JP6986997B2 - Lithium carbonate manufacturing method and lithium carbonate - Google Patents

Description

In the present invention, a lithium ion battery waste containing a battery positive electrode material component containing a predetermined metal is subjected to a wet treatment, and impurities are removed from an acidic solution in which Li and impurities are dissolved to obtain lithium carbonate. The present invention relates to a method for producing lithium carbonate and lithium carbonate.

For example, in recent years, it has been widely considered from the viewpoint of effective use of resources to recover valuable metals such as nickel and cobalt contained in lithium-ion battery waste from lithium-ion battery waste that is discarded due to product life or the like by wet treatment or the like. Has been done.

Specifically, in the recovery of such valuable metals, first, lithium ion battery waste is roasted, and then crushing and sieving are performed in order to remove impurities such as aluminum to some extent (see Patent Document 1 and the like). ).
Next, powdered battery powder obtained under a sieve is added to the leachate and leached out, and lithium, nickel, cobalt, manganese, copper, aluminum and the like that can be contained in the battery powder are dissolved in the liquid. Then, after leaching, each metal element dissolved in the liquid is separated and recovered. Here, in order to separate each metal leached into the leached liquid, the leached liquid is subjected to a plurality of steps of solvent extraction, back extraction, etc. according to the metal to be separated (see Patent Documents 2 and 3 and the like). ).

By the way, for example, in the method of recovering various metals from the lithium ion battery waste as described above, lithium is dissolved together with impurities in the acidic solution obtained after the predetermined solvent extraction, back extraction and the like. Then, it may be required to recover lithium from such an acidic solution.

As a technique related to this, Patent Document 4 describes that lithium ions are extracted from an aqueous solution containing lithium ions by solvent extraction and then back-extraction is repeated, and the resulting high-concentration lithium ion aqueous solution is used as a carbonate. It is described that lithium carbonate is recovered by mixing.
Further, Patent Document 5 describes that nickel and lithium are co-extracted from a solution containing at least lithium and nickel by solvent extraction, and then the lithium solution obtained by back-extracting only lithium is carbonated to recover lithium. Has been done.

Japanese Unexamined Patent Publication No. 2015-195129 Japanese Unexamined Patent Publication No. 2005-149889 Japanese Unexamined Patent Publication No. 2009-193778 Japanese Patent No. 4581553 Japanese Patent No. 5014394

In each of the methods described in Patent Documents 4 and 5, lithium ions in the solution are concentrated by solvent extraction and back extraction, but by such a method, impurities are contained in the finally obtained lithium carbonate. It is undeniable that it is contained to some extent, and as a result, it may not be possible to meet the high-quality requirements for lithium carbonate used for a predetermined purpose.

An object of the present invention is to deal with such a problem, and an object of the present invention is to provide a method for producing lithium carbonate capable of obtaining relatively high-grade lithium carbonate and lithium carbonate. be.

As a result of diligent studies, the inventor finally performed a plurality of predetermined steps on the acidic solution obtained by wet-treating the lithium-ion battery waste to remove impurities contained therein. It has been found that the quality of the obtained lithium carbonate can be significantly improved.

Based on such findings, the method for producing lithium carbonate of the present invention is a lithium ion battery waste containing a battery positive electrode material component containing at least one metal selected from the group consisting of Co, Ni and Mn and Li. On the other hand, by performing a wet treatment, at least one kind of the metal as a component of the positive electrode material of the battery is separated from the lithium ion battery waste, and the impurities are removed from the acidic solution in which Li and impurities dissolved thereby are dissolved. In the method for producing lithium carbonate, a neutralization step for neutralizing the acidic solution, a carbonization step for carbonizing Li in the neutralized liquid obtained in the neutralization step, and the carbonization step. A cleaning step of cleaning the crude lithium carbonate obtained in the step, a dissolution step of dissolving the crude lithium carbonate in the liquid under the supply of carbonate ions after the cleaning step, and a Li dissolution liquid obtained in the dissolution step. heated, viewed contains a decarboxylation step to the carbonate eliminated, in the cleaning step, the 0.5 to 2 times of pure water relative to the wet weight of the crude lithium carbonate, repulped the crude lithium carbonate It's about cleaning .

