JP2022170067A - Cobalt recovery method - Google Patents

Abstract

To provide a cobalt recovery method enabling recovery of a cobalt precipitate having high cobalt purity.SOLUTION: A cobalt recovery method is provided which is used for recovering cobalt from a recycled raw material including the cobalt, the method comprises: a leaching step of dissolving the recycled raw material by acid solution, and leaching the cobalt into the acid solution; an impurity precipitation step of adding aqueous solution of a sodium hydroxide to a leachate produced by the leaching, and thereby precipitating impurity in the leachate; an impurity removal step of removing the precipitated impurity; and a cobalt precipitation step of adding aqueous solution of sodium hypochlorite to the leachate from which the impurity has been removed, and thereby precipitating the cobalt.SELECTED DRAWING: Figure 1

Description

The present invention relates to a cobalt recovery method.

Cobalt is used in mobile phones, laptop computers, electric vehicles, special steel, etc. in Japan. Cobalt is most commonly used as a cathode material in lithium-ion batteries. In particular, applications in automotive lithium-ion batteries are boosting demand, and cobalt compounds such as cobalt oxide and cobalt sulfate are mainly used. Electrolytic cobalt (cobalt bare metal) is mainly used in special steels (superalloys, superalloys), etc., but cobalt oxide is also used in some areas. It is also used for permanent magnets such as alnico magnets (Al--Ni--Co) and samarium-cobalt magnets used in home electric appliances and audio equipment.

However, cobalt is a rare metal and has a higher market price than other metals. In addition, because of the uneven distribution of production areas, the supply is unstable, and at present, most of the demand is dependent on imports.

Therefore, it is desired to recover and recycle rare and valuable materials such as cobalt and nickel from used lithium ion batteries, special steel, and the like. A method for recovering a high-purity cobalt compound from lithium ion battery waste has been proposed (see Patent Document 1).

JP-A-11-6020

However, the conventional recovery method has a problem that the cobalt purity in the cobalt precipitate is not high.

A method for recovering cobalt according to the present invention is a method for recovering cobalt from a recycled raw material containing cobalt, the method comprising: a leaching step of dissolving the recycled raw material in an acid solution and leaching the cobalt into the acid solution; an impurity precipitation step of precipitating impurities in the leachate by adding a sodium hydroxide aqueous solution to the leachate produced by the leach; an impurity removal step of removing the precipitated impurities; and a cobalt precipitation step of precipitating the cobalt by adding an aqueous sodium hypochlorite solution.

According to the present invention, cobalt precipitates with high cobalt purity can be recovered.

It is a flow chart which shows an example of the cobalt recovery method of this embodiment. It shows the composition of sludge measured by a fluorescent X-ray spectrometer. It shows the composition of the sludge measured by ICP emission spectrometry. 4 is a graph showing the relationship between the solid-liquid ratio (sludge/hydrochloric acid) for each concentration at a hydrochloric acid concentration of 1.8 mol/L and the leaching amount of cobalt per 1 g of sludge. 4 is a graph showing the relationship between the solid-liquid ratio (sludge/hydrochloric acid) for each concentration at a hydrochloric acid concentration of 6.0 mol/L and the leaching amount of cobalt per 1 g of sludge. 4 is a graph showing the relationship between the solid-liquid ratio (sludge/hydrochloric acid) for each concentration at a hydrochloric acid concentration of 12 mol/L and the leaching amount of cobalt per 1 g of sludge. The concentration of hydrochloric acid (1.8 mol/L, 6.0 mol/L, and 12 mol/L) and the leaching rate of cobalt, iron, and copper for each concentration (amount of leaching by hydrochloric acid/amount of leaching by aqua regia) and It is a graph showing the relationship between. 4 is a table showing the composition of the leachate used in the precipitation treatment of this embodiment. It is a graph which shows the precipitation rate of each metal by addition of sodium hydroxide aqueous solution. 4 is a graph showing the weight of cobalt in the precipitate with respect to pH changes due to the addition of an aqueous sodium hypochlorite solution. Figure 2 is a graph showing the weight percentages of cobalt, iron, copper, and nickel in the leachate prior to impurity removal and in the leachate of the cobalt precipitate. It shows the composition of cobalt precipitates measured by a fluorescent X-ray spectrometer.

