Applications of Extraction Chromatography in Marine Geochemistry

1
Applications of Extraction Chromatography in
Marine Geochemistry

• Bill Burnett
• Department of Oceanography
• Florida State University

2
Acknowledgments
FSU Mike Schultz, Reide Corbett, Peter Cable,
Jaye Cable, Mike Lambert, Jamie Christoff,
Guebuem Kim, Christine Andre GEL James
Westmoreland, Richard Kinney, Barry Stewart IAEA
(MEL) Pavel Povinic, Jerry LaRosa Eichrom Mike
Fern, Larry Jassin, Anil Thakkar, Michaela
Langer PG Research Foundation Phil Horwitz
3
U-Series Disequilibrium in the Sea
222Rn
210Pb
222Rn
222Rn
4
Example Applications

• U-series (230Th/234U, etc.) dating of fossil
  corals sea level, uplift studies, etc.
• U-series dating of biogenic materials and
  sea-floor minerals ages, growth rates
  directions
• Sediment accumulation rates (230Th, 210Pb, etc.)
• Tracing groundwater flow into the ocean via
  natural Ra isotopes (226Ra, 228Ra, etc.)

5
Analytical Challenges for Environmental Samples

• Complex and variable matrices, e.g., seawater,
  sediment, fish, Mn nodules, etc. methods must
  be versatile
• Very low abundance of certain nuclides yields
  must be high
• Many U/Th-series nuclides are characterized by
  similar alpha decay energies separations must
  be complete

6
Eichrom Technologies, Inc.
Development of an idea at Eichrom Technologies,
Inc...
Anil
Phil
Larry
Mike
7
PHIL...Phil Has Ideas that Last
Billyou need to use extraction chromatography
to make your life easier
Bill
Phil
8
Distribution of Ocean-Floor Phosphorites
fsu
X
X
RELICT
MODERN
UNDIFFERENTIATED
X
AREA OF
UPWELLING
Glenn et al. Fig. 4
9
U-Series Dating
10
Phil, how can we do this separation
Bill, when is FSU going to play a real football
team?
Bill
Phil
11
U/Th/Pa Method
2M HNO3
1
/
2
1M HCl
5
6
0.1M HCl - 0.1M HF
9M HCl
3
4
4M HCl
Recent results have shown that Pa may be
effectively isolated from U and Th on TRU.Resin
alone.
TRU
.
Resin
1
-
4

(
d
i
s
c
a
r
d
)
6
(90-95)
T
h
5
U
/
P
a
Burnett and Yeh, 1995
cation exchange
12
Pa-231 Alpha Spectrum
80
231
Pa
60
40
20
0
4
5
6
7
Energy (MeV)
Pa-231 is determined via low-level alpha-particle
spectrometry after separation by extraction
chromatographic resins.
13
Groundwater Discharge into the Coastal Zone
224Ra
228Ra
224Ra, 228Ra, 226Ra, 222Rn
226Ra
224Ra, 228Ra
226Ra
Naturally-occurring radium isotopes are useful
for tracing groundwater flow into the coastal
ocean.
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Naturally-Occurring Radium Isotopes
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Flow Chart - LnResin Method
Ra concentrated by ppt with BaSO4. Ac separated
from other radioactive species via Ln.Resin
(Burnett et al., 1995)
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Elution Curve LnResin

• The Ac fraction is collected and a CeF3
  precipitate prepared for low-level gas-flow
  proportional counting (Burnett et al., 1995).

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The Double-Pass Approach
1
First Pass
Second Pass
1
2
2
Load sample in 2M HCl
Load sample in 2M HCl
Actinide
1
Actinide
1
Rinse 2M HCl
Rinse 2M HCl
2
2


Resin 2
Process Actinide Elements
Resin 1
1
2
226Ra via Rn emanation
1
2
223,224Ra via ?-spectrometry

• Collect
• Ba-133 yield
• Hold gt30 hrs.

Extrude resin into plastic vial add cocktail,
count via LSC
2nd column options TRU.Resin load 2.5M HNO3
elute Ac 1M HCl, ppt CeF3, count Diphonix load
2M HCl elute Ac 0.5M HEDPA, evap., count
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Water Samples MnO2 ppt

• Seawater, 100-400 liters
• Acidify to pH 2, add Pu/Am tracers, stir/hold
• For 100L sample, add 35 mL sat KMnO4 (2.1g)
  Pu--gtPu(VI), org oxid, purple color
• Adjust pH to 8-9 with NaOH
• Add 0.5M MnCl2 (2x vol of KMnO4) --gt MnO2 ppt,
  dark brown

Seawater
MnO2 Suspension
2MnO4- 3Mn2 2H2O 5MnO2 4H

• Re-adjust pH to 8-9 as necessary
• Stir occasionally to keep MnO2 suspended for few
  hours
• Allow Mn02(Pu, Am) ppt to settle overnight
• Pump supernatant into clean tank for Cs, Sr
  processing
• Drain MnO2 slurry from bottom tap

centrifuge/ filter
MnO2 ppt (Pu, Am, Ra, Ba)
supernatant Cs, Sr,...
(Povinic et al., 2000)
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Large Volume Seawater Samples
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.
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Smaller-Scale MnO2 ppt
MnO4 (purple) is reduced by added MnCl2 to
precipitate MnO2 (brown). MnO2 precipitate
settles relatively quickly.
21
Summary

• U/Th decay-series disequilibrium in nature may be
  exploited to measure environmental processes
• Known source and fixed rate of decay provides
  information stable elements cannot provide
• Extraction chromatographic methods have greatly
  simplified processing of environmental samples.