JP2000328153A - Method for recovering cobalt - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for recovering cobalt which enables metal cobalt to be recovered only with a device of small or middle scale by wet-reducing cobalt valuables in an aqueous solution to generate metallic cobalt and depositing the metallic cobalt as precipitates outside the system and which further promotes recovery of used lithium batteries to dissolve pollution problems thereby. SOLUTION: This method for recovering cobalt comprises a dissolving process in which cobalt in the cobalt valuables is dissolved in an inorganic acid and indissoluble components are refined and excluded to generate a reductive solution, a recovering process in which an amphoteric metal having a standard electrode potential in a range of -2.4 V to -0.6 V is added to the reductive solution to reduce and recover the cobalt by separation and a purifying process in which recovered cobalt is alkali-washed to remove the amphoteric metal. Further, in the recovering process, after cobalt is reduced and recovered by solid-liquid separation, a process in which a new amphoteric metal with larger specific surface area than that used before is added to a solution to be reduced and residual cobalt is reduced and recovered by separation, may be repeated for plural times.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing metallic cobalt from an aqueous solution of a cobalt compound. The present invention relates to a method of recovering cobalt, which forms cobalt having properties and precipitates out of the system as a precipitate.

[0002]

2. Description of the Related Art Cobalt compounds do not exist as independent mines like gold mines, but exist as minor components in mines producing copper and nickel, for example. Therefore, industrially, ore is carefully selected and cobalt is sequentially purified from the main component elements to obtain a cobalt material having a high content, and then metallic cobalt is obtained mainly according to the following processing method.

The method is based on (a) a wet electrolysis method in which a cobalt substance is dissolved and electrolysis is repeatedly performed to obtain a crude cobalt metal. (B) Cobalt oxide in the presence or absence of a reducing agent or the like,
It is based on a dry smelting method to obtain cobalt metal by melting in an inert atmosphere. (C) Refining method using a combination of (a) and (b).
It is.

[0004] However, in the above method (a) based on ore refining, it is necessary to repeat a step of consuming a large amount of electric power. In addition, the method (b) requires an enormous heat source for melting, and also needs to treat exhaust gas generated during melting to eliminate a pollution problem.

Further, in each of the above-mentioned methods, the size of the auxiliary equipment becomes large and the scale of the entire refining equipment becomes large.
In conventional smelters, it was difficult to operate and produce small quantities even if a small amount of cobalt material was received.

In general, a metal having a noble standard electrode potential is ionized in an aqueous solution, and then a metal having a noble standard electrode potential is added to the corresponding element ion. Reduced to metal.

[0007] An industrial method for obtaining reduced copper by utilizing this is disclosed in, for example, Japanese Patent Application Laid-Open No. H7-138620. Metallic iron (Fe) is added to a solution of copper ions (Cu ⁺⁺ ).
Copper ions are reduced and precipitated out of the system as metallic copper for recovery.

[0008] However, in a reaction that is actually carried out industrially, the standard electrode potentials of two elements are far from each other, and one element is more noble than the standard electrode potential of hydrogen.
Actually, only the elements between which other elements are lower than the standard electrode potential of hydrogen are industrially used.

In order to reduce a substance having a lower standard electrode potential than hydrogen, such as a cobalt ion, it is necessary to use a metal having a significantly lower standard electrode potential; in other words, a metal having a high reactivity is required. In the case of industrial trials, a so-called runaway reaction, in which the induction period of the reaction is prolonged, or the reaction proceeds with rapid heat generation, on the contrary, is likely to occur, and it is difficult to control this. However, it has not been performed to precipitate and recover metallic cobalt from an aqueous solution.

[0010] On the other hand, lithium cobalt oxide is used in lithium ion secondary batteries whose production volume is increasing dramatically. Therefore, if it becomes possible to recover cobalt material from a used battery or the like and to metallize cobalt by a simple method, rare resources can be efficiently recycled, and the value in the industry is great.

