JP2006008463A - Method for producing aqueous cobalt sulfate solution and method for producing cobalt hydroxide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing an aqueous cobalt sulfate solution, by which impurities contained in cobalt metal can be sufficiently removed when a high purity aqueous cobalt sulfate solution is produced from the cobalt metal containing impurities, and to provide a method for producing cobalt hydroxide using the aqueous cobalt sulfate solution obtained by the same. <P>SOLUTION: The method for producing the aqueous cobalt sulfate solution includes: a dissolving process for dissolving cobalt metal containing iron and silicon as impurities into an aqueous sulfuric acid solution; a iron-removing process for removing iron by depositing iron hydroxide by adding an oxidizing agent to oxidize the divalent iron to the solution obtained in the dissolving process and controlling the pH of the solution to 3-5; and a silicon-removing process for removing silicon by controlling the pH of the solution obtained in the iron-removing process to 5-6 and depositing the silicon. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing a cobalt sulfate aqueous solution and a method for producing cobalt hydroxide.

  Cobalt compounds such as cobalt oxide and cobalt hydroxide are used as high-performance battery materials in the fields of communication and information processing, such as personal computers, digital cameras, and mobile phones, or in the field of hybrid electric vehicles. Usually, these cobalt compounds are obtained from cobalt metal as a raw material through many steps such as dissolution, purification, neutralization treatment, crystal filtration, drying, and firing.

  The content of impurities contained in the raw material cobalt metal varies depending on the production area, and the impurity components are mainly iron, nickel mainly, iron and nickel mainly, iron, nickel and silicon. And so on. The cobalt metal contains copper, lead, zinc, chromium and the like as impurities in addition to the above components.

  In recent years, high-value-added new functional products have been actively developed in the fields of communication / information processing and automobiles described above, and cobalt compounds used in these applications have high purity from which impurities are sufficiently removed. Things are sought.

  In order to improve the purity of the cobalt compound, it is necessary to remove impurities appropriately according to the composition of the raw material cobalt metal. When only iron or nickel is used as an impurity, only the step of removing iron or nickel is sufficient, but as an impurity, two components of iron and nickel, or three components of iron, nickel and silicon are contained in a relatively large amount. When doing so, it is necessary to take each removal method step by step.

For example, in Patent Literature 1, a cobalt sulfate aqueous solution containing nickel and iron as impurities is allowed to act on a compound that generates divalent sulfide ions such as cobalt powder and sodium sulfide, and then sodium hypochlorite or A method is disclosed in which hydrogen peroxide is added to precipitate impurities such as nickel and iron.
JP-A-63-45131 (Claim 1)

  However, the method of Patent Document 1 does not propose a method for removing silicon, and silicon remains as an impurity when the raw material cobalt metal contains a large amount of silicon.

  Although the viewpoint is different, recently, a new proposal has been made as a positive electrode material for a lithium ion battery. That is, conventionally, a high-purity cobalt compound has been used alone, but a mixed battery material has been proposed instead of a single material. As a mixed material, a mixed material of cobalt, nickel and manganese has been put into practical use. In the case of such a mixed material, it is not always necessary to remove nickel as an impurity.

  In that case, the process of removing nickel in the method of Patent Document 1 is a useless process.

  The present invention has been made in view of the above-described problems of the prior art, and in manufacturing a high-purity cobalt sulfate aqueous solution from an impurity-containing cobalt metal, the cobalt sulfate capable of sufficiently removing impurities contained in the cobalt metal. It is providing the manufacturing method of aqueous solution, and the manufacturing method of cobalt hydroxide using the cobalt sulfate aqueous solution obtained by the manufacturing method.

  In order to solve the above-mentioned problems, the present invention is to dissolve a cobalt metal containing iron and silicon as impurities in an aqueous sulfuric acid solution, and to oxidize divalent iron into the solution obtained in the dissolving step. In addition to adding an oxidizing agent, the pH of the solution is adjusted to 3 to 5, the iron removal step of depositing and removing iron hydroxide, and the pH of the solution obtained in the iron removal step is adjusted to 5 to 6 And a method for producing a cobalt sulfate aqueous solution, comprising a silicon removal step of depositing and removing silicon.

  According to the method for producing an aqueous cobalt sulfate solution of the present invention, by adding an oxidizing agent to an aqueous sulfuric acid solution in which cobalt metal is dissolved and adjusting the pH of the solution to 3 to 5, precipitation of iron with good crystallinity (β -FeOOH) can be generated, and iron in the solution can be sufficiently removed.

