iLA-1721, 4th Ed. UC-4, Chemistry

Issued: April 1975

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Collected Radiochemical Procedures

(Radiochemistry Group CNC-11)

Compiled by

Jacob Kleinberg and Helen L. Smith

Revisions and Additions

Issued: July 1979

This repon was prepared as an account of worksponsored by [he United Slaits fiiwernment. Neither (he JU.nted Stales nor the United States Department ofl:nergy. nor any of then employees, nor any of theircornractors, subcontractors, or their employees, makesim- u">.r inty ( express or implied, or assumes any lepal

r responsibility for the accuracy, completenessess of any inFornv."ion. apparatus, prodout or

process disclosed, or represents thai its use would notinfringe privately owned rights. i

liabiltti

Individuals responsible for developing procedures are named at theheading of each procedure.

1LOS ALAMOS SCIENTIFIC LABORATORYPost Office Box 1663 Los Alamos. New Mexico 87545

CONTENTS

CHEMISTRY OF THE ELEMENTS ON

THE BASIS OF ELECTRONIC CONFIGURATION

SEPARATION TECHNIQUES

americium, antimony, argon, arsenic

barium, beryllium, bismuth

cadmium, calcium, carbon (charcoal, graphite), cerium, cesium

chlorine, chromium, cobalt, curium

germanium, gold, hafnium

indium, iridium, iron

lanthanides, lead

magnesium, manganese, molybdenum

neptunium, nickel, niobium

palladium, phosphorus, plutonium, potassium, protactinium

rhenium, rhodium, rubidium, ruthenium

scandium, silver, sodium, strontium, sulfate

tantalum, tellurium, thallium, thorium, tin, transactinides, tritium, tungsten

uranium

yttrium

zirconium

COMBINED PROCEDURES

GROUP SEPARATIONS OF THE HEAVY ELEMENTS

PROCEDURES FOR QUALITY CONTROL IN COUNTING RADIOACTIVE NUCLIDES

ccount of woi

NOTICE

This rcpnrt was pre pared as asponsored by the Unned Stales Government. Neither IhiUnited Stales not the Uniled Slates Department oEnergy, nor any of their employees, nor any of [hicontractors, subcontractors, or Iheir employees, make:any watraniy. express or impl.ed, or assumes any legaliability 01 responsibility foi the accuracy, completenessor usefulness of any information, apparatus, produci 01proges-i disclosed, or represents that its use would notinfringe privately owned rights.

in

SEPARATION OF CARRIER-FREEBISMUTH FROM LEAD, IRON,

AND URANIUM

R. J. Prestwood

made by fusing a 15-ml conical centrifuge tube toan 8-cm length of 1-cm tubing drawn to a tip. Aglass wool plug is placed in the tip of the column,which is then filled with 1-3/4 to 2 in. of resin.Before using, wash the resin column with conedHC1.

1. Introduction

This procedure was designed to separatemicrogram (or less) quantities of bismuth frommilligram amounts of lead, iron, and uranium in oresamples from the Oklo mine. After separation, thebismuth is determined quantitatively by atomic ab-sorption. A measure of the 209Bi content of the ore isimportant because the isotope is the final decayproduct of '-'"Np.

The procedure was developed from informationgiven on pp. 407 and 408 of "Ion Exchange Separa-tions in Analytical Chemistry" by 0. Samuelson,published by John Wiley & Sons, Inc., New York,1963. The bismuth, in solution in a minimum ofconed HC1, is placed on an anion exchange resincolumn. The column is then treated with the sameacid to remove lead. Next, iron and uranium areeluted with 0.5M HC1, and finally bismuth isremoved with \M H2SO4. The procedure waschecked with carrier-free M7Bi and a chemical yieldof 99% was obtained.

2. Reagents

HC1: coned; 0.5MH2SO,: \MAnion exchange resin: Bio-Rad AG 1-X8, 100-200

mesh. The glass column that holds the resin is

3. Procedure

Step 1. Dissolve the ore f ample and make up to3M HC1 so that there are 5 mg of ore/ml of solution.Evaporate 1-2 ml of sample solution nearly todryness, take up in 1 ml of coned HC1, and, using 1ml of the same acid, transfer the solution onto thetop of the Bio-Rad AG 1-X8 anion exchange resincolumn.

Step 2. Add successively 2, 2, and 1 ml of conedHC1 to the resin column. Lead comes off almost im-mediately and is essentially removed completely af-ter 4 ml of acid have been added.

Step 3. Add three 2-ml portions of 0.5M HC1 tothe column. This treatment removes the iron anduranium completely.

Step 4. Add seven successive 2-ml portions of1M H2SO4 to the column. Although the first threeadditions remove no bismuth, it is removed quan-titatively by the last four portions of the acid.Collect the last 8 ml of the \M H2SO« in a 10-mlvolumetric flask and make up to exactly 10 ml withH:O. Aliquots of this solution are used for the deter-mination of bismuth by atomic absorption.

June 1979

3Oa

SEPARATION OF MILLIGRAM AMOUNTSOF COBALT AND MANGANESE FROM

100 GRAMS OF IRON

R. J. Prestwood

1. Introduction

This procedure was developed for possible use inthe Apollo Space Program. Its major steps include(1) extraction of Fe(III) into isopropyl ether from asolution 7.9M in HCl; (2) passage of the aqueouslayer from the extraction onto an anion exchangeresin column, with the manganese passing throughand the cobalt staying on the column; and (3) elu-tion of the cobalt by means of AM HCl. Chemicalyields are 98% for cobalt and 80% for manganese.

2. Reagents

HCl: coned; 7.9M; 6M; 4MHNO3: conedIsopropyl etherAnion exchange resin: Bio-Rad AG 1-X8, 100-200

mesh (wash the resin column with 7.9M HClbefore using)

3. Procedure

Step 1. Dissolve 100 g of iron in a minimum of6M HCl in a 14 Erlenmeyer flask. Evaporate thesolution to about 300 ml, then add the appropriateamount of coned HNO3 to oxidize the iron to the +3state. With the use of a hot plate and a magneticstirrer, reduce the volume to about 150 ml. (Thesolution is quite viscous at this stage.) Cool andtransfer the solution to a 2-1 separatory funnel with850 ml of 7.9M HCl.

Step 2. Add 1 £ of isopropyl ether and shakethoroughly. Draw off the aqueous (lower) layer but

do not discard because it contains the cobalt andmanganese. Extract the iron from the ether layerwith 1000-, 500-, and 200-ml portions of H2O. Com-bine the aqueous layers in a 4-£ bottle. Return theoriginal water layer containing the cobalt andmanganese to the ether in the separately funnel andadd 200 ml of coned HCl to bring the acid concen-tration back to 7.9M. Shake thoroughly and drainthe aqueous layer into a l-H Erlenmeyer flask.Remove the ether in this layer with an air bubbler.Back-extract the ether layer again, this time with500- and 100-ml portions of H2O. Add the aqueouslayers to the original back-extracts of iron in the 4-£bottle. Remove the ether from the back-extractswith an air bubbler.

Step 3. Boil down the aqueous layer containingthe cobalt and manganese to a few milliliters. Add 2ml of coned HN03 and evaporate to a small volume.Repeat the HN03 treatment. Add 5 ml of coned HCland evaporate the solution to about 2 ml. Repeat theHCl treatment. Adjust the volume to 25 ml and theHCl concentration to 7.9M. Extract with 30 ml ofisopropyl ether in a 60-ml separatory funnel.

Step 4. Drain the aqueous layer onto the top ofa 5-in. Bio-Rad AG 1-X8, 100-200 mesh, anion ex-change resin column. Collect the effluent, whichcontains Mn2 •. Wash the column with 20 ml of 7.9MHCl to remove any remaining manganese and com-bine the wash with the previous effluent. The cobaltremains on the column as a green band about 1 in.wide.

Step 5. Add sufficient AM HCl to remove thegreen band containing the cobalt from the columnand collect the eluate in an Erlenmeyer flask. Anyresidual iron that has collected on the column re-mains there. (Note: The cobalt can be precipitatedand weighed as the anthranilate and the manganeseas MnNH4PCvH2O.)

June 1979

54a

germanium, gold, hafnium)

57

RECOVERY OF RADIOHAFNIUMFROM TANTALUM

R. J. Daniels, P. M. Grant,and H. A. O'Brien, Jr.

1. Introduction

This procedure was designed to isolate mHfproduced by the bombardment of tantalum foilswith 800-MeV protons. The tantalum targets had apurity of >99.9%, weighed approximately 2.5 g, andhad a thickness of 0.25 mm. The length of protonirradiation was 12 ̂ A-h of integrated intensity. Theseparation process consisted of (1) dissolution of thetarget in a mixture of coned HC1 and HN03; (2)coprecipitation of hafnium (presumably as anionicfluorocomplexes) on CaF2; (3) extraction of hafniumfrom HC1O< solution into thenoyltrifluoroacetone(TTA); and (4) back-extraction into coned HC1. Anoverall chemical yield of 93 ± 5% was obtained forradiohafnium.

The 172Hf decays to n2Lu with a half-life of 1.87 yr,and the latter isotope transforms to stable 172Yb witha half-life of 6.70 days. The 172Hf-I72Lu combinationoffers a possible medical generator system, with themLu having potential applications in compoundlabeling and biodistribution studies in animalmodels. The availability of millicurie quantities of17:lHf should serve to stimulate preclinical investiga-tions of the rare-earth compounds in nuclearmedicine.

2. Reagents

Hf carrier: 500-600 ng of metal in HF solutionHF: conedHNO3: conedHC1O4: conedHC1: conedCaCl2: a solution of known concentration47Ca2+ tracer (optional): obtained from Oak Ridge

National LaboratoryA1(NO3)3-9H.O: solid

Thenoyltrifluoroacetone (TTA) reagent: 0.5M solu-tion in benzene (stored in the dark)

Benzene

3. Procedure

Step 1. To the tantalum foil in a Teflon beaker,add 500-600 /ug of hafnium carrier and 2-3 ml ofconed HF per gram of the target. Then add conedHN03, dropwise initially, until dissolution is com-plete. The dissolution process usually requires about3 h and a volume of HNO 3 slightly under half that ofthe HF.

Step 2. Slowly add in dropwise fashion 45 mg ofCa2+ as CaCl2 solution (Note 1) and an additionalmilliliter of coned HF. Permit the fine, white CaFsprecipitate that forms to equilibrate with the rest ofthe solution by stirring and mild heating for 15 minon a steam bath. After the mixture cools, centrifugeand decant the supernate. Add 10 mg of Ca2+ to thesupernate and repeat the coprecipitation procedure.Combine the CaF2 precipitates (Note 2).

Step 3. Dissolve the CaF2 precipitate in conedHCIO4 (approximately 0.25 ml of acid/mg of Ca

2+

precipitant) and dilute the solution to 2M in HC1O4.Add A1(NO3)3'9H2O to complex fluoride ion.[Fluoride ion interferes with the TTA extractionprocess. The quantity of A1(NO3)3-9H2O added de-pends upon the amount of fluoride in the CaF2precipitate; 2.5 g of A1(NO3)3-9H2O is typical,although up to 15 g did not adversely affect the ex-traction.] Transfer the solution to a separatory fun-nel along with 25-30 ml of TTA reagent. Equilibratethe mixture on a Burrell wrist-action shaker for 1 h.If it is determined that the radiohafnium did not ex-tract quantitatively into the organic phase, add ad-ditional A1(NO3)3-9H2O and repeat the extraction.

Step 4. Dilute the organic phase from the TTAextraction tenfold with benzene. Extract twice with25-ml volumes of coned HC1 and combine theaqueoua phases. These contain the radiohafnium.

62a

Notes

1. Calcium-47 tracer was added in some experi-ments to monitor the chemistry of the Ca2+ added inthe coprecipitation procedure and to ensure its com-plete removal from the final product.

