KR20190076677A - Manufacturing method for lithium phosphate - Google Patents

Abstract

The present invention relates to a process for producing a lithium-containing desorbent, comprising the steps of: passing a lithium-containing solution through an aluminum-based adsorbent to produce an adsorbent on which lithium is adsorbed; passing distilled water through the adsorbent on which lithium is adsorbed to obtain a lithium- Adding a precipitant to the lithium-containing concentrate to remove impurities, and introducing the concentrate from which the impurities have been removed into a bipolar electrodialyzer to obtain an aqueous solution of lithium hydroxide, To a process for producing lithium hydroxide.

Description

TECHNICAL FIELD [0001] The present invention relates to a method for producing lithium hydroxide,

Embodiments of the present invention are directed to a process for preparing lithium hydroxide, and more particularly, to a process for effectively producing lithium hydroxide from brine.

Recently, the demand for lithium secondary batteries has been rapidly increasing due to the rapid growth of related markets such as electric cars. Therefore, the demand for lithium hydroxide, which is one of the raw materials for lithium which is a core raw material of lithium secondary batteries, is also increasing rapidly.

Such lithium hydroxide is chemically converted to lithium hydroxide using lithium carbonate produced in a limited area such as Chile or Argentina, and is produced as lithium hydroxide, and it is known that it can not be directly produced from raw materials.

This is because it is very inefficient to use an electrochemical method because the Na concentration in the brine is very high.

Therefore, it is urgent to develop a technique for economically and efficiently producing lithium hydroxide from a lithium-containing solution.

The present embodiments are intended to provide a production method capable of economically and efficiently producing lithium hydroxide from a lithium-containing solution.

In one embodiment of the present invention, there is provided a process for producing a lithium-containing adsorbent, comprising the steps of: passing a lithium-containing solution through an aluminum-based adsorbent to produce an adsorbent on which lithium is adsorbed; passing distilled water through the adsorbent on which lithium is adsorbed to obtain a lithium- Containing concentrate to obtain a lithium-containing concentrate; removing the impurities by adding a precipitant to the lithium-containing concentrate; and introducing the concentrate from which the impurities have been removed into a bipolar electrodialyzer to form a lithium hydroxide aqueous solution ≪ / RTI > to provide a process for preparing lithium hydroxide.

According to the embodiments, since lithium is adsorbed from a lithium-containing solution using an aluminum-based adsorbent, and then subjected to a concentration process using electrodialysis, lithium hydroxide is produced. Therefore, lithium hydroxide Can be prepared.

1 schematically shows a method for producing lithium hydroxide according to one embodiment.
FIG. 2 is a schematic view illustrating a method of producing a lithium hydroxide aqueous solution using a bipolar electrodialyser in the method for producing lithium hydroxide according to one embodiment.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention may be embodied in many different forms and is not limited to the embodiments described herein.

In order to clearly illustrate the present invention, parts not related to the description are omitted, and the same or similar components are denoted by the same reference numerals throughout the specification.

In addition, since the sizes and thicknesses of the respective components shown in the drawings are arbitrarily shown for convenience of explanation, the present invention is not necessarily limited to those shown in the drawings.

Also, throughout the specification, when an element is referred to as "including" an element, it is understood that the element may include other elements as well, without departing from the other elements unless specifically stated otherwise.

In the drawings, the thickness is enlarged to clearly represent the layers and regions. Like parts are designated with like reference numerals throughout the specification. It will be understood that when an element such as a layer, film, region, plate, or the like is referred to as being "on" another portion, it includes not only the element directly over another element, Conversely, when a part is "directly over" another part, it means that there is no other part in the middle.

Hereinafter, a method for producing lithium hydroxide according to an embodiment of the present invention will be described in detail with reference to the drawings.

1 schematically shows a method for producing lithium hydroxide according to one embodiment.