  Furthermore, the silicon in the solution can be efficiently removed by adjusting the pH of the solution obtained by separating and removing iron as crystals to 5-6. That is, by adjusting the pH condition to a suitable range, the silicon concentration can be reduced without impairing the cobalt recovery rate.

  Moreover, the manufacturing method of the cobalt sulfate aqueous solution of the present invention is particularly effective when the cobalt metal contains a large amount of impurities. For example, even if cobalt metal containing 0.5 to 50 mg iron and 2 mg or less of silicon is used per 1 g of cobalt, iron is reduced to 0.05 mg or less and silicon is reduced to 0.3 mg or less per 1 g of cobalt. And a highly pure cobalt sulfate aqueous solution can be obtained.

  Moreover, the present invention adds a compound that generates iron powder and sulfide ions to a solution obtained by dissolving a cobalt metal containing nickel and iron as impurities in an aqueous sulfuric acid solution, and the solution obtained in the above-described dissolution step, A nickel removal step for depositing and removing nickel sulfide, and an oxidant for oxidizing divalent iron is added to the solution obtained in the nickel removal step, and the pH of the solution is adjusted to 3-5. And an iron removal step of depositing and removing iron hydroxide. A method for producing a cobalt sulfate aqueous solution is provided.

  Here, in the method described in Patent Document 1, a large amount of a compound that generates sulfide ions is used to remove nickel which is an impurity. As a result, the amount of coprecipitation of cobalt increases with an increase in the above-mentioned compounds used, the recovery rate of cobalt from the resulting high-purity cobalt sulfate aqueous solution decreases, and the processing cost increases.

  In particular, when low-grade cobalt metal is used as a raw material, since the raw material solution contains a large amount of nickel, it is necessary to increase the amount of the above compound used, and the amount of cobalt coprecipitation increases. The recovery rate is further reduced. As a case where nickel is contained in a large amount in the raw material solution, specifically, cobalt metal containing 1 mg or more of nickel with respect to 1 g of cobalt may be used as the raw material. In addition, the present inventors conducted a test on the amount of coprecipitation of cobalt in the method described in Patent Document 1, and when cobalt metal contained 3 mg of nickel with respect to 1 g of cobalt, the cobalt in the aqueous solution of cobalt sulfate. Of 20% was coprecipitated as cobalt sulfide.

  On the other hand, in the manufacturing method of the cobalt sulfate aqueous solution of the present invention including the nickel removal step, nickel is sulfided by adding iron powder to the solution obtained in the dissolution step, compared to the case where cobalt powder is added. It becomes easy to precipitate as nickel, the amount of cobalt coprecipitation can be reduced, and the amount of the compound that generates sulfide ions can be reduced. Furthermore, iron in the solution can be efficiently removed by adding an oxidizing agent to the solution obtained in the nickel removing step and adjusting the pH of the solution to 3 to 5.

  Therefore, according to the method for producing a cobalt sulfate aqueous solution of the present invention including a nickel removing step, when producing a cobalt sulfate aqueous solution from impurities containing cobalt metal, sufficiently reducing the recovery rate of cobalt in the solution, Impurities contained in the raw material can be efficiently removed, and a high-purity cobalt sulfate aqueous solution can be obtained.

  Moreover, in the manufacturing method of cobalt sulfate aqueous solution of this invention provided with a nickel removal process, in nickel removal process, impurities, such as lead, zinc, and cadmium, can also be removed simultaneously, and higher-purity cobalt sulfate aqueous solution is obtained. Can do.

  In the method for producing a cobalt sulfate aqueous solution of the present invention including a nickel removal step, when the cobalt metal further contains silicon as an impurity, the pH of the solution obtained in the iron removal step is set to 5 after the iron removal step. It is further provided with a silicon removal step of adjusting to ˜6 to deposit and remove silicon.

  Furthermore, the method for producing an aqueous cobalt sulfate solution of the present invention including a nickel removing step is particularly effective when a large amount of impurities are contained in the cobalt metal. For example, even if cobalt metal containing 0.5 to 5 mg of nickel and 0.5 to 50 mg of iron with respect to 1 g of cobalt is used, nickel is 0.3 mg or less and iron is 0.05 mg or less with respect to 1 g of cobalt. And a high-purity cobalt sulfate aqueous solution can be obtained. Moreover, even if cobalt metal containing 0.5 to 5 mg of nickel, 0.5 to 50 mg of iron, and 2 mg or less of silicon is used per 1 g of cobalt, 0.3 mg or less of nickel and iron are added to 1 g of cobalt. 0.05 mg or less and silicon can be reduced to 0.3 mg or less, and a high-purity cobalt sulfate aqueous solution can be obtained.

