JP2002241856A - Method for recovering valuable metal from used nickel- hydrogen secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method by which a solution containing high-purity valu able metal can be obtained by easily removing manganese from a solution prepared by dissolving electrode active material with sulfuric acid in the case of recovering valuable metal, such as nickel and cobalt, from a used nickel- hydrogen secondary battery. SOLUTION: The electrode active material is dissolved with the sulfuric acid, and the resultant solution is held at <=pH 3 and also ORP is regulated in a range of 1,000 to 1,200 mV to precipitate and remove manganese. For the purpose of pH regulation for the solution, trivalent nickel and/or cobalt hydroxide is added as an oxidizing agent. As to another method, manganese can also be precipitated and removed by holding the above solution at 50-90 deg.C reaction temperature and pH 1 to 5.5 and adding ammonium persulfate or sodium persulfate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the recycling of nickel-metal hydride secondary batteries, and to a method of recovering valuable metals such as nickel contained in used and discarded nickel-metal hydride secondary batteries.

[0002]

2. Description of the Related Art In a nickel-metal hydride secondary battery, a positive electrode and a negative electrode each having an electrode active material held on a support are separated by a separator such as polypropylene and stored in a steel or polypropylene container together with an electrolytic solution. A punched plate obtained by plating nickel on porous nickel or iron is used as a support, nickel hydroxide is used as a positive electrode active material, and a hydrogen storage alloy is used as a negative electrode active material.

The nickel-hydrogen secondary battery has recently been used as a secondary battery instead of a nickel-cadmium battery for batteries of electric vehicles, mobile phones, and the like, and the demand has been rapidly increasing. Nickel-metal hydride rechargeable batteries have better characteristics than nickel-cadmium batteries and do not use harmful cadmium.Thus, even if they are disposed, they do not cause serious pollution. And hydrogen storage alloys are valuable resources, and it is extremely important to recycle these valuable metals.

[0004] However, even if valuable metals are recovered from used nickel-metal hydride secondary batteries, it is difficult to recover valuable metals with high purity because batteries are becoming more compact with the miniaturization of electric appliances. It's not easy. Also,
Nickel-metal hydride secondary batteries used in automobile batteries cannot be easily disassembled because they have a structure that is hard to be broken by a car collision or the like. Under such circumstances, development of a method for recovering valuable metals easily and with high purity from used nickel-metal hydride secondary batteries has been desired.

[0005] In general, batteries cannot be easily disassembled due to their safety, and in order to reduce costs, when recovering valuable metals from used batteries, the entire battery is crushed and the crushed material is physically separated. Separation is the first step in the process. For example, iron and other substances are separated by magnetic separation.
In addition to the plastics being separated by specific gravity separation or the like, the electrode active material is separated from iron or plastics, which are the main components of the container or the support, by various physical separations such as sieving.

The separated electrode active material becomes a mixture of the active materials of the positive electrode and the negative electrode, but it is difficult to physically completely separate the positive electrode material and the negative electrode material. For this reason, conventionally, a method of once dissolving the separated electrode active material in a mineral acid such as hydrochloric acid or nitric acid and recovering valuable metals such as nickel and cobalt from the solution by chemical treatment has been adopted.

For example, when the electrode active material is dissolved with hydrochloric acid, a chloride solution of nickel, cobalt, a rare earth element or the like is obtained. However, in consideration of recycling for batteries, it is desirable that the recovered valuable metals can be reused as battery materials. For this reason, it is hated that corrosive chlorine remains, which is not preferable.

On the other hand, when dissolved with sulfuric acid, the entire amount of the electrode active material is dissolved, so that the solution becomes a mixed solution of the active materials of the positive electrode and the negative electrode, and various elements are mixed and dissolved.
Therefore, in order to reuse a valuable metal such as nickel as a battery material, it is necessary to selectively remove rare earth elements and manganese from the solution to recover a solution containing a high-purity valuable metal.

[0009]

As described above, an electrode active material separated from a used nickel-metal hydride secondary battery is dissolved with sulfuric acid, and a valuable metal such as nickel is recovered from the solution with high purity. It is necessary to separate and remove manganese and rare earth elements in the solution. However, rare earth elements can be selectively removed by solvent extraction or ion exchange, but selective removal of manganese is extremely difficult.

For example, it is possible to adsorb manganese to the chelating resin, but the concentration of manganese in the solution is as high as several g / l, so that it can be reduced to about half, but it cannot be completely removed. Impossible. Oxidation by ozone or electrolysis is also known as a method for removing manganese, but without coprecipitating nickel or cobalt,
It is difficult to precipitate and remove only manganese.

