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Analysis of Actinide Elements from Large Samples Henrieta Dulaiova Guebuem Kim Bill Burnett Florida State University and E. Philip Horwitz PG Research Foundation
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Need for Large Volumes Achieve very 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
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Protocol for 10-g Samples Dissolution/ Leaching Diphonix HEDPA oxidation Resins: TRU TEVA UTEVA tracers 0.1M HCl-0.3M HF, AA "Matrix" 0.5M HEDPA H 3 PO 4 + actinides, Ln’s { one or more Separation Am, Pu, etc. alpha spectrometry ICP-MS “Fenton’s Reagent” H 2 O 2 + Fe 2+ OH + OH - +Fe 3+
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Actinide Retention on Diphonix Resin Diphonix Resin high retention of actinides, Ln Low retention common ions Tolerate to HF
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Elution: HEDPA Acid Dependency Curves Indicates that actinides should elute easily at concentrations ~0.5M
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Elution of Am
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Fenton’s Reagent Oxidation finished Treatment: 40 mL 0.5M HEDPA + 1 mL HNO 3 + 40 mL H 2 O 2 + 0.17 g Fe(NH 4 ) 2 (SO 4 ) 2 6H 2 O Temperature ~90 o C H 2 O 2 + Fe 2+ OH + OH - +Fe 3+
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Actinide Separations TRU Resin 1 2 34 5 6 3 2 1 2.5M HNO 3 2.5M HNO 3 /0.1M NaNO 2 2.5M HNO 3 9M HCl 4M HCl 4M HCl/TiCl 3 6 5 4 4M HCl 2.5M HNO 3 2.5M HNO 3 /0.1M NaNO 2 2.5M HNO 3 9M HCl 1M HCl 0.1M Ammonium Bioxalate 1 2 34 5 6 Discard Am Pu Discard Th U Sample (3M HNO 3, 0.7M Al(NO 3 ) 3, FS, AA) Final clean-ups: Am/Ln on TEVA; U on UTEVA TRU Resin tolerates high PO 4
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10-g Samples: Yields Samples (n=7): 3 EML soils 2 IAEA sediments 2 Fe-rich soils 10-gram samples were leached with HNO 3 /HCl.
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10-g Samples: Results Table 1: EML and IAEA intercomparison values.
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Anal. Chem. Paper
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Protocol for 50-g Samples Step10-gram*50-gram Leaching70 mL each: 6M HCl/8M HNO 3 4 hrs., 90 o C 150 mL each: 6M HCl/8M HNO 3 4 hrs., 90 o C Load Sol’n Add HF (0.5M), AA, adjust pH=1 ppt Fe(OH) 3 HCl, HF, AA, H 2 O to ~300 mL 2M HCl – 0.5M HF *Kim, Burnett, & Horwitz ( 2000)
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Conditions - Diphonix Step10-gram50-gram Diphonix Column 1.2-cm diameter 10 mL resin same 13 mL resin Elution0.5M HEDPA 35 mL same 40 mL Oxid HEDPA* Fenton’s Reagent HNO 3 /H 2 O 2 /Fe 2+ same *Oxidation of HEDPA is done in a glass beaker on a hot plate – the reaction is complete in approx. 30 minutes
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Conditions – Final Step10-gram50-gram TRU Column 0.6-cm dia, 5 mL ~15 mL HNO 3 - Al(NO 3 ) 3 -FS-AA 0.6-cm dia, 6 mL ~25 mL HNO 3 - Al(NO 3 ) 3 -FS-AA TEVA* (Am) Thiocyanate separation same Source Prep CeF 3 microprecipitation same *Am fraction purified of lanthanides on TEVA column to prevent thick source; Pu is processed directly after TRU
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Spike Tests (50-g Soil) Am-241 and Pu-239 spiked samples. Matrix = HNO 3 /HCl leach of 50-g soil and sediment samples.
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IAEA-300 (Baltic Sea Sediment) 50-g sample, leached with 6M HCl/8M HNO 3 Run through entire procedure… AnalyteYield % FSU mBq/g IAEA mBq/g* Am-241951.45±0.051.38 1.2-1.5 Pu-239/240373.98±0.123.55 3.44-3.65 Pu-238370.28±0.03~0.15# * recommended value/range # information value only
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EML Soil 0009: 50-g sample, leached with 6M HCl/8M HNO 3 Run through entire procedure… AnalyteYield % FSU mBq/g EML mBq/g* Am-2411006.8±0.21-100 Cm-244100124±3~100 Pu-239/24049*15.3±0.51-100 Pu-23849*17.3±0.6-- *An additional 38% + ~15% recovered during 2 nd and 3 rd ppt; so total recovery through columns ~100%
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Observations: 50-g Samples Solutions highly colored after HEDPA oxidation Load solution occasionally reacts with TRU. Resin – very strong oxidizing agent (CeIV?) Pu does not completely co- precipitate with CeF 3 – hold- back effect?
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Color in Load Solutions Before loading…After ~20 minutes…
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IAEA-300 Am 243 Am 241 Am
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EML Soil 0009 Pu 238 Pu 239/240 P u 242 Pu
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EML 9603 Pu (electro) 238 Pu 239/240 Pu 242 Pu
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Summary Diphonix/HEPDA/oxidation process eliminates matrix Am/Pu separations work well via TRU Resin Reaction on TRU indicates strong oxidizer present Hold-back phenomenon occurs during CeF 3 co-precipitation
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