JP6565591B2 - Calcium separation method - Google Patents

Description

  The present invention relates to a method for separating calcium, and more particularly, a method for separating calcium as an impurity from a mixed aqueous solution of nickel sulfate and cobalt sulfate used as a raw material of a lithium ion battery, particularly a nickel-based or ternary positive electrode material. About.

  Various positive electrode materials have been developed as positive electrode materials for lithium ion batteries, which are secondary batteries. In particular, in recent years, nickel-cobalt-manganese (NCM) -based positive electrode material called ternary system, nickel-cobalt-aluminum (NCA) system called nickel-based material, etc. can be used instead of the conventionally used cobalt lithium acid. Attention has been focused on the positive electrode material.

  The positive electrode material containing nickel as described above is manufactured, for example, by treating a solution containing a metal salt such as nickel with an alkali and subjecting the obtained metal hydroxide to a firing treatment. Such a metal salt is produced, for example, in a nickel smelting process using nickel oxide ore or the like as a raw material, and specific examples include chloride (nickel chloride), sulfate (nickel sulfate) and the like. Of these, when chloride is used, when the hydroxide obtained by neutralizing the chloride is fired, the remaining chloride ions may become chlorine gas, which may cause corrosion damage to the firing furnace. For this reason, in general, sulfate is often used as the metal salt.

  Here, nickel sulfate is obtained as a by-product of the process of smelting electro nickel from nickel oxide ore. However, the nickel oxide ore often contains cobalt, and cobalt is also co-deposited in the electric nickel, so that the quality of the electric nickel is lowered, while the recovery loss of the valuable metal cobalt is also an aspect. Can occur.

  For this reason, nickel and cobalt are separated in the smelting process using a wet process such as a solvent extraction method, but these metals are similar in chemical properties, so it is easy to separate each metal. It was rather expensive.

  Incidentally, positive electrode materials such as NCM-based positive electrode materials and NCA-based positive electrode materials are made of a composite metal oxide containing nickel and cobalt. In other words, if nickel sulfate containing cobalt as an impurity is used as it is as a raw material for producing an NCM-based positive electrode material or an NCA-based positive electrode material, it is not necessary to separate nickel and cobalt. Therefore, it can be a cost-effective material.

  However, the nickel sulfate described above may contain calcium derived from a neutralizing agent added in the process of smelting electric nickel from nickel oxide ore, or calcium present in the raw material nickel oxide ore itself. . Then, when such a nickel sulfate containing calcium is used as a raw material, when an NCM-type positive electrode material or a positive electrode material of an NCA-type positive electrode material is produced, calcium is contained in the electrode as an impurity, thereby a lithium ion battery. The battery characteristics such as the charge / discharge capacity may be significantly reduced. Therefore, in order to use nickel sulfate containing cobalt as a raw material for producing an NCM-based positive electrode material or an NCA-based positive electrode material, it is important to efficiently and easily remove calcium as an impurity.

  Known methods for removing such impurity metals include precipitation methods, cementation methods, crystallization methods, solvent extraction methods, and the like.

  Among these, the precipitation method is to precipitate and remove metal ions to be removed as sulfates or hydroxides. However, calcium ions cannot be precipitated as sulfate. Moreover, in the case of precipitation as a hydroxide, it is necessary to prevent coprecipitation of components such as nickel and cobalt, but under high pH alkaline conditions for calcium to precipitate as a hydroxide, nickel or cobalt Will also precipitate as hydroxide. Therefore, it is difficult to separate calcium from nickel and cobalt by such a precipitation method.

  In addition, the cementation method adds and receives electrons between a metal ion and the added metal when a metal ion is present in the aqueous solution and a metal having a lower redox potential than the metal present as the ion is added. Is performed, and metal ions are reduced to metal and deposited, and the added metal is oxidized and dissolved as ions. However, since the standard oxidation-reduction potential of calcium is lower than the standard oxidation-reduction potential of hydrogen, even if a lower oxidation-reduction potential than calcium is added, protons are reduced and calcium is not reduced. Therefore, calcium cannot be removed even by the cementation method.

