STUDIES OF RECOVERY PROCESSES FOR WESTERN URANIUM- BEARING ORES

Part VIII

EXAMINATION OF CERTAIN ASPECTS OF THE "CARBONATE PROCESSES" AS USED AT MONTICELLO, UTAH

By

R. S. Lowrie and E:. B. Brown

OAK RIDGE NATIONAL LABORATORY Y-12 AREA OPERATED BY CARBIDE AND CARBON CHEMICALS DIVISION UNION CARBIDE AND CARBON CORPORATION OAK RIDGE, TENNESSEE ., Index No. -'----Y::.--'5:..!.7.:::.1'------

Subject Category: Metallurgy Raw­

·I M9.teria1s

STUDIES OF RECOVERY PROCl!SSES FOR limTERN TJRANTUM-BlllARING ORES

PART VIII

Exam1nation of Certain Aspects of the "Carbonate Processes"

as Used at Monticello, Utah

R. s. Lowrie K. B. Brown

Y-12 ChaRdca1 Research Division Mr. G. H. C1ewett, Division Head

OAK RIDGI!: NATIONAL lABORATORY Y - 12 AREA Operated by CARBIDE AND CARBON CHEMICAlS ·DIVISION UNION CARBIDE AND CARBON CORPORATION Oak Ridge, Tennessee

Contract No. W-7405-Eng-26

,v;: ....'"'"' ... >Jm.... _,_:::;:;:::co;w - 2 Index No. Y-571 Metallurg-y-;R;.,a~w:,c-;:;Ma"'te=r"'i7al"s=- Distribution, Series A: No. Copies

Atomic Energy Commission, Washington (Jesse Johnson) 2 Atomic Energy Commission, New York (Wilson) 5 Battelle Memorial Institute (Bearse) 1 Dow Chemical Company 1 Massachusetts Institute of Technology (Gaudin) 1 Patent Br'anch, washington 1 Technical Information Branch, ORE 10 U. s. Geological Survey 1 Colorado Area Office (Frank H. MacPherson) 2

Carbide and Carbon Chemicals Division (Y-12 Plant) internal distribution as follows:

.Mr. c. E. Center 1 Dr. c. E. larson 1 Dr. A. M. Weinberg 1 Dr. E. D. Shipley 1 .Mr. w. D. Lavers 1 Dr. J. A. Swartout 1 .Mr. c. D. Susano 1 .Mr. w. R. Grimes 1 Dr. c. F. Coleman 1 .Mr. G. H. Clewett 1 Mr. K. B. Brown 1 .Mr. R. s. Lowrie J. C. R. I. o. 2

TOTAL: 38

Plant Records Department, Y-12 Plant

Date Issued: MAR 21 1950

- 3

Abstract

The following topics are discussed: ( 1) the maximum build-up of uranium in the recycling carbonate leach liquors of both raw and salt-roasted ore, (2) solubilities of certain uranyl vanadates in sodium carbonate solutions, (3) solubility of sodium uranyl tricarbonate in sodium carbonate solutions,

(4) analyses for carbonate in the mill liquor, and (5) carbonate consumption during leaching. Some information is also pre- sented on the organic content of the mill liquors, the filter- ing and settling of raw leach slurries, and the recycle of effluent liquors from the "yellow-cake" precipitation. 4

Table of Contents

Introduction 7

Ore Samples 10

Cyclic Leaching of Salt Roasted Ores 11

Experimental Procedures 12

Salt Roasting 12

Q,uenching . . 12

Leaching .. 12

Leaching with 3% Na2C03 14 Uranium Build-Up • 14

Vanadium Build-Up 17

Build-Up of Contaminants 18

Leaching with 6% Na2 C0 3 18 Uranium Build-Up • 18

Build-Up of Vanadium and Impurities 22

Leaching with 9% Na2 C0 3 • 22 Uranium and Vanadium Build-Up 22

Summary .•...... 24

Cyclic Leaching of Raw Ores 25

Experimental Procedures 25

First Leach 25

Second Leach 26 5

Table of Contents (cont'd) page

Leaching with 3% Na2 co3 25 Indian Reservation Ore 25

Stockpile No. 7 Ore 28

Stockpile No. 9 Ore 28

Leaching with 5% Na2 C0 3 . 28

Stockpile No. 7 Ore 28

Swnmary . • • . . . • • • 32

Organic Content of Na2 co3 Leach Solutions from Raw Ore 33 Carbonate Consumption during Leaching 34

Analysis for Carbonate in Mill Liquors 34

Filtering and Settling of Raw Ore Leach Slurries 35

Carbonate Leach-Sand ·Slime Separation-Acid Leach 38

Solubility of Synthetic and Natural Minerals in Carbonate Solution • . . • • . • • • • • 41

Description of Materials 41

Experimental Procedure 42

Effect of Sodium Carbonate Concentration 43

Effect of Sodium Vanadate Concentration 43

Effect of Sodium Chloride Concentration 47

Effect of Sodium Vanadate in Combination with Sodium ·• Chloride . 6 • • • • • • • • • • • .- • • • • • • • • . . . 49 Solubility of Natural Mineral in Actual Leach Liquors 49

Solubility Studies on Sodium Uranyl Tricarbonate • 51 6

Table of Contents (~ont'd) page

Preparation of Sodium Uranyl Tricarbonate 54

Effect of Sodium Carbonate Concentration 54

'Effect of Sodium Vanadate Concentration 54

Effect of Sodium Chloride Concentration 56

Recycle of Effluents from Yellow-Cake Precipitation 58

Effect of Na~so4 on Solubility of Natural Mineral 58

Effect of Na2so4 on Raw Ore Leaching 58 Acknowledgements 61

Appendix A 62

Appendix B 63 7

EXAMINATION OF CERTAIN ASPECTS OF THE "CARBONATE PROCESSES"

AS USED AT MONTICELLO, UTAH

INTRODUCTION

Sodium carbonate leaching has been employed in Western uranium mills for many years. Currently, such "carbonate processes" are being used at Naturita and other mills of the Vanadium Corporation of America and at the plant at Monticello, Utah, which was recently constructed and placed in operation by the Galagher Company of Salt Lake City, Utah under the auspices of the A.E.C.

The term "carbonate process" is often used rather loosely to describe somewhat different processing methods. At the VCA mills, a process is used in which the ore is first roasted with salt to form soluble sodium vanadate, and then leached with sodium carbonate to dissolve the vanadium and uranium values1 • Since the roasting step is included only for vanadium recovery, this process is economically feasible only with ores which have a fair concentration of vanadium minerals ( > 1% V205). Also, because of the formation of insoluble calcium vanadates, the ore must be low in calcite.

At the new mill at Monticello, Utah, equipment is available for the salt-roast, carbonate-leach treatment, but, in addition, allowances have been made for other types of processing. The rather copious quantities of ores of low vanadium content and/or high calcite content

1 For simplified flowsheet, see Appendix A. 8

will be processed by leaching the raw ore directly with hot sodium carbon- ate solutions. In instances where the vanadium and calcite are both high, the ore will be leached directly and provision will be made later to remove the calcite by flotation, followed by a roast and leach of the flotation tailings for their vanadium content. These innovations will give rise to processing problems not previously encountered in the Western mills.

An extensive study of the roasting and leaching treatment has been made by the Battelle Memorial Institute at Columbus, Ohio, and by the

U.S. Bureau of Mines, Salt Lake City station. The direct leaching process and the calcite flotation method were also developed and studied by the Bureau of Mines at Salt Lake City.

In April, 1949, the laboratories at Y-12 were requested by, the A.E.C. to investigate whatever solution and analytical chemistry was important to the start-up of the Monticello plant1

After conversation with Messrs. M.G. McGrath2 and John \Vhite3 , a program was set up which included the immediate problems of this nature.

These problems may be summarized as follows:

(1) The supplying of analytical procedures for use in determining uranium at Monticello. The furnishing of Y-12 analysts to set up these procedures at the plant, help organize the plant laboratory, and train the plant personnel.

1 The Monticello plant started operations in September, 1949. 2 Metallurgist for Colorado Raw Material Operation, A.E.C. 3 In charge of construction and start up of Monticello for the Galagher Company. 9

(2) The supplying of analytical methods for plant control of (a) carbonate concentration in the leach circuit, and (b) yellow cake pre­ cipitation.

(3) The determination of the limitations that are imposed on uranium build-up and impurity build-ups when using different concentrations of Na2C03 on raw ores in the Monticello leach circuit. Since raw ore leaching is a recent innovation in the Monticello flowsheet, the critical conditions for such a circuit had not been studied.

(4) As explained above, past practice in the Western mills has been to roast the ores with salt (to convert vanadium to soluble sodium vana­ date) and then leach the calcines with Na2C03 eolution to derive the uranium and vanadium values. Direct leach solutions are different from those formerly obtained with roasted ores in that these solutions contain less vanadium as well as some organic matter. It was of immediate inter­ est to the Monticello plant to determine whether the standard, yellow-cake, precipitation technique would apply·to the direct leach solutions •.