  Thus, since the method for producing a cobalt sulfate aqueous solution of the present invention is particularly effective for cobalt metal containing a large amount of impurities, a high-purity cobalt sulfate aqueous solution can be obtained from low-grade cobalt metal that is generally commercially available. Can be manufactured.

  In the method for producing a cobalt sulfate aqueous solution of the present invention, it is preferable that in the nickel removal step, the compound that generates sulfide ions is at least one of sodium hydrosulfide, sodium sulfide, hydrogen sulfide, and potassium sulfide.

  Moreover, in the manufacturing method of the cobalt sulfate aqueous solution of this invention, it is preferable that the oxidizing agent for oxidizing the said bivalent iron is an aqueous hydrogen peroxide or sodium hypochlorite in an iron removal process.

  Moreover, in the manufacturing method of the cobalt sulfate aqueous solution of this invention, it is preferable to adjust the temperature of the said solution to 40 degreeC or more while adjusting the pH of the solution obtained by the iron removal process to 5-6 in a silicon removal process. . By setting the temperature of the solution obtained in the iron removal step to 40 ° C. or higher, silicon is more likely to precipitate, and the silicon removal efficiency can be improved.

In addition, the present invention adds sodium hydroxide to the cobalt sulfate aqueous solution obtained by the above-described method for producing a cobalt sulfate aqueous solution of the present invention, precipitates and separates cobalt hydroxide (Co (OH) ₂ ). There is provided a method for producing cobalt hydroxide, comprising a cobalt hydroxide separation step for removing produced sodium sulfate.

  According to the method for producing cobalt hydroxide of the present invention, high purity in which impurities are sufficiently reduced by producing cobalt hydroxide using the cobalt sulfate aqueous solution obtained by the method for producing a cobalt sulfate aqueous solution of the present invention. Cobalt hydroxide can be produced.

  According to the method for producing an aqueous cobalt sulfate solution of the present invention, when producing an aqueous cobalt sulfate solution from an impurity-containing cobalt metal, impurities contained in the cobalt metal can be sufficiently removed, and a high-purity cobalt sulfate aqueous solution can be obtained. it can. Moreover, according to the method for producing cobalt hydroxide of the present invention, by using the cobalt sulfate aqueous solution obtained by the method for producing the cobalt sulfate aqueous solution of the present invention, high purity cobalt hydroxide with sufficiently reduced impurities can be obtained. Can be manufactured.

  First, the manufacturing method of the cobalt sulfate aqueous solution of this invention is demonstrated. The manufacturing method of the cobalt sulfate aqueous solution of this invention has a form provided with a melt | dissolution process, an iron removal process, and a silicon removal process, or a melt | dissolution process, a nickel removal process, and an iron removal process by the objective or necessity. In the latter form, the silicon in the solution can be sufficiently removed even if silicon is contained in the cobalt metal by further providing a silicon removal step as necessary. Hereinafter, the form in which the manufacturing method of cobalt sulfate aqueous solution is equipped with a melt | dissolution process, a nickel removal process, an iron removal process, and a silicon removal process is explained in full detail.

(Dissolution process)
In the dissolving step (first step), cobalt metal is dissolved in an aqueous sulfuric acid solution. Here, the cobalt metal is a solid (for example, powder, plate, or granular) containing cobalt as a main component, and contains iron, nickel, silicon, etc. as typical impurities. As such cobalt metal, generally available low-grade cobalt metal can be used.

  Although the said sulfuric acid aqueous solution should just melt | dissolve cobalt metal, Preferably the 3-5N sulfuric acid aqueous solution is preferable. When the concentration of the sulfuric acid aqueous solution is less than 3N, the dissolution rate of cobalt metal is slow, and the concentration of cobalt tends to be thin.

  In addition, when the cobalt metal does not contain silicon, or when the silicon content is very small (for example, when the silicon content is 0.3 mg or less with respect to 1 g of cobalt), a silicon removal step described later. Is not necessary. Further, depending on the use of the obtained cobalt sulfate aqueous solution, the nickel removal step may not be performed.

