Method for extracting lithium, method for preparing lithium carbonate and method for preparing lithium hydroxide

Abstract

The present invention provides a method for extracting lithium, which comprises adding a phosphorus source material to a mixture containing lithium cations (Li + ) and alkaline earth metal cations to produce a precipitate containing lithium, magnesium, calcium, strontium and phosphorus, wherein the total concentration of alkaline earth metal cations in the first solution is above 100,000 mg / L. Also provided are a method for preparing lithium carbonate using the method for extracting lithium, and a method for preparing lithium hydroxide using the method for extracting lithium.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of Korean Patent Application No. 10-2022-0043946, filed on April 8, 2022, in the Korean Intellectual Property Office, and No. 10-2022-0088189, filed on July 18, 2022, in the Korean Intellectual Property Office, the disclosures of which are incorporated herein by reference in their entirety. Technical Field

[0003] The present invention relates to a method for extracting lithium, a method for preparing lithium carbonate using the method for extracting lithium, and a method for preparing lithium hydroxide using the method for extracting lithium. Background Art

[0004] Lithium (Li) is a basic raw material for various industries. Lithium secondary batteries have been widely used as power sources for IT equipment such as mobile phones and laptops, power sources for power tools, and power sources for electric vehicles. Recently, as automobiles using lithium secondary batteries as power sources have attracted attention, the global market demand for lithium is also increasing rapidly. Therefore, there is an urgent need to develop a technology for effectively extracting lithium from lithium resources.

[0005] Examples of naturally occurring lithium resources include seawater, minerals, and brines. While seawater contains approximately 0.17 mg / L of lithium, its concentration is known to be so low that extracting lithium from seawater for industrial use is uneconomical. Several years ago, a technology was developed that selectively adsorbed lithium from seawater using a manganese-based adsorbent and then desorbed it through an acid wash process, but this technology failed to be commercialized due to low efficiency and low economic viability.

[0006] Examples of lithium minerals include spodumene, petalite, and lepidolite, which contain approximately 1-1.5% lithium by weight. However, extracting lithium requires numerous steps, including crushing, producing a concentrate by flotation, high-temperature calcination, grinding, acid leaching, removing impurities, lithium extraction, refining, lithium concentration, and precipitation. Consequently, there are issues such as high capital expenditure for production equipment and environmental pollution caused by the generation of large amounts of acidic sludge.

[0007] Due to the aforementioned issues, extracting lithium from brine in salt lakes is currently the most preferred method. Typically, brine contains lithium as well as various chemical elements, such as magnesium (Mg), calcium (Ca), strontium (Sr), aluminum (Al), silicon (Si), boron (B), sodium (Na), potassium (K), chlorine (Cl), and sulfur (S). The earliest method developed for extracting lithium from brine is to extract dissolved lithium as lithium carbonate (Li2CO3). Because the concentration of lithium in brine is as low as 0.5 g / L to 1.5 g / L, the lithium must be concentrated by evaporating the brine water in solar ponds, causing the dissolved lithium to precipitate as lithium carbonate, which has a high solubility of 13 g / L. Therefore, using current solar evaporation processes, lithium is concentrated from 0.5 g / L to 1.5 g / L to a high concentration of 60 g / L. However, this process takes a long time, approximately 18 months. Furthermore, most of the lithium precipitates along with the other elements and is therefore lost during the concentration process, making the process very inefficient.

[0008] In order to overcome the above problems, a method has been developed to precipitate dissolved lithium in the form of lithium phosphate (Li3PO4) with a very low solubility of 0.39 g / L in the absence of a high concentration of lithium (Korean registered patent No. 10-1353342). Since the solubility of Li3PO4 is very low, dissolved lithium can be easily precipitated in the form of Li3PO4 even at low concentrations. Therefore, in this method, the process of highly concentrating lithium by solar evaporation is not necessary. This makes it possible to prevent the co-precipitation of lithium with other elements that causes serious lithium loss. In order to precipitate lithium in the form of Li3PO4, a phosphorus (P) source material is added to the brine and the phosphorus (P) source material is reacted with lithium, but the added phosphorus preferentially reacts with impurities such as magnesium, calcium, strontium, etc. present in the brine to produce magnesium phosphate, calcium phosphate, strontium phosphate, etc., and therefore lithium phosphate cannot be produced and precipitated. Therefore, in order to extract lithium from brine as lithium phosphate, impurities such as calcium, magnesium, strontium, etc. need to be removed before adding a phosphorus (P) source material (Korean Registered Patent No. 10-1126286 and Korean Registered Patent No. 10-1405488).

[0009] To remove magnesium (Mg) from brine, an alkali such as sodium hydroxide (NaOH) or calcium hydroxide (Ca(OH)2) is typically added. The greater the amount of magnesium present, the more alkali is required. This means that as the magnesium content of the brine increases, the cost of removing the magnesium also increases. Furthermore, the greater the amount of magnesium present, the more magnesium hydroxide (Mg(OH)2) sludge is produced. This makes separating the lithium brine from the sludge very difficult. Consequently, brine containing a large amount of Mg is wasted.