Further, the lithium carbonate of the present invention has a sodium content of 100 mass ppm or less.

According to the method for producing lithium carbonate of the present invention, a relatively high-grade lithium carbonate can be obtained by sequentially performing the above-mentioned neutralization step, carbonization step, cleaning step, dissolution step and decarbonization step. .. Since the lithium carbonate of the present invention has a sufficiently low sodium content, it can be effectively used for a predetermined use, for example, in the production of a lithium ion battery.

It is a flow figure which shows the manufacturing method of lithium carbonate which concerns on one Embodiment of this invention. It is a graph which shows the relationship between the pH and the solubility of Ni and Mg in the case of neutralizing with each of NaOH and Ca (OH) _{2 of an Example.} It is a graph which shows the relationship between _{the SO 4} grade in lithium carbonate before purification of an Example, _{and the SO 4} grade in lithium carbonate after purification. Is a graph showing changes in SO ₄ grade in the lithium carbonate to a change in the amount of washing water in the washing after decarboxylation embodiment.

Hereinafter, embodiments of the present invention will be described in detail.
As illustrated in FIG. 1, the method for producing lithium carbonate according to one embodiment of the present invention is obtained by subjecting lithium ion battery waste to a predetermined wet treatment, and is used for an acidic solution in which Li and impurities are dissolved. Lithium carbonate is produced by sequentially performing each step including a neutralization step, a carbonation step, a cleaning step, a dissolution step and a decarbonation step.

(Lithium-ion battery waste)
Lithium-ion battery waste is lithium-ion battery waste that can be used in various machines or devices such as mobile phones and other various electronic devices and automobiles. More specifically, for example, those discarded or recovered due to the life of battery products, manufacturing defects, or other reasons. By targeting such lithium-ion battery waste, effective utilization of resources can be achieved. Can be planned.

Lithium-ion battery waste includes positive electrode active materials that are lithium metal salts containing Mn, Ni, and Co, negative electrode materials containing C (carbon), Fe, and Cu, and positive electrode active materials, for example, polyvinylidene fluoride. (PVDF) An aluminum foil (positive electrode base material) coated and fixed by another organic binder or the like, and a housing containing aluminum as an exterior wrapping around the lithium ion battery waste may be included. Specifically, the lithium ion battery waste includes a single metal oxide composed of one element of Li, Ni, Co and Mn constituting the positive electrode active material and / or a composite composed of two or more elements. Metal oxides, as well as Al, Cu, Fe, C and the like may be included.

In this embodiment, the lithium ion battery waste comprises at least one metal selected from the group consisting of Co, Ni and Mn, and a battery positive electrode material component containing Li, and in some cases further. It may contain at least one metal selected from the group consisting of Al, Cu, Fe and C.

As pretreatment, the lithium ion battery waste is, for example, a roasting treatment in which the waste is heated at a predetermined temperature and time in a heating facility, a crushing treatment using a rotor rotary type or impact type crusher after roasting, and a crushing treatment. The powder or granules may be subjected to a sieving treatment or the like for sieving with a sieve having a predetermined opening. By obtaining such a pretreatment, in the lithium ion battery waste, the binder that binds the aluminum foil and the positive electrode active material is decomposed, Al, Cu, etc. are removed, and the battery positive electrode material component. Is in a form that is easily dissolved by leaching in the wet treatment.

