954 where
CHARLES
C. TEMPLETON
-
.4ND NORRIS F. HALL
0.5772157 is Euler's constant and (-1)n-l 2.633980 = (r2/6) In z exp (--5)-5-l dx n n!
y =
+
+ /Im
(A18)
To verify equation A17, one may insert into equation 47 the series - E ~ ( - ~= )
-
(1/4) 1n z4
2
- "-1 (-2)" nn!
(A191
and integrate term by term.
THORIUM NITRATE. I V LEACHIXG WITH HIGHERALCOHOLS AND KETONES .4s A MEANSOF ENRICHING MIXEDNITRATESIN THORIUM' CHARLES C. TEMPLETONl A N D NORRIS F. HALL
Department of Chemistry, University of Wisconsin, Madison, Wisconsin Received September 14, 1948
In earlier papers (5, 6, 7) of this series we have considered the possibilities of both liquid-liquid extraction and leaching with a single solvent. Liquid-liquid extraction may be used as a fractionation process and theoretically allows the enrichment in the desired component to be carried to any desired value by the use of a sufficient number of cycles. A leaching process for the separation of two substances, on the other hand, if the system is allowed to come to equilibrium, obviously attains its maximum enrichment in a single step. Only such equilibrium leaching has been considered in this study. In view of these considerations, leaching is applicable only as a process for the initial enrichment of materials in thorium, and would be practical only if a great enrichment in thorium were achieved in a single step. This investigation shows that for higher alcohols and ketones (of six carbon atoms and over) such is the case. Further, we have previously shown (5) that a single wash with an equal volume of water is sufficient to remove practically all the extracted material from the saturated leaching solution. Our general investigation of the solvent extraction of thorium from mixtures with the rare earths has been confined to simple systems without the addition of any specizl anion to cause the thorium to form a complex in the organic phase. We have succeeded only because we chanced to study the distribution of t'horium 1 This paper is based upon the thesis submitted by C. C . Templeton t o the Graduate Faculty of the University of Wisconsin in partial fulfillment of the requirements f o r the degree of Doctor of Philosophy, June, 1948. 2 Present address: Department of Chemistry, University of Michigan, Ann Arbor, Michigan.
955
ENRICHMEKT IN THORIUM BY LEACHING
nitrate between xater and an organic solvent in the concentrated range of aqueous solutions (60-100 per cent saturated in thorium nitrate). This led directly to the leaching idea.3 Our entire investigation is thus in contrast to those of cther authors (1, 2) who, confining their studies of the separation of actinide from lanthanide nitrates by liquid-liquid extraction to the range of quite dilute solutions, hare to add special complex-forming agents to make the actinide preferentially enter the organic phase. EXPERIMENTAL
For this study, we define “thorium enrichment” as the percentage of thoria in the total metal oxides in the material. For equilibrium leaching, the attainable enrichment in thorium would be that of the total material in an organic and 0 the rare earth solution saturated with respect to both T h ( X 0 3 ) ~ . 4 H ~ nitrate of interest. The organic solvents used were all of Eastman Kodak Company “practical” grade. The thorium nitrate (c.P. Th(XOa)r.4Hz0) was purchased from the J. T. Baker Chemical Company. We chose to leach thorium from a mixture of the nitrates of thorium and several rare earths. The mixed rare earth nitrate used, obtained from the University of Wisconsin stocks, was of the following relative composition (percentages as metal in an oxalate sample) : PEP CENT
Ce . , .
,
.. . , .. ..,
Tm. . .. . . . . .
..
0.1
Studies were made of four alcohols and of five methyl ketones. In each case 5-10 ml. of solvent was mixed in a test tube with appropriate amounts of both thorium nitrate and the mixed rare earth nitrates. The samples were then rotated end over end at 30 R.P.M. a t room temperature for 5 days. Saturation was assured by the presence of distinct white (thorium) and pink (neodymium) lumps in the final solid phase. Each solution was then filtered, and the “total solubility” (grams of total metallic oxides per 100 g. of solution) was determined. This vias done in our usual manner by weighing out about 1 ml. of solution into a tared platinum crucible, burning off the solvent, and igniting to the oxides. The remaining solution was decomposed to yield the dissolved material in solid Although most current work in this field of solvent extraction has been concerned with liquid-liquid systems, leaching of mixed solids with a single organic solvent has often been investigated. Misciattelli (4) studied the system uranyl nitrate-thorium nitrate-ethyl ether at various temperatures and claimed t o have prepared the anhydrous nitrates. Regardless of whether he actually had the anhydrous salts, his systems at least had a very low water content. He found that a t any temperature above 20°C only uranyl nitrate dissolved in the anhydrous ether, provided sufficient uranyl nitrate was present t o insure saturation If insufficient uranyl nitrate was present, some thorium nitrate also dissolved.