2. Coprecipitation of hafnium with CaF2 ismost successful when carried out at high HF con-centrations and small volumes. Occasionally, whenless than quantitative coprecipitation of radiohaf-nium occurs, it generally is associated with thepresence of appreciable residual Ca2+ in solution, asindicated by the added 47Ca2+. Volume reduction

and addition of coned HF usually are successful incausing more CaF2 to precipitate; sometimes onlythe addition of more Ca2+ will effect the completeremoval of I72Hf. The latter procedure is to beavoided whenever possible to minimize the volumesrequired in the TTA extraction step.

l. Primary Literature Reference

R. J. Daniels, P. M. Grant, and H. A. O'Brien,Jr., Int. J. Nucl. Med. Biol. 5, 11 (1978).

June 1979

62b

DETERMINATION OF FERROUS IRON ANDTOTAL IRON IN SILICATE ROCKS

R. J. Prestwood and B. P. Bayhurst

1. Introduction

These procedures were adapted from twoprocedures already reported: one, by S. Banerjee,Anal. Chem., 46, 782 (1974), on the direct deter-mination of ferrous iron in silicate rocks andminerals by iodine monochloride; and the other, byK. L. Cheng, R. H. Bray, and T. Kurtz, Anal.Chem., 25, 347 (1953), on the determination of totaliron by d i sod ium d ihydrogen e thy l -enediaminetetraacetate titration. Major modifica-tions of the former procedure include the prepara-tion method of the iodine monochloride solution,elimination of the necessity for blanks, and sometechnique changes. The main modification in thereported method for the determination of total ironis in the preparation of the sample for analysis. Thesample preparation method reported herein im-proves the consistency of the analytical results.

2. Reagents

Analysis for ferrous ironHF: conedHC1: coned; 9M; 6MH2SO4: 6MH3BO3: solidKI: solid; 10% aqueous solutionKIO3: solid; 2.5 x 10 ~

3M (standardized)(NH4)2SO4-FeSO4-6H2O: primary standardCarbon tetrachloride (CC14)

Analysis for total ironHClCv conedHF: conedHN03: conedHC1: 6M; 0.1MNH4OH: conedNaOH: 10MNaC2H3O2: 6M

(NH4)2SCvFeSCv6H2O: primary standardFe: National Bureau of Standards standard sample

55e, open-hearth iron (99.8% pure)Salicylic acid: 1 •» of acid in 100 ml of ethanolEDTA reagent: disodium salt of ethyl-

enediaminetetraacetic acid; 4.0000 g in 11 of H2O(standardized)

3. Determination of Ferrous Iron

(a) Preparation of IC1 reagent.Add 10 g of KI and 6.44 g of KIO3 to 150 ml of

water in a 1-1 bottle that contains a Teflon-coatedmagnetic stirrer. Stir until the salts havo dissolved;then, with continued stirring, add 450 ml of conedHC1. Add 20 ml of CC14 and, while stirring, 10% KIdropwise until the color of I2 appears in the CC14(lower) layer. Remove the CC14 layer with a transferpipet and discard. The liter bottle now contains IC1reagent. To 30 ml of this reagent in a 100-ml glasscontainer equipped with a screw cap, add 10 ml ofCC14 and shak? vigorously for 3 h on a Model DDBurrell wrist-action shaker. Use a transfer pipet toremove the pink CC14 layer and discard. Dilute the30 ml of IC1 solution to 100 ml with 9M HC1.

(b) Standardization of the 2.5 x 10~3JW (approx)KIO3 solution.

In a 1-i volumetric flask, dissolve 7.002 g of(NH4)2SO4-FeSO4-6H2O (primary standard) andcombine with sufficient H2SO4 to make the solution0.3M in acid. This gives a primary Fe(II) standardof 1 mg/ml of solution. For standardization of theKIO3 solution, proceed as described below for thedetermination of ferrous iron but substitute 3 ml (3mg) of the Fe(II) standard for the iron-containingsample.

(c) Analytical procedure.Step 1. Weigh out 50-70 mg of sample (minus

200 mesh) into a Tefzel 50-ml Nalgene centrifugetube fitted with a specially machined male Teflonstopper. (Two-ounce Teflon bottles with caps maybe used for holding the sample.) Carefully cover thesample with 3 ml of CC14. To a polyethylene 50-mlgraduated cylinder, add 20 ml of 6M HC1, 3 ml ofthe diluted IC1 reagent, and 2 ml of coned HF. Pourthe solution into the mixture of sample and CC14

70a

and stopper immediately. Place on a Burrell shakerand shake for at least 4 h. As the sample slowly dis-solves, the Fe,(II) is oxidized to the ferric state byIC1, which then is reduced to I2. The latter dissolvesin the CC14.

Step 2. Prepare a 125-ml Erlenmeyer flask con-taining a Teflon-coated magnetic stirring bar, 10 mlof 6M HC1, and 1 g of H.,BO3. With the stopper at-tached to the centrifuge tube, centrifuge the ox-idized sample from Step 1 to remove any trappedCC14 around the stopper. Remove the stopper andwith a transfer pipet transfer the contents of thetube to the 125-ml Erlenmeyer flask containing theHC1 and H3BO3. Take great care to ensure that someof the aqueous phase is on both sides of the CC14 inthe transfer pipet to prevent loss of I2 to the air.While stirring, titrate the I2 with the standardizedKIO3 solution; disappearance of the pink I2 color inthe CC14 layer indicates titration is complete.Calculate the amount of ferrous iron present interms of percent FeO.

4. Determination of Total Iron

(a) Standardization of EDTA reagent.Accurately measure 1.0000 g of National Bureau

of Standards standard sample 55e, open-hearth iron(99.8% pure) and transfer to a 1-i volumetric flask.Add 10 ml of aqua regia and heat the flask on a hotplate until all the iron has dissolved and oxidized toFe(III). Add 10 ml of coned HC1 and evaporate thesolution to a small volume to remove excess HN03.Repeat the HC1 treatment. Make the solution up to1 I so that it is about 0.1M in HC1.

Dissolve 4.0000 g of the disodium salt ofethylenediaminetetraacetic acid in H2O and diluteto 11 (EDTA reagent). Add 3 ml (3 mg) of standard

Fe(III) solution to a 100-ml beaker containing amagnetic stirrer, then add 3-4 drops of coned HC1.Use a 6M NaC2H3O2 solution to adjust the pH to 2.5(use pH meter) so that the volume of the solution isabout 20 ml. Add 5 drops of salicylic acid indicatorsolution and titrate immediately with the EDTAreagent.

We found that 1.62 ml of EDTA solution isequivalent to 1.00 mg of Fe(III) or 1.43 mg of Fe2O3.

(b) Analytical procedure.Step 1. Weigh out 50-100 mg of sample (minus

200 mesh) into a 75-ml Teflon beaker. Add 7 ml ofconed HC1O4, 2 ml of coned HN03, and 4 ml ofconed HF. Evaporate on a hot plate to HC1O4fumes. Cool, carefully add 4 ml of coned HF, andagain evaporate to HC1O4 fumes. Repeat the HFtreatment. Fume off all but about 1 ml of theHClCv

Step 2. Use 10-15 ml of 0.1M HC1 to transfer thesolution to a 40-ml glass centrifuge tube. Carefullyneutralize the solution with coned NH40H, thenadd 4 drops more of the coned NH40H. Add 4 dropsof 10M NaOH, mix, heat on a steam bath for a fewminutes, and centrifuge. Discard the supernate.

Step 3. Dissolve the Fe(OH)3 precipitate inabout 6 drops of coned HC1. Use 0.1M HC1 totransfer the solution to a 100-ml beaker containing amagnetic stirrer. The volume of solution should beabout 20 ml. Adjust the pH to 2.5 with 6MNaC2H3O2, add 5 drops of salicylic acid indicatorsolution, and titrate with standard EDTA reagent.Calculate the total iron present as percent Fe2O3.

To determine the original percentage of Fe2O3,multiply the percentage of FeO (Sec. 3 above) by1.1115 and subtract from the total Fe2O3.

June 1979

70b

SEPARATION OF IRON AND SCANDIUMFROM A NICKEL TARGET

B. P. Bayhurst

1. Introduction

After the metal target is dissolved in aqua regia,Fe(III) and scandium are separated from the nickelby precipitation of the hydroxides with conedaqueous ammonia and the nickel is converted to theNi(NH3)g

+ ion. The Fe(III) is extracted intoisopropyl ether from a solution 7.9M in HC1. It isthen back-extracted into H2O and placed on ananion exchange resin column from coned HC1medium. After removal of adsorbed cobalt from thecolumn, the Fe(III) is eluted by 0.1M HC1 andfinally converted to the oxide.

The scandium, which remains in the aqueouslayer from the isopropyl ether extraction, is, afterpreliminary treatment, dissolved in coned HC1 andpassed through an anion exchange column toremove the last traces of iron and cobalt. The scan-dium is converted to the ScF|~ complex and, whilein this form, fluoride and hydroxide scavenges areperformed in the presence of lanthanum carrier andFe(M) holdback carrier. The fluorocomplex is thendestroyed and ScF3 is precipitated. The latter isthen converted to the hydroxide and ignited to theoxide. The chemical yields are ~85% for iron and~95% for scandium.

2. Reagents

Standard Fe(III) carrier: 10 mg Fe/ml, made upfrom pure Fe wire (NBS standard)

Fe(III) holdback carrier: 10 mg Fe/ml, added asFeCl3-6H2O in dilute HC1

Sc carrier: 20 mg Sc2Oa/ml, added as ScCl3 in verydilute HC1; standardized (see original SCAN-DIUM procedure)

La carrier: 10 mg La/ml, added as La(NO3)3-6H2Oin very dilute HN03

HC1: coned; 10M; 7.9M; 5.5M; 0.1MHNO3: conedNH,HF2-HF reagent: AM in NH4HF2 and \M in HF

NH40H: conedNaOH: conedIsopropyl etherMethyl red indicator solutionAnion exchange resin: Bio-Rad AG 1-X8, 100-200

mesh (wash the resin column with 7.9M HC1before using)

3. Procedure

Step 1. To a sample of metal target in a 40-mlglass centrifuge tube, add 2 ml of standard Fe(III)carrier and 1 ml of scandium carrier. Place on asteam bath and add sufficient aqua regia to dissolvethe sample. Dilute to 30 ml with H2O and add anexcess of coned NH40H. [Fe(III) and scandiumprecipitate as hydroxides and the nickel is in solu-tion as the deep blue Ni(NH3)»

+ complex.] Cen-trifuge, and discard the supernate.

Step 2. Add sufficient coned HC1 to dissolve theprecipitate. Dilute to 30 ml with H2O andreprecipitate the hydroxides with coned NH4OH.Centrifuge, and discard the supernate. Repeat thedissolution and precipitation processes three moretimes. Wash the final Fe(OH)3-Sc(OH)8 precipitatewith 30 ml of H2O and discard the wash.

Step 3. Dissolve the precipitate in a minimumof coned HC1 and evaporate the solution to

to precipitate Fe(OH)3, centrifuge, and discard thesupernate. Wash the precipitate with 30 ml of H2Oand discard the wash.

Step 5. Dissolve the Fe(OH)3 in a minimum ofconed HCl and add the solution to a 13- by 1-cmBio-Rad AG 1-X8, 100-200 mesh, anion exchangeresin column that has just been washed with 7.9MHCl. Discard the effluent. Wash the column with 10ml of 7.9M HCl, and then with a total of 30 ml of5.5M HCl to remove the cobalt. Discard the washes.

