KR101724289B1 - Method for producing lithium hydroxide monohydrate - Google Patents

Abstract

Disclosed is a production method of lithium hydroxide monohydrate, comprising the steps of: preparing a lithium hydroxide monohydrate wet cake; primary drying at the temperature of 0 to 40C and a relative humidity of 25% or less up to having a water content of the lithium hydroxide monohydrate wet cake of 40 to 50%; and secondarily drying the primary dried lithium hydroxide monohydrate wet cake at the temperature of 0 to 40C and a relative humidity of more than 25% and 50% or less.

Description

METHOD FOR PRODUCING LITHIUM HYDROXIDE MONOHYDRATE [0002]

This disclosure relates to a process for preparing lithium hydroxide monohydrate.

Lithium hydroxide monohydrate (LiOH.H2O) is mainly used for the production of additives for grease and cathode for secondary batteries. In addition, it is used for research reagents and as an antioxidant additive. As the secondary battery market grows, it is expected that the market for lithium hydroxide monohydrate for secondary batteries will continue to increase.

Generally, lithium hydroxide monohydrate is prepared by obtaining a wet cake of lithium hydroxide monohydrate from a lithium source obtained from a salt, a lithium ore, a lithium ion battery or the like, and drying it.

A steam dryer is generally used for drying the wet cake of lithium hydroxide monohydrate. In order to prevent fluctuation of the crystal number of the lithium hydroxide monohydrate, a high temperature (about 60 to 120 DEG C) and a high humidity (relative humidity of about 60% And is under construction.

However, when the drying time is excessive, the lithium hydroxide monohydrate (LiOH.H2O) and the lithium hydroxide anhydride (LiOH) are mixed and discharged when the drying is performed by the steam dryer as described above. On the contrary, when the drying time is not sufficient, The cake is not properly dried and the moisture is discharged in a state of a high water content, so that there is a disadvantage that it is necessary to manage severe drying conditions. In addition, since the inside of the chamber must be maintained at a high temperature throughout the entire drying process, there is a disadvantage that the drying cost is excessively increased.

One of the objects of the present disclosure is to provide a process for producing high purity and high concentration lithium hydroxide monohydrate with high efficiency and low process cost.

One aspect of the present disclosure is a method for preparing a lithium hydroxide monohydrate wet cake, comprising the steps of: preparing a wet cake of lithium hydroxide monohydrate; heating the liquid hydroxide wet cake to a temperature of 0 to 40 DEG C and a relative humidity of 25% And drying the primary dried lithium hydroxide monohydrate wet cake at a temperature of 0 to 40 캜 and a secondary humidity of more than 25% but not more than 50% relative to the total weight of the lithium hydroxide monohydrate, ≪ / RTI >

As one of the effects of the present disclosure, there is an advantage that high purity and high concentration lithium hydroxide monohydrate can be obtained with high efficiency and low process cost.

The various and advantageous advantages and effects of the present disclosure are not limited to those described above, and will be more readily understood in the course of describing a specific embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flow chart schematically illustrating a method for producing lithium hydroxide monohydrate according to the present disclosure. FIG.
2 is a thermogravimetry analysis (TGA) result of a wet cake of lithium hydroxide monohydrate.
3 shows the results of XRD analysis of a crystalline phase obtained by drying a lithium hydroxide monohydrate wet cake.
4 is a schematic diagram that schematically illustrates a drying apparatus 100 for drying a lithium hydroxide monohydrate wet cake in accordance with one embodiment of the present disclosure.
5 is a schematic view schematically showing the monovalent ion-selective electrodialysis device 200. Fig.
6 is a schematic view schematically showing a bipolar electrodialyser 300. Fig.
FIG. 7 is a schematic view schematically showing a general ion-selective electrodialysis apparatus 400. FIG.

Hereinafter, a method for producing lithium hydroxide monohydrate will be described in detail.

All terms (including technical and scientific terms) used herein can be used in a sense commonly understood by one of ordinary skill in the art to which the present invention belongs, unless otherwise defined. Whenever a component is referred to as "including" an element throughout the specification, it is to be understood that the element may include other elements, not the exclusion of any other element, unless the context clearly dictates otherwise. Also, singular forms may include plural forms unless the context clearly dictates otherwise.

As described above, the drying method using the steam drier requires not only a difficult drying condition control but also a disadvantage that the drying cost is excessively required, and a method for replacing the drying method is required.

Accordingly, the present inventors have been able to effectively suppress the discharge of mixed lithium hydroxide monohydrate (LiOH.H ₂ O) and lithium hydroxide anhydride (LiOH) while optimally controlling the water content, and to reduce the operating cost due to maximization of process efficiency The inventors of the present invention have made intensive researches on the methods that can be applied to the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flow chart schematically illustrating a method for producing lithium hydroxide monohydrate according to the present disclosure. FIG. A process for preparing a lithium hydroxide monohydrate according to the present disclosure comprises: preparing a lithium hydroxide monohydrate wet cake; And drying the lithium hydroxide monohydrate wet cake first and secondarily. Herein, the wet cake of lithium hydroxide monohydrate is a concept including a function (remaining number) existing in the grain boundaries of the lithium hydroxide monohydrate of the crystal phase and the lithium hydroxide monohydrate of the crystal phase. In this disclosure, the water content of the lithium hydroxide monohydrate wet cake For example, the water content of the lithium hydroxide monohydrate wet cake may be 20 to 55%.