While the precipitation method and cementation method as described above are methods for precipitating and removing the metal to be removed in the aqueous solution, the crystallization method is a salt of nickel sulfate or cobalt sulfate by heating and concentrating the aqueous solution. Is purified, leaving impurities in the crystallization mother liquor. However, in this method, since a solution containing sulfate ions is used, calcium can react with sulfate ions to form poorly water-soluble gypsum (CaSO ₄ .2H ₂ O). Therefore, when the metal concentration is increased for the purpose of recovering nickel or cobalt at a high recovery rate, the calcium concentration is inevitably increased, and the possibility that gypsum is formed increases. On the other hand, if the formation of gypsum is to be suppressed, the metal concentration cannot be increased, and nickel and cobalt cannot be obtained at a high recovery rate. In addition, in the method using this crystallization method, the cost required for heating for concentration also increases.

  On the other hand, the solvent extraction method is a method of removing impurities by extracting them into an organic solvent, and the impurities can be selectively removed by appropriately setting the extraction agent and the extraction conditions. As a method for removing calcium from an aqueous nickel sulfate solution using a solvent extraction method, for example, Patent Document 1 proposes a method for removing calcium dissolved in a nickel electrolyte solution using an alkyl phosphate ester as an extractant. ing. Specifically, the extraction of calcium, which is an impurity, is performed from the solution by adjusting the pH of the nickel solution during extraction to 1.5 or more and 5.0 or less using an alkyl phosphate ester as an extractant. Is. In particular, by setting the pH of the solution at the time of extraction to 4.0, the calcium content in the nickel sulfate solution can be reduced to 50 mg / l or less.

  However, in the method described in Patent Document 1, if the pH of the solution is adjusted to around 4.0 where the content of calcium in the nickel sulfate solution is reduced, cobalt which is a rare metal is also extracted and removed at the same time. Therefore, cobalt cannot be used effectively. In other words, for example, when manufacturing a positive electrode material such as an NCM-based positive electrode material or an NCA-based positive electrode material, a cobalt feedstock must be prepared separately, which increases the manufacturing cost.

JP2012-072482A

  The present invention has been made in view of such circumstances. For example, from a sulfuric acid solution containing nickel, cobalt, and calcium, which is a raw material for an NCM-based positive electrode material, an NCA-based positive electrode material, and the like, only calcium is used. It is intended to provide a method for efficiently and easily separating the components.

  As a result of intensive research to achieve the above-mentioned object, the present inventors adjusted the pH of the sulfuric acid acidic solution to a predetermined range, and then contacted an organic solvent containing an alkylphosphonic acid ester. It has been found that the above-mentioned problems can be solved by extracting calcium therein, and the present invention has been completed. Specifically, the present invention provides the following.

  (1) The present invention is a calcium separation method for separating calcium from a sulfuric acid acidic solution containing nickel, cobalt and calcium, and the pH of the sulfuric acid acidic solution is adjusted to 2.5 or more and 3.5 or less. A method for separating calcium, comprising: a pH adjustment step; and a calcium extraction step in which an organic solvent containing an alkylphosphonic acid ester is brought into contact with the sulfuric acid acidic solution whose pH has been adjusted, and calcium is extracted from the organic solvent.

  (2) The present invention is the calcium separation method according to (1), wherein in the calcium extraction step, the volume ratio of the organic solvent to the sulfuric acid acidic solution is 1.0 or more and 2.4 or less.

  (3) The present invention is the calcium separation method according to (1) or (2), wherein the sulfuric acid acidic solution is a solution for use as a raw material for a positive electrode material of a lithium ion battery containing nickel and cobalt. is there.

  (4) The present invention further includes a temperature adjustment step of adjusting the temperature of the sulfuric acid acidic solution to a range of 20 ° C. or higher and lower than 40 ° C. prior to the pH adjustment step. It is the separation method of calcium of description.

  (5) The present invention is a method for producing a solution containing nickel and cobalt for use as a raw material for a positive electrode material of a lithium ion battery, from a sulfuric acid acidic solution containing nickel, cobalt and calcium, A pH adjusting step for adjusting the pH of the sulfuric acid acidic solution to 2.5 or more and 3.5 or less, contacting an organic solvent containing an alkylphosphonic acid ester with the sulfuric acid acidic solution whose pH has been adjusted, and adding calcium to the organic solvent It is a manufacturing method of the solution containing nickel and cobalt including the calcium extraction process to extract.

