AU2019275612A1 - Method for producing cobalt powder - Google Patents

Abstract

SUMIKO-380 (Original) Abstract Provided is a method for producing cobalt powder with high reaction efficiency by controlling the amount of added seed crystals when cobalt powder is produced from a solution containing a cobalt ammine sulfate complex. The method sequentially includes: a mixing step of adding, to the solution containing a cobalt ammine sulfate complex, cobalt powder as seed crystals in an amount of 1.5 times or more and 3.0 times or less the amount of cobalt contained in the solution and then adding a dispersant in an amount of 1.5% by weight to 3.0% by weight of the added seed crystals to form a mixture slurry; and a reduction and precipitation step of charging a reaction vessel with the mixture slurry and then blowing hydrogen gas into the mixture slurry to reduce cobalt complex ions contained in the mixture slurry to form cobalt precipitate on the surface of the seed crystals. (149 words) 17

Description

SUMIKO-380 (Original)

Description

METHOD FOR PRODUCING COBALT POWDER

Technical Field

[0001]

The present invention relates to a method for

producing cobalt powder having high reaction efficiency

when cobalt powder is produced from a solution containing

a cobalt ammine sulfate complex, and particularly, the

present invention can be applied to the treatment of an

in-process intermediate solution generated from a cobalt

hydrometallurgical process.

Background Art

[0002]

Examples of known methods for producing fine cobalt

powder include dry methods such as an atomizing method of

dispersing molten cobalt in a gas or in water to obtain

fine powder and a CVD method of volatilizing cobalt and

reducing it in a vapor phase to thereby obtain cobalt

powder as disclosed in Patent Literature 1.

Further, examples of methods for producing cobalt

powder by a wet process include a method of producing

cobalt powder using a reducing agent as disclosed in

Patent Literature 2 and a spray pyrolysis method in which

cobalt powder is obtained by pyrolysis reaction by

SUMIKO-380 (Original)

spraying a cobalt solution into a reducing atmosphere at

high temperatures as disclosed in Patent Literature 3.

[0003]

However, these methods are not economical because

they require expensive reagents and a large amount of

energy.

[0004]

On the other hand, a method of obtaining cobalt

powder by feeding hydrogen gas into a cobalt ammine

sulfate complex solution to reduce cobalt ions in the

complex solution as shown in Non Patent Literature 1 is

industrially inexpensive and useful. However, there has

been a problem that cobalt powder particles obtained by

this method are easily coarsened.

Particularly, when particles are intended to be

generated from an aqueous solution and grown, there is

used a method of obtaining a powder having a

predetermined particle size by allowing a small amount of

fine crystals called seed crystals to coexist and feeding

a reducing agent thereto to grow the seed crystals.

[0005]

According to the above method, high reaction

efficiency cannot be obtained, depending on the cobalt

concentration in the aqueous solution to be used and the

type of seed crystals, and the yield will decrease, which

leads to an increase in cost.

SUMIKO-380 (Original)

Generally, in such a case, it is possible to improve

reaction efficiency by reducing the particle size of seed

crystals to increase the reaction field. However, time

and effort are required in order to reduce the particle

size of seed crystals. Further, in the case where seed

crystals made of different types of metals are used,

there arises a problem such that the purity of products

decreases because the seed crystal component remains.

[0006]

Therefore, there has been required a method of

having high reaction efficiency, without using different

types of metals as seed crystals and not necessarily

using seed crystals having a small particle size.

Citation List

Patent Literature

[0007]

Patent Literature 1:

Japanese Patent Laid-Open No. 2005-505695

Patent Literature 2:

Japanese Patent No. 5407495

Patent Literature 3:

Japanese Patent No. 4286220

Non Patent Literature

[0008]

Non Patent Literature 1:

SUMIKO-380 (Original)

"The Manufacture and properties of Metal powder

produced by the gaseous reduction of aqueous solutions",

Powder metallurgy, No. 1/2 (1958), pp 40-52.

Summary of Invention

Technical Problem

[0009]

In such a situation, the present invention provides

a method for producing cobalt powder by obtaining high

reaction efficiency by controlling the amount of added

seed crystals when cobalt powder is produced from a

solution containing a cobalt ammine sulfate complex.

