958
CHARLES C. TEMPLETON AND NORRIS F. HALL
THORIUM NITRATE. V
EXTRACTION FROM AQUEOUS SOLUTION BY ORGANIC SOLVENTS AS
A
MEAXSOF
ENRICHING MIXED KITRATESIN THORIUM' CHARLES C. TEMPLETOW A N D NORRIS F. HALL Department of Chemistry, University of W i s c o n s i n , Madison, Wisconsin
Received September 1.4, 1948
We have shown (4)that leaching of mixed solid thorium and rare earth nitrates with higher alcohols and ketones results in a considerable increase in the proportion of thorium nitrate. The present paper demonstrates that the last 10-20 per cent of rare earth nitrates can be removed by a liquid-liquid extraction process. EXPERIMENTAL
Apparatus and method An all-glass extraction apparatus (figure 1) was used. Each of the vessels had a total capacity of about 200 ml. Vessels I1 and IV had volumes of about 160 ml. below the overflow arms. All solvent flow wm by gravity. Vessel I was initially filled with the desired organic extraction solvent. Vessel I1 was filled, to within 3 to t in. of the overflow, with a concentrated aqueous solution of the starting mixed nitrates. Vessel I11 was an overflow reservoir. Vessel IV was filled, to within 3 to 3 in. of the overflow, with distilled water. The appropriate stopcocks were adjusted so that a steady drop rate was maintained a t both overflow tubes. The flow rate was usually about 100 ml. per hour, although it could not conveniently be kept absolutely constant. Layers of organic solvent formed above the aqueous phases in both vessels I1 and IV. A motor-driven stirrer, adjusted to about 50 to 100 R.P.M., was arranged to agitate the aqueous phase in vessel IV without disturbing the supernatant organic layer. S o means of stirring was provided in vessel I1 inasmuch as, without stirring, more material was extracted than could be completely washed out in vessel IV even with stirring. The washed solvent which overflowed was returned to vessel I ; in no run was the total amount of solvent required more than the initial 200 ml. Thus all of the solvents investigated remained nearly immiscible with water during the entire process. Owing to the nature of the relation governing the distribution of thorium nitrate between water and any of these organic solvents (1, 3, 5 ) , a t a maximum only about 20 per cent of the thorium nitrate could be practically extracted from an initially saturated aqueous solution. Consequently, for each run vessel I1 was originally filled with an almost saturated solution, and solvent was run through the system until the accumulated material in vessel IV represented 5-10 1 This paper is based upon the thesis submitted by Charles C. Templeton t o the Graduate Faculty of the University of Wisconsin in partial fulfillment of the requirements for the degree of Doctor of Philosophy, June, 1948. 2 Present address: Department of Chemistry, University of Michigan, Ann A r b o r , Michigan.
ENRICHMENT I N THORIUM BY EXTRACTION
959
per cent of the original nitrates. At this point vessel IV was drained, and the aqueous solution evaporated to obtain the yield in solid form.
