KR20180074022A - Method of preparing lithium compound - Google Patents

Abstract

The present invention relates to a method for preparing a lithium compound, comprising: a step of preparing a solid state lithium phosphate in a solvent in a slurry state; a step of converting the lithium phosphate into lithium sulfate by making the lithium phosphate react with sulfuric acid; a step of separating the lithium sulfate to a solid state; a step of washing the separated solid lithium sulfate; and a step of reducing washing water used in the washing step as the step of preparing the solid lithium phosphate in the slurry state.

Description

METHOD OF PREPARING LITHIUM COMPOUND [0002]

The present invention relates to a process for producing a lithium compound.

The lithium compound that is effective in extracting lithium from salting or extracting lithium from a spent cell is lithium phosphate.

This is because the solubility of lithium phosphate is very low, and lithium phosphate can be effectively precipitated by the reaction of phosphoric acid and lithium.

However, due to the high price of phosphoric acid, a method of extracting lithium in the form of lithium phosphate should be accompanied by a technology capable of recovering and recycling a high concentration of phosphoric acid from the extracted lithium phosphate in order to be economical.

A conventional method of directly extracting phosphoric acid at a high concentration from lithium phosphate is not known, and a method of extracting phosphoric acid from a phosphoric acid obtained in the course of conversion to a lithium-lithium lithium compound or a method of extracting phosphoric acid from an organic solvent such as ethanol or methanol And a method of separating and extracting them are known, but a complicated device is required, and distillation and concentration are required, so that a high cost is required

Disclosure of Invention Technical Problem [8] The present invention provides a process for producing a lithium compound capable of increasing the recovery of phosphoric acid.

In order to solve these problems, a method for preparing a lithium compound according to an embodiment of the present invention comprises preparing a solid phosphoric acid lithium salt in a slurry state, reacting the lithium phosphate with sulfuric acid to convert the lithium phosphate to lithium sulfate Separating the lithium sulfate into a solid phase, washing the separated solid phase lithium sulfate, and washing the washing water used in the washing step in the step of preparing the solid lithium phosphate in a slurry state Of the solvent.

In the step of preparing the solid lithium phosphate as a slurry in a solvent, the solvent may be water or phosphoric acid.

Reacting the lithium phosphate with sulfuric acid to convert the lithium phosphate to lithium sulfate; , The total concentration of phosphorus (P) and sulfur (S) in the liquid phase of the lithium phosphate and sulfuric acid mixture may be 5 mol / L or more ([P + S] mol / L).

Reacting the lithium phosphate with sulfuric acid to convert the lithium phosphate to lithium sulfate, and the reaction may include a reaction represented by the following reaction formula (1).

[Reaction 1] 2Li ₃ PO ₄ + 3H ₂ SO ₄ + nH ₂ O -> 3Li ₂ SO ₄ nH ₂ O + 2H ₃ PO ₄

Separating the lithium sulfate from the solid phase and separating lithium sulfate from the solid phase, and recovering the concentrated phosphoric acid remaining in the filtrate.

The recovered high concentration phosphoric acid may be 40 wt% or more.

The recovered high concentration phosphoric acid can be reused as a solvent in the step of preparing the solid phosphoric acid lithium as a slurry in a solvent.

The step of washing the separated solid phase lithium sulfate may use pure water (DI water).

Washing the separated solid phase lithium sulfate with an alcohol-based solvent, and washing water containing the alcohol-based solvent, washing the solid-phase lithium sulfate by recovering the alcohol-based solvent through distillation; Can be reused.

The step of washing the separated solid phase lithium sulfate may include two or more washing steps using pure water (DI water).

Washing the separated solid lithium sulfate, comprising: obtaining n-th wash water by n-th wash; Reusing a part of the n-th wash water as a solvent for preparing the wash water in the slurry state of the solid phosphoric acid lithium as a solvent; And a step of n + 1-rinsing lithium sulfate by mixing remaining balance of the n-th wash water and additional pure water.

Using the entire n + 1th washing water for n + 2nd washing; And reusing part of the (n + 2) -th washing water by the (n + 2) -th washing as a solvent for preparing the washing water in the slurry state of the solid phosphoric acid lithium in the solvent; And n + 3 rinsing the remaining amount of the n + 2nd rinsing water and the additional purified water to wash lithium sulfate.

As described above, in the method for producing a lithium compound according to an embodiment of the present invention, lithium phosphate is slurried in phosphoric acid at a low concentration and reacted with sulfuric acid to precipitate lithium sulfate, extract high concentration phosphoric acid, After that, low concentration phosphoric acid is obtained by washing water, and low concentration phosphoric acid is used again in the slurry of lithium phosphate, so that the recovery rate of phosphoric acid can be increased.