(5) Since the direct leach solutions are very low in vanadium content, it is not possible to use the same precipitation method for vanadium that was formerly employed. Consequently, some satisfactory method for recover­ ing vanadium (economically) from the dilute vanadium liquors should b~ developed.

(6) One way to solve the vanadium recovery problem would be to recycle the plant solutions, after the uranium precipitation step, in order to build-up the vanadium concentration to a normal level -- as well as to conserve water in the process. First, it must be determined whether 10

such an operation can be accomplished without harm to the milling oper- ' ation (liquors from the yellow-cake precipitation contain fairly large

amount• of Na2S04).

(7) Tests should be made to determine the amount of Na2C03 that

will be consumed by an average ore during a direct leaching treatment.

(8) Methods for improving the settling and filtration of raw ores

should be considered.

The results of investigations conducted on items 2, 3, 6, 7, and 8

are discussed in this report. The data collected in studying items 1, 4,

and 5 are discussed in other sections of this series. The information

on which this report is based has been drawn from results presented in

greater detail in previous progress reports. A list of these reports is

given in Appendix B.

ORE SAMPLES

The ores used during most studies of the Monticello operations

included samples from Radium 7 and Wild Steer Mine and from Stockpile 7

and 9 at the Monticello site. Ores from Radium 7 and Wild Steer Mine

are high in vanadium, low in lime (calcite) and will be treated by the

normal, "salt-roast" process. Stockpile 7 is a low vanadium, high lime

ore such as will• be processed by direct leaching. Stockpile 9 is a low

vanadium, low lime ore, and will also be subjected to the direct leaching

treatment. The chemical compositions of the different ore samples are

presented in Table 1. 11

Table 1

Chemical Composition of Ores

Percent b~ Wei~ht In: Constituent Wild 13teer Mine Radium 7 Stockpile 7 Stockpile 9

u3o8 0.35 0.45 0.22 0.22 V205 3.4 2.9 0.7 0.7 Si02 86.6 85.3 77.0 82.7

CaO 1.0 3.3 6.0 2.3

MgO 0.45 1.5 2.8 1.3

Fe2o3 1.0 1.3 1.4 2.4 Al203 3.3 0.5 3.0 5.1

P205 0.12 0.15 0.12 0.25

CYCLIC LEACHING OF SALT-ROASTED ORES

In the salt-roast, carbonate-leach process, the sodium carbonate con- centration of the leach liquor must be maintained at about three percent or above to obtain efficient solubilization of the uranium values. Since all of the carbonate is destroyed in the subsequent precipitation steps, it follows that· the process would be operated most economically in reagents at the point where maximum concentration of uranium was being attained in the leach liquor~ If enough advantage in uranium solubility were gained, it might be feasible to increase the concentration of the sodium carbonate leach liquor. 12

Experimental Procedures

Salt Roasting. The various batches cf ore were roasted in an electric furnace at 850°0 for two hours with occasional rabbling. The bed-depth varied from 2-inches to 2.5-inches and the dry air flow was approximately 0.3 cfm. The salt was thoroughly mixed with the ore previous to roasting.

Quenching. Rapid quenching of the hot calcines is necessary to obtain the maximum extraction of uranium. The easiest method, that of dropping the hot calcine directly into the leach solution, resulted in severe dusting and splattering. Consequently, the calcines were first cooled rapidly to a low temperature on a metal tray and then placed in the leach liquor contained in a stainless steel beaker. A plastic cover and suction system with a trap prevented loss due to dusting and splattering. Total time for quenching and transfer operations varied from two to four minutes.

Leaching. The roast ore batches were subjected to a cascade leaching process. The leach solution for the first stage was either pure NazC03 of the desired concentration or a previously prepared stock solution of about the same mineral composition as the normal plant liquors. After leaching and filtration, the liquors were sampled and = 1 immediately analyzed for C03 content •

1 The procedure consisted of liberating the COzby addition of 1:1 H2So4, and absorbing it in a weighed ascarite tube after removing by appropri­ ate absorbers any HCl and moisture which were evolved. 13

Dry Na2C03 was added as needed to hold the carbonate concentration at the desired level. The pregnant liquor was then used to leach a fresh batch of roasted ore, the resulting liquor again sampled and adjusted for

co3= content, etc. The size of the ore sample was decreased regularly

from stage to stage to compensate for the volume of solution removed for analyses. The ratio of weight of ore to volume of solution was held at

one to three throughout the experiments.

The samples taken from each stage were analyzed for uranium, vanadium, and· sometimes chloride, phosphate, silica, and aluminum, in addition to the carbonate determination for control purposes.

The leaching treatment was carried out at near boiling with con­ tinuous agitation. In the first experiment, the slurries were filtered while hot on a Buchner funnel and the residues were washed on the Buchner vdth a minimum amount of water, allowed to drain under suction for a few minutes, then washed with 100 mls of hot 3 percent Na2C03 solution. The

leach liquor was adjusted to the desired volume either by addition of water or by evaporation.

Later, however, and for reasons presented in the following section, the procedure was modified in two ways. These were (1) equipping the reaction vessel with a reflux condenser to maintain a constant volume, and (2) moving the pregnant liquor from stage to stage without the addition of any wash solutions-- either water or sodium carbonate.

The residues from each stage were also subjected to a second leaching treatment with a fresh solution of Na2C03 (weight of ore to volume of

solution for this leach was one to two). The residues were washed 14

thoroughly with water and the leach liquors and tails were analyzed for their uranium and vanadium content. In this way the effectiveness of the leaching treatments could be ascertained and metal balances could be made for each stage.

Leaching with Three Percent Na2C03

Uranium Build-Up. The data from two different experiments with 3%

Na2Co3 as the leaching agent are shown in Tables 2 and 3. In the first experiment (Table 2), the uranium build-up is shown to be highly dependent upon the carbonate concentration.·

It may be noted that, upon holding the Na2C03 concentration at 3%;

(l) the uranium content reached 2.2 grams u3os/liter during the lst and 2nd stages with quite high percentage extractions, (2) the uranium content continued to increase up to 3.6 grams U30s/liter during the 3rd and 4th stages, but with lower percentage extractions, and (3) the uranium con­ centration actually decreased during the 5th stage, meaning that no uranium was extracted from the fresh batch of ore, but instead, some of the original uranium precipitated out on the ore and was picked up during the second leaching treatment.

Upon increasing the Na2C03 concentration to about 5%, the uranium concentration increased to a maximum of 4.9 grams U30s/liter during the

6th and 7th stages. However, during the 8th stage, a significant decrease in uranium concentration occurred, and during the 9th stage, a much larger decrease (down to 1.4 grams u3os/liter) occurred even though the Na2C03 concentration was 5.7% prior to and 4.4% after the leaching treat­ ment. This decrease was confirmed by the large quantity of uranium ---Table 2 Build-Up of Materials - First 3% Na2 C03 Cascade Leach

= Test Stage *gms. of Vol. of Final UsOa VaOB NaCl Al P04 - Si02 No. No. Ore Leach Na2 C03 (gms. (gms. ( gms. ( gms, (gms. ( gms. Leached Solution Cone. per per per per per per ( mls. ) ( %) liter) liter) liter) liter) liter) !!ter) L-550 1 557 2000 2.79 1.00 9.57 20 0.02 0.024 < 0.005

L-551 2 600 1800 2.72 2.15 19.8 48 0.16 0.010 0.005

L-552 3 533 1500 2.82 2.94 29.5 59 0.21 6~018 < 0.005

L-553 4 457 1400 2.85 3.50 38.9 78 0.32 0.015 0.014

L-554 5 400 1200 1.85 3.35 49.5 99 0.25 0.020 0.052

L-565 5 333 1000 4.50 3.98 50.1 128 0.15 0.018 0.048

L-555 7 267 BOO 4.93 4.90 73.1 139 0.05 0.013 0.034

L-557 8 200 500 5.70 4.48 79.0 152 0.05 0.037 0.022 L-558 9 157 500 4.37 1.35 85.3 157 - 0.037 0.020 L-559 10 133 400 3.35 0.88 89.3 175 - 0.014 0.012

*wild Steer Mine Ore

1-' 01 Table 3

Build-Up of Materials - Second 3% Na~CO~ Cascade Leach

Exp. Stage ore'* Leach Final U30a V205 No. No. Leached Volume Na2C03 tgms. ( gms. ( gms.} (mls.} Cone. per per - .111 liter) liter) Stock Solution --- 3.0 2.30 . 25.0 ~ L-6'71 1 400 1200 2.15 2.84 31.8

L-6'72 2 333 1000 2.'75 3.84 45.0

L-6'73 3 26'7 800 2.4 1.36 52.0

L-6'74 4 21'7 650 3.0 1.18 :58.5

L-6'75 5 lo'Tt' 500 2.8 0.83 6'7.3

.t Radium No. '7 Ore

1-' "' 1?;

found in the second leach of the 9th stage.

There was, however, some cause for uncertainty about the results in Table 2. During the filtration step of stage 4, it was noted that a yellowish green precipitate was distributed throughout the filter cake and that to some extent this precipitate dissolved in the carbonate wash and passed into the main leach liquor.

