KR102145110B1 - Method of extracting lithium - Google Patents

Abstract

A method for extracting lithium, comprising: preparing lithium phosphate containing impurities; Dissolving the lithium phosphate and impurities in an acid; Including a step of obtaining a lithium-containing solution by adding an additive to the solution in which the lithium phosphate and impurities are dissolved in an acid; wherein the additive is a material that simultaneously precipitates phosphate anions and impurities, and is obtained by the additive. The lithium-containing solution can provide a lithium extraction method that is basic.

Description

Lithium extraction method {METHOD OF EXTRACTING LITHIUM}

It relates to a lithium extraction method.

Recently, lithium secondary batteries have been widely used as a power source for IT devices such as mobile phones and laptops, and are attracting attention as a power source for electric vehicles. In the near future, electric vehicles and new and renewable energy electric storage systems It is expected to be greatly activated and its demand will increase rapidly.

It is used as a raw material for cathode materials, anode materials, and electrolytes, which are important parts of electric vehicles and electric storage systems, and lithium is mainly used in the form of lithium carbonate (Li ₂ CO ₃ ). Accordingly, there is a need to develop a technology capable of economically manufacturing lithium carbonate in order to manufacture electric vehicles and electric storage systems that are expected to increase significantly in demand and supply them to the market at low prices.

Lithium carbonate is generally concentrated in a high concentration of 60 g/L by naturally evaporating natural brine containing 0.2 to 1.5 g/L of lithium, and then adding carbonate to lithium carbonate (Li ₂ CO _{3 ).} It is produced by precipitation in the form of ). However, due to the high solubility of lithium carbonate (13g/L), brine must be evaporated and concentrated over a long period of time for at least one year in order to concentrate lithium to about 60g/L, and a large amount of lithium is precipitated and lost during the evaporation and concentration process.

In order to improve this problem, a lithium phosphate (Li ₃ PO ₄ ) extraction method that can minimize the natural evaporation process has been developed (Korean Patent Registration 10-1363342). When lithium is extracted in the form of lithium phosphate using the lithium phosphate extraction method, the low solubility (0.39g/L) of lithium phosphate can eliminate or greatly shorten the evaporation and concentration process of brine over a long period of time, as well as evaporation and concentration. Lithium can be extracted with a high recovery rate by suppressing loss of lithium generated in the process. However, as described above, in order to use lithium phosphate as a raw material for a lithium secondary battery, it must be converted into lithium carbonate.

Recently, a low-concentration lithium hydroxide solution with a lithium concentration of 5 g/L or less is made by mixing Ca(OH) ₂ in a high-temperature (90°C or higher) lithium phosphate-water slurry, and it is evaporated and concentrated to a high concentration of 30 g/L or more. A technology for producing lithium carbonate was developed by making a lithium hydroxide solution and then introducing carbon dioxide (CO ₂ ) gas.

However, when converting lithium phosphate into lithium carbonate by this method, the lithium phosphate suspension must be heated to a high temperature and then reacted for a long time, and the low-concentration lithium hydroxide solution must be evaporated and concentrated, thereby increasing energy cost. (Korean Patent Registration 10-1405486)

In addition, after dissolving lithium phosphate in an acid to prepare a lithium solution having a lithium concentration of 0.05 g/L to 0.16 g/L, divalent ion alkaline earth metal and phosphorus were removed using an ion exchange resin, and bipolar electrodialysis was used. A method of producing lithium carbonate by reacting an aqueous lithium hydroxide solution having a lithium concentration of 3.5 g/L to 4.5 g/L with carbon dioxide gas was developed.