1, a method for producing lithium hydroxide according to an embodiment of the present invention comprises the steps of (S10) adsorbing lithium from a lithium-containing solution, (S20) obtaining a lithium-containing desorbing solution, (S30), removing impurities (S40), and obtaining a lithium hydroxide aqueous solution (S50).

First, a step (S10) of adsorbing lithium from a lithium-containing solution is performed.

Specifically, the lithium-containing solution is passed through an aluminum-based adsorbent to adsorb lithium on the aluminum-based adsorbent.

At this time, the lithium concentration of the lithium-containing solution may be in the range of 0.1 g / L to 2.0 g / L, more specifically, 0.3 g / L to 1.0 g / L. When the lithium concentration of the lithium-containing solution is less than 0.1 g / L, the adsorption rate is slow and productivity may be reduced. When the lithium concentration of the lithium-containing solution exceeds 2.0 g / L, the productivity is increased but the consumption of the adsorbent is increased and the economical efficiency is relatively decreased. Therefore, it is preferable that the lithium concentration contained in the lithium-containing solution satisfies the above range.

The aluminum-based adsorbent is for adsorbing lithium dissolved in the lithium-containing solution, and may include, for example, aluminum hydroxide. When an aluminum-based adsorbent containing aluminum hydroxide is used as in the present embodiment, the amount of lithium adsorbed in the lithium-containing solution is high, and there is little aluminum loss in the desorption process to be described later, so that the lifetime of the adsorbent is long, This is an excellent advantage.

 In addition, the aluminum-based adsorbent may be a molded article including an adsorbent powder and a binder.

The adsorbent powder may be, for example, an adsorbent powder containing aluminum hydroxide. The advantage of using an adsorbent powder containing aluminum hydroxide is the same as described above.

The binder is intended to produce the adsorbent powder in the form of a suitable shaped article and serves to bind the adsorbent powders to each other. The binder may comprise at least one of, for example, polyvinyl chloride (PVC), polysulfone (Poly sulfone), and polyaniline (Polyaniline). In particular, in the present embodiment, the binder preferably includes polyvinyl chloride (PVC) capable of providing an excellent bonding force between adsorbent powders.

At this time, the molded body may contain the binder in an amount ranging from 5% by weight to 30% by weight, more specifically from 10% by weight to 15% by weight, based on the total weight of the adsorbent powder. When the content of the binder is less than 5% by weight based on the total weight of the adsorbent powder, there is a problem that the strength after molding is low and the life of the adsorbent is short. When the content of the binder is more than 30% by weight, the amount of the adsorbent powder to be adsorbed by the lithium-containing solution can be reduced because the amount of the adsorbent powder is relatively reduced. Therefore, it is preferable that the content of the binder satisfies the above range.

On the other hand, the step of passing the lithium-containing solution through the aluminum-based adsorbent to adsorb lithium on the aluminum-based adsorbent includes, for example, the reaction of the following reaction formula (1).

[Reaction Scheme 1]

(1-x) LiCl · Al (OH) 3 · nH 2 O + Li + → LiCl · Al (OH) 3 · nH 2 O + (1-x) Li +

Next, step (S20) of obtaining a lithium-containing desorption liquid is carried out.

Specifically, the lithium-containing desorbent can be obtained by passing distilled water through the aluminum adsorbent on which lithium is adsorbed.

At this time, the amount of the distilled water passing through the lithium-adsorbed aluminum adsorbent can be performed by passing the adsorbent in an amount of 0.5 to 10 times, more specifically 1 to 3 times the volume of the adsorbent based on the volume of the adsorbent.

When the desorption process is performed using distilled water having a volume of less than 0.5 times the volume of the adsorbent in the lithium-adsorbed aluminum-based adsorbent, there is a problem that the amount of desorbed lithium adsorbed on the adsorbent is reduced. Further, when distilled water exceeding 10 times the volume of the adsorbent is used, there is a problem that lithium desorbed in the desorption process is diluted and the concentration of lithium contained in the lithium-containing desorbent is lowered.

