Method for improving yield of lithium solution through concentration and crystallization

Abstract

The present invention relates to a method for improving the yield of a lithium solution through concentration and crystallization, and, more specifically, to improving the yield of a lithium solution by reacting a low-concentration lithium solution with a fluorine compound so as to prepare lithium fluoride, and then concentrating and crystallizing a filtrate.

Description

Method for improving the yield of lithium solution through concentration and crystallization

[0001] The present invention relates to a method for improving the yield of a lithium solution through concentration and crystallization, and more specifically, to improving the yield of a lithium solution by reacting a low-concentration lithium solution with a fluorine compound to produce lithium fluoride, and then concentrating and crystallizing the filtrate.

[0002] In general, a method for producing lithium compounds such as lithium hydroxide or lithium carbonate from a lithium solution is to produce them through a hydration reaction or carbonation reaction of a high-concentration lithium solution.

[0003] These high-concentration lithium solutions are obtained from hard or semi-hard lithium minerals through a number of processes, including evaporative concentration, thermal concentration, electrodialysis, and other chemical treatments.

[0004] In particular, a representative example of a chemical treatment method is a method of manufacturing an insoluble lithium compound by applying a precipitation method from a lithium solution, which converts it into a lithium phosphate compound (Li3PO4) with low solubility using phosphoric acid and then precipitates and separates it.

[0005] In addition, methods for precipitating and separating insoluble lithium-aluminum compounds, such as Li-Al LDH (layered double hydroxide, LiAl2(OH)7?2H2O), using aluminum compounds have been proposed.

[0006] In the process of manufacturing an insoluble lithium compound and concentrating a lithium solution through acid leaching or sulfation / water leaching, the concentration rate of the lithium solution differs depending on the solid / liquid ratio or reaction ratio, and the higher the lithium content per unit weight of the lithium compound, the more advantageous it is for concentration.

[0007] Among insoluble lithium compounds, lithium phosphate has a theoretical lithium content per unit weight of approximately 17.9%, lithium-aluminum compounds have a 2.8-3.2% lithium content, and lithium fluoride has a theoretical lithium content per unit weight of approximately 26.7%. Therefore, among insoluble lithium compounds, lithium fluoride has the highest lithium content per unit weight.

[0008] Therefore, it is very advantageous to concentrate lithium solution using lithium fluoride.

[0009] Meanwhile, Korean Intellectual Property Office Patent Publication No. 10-2242686 (April 21, 2021) discloses a method of preparing a low-concentration lithium solution, treating a fluorine compound to form a high-concentration lithium fluoride after precipitation / separation, and then producing a high-concentration lithium concentrate through a sulfur compound aqueous solution, sulfurization reaction, and acid leaching step, as described above.

[0010] In these documents, a precipitation / separation method is used after a fluorine compound reaction to form high-concentration lithium fluoride from a low-concentration lithium solution. However, since the precipitation / separation method also has certain limitations, the above-mentioned prior literature suggests that the filtrate is concentrated and recirculated to increase the yield.

[0011] However, specific technical details regarding the concentration and recycling process of the filtrate are not disclosed, and only the concentration and crystallization of the filtrate in the subsequent process (referring to the step of producing lithium hydroxide after producing a high-concentration lithium concentrate) are described. Therefore, the present invention aims to present specific technical details regarding the concentration and recycling of the filtrate after forming high-concentration lithium fluoride.

[0012] As described above, we propose a specific concentration and crystallization process for forming high-concentration insoluble lithium fluoride from a low-concentration lithium solution through a precipitation / separation method and concentrating and recycling the remaining solution (filtrate).

[0013] The problems to be solved by the present invention are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the description below.

[0014] In order to solve the above problem, according to one aspect of the present invention, a method for improving the yield of a lithium solution through concentration and crystallization is disclosed, including: (S1) a step of adding a fluorine compound as a precipitant to a low-concentration lithium solution, precipitating and separating the fluorine compound to produce a high-concentration insoluble lithium fluoride (LiF); (S2) a step of evaporating or heating a first residual liquid remaining after producing the high-concentration lithium fluoride; (S3) a step of separating a precipitated solid material from a second residual liquid remaining after evaporation or heating and mixing the solid material with an organic solvent; (S4) a step of filtering the organic solvent mixture; and (S5) a step of mixing an unfiltered insoluble material with the low-concentration lithium solution.

