JP2021172537A - Method for producing lithium hydroxide - Google Patents

Abstract

To provide a method for producing lithium hydroxide which can obtain lithium hydroxide from lithium carbonate at comparatively low cost.SOLUTION: A method for producing lithium hydroxide from lithium carbonate includes: a hydroxylation step of reacting the lithium carbonate with calcium hydroxide in a liquid to obtain a lithium hydroxide solution; a calcium removal step of removing calcium ions in the lithium hydroxide solution using a cation exchange resin and/or a chelate resin; and a crystallization step of depositing lithium hydroxide in the lithium hydroxide solution through the calcium removal step.SELECTED DRAWING: Figure 1

Description

This specification discloses a technique relating to a method for producing lithium hydroxide.

For example, lithium carbonate may be obtained in the process of recovering valuable metals from lithium-ion secondary battery waste or various electronic devices, salt lake brackish water, ore and other treatments.

For example, in an example of treatment for lithium ion secondary battery waste, after the lithium ion secondary battery waste is subjected to a treatment such as roasting, a lithium solution in which lithium contained therein is dissolved is obtained. The lithium solution may be a lithium hydrogen carbonate solution, and lithium carbonate can be obtained from this lithium hydrogen carbonate solution. Examples of the technique related to this include those described in Patent Documents 1 and 2.

Further, the lithium solution may be concentrated by being subjected to extraction with a lithium ion solvent and back extraction from the solvent to the aqueous phase, and the back extraction solution after the extraction and back extraction is, for example, sulfuric acid. It is a lithium solution. Note that this type of extraction and back extraction are described in Patent Documents 3 to 5 and the like.
The liquid after back extraction obtained after the back extraction described above is generally carbonated by adding a carbonate or blowing carbon dioxide gas, as described in Patent Document 5. In this case, lithium is recovered as lithium carbonate.

By the way, Patent Documents 6 and 7 describe a method for producing lithium hydroxide that can be used as a raw material for a positive electrode material of a lithium ion secondary battery from lithium carbonate.
Specifically, Patent Document 6 states, "In an electrolyzer composed of an anode tank, a cathode tank, and a cation exchange membrane, an aqueous solution or suspension of lithium carbonate is supplied to the anode tank for electrolysis to perform cation exchange. A method for producing lithium hydroxide that produces an aqueous solution of lithium hydroxide in a cathode tank via a membrane "is disclosed.
Further, in Patent Document 7, "Cation exchange membranes and cation exchange membranes are alternately arranged between the anode and the cathode, an anode chamber is formed by the anode and the cation exchange membrane, and then from the anode side to the cathode side. An acid chamber partitioned by the cation exchange membrane and the anion membrane, a salt chamber partitioned by the cation exchange membrane and another cation exchange membrane, and a partition between the cation exchange membrane and another anion exchange membrane. One or more sets consisting of an acid chamber, a salt chamber, an alkali chamber, and a water electrolysis chamber, which are arranged in the order of an alkali chamber, an anion exchange membrane, and a water electrolysis chamber partitioned by a new cation exchange membrane, are arranged. The water electrolysis chamber, which is composed of the anion film on the most cathode side, is partitioned by the cathode instead of the cation film, and an aqueous solution of lithium salt is supplied to the salt chamber using an electrodialysis machine that serves as the cathode chamber. A method for producing lithium hydroxide, which comprises taking out an acid from a chamber and an aqueous solution of lithium hydroxide from an alkali chamber. ”Has been proposed.

Patent Documents 6 and 7 both use lithium carbonate as a raw material, and produce lithium hydroxide from the lithium carbonate by electrolysis.