(Wet treatment)
In the wet treatment, the above-mentioned lithium ion battery waste is generally leached with an acid such as sulfuric acid, hydrochloric acid or other mineral acid. Here, hydrogen peroxide solution may be added in order to promote the dissolution of the metal contained in the lithium ion battery waste. As a result, a post-leached liquid in which the metal in the lithium ion battery waste is dissolved is obtained.
Then, the liquid after leaching is neutralized, sulfurized, or solvent extracted to remove, for example, Fe, Al, Cu, etc., and then at least one of Co, Ni, and Mn remaining in the solution is used. Collect in sequence by solvent extraction, back extraction, etc. under the conditions according to each metal.

(Acid solution)
The acidic solution is obtained by subjecting the above-mentioned lithium ion battery waste to a wet treatment, and is obtained by dissolving Li and impurities.
As an example of such an acidic solution, after extracting nickel by solvent extraction for recovering nickel among a plurality of steps of solvent extraction or neutralization applied to the liquid after leaching by the above-mentioned wet treatment. It can be a Ni post-extraction solution obtained, or a Ni post-electrolysis solution obtained after extracting and back-extracting the nickel and then performing electrolytic sampling to recover the nickel.
In addition, as an acidic solution, a Li leachate obtained by adding the above-mentioned lithium ion battery waste to water or the like and leaching lithium thereof into water or the like can also be used. In this case, the wet treatment means a treatment of leaching lithium in the lithium ion battery waste into water or the like.

The pH of the Ni electrolyzed liquid is, for example, -1 to 2, generally 0 to 1, and the pH of the Ni extraction liquid is, for example, 1 to 4, generally 2 to 3, and the pH of the Li leachate is described above. The pH is, for example, 9 to 13, generally 10 to 12.
The above-mentioned Ni extraction solution, Ni electrolysis solution, and Li leachate can be used after concentrating lithium by solvent extraction, if necessary. Generally, such concentration of lithium results in a pH of 0 to 1, for example. It becomes a moderately acidic solution.

Examples of the impurities contained in the acidic solution include those contained in the lithium ion battery waste that remain without being separated by the wet treatment. Specifically, in the embodiment shown in FIG. 1, the acidic solution contains Ni, Na, Ca, Mg and SO ₄ as impurities together with Li.

The acidic solution contains Li ions, for example 2 g / L to 20 g / L, typically 5 g / L to 12 g / L, and Ni ions, for example 50 g / L to 150 g / L, typically 70 g / L. It can be contained at L to 100 g / L. In particular, when the acidic solution is the above-mentioned post-electrolysis solution, Ni ions are often in such a concentration range.
The acidic solution further contains Na ions, for example 30 g / L to 70 g / L, typically 40 g / L to 60 g / L, and Ca ions, for example 0.001 g / L to 0.1 g / L. , Typically at 0.01 g / L to 0.05 g / L, and Mg ions, eg, 0.01 g / L to 10 g / L, typically 0.05 g / L to 5 g / L. SO ₄ ions may be contained, for example, at 1 g / L to 200 g / L, typically 10 g / L to 100 g / L.

Among them, Mg ions that can be contained in the acidic solution are not removed until the purification of lithium carbonate by the conventional method and remain to cause deterioration of quality, so that they are removed by the neutralization step described later as in this embodiment. Is preferable. The Mg ion may be more typically contained at 0.1 g / L to 2 g / L and even 0.2 g / L to 2 g / L.

Although not in the embodiment shown in FIG. 1, examples of the ions that can be contained in the acidic solution include Co, Si, Cl and the like.

(Neutralization process)
Alkali is added to the acidic solution as described above to neutralize the acidic solution, whereby Ni ions and Mg ions in the acidic solution are precipitated as a solid. This is separated and removed by solid-liquid separation. As a result, Ni ions and Mg ions are removed to obtain a neutralized liquid containing lithium ions.

