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Centimeter1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 mm

1 2 3 4 5

, !111t_I2.2

ilili'" jill,',_

11111'_511111"----4Illll'._

. :'. A_a"'os Nat,ona, LaDoratOr_, aS ooerateo Ov tr_e umversJtv of Caldorma 1o, the Umteo States Oeoartment of Energy unoer contract W.7405.ENG-36

TITLE COBALT DICARBOLLIDE CONTAINING POLYMER RESINS FOR CESIUM AND STRONTIUM

UPTAKE

AUTHORIS) W. P. Steckle, Jr., MTL-7

J. R. Duke, Jr., MTL-7

B. S. Jorgensen, MTL-7

SUBMLTTED TO POLYMER MATERIALS SCIENCE AND ENGINEERING, AMERICAN CHEMICAL

SOCIETY, VOL. 71

FALL MEETING 1994

WASHINGTON, D.C. (AUGUST 21-25, 1994)

DISCLAIMER

This report was preparedas an account of work sponsored by an agency of the United StatesGovernment. Neither the United States Government nor any agency thereof, nor any of theiremployees, makes any warranty, express or implied, or assumes any legal liability or responsi-bility for the accuracy, completeness, or usefulness of any information, apparatus, product, orprocess disclosed, or represents that its use would not infringe privately owned rights. Refer-ence herein to any specific commercial product, process, or service by trade name, trademark,manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recom-mendation, or favoring by the United States Governmentor any agency thereof. The viewsand opinions of authors expressed herein do not necessarily state or reflect those of theUnited States Governmentor any agency thereof.

By _cceD'.ance ot tr_,s art,tie the DuDhSher recogmzes that tr_e U S Government retains a nonexclus=ve, royalty.free license to DuOhSr, or reoroOuce

l_eOuDhsnea form O' tins contriDubon or tO allOw otners tO (:0 SO fOr U S Government DurDoses

""e LOS A:a,_os Nal.ona' LaDorator_ rec.Jesls tna'. the DuOhSP, e_ _Oenldv l_,s article as work Dertormeo unOer the auspices of the U S Deoartn, ent ol Energy

LosAlamos.New Mexico 87545

" ": _"_:_' IDISTFIII_JTION OF THIS DOCUMENT IS UNLIM

, ,

I

b

#

COBALT DICARBOLLIDE CONTAINING POLYMER RESINS FOR CESIUM ANDSTRONTIUM UPTAKE W.P. Steckle, Jr., J.R. Duke, Jr., and B.S. Jorgensen;Los Alamos National I.aboratory, MST-7, MS E549, Los Alamos, NM 87504

Large amounts of high level radioactive waste has been generated by the atomic industry over the pastseveral decades. These wastes exist as a mixture of radioactive elements and flocculants that makes

processing difficult. A majority of the thermal energy produced in these wastes arises from 137Cs+ and90Sr2+. Cgbalt(Ill) dicarbollide [(C2B9H11)2Co]" has been found'to selectively extract these cations fromsolution. _Jnfortunately the current technology employs extracting these metals into nitrobenzene. Inorder to avoid the use of organic solvents in processing these wastes it is our goal to attach thesedicarbollide moieties to a base resin in a manner where they can be utilized as a quasi-ion exchange resin.Once these metals have been removed from the waste streams it is hoped that they can be washed off theresins then vitrified into glass logs. The base resins that have successfully derivitized include polystyreneand polyb_nzirrddazole. A series of derivatives was prepared starting with carborane (C2B10H12),lithium carbollide' [(C2B9H11)-Li+], and finally cobalt dicarbollide. The reaction proceeds by anionicallygrafting the carborane derivatives onto a chloromethylated resin. The synthesis and subsequentcharacterization of these materials will be investigated.