Japanese Unexamined Patent Publication No. 2019-26916 JP-A-2019-26531 Japanese Unexamined Patent Publication No. 2010-180439 U.S. Patent Application Publication No. 2011/0135547 Japanese Unexamined Patent Publication No. 2014-162982 Japanese Unexamined Patent Publication No. 2009-270188 Japanese Unexamined Patent Publication No. 2011-31232

If the techniques described in Patent Documents 6 and 7 are used in producing lithium hydroxide from lithium carbonate, the cost will increase significantly due to the implementation of electrolysis.

In particular, this specification discloses a method for producing lithium hydroxide, which can obtain lithium hydroxide from lithium carbonate at a relatively low cost.

The method for producing lithium hydroxide disclosed in this specification is a method for producing lithium hydroxide from lithium carbonate, in which the lithium carbonate is reacted with calcium hydroxide in a liquid to obtain a lithium hydroxide solution. Crystals that precipitate lithium hydroxide in the lithium hydroxide solution that has undergone the steps, a calcium removal step of removing calcium ions in the lithium hydroxide solution using a cation exchange resin and / or a chelate resin, and a calcium hydroxide removal step. It includes an analysis step.

According to the above-mentioned method for producing lithium hydroxide, lithium hydroxide can be obtained from lithium carbonate at a relatively low cost.

It is a flow chart which shows the manufacturing method of lithium hydroxide which concerns on one Embodiment. It is a flow chart which shows the example of the process of obtaining lithium carbonate which can be used in the manufacturing method of lithium hydroxide of FIG. It is a graph which shows the relationship between the lithium concentration and the calcium concentration of the lithium hydroxide solution after passing through the resin of Test Example 2 and BV (Bed Volume).

Hereinafter, embodiments disclosed in this specification will be described in detail.
The method for producing lithium hydroxide according to one embodiment is a method for producing lithium hydroxide from lithium carbonate. For example, as shown in FIG. 1, lithium carbonate is reacted with calcium hydroxide in a solution and water is used. Lithium hydroxide that has undergone a hydroxylation step to obtain a lithium oxide solution, a calcium removal step of adsorbing and removing calcium ions in the lithium hydroxide solution using a cation exchange resin and / or a chelate resin, and a calcium removal step. It includes a crystallization step of precipitating lithium hydroxide in the solution.

Lithium hydroxide has a lower melting point than lithium carbonate, and may be effectively used as a raw material for a positive electrode material of a lithium ion secondary battery. Therefore, in this embodiment, lithium hydroxide can be easily produced from lithium carbonate at low cost. In particular, here, it is an object of the present invention to sufficiently reduce impurities in lithium hydroxide to be produced and to produce high-purity lithium hydroxide suitable for use as a raw material for a positive electrode material.

Here, lithium hydroxide can be obtained relatively easily based on the formula of _{Li 2} CO ₃ + Ca (OH) ₂ → 2 LiOH + CaCO ₃ by the hydroxylation step of reacting lithium carbonate with calcium hydroxide. After the reaction, the calcium carbonate produced by the reaction can be removed to some extent by solid-liquid separation.
However, it is inevitable that calcium ions will remain in the lithium hydroxide solution, and even if crystallization occurs as it is, the purity of lithium hydroxide will decrease due to the presence of the calcium.

Therefore, in this embodiment, after the hydroxylation step, calcium ions existing in the lithium hydroxide solution due to the addition of calcium hydroxide in the hydroxylation step are adsorbed by the cation exchange resin and / or the chelate resin. The calcium removal step of removing the calcium is carried out, and then the crystallization step is carried out. As a result, high-purity lithium hydroxide having a low calcium content can be obtained.

(Lithium carbonate)
Lithium carbonate, which is a raw material for producing lithium hydroxide, can be obtained, for example, by a process of recovering valuable metals from lithium ion secondary battery waste.