However, when producing lithium carbonate by this method, there is a problem that the lithium concentration in the lithium solution is too low, so that the lithium recovery rate is low, an expensive large electrolysis facility is required, and the manufacturing cost is greatly increased as a large amount of electricity is used. (Republic of Korea Patent Registration 10-1888181)

On the other hand, after dissolving the lithium phosphate-metal compound (one of iron, copper, lead, zinc, manganese, calcium, cerium, yttrium, or lanthanum compound) in the mixed suspension, the pH is adjusted to 1 to 1 by adding alkali hydroxide. A method of preparing a high-concentration lithium solution from which metals and phosphorus are removed by adjusting to 10 and adding carbonate to prepare lithium carbonate has been developed. However, using this method increases the amount of acid used to dissolve both lithium phosphate and metal compounds. In addition, when an alkali is added to induce precipitation of metal ions present in the acidic solution in which lithium phosphate is dissolved, heavy metal ions may not be completely removed as the pH of the reaction solution is limited to 1-10. After dissolving the compound mixture and adjusting the pH by adding alkali, the process becomes complicated and the amount of raw materials used is increased, thereby reducing economic efficiency. (Japanese Patent Registration JP5632169B2 & JP5528153B2)

When using the lithium carbonate manufacturing method using lithium phosphate developed so far as described above, there is a problem in that economic feasibility is deteriorated due to low lithium recovery rate, high energy cost and equipment investment, excessive raw material cost, and process complexity. Therefore, there is an urgent need to develop a technology capable of economically producing lithium carbonate using lithium phosphate.

Accordingly, in the present invention, it is intended to provide a method for extracting lithium having a high lithium recovery rate.

In addition, the method has low energy consumption, raw material cost, and equipment investment cost, as well as a simple process, so that a lithium compound can be economically produced from lithium phosphate.

In one embodiment of the present invention, preparing a lithium phosphate containing impurities; Dissolving the lithium phosphate and impurities in an acid; Including a step of obtaining a lithium-containing solution by adding an additive to the solution in which the lithium phosphate and impurities are dissolved in an acid; wherein the additive is a material that simultaneously precipitates phosphate anions and impurities, and is obtained by the additive. The lithium containing solution provides a lithium extraction method that is basic.

The impurity may include an alkaline earth metal.

The alkaline earth metal may be beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra), or a combination thereof.

The lithium concentration in the solution in which the lithium phosphate and impurities are dissolved in an acid may be 10 to 35 g/L.

Dissolving the lithium phosphate and impurities in an acid; In, the acid may be hydrochloric acid, hypochlorous acid, nitric acid, acetic acid, or a combination thereof.

The pH of the solution in which lithium phosphate and impurities are dissolved in an acid may be -0.1 to 4.5.

The additive may be an oxide or a hydroxide.

The additive may be an oxide or hydroxide of a cation of beryllium, magnesium, calcium, strontium, barium, radium, or a combination thereof.

More specifically, the additive may be calcium hydroxide (Ca(OH) ₂ ), magnesium hydroxide (Mg(OH) ₂ ), or a combination thereof.

From this, phosphate anions and impurities may precipitate as poorly soluble precipitates.

The poorly soluble precipitate is hydroxylapatite (Hydroxylapatite, Ca ₅ (PO ₄ ) ₃ OH), brushite (Brushite, CaHPO ₄ ·2H ₂ O), amorphous calcium-phosphorus compound, calcium hydroxide, Newberyite, MgHPO ₄ · 3H ₂ O), magnesium phosphate (Magnesium phosphate, Mg ₃ (PO ₄ ) ₂ ) It may be an amorphous magnesium-phosphorus compound and magnesium hydroxide or a mixture thereof.

In the step of obtaining a lithium-containing solution by adding an additive to a solution in which lithium phosphate and impurities are dissolved in an acid; in, the pH of the obtained lithium-containing solution may be 9 or more.

In the step of obtaining a lithium-containing solution by adding an additive to the solution in which lithium phosphate and impurities are dissolved in an acid; in, the pH of the obtained lithium-containing solution may be 11 or more.

Lithium carbonate can be obtained by adding a carbonic acid supply material to the obtained lithium-containing solution.

The carbonic acid feed material is sodium carbonate (Na ₂ CO ₃ ), potassium carbonate (K ₂ CO ₃ ), ammonium carbonate ((NH ₄ ) ₂ CO ₃ ), sodium bicarbonate (NaHCO ₃ ), potassium bicarbonate (KHCO ₃ ), or these It may be a combination of.

It may further include washing and drying the obtained lithium carbonate.

