Note: Descriptions are shown in the official language in which they were submitted.
365
BAC~GROUND OF T~E IMVE~TION
It is known that cobalt occurs in many nickel ores
and other ores as a relatively minor c:onstituent. Because
the chemistry of cobalt and nickel are so similar, the cobalt
is carried along with the nickel through the mill and smelter.
A tendency exists to separate the cobalt from the main stream
of the material going through the refinery after smelting is
complete to provide a metallurgical or hydrometallurgical
by-product relatively rich in cobalt but with other metals
including usually nickel, iron, copper, etc~ being copresent
ther~with. The nature of the hydrometallurgical by-products
tends to be oxidic with the material being in finely divided
hydrous form as a hydrate or a carbonate with considerable
quantities of water, possibly with residual ammonia and other
compounds. Because of the physical nature of the by-products
and the difficulties of separating nickel from cobalt on a
quantitative basis, these materials are difficult to treat
although the materials and problems associated with their
treatment have been recognized in the art. As an example,
the COFFIELD U.S. Patent No. 3,728,104 is directed tG the
exact problem set forth hereinbefore. The solution suggested
by COFFIELD is to convert the nickel content of the material
in slurry form by treatment with a carbon monoxide containing
gas under conditions whereby the nickel is converted to nickel
carbonyl and the cobalt is converted to cobalttetracarbonyl
anion which is thereafter extracted from the aqueous phase
by means of an organic solvent. The potential for formation
~; of cobalt hydridocarbonyl tHCo(CO)4) is recognixed by
COFFIELD but no attempt to utilize this compound as a means
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for removing cobalt from the mixture is recognized. U.S.
Patents Nos. 4,097,272, 4,148,813, '815 and '816 are
directed to a similar process ~o that of COFFIELD with again
great attention being paid to the make-up of the organic
solvent used to separate cobalt from aqueous mixture. These
prior art processes are said to produce nickel of high
purity but to produce cobalt of "acceptable" purity. It is
pointed out in the art that in order to provide high purity
cobalt in accordance with the tetracarbonyl anion extraction
procedure that foreign anions such as iron and copper should
~e removed from the reaction mixture upstream of the
carbonylation. Canadian Patent No. 986r281 is also known
as disclosing the production of metal hydridocarbonyls from
solid materials contAining iron, cobalt and nickel.
; 15 S~MMAR~ OF TH~ I~VE~TION
The invention provides a process~for the recovery
of nickel and cobalt from oxidic mixtures containing the
same so as to effect the separation of the nickel and cobalt
and to provide nickel and cobalt products of high purity.
The process involves slurrying the initial material which
usually will be a hydrometallurgical by-product in finely
divided oxide, hydrate or carbonate form in water, hydrogen
reducing the nickel and cobalt contents thereof under pres-
sure in the presence of powdered cobalt metal, pressure
carbonylating the reduced slurry under basic conditions to
volatilize and remove nickel as nickel carbonyl therefrom
and to convert cobalt to cobalttetracarbonyl anion, removing
precipitated impurities and then acidifying the resulting
solution with a strong acid to a pH at least as acid as pH
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1.5 while sparging the solution with a reducing gas to vol-
atilize and recover cobalt as cobalt hydridocarbonyl. The
volatile cobalt hydridocarbonyl is stripped from the sparge
gas and thereafter decomposed to provide a metallic cobalt
of high purity.
DESCRIPTIOI~ OF PREFE:RRISD EUBODIM~NTS
The process in accordance with the invention
involves treatment of the starting material which will be an
oxidic precipitate usually finely divided and may, for example,
be a mixed nickel/cobalt carbonate or a nickel/cobalt mixture
resulting from the precipitation of cobaltic hydroxide by
means of chlorine. The material is slurried in water in a
solids concentration of about 3~ to about 30% by weight and
pressure reduced with hydrogen at a temperature in a range
lS of about 150C to about 250C and a hydrogen partial pressure
in a range of about 200 to about 1000 pounds per square inch.
Desirably, finely divided cobalt metal is included in the
slurry to act as a catalyst in promoting the reduction of
the nickel and cobalt oxidic or carbonate material. The
benefits of cobalt powder presence during reduction are par-
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ticularly marked when the cobalt and/or the nickel contents
of the material to be treated are in the trivalent form.
The cobalt metal can be obtained from other sources or by
recycle of some of the reduced metal values prior to carbony-
lation. The finely divided cobalt metal improves reaction
kinetics in reduction. After reduction, the slurry is made
basic with a material which preferably is sodium carbonate
and the slurry is then carbonylated with or without the
copresence of hydrogen. A mixture of 1 to 1 volume propor-
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tions of hydrogen and carbon monoxide is beneficial. Car-
bonylation i5 continued until essentially all the nickel
contained in the slurry is removed as nickel carbonyl.
