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Anion-exchange behaviour of uranium and other elements in the presence of aliphatic di- and tricarboxylic acids
Talanta 1964, Vol. 11. pp. 523 to 530.
Pergamon Press Ltd.
Printed in Northern Ireland
ANION-EXCHANGE BEHAVIOUR OF URANIUM AND OTHER ELEMENTS IN THE PRESENCE OF ALIPHATIC DI- AND TRICARBOXYLIC ACIDS METHOD FOR THE SEPARATION OF URANIUM FROM THORIUM AND RARE EARTHS J. KORKLYCHand I. HAZAN Analytical Institute of University of Vienna, IX Wtihringerstrasse 38, Austria (Received 1 August 1963. Accepted 10 October 1963)
Summary-The exchange behaviour of uranium, thorium, the rare earths and some other elements towards the strongly basic anion exchanger Dowex 1 in aqueous and metbanolic systems containing dior tricarboxylic acids is described. Based on the measurement of the distribution coefficients in such media a method for the separation of uranium from thorium and the rare earths in an aqueous solution containing malonic acid has been developed. INTRODUCTION carried out by Zaki and Shakirl have shown that uranium can be separated from other elements on an anion exchanger by using buffered solutions of oxalic, succiuic or adipic acid. Uranium, thorium and zirconium, as well as other elements, form with these acids negatively charged complexes which are strongly retained by the exchange resin. 1-3 Several other authors have also reported on the adsorption behaviour of uranium and various other elements from solutions containing organic acids, such as acetick and ascorbic acid.7-g INVESTIGATIONS
Previous research work dealing with the anion-exchange behaviour of uranium and other elements in organic acid-organic solvent mixtureslO showed that in such media many separation possibilities for uranium could be uncovered. For this reason we have now investigated the behaviour of some elements in the presence of polyfunctional organic acids, especially the homologous dicarboxylic acids of the aliphatic series. EXPERIMENTAL Reagents Zon-exchange resin. The strongly basic anion exchanger Dowex 1, x 8 (NO-200 mesh, chloride
form) was used. For the equilibrium and separation experiments in the various media the wrresponding organic acid forms of this resin were employed. The preparation of these forms was performed according to the directions previously given for the monocarboxylic acid forms.10 Standard solutions of uranium and other elements. Hydrochloric or nitric acid solutions of the chlorides or nitrates of precisely known element content were employed. For each experiment an aliquot corresponding to the desired amount of the element to be investigated was evaporated to dryness on a water bath. To the residue thus obtained, first the solid organic acid and then the solvent was added. Organic acids and solvenf. The following reagent-grade acids were employed: oxalic, malonic, succinic, glutaric, d,l-tartaric and citric. The methanol employed was also of reagent-grade purity. Apparatus The column operations were carried out in columns of the same type and dimensions as described earlier.’ For the fluorimetric determination of uranium a Galvanek Morrison Mark V fluorimeter 523
524 and for the spectrophotometric photometer was employed.
J. KORKISCHand I. HAZAN determination
of the other elements a Beckman Model B spectro-
Quantitative determinution of elements investigated The determination of uranium was performed fluorimetrically,” and that of thorium and the rare earths spectrophotometrically by employing the azo dye Solochromate Fast Red.l**l* The other elements were determined quantitatively using photometric methods recommended by Sandell.14 Determination of distribution coeficients The distribution coefficients of all elements were determined in the same manner as has earlier been described for the equilibrium experiments in mineral acid-organic solvenP and organic acidorganic solvenP mixtures. Twenty ml of solvent, containing a certain amount of the acid and 5 mg of the element in question, were equilibrated with 1 g of the resin. The results of the experiments shown in Figs. 1 and 2 were obtained by using varying amounts of acid whereas those recorded in Fig. 3 and in Table I were always performed in the presence of 1 g of acid. Column operations All separation experiments on resin columns were performed by employing the following working procedure. Pretreatment of resin bed. In order to transform the chloride form of the resin into the malonate form the resin bed was treated with a lo”/, aaueous malonic acid solution which had been buffered to a pH of approximately 5 to 6 with aqueous ammonia. As soon as the effluent was free from chloride ions (which was usually the case after the passage of leas than 50 ml of this solution), the resin was washed with 50 ml of a solution (washing solution) containing 50 g of malonic acid/l,000 ml of distilled water. Adsorption of uranium. The sorption solution was prepared by dissolving the residue obtained by evaporation of certain