The alkali used in the neutralization step is not particularly limited as long as it can effectively raise the pH of the acidic solution, and examples thereof include NaOH, Ca (OH) ₂ , CaO, and CaCO ₃ . When using a Ca salt, CaSO ₄ becomes SO ₄ ions that may be included in the acid solution by Ca salt, which can be removed by solid-liquid separation.
Among the Ca salts, Ca (OH) ₂ is particularly preferable in terms of reaction control and prevention of equipment scaling. Since the results in heat generation at the time of the addition in CaO, scale generated inside the equipment, could be potentially detrimental and pipes clogging of the reactor actual volume, the CaCO _3, may not be raised to a predetermined pH concerns Will be done.
However, with Ca salt, the amount of neutralized substance may increase and the filter may become large. Therefore, from this viewpoint, it is preferable to use NaOH. NaOH can also effectively remove _{SO 4 ions.}

The amount of alkali added is preferably 1.0 to 1.5 times the molar equivalent of the amount required for neutralization of Ni ions, Mg ions and free acids that can be contained in the acidic solution. If the amount of alkali added is too small, there is a concern that some of the Ni ions, Mg ions, and free acid will not be removed by precipitation. On the other hand, if the amount of alkali added is too large, the cost will simply increase and residues will be generated. If the amount increases, it may lead to deterioration of filterability. From this point of view, the amount of alkali added is preferably 1.1 times molar equivalent to 1.2 times molar equivalent.

By adding the alkali to the acidic solution in this way, it is preferable that the pH of the acidic solution after the addition of the alkali is 12.0 to 13.0. If the pH of the acidic solution after the addition of alkali is too low, the removal of Ni and Mg, which are the components to be removed, may be insufficient, which may cause deterioration of the quality of lithium carbonate. On the other hand, if the pH of the acidic solution after the addition of alkali is too high, the solution may be redissolved if the solution contains an amphoteric metal as an impurity.

Here, when the acidic solution does not contain Mg ions, the pH of the acidic solution after addition of the alkali is set to 9 to 10.5, preferably 10.0 to 10.5 in order to effectively remove Ni ions. be able to.
On the other hand, when the acidic solution contains Mg ions, the pH of the acidic solution after the addition of the alkali is set to 12 to 13, so that Mg also precipitates and can be removed together with Ni. From this point of view, the pH of the acidic solution after addition of alkali is more preferably 12.0 to 13.0, preferably 12.0 to 12.5.

After adding the alkali to the acidic solution, the acidic solution can be stirred for a predetermined time to accelerate the reaction. From the viewpoint of improving the reaction efficiency, it is preferable that the temperature is relatively high and the stirring is relatively strong.

After precipitating Ni and Mg as predetermined compounds such as hydroxides by adding alkali, solid-liquid separation is performed using a known device or method such as a filter press or thickener, and the precipitate and the neutralized liquid are separated. Can be separated into. The precipitate contains a compound of Ni and Mg, while the liquid after neutralization has almost all Ni and Mg removed and Li exists in a dissolved state.
The Ni concentration in the neutralized liquid is preferably 5 mg / L or less, particularly preferably 1 mg / L or less, and the Mg concentration is preferably 5 mg / L or less, particularly preferably 1 mg / L or less. It is preferable to remove as much Ni and Mg as possible in this neutralization step.

(Carbonation process)
The neutralized liquid obtained by removing nickel in the above neutralization step is subjected to a carbonation step to carbonate Li contained in the neutralized liquid, as compared with the finally obtained lithium carbonate. Obtain low-grade crude lithium carbonate for the time being.

Here, in order to carbonate Li in the neutralized liquid, Li ions in the neutralized liquid are recovered as crude lithium carbonate by adding a carbonate to the neutralized liquid or blowing carbonic acid gas. .. From the viewpoint of preventing the increase of impurities, it is preferable to blow carbon dioxide gas. This is because the addition of carbonate results in the addition of impurity components.