  (6) The present invention further includes a temperature adjusting step of adjusting the temperature of the sulfuric acid acidic solution to a range of 20 ° C. or higher and lower than 40 ° C. prior to the pH adjusting step. It is a manufacturing method of the solution to contain.

  According to the present invention, calcium can be easily removed from a sulfuric acid acidic solution containing nickel, cobalt, and calcium while suppressing loss of nickel and cobalt.

It is a figure which shows the relationship between pH and the extraction rate of a metal component based on the result of Example 1 and Comparative Example 1. FIG. It is a figure which shows the relationship between O / A ratio and the extraction rate of a metal component based on the result of Example 2 and Comparative Example 2. FIG. It is a figure which shows the relationship between pH and the extraction rate of a nickel component based on the result of Example 3 and Comparative Example 3. FIG. It is a figure which shows the relationship between pH and the extraction rate of a cobalt component based on the result of Example 3 and Comparative Example 3. FIG. It is a figure which shows the relationship between pH and the extraction rate of a calcium component based on the result of Example 3 and Comparative Example 3. FIG. It is a figure which shows the relationship between pH and the separation factor of calcium / nickel based on the result of Example 3 and Comparative Example 3. It is a figure which shows the relationship between pH and the separation factor of calcium / cobalt based on the result of Example 3 and Comparative Example 3.

  Hereinafter, specific embodiments of the present invention (hereinafter referred to as “present embodiments”) will be described in detail. However, the present invention is not limited to the following embodiments, and the gist of the present invention is changed. In the range which does not carry out, it can implement by adding a change suitably.

<< 1. Calcium separation method >>
The calcium separation method according to the present embodiment is a method for efficiently and easily separating only calcium from a sulfuric acid acidic solution containing nickel, cobalt, and calcium. Specifically, this calcium separation method includes a pH adjustment step of adjusting the pH of the sulfuric acid acidic solution and a calcium extraction step of extracting calcium in the solution by solvent extraction using a specific extractant. Moreover, although it is not an essential aspect, the calcium separation method according to the present embodiment may include a temperature adjustment step of adjusting the temperature of the sulfuric acid acidic solution prior to the pH adjustment step. Hereinafter, each process will be described.

<PH adjustment step>
The pH adjustment step is a step of adjusting the pH of the sulfuric acid acidic solution containing nickel, cobalt, and calcium.

  The acidic sulfuric acid solution for separating calcium is not particularly limited as long as it is a solution containing nickel, cobalt, and calcium. Specifically, for example, as the sulfuric acid acidic solution, a solution for use as a raw material for producing a positive electrode material of a lithium ion battery containing nickel and cobalt, that is, an NCM positive electrode material, an NCA positive electrode material, or the like is used. be able to. In the present embodiment, by applying the calcium separation method to such a sulfuric acid acidic solution, a sulfuric acid acidic solution containing nickel and cobalt in which only calcium as an impurity is reduced can be obtained. This can be used as a raw material for producing a positive electrode material containing nickel and cobalt, whereby a positive electrode material can be produced at a low cost.

  In this pH adjustment step, the pH of the sulfuric acid acidic solution is adjusted to a range of 2.5 to 3.5. Here, in the sulfuric acid acidic solution used for the extraction process in the calcium extraction step described later, the amount of calcium extracted increases as the pH increases. However, when the pH increases, cobalt is also extracted from the sulfuric acid acidic solution. Therefore, in the present embodiment, the pH of the sulfuric acid acidic solution is adjusted to a predetermined range, that is, a range of 2.5 to 3.5. By adjusting the pH of the sulfuric acid acidic solution to the above range, only calcium can be efficiently removed in the calcium extraction step, while nickel and cobalt can be suppressed from being extracted. Recovery loss can be reduced.

  The pH adjustment for the sulfuric acid acidic solution in the pH adjustment step can be performed using a pH adjuster. The pH adjuster is not particularly limited, and various acids and alkalis can be used.