Step 6. Elute the Fe(III) with 30 ml of 0.1MHCl, collecting the eluate in a clean glass centrifugetube. Add an excess of coned NH4OH to precipitateFe(OH)3, centrifuge, and discard the supernate.Dissolve the precipitate in a minimum of conedHCl, add 6 ml of filter paper pulp slurry, andreprecipitate Fe(OH)3 with coned NH40H. Filterthrough a 9-cm Whatman No. 541 filter paper,transfer to a Coors 00 porcelain crucible, and ignitein a furnace that is brought slowly to 1000°C. Main-tain at 1000°C for 1 h, then cool, weigh, and mountthe Fe2O3.

Step 7. Wash the aqueous layer containing thescandium (Step 3) twice with 10 ml of isopropylether and discard the washes. Transfer the solutionto a clean glass centrifuge tube and evaporate toabout 5 ml. Add an excess of 10M NaOH toprecipitate Sc(OH)3, centrifuge, and discard thesupernate. Dissolve the precipitate in a minimum ofconed HCl and reprecipitate the hydroxide withconed NH4OH. Centrifuge, and discard the super-nate. Wash the precipitate with 30 ml of H2O anddiscard the wash.

Step 8. Dissolve the Sc(OH)3 in a minimum ofconed HCl and pass the solution through an anionexchange resin column like the one used in Step 5.

Collect the effluent in a clean glass centrifuge tube.Add 20 ml of 10M HCl to the resin column and com-bine the effluent with the previous one. (The lasttraces of iron and cobalt are adsorbed on thecolumn.) Evaporate the combined effluent to about5 ml and transfer to a clean polyethylene centrifugetube.

Step 9. Add an excess of coned NH40H toprecipitate Sc(OH)3. Centrifuge, and discard thesupernate. To the precipitate add 3 ml of NH4HF2-HF reagent (the scandium is converted to ScFi")and bring the solution to a methyl red end pointwith coned NH4OH. Add 2 drops of lanthanumcarrier, centrifuge, and transfer the supernate to aclean polyethylene tube. Discard the precipitate.Repeat the LaF3 scavenge twice. To the supernate,add 1.5 ml of coned NH40H and 2 drops each ofFe(III) holdback and lanthanum carriers, cen-trifuge, transfer the supernate to a cleanpolyethylene centrifuge tube, and discard theprecipitate. Add 6 ml of coned HCl and place on asteam bath until the ScF3 precipitate coagulates.Centrifuge, and discard the supernate.

Step 10. Add 1 ml of 10M NaOH to the ScF3and heat, while stirring, on a steam bath for a fewminutes. Add 9 ml of H2O, centrifuge, and discardthe supernate. Dissolve the Sc(OH)3 formed in aminimum of coned HCl and reprecipitate thehydroxide with coned NH40H. Dissolve theprecipitate in a minimum of coned HCl, add 6 ml offilter paper palp slurry, and reprecipitate Sc(OH)3with coned NH40H. Filter onto 9-cm Whatman No.541 filter paper, transfer the paper to a Coors 00 por-celain crucible, and ignite at 1000°C for 15 min.Cool, weigh, and mount the Sc2O3.

June 1979

7Od

THE LANTHANIDES

K. Wolfsberg and D. Handel

1. Introduction

After the radiochemical purification of thelanthanides (rare earths) as a group, the individuallanthanides are separated on a cation column of lowcross linkage and fine particle size at room tem-perature by eluting with a-hydroxyisobutyric acid.The separation of many lanthanides, such as yt-trium (which behaves as a middle lanthanide),europium, samarium, promethium, neodymium,praseodymium, cerium, and lanthanum, is bestachieved in a reasonable length of time by changingthe pH of the eluent continuously. Individual orsmall groups of lanthanides also may be separatedby elution at only 1 pH or by making a step changein concentration or pH of thp ft-hydroxyisobutyricacid.

2. Reagents

HClCv conedHC1: conedHNO3: conedH3BO3: saturatedH2C2O4: saturated; 0.5%HF: conedH3PO4: conedH2SO4: conedH2O2: 30%NH

Erlenmeyer flasks and titrate with EDTA solution,as described in Sec. 10. The titrations should agreewithin 0.5%.

4. Standardization of lt5Pm

The solution should contain 800-1200 counts/minof "5Pm/ml. Pipet 5 ml of the solution and about 20mg of standardized neodymium carrier into each offour centrifuge tubes. Dilute to about 20 ml, heat ona steam bath, and add approximately 6 ml of conedNH

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solution by gravitational leveling. Th".s, the pH ofthe eluent changes continuously from that of the lowpH solution at the beginning of elution to that of thehigh pH solution at the end of elution.

For some applications it is desirable to change therate of change in pH or concentration of the a-hydroxyisobutyric acid during a gradient elution.This can be done by using graduated cylinders in-stead of flasks (Fig. 1). Glass cylinders oi Suitablelength and diameter are then inserted into thegraduated cylinders to give the desired change. Forexample, a cylinder inserted into the "high-pH"reservoir will decrease the rate of change in pH whenthe top of the solution reaches the reservoir.

Elution with a single eluent requires only onereservoir. If a stepwise change in eluent is desired, itcan be achieved with a manual changeover. If thestep change is to occur during nonworking hours, itcan be made by connecting lines from both reser-voirs to the column through solenoid valves ac-tuated by an electric timer. Several plastic solenoidvalves are available commercially.

10. EDTA Titrations

EDTA titration is a convenient method forchemical yield determination. Titration must becarried out after counting is completed. If the sam-ple cannot be sacrificed or if preliminary answersare required, chemical yield must be determined byweighing of lanthanide oxide.

Dilute the sample to about 30 ml in a 125-mlErlenmeyer flask and add an excess of 0.01MEDTAfrom a 10-ml buret (0.6-0.7 ml for each milligram ofrare-earth oxide and about 0.9 ml for each milligramof yttrium oxide). Add about 4 ml of 25% NH4C1 and1 drop of phenolphthalein. Then add pH 10 bufferuntil the solution turns pink (the pH will be be-tween 8 and 9). Bring the solution almost to boiling.The pink color is destroyed. Add 1 or 2 drops of ar-senazo indicator and back titrate with 0.01M Las+

solution from another 10-ml buret while the solutionis still hot. The end point is reached when the solu-tion turns from salmon to violet or red-violet whenapproximately 1/2 drop of EDTA is added. MoreEDTA may be added and another back titrationperformed.

The relative strengths of the EDTA and La3+

solution titrants are obtained by starting the backtitration from a solution of about 6 ml La3+ solutionand an excess of EDTA. The volume of lanthanumused in any titration is multiplied by the EDTA:La3+ solution ratio. This number is then subtractedfrom the volume of EDTA delivered to obtain thenet volume of EDTA.

The chemical yield of a sample is the net volumeof EDTA required to titrate the sample divided bythe net volume required to titrate 2 ml of carrier. Forthickness corrections, the weight of the sample canbe calculated from the titration of the sample, thetitration of 2 ml of carrier, and the gravimetric stan-dardization of the carrier (Sec. 3).

If accurate standardization of the EDTA solutionis desired, the solution may be standardized againstzinc (using Eriochrome Black T as an indicator) oragainst a rare-earth oxide that has been ignited at950°C (Note 1).

11. Procedure

In this procedure all precipitates are digested on asteam bath. They may be centrifuged while thesolutions are still hot.

Step 1. Into a 125-ml Erlenmeyer flask, pipet 2ml of desired carrier and the active sample, as wellas 4 ml of coned HC1O4 and 1 ml of coned HNOS,and fume to near dryness. Add 3 ml of coned HN03and enough H2O to transfer the solution to a 40-ml

75

polycarbonate centrifuge tube. Add H2O to bringvolume to about 15 ml, then add 2-5 ml of coned HF,digest on a steam bath for 30 min, and centrifuge for15 min. Decant the supernate and wash theprecipitate with about 20 ml of H2O containing afew drops of coned HF. Centrifuge, and discard thesupernate (Note 2).

Step 2. Slurry the precipitate with 2 ml ofsaturated H3BO3 and add 2 ml of coned HNO.,, 10ml of H2O. and 2 drops of zirconium carrier. Heat todissolve any precipitate. Add 2-5 ml of coned HF,heat on a steam bath for a few minutes, and cen-trifuge (Note 3). Wash the precipitate with H2Ocontaining a few drops of HF. Centrifuge, and dis-card the supernate.

Step 3. Slurry the precipitate with 2 ml ofsaturated H3BO3, add 2 ml of coned HNO3, and heaton a steam bath, if necessary, to dissolve theprecipitate. Add 15 ml of H2O.

Step 4. Add 8 ml of coned NH40H, heat for 1min on a steam bath, digest, and centrifuge. Discardthe supernate. (The anion resin column may beprepared at this time.) Wash the precipitate with 15ml of H2O to which a few drops of coned NH,0H hasbeen added. Centrifuge, and discard the supernate.

Step 5. Dissolve the hydroxide precipitate in 4ml of coned HC1 and 1 drop of coned HN03 and add2 drops each of zirconium and tellurium carriers.Heat the sample for only 30 s on a steam bath (topromote tellurium exchange but not to reduce theHC1 concentration). Pass the solution through ananion resin column and collect the eluate in a 125-ml Erlenmeyer flask. Rinse the column with one 4-and one 6-ml HC1 rinse solution (see Sec. 2,Reagents), and collect the rinsings in the flask.

Step 6. Boil out excess HC1 by heating the flaskover a flame and reduce the volume to 4-5 ml.Transfer the solution to a long, tapered centrifugetube with 15 ml of H2O. Add 8 ml of coned NH40Hand 3 drops of 5M NH2OH-HC1. Heat on a steambath for about 1 min, digest, centrifuge, and discardthe supernate. Wash the precipitate with 15 ml ofH2O containing a few drops of NH40H.

Step 7. Dissolve the precipitate in 6 drops ofconed HC1 and dilute the solution to about 30 mlwith H2O. Add about 30 drops (transfer p'pet) ofminus 400 mesh or 200-400 mesh cation resin slurryin H2O Stir or shake for about 5 min and centrifugefor 5 min, letting the centrifuge stop without the useof the brake (Note 4). (The centrifuged resin has avolume of about 1 ml.) Discard the supernate.

Step 8. Slurry the resin with about 1 ml of H2Oand, with a transfer pipet, transfer it to the -p of apreviously prepared cation resin column. After theresin settles, remove the H2O. Rinse the centrifugetube with 1-2 ml of H2O, add the rinsings to thecolumn, allow to settle, and remove the H2O. (Asmall piece of glass wool may be put in the top of thecolumn.)

.Step 9. Connect the column to a delivery tuhefrom the elution equipment. For terbium-europiumelution, use a pH gradient setup (Fig. 1) with 150 mlof a-hydroxyisobutyric acid reagent solution of pH3.34 on the low side and 150 ml of rep ̂ ent solution ofpH 3.73 on the high side. If sev̂

is set to deliver the 0.08A/ acid solution approx-imately lfi h later (Notes 5. 6, and 7).

Step 10A. For the light lanthanides and yt-trium, add a few drops of saturated H2C2O4 to eachfraction to precipitate and locate the individuallanthanides. Promethium is located by measuringthe activity in the tubes between samarium andneodymium. Combine the individual lanthanidefractions in centrifuge tubes. To the promethiumfraction, add 2 ml of neodymium carrier. Add 5 mlof saturated oxalic acid to the centrifuge tubes anddigest the oxalates for 15 min on a steam bath. Cen-trifuge, suspend the oxalates in about 5 ml of H2O,and filter on a 2.5-cm circle of Whatman No. 42paper using a filter chimney assembly. Ignite the ox-alates in a Coors 00 porcelain crucible for aprox-imately 1 h at 950°C. Oxalates may be mounteddirectly without weighing if chemical yield is to bedetermined by EDTA titration (Note 8).

