Crystal 7

displacement

Cs(2)

-

-

-2.41

-2.40

-2.41

-2.31

-2.17

Cs(3)

-

-

-

-

-

2.09

1.92

Na(1)

-0.63

-

-

-

-

-

-

Na(2)

0.25

0.22

0.31

0.30

0.36

0.39

0.37

Na(4)

-

0.46

0.67

0.69

0.66

0.85

-

a

A positive deviation indicates that the ion lies in the large cavity. A negative deviation indicates that the atom lies on the same side of the plane as the origin, i.e.,

inside the sodalite unit.



Page 36 of 53

Table 6. Distribution and occupanciesa of Cs+ and Na+ ions in dehydrated Cs+-exchanged zeolite A

in 8-oxygen rings

crystal (component) |Cs2Na10|-LTA, (crystal 1) |Cs3Na9 |-LTA, (crystal 2) |Cs3.5Na8.5|-LTA, (crystal 3) |Cs3.5Na8.5|-LTA, (crystal 4) |Cs3.5Na8.5|-LTA, (crystal 5) |Cs4.5Na7.5|-LTA, (crystal 6) |Cs5.5Na6.5|-LTA, (crystal 7) |Cs12.5|-LTAb

Cs 2 3 3 3 3 3 3 3

|Cs12CsOH|-LTAc

3

a

Number of ions per unit cell.

with cesium vapor.

b

Na

Cs

0.5 1.5 7 4

Reference 22, first crystal.

c

Reference 22, second crystal.

opposite 6-oxygen rings α-cage β-cage Na Cs Na 8.5 0.5 8 7.5 0.5 8 0.5 8 0.5 7.5 1 6.5 1 2 2

opposite 4-oxygen rings Cs Na 1 1 1 0.5 0.5

Total charge of cations

0.5

12 12 12 12 12 12 12 12.5

4

13

A single crystal was prepared by the reduction of Na+ in dehydrated Na12-A

A single crystal was prepared by the reaction of hydrated (NH4+)12-A with cesium

hydroxide, followed by dehydration at 297 K for 14 h.

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Table 7. The elements of zeolite Rho and NH4+-Rho

Sample

Element

Na

Cs

Si

Al

Rho

wt%

8.24

16.50

59.49

15.77

wt%

0

0

82.24

17.76

+

NH4 -Rho

37



Page 38 of 53

Table 8. Adsorption model parameters for adsorption of Cs+ onto NH4+- Rho.

Single-site Langmuir 2

qsat

b

R

3.4775±0.1758

1.9069±0.4738

0.8390

Dual-site Langmuir q1sat

q2sat

b1

b2

R2

2.6291±0.1228

2.5184±0.1153

3.4839±0.24529

0.05054±0.01103

0.9227

Units: qsat = mmol/g and b = L/mmol

38


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Table 9. Comparison of Cs+ removal efficiency using some sorbents from seawater at various initial Cs concentrations. Zeolite Rhoa

Titanosilicatea

Chabaziteb

Clinoptiloliteb

Mordeniteb

Mordenitec

Cs (ppm)d

1000

1000

1.06

10.9

1.06

10.9

1.06

10.9

1.0

100

Shaking condition, t(h), T(K)

2, 298

2, 298

24, 298

24,298

24, 298

24, 298

24, 298

24, 298

2, 298

2, 298

m/ve

10

10

4

4

4

4

4

4

40

40

Cs(%)f

84

38

53

81

36

35

28

29

99

99

Adsorption capacity (ppm)g

84

38

0.14

2.21

0.10

0.95

0.07

0.79

0.03

2.48

c

d

a

In this work.

solution).

f

b

Reference 35.

Cs removal efficiency.

Reference 36. g

Initial Cs concentration in adsorption experiment solution.

Adsorption concentration of Cs on 1 g of adsorbent from 1 L of seawater.

39


e

m/v(g-adsorbent/L –adsorption


Page 40 of 53

(figure captions)

Fig. 1. Stereoviews of representative sodalite cavity (a) and large cavity (b) in crystal 1. The zeolite A framework is drawn with heavy bonds. The coordination of the exchangeable cations to oxygen atoms of the zeolite framework is indicated by light bonds.

Ellipsoids of 25%

probability are shown. Fig. 2. Stereoviews of representative sodalite cavity (a) and large cavity (b) in crystal 2. See the caption to Figure 1 for other details. Fig. 3. Stereoviews of representative sodalite cavity (a) and large cavity (b) in crystals 3, 4, and 5. See the caption to Figure 1 for other details. Fig. 4. Stereoviews of representative sodalite cavity (a) and large cavity (b) in crystal 6.

See the caption to Figure 1 for other details.

Fig. 5. Stereoviews of representative sodalite cavity (a) and large cavity (b) in crystal 7. Fig. 6.

See the caption to Figure 1 for other details.

Position and the share of cesium according to the concentration of cesium and sodium

Fig. 7.

X-ray diffraction patterns of zeolite Rho and NH4+-Rho

Fig. 8. SEM image of zeolite Rho Fig. 9.

Adsorption isotherm of Cs on NH4+-Rho and fits by single-site and dual-site Langmuir models

Fig. 10.

(A) Adsorption yield (%) and distribution coefficient (Kd) of Cs by zeolite Rho, titanosilicate and zeolite Fau with different m/V (gadsorbent/L dose), and (B) Cs adsorption capacity with 1 g/L dose


Page 41 of 53 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


after shaking for 2 h in deionized water at room temperature. Fig. 11.

(A) Adsorption yield (%) and distribution coefficient (Kd) of Cs by zeolite Rho, titanosilicate and zeolite FAU with different m/V (gadsorbent/L dose), and (B) Cs adsorption capacity with 1 g/L dose after shaking for 2 h in seawater at room temperature.

41



Page 42 of 53

(a)

(b)

Figure 1. Lee et al.

Note to editor: These stereoviews are the correct size for clearest viewing, ca. 4 1/4 inches black to black.

If

necessary to save journal space, they may be reduced to one full column width, ca. 3 1/8 inches black to black.

They must not be enlarged.

42


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(a)

(b)



If



43



Page 44 of 53

(a)

(b)



If



44


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(a)

(b)



If



45



Page 46 of 53

(a)

(b)



If



46


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Figure 6.

Lee et al.

47



Figure 7.

Lee et al.

48


Page 48 of 53

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Figure 8.

Lee et al.

49



Figure 9.

Lee et al.

50


Page 50 of 53

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Figure 10.

Lee et al.

51



Figure 11.

Lee et al.

52


Page 52 of 53

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TOC Graphic

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Selective Removal of Radioactive Cesium from Nuclear Waste by

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