Conventionally, a method of recovering cobalt valuables from a lithium battery is disclosed in, for example, JP-A-6-346160.
According to this method, a used battery is directly roasted and stabilized, and then pulverized to obtain a cobalt-containing material.

This method has a drawback that a large amount of harmful HF gas or the like may be released at the time of roasting. Therefore, even if the recycling of cobalt metal from a used lithium battery or the like is considered for commercialization, it is not profitable if the amount of the target raw material is too small.

[0013] Therefore, it cannot be said that the cobalt resources can be easily recovered to provide the cobalt metal, and the used batteries cannot be smoothly recovered by pulling, which may cause a new pollution. Had occurred.

Recently, a new method for recovering valuable materials containing cobalt from a lithium battery by the present inventors has been disclosed (Kudo, Shimizu, Japanese Patent Application No. 09-026759). According to this, even a charged lithium battery is stabilized by discharging in an aqueous solution, and then undergoes a heating and pulverizing process, so that a pure cobalt content composed of a cobalt compound and carbon powder is about 50%. (Referred to as cobalt slag) can be obtained, but a new technique for further purifying cobalt valuables into cobalt metal has been desired.

[0015]

The present invention has been made in view of the above-mentioned problems, and is intended to reduce a cobalt valuable material in an aqueous solution by wet reduction to produce metallic metallic cobalt and to precipitate it out of the system as a precipitate. It is intended to provide a new method of recovering cobalt, which makes it possible to recover cobalt metal with only the above-mentioned equipment, further promotes the recovery of used lithium batteries, and solves the problem of pollution.

[0016]

The method for recovering cobalt of the present invention is constituted as follows. That is, a dissolving step of dissolving cobalt in a cobalt valuable material with an inorganic acid and purifying and eliminating insoluble components to produce a reduced dissolving solution, and forming the reduced dissolving solution in a range of -2.4V to -0.6V. A reduction step of separating and recovering cobalt by adding one or more reducing metals having a standard electrode potential of.

Alternatively, a dissolving step of dissolving cobalt in the cobalt valuables with an inorganic acid and purifying and eliminating insoluble components to form a reduced dissolving solution;
1 or 2 having a standard electrode potential in the range of V to -0.6V
By the addition of the amphoteric metal, a recovery step of reducing and separating and recovering cobalt, a purification step of removing the amphoteric metal by washing the cobalt recovered in the recovery step with alkali,
It is characterized by consisting of.

In the above-described recovery step, after the cobalt is reduced by adding a reducing metal or an amphoteric metal to recover the solid-liquid separation, the specific surface area of the liquid to be reduced and dissolved is further increased from the previous time. The process of reducing and separating and collecting cobalt by adding a new reduced metal or amphoteric metal may be repeated a plurality of times.

[0019]

The operation of the method for recovering cobalt of the present invention will be described below in detail according to the operation procedure. (1) Dissolution step In the dissolution step, cobalt valuables are dissolved with an inorganic acid,
The insoluble components are purified to obtain a reduced solution. In addition, although the raw material used as the said cobalt valuables is not specifically limited, it is important from the viewpoint of improving the purity of metallic cobalt that the cobalt content is high and the other metal contents are low.

For example, the aforementioned Japanese Patent Application No. 09-02675 is disclosed.
By treating the used lithium ion battery recovered by the method disclosed in No. 9, the cobalt content becomes 50% by weight.
To the extent that most of the remaining carbon slag, which is a carbon powder, can be obtained, it is suitable as a target for implementing the cobalt recovery method of the present invention.

The inorganic acid used in the dissolving step is not particularly limited as long as it can dissolve the cobalt in the cobalt valuables in the aqueous acid solution, and is not particularly limited. However, other contents contained in the cobalt valuables are considered. In addition, it is preferable to use hydrochloric acid or sulfuric acid from the viewpoint of post-treatment including workability, handling, and pollution prevention.

(2) Recovery Step In the recovery step, one or more metals or amphoteric metals having a standard electrode potential in the range of -2.4 V to -0.6 V in an acidic solution are reduced as a reducing metal to obtain a reduced solution. To reduce and recover cobalt.