When a carbonate is added to the solution after neutralization, examples of the carbonate include sodium carbonate and the like. Specifically, for example, with respect to Li in the solution after neutralization, 1.0 to 2.0 times the molar equivalent in the assumed reaction of _{Li 2} SO ₄ + Na ₂ CO ₃ → Li ₂ CO ₃ + Na ₂ SO _4. Preferably, 1.0 to 1.2 times the molar equivalent of carbonate can be added. If the amount of carbonate added is too small, there is a concern that Li in the solution after neutralization cannot be converted to lithium carbonate and will be lost. On the other hand, if the amount is too large, the amount of sodium sulfate mixed in lithium carbonate will increase. It becomes necessary to strengthen the cleaning in the subsequent process, and there is a possibility that the loss of dissolution of Li in the cleaning liquid will increase.

After the addition of carbonate or the blowing of carbon dioxide gas, for example, the liquid temperature is set in the range of 50 ° C. to 90 ° C., and the mixture is stirred as necessary, and this is carried out for 0.5 hours to 2 hours, typically 1 hour. The temperature can be maintained.

(Washing process)
In the cleaning step, the crude lithium carbonate obtained in the above carbonation step is washed. Here, it is an object of the present invention to remove at least a part of _{SO 4} and at least a part of Na among impurities contained in crude lithium carbonate. In particular, at this stage, the _{lower the grade of SO 4 contained in crude lithium carbonate, the more the grade of SO 4} of lithium carbonate finally obtained through the dissolution step and decarboxylation step described later can be significantly reduced. So it is effective.

More specifically, crude lithium carbonate can be repulped with washing water such as pure water 0.5 to 2 times, preferably 1 to 1.5 times the wet weight of the crude lithium carbonate. can. If the amount of pure water used for cleaning is too large, there is a concern about loss of Li due to the large solubility of crude lithium carbonate. On the other hand, if the amount of pure water is too small, it is possible that SO ₄ cannot be removed as expected. Here, the wet weight means the weight (kg-wet) of lithium carbonate recovered by solid-liquid separation after carbonation in an undried state.
Here, the repulp washing means that the cake after solid-liquid separation is put into a predetermined amount of water, stirred and made into a slurry, and the solid-liquid separation operation is performed again. Further, pure water means water containing at least Mg, preferably Na and Ca.

The temperature at the time of washing is preferably 50 ° C. to 90 ° C., and the washing time is preferably 0.5 hour to 1 hour. If the temperature is out of this range, the solubility of lithium carbonate will increase on the low temperature side and the dissolution loss will increase, and on the high temperature side, impurities will be reconcentrated due to the volatilization of water. There is a possibility that washing with water will be insufficient on the time side and cost will increase on the long time side.

It is preferable that the above-mentioned cleaning operation is performed a plurality of times. When the number of washings is one and the amount of pure water with respect to the above-mentioned wet weight is increased, the loss of Li in the washing water is large when reducing to the _{predetermined SO 4 grade due to the large solubility of crude lithium carbonate.} Because it becomes. From this point of view, the number of washings is preferably 2 to 3 times, and particularly preferably 2 times. Even if the number of times is too large, the dissolution loss of Li in the washing water will increase.

(Dissolution step)
For the crude lithium carbonate that has undergone the washing step, a dissolution step of dissolving the crude lithium carbonate in the liquid under the supply of carbonate ions is performed.
More specifically, for example, first, crude lithium carbonate is repulped with a liquid such as pure water. Then, carbonic acid ions are supplied to the liquid by blowing carbon dioxide gas or adding a carbonate, and the carbonic acid is dissolved in the liquid. As a result, _{crude lithium carbonate is dissolved in the solution by the reaction of Li 2} CO ₃ + H ₂ CO ₃ → _{2 LiHCO 3} , and a Li solution as a lithium hydrogen carbonate solution is obtained.

Here, when repulping crude lithium carbonate, the amount of pure water having a Li concentration of 7 g / L to 9 g / L when it is assumed that the entire amount of the crude lithium carbonate is dissolved in the pure water at 25 ° C. It is preferable to use. This Li concentration is in a range close to the solubility as lithium hydrogen carbonate and changes depending on the temperature. Therefore, it is desirable to appropriately adjust the Li concentration within the range according to the temperature at the time of washing. More preferably, pure water having a Li concentration of 8 g / L to 9 g / L is used when it is assumed that the entire amount of the crude lithium carbonate is dissolved in the pure water at 25 ° C.