In one embodiment of the present invention, by providing a method for extracting lithium from lithium phosphate containing impurities (more specifically, alkaline earth metal), a lithium compound (e.g., a lithium compound (e.g., a high lithium recovery rate) and a low raw material, energy and equipment cost For example, lithium carbonate) can be produced economically.

1 and Table 1 show a reaction filtrate obtained by mixing 10 g of lithium phosphate containing magnesium and 0.1 L of aqueous hydrochloric acid solutions having different acidities at room temperature, stirring for 60 minutes, and filtering to prepare a high-concentration lithium solution having a lithium concentration of 10 g/L. Indicate the pH and lithium concentration.
Table 2 shows that 10 g of lithium phosphate containing magnesium was added to 0.1 L of aqueous hydrochloric acid solution at room temperature to prepare a lithium phosphate solution containing magnesium having a pH of 4.33, and 2.3 g to 23.8 g of calcium hydroxide were added respectively, followed by stirring for 2 hours, The chemical component content and pH of the reaction filtrate obtained by filtration are shown.
FIG. 2 shows a solution of lithium phosphate containing magnesium having a pH of 4.33 by adding 10 g of lithium phosphate containing magnesium to 0.1 L of an aqueous hydrochloric acid solution at room temperature, and adding 2.3 g to 23.8 g of calcium hydroxide, respectively, and stirring for 2 hours, The X-ray diffraction pattern of the precipitate obtained by filtration, washing and drying is shown.
3 shows an X-ray diffraction pattern of a precipitate obtained by adding 6.478 g of Na ₂ CO _{3 to} 0.1 L of a lithium phosphate solution at room temperature from which magnesium and phosphorus have been removed, followed by stirring, filtering, washing, and drying for 2 hours.

Hereinafter, various embodiments of the present invention will be described in detail so that those of ordinary skill in the art to which the present invention pertains can easily implement it. The present invention may be implemented in various different forms and is not limited to the embodiments described herein.

In order to clearly describe the present invention, parts irrelevant to the description are omitted, and the same reference numerals are attached to the same or similar components throughout the specification.

In addition, throughout the specification, when a certain part "includes" a certain component, it means that other components may be further included rather than excluding other components unless otherwise stated.

In one embodiment of the present invention, preparing a lithium phosphate containing impurities; Dissolving the lithium phosphate and impurities in an acid; Including a step of obtaining a lithium-containing solution by adding an additive to the solution in which the lithium phosphate and impurities are dissolved in an acid; wherein the additive is a material that simultaneously precipitates phosphate anions and impurities, and is obtained by the additive. The lithium containing solution provides a lithium extraction method that is basic.

An embodiment of the present invention is to obtain a high concentration lithium phosphate solution by dissolving lithium phosphate containing impurities (eg, alkaline earth metal) at room temperature using an aqueous hydrochloric acid solution as an example of the acidic solution; A method of removing impurities and phosphorus by adding calcium hydroxide, which is an example of the additive, at room temperature will be described in detail.

In a later step, sodium carbonate, which is an example of a carbonate, is added to the obtained lithium-containing solution at room temperature to obtain lithium carbonate; It will be described a method of economically manufacturing lithium carbonate by washing it with tap water and drying it at a high temperature (eg, 105°C).

The dissolution of lithium phosphate containing impurities (magnesium, which is a kind of alkaline earth metal) by the aqueous hydrochloric acid solution according to an embodiment of the present invention may be performed by the following Reaction Formula 1.

[Scheme 1]

_{(Mg, Li) PO 4 +} 2HCl + 3H 2 O -> Li + + Mg 2+ + H 2 PO 4 - + 2Cl - + 3H 2 O

That is, the magnesium-containing lithium phosphate is dissolved in hydrochloric acid at room temperature, _{^{Li +, Mg 2+, H 2}} PO 4 - is converted into a lithium phosphate-containing solution was a ^-, Cl.

Specific examples of the acid for dissolving the lithium phosphate may be hydrochloric acid, hypochlorous acid, nitric acid, acetic acid, or a combination thereof. Sulfuric acid can react with alkaline earth metals such as calcium to generate precipitates to generate acidic sludge. Since phosphorus contained in phosphoric acid is a substance that must be finally removed, it is not preferable to use it to reduce removal costs. However, some sulfuric acid may be selectively used by a combination of various impurities.