The present inventors have proposed a cobalt metal element (cobalt-0.28 V) whose standard electrode potential is lower than hydrogen,
As a result of intensive studies on the conditions that can be industrially produced by a combination of elements whose standard electrode potential is lower than that of the cobalt element, cobalt was reduced from the above-mentioned reduced solution using a metal having a standard electrode potential in the above range. And found a method of recovery. Examples of the metal simple substance within the range include Cr, Zn, Mn, Al, and Mg.

In the case of a metal having a standard electrode potential outside the above range in an acidic solution, the following problems occur. That is, in the range of -0.28 V to -0.6 V, which is the standard electrode potential of cobalt, the standard electrode potential of cobalt is too close to the standard electrode potential of cobalt, and the reduction reaction is slow. The standard electrode potential is-
At 2.4V or less, potassium metal (-2.925V),
Like calcium metal (-2.713V), the reduction reaction runs away because of its high reactivity.

Here, the addition amount of the reducing metal is 1 to 1.5 equivalents to the cobalt element, but from the viewpoint of controlling runaway of the reduction reaction of cobalt and improving the recovery rate of cobalt, When adding a metal, it is necessary to consider a reduction method according to the cobalt content (cobalt concentration) in the reduction solution.

That is, when a relatively high concentration of cobalt ions is reduced at once with a powdery reducing metal having a large specific surface area to precipitate cobalt from a reducing solution, a reduction reaction accompanied by heat generation rapidly progresses, and often a runaway occurs. It becomes impossible to control. For example, when a cobalt chloride aqueous solution containing 50 g / L of cobalt is externally water-cooled with stirring and a predetermined amount of aluminum powder is added little by little, a significant gas is generated after an induction period of 2 to 3 minutes. At the same time, it was observed that the temperature of the system rapidly increased, and the system was brought to a boiling state and became a dangerous state.

Further, even if another experiment was conducted in which the aluminum powder to be added to the aqueous solution of cobalt chloride was added to a very small amount over a long period of time, the reaction did not remarkably occur until the certain amount was added, and the induction period was short. Just become longer (5-7
Minute), after the induction period, the reaction went out of control and became uncontrollable.

Further, the temperature of the system was set to 45 to 50 ° C., and a small amount of aluminum powder was added over a long period of time. However, only the time of the induction period was shortened. Violent and dangerous. From the above facts, it was concluded that the method in which the aluminum powder was put into the high-concentration cobalt solution in one step to reduce it could not prevent the runaway reaction on an industrial scale.

Therefore, it is preferable to reduce the runaway of the reduction reaction by performing the reduction in a plurality of times for the reduction solution containing a relatively high concentration of cobalt ions. That is, it is preferable to add a reducing metal having a small specific surface area (for example, a lump having a particle size of 5 mm or more) to reduce and recover cobalt while suppressing runaway of the reaction accompanying the reduction.

Subsequently, a reduced metal having a large specific surface area (for example, a particle diameter of 1 mm) is applied to the reduced solution of the liquid (filtrate) in which the concentration of cobalt ions has become low due to the recovery of cobalt.
It is preferable to reduce and collect cobalt by adding the following or powdery substances). This is because, if the concentration of cobalt ions remaining in the reduction solution is low, the cobalt content is small relative to the amount of the reduction solution, so that even if the reduction is performed quickly, the calorific value is small and the reduction reaction does not run away. .

As described above, the step of adding a reducing metal having a larger specific surface area as the concentration of cobalt ions lowers is repeated a plurality of times as necessary, so that the work efficiency and the recovery efficiency can be improved, and the industrial efficiency can be improved. This is preferable as a cobalt recovery method.

According to the above method, cobalt ions are easily reduced. For example, cobalt powder having a purity of 95% or more and a yield of 90% or more can be obtained from valuable materials obtained by treating a used lithium ion battery. Becomes Although the produced cobalt powder has a different particle size (accordingly, its specific surface area) depending on the reaction conditions, any of them is oxidized and easily generates heat when dried, so care must be taken when storing it in the air.

