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Патент USA US3072469

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United States Patent O?hce
Patented Jan. 8, 1963
Raymond A. Foos, Freemont, Ohio, and Robert L. Ripley,
Lockport, N.Y., assignors to Union Carbide Corpora
HgTaFq in the ?uoride solution and at least 21/2 moles of
sulfuric acid for each mole of H2CbOF5 in the ?uoride
solution. Excesses of sulfuric acid over this amount may
be advantageously employed in accordance with the dic
tates of the economics of the process.
When the ?uorine has satisfactorily been removed by
volatilization as hydrogen ?uoride, precipitating reagent
is added to precipitate the metal values as hydrated pent
oxides substantially free from ?uoride contamination.
This invention relates to a method for producing 10
The metal components of the solution which have been
columbium and/ or tantalum pentoxides substantially free
freed from ?uorine may be precipitated by adding a base
tion, a corporation of New York
No Drawing. Filed Dec. 30, 1959, Ser. No. 862,809
5 Claims. (Cl. 23-23)
from ?uorine contamination.
In the puri?cation and separation of tantalum and
columbium values, from solid starting materials such as
such as ammonium hydroxide. However, if the amount
of concentrated sulfuric acid employed is substantially in
excess over that necessary to remove the ?uoride con
the ores of these metals, it is common practice to ?rst 15 tamination, no further precipitating agent need be added.
solubilize the metal values in an aqueous acid solution
The precipitated material is then separated from the
containing ?uorides.
The tantalum and columbium
mother liquor.
values are then extracted from the acid solution with an
To illustrate the process of the present invention 25
organic solvent; the extracted metal values are then
milliliters of a hydro?uoric acid solution of 3.80 grams
selectively stripped from the organic phase with an aque 20 of Ta2-O5 were digested with 5 milliliters of concentrated
ous solution. The aqueous strip liquor is treated so as
sulfuric acid. The mixture was boiled until the hydro
to precipitate tantalum and columbium oxides. A typi
gen ?uoride was completely volatilized. A stoichiometric
cal analysis of a wet ?lter cake from a tantalum precipi
amount of ammonium hydroxide was then added and 100
tate is 7 percent ?uorine, 3 percent ammonia, 40 percent
percent recovery of tantalum as a hydrated oxide con
water and 50 percent tantalum pentoxide. A typical anal
taining only 0.06 percent ?uorine was obtained. The
ysis of a columbium wet cake is 4 percent ?uorine, 2 per
‘ precipitated hydrated oxide was calcined at about 500° C.
cent ammonia, 60 percent water and 34 percent colum
to insure elimination of any residual sulphur. Analysis
'bium pentoxide.
of the calcined metal showed a sulphur content of less
As may be seen from these analyses, the cakes contain
30 than 0.005 percent.
a high percentage of ?uoride material. Before either of
To illustrate the process wherein sulfuric acid is em
the metal oxide materials can be. processed to the ele
ployed as the precipitating reagent, a mixture consisting
mental metal, the water of hydration and the ?uorides
of 25 milliliters of concentrated sulfuric acid and 25
must be removed. The presence of ?uorine lowers the
milliliters of an aqueous hydro?uoric acid solution of
metal recovery and fouls and corrodes the reduction 35 3.80 grams of Ta2O5 was boiled to evolve gaseous hydro
equipment. Further, for direct sale of the cake material,
gen ?uoride. Once the ?uorine was eliminated, the tan
a low ?uorine content is required, since the usual com
talum automatically precipitated from the solution in the
mercial ?uoride speci?cation for saleable oxides is a
form of a hydrated oxide containing 1.9 percent ?uorine.
'maximum of 0.1 percent.