Solution to Problem

[0010]

A first aspect of the present invention to solve

such a problem is a method for producing cobalt powder,

sequentially including: a mixing step of adding, to a

solution containing a cobalt ammine sulfate complex,

cobalt powder as seed crystals in an amount of 1.5 times

or more and 3.0 times or less the amount of cobalt

contained in the starting solution and then adding a

dispersant in an amount of 1.5% by weight to 3.0% by

weight of the added seed crystals to form a mixture

slurry; and a reduction and precipitation step of

charging a reaction vessel with the mixture slurry and

then blowing hydrogen gas into the mixture slurry to

SUMIKO-380 (Original)

reduce cobalt complex ions contained in the mixture

slurry to form cobalt precipitate on a surface of the

seed crystals.

[0011]

A second aspect of the present invention is a method

for producing cobalt powder according to the first aspect

of the invention, wherein the concentration of ammonium

sulfate in the solution containing a cobalt ammine

sulfate complex is in the range of 10 to 500 g/L.

[0012]

A third aspect of the present invention is a method

for producing cobalt powder according to the first and

second aspects of the invention, wherein, in the

reduction step, the temperature of the mixture slurry

when hydrogen gas is blown is 150 to 200°C.

[0013]

A fourth aspect of the present invention is a method

for producing cobalt powder according to the first to

third aspects of the invention, wherein, in the reduction

step, the pressure of the gas phase part in the reaction

vessel when hydrogen gas is blown is in the range of 1.0

to 4.0 MPa.

Advantageous Effect of Invention

[0014]

According to the present invention, in the method of

adding a dispersant to a cobalt ammine complex solution

SUMIKO-380 (Original)

and subjecting the resulting mixture to hydrogen

reduction under high temperatures and high pressures,

cobalt powder can be produced at high reaction efficiency.

Brief Description of Drawings

[0015]

[Figure 1] Figure 1 is a production flow chart of the

method for producing cobalt powder according to the

present invention.

[Figure 2] Figure 2 is a SEM image showing the appearance

of cobalt powder produced in Example 1.

Description of Embodiments

[0016]

The method for producing high purity cobalt powder

according to the present invention is a method for

producing cobalt powder in which, when seed crystals are

added to a cobalt ammine sulfate complex solution using a

high-pressure vessel such as an autoclave and the

resulting mixture is subjected to pressurized hydrogen

reduction treatment including reduction treatment with

hydrogen at high temperatures and high pressures, cobalt

powder is produced by adding cobalt powder as seed

crystals in an amount 1.5 times or more and 10.0 times or

less the amount of cobalt in the starting solution,

preferably 1.5 times or more and 3.0 times or less, and

more preferably 2.0 times.

SUMIKO-380 (Original)

Hereinafter, the method for producing cobalt powder

according to the present invention will be described with

reference to the production flow chart shown in Figure 1.

[0017]

[Cobalt Ammine Sulfate Complex Solution]

Examples of a suitable cobalt ammine sulfate complex

solution used in the present invention include, but are

not limited to, a cobalt ammine sulfate complex solution

obtained by dissolving a cobalt-containing material such

as an industrial intermediate including one or a mixture

of two or more selected from cobalt and cobalt mixed

sulfide, crude cobalt sulfate, cobalt oxide, cobalt

hydroxide, cobalt carbonate, cobalt powder, and the like

with sulfuric acid or ammonia to obtain a cobalt leaching

solution (solution containing cobalt), subjecting the

cobalt leaching solution to a purification step such as

solvent extraction, ion exchange, and neutralization to

obtain a solution from which impurity elements in the

cobalt leaching solution have been removed, and adding

ammonia to the resulting solution to form the cobalt

ammine sulfate complex solution, in which cobalt is

contained in the form of cobalt complex ions.

[0018]

[Mixing Step]

In this step, a mixture slurry is produced by adding

seed crystals to the cobalt ammine sulfate complex

SUMIKO-380 (Original)

solution produced above and adding a dispersant thereto

depending on the amount of the added seed crystals.

Cobalt powder is used as the seed crystals to be

added here.

Although commercially available products may be used

as the cobalt powder to be used as the seed crystals, it

is more preferred to repeatedly use a part of products

obtained by the production method of the present

invention.

[0019]

The particle size of the cobalt powder preferably

has an average particle size of about 0.1 to 5 tm, and

particularly preferably has a particle size of around 1

tm, where the particle size does not vary but is uniform.

