KR20180026864A - Method for manufacturing lithium chloride and method for manufacturing lithium carbonate - Google Patents

Abstract

The present invention relates to a method for manufacturing a lithium chloride solution and a method for manufacturing lithium carbonate, comprising the following steps: manufacturing a mixture by mixing homogenously phosphate containing lithium and calcium chloride; manufacturing a product in which chloroapatite and lithium chloride are mixed by heating the mixture at a high temperature higher than 450°C; obtaining slurries which is a mixture of insoluble chloroapatite (CAp) and soluble lithium chloride by adding water to the product; and obtaining chloroapatite and a lithium chloride solution by solid-liquid separating the slurries. Moreover, the present invention provides a method for manufacturing lithium carbonate by adding sodium carbonate to the lithium chloride solution. The present invention can provide a method for manufacturing lithium carbonate in which the solution has a lithium concentration higher than 10000 ppm.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method for producing lithium chloride, and a method for producing lithium carbonate,

A process for producing lithium chloride and a process for producing lithium carbonate.

Recently, as electric vehicles and mobile devices are rapidly spreading, the demand for lithium used as an electrode material of a battery is gradually increasing. In particular, lithium carbonate is used as a raw material in the manufacture of batteries for electric vehicles. The following methods are known as methods for producing such lithium carbonate.

(1) Lithium is extracted from minerals containing about 1 to 1.5% of lithium, such as spodumene, petalite or lepidolite, and then reacted with CO ₂ to finally obtain lithium Thereby producing lithium carbonate.

However, in order to extract lithium from minerals, it is necessary to perform processes such as flotation, high-temperature heating, crushing, acid mixing, extraction, purification, concentration, and precipitation, so that the collection procedure is complicated, , There is a severe problem of environmental pollution by using strong acid in the process of extracting lithium.

(2) Lithium in brine containing lithium is directly used.

However, the concentration of lithium contained in the brine is about 0.3 to 1.5 g / L, and lithium contained in the brine is mainly extracted in the form of lithium carbonate by adding CO ₂ under pressure. The solubility of the lithium carbonate is 0 ° C The amount of lithium carbonate in the brine is 1.59 to 7.95 g / L even if it is assumed that the lithium contained in the brine is converted into lithium carbonate at about 15.4 g / L and about 7.2 g / L at 100 DEG C, The solubility of lithium carbonate is lower than that of lithium carbonate, so that the amount of lithium carbonate precipitated is so small that the lithium recovery rate is very low.

Therefore, conventionally, in order to extract the salt-containing lithium into the form of lithium carbonate, the salt is pumped in the natural salt water and is spontaneously evaporated over the evaporation ponds of the open space for a long period of time of one year or more, Next, after impurities such as Mg, Ca and B are precipitated and removed, a method in which lithium is recovered by precipitating an amount of solubility of lithium carbonate or more has been used.

However, such a conventional method takes a long time to evaporate and concentrate the brine, resulting in low productivity. In the process of evaporating and concentrating the brine, lithium is precipitated in a salt form together with other impurities and lithium is lost. There was a problem with this limitation.

(3) On the other hand, the other hand, in the invention arc Korea Patent Publication No. 2013-0113287 reacting a lithium phosphate with a water-soluble agent reacting calcium hydroxide in the water, and then preparing a first aqueous lithium hydroxide solution, by blowing a CO ₂ gas produced lithium carbonate And how to do it. Since the solubility of lithium phosphate in water is as low as 0.39 g / L at 20 DEG C, lithium phosphate was dissolved in an acid in an ordinary method to leach lithium ions. However, in this patent, calcium hydroxide, which is a water- By direct reaction, it was tried to obtain lithium ion in the form of lithium hydroxide aqueous solution through reaction in an aqueous solution, without any additional acid treatment.

However, in this method, the reaction rate of calcium hydroxide with lithium phosphate is not fast, and it takes a long time to obtain lithium ions to an economical level of concentration. When the reaction time of calcium hydroxide and lithium phosphate is limited in view of economical efficiency, there is a problem that the concentration of lithium ions in the aqueous solution of lithium hydroxide obtained is low and the recovery rate of lithium ions is not high. Concretely, since the reaction rate of calcium hydroxide with lithium phosphate is not sufficiently fast, it is possible to recover lithium ions at a low concentration of about 5,000 ppm within an economically acceptable reaction time. Accordingly, it is necessary to concentrate the solution at a high concentration before the production of lithium carbonate in the subsequent step, which requires additional steps for concentration and energy consumption due to evaporation.

(4) As another known technology, CN201210404254.0 discloses a method for producing lithium chloride from a phosphoric acid-lithium-iron compound which is a cathode material of a lithium battery containing lithium. In this patent, a solution containing iron phosphate, lithium phosphate, and iron chloride is obtained by leaching a phosphoric acid-lithium-iron compound with hydrochloric acid and the constituents are leached into a solution, and the pH of the solution is increased to 2.0-2.5, After the pH was adjusted to 6.0-7.0 by adding an alkali substance to the filtrate, CaCl ₂ was added to precipitate and remove calcium phosphate, and the remaining filtrate was concentrated by evaporation to precipitate LiCl crystals, followed by filtration The product LiCl is obtained.

However, in the present invention, lithium is leached from the lithium-containing phosphate by using a strong acid, so it is not environmentally friendly and the chemical acid needs to be neutralized.

In order to solve the above-mentioned problems, one embodiment of the present invention is to provide a process for producing an environmentally friendly lithium chloride aqueous solution capable of extracting lithium ions at a high concentration from a lithium-containing phosphate in a short time.

And a method for economically preparing lithium carbonate from an aqueous solution of lithium chloride.

One embodiment of the present invention is a process for producing a mixture (hereinafter referred to as Mixture-1) (hereinafter referred to as Step-1) by uniformly mixing calcium chloride with a phosphate containing lithium; And a step (hereinafter referred to as step 2) of heating the mixture 1 at a temperature of 450 ° C or higher to prepare a product (hereinafter referred to as product-1) in which chloroapatite and lithium chloride are mixed; And adding water to the product-1 to obtain a slurry (hereafter referred to as slurry-1) which is a mixture of weakly soluble chloroapatite (CAp) and water-soluble lithium chloride (hereinafter referred to as step 3); And a step (hereinafter referred to as step 4) of obtaining aqueous solution of lithium chloride (hereinafter referred to as aqueous solution-1) of chloropatite (hereinafter referred to as CAp-1) and slurry-1 by solid-liquid separation .

In the step-1, the lithium-containing phosphate may be prepared directly from lithium in brine.

In step-1, the lithium-containing phosphate may be prepared directly from the lithium of the waste battery.

In step-1, the lithium-containing phosphate may be prepared directly from ores such as spodumene, petalite or lepidolite.

In the step-1, the charged lithium containing phosphate may be in a dry powder state, a filter cake containing water, or water may be added so as to artificially contain water three times or less than the weight of the phosphate You can prepare.

In step-1, the mixture of lithium chloride-containing phosphate and calcium chloride may be mixed in a mixer.

In the step-1, the amount of the introduced calcium chloride may be 1.25 times or more and 2.0 times or less as much as the lithium phosphate based on the molar amount.

In the step-2, heating the mixture-1 may heat the mixture to a temperature of 450 ° C or higher and 850 ° C or lower.

In the step-2, the heating time of the mixture-1 may be from 30 minutes to 5 hours after the mixture reaches 450 ° C or higher.

In the step-2, the product-1 may contain, in addition to the chloropatite and the lithium chloride, some of the calcium chloride of the step-1 in an unreacted state, and some of the calcium chloride of the step- Can be included in the reaction state.

In Step-2, the product-1 may contain lithium chloride by an amount of the lithium-containing phosphate reacted with calcium chloride in an amount of 80% or more.

In step-2, a heating method such as heating the container in a box furnace or tunnel furnace, or placing the container in a bath to heat the container to efficiently heat the mixture-1 contained in the container may be included.

In the step-2, the mixture may be stirred during heating so that the mixture-1 contained in the vessel can be heated evenly and simultaneously, or the mixture may be stirred in a manner such that heating is temporarily stopped, stirring is continued, Process.

In the step-3, the amount of water added to the product-1 can be determined so that the concentration of lithium ions becomes 10,000 ppm or more and 200,000 ppm or less when the lithium chloride is dissolved in water in the product-1.

In Step 4, in order to recover lithium chloride remaining in chloroapatite-1 in the filtration process, water is added to chloroapatite-1, washed with water and filtered again to obtain a filtrate containing lithium chloride (hereinafter referred to as " 1a) can be obtained, and the filtrate-1 a can be mixed with the filtrate 1, and this process can be carried out at least once. And the amount of water added per wash may be 0.5 to 5 times the weight of CAp-1 solids.

In the step-4, a method may be employed in which lithium chloride crystals are precipitated by evaporating aqueous solution-1 and subjected to solid-liquid separation to obtain lithium chloride as a solid.

The step 4 may include a step of adding sulfuric acid to the aqueous solution-1 to precipitate calcium ions present in the aqueous solution-1 resulting from the calcium chloride introduced in the step-1 and precipitating the calcium sulfate into calcium sulfate, have. And then adding sodium hydroxide or potassium hydroxide to neutralize the acidified solution.

In Step 4, calcium ions present in the aqueous solution-1 originated from the calcium chloride introduced in the step-1 are introduced into the aqueous solution-1 by the addition of strong alkali such as sodium hydroxide or potassium hydroxide, precipitated with calcium hydroxide, And removing the catalyst.

Step 4 includes a step of adding calcium carbonate present in the aqueous solution-1 derived from the calcium chloride introduced in the step-1 to sodium carbonate in the aqueous solution-1 to precipitate calcium carbonate, followed by filtration . The amount added is limited to the amount that calcium carbonate can preferentially precipitate.

Step-4 may include a step of adding insoluble gypsum and water-soluble phosphoric acid by adding sulfuric acid to CAp-1 obtained after filtration and then subjecting it to solid-liquid separation to obtain a gypsum and phosphoric acid solution. And recovering phosphoric acid remaining in the gypsum by washing the separated gypsum with water.

Another embodiment of the present invention is a method for preparing a lithium salt, comprising: preparing an aqueous lithium chloride solution; Sodium carbonate is added to the lithium chloride aqueous solution to precipitate lithium carbonate and filtrate to obtain solid lithium carbonate (hereinafter referred to as lithium carbonate-1) and a filtrate (hereinafter referred to as filtrate-2); Wherein the concentration of lithium ions in the lithium chloride aqueous solution is 10,000 ppm or more.

In preparing the lithium chloride aqueous solution of step 5, the lithium chloride aqueous solution may be prepared from the lithium chloride aqueous solution of the embodiment of the present invention.

In step 5, the obtained lithium carbonate-1 may be washed with water and filtered. The filtrate-2a obtained after washing with water may be combined with the filtrate-2, and the washing may be performed at least once .

Step 5 may further include the step of injecting a phosphorus supply material into the filtrate-2 to recover lithium phosphate to recover residual lithium ions in the filtrate-2.

In the step 5, the molar ratio of lithium ions in the lithium chloride aqueous solution to sodium ions in the sodium carbonate introduced (lithium ion: sodium ion) may be 1: 0.8 to 1: 1.2.

In step 5, the temperature of the reaction of introducing sodium carbonate into the lithium chloride aqueous solution to precipitate lithium carbonate may be 20 ° C or higher and 100 ° C or lower.

According to the method for producing an aqueous solution of lithium chloride according to an embodiment of the present invention, it is possible to produce a lithium chloride aqueous solution having a lithium ion concentration of 10,000 ppm or more and a high concentration of 60,000 ppm or more in a short period of time. Thus, before the production of lithium carbonate in the subsequent step, the amount of evaporation energy required for concentration of the lithium chloride aqueous solution is reduced, and a much larger amount of lithium chloride aqueous solution can be obtained in one treatment unit, thereby remarkably improving the economical efficiency .

Further, the method for producing an aqueous solution of lithium chloride according to an embodiment of the present invention is an environmentally friendly manufacturing method since it does not include an acid treatment step in the whole process.

In addition, according to the method for producing lithium carbonate according to an embodiment of the present invention, lithium carbonate can be produced economically and economically by a simple process.

1 is a process diagram according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail. However, it should be understood that the present invention is not limited thereto, and the present invention is only defined by the scope of the following claims.

Unless defined otherwise, all terms (including technical and scientific terms) used herein may be used in a sense commonly understood by one of ordinary skill in the art to which this invention belongs. 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 include plural forms unless the context clearly dictates otherwise.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a schematic block diagram of a method for producing lithium chloride aqueous solution and a method for producing lithium carbonate according to an embodiment of the present invention. FIG. However, the present invention is not limited thereto, and various modifications can be made without departing from the technical idea of the present invention.

Hereinafter, a method for producing lithium chloride aqueous solution and a method for producing lithium carbonate according to an embodiment of the present invention will be described with reference to FIG.

[Method for producing lithium chloride aqueous solution]

One embodiment of the present invention is a method for preparing a mixture (hereinafter referred to as " mixture-1 ") (hereinafter referred to as step-1) by uniformly mixing calcium phosphate with lithium phosphate. And a step (hereinafter referred to as step 2) of heating the mixture 1 at a temperature of 450 ° C or higher to prepare a product (hereinafter referred to as product-1) in which chloroapatite and lithium chloride are mixed; And adding water to the product to obtain a slurry (hereinafter referred to as slurry-1) which is a mixture of weakly soluble chloroapatite (CAp) and water-soluble lithium chloride (hereinafter referred to as step 3); And a step (hereinafter referred to as step 4) of obtaining aqueous solution of lithium chloride (hereinafter referred to as aqueous solution-1) of chloropatite (hereinafter referred to as CAp-1) and slurry-1 by solid-liquid separation .

This method is a method capable of producing a lithium chloride aqueous solution at a high concentration without any additional acid treatment. In addition, in the method for producing lithium chloride according to one embodiment of the present invention, the reaction rate can be improved as compared with the conventional process.

Through the reaction of lithium phosphate and calcium chloride at a high temperature, CAp, which is a poorly soluble substance, and LiCl, which is water soluble, are produced.

[Reaction Scheme-1]

3Li ₃ PO ₄ + ₅ CaCl ₂ ? Ca ₅ (PO ₄ ) ₃ Cl + 9 LiCl

Reaction formula-1 is a reaction in which the free energy is thermodynamically reduced, so that the reaction on the left reacts with the product on the right, but the reaction is actively performed at a temperature of at least 450 ° C because of the activation energy.

In Reaction Equation-1, all of the reactants are in a solid state. At 450 ° C or higher, the reaction of Reaction Formula-1 starts to occur at a site where lithium phosphate and calcium chloride are in contact with each other. The reaction rate is fast because of the eutectic composition having a melting point of 475 ° C.

In order to increase the amount of the reaction of formula (1) to be produced at a time, for example, Mixture-1 may be introduced into the heating step by adding the reactant into a container having a volume of 1 m ³ or more. At this time, the heating method may be performed by heating in an industrialized box furnace or tunnel furnace. In order to transfer the heat transferred to the container to the mixture rapidly, the mixture is stirred during heating or the heating is temporarily stopped, Heating and reaction can be promoted by various methods such as stirring and stirring the mixture, and then feeding it into a heater. Heating in parallel with stirring has two effects. First, it can accelerate the rate of temperature rise of Mixture-1 inside the vessel and it acts to raise the temperature uniformly. Secondly, during the reaction of Scheme-1, as described above, a process-forming material having a melting point of 475 DEG C may form droplets, which act to accelerate the reaction rate more rapidly by contacting the unreacted material .

In the present invention, the heating temperature of the mixture-1 for promoting the reaction formula-1 is limited to 450 ° C or more and 850 ° C or less. If the temperature is below 450 ° C, the reaction is delayed because the activation energy of Scheme-1 can not be overcome. Therefore, a temperature of at least 450 ° C is required. If the heating temperature is 850 DEG C or higher, evaporation of lithium chloride, which is a product of reaction formula-1, starts to occur and is lost as vapor. Reaction formula-1 shows that the higher the temperature, the faster the reaction, but the maximum temperature is limited to 850 ° C to suppress the evaporation loss of lithium chloride.

The time required for the reaction formula-1 is greatly influenced by the degree of mixing of the lithium-containing phosphate and calcium chloride. Thus, the time for heating the mixture-1 can be adjusted to match the subsequent process time, and can be adjusted within a range of 30 minutes to 5 hours after the mixture reaches 450 DEG C or higher. However, this is not necessarily limited to this range, and it may be made shorter or longer considering the rate of occurrence of lithium, the heating energy, and the productivity.

In order for Reaction Equation (1) to occur smoothly, it is desirable to mix lithium-containing phosphate with calcium chloride in a particle-by-particle basis. If the lithium-containing phosphate is in a fine powder state, it may be mixed with calcium chloride in a powder form and mixed for a sufficient time in a mixer. If the lithium-containing phosphate is faded with a small amount of water such as a filter cake, water Is added and mixed with calcium chloride. The mixer runs until the phosphate is separated into minute particles. If the water is insufficient, the filter cake is not melted and mixed. If the water is more than 3 times, the mixture is advantageous. However, since the water in the mixture-1 evaporates in the heating furnace and the energy input is increased, .

The reaction equation (1) determines the amount of reaction depending on the thermodynamic energy state between the reactant and the product. It is difficult to define the value of the thermodynamic free energy as one value because the reactant contains components other than lithium phosphate and calcium chloride and can change the compounding ratio of the raw material. However, at an ambient temperature of 450 ° C or higher, Is converted to lithium chloride.

In Equation (1), the equivalent amount of calcium chloride in Mixture-1 is 1.667 times the number of moles of lithium phosphate. In the present patent, the preferable addition amount of calcium chloride is limited to 0.7 times or more and 1.3 times or less the equivalence ratio of the reaction formula-1. The equivalent ratio of calcium chloride 0.7 times is the number of moles corresponding to 1.167 times the number of moles of lithium phosphate, and 1.3 times the equivalent ratio is the number of moles corresponding to 2.167 times the number of moles of lithium phosphate. Disadvantages ten thousand and one equivalent ratio of calcium chloride after the reaction is less than 0.7 times is that the content of Ca ^{2 +,} which acts as impurities in the aqueous solution is less advantageous -1, the scheme -1 reaction rate becomes low, so this decreases the recovery of lithium involved in most responses . The equivalent ratio is not less than 1.3-fold higher in the reaction formula-1 is the reaction rate increases, but the amount of lithium chloride is unreacted becomes the impurity content of Ca ^{2 +} in the aqueous solution of calcium chloride -1 increases with the increase, the cost of its removal becomes more .

In Scheme-1, both the reactant and the product are salts, which do not deviate to strong acids or strong alkalis when dissolved in water. Depending on the amount of impurities, the pH of the weak acid or weak alkali is shown.

After completion of the reaction by heating in Reaction Scheme-1, water is added to the product-1 to dissolve lithium chloride in an aqueous solution. Lithium chloride has a very high solubility of 69 to 128 g per 100 cc of water having a solubility of 0 to 100 ° C and a very high lithium ion content of 113,000 to 210,000 ppm. Thus, the amount of water to be added can be arbitrarily determined depending on the concentration of the desired aqueous solution. As described above, water is added to Product-1 to perform primary filtration to obtain aqueous solution-1, and solid CAp-1 is washed with water to obtain aqueous solution-1a and aqueous solution-1a can be added again to aqueous solution- The amount of water can be determined in consideration of the lithium ion concentration of the final aqueous solution-1. The weight of the liquid remaining in the solid CAp-1 depends on the filtration method, which is 0.1 to 0.5 times that of the solid CAp-1. Therefore, it is preferable to recover the liquid by adding water thereto and filtering again. Particularly, as the concentration of lithium chloride in aqueous solution-1 increases, it is preferable to wash CAp-1 with water in order to increase the recovery rate of lithium chloride. There are many ways to determine the amount of water and follow the existing method. However, in the present invention, the amount of the washing liquid is preferably 0.5 times or more and 5 times or less the CAp-1 mass. If it is less than 0.5 times, the recovery rate of the lithium ion is low because the washing liquid remains in the solid after filtration. If it is more than 5 times, the washing effect and the recovery of lithium ion are good, but the concentration of the filtrate becomes thin, It is inefficient.

As described above, the aqueous solution-1 can theoretically obtain the lithium ion concentration up to the solubility limit, and can easily be obtained at 40,000 ppm or more. If a precipitate of lithium chloride is prepared using aqueous solution-1, the solubility of lithium chloride can be easily reached even if the solution is slightly evaporated, so that precipitation can be facilitated. If sodium carbonate is added to aqueous solution-1 to precipitate lithium carbonate, it is not necessary to carry out a costly evaporation process.

On the other hand, the lithium phosphate may be in a form including other cation components. For example, when lithium in the lithium phosphate is derived from lithium in brine, the brine may contain cations such as calcium, magnesium, iron, potassium, sodium, chromium, lead, or cadmium in combination with lithium When a phosphorus-containing phosphorus-containing phosphorus-containing phosphorus-containing feed material is added thereto, lithium may be phosphorylated and precipitated in the form of lithium phosphate.

Here, lithium phosphate is a substance having a low solubility in water (~ 0.39 g / L) and can be extracted in the form of a slurry in the phosphorylation process. When lithium phosphate is extracted in this way, the lithium cation becomes an impurity, and impurity removal can be performed before, after, or both before and after the phosphorylation step in a manner generally known in the art.

When the lithium phosphate slurry is heated or naturally dried to obtain dried lithium phosphate powder, the lithium phosphate slurry is filtered to obtain lithium phosphate in a filter cake state .

However, even if the impurity removal step is not performed or the impurity removal step is carried out, the lithium phosphate may inevitably contain some cationic impurities as mentioned above.

[Removal of Unreacted Calcium Ion in Lithium Chloride Aqueous Solution]

Although not shown in FIG. 1, in order to use aqueous solution-1, which is an aqueous solution of lithium chloride prepared according to the above-described method for producing lithium chloride aqueous solution, as an actual use, it further includes a step of removing unreacted calcium ions remaining in aqueous solution- .

As described above, when the calcium chloride present in the mixture-1 does not completely react in the reaction formula-1 and remains in the aqueous solution-1, a large amount of Ca ^{2 +} ions may be present in the aqueous solution-1. When this lithium-chloride is precipitated by evaporating the aqueous solution-1 to obtain solid lithium chloride, the Ca ^{2 +} component is incorporated into the lithium chloride precipitate and the purity of the lithium chloride is lowered. When sodium carbonate is added to the aqueous solution-1 to obtain solid lithium carbonate, calcium carbonate precipitates preferentially to lithium carbonate and is mixed with lithium carbonate to lower the purity of lithium carbonate. In order to suppress this, the present invention provides a method for separating Ca ^{2 +} ions from the aqueous solution-1 by filtration by three methods.

First removing the Ca ^{2 +} ion in the aqueous solution is -1 method provides a method of precipitation with plaster (gypsum) the Ca ²⁺ was added to the sulfuric acid aqueous solution as shown in Reaction Scheme-2.

[Reaction Scheme-2]

Ca ^{2 +} _(aq) + H ₂ SO _{4 (aq)} + 2H ₂ O? CaSO ₄ .2H ₂ O _(S) + 2H ⁺

Precipitate CaSO ₄ · 2H ₂ O Almost all of the Ca ^{2 +} ions are precipitated out because the solubility in water is about 0.2 g / 100 cc-water. However, since the solution is acidic at this time, a method of neutralizing the reaction vessel with a solution with an alkali such as NaOH or KOH is proposed in order to suppress the corrosion of the reaction vessel and to make it environmentally friendly.

The present invention provides a method of adding the alkali in the Group 1 system, such as NaOH, KOH in the aqueous solution to an aqueous solution -1 -1 The second method of removing the Ca ^{2 +} ions. As the pH rises, the solubility of Ca (OH) ₂ decreases sharply, with a solubility of 0.008 mol at pH 13 and a low solubility of 0.06 g / 100 cc-water. Most of Ca ^{2 +} is precipitated as Ca (OH) ₂ and can be removed.

In the present invention, as a third method for removing Ca ^{2 +} ions in the aqueous solution-1, there is provided a method of adding sodium carbonate to the equivalent ratio of Ca ^{2 +} . Calcium carbonate is chemically more stable than lithium carbonate and precipitates preferentially. Carbonic anion CO ₃ ^2- most of the Ca ^{2 +} ions are precipitated as CaCO ₃ in the reaction formula-3.

[Reaction Scheme-3]

Ca ^{2 +} _(aq) + Na ₂ CO _{3 (aq)} → CaCO _{3 (S)} + 2 Na ⁺

Since the solubility of CaCO ₃ in water is very low at 0.0007 g / 100 cc-water, almost all the Ca ^{2 +} ions can be removed by adding sodium carbonate as much as the mole number of Ca ^{2 +} present in the solution.

Thus, by removing the Ca ^{2 +} ions in the aqueous solution-1 by the above three methods, when sodium carbonate is subsequently added to precipitate lithium carbonate, calcium carbonate can be prevented from being mixed with impurities.

[Recovery method of phosphoric acid]

In the present invention, there is provided a method of reacting CAp-1 obtained in the step-4 with sulfuric acid to obtain phosphoric acid and gypsum. Equation (4) is an industrial method of obtaining gypsum by adding sulfuric acid and water to the mineral apatite. In the present invention, a method for obtaining gypsum and a phosphoric acid having a high economic value is provided from the product produced in the step-4 according to the reaction formula-4. As shown in Scheme-4, the reaction of Scheme-4 can be rapidly performed by adding sulfuric acid and water corresponding to the equivalent ratio of CAp-1 and maintaining the temperature of the reaction system at 42.35 ° C or higher, which is the melting point of phosphoric acid. Since the HCl (g) gas generated in Scheme-4 is removed, it is possible to recover the economically valuable phosphate H ₃ PO ₄ by adding water after solid-liquid separation after the reaction of Scheme-4 is terminated.

[Reaction Scheme 4]

Ca ₅ (PO ₄ ) ₃ Cl + 5 H ₂ SO ₄ + 10 H ₂ O? 3 H ₃ PO ₄ + 5 CaSO ₄ .2H ₂ O _{(S )}

[Production method of lithium carbonate]

Another embodiment of the present invention is a method for preparing a lithium salt, comprising: preparing an aqueous lithium chloride solution; And adding sodium carbonate to the lithium chloride aqueous solution to precipitate lithium carbonate and filtrate it to obtain solid lithium carbonate (hereinafter referred to as lithium carbonate-1) and a filtrate (hereinafter referred to as filtrate-2) ; Wherein the concentration of lithium ions in the lithium chloride aqueous solution is 10,000 ppm or more.

Lithium carbonate can be precipitated from a lithium chloride aqueous solution having a lithium ion concentration of 10,000 ppm or more at a high concentration through the reaction of lithium chloride and sodium carbonate. Therefore, there is no need to further concentrate the lithium chloride aqueous solution to increase the concentration thereof, and thus lithium carbonate can be economically produced.

Soda ash may be used as a raw material of the sodium carbonate. Soda ash is about 98% or more of sodium carbonate and can be used as a raw material for sodium carbonate. However, it should be understood that other materials usable as a raw material of sodium carbonate may be used, but the present invention is not limited thereto.

The use of a high-pressure vessel becomes unnecessary compared with a conventional method of producing lithium carbonate using CO ₂ gas by precipitating lithium carbonate through reaction with lithium cations using a solid carbonate raw material. Thus, the facility can be made more compact. Therefore, the process cost can be remarkably reduced. In addition, as in the above-mentioned lithium chloride aqueous solution production method, since no acid or base sample is used even in the additional lithium carbonate production step, corrosion of equipment can be minimized and environmental pollution can be prevented.

The sodium carbonate may be added in such an amount that the molar ratio (lithium ion: sodium ion) of the lithium ion in the lithium chloride aqueous solution to the sodium ion of the sodium carbonate is 1: 0.8 to 1: 1.2. If the amount of sodium carbonate is too small, lithium carbonate may not sufficiently precipitate and the recovery rate of lithium may be decreased. If too much, the amount of precipitated lithium carbonate may increase, but the cost of sodium carbonate may increase. More specifically in an amount of 1: 0.9 to 1: 1.1.

The reaction temperature of the step of adding sodium carbonate to the lithium chloride aqueous solution to obtain the lithium carbonate and the filtrate may be 20 ° C or higher and 100 ° C or lower. When sodium carbonate is added to the aqueous solution of lithium chloride, lithium carbonate precipitates and exothermic reaction is caused to raise the temperature of the solution, so that the reaction temperature is not lower than 20 ° C and not higher than 100 ° C. If the reaction temperature is too low, the solubility of lithium carbonate increases and the recovery rate of lithium decreases. If the reaction temperature is too high, the solubility of lithium carbonate decreases and the recovery rate of lithium increases. However, Maintenance of the filtration apparatus may become difficult. Solubility of lithium carbonate in water is 20 ℃ 0.018 g / 100cc-water , and the 100 ℃ 0.010 g / 100cc-water , the concentration of Li ⁺ ions are respectively 1,249 ppm and 676 ppm.

At this time, in step-5, the temperature at the time of filtration may be 15 ° C or higher and 95 ° C or lower. The reason for limiting the temperature range in this way is that if the temperature is lower than 15 ° C, the viscosity of the slurry becomes higher and the filtration is not smooth. If the temperature is higher than 95 ° C, the energy input cost increases and the filtration equipment is difficult to operate.

In addition, impurities such as sodium chloride in the aqueous solution state may be present in the filter cake containing the filtered lithium carbonate. In order to remove this, lithium carbonate in which impurities are removed can be obtained through a solid-liquid separation step in which water is added as a solvent and washed and then filtered again. Washing and solid-liquid separation can be performed at least once or more and can be repeatedly carried out until the content of impurities is reduced to a desired level.

Alternatively, since lithium ions are dissolved in the obtained filtrates, they can be recovered as lithium phosphate by adding a salt containing phosphoric acid ions or phosphoric acid, and the recovered lithium phosphate-containing solution is again subjected to filtration and washing After removing the impurities, they can be recycled as lithium phosphate material.

Hereinafter, preferred embodiments of the present invention 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

Lithium phosphate and calcium chloride in powder form were prepared in an equivalent ratio according to the above reaction formula-1 so that the initial total amount of lithium was 4 kg.

