Cation-exchange behaviour of barium on dowex 50W-X8 separation from mixtures

ANALYTICACHIMICAACTA

C A T I O N - E X C H A N G E B E H A V I O U R O F B A R I U M ON D O W E X

441

50W-X8

S E P A R A T I O N FROM M I X T U R E S SHRIPAD M. KHOPKAR* ANDANIL K. DE Department o[ Chemistry, Jadavpur University, Calcutta (India)

(Received May 27th, 196o)

As one of the major constituents of fission products, barium has attracted considerable attention in recent years. Several ion-exchange methods have been applied to barium in this laboratory 1-3. Ion-exchange separations of barium from various elements, e.g. lead, strontium, radium and lanthanum, have been effected by different workers 4-1o. MINAMIAND ISHIMORI4 explored the possibility of separating barium from lead on a cation-exchanger by first eluting the adsorbed lead with ammonium acetate at pH 6.0 and then barium with lO% ammonium chloride. The difference in the stability of the anionic complexes of barium and lead with ethylenediaminetetraacetic acid at pH 4"5 and lO.5 respectively has been utilised for their separation 5; lead (pH 4"5) passed out of bed and the adsorbed barium was eluted with ethylenediaminetetraacetic acid (disodium salt) at pH 10.5. The anion-exchange separation 6 of lead from barium has been effected by adsorbing the anionic lead chloride complex on an anionite while barium passed through. The separation of barium from strontium has been done by govY AND DUYCKAERTST;the metals were eluted selectively with EDTA at varying pH. A direct method has been devisedS, 9 for the separation of barium from radium using 0.5 M ammonium citrate solution adjusted to pI~ 7.5-8.o. Selective elution with 5 % citric acid at p i ca. 4.0 permits the separation of lanthanum from barium 10. However, systematic cation-exchange studies of barium have not been reported so far. The objective of this investigation was to carry out exploratory studies on the cation-exchange behaviour of barium on Dowex 5oW-X8 (hydrogen form). In the present paper nitric acid, hydrochloric acid, ammonium chloride, sodium nitrate, sodium chloride, ammonium acetate, citric acid, tartaric acid and E D T A have been studied as the eluting agents. Barium has been separated from uranium(VI), copper(II), mercury(II), caesium, zinc, cadmium, silver, cerium(IV), zirconium, thorium, iron(III) and bismuth(III). EXPERIMENTAL Apparatus

Ion-exchange column and Cambridge pH indicator. The ion-exchange column was similar to that described previously 1-3. A resin bed 1.4 X 2o em was used. Reagents

Barium nitrate solution (5 mg Ba/ml). 4,6115 g of barium nitrate (E. Merck) was dissolved in 5o0 ml of distilled water. The solution was standardised by the chromate method 11. Dowex * Research Fellow, Council of Scientific and Industrial Research, India. Anal. Chim. Acta, 23 (196o) 441-445

44:2

S. M. KHOPKAR, A. K. DE

5oW-X8 (Dow Chemical Co., Midland, Mich. U.S.A.), 5O-lOO mesh (hydrogen form) cationexchange resin. The resin was treated as before~. Chemicals used were all of reagent grade, unless otherwise mentioned. RESULTS AND DISCUSSION

Ion-exchange studies An aliquot of barium nitrate solution containing 29.1 mg of barium was passed through the column at a rate of 2 ml per minute. The resin was washed with 50 ml of water and barium eluted with 200 ml of the different eluants. I n each case the eluate was collected in 5o-ml fractions. In case of mineral acid eluants each fraction was evaporated to dryness; the resulting mass was taken up with IO ml of water and barium was estimated iodometrically zl. With salt eluants barium was directly precipitated from the effluent fractions as barium chromate and determined iodometrically. The elution constant (E) for each eluting agent was calculated as before 1 and an additional correction 3 of 7 ml was made in order to allow for the volume of the solution from the b o t t o m of the resin bed to the tip of the delivery tube. F r o m the values of elution constants the bed distribution coefficient (D) (barium per ml bed/barium per ml solution) was c o m p u t e d b y using the relationship 12, la: I E

Effluent volume to peak - - free column volume Bed volume

The results are shown in Table I. The elution behaviour with respect to nitric acid, hydrochloric acid and sodium nitrate, are illustrated as histograms in Fig. I ; elution

c

A ~80 ill > O O

3M

- 4M 9

y_M.