  For example, as an acidic pH adjuster, for example, an inorganic acid such as sulfuric acid, nitric acid, phosphoric acid, or an organic acid can be used. Since the addition target of the pH adjuster is a sulfuric acid acidic solution, it is preferable to use sulfuric acid in that impurities can be prevented from being mixed into the solution. Examples of the alkaline pH adjuster include those derived from alkali metals such as lithium hydroxide, sodium hydroxide, potassium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, lithium hydrogen carbonate, sodium hydrogen carbonate, and potassium hydrogen carbonate. An inorganic alkali compound or organic alkali compounds such as ammonia and various amines can be used.

<Calcium extraction process>
A calcium extraction process is a process of extracting calcium from the sulfuric acid acidic solution containing nickel, cobalt, and calcium which adjusted pH to the predetermined range.

  In this calcium extraction step, calcium in the sulfuric acid acidic solution is extracted into the organic layer by solvent extraction using an organic solvent containing a specific extractant. By this extraction treatment, it is possible to obtain an organic solvent after extraction from which calcium has been extracted and an acidic solution after extraction, and only calcium can be effectively separated from the raw sulfuric acid solution.

  Specifically, in the calcium extraction step, a solvent extraction process is performed using an alkylphosphonic acid ester capable of selectively extracting calcium as an extractant to extract calcium from the sulfuric acid acidic solution. In this extractant, calcium is selectively extracted by reacting phosphonate with calcium ions to form a metal salt. Specifically, as an extractant for alkylphosphonic acid ester, for example, trade name: PC88A (2-ethylhexyl, 2-ethylhexylphosphonate: manufactured by Daihachi Chemical Industry Co., Ltd.) is commercially available. In addition, such an extracting agent can be used individually by 1 type, and can also be used in mixture of 2 or more types.

  As an organic solvent for extracting calcium, it can be used without mixing the extractant itself, and a mixed solvent in which the extractant and the diluent are mixed can also be used. It is preferable to use a mixed solvent of an extractant and a diluent in that the viscosity and specific gravity of the solvent can be appropriately adjusted according to the type of extraction agent, extraction conditions, and the like. In addition, the ratio of the extractant and the diluent in the mixed solvent can be arbitrarily determined according to the viscosity and specific gravity of the extractant.

  The diluent constituting the mixed solvent with the extractant is not particularly limited as long as it forms an organic layer (organic extract layer) separated from the aqueous layer (sulfuric acid acidic solution) and can dissolve the extractant described above. Is not to be done. Specifically, as the diluent, for example, a naphthenic solvent or an aromatic solvent can be used. In addition, as a naphthenic solvent, trade name: Teclean N20 (manufactured by JX Nippon Mining & Energy Corporation) is commercially available, and as an aromatic solvent, trade name: Shellsol A150 (Shell Chemicals Japan Co., Ltd.) Etc.) are commercially available.

  Further, the volume ratio (O / A ratio) of the organic solvent to the sulfuric acid acidic solution is not particularly limited. However, the higher the O / A ratio, the higher the calcium extraction rate. 1.0 or more, and more preferably 1.5 or more. On the other hand, even if the O / A ratio is increased too much, the effect on calcium extraction is not improved, but rather the economy may be deteriorated due to an increase in the amount of organic solvent used. Therefore, the upper limit value is preferably 2.4 or less, and more preferably 2.0 or less.

  The specific method of the extraction treatment or back extraction treatment is not particularly limited, and for example, a method in which a sulfuric acid acidic solution and an organic solvent are stirred and mixed with a mixer or the like and then allowed to stand and phase-separate is used. be able to. Also, a batch mixing method using a stirring tank or a continuous extraction method using an extraction device such as a mixer setra can be used. Alternatively, a column system (for example, a pulse column) that performs extraction / back-extraction by bringing a sulfuric acid acidic solution into contact with an organic solvent can also be used. In this calcium extraction step, calcium can be extracted satisfactorily regardless of which method is selected, and therefore an extraction / back-extraction method according to the operation can be appropriately selected.

  In addition, a back extraction process can be performed by making acids, such as a sulfuric acid and hydrochloric acid, contact with the organic solvent after extracting calcium on the pH conditions different from the time of the calcium extraction process. Thereby, calcium extracted in the organic solvent can be recovered as a solution containing sulfate or chloride, and can be disposed of separately through wastewater treatment. Moreover, the organic solvent after back extraction can be repeatedly used for the extraction process with respect to the sulfuric acid acidic solution containing calcium.