(Nickel removal process)
In the nickel removal step (second step), a compound that generates iron powder and sulfide ions is added to the solution obtained in the dissolution step, and nickel sulfide is precipitated and removed. In this process, cobalt sulfide (CoS) and nickel sulfide (NiS) are simultaneously precipitated (co-precipitated) by the action of sulfide ions generated in the solution, but when adding iron powder to the solution, cobalt powder is added. Compared with the case where it adds, nickel sulfide becomes easy to precipitate and the amount of coprecipitation of cobalt sulfide can be reduced.

  As the iron powder, a commercially available general powder can be used, and the addition amount is preferably 0.01 to 0.1 g with respect to 1 g of cobalt. When the addition amount of iron powder is less than 0.01 g, the effect of addition cannot be obtained sufficiently, and the precipitation amount of nickel sulfide tends to be insufficient. On the other hand, when the amount exceeds 0.1 g, no difference is observed from the case where the amount of impurities (particularly nickel) deposited is less than the above lower limit value, and the amount of iron dissolved in the solution tends to increase.

  The compound that generates sulfide ions may be any compound that generates sulfide ions in an aqueous sulfuric acid solution, and at least one of sodium hydrosulfide, sodium sulfide, hydrogen sulfide, and potassium sulfide is preferable. The amount of the compound that generates sulfide ions is preferably 0.0005 to 0.002 mol with respect to 1 g (0.017 mol) of cobalt. When the addition amount is less than 0.0005 mol, there is a tendency that a sufficient effect for precipitating nickel sulfide cannot be obtained. On the other hand, if it exceeds 0.002 mol, cobalt sulfide precipitation tends to increase, the cobalt recovery rate tends to decrease, and the effect of removing impurities (particularly nickel) is less than the above lower limit. can not see.

  The deposit (precipitate) of nickel sulfide and other compounds is separated and removed from the solution by a method such as filtration. By removing the precipitate, an aqueous cobalt sulfate solution from which impurities (particularly nickel) are removed to an extremely low concentration can be obtained. In addition, when the iron removal step is performed without separating the precipitate, the precipitate re-dissolves and nickel in the cobalt sulfate aqueous solution increases, so the precipitate is separated before moving to the next step. It is necessary to keep. In each of the following steps, the precipitate can be removed in the same manner as described above.

(Iron removal process)
In the iron removal step (third step), an oxidant for oxidizing the divalent iron remaining in the solution is added to the solution obtained in the dissolution step or the solution obtained in the nickel removal step, and oxidation is performed. The pH of the solution to which the agent is added is adjusted to 3 to 5 (more preferably 3 to 4), and iron (III) hydroxide is precipitated and removed. When the nickel removal step is performed, the concentration of iron in the cobalt sulfate aqueous solution increases in order to add iron powder to the solution, but the iron is sufficiently removed in this iron removal step. Here, the removal of iron is sufficient if the solution and the precipitate are separated, and separation by filtration is not necessarily performed.

  In the iron removal step, divalent iron in the solution is oxidized to trivalent by adding an oxidizing agent. Any oxidizing agent may be used as long as it can oxidize divalent iron to trivalent, and examples thereof include hydrogen peroxide and sodium hypochlorite.

  In the iron removal step, it is preferable to adjust the redox potential of the solution to 200 to 400 mV. By setting the oxidation-reduction potential in the above range, iron hydroxide is more likely to precipitate, and the iron removal efficiency can be improved.

Moreover, it is preferable to adjust pH by adding an alkali to the solution obtained at the nickel removal process. Examples of the alkali include sodium hydroxide (NaOH), potassium hydroxide (KOH), and cobalt hydroxide (Co (OH) ₂ ). Sodium hydroxide and potassium hydroxide are preferable from the viewpoint of economy.

  In addition, by adjusting pH to 3-5, the precipitate (precipitation) of the iron hydroxide produced | generated becomes the thing excellent in sedimentation property and filterability, and removal of iron can be performed efficiently. In addition, when the pH of a solution exceeds 5, the sedimentation property and filterability of precipitated iron hydroxide will worsen, it will become difficult to refine | purify cobalt sulfate aqueous solution, and the recovery rate of cobalt will fall. On the other hand, when the pH is less than 3, iron is not completely converted into a hydroxide, so that the amount of iron hydroxide deposited is reduced and the removal of iron in the solution becomes insufficient.