The lithium ion secondary battery has a housing containing aluminum as an exterior wrapping around the lithium ion secondary battery. As the housing, for example, there are those made of only aluminum and those containing aluminum, iron, aluminum laminate and the like. Further, the lithium ion secondary battery has a positive electrode activity in the above-mentioned housing, which is composed of a single metal oxide selected from the group consisting of lithium, nickel, cobalt and manganese, or a composite metal oxide of two or more kinds. The material or the positive electrode active material may include an aluminum foil (positive electrode base material) coated and fixed with, for example, polyvinylidene fluoride (PVDF) or other organic binder. In addition, the lithium ion secondary battery may contain copper, iron and the like. Further, the lithium ion secondary battery usually contains an electrolytic solution in the housing. As the electrolytic solution, for example, ethylene carbonate, diethyl carbonate and the like may be used.
An example of lithium carbonate obtained from such lithium ion secondary battery waste is shown below.

(Lithium melting process)
As illustrated in FIG. 2, a lithium ion dissolution step of treating lithium ion secondary battery waste by roasting, crushing, sieving, etc., if necessary, and then dissolving the lithium contained therein in water or an acidic solution. Then, a solution containing lithium (hereinafter referred to as a lithium solution) can be obtained. Since the lithium dissolution step becomes alkaline as lithium dissolves, the pH of the lithium solution may be adjusted as necessary so that the pH of the lithium solution is finally 7 to 10. In this case, if the pH is 7 to 10, the elution of cobalt, nickel, aluminum and the like can be suppressed, and mainly lithium can be selectively dissolved.

In the lithium dissolution step, lithium can be dissolved while supplying carbonic acid ions by, for example, blowing carbon dioxide gas or supplying carbonate or carbonated water. In this case, for lithium carbonate, the reaction of H ₂ O + CO ₂ → H ₂ CO ₃ and Li ₂ CO ₃ + H ₂ CO ₃ → _{2 LiHoCO 3} , and for lithium hydroxide and lithium oxide, ₂ LiOH → Li 2 O + H ₂ O and Li ₂ Under the reaction of O + H ₂ CO ₃ + CO ₂ → _{2 LiHCO 3} or Li ₂ O + CO ₂ → Li ₂ CO ₃ and Li ₂ CO ₃ + H ₂ CO ₃ → _{2 LiHoCO 3} , a lithium hydrogen carbonate solution as a lithium solution is obtained. The blowing of carbon dioxide gas is preferable in that the contamination of impurities can be suppressed and the increase in the amount of liquid can be suppressed, so that the lithium concentration does not dilute. Specific examples of the carbonate when adding the carbonate include sodium carbonate and the like, and the amount of the carbonate added in this case is, for example, 1.0 to 2.0 times the molar equivalent, preferably 1.0 to 2.0 times the molar equivalent. It can be 1.0 to 1.2 times the molar equivalent.

The lithium solution obtained by treating the lithium ion secondary battery waste by roasting or the like and then dissolving it in water or an acidic solution has few impurities and is suitable as a raw material for lithium hydroxide, which will be described later. The residue generated in the lithium dissolution step can be used in the recovery process of valuable metals such as cobalt and nickel by acid leaching, neutralization, solvent extraction and the like.

Alternatively, the lithium solution does not recover lithium first from the sieving product obtained by roasting, crushing, and sieving the lithium ion secondary battery waste, but leaches all the elements to remove impurities. At the same time, valuable metals such as cobalt, nickel, and manganese may be recovered to form a solution in which lithium remains.

(Lithium concentration process)
When the lithium solution is a lithium hydrogen carbonate solution, the lithium concentration can be increased and concentrated by heat concentration or the like as shown in FIG. 2 (a). Here, the lithium solution can be concentrated by heating it to a temperature of, for example, 50 ° C. to 90 ° C. As a result, carbonic acid can be desorbed from the lithium solution as carbon dioxide gas, and lithium carbonate can be obtained. Alternatively, it is also possible to add methanol, ethanol or the like to the lithium solution to remove carbonic acid with such a non-aqueous solvent. Of these, methanol and ethanol are preferably used as non-aqueous solvents because they are inexpensive. Here, as a specific addition method, a non-aqueous solvent may be mixed and stirred with the lithium solution.
The resulting lithium carbonate can be purified as needed. Specifically, in the purification of lithium carbonate, lithium carbonate obtained by desorption of carbonic acid from the lithium solution is washed with repulp, and carbonic acid gas is blown into the lithium carbonate to dissolve the carbonic acid in the solution. Next, the lithium hydrogen carbonate solution is separated from calcium, magnesium, etc. by solid-liquid separation. Then, after decarboxylation and concentration, it is separated into purified lithium carbonate and a filtrate by solid-liquid separation. If the impurity grade in the purified lithium carbonate is high, further cleaning can be performed.

