Analysis of Actinide Elements from Large Environmental Samples

1
Analysis of Actinide Elements from Large
Environmental Samples

• Guebuem Kim
• Bill Burnett
• Florida State University
• and
• E. Philip Horwitz
• PG Research Foundation, Inc.

2
Need for Large Volumes

• Achieve low MDA's for environmental monitoring
• Specialized scientific studies often require
  large volumes to obtain necessary sensitivity,
  e.g., Am/Pu in seawater, global fallout in recent
  soils

3
Analytical Challenges

• Preconcentration of actinides from natural water
  samples may require handling up to 100-400 liters
• Large (5-10 grams or more) soil/sediment samples
  may require difficult and lengthy dissolution
  procedures
• Separation chemistry, especially from large
  soil/sediment samples, suffers from matrix
  effects.

4
Actinides in Natural Waters
Precipitate MnO2
pH 2 KMnO4 NaOH, pH 8 MnCl2
10's - 100's liters tracers
2M HCl/NH2OH.HCl 50 mg Fe NaNO2 pH 6-7
Precipitate Fe(OH)3

• Resins
• UTEVA
• TRU

Separation

• Am, Pu, etc.
• alpha spectrometry
• ICP-MS

5
Marine Environment LaboratoryMonaco
6
Am/Pu from 200-L Seawater
Supernatant seawater transferred from one plastic
tank to another via pumping this will be used
for 90Sr and 137Cs.
MnO2 suspension withdrawn from bottom of
conical-shaped plastic tanks processed for Am
and Pu.
7
Irish Sea Water Results
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Soils and Sediments
Dissolution/ Leaching
tracers Fe(OH)3 ppt 0.1M HCl-0.3M HF, AA
0.5M HEDPA
Diphonix
"Matrix"

• Ozonation
• Fentons Reagent

oxidation
H3PO4

• Resins
• TRU
• TEVA
• UTEVA

• Am, Pu, etc.
• alpha spectrometry
• ICP-MS

one or more
Separation
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DiphonixIon Exchange Resin

• Features of Diphonix
• diphosphonic sulfonic acid groups
• polystyrene/divinylbenzene matrix
• extremely high actinide retention, low common ion
  adsorption
• tolerant to HF

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Actinide Retention on Diphonix Resin
Diphonix Resin shows high retention for all
Actinides
11
Adsorption of 241Am
Adsorption of actinides highest at pH 1-2
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HEDPA

• 1-hydroxyethane-1, 1-diphosphonic acid
• Molecular weight 206.03
• Elution sequence Th(IV) Pu(IV) gt U(VI) gt
  Am(III)
• Reagent-grade expensive (Fluka 50 g 165)
  option to purify industrial grade (Albright
  Wilson BRIQUEST ADPA-60AW U)

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ElutionHEDPAAcid DependencyCurves
Indicates that actinides should elute easily at
concentrations 0.5M
14
Elution of Am
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HEDPA Destruction via Ozone
20-mL elution was diluted to 70 mL, H2O2 added
(0.5M), pH adjusted to 9.0 with NaOH, and samples
ozonated for variable lengths of time
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Ozonation Process
sample
Ozone delivered from an ozone generator via a gas
diffusion stone oxidizes the HEDPA
17
Oxidation by Fentons Reagent
finished
Treatment 40 mL 0.5M HEDPA 1 mL HNO3 40 mL
H2O2 0.17 g Fe(NH4)2(SO4)26H2O Temperature
90oC
H2O2 Fe2 OH OH- Fe3
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Actinide Separations
Sample (3M HNO3, 0.7M Al(NO3)3, FS, AA)
TRUResin tolerates high PO4
Final clean-ups Am/Ln on TEVA U on UTEVA
19
Sensitivity to PO4
TRU.Resin
UTEVA.Resin
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Preliminary Tests
Am-241 and Th-234 spiked samples. Matrix
HNO3/HCl leach of 10-g NIST Rocky Flats II soil
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Standard Samples Yields

• Samples (n7)
• 3 EML soils
• 2 IAEA sediments
• 2 Fe-rich soils

5 intercomparison samples and 2 Fe-rich samples
run through entire procedure and analyzed for Am,
Pu, U, and Th. 10-gram samples were leached with
HNO3/HCl.
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Standard Samples Results
Table 1 EML and IAEA intercomparison values.
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Summary

• Uptake of actinides onto Diphonix from complex
  matrices is very efficient
• 0.5M HEDPA easily elutes actinides
• Fentons Reagent or O3 successfully oxidizes
  HEDPA
• Separations starting with TRUResin prevent PO4
  interference