In the present disclosure, when the lithium hydroxide monohydrate wet cake is dried, lithium hydroxide monohydrate (LiOH.H ₂ O) and lithium hydroxide anhydride (LiOH) are mixed and discharged, or the lithium hydroxide monohydrate wet cake is not dried properly, (Primary drying and secondary drying) is carried out by optimizing the drying conditions in order to effectively suppress the discharge of the organic solvent to the high-temperature state.

Hereinafter, preferred drying conditions for drying the wet cake of lithium hydroxide monohydrate will be described in detail.

Lithium hydroxide Monohydrate  During the primary and secondary drying of the wet cake, the temperature condition

2 is a thermogravimetry analysis (TGA) result of lithium hydroxide monohydrate. More specifically, Fig. 2 shows a graph showing changes in weight and heat flow of a wet cake of lithium hydroxide monohydrate, while charging a wet cake of lithium hydroxide monohydrate into a drier and then raising the temperature from 0 DEG C to 400 DEG C at a constant rate (TGA) of the lithium hydroxide monohydrate measured as a result of the thermogravimetry analysis (TGA).

Referring to FIG. 2, it can be seen that the weight change and the heat flow of the wet cake of lithium hydroxide monohydrate are significantly changed in the temperature range of 50 to 100 ° C. This means that the drying was actively carried out in the above-mentioned temperature range, which is consistent with the drying conditions in the conventional steam dryer.

However, since the weight change of the lithium hydroxide monohydrate wet cake is no longer observed in the temperature range of 100 占 폚 or more, it can be expected that not only the evaporation of the function but also the elimination of the crystal number occurs in the above temperature range.

Meanwhile, the heat flow graph of FIG. 2 will be described in more detail. It can be seen that a change in heat flow is observed in a temperature range of 40 ° C or lower in addition to the temperature range of 50-100 ° C. This means that drying of the lithium hydroxide monohydrate wet cake can occur even in the temperature range of 40 DEG C or less. Furthermore, since the amount of change in the heat flow is relatively smaller than that in the temperature range of 50 to 100 占 폚, drying of the lithium hydroxide monohydrate wet cake can be proceeded effectively while preventing the desorption of the crystal water in the above- Can be expected.

The present inventors have carried out the following experiments in order to prove it. Specifically, a wet cake of lithium hydroxide monohydrate (moisture content: 20% by weight) was charged into a drier and dried for 24 hours under conditions of relative humidity of 40% and drying temperature of 20 ° C, And XRD analysis of the crystal phase was carried out. In addition, for comparison, XRD analysis was performed on the crystalline phase after drying at 50 ° C only.

Fig. 3 is a result of XRD analysis of a crystalline phase obtained by drying a wet cake of lithium hydroxide monohydrate. Fig. 3 (a) shows the result of XRD analysis when the drying temperature is 20 캜, and Fig. 3 And XRD analysis results when the drying temperature was 50 캜.

Referring to FIG. 3, when the drying temperature is 50 ° C, only lithium hydroxide monohydrate in the crystalline phase exists only at a drying temperature of 20 ° C, unlike lithium hydroxide monohydrate and lithium hydroxide anhydride in the crystalline phase. .

That is, in order to effectively prevent mixing of the lithium hydroxide anhydride when the wet cake of lithium hydroxide monohydrate is dried, it is preferable to control the drying temperature to 40 ° C or less, more preferably to 20 ° C or less, Or more.

However, when the drying temperature is too low, there is a possibility that the function (residual water) present in the grain boundary of the lithium hydroxide monohydrate of the crystal phase is frozen and the drying efficiency is reduced drastically. Therefore, in order to prevent this, it is preferable to control the drying temperature of the lithium hydroxide monohydrate to 0 ° C or higher.

Lithium hydroxide Monohydrate  During the primary and secondary drying of the wet cake, relative humidity conditions

As a result of further studies conducted by the inventors of the present invention, the crystal water constituting the lithium hydroxide monohydrate of the crystal phase mostly disappeared in the latter stage of drying, and only the function (remaining number) existing in the grain boundaries of the crystal lithium hydroxide monohydrate was mostly eliminated . In order to effectively suppress the fluctuation of the number of crystals and to improve the drying efficiency, it is necessary to change the relative humidity conditions of the initial stage and the latter stage of drying.

First, it is preferable to perform drying under a relative humidity of 25% or less at the time of primary drying (initial stage of drying). Here, the initial drying period may mean up to the time when the moisture content of the lithium hydroxide monohydrate wet cake before drying becomes 40 to 50% (by weight) of the water content contained in the wet cake.

If the relative humidity exceeds 25% at the time of the first drying, the drying time becomes excessively long and the drying efficiency may be excessively lowered. In addition, there is a fear that grain growth during drying occurs and quality deterioration due to lowering of grain size uniformity may occur. On the other hand, the lower the relative humidity in the primary drying is, the more advantageous is the drying efficiency and the quality improvement, so the lower limit of the relative humidity in the primary drying is not particularly limited.

Next, it is preferable to carry out drying under a relative humidity of more than 25% but not more than 50% at the second drying (late stage of drying), more preferably 30% to 50% Or more and 45% or less relative humidity.

If the relative humidity is lower than 25% during the secondary drying, not only the drying cost increases but also the crystal water constituting the lithium hydroxide monohydrate on the crystal phase may be dropped. On the other hand, when the relative humidity exceeds 50% in the secondary drying, the drying efficiency may be low or the drying may not be sufficiently performed.

Lithium hydroxide Monohydrate  During the first and second drying of the wet cake, the carbon dioxide concentration condition

The lithium hydroxide monohydrate wet cake may be converted to lithium carbonate when contacted with carbon dioxide. Accordingly, it is necessary to minimize contact with carbon dioxide during drying. According to one example, it is preferable to dry the wet cake of lithium hydroxide monohydrate under a carbon dioxide condition of 100 ppm or less (including 0 ppm). Here, the carbon dioxide condition of 1 ppm means that the mass of carbon dioxide is 1 mg when the mass of total air in the drying apparatus is 1000 g.