The prepared lithium phosphate and calcium chloride were 22.24 kg and 35.53 kg, respectively (the amount of calcium chloride was 1.667 times that of lithium phosphate based on the molar amount), and these were put into a mixer and mixed for 30 minutes so that the two materials were well mixed.

Thereafter, the mixture was placed in a crucible, charged into a box furnace maintained at 650 ° C, and maintained for three hours. At this time, the crucible was taken out of the furnace every 30 minutes, and the mixture was stirred with a metal rod and charged again.

After 3 hours, the crucible was taken out from the furnace and air-cooled for 1 hour. Then, 50 liters of water was added thereto, and the mixture was well stirred with a metal rod.

Thereafter, the slurry was filtered through a filter press at a temperature of 65 캜 to obtain a filtrate-1. The volume of the filtrate-1 was 89.3 liters and the Li concentration was 34,000 ppm. The reaction rate of Li ₃ PO ₄ calculated from this reaction with CaCl ₂ and converted into lithium chloride was 85%. Then, 42.68 liters of water was added to the filter cake, stirred and mixed, and then filtered once to obtain a filtrate-1a. The final filtrate-1 after mixing the filtrate-1-a with the filtrate-1 had a volume of 132 liters and a lithium concentration of 25,200 ppm.

Thereafter, the temperature of the first filtrate was adjusted to 65 ° C, and 25.40 kg of sodium carbonate (Na ₂ CO ₃ ) was added to precipitate lithium carbonate. At this time, the amount of sodium carbonate added is an amount corresponding to a molar ratio (lithium ion: sodium ion) of lithium ions in the first filtrate to sodium ions of sodium carbonate to be added in a ratio of 1: 1. Thereafter, filter pressing was performed at 70 ° C to separate the solid lithium carbonate and the second filtrate.

Thereafter, the separated lithium carbonate was washed twice with 58.07 liters of water and again subjected to filter pressing, and dried to obtain 15.61 kg of lithium carbonate.

The amount of lithium in the product was 2.93 kg, which was a very high value corresponding to a yield of 73.2% at the initial charge of 4.0 kg.

On the other hand, after collecting the second filtrate and the washing solution of lithium carbonate, 3.10 kg of sodium phosphate was added thereto to recover 0.39 kg of lithium phosphate, which was 1.8% of the initial amount of 22.24 kg .

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 (11)

Mixing lithium phosphate and calcium chloride; And
Heating the mixture to obtain a product in which chloroapatite and lithium chloride are mixed by a solid phase reaction;
≪ / RTI >
The method according to claim 1,
Further comprising the step of adding a solvent to the product to obtain a slurry in which chlorapatite and water-soluble lithium chloride are mixed.
3. The method of claim 2,
Further comprising the step of solid-liquid separation of the slurry to obtain a chloropatite and an aqueous solution of lithium chloride.
The method according to claim 1,
Wherein the lithium phosphate is in a dry powder state, in a filter cake state containing water, or in a state in which water is added so as to contain water not more than three times the weight of lithium phosphate.
The method according to claim 1,
Wherein the heating temperature of the mixture is in the range of 450 to 850 degrees.
6. The method of claim 5,
Wherein the heating time of the mixture is maintained at 450 DEG C or more for 30 minutes to 5 hours or more.
The method of claim 3,
The method for producing lithium chloride according to claim 1, wherein water is added to the solid-liquid separated chloroapatite, and the water washing liquid is washed with water and then added to the lithium chloride aqueous solution.
The method of claim 3,
Wherein the lithium chloride aqueous solution is evaporated to precipitate lithium chloride crystals.
The method of claim 3,
Wherein at least one of sulfuric acid, sodium hydroxide, potassium hydroxide and sodium carbonate is added to the lithium chloride aqueous solution to precipitate unreacted calcium present in the aqueous solution.
Mixing lithium phosphate and calcium chloride;
Heating the mixture to obtain a product in which chloroapatite and lithium chloride are mixed by a solid phase reaction;
Adding a solvent to the product to obtain a slurry in which chlorapatite and water-soluble lithium chloride are mixed;
Separating the slurry by solid-liquid separation to obtain chloroapatite and lithium chloride aqueous solution; And
Wherein sodium carbonate is added to the lithium chloride aqueous solution to precipitate lithium carbonate.
11. The method of claim 10,
Separating the lithium carbonate by solid-liquid separation, and adding phosphate to the remaining filtrate to obtain lithium phosphate.

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