It was felt that the "maximum build-up" values were, therefore, erroneous and that the true values were represented by the uranium concentrations at the point where the precipitate first appeared.

To eliminate the dependence upon physical observations, other tests were made using a modified procedure in which no washing was made of the filter cake from the first leach (see Experimental Procedur.e). The data from these experiments are presented in Table 3 and show a maximum uranium concentration of 3.8 grams U308/liter. This value is in good agreement with that obtained at the observed point of precipitation in the first experiment.

The over-all extractions of uranium by the two leach solutions ranged from 80 to 90 percent as indicated by analyses of the residues.1

These values are in good general agreement with those reported by other laboratories with similar roasting, quenching and leaching conditions.

Vanadium Build-Up. The vanadium concentration in both experiments increased quite regularly to as high as 80 grams v2os/liter. This is three to four times the concentration usually attained in the present

1 Report Y-415, Tables 1 and 2, pages 7 and 10. 18

plant operations. The over-all vanadium extractions by the double leach­ 1 ing treatments were 90-92% with 80-90% being extracted by the first leach

Build-Up of Contaminants. The concentrations of silica,phosphate, and aluminum remained relatively constant and at a low level throughout the cascade treatment. The NaCl concentration increased quite regularly up to 175 grams NaCl/li tar. This represents a rout 50% of the saturation value in an aqueous solution. The build-up of NaCl is of course dependent on the roasting conditions. Since a 9% NaCl charge and a relatively deep bed were used in these roasts, the residual chloride concentration in the calcine is much greater than would be encountered in plant operations: hence, the build-up of chloride in the leach solution is much faster.

It appears that the sodium chloride concentration has little, if any, effect on vanadium build-up in the. leach liquor. Its effect on urani·um build-up can not be accurately evaluated from these data, since a more critical variable, the carbonate concentration, was in effect.

Leaching with 6 Percent Na2C03

Uranium Build-Up. About nine liters of stook solution approximately representative of the plant pregnant liquors were prepared by quenching salt-roasted Uravan ore in sodium carbonate solution. This solution analyzed 2.32 grams u3o8 per liter, 28.1 grams V205 per liter, 26.7 grams

Na2co3 per liter, and 92.3 grams NaCl per liter. For the first experiment a portion of this stock solution was used in the first stage after

1 Report Y-415, Tables 1 apd 2, pages 7 and 10. 19

adjusting the Na2Co3 concentration to 6 percent. It may be observed in Table 4 that the uranium concentration increased regularly during the

1st and 2nd stages to a value of 4.2 grams U309 per liter, and extractions were quite high (75 percent). During the filtration step of the 3rd stage, it was noted that a finely divided, greenish-yellow precipitate was distributed throughout the unwashed residue. This phenomenon had been observed previously in the 3 percent Na2C03 cascade, and the washing procedure for the 6 percent Na2C03 cascade was changed with the idea that the precipitate would be much less soluble in water than in sodium carbon­ ate solutions. However, upon washing the residue with several portions of hot water, it was found that the yellow precipitate dissolved readily and passed into the main leach liquor. The formation of this yellow precipitate was noted in the 4th, 5th, and 6th stages, but the practice of washing with hot water resulted in it being redissolved and returned to the cycle. In the 7th stage, the ore was not washed after leaching and the uranium content of the solution dropped to only 0.08 grams U309 per liter. For a plant counter-current system, the true value for maximum uranium concentration would be that correspondent to the first formation of the precipitate. According to the results in Table 4, the value would be 4.3 -5 grams U309 per liter for a 6 percent Na2C03 leach.

As in the case of the 3 percent Na2C03 work, further tests were made to check this value, using the modified experimental procedure described above. The data in Table 5 show a maximum uranium build-up of about 5.5 grams u3o8 per liter. This value is only slightly higher than that obtained in the previous experiments -- the difference might be explained Table 4

Build-Up ~f_Materials - First 6% Na2C0 3 Cascade Leach

Stage Amount Vol. of Final U30s V205 NaCl Al Po4- Si02 No. Ore Leach Na2C03 ( gms. {gms. ( gms. {gms. {gms. ( gms. Leachef Solution Cone .. per per per per per per (gms.) (mls.) ( %) liter) liter) liter) liter) liter) liter)

Stock Solution - - 6.0 2,32 28.1 92

1 '700 2100 5,16 3.28 34 106 1.5 0,05 0,05

2 633 1900 5.01 4.24 45 120 0.5 0.04 0.19

3 56'7 1'700 4,83 5,02 53 133 0.3 0.01 0.12

4 500 1500 5.01 4,95~ 62 154 0.1 0.10 0.10

5 433 1300 5.9 6.68 '70 168 0.1 0.10 0.11

6 36'7 1100 4.9 5.60 80 1'78 0.1 0.10 0.15

'7 2'70 900 5.1 0.08 91 225 0.4 0.01 < 0.01

*Radium No. '7 Ore

~Metal balance data show this value to be in error

0"" '..J

Table 5

Build-Up of Materials - Second 6% Na2 C03 Cascade Leach

Stage Amount Vol, of Final U30e V2 05 No. Ore JA Leach NasC03 (gms. (gms. Leache Solution Cone. per per -- (gms.} (ml.) !%) liter) liter) stock Solution - - 6.00 2.8 23 1 400 1200 4. 76 4.3 32

2 354 975 5.53 5.7 43

3 281 845 4.8 4.85 53

4 238 715 5.88 0.99 70

-It Radium No. 7 Ore

!I> 1-' 22

by the different compositions of the leach liquors (i.e. less vanadium in the latter experiment).

Build-Up cf Vanadium and Impurities. The vanadium build-up behaves similarly to that in the 3 percent NazC03 cascade, increasing regularly throughout the cascade. The concentration of silica, P04 , and aluminum again remained relatively constant and at a low level.

Leaching with 9 Percent Na 2C03 Another portion of the stock solution was adjusted to 9 percent

NazC03 and used in the first stage of this cascade experiment. The procedure was identical with that used for the 6 percent Na2Co3 cascade. Uranium and Vanadium Build-Up. Again it was found that the uranium concentration increased regularly during the 1st and 2nd stages, reaching a value of 4.5 grams U30s per liter (Table 6). During the 3rd and 4th stages, the yellowish-green precipitate was again noted on the unwashed residues during filtration. However, upon washing the residue with hot water, this precipitate was dissolved and returned to the main leach liquor, thus causing the uranium concentration to increase quite normally.

For the 5th stage, the residue was not washed, and the liquor in equi­ librium with the ore was analyzed for uranium. It was found that the uranium concentration had decreased from 6.3 grams U30s per liter to the low value of 0.3 grams u3os per liter. Upon continuing for the 6th and 7th stages with no wash of the residue, the mother liquor was found to remain low in uranium (0.1 to 0.2 grams U30s per liter).

If we again base our conclusion on the physical observation of the Table 6

Build-Up o:f Material:;:. - 9\11. Na2C03 CasCJade Leach

Stage Amount Vol. o:f Final U308 V205 NaCl Al Po4= Si02 No. Ore'* Leach Na2 C03 ( gms. ( gms. ( gms. ( gms. ( gms. (gms. Leached (mls.) Cone. per per per pE!I" per pE!I" \ gms.) ( %) liter) liter) liter) liter) liter) liter)

Stock Solution - - 9.0 2.32 28.1 92.3

1 '700 2100 9.0 3.36 36 104 1.3 0.15 0.22

2 633 1900 9.0 4.54 45 122 0.9 0.06 0.12

3 56'7 1'700 10.2 5.4 54 132 0.6 0.05 0.12

4 500 1500 9.0 6.3 6'7 15'7 0.3 0.0'7 0.65

5 433 1300 10.0 0.30 93 210 0.4 0.0'7 0.12

6 280 840 9.0 0.11 12'7 200 0.4 0.51 0.52

7 166 500 10.0 0.16 163 210 0.6 0.12 0.68

*Radium No. '7 Ore

!\:1 C>l 24

point at '~ich the yellow precipitate formed during the leaching treatment, it may be said that the maximum build-up of uranium in a 9 percent Na2C03 liquor is limited to about 4.5 to 5.4 grams U308 per liter. This is about the same range as was found for the 6 percent Na2C03 liquor.

Summary

The concentration of uranium that may be attained in the carbonate leach liquors of salt-roasted ore is limited by the carbonate concen­ tration of the leach liquors and by the presence of high concentrations of sodium vanadate and sodium chloride. Maximum concentrations of about

3.5, 4.5-5.0, and 4.5-5.5 grams U30s per liter can be expected when using

Na 2Co3 solutions of 3, 6, and 9 percent, r~spectively. From the standpoint of plant operational costs, it would not be practical to raise the carbonate concentration from say 3 to 6 percent in order to gain the higher uranium solubility. The cost of H2S04 for each pound of uranium in the neutralization step (yellow-cake precipitation) would actually be greater in the latter case.