If the particle size is too small, the cobalt powder

obtained in the reaction will be too small, which has

difficulty in handling and is not preferred. On the

other hand, if the particle size is too large, the cobalt

powder will easily settle during stirring, which poses a

problem that uniform cobalt powder is not easily obtained.

[0020]

The amount of cobalt powder to be added is 1.5 times

or more and 3.0 times or less, preferably 2.0 times the

amount of cobalt contained in the original solution, in

order to maintain reaction efficiency.

If the amount of cobalt powder added is less than

1.5 times of the amount of cobalt contained in the

SUMIKO-380 (Original)

original solution, high reaction efficiency cannot be

obtained because the number of seed crystals is

insufficient, reducing reaction fields. Further, even if

the amount of cobalt powder added is more than 3.0 times,

reaction efficiency will not be improved, and the

efficiency will not be improved considering that too much

time and effort and cost are required. The number of

seed crystals will be rather too large, and the growth of

the cobalt powder obtained will be insufficient, reducing

the particle size. Therefore, when the cobalt powder is

used as products, a problem in use will easily occur,

such as requiring time and effort in handling thereof.

Further, a problem of properties, such as being easily

dissolved or oxidized, will occur, which is not preferred.

[0021]

Furthermore, when a dispersant is added so that it

is contained at a concentration in the range of 1.5% by

weight or more and 3.0% by weight or less relative to the

amount of seed crystals added to the cobalt ammine

sulfate complex solution, the added seed crystals are

dispersed more uniformly, and desired nickel powder is

thus more easily obtained, which is desirable.

[0022]

Further, the concentration of ammonium sulfate in

the solution is preferably in the range of 10 to 500 g/L.

If the concentration is 500 g/L or more, the

solubility will be exceeded, and crystals will be

SUMIKO-380 (Original)

precipitated. With respect to the lower limit, since

ammonium sulfate is newly produced by reaction, it is

difficult to achieve a concentration of less than 10 g/L.

[0023]

[Reduction and Precipitation Step]

Next, a reaction vessel resistant to high pressure

and high temperature is charged with the slurry formed by

adding seed crystals in the previous step, and hydrogen

gas is blown into the slurry stored in the reaction

vessel to reduce cobalt complex ions in the slurry to

precipitate cobalt on the seed crystals contained.

[0024]

The temperature of the mixture slurry at this time,

that is, reaction temperature, is preferably in the range

of 150 to 2000C. If the reaction temperature is less

than 1500C, reduction efficiency will be reduced, and

even if it is 2000C or more, the reaction will not be

affected, but the loss of thermal energy will increase.

Therefore, these temperatures are not suitable.

[0025]

Further, the pressure of the gas phase part in the

reaction vessel (refers to a space in the reaction vessel

remaining after the solution is stored in the reaction

vessel) during the reaction is preferably maintained in

the range of 1.0 to 4.0 MPa by controlling the feed rate

of hydrogen gas. If the pressure is less than 1.0 MPa,

reaction efficiency will be reduced, which is not

SUMIKO-380 (Original)

preferred. Further, even if the pressure is higher than

4.0 MPa, the reaction efficiency will not be affected,

but the loss of hydrogen gas will increase.

In this regard, when hydrogen gas is blown into the

mixture slurry, the cobalt complex ions in the slurry can

also be reduced either by directly blowing hydrogen gas

into the liquid in the reaction vessel or by blowing

hydrogen gas into the gas phase part in the reaction

vessel.

[0026]

A precipitate of cobalt is formed on the seed

crystals by reduction and precipitation treatment of the

present invention, and the cobalt contained in the

solution can be recovered and repeatedly used as a

precipitate of fine powdered cobalt.

[0027]

As described above, by producing the seed crystals

of cobalt powder in fine powder form which can be used as

seed crystals and repeating hydrogen reduction, particles

in which cobalt precipitate is provided on the surface of

the seed crystals are formed, and the particles can be

grown up to produce high purity cobalt metal.

Examples

[0028]

The present invention will be described below using

Examples.