<Temperature adjustment process>
Although not an essential aspect, in this calcium separation method, a temperature adjustment step of adjusting the temperature of the sulfuric acid acidic solution can be performed prior to the pH adjustment step.

  Here, as described above, the sulfuric acid acidic solution containing nickel, cobalt, and calcium, which is a raw material for the calcium separation method, includes nickel sulfate produced as a by-product in the process of smelting nickel from nickel oxide ore. Can be used. For example, the process of smelting electric nickel from the nickel oxide ore is often performed under high-temperature and high-pressure conditions such as autoclave, and the temperature of the sulfuric acid acidic solution discharged from the autoclave is as high as about 100 ° C. Since it is difficult to perform the subsequent processing in such a high temperature state, it is cooled while being held in the atmosphere, but the subsequent processing is generally performed at a high temperature of 40 ° C. or higher.

  In contrast, in the calcium separation method according to the present embodiment, it is preferable to adjust the temperature of the sulfuric acid acidic solution containing nickel, cobalt, and calcium to 20 ° C. or higher and lower than 40 ° C. The pH of the sulfated acidic solution is adjusted to a range of 2.5 to 3.5. In this Embodiment, after adjusting the temperature of the sulfuric acid acidic solution used as a raw material to 20 ° C. or more and less than 40 ° C., the pH is adjusted to a range of 2.5 or more and 3.5 or less, and thus in the above calcium extraction step. The extraction rate of calcium from the sulfuric acid acidic solution can be increased. In addition, when the temperature of the sulfuric acid acidic solution to be adjusted is less than 20 ° C., there is a possibility that the cooling cost increases and an efficient treatment cannot be performed. On the other hand, when the adjustment temperature is 40 ° C. or higher, the effect of improving the calcium extraction rate cannot be sufficiently obtained.

  The temperature adjustment of the sulfuric acid acidic solution in the temperature adjustment step can be performed using various heating and cooling devices. Although it does not restrict | limit especially as a heating-cooling apparatus, Specifically, a plate-type heat exchanger, a multi-tube heat exchanger, a double-tube heat exchanger, etc. can be used.

  The treatment in the temperature adjustment step does not need to be distinguished from the treatment in the pH adjustment step in terms of equipment and location. In addition, the temperature adjustment of the sulfuric acid acidic solution can be performed simultaneously with the pH adjustment of the sulfuric acid acidic solution in the pH adjustment step. However, from the viewpoint of the ease and accuracy of temperature and pH control, the pH adjustment in the pH adjustment step. Prior to the temperature adjustment, it is preferable to adjust the temperature.

≪2. Applications of solutions containing nickel and cobalt >>
Applying the calcium separation method described above to a sulfuric acid acidic solution containing nickel, cobalt and calcium, and separating and removing calcium from the solution to produce a solution containing nickel and cobalt Can do.

  The use of the solution thus obtained, that is, the acidic sulfuric acid solution containing nickel and cobalt, is not particularly limited. For example, nickel and cobalt, which are constituent materials for lithium ion batteries, etc. It can be used as a raw material for producing an NCM-based positive electrode material and an NCA-based positive electrode material. In addition, it can be used as a raw material for producing various alloys, composite oxides and the like containing nickel and cobalt.

  A positive electrode material such as an NCM-based positive electrode material or an NCA-based positive electrode material is a positive electrode material made of a composite oxide containing nickel and cobalt. This positive electrode material can be manufactured using the solution after effectively separating and removing only the impurity element from a solution containing at least nickel and cobalt as a manufacturing raw material. In this respect, according to the calcium separation method according to the present embodiment, it is possible to selectively separate and remove only calcium from a sulfuric acid acidic solution containing nickel, cobalt, and calcium. The sulfuric acid acidic solution after extracting and separating calcium becomes a sulfuric acid acidic solution containing nickel and cobalt with reduced impurities. Therefore, by using this sulfuric acid acidic solution as a raw material, a positive electrode material containing nickel and cobalt can be produced at low cost.