(Silicon removal process)
In the silicon removal step (fourth step), the pH of the solution obtained in the iron removal step is adjusted to 5 to 6 to precipitate and remove silicon. If the pH of the solution is less than 5, removal of silicon becomes insufficient, while if the pH exceeds 6, a large amount of cobalt hydroxide precipitates are produced, so that the cobalt recovery rate decreases.

  In the silicon removal step, the pH of the solution obtained in the iron removal step is preferably adjusted to 5-6, and the temperature of the solution is preferably adjusted to 40 ° C or higher, and more preferably adjusted to 50-70 ° C. . When the temperature of the solution is lower than 40 ° C., it takes a long time to precipitate silicon, and the production efficiency tends to decrease.

  As described above, by the method for producing a cobalt sulfate aqueous solution of the present invention, main impurities are sufficiently removed, and a high purity cobalt sulfate aqueous solution is obtained. In addition, as cobalt metal, for example, even if cobalt metal containing 0.5 to 5 mg of nickel and 0.5 to 50 mg of iron is used with respect to 1 g of cobalt, 0.3 mg or less of nickel with respect to 1 g of cobalt, iron Can be reduced to 0.05 mg or less, and a high-purity cobalt sulfate aqueous solution can be obtained. Moreover, even if cobalt metal containing 0.5 to 5 mg of nickel, 0.5 to 50 mg of iron, and 2 mg or less of silicon is used per 1 g of cobalt, 0.3 mg or less of nickel and iron are added to 1 g of cobalt. 0.05 mg or less and silicon can be reduced to 0.3 mg or less, and a high-purity cobalt sulfate aqueous solution can be obtained.

  And when cobalt compounds, such as cobalt sulfate, cobalt hydroxide, cobalt oxyhydroxide, and tricobalt tetroxide, are manufactured using the obtained high purity cobalt sulfate aqueous solution, a high purity cobalt compound can be obtained.

Next, the manufacturing method of the cobalt hydroxide of this invention is demonstrated. In the method for producing cobalt hydroxide of the present invention, sodium hydroxide is added to the cobalt sulfate aqueous solution obtained by the method for producing a cobalt sulfate aqueous solution of the present invention to precipitate cobalt hydroxide (Co (OH) ₂ ). And a cobalt hydroxide separation step for removing by-product sodium sulfate.

  Hereinafter, the content of the present invention will be described more specifically using examples and comparative examples, but the present invention is not limited to these examples.

Example 1
62.7 g of cobalt metal containing nickel, iron and silicon as impurities was added to and dissolved in 500 mL of a 4.1N sulfuric acid aqueous solution to prepare a cobalt sulfate aqueous solution having a cobalt concentration of 120 g / L and a pH of 3.5. The pH was measured with a pH meter (manufactured by Toa Denpa Kogyo Co., Ltd., ion / pH meter IM-55G, pH measurement electrode: glass composite electrode GST-5721C) (the same applies hereinafter). Moreover, the same apparatus was used also for the measurement of the oxidation-reduction potential described later.

  In addition, the obtained aqueous solution of cobalt sulfate was used as a step 1 solution, and the content (g / L) of cobalt (Co), nickel (Ni), iron (Fe), and silicon (Fe) in the solution was determined by ICP (Shimadzu Corporation). ICPS-8000) manufactured by the company. Table 1 shows the content of each metal in the Step 1 solution.

  500 mL of the obtained Step 1 liquid was taken in a conical beaker, the liquid temperature was adjusted to 60 ° C. in a thermostatic bath, and 2.5 g of reagent electrolytic iron powder was added with stirring. Next, 25 ml of an aqueous sodium sulfide solution adjusted to 200 g / L was added to the solution to which the iron powder was added, and the mixture was reacted for 30 minutes while being kept at 60 ° C. in a thermostatic bath. After completion of the reaction, the precipitate was filtered off, and the aqueous solution of cobalt sulfate from which the precipitate was separated was used as Step 2 liquid, and the content of each metal was measured in the same manner as in Step 1 liquid. The obtained results are shown in Table 1.

  Next, while maintaining the liquid temperature at 60 ° C. using a thermostatic bath, 3% hydrogen peroxide solution and 2 mol / L sodium hydroxide aqueous solution are added to Step 2 solution, the oxidation-reduction potential is 380 mV, and the pH is 4. The mixture was adjusted to 5 and stirred for 5 hours. The resulting slurry precipitate was filtered off to obtain Step 3 solution, and the content of each metal was measured in the same manner as Step 1 solution. The obtained results are shown in Table 1.