The concentration of silica, alumina, and phosphate in the cycling liquors were quite small and remained fairly constant in each stage. The vanadium built-up regularly from stage to stage and at one point reached a concentration of 160 grams V205 per liter. 25

CYCLIC LEACHING OF RAW ORES

As explained previously, certain of the Western ores are "normal" in uranium content but are low in vanadium and/or high in lime. These ores can not be treated economically by the salt-roasting process, but can be treated for their uranium content by direct leaching with sodium carbonate solutions.

Arrangements have been made at Monticello to treat such ores by direct leaching, and as a consequence, the build-ups of uranium, vanadium, and other materials have been studied for this system. Stockpile 7 and

9 ores are typical low vanadium materials (see Ore Samples) and were used in the following experiments. (Some work was also done with Indian

Reservation ore.)

~erimental Procedures

As in the tests with salt-roasted ore, each batch of raw ore was treated with two leach solutions. The first leach progressed in cascade fashion to determine the maximum uranium build-up. The second leach was made with fresh carbonate solution and served to strip the ore.

First Leach. For the first stage either sodium carbonate solution of the correct C03= concentration or a stock solution of approximately the same mineral concentration as the usual plant solution was reacted with the ore under reflux conditions for four hours. The slurry was filtered and the filtrate cooled, its volume measured, and the Co3= content determined and adjusted with anhydrous Na2C03. This solution was then reacted with more ore in the second stage, etc. The ratio of 26

weight of ore to volume of solution was maintained at 1 to 3 by decreasing the size of each succeeding ore batch to allow for the solution lost by retention on the ore and in sampling.

Second Leach. The residue from the first leach was reacted with fresh carbonate solution (added in ratio of one gram of ore per 2 mls. of solution) between 90-100° C for one hour. The samples were then filtered and washed and the filtrate and tailings analyzed for uranium and vanadium.

Leaching with 3 Percent Na2C03

Indian Reservation Ore. Preliminary experiments were made with

Indian Reservation ore because the uranium content of this material is high enough to allow a very rapid build-up of uranium in the recycled liquors1 • Also, the vanadium to uranium ratio is about the same as found in the typical low vanadium ores. Data from these tests are given in

Table 7.

It may be noted that the uranium concentration increased to about

4.7 grams U30s per liter after two stages and remained constant at this level. The vanadium concentration increased regularly as expected, though the final concentrations were stili low as compared to the tests with salt-roasted ore due to the smaller quantities of carbonate soluble vanadates in the raw material. The concentration of other constituents remained relatively constant at a low level.

1 For chemical composition of Indian Reservation ore see Report Y-499, page 9. -.:

----Table 7 Material Build-Up - 3% Na2 C03 Cascade of Raw Indian_Reservation Ore

Stage U30a Va05 Si02 po4"' Al Final No. ( gms. (gms. ( gms. (gms. ( gms, Na2C03 per per per per per Cone. - liter) liter) liter) liter) liter) _11) 1 3.7 3.8 0.08 0.11 0.03 2.54

2 4.7 7,1 0.09 0.20 0.08 2,63

3 4,7 10.0 0,16 0.13 0.25 2.99

4 4.7 13.4 0.08 0.10 0.09 2.87

"'.., 28

Stockpile 7 Ore. Raw stockpile 7 ore was subjected to a 14 stage treatment using fresh Na2C03 solution in the starting leach (Table 8).

The uranium concentration increased regularly for ten stages, attaining a concentration of 5.2 grams U308 per liter at this point, and remained constant at that level for the next four stages.

Considerable difficulty in filtration was encountered in the latter stages due to the presence of large concentrations of organic material.

It was noticed during the carbonate analyses that excessive foaming also occurred during neutralization of the solution.

Stockpile 9 Ore. Raw stockpile 9 ore was treated in a cascade fashion starting with a stock solution containing 1.8 grams U308 and 0.6 grams V205 per liter. The experiment was carried through 12 stages and results for the first 7 stages are presented in Table 9. Data for the subsequent stages are not reported because of uncertainty in the sample analyses. After 7 stages the concentration was 6.7 grams U308 per liter and the maximum build-up had not been attained.

Leaching with 5 Percent Na2C03

Stockpile 7 Ore. A nine stage cascade leach was made with No. 7 stockpile ore starting with a stock solution containing 1.9 grams U308 and 1.2 grams V205 per liter and maintaining the Na2C03 concentrations at

5 percent. The experimental results are presented in Table 10.

The uranium concentration was 9.2 grams U308 per liter at the end of the nine stages and the value for a maximum uranium build-up was not attained. The build-up of organic material caused difficulty in filtering 29

,,.- 'l'able 8

Material Build-Up - 3% NaaC03 Cascade of Raw ~tockpile No. 7 Ore

Stage Amt. Ore Vol. Leach Final Cone. U308 V205 No. Leached Solution NaeC03 (g./liter) (g./liter) -- ( gms.) (mls.) (~} 1 1000 3000 2.7 0.61 0.36

2 863 2650 2.8 1.21 0.71

3 734 2200 2.6 1.80 0.98

4 600 1800 2.9 2.48 1.40

5 466 1400 3.3 3.30 1. 79

6 333 1000 3.1 3.72 2.24

7 200 600 3.2 4.25 2.94

8 166 500 3.1 4.40 3.1

9 133 400 2.4 4.95 3.6

10 103 310 2.7 5.20 3.7

11 84 250 2.7 5.10 3.9

12 67 200 2.5 5.10 3.9

13 57 :).70 2.3 5.20 4.0

14 47 140 2.7 5.10 4.0 30

.. Table 9

Material Build-Up - 3% Na2C03 Cascade of Raw Stockpile No._~~

Stage Amt. Ore Volume Final UaOs V206 No. Leached Leach cone. ( g./li tar) (g./liter) ( gms.) Solution Na2co3 (mls.) (}<)

Stock Solution 3.0 1.77 0.64

1 1000 3000 2.8 2.48 0.90

2 800 2400 3.3 3.07 1.15 - 3 667 2000 3.1 3,78 1.40

4 516 1550 2.6 4.14 1.60

5 433 1300 3.0 4. 70 1.95 6 327 980 3,0 5,55 2.30

7 253 760 3.1 6.65 2.75 31

"7 Table 10

Material Build-Up - 5% Na2 C03 Cascade of Raw Stockpile No. 7 Ore

Stage Amt; Ore Vol. Leach Final U30e Va05 No. Leached Solution Cone. (g./liter) ( g,/11 ter) (gms.) ( mls. ) Na2 C03 (%)

Stock Solution 5,0 1.89 1.2

1 1000 3000 5,4 3,00 1.6

2 872 2615 4.9 3,54 1.9

3 733 2200 4.7 4.25 2.1

4 605 1815 4,7 4,95 2.3

5 545 1635 4.3 5.40 2.7

6 452 1355 4.5 6.3 2,9

7 353 1060 5,3 7.7 3.7

8 267 800 4,4 8.3 4.2

9 200 600 4.8 9.2 4.8 32

and excessive foaming was noticed during neutralization of the solution for co3 = analyses •

J- .) ( . Sunnnary

As expected, for any given_ carbonate concentration, the amount of

uranium that can be dissolved by the leach liquors is considerably greater

for raw ore than for the salt roasted calcines. Apparently due to vari-

ations in mineral composition, differences in uranium build-up may be

attained with different raw ores.

In some of the tests described above, the maximum build-up of uranium

was not attained, Further work was not performed, however, since it was

believed that the present information was sufficient to act as a plant

guide. For instance, the Monticello plant will probably use 5 percent

Na2C03 solution in the raw ore circuit for best extractions of the

uranium values, and the data above show that at least 9 grams U30a per

liter can be attained in the solution. It is unlikely that the Monticello

phy§i,g!l,'!, "'J?"r"ti@n of il!1f3 p'!.emi; r"ilh€1r iloon thrl §olu'I:!Hii;y of tl],g ur!l,ni1,11!!

miner!!,'!,§ in th€1 ~!l,rbon!!,'\i§ §©lui;ign, 33

ORGANIC CONTENT OF Na2C03 LEACH SOLUTIONS FROM RAW ORE

All or the carnotite ores treated (with the exception of Indian Reservation) contained a small amount of organic matter (probably humus) which is dissolved or dispersed by a sodium carbonate leach of the raw ore. In the case of Stockpile 7 ore, one gram of the material was extracted per 500 grams or ore treated. Fairly large amounts are present in the mill liquor after several recycle stages. The liquors became increasingly dirricult to filter and also (perhaps more important) extensive foaming occurred during neutral­ ization of the carbonate solutions with acid. Addition of hexanol alleviated the foaming somewhat and it is believed that the use of an alcohol of higher molecular weight will be more helprul1 •

Uranium in the leach liquors is apparently associated to some extent with the organic material. Since the material is readily coagu­ lated upon addition of sufficient acid, a small sample was separated in this manner and analyzed ror its uranium content. The analysis showed

400 ppm of uranium in the organic coagulate, but this amount represents only about 0.04 percent or the uranium which was contained in the con­ tacting leach liquor.