Analytical methods Two samples of a given nitrate mixture were weighed out at the same time. One sample was ignited in a platinum crucible to give the percentage of total oxides. The amount of N&03 was determined by measuring the absorption of
FIG.1. Continuous liquid-liquid extraction appsratus
light a t 525 and 579 milIimicrons by a solution of the other sample in 2 N nitric acid, using the Beckman Model DU quartz spectrophotometer. Results were read from an empirical calibration curve, based on measurements made on solutions prepared from pure Nd(N03)3.6H20. For those runs where a mixture of the rare earths was used in the starting material, neodymium was determined as above and the total rare earth oxides mere calculated on the assumption that the proportions of the various rare earths were not changed during the extraction. That this assumption does not seriously affect the results in question (runs B and I) may be seen from the fact that the separation factor for fractionating neodymium and lanthanum nitrates with n-hexyl alcohol is about 1.5 (2). En-
960
CHARLES C. TEMPLETON AND NORRIS F. HALL
richments in thorium and neodymium were then calculated as the percentage of the respective oxide in the total oxides. DATA
A preliminary test3 of the apparatus was made using n-hexyl alcohol, first with pure thorium nitrate as the starting material (run A), and then with a mixture of thorium and mixed rape earth4 nitrates as the starting material (run B). In run I methyl n-hexyl ketone was used to enrich a mixture of thorium and mixed rare earth nitrates of an initial thorium enrichment of 84.9 per cent. For runs 11, 111, and IV the starting material was a mixture of thorium and neodymium nitrates only, the solvents being methyl n-hexyl ketone, methyl isobutyl ketone, and ethyl butyrate, respectively. The detailed data are given in table 1. Yields are given as percentages of the total weight of hydrated nitrates used in the starting material. Separation factors have been calculated as the ratio of thoria to rare earth oxides in the yield divided by the same ratio in the starting material. DISCUSSION
These data show that the separation of thorium from the rare earths by extraction from aqueous solution with organic solvents is feasible. The major consideration is that the aqueous phase must be quite concentrated (80 per cent or more of saturation) in thorium nitrate for any appreciable portion of the thorium to enter the organic phase. I t is a corollary that any organic solution of thorium nitrate will surrender its solute almost completely to an equal volume of water, if given a reasonable amount of time and agitation. The periodic removal and resaturation of the starting aqueous nitrate solution is an inherent feature of the process. In view of this feature, the apparently low yields of 5-10 per cent are not significant, since eventually most of the thorium may be extracted with a reasonable number of resaturations of the starting solution. In this work, no trouble was encountered due either to indistinct phase boundaries or to loss of organic solvent because of increased miscibility with the aqueous phase. CONCLUSIONS
1. The extraction of thorium nitrate from aqueous solutions also containing the nitrates of the rare earths by the use of higher organic solvents has been shown to be possible. Appreciable yields of thorium nitrate of high purity were obtained. 2. The only condition which is critical to the process is that the starting aqueous solution must be kept quite near to saturation with respect to thorium nitrate. The method is mainly applicable to materials which have been enriched to about 80 per cent in thorium by some other means, such as the leaching scheme previously described (4). 3 4
This test was performed by Mr Bill F. Rothschild. The mixed rare earth nitrates were from the lot used in the work described in reference 4 .
961
EKRICHMENT IN THORIUM BY EXTRACTION
T.4BLE 1 Liquid-liquid eztractions with organic solvents Run A Solvent : n-hexyl alcohol (Eastman Kodak Company, practical) Starting material: C.P. Th(KOs)4.4H20 Flow rate: about 50 ml./hr. Vessel 11: 130 ml. aqueous thorium nitrate solution Vessel I\': 120 ml. water CONCENIR.4TIO?I C E A S G E S PEPLENTAGES OF Th(NOs), IN SOLUTION
10T*L SOLVENT FLOW
Vessel I1 mi.
per can1
0
60.81 59.02 57.65
100 150 200 250
Vessel I l l per
Vessel V
per Lent
per ccni
0.0 0.43 1.84 3.05 3.81 5.12 6.35
0.0 3.81 3.38 4.16 6.53 4.58 5.13
300
54.54
350
Vessel IV
Cenl
0.0 0.72 1.88 1.42 1.85 1.67 1.75
Solvent: n-hexyl alcohol (Eastman Kodak Company, practical) Starting material: mixture of Th(SOa)4,4H20and mixed rare earth nitrates; enrichment, 83.0 per cent Flow rate: 50 ml./hr. Vessel 11: 130 ml. aqueous mixed nitrate solution Vessel IV: 120 ml. water
I
CONCENTRATION CAANOES PERCESIAGES OF IOIAL OXIDES IN SOLDIlOS
TOTAL SOLYEN1 FLOW
Vessel 11
Vessel IV
mi.