[0015] A method for improving the yield of a lithium solution through concentration and crystallization is disclosed, characterized in that the low-concentration lithium solution is a solution of one or more lithium compounds selected from the group consisting of LiOH, LiCl, LiBr, Li2CO3, Li2SO4, Li3PO4, and LiAl(Si2O5)2.

[0016] The present invention discloses a method for improving the yield of a lithium solution through concentration and crystallization, wherein the fluorine compound comprises at least one selected from the group consisting of sodium fluoride (NaF), ammonium fluoride (NH4F), potassium fluoride (KF), ferrous fluoride (FeF2), ferric fluoride (FeF3), aluminum fluoride (AlF3), and hydrogen fluoride (HF), and the shape of the fluorine compound comprises a powder, a solution, or a slurry.

[0017] The present invention discloses a method for improving the yield of a lithium solution through concentration and crystallization, characterized in that the high-concentration lithium concentrate contains lithium ions, fluorine ions, sulfate ions, or metal ions as ionic components.

[0018] A method for improving the yield of a lithium solution through concentration and crystallization is disclosed, characterized in that, after the above step S2, (S21) a step of capturing and cooling a vaporized substance by evaporation or heating to obtain a condensate; and (S22) a step of re-introducing the condensate into the step S2; wherein the steps S21 and S22 are performed at least once.

[0019] The above step S3 further includes a step of (S31) mixing a third residual liquid after separating the solid material precipitated from the second residual liquid with the condensate; and a step of (S32) injecting a mixed solution of the third residual liquid and the condensate into the low-concentration lithium solution or into the first residual liquid. The present invention discloses a method for improving the yield of a lithium solution through concentration and crystallization.

[0020] The above step S3 discloses a method for improving the yield of a lithium solution through concentration and crystallization, characterized in that it includes performing the process using organic solvents having different solubilities of the precipitated solid components.

[0021] The above step S4 discloses a method for improving the yield of a lithium solution through concentration and crystallization, characterized in that the organic solvent mixture is divided into soluble and insoluble substances and only the insoluble substances are collected by a filter device.

[0022] A method for improving the yield of a lithium solution through concentration and crystallization is disclosed, characterized in that after the above step S4, (S41) a step of collecting a fourth residual liquid consisting of an available substance that has passed the organic solvent mixture through a filter device; and (S42) a step of introducing the fourth residual liquid into the low-concentration lithium solution or into the first residual liquid.

[0023] According to the present invention, a specific concentration and crystallization process can be performed to form a high-concentration insoluble lithium fluoride from a low-concentration lithium solution through a precipitation / separation method and to concentrate and recycle the remaining solution (filtrate).

[0024] The effects of the present invention are not limited to the effects described above, and should be understood to include all effects that can be inferred from the detailed description of the present invention or the composition of the invention described in the claims.

[0025] Figure 1 is a front-end process flow diagram in a method for producing a high-concentration lithium concentrate according to one embodiment of the present invention.

[0026] Figure 2 is a flow chart of the entire process of evaporation / heating concentration and dissolution / filtration using an organic solvent, and schematically illustrates the process of recycling the residual liquid in each process.

[0027] Figure 3 is a schematic diagram showing the entire flow chart of the evaporation / heating concentration process.

[0028] Figure 4 is a schematic diagram showing the entire flow of the concentrated supernatant through the dissolution and filtration process using an organic solvent.

[0029] Hereinafter, a preferred embodiment according to the present invention will be described in detail with reference to the attached drawings.

[0030] The advantages and features of the present invention and the method for achieving them will become clear with reference to the embodiments described in detail below together with the attached drawings.

[0031] However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms, and these embodiments are provided only to make the disclosure of the present invention complete and to fully inform a person having ordinary skill in the art to which the present invention pertains of the scope of the invention, and the present invention is defined only by the scope of the claims.

[0032] In addition, when describing the present invention, if it is determined that related known technologies, etc. may obscure the gist of the present invention, a detailed description thereof will be omitted.

[0033] Hereinafter, the present invention will be described in detail.

[0034] Summary of the present invention

[0035] According to the present invention, a method for improving the yield of a lithium solution through concentration and crystallization is disclosed, comprising: (S1) a step of adding a fluorine compound as a precipitant to a low-concentration lithium solution, precipitating and separating the fluorine compound to produce a high-concentration insoluble lithium fluoride (LiF); (S2) a step of evaporating or heating a first residual liquid remaining after producing the high-concentration lithium fluoride; (S3) a step of separating a precipitated solid material from a second residual liquid remaining after evaporation or heating and mixing the solid material with an organic solvent; (S4) a step of filtering the organic solvent mixture; and (S5) a step of mixing an unfiltered insoluble material with the low-concentration lithium solution.