...... IPl '

.,b° g

COBALT DICARI_OLLIDE CONTAINING POLYMER RESINS,e FOR CESIUM AND STRONTIUM UPTAKE

W.P. Steckle, Jr., J.R. Duke, Jr., and B.S. JorgensenLos Alamos National Laboratory, Polymer and Coatings Group

MST-7, MS E549, Los Alamos, NM 87504

Introduction

Over the past several decades large quantities of high level radioactive wastehave been generated by the atomic industry. 137Cs+ and 90Sr2+ occur innuclear waste as the result of fission in reactor fuels. One of the majorproblems presented by these particular isotopes present in storage is that theycontribute upwards of 97% of the thermal energy to the storage tanks. 1Wastes have been generated in such a manner that they contain a wide varietyof metals and isotopes along with a variety of flocculating agents Priortreatment methods have employed the use of phosphotungstic acid, ferro-and ferricyanides and tetraphenylborate to precipitate these metals. In multi-element streams this leads to a long tedious process where many precipitatesare formed adding to the quantity of waste being processed.

Macrocyclic crown ethers have also been employed for removal of Cs andSr. Selectivity can be achieved by selecting the size of the cavity of thecrown ether in which the metal cation fits. The drawbacks to crown ethersare their cost and the inability to remove the metal from the crown ether onceit has been extracted. 2

Although cobalt(III) dicarbollide [(C2B9Ha i)2Co]" (CB2), Fig. 1, was firstmade in the 1960's 3 it was not until the 1970's that its use for Cs and Sr

extraction was investigated by Russians and Czech researchers 4-5. CB2showed high levels of selectivity and extraction in an organic phase.Nitrobenzene exhibited the highest distribution coefficient of the solventsinvestigated, three time greater than that of ethyl acetate. 4 Due to thecarcinogenic and toxic nature of this solvent coupled with more stringent

} environmental regulations the use of nitrobenzene, and in general, anyorganic solvent, should be avoided.

./_,',--I---)I%/ , B_I

B___--_"I_I/"_. ,,._:::''_.... x./i

11

Fig. 1. Cobalt dicarbollide. Protonsattachedto boronsandcarbonsomittedfor the sakeof clarity.

Dicarbollides are useful in this application in that they are highly stable toredox, thermal, chemical, and radiolytic attack. Of the metals (Co, Fe, orNi) that can be placed between the carbollide cages, cobalt is essentiallyinsoluble in water and creates the complex with the greatest stability. 6 Initialefforts to modify a resin was to simply adsorb the CB2 onto the surface ofthe resins. Although there is limited solubility in water, there was notic?abledesorption of the CB2 under acidic conditions. This led to the need forcovalently bonding the CB2 to a resin substrate.

Synthesis of Resins with Grafted Cobalt Dicarboilide

l"_e,,_ ,,.,,..a_.,a,¢_,ll. ;,.,,.- _.1,.,._ ¢...,_,¢ ,_l_z_._l,(._iI_l_._.. _.,._l,.,..,_...,..,:_p..! _._1 i_,¢.;_.cl_tq_. ¢ ll..e. _ I_.._1 _..._ .1,..,. a

Macrocyclic crown ethers have also been employed for removal of Cs and rSr. Selectivity can be achieved by selecting the size of the cavity of thecrown ether in which the metal cation fits. The drawbacks to crown ethersare their cost and the inability to remove the metal from the crown ether onceit has been extracted. 2

Although cobalt(III) dicarbollide [(C2B9H1 l)2Co] (cB2), Fig. 1, was firstmade in the 1960's 3 it was not until the 1970's that its use for Cs and Sr

extraction was investigated by Russians and Czech researchers 4-5. CB2showed high levels of selectivity and extraction in an organic phase.Nitrobenzene exhibited the highest distribution coefficient of the solventsinvestigated, three time greater than that of ethyl acetate. 4 Due to thecarcinogenic and toxic nature of this solvent coupled with nore stringent

1 environmental regulations the use of nitrobenzene, and in general, anyorganic solvent, should be avoided.

(,

[kt --"-_I,. ¢_---\/I

./__2<t_,--"_. ,,_/n

LI

Fig. 1. Cobalt dicarbollide. Protons attachedto boronsand carbonsomitted for the sakeof clarity.

Dicarbollides are useful in this application in that they are highly stable toredox, thermal, chemical, and radiolytic attack. Of the metals (Co, Fe, orNi) that can be placed between the carbollide cages, cobalt is essentiallyinsoluble in water and creates the complex with the greatest stability. 6 Initialefforts to modify a resin was to simply adsorb the CB2 onto the surface ofthe resins. Although there is limited solubility in water, there was noticeabledesorption of the CB2 under acidic conditions. This led to the need forcovalently bonding the CB2 to a resin substrate.