Hereinafter, a drying apparatus which can be suitably used for drying the wet cake of lithium hydroxide monohydrate will be described in detail.

4 is a schematic diagram that schematically illustrates a drying apparatus 100 for drying a lithium hydroxide monohydrate wet cake in accordance with one embodiment of the present disclosure. The drying apparatus of FIG. 4 is for illustrative purposes only, and the present disclosure is not limited thereto.

The drying apparatus 100 for drying the lithium hydroxide monohydrate wet cake comprises a drying unit 110 in which the lithium hydroxide monohydrate wet cake 160 is dried; A cradle 120 located within the drying unit 110 for receiving the lithium hydroxide monohydrate wet cake 160; An air injection unit 150 for injecting dry air 141 into the drying unit 110; A circulation fan 130 for circulating the drying air 141 smoothly inside the drying unit 110; And a dehumidifying part 140 for removing moisture of the saturated air 142 supplied with moisture from the lithium hydroxide monohydrate wet cake 160 and converting it into dry air 141. In addition, It is to be understood that other configurations may be further included.

The holder 120 may be located at the center of the drying unit 110 and may be disposed in a multi-stage shape according to the capacity and size of the drying unit 110. The lithium hydroxide monohydrate wet cake 160 may be loaded into the drying unit through the drying unit door 111 located on one side of the drying unit 110 and mounted on the mounting platform 120.

The drying air 141 is injected through the air injection unit 150. The drying air is injected through the air injecting unit 150 and the ventilation valve 112 is opened to discharge the air inside the drying unit to the outside to fill the inside of the drying unit with the drying air 141 can do.

According to an example, a carbon dioxide filter 151 may be installed in the air injection unit 150 to control the carbon dioxide concentration of the dry air 141.

The dry air 141 injected through the air injecting unit 150 can be uniformly dispersed in the drying unit 110 through the gas distributor 131.

The dry air 141 dispersed through the gas distributor 131 passes through the lithium hydroxide monohydrate wet cake 160 through the circulation fan 130 and absorbs moisture in the lithium hydroxide monohydrate wet cake 160 and is saturated Air 142 as shown in FIG.

The saturated air 142 is injected into the dehumidifying part 140 and the injected saturated air 142 can be separated into the drying air 141 and the condensed water 143 through the dehumidifying part 140. The dehumidifying part 140 may be located below the drying part 110.

The condensed water 143 is discharged to the outside and the dry air 141 can be circulated back into the drying unit 110 through the gas distributor 131. At this time, the lost dry air 141 can be replenished from the air injection unit 150.

Hereinafter, a method of preparing a wet cake of lithium hydroxide monohydrate will be described in detail.

In the present disclosure, a specific method for preparing the lithium hydroxide monohydrate wet cake is not particularly limited, but for example, preparing the wet cake of lithium hydroxide monohydrate may include preparing an aqueous solution of lithium hydroxide; Concentrating the aqueous lithium hydroxide solution; Crystallizing the concentrated lithium hydroxide aqueous solution at a temperature lower than 100 캜 to obtain a lithium hydroxide monohydrate crystal; And separating the lithium hydroxide monohydrate crystals by solid-liquid separation to obtain a wet cake of lithium hydroxide monohydrate.

(1) preparing a lithium hydroxide aqueous solution

First, an aqueous solution of lithium hydroxide is prepared.

According to one embodiment of the present disclosure, the step of preparing the lithium hydroxide aqueous solution comprises: preparing lithium phosphate; Dissolving the lithium phosphate in a monovalent acid (HX, wherein X represents a conjugated base of the monovalent acid); Obtaining a lithium salt (LiX) aqueous solution from lithium phosphate dissolved in the monovalent acid, using a monovalent ion selective electrodialysis apparatus; And obtaining a lithium hydroxide aqueous solution from the lithium salt (LiX) aqueous solution using a bipolar electrodialysis device.

Lithium phosphate is a solution containing a lithium-containing solution (for example, a solution obtained by extracting lithium dissolved in the ocean, a solution generated in the process of recycling a spent lithium battery, a solution obtained by leaching lithium ore, brine, a lithium-containing spring water, Containing solution, etc.), and then introducing a phosphorus supplying material into the lithium-containing solution to precipitate the dissolved lithium into lithium phosphate.

Typical ingredients included in the lithium-containing solution are ^{Li +, Na +, K +} , Ca 2 +, Mg 2 +, Cl - and the like ^-, SO ₄ ^2. However, in the production process of the lithium chloride monohydrate wet cake according to the embodiments of the present invention, all components other than Li ⁺ are impurities, and therefore, these impurities must be removed in advance.

Particularly, among the above impurities, ^divalent ions such as Ca ²⁺ and Mg ^{2 +} are not only components that are difficult to remove due to their low solubility due to hot water cleaning, but also have a problem in that they are not easily removed on the surface of the cation- It is preferable that the lithium-containing solution is removed before the phosphorus-supplying substance is introduced.

The method of removing Ca ^{2 +} and Mg ^{2 +} is not particularly limited, but may be one using the following Reaction Schemes 1 to 3.