amounts of the standard solutions of the elements in question, first by adding 5 g of malonic acid to the dry residue, followed by 100 ml of distilled water. This solution was passed through the column at a flow rate of 0.5475 ml/min. During this operation uranium was strongly adsorbed whereas the other elements, i.e., thorium, cerium and gadolinium, passed into the effluent. Washing process. In order to remove the last traces of the other elements the resin bed was washed with 50 ml of the washing solution. Elution. The uranium was eluted with 100 ml of 1M hydrochloric acid. Further treatment of eluate and efpuent. After evaporation of the eluate to dryness (water bath) the uranium was determined as previously described .I4 During this process as well as when evaporating the effluent, malonic acid was decarboxylated, whereby acetic acid was formed, so that very little organic matter was present in the residue. In the residues obtained after evaporation of the effluents, thorium and the rare earths were determined by previously described procedures.1g~18 The results of a series of such column separations are recorded in Table PI. RESULTS
Effect of acid concentration on distribution coeficients of uranium and thorium In Figs. 1 and 2 the results of the experiments performed in aqueous and methanolic solutions containing varying amounts of the organic acids are recorded. Although the adsorption of uranium from oxalic acid solutions is higher than from all mixtures containing other acids, it did not seem practical to use this acid for further investigations because its solubility in water is rather low; furthermore, it forms insoluble precipitates with thorium, the rare earths and other elements in aqueous as well as in methanolic media. In malonic acid mixtures, however, both these adverse effects are not observed so that this acid was employed for the separation of uranium, thorium and rare earths on ion-exchange columns. By comparing Fig. 1 with Fig. 2 it can clearly be seen that the difference existing between the adsorption of uranium in aqueous and methanolic solutions is rather large (especially at a higher acid concentration) in comparison with that of thorium, which shows in both solvents a practically identical adsorption behaviour. Besides,
Anion-exchange
behaviour of uranium and other elements
525
6
5
4
y” d s 3
2
!ULI(Th) a(T h) L.-A-. I
I
I
2
-t”=(Th)
3
4
5
Acid (g) t IO ml of water
FIG. L-Adsorption
of uranium and thorium from aqueous solutions containing di- and tricarboxylic acids: I-oxalic acid, IV-glutaric acid, II-malonic acid, V-tartaric acid, III-succinic acid, VI-citric acid.
its solubility in methanolic solutions is rather limited. That is why in Fig. 2 only two curves for thorium could be established. Several experiments in other solvents, e.g., ethanol, n-propanol, acetone, etc., with some of the acids have shown that the adsorption of uranium from tartaric and citric acid media did not deviate appreciably from the results obtained in methanolic solutions, whereas in the presence of the other acids a decrease of uranium adsorption with increasing chain length of the alcohols could be observed15 in the case of oxalic acid. Because of the low solubility of the acids, however, no systematic investigations as to the adsorption of uranium or other elements were conducted in solvents other than water and methanol. Effect of water-methanol concentration In Fig. 3 the variation of the distribution coefficients of uranium at different water to methanol ratios is shown. From the results it is seen that the Kd of uranium in the dicarboxylic acid-methanol-water mixtures does not vary as much with increasing percentage of methanol as in tartaric and citric acid media, where a sharp decline of the Kd occurs when increasing the methanol content of the mixtures from 80 to 100%. This is because the hydrophilic hydroxyl groups of these acids gradually lose their complex-forming tendencies by a decrease in the water content of the mixtures. In
J. KORKISCH and I. HAZAN
526
lI(Thli, a
(U).-.-*y-o 0 I Acid
FIG. 2.-Adsorption
2
I 3
lxLuJ) 4
(g) + IO ml of Methonol
of uranium and thorium from methanolic solutions containing di- and tricarboxylic acids: IV-glutamic acid, I-oxalic acid, V-tartaric acid, II-malonic acid, VI-citric acid, III-succinic acid, - - - - region of insolubility.
the case of the dicarboxylic acids without hydroxyl groups, however, the adsorption of uranium in 100% aqueous solutions of the acids is less than in 100% methanol solutions of the acids, so that in the presence of these acids an increase of the methanol concentration increases the uranium adsorption. Adsorption behaviour of other elements
In Table I the distribution coefficients of a series of other elements in aqueous and methanolic media containing malonic, succinic, glutaric, tartaric and citric acid are recorded. For comparison purposes the distribution coefficients of uranium and thorium in the various media have also been included in this table.