I.SM

240

K, 1[ al

b VOLUME

t00

OF EF FLUENT, IF(l[

Fig. I. Elution of barium on Dowex 5oW-X8. A-HNO3; B-HC1; C-NaNO~. curves are drawn through the midpoints on the histograms. With 200 ml of nitric acid (2-4M), hydrochloric acid (3-4 M), sodium nitrate (2-3 M), a m m o n i u m chloride (4 M), sodium chloride (4 M) or a m m o n i u m acetate (4 M) as eluant barium can be recovered quantitatively. Where the elution peak was observed in some fraction other t h a n the first, t h a t particular fraction was further collected as two 25-ml portions to trace the exact position of the peak (e.g. with mineral acids as eluants). W h e n the peak was observed in the first fraction (50 ml), it invariably appeared in the second 25-ml fraction of this portion since the first 17.37 ml of the effluent was due to the free column volume along with extra liquid in the columna. The eiution constants and the bed distribution coefficients give a measure of the relative efficiency of various eluting agents (Table I). The eluting agents can be arranged in order of increasing

Anal. Chim. Acta, 23 (196o) 441-445

C A T I O N - E X C H A N G E OF B A ON D O W E X 5 o W - X 8 TABLE

443

I

BEHAVIOUR OF BARIUM TOWARDS VARIOUS ELUTING AGENTS B a r i u m = 29.1 rag. W e i g h t of o v e n d r i e d r e s i n =

No.

I

2

3

4

5

6 7a

Barium recovery % (5o-ml fraction of effluent) I II III IV

Eluting agent

HNOs, HNO3, HNO3, HNO3, HNO3,

I M 1.5 M 2 M 3 M 4 3/1

... 3"7 6o.1 62. 4 22.6

2. 5 10.8 32.9 71.6

I7"8 25. 7 4.2 4.5

56.; 3.7 1.4 2.5

16.3236 g

Total barium recovery %

Elution constant, E

Bed distribution coefficient D = I / E

4.6 8o.1 10~ 1~176 IOI.2

-o.1686 0.3727 0'5343 0.9439

__ 5.93 ~ 2"683 1.872 1.o6o

HC1, 2 M HC1, 3 M HC1, 4 M

3.1 4.0

. . . . . . . . . 13. 4 21.2 61.9 15. 9 65.8 15. 5

12. 3 99.6 lOl.2

-o.1954 o.2861

__ 5.119 3.495

NH4C1, 2 M NH4C1, 3 M NH4C1, 4 M

1.9 1.6

. . . . . . . . . 2.2 35.2 62.9 3.9 68.3 22.2

9.4 lO2.2 96.0

-o.1686 o.2322

-5.93 o 4.306

NaNO~, I M NaNO3, 2 M NaNO~, 3 M

. . . . . . . . . 4.3 50.3 39 .8 74.3 17-2 5 .6

IO. 5 96.2 98"7

--

__

1.8 1.6

0.2322 0"3727

4.3o6 2"683

NaC1, 2 M l~aC1, 3 M NaC1, 4 M

2. 7 2. 4

. . . . . . . . . 3 .6 17-1 45.5 4 .2 44.4 42.9

10. 7 68.9 93.9

-o.1686 O.2322

__ 5.93 ~ 4.396

CHaCOONH4, 2 M CHsCOONH4, 4 M

1. 3

. . . . . . . . . 78.7 21. 5 1.6

24.1 IO3.I

-0.3727

__ 2.683

Citric acid 5 % pH

=

39.2

5.0

8a

Tartaric acid 5 % p H = 6.8

9

EDTA, o.oi M p H = 9.0

9.1 IO.I

a E f f l u e n t c o l l e c t e d u p t o 300 m l .

efficiency as: Tartaric acid < E D T A < citric acid < a m m o n i u m acetate < sodium chloride < ammonium chloride < hydrochloric acid < sodium nitrate < nitric acid. For routine work, however, hydrochloric acid (3-4 M) is appropriate owing to its ease of volatility in the assaying step. Ammonium chloride (3-4 M) m a y be used with the advantage that no evaporation is required and barium m a y be directly estimated.