1 Unpublished data from this laboratory. 34

CARBONATE CONSUMPTION DURING LEACHING

Measurements have been made of the NazC03 which is consumed during the leaching of both salt-roasted and raw ores. These tests were carried out by leaching both types of ore with carbonate solution of varying con­ centrations and pulp density, and under reflux to maintain a constant volume. Carbonate analyses were made prior to and after the leaching operation. From the experimental results in Table 11, it may be observed that the NazC03 consumption was about one percent of the ore weight for both the raw and roasted samples.

In the countercurrent, plant leaching cycle, the ore will be in contact with about three times its weight of 5 percent NazC03 solution.

Therefore, during any particular leaching stage, the carbonate concen­ tration should not drop by more than a fraction of one percent.

ANALYSIS FOR CARBONATE IN THE MILL LIQUORS

Plant control of the carbonate concentration in the mill liquor requires a simple and rapid method of analysis. Usual mill practice has been to titrate the solutions with acid to a methyl orange end point.

This,method works fairly well on some leach solutions, but is not depend­ able when applied to solutions of high vanadium concentration.

Great accuracy can be obtained by the standard laboratory technique in which the COz is evolved, adsorbed, and weighed but the procedure is too involved and time-consuming for use in the plant.

To gain sufficient accuracy, as well as simplicity of operation, a 35

Table 11

Carbonate Consumption During Leachinif

Description of Ore Volume Na2 C0 3 Con­ (ml. per sumed 100 g,Ore) ( g./100 g. Ore~

Stockpile No. 7 Raw 3.23 300 1.56 3,23 200 1.66 3.23 100 1.42 5.00 300 1.35 1.00 300 1.32

Stockpile No. 9 Raw 3.23 300 1.05 3.23 200. 1.30 5.00 300 0.94 1.00 30.0 1.02

Radium No. 7 Raw 1.00 300 0.24 3.23 300 0.54 5.00 300 0.54

Uravan, Raw 5.00 300 0.51 3.23 300 0.51 1.00 300 1.26

Uravan, Roast 3.23 300 0.93 5.00 300 0..57

Stockpile No. 7 Roast 3,23 300 1.35 5.00 300 1.59

Radium No. 7 Roast 3,23 300 1.26 5.00 300 1.17

itThe rather small consumption values were arrived at by subtracting two comparatively large numbers. The results are, therefore, not highly accurate but should be reasonably close to the true values. 36

-· method has been set up in which the carbonate is determined by evolution of the C02 and. measurement of the gas volume1 • The final result may be

read from previously constructed graphs in which the_ percent Na2co3 is plotted against the gas volume (for different temperatures);

A typical graph calculated for conditions existing at Monticello,

is shown in Figure 1. A schematic diagram of the apparatus is shown in Figure 2, page 8, Y-481.

The accuracy of the method is quite good. A variation of as much

as ± 20 mm of Hg in the atmospheric pressure gives only about a 3 percent

change in analytical results. Temperature variations can cause greater

deviations in gas volume, but these errors can be minimized by using

charts calculated for various temperatures.

FILTERING AND SETTLING OF RAW ORE LEACH SLURRIES

Only a few experiments were made to test the effectiveness of certain

flocculating agents and filter aids on the settling and filtering of'the

raw ore leach slurries. The testing procedure was as follows: A slurry

was prepared by leaching Stockpile No.7 ore, -60 mesh, with 3 percent

Na 2co3, maintaining a pulp density of 25 percent. The pulp (250 ml) was then filtered under vacuum (15 in. Hg) through a No. 42 filter paper

supported on a Buchner funnel (10 sq. in. area) and its filtration time

measured. As a further indication of the resistance of the filter cake

formed, 50 ml. of wash water was added and the filtration time again

measured. The settling rate was determined by measuring the subsidence

1 A detailed description of this procedure may be found in Report Y-481, "Progress Report for Month of August- Carbonate Process". - II I I I I I I I J I I 6.0 32° F- 0° C S0° F - 10° C ·fi 68° F - 20° C ·.sl ,•; 86° F- 30° C .•. 5.0

4.0

~ 0.. ~ 3.0 +' .," ...0 ,. Q) p. 2.0

1.0

-'~!--'­ ·~-=.

•A n~ ~~ ~~ ., 0 ·~ "~

Gas Volume in Milliliters

Figure 1. Gas Volume vs. Percent Na2 Co3• Calculated on an Average Barometric Pressure of 580 mm of Hg for a \}l .....:j Sample Volume of 5 ml. 38

. ...:-... of the top of the settled solids in a graduated cylinder. The results

of these experiments are presented in Table 12.

Examination of the data indicates that only moderate improvements

were realized by using any of the agents tested. The addition of filter

paper pulp effected the greatest improvement' ili the filterability of the

slurry and slightly increased the settling rate. Numerous other floccu-

lating and surface active agents were tested with indifferent results.

CARBONATE LEACH - SAND SLIME SEPARATION - ACID LEACH

At the suggestion of Mr. F. H. McQuiston of the A.E.C. Raw Materials

Operation, a brief stuny was made of a process involving a carbonate

leach of raw ore, a sand-slime separation, and an acid leach of the sand

fraction.

Samples of two different ore batches, Uravan and Stockpile 9, were

leached with three percent Na (2 :1 ratio). The leach slurreis were 2co3 filtered and the filter, cake subjected to the wet concentration process

in order to separate the slimes (~200 mesh) from the sands, The sands

were then given ·a dilute HCl leach, Material balance figures were taken.

for U and V on all the steps and the over-all results are presented in

Table 13. t .. ' --.u> Table 12 '~~-

~f!~t o~_Fl~££~~ati~~~~~~!~-~~~~ilter-~id~_6n~Fil!~~abili!~ ::;-,· ~~~-Settling Rate ~!~~2~~-~lps

Filter-Aid Time to Increase Time to Increase Effect on Filter in Filter Pass 50 ml. in Washing the Slurry Rate Wash Water Rate Settling ~~12;.:1__ --~L-- _J.mi~.:.L_ _JJfL_ Rate None 4. 75 5.6

2% Celite 3.5 26 -(- Decreased

1/2% Celite 3.7 22 4.4 39 Decreased

1% Paper Pulp (filter-paper) 3.5 26 2.7 52 Increased

1/2% Paper Pulp (filter-paper) .3.5 26 4.0 29 Increased

1/2% Paper rulp (newspaper) ·3. 75 21 3.7 34 Increased

.05% Gelatin 4.2 ,:," 12 Slightly ,:'i:' .·''· ., . ,.,:.,, Decreased

.4% BaC12 • 2H2 0 4.45 6 5.5 2 Decreased

.1% Soluble Starch 4.0 16 Decreased

.2% CaO 4.6 3 5.1 9 Decreased

.1 Triton N-100 5.15 - 8 6.8 - 23 Decreased ;, .05% Tergitol No. 4 3.9 18 5:3 5 None ;5 Conditions: 1. 250 mls. of pulp (density 25%) were used for each test.

2. Vacuum ( 15" Hg) was applied to a Buchner funnel ( 10 sq. in. area) for filtration. • ?) 0.nnro r.f' .ctrlr~i+.i,re.<::! ~.n?.o he~C!e.r'1 rvn +_he. l•J.cdCl'h+ r.f' +.hP f'IT>t:> 40

Table 13 " . i .. ~~,, -~ -·

c·arbonate Leach - Sand Slime Separation - Acid Leach

~fo Increase in U Extr' d V Extr'd Extraction by by 3% by 3% U in V in Acid Leach of Exp. It"· Na2co 3 Na2C03 Sands Sands Sands No. Type of Ore (%) (%) (%) (%) u v

C-78 Stockpile 9 80 27 2 32 1.5 10

C-78 Uravan 82 28 3 36 1.5 10 ·.... .' ~~ ·.:~ Leach Conditions. Five-hundred grams ore ground to -20 mesh we.s leached two hours at 90-100°0 with 1000 ml. of three percent Na2co3 • The' sands were separated from the slimes by the wet concentration process. For the acid leach, 100 grams samples were leached with 200 ml. of five percent HCl for two hours at 80°C.

These data show that an acid leach of the sands increased the over-

all extraction of vanadium by only 10 percent for both ores, i.e., for

Stockpile 9 the increase was from 27 percent to 37 percent and for Uravan

from 28 to 38 percent. This is an insignificant increase in comparison

to an additional cost for subsequent processing of the acid leach liquors.

As for uranium, only an insignificant amount was in the sands after the

slime separation. "·.,! ... )!i'· 41

.- SOLUBILITY STUDIES OF SYNTHETIC AND NATURAL MINERALS IN CARBONATE SOLUTION

It was observed during the study o£ material build-up in salt roasted-

carbonate leach cascades that, £or any given carbonate concentration, the

uranium concentration built-up to a maximum £igure and then decreased

sharply as additional stages were run. This fact suggested that the solu-

bility of the complex sodium, vanadium, uranium compound, on which the

uranium concentration depended, was influenced by the "common ion" e£fect.