Step 10B. For the heavy lanthanides, add about0.5 ml of 8-quinolinoi reagent I to each fraction. Addconed NHLOH to make each fraction basic (red) andcombine the fractions containing an individual ele-ment in a 250-ml beaker. (At least 10 ml of reagent Ishould be used in those tubes containing the ele-ment.) Add about 1.5 ml of filter aid and digest themixture on a steam bath for 15 to 30 min. Cool toroom temperature and filter on a 4.5-cm circle ofWhatman No. 42 paper using a large Millipore filterchimney assembly. Wash with 8-quinolinol reagentII. Ignite the quinolinate for 1.5 h at 950°C (Note 8).

Step IOC. If a given light lanthanide is to becycled t' • ,«gh a second cation exchange columnwhen a separation of 105 from other lanthanides isrequired, the oxalate may be dissolved anddestroyed by heating it in a centrifuge tube withabout 1 ml of coned HN03 containing about 100 mgof KC1O3. For heavy lanthanides, the 8-quinolinateis ignited and dissolved in about 2 ml of coned HC1and 0.5 ml of coned HN03. Then one performs Step6 for the hydroxide precipitation before the cationcolumn step. This usually is done for europium,gadolinium, terbium, lutetium, and thulium, and,when large amounts of americium are present, alsofor neodymium. (If lutetium is to be recycled, theoxide formed by ignition of the 8-quinolinate is dis-

solved in 2 ml of coned HC1 and 1 drop of conedH\'O3. The solution is heated on a steam bath andcooled. Then 6 ml of coned HC1 is added and theprocedure taken up at Step 5.)

Step 11. After the crucibles have cooled, add afew drops of ethanol to each sample and grind upthe oxides with the fire-polished end of a stirring rodor break them up in an ultrasonic cleaner. Suspendeach sample in several milliliters of ethanol andfilter onto a circle of Whatman No. 42 paper using afilter assembly with an 11-mm-i.d. glass chimney.Dry the sample for 15 min at 110°C, mount it on analuminum plate, and cover with Scotch No. 850type 2PTA polyester film tape (Note 9).

If chemical yield is to be determined by weight ofthe oxide, the circle of paper on which the sample ismounted should be washed, dried, and tared beforethe mounting operation. The papers and samplesshould be cooled for 20 min before weighing.

Step 12. After sample counting is completed,yield determination by EDTA titration may be per-formed. Remove the sample, filter paper, and tapecover from the counting plate by cutting around theoutside of the filter paper with a sharp blade. Placethis sandwich ir. a 125-ml Erlenmeyer flask. Add 10ml of H2O and 2 ml of coned HC1. Bring to boilingand place the flask on a hot plate set to maintain thetemperature just below boiling for about 20 min.The filter paper may disintegrate, but this does notinterfere. Titrate the sample in the mannerdescribed in Sec. 10.

The CeO2 does not dissolve with the HC1 treat-ment described above. After the sample sandwich isplaced in the flask, add about 2 ml of coned HjSO4and heat the mixture to SO3 fumes over a flame.Then cautiously add a mixture of 2 parts of conedH2SO4 and 1 part of 30% H2O2 dropwise to destroythe charred paper and tape. Fume the clear solutiondown to about 0.25 ml. Dilute to 30 ml, add 0.1-0.2 gof ascorbic acid, and proceed with the EDTA titra-tion as described in Sec. 10.

Notes

1. Consult the following references for general in-formation on EDTA titrations.

77

G. Schwarzenbach, "Complexometric Titrations,"Interscience Publishers, New York (1955).

H. Flaschka, H. T. Barnard, Jr., and W. C. Broad,Chemist Analyst 46, 106 (1958).

A review of EDTA methods for the lanthanides isgiven by H. Flaschka, H. T. Barnard, Jr., and W. C.Broad, Chemist Analyst 47, 78 (1959).

This procedure was adapted from J. S. Fritz, R.T. Oliver, and D. J. Pietrzyk, Anal. Chem. 30, 1111(1958).

2. If cerium is to be determined, steps must bemade to promote exchange between radioceriumand carrier. (See Steps 1 and 2 of the CERIUMprocedure.)

3. If the sample contains large amounts of ele-ments, such as aluminum, that form amphoterichydroxides, treatment of the lanthanide fluorideprecipitate with an excess of 6M NaOH willprecipitate lanthanide hydroxides and dissolve theamphoteric elements. If the amount of fluorideprecipitate in Step 1 seems to be too great for thequantity of carrier added, it may be washed withabout 10 ml of 6M NaOH and then with H2O beforecarrying out Step 2. The same treatment may beused after Step 2. Precipitation of hydroxides withQM NaOH may precede or follow Step 3 or mayprecede the precipitation with NH4OH in Step 6. Inthese instances, the precipitate is first washed with10 ml of 6M NaOH and then with H2O.

4. The 200-400 mesh resin may be centrifugedmore easily than the finer resin that is used in thecolumn, and it also settles faster when added to thecolumn. The resin is suspended in water.

5. For the analysis of yttrium, europium,samarium, promethium, praseodymium, cerium,and lanthanum, the initial pH of the eluent («-hydroxyisobutyric acid reagent) is 3.40 and the pHis changed at an average rate of approximately 0.025pH unit per hour. For the operation of one column,this condition is met by starting with 144 ml of0.394M «-hydroxyisobutyric acid, pH 3.40, in thefirst flask and with 144 ml of eluent, pH 4.20, in the

second flask. If several columns are operated fromone set of flasks, the volumes of eluents are in-creased proportionally. A small additional volumeof low pH solution is added to the first flask to com-pensate for the difference in volumes caused by thedelivery tubing and the stirring bar. The rate of elu-tion is controlled by the air pressure applied to thereservoirs. Collect the eluate in 15-min fractions us-ing a fraction collector.

When this step is performed, the lanthanideselute in the following manner.

Time that element startsElement eluting off column (h)

YGdEuSmPmNdPrCeLa

3.16.58.2

10.513.216.519.522.528.0

Those lantanides that are present in 6- to 9-mgquantities have elution widths of

discarded. It is recommended that about 10 mg ofpraseodymium be added to spread the peak of thatelement.

8. For the preparation of a sample as a massseparator chlorination source, separation of thedesired lanthanide is done without adding thecarrier of that element. Ten milligrams of a lighterIanthanide carrier usually are added for hydroxideprecipitation before the cation column separation.The activity peaks are located by gross 7-counting.About 3 mg of the appropriate carrier are then ad-ded to the «-hydroxyisobutyrate solution containingthe activity of interest, and the element isprecipitated and ignited as in Step 10.

After the sample has been ignited, transfer the ox-ide into a long, tapered centrifuge tube. Add 2 ml ofconed HC1 and 3-5 drops of coned HN03. Heat gen-tly on a steam bath for 15 min or until the oxide hasdissolved and the solution is clear. (A few moredrops of HNO3 may be necessary to effect solution ofthe oxide.) Place the centrifuge tube in an oil bathand evaporate to a volume of a drop or two using anair jet. Transfer the drops in 20-A portions to the ap-propriate end of a quartz vial that contains quartzwool that has been weighed previously. Dry forabout 8 min under a heat lamp after each transfer.Rinse the centrifuge tube with 1 drop of coned HC1and transfer the rinse to the quartz vial. Heat thevial at 600°C for 20 min, cool for 20 min, and weigh.

9. The thickness of Scotch polyester film tape(No. 850 type 2PTA) is uniform along the length of aroll and among most rolls produced from the samebatch; its variation is only about 1,5%. However,there may be a large variation between batches. Thetape from two batches examined had thicknesses of4.9 and 6.3 mg cm ~2. This variation does not pose aserious problem because several rolls of tape can beobtained from one batch.

ADDENDUM I TO THELANTHANIDE PROCEDURE

1. Alternative Group Purification

The steps described below are alternatives forSteps 1 through 7 96 for the lanthanides and

Step 2. Add 3 ml of coned HC10

tube. Thus, there will be a tube for neodymium ac-tivity, one for europium activity, etc. To the tubecontaining the promethium activity, add 2 ml ofneodymium carrier. To each tube, add 5 ml ofsaturated H2C2O4 and digest the oxalateprecipitates for 15 min on a steam bath. Centrifuge,and discard the supernates. Suspend eachprecipitate in 5 ml of H2O, break up the lumps, andfilter onto a l-in.-diam circle of Whatman No. 42filter paper using a ground-off Hirsch funnel and afilter chimney setup. Wash each oxalate with threesuccessive 5-ml portions of H2O, then ethanol, andfinally ether. Dry the sample for 10 min at 110°C,then mount on an aluminum plate and cover withScotch polyester film tape (No. 850 type 2PTA).

Alternative Step 11. After counting has been com-pleted, determine the chemical yield by EDTAtitration. Remove the sample, filter paper, and tape

cover by cutting around the outside of the filterpaper with a sharp blade. Place the sandwich in thetitration vessel, and add 10 ml of H2O and 2 ml ofconed HC1. Pipet in an excess of EDTA solution.Heat the solution on a hot plate for about 20 minand adjust the pH to 8 or 9 as described in Sec. 10 ofthe LANTHANIDE procedure. Back titrate theexcess EDTA with La34 solution (see Note).

Note

The titration may also be performed with anautomatic photoelectric titrator. If done in thismanner, Eriochrome Black T is used, as the in-dicator, the wave length is set at 6600 A, and0.0125M EDTA and 0.025M La3( solutions are used.

June 1979

80a

palladium, phosphorus, plutonium, potassium, protactinium

101

An Additional Note

When the plutonium sample is from soil debrisand is to be subjected to mass spectrometricanalysis, as well as the regular procedure, aluminummust be removed before Step 2 of the regularPLUTONIUM procedure is performed.

Add the recommended amount of lanthanumcarrier, then add several drops of thymolphthaleinindicator solution to the sample which is 3M in HCl.Place the sample in an ice bath and add enough 50%NaOH to turn the indicator blue. Stir, centrifuge,and discard the supernate. Wash the precipitatewith a small amount of H2O, stir, centrifuge, anddiscard the supernate. Dissolve the precipitate in 1-2 drops of coned HCl and dilute to 2-3 ml with 3MHCl. Continue with Step 2 of the procedure,omitting addition of lanthanium carrier.

June 1979

ELECTRODEPOSITION OF PLUTONIUMFOR FISSION COUNTING

D. C. Hoffman

1. Introduction

The procedure described below is an adaptation ofone by R. F. Mitchell, Anal. Chem., 32, No. 3, 326(1960). The plating setup is the same as that used inthe Uranium-235 procedure.

same amount of eluate as would normally be collected onthe Pt disk for pulse analysis is collected). To the eluateadd 2-3 drops of coned HNO3 and place the tube in an oilbath which is maintained at about 100°. With the aid ofan air jet, evaporate the solution to dryness. Add 3 dropsof coned HCl and take the resulting solution to dryness.Repeat the HCl treatment four times.

Step 2. After the final evaporation, take theresidue up in 0.5 ml of -oncd HCl and transfer to theelectroplating cell. Use a 1" Pt plating disk, a thin-walled chimney, and a plastic gasket. Wash thecentrifuge tube with two 0.5-ml portions of distilledH2O, transferring the washings to the plating cell(vol. ~1.5 ml). Add two small spatulafuls of NH4C1and 2 drops of methyl red indicator solution. Makethe solution basic with coned NH«0H and then add\M HCl dropwise until the ioiution is barely acidic.

Step 3. Electroplate at 2 amp and about 6.8 v for15 min while the solution is stirred with a graphite rod.Just before plating is completed, add 0.5 ml of conedNH4OH. Immediately turn off the stirrer and the currentand pour the plating liquid back into the centrifuge tube.Remove the chimney and wash the Pt disk, first with H2Oand then with ethanol. Flame the plate and count for 1min on an alpha counter.