[0036] In other words, the present invention comprises the steps of adding a fluorine compound as a precipitant to a low-concentration lithium solution, precipitating and separating the fluorine compound to produce a high-concentration insoluble lithium compound, lithium fluoride (LiF); and then concentrating and recycling the filtrate and adding it to a low-concentration lithium solution, thereby recovering lithium ions from the filtrate, thereby recovering discarded resources, and improving the yield of lithium fluoride and, further, the yield of the lithium solution.

[0037] In light of the disclosure in the prior art, it may seem like a method to directly inject the filtrate into a low-concentration lithium solution, but in this case, the lithium recovered from the filtrate is relatively small. Therefore, a separate concentration process is used to concentrate the lithium in the filtrate and then inject it back into the lithium solution to facilitate conversion into lithium fluoride. Of course, it is not limited to this from the perspective of resource recovery and yield improvement, but it can also be said that the technical significance of the present invention is in itself a method for recovering lithium as a simple method for treating the filtrate after the reaction.

[0038] Step of forming high-concentration lithium fluoride by precipitation / separation after reaction with fluorine compounds from low-concentration lithium solution

[0039] In the above outline, it refers to a step of adding a fluorine compound as a precipitant to a low-concentration lithium solution, precipitating and separating it, and manufacturing lithium fluoride (LiF), an insoluble lithium compound, at a high concentration.

[0040] At this time, the low-concentration lithium solution is a solution of one or more lithium compounds selected from the group consisting of LiOH, LiCl, LiBr, Li2CO3, Li2SO4, Li3PO4, and LiAl(Si2O5)2. However, the present invention is not limited thereto, but experiments were conducted in the extension of the prior invention, and the components included in the low-concentration lithium solution were made the same.

[0041] Next, the fluorine compound includes at least one selected from the group consisting of sodium fluoride (NaF), ammonium fluoride (NH4F), potassium fluoride (KF), ferrous fluoride (FeF2), ferric fluoride (FeF3), aluminum fluoride (AlF3), and hydrogen fluoride (HF). In addition, the shape of the fluorine compound may be characterized by including a powder, a solution, or a slurry. However, the present invention is not limited thereto, but experiments were conducted in the extension of the prior art, and the components included in the low-concentration lithium solution were made to be the same.

[0042] This relates to the front-end process among the processes disclosed in the above-mentioned prior literature, and in particular, a precipitation / separation method is used after a fluorine compound reaction to create a high-concentration lithium solution from a low-concentration lithium solution.

[0043] However, since there is a limit to the yield even in the case of the precipitation / separation method, the above prior literature suggests that the yield is increased by forming high-concentration lithium fluoride, concentrating the filtrate, and then recirculating it.

[0044] This description may be understood as meaning that the residue is directly added to a low-concentration lithium solution and the same reaction and process is performed again, but it is also possible that a separate concentration process / process is performed instead.

[0045] In particular, in the latter case, specific technical details are not disclosed, and only the subsequent process disclosed in the prior art (concentration and crystallization are described in the process of obtaining lithium hydroxide from a high-concentration lithium concentrate) is briefly presented. Therefore, the present inventors decide to disclose a separate concentration process for the filtrate after obtaining high-concentration lithium fluoride from a low-concentration lithium solution.

[0046] Concentration and recirculation stage of the filtrate

[0047] The present invention relates to a process for concentrating and recycling such a filtrate, and more specifically, discloses an evaporation / heating process, a precipitation process, a mixing process of a solid component (meaning a precipitated component) and an organic solvent, a process for filtering an organic solvent mixture, or a process for mixing an unfiltered solid substance back into a low-concentration lithium solution, etc., thereby recovering residual lithium remaining in the filtrate and increasing the yield of lithium fluoride and, further, the production yield of a lithium solution that can be used as a valuable metal.

[0048] Evaporation / heating concentration step

[0049] First, a step of manufacturing the high-concentration lithium fluoride and evaporating / heating the remaining residue (for convenience of explanation, referred to as “first residue” in the specific description paragraph of the present invention) is initiated.