  Further, as described above, the obtained sulfuric acid acidic solution containing nickel and cobalt can be used as a raw material for producing alloys, composite metal oxides and the like. At this time, when the amount of the element contained in the obtained sulfuric acid acidic solution is small as compared with the composition of the target alloy or composite oxide, it can be supplied from other raw materials. In this case, by analyzing the amount of the metal or ions contained in the sulfuric acid acidic solution containing nickel and cobalt and the nickel and cobalt mixture recovered from the solution in advance, By appropriately grasping the amount, a desired alloy or composite metal oxide can be produced.

  EXAMPLES Hereinafter, although the Example of this invention is shown and demonstrated in detail, this invention is not limited to these Examples at all.

≪About the effect of pH≫
[Example 1]
A sulfuric acid acidic solution having a nickel concentration of 100 g / L, a cobalt concentration of 10 g / L, and a calcium concentration of 0.14 g / L was used as a base solution, and 20 ml was collected.

  As an extractant, trade name: PC88A (2-ethylhexyl, 2-ethylhexyl phosphonate: manufactured by Daihachi Chemical Industry Co., Ltd.) is used as a diluent, and trade name: Tecrine N20 (manufactured by JX Nippon Mining & Energy Corporation) is used. These two agents were mixed so as to be 20% by volume of the extractant and 80% by volume of the diluent, and used as an organic solvent for extraction in this example.

  Next, by adding sulfuric acid or sodium hydroxide aqueous solution to 20 ml of the original solution, the pH of the aqueous layer (sulfuric acid acidic solution) was 2.5 (Example 1-1) and 3.0 (Example 1-2), respectively. 3.5 (Example 1-3). Thereafter, 20 ml of an organic solvent was collected, added to and mixed with the original liquid whose pH was adjusted, and stirred at room temperature for 20 minutes. In addition, about the ratio (O / A ratio) of the organic solvent with respect to aqueous solution, it adjusted so that it might finally become 1.0.

  After completion of stirring, the mixture is allowed to stand for phase separation, and the aqueous layer (sulfuric acid solution) and the organic layer (organic solvent) are collected, and the metal concentration in the sulfuric acid solution and in the organic solvent is determined using an ICP emission analyzer. analyzed. The extraction ratio was calculated by dividing the mass of each metal component in the organic solvent determined from the analytical value by the mass of each metal component in the original solution.

[Comparative Example 1]
The pH during mixing and stirring is 1.5 (Comparative Example 2-1), 2.0 (Comparative Example 2-2), 4.0 (Comparative Example 2-3), and 4.5 (Comparative Example 2-4). The same operation as in Example 1 was performed except that the adjustment was changed. And the metal concentration in a sulfuric acid acidic solution and an organic solvent was analyzed, and the extraction rate was computed.

  In Table 1 below, for each of Examples 1-1 to 1-3 and Comparative Examples 1-1 to 1-4, pH conditions of the adjusted sulfuric acid solution and each metal component in the organic solvent The result of the extraction rate is shown. Moreover, the graph showing the relationship between the pH conditions of the sulfuric acid acidic solution (aqueous layer) at the time of extraction and the extraction rate of each metal component in an organic solvent at the time of extraction is shown in FIG. In FIG. 1, the horizontal axis indicates the pH condition during extraction, and the vertical axis indicates the extraction rate.

  As can be seen from the results shown in Table 1 and the graph of FIG. 1, calcium was hardly extracted under the condition that the pH was less than 2.5. On the other hand, when the pH exceeded 3.5, cobalt was extracted in a large amount together with calcium, and the loss of cobalt increased. Furthermore, when pH exceeded 4.0, it turned out that it turns into the tendency for the amount of calcium extraction to reduce.

  On the other hand, about nickel, it turned out that it is hardly extracted as it is the range of 1.5-4.5 as pH at the time of extraction. That is, it was found that in such a range, the separation from calcium was not adversely affected.

  From the above results, it was found that the pH condition for separating calcium from a sulfuric acid acidic solution containing nickel, cobalt, and calcium is preferably in the range of 2.5 to 3.5.