Step 4. By means of Duco cement, mount the Ptplate on a standard fission mount.

REMOVAL OF PLUTONIUM-239 FROMRARE EARTHS, CESIUM, AND ZIRCONIUM

B. E. Cushing

2. Reagents

HCh coned; 1MHNO3: conedNH4OH: conedEthanol: absoluteNH4CI: solidMethyl red indicator solution

3. Procedure

Step 1. In a graduated centrifuge tube, collect theeluate from Step 9 of the PLUTONIUM procedure. (The

I. Introduction

Plutonium (IV) can be quantatively removedfrom the rare earths, cesium, and zirconium byextraction with triisooctylamine. The separationis not satisfactory if the plutonium is in an oxida-tion state other than +4. The extraction is carriedout in the presence of the appropriate carrier orcarriers; for example, if the solution, after re-moval of plutonium. is to be used for analysis ofzirconium, then this element is employed ascarrier.

109

2. Reagents

La carrier: 10 mg La/ml, added as La(NO3)3-6H2O in H2O

Cs carrier: 10 mg Cs/ml, added as CsCl in H^OZr carrier: 10 mg Zr/ml, added as ZrO(N03)2-

2H2O in \M HNO3HC1: 5M; conedHjSO,: conedNaNO,: 0.1MTriisooctylamine: 20% by volume in Amsco-95

3. Procedure

All operations are performed in a glove box.

Step 1. Pipet an aliquot of the sample intoa •DO-ml erlenmeyer flask and add 1 ml each of thedesired carriers. Add 10-20 drops of coned H0SO4and heat to fumes of SO3.

Step 2. Cool the solution and transfer to a40-ml centrifuge cone with 5-10 ml of 5M HC1.Add about 10 drops of 0.1M NaNO, and heat ina boiling water bath for 5 min.

Step 3. Transfer the solution to a 125-mlseparatory funnel and rinse the centrifuge conewith a minimum amount of SM HC1, adding therinsings to the separatory funnel. Add an equalvolume of 20% (by volume) triisooctylamine inAmsco-95 and shake well.

Step 5. To the aqueous extract add 10drops of 0.1 M NaNO2 and heat in a boiling waterbath for 5 min.

Step 6. Repeat Step 3 (Notes 1 and 2).

Notes

1. The extraction is repeated if necessary.In one experiment it was found that three extrac-tions were sufficient to completely remove 47 mgof plutonium in the sample.

2. The procedure does not remove 241Amactivity. Americium activity may be separatedfrom the plutonium-free aqueous solution in thefollowing manner:

(a) Precipitate hydroxides by means of ammoniagas. Centrifuge, discard the supernate, and wash theprecipitate with H..O. Centrifuge and discard thesupernate.

(b) Dissolve the precipitate in 1-2 drops of conedHC1 and add 1 ml of 5M NH^CNS buffered at pH1.2. Put the solution on an AG 1-X8 anion column (100-200 mesh and 1 cm X 6 cm) which has been previous-ly equilibrated with the 5M NH4CNS solution.

(c) Elute with 10 ml of the cold 5M NH.CNSsolution. This procedure gives a decontamination fac-tor of about 5 X 103 and should be repeated to en-sure removal of americium.

Step 4. Allow the phases to separate anddraw off the aqueous phase into a clean 40-mlcentrifuge tube.

110

THE SEPARATION OF PLUTONIUM FROMLARGE VOLUMES OF SOLUTION. II

F. O. Lawrence and D. C. Hoffman

1. Introduction

In this procedure, DBHQ, (2,5-di-terriary butylhy-droquinone) in 2-eth/l-!-hexanol solution is utilized forthe back-extraction of plutonium (IV) from solutions ofHDEHP (di-2-ethylhexyl orthophosphoric acid) in n-heptane. The use of DBHQ as a reagent for this purposewas suggested in the May 31, 1968, annual progress reportof the Chemical Technology Division of ORNL, ORNL-4272.

Work in our laboratory has shown that treatmentwith DBHQ reagent followed by contact with 6/W HC1 willback-extract both plutonium-(lV) and (VI) quantativelyfrom HDEHP-H-heptane solutions. It should be noted thatplutonium (IV), once extracted into HDEHP solutions, isapparently so tightly complexed that previous attempts toback-extract it quantitatively with other reagents, evenwith those which should reduce the element to the tri-positive state, have been unsuccessful. Presumably, in theback-extraction with the DBHQ solution, the plutoniumis reduced to the +3 state and then strongly complexed bythe DBHQ.

The extraction coefficients (for transfer fromaqueous media to HDEHP solutions) for plutonium (IV)are very much higher than for plutonium (VI) and thevolume of HDEHP extractant for the former species canbe as little as one-fifth the volume of the sample. Theprocedure can be adapted readily to a mixture of the twoplutonium species by increasing the volume of HDEHPextractant to one-third of the sample volume.

To determine the element quantitatively, 236Putracer is added and sodium nitrite is used to ensure thatall the plutonium is converted to the +4 state to effectcomplete exchange.

2. Reagents

236Pu standardized tracer solution, in 3 M HC1HDEHP solution: 0.75 M solution of di-2-ethylhexylorthosphosphoric acid in w-heptane; aource: EastmanOrganic ChemicalsDBHQ solution: 0.2M solution of 2,5-di-tertiary butylhy-droquinone in 2-ethyl-l-hexanol; Source: Eastman Organ-ic Chemicals.HC1: 6M;3MNaN02: 10M

3. Procedure

Step 1. Pre-quilibrate the 0.75 M HDEHP solutionwith an equal volume of 3/W HC1 in a separato y funnel.(The size of the funnel should be about twice that of thealiquot of sample that will be used.) Add sufficient 10/VINaN02 to an aliquot of the sample and the Pu tracer (ineither a narrow-necked conical centrifuge tube or anerlenmeyer flask) to make the final concentration of thesalt about 0.2/W (for example, 1 ml of 10M NaNO2 to 50ml of aliquot of sample). Heat the solution to boiling andthen permit it to cool to room temperature. Add thesample to one-third its volume of pre-equilibratedHDEHP, shake for 1 min, and allow the two phases toseparate, centrifuging if necessary (Note). Remove theaqueous (bottom) layer and discard. Wash the organiclayer by shaking for 1 min with an equal volume of 6/WHC1 and discard the wash.

Step 2. To the organic phase, add one-third volumeof the 0.2/M DBHQ solution and shake for about 10 sec.Add one-half volume of 6/W HC!, shake for about 2 min,and allow 5 min for the separation of the two phases.Drain and save the aqueous (lower) phase and discard theorganic layer.

Step 3. If the volume of the aqueous phase is lessthan 5 ml, add H2O to make the solution 3/W in acid andproceed to Step 2 of the PLUTONIUM procedure. If thevolume of the aqueous phase is greater than 5 ml, transferthe solution to a 125-ml erlenmeyer flask and evaporateto 2-5 ml over a burner. Transfer the solution to a 40-mlconical centrifuge tube, dilute to make the solution 3Af inacid by means of water washes from the erlenmeytflasks, and then continue with Step 2 of the PLUTONI-UM procedure.

Note

If very large aliquots (150-200 ml) of sample areused, the volume of HDEHP solution may be increased toone-half volume of that of the sample, and a secondback-extraction with 6/W HC1 may be performed.

113

ADDENDUM TO PROCEDURE FORTHE SEPARATION OF PLUTONIUM

FROM LARGE VOLUMES OF SOLUTION. II

F. O. Lawrence and D. C. Hoffman

If large amounts of thorium are present, completethe above procedure and then carry out Steps 2, 3,and 4 of the regular PLUTONIUM procedure. Thendissolve the LaF3 by stirring with 2-3 drops ofsaturated H3BO3 solution. Add 3 ml of 10M HC1 andtransfer the solution to a 6-cm by 4-mm Bio-Rad AG50W-X4, minus 400 mesh, cation resin (H+ form)column. (Before using, wash the column with 10MHC1.) Collect the effluent in a 125-ml Erlenmeyerflask. Wash the column once with 3 ml of WM HC1and twice with 6 ml of coned HC1, collecting the ef-fluents in the Erlenmeyer flask. Boil down the com-bined effluents to a small volume (0.5-2 ml) andtransfer the solution to a 40-ml glass centrifugetube. Dilute with sufficient H2O to make the solu-tion 3M in HC1 and proceed with Step 2 of theregular PLUTONIUM procedure.

June 1979

EXTRACTION OF PLUTONIUMFROM PHOSPHORIC ACID SOLUTIONS BY

OCTYLPYROPHOSPHORIC ACID

S. DeVilliers, F. 0. Lawrence,and D. C. Hoffman

fluoride in boric acid solution, further purification ofthe plutonium is effected by proceeding with theregular PLUTONIUM procedure at the appropriateplace. Between 70-75% of the plutonium activity isrecovered by the extraction procedure, provided theOPPA reagent is less than 30 days old.

2. Reagents

Preparation of 236Pu tracer solution.Take standardized 236Pu tracer in 3M HC1 to

dryness and dissolve the residue in 10 ml of 42.5%H3PO,

La carrier: 5 mg La3+/ml, added as La(NO3)3-6H2Oin H2O

H3PO4: 53% by weightHF: conedHC1: conedH3BO3: saturated aqueous solutionNaNO2: 1M aqueous solution

Preparation of octylpyrophosphoric acid (OPPA/reagent.

Introduce 500 ml of kerosene into a 2-1 «octernall3cooled reaction vessel. Add .142 g (0.5 mole) of F4Oi0with constant stirring. Then slowly (30 min) add 260g (2 moles) of octanol and continue stirring for about1 h, taking care that the temperature does not riseabove 40°C. Make up to a volume of 1 I withkerosene. Prepare 0.2M OPPA reagent by ap-propriate dilution of the \M solution with kerosene.

3. Procedure

1. Introduction

This procedure for extracting plutonium fromphosphoric acid solutions is a modification of onedeveloped by S. Amiel of the Israel Atomic EnergyCommission, Soreq Nuclear Research Centre.Plutonium in the +3 or +4 condition in 53%phosphoric solution is extracted into a solution of0.2M octylpyrophosphoric acid (OPPA) in kerosene.The plutonium is back-extracted into concentratedhydrofluoric acid solution and is then coprecipitatedon lanthanum fluoride. After dissolution of the

Step 1. To 1 ml of the 236Pu tracer solution in a40-ml glass centrifuge tube, add 25 ml of theplutonium sample in 53% HgPOi solution (Note 1).(Samples containing as much as 20 nCi ofplutonium have been used successfully in theprocedure.) Add 1 ml of 1M NaNO2 solution, warmin a water bath, and cool (Note 2).

Step 2. In a 60-ml separatory funnel,equilibrate 5 ml of 0.2M OPPA reagent with anequal volume of 53% HaPO*. Centrifuge, and dis-card the aqueous (lower) layer.

114

Step 3. To the OPPA layer in the separatoryfunnel, add the sample solution and shake the mix-ture for 2 min. Transfer to a 40-ml glass centrifugetube, centrifuge for 10 min, transfer the OPPA •• *.yerto a 40-ml polyethylene centrifuge tube, and discardthe aqueous layer.

Step 4. Add 0.5 ml of coned HF, shake the mix-ture for 2 min, and centrifuge. Transfer the lowerlayer to a clean polyethylene tube and dilute to 5 mlwith distilled H2O.

Step 5. Extract the OPPA layer a second timewith 0.5 ml of coned HF and again dilute theaqueous layer to 5 ml with distilled H2O. Discardthe organic phase.

Step 6. To the combined aqueous layers, add 10drops of La3+ carrier. Centrifuge, and transfer thesupernate to a clean polyethylene tube. Add La3+

carrier dropwise to the supernate until no moreprecipitate is formed, centrifuge, and discard thesupernate. Combine the fluoride precipitates.

