Analysis of Actinide Elements from Large Environmental Samples

Guebuem KimBill Burnett

Florida State Universityand

E. Philip HorwitzPG Research Foundation, Inc.

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

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.”

Actinides in Natural Waters

PrecipitateMnO2

Sepa

rati

on

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

10's - 100's liters+ tracers

pH = 2KMnO4

NaOH, pH = 8MnCl2

Resins:• UTEVA• TRU

2M HCl/NH2OH.HCl50 mg FeNaNO2

pH = 6-7

PrecipitateFe(OH)3

Marine Environment LaboratoryMonaco

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MnO2 suspension withdrawn from bottom of conical-shaped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.

Irish Sea Water Results

P ara m e t er

IAEA

R ec omm e nd e d

Va lu e

mBq/kg

IAEA

Con f id e n ce

I nt er v a l

mBq/kg

M EL /FS U

R e sult

mBq/kg

M EL /FS U

Y i e ld

%

239,240P u 13.2 12.4 - 14.0 14.1±0.8 99.0

238P u 3.16 2.80 - 3.82 3.0±0.2 99.0

241Am 16.0 8.40 - 20.0 17.0±1.1 95.0

Soils and Sediments

Dissolution/Leaching

Dip

honi

xoxidation

Resins:• TRU• TEVA• UTEVA

tracersFe(OH)3 ppt0.1M HCl-0.3M HF, AA

"Matrix"

0.5M HEDPA

H3PO4

{oneor

more

Sepa

rati

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

• Ozonation• “Fenton’s Reagent”

DiphonixIon Exchange Resin

Features of Diphonix:• diphosphonic & sulfonic acid groups• polystyrene/divinylbenzene matrix• extremely high actinide retention,

low common ion adsorption• tolerant to HF

Actinide Retention on Diphonix Resin

Diphonix Resin shows high

retention for all Actinides

Adsorption of 241Am

HCl (Molarity)

10-2 10-1 100 10150

60

70

80

90

100

Adsorption of actinides highest at pH ~1-2

HEDPA

1-hydroxyethane-1, 1-diphosphonic acid

Molecular weight = 206.03Elution 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)

Elution:HEDPA

Acid Dependency

Curves

Indicates that actinides should

elute easily at concentrations

~0.5M

Elution of Am

0.5M HEDPA Elution Volume (mL)

0 5 10 15 20 25 30 35 400

20

40

60

80

100

Prior ResultIncremental

HEDPA Destruction via Ozone

0%

20%

40%

60%

80%

100%

120%

50 70 90 110 130 150 170

Time (min)

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

Ozonation Process

Ozone delivered from an ozone generator via a gas diffusion stone oxidizes the HEDPA

sample

Oxidation by Fenton’s 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+

Actinide Separations

TRUTRU

Resin

12

3 45

6

3

2

12.5M HNO3

2.5M HNO3/0.1M NaNO2

2.5M HNO3

9M HCl4M HCl

4M HCl/TiCl3 6

5

4

4M HCl2.5M HNO3

2.5M HNO3/0.1M NaNO2

2.5M HNO3

9M HCl1M HCl

0.1M Ammonium Bioxalate

12

3 45

6DiscardAm

Pu DiscardTh

U

Sample(3M HNO3, 0.7M Al(NO3)3, FS, AA)

Final clean-ups: Am/Ln on TEVA; U on UTEVA

TRUResin tolerates high PO4

Sensitivity to PO4

UTEVA.Resin TRU.Resin

Preliminary Tests

50 60 70 80 90 100

TRU.Resin

HEDPA Destruction

HEDPA Elution

Diphonix Adsorption

Fe(OH)3 ppt

Yield (%)

AmTh

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

Standard Samples: Yields

Am Pu Th U50

60

70

80

90

100

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.

Standard Samples: Results

0.60 0.70 0.80 0.90 1.00 1.10

EML-9409

EML-9509

EML-9803

IAEA-300

IAEA-135

Activity Ratio: FSU/Standard

Am-241 Pu-239/240

Table 1: EML and IAEA intercomparison values.

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 HEDPASeparations starting with TRUResin

prevent PO4 interference