[Reaction Scheme 1]

^{Ca 2 + + 2NaOH → 2Na +} + Ca (OH) 2 (↓), Mg 2 + + 2NaOH → 2Na 2 + + Mg (OH) 2 (↓)

[Reaction Scheme 2]

Ca ^{2 +} + 2Na ₂ CO _{3 -} > 2Na + + CaCO ₃ (↓), Mg ^{2 +} + 2Na ₂ CO _{3 -} > 2Na ^{2 +} + MgCO ₃

[Reaction Scheme 3]

Ca ^{2 +} + 2Na ₂ SO ₄ ? 2Na ⁺ + CaSO ₄ (↓), Mg ^{2 +} + 2Na ₂ SO ₄ ? 2Na ^{2 +} + MgSO ₄ (↓)

When Ca ^{2 +} and Mg ^{2 +} contained in the lithium-containing solution are adjusted to Ca (OH) ² by appropriately adding NaOH, Na ₂ CO ₃ , Na ₂ SO _4, etc. to the lithium- ₂ , Mg (OH) ₂ , CaCO ₃ , MgCO ₃ , CaSO ₄ , MgSO ₄ and the like.

Li ⁺ , Na ⁺ , K ⁺ and Cl ^- remain in the lithium-containing solution in which Ca ^{2 +} and Mg ^{2 +} are selectively removed. When the phosphorus feed material is added thereto and the pH is adjusted appropriately, lithium phosphate can be obtained.

Examples of the phosphorus-supplying material include phosphoric acid (H ₃ PO ₄ ) and the like. In one embodiment of the present invention, in the step of converting lithium phosphate into a lithium salt (LiX, wherein X represents a conjugated base of monovalent acid) in order to reduce environmental pollution while reducing raw material costs, Can be recycled and used as the phosphorus-supplying material.

Thereafter, optionally, the lithium phosphate can be washed with distilled water. This is to improve the purity of lithium phosphate by removing Li ⁺ , Na ⁺ , K ⁺ , Cl ^- and the like remaining in the obtained lithium phosphate.

Thereafter, in order to recover the lithium salt separately from the lithium salt and to recycle the lithium salt separately, the lithium phosphate is dissolved in a monovalent acid (HX, where X represents a monovalent acid addition base) , And the resulting solution is added to a monovalent ion-selective electrodialysis apparatus together with water to separate into a lithium salt (LiX) aqueous solution and an aqueous phosphoric acid solution.

At this time, the lithium ion concentration of the lithium phosphate dissolved in the monovalent acid is preferably controlled to 1 to 5 g / L. This is to suppress the occurrence of scales and fouling that may occur during electrodialysis. More specifically, when the lithium ion concentration is less than 1 g / L, the electrodialysis treatment capacity becomes large, If it exceeds 5 g / L, excessive impurities may be dissolved together and fouling may occur in the electrodialysis process.

On the other hand, when a large amount of divalent cations such as Ca ^{2 +} and Mg ^{2 + in} lithium phosphate dissolved in monovalent acid are contained, a large amount of precipitates such as calcium hydroxide and magnesium hydroxide are generated, Dialysis efficiency can be reduced. In order to prevent this, the sum of the concentration of divalent cations, such as the one that the lithium phosphate in the acid soluble Ca ^{2 +} and Mg ^{+ 2} is preferably also controlled to less than 20mg / L.

The monovalent acids of (monobasic acid) is not particularly restricted but includes, for example, hydrochloric acid (HCl), nitric acid (HNO _3), hydrofluoric acid one or more member selected from the group consisting of (HF) and hydrobromic acid (HBr) However, considering economy, hydrochloric acid (HCl) is more preferable.

5 is a schematic view schematically showing the monovalent ion-selective electrodialysis device 200. Fig. 4, the monovalent ion-selective electrodialyzer 200 includes a monovalent cation-selective membrane 240 and a monovalent anion-selective membrane 230 that selectively transmit monovalent cation and monovalent anion, respectively, And may be disposed between the anode cell and the cathode cell. The anode cell includes a cathode 260 and a cathode separator 250. The cathode cell includes a cathode 210 and a cathode separator 220. The anode 260 includes a cathode separator 250 and a cathode 210 And the negative electrode separator 220. The negative electrode separator 220 may be formed of a non-aqueous electrolyte.

After the lithium phosphate is dissolved in monovalent acid, the lithium phosphate is separated from the anode separator 250 of the anode cell and the monovalent cation-selective membrane 240, and the anode separator 220 of the cathode cell and the monovalent anion- And the dialysis membrane 230. Water can be injected between the monovalent cation-selective membrane 240 and the monovalent anion-selective dialysis membrane 230 to prepare electrodialysis.

(Li ₂ SO ₄ ), lithium hydroxide (LiOH), lithium dihydrogenphosphate (LiH ₂ PO ₄ ), phosphoric acid (H ₃ PO ₄ ), and an electrolyte solution of these And a combination of electrode solutions selected from the group consisting of combinations thereof. This electrode solution circulates and smoothes the movement of electrons in each cell.

At this time, the concentration of the electrode solution may be 0.1 to 20 wt%. The electrical conductivity of the electrode solution may be 10 to 100 ms / cm. Specifically, the electrical conductivity of the electrode solution is proportional to the concentration of the electrode solution. However, the meaning of the term "proportional" does not necessarily mean that it is in direct proportion, but generally means that the electric conductivity also tends to increase as the concentration of the electrode solution increases.

In this regard, it is necessary to facilitate the movement of ions within the monovalent ion-selective electrodialyzer 200. For this purpose, the concentration and the electric conductivity of the electrode solution must be equal to or greater than a predetermined value.

However, when the concentration and the electrical conductivity of the electrode solution are excessively high, the rate at which the ions move within the monovalent ion-selective electrodialyzer 200 is lowered, and electrical resistance is generated to increase the voltage, The current efficiency is reduced, and the power ratio is increased.

