Rapid Sample Preparation for Alpha Spectroscopy with Ultrafiltration

Feb 26, 2018 - ... rapid, fieldable alpha spectroscopy sample preparation technique that minimizes consumables and decreases the nuclear forensics tim...
0 downloads 0 Views 743KB Size
Subscriber access provided by UNIV OF SCIENCES PHILADELPHIA

Article

Rapid Sample Preparation for Alpha Spectroscopy with Ultrafiltration Membranes Christine Elizabeth Duval, Abenazer W. Darge, Cody L. Ruff, Timothy A DeVol, and Scott Michael Husson Anal. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.analchem.8b00135 • Publication Date (Web): 26 Feb 2018 Downloaded from http://pubs.acs.org on February 26, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Analytical Chemistry is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 20 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

Analytical Chemistry

1

Rapid Sample Preparation for Alpha Spectroscopy with Ultrafiltration Membranes

2

Christine E. Duval†§, Abenazer W. Darge†, Cody Ruff†, Timothy A. DeVol‡, and Scott M.

3

Husson*†

4



5

Clemson, SC 29634 USA

6



7

Computer Court, Anderson, SC 29625 USA

8

§

9

Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106

Department of Chemical and Biomolecular Engineering, Clemson University, 127 Earle Hall,

Department of Environmental Engineering and Earth Sciences, Clemson University, 342

Current address: Department of Chemical and Biomolecular Engineering, Case Western

10

*Corresponding author. Current address: Department of Chemical and Biomolecular

11

Engineering, Clemson University, 127 Earle Hall, Clemson SC 29634, USA. Tel: +1 (864) 656-

12

4502, Fax: +1 (864)-656-0784. Email: [email protected]

13 14

Abstract: This contribution describes a rapid, fieldable alpha spectroscopy sample preparation

15

technique that minimizes consumables and decreases the nuclear forensics timeline. Functional

16

ultrafiltration membranes are presented that selectively concentrate uranium directly from pH 6

17

ground water and serve as the alpha spectroscopy substrate. Membranes were prepared by

18

ultraviolet-grafting of uranium-selective polymer chains from the membrane surface. Membranes

19

were characterized by Fourier-transform infrared spectroscopy before and after modification to

20

support functionalization. Membrane performance was evaluated using uranium-233 or depleted

21

uranium in both deionized and simulated ground water at pH 6. Functionalized membranes

22

achieved peak energy resolutions of 31 ± 2 keV and recoveries of 81 ± 4% when prepared

23

directly from pH 6 simulated ground water. For simulated ground water spiked with depleted

1 ACS Paragon Plus Environment

Analytical 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

24

uranium, baseline energy resolution was achieved for both isotopes (uranium-238 and uranium-

25

234). The porous, uranium-selective substrate designs can process liters per hour of uranium-

26

contaminated ground water using low-pressure (< 150 kPa) filtration and a 45 mm diameter

27

membrane filter, leading to a high throughput, one-step concentration, purification, and sample

28

mounting process.

29 30

Keywords: EGMP, ethylene glycol methacrylate phosphate, nuclear forensics, phosphoric acid 2-

31

hydroxy-ethyl methacrylate ester, phosphate ligands, uranium selective membrane

32 33

Manipulation of special nuclear material (SNM) for the express purpose of assembling a weapon

34

of mass destruction is likely to contaminate the environment with trace-levels of SNM (i.e.

35

plutonium, uranium-233, and uranium enriched in the isotopes uranium-233 or uranium-235).

36

Today, no fieldable technique exists for the direct isotopic analysis of environmental samples

37

containing SNM. A fieldable technique should be portable, robust and minimize consumables.

38

Presently, the limiting factor is not the isotopic detection method (alpha spectroscopy), but rather

39

the unavailability of separation materials to prepare samples for analysis directly from neutral pH

40

environmental waters.

41

Traditional methods of sample preparation for alpha-spectroscopy require a two-step process:

42

(1) sample isolation and purification followed by (2) sample mounting1. Methods of chemical

43

separation include co-precipitation, purification by solid-phase separation agents, and liquid-

44

liquid extraction (LLE)—all of which have drawbacks when considering a fieldable protocol.