The concentration of lithium contained in the lithium-containing desorption liquid obtained by the above-described method may be in the range of 0.2 g / L to 2.0 g / L, more specifically 0.8 g / L to 1.5 g / L. When the lithium concentration contained in the lithium-containing desorption liquid satisfies the above range, the recovery rate of lithium hydroxide obtained after the subsequent process is excellent.

The step of passing the distilled water through the lithium adsorbed aluminum adsorbent to obtain a lithium-containing desorption liquid includes, for example, the reaction of the following reaction formula (2).

[Reaction Scheme 2]

_{LiCl · Al (OH) 3 ·} nH 2 O + H 2 O → (1-x) LiCl · Al (OH) 3 · nH 2 O + xLiCl

Thereafter, step (S30) of obtaining a lithium-containing concentrate is carried out.

That is, the step of adding the lithium-containing desorption liquid to the electrodialyser to obtain a lithium-containing concentrate may be performed.

At this time, the electrodialyzer may include a cathode cell including a cathode separator, an anion selective permeable membrane selectively transmitting anions, a cation selective permeable membrane selectively permeable to cations, and a cathode cell including a cathode separator. have. Further, the electrode solution is injected into the positive electrode cell and the negative electrode cell.

The step of obtaining the lithium-containing concentrate may include the steps of charging the lithium-containing desorbing liquid between the cathode separating membrane and the anion-selective permeable membrane, between the cation-selective permeable membrane and the anode separating membrane, And then applying the electric current to the electrodialyser. That is, when an electric current is applied to the electrodialysis device after charging the lithium-containing desorption liquid and the distilled water as described above, the anion moves to the anode and the cation moves to the cathode due to the electrophoresis effect.

Therefore, the chloride ion in the lithium-containing solution can permeate the anion-selective permeable membrane, and the lithium ion can permeate the cation-selective permeable membrane in the direction opposite to the chlorine ion. Accordingly, between the cation-selective permeable membrane and the anion permeable membrane, chloride ion and lithium ion can be continuously concentrated and made into lithium chloride aqueous solution.

On the other hand, between the anode separator and the cation-selective permeable membrane, and between the cathode separator membrane and the anion-selective permeable membrane, a desalted solution having a remarkably reduced lithium concentration is produced.

In this step, the concentration of lithium contained in the obtained lithium-containing concentrate may be in the range of 1 g / L to 15 g / L, more specifically 2 g / L to 6 g / L. When the concentration of lithium contained in the lithium-containing concentrate is less than 1 g / L, there is a problem in that the recovery rate in the production of lithium hydroxide is low. Further, when the lithium concentration of the lithium-containing concentrate exceeds 15 g / L, the lithium recovery rate is increased but the current efficiency is decreased when the electrodialysis is performed, so that the power ratio can be increased.

Next, a step of removing impurities (S40) is performed.

Specifically, the precipitating agent may be added to the lithium-containing concentrate to remove impurities.

The content of the precipitant to be added to the step of removing the impurities may be 1 to 2 equivalents, more specifically 1.2 to 1.5 equivalents based on the equivalents of the impurity ions. When the amount of the precipitant to be added satisfies the above range, it is possible to optimize the amount of the feed while maintaining the high impurity removal rate, and it is possible to efficiently remove the impurities without using an excessive amount of the precipitant.

At this time, the impurities to be removed may be at least one of divalent cations, for example, calcium, magnesium and strontium.

When a precipitant is added to the lithium-containing concentrate, the divalent cations and the precipitant bind to each other to form a precipitate, which can be removed by solid-liquid separation to remove impurities.

Specifically, the divalent precipitating agent for the removal of cations, e.g., sodium hydroxide (NaOH), sodium carbonate (Na ₂ CO _3), calcium hydroxide (Ca (OH) _2), sodium sulfate (Na ₂ SO _4), and Potassium hydroxide (KOH) may be used.

Of these, when sodium hydroxide or sodium carbonate is used as a precipitant, calcium and magnesium ions can be removed by the reaction of the following Reaction Schemes 3 and 4.