Synthesis of Resins with Grafted Cobalt Dicarbollide

Prior research in the area of polymer supported metal catalysts has led to theattachment of 1,2-dicarbadodecaborane, a precursor of CB2, to polystyrene ......(PS). Chandrasekaran et al.7 prepared a rhodium complex for use as ahydrogenation caialyst in this manner. An anion of the carborane cage wasprepared by the reaction of the decaborane with n-buLl and was thensubsequently reacted with a chloromethylated PS.

In this study a series of cross linked resins was used. Different solventswere investigated in order to determine the rate of reaction and whether ornot the degree of swelling effected the substitution. Once it was determined

,_ , , ......... i,...... " _,<........ _II' ',' ' ',""" " ' "Jl' I l'jIl'ltlr'', " I

,i

" that the carborane cage was actually grafted onto the resin and not merelyadsorbed onto the surface, a series was prepared incorporating lithiumcarbollide [(C2B9Hll)'Li +] and cobNt dicarbollide onto a resin.

Another resin investigated was polybenzimidazole (PBI). Since PBI doesnot contain a reactive chlorine site, epichlorohydrin was grafted on asreported by Chanda et al.8 The resulting hydroxyl group from the openingof the epoxide was then protected by hexamethyldisilazane. The reactionscheme for the grafting of CB2 onto PBI is given below:

O ©oft

CICH2 -CH -CH2 _/f_--_- H_

t [- +N. I

C1 C1

(CH.-)3SiNHSi(CH3)

ICl Cl

I CB2

n-buLl

Experimental

Some of the chloromethyl polystyrene (CMPS) resins that were used are.... _ _ ,

CICH2-CH'-_CH 2 1 <_I-13

7)o i J

C1 CI

(CH3)3SiNHSi(CH3)

CI C1

I CB2

n-buLl

Experimental

Some of the chloromethyl polystyrene (CMPS) resins that were used arecommercially available from Polysciences and so_,_ewere made in house.

_The PBI resin was Aurorez microporous resin beads made by Hoechst-Celanese and was used as supplied. Cyclohexane, toluene, andtetrahydrofuran (THF) used during grafting reactions were freshly distilledfrom sodium under _n argon purge, n-buLi, hexamethyldisilazane,methanol, and ethanol was purchased from Aldrich and used as received.Carborane was purchased from Alfa was purified by sublimation prior touse. Lithium carbollide and CB2 was prepared at Los Alamos NationalLaboratory, CST- 12.

i, , i _ i i

Reaction conditions for both the grafting of the carborane series as well asthe preparation of the PBI prior to the CB2 reaction were as previouslycited.7, 8 In order to insure that the carboranes were not merely adsorbed tothe surface of the resins all samples were washed three times with methanolbefore soxhlet extraction for 48-72 hours in ethanol. Samples with adsorbed

i carborane or CB2 that were subjected to similar work up were found to befree of either the carborane or CB2.

Samples were analyzed using a Perkin Elmer 1600 FTIR and a Nicolet 730FTIR equipped with a Nic-Plan IR microscope. Diamond windows wereused in order to compress the resin beads. Beads were looked at both intransmission as well as reflectance modes. Solid state 13C and 11B NMR of

t these resins done Braker ASX 300.was using a

Elemental analYsis is currently be done in order to quantify the extent ofreac.ion.

Results and Discussion

Two reaction routes were first envisioned for obtaining CB2 grafted onto aresin. One involved directly grafting CB2 to the CMPS if that were possible.This route would be easier on the resin than having to expose the resin to theharsh conditions under which a B-H is extracted from the carborane cage.Steric hindrance and the fact that each cage on CB2 itself is a dianion neededto be taken intoconsideration. Since carborane had previously been shown

to react with CMPS 7, this reaction was optimized before trying to graft thecarbollides. This reaction can be followed using IR spectroscopy by

monitoring the disappearance of the CH2-C1 stretch, ca. 1265 cm -1, and thegrowth of the strong B-H absorbance ca. 2580 cm -1 as seen in Fig. 2. Notonly is the B-H absorbance dependent on the type of cage, it can been seen

to shift 5 - 10 cm "1 upon grafting. The second cage in the series to beattached was the lithium carbollide. Somewhat less sterically hindered thanCB2 this too could be readily attached to CMPS. Being an anionic speciesapparently did not prevent the formation of the carbanion. Surprisingly theCB2 reaction also proceeded smoothly.