Anion-exchange
behaviour of uranium and other elements Methanol,
100
80
%
60
40
20
I
I
527
0
I
, --
I-
3-
,-
I-
I0
20
40
60 Water,
FIG. 3.-Effect
of water-methanol I-malonic II-succinic
80 %
concentration
acid, acid, V-citric
on uranium adsorption:
III-glutaric IV-tartaric acid.
acid, acid,
From the results it is seen that malonic acid in methanol is superior to the other di- and tricarboxylic acids in-so-far as it shows the greatest solubility and sufficient acid strength to keep most of the investigated elements in solution without forming precipitates or causing hydrolysis. In aqueous solutions, however, all of the acids can be employed for the adsorption of uranium with nearly equal effect, irrespective of their chemical constitution. For the purpose of separating uranium from thorium and other elements (with the exception of iron, which could easily be separated from uranium in a water-succinic acid medium), the use of malonic acid seemed to be advantageous because most of the elements, except for iron and yttrium, show rather low distribution coefficients in aqueous malonic acid solutions. 11
528
J. KORKWH
and I.HAZAN
TABLE L-DISTRIBUTIONCOEFFICIENTS OF VARIOUS ELEMENTS Solvent Element
uop Th4+ Las+ Ces+ Prs+ Nd*+ Sms+ Eua+ GdS* TbS+ Dy3+ Hoa’ ErSf Tms+ Yb8+ Lua+ Sea+ e+ Es+ SrB+ Zn%+ Cda+ Ata+ In*+ cua+ Pb2+ 33is+ Mn%+ Fea+ cog+ Nis+ uo,p+ The+ Ce*+ GdS’ cue+ Big+ Fes+ cog+ Ni2+ uop Pb2’ Bi*+ uo,*+ Thd+ Cea+ cua+ Bin+ Fe*+ Coa+ Ni”* uog+ Th’ +
Acid
Malonic acid Malonic acid Malonic acid MaIonic acid Malonic acid MaSonic acid Malonic acid Malonic acid Malonic acid Malonic acid MaIonic acid Malonic acid Malonic acid Malonic acid Malonic acid Malonic acid Malonic acid MaIonic acid Malonic acid Matonic acid Malonic acid Malonic acid Malonic acid Malonic acid Malonic acid MaIonic acid Malonic acid Malonic acid Malonic acid Malonic acid Malonic acid Succinic acid Succinic acid Succinic acid Succinic acid Succinic acid Succinic acid Succinic acid Succinic acid Succinic acid GIutaric acid Glutark acid Gtutaric acid Tar&c acid Tartaric acid Tartaric acid Tartaric acid Tartaric acid Tartaric acid Tartaric acid Tartaric acid Citric acid Citric acid
Water
Methanol
1,540 45 12 33 1.0 1-o 0.1 0.1 1.0
77,ooo 142
;:; O-1 1-O 1-O 1.0 1.0 100 1.0 0.5 10-o 1.0 1.0 I.0 1.0 6.3 O-1 33.5 1-o 324 0.1 3.2 2,400 84 X 40 7.0 65-O 1-o 0.1 66 9,500 O-1 107 1,000 147 40 7.0 507 160 0-f 17.2 5,900 200
:z 465 550 505 650 670
I,:% ;o 670 708 885
X
8-O X
10.0 170 16,6: 1,920 435 &O X X 0.1 120 6,ooO X X X X X X 0.1 66 340,000 X X 7-o X X X X X o-1 6.6 1.0 X
Anion-exchange
behaviour of uranium and other elements TABLEI
529
(Continued) Solvent
Acid
Element
Water Cea+ Gd*+ cue+
BP+ Fes+ co*+
Ni*+
Citric Citric Citric Citric Citric Citric Citric
acid acid acid acid tid acid acid
Methanol
11.5 815 48.5
X
2;3 0.1 1.0
X
X X X
0.1 1.0
x In these media completely or partially insoluble.