More specifically, when the concentration and the electric conductivity of the electrode solution become excessively high, the concentration of each solution (that is, the lithium phosphate and the water dissolved in the acid) charged into the monovalent ion-selective electrodialyzer 200 The concentration difference can be increased, and the diffusion force is generated due to such a difference in concentration, and the diffusion force acts in a direction opposite to the originally intended movement direction of the ions.

Taking this into consideration, it is necessary that the concentration of the electrode solution should be 0.1 wt% to 20 wt%, and the electric conductivity should be 10 ms / cm to 100 ms / cm.

On the other hand, when current is applied to the lithium phosphate dissolved in the monovalent acid and the monovalent ion-selective electrodialyzer 200 into which the water is introduced, the anion moves toward the anode 260 due to the electrophoresis effect, And the positive ions move toward the cathode 210.

Specifically, lithium phosphate and monovalent acid in lithium phosphate dissolved in the acid reacts as shown in the following Reaction Scheme 4. As a result, the ions migrating due to the electrophoretic effect are Li ⁺ , X ^- , PO ₄ ^{3 -} H ⁺ .

[Reaction Scheme 4]

Li ₃ PO ₄ + 3HX -> H ₃ PO ₄ + 3LiX

At this time, only the X-ion, which is a monovalent ion among the anions, can permeate the monovalent anion-selective membrane 230, and phosphate ions can not permeate. Also, the lithium ion, which is a monovalent cation, can penetrate the monovalent cation-selective membrane 240 in a direction opposite to the X-ion.

Accordingly, the lithium ion can be continuously concentrated together with the X-ion between the monovalent cation-selective membrane 240 and the monovalent anion-selective dialysis membrane 230 to form a lithium salt (LiX) aqueous solution . On the other hand, in the case where the anode separator 250 of the anode cell and the monovalent cation selective membrane 240 and the acid remaining between the cathode separator 220 of the cathode cell and the monovalent anion- The dissolved phosphoric acid ions and hydrochloric acid ions in lithium phosphate are concentrated and made into an aqueous solution of phosphoric acid.

Accordingly, the lithium salt (LiX) aqueous solution is recovered between the monovalent cation-selective membrane 240 and the monovalent anion-selective dialysis membrane 230, and the aqueous phosphoric acid solution is separated from the anode separation membrane 250 of the anode cell, 1 can be recovered between the cation-selective membrane 240 and between the cathode separator 220 of the cathode cell and the monovalent anion-selective dialysis membrane 230.

As a result, when the lithium phosphate is used as a raw material and the monovalent ion-selective electrodialyzer 200 is used, an aqueous solution of lithium salt (LiX) in which lithium is concentrated at a high concentration is produced, and an aqueous solution of phosphoric acid Can be effectively separated.

At this time, the concentration of the aqueous phosphoric acid solution may be 0.1 to 3.0 M. Specifically, in order to recover and reuse the aqueous solution of phosphoric acid, its concentration needs to be secured at 0.1 M or more. However, when the aqueous solution of phosphoric acid having a concentration exceeding 3.0 M is reused, a diffusing force due to the concentration difference is generated to cause voltage rise, current decrease, current efficiency decrease, and power ratio increase. Needs to be.

In this case, as described above, the aqueous phosphoric acid solution can be recovered and reused as a phosphorus supply material in the lithium phosphate manufacturing process.

The lithium salt (LiX) aqueous solution separated from the aqueous phosphoric acid solution may be used as a raw material for conversion to an aqueous solution of lithium hydroxide.

Thereafter, a lithium hydroxide aqueous solution is obtained from the lithium salt (LiX) aqueous solution using a bipolar electrodialysis apparatus.

6 is a schematic view schematically showing a bipolar electrodialyser 300. Fig. 6, the bipolar electrodialyzer 300 includes a bipolar cell including the anode 310, a first bipolar membrane 320, an anion-selective membrane 330, a cation-selective membrane 340, The cathode 350 including the cathode 350, and the cathode cell including the cathode 360 may be arranged in order.

The lithium salt (LiX) aqueous solution is introduced into the bipolar electrodialyzer 300 between the anion selective dialysis membrane 330 and the cation-selective dialysis membrane 340, water is supplied to the first bipolar membrane 320, Bipolar electrodialysis can be prepared by charging the anion-selective-type dialysis membrane 330 and between the second bipolar membrane 350 and the cation-selective dialysis membrane 340, respectively.

When electricity is applied to the lithium salt (LiX) aqueous solution and the bipolar electrodialyser into which the water is introduced, hydrolysis of water as the concentrate occurs in each of the bipolar membranes, and cations and anions in the lithium salt (LiX) And are moved toward the cathode 360 and the anode 310 by the electrophoretic effect.

At this time, the ratio of the weight of the lithium salt (LiX) aqueous solution to the weight of the water introduced into the bipolar electrodialyser may be 2 to 20. Here, the amount of the water to be supplied is set so that the amount of water charged between the first bipolar membrane 320 and the anion selective permeability membrane 330 and between the second bipolar membrane 350 and the cation selective membrane 340 is it means.

If the amount of water is smaller than the above range, the concentration of the obtained lithium salt (LiX) aqueous solution becomes excessively high, and a diffusion force due to the concentration difference is generated to cause a rise in voltage, a decrease in current, a decrease in current efficiency, .

Alternatively, when the amount of water is excessive, the concentration of the obtained lithium salt (LiX) aqueous solution becomes excessively low. Further, in order to prepare lithium hydroxide and lithium carbonate using this, an additional concentration step is required. .

Here, the water used in the embodiment of the present invention is preferably pure water containing no impurities, and this pure water contains distilled water and is more preferable to ion exchange water.