The solubility of the lithium carbonate is 13 g/L, which is 2.5 g/L in terms of lithium concentration. Therefore, when preparing by depositing lithium carbonate from a lithium phosphate solution, the lithium concentration in the lithium phosphate solution must be 10 g/L or more in order to obtain a high lithium recovery rate of 75% or more.

Therefore, in the present invention, the lithium concentration of the lithium phosphate solution is limited to 10 g/L or more. On the other hand, if the lithium concentration of the lithium phosphate solution is 30 g/L, the lithium recovery rate is more preferably 91.7%.

As shown in the following examples, in order to obtain a lithium phosphate solution having a lithium concentration of 10 g/L or more, the pH of the reaction solution obtained by mixing lithium phosphate and an aqueous acid solution should be 4.5 or less. This will be described in more detail in the following examples.

The removal of alkaline earth metal and phosphorus according to an embodiment of the present invention may be performed by the following Reaction Scheme 2 or Scheme 3.

[Scheme 2]

_{^{Li + + Mg 2+ + H 2}} PO 4 - + 2Cl - + 3H 2 O + Ca (OH) 2 -> Li + + H + + 2Cl - + Mg (OH) 2 + CaHPO 4 · 2H 2 O + H ₂ O

[Scheme 3]

_{^{3Li + + 3Mg 2+ + 3H 2}} PO 4 - + 6Cl - + 9H 2 O + 5Ca (OH) 2 -> 3Li + + Cl - + 2OH - + 3Mg (OH) 2 + Ca 5 (PO 4) 3 · OH + 10H ₂ O + 5HCl (g)

The additive for removing the alkaline earth metal and phosphorus may be a material that reacts with phosphorus at room temperature to generate a poorly soluble compound and generates hydroxide ions (OH ⁻ ) that generate alkaline earth metals and poorly soluble compounds. As a result, phosphorus and an impurity alkaline earth metal can be simultaneously precipitated.

More specifically, the additive may be an alkaline earth metal oxide or hydroxide.

As a specific example, the cation of the additive may be beryllium, magnesium, calcium, barium, radium, or a combination thereof, and the additive may be an oxide or hydroxide thereof.

For example, the additive may be calcium hydroxide, magnesium hydroxide, or a combination thereof. Another example is calcium oxide or magnesium oxide.

For example, calcium oxide or magnesium oxide can be obtained by heating calcium carbonate (CaCO ₃ ) or magnesium carbonate (MgCO ₃ ). When water is added to the calcium oxide or magnesium oxide obtained therefrom, calcium hydroxide and magnesium hydroxide can be obtained.

Calcium hydroxide, which is an example of an additive, may be added at room temperature to remove impurities (eg, alkaline earth metal) and phosphorus from the lithium phosphate solution containing the impurities (eg, alkaline earth metal).

In the above specific example, magnesium may be precipitated as poorly soluble magnesium hydroxide, and phosphorus is in the form of poorly soluble hydroxyapatite (Hydroxylapatite, Ca ₅ (PO ₄ ) ₃ ·OH) or brushite (CaHPO ₄ · 2H ₂ O) It can be precipitated as. They can be filtered and removed from the lithium phosphate solution.

The amount of the additive added may be 1 equivalent or more based on the phosphorus content in order to completely remove phosphorus present in the lithium phosphate solution. When the above range is satisfied, phosphorus may be completely removed, and it may be advantageous in terms of reaction rate.

The amount of the additive added may be an amount capable of maintaining the pH of the lithium phosphate solution to 9 or more or preferably 11 or more so that alkaline earth metals and phosphorus present in the lithium phosphate solution are precipitated and completely removed.

The preparation of lithium carbonate according to an embodiment of the present invention may be performed by the following Reaction Scheme 4.

Sodium carbonate, which is an example of a carbonic acid supply material, may be added to precipitate lithium carbonate from the lithium-containing solution at room temperature from which the alkaline earth metal and phosphorus have been removed according to the embodiment of the present invention.