In methanolic solutions of this acid, on the other hand, the possibility of coadsorbing uranium together with thorium, the rare earths and other elements exists, so that malonic acid can be regarded as a more versatile complexing agent than the other acids, the element salts of which are also poorly soluble in methanol. Separation procedure Based on the results presented in Figs. 1 and 2 and in Table I a method of separating uranium from thorium, cerium and gadolinium (as representatives of the rare earth elements) in an aqueous medium was developed. The experimental steps involved in this ion-exchange procedure have been described above under Column operations. In Table II the results of these resin column separations are recorded. It is seen that all separations of uranium from the other elements were practically quantitative. For this reason and because the break-through capacity for uranium under these conditions (2g of resin in column 15 cm high and 0.5 cm diameter) was found to be TABLEIL-SEPARATION OF URANIUMFROMOTHER ELEMENTS
Uranium taken, .% 10,000
5,000 5,ooo 5,000 5wO 10,000 5,000 5,ooo 5,000 5,000 10,000 5wO 5,000 5,000 5,000
IN
AQUEOUS
MALONIC!
ACID
Element to be Uranium separated from recovered, uranium, pg w Th: 5,000 Th: 1,000 zi Th: Ce: Ce: Ce: Ce: Ce:
100 50 20 500 100 50 25 10
::i Gd: Gd: Gd:
500 100 50 25 10
9,950 4,915 4,937 4,950 5,010 9,980 4,978 4,967 2% 10:013 5,000 4,980 4,978 5,000
MIXTURES*
Other element recovered, rug 4,960 985 100 48 95.8 50 24 9.5 497 97 48 27 11
* Each result is the average of 3 separations performed under the same experimental conditions.
530
J. KORKISCH and I. HAZAN
60 mg of uranium, this procedure could be employed effectively for the removal of fission products like the rare earths, strontium, etc., from uranium. By this anion-exchange method not only the separation of these elements from uranium can be accomplished but also from a series of other elements (those having sufficiently low distribution coefficients, viz. <50). It is, therefore, of broad applicability, unlike the method described by Zaki and Shakirl which has only limited use for analytical purposes. Acknowledgements-This research was sponsored by the International Atomic Energy Agency and the United States Atomic Energy Commission under Contract No. 67/US (AT(30-l)-2623). The generous support from these agencies is gratefully acknowledged. Zusammenfassung-Es wurde das Ionenaustauschverhalten von Uran, Thorium, der seltenen Erden und einiger anderer Elemente gegeniiber dem stark basischen Anionenaustauscher Dowex 1 in w%&igen und methanolischen Systemen die Di- oder Tricarboxylsauren enthalten untersucht. Auf Grund von Messungen der Verteilungskoethzienten in derartigen Medien konnte eine Methode zur Trennung des Urans von Thorium und den seltenen Erden in malonsaurer wtiriger L&sung entwickelr werden. R&m&-On d&it l’echange de l’uranium, du thorium, des elements de terres rares et de quelques autres elements en presence de l’echangeur d’anions fortement basique Dowex 1 dans des systemes aqueux ou methanoliques contenant des acides di- ou tricarboxyliques. Devel, oppement d’une methode basee sur la mesure des coefficients de distribution dans de tels milieux, pour s&parer l’uranium du thorium et des elements des terres rares en solution aqueuse contenant de I’acide malonique. REFERENCES 1 M. R. Zaki and K. Shakir, Z. Analyt. Chem., 1962,185,423. 2 Idem, ibid., 1961, 180, 188. * H. Khalifa and M. R. Zaki, ibid., 1957, 158, 1. 4 F. Hecht, J. Korkisch, R. Patzak and A. Thiard, Mikrochim. Acta, 1956, 1283. 5 J. Korkisch, A. Thiard and F. Hecht, ibid., 1956, 1422. BJ. P. Riley and H. P. Williams, ibid., 1959, 825. ’ J. Korkisch, A. Farag and F. Hecbt, ibid., 1958,415. 8 J. Korkisch, P. Antal and F. Hecht, ibid., 1959, 693. s J. Korkisch and F. Tera, Analyt. Chem., 1961, 33, 1265. lo J. Korkisch, Report to International Atomic Energy Agency and U.S. Atomic Energy Commission under contract No 67/US(AT(3&1)-2623). September 1963. I1 T. Schiinfeld, M. El Garhy, C. Friedmann and J. Veselsky, Mikrochim. Acta, 1960, 883. I2 J. Korkisch and G. E. Janauer, Analyt. Chem., 1961,33, 1930. I3 J. Korkisch, I. Hazan and G. Arrhenius, Talanta, 1963, 10, 865. I4 E. B. Sandell, Calorimetric Determination of Traces of Metals. Interscience Publ. Inc., New York, 3rd Ed., 1959. I6 J. Korkisch and G. E. Janauer, Talanta, 1962, 9, 957.