The cobalt recovery method of the present invention will be described with reference to the drawings. FIG. 1 is a flow chart showing an example of the cobalt recovery method of this embodiment.

As shown in FIG. 1, the cobalt recovery method is a method for recovering cobalt from recycled raw materials containing cobalt, wherein the recycled raw materials are dissolved in an acid solution, and the cobalt is leached into the acid solution. a leaching step (step 50); an impurity precipitation step (step 51) of precipitating impurities in the leaching solution by adding an aqueous sodium hydroxide solution to the leaching solution produced by the leaching; and an impurity removal step of removing the precipitated impurities. and a cobalt precipitation step (step 53) of precipitating the cobalt by adding an aqueous sodium hypochlorite solution to the leachate from which the impurities have been removed. Note that the impurities include at least one element of iron and copper.

In this embodiment, an experiment was conducted using sludge obtained by firing and processing waste containing lithium ion batteries, neodymium magnets, and the like. Sludge contains rare metals such as cobalt, neodymium, and nickel, as well as impurities such as iron and copper. Therefore, in order to recover cobalt contained in the sludge, metals such as iron and copper are removed as impurities, and cobalt is recovered as a high-purity cobalt precipitate.

First, the leaching process (step 50) of this embodiment will be described. Sludge, which is a recycled raw material, was measured by an energy dispersive X-ray fluorescence spectrometer (SHIMADZU EDX-7000). FIG. 2 shows the composition of sludge measured by a fluorescent X-ray spectrometer. As shown in FIG. 2, the main composition weight percent of the sludge is 31.2 weight percent cobalt, 25.7 weight percent iron, 22.7 weight percent neodymium, 3.85 weight percent copper, It resulted in 1.16 wt% nickel, 9.68 wt% chlorine, and about 5.71 wt% others.

In addition, sludge, which is a recycled raw material, was leached with aqua regia, and the amount of leaching of major metals was measured by ICP emission spectrometry (ICP-AES). 1 g of sludge was leached into 20 mL of aqua regia (15 mL of concentrated sulfuric acid + 5 mL of concentrated nitric acid), and the leaching amount of each metal was measured for cobalt, iron, and copper by ICP-AES (SHIMADZU ICPS-9000). FIG. 3 shows the composition of the sludge measured by ICP emission spectrometry. As shown in FIG. 3, the weight of the main composition of the sludge was 161.3 mg cobalt, 127.2 mg iron and 23.6 mg copper per gram of sludge.

In the present embodiment, it is assumed that metals in the sludge are completely leached by aqua regia, and the leaching experiment with hydrochloric acid is performed based on the amount of leaching by aqua regia.

4 to 6 show the solid-liquid ratio (sludge/hydrochloric acid) 1/20 g/ 1 is a graph showing the relationship between mL, 1/40 g/mL, 1/60 g/mL, 1/80 g/mL, and 1/100 g/mL and the amount of cobalt leached per 1 g of sludge.

FIG. 4 is a graph showing the relationship between the solid-liquid ratio (sludge/hydrochloric acid) for each concentration at a hydrochloric acid concentration of 1.8 mol/L and the leaching amount of cobalt per 1 g of sludge. FIG. 5 is a graph showing the relationship between the solid-liquid ratio (sludge/hydrochloric acid) for each concentration at a hydrochloric acid concentration of 6.0 mol/L and the leaching amount of cobalt per 1 g of sludge. FIG. 6 is a graph showing the relationship between the solid-liquid ratio (sludge/hydrochloric acid) for each concentration at a hydrochloric acid concentration of 12 mol/L and the leaching amount of cobalt per 1 g of sludge.