Step 7. Dissolve the combined precipitates in amixture of 2 drops of saturated H3BO3 and 1 ml ofconed HC1 and perform Steps 6-10 of the regularPLUTONIUM procedure.

Notes

1. Samples of different volumes may be processedby making appropriate adjustments in the amountsof reagents used. The volume ratio of OPPA reagentto H3PO4 is maintained at 1:5 and that of coned HFto OPPA reagent in the back-extraction is main-tained at 1:10.

2. Sodium nitrite treatment ensures reduction ofany Pu(VI) to Pu(IV) and oxidation of Pu(III) toPu(IV). If the plutonium is known to be in the +4state, do not carry out the NaNO2 treatment. If thetreatment is used, extraction with the OPPAreagent is performed as soon as the solution hascooled.

RECOVERY OF RADIOPOTASSIUMFROM VANADIUM

V. R. Casella, P. M. Grant,and H. A. O'Brien, Jr.

1. Introduction

This procedure describes the recovery ofpotassium-43 produced by the bombardment ofvanadium targets with 800-MeV protons. Thetargets were 0.25 mm thick and had a purity ofabout 99.9%. Typical proton bombardments werefor a duration of approximately 3 ,uA-h integratedintensity.

An irradiated foil was dissolved in 8M HN03, thesolution diluted to AM in acid, and scandium andpotassium carriers added. The solution was thenpassed through a hydrated antimony pentoxide(HAP) exchange column; potassium and otheralkali metals, as well as alkaaue earth metals, areadsorbed on the column. The column was washedwith AM HNO3, and then with \M HC1; the latterremoved nitrate ion, a biological poison. Potassiumwas eluted from the column with 12M HC1. Theconcentrated acid also carried some antimony fromthe HAP, and it was removed by adsorption on ananion exchange resin from a solution 8M in HC1.The final decontamination step consisted of passingthe eluant, adjusted to pH 10, through a chelatingion exchange resin and washing the resin withNH4OH-NH

Sc carrier: ScCI3 in very dilute HC1; of known con-centration

HC1: 12M; 8M; 1MHNO3: 8MNH4OH: QMH2O2: 30% aqueous solutionNH4OH-NH,C1 buffer: O.lAf in both NH40H and

NH4CI; pH 9.4Carbazole reagent: 2-3 mg of carbazole

(CSHS-NH-CBHS, diphenylimide) per 1 ml ofconed H2SO4

Hydrated antimony pentoxide (HAP) exchanger:source, Carlo Erba, Industrial Chemicals Divi-sion, Milan, Italy; washed with distilled waterbefore using to remove fine particulates

Bio-Rad AG 1-X8: 50-100 mesh, anion exchangeresin

Bio-Rad Chelex-100: 100-200 mesh, cation exchangeresin

3. Procedure

Step 1. Dissolve the vanadium target in 8MHNO3 and dilute with H2O to make the solution AMin acid. Add 150 ng each of potassium and scandiumcarriers.

Step 2. Pass the solution through a column (0.8-cm-i.d. and 2-cm-long) of hydrated antimony pen-toxide (HAP) exchanger at a rate of about 0.2ml/min. Discard the eluant. Wash the column with

several column volumes of AM HNO3 and discardthe washes. Wash the column with 1M HC1 until theeluant gives a negative test for NO3" ion with car-bazole reagent. (If NO3~ is present, a deep greencolor will Torm). Discard the eluant.

Step 3. Elute potassium with several columnvolumes of 12M HC1. Add 2 ml of 30% H2O2 to theeluant to enhance the Sb(V) oxidation state andevaporate to near dryness. Take up the residue in 15ml of 8M HC1 and pass the solution at a flow rate ofabout 0.3 ml/min through a column (0.8-cm-i.d. and10-cm-long) of Bio-Rad AG 1-X8 anion exchangeresin to remove any antimony present. Collect theeluant.

Step 4. Adjust the pH of the eluant to 10 byevaporation and addition of NH4OH. Pass the solu-tion through a column (0.8-cm-i.d. and 10-cm-long)of Bio-Rad Chelex-100 cation exchange resin.Collect the eluant. Wash the column with severalcolumn volumes of NH^OH-NH^l buffer (pH 9.4)to effect quantitative elution of potassium. Combinethe eiuants.

4. Primary Literature Reference

V. R. Casella, P. M. Grant, and H. A. O'Brien,Jr., J. Radioanal. Chem. 36, 337 (1977).

June 1979

114b

rhenium, rhodium, rubidium, ruthenium

117

RHENIUM

B. P. Bayhurst

I. Introduction

This procedure was designed for the separation ofrhenium from soil samples containing fissionproducts. Steps in the analysis include (1) LaF3 andLa(OH)3 scavenges, (2) Re2S7 precipitations, (3)passage of Re(VII) in 0.1M HCl solution through acation exchange resin column, (4) Cu(II)- andFe(III)-8-hydroxyquinolate scavenges, and (5)removal of Ru(III) by precipitation of the hydroxide.The rhenium is finally precipitated as[(C6Hs)4As]Re04. The chemical yield is about 50%.

2. Reagents

Re(VII) carrier: KReO4 in H2O, corresponding toabout 15 mg of [(CnHsJ^JReOVml; standard-ized (see procedure for THE SEPARATION OFRHENIUM FROM TUNGSTEN)

La carrier: 10 mg La/ml, added as La(NOa)-6H2OinH2O

Cu(II) carrier: 10 mg Cu/ml, added as CuCl2-2H2Oin H2O

Fe(III) carrier: 10 mg Fe/ml, added as FeCl3-6H2Oin dilute HCl

Ru(III) carrier: 10 mg Ru/ml, added as RuCl3 in0.1M HCl; probably contains some Ru(IV)

HN03: fuming; conedHCl: coned; 6M; 0.2M; 0.1MHF: conedHF-HC1 solution: bM in eachHC2H3O2: 6MNH

HOI. Add an equal volume of 0.2A/HC1 and pass thesolution through a Dowex 50-X8, 100-200 mesh ca-tion exchange resin column (H' form). Collect theeffluent in a glass centrifuge tube. Wash the columnwith 20 ml of 0.1M HC1 and collect the effluent inthe same tube.

Step 7. Evaporate the solution to about 2 mland dilute to 15 ml with H2O. Add 2 ml of 8-hydroxyquinoline reagent and adjust the pH to 6with 10M NaOH. Add 2 drops of Cu(II) carrier andheat to coagulate the precipitate. [The Cu(II)-8-hydroxyquinolate carries down a substantialamount of contaminant activity.] Centrifuge,transfer the supernate to a clean glass centrifugetube, and discard the precipitate. Repeat theCu(II)-8-hydroxyquinolate scavenge, but, after cen-trifugation, filter the supernate through a 9-cmWhatman No. 541 filter paper and collect thefiltrate in a clean glass tube.

Step 8. To the filtrate, add 2 ml of 6MHC2H3O2and 2 drops of Fe(III) carrier and heat on a steambath until the precipitate coagulates. [Theprecipitate of Fe(HI)-8-hydroxyquinolate carriesdown molybdenum activity.] Centrifuge, transferthe supernate to a clean glass centrifuge tube, anddiscard the precipitate. Repeat the Fe(III)-8-hydroxyquinolate scavenge twice more. After thelast centrifugation, filter the supernate through a 9-cm Whatman No. 541 filter paper and collect thefiltrate in a 40-ml polyethylene centrifuge tube.

Step ft To the filtrate, add 5.5 ml of coned HFand 8 ml of coned HC1. Heat on a steam bath andsaturate with H2S for 15 min. Stopper the centrifugetube and permit the Re2S7 to coagulate. Then treatthe precipitate with HF-HC1 solution and 6M HC1as described in Step 4.

Step 10. Dissolve the Re2S7 with 10M NaOHand 30% H2O2 as in Step 5. Use H2O to transfer theperrhenate solution to a 125-ml Erlenmeyer flask.Boil the solution until all the H2O2 has been decom-posed. Add 5 ml of absolute ethanol, 2 ml of 10MNaOH, heat on a hot plate, then add 2 drops ofRu(III) carrier. Boil on a hot plate until Ru(0H)3has precipitated completely and the solution has nocolor. Transfer the mixture to a glass centrifugetube, centrifuge, and pour the supernate into a cleanErlenmeyer flask. Discard the precipitate. Repeatthe Ru(OH)3 scavenge twice more, adding ethanoleach time to ensure that any Ru(IV) in the carrier isreduced to Ru(III).

Step 11. Evaporate the perrhenate solution in aglass centrifuge tube to about 2 ml, make it 9-10Min HC1, and heat for 30 min on a steam bath (to con-vert any technetium to the +4 oxidation state).Saturate with H2S for 15 min, centrifuge, and dis-card the supernate. Wash the Re2S7 precipitate with20 ml of 6M HC1 and discard the wash.

Step 12. Add 1 ml of coned NH«OH and 5-6drops of 30% H2O2 to the sulfide. Heat on a steambath until the solution is completely clear and diluteit to 15 ml with H2O. Add 4 ml of [(C6H6)4As]Clreagent, boil the mixture for 2 min, then cool in anice bath. Filter the [(CsHs^sJReO, through a taredNo. 42 Whatman filter circle, using a ground-offHirsch funnel and filter chimney. Wash theprecipitate with cold H2O and then with cold ab-solute ethanol. Dry in an oven at 110°C for 5 min,cool, weigh, and mount for counting.

June 1979

120

RHODIUM

J. S. Gilmore

I. Introduction

In the determination of radiorhodtuni ihoprincipal decontamination slops include d\) re-moval of ruthenium as the volatile RnO,. (h)precipitation of RhI;. and (c) ironCIIli hydroxideand acid sulfide scavenges from solutions con-taining the extremely stable [RhfCNVJ3" com-plex ion. The rhodium is finally electroplatedfrom sulfuric acid solution after destruction ofthe complex. The chemical yield is about 60°;',.and six samples can be analyzed in about one day.

2. Reagents

Rh carrier: 10 mg Rh nil. standardizedCo carrier: 10 mg Co'ml. added as CoCLGrLO

inHX)Fe carrier: 10 mg Fe nil. added as FoCl,-6H_O

in 1.1/HC1Mo carrier: 10 mg Mo'ml. added as

(NH,),;MorOJ,-4H,6 j n H , 0Ba carrier: 10 mg Ba ml. added as BnCL-21-LO

in B OSbdlT) carrier: 10 mg Sb'ml. added as SbCl: in

1MHC1Te(IV) carrier: 10 mg Te ml. added as Na,TeO,

ini . i /HClHC1: 6.1/; conedUNO.: conedH.SO,: conedHC1O,: conedNII.OH: conedKCN: 3MNaNO,: 5MNa,CO.: 0.11'/CufNO..1), solution: 100 mg Cu.'mlKI: solidH,S: gasKlhanol:

evolution of CO, ceases. Add 1 ml of 6M HC1, 1ml each of Te(IV) and Sb(III) carriers, andsaturate with HS. Centrifuge, transfer the super-nate to a clean centrifuge tube, and discard theprecipitate.

Step 8. Boil the solution for about 30 secto remove H,S. Add 7 ml of coned HC1. 2 ml ofCu(NTO,)u. solution, and cool in an ice bath. (TheRh is precipitated, presumably as the compoundCu:[Rh('CN),.];..) Centrifuge and discard thesupernate.

Step 9. Dissolve the precipitate in 2 ml of

coned NH.OH and dilute to 10 ml with H,O.Transfer to the Dowex 50 cation exchange columnand allow the solution to pass through undergravity, catching the eluate in a 125-ml erlen-meyer flask. [Cu(NH:,) , ]

2 + is removed on thecolumn, the [Rh(CN),i]3- passing through.