1 is a graph showing the change in solubility of lithium depending on the concentration of phosphorus (P) and sulfur (S) in phosphoric acid.
2 is a process diagram according to the first embodiment.
3 is a process diagram according to the second embodiment.
4 is a process drawing showing the process according to the fourth embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which: FIG. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

In the drawings, the thicknesses are enlarged to clearly indicate 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.

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

The present inventors have experimentally confirmed that solubility is drastically lowered in a high concentration phosphoric acid solution in which lithium is highly soluble in water or low concentration phosphoric acid but sulfate ions are present. In a high concentration phosphoric acid solution in which sulfate ions exist, Li of solubility is precipitated in the form of lithium sulfate (Li ₂ SO ₄ ) and a high concentration of phosphoric acid solution is produced through direct reaction between lithium phosphate and sulfuric acid. Thereafter, lithium sulfate precipitated through solid-liquid separation can be separated, and at the same time, high concentration phosphoric acid as a filtrate can be directly recovered.

1 is a graph showing the change in solubility of lithium depending on the concentration of phosphorus (P) and sulfur (S) in phosphoric acid. As can be seen from FIG. 1, when the concentration of phosphoric acid and sulfuric acid is increased, the concentration of lithium in the solution is drastically lowered. That is, it can be seen that lithium is mostly precipitated in the form of lithium sulfate.

Hereinafter, a method for producing a lithium compound according to an embodiment of the present invention will be described below. The method for preparing a lithium compound according to an embodiment of the present invention comprises preparing a solid phase lithium phosphate as a slurry in a solvent, reacting the lithium phosphate with sulfuric acid to convert the lithium phosphate to lithium sulfate, Separating the separated solid phase lithium sulfate, and washing water used in the washing step as a solvent in the step of preparing the solid phase lithium phosphate as a slurry in a solvent .

In the step of preparing lithium phosphate as a slurry in a solvent, lithium phosphate powder may be used. The size of the lithium phosphate powder may have a particle size of 1 to 200 mu m or more. Sulfuric acid has a concentration of 5 ~ 98 wt% in the solution phase. The higher concentration of sulfuric acid, the higher the concentration of phosphoric acid can be extracted.

The lithium phosphate powder may be slurried by mixing with 1 to 50 wt% of a phosphoric acid solution or water. Although the step of slurrying the lithium phosphate powder may be omitted, when the lithium phosphate powder is directly reacted with sulfuric acid, the uniformity of the reaction is lowered, and it is difficult to precipitate highly permeable lithium sulfate, so that the recovery rate of phosphoric acid may be lowered.

Then, sulfuric acid is added to the lithium phosphate powder or slurry, and the phosphoric acid is separated by converting lithium phosphate into lithium sulfate according to the following reaction formula.

[Reaction Scheme 1]

2Li ₃ PO ₄ + 3H ₂ SO ₄ + nH ₂ O -> 3Li ₂ SO ₄ nH ₂ O + 2H ₃ PO ₄

At this time, the total concentration of phosphorus (P) and sulfur (S) in the liquid phase of the mixture of lithium phosphate and sulfuric acid may be ([P + S] mol / L) 5 mol / L or more.

The converted lithium sulfate precipitates as the concentration of phosphoric acid increases. As the reaction progresses, the concentration of phosphoric acid increases and the solubility of lithium in phosphoric acid decreases. The solubility of lithium in phosphoric acid can be expressed as a function of the concentration of P and S elements of phosphoric acid.

The following equation (1) approximates the data of FIG.

[Equation 1]

Lithium concentration in the filtrate = 0.048 * (P concentration + S concentration) ² - 1.2773 * (P concentration + S concentration) +9.4367 (占 0.6)

The unit of lithium solubility, P concentration and S concentration in the above formula (1) is mol / L.

After completion of the reaction, the phosphoric acid-lithium sulfate mixture is separated by solid-liquid separation

The separated lithium sulfate cake is washed with an organic solvent such as ethanol or methanol or water.

The washing liquid contains a large amount of phosphoric acid, and in the case of washing with an organic solvent, the phosphoric acid is recovered through distillation, and the washing liquid or the recovered phosphoric acid can be reused in the lithium phosphate slurry manufacturing process. That is, the washing water used in the washing step can be reused as a solvent in the step of preparing the solid lithium phosphate as a slurry in a solvent, thereby increasing the efficiency.

Hereinafter, examples and comparative examples of the present invention will be described. However, the following examples are only illustrative of the present invention and are not intended to limit the scope of the present invention.