(3) Purification Step In the purification step, washing with an alkaline solution is preferable because the amphoteric metal mixed in cobalt can be dissolved and removed for purification. In the recovery step (2), it is only necessary to separate and recover the precipitate of cobalt metal generated by the addition of the reducing metal, and it is possible to increase the cobalt purity only by washing it. The cobalt precipitate is separated and recovered, and then washed with an alkali to elute and remove the amphoteric metal in the washing solution, thereby further improving the purity of cobalt.

The amphoteric metal having a standard electrode potential within the above range is selected from aluminum (-1.66 V) or (and) from the viewpoints of availability, handling, and pollution prevention.
It is preferable to use zinc (-0.763 V).

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment of a method for recovering cobalt according to the present invention will be described in detail. FIG. 1 is a process chart of Examples 1 and 2, and FIG.
FIG.

[Preparation of sample] (1) Cobalt compound (cobalt slag) from lithium battery
Adjustment of the cobalt compound, using a cobalt oxide-containing material (called cobalt slag) recovered from a lithium ion secondary battery,
Its manufacturing method is based on the Asaka Riken Industrial Open Law (Japanese Patent Application No. 09-02 / 2009).
6759).

(2) Preparation of aqueous cobalt chloride solution and aqueous cobalt sulfate solution 10 k of cobalt slag having a cobalt content of 40% obtained in (1)
g was dissolved in 31.8 kg of 35% industrial hydrochloric acid, the insoluble carbon powder was removed by filtration, and water was added to this aqueous solution to make the whole to 80 L. The cobalt content of the aqueous cobalt chloride solution was 50 g / L.

The 40% cobalt slag obtained in (1) 10
was added to 68 kg of 20% sulfuric acid and dissolved at 70 ° C., and then the system was filtered.
I made it. The cobalt content of this aqueous cobalt sulfate solution is 5
It was 0 g / L.

Example 1 Two-Step Reduction of Cobalt Chloride Aqueous Solution with Manganese 450 g of manganese lump having a diameter of about 5 mm was added to 8 L of the aqueous cobalt chloride solution obtained in (2), and the temperature of the system was adjusted to 9 under stirring.
Increased to 5 ° C. Gas evolution was observed as the temperature of the system increased. After continuing the reaction for 2 hours as it was, the mixture was allowed to cool and then filtered to collect a precipitate 1 of reduced cobalt powder. Since cobalt remained in the filtrate, the color of the solution was purple-red. Manganese powder (particle size # 0.
(2 mm mesh) was added several times to the system for 20 gr. When the stirring was stopped, the system was separated into two layers, and the reddish purple supernatant liquid became thinner with the progress of the reaction and became almost colorless and transparent.
After the reaction, the supernatant was removed by decantation to obtain a precipitate 2. The precipitates 1 and 2 were combined and washed with water to obtain 300 g (75%) of cobalt metal powder. At this time, the purity of the cobalt metal powder was 87%.

Example 2 Two-Step Reduction of Cobalt Chloride Aqueous Solution with Aluminum 80 L of cobalt chloride aqueous solution obtained in (2) was added
About 2200 gr of aluminum lump was added, and the temperature of the system was raised to 80 ° C. with stirring. Gas evolution was observed as the temperature of the system increased. After continuing the reaction for 2 hours as it was, the mixture was allowed to cool and then filtered to collect reduced cobalt powder precipitate 3. Since cobalt remained in the filtrate, the color of the solution was purple-red. To this filtrate, powdered aluminum (particle size # 0.1 mm mesh) was added several times to the system for 100 gr. When the stirring was stopped, the system separated into two layers,
The red-purified supernatant liquid became thinner with the progress of the reaction and became almost colorless and transparent. After the reaction, the supernatant was removed by decantation to obtain a precipitate 4. The precipitates 3 and 4 were combined and washed with water to obtain 3.8 kg (95%) of cobalt metal powder. At this time, the purity of the cobalt metal powder was 90%.