≪About influence of ratio (O / A ratio) of organic solvent to sulfuric acid acidic solution≫
[Example 2]
By changing the volume of the organic solvent in the range of 10 to 40.5 ml and changing the volume of the original solution (sulfuric acid acidic solution) in the range of 15 to 20 ml in the range of 15 to 20 ml, The ratio is 1.0 (Example 2-1), 1.5 (Example 2-2), 2.0 (Example 2-3), 2.4 (Example 2-4), respectively. Mixed. In addition, pH conditions at the time of extraction were adjusted to pH 3, and the same operation as in Example 1 was performed otherwise.

[Comparative Example 2]
The volume of the organic solvent and the volume of the sulfuric acid acidic solution were changed, and mixing was performed so that the O / A ratio was 0.5 (Comparative Example 2-1) and 2.7 (Comparative Example 2.7), respectively. In addition, pH conditions at the time of extraction were adjusted to pH 3, and the same operation as in Example 1 was performed otherwise.

  In Table 2 below, for each of Example 2-1 to Example 2-4 and Comparative Example 2-1 to Comparative Example 2-2, the addition amount of the organic solvent, the addition amount of the sulfuric acid acidic solution, O / A The ratio and the extraction rate of each metal component in the organic solvent are shown. Moreover, the graph showing the relationship between the O / A ratio and the extraction rate of each metal component in an organic solvent is shown in FIG. In FIG. 2, the horizontal axis indicates the O / A ratio, and the vertical axis indicates the extraction rate.

  As can be seen from the results shown in Table 2 and the graph of FIG. 2, the extraction rate of calcium having an O / A ratio of less than 1.0 was low. Further, when the O / A ratio was 2.4 or more, the extraction rate of calcium did not change any more. From this, it was found that even if the O / A ratio exceeds 2.4, the extraction rate is hardly changed, but the economy may be deteriorated due to an increase in running cost or the like.

  From the above results, it was found that the O / A ratio for separating calcium from the sulfuric acid acidic solution containing nickel, cobalt and calcium is preferably in the range of 1.0 or more and 2.4 or less.

≪About the influence of temperature≫
[Example 3]
A sulfuric acid acidic solution having a nickel concentration of 100 g / L, a cobalt concentration of 10 g / L, and a calcium concentration of 0.5 g / L was used as a base solution, and 20 ml was dispensed into a 50 ml beaker.

  The organic solvent for extraction was prepared in the same manner as in Example 1.

  Next, the temperature of the original solution 20 ml was adjusted to 24 ° C. (Example 3-1) or 30 ° C. (Example 3-2) with a hot stirrer manufactured by AS ONE Co., Ltd. Sulfuric acid or sodium hydroxide aqueous solution was added there, and it adjusted so that pH of an aqueous layer (sulfuric acid acidic solution) might be 2.5, 3.0, 3.25, 3.5, 4.0, respectively. Thereafter, 20 ml of an organic solvent was collected, added and mixed with the original liquid whose pH was adjusted while maintaining the above temperature, and stirred for 20 minutes.

  The ratio of the organic solvent to the aqueous solution (O / A ratio) was adjusted to 1.0. The temperature was kept constant during stirring.

  Then, after completion of stirring, the mixture is allowed to stand for phase separation. The aqueous layer (sulfuric acid solution) and the organic layer (organic solvent) are collected, and the metal concentration in the sulfuric acid solution and in the organic solvent is analyzed by ICP emission spectrometry. Analyzed with a vessel. The extraction ratio was calculated by dividing the mass of each metal component in the organic solvent determined from the analytical value by the mass of each metal component in the original solution.

[Comparative Example 3]
The same operation as in Example 3 was performed except that the temperature after temperature adjustment was changed to 40 ° C. (Comparative Example 3-1) and 60 ° C. (Comparative Example 3-2). And the metal concentration in a sulfuric acid acidic solution and an organic solvent was analyzed, and the extraction rate was computed.