Alternatively, as shown in FIG. 2B, a lithium concentration step may be performed in which the lithium ions in the lithium solution are extracted with a solvent and the lithium ions in the solvent are back-extracted. When the lithium ion concentration step of extraction with a solvent and back extraction is performed, lithium ions are concentrated to obtain, for example, a lithium sulfate solution. In this lithium concentration step, the solvent after extracting the lithium ions may be scrubbed with a lithium solution containing lithium ions. In this case, back extraction is performed on the solvent after scrubbing. The lithium sulfate solution thus obtained can be made into lithium carbonate by carrying out the carbonation step described later. The details of this extraction and back extraction will be described below.

Specifically, for example, the extraction is carried out by bringing the lithium solution (aqueous phase) and the solvent (organic phase) into contact with each other, stirring and mixing them with a mixer, and transferring lithium ions or the like in the lithium solution to the solvent. Then, the organic phase and the aqueous phase are separated by a settler based on the difference in specific densities. The O / A ratio as the volume ratio of the organic phase to the aqueous phase can be made larger than 1.5 / 1.0, although it depends on the lithium ion concentration and other conditions. In order to increase the extraction rate of lithium ions, the O / A ratio can be adjusted and the number of extraction stages can be increased.

Here, the phosphonic acid ester-based extractant alone, the phosphoric acid ester-based extractant alone, or the phosphonic acid ester-based extractant and the phosphoric acid ester-based extractant are used as the solvent with respect to the lithium solution. A mixed extract can be used. As the phosphonic acid ester-based extractant, 2-ethylhexyl 2-ethylhexyl phosphonate (trade name: PC-88A, Ionquest801) is preferable from the viewpoint of separation efficiency of nickel and cobalt. Examples of the phosphoric acid ester-based extractant include di-2-ethylhexyl phosphoric acid (trade name: D2EHPA or DP8R).

The extractant can be used by diluting it with a hydrocarbon-based organic solvent such as an aromatic-based, paraffin-based, or naphthenic-based solvent, if necessary. In this case, the concentration of the extractant can be, for example, 15% by volume to 35% by volume.

The equilibrium pH at the time of extraction is preferably 7 to 8. This is because if the equilibrium pH is less than 7, the lithium extraction rate will be low and phase separation may be poor. On the other hand, if the equilibrium pH is higher than 8, the alkali concentration derived from the pH adjuster will be high. This is because the extractant and the diluent may separate. From this point of view, it is more preferable that the equilibrium pH at the time of extraction is 7.2 to 7.5. The "equilibrium pH" referred to here is the pH of the aqueous phase when the aqueous phase and the oil phase are separated by allowing them to stand after the solvent extraction operation, the scrubbing operation, and the back extraction operation.

In order to adjust the pH to the above level at the time of extraction, a pH adjusting agent such as sodium hydroxide, lithium hydroxide, aqueous ammonia or an alkaline solution can be used. Among them, sodium hydroxide is preferable because it is cheaper than other reagents and has no odor.

The solvent from which the lithium ions have been extracted can be scrubbed with a lithium solution. The lithium ion concentration in the lithium solution used for scrubbing is preferably 1.0 g / L to 10.0 g / L, and more preferably 1.0 g / L to 5.0 g / L. At the time of scrubbing, it is preferable to adjust the pH of the mixture of the solvent and the lithium solution to be 5.0 to 9.0, and further to adjust the pH to 6.0 to 8.0. It is even more preferable to adjust to.