Example 3 Two-Step Reduction of Cobalt Chloride Aqueous Solution with Aluminum A 5 mm diameter was added to 80 L of the cobalt chloride aqueous solution obtained in (2).
About 2200 gr of aluminum lump was added, and the temperature of the system was raised to 95 ° C. with stirring. Gas evolution was observed as the temperature of the system increased. After continuing the reaction for 2 hours as it was, the mixture was allowed to cool and filtered to collect a precipitate 5 of reduced cobalt powder.

Since cobalt remains in the filtrate,
The color of the solution was reddish purple. To this filtrate, powdered aluminum (particle size # 0.1 mm mesh) was added several times to the system for 100 gr. When the stirring was stopped, the system was separated into two layers, and the reddish purple supernatant liquid became thinner with the progress of the reaction and became almost colorless and transparent. After the reaction, the supernatant was removed by decantation to obtain a precipitate 6. The operation of combining Precipitate 5 and Precipitate 6 and adjusting the pH to 14 with an aqueous solution of caustic soda was carried out, and the operation of stirring for 1 hour to elute and remove aluminum as a reducing agent was repeated twice.

Finally, the slurry was washed with water to obtain 3.9 kg (97.5%) of cobalt metal powder. At this time, the purity of the cobalt metal powder was 98.5%. When the resulting cobalt powder was filtered and dried in the air, it generated heat due to oxidation.

Example 4 One-Step Reduction of Aqueous Cobalt Chloride with Aluminum Using only powdered aluminum, using 10 L of the aqueous cobalt chloride solution obtained in (2) under the same conditions as in Example 3 except for the reaction temperature. A reduction reaction was attempted. That is, under stirring, water was cooled from the outside, and a predetermined amount of aluminum powder was added little by little. After an induction period of 2 to 3 minutes, remarkable gas generation occurred and the system temperature rose rapidly, The test was stopped because it was boiling and dangerous.

Example 5 Two-Step Reduction of Cobalt Sulfate Aqueous Solution with Aluminum To 200 L of the aqueous solution of cobalt sulfate obtained in (2), 2200 gr of aluminum lump was added, and while stirring, the temperature of the system was reduced to 8%.
Increased to 0 ° C. As the temperature of the system rose, the reddish purple color of the supernatant liquid faded, indicating that the reaction proceeded.

However, the progress of the reaction was slightly slower than in the case of the hydrochloric acid solution of Example 3. When the temperature of the system was raised to 95 ° C. to increase the reaction rate, or even when a small amount of 35% hydrochloric acid was added to promote the reaction, the entire system did not run away.

After continuing the reaction for 2 hours, the mixture was allowed to cool and then filtered to collect a precipitate 7 of reduced cobalt. Further, since cobalt remained in the filtrate, the solution exhibited a purple-red color. While stirring the filtrate, powdery aluminum
It was added to the system several times for 00 gr.

When the stirring was stopped, the system was separated into two layers, and the reddish purple supernatant liquid became thinner with the progress of the reaction and became almost colorless and transparent. After the reaction, the supernatant was removed by decanting to obtain cobalt precipitate 8. The operation of combining Precipitate 7 and Precipitate 8, adjusting the pH to 14 by adding an aqueous solution of caustic soda, stirring for 1 hour, and eluting and removing aluminum as a reducing agent was repeated twice.

Finally, the cobalt precipitate was washed with water to obtain 3.8 kg (yield 95.0%) of cobalt metal powder and 98.8% purity of cobalt metal powder. When the resulting cobalt powder was filtered and dried in the air, it generated heat due to oxidation.

Example 6 One-Step Reduction of Aqueous Solution of Cobalt Sulfate with Aluminum A small amount of a predetermined amount of aluminum powder was added to 1.0 kg of the aqueous solution of cobalt sulfate obtained in Experimental Example 2 while stirring under water cooling. At first glance, the reaction seemed to be slow.
For this reason, when the temperature was raised to 60 ° C., the temperature of the system rose rapidly and steam was bumped, and the reaction was no longer controllable.