..........carborane 40...I ..........carborane/ -"--'- grafted carborane

.---'-- grafted carborane ..... CMPS ,.,...... CMPS / ....

•++........,,+,, :.'i:"'--."I'A'iVl.20 } _ i .,4"_ ' 0 i

', tl 4 4: ::;Hl_

k.,'i'_ "_II|I 0_ al ol d, ,0 o

. .,il iI ,,, ......"'"'""'"''"""-''i'i'"i.i,.,,i:".,,_"_-" i ' ' ' _ ..... '"' "• +, ,_ ,0 t [I ii Ii o H _l l :It I •

_o _o "" ' ' il, l::! l _-- _ ' "'T-- _ OI! ! x . , ,,

I0 i i '_,li;,li!i:, " i ! I0- ,....,

"!iJill+ I e

i Ii J Jll _1I II IIII

11 I II i I

l I II III I IV Ii

Ii

, , ,,_ ,.P_ ,'

Ii i

0 , , , I ' ' ' ' I ' " O-l'''rl ''''I' ''+

3000 2500 2000 1500-1 -1

Wavenumber(cm ) Wavenumber(cm )

Fig. 2 FTIR spectra of carborane and the starting CMPS resin along withthe grafted carborane resin.

Elemental analYsis is currently be done in order to quantify the extent ofi reaction.

Results and Discussion

Two reaction routes were first envisioned for obtaining CB2 grafted onto aresin. One involved directly grafting CB2 to the CMPS if that were possible.This route would be easier on the resin than having to expose the resin to theharsh conditions under which a B-H is extracted from the carborane cage.Steric hindrance and the fact that each cage on CB2 itself is a dianion neededto be taken into.consideration. Since oarborane had previously been shownto react with CMPS 7, this reaction was optimized before trying to graft thecarbollides. This reaction can be followed using IR spectroscopy bymonitoring the disappearance of the CH2-CI stretch, ca. 1265 cm "1, and thegrowth of the strong B-H absorbance ca. 2580 cm -1 as seen in Fig. 2. Notonly is the B-H absorbance dependent on the type of cage, it can been seento shift 5 - 10 cm -1 upon grafting. The second cage in the series to beattached was the lithium carbollide. Somewhat less sterically hindered thanCB2 this too could be readily attached to CMPS. Being an anionic speciesapparently did not prevent the formation of the carbanion. Surprisingly theCB2 reaction also proceeded smoothly.

..........carborano 40.. I ..........carborano

/

-'--'- grafted carborane•--- graftedcarborane ..... CMPS...... CMPS ,....

, ...- ., .,.,...../'.-30- "" .

if ' ., ,

! q" ....,:,:.,.=,,,--,i ii i_, i_ fl; '11II ,

'J _' i' : : _! LI I

_. _. i' I !, :llll

• I I _ IIX

I i X o II i IIt I oli , }liilii,:ii i ii ii I "111

i I| I i ii i ii | i,, ,,,, :,'v

"....ii _%j li I i Ii

I | Ii ii

,, ,, I:I I _ Io

|_1 i i t 14to tt

0' ' ' I '' '' I ' ' O- l'',,n',,'l,,,,

3000 2500 2000 1500.1 .1

Wavenumber(cm ) Wavenumber(cm )

Fig. 2 FTIR spectra of carborane and the st_trting CMPS resin along withthe grafted carborane resin.

i Another consideration was whether or not the extent of swelling effected the-_ reaction rate and whether the carborane was reacting uniformly throughoutiI the resin. THF and toluene were chosen as swelling solvents and

cyclohexane as the non-swelling solvent. Samples were taken off viasyringe and quenched with methanol. They were then washed several timeswith methanol to insure the removal of any unreacted carborane. Fig. 3shows the rate of reaction as a function of the normalized intensity of theB-H stretch. Values of the absorbance were normalized against a C=Caromatic stretch @ 1600 cm -1. There is a corresponding decrease in theabsorbance of the CH2-C1 stretch. The reaction in THF goes to completion

I m , _1

-' in under 15 minutes whereas it takes over 4 hours in toluene. After 72 hours

t in cyclohexane the reaction had considerably slowed down at a conversion ofapproximately 60%. This is due to better solvation of both the n-buLl andcarborane carbanion ion pairs in THF. This coupled with the inability of thereactants to swell into the pores of the resin the cyclohexane was the leasteffective solvent.