Step 10. Evaporate the solution nearly todryness, add 3 ml of coned FLSO.,, and concen-

trate to a volume of 1 ml to remove Rh-cyanidecomplex.

Step 11. Repeat Steps 3 through 9. butcollect the column eluate in a 40-ml centrifugetube.

Step 12. Repeat Steps 6 through 10.

Step 13. Add 2 ml of coned HCIO,. 1 ml ofconed HNO,, and heat until SO., fumes are evolved.Transfer to the plating cell with 20 ml of HLO.Electroplate at room temperature and 0.1 ampfor lfi hr on a weighed Pt cathode disk. Washthe cathode with I-T.O and then with 95% ethnnol.Dry in an oven at 110° for 15 min. Cool, weigh,mount, and /3-count.

Note

The components of the plating cell must beextremely clean in order lo obtain a smooth, ad-herent cathode deposit.

122

ADDENDUM TO THERHODIUM PROCEDURE

J. S. Gilmore

ll has been found convenient to substitute forStep 0 the following method for the removal ofC.u from the precipitate, which presumably hasthe formula Cu.[Ru(CN)(1],:

To the precipitate add 20 nil of FLO. warmthe mixture, and then add sufficient 6MNaOH to convert all the copper to the in-soluble oxide, leaving the rhodium cyanocomplex in solution as the sodium salt. Whenconversion is complete (the precipitate willbe black and the solution colorless), centri-fuge, transfer the supernate to a clean centri-fuge tube, and discard the precipitate. Pro-ceed to Step 10.

May 1968

122a

SCANDIUM II

B. P. Bayhurst

1. Introduction

In the analysis for scandium in soil samples, thethree major decontamination steps are (1) removalof iron and some zirconium on a Dowex AG 1-X8anion exchange resin from a solution 10M in HCl,(2) Zr3(PO4)4 scavenges, and (3) LaF3 scavengesfrom solutions containing scandium in the form offluorocomplexes. Following the decontaminationsteps, scandium is precipitated as the fluoride andconverted to the hydroxide. It is then placed on aBio-Rad AG 50W-X4 cation exchange resin fromdilute HNO3 solution. Elution from the column iseffected with «-HIB («-hydroxyisobutyric acid) andthe scandium is finally precipitated as the hydrox-ide and ignited to the oxide. The chemical yield is60-70%.

2. Reagents

Sc carrier: 20 mg ScjOa/ml, added as ScCl3 in verydilute HCl; standardized (see original SCAN-DIUM procedure)

Zr holdback carrier: 10 mg Zr/ml, added asZrO(NO3)2-2H2O in IM HNO3

La carrier: 10 mg La/ml, added as La(NO3)3-6H2Oin very dilute HNO3

HCl: coned; 10MHNO3: conedHClCv conedNH4OH: conedNaOH: conedNH4H2PCv 1.5MNH4HF2-HF reagent: AM in NH4HF2 and IM in HFNH2OH-HC1: solidMethyl red indicator solution0.05M a-HIB(a-hydroxyisobutyric acid): adjusted

to pH 5.2 with NH4OHAnion exchange resin: Dowex AG 1-X8, 50-200 mesh

(washed with 10M HCl)Cation exchange resin: Bio-Rad AG 50W-X4, minus

400 mesh (NH4+ form)

3. Procedure

Step ]. To the sample in a 40-ml centrifugetube, add 1.0 ml of standard scandium carrier and 5ml of coned HC1O4, and fume nearly to dryness.Dilute to 20 ml with H2O and precipitate Sc(OH)3with 10M NaOH. Centrifuge, and discard the super-nate. Dissolve the precipitate in a .minimum ofconed HCl, dilute to 20 ml with H2O, andprecipitate Sc(OH)3 with coned NH4OH.

Step 2. Dissolve the precipitate in a minimumof coned HCl, dilute to 20 ml with H2O, and repeatthe precipitations of Sc(OH)3 with NaOH andNH4OH. Centrifuge, discard the supernate, andwash the precipitate with 20 ml of H2O.

Step 3. Dissolve the precipitate in 5 ml of conedHCl and place the solution on a Dowex AG1-X8anion exchange resin column (50-200 mesh). Collectthe effluent in a 125-ml Erlenmeyer flask. Pass 15ml of 10M HCl through the column and combine theeffluent with the previous one.

Step 4. Add 2 drops of zirconium holdbackcarrier and evaporate to about 3 ml on a steam bath.Transfer the solution to a 40-ml glass centrifugetube, dilute to 20 ml with H2O, and make the solu-tion 2-3M in HCl. Add 5 drops of 1.5M NH4H2PO4solution, heat on a steam bath for a few minutes,and let stand until the Zr3(PO4)4 precipitatecoagulates. Centrifuge, transfer the supernate to aclean tube, and discard the precipitate. Add another2 drops of zirconium carrier and again precipitateZr3(PO4)4. Carry out three to four additionalZr3(PO4)4 precipitations. Transfer the supernate (af-ter the final precipitation) to a 40-ml polyethylenecentrifuge tube.

Step 5. Add 3 ml of NH4HF2-HF reagent andneutralize the solution to a methyl red end pointwith coned NH4OH. (The scandium is now in theform of fluorocomplexes.) Add 100 mg ofNH2OH-HC1, heat on a steam bath, add 3 drops oflanthanium carrier, and heat again on a steam bathfor a few minutes Centrifuge, transfer the supernateto a clean polysthylene tube, and discard theprecipitate. Repeal the LaF3 scavenge three times

131

and transfer the final supernate to a cleanpolyethylene tube.

Step 6. Add 6 ml of coned HC1 to precipitateScF3, centrifuge, and discard the supernate. Add 1ml of 10M NaOH, stir, and heat to convert ScF3 toSc(OH)3. Dilute to 15 ml with H2O, centrifuge, anddiscard the supernate. Dissolve the precipitate in aminimum of coned HC1 and precipitate Sc(OH)3 byadding coned NH4OH. Centrifuge, discard thesupernate, and wash the precipitate with 30 ml ofH2O to remrv'e NH4' ion. Centrifuge, and discardthe superna e.

Step 7. Dissolve the precipitate in 4-6 drops ofconed HNO3 and dilute to 30 ml with H2O. Add 2-3ml of Bio-Rad AG 50W-X4, minus 400 mesh, cationexchange resin, stir for about 1 min, centrifuge, anddiscard the supernate. Use a small amount of H2Oand a transfer pipet to add the resin to the top of acolumn of the same resin. Use some rubber tubing toconnect the top of the column to a reservoir of 0.05M

SEPARATION OF SCANDIUM FROMLARGE AMOUNTS OF TITANIUM METAL

B. P. Bayhurst

1. Introduction

In this procedure, the titanium metal is dissolvedby treatment with H2O, coned HF, and conedHNOS. (The quantities of these reagents are givenfor a 55-g metal sample; the same proportions ofmetal, H2O, HF, and HNO3 are maintained forlarger, and smaller, sample sizes.) After dissolutionof the titanium, standard scandium carrier is addedto precipitate ScF3 away from TiF?". The fluoride isthen converted to Sc(OH)3, and the latter is dis-solved and reprecipitated. The hydroxide is finallyignited to Sc2O3. The chemical yield is ~85%.

2. Reagents

Sc carrier: 20 mg Sc2O3/ml, added as ScCl3 is verydilute HC1; standardized (see original SCAN-DIUM procedure).

HN03: conedHF: conedHC1: conedHF-HCl reagent: 1.2M in HF and 2M in HC1NaOH: 10MNH.OH: coned

3. Procedure

Step l.Toa 55-g sample of titanium metal in a1000-ml Teflon beaker, add 180 ml of H2O and place

on a hot plate. Add 145 ml of coned HF in 5-ml in-crements, heating after each addition until reactionceases. Add 20 ml of coned HN03 and heat untilreaction is no longer apparent. Then, with heating,add another 35 ml of HN03 in portions of 5 ml, eachincrement being added after the previous one is con-sumed. The metal should now be in solution.

Step 2. Dilute the solution to 500 ml with H2O,add 4.0 ml of standard scandium carrier, and heaton a hot plate for 3 h. Let the mixture stand over-night, heat for 1 h, then cool in an ice bath. Transferthe mixture in portions to clean 40-ml polyethylenecentrifuge tubes. Centrifuge, discard the super-nates, and combine the precipitates in a singlepolyethylene tube with the aid of HF-HCl reagent(1.2M in HF and 2M in HC1). Wash the precipitatewith 20 ml of the HF-HCl reagent and discard thewash.

Step 3. Add 40 drops of 10M NaOH to theprecipitate, dilute to 10 ml with H2O, and heat on asteam bath until the Sc(OH)3 formed coagulates.Centrifuge, and d;°card the supernate.

Step 4. Dissolve the precipitate in 2 ml of conedHC1, add excess coned NH,0H to precipitateSc(OH)3, centrifuge, and discard the supernate.Add 2 ml of coned HC1 to dissolve the precipitate,then add 6 ml of filter paper pulp slurry and anexcess of coned NH40H to reprecipitate Sc(OH)3.Filter onto a 9-cm No. 541 Whatman filter paper,transfer the paper to a Coors 00 porcelain crucible,and ignite at 1000°C for 15 min. Cool, weigh, andmount the Sc2O3.

June 1979

132a

QUANTITATIVE CHEMICAL RECOVERYOF SPALLATION-PRODUCED ELEMENTS.

MOLYBDENUM TARGET

Spallation reactions have been induced in molyb-denum targets by using 200- to 800-MeV protons toproduce microcurie amounts of various radioele-ments. The targets were in the form of 99.90% purefoils, usually 0.51 mm thick, and were irradiated for1 to 2 fiA-h of integrated intensity. Followingirradiation, a target was permitted to stand forseveral days to permit the activities to decay toreasonable levels. The target was then radiographedand the hot spot was cut away from surrounding in-active metal. The radioactive section was cleaned ofsurface contaminants by immersion in chromic acidcleaning solution for 1-2 min, rinsed with distilledwater, dried, and weighed. Typical molybdenumweights ranged from 1-10 g.

A. SEPARATION OF STRONTIUM

P. M. Grant, M. Kahn,and H. A. O'Brien, Jr.

1. Introduction

Strontium is quantitatively separated from theirradiated molybdenum by a six-step procedure con-sisting of precipitation, solvent extraction, and ionexchange techniques. The molybdenum metal isfirst dissolved in 30% H2O2 to give a solution ofmolybdic acid, H2Mo04. Following removal ofexcess H2O2, the acid is converted to its ammoniumsalt and then lead molybdate is precipitated. Ex-traction of the lead molybdate with a 0.12M HC1-50% solution of bis-(2-ethylhexyl)phosphoric acid(HDEHP) in toluene effectively separates strontiumfrom yttrium; the former is concentrated in theaqueous phase, whereas the yttrium and some othercontaminants are extracted into the organic phase.Macroscopic amounts of lead and molybdenum areremoved from the aqueous solution by precipitationas sulfides. Last traces of contaminants are removedby adsorption on a ZrO2 ion exchanger at pH 6.0;strontium is not retained by the exchanger. The

yield of strontium, based on radioactivity deter-minations, is 94 ± 2% and separation is effectedfrom molybdenum, technetium, niobium, zir-conium, yttrium, rubidium, selenium, arsenic, zinc,and cobalt.

The long-lived strontium isotopes 82 and 85 areobtained from the irradiation process. Because *2Srhas a reasonably long half-life (25.55 days) anddecays to an alkali metal of very short half-life(82Rb; 1.273 min), this system is of potential interestfor cardiovascular investigations in nuclearmedicine.

If one is primarily interested in strontium ac-tivities and the irradiation of the molybdenumtarget has not been sufficiently intense to producemilligram quantities of the element, strontiumcarrier is added at an appropriate place in theprocedure.