[Reaction Scheme 3]

Me ^{2 +} + ² NaOH - > Me (OH) ₂ + ₂ Na ⁺

[Reaction Scheme 4]

Me ^{2 +} + Na ₂ CO _{3 -} > MeCO ₃ + 2Na ⁺

In the above Reaction Schemes 3 and 4, Me is Ca or Mg.

That is, the precipitates of Ca (OH) ₂ , CaCO ₃ , Mg (OH) ₂ and MgCO ₃ are formed by the reaction of Reaction Formula 3 and Reaction Formula 4 and calcium and magnesium ions can be removed have.

In the present step, a physical separation method such as nanofiltration capable of physically separating at least one of a monovalent cation and a divalent cation and a chemical removal method may be used at the same time in order to reduce the amount of the precipitant to be added. Further, in order to control the concentration of impurities to the level of ppb, a process of removing residual divalent cation impurities using a chelate ion exchange resin may be further performed.

Thereafter, a step (S50) of obtaining a lithium hydroxide aqueous solution is carried out.

FIG. 2 schematically shows a process of converting a lithium hydroxide aqueous solution using a bipolar electrodialyzer.

2, the electrodialyzer 200 used in the lithium hydroxide aqueous solution conversion process includes a cathode cell including the anode 210, a first bipolar membrane 220, an anion-selective-type dialysis membrane 230, a cation- A cathode bipolar layer 240, a second bipolar layer 250, and a cathode 260 may be sequentially arranged.

In the step of converting into the aqueous solution of lithium hydroxide, a concentrated solution from which impurities have been removed by the above-described method is put between the anion-selective-type dialysis membrane 230 and the cation-selective dialysis membrane 240, distilled water is introduced into the first bipolar membrane 220, And the anion-selective-type dialysis membrane 230, and between the second bipolar membrane 250 and the cation-selective dialysis membrane 240, thereby performing bipolar electrodialysis.

That is, when a voltage in the range of 1.8 to 2.2 V is applied to the bipolar electrodialyser into which the lithium chloride aqueous solution and the distilled water have been added, the water-splitting occurs in each of the bipolar membranes, The positive and negative ions move toward the cathode 260 and the anode 210, respectively, due to the electrophoretic effect.

More specifically, Cl < ^- > is obtained by hydrochloric acid (HCl) with hydrogen hydrolyzed in the first bipolar membrane 220 on the anode side, and lithium ions migrating to the cathode through the cation- Is reacted with OH < ^- > generated in the film 250 and is obtained as lithium hydroxide (LiOH). That is, the overall reaction is shown in the following Reaction Scheme 5.

[Reaction Scheme 5]

LiCl + H ₂ O -> LiOH + HCl

At this time, between the anion-selective-type dialysis membrane 230 and the cation-selective membrane 240, lithium and chlorine ions escape from the aqueous solution of lithium chloride, which is a raw material to be supplied to the bipolar electrodialyser, and a partially desalted solution is generated.

That is, the hydrochloric acid aqueous solution is recovered between the first bipolar membrane 220 and the anion selective permeable membrane 230 of the positive electrode, and the desalted solution is recovered between the anionic selective permeable membrane 230 and the cation selective membrane 240 And the lithium hydroxide aqueous solution can be recovered between the cation-selective separation membrane 240 and the second bipolar membrane 250 of the cathode cell.

In the step of converting into the aqueous solution of lithium hydroxide, the bipolar electrodialyzer may use a plurality of bipolar electrodialyzing stacking apparatuses each having the first bipolar membrane, the anion-selective dialysis membrane, the cation-selective dialysis membrane, and the second bipolar membrane as one set It is possible. Also, the voltage applied per set may range from 1.8 to 2.2V. The applied current density may be 30 mA / cm ² to 90 mA / cm ² . If the current density is lower than 30 mA / cm ² , the transfer speed of the lithium is slowed down and the production rate is reduced. If the current density exceeds 90 mA / cm ² , heat may be generated and the bipolar electrodialysis membrane damage may occur.