45

Co-precipitation is not necessarily a selective process and requires that the analyte is purified by

46

removing interfering ions that can lower spectral resolution. Actinide selectivity can be achieved

2 ACS Paragon Plus Environment

Page 2 of 20

Page 3 of 20 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

Analytical Chemistry

47

with LLE; however, it requires organic solvents, ligands, and acid while creating mixed

48

radioactive-hazardous waste. Solid-phase separation agents, like extractive resins, produce less

49

waste than LLE; however, commercial resins, like UTEVA® and Diphonix® (Eichrom

50

Technologies) require solutions to be acidified to pH < 2 to achieve uranium-selectivity.

51

After isolation and purification, samples are mounted onto a substrate for analysis. The state-

52

of-the-art technique for sample mounting is electrodeposition. This technique can achieve a high

53

resolution of ~20 keV in the pulse-height spectrum2; however, mounting takes 1-2 h and requires

54

an expensive platinum anode in an electrolytic cell. Other sample mounting methods for lower

55

resolution needs are evaporation, which yields resolutions of 40-70 keV3, and a combination of

56

precipitation and filtration, which yields resolutions of 75-100 keV4. Mounting purified samples

57

by precipitation with neodymium fluoride yields resolutions comparable to electrodeposition5.

58

Recent studies have focused on the use of selective polymer films as alpha spectroscopy

59

substrates to avoid the expense associated with electrodeposition6-11. These substrates combine

60

the steps of chemical separation and sample mounting while overcoming the poor resolution

61

associated with non-selective films used for complex sample matrices12. Pantchev et al.7

62

functionalized nylon-6,6 membranes with amidoxime ligands to concentrate uranium from

63

potable water. Spectral resolutions of 40 keV were achieved, but uranium was loaded on the

64

membranes through batch-sorption (not by filtration), which required a long 24-h equilibration

65

time. Surbeck et al.9 impregnated spin-coated polyacrylonitrile films with MnO2 for the

66

concentration of radium from potable water. After a 20-h equilibration time, resolutions of 40

67

keV were achieved in the alpha spectrum. Gonzales et al.8 developed polymer films containing

68

the commercial Dipex® ligand for the simultaneous separation and mounting of americium and

69

plutonium from urine samples. Despite excellent resolutions of 20-30 keV and a shorter

3 ACS Paragon Plus Environment

Analytical 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

70

equilibration time (1 h) than Pantchev and Surbeck, sample preparation required the acidification

71

of urine to pH 1 and addition of sodium nitrite. Paul et al.13 functionalized polyether sulfone

72

(PES) membranes with a thin phosphonate-sulfate bifunctional layer. Uranium and plutonium

73

were loaded from 3-4 M nitric acid solutions and achieved high resolutions of 20-35 keV from

74

dissolved spent fuel. Membranes were loaded with activity in a batch system (not by filtration)

75

and required an equilibration time of 1 h. While selective polymer films have proven effective in

76

achieving high resolutions, the current designs are not ideal for rapid, field-based measurements

77

due to the need for consumable chemicals and/or long isolation, purification and mounting times.

78

The objective of this work was to develop a rapid, fieldable, alpha spectroscopy sample

79

preparation technique that minimizes consumables and decreases the nuclear forensics timeline.

80

In this work, we present functional ultrafiltration membranes that (1) selectively and rapidly

81

concentrate uranium directly from neutral pH ground water and (2) serve as the alpha

82

spectroscopy substrate. Uranium selectivity was introduced to the membrane through UV-

83

grafting an ethylene glycol methacrylate phosphate-based polymer. Membranes were evaluated

84

for permeability and peak energy resolution in the pulse height spectrum. The new substrate

85

design allows for the filtration of uranium-contaminated ground water through the uranium-

86

binding membrane material, leading to a high throughput separation and sample mounting

87

process.

