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Патент USA US3092459

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HQQ
1
2
3,092,449
bonates. According to another embodiment of this in
vention the carbonates or hydroxides are dissolved in
sulfuric acid, the pH of the solution is adjusted to be
PROCESS FOR THE RECDVERY 0F EUROPIUM
FROM LOW GRADE EUROPlUM MTXTURES
‘WITH OTHER
3,092,449
Patented June 4, 1963
EARTHS
_
tween 1 and 2.5, the solution is reduced With zinc dust
and again 5—10% of the rare earths are precipitated in
the form of double alkali sulfates by addition of an
alkali sulfate. The'process can be repeated until the de
sired grade of europium enrichment in the rare earths
double alkali sulfates is obtained.
Kazimierz Jozef Bl‘il, Rua 4, 89 Jardim Elvira, Eianto
Amaro, and Jose Behrnoiras Madjar, Av. Adolfo Pin
heiro, 4036 Bloco G, Apto. 12‘, both of Sao Paulo,
Brazil
No Drawing. Filed July 13, 1959, Ser. No. 826,495
Claims priority, application Brazil July 22, 1958
6 Claims. (Cl. 23—22)
The presence of heavy metals, like copper and lead,
in the original rare earths sulfate solution may render
The trivalent europium ion can be easily reduced to
difficult or even prevent the reduction of europium.
the bivalent state whose chemical properties are radically
These undesirable materials, if present, should be re
different from the trivalent rare earth ions. Methods
moved before performing the reduction of europium.
of separation and puri?cation of europium salts are, in 15 This can be realized by pretreating the rare earths sulfate
general, based upon that difference and on the relative
solution With a small amount of zinc dust until the inter
stability of the europous ion. For instance, europium
can be reduced and then precipitated as europous sulfate,
10
fering metals deposit upon the zinc. The solution now
free from heavy metals is decanted from the metallic
the solubility of which is much lower than the solubility
residue and submitted to the process of the present in
of the trivalent rare earth sulfates. This method, how 20 vention.
ever, cannot be applied directly to low grade europium
As an illustrative embodiment of a manner in which
mixtures with other rare earths as naturally occurring,
the invention may 'be practiced, the following examples
are presented.
for instance in monazite; the solubility of the europous
sulfate is not low enough to allow in such a case direct
Example I
precipitation of europous sulfate. It is known that the 25
46
kg.
of
oxides
of
rare
earths, obtained by an alkaline
sulfates of some bivalent metals, like strontium and
attack of monazite and containing about ‘0.05% of europi
barium, are isomorphic with europous sulfate and that
europous sulfate can be coprecipitated with a sulfate of
um oxide, are dissolved in 2 M sulfuric acid and the
solution is diluted to a volume of 700 liters; free acidity
process presents serious technical and economical di?i 30 is adjusted to 0.08 N. 350 g. of zinc dust are added
and the suspension is agitated for two hours. The solu
culties during the recovery of the coprecipitated europous
tion,
now free of heavy metals, is decanted from the
sulfate. Furthermore the yield of this coprecipitation
metallic residue, and placed in a closed, enamelled vesselv
process rarely exceeds 90%.
with a capacity of 800 liters, equipped with an agitator.
We found, and this is the principal object of this in—
vention, that europous sulfate can be coprecipitated from 35 Carbon dioxide is allowed to bubble through the solution
for half an hour in order to remove oxygen; 2000 g.
sulfate solutions using rare earths alkali double sulfates
of zinc dust are added and, immediately afterwards, a
as coprecipitating agents. This fact could by no means
solution of 2000 g. of anhydrous sodium sulfate in 10
be foreseen, since the rare earths alkali double sulfates
liters of water. The system is agitated during two hours
are not known to be isomorphic with europous sulfate.
in an atmosphere of carbon dioxide, at a temperature be
According to the present invention a solution of rare 40 tween 30 and 35 C. Thereafter the rare earths alkali
earths sulfates containing europium is, under exclusion
double sulfates are recovered by ?ltration. They con
of oxygen, reduced at a pH between 1 and 2.5 with zinc
tain a total of 4340 g. rare earths oxides with 0.44%
dust. The concentration of the rare earths sulfates solu
europium oxide. The rare earths remaining in the ?l
tion may be 50-75 grams of rare earth oxides per liter.
trate contain less than 0.002% of europium oxide, calcu
The quantity of zinc dust necessary for complete reduc 45 lated
on oxide basis.
tion of the europium varies between 2 and 4 grams per
This
corresponds to an europium recovery of about
liter. Sodium or potassium sulfate is then added to the
96%.
solution. The europous sulfate coprecipitates with the
Example II
such a metal. Although widely used, this coprecipitation
rare earths double alkali sulfates.