per Len1
per ccttf
0 100 150
29.12
0.0 0.08 0.36 0.73 1.02 1.31 1.51
200 2-33 300 350
28.86
Total solvent flow:350 ml. Yield: 2.5 per cent Thorium enrichment: 96.2 per cent Separation factor: 5.2
Vessel V pcr
LC"1
0.0 0.51 0.81 0.67 0.59 0.45 0.39
962
CAARLES C. T E M P L E T O N AND NORRIS F. HALL
TABLE 1-Continued Liquid-liquid extractions with organic solvents Run I Solvent: methyl n-hexyl ketone ( t . p . , 172-173OC.) Starting material: 160 g. mixture of Th(iYOa)r.4H20and mixed rare earth nitrates; thorium enrichment, 84.9 per cent Flow rate: about 100 ml./hr. Vessel 11:130 ml. aqueous mixed nitrate solution Vessel IV: 130 ml. water IOTAL SOLVENT FLOW
1
CONCENTRATION CHASGES PERCEKTAOES OF IOTAL OXIDES IN SOLG'TION
Vessel I1
ml.
per Cent
0 50
32.9 0.40 0.91 1.11 1.58 1.92 2.46 3.37
100 150
250 400 600 loo0 Total solvent flow: 5200 ml P m T i o h ' OF PROCESS
0 to 1100 ml. 1100 t o 2100 ml. 2100 t o 5200 ml
I
1 ~
YIELDS AS HYDRATED NITRATES
, ~
grams
10.0 3.3 6.8
1
j
1
RARE EARTH ENPICHXENT
0.57 0.77 0.49 0.72 0.76 0.68 0.21
1
THOPIUY ESRICHJ6ENT (ny DIFFERENCE)
pcr cent
per cent
0.3 1.1 0.4
99.7 98.9 99.6
963
EXRICHMEKT IN THORIUM BY E X T R A C T I O S
TABLE 1-Concluded Liquid-liquid extractions w i t h oryanic solvents Run III Solvent: methyl isobutyl ketone (Eastman Kodak Compan Starting material: 155 g. mixed Th(SOa)i,1H20and Sd(S03 enrichment, 97.0 per cent Flow rate: about 100 nil.ihr. Vessel 11: 110 ml. aqueous mixed nitrate solution Vessel IV: 120 ml. water
~ - ~ _ _ _ _ _ _ ,
,
C O S C E S T R A I l O S S 1s
~~,
Vessel I1 (initial) . . . . . . . Vessel IV (final) . . . . . . . .
.
.
P E R CEKT T O I l L OXIDES IS SOLLTIOK
-
34.0 5.5
.I
. . .
Total solvent flow: 1280 ml. Yield: 10.3 per cent Thorium enrichment: 99,7 per cent Seodymium enrichment: 0.3 per cent Separation factor: 10.3
-
Run II' Solvent: ethyl butyrate (Eastman Kodak Company, practical) ; Starting material: 160 g. mixed T h ( S O s ) r ' 4 H 2 0and K d ( S 0 3 ) 3 . 6 H 2 0thorium enrichment, 9 i . 0 per cent Flow rate: about 1M) ml./hr. Vessel 11: 115 ml. aqueous mixed nitrate solution Vessel IV: 120 ml. water. PER CENT TOTAL OXIDES
COSCEXTRAIIOSS IZ
Vessel I1 (initial), . . . . . . . . . . . . . . . . . . . Vessel IV (final). . . . . . . . . . . . . . . .
IS SOLUIlOH
. . . . . . . . .
I
33.9 1.02
Total solvent flow: 2000 ml. Yield: 1.4 per cent Thorium enrichment: 99.97 per cent (limit of analytical method) Xeodymium enrichment: 0.03 per cent (KO neodymium was detectable) Separation factor: 103
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) (2) (3) (4) (5)
ROTHSCHILD, TEMPLETON, .mu H A L L :J. Phys. & Colloid Chem. 62, 1M)6 (1948) TEXPLETON: J. Ani. Chem. Sac. 71, 218i (1949). TEXPLETON A K D HALL:J. Phys. & Colloid Chem. 61, 1141 (1947). TEMPLETON A K D HALL:J . Phys. & Colloid Chem. 64, 9% (1950). TEYPLETON, ROTHSCHILU, AKD HALL:J. Thys. 8: Colloid Chem. 63,838 (1949).