Pergamon Press Ltd.
Printed in Northern Ireland
ANION-EXCHANGE BEHAVIOUR OF URANIUM AND OTHER ELEMENTS IN THE PRESENCE OF ALIPHATIC DI- AND TRICARBOXYLIC ACIDS METHOD FOR THE SEPARATION OF URANIUM FROM THORIUM AND RARE EARTHS J. KORKLYCHand I. HAZAN Analytical Institute of University of Vienna, IX Wtihringerstrasse 38, Austria (Received 1 August 1963. Accepted 10 October 1963)
Summary-The exchange behaviour of uranium, thorium, the rare earths and some other elements towards the strongly basic anion exchanger Dowex 1 in aqueous and metbanolic systems containing dior tricarboxylic acids is described. Based on the measurement of the distribution coefficients in such media a method for the separation of uranium from thorium and the rare earths in an aqueous solution containing malonic acid has been developed. INTRODUCTION carried out by Zaki and Shakirl have shown that uranium can be separated from other elements on an anion exchanger by using buffered solutions of oxalic, succiuic or adipic acid. Uranium, thorium and zirconium, as well as other elements, form with these acids negatively charged complexes which are strongly retained by the exchange resin. 1-3 Several other authors have also reported on the adsorption behaviour of uranium and various other elements from solutions containing organic acids, such as acetick and ascorbic acid.7-g INVESTIGATIONS
Previous research work dealing with the anion-exchange behaviour of uranium and other elements in organic acid-organic solvent mixtureslO showed that in such media many separation possibilities for uranium could be uncovered. For this reason we have now investigated the behaviour of some elements in the presence of polyfunctional organic acids, especially the homologous dicarboxylic acids of the aliphatic series. EXPERIMENTAL Reagents Zon-exchange resin. The strongly basic anion exchanger Dowex 1, x 8 (NO-200 mesh, chloride
form) was used. For the equilibrium and separation experiments in the various media the wrresponding organic acid forms of this resin were employed. The preparation of these forms was performed according to the directions previously given for the monocarboxylic acid forms.10 Standard solutions of uranium and other elements. Hydrochloric or nitric acid solutions of the chlorides or nitrates of precisely known element content were employed. For each experiment an aliquot corresponding to the desired amount of the element to be investigated was evaporated to dryness on a water bath. To the residue thus obtained, first the solid organic acid and then the solvent was added. Organic acids and solvenf. The following reagent-grade acids were employed: oxalic, malonic, succinic, glutaric, d,l-tartaric and citric. The methanol employed was also of reagent-grade purity. Apparatus The column operations were carried out in columns of the same type and dimensions as described earlier.’ For the fluorimetric determination of uranium a Galvanek Morrison Mark V fluorimeter 523
524 and for the spectrophotometric photometer was employed.
J. KORKISCHand I. HAZAN determination
of the other elements a Beckman Model B spectro-
Quantitative determinution of elements investigated The determination of uranium was performed fluorimetrically,” and that of thorium and the rare earths spectrophotometrically by employing the azo dye Solochromate Fast Red.l**l* The other elements were determined quantitatively using photometric methods recommended by Sandell.14 Determination of distribution coeficients The distribution coefficients of all elements were determined in the same manner as has earlier been described for the equilibrium experiments in mineral acid-organic solvenP and organic acidorganic solvenP mixtures. Twenty ml of solvent, containing a certain amount of the acid and 5 mg of the element in question, were equilibrated with 1 g of the resin. The results of the experiments shown in Figs. 1 and 2 were obtained by using varying amounts of acid whereas those recorded in Fig. 3 and in Table I were always performed in the presence of 1 g of acid. Column operations All separation experiments on resin columns were performed by employing the following working procedure. Pretreatment of resin bed. In order to transform the chloride form of the resin into the malonate form the resin bed was treated with a lo”/, aaueous malonic acid solution which had been buffered to a pH of approximately 5 to 6 with aqueous ammonia. As soon as the effluent was free from chloride ions (which was usually the case after the passage of leas than 50 ml of this solution), the resin was washed with 50 ml of a solution (washing solution) containing 50 g of malonic acid/l,000 ml of distilled water. Adsorption of uranium. The sorption solution was prepared by dissolving the residue obtained by evaporation of certain amounts of the standard solutions of the elements in question, first by adding 5 g of malonic acid to