SUMIKO-380 (Original)

[Example 1]

[0029]

[Mixing Step]

To a cobalt sulfate solution containing 75 g of

cobalt, was added 465 g of ammonium sulfate, and thereto

was added 191 ml of 25% aqueous ammonia to form an

original solution. A mixture slurry containing a cobalt

ammine sulfate complex containing seed crystals was

prepared by adding, to the original solution, cobalt

powder having an average particle size of about 0.1 to 5

tm, as seed crystals, in an amount of 150 g which is 2.0

times the amount of cobalt in the original solution,

further adding 40 wt% polyacrylic acid, as a dispersant,

in an amount 2.0% by weight relative to the amount of the

seed crystals, and then adjusting the total volume of the

solution to 1000 ml.

[0030]

[Reduction and Precipitation Step]

Next, an inner cylinder of an autoclave was charged

with the mixture slurry; the mixture slurry was heated to

1850C with stirring after the autoclave was sealed;

hydrogen gas was blown into the mixture slurry while

keeping the temperature; and hydrogen gas was fed from

its cylinder so as to maintain the pressure in the inner

cylinder of the autoclave at 3.5 MPa.

SUMIKO-380 (Original)

After a lapse of 60 minutes from the start of the

feeding of hydrogen gas, the feeding of hydrogen gas was

stopped, and the inner cylinder was cooled.

[0031]

After cooling, when the mixture slurry in the inner

cylinder was filtered and the recovered cobalt powder was

observed with an electron microscope (SEM), it was

verified that fine cobalt powder was produced as shown in

Figure 2.

Further, the amount of precipitated cobalt obtained

by deducting the amount of seed crystals from the amount

of cobalt that was able to be recovered was divided by

the amount of cobalt contained in the original solution

to determine the yield of the cobalt powder produced by

the reaction, that is, by reduction, which was found to

be 72%.

[0032]

(Comparative Example 1)

An original solution containing cobalt was prepared

under the same conditions and in the same manner as in

Example 1 above. A mixture slurry according to

Comparative Example 1 was prepared by adding, to the

original solution, cobalt powder as seed crystals in an

amount of 75 g which is 1.0 times the amount of cobalt in

the original solution and adjusting the total volume of

the solution to 1000 ml. Next, an inner cylinder of an

autoclave was charged with the mixture slurry; the

SUMIKO-380 (Original)

mixture slurry was then heated to 1850C with stirring;

hydrogen gas was blown into the mixture slurry while

keeping the temperature; and hydrogen gas was fed so as

to maintain the pressure in the inner cylinder of the

autoclave at 3.5 MPa.

After a lapse of 60 minutes from the start of the

feeding of hydrogen gas, the feeding of hydrogen gas was

stopped, and the inner cylinder was cooled.

[0033]

After cooling, when the solution in the inner

cylinder was filtered, fine cobalt powder was found to be

produced.

However, the yield of the cobalt powder produced by

the reaction was only 36%, and high efficiency as in

Example 1 of the present invention was not obtained.

Claims (4)

1. SUMIKO-380 (Original)

   Claims

   [Claim 1]

   A method of producing cobalt powder, sequentially

   comprising:

   a mixing step of adding, to a solution containing a

   cobalt ammine sulfate complex, cobalt powder as seed

   crystals in an amount of 1.5 times or more and 3.0 times

   or less an amount of cobalt contained in the solution and

   then adding a dispersant in an amount of 1.5% by weight

   to 3.0% by weight of the seed crystals added to form a

   mixture slurry; and

   a reduction and precipitation step of charging a

   reaction vessel with the mixture slurry and then blowing

   hydrogen gas into the mixture slurry to reduce cobalt

   complex ions contained in the mixture slurry to form

   cobalt precipitate on a surface of the seed crystals.
2. [Claim 2]

   The method of producing cobalt powder according to

   claim 1, wherein a concentration of ammonium sulfate in

   the solution containing a cobalt ammine sulfate complex

   is in a range of 10 to 500 g/L.
3. [Claim 3]

   The method of producing cobalt powder according to

   claim 1 or 2, wherein, in the reduction step, a

   temperature of the mixture slurry when hydrogen gas is

   blown is 150 to 2000 C.

   SUMIKO-380 (Original)
4. [Claim 4]

   The method of producing cobalt powder according to

   any one of claims 1 to 3, wherein, in the reduction step,

   a pressure of a gas phase part in the reaction vessel

   when hydrogen gas is blown is in a range of 1.0 to 4.0

   MPa.