Here, when carbon dioxide gas is blown into the pure water after washing the repulp, the carbon dioxide gas having a 1-fold molar equivalent to a 3-fold molar equivalent, particularly a 1.5-fold molar equivalent to a 2.3-fold molar equivalent in the above assumed reaction. It is preferable to blow in. If the amount of carbon dioxide gas is too large, there is a concern that Ca, which is a component to be removed, may be dissolved, and if it is too small, the dissolution of lithium carbonate may be insufficient, resulting in a loss of lithium, which is a component to be recovered.

However, even before the blowing of the above amount of carbon dioxide gas is completed, the blowing can be stopped at the time when a small amount of undissolved residue remains (pH 7.6 to 7.9). This makes it possible to separate Ca by leaving it as a residue. Here, the property that the solubility of calcium sulfate is sufficiently smaller than the solubility of calcium carbonate and calcium hydrogen carbonate is utilized.

(Decarboxylation process)
After the dissolution step, the Li solution obtained there is heated to desorb carbon dioxide, and Li ions in the Li solution are precipitated as lithium carbonate.
Here, the Li-dissolved solution is preferably heated to a temperature of 50 ° C. to 90 ° C. to concentrate, and carbonic acid can be desorbed from the Li-dissolved solution as carbon dioxide gas. The solubility of lithium hydrogen carbonate decreases as the temperature rises. In the decarbonization step, the difference in solubility between lithium hydrogen carbonate and lithium carbonate is used to effectively crystallize Li, which is sufficiently dissolved in the Li solution by the formation of lithium hydrogen carbonate, as lithium carbonate by heating. be able to.

If the heating temperature of the Li solution is less than 50 ° C., there is a concern that carbonic acid will not be effectively desorbed. On the other hand, if the heating temperature exceeds 90 ° C., a problem due to boiling may occur, so 90 ° C. can be set as the upper limit. From this viewpoint, it is more preferable that the heating temperature of the lithium solution is 70 ° C to 80 ° C.

At this time, it is possible to heat and concentrate about 3 times by volume, but even if it is heated and concentrated until it evaporates to dryness, the recovery rate of Li can be improved without significantly affecting the impurity grade. Can be done.
By the decarboxylation step, relatively high quality lithium carbonate can be obtained.

(Washing process)
After the decarboxylation step, a washing step of washing lithium carbonate may be performed depending on the impurity grade of lithium carbonate and other conditions. However, this cleaning step after the decarboxylation step can be omitted.

This cleaning step can be carried out under the same conditions and methods as the cleaning step before the dissolution step. Thereby, impurities derived from the adhered water that may be contained in lithium carbonate, such as SO ₄ , and even Na may be removed. Increasing the amount of wash water in this wash step may not improve the impurity grade of the soluble component, in which case such impurities may be involved in the crystals during the decarboxylation step. ..
When the concentration ratio at the time of heating in the decarboxylation step is large, it is preferable to perform this cleaning step from the viewpoint of further removal of impurities.

(Lithium carbonate)
The lithium carbonate obtained from the above preferably has a lithium carbonate grade (purity) of preferably 99.2% by mass or more, more preferably 99.5% by mass or more.
In particular, by manufacturing by the above-mentioned manufacturing method, the content of sodium in lithium carbonate can be 100 mass ppm or less. Sodium may interfere with the movement of lithium ions, for example, when the lithium carbonate is used in the manufacture of a lithium ion battery, so it is effective to be able to reduce the concentration of sodium in this way. The sodium content of lithium carbonate can be further set to 80% by mass or less and 50% by mass or less.