The hydroxide ions generated in the second bipolar membrane 350 and the transferred lithium ions may be concentrated between the cation selective membrane 340 and the second bipolar membrane 350 to form a lithium hydroxide aqueous solution. Also, the hydrogen ions generated in the first bipolar membrane 320 and the conjugated base (X ^- ) of the transferred monovalent acid are concentrated between the anion selective membrane 330 and the first bipolar membrane 320, Monohydric acid (HX) solution.

Accordingly, the aqueous solution of lithium hydroxide is recovered between the second bipolar membrane 350 and the cation-selective membrane 340, and the aqueous solution of monovalent acid (HX) is separated from the first bipolar membrane 320 and the anion- (Not shown).

As a result, when the lithium chloride aqueous solution is used as a raw material and the bipolar electrodialyzer 300 is used, a lithium hydroxide aqueous solution in which lithium is concentrated at a high concentration is produced, and a monovalent acid (HX) aqueous solution Can be effectively separated.

The chemical reaction at this time can be summarized as shown in the following reaction formula (5).

 [Reaction Scheme 5]

LiX + H ₂ O → LiOH + HX

At this time, the concentration of the monovalent acid aqueous solution may be 0.05M to 3.0M. Specifically, in order to recover and reuse the monovalent acid aqueous solution, its concentration needs to be secured to 0.05M or more. However, when the monovalent acid aqueous solution having a concentration exceeding 3.0 M is reused, a diffusing force due to the concentration difference is generated to cause a rise in voltage, a decrease in current, a decrease in current efficiency and an increase in power ratio. M or less.

The monovalent acid aqueous solution may be used as all or a part of the monovalent acid in the step of dissolving lithium phosphate in an acid.

The lithium hydroxide aqueous solution may be recovered as a concentrated solution through a concentrating step described later or may be crystallized by concentration by a vacuum evaporation method and then dried in a steam drier to recover in the form of powder, It can be used as raw material.

(2) Concentrating the lithium hydroxide aqueous solution

Thereafter, the lithium hydroxide aqueous solution is concentrated. In this case, enrichment of the lithium hydroxide aqueous solution can be achieved by a general ion-selective electrodialysis device, for example, but not limited to.

FIG. 7 is a schematic view schematically showing a general ion-selective electrodialysis apparatus 400. FIG. 7, in the general ion-selective electrodialyser 400, a cation-selective membrane 440 and an anion-selective membrane 430, which selectively transmit only positive ions and anions, respectively, are disposed between the anode and cathode cells Can be. The cathode cell includes a cathode 460 and a cathode separator 450. The cathode cell includes a cathode 410 and a cathode separator 420. The cathode 460 includes a cathode separator 450 and a cathode 410 And the cathode separator 420. The electrode separator 420 may be formed of the same material.

The lithium hydroxide aqueous solution is introduced between the cathode separator 450 of the anode cell and the cation selective membrane 440 and between the anode separator 420 of the cathode cell and the anion selective membrane 430, Electrodialysis can be prepared by injecting water or a separately prepared lithium hydroxide aqueous solution between the selective dialysis membrane 440 and the anion selective dialysis membrane 430.

At this time, when an aqueous solution of lithium hydroxide prepared separately from water is added between the cation-selective membrane 440 and the anion-selective membrane 430, the concentration time can be further shortened and the concentration can be further improved have.

On the other hand, when the current is applied to the general ion-selective electrodialyser 400 prepared as described above, the anion moves toward the anode 460 due to the electrophoresis effect, and the cation moves toward the cathode 410 .

Accordingly, the lithium ion and the hydroxide ion pass through the cation-selective membrane 440 and the anion-selective membrane 430, respectively, and are concentrated between the cation-selective membrane 440 and the anion-selective membrane 430.

At this time, the lithium ion concentration of the concentrated aqueous lithium hydroxide solution may be 15 to 35 g / L. When the lithium ion concentration is less than 15 g / L, the recovery rate may be lowered in the production of lithium carbonate and the economical efficiency may be lowered. On the other hand, when the lithium ion concentration exceeds 35 g / L, lithium hydroxide precipitation may occur and fouling of the electrodialytic membrane may occur have.

(3) obtaining lithium hydroxide monohydrate crystals, followed by solid-liquid separation, to obtain a wet cake of lithium hydroxide

Thereafter, the concentrated lithium hydroxide aqueous solution is crystallized at a temperature of less than 100 캜 to obtain lithium hydroxide monohydrate crystals, which are subjected to solid-liquid separation to obtain a wet cake of lithium hydroxide monohydrate.

When the concentrated lithium hydroxide aqueous solution is crystallized at a crystallization temperature of 100 ° C or higher, lithium hydroxide monohydrate crystals and lithium hydroxide anhydride crystals may be mixed and formed.

Hereinafter, the present invention will be described more specifically by way of examples. It should be noted, however, that the following examples are intended to illustrate and specify the present invention and not to limit the scope of the present invention. And the scope of the present invention is determined by the matters described in the claims and the matters reasonably deduced therefrom.

( Example )

(1) Preparation of lithium hydroxide monohydrate wet cake

First, the ^{Li + 1,000mg / L, Na +} 90,000mg / L, K + 10,000mg / L, Ca 2 + 9,000mg / L, simulated brine solution containing Mg ^{2 +} 7,000mg / L (lithium-containing solution) Prepared. Then, Ca (OH) ₂ and Na ₂ CO ₃ were added to the saline solution to remove Ca ^{2 +} and Mg ^{2 +} . Then, phosphoric acid and sodium hydroxide were added to prepare lithium phosphate, which was then washed with distilled water.