  In addition, in order to measure the filtration rate at the time of filtration of a process 3 liquid, suction filtration was performed using 5 C filter paper with a diameter of 150 mm, and the filtration rate was measured. Moreover, the cobalt recovery rate (%) was calculated | required from the cobalt content in the process 1 liquid, and the cobalt content in the process 3 liquid. Table 1 shows the filtration rate and the cobalt recovery rate.

  As can be seen from the results shown in Table 1, in Example 1, nickel is sufficiently removed by the nickel removing step and iron is sufficiently removed by the iron removing step without greatly reducing the cobalt recovery rate. Was confirmed.

(Example 2)
Using the same solution as the Step 1 solution used in Example 1, nickel was removed in the same manner as in Example 1 to obtain Step 2 solution. In the same manner as in Example 1, the content of each metal in Step 1 solution and Step 2 solution was measured. The obtained results are shown in Table 2.

  Next, while maintaining the liquid temperature at 60 ° C. using a thermostatic bath, 3% hydrogen peroxide solution and 2 mol / L sodium hydroxide aqueous solution are added to Step 2 solution, the oxidation-reduction potential is 380 mV, and the pH is 3. The mixture was adjusted to 5 and stirred for 5 hours. The obtained slurry was used as Step 3 liquid, and the content of each metal was measured in the same manner as in Step 1 liquid for the filtrate obtained by filtering a part of Step 3 liquid. The obtained results are shown in Table 2.

  Next, 2 mol / L sodium hydroxide was added to Step 3 solution, the pH was adjusted to 5.7, and the mixture was stirred for 5 hours. The precipitate of the obtained solution was separated by filtration to prepare Step 4 solution, and the content of each metal was measured in the same manner as Step 1 solution. The obtained results are shown in Table 2.

  In addition, in order to measure the filtration rate at the time of filtration of process 4 liquid, suction filtration was performed using 5 C filter paper with a diameter of 150 mm, and the filtration rate was measured. Moreover, the cobalt recovery rate was calculated | required from the cobalt content in the process 1 liquid, and the cobalt content in the process 4 liquid. The results of filtration rate and cobalt recovery are shown in Table 2.

  As can be seen from the results shown in Table 2, it was confirmed that silicon was sufficiently removed by the silicon removal step.

(Comparative Example 1)
Using the same solution as the Step 1 solution used in Example 2, nickel was removed in the same manner as in Example 2 to obtain Step 2 solution. Table 3 shows the content of each metal in Step 1 as in Example 2. In addition, since content of each metal of process 2 liquid was the same as that of Example 2, the description was abbreviate | omitted.

  Next, while maintaining the liquid temperature at 60 ° C. using a thermostatic bath, 3% hydrogen peroxide solution and 2 mol / L sodium hydroxide were added to the liquid in Step 2, and the oxidation-reduction potential was set to 380 mV and the pH to 2.5. Adjusted and stirred for 5 hours. The obtained slurry was used as Step 3 liquid, and the content of each metal was measured in the same manner as in Step 1 liquid for the filtrate obtained by filtering a part of Step 3 liquid. The obtained results are shown in Table 3.

  Next, 2 mol / L sodium hydroxide was added to Step 3 solution, the pH was adjusted to 5.7, and the mixture was stirred for 5 hours. The resulting slurry precipitate was filtered off to prepare Step 4 solution, and the content of each metal was measured in the same manner as Step 1 solution. The obtained results are shown in Table 3.

  In addition, in order to measure the filtration rate at the time of filtration of process 4 liquid, suction filtration was performed using 5 C filter paper with a diameter of 150 mm, and the filtration rate was measured. Moreover, the cobalt recovery rate was calculated | required from the cobalt content in the process 1 liquid, and the cobalt content in the process 4 liquid. The results of filtration rate and cobalt recovery are shown in Table 3.

  As can be seen from the results shown in Table 3, in Comparative Example 1, since the pH was less than 3 in the iron removal step, the amount of iron hydroxide deposited was small, and the removal of iron was insufficient. Moreover, since the pH of the iron hydroxide precipitated in the silicon removal step was greater than 5, precipitation with poor filterability occurred, and it was confirmed that the filtration rate was slower than that of Example 2.

(Comparative Example 2)
Using the same solution as the Step 1 solution used in Example 2, nickel was removed in the same manner as in Example 2 to obtain Step 2 solution. Table 4 shows the content of each metal in Step 1 as in Example 2. In addition, since content of each metal of process 2 liquid was the same as that of Example 2, the description was abbreviate | omitted.