the dry residue, followed by 100 ml of distilled water. This solution was passed through the column at a flow rate of 0.5475 ml/min. During this operation uranium was strongly adsorbed whereas the other elements, i.e., thorium, cerium and gadolinium, passed into the effluent. Washing process. In order to remove the last traces of the other elements the resin bed was washed with 50 ml of the washing solution. Elution. The uranium was eluted with 100 ml of 1M hydrochloric acid. Further treatment of eluate and efpuent. After evaporation of the eluate to dryness (water bath) the uranium was determined as previously described .I4 During this process as well as when evaporating the effluent, malonic acid was decarboxylated, whereby acetic acid was formed, so that very little organic matter was present in the residue. In the residues obtained after evaporation of the effluents, thorium and the rare earths were determined by previously described procedures.1g~18 The results of a series of such column separations are recorded in Table PI. RESULTS
Effect of acid concentration on distribution coeficients of uranium and thorium In Figs. 1 and 2 the results of the experiments performed in aqueous and methanolic solutions containing varying amounts of the organic acids are recorded. Although the adsorption of uranium from oxalic acid solutions is higher than from all mixtures containing other acids, it did not seem practical to use this acid for further investigations because its solubility in water is rather low; furthermore, it forms insoluble precipitates with thorium, the rare earths and other elements in aqueous as well as in methanolic media. In malonic acid mixtures, however, both these adverse effects are not observed so that this acid was employed for the separation of uranium, thorium and rare earths on ion-exchange columns. By comparing Fig. 1 with Fig. 2 it can clearly be seen that the difference existing between the adsorption of uranium in aqueous and methanolic solutions is rather large (especially at a higher acid concentration) in comparison with that of thorium, which shows in both solvents a practically identical adsorption behaviour. Besides,
Anion-exchange
behaviour of uranium and other elements
525
6
5
4
y” d s 3
2
!ULI(Th) a(T h) L.-A-. I
I
I
2
-t”=(Th)
3
4
5
Acid (g) t IO ml of water
FIG. L-Adsorption
of uranium and thorium from aqueous solutions containing di- and tricarboxylic acids: I-oxalic acid, IV-glutaric acid, II-malonic acid, V-tartaric acid, III-succinic acid, VI-citric acid.
its solubility in methanolic solutions is rather limited. That is why in Fig. 2 only two curves for thorium could be established. Several experiments in other solvents, e.g., ethanol, n-propanol, acetone, etc., with some of the acids have shown that the adsorption of uranium from tartaric and citric acid media did not deviate appreciably from the results obtained in methanolic solutions, whereas in the presence of the other acids a decrease of uranium adsorption with increasing chain length of the alcohols could be observed15 in the case of oxalic acid. Because of the low solubility of the acids, however, no systematic investigations as to the adsorption of uranium or other elements were conducted in solvents other than water and methanol. Effect of water-methanol concentration In Fig. 3 the variation of the distribution coefficients of uranium at different water to methanol ratios is shown. From the results it is seen that the Kd of uranium in the dicarboxylic acid-methanol-water mixtures does not vary as much with increasing percentage of methanol as in tartaric and citric acid media, where a sharp decline of the Kd occurs when increasing the methanol content of the mixtures from 80 to 100%. This is because the hydrophilic hydroxyl groups of these acids gradually lose their complex-forming tendencies by a decrease in the water content of the mixtures. In
J. KORKISCH and I. HAZAN
526
lI(Thli, a
(U).-.-*y-o 0 I Acid
FIG. 2.-Adsorption
2
I 3
lxLuJ) 4
(g) + IO ml of Methonol
of uranium and thorium from methanolic solutions containing di- and tricarboxylic acids: IV-glutamic acid, I-oxalic acid, V-tartaric acid, II-malonic acid, VI-citric acid, III-succinic acid, - - - - region of insolubility.
the case of the dicarboxylic acids without hydroxyl groups, however, the adsorption of uranium in 100% aqueous solutions of the acids is less than in 100% methanol solutions of the acids, so that in the presence of these acids an increase of the methanol concentration increases the uranium adsorption. Adsorption behaviour of other elements
In Table I the distribution coefficients of a series of other elements in aqueous and methanolic media containing malonic, succinic, glutaric, tartaric and citric acid are recorded. For comparison purposes the distribution coefficients of uranium and thorium in the various media have also been included in this table.
