Germanium could not be detected by the very sensitive color reaction which germanium gives with an anion exchanger in the presence of hematoxin ( 3 ) . However, the decay of 2.6day arsenic-71 gives rise to 12-day germanium-71. Therefore, the arsenic n-iU he contaminated 17-ith germanium activity unless the separation is done after a cooling period of a t least two weeks to give 2.6-day arsenic-71 time to die out. After evaporation of the arsenic(111) from concentrated hydrochloric acid and precipitation of gallium hydrovide from the residue, no gallium activity was detected. Because of the 1-ery large distribution coefficients of germanium and gallium between anion evchaager and dilute hydrofluoric acid, the decontamination factor is estimated to be larger than lo4. No attempt was made to obtain carrier-free gallium activities from the gcrinaniuni target
because they can be obtained in a higher yield by a deuteron bombardment of zinc. ACKNOWLEDGMENT
The authors are grateful to Charles
D. Coryell for helpful advice, and to members of the Rlassachusetts Institute of Technology cyclotron group for assistance in the preparation of tracers. LITERATURE CITED
(1) Fording,
IT, Arkiv Kenzz 5, 503 (1953). (2) Hague, J. L., Brown, E. D., Bright, H. A , J . Research S a t l . Bur. Standards 53, 261 (1951). (3) Kakihana, H., Xzkrochzna. Acta 1956, 682. (4) Iiraue. K. 8.,Selson, F., Am. Soc. Testing Materials, Symposium on Ion Exchange and Chromatography in -4nalytical Chemistry, Atlantic City, K. J., June 1956.
( 5 ) Iiraus, K. A , , Selson, F., Proc. Intern. Conf. Peaceful Uses Atomic Energy,
Paper 837, Vol. 7, p . 113, Session 9 B.1, United Satioiie, Sew York, 1956. (6) Kraus, K. A , , Selson, F., Moore, G. E.. J . Am. Chem. Soc. 77, 3972 (1955). ( 7 ) Kraus, K. A , , Selson, F., Smith, G. W., J . Phys. Chetn. 58, 11 (1954). (8) Sandell, E. B., .‘Colorimetric Determinations of Traces of Metals,” 2nd ed., Interscience, S e x York, 1950. (9) Schindewolf. U.. d i m e x ’ . Chem. 69. 226 (1957): llassachusetts Insti: tute of Technology, 1.alioratory for Suclear Science, Tech. Rept. 68 (1955).
Sullivan, K . H, L-. S. +tomic Energy Commission, “Trilinear Chart of Suclides,” C . S. Government Printing Office, Washington, D. C., 1957. RLCEIIEDfor review Ma)- 13, 1957. Accepted February 10, 1958. K o r k supportedjn,part by the U. S. -4tomic Energy Commission.
Liquid-Liquid Extraction of Uranium and Plutonium from Hydrochloric Acid Solution with Tri(iso-0ctyI)amine Separation from Thorium and Fission Products FLETCHER L. MOORE Oak Ridge National laboratory, Oak Ridge, Tenn.
b A new and rapid method for the liquid-liquid extraction of uranium and plutonium from hydrochloric acid solution is based on the use of tri(isoocty1)amine dissolved in xylene or methyl isobutyl ketone. Uranium and/ or plutonium are separated from thorium, alkalies, alkaline earths, rare earths, zirconium, niobium, ruthenium, and other elements which do not form anionic species under the conditions described. The technique may be used for either tracer or macro quantities of uranium. Several practical applications of the method are proposed.