Then, using lithium phosphate as a raw material, lithium chloride was prepared using the monovalent ion-selective electrodialysis device of FIG. Specifically, 0.5 mol of lithium phosphate was dissolved in 1.5 M of hydrochloric acid to make a total of 1 L of the solution, and 1.0 L of water was prepared. As shown in FIG. 4, a current was applied Respectively.

At this time, a 0.5 M aqueous phosphoric acid solution was used as the electrode solution in the monovalent ion-selective electrodialysis device, and a current of 2.2 A was applied at a voltage of 12 V for 120 minutes.

As a result, the lithium chloride aqueous solution concentrated between the monovalent cation-selective membrane and the monovalent anion-selective dialysis membrane of the monovalent ion-selective electrodialysis device was recovered, and the aqueous solution of the separated phosphoric acid was recovered.

The recovered lithium chloride aqueous solution was measured to have a lithium concentration of 4.0 g / L and a phosphorus concentration of 0.35 g / L. The recovered aqueous solution of phosphoric acid was measured to have a phosphorus concentration of 6.6 g / L and a lithium concentration of 0.82 g / L.

On the other hand, the residual phosphoric acid in the aqueous solution of lithium chloride can be precipitated as lithium phosphate in the step of converting it into aqueous solution of lithium hydroxide, so that it can be recovered in the process. Further, since there is residual lithium in the aqueous phosphoric acid solution, the aqueous phosphoric acid solution can be used as a raw material for extracting lithium phosphate.

Thereafter, lithium hydroxide was prepared by using the recovered lithium chloride aqueous solution as a raw material and using the bipolar electrodialysis apparatus of FIG.

Specifically, 1 L of a lithium chloride aqueous solution having a lithium concentration of 4.018 g / L was used, and 0.5 L of water was added to the bipolar electrodialyser as shown in FIG. 5, A was applied.

As a result, the aqueous hydrochloric acid solution was recovered between the anion-selective membrane and the first bipolar membrane of the bipolar electrodialysis device, and the aqueous solution of lithium hydroxide was recovered between the cation-selective membrane and the second bipolar membrane.

At this time, the lithium concentration in the recovered lithium hydroxide aqueous solution was measured to be 7.2 g / L.

Thereafter, the recovered lithium hydroxide aqueous solution was used as a raw material, and the lithium hydroxide aqueous solution was concentrated using the general ion-selective electrodialysis apparatus of FIG.

Specifically, using 1 L of a lithium hydroxide aqueous solution having a lithium concentration of 7.2 g / L and using 0.2 L of a separately prepared aqueous lithium hydroxide solution (lithium concentration: 7.2 g / L), as shown in FIG. 6, A current of 2.1 A was applied to the dialyzer at a voltage of 12 V for 150 minutes.

As a result, it was possible to recover a concentrated aqueous solution of lithium hydroxide between the cation-selective membrane and the anion-selective membrane of the general ion-selective electrodialysis unit.

At this time, the lithium concentration in the concentrated aqueous lithium hydroxide solution was measured to be 28.9 g / L.

Thereafter, the concentrated lithium hydroxide aqueous solution was crystallized at a temperature of 90 캜 to obtain lithium hydroxide monohydrate crystals, which were then subjected to solid-liquid separation to obtain 48 g of a wet cake of lithium hydroxide monohydrate (water content: 25 g).

(2) drying lithium hydroxide monohydrate wet cake

Thereafter, the wet cake of lithium hydroxide monohydrate was charged into the drying apparatus of Fig. 2 and dried for 3 hours at a temperature ranging from 10 to 50 캜 while changing the temperature and the humidity. At this time, in each example, the concentration of carbon dioxide in the drying apparatus was less than 50 ppm, and at the time of completion of the first drying, the time point at which the water content of the wet cake of lithium hydroxide monohydrate wet cake before drying was 45% And relative humidity. This is shown in Table 1 below.

Thereafter, the dried white powder was recovered, and water content (mass of water / mass of powder) and mixing ratio of anhydrate (mass of anhydrate / (sum of mass of anhydrate and monohydrate)) were measured. 1. At this time, in each example, the water content and the anhydride content were measured at arbitrary 10 points.

Specimen Number Drying conditions Moisture content (%) Mixing ratio of anhydrous cargo (%) Remarks Temperature (℃) Primary relative humidity
(%) Secondary relative humidity
(%) One 10 20 40 <2 0 Inventory 1 3 10 20 55 <5 0 Comparative Example 1 5 20 20 40 <2 0 Inventory 2 7 20 20 55 <5 0 Comparative Example 2 9 40 20 40 <2 1-3 Inventory 3 11 40 20 55 <5 1-3 Comparative Example 3 13 50 20 40 <2 50 to 80 Comparative Example 4 15 50 20 55 <2 50 to 80 Comparative Example 5

Referring to Table 1, Examples 1 to 3, which satisfy all of the conditions proposed in the present invention, showed a water content of 2% or less and a mixed anhydride content of 5% or less. In addition, the grain growth during drying was effectively suppressed, and fine white powder with uniform particle size was obtained.

On the other hand, in the case of Comparative Examples 1 to 3, the drying was insufficient due to the secondary relative humidity exceeding the range proposed by the present invention, and in the case of Comparative Examples 4 and 5, By mass, and lithium hydroxide anhydride was produced in a large amount.