In an alternative em~
bodiment of this invention the alkali sulfate may be
The rare earths alkali double sulfates obtained in
added simultaneously with the reducing agent. The
Example I are treated with a solution of sodium car
amount of rare earths double alkali sulfates to be pre
bonate, and the carbonates thus obtained are ?ltered,
Washed and dissolved in sulfuric acid; the volume of the
solution is adjusted to 66 liters and the pH is adjusted to
cipitated depends upon the composition of the rare earth
mixture and on the desired degree of recovery of the
europium.
For rare earth mixtures such as occur in
monazite, precipitation of between 5 and 10% of the
rare earths originally present in the solution is su?icient
to coprecipitate 95 to 99% of the europium originally
1.5.
After addition of 45 g. of Zinc dust and two hours
of agitation, the metallic residue is separated from the
solution by ?ltration. The solution is placed in an
enamelled container (as described in Example I) with
a capacity of 100 liters, and carbon dioxide is allowed
present. This process thus gives in one operation an 60
to bubble through the solution for half an hour. 200 g.
enrichment factor for europium of 10 to 20.
of
zinc dust and right afterwards 230 g. of anhydrous
The rare earths double alkali sulfates so obtained and
sodium sulfate dissolved in a liter of water, are added.
containing 95-99% of the europium originally present,
After four hours of agitation, the rare earths alkali double
can now be easily transformed into hydroxides or car
sulfates are ?ltered. They contain 385 g. of rare earths
3,092,449
3
4
oxides with 4.9% of europium oxide.‘ The rare earths ’
values as compared to the percentage of europium values
remaining in the ?ltrate contain 0.014% of europium,
in said original europium-containing mixture.
calculated on oxide basis. This corresponds to an
europium recovery of about 97% .
4. In a method of recovering europium values from
low grade europium-containing mixtures with other rare
earths wherein the amount of europium values is small
relative to the other rare earths, the steps of adding an
alkali metal sulfate selected from the group consisting
of sodium sulfate and potassium sulfate to a solution in
which the solubility of europous sulfate is not su?iciently
Having described our invention, what is claimed is:
1. In a method of recovering europium values from
low grade europium-containing mixtures with other rare
earths wherein the amount of europium values is small
relative to the other rare earths, the steps of adding an
alkali metal sulfate selected from the group consisting
of sodium sulfate and potassium sulfate to a solution in
low for a substantial portion of europous sulfate to pre
cipitate therefrom, said solution containing rare earth
low for a substantial portion of europous sulfate to pre
sulfates and europium values in europous form in an
amount sufficient to precipitate part of said rare earths
cipitate therefrom, said solution containing rare earth
in the form of alkali metal double sulfates, thereby co~
which the solubility of europous sulfate is not sufficiently
sulfates and europium values in europous form in an 15 precipitating said europium values in the form of europous
sulfate with said part of said rare earth-alkali metal
amount su?icient to precipitate part of said rare earths
double sulfates; transforming said rare earth-alkali metal
in the form of rare earth-alkali metal-double sulfates,
thereby coprecipitating said europium values in the form
double sulfates precipitate containing the europium values
of europous sulfate with said part of said rare earth
into acid soluble compounds selected from the group con
alkali metal-double sulfates; and recovering a product
containing an increased percentage of europium values
as compared to the percentage of europium values in
sisting of hydroxides and carbonates; dissolving said com
pounds in sulfuric acid; forming therefrom a solution of
said original europium-containing mixture.
' rare earth sulfates having a pH between 1 and 2.5 and
a concentration of 50—75 grams of rare earth oxides per
liter and being substantially free of heavy metals which
2. In a method of recovering europium values from
low grade europium-containing mixtures with other rare 25 interfere with the reduction vby zinc dust of europium to
the europous state; and treating said solution with zinc
earths wherein the amount of europium values is small
dust in an amount of between 2 and 4 gramsrper liter
relative to the other rare earths, the steps of treating a
of solution so as to reduce said europium values to
solution of rare earth sulfates in which the solubility of
europous sulfate is not suf?ciently low for a substantial
europous form and with an alkali metal sulfate selected
portion of europous sulfate to precipitate therefrom, said 30 from the group consisting of sodium sulfate and potas
sium sulfate in an amount su?icient to precipitate be
solution containing europium values and being at a pH
tween 5 and 10% of said rare earths in the form of rare
of 1—2.5 and being substantially free of heavy metals
earth-alkali metal-double sulfates, thereby precipitating
which interfere with the reduction by zinc dust of en
ropium to the europous state with zinc dust so as to re
said part of said rare earths in the form of rare earth
alkali metal-double sulfates and, thereby coprecipitating
duce said europium values to europous form; adding an
said europium values in the form of europous sulfate
alkali metal sulfate selected from the group consisting of
with said part of said rare earth-alkali metal-double sul~
sodium sulfate and potassium sulfate in an amount su?i
fates; and recovering a product containing an increased
cient to precipitate part of said rare earths in the form of
percentage of europium values as compared to the per
rare earth-alkali metal-double sulfates, thereby copre
cipitating said europium values in the form of europous 40 centage of europium values in said original europium
containing mixture.
sulfate with said part of said rare earth-alkali metal
5. In a method of recovering europium values from
double sulfates; and recovering a product containing an
low grade europium-containing mixtures with other rare
increased percentage of europium values as compared to
the percentage of europium values in said original eu
earths wherein the amount of europium values is small
ropium-containing mixture.