Then, the lithium ions contained therein are back-extracted from the solvent. In the back extraction, for example, a back extraction pre-extraction solution which is an acidic aqueous solution is used, and the mixture is stirred and mixed with a mixer or the like. As a result, the lithium ions contained in the solvent are transferred to the aqueous phase.

The pre-extraction liquid used for back extraction may be any of inorganic acids such as sulfuric acid, hydrochloric acid and nitric acid, but sulfuric acid is preferable. This is because by using sulfuric acid, the liquid after back extraction becomes a lithium sulfate liquid, which can be used as a raw material for lithium hydroxide.

In the back extraction, the pH is maintained so that the equilibrium pH is preferably in the range of 0.5 to 2.0, more preferably in the range of 1.0 to 1.5. If the equilibrium pH at the time of back extraction is out of the range and becomes low, the amount of the pH adjuster at the time of extraction may increase. Further, when the equilibrium pH becomes higher than the above range, there is a concern that lithium ions may remain in the solvent. If the back extraction is performed in multiple stages, the pH may increase as the number of stages increases. In this case as well, for example, sulfuric acid is added so that the equilibrium pH is maintained within the above range. It is preferable to manage it.
Although other conditions are appropriately set, the O / A ratio can be, for example, 1.0 or more, preferably 1.0 to 1.5.

The post-extraction solution obtained in the back-extraction step can be further subjected to the back-extraction step as a pre-extraction solution, whereby the lithium ion concentration can be further increased. The back-extracted liquid can also be used in the scrubbing step as a lithium solution.

The liquid after back extraction (lithium sulfate solution) has a lithium ion concentration of, for example, 10 g / L to 30 g / L, typically 20 g / L to 25 g / L.

In particular, the lithium ion concentration in the lithium sulfate solution obtained from the lithium ion secondary battery waste as described above is, for example, 10.0 g / L to 30.0 g / L, typically 20.0 g / L. It is ~ 25.0 g / L. For example, potassium, calcium, iron, copper, zinc, aluminum, nickel, cobalt, manganese and the like are maintained in a low state even before solvent extraction. On the other hand, impurities such as phosphorus and chlorine are removed before solvent extraction, resulting in a low concentration.

However, it can be applied not only to the process of recovering valuable metals from lithium ion secondary battery waste but also to various processes for obtaining liquid or solid lithium sulfate.

(Carbonation process)
By performing extraction with a solvent and back extraction in the above-mentioned lithium concentration step, for example, the lithium concentration is concentrated above the solubility of lithium carbonate, and as shown in FIG. 2 (b), when a lithium sulfate solution is obtained, carbon dioxide is obtained. Perform the chemical conversion process.

Here, by adding a carbonate to the lithium sulfate solution or blowing carbon dioxide gas, the lithium ions in the lithium sulfate solution are converted into lithium carbonate. After the addition of the carbonate or the blowing of the carbon dioxide gas, for example, the liquid temperature is set in the range of 20 ° C. to 50 ° C., and the mixture is stirred as necessary to maintain a predetermined time. Examples of the carbonate include sodium carbonate, ammonium carbonate and the like, but sodium carbonate is preferable from the viewpoint of recovery rate.

It is preferable that the pH of the lithium sulfate solution at the time of carbonation is relatively high, 10 to 13. If carbonate is added in a low pH state, it will be released as carbon dioxide gas, so there is a concern that the reaction efficiency will decrease.

Lithium carbonate is obtained by performing a carbonation step on a lithium sulfate solution.