[0010] Calcium (Ca) is also removed by adding salts such as sodium carbonate (Na2CO3) or sodium sulfate (Na2SO4). The higher the calcium content, the more salt is required. This means that as the calcium content of the brine increases, the cost of decalcification also increases. Furthermore, the greater the amount of Ca present, the more calcium carbonate (CaCO3) or calcium sulfate (CaSO4·2H2O) sludge is produced. This makes it difficult to separate the lithium brine from the sludge. Consequently, brine containing a large amount of Ca is also discarded uselessly, just like brines rich in Mg.

[0011] For these reasons, only very few brines with low impurity contents can produce lithium. Therefore, to meet the rapidly growing demand for lithium, there is an urgent need to develop a technology that can cost-effectively extract lithium even from brines with high impurity contents.

[0012] A series of efforts have been made to extract lithium from brine in the form of Li3PO4, a poorly soluble compound with a very low solubility in water of 0.39 g / L. However, Li3PO4 cannot be used as a raw material for manufacturing positive electrode materials for lithium secondary batteries. Therefore, lithium phosphate needs to be converted into lithium hydroxide (LiOH·H2O) or lithium carbonate (Li2CO3) to be used as a raw material for positive electrode materials. In order to convert lithium phosphate into lithium hydroxide or lithium carbonate, a process of dissolving lithium phosphate is essential, and a strong acid is usually used. When lithium phosphate is dissolved in a strongly acidic solution, the phosphorus present in the lithium phosphate dissolves in the lithium phosphate solution. Therefore, a process of removing phosphorus using a phosphorus anion remover is necessary. This complicates the process of converting Li3PO4 into LiOH·H2O and Li2CO3 and results in lithium loss, so there is a problem of reduced process efficiency. Summary of the Invention

[0013] The present invention aims to provide a method for extracting lithium from a lithium solution by an economical, effective and simple method.

[0014] The present invention also aims to provide a method for preparing lithium carbonate or lithium hydroxide from a lithium solution in an economical, effective and simple manner.

[0015] One aspect of the present invention provides a method for extracting lithium.

[0016] The method for extracting lithium comprises: + ) and alkaline earth metal cations to produce a lithium precipitate comprising magnesium, calcium and phosphorus, wherein the total concentration of alkaline earth metal cations in the first solution is above 100,000 mg / L.

[0017] The lithium precipitate may have a lithium dissolution rate greater than 25% as calculated by the following equation 2:

[0018] [Equation 2]

[0019] Lithium dissolution rate = A / B × 100

[0020] (In Equation 2, B = the total concentration of lithium cations contained in the lithium precipitate (unit: mg / L),

[0021] A = total concentration of lithium cations in a filtrate obtained by stirring a lithium precipitate in 90°C water in an amount 15 times the weight of the lithium precipitate for 60 hours and filtering the slurry (unit: mg / L).

[0022] The alkaline earth metal cation may be a magnesium cation (Mg 2+ ), calcium cation (Ca 2+ ) and strontium cations (Sr 2+ ).

[0023] The first solution may further contain alkali metal cations.

[0024] The alkali metal cation may be a sodium cation (Na + ) and potassium cation (K + )

[0025] The first solution may further include cations or anions derived from one or more of iron, manganese, cobalt, silicon, aluminum, boron, chlorine, and sulfur.

[0026] The first solution may be derived from any of brine, geothermal water, seawater, minerals, and spent batteries.

[0027] The concentration of lithium cations in the first solution may be 70 mg / L or higher.

[0028] The lithium precipitate may further contain one or more of sodium, potassium, chlorine, and sulfur.

[0029] The phosphorus source may be one or more selected from phosphorus, phosphoric acid, phosphates, hydrogen phosphates, and phosphorus-containing solutions.

[0030] The first solution contains lithium cations (Li + ) and alkaline earth metal cations can have a total concentration of 100,100 mg / L or more.

[0031] The total concentration of lithium cations, alkaline earth metal cations, and alkali metal cations in the first solution may exceed 100,000 mg / L.

[0032] The method may further include adding 80° C. to 100° C. water in an amount 5 to 20 times the weight of the lithium precipitate, stirring the slurry of the lithium precipitate for 12 to 60 hours, and then filtering the slurry to obtain a second solution, wherein the second solution may contain lithium cations.

[0033] The concentration of lithium cations in the second solution may be greater than 200 mg / L.

[0034] The method may further include adding 0.1 wt % to 5 wt % of dilute hydrochloric acid, which is 5 to 20 times the weight of the lithium precipitate, to the lithium precipitate at room temperature, stirring the slurry of the lithium precipitate for 1 to 5 hours, and then filtering the slurry to obtain a third solution, wherein the third solution may contain lithium cations.