[0050] Evaporating / heating the first residual liquid may be accomplished by placing the first residual liquid in a reservoir (container) and drying it in a natural state or under hot air conditions to evaporate the liquid component, or by artificially heating the first residual liquid to vaporize the liquid component.

[0051] The vaporized (gaseous substance) from the above-mentioned first residue can be captured and recycled. For example, a membrane can be placed over a reservoir (container), or a cooling passage can be installed so that the vaporized substance is captured and liquefied as it passes through the cooling passage, thereby recycling the vaporized substance. The substance obtained by liquefying the gaseous substance here is called condensate, and the condensate can be recycled through the evaporation / heating process at least once.

[0052] The first residue is evaporated / heated and the remaining substance is called the second residue, and some of the substances in the first residue are precipitated as solid components, and the second residue and the precipitated solid components can be recycled.

[0053] More specifically, the process of evaporation / heat concentration may be described as follows: a step of adjusting the pH by adding acid to the first residue; a step of heating to increase the temperature at atmospheric pressure or under reduced pressure; a step of continuously heating and maintaining the temperature until 80 to 97.5% of the volume of the first residue is vaporized; a step of stopping the heating when 2.5 to 20% of the volume of the first residue remains and gradually cooling to obtain a second residue; a step of collecting and liquefying gaseous components generated during the heating, temperature increase, and temperature maintenance processes to collect condensate; a step of separating and obtaining a solid substance from the second residue; a step of mixing a mixed solution of a third residue from which a solid substance is separated from the second residue and the condensate with the first residue and recycling the mixed solution;

[0054] The step of adjusting the pH by adding acid to the first residual solution is described.

[0055] The above first residual solution becomes basic - particularly strongly basic - due to lithium hydroxide or sodium hydroxide, due to the residual substances (including lithium ions, hydroxyl ions, sodium ions, fluoride ions, etc.) remaining after insoluble lithium fluoride (LiF) is precipitated / separated.

[0056] Here, acid is added to adjust the pH to make it weakly basic or close to neutral. At this time, the pH of the first residual solution and the pH of the product that has undergone a neutralization reaction due to the addition of acid cannot be known exactly, and it may be difficult to measure the pH each time, so an indicator can be added to indicate that a neutral state has been reached more simply, and since it is not necessary to know the exact pH value, it is sufficient to only read the general pH with the indicator rather than measuring the pH each time.

[0057] Next, the step of heating and temperature raising at atmospheric pressure is described.

[0058] When the pH-adjusted first residual liquid is heated at atmospheric pressure to increase temperature, evaporation or vaporization may occur. Since effective substances (e.g., lithium ions) may also be dissolved and separated from these components, a membrane or a separate cooling device is used to capture the gaseous components and undergo a liquefaction process to obtain condensate.

[0059] However, it is not limited to the above explanation, and it is of course possible to obtain condensate by evaporating / vaporizing at different boiling points for each component under normal pressure, pressurization, or depressurization depending on the components of the first residual liquid.

[0060] The first residual liquid is continuously heated to maintain the temperature so that the liquid component among the residual components can evaporate / vaporize. Thereafter, when the remaining volume of the first residual liquid is 2.5 to 20% of the initial volume, the heating is stopped, and the evaporated / vaporized liquid remaining in the second residual liquid is obtained.

[0061] In the second residual liquid, some of the components present in the first residual liquid may be precipitated during the heating process, and a third residual liquid may be obtained as the precipitated solid substance and the liquid substance removed / separated from it.

[0062] At this time, it is possible to heat completely so that no liquid component remains. However, this can cause soot to form on the precipitate or cause unnecessary reactions, which can be a nuisance. Therefore, heating is stopped and cooling is performed so that a small amount of liquid component remains. However, during this process, evaporation / vaporization continues due to the residual heat remaining until cooling begins after heating is stopped.

[0063] Next, the third residual liquid (i.e., the liquid component remaining after the solid component is precipitated from the second residual liquid) and the condensate are mixed with the first residual liquid again to circulate the evaporation / heating concentration process, thereby improving the yield of the precipitate in the evaporation / heating concentration process.

[0064] Alternatively, the third residual liquid and the condensate may be mixed and directly mixed into a low-concentration lithium solution to cause the residual lithium to react with a fluorine compound, thereby forming insoluble lithium fluoride, thereby diversifying the method of recovering lithium in addition to evaporation / heat concentration.