As shown in FIGS. 4 to 6, the weight of cobalt leached with hydrochloric acid was almost constant without being affected by the solid-liquid ratio. From this result, it was clarified that the optimum solid-liquid ratio (sludge/hydrochloric acid) for leaching cobalt is 1/20 g/mL (20 mL of hydrochloric acid for 1.0 g of sludge). In subsequent experiments, sludge, which is a recycled raw material, was dissolved under these conditions.

FIG. 7 shows the concentrations of hydrochloric acid (manufactured by Wako) (1.8 mol/L, 6.0 mol/L, and 12 mol/L) and the leaching rates of cobalt, iron, and copper for each concentration (the amount of leaching by hydrochloric acid). / amount of leaching by aqua regia). As described above, in the present embodiment, it is assumed that metals in the sludge are completely leached by aqua regia, and as shown in Equation (1), leaching experiments with hydrochloric acid are performed based on the amount of leaching by aqua regia. rice field.

Leaching rate [%] = (WD/WA) x 100 (1)

Here, WD is the leaching amount (weight [mg]) of each metal dissolved in 20 mL of hydrochloric acid, and WA is the leaching amount (weight [mg]) of each metal dissolved in 20 mL of aqua regia.

As shown in FIG. 7, at a hydrochloric acid concentration of 1.8 mol/L, the leaching rate was insufficient for any metal. At a hydrochloric acid concentration of 6.0 mol/L, the leaching rate of iron and copper was 95% or more, and the leaching rate of cobalt was about 80%. At a hydrochloric acid concentration of 12 mol/L, the leaching rate of any metal was over 95%. It was found that the leaching rate of cobalt increased in the order of hydrochloric acid concentrations of 1.8 mol/L, 6.0 mol/L and 12 mol/L, and that the leaching rate increased as the hydrochloric acid concentration increased.

However, hydrochloric acid with a concentration of 12 mol/L is highly concentrated, which increases the risk of subsequent reactions and treatments and increases the amount of reagents used in subsequent reactions. For recovery, it is preferable to reduce the concentration of hydrochloric acid while obtaining a sufficient leaching rate of cobalt. Therefore, with hydrochloric acid having a hydrochloric acid concentration of 6.0 mol / L or more and 8.0 mol / L or less (preferably 6.0 mol / L), the solid-liquid ratio (sludge / hydrochloric acid) is 1/18 g / mL or more. / 22 g / mL or less (preferably 1/20 g / mL) of hydrochloric acid, at a temperature of 45 ° C. or higher and 55 ° C. or lower (preferably 45 ° C. or higher and 50 ° C. or lower) for 10 hours or more and 14 hours or less (preferably , 12 hours), when the sludge was dissolved, the sludge was completely dissolved with no solid residue of sludge after filtration.

The acid solution in which sludge is most soluble is hydrochloric acid, and hydrochloric acid is safe among acid solutions and is suitable for industrialization in that it is easy to handle. The optimum leaching conditions for the metal content of the sludge under the conditions were verified.

Next, the precipitation process (steps 51 to 54) will be described. FIG. 8 is a table showing the composition of the leachate used in the precipitation treatment of this embodiment. The sludge was dissolved by stirring at a temperature of 50° C. for 12 hours with hydrochloric acid having a hydrochloric acid concentration of 6.0 mol/L and a solid-liquid ratio (sludge/hydrochloric acid) of 1/20 g/mL.

As shown in FIG. 8, the main composition of the leachate obtained by dissolving the recycled raw material sludge with hydrochloric acid is 51.7% by weight of cobalt, 39.6% by weight of iron, and 6.8% by weight of copper. % by weight.

In the composition of sludge, iron is the second most abundant metal after cobalt. In order to remove iron efficiently, there is a method of precipitating iron hydroxide by hydroxide precipitation. Copper can also be removed by this hydroxide precipitation. From the experimental results of hydrogen ion exponent (pH) dependence for hydrolysis reaction of metal ions, it was found that as the hydrogen ion exponent increases, precipitates are deposited in the order of trivalent iron, copper, divalent iron, and cobalt. is shown, and selective precipitation of iron and copper is possible by adjusting the hydrogen ion exponent.