I0.6

THF

0.5 "-'-'" "--'-'-°------ °-- °--'-'-'-'-'-'-'-'=_"*--"_"--'-_

"_ 0.4

0.3

! _ 0.2

"_' 0.1

O _I -- ! I I I I I I II II I I

eq _ cq _ _-

Time (hours)

Fig. 3 Reaction rate of CB2 as a function of the normalized intensity of theB-H absorbance.

13C and llB solids NMR has been used to confirm the presence of carboraneand CB2 on both the PS and PBI resins. Unfortunately quadripolarrelaxations of llB leads to a significant amount of broadening of the peaks.Fortunately carborane and CB2 are the only sources of boron in the system.

Conclusions

CB2 has been successfully covalently bonded to both PS and PBI resins.THF was found to be the most efficient solvent for the grafting reaction.Further analysis is currently being performed in order to quantify the extentof these reactions. Separation coefficients are also being determined forthese resins in order to see whether or not these materials perform as well asthe non-grafted CB2.

Acknowledgments

Funding was provided by the DOE. We would also like to thank P.Hurlburt, R. Miller, T. Foreman, K. Abney, and S. Kinkead of CST forproviding all the carborane derivatives for this work.

1. U.S. Dept. of Energy, " Department of Energy Plan for Recovery andUtilization of Nuclear Byproducts from Defense Wastes", DOE/DP-0013,Vol.2, August 1983.2. W. Schulz and L. Bray, Sep_ Sci. Tech, 22, 191, 1987.3. M. Hawthorne and T. Andrews, Chem. Commun., 443, 1965.4. J. Rais, P. Selucky, and M. Kyrs, J. Inorg. Nucl. Chem., 38, 1376,1976.

o 0.5 [ '_'-'. ..-----"----"----" • '---"-e-'--'-_

/_" toluene"_ 0.4 l_ 0.3

_ 0.1

,, I t ...... I , I I , i ..... 1 I I

Time (hours)

Fig. 3 Reaction rate of CB2 as a function of the non'nalized intensity of theB-H absorbance.

13C and 11B solids NMR has been used to confirm the presence of carboraneand CB2 on both the PS and PBI resins. Unfortunately quadripolarrelaxations of 11B leads to a significant amount of broadening of the peaks.Fortunately carborane and CB2 are the only sources of boron in the system.

Conclusions

CB2 has been successfully covalently bonded to both PS and PBI resins.THF was found to be the most efficient solvent for the grafting reaction.Further analysis is currently being performed in order to quantify the extentof these reactions. Separation coefficients are also being determined forthese resins in order to see whether or not these materials perform as well asthe non-grafted CB2.

Acknowledgments

Funding was provided by the DOE. We would also like to thank P.Hurlburt, R. Miller, T. Foreman, K. Abney, and S. Kinkead of CST forproviding all the carborane derivatives for this work.

!. U.S. Dept. of Energy, " Department of Energy Plan for Recovery andUtilization of Nuclear Byproducts from Defense Wastes", DOE/DP-00a 3,Vol.2, August 1983.2. W. Schulz and L. Bray, Sep. Sci. Tech, 22, 191, 1987.3. M. Hawthorne and T. Andrews, _hem. Comm.un., 443, 1965.4. J. Rais, P. Selucky, and M. Kyrs, J. Inorg. Nucl. Chem., 38, 1376,1976.5. V. Scasnar and V. Koprda, Radiochem. Radi.o.anal. Letters, 34, 23,1978.6. J. Plesek, K. Base, F. Mares, F. Hanousek, B. Stbir; andS. Hermanek,.CQllect.Czech..Chem., (Sommun,, 49, 2776, 1984.7. E.S. Chandrasekaran; D.A. Thompson; and R.W. Rudolph, Ioorg.Chem., 17, 760, 1978.8. M. Chanda, K.F. O'Driscoll, and G.L. Rempel, Reactive Polymers, 9,277, 1988.

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