956
CHARLES C. TEMPLETON AND NORRIS F. HALL
form. For methyl and n-propyl alcohols, and for acetone and methyl ethyl ketone, the decomposition was accomplished by pouring the solution into water and boiling until only an aqueous solution remained, followed by the addition of a little nitric acid, evaporation, and crystallization. For the higher alcohols and ketones, the organic solution was washed with about twice its volume of TABLE 1 T h o r i u m enrichments attainable in organic solutions saturated in both thorium and rare earth nitrales I
(PER CEXI T h o 2 IS TOTAL OXIDES)
'
TOTAL SOLUBILITY RATIO
SFThOi IO
SOLVEIT
1 ~
Single determinations
(R.E.)nOi
~
Average grams
grams
Acetone. . . . . . . . . . . . . . . . . . . . . . . Methyl ethyl ketone., . . . . . . . . . . . . . . . . . . 79.1 ~
~
79.1
Methyl isobutyl ketone Methyl n-amyl ketone. . . . . . . . . . . . . . . . . 90.4 ~
I
1
90.4
Methyl n-hexyl ketone
2.42
35.6
45.7
3.78
32.0
46.0
7.7
24.0
38.5
9.4
21.4
35.1
13.5
17.8
30.2
Methyl alcohol
1.21
36.2
36.0
n-Propyl alcohol
3.3
28.4
39.6
Isoamyl alcohol.,
, , , , , ,
., , , , , ., , ., , ., , 12.0
n-Hexyl alcohol. . . . . . . . . . . . . . . . . . . . . . . Ethyl butyrate (7 days' agitation). . . .
,I
91.0
I
91.0
10.1
1
19.5
I
32.7
1 18.5
I
30.5
water, and the solid nitrates were crystallized from the aqueous extract. No metallic nitrates could be detected in 1 ml. of the washed organic solutions. The solid nitrates mere in an indefinite state of hydration, but this uncertainty was cancelled out in the analytical scheme. I n each case two samples were weighed out rapidly enough for both to be in the same condition. I n one of these, the amount of total oxides n as determined by precipitating the hydroxides with ammonia, filtering, and igniting. In the other, thoria was determined after separating thorium and the rare earths by the iodate method (3). Thorium enrichments were then calculated as the percentage of thoria in the total oxides.
ENRICHMENT I N THORIUM BY LEACHINQ
957
The total solubilities and the thorium enrichments are listed in table 1. From these have been calculated the ratio of thoria to rare earth oxides and the total amount of thorium nitrate extracted per gram of resultant leaching solution. The results on ethyl butyrate already reported are included for comparison. DISCUSSION
The type of leaching being considered consists simply in agitating the solid mixed nitrates with an appropriate amount of any of the higher alcohols or ketones. A batch of saturated solution is withdrawn and agitated with an equal volume of water until practically all the extracted nitrates enter the aqueous phase. The product is crystallized from the aqueous phase by evaporation and the washed organic solvent saved for re-use. The increase in thorium enrichment with increasing molecular weight of the solvent in either homologous series is apparent from the data in table 1. The thorium nitrate content of all the solutions is only slightly less than the solubility of Th(NO&.4HzO alone in the same solvent (6). The increase in thorium enrichment is thus due to the greater decrease in solubility of rate earth nitrates, as compared to thorium nitrate, with increasing molecular weight of the solvent. SUMMARY
1. Mixed nitrates of thorium and rare earths may be enriched to over 80 per cent in thorium nitrate by leaching with any of several alcohols or ketones. 2. The attainable thorium enrichment increases within an homologous series of alcohols or ketones with increasing molecular weight.
This research was supported in part by the Research Committee of the University of Wisconsin Graduate School from funds obtained from the Wisconsin Alumni Research Foundation. REFERENCES (1) AUDRIETH, L. F.: Private communication t o N . F. Hall. (2) HARVEY, HEAL,MADDOCK, AND ROWLEY: J. Chem. SOC.1847, 1010. (3) HILLEBRAND LVD LUXDELL: A p p l i e d Inorganic A n a l y s i s . John Wiley and Sons, Inc., New York (1929). (4) MISCIATTELLI: Phil. Mag. 171 7, 670 (1929). ( 5 ) ROTHSCHILD, TEMPLETOX, AND HALL:J. Phys. & Colloid Chem. 61, 1006 (1948). (6) TEMPLETON AND HALL:J. Phys. & Colloid Chem. 61, 1441 (1947). (7) TEMPLETON, ROTHSCHILD, AND HALL:J. Phys. & Colloid Chem. 63, 838 (1949).