88 89 90

EXPERIMENTAL SECTION Materials. The following reagents were used as received: 2,2’-Azobis(2-methylpropionitrile)

91

(AIBN, 98%, Aldrich), ethanol (reagent grade, Sigma Aldrich), nitric acid (90%, Fisher

92

Scientific), N,N’-methylenebis(acrylamide) (N-MBA, 99%, Sigma Aldrich), ethylene glycol

4 ACS Paragon Plus Environment

Page 4 of 20

Page 5 of 20 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

Analytical Chemistry

93

methacrylate phosphate (EGMP, 90%, Aldrich), sodium hydroxide (NaOH, Sigma Aldrich),

94

UltimaGold AB liquid scintillation cocktail (PerkinElmer), uranium-233 (Eckert & Ziegler), and

95

uranyl nitrate hexahydrate (depleted uranium, PerkinElmer). Water was distilled and then

96

deionized with a SuperQ Water System (DDI water, Millipore, Molsheim, France).

97

Membrane preparation by UV-initiated polymerization. Poly[(ether sulfone)-graft-

98

(ethylene glycol methacrylate phosphate)-graft-( N,N’-methylenebis(acrylamide))] membranes

99

(UVMs) were synthesized by UV-initiated free radical polymerization according to Scheme 1.

100

Biomax® PES membranes of varying molecular weight cut-offs (MWCO) were purchased from

101

MilliporeSigma and rinsed with ethanol to remove pore fillers prior to functionalization. The

102

polymerization solution was prepared in a 20 mL glass vial by dissolving 0.4 g EGMP (uranium-

103

binding ligand), 24 mg AIBN (photo-initiator) and 0.01 mg of N-MBA (cross-linker) in 6 mL of

104

ethanol. Membranes were placed in a petri dish with the active layer (shiny side) face up and 2

105

mL of the polymerization solution was pipetted onto each membrane. A second petri dish was

106

placed directly on top of the membrane. Care was taken to assure that there were no air bubbles

107

between the membrane surface and the second petri dish. The membrane-containing petri dishes

108

were positioned underneath an 8 W UVLS-28 EL Series UV lamp (UVP, Upland, CA).

109

Membranes were irradiated with 365 nm UV light for 10 min at a distance of 7.6 cm from the

110

UV lamp. After the reaction, the UVMs were rinsed with DDI water, submerged in a 50% (v/v)

111

mixture of ethanol and DDI water, and then placed in a reciprocal shaking bath (Precision

112

Scientific Inc., Winchester, IL) at 100 RPM and 25oC overnight to remove any residual reactants

113

and/or physically adsorbed polymer from the membrane. Membranes were rinsed with DDI

114

water then stored in a 50% (v/v) mixture of ethanol and DDI water between synthesis and use.

5 ACS Paragon Plus Environment

Analytical 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

115 116 117 118

Scheme 1. UV-grafting of poly(EGMP)-co-(N-MBA) from a PES membrane.

119

Membrane characterization by infrared spectroscopy. Attenuated total reflectance

120

Fourier-transform infrared spectroscopy (ATR-FTIR) was used to characterize the membranes

121

before and after functionalization. Samples were analyzed using a nitrogen purged Nicolet Nexus

122

870 FTIR Spectrometer (Thermo Scientific, USA) with a zinc sulfide ATR crystal for 64 scans at

123

a resolution of 4 cm-1. Data were collected and analyzed using Omnic 8.3.103 software (Thermo

124

Scientific).

125

Direct-flow water flux measurements. Pure water flux experiments for pristine PES

126

membranes and UVMs were conducted according to a previously described procedure15.

127

Experiments were performed with pressures from 50 to 138 kPa using a 50 mL Amicon direct

128

flow ultrafiltration cell (Amicon Biosepartaions, Jaffrey, NH) connected to an air cylinder.

129

Membranes were compressed at 138 kPa for 15 min before data collection. Permeate fractions

130

were collected in 30 s intervals and weighed to determine the mass flowrate through the 6 ACS Paragon Plus Environment

Page 6 of 20

Page 7 of 20 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

Analytical Chemistry

131

membrane. Flux data were used to calculate the pure water permeability coefficient of the

132

membranes. Permeability coefficients are reported as the average from triplicate measurements

133

of different membranes.