Ion-exchange separations These separations are feasible because of the difference in the exchange potential of a number of cations with respect to the resin. The cations m a y be arranged 14 qualitatively in order of decreasing selectivity of the Dowex 5oW: Ba+2

>

Ag+ >

Sr+2 >

TI+ >

Ca+2 >

Cs + >

Mg+2 >

Rb + >

Be+2

N H 4 + ~> K + ~

1Na + ~

H+ ~

Li+

I M hydrochloric acid is an efficient eluant for cations such as uranium(VI), copper(I!), mercury(II), caesium, zinc and cadmium but it is a poor eluant for barium. Hence it is possible to remove first the aforesaid cations with I M hydrochloric acid A n a l . C h i m . Acta, 23 (196o) 4 4 1 - 4 4 5

444

s . M . KHOPKAR, A. K. DE

and subsequently barium with 4 M hydrochloric acid. The effluent lot containing barium was evaporated to dryness and estimated as before. Attempts to separate aluminium were not successful since part of it was eluted along with barium giving high results. In case of the separation of silver from barium, nitric acid was substituted for hydrochloric acid as an eluant. Barium does not form any complex 15 with citric acid at pH ca. 3.O or with EDTA (disodium salt) at pH 2.0-3.0. Hence cerium(IV), zirconium(IV), iron(II), bismuth(III) and thorium complexes under these conditions can be easily separated from barium by passage through the cation exchange column. Cerium(IV) and zirconium(IV) were separated by complexing with 5 % citric acid at pH 2. 7 whereas the others were complexed with EDTA at pH 2.0-2.2. In both cases 4 M hydrochloric acid was the eluant; the effluent lot was evaporated completely to dryness and excess of citric acid or EDTA was destroyed by nitric-perchloric acid treatment before the estimation of barium. TABLE II ION-EXCHANGE SEPARATIONS OF BARIUM B a = 14.50 mg No.

I 2 3 4 5

F o r e i g n ion

Added, mg

U(VI)

69.7 30.0 30.0 28.8 30.o

14.8o 14.25 14.43 14.48 14.62

l O l .7 97.9 99.3 99-4 lOO. 5

14.39 16.28 14.56 15.11 14.21

98.9 111.8 IOO.O lO3.8 97.7 99.1 99.4 98. 5

Cu(II) Hg(II) Cs Zn

Barium found, mg Total barium recovery %

6 7 8 9 lO

Cd A1 Ag

Zr(IV)

29.0 29.0 14.o 29.0 20.9

II

Th

30.0

14.42

12

Bi(III) Fe(III)

29 .o

14.46

14. 5

14.33

13

Ce(IV)

Separations/rom lead

The ion-exchange characteristics of lead on a Dowex-5o column have already been studiedZ. It is worthwhile to compare the separation factors for barium/lead on the basis of their bed distribution coefficients under comparable conditions. The common eluting agents, nitric acid (2-4 M), sodium nitrate (2 M) and ammonium acetate TABLE III SEPARATION FACTORS FOR BARIUM--LEAD BED DISTRIBUTION COEFFICIENT ( D ) Eluant

HNOs, 2 M HNOa, 3 M HNO3, 4 M NaNO3, 2 M CHaCOOb~Ha, I M CHsCOONH4, 4 M

Bed distribution coefficient (D) Barium Lead

2.683 1.872 1.o6o 4.306

Separation factor = DB~/Dpb

2.564 1.443 1.443 3.684

i .o47 1.297 0.7345 1.169

V e r y large

2.564

V e r y large

2.683

1.443

1.86o

J

A n a l . C h i m . A c l a , 23 (196o) 441-445

CATION-EXCHANGE OF B A ON DOWEX 5 0 W - X 8

445

(4 M) were used for these calculations. It follows from Table n I that the best separation is obtained with I M ammonium acetate since the separation factor is very large. This has been actually confirmed a. The separations of barium from other important fission product elements such as cerium, zirconium, caesium, zinc, cadmium and silver and also from uranium and thorium attach unique significance to the technique of ion-exchange chromatography since such procedures are valuable in nuclear energy programmes. Again separations from common metals like copper, bismuth and iron are also of importance. The overall operations in this method take 3 - 4 h. The results are reproducible to :~ 30/0. ACKNOWLEDGEMENTS The authors