Concommitantly the reduced cobalt is converted to the form
of a cobalttetracarbonyl anion (Co~CO)4-~. At this point
the slurry may be filtered to remove precipitated impurities
including any copper and iron initially present in the crude
by-product material. A liquor containing ~he cobalt as cobalt-
tetracarbonyl anion and essentially devoid of other metallic
ions results. The solution is then acidified with a strong
acid to a pH at least as acid as pH 1.5 and sparged with a
reducing gas from the group consisting of hydrogen and CO to
remove the cobalt as volatile cobalt hydridocarbonyl.
!: Carbonylation, which may be accomplished using carbon monoxide
alone or diluted up to approximately equal volume parts with
hydrogen is conducted over the carbon monoxide partial pres-
` sure range of about 100 pounds per square inch to about 2000
- pounds per square inch at a temperature in the range of about
~; 50 to 225C. A partial pressure of carbon monoxide on the
order of 500 pounds per square inch is advantageousO
It will be appreciated that the pH of the water
slurry of material initially to be treated will generally be
in the neutral to slightly acid range and that the pH oi the
slurry will generally become more acid as hydrogenation pro-
ceeds. However, if the nature of the starting material is
such that the initial water slurry is on the alkaline side
of pH 7 no untoward effect results. Carbonylation, of course,
is conducted under basic conditions preferably generated
through use of a base such as sodium carbonate. For reasons
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which are not presently understood, sodium carbonate appears
to be a more effective base than does sodium hydroxide.
Carbon monoxide or a mixture of hydrogen and carbon monoxide
are passed through the basic mixture at a sufficient rate
and for a sufficient time to convert essentially all of the
nickel present in the reduced state in the mixture to volatile
nickel tetracarbonyl. The nickel tetracarbonyl product is
carried from the reaction environment by the stream of car-
bonylating gas and is separated therefrom outside the vessel
in which carbonylation is taking place. The evolving gas
mixture is checked for the presence of nickel and when nickel
is no longer detected therein, the carbonylation operation
is regarded as being complete. At this point, the reaction
mixture is filtered, then acidified to a pH to at least as
low as p~l 1.5 with a strong acid which may be for example
sulfuric or hydrochloric acid and sparging with a gas from
the group consisting of hydrogen and carbon monoxide is started
to remove from the reaction mixture cobalt as volatile cobalt
hydridocarbonyL IHCo(CO)~]. The sparge gas should be in the
amount of at least about 5 milliliters per milliliter of
liquor per minute on a carbon monoxide basis. The temperature
of the reaction mixture during the evolution of cobalt hydrido-
carbonyl should be maintained in the range of about 20 to
preferably not more than 55C. The retention time of the
mixture during cobalt evolution should preferably be about 1
hour when the pH is about 0.1 up to about 2 hours when the
pH is about 1. Desirably, the content of electrolytes such ;
as sodium sulfate should be high for example at least about
20 grams per liter during the evolution of cobalt
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336~ii
hydridocarbonyl as the presence of a large electrolyte content
in solu~ion increases the ionic strength of the solution and
assists in the removal of the cobalt hydridocarbonyl therefrom.
In this connection, it can be pointed that the cobalt hydrido-
carbonyl is not a strongly polar compound and that increasing
the polarity of the solution appears to create a salting out
effect with respect to cobalt hydridocarbonyl. Sulfates and
phosphates are desirable anions for this purpose.
Some examples will now be given. In the examples,
reduction and carbonylation were performed batchwise at ele-
vated temperature and pressure while evolution of cobalt
hydridocarbonyl was performed continuously at atmospheric
pressure to avoid formation of Co2(Co)g.
` ~XAMPLE I
' ~ 15 Into a single stage reactor provided with a stirring
device, were fed 100 grams of wet cobaltic hydroxide or 44.5g
dry cake analyzing about 54.5~ weight percent cobalt, 1%
nickel, 0.03~ copper and 0.15% iron. The crude cobaltic
hydroxide material was slurried in 1.1 liters of slurry and
80 grams of crude cobalt metal analyzing in weight percent
97.9% cobalt, 1.8~ nickel, 0.05% copper and 0.27% iron and
having a particle size of less than 400 Tyler mesh was also
introduced. The reactor was heated to 180C and hydrogen at
l a partial pressure of 500 pounds per square inch was fed
-~ 25 into the reactor for 13 minutes. At the end of hydrogen
reduction, the slurry pH was 6.3. Analysis confirmed that
more than 99% of the cobalt from the initial cobaltic hydrox-
ide slurry was reported to a crude cobalt meta~. The reaction
mixture resultlng from hydrogenation was then treated at
36~;i
150C with a gaseous mixture of equal volume proportions of
hydrogen and carbon monoxide at a partial pressure of 1000
pounds per square inch in the pre~ence of 110% stoichoimetric
excess of sodium carbonate. A gas containing nickel carbonyl
resulted which was evolved from the reactor. After the com-
pletion of nickel carbonyl evolution, which occurred after
about 240 minutes, the slurry was filtered and washed provid-
ing a copper-iron cake and a clear yellow liquor assaying in
grams per liter, 38.8 cobalt, 0.012 nickel, O.OQ2 copper and
0.022 iron. A portion of the cobalt carbonylate solution
thus produced was diluted to a cobalt content of 28 grams
per liter, was acidified at atmospheric pressure and 22C
with 6 normal hydrochloric acid and sparged with 5.33 milli-
liters of hydrogen per milliliter of solution per minute.