T
for a rapid and clean separation of uranium and thorium led to the development of the new liquid-liquid extraction technique described here. Previous methods have described the extraction of uranium and thorium from nitrate solutions. Generally, the separation of uranium from thorium in these systems is not too effective or is critically dependent on the nitrate salting strength and free acid concentration of the aqueous solution (8). Both thorium and uraniuni 908
HE NEED
ANALYTICAL CHEMISTRY
extract with iiiesityl oxide ( I S ) , and the use of 2-thenoyltrifluoroacetone is impractical for ‘this separation because of the similar p H dependence for the extraction of uranyl and thorium ( 7 ) . One of the more recent uraniuni extractants, tri-n-butyl phosphate, estracts varying amounts of thorium, depending on the aqueous nitrate salting strength. I n fact, this reagent is often used to extract uranium and thorium from fission products (6, 9 ) . Uranium can be separated from thorium by eytraction into diethjl ether (.$), but it was desirable to find a safer solvent. The separation of uranium and thorium in dilute sulfate solution by the use of long-chain tertiary or secondary aniines has been reported ( 2 ) . However, experience by the writer indicates that poor selectivity from zirconium and niobium would be effected in the sulfate system described. The extraction of the actinide elements from hydrochloric acid solution with tri-n-butyl phosphate has been studied recently (3, 17). Inasmuch as thorium does not forni anionic complexes with the chloride ion, it was reasoned that the extraction
of anionic uranyl complexes from hydrochloric acid solution n-ould result in a clean separation of these t n o elements. The observation that uranium may be extracted efficiently from hydrochloric acid solution with long-chain amines has been noted previously (I, 16). With the advent of new-type fuel elements, an increased interest has developed in the hydrochloric acid system. Therefore, this system w m investigat’ed, primarily to find an effectiye method for the separation of uranium and thorium, but also to stud>-the lieliavior of the major fission products and several relat’cd elements. The long-chain aniine. tri(iso-octj-1)aniine, as select’ed for this study. It is cheap, readily available, and possesses the desirable praperties of lon- aqueous solubilit,y and high organic solubility. =iccording to the vendor (Union Carbide Chemicals Co., Sen- York 17, K.Y,), the exact’ struct,ure of the molecule cannot be defined because of the isometric nature of tri(iso-octy1)amine. The major constituents are thought to be dimethylhexyls and trimethylpentyls, with branching of the alkyl groups
starting a t least two carbon atoms’ distance from the nitrogen.
i
EXTRACTIONS FROM HYDROCHLORIC‘ ACID SOLUTION W I T H 5% TRI(IS0-0CTYL)AMINEXYLENE
Uranium-233 Tracer. The extraction of uranium-233 tracer with 5% tri(iso-octy1)amine-xylene as a function of hydrochloric acid concentration is shown in Figure 1. Aqueous solutions of varying hydrochloric acid concentration containing 4 X lo4 a! counts per minute per ml. of uranium233 tracer were extracted with equal volumes of 5% (w./v.) tri(iso-octy1)amine-xylene for 2 minutes a t room temperature. A high-speed motor stirrer (Palo Laboratory Supplies, New York, N.Y.) with a glass paddle gave excellent mixing of the phases. Each phase was analyzed for uranium233 tracer. Figure 1 indicates that it readily extracts with 570 tri(iso-octy1)amine even from dilute hydrochloric acid solution. While the extent of the extraction of hydrochloric acid was not determined in this particular system, it is probable that an equivalent amount of the acid extracts with the tertiary amine, as in similar systems (15). The extraction of uranium-233 tracer from 7 M hydrochloric acid as a function of time was next investigated with the same procedure. Based on the following data, n-hich indicate that equilibrium is attained rapidly in a manner typical of acid-type extractions, a 2minute extraction time was chosen for subsequent n-ork.