[Scheme 4]

^{6Li + + 2Cl - + 4OH -} + 20H 2 O + 3Na 2 CO 3 -> 3Li 2 CO 3 + 6Na + + 2Cl - + 4OH - + 20H 2 O

That is, the sodium carbonate reacts with lithium at room temperature to generate and precipitate lithium carbonate. In addition, when 1 equivalent or more of a lithium-containing solution from which alkaline earth metals and phosphorus have been removed are added, lithium carbonate can be obtained with a high recovery rate of 75% or more.

Specific examples of the carbonate are sodium carbonate, potassium carbonate, and ammonium carbonate.

More specifically, the carbonate may be sodium bicarbonate, sodium carbonate, potassium bicarbonate, sodium bicarbonate, ammonium carbonate, or a combination thereof.

The amount of lithium carbonate added may be 1 equivalent or more based on the lithium content of the lithium-containing solution. If the above range is satisfied, it may be advantageous in terms of reaction rate.

In the present specification, room temperature does not mean a constant temperature, but refers to a temperature in which no external energy is added. Therefore, the room temperature may change depending on the location and time.

Hereinafter, the present invention will be described with reference to specific examples. However, the claims of the present invention are not limited to the following examples.

[Example 1]

In order to prepare a high-concentration lithium solution having a lithium concentration of 10 g/L, 10 g of magnesium-containing lithium phosphate and 0.1 L of an aqueous hydrochloric acid solution having a different acidity were each mixed at room temperature and stirred for 60 minutes.

After the stirring was completed, the reaction solutions were filtered to measure pH and lithium concentration, and the results are shown in FIG. 1 and Table 1.

As shown in FIG. 1, as the pH of the reaction solution decreased, lithium phosphate was dissolved and the lithium concentration gradually increased. When the reaction filtrate pH reached 4.5 or less, the lithium concentration was about 10 g/L, and it was found that the lithium concentration no longer increased even when the pH of the reaction filtrate was decreased to 4.5 or less.

From this, it can be seen that in the reaction filtrate pH of 4.5 or less, all the lithium phosphate added is dissolved. On the other hand, even when the pH of the reaction filtrate is excessively low to -1.0 or less, all lithium phosphate can be dissolved, but there is a problem that the amount of hydrochloric acid is excessively increased.

Reaction filtrate
Lithium concentration
(g/L) 0.789 3.165 4.841 6.884 9.070 10.003 11.008 Reaction filtrate
pH 8.26 6.89 5.80 5.13 4.73 4.48 3.93 Reaction filtrate
Lithium concentration
(g/L) 9.997 9.667 9.829 9.769 9.669 - - Reaction filtrate
pH 3.10 1.72 1.03 -0.55 -1.0 - -

[Example 2]

10 g of lithium phosphate containing magnesium was added to 0.1 L of aqueous hydrochloric acid solution at room temperature and stirred for 1 hour to prepare a lithium phosphate solution containing magnesium having a pH of 4.33.

2.3 g to 23.8 g of calcium hydroxide were added to the lithium phosphate solution, respectively, and stirred for 2 hours, and then the precipitate was filtered.

As shown in Table 2 below, when the pH of the reaction filtrate is 11 or higher, it can be seen that phosphorus and magnesium are completely removed. Phosphorus and magnesium can be completely removed even if the pH of the reaction solution is increased to 14 or more by adding a large amount of calcium hydroxide, but since the cost of raw materials increases and interlayer water exists between unreacted precipitates, the lithium recovery rate is reduced. The pH of the lithium phosphate solution into which the oxide or hydroxide is added can be controlled to 11 to 14 or less.

Meanwhile, the precipitate filtered from the reaction solution was washed with tap water and then dried at 105° C. for 24 hours. The mineral phase of the precipitate showing the reaction solution pH 11.35 was analyzed using an X-ray diffractometer, and the results are shown in FIG. 2.