If such a supposition was correct, the solubility of the complex should

be affected in certain de£inite ways by changing the comcentration of the

• ions involved. Brie£ly, then, an increase in the sodium ion concentration

should result in a decrease in the solubility of the compound, an 'iltirease

in the carbonate concentration should increase the solubility by complex­ 'jo--: 0 ing the uranyl ion, thus removing it from the Na + , U 2 ++ , vo 3 = equ~-•

librium and, finally, an increase in the vanadate ion concentration

should decrease the solubility o£ the complex. The species· o£ vanadate

ion present, i.e., meta-, ortho-, pyro-, or poly- might also affect the

solubility, further increasing the complexity o£ the system.

To test the validity of the above supposition and to gain supple-

mental information for material build~up data obtained previously,

experiments were made.to determine the solubility of "synthetic carnotite"

(yellow cake), and also a natural uranium mineral, in sodium carbonate

solutions under various conditions.

Description of Materials. The "synthetic carnotite" was obtained by

precipitating the uranium from a carbonate leach solution by the controlled 42 ,.•.

·' addition of acid. The "yellow-cake" thus obtained contained 39.0 percent uranium and 10.8 percent vanadium.

The natural uranium mineral used in these experiments was obtained by

,., hand-picking the bright yellow mineral from a large sample of Indian Reser-

vation'-ore. The mineral assayed 15.1 percent uranium and 3.66 percent

Y.~~adium, and was first thought to be carnotite. Further analyses showed,

-.· :... _h9wever, a large deficiency of potassium for carnotite but sufficient .... "·'!-. calcium for tyuyamunite. The material is probably the latter mineral.' ·'

Experimental Procedure

In the procedure adopted for these experiments, a known amount (1.0

gram synthetic carnotite or 3.0 grams natural mineral) of the uranium

bearing material, together with known amounts of any material whose effect

on the solubility was to be determined, were placed in a two ounce bottle

and treated with 25 ml. of sodium carbonate solution. The slurry was

heated to 95-100°0 for 15 or 20 minutes to simulate plant leach conditions

and to approach equilibrium from a saturated solution. The volume was

readjusted to 25 ml by the addition of water, and the bottles tightly

capped. The samples were then agitated mechanically for two days, allowed

to settle for two more days and the clear, supernatant liquid sampled.

These operations were carried out at room temperature. Samples were taken

at lengthier time intervals to assure that equilibrium conditions were

established. The samples were analyzed for uranium, vanadium, and other

ions as desired. 43

Effect of Sodium Carbonate Concentration1

The influence of sodium carbonate concentration on the solubility

of yellovr cake and the natural uranium mineral is illustrated in Table 14 and Figure 2. It may be observed that from either of these uranium

compounds the equilibrium uranium concentration in solutions of equal

carbonate concentration is about the same. In a three percent Na2C03

solution, the uranium concentration reaches five to six grams U308 per liter. Up?n increasing the Na2C03 concentration to 12 percent, the uranium concentration is increased in a near· linear fashion to 13 to 14

It is evident that equilibrium conditions are· approached rather rapidly in these determinations -- the "A" samples, taken six days after mixing, are in excellent agreement with the "D" samples taken 70 days after mixing. The average analysis reported in Tables 14 and 15 and used

in constructing Figure 2 was obtained by averaging the results of the three separate samples.

Effect of Sodium Vanadate Concentration

The influence of sodium meta-vanadate concentration on the solubility

of the two compounds was determined by adding pure NaV03 to the system

in varying amounts, while holding the Na2C03 concentration consta~t. The data are contained in Table 15.

1 The values for sodium carbonate concentration were obtained by analyzing the solutions for total Co 2 evolved upon acidification and boiling, and converting to Na2C03. Thus, any carbonate associated •vith the uranyl ion in the solution is included in the value for percent Na2C03. .. .. , .. ~-;.-..;)-·~·- r~ ''· (,- ";,..~ ~::..-·r· Table 14 ::cu:: The Effect of Sodium Carbonate Concentration on Solubility

·of Synthetic Carnotite and Natural Uranium-Bearing Mineral "1i.:.-;

2 Ex:p. % Na2co3 "A" SamiJ.les(l) "B" Samples ·"D" Samples Ave.Analysis ( ) No. in Sol'n gms.U308 gms.VaOs gms.U308 gms.VaOs gms·. tr3o8 gms. V2 05 gms.U3o8 gms.V2 05 (by per per per per p Eil:' per per per analysis) -liter liter liter liter liter liter liter liter Synthetic Carnotite(3 )

V-767 2.5 5.7 3.6 4.9 3.4 5.3 3.0 5.3 3.3

V-768 5.5 9.2 5.5 8.7 5.1 10.0 4.9 9.3 5.2

V-713 11.7 14.6 6.7 14.9 6.7 14.4 6.7 14.6 6.7

( 3) Natural Mineral

V-773 2.4 4. 9 1.9 4.2 2.1 5.0 1.6 4.7 1.9

V-751 2.9 6.9 2.5 6.7 2.5 6.3 2.4 6.6 2.5

V-752 6.2 9.8 3.'7 9.8 3.3 9.1 3.3 9.6 3.4

V-'753 9.5 12.0 4.9 12.1 4.2 11.8 3.9 12.0 4.3

V-754 12.4 13.4 5.1 12.8 4.8 13.4 4.6 13.2 4.8

Remarks: ( 1) "A" samples were withdrawn 4 to 6 days after mixing the ingredients, "B"· .. samples 2 to 3 weeks after mixing, and "D" samples from 8 to 10 weeks after mixing.

(2) The average analyses were obtained by averaging the results of "A", "B", and "D" samples. ~ (3) Sample size - 1.0 gm. synthetic carnotite or 3.0 g. natural mineral to 25 mls. Na2 C0 3 solution (the synthetic carnotite contained 39.0% U and 10.8% Vd the natural mineral contained 15.1% U and 3.66% V). Experiments made at 23 C. "" Table 15

0 Effect of Sodium Vanadate Concentration on Solubility of S~thetic Carnotite and Natural ~ral (23 _.Sl

Exp. Navo 3 "/o Na2C03 "A" Sample "B" Sample "D" ~~~l_e ___ No. Added in Sol'n gms.U308 gms. Vz0 5 gms.u3o8 gms. V206 gms.U308 gms.V205 ( gm,) (by per per per per per per - analysis) liter liter liter liter liter liter Synthetic Carnotite

V-761 none 3.0 4.7 2,4 4.1 2.4 4.6 2.4

V-762 0.67 2.8 5.5 19.8 5.0 19.8 5.3 18.7

V-763 1.68 2.8 5.1 44.4 4.3 44.3 4.5 44.6

V-764 2.68 2.8 4.4 68.7 4.0 72.9 3.9 63.9

Natural Mineral

V-'773 none 2.4 4. 9 1.9 4.2 2,1 5.0 1.6

V-755 0.67 2.5 4.4 19.6 4.4 19.2 3.2 18.0

V-771 1.17 2.3 3,8 30.5 3.2 31.1 3,1 31.2

V-756 1.68 2,3 3.6 50.0 3.3 48.0 2.4 47.6

V-772 3.25 2.2 2.9 76.6 2,2 78.7 1.9 80,3

The remarks made under Table 14 apply also to these data (with the exception that .5 g. synthetic

carnotite was used instead of 1 g. ) • "'01 ......

12

1:1 ...,.....0 v .... 0"' Ul .... II I ../0 0 ...... ,...... 8

Q)... P... 0 ~ • ~ .~u I I 0 Natural. carnotite Mineral e Yellow Cake

0 4 8 12 16 'f, Na2 co3 in Solution . Figure2. Effect of Na2 co3 Concentration on Solubility ~ of' Synthetic and Natural Carnotites 47

It appears that equilibrium conditions are attained much more slowly

in systems containing added meta-vanadate. This is probably due. to slow reactions in which the meta-vanadate ion converts to more complex species of pQlyvanadates. It is probable that equilibrium conditions were not reached in the data reported, although the "D" samples were taken 70 days after mixing.

The sodium vanadate concentration served to exert only a slight effect on the solubility of yellow cake, even in concentrations as high as 70 grams V205 per liter. A considerably greater effect was exhibited

on the natural uranium mineral; the uranium concentration decreased quite regularly from a value of five grams U30s per liter to a value of two grams

U30s per liter, when the vanadium concentration was increased frolll 2.0 to

75 grams V205 per liter. The difference in behavior of the synthetic and natural materials is not understood at the present time.

The E!'fect of Sodium Chloride Concentration

The influence of sodium chloride on the solubility of synthetic

carnotite and the natural mineral in Na2C03 solution is shown by the data

in Table 16.