Time, Minutes 0.5 1 2
U-233 Extracted, 90.2 99.1 99.2
70
Several experiments were performed to determine the uranium loss due to scrubbing. Equal volumes of 570 tri(iso-octy1)amine-xylene containing 8 X 106 (Y counts per minute per ml. of uranium-233 were scrubbed for 2 minutes and, after centrifugation, each phase was analyzed for uranium-233 tracer. With 4.6M and 6M hydrochloric acid scrubs the losses were 0.2 and O.l%, respectively. The uranium-233 tracer could be stripped almost quantitatively from the organic phase by mixing thoroughly for 2 minutes with a n equal volume of either 0.1M hydrochloric acid, 0 . l X nitric acid, or distilled water. The amount of uranium-233 tracer stripped with these agents was 98.9, 99.2, and 99.8’%, respectively. Ammonium hydroxide can also be used to strip and precipitate the uranium. The extraction of thorium-230 tracer from hydrochloric acid solution with tri(iso-octy1)aniine-xylene was negligible (Table I). Further experiments with 1.9 mg. per ml. of thorium carrier verified the inextractability of thorium. The presence of uranium did not appear to affect the behavior of thorium. The extraction behavior of the major fission products was investigated in a series of experiments. Tracer solutions
Figure 1. Extraction of uranium-233 tracer with 5% tri(iso-0ctyl)aminexylene from hydrochloric acid solution
Table I. Extraction of Thorium-230 (Ionium) Tracer from Hydrochloric Acid with 5% Tri(iso-octy1)amine-Xylene HC1, .If ThZ3O Extracted, 70 2.2 0.003 4.5 0.005 0.010 6.7 8.9 0.016 11.1 0.020
of various hydrochloric acid concentrations were extracted for 2 minutes with equal volumes of 5% tri(iso-octy1)amine-xylene. After centrifugation each phase was analyzed. The results (Table 11) may be regarded as conservative because the organic phases were not scrubbed. The extraction of the fission product elements from hydrochloric acid solution is approximately that which would be predicted from known anionic chlorocomplexing studies (10) Strontium and trivalent rare earths do not extract appreciably from any hydrochloric acid concentration. The extraction of zirconium is negligible from low to intermediate hydrochloric acid concentrations. The extraction of niobium can be rendered slight by using lower concentrations of hydrochloric acid, a t which the recovery of uranium is still efficient (Figure 1). Obviously, greater decontamination can
-
be effected by stripping into 0 . l U hydrochloric acid and reextracting the uranium. Rutheniuni exhibits the highest extractability of any fission product tested. However, less than 1% of the original ruthenium-106 tracer accompanied the uranium through the extraction and stripping (0.liZI hydrochloric acid) steps described above. The fact that the extractable ruthenium, perhaps ruthenium(IS’), does not strip with 0.1JI hydrochloric acid solution appears to offer a satisfactory separation of these two elements. However, it is dangerous to predict the behavior of ruthenium tracer, and the extraction behavior of any particular solution must be tested. The extraction behavior of radioccsium was not studied because it does not form anionic species in hydrochloric acid solution. The extraction behavior of protactinium(\-) is similar to that of uraniuni(\‘I), and the neptunium cheniistry is essentially the same as that of plutonium of the same valence state (15). rlme~icium(II1)and curium(II1) d o not extract in this system. Those elements n-hich form anionic complexes a t the particular hydrochloric acid concentration used for the extraction of uranium nould, of course, extract also (19, 14, 1 5 ) . I n fact, this offers a rapid method of removing elements such as iron(III), cobalt(II), zinc(II), zirconium(IV), hafnium(IV), vanadium (V), niobium (V), protactinium (V), chroniium(T’I), molybdenum(VI), manium(V1) and (ITr),plutonium(V1) and (IV), and neptunium(VI), (V), and (IV) from thorium in hydrochloric acid solution. The extraction of iron, vanadium, and chromium may be minimized by reduction to the lon-er oxidation states, if desired. Also, vanadium(V) will not extract appreciably nith uranium from dilute hydrochloric acid solution. The data given here refer strictly to the hydrochloric acid system. The presence of other anions may change the
Table It. Extraction of Fission Products from Hydrochloric Acid with 5% Tri(iso-octyl)amine-Xylene
Element
HC1, 111
Sb-95
2.2 4.4 4.6 4.8 5.0 6.5 6.8 9.0 0.1 0.2 1.1 2.1 4.2 6.4 8.5 10.6
Ru-106
Tracer Extracted, % 0.3
3.1 6.2 9.5 17.4 90.2 96.8 99.2 82.3
Element Zr-95
Eu-152-154
0.02 0.4 0.7 89.6 90.0
2.2 4.3