The present invention has been made in view of such a conventional situation,
This is a method of recovering valuable metals such as nickel and cobalt from used nickel-metal hydride secondary batteries.Easily removes manganese from a solution obtained by dissolving the separated electrode active material with sulfuric acid to recover high-purity valuable metals. It is an object to provide a method for obtaining a solution containing the same.

[0012]

In order to achieve the above object, the present invention provides a method for recovering valuable metals from a used nickel-metal hydride secondary battery. By dissolving with sulfuric acid, maintaining the resulting solution at pH 3 or less and adjusting the oxidation-reduction potential to a range of 1000 to 1200 mV with respect to a silver-silver chloride electrode, thereby precipitating and removing manganese and containing a valuable metal. It is characterized by obtaining a solution.

In the method for recovering valuable metals from a used nickel-metal hydride secondary battery according to the present invention, in order to adjust the oxidation-reduction potential of the solution, a hydroxide of trivalent nickel and / or cobalt is used as an oxidizing agent. Is added. The addition amount of the trivalent nickel and / or cobalt hydroxide is preferably 1.2 to 1.4 equivalents in terms of the total amount of nickel and cobalt with respect to manganese in the solution.

[0014] Alternatively, a second method for recovering valuable metals from a used nickel-metal hydride secondary battery provided by the present invention comprises dissolving the electrode active material separated from the used nickel-metal hydride secondary battery with sulfuric acid. The obtained solution is reacted at a reaction temperature of 50.
The solution containing valuable metals is obtained by precipitating and removing manganese by adding ammonium persulfate or sodium persulfate in an amount of 1 to 10 equivalents to manganese in the solution while maintaining the temperature at ~ 90 ° C and the pH at 1 to 5.5. It is characterized by the following.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, in carrying out the method of the present invention, as a preceding step, an electrode active material is separated and recovered from a used nickel hydrogen secondary battery. The method for separating and recovering the electrode active material is not particularly limited, but the method described in Japanese Patent Application No. 2000-37709 already proposed by the present inventors is preferable.

Specifically, first, a used nickel-metal hydride secondary battery is crushed, and the crushed material is stirred in water to form a slurry. At this time, plastics such as a separator easily float, and the plastics can be separated by using the plastics. Next, the crushed material dispersed in water is sieved, the support for the positive electrode and the negative electrode, the container, and the plastics are separated on a sieve, and the electrode active material is collected under the sieve.

In the present invention, the electrode active material separated under the sieve as described above is dissolved with sulfuric acid to obtain a solution in which the entire electrode active material is dissolved. In this solution, nickel, cobalt, zinc contained in the positive electrode active material, and nickel, cobalt, manganese, and rare earth elements contained in the negative electrode active material are dissolved.

First, according to the first method of the present invention, an oxidizing agent is added to keep the redox potential (ORP) of silver-dissolved solution at a level not higher than pH 3, preferably pH 1 to 2, while maintaining the solution at pH 3 or lower.
1000-1200 mV at a silver chloride electrode, preferably 11
It is adjusted to the range of 00 to 1200 mV. According to the first method, manganese can be selectively precipitated from the solution, and the manganese concentration can be reduced to a solution that is equal to or less than the specification required for the starting solution for producing nickel hydroxide for battery materials.

As an oxidizing agent to be used, a strong oxidizing agent such as ozone oxidizes nickel and cobalt, and co-precipitation is likely to occur. Accordingly, the oxidizing agent used in the first method is particularly preferably a hydroxide of trivalent nickel and a hydroxide of trivalent cobalt. This trivalent nickel or cobalt hydroxide is produced in a separate step by adding an oxidizing agent such as sodium hypochlorite or chlorine gas to a nickel solution or a cobalt solution. The obtained trivalent nickel and cobalt hydroxides are preferably washed with water before being added to the solution, so that chlorine remaining in the solution after the removal of manganese can be suppressed.

In the above-mentioned first method, 3 as an oxidizing agent is used.
When using nickel and / or cobalt hydroxides with a valency of 1, the total amount is 1 to manganese in the solution.
It is preferable that the amount is equal to or more than the equivalent. In particular, by setting the amount of hydroxide to be at least 1.2 equivalents in total of nickel and cobalt with respect to manganese, manganese can be almost completely removed to a liquid concentration of 0.001 g / l or less. .

According to the first method, trivalent nickel and / or
Alternatively, a reaction when a hydroxide of cobalt oxidizes and removes manganese is represented by the following chemical formula. At this time, since iron ions contained in the solution also become trivalent, it is possible to omit operations such as blowing air into the solution at the time of removing the rare earth element and iron in the next step, and in a subsequent step. , The removal of rare earth elements and iron becomes easier.