In this embodiment, in the impurity removal process (step 51), a sodium hydroxide aqueous solution (manufactured by Wako) with a concentration of 2.5 mol/L was added to the leachate to change the hydrogen ion concentration.

Then, in the impurity recovery process (step 52), the deposited sediment was separated by a centrifugal separator. To determine the composition of the precipitate, the precipitate was dissolved in 20 mL of hydrochloric acid with a concentration of 12 mol/L and the weight of cobalt, iron, copper and nickel was determined by ICP-AES. In addition, the weights of cobalt, iron, copper and nickel in the leachate after sediment separation were measured by ICP-AES.

FIG. 9 is a graph showing the precipitation rate of each metal due to the addition of sodium hydroxide aqueous solution. FIG. 9 shows the effect of pH on the precipitation rate of cobalt, iron, copper, and nickel with sodium hydroxide addition. The precipitation rate of each metal is calculated by Equation (2).

Sedimentation rate [%] = [WP / (WP + WS)] × 100 (2)

Here, WP is the weight [mg] of the precipitate of each metal, and WS is the weight [mg] of each metal in the supernatant liquid (leaching liquid) after separation of the precipitate.

As shown in FIG. 9, the selectivity of precipitation was in order of iron, copper and cobalt with increasing pH of the leachate. Iron was almost completely precipitated at a leachate pH of 3 or higher, and copper was almost completely precipitated at a leachate pH of 5 or higher.

Also, iron and copper were completely precipitated at a leachate pH of 5.42. The precipitation rate of cobalt at this time was 21.2%, and the precipitation rate of cobalt was the lowest under the conditions of the leachate in which iron and copper completely precipitated.

It has been shown that iron (II) hydroxide hardly precipitates when the pH of the leachate is 3. However, in this measurement, almost 100% of iron precipitates when the pH of the leachate is 3. It is believed that the iron in the leachate in the morphology was trivalent. The reason for this is that the divalent iron contained in the leachate is oxidized into trivalent iron when dissolved in hydrochloric acid at a predetermined temperature (45° C. or higher and 55° C. or lower, preferably 45° C. or higher and 50° C. or lower). It is presumed that this is because Therefore, in the present embodiment, by leaching the sludge with hydrochloric acid at a predetermined temperature in the above-described leaching step, the iron in the leachate is present as approximately trivalent, and by making the pH of the leachate 3 or higher, iron precipitated as iron(III) hydroxide.

In addition, in the present embodiment, copper was almost completely precipitated when the pH of the leaching solution was 5 or higher. Therefore, it was found that the copper could be removed by increasing the pH of the leaching solution to 5 or higher.

However, a small amount of cobalt precipitate was deposited along with iron and copper precipitates. From FIG. 9, the precipitation of cobalt started when the pH of the leachate was 3 or higher. In this case, since the pH of the leachate was 3 and iron was almost completely precipitated, it is presumed that cobalt was coprecipitated with iron(III) hydroxide. Also, when the pH of the leachate reached 5, the cobalt precipitation rate increased. In this case, since copper was almost completely precipitated at a pH of 5 in the leachate, it is presumed that cobalt was coprecipitated with copper(II) hydroxide.

This is considered to be due to the coprecipitation action of iron (III) hydroxide and copper (II) hydroxide together with coexisting heavy metals when they are precipitated. Therefore, the reason why the cobalt precipitated was that the cobalt remaining in the supernatant of the leachate was induced by iron(III) hydroxide and copper(II) hydroxide to co-precipitate.

As described above, the removal of iron from the leachate after dissolving the sludge by using sodium hydroxide is achieved by the oxidation action of hydrochloric acid at a predetermined temperature (45° C. or higher and 55° C. or lower, preferably 45° C. or higher and 50° C. or lower). Iron in the leachate was almost completely recovered as iron(III) hydroxide. When the pH of the leachate was 3 or higher, it was possible to precipitate and recover iron with high efficiency. Also, when the pH of the leachate was 5 or more, 0.13% of copper remained, but it was possible to precipitate and recover copper with high efficiency.