The product was calcined and the calcined material was
In the aqueous extracts and aqueous strip liquors ob 40 analyzed and found tov contain less than 0.005 percent
7‘. tained in the separation of columbium and tantalum the
columbium is generally present as HzCbFI] or H2CbOF5
Where the columbium or tantalum product is even
and the tantalum as H2TaF7. The precipitated material
tually to-be converted to the corresponding pentachloride
generally contains ?uorine also and it is believed the
up to about 2 percent ?uorine is not harmful. For the
compounds precipitate as CbOFa and TaOF3.
preparation of the pure pentoxide, however, the preferred
attempts have been made to remove the ?uoride con 45 method of digesting with smaller quantities of sulfuric
tamination but these methods ‘generally involve special
equipment because of the corrosive nature of the ?uoride
acid and precipitating with ammonium hydroxide is pre
ion. Other methods, for example washing with water,
What is claimed is:
have proven unsuccessful to obtain a ?uorine content of
1. A process for producing a substantially ?uoride~free
less than about 4 percent.
pentoxide of at least one metal selected from the group
Accordingly, it is an object of this invention to pro
consisting of columbium and tantalum from an aqueous
vide a process for the production of columbium and tan
hydro?uoric acid solution containing a compound selected
talum pentoxides by means of which columbium and tan
from the group consisting of HzCbFq, H2CbOF5 and
talum pentoxides containing less than about 0.1 percent
of ?uoride contamination may be obtained.
55 HzTaFq which process comprises adding at least 21/2
moles of sulfuric acid to said solution for every mole of
Other objects will be apparent ‘from the subsequent dis
H2CbF-7 and HzTaFq contained therein and at least 11/2
closure and appended claims.
moles of sulfuric acid for every mole of H2CbOF5 con
The process which satis?es the objects of the present
tained therein; digesting the so-acidi?ed solution by boil
invention comprises treating a ?uoride solution contain
it whereby the combined ?uorine is dissociated from
ing columbium values in the form of H2CbFq and 60 the metal compounds and volatilized during said diges
H2CbOF5 and/ or tantalum values in the ‘form of HzTaFq
tion as gaseous hydrogen ?uoride; continuing said diges
with at least 21/2 moles of sulfuric acid for each mole of
tion until the evolution of gaseous hydrogen ?uoride
HzCbFq and HzTaFq in the ?uoride solution and at least
from said solution has substantially subsided; and precipi
11/2 moles of sulfuric acid for each mole of H2CbOF5 in 65 tating said selected metal from the solution as a hydrated
the ?uoride solution and digesting said acid treated solu
pentoxide of said metal.
tion by boiling it whereby the ?uorine is dissociated from
2. A process in accordance with claim 1 wherein the
the metal compound and volatilized during the digestion
amount of sulfuric acid added is insuf?cient for the pre
as gaseous hydrogen ?uoride.
cipitation of the metal values and wherein ammonium
‘In the preferred form of the invention the ?uoride solu 70 hydroxide is added to the digested solution to precipitate
tion containing the metal values is treated with at least
the selected metal pentoxide.
31/2 moles of sulfuric acid for each mole of HzCbFq and
3. A process in accordance with claim 1 wherein at‘v
least 31/2 moles of sulfuric acid are added to said solution
in the acidi?cation step for every mole of HzCbFq and
H2TaF7 contained therein and at least 21/2 moles of sul
furic acid for every mole of H2CbOF5 contained therein.
4. A process in accordance with claim 3 wherein the
amount of sulfuric acid added is insuf?cient for the pre
cipitation of the metal values and wherein ammonium
hydroxide is added to the digested solution to precipitate
the selected metal pentoxide.
5. A process in accordance with claim 3 wherein a sub 10
stantial excess of sulfuric acid is added to said solution
in the acidi?cation step whereby the selected metal pent
oxide precipitates from the digested solution without addi
tional treatment.
References Cited in the ?le of this patent
Hicks et a1. __________ __ June 11,
Ruhoff et a1. __________ __ Jan. 7,
Ruhoff et a1. _________ __ Jan. 14,
Foos _______________ __ Aug. 30,
Foos _______________ .__ Sept. 20,
Wettler ______________ __ Apr. 18,
Jacobson: “Encyclopedia of Chemical Reactions,”
Reinhold Pub. Corp., New York, 1958, vol. 7, Reaction
VII—690, page 166.
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