As shown in FIG. 2, magnesium was precipitated in the form of poorly soluble magnesium hydroxide, and phosphorus was mostly precipitated as poorly soluble hydroxylapatite, and some of it was precipitated as lithium phosphate and completely removed from the magnesium-containing lithium phosphate solution.

division Li P Mg Reaction solution pH reaction
Filtrate
chemistry
ingredient
content
(mg/L) Lithium phosphate containing magnesium
Solution 10,198 16,751 2,394 4.33 Ca(OH) ₂
Input amount (g) 2.31 8,160 959 653 5.40 3 8,132 429 380 7.50 3.79 7,691 7 309 9.41 5.05 8,230 3 19 9.81 5.4 8,199 One 13 10.34 5.68 8,017 0 0 11.35 5.92 8,015 0 0 11.75 23.8 9,498 0 0 12.23

[Example 3]

After adding 64.78 g of Na ₂ CO _{3 to} 1 L of a lithium-containing solution at room temperature from which magnesium and phosphorus were removed, the mixture was stirred for 2 hours to react, and the precipitate was filtered.

The precipitate filtered from the reaction solution was washed with tap water, dried at 105° C. for 24 hours, and mineral phase analysis was performed using an X-ray diffractometer. The analysis results are shown in FIG. 3. As shown in FIG. 3, as the precipitate was observed as a single phase of lithium carbonate, it can be seen that lithium carbonate was well synthesized.

The present invention is not limited to the above embodiments, but may be manufactured in a variety of different forms, and those of ordinary skill in the art to which the present invention pertains, other specific forms without changing the technical spirit or essential features of the present invention. It will be appreciated that it can be implemented with. Therefore, it should be understood that the embodiments described above are illustrative and non-limiting in all respects.

Claims (12)

Preparing lithium phosphate containing impurities;
Dissolving the lithium phosphate and impurities in an acid;
Including a step of obtaining a lithium-containing solution by adding an additive to the solution in which the lithium phosphate and impurities are dissolved in an acid,
The additive is a substance that simultaneously precipitates phosphate anions and impurities, and the lithium-containing solution obtained by the additive is basic,
The impurities include alkaline earth metal, and dissolving the lithium phosphate and the impurities in an acid; A lithium extraction method that does not perform an impurity removal step for removing an impurity alkaline earth metal before, and the acid is hydrochloric acid, hypochlorous acid, nitric acid, acetic acid, or a combination thereof.
delete The method of claim 1,
The alkaline earth metal is beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra), or a combination thereof.
The method of claim 1,
The lithium concentration in the solution in which the lithium phosphate and impurities are dissolved in an acid is,
The lithium extraction method of 10 to 35 g / L.
delete The method of claim 1,
The lithium extraction method that the pH of the solution in which the lithium phosphate and impurities are dissolved in an acid is -0.1 to 4.5.
The method of claim 1,
The lithium extraction method that the additive is an oxide or hydroxide.
The method of claim 7,
The additive is an oxide or hydroxide of a cation of beryllium, magnesium, calcium, strontium, barium, radium, or a combination thereof.
Preparing lithium phosphate containing impurities;
Dissolving the lithium phosphate and impurities in an acid;
Including a step of obtaining a lithium-containing solution by adding an additive to the solution in which the lithium phosphate and impurities are dissolved in an acid; wherein the additive is a material that simultaneously precipitates phosphate anions and impurities, and is obtained by the additive. The lithium-containing solution is basic, the step of obtaining a lithium-containing solution by adding an additive to the solution in which the lithium phosphate and impurities are dissolved in an acid; In, the pH of the obtained lithium-containing solution is 9 to 14 or less, the The acid (acid) is a lithium extraction method that is hydrochloric acid, hypochlorous acid, nitric acid, acetic acid, or a combination thereof.
delete The method of claim 1,
Lithium extraction method to obtain lithium carbonate by adding a carbonic acid supply material to the obtained lithium-containing solution
The method of claim 11,
The carbonic acid feed material is sodium carbonate (Na ₂ CO ₃ ), potassium carbonate (K ₂ CO ₃ ), ammonium carbonate ((NH ₄ ) ₂ CO ₃ ), sodium bicarbonate (NaHCO ₃ ), potassium bicarbonate (KHCO ₃ ), or these Lithium extraction method that is a combination of.

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