The cobalt-containing liquor, acid and sparge gas were fed
continuously to the bottom of a sealed single stage vessel,
with spent liquor and HCo(CO)4 containing gas being taken
off the top. Cobalt volatilization from the reaction
mixture was checked at pH levels from pH 3 to pH -0.26 with
the results set forth in the following Table I~
TABLE I
% CO volatilizedR.T. (min)
. .
-.26 95.8 60'
0 97.3 77'
1.0 86.9 149'
3.0 45.6 103'
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8365
Example II
A further portion of the basic cobalt carbonylate
solution having a cobalt content of 28 grams per liter was
; treated at 23C in the manner described in Example I with a
6 normal sulfuric acid solution to provide a pH of 1. A
mixture of hydrogen and CO was sparged through the solution
at a rate of 5.33 milliliters per milliliter per minute for
various times. It was found that, at 89 minutes, 74.2% of
the cobalt was volatilized; at 96 minutes, 84% of the cobalt
was volatilized; and at 149 minutes, 86.9~ of the cobalt was
volatilized as cobalt hydridocarbonyl.
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~ample YII
`~ A cobalt carbonylate basic solution prepared gen-
~ eralIy as in the method set forth in Example I and containing
; 15 80 grams per liter of cobalt was treated at 23~C with 12
normal sulfuric acid to yield a pH of 1. The solution was
sparged with 5 milliliters per milliliter per minute of a 1
to 1 mixture of hydrogen and carbon monoxide at a retention
time of 83 minutes~ Two tests were conducted, in one of
which the solution also contained 154 grams per liter of
sodium sulfate and in the other of which no sodium sulfate
was present. It was found that, in the retention time
employed, the cobalt carbonylate solution containing sodium
sulfate yielded a 73.2% cobalt volatilization at 83 minutes
whereas the solution containing no sodium sulfate yielded a
volatization of only 47.2% of the cobalt in the same timeO
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~ample IV
To illustrate the effect of temperature during the
evolution of cobalt hydridocarbonyl from a basic solution
containing cobalt carbonylate~ i.e., cobalttetracarbonyl
anion, a run was made at a temperature of 90C treating a
basic solution containing 70 grams per liter of cobalt with
a 12 normal sulfuric acid solution to yield a pH of 2. In
90 minutes of sparging with 5 milliliters per milliliter per
minute carbon monoxide, 96% of the cobalt was volatilized
but the formation of insoluble black solids (likely tetra-
cobalt dodecacarbonyl) occurred.
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Example V
A cobalt carbonylate basic solution containing 25
grams per liter of cobalt was treated in the manner described
in Example I with 3 normal sulfuric acid to pH 1~ I'he solu-
tion was sparged with carbon monoxide at rates of 2, 5 and
lO milliliters per milliliter per minute for 59 minutes
residence time at each sparging rate and it was found that,
respectively, 51.6%, 64% and 83.7% of cobalt was volatilized.
.
~ample VI
A comparison between the use of carbon monoxide
alone and an equal volume of mixture of hydrogen and carbon
monoxide was conducted in the treatment of an 80 grams per
liter cobalt-containing basic solution treated with 12 normal
sulfuric acid to pH 1 using a sparge rate of 10 milllliters
per milliliter per minute as in Example I. It was found
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that after 92 minutes using carbon monoxide alone 96% of the
cobalt was volatilized, and after 83 minutes using the mixture
of hydrogen and carbon monoxide, 73.2% of the cobalt was
volatilized indicating a superior result for the use of carbon
monoxide alone as sparge gas.
Cobalt powder produced by the decomposition of
cobalt hydridocarbonyl gas when thermally decomposed in a
temperature range of 150 to 300C was found to yield a cobalt
powder containing as impurities only 30 parts per million of
nickel, 0.4 part per million of iron, and 0~1 parts per
million of copper. The process of the invention provides a
means for separating nickel and cobalt contained in crude
material which heretobefore had been regarded as being diffi-
~` cult to handle. In addition, the process of the invention
affords the means not only of separating the nickel and cobalt
but of providing nickel and cobalt in highly pure form.
Although the present invention has been described
in con~unction with preferred embodiments, it is to be under-
stood that modifications and variations may be resorted to
without departing from the spirit and scope of the inven-
tion, as those skilled in the art will readily understand.
Such modifications and variations are considered to be within
the purview and scope oi the invention and appended claims.