(Hydroxide process)
In the hydroxylation step using Ca, the above lithium carbonate is reacted with calcium hydroxide in a solution to obtain a lithium hydroxide solution. The reaction here can be represented _{by Li 2} CO ₃ + Ca (OH) ₂ → 2 LiOH + CaCO _3. As a result, a lithium hydroxide solution in which lithium hydroxide is dissolved is generated, and calcium carbonate is precipitated. The use of calcium hydroxide in the hydroxylation step is effective in that, for example, after converting lithium sulfate to lithium carbonate, a lithium hydroxide solution can be produced by a chemical reaction with lithium carbonate.

More specifically, in the case of a lithium carbonate solution, calcium hydroxide is added to the lithium carbonate solution and reacted in the solution. Alternatively, in the case of solid lithium carbonate, the lithium carbonate and calcium hydroxide are added to a liquid such as water to form a slurry, which causes a reaction.

In the above reaction formula, calcium hydroxide is preferably added 1.05 to 1.10 times as much as lithium hydroxide in a molar equivalent amount. If the amount of calcium hydroxide added is excessive, the amount of calcium hydroxide that does not contribute to the reaction increases. Calcium hydroxide, which does not contribute to the reaction, increases the amount of residue during solid-liquid separation and becomes an impurity during crystallization, which increases the load on the calcium removal step and may increase the total cost.

When reacting lithium carbonate with calcium hydroxide, the pH of the liquid may be 9 or more. The upper limit is not particularly specified, but if the pH exceeds 12, it will only become excessive, so 12 or less is preferable. If the pH is low, the reaction from lithium carbonate to lithium hydroxide may be insufficient, while if the pH is high, calcium hydroxide is excessive, resulting in drug cost and cost for removal. There is a risk.

Most of the calcium carbonate produced by the above reaction can be removed by performing solid-liquid separation using a thickener or a filter press after the reaction. That is, most of the calcium carbonate can be separated from the lithium hydroxide solution by solid-liquid separation after the reaction.

However, even if solid-liquid separation is performed, calcium may dissolve and remain in the lithium hydroxide solution. Calcium ions contained in the lithium hydroxide solution deteriorate the quality of lithium hydroxide after crystallization. Therefore, in this embodiment, the calcium ion is removed by performing the calcium removal step described below.

(Calcium removal process)
In the calcium removal step, in order to remove calcium ions in the lithium hydroxide solution obtained in the above-mentioned hydroxylation step, the lithium hydroxide solution is brought into contact with a cation exchange resin and / or a chelate resin to remove the impurities. .. Specifically, a lithium hydroxide solution is passed through the resin. As a result, calcium ions that can be contained in the lithium hydroxide solution are adsorbed on the resin, so that calcium can be removed from the lithium hydroxide solution. As a result, high-purity lithium hydroxide can be obtained after the crystallization step described later.

Here, it is important to select the resin and conditions so that the calcium ions in the lithium hydroxide solution are efficiently removed in the calcium removal step.

The resin from which calcium ions and the like are removed is at least one of a cation exchange resin and a chelate resin. The lithium hydroxide solution may be brought into contact with either the cation exchange resin or the chelate resin, and then with the other. That is, the resin adsorption process may be performed in a plurality of steps.

A cation exchange resin is a synthetic resin that binds to cations by having an acidic group on the surface. The chelate resin is a resin having a functional group that forms a complex with a metal ion. Since the lithium hydroxide solution contains lithium ions and the like in addition to calcium ions, it is desirable to use a cation exchange resin and / or a chelate resin having a high selectivity difference from lithium ions in this impurity removal step.

When a cation exchange resin is used, it is preferable to use a weakly acidic cation exchange resin having a carboxyl group as a functional group as the cation exchange resin. Since the strong acid cation exchange resin has a low difference in selectivity between the monovalent metal and the divalent metal, the divalent metal may leak from a relatively early stage of liquid passage. On the other hand, the weakly acidic cation exchange resin has high selectivity for a divalent metal because it is adsorbed so as to sandwich the metal between two carboxyl groups. In particular, a weakly acidic cation exchange resin having a high ion exchange capacity and excellent physical strength is suitable.