[0065] In addition, as the mixed solution of the third residue and condensate is reintroduced into the first residue, the pH immediately before the evaporation / heating concentration process gradually changes to weakly alkaline or neutral, so that the amount of acid input for the initial neutralization process can be reduced, thereby increasing economic efficiency.

[0066] Filtration and concentration steps based on differences in solubility in organic solvents

[0067] Meanwhile, a step of separating a solid component, a precipitate, from the second residue obtained by evaporating / heating the first residue and then mixing the separated precipitate with an organic solvent (i.e., generating an organic solvent mixture) is performed.

[0068] The precipitate, which is a solid component precipitated in the above evaporation / heating concentration step, is a polar substance formed by the combination of ions. In organic solvents, it has relatively low solubility compared to water, and since it contains various substances, it can be divided into those that are relatively soluble and those that are less soluble due to the difference in solubility between each substance.

[0069] That is, even if it is a polar substance, those with high solubility in an organic solvent will dissolve, but those with low solubility will remain in the organic solvent as a solid or with very little solubility.

[0070] For example, lithium hydroxide is known to be very soluble in ethanol, with an approximate solubility of 108 g / 100 ml, sodium fluoride is known to be soluble in ethanol, but its solubility is 4.5 g / 100 ml, and neither sodium hydroxide nor lithium fluoride is known to be very soluble in ethanol.

[0071] In this way, when the precipitate obtained through the evaporation / heating concentration process is mixed with an organic solvent, the substance is divided into soluble substances and insoluble substances depending on the solubility in the solvent.

[0072] Next, the step of filtering the organic solvent mixture separates insoluble substances from soluble substances. That is, soluble substances pass through the filter as is and become the fourth residue, while insoluble substances do not pass through the filter and are separated.

[0073] Here, the unfiltered components, i.e., substances that do not pass through the filter due to low solubility, are separated / dried and obtained in powder form.

[0074] The above insoluble material in powder form can be directly added to a low-concentration lithium solution, and after a reaction with a fluorine compound, etc., lithium can be recovered, and then added to the first residual solution to cycle the above process again.

[0075] Alternatively, the insoluble substances in powder form can be further classified into dissolved and insoluble substances based on differences in their solubility in water. In other words, insoluble substances with low solubility in organic solvents and thus insoluble may have high solubility in water and thus become soluble substances, allowing for separation.

[0076] For example, when the precipitate obtained in the evaporation / heating concentration step is mixed with ethanol, sodium hydroxide and lithium fluoride, which are hardly soluble in ethanol, remain in the solid phase and are not filtered, lithium hydroxide is dissolved in ethanol and is filtered, and sodium fluoride is partially soluble in ethanol, so some of it is dissolved, and the rest is insoluble and remains in the solid phase and is not filtered.

[0077] Here, the solid sodium hydroxide, lithium fluoride, and some of the sodium fluoride, which are insoluble substances that have not been dissolved or filtered, are separated / dried to obtain them in powder form, and then dissolved in water again. The sodium hydroxide and sodium fluoride dissolve well in water, but the lithium fluoride is insoluble and does not dissolve well and remains in a solid state. Therefore, only the lithium fluoride is separated and used, and the sodium hydroxide and sodium fluoride that are well dissolved in water can be added to a low-concentration lithium solution and used again as raw materials.

[0078] Meanwhile, the above example may not dissolve well in either polar organic solvents like ethanol or non-polar organic solvents like hexane. Therefore, when selecting an organic solvent, one should select one with a difference in solubility.

[0079] Concentration, recirculation, and solvent extraction of the residual solution after filtration

[0080] The fourth residual liquid is dissolved in the organic solvent mixture and passed through the filter, and it can be seen that the fourth residual liquid contains soluble substances in the organic solvent.

[0081] For example, in the case of an ethanol mixture, lithium hydroxide and some of sodium fluoride can be said to be the main substances (of course, lithium fluoride can continue to be produced during this process, and lithium fluoride has very low solubility in ethanol, so it forms a solid phase and cannot be filtered out, so it can be filtered out).

[0082] The fourth residue can be reintroduced into the first residue to undergo the evaporation / heating concentration step (3.1), or can be recycled by mixing it with a low-concentration lithium solution, and a process for removing the organic solvent before injection, or a process for fractional extraction according to the density and polarity of the solvent by mixing it with water, can be added to remove or minimize the organic solvent before reintroduction. Through this, components such as valuable metals remaining in the fourth residue can be recovered, thereby increasing the yield.