Further, according to the production method using lithium ion battery waste as a raw material as described above, the chlorine content of lithium carbonate can be 10 mass ppm or less. Since chlorine is compounded with a lithium compound in a lithium ion battery and has hygroscopicity, it is preferable that the content of chlorine is low. In general, lithium carbonate is often produced from seawater, but it is difficult for lithium carbonate produced from seawater to reduce chlorine as described above.
The above-mentioned sodium and chlorine contents and grades are measured by an automatic sample combustion device ion chromatograph.

Further, this lithium carbonate preferably has a tap density of 0.75 to 1 g / cm ³ and a bulk density of 0.35 to 0.4. The tap density is measured by JIS Z2512, and the bulk density is measured by JIS Z8807.
Such lithium carbonate can be used for various purposes, but can be particularly effectively used for manufacturing a lithium ion battery.

Next, since the method for producing lithium carbonate of the present invention was carried out on a trial basis, it will be described below. However, the description here is for the purpose of mere illustration, and is not intended to be limited thereto.

The following steps were performed using acidic solutions of the three raw materials 1 to 3 having the compositions shown in Table 1, respectively. This acidic solution leaches lithium-ion battery waste containing a battery positive electrode material component containing Co, Ni, Mn and Li with sulfuric acid, removes a predetermined metal from the leaching solution, and then Mn, Co, Ni. Each of these was obtained by sequentially recovering them by solvent extraction in a plurality of steps, and Li and Ni, Na, Ca, Mg and SO ₄ as impurities remained in the solution in a dissolved state.

(Neutralization)
NaOH was added to the above acidic solution to raise the pH of the acidic solution to 12. As a result, almost all of Ni and Mg were precipitated, and they could be removed by solid-liquid separation. The composition of the liquid after neutralization is shown in Table 2.
For reference, FIG. 2 shows the relationship between the pH and the solubility of Ni and Mg when neutralized with each of NaOH and Ca (OH) _2. From FIG. 2, it can be seen that when the pH is raised to 12, both Ni and Mg are sufficiently precipitated.

(Carbonated)
To Li in the above neutralized liquid, 1.2 times the molar equivalent of Na ₂ CO _{3 was added in the assumed reaction of Li 2} SO ₄ + Na ₂ CO ₃ → Li ₂ CO ₃ + Na ₂ SO ₄ to 50 ° C. The mixture was stirred and held for 1.5 hours. As a result, Li was once recovered as crude lithium carbonate.

(Washing)
The crude lithium carbonate was repulped at 60 ° C. for 0.5 hours with pure water 1 times the wet weight of the crude lithium carbonate. This cleaning operation was performed twice. As a result, crude lithium carbonate was obtained after washing with the grades shown in Table 3.

Note here, the difference in the conditions of this washing, purified and confirmed the effect before and after the SO ₄ grade and Li loss rate at the time of washing (lysis and decarboxylation below). When washing twice with pure water that is 1 times the wet weight of crude lithium carbonate, the SO ₄ grade before and after purification was reduced from 5600 ppm to 210 ppm, and the Li loss rate during washing was 5%. rice field. On the other hand, when one wash is performed with pure water 5 times the wet weight of crude lithium carbonate, the SO ₄ grade before and after purification is reduced from 29000 ppm to 600 ppm, and the Li loss rate during washing is 15%. Met. From this, it can be seen that increasing the amount of wash water _{not only does not significantly reduce the SO 4} grade before and after purification, but also increases the Li loss rate.
_{Further, the relationship between the SO 4} grade in lithium carbonate before purification (after the washing) and the SO ₄ grade in lithium carbonate after purification is shown in a graph in FIG. From this graph, it can be seen _{that the lower the SO 4} grade before purification, the lower the SO _{4 grade after purification.}

(Dissolution)
The crude lithium carbonate after washing is repulped with pure water so that the Li concentration when the entire amount is dissolved is 9 g / L (at 25 ° C.), and after the repulp washing, the carbon dioxide gas is added to Li ₂ CO ₃ + H ₂ CO. _In the assumed reaction of 3 → 2 LiHCO ₃ , crude lithium carbonate was dissolved again by blowing in a 1.2-fold molar equivalent. At this time, the blowing of carbon dioxide gas was stopped before the predetermined amount was blown and when a small amount of undissolved residue remained. As a result, Ca could be separated leaving it as a residue.