Anion-exchange
behaviour of uranium and other elements Methanol,
100
80
%
60
40
20
I
I
527
0
I
, --
I-
3-
,-
I-
I0
20
40
60 Water,
FIG. 3.-Effect
of water-methanol I-malonic II-succinic
80 %
concentration
acid, acid, V-citric
on uranium adsorption:
III-glutaric IV-tartaric acid.
acid, acid,
From the results it is seen that malonic acid in methanol is superior to the other di- and tricarboxylic acids in-so-far as it shows the greatest solubility and sufficient acid strength to keep most of the investigated elements in solution without forming precipitates or causing hydrolysis. In aqueous solutions, however, all of the acids can be employed for the adsorption of uranium with nearly equal effect, irrespective of their chemical constitution. For the purpose of separating uranium from thorium and other elements (with the exception of iron, which could easily be separated from uranium in a water-succinic acid medium), the use of malonic acid seemed to be advantageous because most of the elements, except for iron and yttrium, show rather low distribution coefficients in aqueous malonic acid solutions. 11
528
J. KORKWH
and I.HAZAN
TABLE L-DISTRIBUTIONCOEFFICIENTS OF VARIOUS ELEMENTS Solvent Element
uop Th4+ Las+ Ces+ Prs+ Nd*+ Sms+ Eua+ GdS* TbS+ Dy3+ Hoa’ ErSf Tms+ Yb8+ Lua+ Sea+ e+ Es+ SrB+ Zn%+ Cda+ Ata+ In*+ cua+ Pb2+ 33is+ Mn%+ Fea+ cog+ Nis+ uo,p+ The+ Ce*+ GdS’ cue+ Big+ Fes+ cog+ Ni2+ uop Pb2’ Bi*+ uo,*+ Thd+ Cea+ cua+ Bin+ Fe*+ Coa+ Ni”* uog+ Th’ +
Acid
Malonic acid Malonic acid Malonic acid MaIonic acid Malonic acid MaSonic acid Malonic acid Malonic acid Malonic acid Malonic acid MaIonic acid Malonic acid Malonic acid Malonic acid Malonic acid Malonic acid Malonic acid MaIonic acid Malonic acid Matonic acid Malonic acid Malonic acid Malonic acid Malonic acid Malonic acid MaIonic acid Malonic acid Malonic acid Malonic acid Malonic acid Malonic acid Succinic acid Succinic acid Succinic acid Succinic acid Succinic acid Succinic acid Succinic acid Succinic acid Succinic acid GIutaric acid Glutark acid Gtutaric acid Tar&c acid Tartaric acid Tartaric acid Tartaric acid Tartaric acid Tartaric acid Tartaric acid Tartaric acid Citric acid Citric acid
Water
Methanol
1,540 45 12 33 1.0 1-o 0.1 0.1 1.0
77,ooo 142
;:; O-1 1-O 1-O 1.0 1.0 100 1.0 0.5 10-o 1.0 1.0 I.0 1.0 6.3 O-1 33.5 1-o 324 0.1 3.2 2,400 84 X 40 7.0 65-O 1-o 0.1 66 9,500 O-1 107 1,000 147 40 7.0 507 160 0-f 17.2 5,900 200
:z 465 550 505 650 670
I,:% ;o 670 708 885
X
8-O X
10.0 170 16,6: 1,920 435 &O X X 0.1 120 6,ooO X X X X X X 0.1 66 340,000 X X 7-o X X X X X o-1 6.6 1.0 X
Anion-exchange
behaviour of uranium and other elements TABLEI
529
(Continued) Solvent
Acid
Element
Water Cea+ Gd*+ cue+
BP+ Fes+ co*+
Ni*+
Citric Citric Citric Citric Citric Citric Citric
acid acid acid acid tid acid acid
Methanol
11.5 815 48.5
X
2;3 0.1 1.0
X
X X X
0.1 1.0
x In these media completely or partially insoluble.