2. Reagents

Sr carrier: 10 mg Sr2+/ml, added as Sr(NO3)2 solu-tion

HN03: 7-8MHC1: 0.12MH2S: gasH2O2: 30% aqueous solution (unstabilized)NH,OH: coned; 3.7MNH4C1: 0.1M aqueous solutionPb(NO3)2: 5 mg of Pb

2+/ml of aqueous solutionChromic acid cleaning solution: 35 ml of saturated

aqueous Na2Cr207 in 1 I of coned H2SO4HDEHP solution: 50% solution by volume of bis-(2-

ethylhexyl)phosphoric acid (source: EastmanOrganic Chemicals) in toluene

Hydrous ZrO2 ion exchanger: HZO-1 crystals;source: Bio-Rad Laboratories

3. Procedure

Step 1. To the molybdenum sample in a 400-mlbeaker, add sufficient 30% H2O2 to dissolve themetal with mild heating. (Typically, 10-20 ml of theperoxide is required per gram of molybdenum.)Heat the yellow molybdic acid solution gently todrive off excess H2O2.

139

Step 2. By a careful combination of evaporationwith gentle heating and the addition of conedNH

stable *aSr with prominent gamma emissions of898.04 keV (93.4%) and 1836.13 keV (99.4%). Thelatter photon will interact with "Be to producemonoenergetic neutrons of about 150-keV kineticenergy. The properties of 88Y make it attractive foruse with 9Be as a photoneutron source in nuclearsafeguards and other areas of research.

2. Reagents

HC1: 12M; 8M; 0.12MHDEHP solution: 50% solution by volume of bis-(2-

ethylhexyl)phosphoric acid (source: EastmanOrganic Chemicals) in toluene.

Anion exchange resin: Bio-rad AG 1-X10, 100-200mesh; preconditioned with coned HC1; columnparameters: 0.8-cm i.d., 9-cm length, 0.1-ml/minflow rate.

3. Procedure

Step 1. Dissolve the hydrous molybdenum ox-ides from Step 2 of Procedure A in 10 ml of 0.12MHC1. Add 10 ml of HDEHP solution and equilibratethe mixture on a Burrell shaker for 50 min. Combinethe organic phase (upper layer) with that from Step4 of Procedure A. (If radiozirconium is to be isolatedlater, repeat the HDEHP extraction and add theorganic layer to the other two layers.)

Step 2. Back-extract the combined organicphase twice successively with equal volumes of 8MHC1 on the Burrell shaker, each time for 50 min.Combine the aqueous phases and set aside theorganic phase for the separation of zirconium.

Step 3. Evaporate the aqueous solution to neardryness, then dissolve the mixture in 10 ml of 12MHC1. Pass the solution through the Bio-Rad AG1-X10 anion exchange resin and collect the eluantcontaining the yttrium.

4. Primary Literature Reference

V. R. Casella, P. M. Grant, and H. A. O'Brien,Jr., Radiochim. Acta 22, 31 (1975).

C. SEPARATION OF ZIRCONIUM

R. E. Whipple, P. M. Grant, R. J. Daniels,W. R. Daniels, and H. A. O'Brien, Jr.

1. Introduction

If the HDEHP extraction (Step 1) of the yttriumprocedure (Procedure B) is performed twice, 99% ofthe zirconium is taken into the organic phase and re-mains there after back-extraction of the yttriumwith 8M HC1. Subsequent treatment of the organicphase with 30% H2O2 extracts molybdenum into theaqueous phase but has no effect on the zirconium.Extraction of the organic phase with 3.5M HF thenremoves the zirconium, as well as any niobium thatis present. The latter is separated from the zir-conium by extraction into diisobutylcarbinol(DIBC), after the aqueous phase has been made5.8M in both HF and HjSO,. The overall yield of zir-conium is 96 ± 6%.

Zirconium-88 (half-life, 83.4 days) is the precur-sor of 88Y. There would appear to be advantages inthe incorporation of the parent isotope into an MY-Be photoneutron source as well. A combined 88Y-89Zractive component could ease hot-cell processing,eliminate long storage time for the attainment ofradioactive equilibrium, and increase the usefullifetime of the photoneutron source.

2. Reagents

HF: coned; 3.5MH2SO4: conedH2O2: 30% aqueous solution (unstabilized)Diisobutylcarbinol (DIBC): source, Carbide and

Chemicals Company, Division of Union Carbideand Carbon Corporation

3. Procedure

Step 1. Back-extract molybdenum from theHDEHP phase of Step 2 of the yttrium procedure(Procedure B) with an equal volume of 30% H2O2.Discard the aqueous (lower) layer.

140a

Step 2. Back-extract the HDEHP layer with anequal volume of 3.5MHF to remove zirconium. Dis-card the organic layer.

Step 3. Make the aqueous phase 5.8M in bothHF and H2SO4 and extract twice with equal volumesof diisobutylcarbinol (DIBC), discarding the organic(upper) phase after each extraction. Centrifugationfacilitates phase separation in this step. The finalradiozirconium solution is the aqueous phase of thisextraction.

4. Primary Literature Reference

R. E. Whipple, P. M. Grant, R. J. Daniels, W. R.Daniels, and H. A. O'Brien, Jr., Radiochem.Radioanal. Lett. 27, 137 (1976).

June 1979

SEPARATION OF MILLIGRAM QUANTITIESOF STRONTIUM AND ZIRCONIUM FROM

100 GRAMS OF YTTRIUM

R. J. Prestwood

1. Introduction

Yttrium metal was used on the Apollo space shipas a possible high-energy particle monitor. Thepotential reactions of interest were "Y(n,2n)88Y,89Y(n,3n)87Y-87Sr, 89Y(n,p)89Sr, and 89Y(p,n)89Zr. Itwas therefore necessary to be able to analyze forvery small amounts of strontium and zirconium inthe presence of 100 g of yttrium (the weight of themetal used as monitor).

In the procedure, the yttrium metal sample is dis-solved in HNO3 and strontium is precipitated asSr(NO3)2 by means of yellow fuming HN03. Afterappropriate purification of the Sr(NO3)2 to removeyttrium contaminant, SrCO3 is precipitated forcounting. The chemical yield is ~75%.

Following removal of strontium, zirconium is con-verted to the insoluble Zr3(PO

Step 3. Dissolve the precipitate in a minimumof coned HNO3. Precipitate Sr(NO3)2 by adding 20ml of yellow fuming HN03. Centrifuge, and transferthe supernate to the original filtrate (Step 1). Dis-solve the Sr(NO3)2 in a minimum of H2O and againprecipitate the nitrate with yellow fuming HN03.Centrifuge, and discard the supernate.

Step 4. Dissolve the Sr(NO3)2 in a minimum ofH2O and make the volume up to 20 ml. Make thesolution basic with coned NH40H to precipitate anyyttrium present. Centrifuge, and transfer the super-nate to a clean glass centrifuge tube and discard anyY(OH)3 that has formed. Add 10% (NH4)2CO3 solu-tion to precipitate SrCO3. Filter onto a 1-in. What-man No. 42 filter paper. Transfer the SrCO3 fromthe paper to a tared plastic tube and weigh for Nalwell counting.

Step 5. Transfer the combined filtrate andsupernate from the 2-1 suction flask to a \-t Erlen-meyer flask. Add 60 mg of zirconium carrier (asZrOCl2-8H2O in 1M HN03) and evaporate the solu-tion to a volume of 300 ml. Add 25 ml of 1.5MNH4H2P04 solution and dilute the mixture to 550ml. [This treatment precipitates Zr3(PO4)4 and largeamounts of YPO

TANTALUM

B. P. Bayhurst

1. Introduction

In the separation of tantalum from niobium andother fission products, decontamination is effectedby LaF3 and Sb2S3 scavenges, BaZrF6 precipitation,and extraction of tantalum into hexone from a solu-tion 2.88M in HNO3 and 1.1M in HF. The tantalumis back-extracted from hexone by means of a 1.5%hydrogen peroxide solution and precipitated as thehydrous oxide, Ta2O,-XH2O, which is ignited to theanhydrous compound. The chemical yield is 60-70%.

2. Reagents

Ta carrier: 10 mg Ta/ml, prepared by dissolving thepure metal in a minimum of a mixture of conedHN03 and HF and diluting to the appropriatevolume with H2O.

Sb(III) carrier: 10 mg Sb(III)/ml, added as SbCl3 in1MHC1

La carrier: 10 mg La/ml, added as aqueous La(NO3)3-6H2O

Zr carrier: 10 mg Zr/ml, added as purifiedZrOCl2-8H2O in 0.1M HC1

HNO3: coned, fumingHF: conedH3BO3: saturated aqueous solutionH2S: gasNH2OH-HC1: solidHNO3-HF solution: 2.88M in HNO3 and 1.1M in HFNH4OH: dilute; conedBaCl2: 1MNH4NO3: saturated aqueous solutionHexone (4-methyl-2-pentanone)H2O2: 1.5% by volumeEthanol: absolutePhenolphthalein indicator solution

3. Procedure

Step 1. To the sample in a 40-ml polyethylenecentrifuge tube, add 4.0 ml of tantalum carrier and 3

ml each of saturated NH,NO3 and HsBOa. Make thesolution basic to phenolphthalein with conedNH4OH, centrifuge, and discard the supernate.Wash the precipitate with 30 ml of dilute NH..OH (1ml of coned NH4OH and 29 ml of H2O) and 2 ml ofsaturated NTI4NO3, centrifuge, and discard thewash.

Step 2. Add 10 ml of fuming HNO3, place on asteam bath, and permit the Ta2O5-XH2O tocoagulate. Centrifuge, and discard the supernate.Dissolve the precipitate in 7 drops of coned HF,dilute to 10 ml with H2O, and add 100 mg ofNH2OH-HC1. Add 3 drops of lanthanum carrier,heat on a steam bath for a few minutes, centrifuge,and transfer the supernate to a clean polyethylenetube. Repeat the LaF3 scavenge twice more.

Step 3. To the supernate from the final LaF3scavenge, add 4 drops of Sbdll) carrier and saturatewith H2S on a steam bath. Remove the tube fromthe bath, cap it, and permit the Sb2S3 to coagulate.Centrifuge, transfer the supernate to a cleanpolyethylene tube, and repeat the Sb2S3 scavenge.In this scavenge, add 1 ml of filter pulp to bringdown "floaters."

Step 4. Transfer the supernate to a cleanpolyethylene tube and heat on a steam bath to expelH2S. Add 6 drops of coned HF and 2.75 ml of conedHNO3 and bring the volume to 15 ml with H2O. Add2 drops of zirconium holdback carrier and 4 drops of1M BaCl2 and heat on a steam bath until BaZrF6coagulates. Centrifuge, transfer the supernate to aclean polyethylene tube, and repeat the BaZrF6scavenge. Transfer the supernate to a 1-ozpolyethylene bottle.

Step 5. Add 10 ml of hexone and extract tan-talum (as fluorocomplex) into the organic solvent(upper layer). Wash the hexone layer five times withHNCvHF solution (2.88M in HN03 and 1.1M inHF) and discard the washings.

Step 6. Extract the tantalum from the hexonesolution with about one-fourth of its volume of 1.5%H2O2. Repeat the extraction three times, combiningall extracts in a Teflon beaker and discarding thehexone layer.

145

Step 7. Add 5 ml of coned HNO3 and boil thesolution to a volume of 2-3 ml. Repeat. Add 5 ml ofconed HNO3, boil down the solution to about 2-3 ml,and transfer the mixture to a 40-ml polyethylenecentrifuge tube using coned HNO3. Centrifuge, anddiscard the supernate. Wash the precipitate twicewith coned HNO3, each time centrifuging and dis-carding the supernate.

Step 8. To the precipitate, add a slurry of filterpaper pulp, stir, and filter through a 9-cm No. 40Whatman filter