[0022]

[Formula 1] _{^{Mn 2+ + 2Co (OH) 3}} → MnO 2 + 2Co 2+ Mn 2+ + 2Ni (OH) 3 → MnO 2 + 2Ni 2+

Next, in the second method of the present invention, a solution in which all of the electrode active material is dissolved is reacted with a reaction temperature of 50-9.
Maintain at 0 ° C. and pH 1-5.5 and add ammonium or sodium persulfate as oxidizing agent. The addition amount of ammonium persulfate or sodium persulfate is 1 to 10 equivalents to manganese in the solution. By this second method, manganese in the solution can be removed by precipitation.

In the second method, the higher the reaction temperature of the solution, the more efficiently manganese can be precipitated and removed.
At a high temperature exceeding the above, the precipitation rate of cobalt also increases to about 30%, so that a reaction temperature of 70 to 90 ° C is preferable.
The precipitation rate of manganese increases as the pH of the solution increases, but the precipitation rates of nickel and cobalt also increase at the same time. Therefore, the pH is preferably about 3 to 4.

Particularly, the reaction conditions at a reaction temperature of 90 ° C. and a pH of about 4 are most preferable. When the amount of ammonium persulfate or sodium persulfate is 2 equivalents of manganese in the solution, the precipitation rate of manganese is 100%, A solution having a manganese concentration of 0.001 g / l or less is obtained.

The solution after removing the precipitate of manganese by filtration according to the method of the present invention contains valuable metals such as high-purity nickel and cobalt, and it is necessary to recover these valuable metals by a chemical treatment in a subsequent step. Can be. In addition, the rare earth element contained in the solution of the electrode active material can be selectively removed by solvent extraction or ion exchange before or after the treatment according to the method of the present invention.

[0027]

【Example】Example 1  The electrode active material recovered from nickel-metal hydride secondary batteries is
Dissolve and add 100 ml of the solution as a trivalent
After adding nickel and cobalt hydroxide, the reaction temperature was increased to 60.
Manganese was precipitated by stirring at 2 ° C. for 2 hours.
The trivalent nickel and cobalt used as the oxidizing agent
The composition of the hydroxide was 28% by weight of Ni and 18% by weight of Co.
% And moisture 35% by weight.

At this time, the amount of the oxidizing agent (total amount of nickel and cobalt in the hydroxide relative to the manganese in the solution), the pH of the solution, and the oxidation-reduction potential (OPR) with respect to the silver-silver chloride electrode Was changed as shown in Table 1 below. After removing the generated manganese precipitate,
The concentrations of Ni, Co, Mn, and Cl in the obtained filtrate were measured, and the results are shown in Table 1.

[0029]

[Table 1]

As can be seen from Table 1, the amount of the oxidizing agent (trivalent nickel and cobalt hydroxide) that can remove manganese almost completely is not less than 1.2 equivalents. , 6-8, manganese could be reduced to 0.001 g / l or less at a filtrate concentration of pH 1-2. However, in Samples 1, 2, 4, and 5 in which the amount of the oxidizing agent added was reduced to 1.0 equivalent or less, manganese could not be completely removed. In sample 8 in which the amount of the oxidizing agent added was increased to 1.6 equivalents, manganese could be completely removed, but only the amount required to reduce manganese and iron was dissolved, so that nickel and cobalt in the residue were not dissolved. Increase
Losses to the residue increased.

Regarding the ORP, from samples 3, 6 to 8,
It turns out that manganese completely precipitates at 1100 to 1200 mV. Further, since iron ions are also trivalent in the ORP region, oxidation is not required when removing rare earth elements and iron in a later step.

On the other hand, the chlorine concentration in the filtrate after the removal of manganese can be reduced to one-fourth to one-tenth by cleaning the hydroxide added as an oxidizing agent, as compared with the case without cleaning. I understand. When the hydroxide was not washed with water, the concentration of chlorine remaining in the filtrate was 0.5 g / l by adding 1.2 equivalents of the hydroxide. Excessive addition of hydroxide causes an increase in chlorine concentration.

Therefore, in consideration of suppressing the incorporation of chlorine and removing the rare earth element in a later step, the hydroxide, which is an oxidizing agent, is washed with water and used at a redox potential of 1100 to 1200 mV or more and a pH of 1 to 2. Is the optimal condition.

[0034]Example 2  Table 2 below shows a solution obtained by dissolving the electrode active material with sulfuric acid.
The three types of dissolution solutions shown were prepared. Dissolution A is a rare earth element
Is assumed to have been removed.
G contains only manganese. In addition, the solution B
Liquid C contains different concentrations of lanthanum and neonate as rare earth elements.
Contains Jium.