100: dryer 110: dryer
111: Drying door 112: Ventilation valve
120: Cradle 130: Circulating fan
131: Gas distributor 140: Dehumidifier
141: Dry air 142: Saturated air
143: condensed water 150:
151: carbon dioxide filter 160: wet cake
200: 1 ion-selective electrodialysis device 210: cathode
220: cathode separator 230: monovalent anion-selective type dialysis membrane
240: 1 cation-selective membrane 250: anode separator
260: anode 300: bipolar electrodialysis device
310: anode 320: first bipolar membrane
330: Anion-selective type membrane 340: Cation-type selective type membrane
350: second bipolar membrane 360: cathode
400: general ion-selective electrodialysis device 410: negative electrode
420: Negative electrode separator 430: Negative ion selective membrane
440: cation-selective membrane 450: anode membrane
460: anode

Claims (12)

Preparing a lithium hydroxide monohydrate wet cake;
Drying the lithium hydroxide monohydrate wet cake at a temperature of 0 to 40 캜 and a relative humidity of 25% or less until a water content of the wet cake of lithium hydroxide monohydrate becomes 40 to 50% by weight; And
Drying the primary dried lithium hydroxide monohydrate wet cake at a temperature of 0 to 40 캜 and a relative humidity of more than 25% but not more than 50%;
Lt; / RTI &gt;
The method for producing lithium hydroxide monohydrate by drying under the carbon dioxide condition of not more than 100 ppm (including 0 ppm) in the primary and secondary drying.
The method according to claim 1,
The method of producing lithium hydroxide monohydrate by drying under the temperature condition of 0 to 30 占 폚 in the primary and secondary drying.
The method according to claim 1,
The method for producing lithium hydroxide monohydrate by drying under the temperature condition of 0 to 20 占 폚 in the primary and secondary drying.
delete The method according to claim 1,
Wherein preparing the lithium hydroxide monohydrate wet cake comprises:
Preparing a lithium hydroxide aqueous solution;
Concentrating the aqueous lithium hydroxide solution;
Crystallizing the concentrated lithium hydroxide aqueous solution at a temperature lower than 100 캜 to obtain a lithium hydroxide monohydrate crystal; And
Separating the lithium hydroxide monohydrate crystals by solid-liquid separation to obtain a wet cake of lithium hydroxide monohydrate;
&Lt; / RTI &gt;
6. The method of claim 5,
The step of preparing the lithium hydroxide aqueous solution comprises:
Preparing lithium phosphate;
Dissolving the lithium phosphate in a monovalent acid (HX, wherein X represents a conjugated base of the monovalent acid);
Obtaining a lithium salt (LiX) aqueous solution from lithium phosphate dissolved in the monovalent acid, using a monovalent ion selective electrodialysis apparatus; And
Obtaining a lithium hydroxide aqueous solution from the lithium salt (LiX) aqueous solution using a bipolar electrodialysis device;
&Lt; / RTI &gt;
The method according to claim 6,
The step of preparing the lithium phosphate comprises:
Preparing a lithium-containing solution; And
And introducing a phosphorus supplying material into the lithium-containing solution to precipitate dissolved lithium into lithium phosphate.
8. The method of claim 7,
The lithium-containing solution may be a solution obtained by dissolving lithium dissolved in the ocean, a solution generated in a process of recycling a spent lithium battery, a solution obtained by leaching lithium ore, a salt, a lithium-containing hot spring water, Lt; RTI ID = 0.0 &gt; 1, &lt; / RTI &gt;
The method according to claim 6,
The monovalent acid is hydrochloric acid (HCl), nitric acid (HNO _3), hydrofluoric acid at least one member of the process for producing lithium hydroxide monohydrate, selected from the group consisting of a (HF) and hydrobromic acid (HBr).
The method according to claim 6,
The step of obtaining the aqueous lithium salt (LiX)
A cathode cell including a cathode separator, a monovalent anion selective membrane for selectively transmitting a monovalent anion, a monovalent cation selective membrane for selectively permeating a monovalent cation, and a positive electrode comprising a positive electrode separator, Preparing an ion-selective electrodialysis device;
Lithium phosphate dissolved in the monovalent acid is added between the separator membrane of the anode cell and the separator membrane of the separator and between the separator membrane of the cathode cell and the separator membrane of the separator, Introducing between the cation-selective dialysis membrane and the monovalent cation-selective dialysis membrane; And
And a step of applying a current to the monovalent ion-selective electrodialyzing device.
The method according to claim 6,
The step of obtaining the lithium hydroxide aqueous solution comprises:
Preparing a bipolar electrodialyser in which a cathode cell including a positive electrode, a first bipolar membrane, an anion-selective-type dialysis membrane, a cation-selective-type dialysis membrane, a second bipolar membrane and a negative electrode are sequentially arranged;
The lithium salt (LiX) aqueous solution is introduced between the cation-selective dialysis membrane and the anion-selective dialysis membrane, water is introduced between the first bipolar membrane and the anion-selective dialysis membrane, and between the second bipolar membrane and the cation- Inputting; And
And applying an electric current to the bipolar electrodialyser.
6. The method of claim 5,
The step of concentrating the lithium hydroxide aqueous solution comprises:
Preparing a general ion selective electrodialysis device in which a cathode cell including a cathode separation membrane, an anion selection type dialysis membrane selectively transmitting anions, a cation selection type dialysis membrane selectively permeable to cations, and a cathode cell including a cathode separation membrane are sequentially arranged ;
The lithium hydroxide aqueous solution is injected between the cathode separation membrane of the anode cell and the cation selection type dialysis membrane and between the cathode separation membrane of the cathode cell and the anion selection type dialysis membrane respectively and a water or lithium hydroxide aqueous solution is mixed with the cation selection type dialysis membrane and the cation selection type Into a dialysis membrane; And
And applying a current to the general ion-selective electrodialyser.

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