On the other hand, since cobalt precipitates when the pH of the leachate increases, it is necessary to suppress the precipitation of cobalt while recovering iron and copper with high efficiency.

Therefore, in the present embodiment, in the impurity precipitation step, an aqueous sodium hydroxide solution is added so that the hydrogen ion exponent of the leachate is pH 5.0 or more and pH 6.0 or less (preferably pH 5.0 or more and pH 5.5 or less). Precipitating said impurities (such as iron and copper) in said leachate by adding.

In this embodiment, sodium hydroxide is used to verify the conditions of the optimum impurity removal treatment (steps 51 and 52) for removing impurities from the leachate of the sludge, which is a recycled raw material.

Iron and copper were removed from the sludge leachate, leaving cobalt and nickel as the main metals remaining in the liquor. The content of nickel is as low as about 1% in the composition of the sludge. Therefore, in the present embodiment, in the cobalt precipitation process (step 53), an operation of selectively precipitating cobalt to recover a precipitate with high cobalt purity was performed.

As a method of selectively recovering cobalt, a method of obtaining a precipitate with sodium hypochlorite is used. In this embodiment, sodium hypochlorite was added as an oxidizing agent to precipitate and recover cobalt (step 54).

The solid-liquid ratio (sludge/hydrochloric acid) is 1/20 g/mL with hydrochloric acid having a concentration of 6.0 mol/L, and the sludge is dissolved by stirring at a temperature of 50°C for 12 hours, followed by filtration. A sodium hydroxide aqueous solution with a concentration of 2.5 mol/L was added to the resulting leachate so that the pH of the leachate was 5 or more and 6 or less, thereby precipitating iron and copper. After removing the precipitate by centrifugation, sodium hypochlorite (manufactured by Wako) was added to the supernatant to precipitate cobalt. Collect the precipitate by centrifugation, dissolve the collected material with 20 mL of hydrochloric acid having a concentration of 12 mol / L, measure cobalt, iron, copper, and nickel by ICP-AES, and obtain the weight and recovery rate of each metal. rice field.

FIG. 10 is a graph showing the weight of cobalt in the precipitate with respect to pH change due to the addition of sodium hypochlorite aqueous solution. When the pH of the leachate after removing impurities was 3.0 or more and 3.3 or less, the amount of cobalt precipitated was relatively small, and the recovery rate was about 10%. The amount of cobalt precipitated was the largest when the pH of the leachate after removing impurities was 3.34, and thereafter decreased as the pH increased.

Therefore, cobalt precipitated most when the pH of the leachate after impurity removal was between 3.3 and 3.5 (preferably between 3.3 and 3.4).

FIG. 11 is a graph showing the weight percentages of cobalt, iron, copper, and nickel in the leachate before impurity removal and in the leachate of the cobalt precipitate. FIG. 11(a) is a graph showing the weight % of the composition of the leachate before the impurities shown in FIG. 8 are removed. FIG. 11(b) shows that 5 mL of sodium hypochlorite was added to the leachate after removing impurities, and the cobalt precipitate precipitated when the pH reached 3.5 was treated with 20 mL of hydrochloric acid having a concentration of 12 mol/L. 1 is a graph showing the weight percent composition of the leachate of the cobalt precipitate, leached and leached in hydrochloric acid by ICP-AES.

As shown in FIG. 11, the cobalt purity of the cobalt precipitate was 98.2% after sodium hypochlorite addition. Since the cobalt purity in the leachate before impurity removal was 51.7%, cobalt could be recovered as a high-purity cobalt precipitate in this embodiment.

Also, in this embodiment, no precipitate of nickel was deposited. The reason for this is that cobalt was oxidized from divalent to trivalent by adding sodium hypochlorite, but nickel was not oxidized to trivalent while remaining divalent. It is thought that selective collection became possible. As a result, cobalt could be recovered as a high-purity cobalt precipitate containing little nickel. Therefore, although not shown in FIG. 11, the cobalt purity in the leachate after removing impurities was 96.5%, and after adding sodium hypochlorite, the cobalt purity of the cobalt precipitate further increased to 98.2%.

