Andrew Knight, PhD CandidateSchultz Research GroupDepartment of Chemistry

University of Iowa

Inferred Pa(V) complex formation via selective

extraction by aliphatic alcohols

Radiobioassay & Radiochemical Measurement ConferenceKnoxville, TNOctober 2014

1

“One author [Harold Kirby, 1958] expressed the opinion that the present decade ‘will see much of the mystery and witchcraft eliminated from protactinium chemistry.’ This objective would be facilitated greatly if a convenient radioactive tracer were more easily available to a large number of potential investigators.”

~Claude Sill, Anal. Chem. (1966)

2

Th Pa U Np Pu

5f6d

Pa

O

An

O

O

+/2+

Schadel, M., Nat. 1997, 388. 55-57.De Sio, S. M., Inorg Chem. 2014, 53. 1750-1755Le Naour, C., Inorg Chem. 2005, 44. 9542-9546

3+

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Geology

Nuclear Forensics

Nuclear Fuel

Nuclear Medicine4

Geology Geo-chronology

Figure by Andy Nelson

231Pa230Th

234U or 235U activity

32,760 y 75,400 y

(50% parent activity)

5

Nuclear Forensics Chronology- Uranium and plutonium materials

0.0E+00

1.0E+17

2.0E+17

3.0E+17

4.0E+17

5.0E+17

0 10 20 30 40 50

Atom

s N

p

Time (years)

Time Function

Initial Np atoms at time of purification

Keegan, R. P., Applied Radiation and Isotopes 2003, 59. 137-143 Figure by Andy Nelson

*Np is measured by 233Pa gamma emission

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Nuclear Fuel Waste remediation of

conventional reactors Fuel production of

alternative fuel cycles (i.e. thorium)

http://energyfromthorium.com/2011/01/30/china-initiates-tmsr/ Figure by Andy Nelson

Pa-231

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Nuclear Medicine Production of 230U/226Th generator for alpha therapy

231Pa (p, 2n)

232Th (p,3n) 230Pa (β-: 17 days)

Morgenstern, A., Anal. Chem. 2008, 80. 8763-8770

Generator Source

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Utilize solvent extraction and extraction chromatography with “protactinium selective extractants” to:

1.) Facilitate Pa separations to allow for ease of use and promote further Pa research

2.) Establish the dominant solution and solid-state complexes of Pa extracted in acid matrices

3.) Determine the extraction mechanism of Pa with aliphatic alcohols

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Produced by Eichrom Based upon previous literature Hypothesized that aliphatic alcohols will

show selectivity for Pa over other actinides

1-octanol 2,6-dimethyl-4-heptanol

(diisobutylcarbinol)

2-ethyl-hexanol10

1-octanol was chosen based on Sill (1966) and Burnett (1995)

Submitted to: Analytica Chimica Acta 11

0

400

800

1200

1600

Coun

ts (a

rb.)

0 30 60

Radionuclide Radiochemical Yield,%

Purity,%

Protactinium 99 ± 1 100 ± 0.2

Neptunium 92 ± 3 99 ± 2

237Np 9 M HCl 233Pa 1 M HCl

Volume Solvent (mL)

12

% Extracted≈ [Pa]A

[Pa]O

40% extractant60% dodecane

Acid (HCl , HNO3) Ranging from 1-9 M

+ [Pa]O

13

Log D = Log Kex + nLog [ROHorg] + m Log [Cl-aq] – jLog[H+] ;

[Cl-] = 6 M, [H+] = 6 M

: (Slope= 1.58 ± 0.08): (Slope = 2.07 ± 0.15)

: (Slope= 2.30 ± 0.19)

14

15

16

17

[DIBC] =2.31 [2-Ethyl-hexanol] =2.56 [1-Octanol] =2.53

Pa Ga

Po

PaGa

Po

PaGa

Po

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[DIBC] =2.31 [2-Ethyl-hexanol] =2.56 [1-Octanol] =2.53

Pa

Ga Po*Ga

Po*

Pa

Ga

Po*

Pa

*potentially slow kinetics

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0

400

800

1200

1600

2000

0 25 50 75 100

Cou

nts

Solvent Volume (mL)

Actinides:241Am,239Pu, 237Np, 232U, 229Th, 228Th,

Decay Products:

(From 228Th): 224Ra, 220Rn, 212Pb, 212Bi

(From 229Th): 225Ra, 225Ac, 221Fr, 217At, 213Bi,209Pb, 209Bi

233Pa

6 M HCl 1 M HCl

To be submitted: Analytical Chemistry 20

Pa extraction is unique to the actinides, likely due to orbital near degeneracy.

More data is needed to conclude about Poand Ga extraction

Th Pa U Np Pu

5f6d

21

Further characterize the extraction behavior of elements

Establish stoichiometric identification of extracted metallic species

Answer the question of WHY?

22

Access higher quantities of Protactinium for spectroscopic studies: Compare speciation of Pa relative to the other

actinides in aqueous conditions Investigate the extraction mechanism of

aliphatic alcohols with Pa

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University of Iowa Dr. Schultz

▪ Eric Eitrheim▪ Andy Nelson▪ Madeline Peterson

Dr. Forbes▪ Daniel Unruh ▪ Josh DeGroot▪ Ashini Jayasingh▪ Madeline Basile▪ Maurice Payne

Eichrom Technlogies, LLC Idaho National Laboratory Savannah River National Laboratory

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Questions? 25