The chelate resin has high selectivity for a specific metal due to the chelating effect of the ion exchange of functional groups and the coordination bond. In particular, a chelate resin can be effectively used in a lithium hydroxide solution in which lithium ions and the like coexist. There are iminodiacetic acid type and aminophosphate type chelating resins. Among them, the aminophosphate type chelating resin is preferable in that the selectivity of calcium and the like with respect to monovalent ions is higher than that of other chelating resins.

When the column is filled with a cation exchange resin or a chelate resin and a lithium hydroxide solution is passed through the column, the space velocity (SV) in the column is preferably in the range of 5 to 20. This space velocity (SV) means the ratio (double amount) of the amount of passage of the lithium hydroxide solution per hour to the cation exchange resin or chelate resin packed in the column. Generally, if the space velocity (SV) is too high, there is a concern that the adsorption time of calcium ions on the resin is insufficient and the calcium ions in the lithium hydroxide solution are not sufficiently removed. If the space speed (SV) is too slow, the processing speed decreases and the processing time increases.

When the lithium hydroxide solution is brought into contact with the cation exchange resin and / or the chelate resin, the pH of the lithium hydroxide solution is preferably 9 or more, that is, the lithium hydroxide solution is preferably alkaline. This is because if the pH of the lithium hydroxide solution here is less than 9, the removal efficiency of calcium ions may decrease or even lithium ions may be adsorbed depending on the resin used here. Because. The pH of the lithium hydroxide solution at the time of contact with the resin may be changed depending on the type of resin to be selected and the like.

(Crystalization process)
In the crystallization step, lithium hydroxide in the lithium hydroxide solution from which impurities have been removed in the above calcium removal step is precipitated. Thereby, lithium hydroxide can be obtained.

In the crystallization step, since lithium hydroxide is precipitated, a crystallization operation such as heat concentration or vacuum distillation can be performed. In the case of heat concentration, the higher the temperature at the time of crystallization, the faster the treatment proceeds, which is preferable. However, after crystallization, the drying temperature of the crystallized product is preferably a temperature of less than 60 ° C. at which water of crystallization does not desorb. This is because when the water of crystallization is desorbed, it becomes anhydrous lithium hydroxide and has deliquescent property, which makes it difficult to handle.

After that, in order to adjust the above-mentioned lithium hydroxide to the required physical properties, a pulverization treatment or the like can be performed.

The lithium hydroxide thus obtained has a calcium content sufficiently reduced to, for example, 10 mass ppm or less by undergoing the above-mentioned calcium removal step. Such high-purity lithium hydroxide is suitable for use as a raw material for manufacturing a lithium ion secondary battery.

Next, the above-mentioned method for producing lithium hydroxide was carried out on a trial basis, and its effect was confirmed, which will be described below. However, the description here is for the purpose of mere illustration, and is not intended to be limited thereto.

(Test Example 1)
After adding 250 g of lithium carbonate and 648 g of calcium hydroxide to 5000 mL of water, solid-liquid separation by filtration was performed to obtain a lithium hydroxide solution. The Li concentration in the lithium hydroxide solution was 6.0 g / L, the Ca concentration was 0.03 g / L, and the pH was 12.

In Example 1, the lithium hydroxide solution obtained as described above is passed through a column packed with 20 mL of a cation exchange resin having a carboxyl group (AMBERLITE IRC76 manufactured by Organo Corporation) at room temperature to remove impurities. It was removed. The pH of the lithium hydroxide solution during this liquid passage was 12, and the space velocity (SV) was 9.

In Example 2, impurities were removed by passing the above lithium hydroxide solution at room temperature through a column filled with 20 mL of a chelate resin (AMBERLITE IRC747UPS manufactured by Organo Corporation). The pH of the lithium hydroxide solution during this liquid passage was 12, and the space velocity (SV) was 9.