It is evident that the amount of uranium dissolved is practically

independent of sodium chloride concentration (up to a concentration of

12 percent NaCl). It ms.y be observed also that the system apparently reaches equilibrium conditions within a few days in the absence of large

concentrations of vanadium. -._)

----Table 16 Effect of Sodium Chloride Concentration on Solubility of Synthetic Carnotite and Natural Mineral

( 1) E:xp. % NaCl %Na2C03 "A" Samples "B" Samples "C" Samples · No. (by (by gm.U30a gm, V205 gm. U30a gm.Ve05 gm.U30e gm,V205 analysis) analysis) per per per per per per liter liter liter liter liter liter (2) -Natural Mineral-- V-773 o.o 2,43 4.86 1.93 4.18 2.08 4.27 2.08

V-774 3.8 2.44 5.31 1.93 4.27 2.08 4.18 2.08

V-775 7.6 2,55 5.26 1.93 4.57 1.93 4.37 2.08

V-776 ll.l 2.38 5.31 1.93 4.08 2.08 4.08 1.93

Synthetic Carnotitel 2 l

V-761 0.0 2.97 4.67 2.38 4.08 2.38 4.08 2.38

V-765 5.1 2.96 4. '72 2,38 4.37 2.38 4.22 2.38

V-766 9.5 2.88 4.86 2,23 4.18 2.23 4.42 2.38

V-714 18.6 2.15 3,73 2.68 3.73 2.53 3,83 2.68

Remarks: (1) "A" Samples withdrawn 4 to 6 days after mixing.

"B" Samples withdrawn 2 to 3 weeks after mixing.

"C" Samples withdrawn 4 to 5 weeks after mixing. ~ (2) Sample Size - 3.0 g. Natural Mineral or 0.5 g. Synthetic Carnotite to 25 ml. Na2C03 solution. 49

Ef'f'ect of' Sodium Vanadate in Combination with Sodium Chloride

The influence of' sodium vanadate in the absence of' sodium chloride, J and sodium chloride in the absence of' sodium vanadate was determined as

previously discussed. It was then felt that one series of' runs should be

made in which both these salts were present in varying amounts. These

data were obtained only on the natural mineral (Table 17).

It may be observed in experiments V-792, -3, -4, in which the con­

centrations of' NaCl and NaV03 were held constant, and the Na 2co3 concen­ tration varied f'rom 3 to 10 percent, that the uranium concentration in­

creased with carbonate concentration in much the same manner as was

obtained in the absence of' NaCl and NaV03, but to a lesser degree,

In experiments V-792, -5, -6, the weight ratio of' NaCl to NaV03

added was held constant, but the amount was increased regularly, and the

Na2co3 concentration was held constant at abcut 3 percent. It may be noted that the uranium concentration is decreased with the increase in

vanadate concentration in about the same manner as was obtained in the

absence of' NaCl (see Table 15). However, the uranium concentration does

not decrease regularly with time as was the case with the high vanadium

runs in the absence of' sodium chloride. The equilibrium conditions

appear to be reached more rapidly when sodium chloride is present.

Solubility of' Natural Mineral in Actual Leach Liquors

All systems discussed thus f'ar were prepared by mixing the natural

mineral with sodium carbonate solutions to which pure sodium metavanadate

and pure sodium chloride were added as desired. It was f'elt that some '

Table 17

Effect of Sodium Vanadate in Combination ;with Sodium Chloride on the Solubility of Natural Mineral(l)

2 Exp. NaV03 % Na2 C03 %NaCl "A" Sam~les( ) "B" Samples "C" Samples No. Added (by (by gms.U308 gms. VsOo gms.U308 gms.Vs05 gms.U3 0 8 gms.V2 06 ( gm.) analysis) analysis) per per per per per per liter ..- liter liter liter liter liter ' V-791 none 2.6 0.0 5.0 2.1 5.3 1.9 5.2 2.1

V-792 0.67 2.2 3.8 4.2 17.5 4.3 17.5 4.1 17.5

V-'793 0.67 5.3 3.6 8.4 19.2 9.4 18.6 9.4 18.9

'T-794 0.67 10.8 3.7 lLl 20.4 12.4 20.5 12.7 19.3 3 V-795( ) 1.34 2.4 7.4 4.2 33.9 4.4 32". 7 3.9 34.2 3 V-796( ) L91 3.0 lLO 4.1 30.6 4.4 32.? 4.2 28.3

----Remarks: (1) 3.0 gms. of natural mineral added to 25 ml. Na2co3 solution. ( 2) "A" samples were withdrawn 5 days after mixing the ingredients, "B" samples 15 days after mixing, and ''C" ·samples 36 days after mixing.

(3) Note in Experiments V-795 and 796 that the high NaCl concentration appears to limit the solubility of NaV03 • Had all the NaV0 3 gone into solution, the vanadium concentration should be about 40 and 60 gms .• V2 05 /liter, respectively.

Ul 0 51

data should be obtained by using solutions derived from actual leaching

of salt roasted ores, Therefore, a series of experiments were made in which actual leach liquors were treated with an excess of the natural mineral (Table 18),

It may be observed in experiment V-801 that a typical leach liquor containing 2 ,3 grams 1J308 per liter and 2 8 grams V2 05 per liter is capable

of dissolving additional uranium up to a concentration of 4.6 grams U308 per liter in a 4 percent sodium carbonate solution, Upon adjusting the

sodium carbonate concentration of this typical leach liquor to about 6 percent Na2C03 (experiment V-802), the uranium concentration was increased to 9 grams U308 per liter,

In other experiments (V-803, -4, -5, -6) in which leach liquors con-

taining from 3,3 to 4.5 grams U308 per liter were used, the uranium con-

centration was increased in a similar manner, the value in each case being primarily dependent on the sodium carbonate concentration.

SOLUBILITY STUDIES ON SODIUM URANYL TRICARBONATE

During the salt roasted-carbonate leach cascade, a greenish-yellow precipitate was observed to form in solutions of high uranium content,

(See section on Salt Roasted Ore), The fact that this precipitate

dissolved readily in water and evolved carbonate dioxide when treated with acid, suggested that it might be sodium uranyl tricarbonate, With this thought in mind, it was decided to briefly study the solubility of sodium uranyl tricarbonate in systems of similar complexity, --~ ...

Table 18

Solubility of Natural Mineral in Actual Leach Liquors

{2) E:x;p. Leach Liquor Used(l) %Na2C03 %NaCl No. Source gm.U30s gm.V205 %Na 2 C03 in Final in Final per per Solution Solution liter liter -- V-801 Stock 3olution 2,3 28 2.'7 3.1 9.2

V-802 Stock solution 2.3 28 2.'7 5,6 9.6

V-803 Cascade Exp.L-581 3.3 36 5,2 6.0 10.9

V-804 Cascade Exp.L-582 4.2 45 5.0 5.7 12.5

V-805 Cascade Exp.L-591 3.4 36 8.5 8.0 10.5

V-806 Cascade Exp.L-592 4.5 45 8.0 '7.5 12.3

-----Remarlcs: (1) 3,0 gm, Natural mineral added to 25 ml, solution. (2) In experiments V-801 and V-802, the stock solution was fortified with

dry Na2C03 to boost the Na2co 3 concentration to about 3 and 6%, respectively.

"'t\0 ~--..

Table 18 (continued}

( 3} Exp. ~A" S!).lllples "B" Samples "C" Samples No. gn;s.- U30e giii8:"-v2o6 · gms. U3 08 gms. V205 gms. U3 08 gms. V2 0 5 per per per per per per liter liter liter liter liter liter

V-801 4.6 24.2 4.1 25.3 4.0 24,8

V-802 8. 9 29.1 9.0 28.6 9.0 28.1

V-803 8.8 34.9 8.4 34.2 9.0 34,5

V-804 9.3 42.2 8.6 40.1 8.4 40.'7

V-805 10.5 34.9 10.2 32.'7 10.2 35.5

V-806 8.8 42.2 8.0 41.6 6.8 42.5

Remarks: ( 3} "A" samples were wi thdra¥m 4 days after mixing the ingredients,

"B" samples 14 days after mixing, and

"C" samples 35 days after mixing.

g: 54

Preparation of Sodium Uranyl Tricarbonate

The sodium uranyl tricarbonate (2 Na2co3 .uo2C03) was prepared by dissolving freshly precipitated diuranate in 3 percent sodium carbonate

solution, then evaporating to a small volume. The precipitate was further

purified by dissolving in water and reprecipitating by evaporation. The

chemical analyses showed 43.3 percent uranium, 16,95 percent sodium and

24.38 percent carbon dioxide. The theoretical percentage based on the

formula are 43.9 percent uranium, 16.97 percent sodium, and 24.54 percent

carbon dioxide.