In methanolic solutions of this acid, on the other hand, the possibility of coadsorbing uranium together with thorium, the rare earths and other elements exists, so that malonic acid can be regarded as a more versatile complexing agent than the other acids, the element salts of which are also poorly soluble in methanol. Separation procedure Based on the results presented in Figs. 1 and 2 and in Table I a method of separating uranium from thorium, cerium and gadolinium (as representatives of the rare earth elements) in an aqueous medium was developed. The experimental steps involved in this ion-exchange procedure have been described above under Column operations. In Table II the results of these resin column separations are recorded. It is seen that all separations of uranium from the other elements were practically quantitative. For this reason and because the break-through capacity for uranium under these conditions (2g of resin in column 15 cm high and 0.5 cm diameter) was found to be TABLEIL-SEPARATION OF URANIUMFROMOTHER ELEMENTS
Uranium taken, .% 10,000
5,000 5,ooo 5,000 5wO 10,000 5,000 5,ooo 5,000 5,000 10,000 5wO 5,000 5,000 5,000
IN
AQUEOUS
MALONIC!
ACID
Element to be Uranium separated from recovered, uranium, pg w Th: 5,000 Th: 1,000 zi Th: Ce: Ce: Ce: Ce: Ce:
100 50 20 500 100 50 25 10
::i Gd: Gd: Gd:
500 100 50 25 10
9,950 4,915 4,937 4,950 5,010 9,980 4,978 4,967 2% 10:013 5,000 4,980 4,978 5,000
MIXTURES*
Other element recovered, rug 4,960 985 100 48 95.8 50 24 9.5 497 97 48 27 11
* Each result is the average of 3 separations performed under the same experimental conditions.
530
J. KORKISCH and I. HAZAN
60 mg of uranium, this procedure could be employed effectively for the removal of fission products like the rare earths, strontium, etc., from uranium. By this anion-exchange method not only the separation of these elements from uranium can be accomplished but also from a series of other elements (those having sufficiently low distribution coefficients, viz. <50). It is, therefore, of broad applicability, unlike the method described by Zaki and Shakirl which has only limited use for analytical purposes. Acknowledgements-This research was sponsored by the International Atomic Energy Agency and the United States Atomic Energy Commission under Contract No. 67/US (AT(30-l)-2623). The generous support from these agencies is gratefully acknowledged. Zusammenfassung-Es wurde das Ionenaustauschverhalten von Uran, Thorium, der seltenen Erden und einiger anderer Elemente gegeniiber dem stark basischen Anionenaustauscher Dowex 1 in w%&igen und methanolischen Systemen die Di- oder Tricarboxylsauren enthalten untersucht. Auf Grund von Messungen der Verteilungskoethzienten in derartigen Medien konnte eine Methode zur Trennung des Urans von Thorium und den seltenen Erden in malonsaurer wtiriger L&sung entwickelr werden. R&m&-On d&it l’echange de l’uranium, du thorium, des elements de terres rares et de quelques autres elements en presence de l’echangeur d’anions fortement basique Dowex 1 dans des systemes aqueux ou methanoliques contenant des acides di- ou tricarboxyliques. Devel, oppement d’une methode basee sur la mesure des coefficients de distribution dans de tels milieux, pour s&parer l’uranium du thorium et des elements des terres rares en solution aqueuse contenant de I’acide malonique. REFERENCES 1 M. R. Zaki and K. Shakir, Z. Analyt. Chem., 1962,185,423. 2 Idem, ibid., 1961, 180, 188. * H. Khalifa and M. R. Zaki, ibid., 1957, 158, 1. 4 F. Hecht, J. Korkisch, R. Patzak and A. Thiard, Mikrochim. Acta, 1956, 1283. 5 J. Korkisch, A. Thiard and F. Hecht, ibid., 1956, 1422. BJ. P. Riley and H. P. Williams, ibid., 1959, 825. ’ J. Korkisch, A. Farag and F. Hecbt, ibid., 1958,415. 8 J. Korkisch, P. Antal and F. Hecht, ibid., 1959, 693. s J. Korkisch and F. Tera, Analyt. Chem., 1961, 33, 1265. lo J. Korkisch, Report to International Atomic Energy Agency and U.S. Atomic Energy Commission under contract No 67/US(AT(3&1)-2623). September 1963. I1 T. Schiinfeld, M. El Garhy, C. Friedmann and J. Veselsky, Mikrochim. Acta, 1960, 883. I2 J. Korkisch and G. E. Janauer, Analyt. Chem., 1961,33, 1930. I3 J. Korkisch, I. Hazan and G. Arrhenius, Talanta, 1963, 10, 865. I4 E. B. Sandell, Calorimetric Determination of Traces of Metals. Interscience Publ. Inc., New York, 3rd Ed., 1959. I6 J. Korkisch and G. E. Janauer, Talanta, 1962, 9, 957.