[0035]

[Table 2]

Using each of the solutions shown in Table 2 above, the following Table 3
As shown in Table 2, while adjusting the reaction temperature and pH, manganese was precipitated by adding ammonium persulfate as an oxidizing agent. At this time, the amount of ammonium persulfate was changed with respect to manganese in the solution as shown in Table 3, but the reaction time was 1 hour for all samples. Table 4 below shows the concentration of the filtrate after the removal of manganese and the precipitation rate of manganese.

[0037]

[Table 3]

[0038]

[Table 4]

As can be seen from the above results, the reaction temperature and p
H has a great effect on the precipitation rate of manganese and nickel, but the amount of ammonium persulfate added as an oxidizing agent is 1 to 1
What is necessary is just to be in the range of 0 equivalent. For example, if the reaction temperature is 50
In the case of ° C., in Samples 15 and 18 at pH 4, the greater the amount of ammonium persulfate added, the higher the manganese precipitation rate, but the maximum is 13.3%.
Among the samples 16, the sample 14 with an added amount of 1.5 equivalents had the highest manganese precipitation rate of 21.2%.

Regarding the change in pH, the reaction temperature was 50 ° C.
And the addition amount of ammonium persulfate as an oxidizing agent is 1.5
Comparing the equivalent amounts of Samples 11 to 14, it can be seen that the manganese precipitation rate increases as the pH increases. However, when the pH exceeds 5.5, the precipitation rate of nickel becomes 10% or more, for example, as in Sample 10, which has a pH of 5.87, which is not preferable. In Sample 17, which has a pH of 6.81, almost 100% of manganese can be precipitated. However, most of nickel and cobalt also precipitate.

On the other hand, it can be seen from a comparison between Samples 19 and 20 that the manganese precipitation rate increases significantly when the reaction temperature is increased. In particular, in Sample 20 in which the addition amount of ammonium persulfate was 2 equivalents and the pH was 4, the precipitation rate of manganese was 100%, and at this time, the precipitation rate of nickel was about 0.4%.
However, about 30% of the cobalt was precipitated.

From the above results, in the second method using ammonium persulfate or sodium persulfate as the oxidizing agent, the amount of ammonium persulfate or sodium persulfate was set to 1.5 to 2 equivalents, the reaction temperature was 90 ° C. and the pH was about 4. Then, it can be seen that nickel and manganese can be efficiently separated.

[0043]

According to the present invention, manganese can be easily and efficiently removed from a solution obtained by dissolving an electrode active material separated from a nickel-metal hydride secondary battery with sulfuric acid to leave corrosive chlorine. In addition, valuable metals such as nickel and cobalt can be recovered as high-purity solutions, and valuable metals such as nickel and cobalt, which are valuable resources, can be recycled.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Keiji Kudo 17-5 Isoura-cho, Niihama-shi, Ehime F-term in Niihama Research Laboratory, Sumitomo Metal Mining Co., Ltd. 4G048 AA10 AB08 AC06 AE02 4K001 AA07 AA19 AA39 BA22 CA01 CA02 DB03 DB23 JA05 5H031 AA02 BB09 EE03 HH01 HH03 HH06 RR02

Claims (4)

[Claims] An electrode active material separated from a used nickel metal hydride secondary battery is dissolved with sulfuric acid, and the obtained solution is adjusted to pH.
Spent nickel is obtained by precipitating and removing manganese to obtain a solution containing valuable metals by maintaining the oxidation-reduction potential in the range of 1000 to 1200 mV with respect to the silver-silver chloride electrode while maintaining the nickel content at 3 or less. A method for recovering valuable metals from hydrogen secondary batteries. 2. The used nickel according to claim 1, wherein a trivalent nickel and / or cobalt hydroxide is added as an oxidizing agent in order to adjust the oxidation-reduction potential of the solution. A method for recovering valuable metals from hydrogen secondary batteries. 3. The total addition amount of the trivalent nickel and / or cobalt hydroxide is 1.2 to 1.4 equivalents in terms of the total amount of nickel and cobalt with respect to manganese in the solution. The method for recovering valuable metals from used nickel-metal hydride secondary batteries according to claim 1, wherein the method comprises: 4. An electrode active material separated from a used nickel-metal hydride secondary battery is dissolved with sulfuric acid, and the obtained solution is maintained at a reaction temperature of 50 to 90 ° C. and a pH of 1 to 5.5, and is treated with ammonium persulfate or peroxide. Recycling of valuable metals from used nickel-metal hydride secondary batteries by adding 1 to 10 equivalents of sodium sulfate to manganese in the solution to precipitate and remove manganese to obtain a solution containing valuable metals Method.