45 relative to the other rare earths, the steps of treating at
' 3. In a method of recovering europium values from
a pH 1-2.5 a solution of rare earth sulfates in which the
low grade europium-containing mixtures with other rare
earths wherein the amount of europium values is small
relative to the other rare earths, the steps of treating at
solubility of europous sulfate is not sufficiently low for
a substantial portion of europous sulfate to precipitate
therefrom, said solution having a concentration of rare
earth sulfates equivalent to 50-75 grams of rare earth
oxides per liter and containing europium values and be
a pH of 1—2.5 a solution of rare earth sulfates in which
the solubility of europous sulfate is not su?iciently low
for a substantial portion of europous sulfate to precipi
tate therefrom, said solution having a concentration of
rare earth sulfates equivalent to 50-75 grams of rare
ing substantially free of heavy metals which interfere
with the reduction by zinc dust of europium to the
europous state with zinc dust in an amount sufficient to
earth oxides per liter and containing europium values 55 reduce said europium values to europous form and with
and also containing heavy metal values which interfere V I an alkali metal sulfate elected from the group consisting
with the reduction of europium to europous form with
zinc dust in an amount sufficient to reduce said heavy
of sodium sulfate and potassium sulfate in an amount
su?icient to precipitate between about 5 and 10% of
said rare earths in the form of rare earth-alkali metal
on said zinc to form a metallic residue; separating the 60 double sulfates, thereby precipitating said part of said
rare earths in the form of rare earth-alkali metal-double
thus obtained solution from the remaining metallic resi
metal values, thereby depositing said heavy metal values
due; treating the thus separated solution with zinc dust
sulfates and coprecipitating said europium values in the
group consisting of sodium sulfate and potassium sulfate
original europium-containing mixture.
form of europous sulfate with said part of said rare earth
in an amount of between 2 and 4 grams per liter of
alkali metal-double sulfate; and recovering a product con
solution so as to reduce said europium values to europous
taining
an increased percentage of europium values as
form and with an alkali metal sulfate selected from the 65 compared to the percentage of europium values in said
in an amount su?icient to precipitate ‘between 5 and 10%
of said rare earths in the form of rare earth-alkali metal
6. In a method of recovering europium values from
low grade europium-containing mixtures with other rare
double sulfates, thereby precipitating said part of said
70 earths wherein the amount of europium values is small
rare earths in the form of rare earth-alkali metal-double
relative to the other rare earths, the steps of treating at
sulfates and, thereby coprecipitating said europium values
a pH of l—2.5 a solution of rare earth sulfates in which
in the form of europous sulfate with said part of said
the solubility of europous sulfate is not su?iciently low
rare earth-alkali metal-double sulfates; and recovering
for a substantial portion of europous sulfate to precipi~
a product containing an increased percentage of europium 75 tate therefrom, said .solution having a concentration of
5
3,092,449
rare earth sulfates equivalent to 50-75 grams of rarei
earth CDL'deS per liter and containing europium values
and ‘being substantially free of heavy metals which inter
fere with the reduction by zinc dust of europiurn to the
europous state with zinc dust in an amount of between 2
and 4 grams per liter of solution and sufficient to reduce
said europium values to europous form and with an
alkali metal sulfate elected from the group consisting of
sodium sulfate and potassium sulfate in an amount su?i—
cient to precipitate between about 5 and 10% of said
rare earths in the form of rare earth~alkali metal-double
sulfates, thereby precipitating said part of said rare earths
in the form of rare earth-alkali metal-double sulfates
and coprecipitating said europium values in the form of
europous sulfate with said part of said rare earth-alkali 15
metal-double sulfate; and recovering a product contain
ing an increased percentage of europium values as com
pared to the percentage of europi-um values in said origi
nal europium-containing mixture.
References Cited in the ?le of this patent
McCoy: “Journal of the American Chemical Society,”
vol. 58, November 1936, pages 2279-2281.
Vickery: “Chemistry of the Lanthanons,” Academic
Press, Inc., ‘N.Y., 1953, pages 75, 76, 87-92, 132-140,
182-185 and 234.
Yost, D. M., et al.: “The Rare Earth Elements and
Their Compounds," John Wiley & Sons, Inc., 1947,
page 43.
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