134

Simultaneous purification and mounting for alpha spectroscopy. Samples were prepared

135

for alpha spectroscopy by mounting the membranes in a 50 mL Amicon ultrafiltration cell and

136

filtering the uranium-containing solutions at 138 kPa, shown in Scheme 2.

137 138

Scheme 2. Alpha spectroscopy substrates were prepared in a 50-mL ultrafiltration cell (left),

139

removed from the cell (center) and mounted in a custom sample holder (right).

140 141

Alpha spectroscopy. Isotopic analysis was performed by alpha spectroscopy using the

142

ultrafiltration membranes as the substrate for analysis. Immediately after sample purification and

143

mounting, membranes were placed on a stainless-steel plate, immobilized with a custom 3-D

144

printed sample holder and inserted in a Canberra Model 7401 alpha spectrometer (Canberra

145

Industries, Inc., Oak Ridge, TN). The 3-D printed sample holder positioned the sample under the

146

detector and prevented curling of the membrane edges during measurement. Samples were

147

counted under vacuum at a distance of 9 mm from the detector surface. Counting time was 1 h

148

for uranium-233 and 48 h for depleted uranium samples. The vacuum chamber pressure for all

149

measurements was 500 LMH/bar), demonstrating the potential for

312

high-throughput analysis. Peak energy resolutions were found to be independent of the MWCO

313

of the membrane and the sample matrix for the conditions tested, indicating that still higher

314

MWCO membranes could be used to achieve higher permeabilities (faster processing time). 16 ACS Paragon Plus Environment

Page 17 of 20 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

Analytical Chemistry

315

Experiments with depleted uranium in simulated ground water yielded resolutions for uranium-

316

238 and uranium-234 of 27 ± 5 keV and 26 ± 3 keV, with fully resolved peaks, as needed for the

317

isotopic analysis of uranium in nuclear forensics applications. The results of this research offer

318

the first evidence of a high-throughput sample preparation method for isotopic analysis with

319

alpha spectroscopy that directly concentrates uranium from pH neutral ground water.

320

Furthermore, they lay the groundwork for the development of ultrafiltration alpha spectroscopy

321

substrates that target other radioisotopes of interest.

322 323

ASSOCIATED CONTENT

324

Supporting information

325

The Supporting Information is available free of charge on the ACS Publications website.

326

Example water flux data used to calculate permeability coefficients, alpha spectra of

327

UVMs with MWCO 30 kDa and 50 kDa exposed to 10 Bq of uranium-233, and pulse-

328

height spectrum of unmodified 50 kDa PES membrane after filtering 10 mL of 500 Bq L-

329

1

uranium at pH 6.

330 331

AUTHOR INFORMATION

332

Corresponding Author

333

*Email: [email protected]. Tel: +1 (864) 656-4502, Fax: +1 (864)-656-0784.

334 335

ACKNOWLEDGMENTS

336

This work was supported by the Defense Threat Reduction Agency, Basic Research Award

337

#HDTRA1-16-1-0016, to Clemson University.