  Next, 3% hydrogen peroxide solution and 2 mol / L sodium hydroxide are added to Step 2 solution while maintaining the solution temperature at 60 ° C. using a thermostat, and the oxidation-reduction potential is 380 mV and the pH is 5.2. Adjusted and stirred for 5 hours. The obtained slurry was used as Step 3 liquid, and the content of each metal was measured in the same manner as in Step 1 liquid for the filtrate obtained by filtering a part of Step 3 liquid. Table 4 shows the obtained results.

  Next, 2 mol / L sodium hydroxide was added to Step 3 solution, the pH was adjusted to 5.7, and the mixture was stirred for 5 hours. The resulting slurry precipitate was filtered off to obtain Step 4 liquid, and the content of each metal was measured in the same manner as Step 1 liquid. Table 4 shows the obtained results.

  In addition, in order to measure the filtration rate at the time of filtration of process 4 liquid, suction filtration was performed using 5 C filter paper with a diameter of 150 mm, and the filtration rate was measured. Moreover, the cobalt recovery rate was calculated | required from the cobalt content in the process 1 liquid, and the cobalt content in the process 4 liquid. Table 4 shows the results of filtration rate and cobalt recovery.

  As can be seen from the results shown in Table 4, in Comparative Example 2, since the pH exceeded 5 in the iron removal step, it was confirmed that the filtration rate was slower than in Example 2.

(Reference Example 1)
Using the same solution as the Step 1 solution used in Example 2, nickel was removed in the same manner as in Example 2 to obtain Step 2 solution. Table 5 shows the content of each metal in Step 1 as in Example 2. In addition, since content of each metal of process 2 liquid was the same as that of Example 2, the description was abbreviate | omitted.

  Next, in the same manner as in Example 2, while maintaining the liquid temperature at 60 ° C. using a thermostatic bath, 3% hydrogen peroxide solution and 2 mol / L sodium hydroxide were added to Step 2 liquid, and the oxidation-reduction potential was set. The slurry was adjusted to 380 mV and pH 3.5 and stirred for 5 hours, and the resulting slurry was designated as Step 3 liquid. In addition, since content of each metal of the filtrate which filtered a part of process 3 liquid was the same as that of Example 2, the description was abbreviate | omitted.

  Next, 2 mol / L sodium hydroxide was added to Step 3 solution, the pH was adjusted to 6.5, and the mixture was stirred for 5 hours. The obtained Step 4 solution was used, and the content of each metal was measured in the same manner as Step 1 solution. The results obtained are shown in Table 5.

  Step 4 Suction filtration was performed using 5C filter paper having a diameter of 150 mm in order to measure the filtration rate when the liquid was filtered, and the filtration rate was measured. Moreover, the cobalt recovery rate was calculated | required from the cobalt content in the process 1 liquid, and the cobalt content in the process 4 liquid. The results of filtration rate and cobalt recovery are shown in Table 5.

  As can be seen from the results shown in Table 5, in Reference Example 1, since the pH exceeded 6 in the silicon removal step, it was confirmed that the cobalt recovery rate was significantly reduced.

Example 3
Using cobalt metal containing nickel, iron and silicon as impurities as raw materials, a dissolution step, a nickel removal step, an iron removal step and a silicon removal step were performed in the same manner as in Example 2 to obtain a cobalt sulfate aqueous solution. About 190 mL of 5N sodium hydroxide was added to 300 mL of the obtained cobalt sulfate aqueous solution and stirred, and reacted to precipitate cobalt hydroxide. The cobalt hydroxide was filtered from the solution to obtain a cobalt hydroxide precipitate. The precipitate was dried at 800 ° C. for about 5 hours to obtain about 43 g of crystals. Moreover, the cobalt hydroxide was baked to produce cobalt oxide (Co ₃ O ₄ ). Table 6 shows the content (mass%) of each component of the obtained cobalt hydroxide and cobalt oxide.

  As can be seen from the results shown in Table 6, it was confirmed that the cobalt hydroxide obtained by the production method of the present invention had high purity. Moreover, it was confirmed that the cobalt oxide manufactured from the obtained cobalt hydroxide is also highly pure.

Example 4
62.7 g of cobalt metal containing nickel, iron and silicon as impurities was added to and dissolved in 500 mL of a 4.1N sulfuric acid aqueous solution to prepare a cobalt sulfate aqueous solution having a cobalt concentration of 120 g / L and a pH of 3.5.