[0083] Experimental example

[0084] 4.1. Formation of lithium fluoride from low-concentration lithium aqueous solution (Li(OH)) and fluorine compound (NaF), etc.

[0085] With reference to prior art patent No. 10-2242686, lithium fluoride is obtained by reacting 300 ml of lithium hydroxide solution (Li concentration 1000 ppm) and 50 ml of sodium fluoride slurry at a stirring speed of 300 rpm for 1 day. As a result, the lithium ion mobility and its recovery rate vary depending on the molar ratio of lithium and fluorine (see Table 2 of the prior art patent).

[0086] As a result of the reaction between lithium hydroxide and sodium fluoride, it can be expected that lithium fluoride will be produced as a precipitate, and the remainder will be hydroxide ions, lithium ions, fluoride ions, and sodium ions.

[0087] Here, a filtrate ("first residue") from which lithium fluoride was removed was obtained. However, when the molar ratio of lithium and fluorine was 1:1, the recovery rate of lithium contained in the reactant was the lowest as lithium fluoride was generated. Therefore, it was judged to be suitable for confirming the lithium recovery rate of the filtrate, and several experiments were conducted based on this.

[0088] However, the volume of the first residual liquid was not significantly different from the volume obtained by simply adding the initial reactants, and even if lithium fluoride was produced, the volume of the first residual liquid as a product was not significantly different from the initial volume because the volume of the initial reactants was small.

[0089] Lithium hydroxide solution (300 ml) + sodium fluoride slurry (50 ml) Sample number Molar ratio Li ion concentration (ppm) (Recovery rate, %) First residual solution #1 Li:F = 1:1618.600 (38.714) Not significantly different from the initial volume (350 ml) #2620.192 (38.813) #3616.879 (38.606)

[0090] 4.2. Evaporation / heating concentration of the first residue

[0091] Phenolphthalein was added as an indicator to the first residue, and the pink color confirmed its basicity. Then, hydrofluoric acid (HF), a weak acid, was added, and titration was continued until the color changed (phenolphthalein becomes colorless when neutralized).

[0092] The amount of hydrofluoric acid (HF) added to titrate the first residue was very small, so that there was almost no change in volume before and after the titration.

[0093] That is, even if lithium hydroxide is a strong base and a precipitate is formed by lithium fluoride, the product remains a very strong base and may be dangerous during handling or evaporation / heating concentration. Therefore, hydrofluoric acid (HF) was selected as an acid that can neutralize it without inducing unnecessary reactions and was titrated.

[0094] Next, the second residue was obtained by heating under atmospheric pressure and going through a temperature-raising process to evaporate / heat the liquid component from the first residue as much as possible, but to an extent that the volume was 10% of the initial volume (the volume of the first residue and after adding acid), and at the same time, the evaporated and vaporized portion was captured during this process and liquefied through a cooler to obtain a condensate. In addition, a third residue was also obtained by separating the precipitate from the second residue.

[0095] [Table 2] summarizes the initial volume, the volume of each of the second residual liquid and the condensate, and the amount of precipitate in this process, and [Table 3] analyzes the concentration of lithium remaining after mixing the second residual liquid and the condensate using ICP-OES.

[0096] Sample numberInitial volume (ml)Second residual liquid (ml)Condensate (ml)Precipitate (g)#1350ml around (slight difference)8.75ml (97.5% heating / evaporation)330ml4.87g#217.5ml (95% heating / evaporation)311ml3.45g#335.0ml (90% heating / evaporation)305ml1.23g

[0097] Sample number concentration (%) #118.56 #218.23 #317.89

[0098] At this time, the condensate and the third residual liquid were mixed, and samples #1 and #2 were added to the low-concentration lithium solution, and sample #3 was added to the first residual liquid for recycling. It was confirmed that the low-concentration lithium solution and the first residual liquid had a relatively higher concentration than the initial lithium concentration due to recycling (ICP-OES analysis).

[0099] 4.3. Dissolution of precipitates using organic solvents (ethanol)

[0100] The precipitate obtained during the evaporation / heat concentration process was dissolved in ethanol. Although lithium hydroxide, sodium fluoride, sodium hydroxide, and lithium fluoride were selected due to their differences in solubility in ethanol, the solvent is not limited to these, and the solvent may be selected based on the solubility of the ions remaining in the solution.