Example  One

2 is a process diagram according to the first embodiment. Washing step, and specifically includes an ethanol washing step.

After reacting lithium phosphate with sulfuric acid under the conditions shown in Table 1 below, a high concentration phosphoric acid recovery experiment was conducted through solid-liquid separation. In addition, the component analysis of the recovered washed water was also carried out. The results are shown in Tables 2, 3 and 4.

Lithium phosphate extracted from waste batteries was used. In order to reduce the test error due to the difference in water content, the water was removed by drying at 105 ° C for 24 hours and then used. The amount of the dried lithium phosphate was measured by ICP (Inductively Coupled Plasma), and the amount of sulfuric acid corresponding to the equivalence ratio according to the reaction formula 1 was calculated. The purity of the used sulfuric acid was 95%.

A phosphoric acid solution having a phosphoric acid silver concentration of 21 to 30 wt% for slurrying lithium phosphate was used, and the phosphoric acid solution was prepared by mixing 85% phosphoric acid solution (purified water) and ultrapure water.

The phosphoric acid solution and lithium phosphate were mixed in a reactor to form a slurry, which was then stirred at 200 rpm and sulfuric acid was added. At this time, the feed rate of sulfuric acid was about 10 g / min.

After completion of the addition of sulfuric acid, the reactant slurry was further stirred for about 40 minutes and then subjected to solid-liquid separation through ordinary vacuum filtration. The pressure during filtration was about 50 mbar.

After the solid - liquid separation, the solid cake was washed with ethanol, and the washing was carried out by a conventional vacuum filtration and uniformly spraying a predetermined amount of ethanol onto the cake. In the case of Experiment No. Sample 1, after spraying 400 g of ethanol, 500 g of ethanol was further sprayed, and Sample 2 and Sample 3 were sprayed with 500 g of ethanol.

The recovered phosphoric acid, wash water (ethanol) and solid content were analyzed by ICP.

number Slurry Phosphoric acid concentration  (wt.%) Amount of phosphoric acid (g) Lithium phosphate  (g) Sulfuric acid 95 wt% ) Equivalence ratio Weight (g) Sample 1 30 300 315 1.1eq 434 Sample 2 21 300 315 1.0ep 394 Sample 3 21 300 315 1.1eq 433

number Recovery filtrate component (g / L) Density (g / cc) Concentration of phosphoric acid in the recovered filtrate (% by weight) Recovery Quantity Li  confiscation P + S M Li Na P S Ca Mg (g) Sample 1 7.40 7.64 261.85 77.16 0.054 0.027 1.5248 54.3 335.46 1.066 10.860 Sample 2 12.10 7.98 235.23 51.89 0.11 0.027 1.5191 49.0 363.81 1.743 9.213 Sample 3 9.89 7.85 225.48 78.68 0.072 0.026 1.5619 45.8 300.87 1.425 9.733

number Water (ethanol) component (g / L) Input (g) Recovery (g) Li Na P S Ca Mg Sample 1 0.458 0.101 58.72 12.18 <0.003 0.006 400 229.82 0.259 0.027 21.81 4.24 <0.003 0.003 500 439.43 Sample 2 0.678 0.133 55.39 3.69 <0.003 0.008 500 575.60 Sample 3 0.559 0.087 45.88 9.13 <0.003 0.006 500 583.41

number Solid component (wt. % ) Precipitation amount  (g) Moisture content (%) Li Na P S Ca Mg Sample 1 10.13 0.21 0.76 24.68 0.0082 0.0006 496.79 8.5 Sample 2 10.10 0.15 1.25 24.61 0.0038 <0.001 521.08 12.2 Sample 3 10.31 0.12 0.78 25.35 0.0016 <0.001 575.24 21.9

As a result of the test, the recovered liquid phase showed high concentration of phosphoric acid of 45 ~ 54 wt% and contained lithium of 7.5 ~ 12.1 g / L. The content of lithium was inversely proportional to the sum of phosphorus (P) and sulfur (S) contents in the phosphoric acid component. P (45 ~ 59g / L S) was present in the washing water (ethanol) at the level of 3.7 ~ 12.2g / L and the content of the other element including lithium was less than 1g / L. Solids consisted mainly of lithium and sulfur, and P contained 0.76 ~ 1.25% by weight. It was found that more than 90% of P was recovered with phosphoric acid solution and washing water (ethanol).

Example  2

3 is a process diagram according to the second embodiment. Specifically, it includes a DI water washing step.

After reacting lithium phosphate with sulfuric acid under the conditions shown in Table 5 below, high concentration phosphoric acid recovery experiment was carried out through solid-liquid separation. In addition, the component analysis of the recovered washed water was also carried out. The results are shown in Tables 6, 7, and 9.