  In Tables 3-7, Example 3-1 to Example 3-2 and Comparative Example 3- when the pH was adjusted to 2.5, 3.0, 3.25, 3.5, 4.0, respectively. About 1-Comparative Example 3-2, the temperature conditions of a sulfuric acid acidic solution and the extraction rate of each metal component in an organic solvent are shown. 3-5, pH conditions of the sulfuric acid acidic solution (aqueous layer) at the time of extraction of Example 3-1 to Example 3-2 and Comparative Example 3-1 to Comparative Example 3-2 respectively, and organic The graph showing the relationship between the extraction rate of the nickel component in a solvent (FIG. 3), the extraction rate of a cobalt component (FIG. 4), and the extraction rate of a calcium component (FIG. 5) is shown. 3 to 5, the horizontal axis indicates the pH condition during extraction, and the vertical axis indicates the extraction rate of the metal component.

  FIGS. 6 and 7 show the pH condition of the sulfuric acid acidic solution (aqueous layer) during extraction of Example 3-1 to Example 3-2 and Comparative Example 3-1 to Comparative Example 3-2, respectively, and calcium. The graph showing the relationship between the separation factor of / nickel (FIG. 6) and the separation factor of calcium / cobalt (FIG. 7) is shown. 6 and 7, the horizontal axis represents the pH condition during extraction, and the vertical axis represents the separation factor of the metal component.

  As can be seen from the results shown in Tables 3 to 7 and the graphs of FIGS. 3 to 5, it was found that the extraction rate of calcium increases as the temperature of the sulfuric acid acidic solution at the time of extraction decreases. Moreover, it turned out that the extraction rate of cobalt decreases, so that the temperature of a sulfuric acid acidic solution is low. Although the nickel extraction rate slightly increased, it was almost constant.

  As can be seen from the results shown in Tables 3 to 7 and the graphs of FIGS. 6 and 7, the lower the temperature of the sulfuric acid acidic solution during extraction, the higher the calcium / nickel separation factor and the calcium / cobalt separation factor. I understood.

  From the above results, it was found that as the temperature condition of the sulfuric acid acidic solution for separating calcium from the sulfuric acid acidic solution containing nickel, cobalt, and calcium, the lower the temperature, the more selectively calcium can be separated.

  As shown in the results of FIG. 5, the extraction rate of calcium does not change between pH 3.5 and pH 4.0 of the pH condition of the sulfuric acid solution, so the amount of alkali added to the sulfuric acid solution From the viewpoint of suppressing the pH, it was found that the pH is preferably adjusted to 3.5 or less. On the other hand, it was found that the pH is preferably adjusted to 2.5 or higher because the extraction rate of calcium is lowered at pH 2.5 or lower.

Claims (6)

A calcium separation method for separating calcium from a sulfuric acid acidic solution containing nickel, cobalt and calcium,
A pH adjusting step of adjusting the pH of the sulfuric acid acidic solution to 3.0 or more and 3.5 or less;
and a calcium extraction step in which an organic solvent containing 2-ethylhexyl and 2-ethylhexylphosphonate is brought into contact with the sulfuric acid acidic solution adjusted in pH, and calcium is extracted from the organic solvent.   The calcium separation method according to claim 1, wherein in the calcium extraction step, a volume ratio of the organic solvent to the sulfuric acid acidic solution is 1.0 or more and 2.4 or less.   The method for separating calcium according to claim 1 or 2, wherein the sulfuric acid acidic solution is a solution for use as a raw material of a positive electrode material of a lithium ion battery containing nickel and cobalt.   The calcium separation method according to any one of claims 1 to 3, further comprising a temperature adjusting step of adjusting the temperature of the sulfuric acid acidic solution to a range of 20 ° C or higher and lower than 40 ° C prior to the pH adjusting step. A method for producing a solution containing nickel and cobalt for use as a raw material for a positive electrode material of a lithium ion battery, from a sulfuric acid acidic solution containing nickel, cobalt and calcium,
A pH adjusting step of adjusting the pH of the sulfuric acid acidic solution to 3.0 or more and 3.5 or less;
a method of producing a solution containing nickel and cobalt, comprising: bringing the organic acid solution containing 2-ethylhexyl and 2-ethylhexylphosphonate into contact with the acidic sulfuric acid solution whose pH has been adjusted; and extracting the calcium into the organic solvent. . The method for producing a solution containing nickel and cobalt according to claim 5, further comprising a temperature adjusting step of adjusting the temperature of the acidic sulfuric acid solution to a range of 20 ° C or higher and lower than 40 ° C prior to the pH adjusting step.

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