(Decarboxylation)
The dissolved filtrate (Li solution) was heated at 70 ° C. to desorb carbon dioxide gas, and recrystallized by utilizing the difference in solubility between lithium hydrogen carbonate and lithium carbonate. The heating temperature was 50 ° C. or higher. As a result, lithium carbonate was obtained.

(Washing)
After decarboxylation, lithium carbonate was washed under the same conditions as the washing before dissolution. As a result, lithium carbonate having the grade shown in Table 4 was obtained.
From Table 4, in all of the raw materials 1 to 3, Ni is 10 mass ppm or less, Na is 100 mass ppm or less, Ca is 100 mass ppm or less, Mg is 10 mass ppm or less, and SO ₄ is 600 mass ppm or less. It can be seen that it was reduced to. Among them, SO ₄ was 300 mass ppm or less in the raw materials 1 and 3. Although not shown in Table 4, the chlorine content of any of the raw materials 1 to 3 was 10 mass ppm or less.

_{The change in SO 4} grade in lithium carbonate when the amount of washing water is changed by this washing after decarboxylation is shown in a graph in FIG. _{From FIG. 4, it can be seen that the SO 4} grade did not change significantly even if the amount of washing water was increased. From this, it is _{presumed that SO 4} was not removed by washing in this lithium carbonate because it was caught in the crystal at the stage of decarboxylation.

From the above, it can be seen that according to this method for producing lithium carbonate, high-purity lithium carbonate having a relatively low impurity grade can be obtained.

Claims (7)

By subjecting a lithium ion battery waste containing a battery positive electrode material component containing at least one metal selected from the group consisting of Co, Ni and Mn and Li to a wet treatment, the lithium ion battery waste can be removed from the lithium ion battery waste. A method for producing lithium carbonate by separating at least one of the metals as a component of the battery positive electrode material and removing impurities from the acidic solution in which Li and impurities are dissolved.
A neutralization step for neutralizing the acidic solution, a carbonation step for carbonating Li in the neutralized liquid obtained in the neutralization step, and a cleaning step for cleaning the crude lithium carbonate obtained in the carbonation step. After the cleaning step, a dissolution step of dissolving the crude lithium carbonate in a solution under the supply of carbonate ions, and a decarbonation step of heating the Li solution obtained in the dissolution step to desorb carbonic acid. viewing including the door,
A method for producing lithium carbonate, wherein in the washing step, the crude lithium carbonate is repulp washed with pure water 0.5 to 2 times the wet weight of the crude lithium carbonate. The acidic solution contains Mg ions
The method for producing lithium carbonate according to claim 1, wherein the pH of the acidic solution is raised to 12.0 to 13.0 in the neutralization step. The acidic solution does not contain Mg ions and
The method for producing lithium carbonate according to claim 1, wherein the pH of the acidic solution is raised to 10.0 to 10.5 in the neutralization step. The method for producing lithium carbonate according to any one of claims 1 to 3, wherein the repulp washing is repeated a plurality of times in the washing step. The carbonic acid according to any one of claims 1 to 4 , wherein in the dissolution step, the crude lithium carbonate is repulp washed with pure water, and carbonate ions are supplied to the pure water to dissolve the crude lithium carbonate. Lithium manufacturing method. In the melting step, an amount of the pure water is Li concentration assuming that the total amount of the crude lithium carbonate the pure water is dissolved at 25 ° C. a 7g / L~9g / L, to claim 5 The method for producing lithium carbonate according to the above method. The method for producing lithium carbonate according to any one of claims 1 to 6 , wherein the lithium carbonate used for producing the lithium ion battery is produced.

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