Lithium phosphate extracted from waste batteries was used. In order to reduce the test error due to the difference in water content, the water was removed by drying at 105 ° C for 24 hours and then used. The amount of the dried lithium phosphate was measured by ICP (Inductively Coupled Plasma), and the amount of sulfuric acid corresponding to the equivalence ratio according to the reaction formula 1 was calculated. The purity of the used sulfuric acid was 95%.

A phosphoric acid solution having a phosphoric acid silver concentration of 21 to 30 wt% for slurrying lithium phosphate was used, and the phosphoric acid solution was prepared by mixing 85% phosphoric acid solution (purified water) and ultrapure water.

The phosphoric acid solution and lithium phosphate were mixed in a reactor to form a slurry, which was then stirred at 200 rpm and sulfuric acid was added. At this time, the feed rate of sulfuric acid was about 10 g / min.

After completion of the addition of sulfuric acid, the reactant slurry was further stirred for about 40 minutes and then subjected to solid-liquid separation through ordinary vacuum filtration. The pressure during filtration was about 50 mbar.

After the solid - liquid separation, the solid cake was washed with water (ultrapure water), and the washing was carried out by a general vacuum filtration and uniformly spraying a certain amount of water onto the cake.

The recovered phosphoric acid and wash water were analyzed using ICP, and the solids were dried at 105 ° C for 24 hours and then analyzed using ICP.

number Slurry phosphoric acid concentration  (wt.%) Amount of phosphoric acid (g) Lithium phosphate  (g) Sulfuric acid 95 wt% ) Equivalence ratio Weight (g) Sample 4 21 300 315 1.0eq 394 Sample 5 30 300 315 1.0ep 394

number Recovery filtrate component (g / L) Density (g / cc) Concentration of phosphoric acid in recovered filtrate Recovery (g) Li  confiscation P + S M Li Na P S Ca Mg ( weight% ) Sample 4 9.90 7.92 237.75 49.48 0.078 0.029 1.5191 49.5 355.48 1.426 9.219 Sample 5 8.65 7.95 295.52 45.53 0.079 0.03 1.5619 59.9 287.4 1.246 10.961

number Recovery Wash Component (g / L) Input (g) Recovery (g) Phosphoric acid concentration ( % ) Li  confiscation P + S M Li Na P S Ca Mg Sample 4 23.84 4.7 116.01 70.11 0.041 0.014 200 329.81 26.7 3.435 5.932 Sample 5 21.20 4.88 146.88 63.96 0.043 0.015 200 423.69 33.4 3.054 6.737

number The solid component (wt. % ) Precipitation amount  (g) Moisture content (%) Li Na P S Ca Mg Sample 4 11.06 0.058 0.68 28.60 0.0042 <0.0010 414.85 18.2 Sample 5 11.14 0.034 0.47 28.51 0.0020 <0.0005 385.53 15.4

As a result of the test, the recovered liquid phase showed 49 ~ 59 wt% high concentration of phosphoric acid and contained 8.7 ~ 9.8 g / L of lithium. The content of lithium was inversely proportional to the sum of phosphorus (P) and sulfur (S) contents in the phosphoric acid component. In the wash water, the P content was 116 ~ 147g / LS and the lithium content was 21.2 ~ 23.5 g / L, which was inversely proportional to the sum of phosphorus (P) and sulfur (S) And

Solids consisted mainly of lithium and sulfur, and P contained 0.68 ~ 0.47% by weight. It was found that more than 90% of P was recovered as a phosphate solution and washing water

Example  3

The process cycle cycle was tested using the wash water recovered from Sample 4 above.

The wash water obtained in Sample 4 was again used to slurry the lithium phosphate, and this circulation was repeated twice.

The results are shown in Table 9 below.

Cycle no. Materials Input (g) Output (g) Li ₃ PO ₄ Circulated H ₃ PO ₄ Total Li ₂ SO ₄ H ₂ O Recovered H ₃ PO ₄ Circulated H ₃ PO ₄ One ^st Li 53.1 0 53.1 44.6 84% 2.32 4.4% 5.72 P 77.1 18.0 95.1 1.57 1.7% 55.6 59% 27.9 2 ^nd Li 47.8 5.20 53.0 46.0 96% 1.21 2.5% 5.80 P 69.4 25.3 94.7 4.06 5.9% 65.1 94% 25.5 3 ^rd Li 45.6 5.65 51.3 44.0 98% 0.67 1.3% 6.63 P 66.3 24.8 91.1 4.47 4.9% 65.0 96% 22.9

As a result, it was confirmed that the recovery rate of P was 94 ~ 96% when the process was continuously performed, and the recovery rate of Li was 96 ~ 98%.