17 ACS Paragon Plus Environment

Analytical 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

338

REFERENCES

339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380

1. Vajda, N.; Kim, C. K., Determination of Pu isotopes by alpha spectrometry: a review of analytical methodology. Journal of Radioanalytical and Nuclear Chemistry 2010, 283 (1), 203223. 2. Alpha Spectroscopy --An Art of a Science?; Canberra Industries, Inc.: online, 2006. 3. Semkow, T. M.; Khan, A. J.; Haines, D. K.; Bari, A., Rapid Alpha Spectroscopy of Evaporated Liquid Residues for Emergency Response. Health Phys 2009, 96 (4), 432-441. 4. Sill, C. W.; Williams, R. L., Preparation of actinides for alpha spectrometry without electrodeposition. Analytical Chemistry 1981, 53, 412-415. 5. Hindman, F., Neodymium fluoride mounting for alpha-spectrometric determination of uranium, plutonium, and americium. Analytical Chemistry 1983, 55 (14), 2460-2461. 6. Rim, J. H.; Gonzales, E. R.; Armenta, C. E.; Unlu, K.; Peterson, D. S., Developing and evaluating di(2-ethylhexyl) orthophosphoric acid (HDEP) based polymer ligand film (PLF) for plutonium extraction. Journal of Radioanalytical and Nuclear Chemistry 2009, 296 (2), 10991103. 7. Pantchev, I.; Farquet, P.; Surbeck, H.; Meyer, T., Surface modified Nylon 6,6 and application for adsorption and detection of uranium in potable water. Reactive and Functional Polymers 2009, 67 (2), 127-135. 8. Gonzales, E. R.; Peterson, D. S., Rapid radiochemical sample preparation for alpha spectrometry using polymer ligand films. Journal of Radioanalytical and Nuclear Chemistry 2009, 282 (2), 543-547. 9. Surbeck, H., Determination of natural radionuclides in drinking water; a tentative protocol. The Science of the Total Environment 1995, 173/174, 91-99. 10. Locklair, W. D.; Mannion, J. M.; Husson, S. M.; Powell, B. A., Uptake of plutonium on a novel thin film for use in spectrometry. Journal of Radioanalytical and Nuclear Chemistry 2016, 307, 2333-2338. 11. Rim, J. H.; Armenta, C. E.; Gonzales, E. R.; Unlu, K.; Peterson, D. S., Evaluating bis(2ethylhexyl) methanediphosphonic acid (H2DEH[MDP]) based polymer ligand film (PLF) for plutonium and uranium extraction. Journal of Radioanalytical and Nuclear Chemistry 2016, 307 (3), 2327-2332. 12. Mannion, J. M.; Locklair, W. D.; Powell, B. A.; Husson, S. M., Alpha spectroscopy substrates based on thin polymer films. Journal of Radioanalytical and Nuclear Chemistry 2016, 307, 2339-2345. 13. Paul, S.; Pandey, A. K.; Shah, R. V.; Aggarwal, S. K., Chemically selective polymer substrate based direct isotope dilution alpha spectrometry of Pu. Analytica Chimica Acta 2015, 878, 54-62. 14. He, D.; Susanto, H.; Ulbricht, M., Photo-irradiation for preparation, modification and stimulation of polymeric membranes. Progress in Polymer Science 2009, 34 (1), 62-98. 15. Chitpong, N.; Husson, S. M., Polyacid Functionalized Cellulose Nanofiber Membranes for Removal of Heavy Metals from Impaired Waters. Journal of Membrane Science 2016. 16. Duval, C. E.; DeVol, T. A.; Husson, S. M., Evaluation of resin radius and column diameter for the implementation of extractive scintillating resin in flow-cell detectors. Journal of Radioanalytical and Nuclear Chemistry 2016, 307, 2253-2258.

18 ACS Paragon Plus Environment

Page 18 of 20

Page 19 of 20 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

381 382 383 384 385 386 387 388 389 390 391

Analytical Chemistry

17. Roane, J. E.; DeVol, T. A., Evaluation of an extractive scintillation medium for the detection of uranium in water. Journal of Radioanalytical and Nuclear Chemistry 2005, 263 (1), 51-57. 18. Hanson, S. K.; Mueller, A. H.; Oldham, W. J., Klaui Ligand Thin Films for Rapid Plutonium Analysis by Alpha Spectrometry. Analytical Chemistry 2014, 86, 1153-1159. 19. US Department of Energy Office of Environmental Management. Depleted Uranium Hexafluoride Management Program: Characteristics and its Compounds; 2001. 20. Uranium Enrichment. http://www.world-nuclear.org/information-library/nuclear-fuelcycle/conversion-enrichment-and-fabrication/uranium-enrichment.aspx (accessed March 3, 2016).

19 ACS Paragon Plus Environment

Analytical 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

338x190mm (300 x 300 DPI)

ACS Paragon Plus Environment

Page 20 of 20