  In addition, the obtained aqueous solution of cobalt sulfate was used as a step 1 solution, and the content (g / L) of cobalt (Co), nickel (Ni), iron (Fe), and silicon (Fe) in the solution was determined by ICP (Shimadzu Corporation). ICPS-8000) manufactured by the company. Table 7 shows the content of each metal in Step 1 solution.

  Take 500 mL of the obtained Step 1 liquid in a conical beaker, and while maintaining the liquid temperature at 60 ° C. using a thermostatic bath, add 3% hydrogen peroxide solution, 2 mol / L sodium hydroxide aqueous solution, and set the redox potential to 380 mV. The pH was adjusted to 3.5 and stirred for 5 hours. The resulting slurry precipitate was filtered off to obtain Step 3 solution, and the content of each metal was measured in the same manner as Step 1 solution. The results obtained are shown in Table 7.

  Thereafter, the pH of the Step 3 liquid was again adjusted to 5.7 using sodium hydroxide and stirred for 5 hours, and then the silicon removal process liquid (Step 4 liquid) from which the precipitate was filtered was obtained. Table 7 shows the results of analyzing the content of each metal in the same manner as described above. In addition, Table 7 shows the results of obtaining the cobalt recovery rate from the cobalt content in the Step 1 solution and the cobalt content in the Step 4 solution.

  As can be seen from the results shown in Table 7, in Example 7, it was confirmed that iron and silicon were sufficiently reduced by the iron removal step and the silicon removal step.

The present invention can be used when producing a cobalt compound used for a magnetic material, a battery material, an electronic material, and the like.

Claims (9)

A dissolution step of dissolving cobalt metal containing iron and silicon as impurities in an aqueous sulfuric acid solution;
An iron removing step of adding an oxidizing agent for oxidizing divalent iron to the solution obtained in the dissolving step and adjusting the pH of the solution to 3 to 5 to precipitate and remove iron hydroxide; ,
A silicon removal step of adjusting the pH of the solution obtained in the iron removal step to 5 to 6 to precipitate and remove silicon;
A method for producing an aqueous cobalt sulfate solution. A dissolution step of dissolving cobalt metal containing nickel and iron as impurities in an aqueous sulfuric acid solution;
A nickel removing step of adding a compound that generates iron powder and sulfide ions to the solution obtained in the dissolving step, and depositing and removing nickel sulfide;
An iron removing step of adding an oxidizing agent for oxidizing divalent iron to the solution obtained in the nickel removing step and adjusting the pH of the solution to 3 to 5 to precipitate and remove iron hydroxide. When,
A method for producing an aqueous cobalt sulfate solution. In the melting step, the cobalt metal further contains silicon as an impurity,
The method for producing an aqueous cobalt sulfate solution according to claim 2, further comprising a silicon removal step of adjusting the pH of the solution obtained in the iron removal step to 5 to 6 to precipitate and remove silicon.   In the said melt | dissolution process, the said cobalt metal contains 0.5-50 mg of iron and 2 mg or less of silicon with respect to 1 g of cobalt, The manufacture of the cobalt sulfate aqueous solution of Claim 1 or 3 characterized by the above-mentioned. Method.   4. The cobalt sulfate according to claim 2, wherein in the melting step, the cobalt metal contains 0.5 to 5 mg of nickel and 0.5 to 50 mg of iron with respect to 1 g of cobalt. 5. A method for producing an aqueous solution.   4. The cobalt sulfate according to claim 2, wherein in the nickel removal step, the compound that generates the sulfide ion is at least one of sodium hydrosulfide, sodium sulfide, hydrogen sulfide, and potassium sulfide. 5. A method for producing an aqueous solution.   4. The method for producing an aqueous cobalt sulfate solution according to claim 1, wherein in the silicon removal step, the temperature of the solution obtained in the iron removal step is adjusted to 40 ° C. or higher.   In the said iron removal process, the oxidizing agent for oxidizing the said bivalent iron is hydrogen peroxide solution or sodium hypochlorite, It is any one of Claims 1-3 characterized by the above-mentioned. Of producing an aqueous cobalt sulfate solution. Cobalt hydroxide separation in which sodium hydroxide is added to the cobalt sulfate aqueous solution obtained by the method for producing a cobalt sulfate aqueous solution according to any one of claims 1 to 8 to precipitate and separate the cobalt hydroxide. Process,
A process for producing cobalt hydroxide, comprising: