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Патент USA US3034866

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3,634,855
rice
Patented May 15, v1962.
2.
1
lie-leached. During the subsequent precipitation of the
3,034,856
pregnant leach solution with caustic, some of the vanadi- .
PURIFICATIUN 0F SODIUM DIURANATE
um values present in the ‘pregnant liquor will ‘also ‘be pre
Robert E. Fteusser, llartlesville, (91512., assignor to Phillips
l’etroleum ‘Company, a corporation or’ Delaware
cipitated together with the ‘uranium values, for exam=
N0 Drawing. Filed Dec. 31, 1959, Ser. No. 863,0?3
ple 40 to 60% of the V205 present in the pregnant liquor
will precipitate with the yellow cake. In fact, up to 85%
6 Claims.
(Cl. 23—14.5)
'
of the vanadium extracted vfrom the ore may turn up in
This invention relates to the recovery of uranium from
uranium-bearing materials, Such as coil-‘mite and other
the yellow cake- .produced. The other metals and non
metals, present as impurities in the pregnant liquor will
also tend to be precipitated with the yellow cake or be
come occluded therein. Thus, an impure yellow cake
ores, by the carbonate leaching process. More particu
larly, it relates to the puri?cation of sodium diuranate
(“yellow cake”) obtaining by the carbonate leaching proc—
product is often obtained, and, for example, the vanadi
um content of the yellow cakewill ‘often be considerable,
ess.
An important and widely used hydromet-allurgical “proc
e.g., 2 to 7 weight percent.
ess for recovering uranium from uranium-bearing ma
terials is the “carbonate leaching process.” Thisleach
ing process has been applied to both primary and second
at‘; uranium mineral deposits, such as pitchblende, cof
?nite, carnotite, uraninite, tyuyamunite, and the like, etc.,
but the process is especially useful when leaching ore of
high carbonate content. It is this leaching process that
diii'lcult. The Atomic Energy Commission, the purchaser
of all the yellow cake produced in this country, penalizes
producers of yellow cake if the purity of the yellow cake
is the concern of the subject invention. .
The carbonate leaching process for extracting uranium
is not as high as desirable, and it will even refuse to pur
chase such impure yellow cake. In the case of the vana
values from uranium-bearing materials comprises con
acting crushed uranium-bearing ore with hot aqueous al
kaline carbonate-bicarbonate leaching solution and, where
the material contains uranium» in the quadrivalent state,
an oxidizing agent such as ‘permanganate or air, to form
a slurry of insoluble leached pulp and pregnant leach so
,
The presence of these other metals-and nonmetals in
the yellow cake, especially the presence of vanadium, is
undesirable because it renders the subsequent conversion
of the yellow cake intouranium metal, or into other ura
— niu'm compounds such as the hexachloride, much more
dium impurity, the Atomic Energy Commission may
exact a penalty if the vanadium’ content, expressed as,
' 39
lution containing the stable, soluble uranyl tricarbonate
complex anion. The pregnant leach solution is then sep
arated from the tailings, for example by multi-stage vacu
um ?ltration, and the uranium values are precipitated
from clari?ed pregnant leach solution, for example by the
addition of an excess of sodium hydroxide. The precipi
tate-containing leach solution is thickened and the precip
V205, exceeds 2 Weight percent of the ‘U308v in the yellow
cake, or the AEC may refuse to buy the yellow cake if
p content is excessive. In ‘many
‘the vanadium contaminant
‘cases, the vanadium content or the yellow cake may be as
high as 6 or 7'p'ercent'. Thus, there has arisen a need
for an improved method for producing a purer yellow
cake, especially-a yellow cake having a relatively low
vanadium content.
>
~
Accordingly, an object of this invention is to'improve
the recovery of uranium from uranium-bearing materials. 7» '
itate, sodium diuranate (called “yellow cake”), is then sep 4.0 Another object is to provide'an improved method for re-v '
arated, for example by ?ltration, from the carbonate so
covering uranium values from uranium ores treated ac
lution. The carbonate solution recovered from the thick
cording to the carbonate leaching process. Another ob
ening operation is commonly called “barren liquor” and
ject
is to purify the sodium diuranate, yellow cake, ob
it is regenerated by passing carbon dioxide through it, us
tained by the carbonate leaching process for uranium ores.
ing, for example, a supply of ‘waste carbon dioxide, such
Another object is to‘ substantially remove metals, such as
as flue gas. The recarbonated barren liquor is then used
vanadium, zirconium, iron, titanium, barium, aluminum,
as a wash liquor in the separation of the tailings from the
antimony
and. cobalt, and such nonmetallic elements as
pregnant leach solution and then recycled to the process
phosphorous'and
silicon, commonly associated with ura
for reuse as leaching solution. The ?ltered yellow cake
nium-bearing.materials, from yellow cake produced -by
is then generally dried, packaged, and sold to the Atomic 50; the carbonate leaching process.
Another object is ,to I
Energy Commission.
.
lower,v the vanadium content of yellow cake produced ac
Many other metals, especially vanadium, are ‘common
ly associated with uranium in uranium-beating‘ ores. .
cording to the carbonate leaching process.g'-Other ‘ob
Other metals associated with uranium-bearing ores include 55 jects and advantages of this invention willbecome appar
out to those skilled in the art, without departing fro'm’the
iron, titanium, barium, aluminum, antimony, cobalt; non
metal ic elements, such as phosphorous and silicon, are
also commonly associated with uranium-bearing ores.
scope and spirit of this invention, from the following dis
cussion and appended claims.
' ‘
Brie?y stated, the subject‘ invention provides av method
These other metals and nonmetals, especially vanadium,
are commonly extracted with the uranium values in the 60 Iior purifying sodium diuranate by contacting the same.
‘with sulfamic acid (HSO3NH2), precipitating thesoluble
uranium values present ‘in the resulting‘sulfamic’acid so;
carbonate leaching step and gradually build up in concen
tration in the process. For example, a typical second—
ary uranium ore such as coi?nite will containabout 0.25%
, lution as sodiumdiuranate, and recovering the latter. 'The
U308 and 0.1% V205, and during the leaching step about
. yellowxcake containing v‘thesodium diura'nate is contacted
10 to 20% of the vanadium ‘present in the ore ‘will also
with aqueous sulfami'c acid solution and the residue o'r '
8,034,856
3
4
precipitate of complex and unknown structure subsequent
ly is separated, this residue containing a higher percentage
of the metallic and nonmetallic impurities than the orig
inal or initial yellow cake produced by the carbonate
leaching process. After the residue is separated from the
sulfamic acid solution, the dissolved uranium values in
the solution are recovered therefrom by reprecipitation
the aqueous solution of sulfamic acid will be in the range
of about 20 and 100° C.
‘
The following detailed discussion presents a preferred
set of conditions used in obtaining the objects and advan
tages of this invention.
In purifying sodium diuranate according to the pre
ferred operation of this invention, the yellow cake is
mixed with aqueous sulfamic acid, thus causing at least
a' portion of the yellow cake to be dissolved. The tem
The smaller the amount of sulfamic acid used accord
ing to this invention, the greater the amount of resulting 10 perature of this treatment depends on the desired purity
as sodium diuranate.
residue, and the greater the purity of the reprecipitated
yellow cake.
However, when using a smaller amount of
the sulfamic acid, the subsequent yield of reprecipitated
of the subsequently reprecipitated yellow cake, but in a
typical run, the yellow cake and acid are mixed together
at room temperature (approximately 25° C.) and the re
sulting mixture is heated to the boiling point (approxi
yellow cake is lower than when using a larger amount of
sulfamic acid. In some cases, this lower yield of yellow 15 mately 100° C.). The solution is maintained at this
cake will be desired, especially where a higher purity yel
temperature or some other chosen temperature for at
low cake is required.
least 2 minutes, and generally in the range of 30 minutes
to 3 hours. At the end of the reaction time, the solution
In other cases, a less pure, higher
yield of reprecipitated yellow cake can be produced by
is cooled to ambient temperature and ?ltered to remove
using a larger amount of sulfamic acid, this treatment pro
ducing less residue. But a high yield of reprecipitated 20 the residue. The soluble uranium values remain in solu
yellow cake may be desired since even in this case the re
precipitated yellow cake will contain a lower content of
tion in the ?ltrate, and these uranium values are re
covered from this solution, for example, by raising the pH
thereof from about 8.0 to about 9.5 with the addition
the metallic and noumetallic impurities than the orig
of a basic material. Any of the alkali metal hydroxides
inal or initial yellow cake produced by the carbonate
leaching process, i.e., below the penalty level-in the case 25 can be employed to raise this pH and cause the subse
quent precipitation of the soluble ‘uranium values, but it
of the vanadium impurity, below 2 weight percent, based
is preferred to utilize an ‘alkali metal hydroxide which
on the U308 content. When smaller volumes of less con
corresponds to the uranate being puri?ed. Thus, if
centrated sulfamic acid are employed, only a portion of
sodium diuranate is being puri?ed, aqueous sodium hy
the yellow cake is dissolved, leaving an impure residue
behind. If larger amounts of sulfamic acid are em 30 drox-ide, having a concentration of about 10 to 25 weight
percent, will be utilized to precipitate the soluble uranium
ployed, all of the yellow cake goes into solution, after
values. After reprecipitating the sodium diuran'ate, the
which a residue forms and settles out. In either case, the
sulfamic acid contains an extremely low amount of
residue contains a higher percentage of the original im
uranium values, usually less than 0.002 gram per liter of
purities than the yellow cake which is subsequently pre
U308; further treatment for the recovery of these low
cipitated from solution.
uranium values is generally not practical. The aqueous
The amount of aqueous sulfamic acid used according
solution of sodium sulfamate can then be reacidi?ed with
to this invention generally will be an amount sufficient to
sulfuric acid to recover the sulfamic acid for reuse in the
render the reprecipitated yellow cake purer than the orig
process.
inal yellow cake. Generally, the weight ratio of sul
The process of the present invention can be carried out
famic acid to the initial yellow cake will be within the 40
either batchwise or continuously, although in large scale
range of 0.2 and 1.75, preferably within the range of 0.7
commercial plants it is most likely that a continuous
and 1.6. As mentioned above, the degree of puri?cation
method would be employed. The residues resulting from
will determine, to a certain degree, the optimum weight
this sulfamic acid treatment can be treated by a‘variety
ratio of the sulfamic acid to the yellow cake. If it is de
of methods for the recovery of the various metallic values
sired to remove as much of the impurities as possible,
especially the vanadium impurity, from the yellow cake,
therefrom, or they can be discarded.
.
I
The following examples further illustrate the objects
the weight ratio will preferably be in the lower end of
and advantages of this invention, but it should be under
the above range. If it is desired to produce a yellow
cake which contains as much impurities as possible with 50 stood that the various amounts, conditions, etc., expressed
in these examples are merely illustrative and should not
out going over the penalty levels, ‘then the ratio in the
be construed so as to unduly limit this invention.
upper part of the above range will be utilized. If the
optimum value of minimum residue and greatest purity
EXAMPLE I
of the yellow cake is desired, a weight ratio within the
Two
impure
yellow
cake samples, ‘were obtained from
preferred range of from 0.8 to 1.0 parts by weight of 55
a commercial carbonate leaching plant and treated with
sulfamic acid per part by weight of yellow cake is em
various concentrations of sulfamic acid, according to the
ployed.
practice of this invention. In each of these runs, 15 g.
The sulfamic acid used in this invention is an'aqueous
of the yellow cake were mixed with 500 ml. of aqueous
solution of sulfamic acid containing from 0.5 to 25 weight
sulfamic acid. The mixtures were heated to 90—l00° 0.,
percent acid; thus, the volume of acid per weight or vol 60 except in one run where the mixture was maintained at
ume of yellow cake will be determined by theacid con
room temperature (approximately 25 °. C.), and held at
centration and the weight ratio of sulfamic acid to yellow
this temperature for one hour with agitation. Each mix~
cake which is to be employed. As described above, the
ture was then cooled to room temperature ‘and the resi
weight ratio of sulfamic acid to yellow cake will be de
due which formed was ?ltered off. The ?ltrate was then
termined by the desired purity of the yellow cake and 65 treated to reprecipitate the dissolved yellow cake by add
the amount of residue which is desired to be obtained.
ing aqueous sodium hydroxide until pH 8.0-9.5 was
The temperature of the sulfamic acid treatment will
reached. The residue and the reprecipitated yellow cake
,was then analyzed. The barren liquors after reprecipita
also determine, to a certain degree, the purity of the re
tion were extremely low in uranium content (less than
sulting repreoipitated yellow cake. Higher temperatures
generally result in a greater weight percent of residue
0.002 g./l. U303) in all runs. vl'n all these runs, the
yellow cake dissolved almost completely as soon'as the '
formed but also produce a more pure yellow cake; con
sulfamic acid solution was heated. The residue did not
versely, colder temperatures will produce less residue
appear until the material was heated. The results of this
and a more impure yellow cake product. Generally, the
temperature at which the yellow cake is contacted with 75 investigation are set forth in Table I.
Table I
Composition of
yellow cake sample
Run N0.
Wt.
ratio of
Aq.
pure
sulfamio
Residue
Composition of
reppted. yellow cake
sulfamio
acid to
acid
cone,
Wt.
percent
Wt.
percent
Wt.
percent
percent
Wt.
yellow
calc. wt.
of orig.
of orig.
of orig.
V205
percent
U308
cake
sample
percent
yellow
cake
U308 in V205 in
residue residue
0. 09
95. 2
74. 5
Wt.
78. 03
78.03
0. 03
1. 80
0.27
1.1
1. 80
1. 80
78. 03
0. 87
2. 6
l6. 9
11.5
1. 80
78. 03
1.0
2. 96
1. 80
78.03
1.0
2. 96
NaaVOr N azUzov
calc. as
calc. as
Wt.
percent
V205
Wt.
percent
U303
5.0
1. 80
78. 03
2. 0
5. 84
0. 5
2. 86
2. 86
77. 63
77. 63
0. 5
0. 75
1. 49
2. 23
45. 1
20. 7
2. 86
2. 86
77. 63
77.63
l. 25
1. 50
3. 69
4. 42
7. 1
4. 8
1 In this run the suliamic acid solution was maintained at room temperature (approx. 25" O.) for one hour.
~
The data in Table I show that the reprecipitated yel .20 dium content of less than about 2 weight percent V205,
based onthe weight percent U308.
.. ~ .
low cake, prepared according ‘to this invention, has a
5. A method for purifying yellow cake comprising so
higher purity as compared to the original yellow cake.
The data also show that greater amounts of sulfamic. - dium diuranate obtained by extracting uranium values
from uranium-bearing materials according to the carbo- ;
acid used in treating the original yellow cake result in
higher yields of reprecipitated yellow cake, and, con
25
nate leaching process,’ which method comprises treating,
said yellow cake with ‘an 0.5 to 25 weight percent aque
ous sulfamic acid solution, the weight ratio of sulfamic
acid to yellow cake being in the range of about 0.7 to 1.6,
The residues from run numbers 4, 5, and 6, of Table I
the temperature of said treatment being the range of
were analyzed by semi-quantitative spectrographic meth
ods. The results of these analyses are reported in 30 about 20 to 100° C., ?ltering the resulting residue from
versely, that lower amounts of sulfamic acid result in
lower yields of purer reprecipitated yellow cake.
Table II.
the resulting sulfamic acid solution, treating the resulting
Table II
Element in Residue, Wt. percent
Run No.
U
v
P
Zr
Fe
Cu
Pb
L1
Sr
Ba
5040
are
5
0.22
3.5
10
>5
0.22
1.2
3.0
__________________ ._
......... _.
1.2
0.078
1.2
0. 37
2.5
0.034
0.87
50
5
5
1. s
2. 5
0. 039 ........ ..
0. 18
0. 53
0. 034
The data in Table II show that the sulfarnic acid treat
ment ‘of yellow cake, according to the practice of this in
A1
so
00
____________________________ __
0. 4s
Trace
________ _.
0.62
0
0. 22
?ltered sulfamic, acid solution with an amount of aqueous
sodium hydroxide 'su?‘icient to raise the pH of said. sul
famic acid solution to a pH in the range of about 8 to 9.5
vention, serves to remove other metallic and nonmetallic,
impurities in addition to ‘removing vanadium.
’ 45 and precipitate the uranium values present in said sul
famic acid solution as sodium diuranate, and ?ltering the
Various modi?cations vand alterations of this invention
resulting neutralized solution to recover puri?ed sodium ‘
will become apparent to those skilled in the art from the
diuranate therefrom.
.
foregoing discussion, and it should be understood that
6. A method for purifying yellow cake comprising
the subject invention is not to be unduly limited to the
50 sodium diuranate obtained by extracting uranium values
examples set forth above for illustrative purposes.
I claim:
from uranium-bearing materials according to the car
bonate leaching process, which method comprises treat
ing said yellow cake with aqueous sulfamic acid, clarify
sodium diuranate obtained by extracting uranium values
ing the resulting sulfamic acid solution, and recovering
from uranium-bearing materials according to the car
bonate leaching process, which method comprises treat 55 pure yellow cake from the resulting clari?ed sulfamic
acid solution. ing said yellow cake with aqueous sulfamic acid in an
1. A method for purifying yellow cake comprising
1p9-.—“).
amount suf?cient to dissolve at least a portion of said
sodium diuranate, separating the resulting residue from
the resulting sulfarnic acid solution, neutralizing the ‘re
sulting separated sulfamic acid solution with aqueous 60
sodium hydroxide to precipitate the uranium values pres
ent in said su'lfamic acid solution as sodium diuranate,
and recovering the resulting precipitate vfrom the resulting
neutralized solution.
2. The method according to claim 1 wherein the weight
ratio of sulfarnic acid to yellow cake is in the range of
about 0.2 and 1.75.
References Cited in the ?le of this patent
UNITED STATES PATENTS
'
2,813,003
Thunaes ________ __-____ Nov. 12, 1957
2,849,277
Thomas ____________ __' \Aug. 26, 1958
2,874,025
2,900,229
Moore ___________ __.-____ Feb. 17, 1959
McClainc __________ __ Aug. 18, 1959
OTHER REFERENCES
AEC Document TI-D—7543, pages 45-68, May 20-25,
1957.
3. The method according to claim 1 wherein the weight
Harrington et al.: “Uranium Production Technology,”
ratio of sulfamic acid to yellow cake is in the range of
page
1-37 (1959). (Copy in Sci. Library, Rcd. Feb. 16,
70
about 0.8 and 1.
1960.)
.
4. The method according to claim 1 wherein the
Bruce et al.: “Process Chemistry,” page285 (1956),
amount of sulfamic acid used is su?'icient to yield a
Pergamon Press, (Copy in Sci. Library.)
reprecipitated sodium diuranate ‘product having a vana
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