[Experimental Example 7] Two-stage reduction of cobalt chloride aqueous solution with zinc 10 L of aqueous cobalt chloride solution obtained by (2)
About 666 gr of zinc metal in a granular form was added, and the temperature of the system was raised to 80 ° C. with stirring.

Gas generation was observed as the temperature of the system increased. After continuing the reaction for 3 hours, the system cooled to room temperature was filtered to collect reduced cobalt precipitate 9. Since cobalt remained in the filtrate, the color of the solution was purple-red. Subsequently, powdery metallic zinc was added to the filtrate several times in an amount of 35 gr.

When the stirring was stopped, the system was separated into two layers, and the reddish purple supernatant liquid became thinner with the progress of the reaction and became almost colorless and transparent. After the reaction, the supernatant was removed by decantation to obtain a precipitate 10. The precipitates 9 and 10 were combined, adjusted to pH 14 by adding an aqueous solution of caustic soda, and stirred for 2 hours to elute and remove zinc powder as a reducing agent.

Finally, the precipitate was washed with water to obtain 487 gr (95.9%) of cobalt metal powder. At this time, the purity of the cobalt metal powder was 98.5%. When the resulting cobalt powder was filtered and dried in the air, it generated heat due to oxidation.

Example 8 One-Step Reduction of Cobalt Chloride with Zinc Powder While stirring 1.0 L of the aqueous cobalt chloride solution obtained in Experimental Example 2, 1/10 of a predetermined amount of zinc powder was added to the solution, followed by mixing.
When the temperature was raised to ° C., the temperature of the system rapidly increased and steam was bumped, and the experiment was stopped because the reaction could not be controlled.

[0056]

[Possibility of Other Embodiments] In order to achieve the object of the present invention, the present embodiment can be modified as follows. That is, as a raw material of the cobalt valuables, a lithium battery using cobalt is suitable, but not limited thereto. Furthermore, a reducing metal or an amphoteric metal is further added to the filtrate after the cobalt has been recovered, and the cobalt ions remaining in the filtrate are reduced and recovered, but this step is optional. Yes, and can be omitted.

[0057]

As described above, according to the cobalt recovery method of the present invention, cobalt valuables can be industrially wet-reduced in an aqueous solution to produce metallic cobalt and precipitate out of the system as a precipitate. .

In particular, by using an amphoteric metal as the reducing metal, the cobalt metal precipitate generated by the reduction of cobalt ions is washed with an alkaline solution and purified by eluting the amphoteric metal with an alkali to further improve the cobalt purity. It is possible to improve.

Therefore, it is possible to recover cobalt metal with only small and medium-sized facilities, further promote the recovery of used lithium batteries, and solve the problem of pollution. It is.

[Brief description of the drawings]

FIG. 1 is a process chart of Examples 1 and 2.

FIG. 2 is a process chart of Examples 3, 5 and 7.

Claims (3)

[Claims] (1) a dissolving step of dissolving cobalt in a cobalt valuable material with an inorganic acid and purifying and eliminating insoluble components to produce a reduced dissolving solution; A recovery step for reducing and separating and recovering cobalt by adding one or more reducing metals having a standard electrode potential in the range of 6 V. 2. A dissolving step of dissolving cobalt in a cobalt valuable material with an inorganic acid and purifying and eliminating insoluble components to produce a reduced dissolving solution; and dissolving the reduced dissolving solution in a range of -2.4V to -0.4V. A recovery step of reducing and separating and recovering cobalt by adding one or more amphoteric metals having a standard electrode potential in the range of 6 V, and a purification step of removing the amphoteric metal by washing the cobalt recovered in the recovery step with an alkali. And a process for recovering cobalt. 3. In the recovery step, after reducing and cobalt-reducing cobalt by adding a reducing metal or an amphoteric metal and recovering the liquid, the specific surface area of the liquid to be reduced and dissolved is further increased from the previous time. 3. The method for recovering cobalt according to claim 1, wherein the step of reducing and separating and recovering cobalt is repeated a plurality of times by adding a new reducing metal or amphoteric metal.