Example  4

4 is a process drawing showing the process according to the fourth embodiment. Specifically, this shows a continuous process in which the cleaning step is performed for two or more cycles. After the solid-liquid separation, the process of washing the solid cake was carried out in two stages of washing 1/2 and washing 2/2, and ultrapure water was used as the input washing water in the washing 2/2 stage. Was used for the washing of the previous 2/2 washing step.

Washing was carried out in a manner such that a constant amount of water was sprayed uniformly onto the cake by performing a general vacuum filtration.

The amount of added lithium phosphate, the concentration and amount of sulfuric acid, the amount of recovered phosphoric acid, and the amount of phosphoric acid contained in the washing liquid at each step are as shown in FIG.

As described above, in the method for producing a lithium compound according to an embodiment of the present invention, lithium phosphate is slurried in phosphoric acid at a low concentration and reacted with sulfuric acid to precipitate lithium sulfate, extract high concentration phosphoric acid, After that, low concentration phosphoric acid is obtained by washing water and low concentration phosphoric acid is used again for slurrying of lithium phosphate, so that the recovery rate of phosphoric acid can be increased. Further, the washing can be carried out in two or more stages, so that the concentration of phosphoric acid used for slurrying can be increased to increase the concentration of manufactured phosphoric acid.

Such a method for producing a lithium compound is an environmentally friendly process that can extract a high concentration of phosphoric acid from lithium phosphate and does not involve harmful processing by-products, has a simple process configuration, and has a high recovery rate of phosphoric acid.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, Of the right.

Claims (12)

Preparing a solid phosphoric acid lithium in a solvent in a slurry state;
Reacting the lithium phosphate with sulfuric acid to convert the lithium phosphate to lithium sulfate;
Separating the lithium sulfate into a solid phase;
Washing the separated solid lithium sulfate; And
And reusing the washing water used in the washing step as a solvent in the step of preparing the solid lithium phosphate as a slurry in a solvent. The method of claim 1,
Wherein the solvent is water or a lithium phosphate compound in the step of preparing a lithium phosphate solid phase in a slurry state. The method of claim 1,
Reacting the lithium phosphate with sulfuric acid to convert the lithium phosphate to lithium sulfate; Wherein the total concentration of phosphorus (P) and sulfur (S) in the liquid phase of the lithium phosphate and sulfuric acid mixture is 5 mol / L or more ([P + S] mol / L). 4. The method of claim 3,
And reacting the lithium phosphate with sulfuric acid to convert the lithium phosphate to lithium sulfate, wherein the reaction comprises the reaction of the following Reaction Scheme 1:
[Reaction Scheme 1]
2Li ₃ PO ₄ + 3H ₂ SO ₄ + nH ₂ O -> 3Li ₂ SO ₄ nH ₂ O + 2H ₃ PO ₄ The method of claim 1,
Separating the solid lithium sulfate from the solid phase and separating lithium sulfate from the solid phase, and recovering the concentrated phosphoric acid as a remaining filtrate. The method of claim 5,
Wherein the recovered high concentration phosphoric acid is 40 wt% or more. The method of claim 6,
The recovered high concentration phosphoric acid,
Preparing a solid lithium phosphate as a slurry in a solvent; and reusing the lithium compound as a solvent. The method of claim 1,
Washing the separated solid phase lithium sulfate with DI water using a DI water. The method of claim 1,
Washing the separated solid phase lithium sulfate with an alcohol-based solvent, and washing water containing the alcohol-based solvent, washing the solid-phase lithium sulfate by recovering the alcohol-based solvent through distillation; A method for producing a lithium compound to be reused. The method of claim 1,
Washing the separated solid lithium sulfate with pure water (DI water)
Wherein the method comprises two or more washing steps. 11. The method of claim 10,
Washing the separated solid lithium sulfate,
obtaining n-th wash water by n-th wash;
Reusing a part of the n-th wash water as a solvent for preparing the wash water in the slurry state of the solid phosphoric acid lithium as a solvent; And
(N + 1) washing of the lithium sulfate by mixing the remaining balance of the n-th wash water and the additional pure water;
&Lt; / RTI &gt; 12. The method of claim 11,
Using the entire n + 1th washing water for n + 2nd washing;
And reusing part of the (n + 2) -th washing water by the (n + 2) -th washing as a solvent for preparing the washing water in the slurry state of the solid phosphoric acid lithium in the solvent; And
And n + 3-rinsing the lithium sulfate by mixing the remaining balance of the n + 2nd-order washing water and the additional pure water.

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