The lithium hydroxide aqueous solution obtained as above can be crystallized and then separated and dried to obtain lithium hydroxide in powder form.

That is, for example, vacuum filtration, pressure filtration, centrifugal separation, etc. can be used to separate the lithium hydroxide crystals after concentrating and crystallizing the aqueous lithium hydroxide solution converted into the reaction as shown in Reaction Scheme 5. The dried lithium hydroxide crystals may further be washed with distilled water to improve purity before drying. After washing, the obtained precipitate is dried to obtain lithium hydroxide in powder form.

Containing solution was obtained from the lithium-containing solution using an aluminum-based adsorbent in the same manner as in this Example, and a lithium-containing concentrate was obtained by using an electrodialyzer. After the impurities were removed therefrom, a lithium hydroxide aqueous solution The yield of lithium hydroxide can be easily improved not only from a solution having a high lithium concentration but also from a solution having a low lithium concentration.

Further, since a lithium-containing desorption liquid is obtained from the lithium-containing solution by using an aluminum-based adsorbent, a lithium-containing desorption liquid having a high lithium concentration can be obtained as an intermediate product without adding an additional step such as the use of an acid solution.

Therefore, finally, lithium hydroxide of high purity can be produced, and the yield of lithium can also be improved.

Hereinafter, preferred embodiments of the present invention and experimental examples therefor will be described. However, the following examples are only a preferred embodiment of the present invention, and the present invention is not limited to the following examples.

Example  One

Salt water having the composition shown in Table 1 was prepared.

Classification (mg / L) Li Na K Ca Mg Salt water composition 1020 94430 23000 8550 6490

80 L of the brine was passed through an adsorbent containing aluminum hydroxide.

Next, 30 L of the distilled water was passed through the adsorbent to which lithium was adsorbed to obtain a lithium-containing desorbent.

30 L of the lithium-containing desorption liquid was charged into an electrodialyser to obtain a lithium-containing concentrate.

The Ca (OH) ₂ and Na ₂ CO ₃ were added to the lithium-containing concentrate to remove impurities, and the lithium-containing concentrate from which the impurities had been removed was charged into a bipolar electrodialyzer to convert it to a lithium hydroxide aqueous solution and then crystallized to produce lithium hydroxide.

The composition of each component with respect to the solution obtained in each step is shown in Table 2 below.

Classification (mg / L) Li Na K Ca Mg Lithium-containing desorption liquid 950 200 50 60 70 After electrodialysis, a lithium-containing concentrate 12,500 2,900 650 733 860 After impurity removal 12,100 4,300 700 <1 <1 A lithium hydroxide aqueous solution obtained after bipolar electrodialysis 20,560 4,250 680 <1 <1 Lithium hydroxide aqueous solution After crystallization 30,150 25,500 4,300 <1 <1

Referring to Table 2, the yield of lithium is about 70%. In addition, the purity of lithium hydroxide was 99% or more and high-purity lithium hydroxide could be extracted.

Therefore, when lithium hydroxide is produced by conducting electrodialysis after obtaining a desorbing solution using an aluminum hydroxide adsorbent and converting it to an aqueous solution of lithium hydroxide through bipolar electrodialysis after removing impurities, as in this embodiment, lithium hydroxide It can be confirmed that lithium hydroxide having a high purity can be produced.

Comparative Example  One

Salt water having the composition shown in Table 1 of Example 1 was prepared.

Lithium phosphate was prepared by using 80 L of the saline solution and dissolved in hydrochloric acid, followed by electrodialysis and bipolar electrodialysis. The concentration of each step is shown in Table 3 below.