Effect of Sodium Carbonate Concentration

The influence of sodium carbonate concentration on the solubility of

sodium uranyl carbonate is illustrated by experiments V-781, 2, and 3,

(Table 19). It is apparent that the solubility of this salt decreases

markedly with sodium carbonate concentration. About '70 grams U308 per

liter may be obtained in a water solution; this is reduced to about 50

grams U308 per liter in a 3 percent Na2C03 solution, and further reduced

to about 30 grams U308 per liter in a 6 percent Na2C03 solution. It is

of interest to mention that the data are in good agreement with that

obtained by investigators at Princeton University1

Effect of Sodium Vanadate Concentration

It may be observed from experiments V-784 and '785 that sodium meta-

vanadate in concentrations of 10 to 20 grams V205 per liter tends to ' 1 Furman, Munday, and Bruce, "The Solubility of Sodium Uranyl Carbonate in Water and in Solutions of Various Salts". ' .,0 ..,_

Table 19

Solubility Studies on Sodium Uranyl Tricarbonate

Expo Solvent Sodium NaV03 % Na2C03 % NaCl gm.V205 gm. U~Oa per liter No. (25 ml. Uranyl ( gm.) (by (by per "A" SalJ1Ple "B" Sample "C" Sample volume) Tricar- analysis) analysis) liter bonate ( gm.) --- V-781 Water 4.0 - 8.9 0.0 o.o 60.1 63,8 70.7 V-782 3% Na2C03 3,0 - 9,2 o.o 0.0 - 41.9 49.1 V-783 6% Na2C0 3 2.0 - 9.9 0.0 o.o 2?,5 28.6 31.5 V-784 3% Na2C0 3 2.0 Oo35 8.0 0.0 8.9 32,1 33.6 3502 V-785 3% Na2C0 3 2,0 0.67 7.5 o.o 18,0 31.3 31.8 36,5 V-786 3% Na2co3 2,0 - 5,3 7.9 o.o 8,4 6o7 8o9, V-811 water 4.0 - 9,0 o.o 0.0 60o0 69o8 V-812 3% Na2C0 3 3,0 - 9.0 0"0 0"0 39,3 49ol V-813 3% Na2C03 2,0 - 7o0 1.8 0.0 26o5 30o4 V-814 3% Na2C03 2oO - 5.8 3,9 0"0 21.2 19.0 V-815 3% Na2C03 2,0 - 4.6 7.9 0"0 7,5 8.4 V-816 3% Na2C0 3 2,0 - 3.4 15.2 o.o 2.1 2,4

Remarks: For V-781 Series - "A" samples were withdrawn 2 days after mixing, "B" samples 20 days, and "C" samples 50 days after mixing.

For V-811 Series - "A" samples were withdrawn 8 days after mixing, and the "B" samples 30 days after mixing.

"' 56

decrease the solubility in three percent Na2C03 solution from about 50

grams to about 35 grams U308 per liter. Further data on the effect of

sodium vanadate were not obtained, since it appeared that its effect was much less than that of sodium chloride.

Effect of Sodium Chloride Concentration

The very pronounced effect of sodium chloride concentration on the

solubility of sodium uranyl carbonate as shown by the preliminary

experiment V-786 prompted further study of this phenomenon. A series of

experiments was conducted in which the NaCl concentration in three percent

Na2C03 solution was varied from two percent to 15 percent. As shown by experiments V-812 through V-816, the solubility of sodium uranyl carbonate

decreases regularly with NaCl concentration. In Figure 3 this effect is

illustrated by plotting the uranium concentration against the molarity

of the solution in NaCl. Included in this plot are the two experiments

on NaV03 effect (V-784-5). Since the NaV03 data appear to fall on the

curve for the NaCl effect, it may be speculated that the vanadate ion has no particular effect on the solubility of sodium uranyl carbonate in the range of vanadate concentration studied. It would appear that the sodium

ion, the only ion common to the salt being studied, exerts the most

important effect. The differences observed in the data from studies of the solubilities of yellow cake, a natural mineral, and sodium uranyl tricarbonate are quite interesting. More work on these systems may be

conducted in the fu·bure as a part of another program at Y-12, \/ ••

50 )

;::• .....0 +' r-i \ .."'0 40 .... 0,.. CD ' ...... ri,.. 30 ~ CD Po \ 0., "' p I • 20 &, I 0 NaCl Added I "' • NaVela Added

10 I ' ~ I '-a.__ I -- ....,- -- ~ 1..------'------0 0.4 0,8 1.2 l.6 2,0 2.4 2.8 Molarity of Solution in NaCl or NaVOa ~

Figure 3 • Effect of NaCl and NaVOa Concentration on Solubility of Sodi~~ Uranyl Carbonate in ~ Napco~ Solution. 58

RECYCLE OF EFFLUENTS FROM YELLOW-CAKE PRECIPITATION • As pointed out in the "Introduction", consideration has been given

to the recycle of the filtrates from the yellow-cake precipitation (from

raw ore leaching) in order to build up vanadium in the mill liquors and

save water in the processing. Since the yellow-cake precipitation con­

sists simply of H2S04 addition to the carbonate solutions, the effluent

liquors are characterized by high concentrations of Na2S04.

Effect of Na2S04 On Solubility of Natural Mineral

The influence of NazS04 on the solubility of natural mineral in

three and six percent sodium carbonate solutions is depicted by the

results in Table 20. Increasing concentrations of Na2S04 in a six per­

cent Na2C03 solution seemed to decrease the solubility of the material

whereas the same was not the case with three percent Na2C03. None of the

mixtures were proved to have reached a state of equilibrium, however, so

rigorous conclusions cannot be drawn. Contrary to the tests with NaCl

(see previous data), the presence of Na2S04 seemed to retard the speed

with which equilibrium conditions were approached.

Effect of Na2S04 on Raw Ore Leaching

In the direct leaching tests, varying amounts of Na2S04 were added

to a previously prepared stock solution containing 3.8 grams U308 per

• liter and 1.5 grams VzOs per liter. These 1 iquors were then used to

leach in cascade fashion two batches of raw Stockpile 7 oreo Samples

were taken for analysis at each stage and these data are presented in

Table 21. - :; • ""

Table 20

Effect of Na 2 SO~ on Solubility of Natural Miner~l (23°C.)

E:xp. Na2 S04 % Na2 C0 3 "A" Sample "B'' Sample "C" Sample No, Added (by gms.u3 o8 gms. V2 05 · gms.U3 02 gms, V20 5 gms.U3 08 gms.Vz05 (%) analysis) per per per per per per --liter liter liter liter liter liter 539 8 5.88 2,83 1.60 4,36 1. 79 10.7 3,75

540 16 6.11 2.24 1,60 3,42 1.60

541 24 5,86 2,12 1.10 3,18 1,48 5,1 2,12

542 8 2,99 1.18 0.65 1.65 0.75 2,48 1.15

543 16 2.99 1.42 0,57 2,83 0.91 4,25 1.08

544 24 2,57 1.30 0.55 2,48 0.66 4.0 1.27

Remarks: (1) 5 grams mineral added in each case (39.0% U, 10.8% V).

( 2) "A" sample withdrawn 6 days after mixing,

"B" sample 13 days, and

"O" sample 49 days.

1B ~ ...... ;>

Table 21

The Effect of Sodium Sulfate on Material Build-Up in Raw Ore Carbonate Leaches

Exp. % Na2S04 % Na2C03 1st Cycle 2nd Cycle No. 1st Leach Overall 1st Leach· --overan gms.U:30e gms.V206 'f. Ext~ gms.U:30e gms. V206 %Ext.* per per per per - liter liter liter liter C-82-1 0 3.5 4.2 1.4 85 4.2 1.9 83

C-82-2 5 3.5 4.2 1.5 92 5.2 1.9 87

C-82-3 10 3.5 4.3 1.9 93 4.5 1.9 88

C-82-4 18 3.5 4.1 1.5 93 4.5 1.9 87

C-82-5 25 3.5 4.3 1.5 92 4.6 1.9 90

Stock solution contained 3.8 g. U:3o8 per liter and 1.5 g. v2 o6 pet' liter, 0% Na2so4 •

;ifOverall extractions were obtained from material balance data.

0> q 61

Na2S04 apparently does not seriously erfeot the maximum uranium

concentration obtainable with a three percent Na2C03 leach solution. A

24 percent Na2S04 leach attained a value or 4.6 grams UsOs per liter

while previous data indicated a maximum or 5.2 grams u3o8 per liter. Further data on the erfect or Na2S04 on the rate of solubility and

maximum solubility should be obtained, however, before such a process

is tried in the plant.

ACKNOWLEDGMENTS

A large number or the experiments were performed by Dr. V. L. Saine,

Mr. J. M. Schmitt, Mr. D. J. Crouse, and Mr. F. J. Hurst.

Most of the analytical work was perrormed by the Technical Service

Laboratory under the supervision or Mr. C. D. Susana.

The authors also wish to acknowledge the extensive consultant

service of Mr. M. G. McGrath of the A .E .C., Colorado Raw Material

Operations and Mr. John White or the Galagher Company, Salt Lake City,

Utah.

I 62

1

' ------APPE1..1DIX A

Simpli!~~~owsheet ~~~~~st~_£arbonate-Leach Process

ORE CRUSHING ll FINE ORE BIN I t i l SALT ROASTING I COlLECTOR dust ~ MULTIPLE HEARTH NaCl ROASTER l QUENCH TANK ~ LEACHING AND WASHING CIRCUIT Sand Tailings to waste ~ YELLOW CAKE PRECIPITATION Yellow Cake to ....------Refinery l RED CAKE PRECIPITATION Filtrate to ~ Waste ~ REVERB. FUSION FURNACE - Black+ Oxide (Fused) 63

----APPENDIX B

of the Carbonate Process Studies

1. Monthly Progress Report tor April, 1949. Y-398

2. Monthly Progress Report tor May, 1949 Y-415 I 3. Monthly Progress Report tor June, 1949 .. •. Y-441 4. Monthly Progress Report ror July, 1949 Y-460

5. Monthly Progress Report tor August, 1949 Y-481

6. •onthly Progress Report tor September, 1949 :(-498

. '