FIG. 12 shows the composition of cobalt precipitates measured by a fluorescent X-ray spectrometer. As shown in FIG. 12, the main composition weight percent of the cobalt precipitate is 51.7 weight percent cobalt, 5.43 weight percent neodymium, 1.20 weight percent copper, and 39.3 weight percent chlorine. %, and others were 2.37% by weight. Therefore, it can be said that the recovered metal is mostly cobalt.

As described above, when sodium hypochlorite is added to the leachate after impurities (iron, copper, etc.) have been removed, a precipitate of high-purity cobalt precipitates, making it possible to recover high-purity cobalt precipitate. there were. Comparing the pH of the leachate after removing the impurities and the amount of cobalt precipitated, the most cobalt precipitated when the pH was 3.3 or more and 3.5 or less (preferably 3.3 or more and 3.4 or less). As a result, the optimal condition is to add sodium hypochlorite so that the pH of the leachate after removing impurities is 3.3 or more and 3.5 or less (preferably 3.3 or more and 3.4 or less). made it clear that

Therefore, in the present embodiment, in the cobalt precipitation step (step 53), a sodium hypochlorite aqueous solution is added so that the hydrogen ion exponent of the leachate from which the impurities have been removed becomes pH 3.3 or more and pH 3.5 or less. precipitating said cobalt in said leachate by:

Although the embodiments according to the present invention have been described above, the present invention is not limited to these, and can be changed and modified within the scope described in the claims.

INDUSTRIAL APPLICABILITY The present invention is useful as a cobalt recovery method capable of recovering cobalt precipitates with high cobalt purity.

50 Leaching treatment 51 Impurity precipitation treatment 52 Impurity removal treatment 53 Cobalt precipitation treatment 54 Cobalt precipitate recovery treatment

Claims (6)

A cobalt recovery method for recovering cobalt from a recycled raw material containing cobalt,
a leaching step of dissolving the recycled raw material in an acid solution and leaching the cobalt into the acid solution;
an impurity precipitation step of precipitating impurities in the leachate by adding an aqueous sodium hydroxide solution to the leachate produced by the leachate;
an impurity removal step of removing the precipitated impurities;
a cobalt precipitation step of precipitating the cobalt by adding an aqueous sodium hypochlorite solution to the leachate from which the impurities have been removed;
A method for recovering cobalt, comprising: 2. The method according to claim 1, wherein the leaching step includes a step of leaching the cobalt with hydrochloric acid having a concentration of 6.0 mol/L or more and 8.0 mol/L or less at a temperature of 45° C. or more and 55° C. or less. Cobalt recovery method as described. In the leaching step, the solid-liquid ratio of the recycled raw material and the hydrochloric acid is 1/18 g/mL or more and 1/22 g/mL or less with hydrochloric acid having a concentration of 6.0 mol/L or more and 8.0 mol/L or less. 3. The method for recovering cobalt according to claim 1, further comprising the step of leaching said cobalt by stirring at a temperature of 45[deg.] C. or higher and 55[deg.] C. or lower for 10 hours or more and 14 hours or less with an amount of hydrochloric acid. The step of precipitating impurities includes a step of precipitating the impurities in the leachate by adding an aqueous sodium hydroxide solution so that the leachate has a hydrogen ion exponent of pH 5.0 or more and pH 6.0 or less. The method for recovering cobalt according to any one of claims 1 to 3. In the cobalt precipitation step, the cobalt in the leachate is removed by adding an aqueous sodium hypochlorite solution so that the hydrogen ion exponent of the leachate from which the impurities have been removed is pH 3.3 or more and pH 3.5 or less. 5. A method for recovering cobalt according to any one of claims 1 to 4, comprising a step of precipitating. 6. The cobalt recovery method according to any one of claims 1 to 5, wherein the impurities include at least one element of iron and copper.

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