Classification (mg / L) Li Na K Ca Mg Lithium-containing desorption liquid 1200 400 205 1000 500 After electrodialysis, a lithium-containing concentrate 8500 2830 1450 7050 3540 After impurity removal 8400 7950 1400 <3 <3 After lithium phosphate extraction 330 9600 1410 <3 <3 After dissolving lithium phosphate in hydrochloric acid 10,435 92 4.1 0.3 0.2 After electrodialysis and bipolar electrodialysis 19,630 440 43 1.4 0.2 Lithium hydroxide aqueous solution After crystallization 30,100 2,400 240 <1 <1

In the case of producing lithium hydroxide according to Comparative Example 1, a process of dissolving hydrochloric acid after preparing lithium phosphate from saline water as described above needs to be added. In this process, there are more steps to be added than in Example 1, , The yield of lithium is also lowered to 60% or less.

Comparative Example  2

Salt water having the composition shown in Table 1 of Example 1 was prepared.

100 L of the brine was charged into an electrodialyser to obtain a lithium-containing concentrate.

However, after the brine was directly put into the electrodialyser, the precipitate of NaCl precipitated. This is because the composition of salt water is saturated NaCl.

That is, since the NaCl precipitate contaminates the membrane of the electrodialyzer, the electrodialysis process does not proceed smoothly, and thus the impurity removal process and the bipolar electrodialysis process can not be performed.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. As will be understood by those skilled in the art. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

Claims (14)

Passing a lithium-containing solution through an aluminum-based adsorbent to produce a lithium-adsorbed adsorbent;
Passing the distilled water through the adsorbent on which lithium is adsorbed to obtain a lithium-containing desorbent;
Adding the lithium-containing desorbing liquid to an electrodialyzer to obtain a lithium-containing concentrate;
Adding a precipitant to the lithium-containing concentrate to remove impurities; And
Introducing the concentrated solution from which the impurities have been removed into a bipolar electrodialyzer to obtain an aqueous solution of lithium hydroxide;
&Lt; / RTI &gt; The method according to claim 1,
Wherein the lithium concentration of the lithium-containing solution is 0.1 g / L to 2.0 g / L. The method according to claim 1,
Wherein the aluminum-based adsorbent comprises aluminum hydroxide. The method according to claim 1,
Wherein the aluminum-based adsorbent comprises an adsorbent powder and a binder. The method according to claim 1,
The step of obtaining the lithium-
Wherein the distilled water is passed through an amount of 0.5 to 10 times the volume of the lithium-adsorbed aluminum-based adsorbent. The method according to claim 1,
Wherein the concentration of lithium contained in the lithium-containing desorption liquid is 0.2 g / L to 2.0 g / L. The method according to claim 1,
The electrodialyzer comprises a cathode cell including a cathode separation membrane, an anion selective permeable membrane selectively permeable to anions, a cation selective permeable membrane selectively permeable to cations, and a cathode cell including a cathode separation membrane, &Lt; / RTI &gt; The method according to claim 1,
Wherein the concentration of lithium contained in the lithium-containing concentrate is 1 g / L to 15 g / L. The method according to claim 1,
Wherein the impurity removed in the step of removing impurities is a divalent cation. 10. The method of claim 9,
Wherein the divalent cation comprises at least one of calcium, magnesium and strontium. The method according to claim 1,
The precipitating agent is added to the step of removing the impurities is sodium hydroxide (NaOH), sodium carbonate (Na ₂ CO _3), calcium hydroxide (Ca (OH) _2), at least one of sodium sulfate (Na ₂ SO ₄₎ and potassium hydroxide (KOH) &Lt; / RTI &gt; The method according to claim 1,
Wherein the content of the precipitant to be added to the step of removing the impurities is in the range of 1 to 2 equivalents based on the equivalent amount of the impurity ions. The method according to claim 1,
Wherein the bipolar electro-
Wherein the first bipolar membrane, the anion-selective-type dialysis membrane, the cation-selective-type dialysis membrane, and the second bipolar membrane are sequentially arranged. The method according to claim 1,
And crystallizing the lithium hydroxide aqueous solution and separating it to obtain lithium hydroxide.

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