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Analysis of Actinide Elements from Large Environmental Samples

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Presentation on theme: "Analysis of Actinide Elements from Large Environmental Samples"— Presentation transcript:

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 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 Precipitate Fe(OH)3 2M HCl/NH2OH.HCl 50 mg Fe NaNO2 pH = 6-7 Resins: UTEVA TRU Separation Am, Pu, etc. alpha spectrometry ICP-MS

5 Marine Environment Laboratory Monaco

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 MnO2 suspension withdrawn from bottom of conical-shaped plastic tanks — processed for Am and Pu.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

8 { Soils and Sediments Dissolution/ Leaching Ozonation
tracers Fe(OH)3 ppt 0.1M HCl-0.3M HF, AA 0.5M HEDPA Diphonix "Matrix" Ozonation “Fenton’s Reagent” oxidation H3PO4 Resins: TRU TEVA UTEVA Am, Pu, etc. alpha spectrometry ICP-MS { one or more Separation

9 Diphonix Ion Exchange Resin
Features of Diphonix: diphosphonic & sulfonic acid groups polystyrene/divinylbenzene matrix extremely high actinide retention, low common ion adsorption tolerant to HF

10 Actinide Retention on Diphonix Resin
Diphonix Resin shows high retention for all Actinides

11 Adsorption of actinides highest at pH ~1-2
Adsorption of 241Am Adsorption of actinides highest at pH ~1-2

12 HEDPA 1-hydroxyethane-1, 1-diphosphonic acid Molecular weight = 206.03
Elution sequence: Th(IV) = Pu(IV) > U(VI) > Am(III) Reagent-grade expensive (Fluka: 50 g ~ $165) — option to purify industrial grade (Albright & Wilson: “BRIQUEST” ADPA-60AW U)

13 Elution: HEDPA Acid Dependency Curves
Indicates that actinides should elute easily at concentrations ~0.5M

14 Elution of Am

15 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

16 Ozonation Process sample Ozone delivered from an ozone generator via a gas diffusion stone oxidizes the HEDPA

17 Oxidation by Fenton’s Reagent
finished Treatment: 40 mL 0.5M HEDPA + 1 mL HNO mL H2O g Fe(NH4)2(SO4)2·6H2O Temperature ~90oC H2O2 + Fe2+ ® OH + OH- +Fe3+

18 Final clean-ups: Am/Ln on TEVA; U on UTEVA
Actinide Separations Sample (3M HNO3, 0.7M Al(NO3)3, FS, AA) TRU Resin 1 2 3 4 5 6 2.5M HNO3 2.5M HNO3/0.1M NaNO2 9M HCl 4M HCl 4M HCl/TiCl3 1M HCl 0.1M Ammonium Bioxalate Discard Am Pu Th U TRU·Resin tolerates high PO4 Final clean-ups: Am/Ln on TEVA; U on UTEVA

19 Sensitivity to PO4 TRU.Resin UTEVA.Resin

20 Preliminary Tests Am-241 and Th-234 spiked samples. Matrix = HNO3/HCl leach of 10-g NIST Rocky Flats II soil

21 Standard Samples: Yields
Samples (n=7): 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.

22 Standard Samples: Results
Table 1: EML and IAEA intercomparison values.

23 Summary Uptake of actinides onto Diphonix from complex matrices is very efficient 0.5M HEDPA easily elutes actinides “Fenton’s Reagent” or O3 successfully oxidizes HEDPA Separations starting with TRU·Resin prevent PO4 interference

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