In Comparative Example 1, resin adsorption was not performed on the above lithium hydroxide solution.

Then, in each of Examples 1 and 2 and Comparative Example 1, the lithium hydroxide solution was heated and concentrated at a temperature of 50 ° C. to crystallize lithium hydroxide.

Table 1 shows the impurity content of lithium hydroxide obtained in each of Examples 1 and 2 and Comparative Example 1 above.

From Table 1, since the Ca content in lithium hydroxide was sufficiently reduced in both Examples 1 and 2 as compared with Comparative Example 1, calcium was treated with a cation exchange resin or a chelate resin. It can be seen that the ions were effectively removed.

(Test Example 2)
For each of the cation exchange resin used in Example 1 and the chelate resin used in Example 2 described above, when the BV (Bed Volume), which is a flow rate multiple of the amount of water flowing through the resin, is changed. Changes in Li concentration and Ca concentration in the lithium hydroxide solution after passing through the resin were confirmed. BV is represented by BV = liquid flow rate (L) / resin volume (L). Here, the same lithium hydroxide solution as in Test Example 1 was used. The result is shown in a graph in FIG.

From FIG. 3, it can be seen that the high Li concentration and the low Ca concentration in the lithium hydroxide solution after passing the liquid are maintained over a relatively wide range of BV. Therefore, it was found that this can contribute to the production of relatively high-purity lithium hydroxide from lithium sulfate.

(Test Example 3)
Lithium ion after roasting Lithium in secondary battery waste is dissolved in water or an acidic solution, lithium ions are extracted from the obtained lithium solution with a solvent, and the solvent after extraction is scrubbed with a lithium solution for scrubbing. Lithium ions were back-extracted from the solvent after the process, thereby obtaining a lithium sulfate solution as a solution after back-extraction. Table 2 shows the impurity composition of the liquid after back extraction.

Sodium carbonate was added to the above lithium sulfate solution for carbonation, calcium hydroxide was added, and solid-liquid separation was performed by filtration to obtain a lithium hydroxide solution. Using each of the cation exchange resin used in Example 1 and the chelate resin used in Example 2, the lithium hydroxide solution after passing through the resin was heated and concentrated at a temperature of 50 ° C. to hydroxylate. Lithium was crystallized.
As a result, high-purity lithium hydroxide at the same level as in Examples 1 and 2 in Table 1 was obtained.

Claims (6)

A method of producing lithium hydroxide from lithium carbonate.
The calcium ion in the lithium hydroxide solution is removed by reacting the lithium carbonate with calcium hydroxide in a solution to obtain a lithium hydroxide solution and using a cation exchange resin and / or a chelate resin. A method for producing lithium hydroxide, which comprises a calcium removing step and a crystallization step of precipitating lithium hydroxide with a lithium hydroxide solution that has undergone the calcium removing step. The method for producing lithium hydroxide according to claim 1, wherein the pH of the lithium hydroxide solution when brought into contact with the cation exchange resin and / or the chelate resin in the calcium removal step is 9 or more. The production of lithium hydroxide according to claim 1 or 2, wherein in the calcium removal step, the space velocity (SV) when the lithium hydroxide solution is passed through the cation exchange resin and / or the chelate resin is 5 to 20. Method. The method for producing lithium hydroxide according to any one of claims 1 to 3, wherein a weakly acidic cation exchange resin having a carboxyl group as a functional group is used in the calcium removal step. The lithium carbonate step of obtaining a lithium solution by dissolving lithium in the lithium ion secondary battery waste after roasting with water or an acidic solution, and the lithium concentration step of concentrating the lithium ions of the lithium solution. The method for producing lithium hydroxide according to any one of claims 1 to 4, which is obtained by a treatment including. The method for producing lithium hydroxide according to any one of claims 1 to 5, wherein the lithium hydroxide used for producing the lithium ion secondary battery is produced.

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