[0101] Ethanol was continuously added until the volume exceeding the maximum dissolution of the precipitate reached a sufficiently saturated solution. The ethanol solution was then filtered to separate insoluble and soluble substances using a filter, and the insoluble substances were dried and powdered.

[0102] At this time, the volume of each ethanol solution, the insoluble substances filtered by the filter device, dried and powdered, and the weight are summarized below [Table 4].

[0103] Sample number Ethanol solution (ml) Insoluble substance powder (g) #150.12 #250.07 #350.03

[0104] The above insoluble material powder was directly added to a low-concentration lithium solution.

[0105] Next, among the fourth residual solution that passed through the filter, samples #1 and 2 were directly added to the low-concentration lithium solution and #3 was recycled into the first residual solution. It was confirmed that the low-concentration lithium solution and the first residual solution had relatively higher lithium concentrations than the initial lithium concentration due to recycling (ICP-OES analysis).

[0106] Although specific examples of a method for improving the yield of a lithium solution through concentration and crystallization according to the present invention have been described so far, it is obvious that various modifications are possible within the scope of the present invention.

[0107] Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the claims described below but also by equivalents of the claims.

[0108] That is, it should be understood that the above-described embodiments are exemplary in all respects and not restrictive, and the scope of the present invention is indicated by the claims to be described later rather than the detailed description, and all changes or modified forms derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present invention.

Claims

1. (S1) A step of adding a fluorine compound as a precipitant to a low-concentration lithium solution, precipitating and separating the fluorine compound, and manufacturing a high-concentration insoluble lithium compound, lithium fluoride (LiF); (S2) A step of evaporating or heating the first residual liquid remaining after producing the high-concentration lithium fluoride; (S3) A step of separating the solid material precipitated from the second residual liquid remaining after evaporation or heating and mixing it with an organic solvent; (S4) a step of filtering the organic solvent mixture; and (S5) A step of mixing unfiltered insoluble material into the low concentration lithium solution; including, Method for improving the yield of lithium solution through concentration and crystallization.

2. In paragraph 1, The above low concentration lithium solution is characterized in that it is a solution of one or more lithium compounds selected from the group consisting of LiOH, LiCl, LiBr, Li2CO3, Li2SO4, Li3PO4, and LiAl(Si2O5)2. Method for improving the yield of lithium solution through concentration and crystallization.

3. In paragraph 1, The above fluorine compound includes at least one selected from the group consisting of sodium fluoride (NaF), ammonium fluoride (NH4F), potassium fluoride (KF), ferrous fluoride (FeF2), ferric fluoride (FeF3), aluminum fluoride (AlF3), and hydrogen fluoride (HF). The form of the above fluorine compound is characterized by including a powder, solution or slurry. Method for improving the yield of lithium solution through concentration and crystallization.

4. In paragraph 1, The above high concentration lithium concentrate is characterized in that it contains lithium ions, fluorine ions, sulfate ions, or metal ions as ionic components. Method for improving the yield of lithium solution through concentration and crystallization.

5. In paragraph 1, After the above S2 step, (S21) A step of capturing and cooling a substance vaporized by evaporation or heating to obtain condensate; and (S22) A step of re-injecting the condensate into the S2 step; The above steps S21 and S22 are characterized in that they are performed at least once. Method for improving the yield of lithium solution through concentration and crystallization.

6. In paragraph 5, The above S3 step is, (S31) A step of mixing the third residual liquid from which the solid material precipitated from the second residual liquid has been separated with the condensate; and (S32) characterized in that it further includes a step of injecting a mixed solution of the third residual liquid and the condensate into the low-concentration lithium solution or into the first residual liquid; Method for improving the yield of lithium solution through concentration and crystallization.

7. In paragraph 1, The above S3 step is, Characterized in that the solubility of the above-deposited solid component is carried out by an organic solvent with different solubility. Method for improving the yield of lithium solution through concentration and crystallization.

8. In paragraph 1, The above S4 step is, It is characterized in that the organic solvent mixture is divided into soluble and insoluble substances, and only the insoluble substances are collected by a filter device. Method for improving the yield of lithium solution through concentration and crystallization.

9. In paragraph 1, After the above S4 step, (S41) A step of collecting a fourth residual liquid consisting of soluble substances that have passed through a filter device through an organic solvent mixture; and (S42) characterized in that it further includes a step of adding the fourth residual solution to the low concentration lithium solution or adding it to the first residual solution; Method for improving the yield of lithium solution through concentration and crystallization.

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