gratefully

acknowledge

Co., Midland, Mich., U.S.A. They

the gift sample of the resin from Dow Chemical

also thank

Prof. A. K. MAJUMDAR for laboratory

facilities. SUMMARY T h e c a t i o n - e x c h a n g e b e h a v i o u r of m i l l i g r a m a m o u n t s of b a r i u m on D o w e x 5 o W - X 8 h a s b e e n studied. Nitric acid, hydrochloric acid, a m m o n i u m chloride, s o d i u m n i t r a t e , s o d i u m chloride, a m m o n i u m acetate, citric acid, t a r t a r i c acid a n d E D T A were t e s t e d as e l u a n t s . 2 o o - 3 o o m l of 3 M nitric acid, h y d r o c h l o r i c acid, s o d i u m n i t r a t e or a m m o n i u m chloride elute 3 ~ m g of b a r i u m from a 1.4 • 2o c m bed. T h e relative efficiency of t h e e l u a n t s is d i s c u s s e d in t e r m s of t h e i r elution c o n s t a n t s a n d b e d - d i s t r i b u t i o n coefficients. B a r i u m c a n be s e p a r a t e d f r o m a wide v a r i e t y of m e t a l s .

R~SUM~ L e s a u t e u r s o n t effectu6 u n e 6 t u d e d u c o m p o r t e m e n t d u b a r y u m s u r u n e colonne 6 c h a n g e u r de cations. Cet @l@ment a ainsi p u 6tre s4par@ de p r o d u i t s de fission i m p o r t a n t s tels q u e Cs, Zn, Cd, Ag, Ce(IV) et Zr, de mGme q u e des 61dments s u i v a n t s : U(VI), T h , Bi, Cu, H g ( I I ) et Fe(III). ZUSAMMENFASSUNG B e s c h r e i b u n g einer U n t e r s u c h u n g fiber d a s V e r h a l t e n y o n B a r i u m gegenfiber e i n e m K a t i o n e n A u s t a u s c h e r h a r z m i t A n g a b e n fiber E l u i e r u n g s m i t t e l . B a r i u m k a n n n a c h dieser M e t h o d e g e t r e n n t w e r d e n y o n : Cs, Zn, Cd, Ag, Ce(IV), Zr, U(VI), T h , Bi, Cu, Hg(II) u n d Fe(III). REFERENCES 1 S. M. KHOPKAR AND A. K. DE, Anal. Chim. Acla, 22 (196o) 153. 2 S. M. KHOPKAR AND A. K. DE, Anal. Chim. Acta, 23 (196o) 147. S. M. KI-IOI~KARAND A. K. DE, Talanta ( c o m m u n i c a t e d ) . 4 E. MINAVlI AND T. ISHIMORI, J. Chem. Soc. Japan, Pure Chem. Sect., 74 (1953) 378; C. A., 47 (1953) lO4OOC. 5 j. j. TAKETATSU, J. Chem. Soc. Japan, Pure Chem. Sect., 76 (1955) 756; C. A., 5 ~ (1956) i365oa. 6 Y u . V. MORACHEVSKII, M. N. ZVEREVA AND R. SH. RABINOVICH, Zavodskaya Lab. 22 (1956) 541 ; Anal. Abstr., 3 (1956) 3593. 7 R. BovY AND G. DUYCKAERTS, Anal. Chim. Acta, I I (1954) 134. s W. H. POWER, H. W. KIRBY, W. C. McCLUGGAGE, G. D. NELSON AND J. H. PAYNE JR., Anal. Chem., 31 (1959) lO77. 9 E. R. TOMPKINS, J. Am. Chem. Soc., 7 ~ (1948) 3520. lo p. KRUGER AND C. D. CORYELL, J. Chem. Educ., 32 (1955) 280. 11 A. I. VOGEL,A Text Book o[ Quantitative Inorganic Analysis, L o n g m a n s , G r e e n & Co., L o n d o n , 1955, pp. 347, 48~ 12 K. A. KRAUS AND G. E. MOORE, J. Am. Chem. Soc., 73 (1951) 9. 13 C. Y. MANN, Anal. Chem., 32 (196o) 67. la Dowex Ion Exchange, D o w Chemical Co., M i d l a n d Mich. 1958, p. 915 E. R. TOMPKINS, J. X. KHYM AND W. E. COHN, J. Am. Chem. Soc., 69 (1947) 2769.

Anal. Chim. Acta, 23 (196o) 441-445