[0035] The concentration of lithium cations in the third solution may be greater than 200 mg / L.

[0036] The method may further include producing lithium hydroxide or lithium carbonate from the second solution.

[0037] Another aspect of the present invention provides a method for preparing lithium carbonate.

[0038] The method for preparing lithium carbonate comprises using the lithium precipitate of the lithium extraction method of the present invention.

[0039] Another aspect of the present invention provides a method for preparing lithium hydroxide.

[0040] The method for preparing lithium hydroxide comprises using the lithium precipitate of the lithium extraction method of the present invention.

[0041] The present invention provides a method for extracting lithium from a lithium solution by an economical, effective and simple method.

[0042] The present invention provides a method for preparing lithium hydroxide or lithium carbonate from a lithium solution in an economical, effective and simple manner. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The above and other objects, features and advantages of the present invention will become apparent to those skilled in the art by describing in detail exemplary embodiments of the present invention with reference to the accompanying drawings, in which:

[0044] Figure 1 shows the changes in the concentration of lithium cations remaining in the first solution and the lithium extraction rate (lithium extraction rate) as a function of reaction time after a phosphorus source is added to a first solution containing impurities and lithium cations;

[0045] Figure 2A A first solution containing impurities and lithium cations is shown; Figure 2BIt shows that when the phosphorus source is added to Figure 2A a slurry obtained by reacting the first solution of Figure 2C shows the appearance of a lithium precipitate comprising magnesium, calcium, strontium, and phosphorus, which is separated from a slurry obtained after adding a phosphorus source to a first solution and reacting the solution;

[0046] Figure 3 shows an X-ray diffraction pattern of lithium phosphate (Li3PO4);

[0047] Figure 4 Shown are changes in lithium dissolution rate with stirring time when lithium phosphate and a lithium precipitate containing magnesium, calcium, strontium, and phosphorus were each added to water at 90° C. and then stirred for 12 to 60 hours. DETAILED DESCRIPTION

[0048] Hereinafter, embodiments of the present invention will be described in detail. However, the embodiments are provided as examples, and the present invention is not limited thereto and will only be limited by the scope of the claims to be described below.

[0049] As used herein, the concentrations of various cations and anions can be measured by atomic emission spectroscopy, such as inductively coupled plasma atomic emission spectroscopy (ICP-AES).

[0050] As used herein, "impurities" refer to impurities in the first solution other than lithium cations (Li + ) or more cations and anions other than .

[0051] As used herein, "first solution" is a lithium feed solution used to extract lithium, and refers to one or more solutions directly or indirectly derived from brine, underground hot water, seawater, minerals, and spent batteries.

[0052] As used herein, "room temperature" is not particularly limited and refers to the ambient temperature when a task is performed, for example, a temperature of 0°C to 50°C.

[0053] The present invention involves adding a phosphorus source to a first solution containing various impurities to produce a lithium precipitate containing magnesium, calcium, strontium, and phosphorus without removing these impurities. The present invention directly extracts lithium without removing impurities, enabling efficient and economical extraction of lithium from a lithium-containing solution.

[0054] As described below, lithium precipitate is a completely different substance from poorly soluble lithium phosphate (Li3PO4), which has a very low solubility in water of 0.39 g / L. The chemical composition of lithium precipitate is very different from that of Li3PO4. Lithium phosphate (Li3PO4) has 17.98 wt% Li and 26.75 wt% P. The Li to P ratio (Li / P) in Li3PO4 is 0.67, which is 17.98 / 26.75. In contrast, lithium precipitate has 3.7 wt% Li and 10.4 wt% P. The Li to P ratio (Li / P) in lithium precipitate is 0.36, which is 3.7 / 10.4. The chemical composition of lithium precipitate will be described in further detail below.

[0055] When stirred in 90°C water for 12 to 60 hours, the lithium precipitate exhibits completely different water dissolution behavior from that of sparingly soluble lithium phosphate (Li3PO4). Specifically, the lithium precipitate has a significantly higher lithium dissolution rate than sparingly soluble lithium phosphate. This feature of the present invention enables the cost-effective production of lithium hydroxide and lithium carbonate. The lithium dissolution rate will be described in more detail below.

[0056] Furthermore, according to the present invention, since a precipitate having a high lithium dissolution rate and minimized phosphorus elution is generated, lithium carbonate or lithium hydroxide can be prepared by an economical, efficient and simple method compared to a method of preparing lithium hydroxide or lithium carbonate from poorly soluble lithium phosphate.

[0057] Lithium is used in the form of lithium carbonate or lithium hydroxide. Therefore, a process for converting lithium phosphate into lithium hydroxide or lithium carbonate is needed. Lithium phosphate typically dissolves in a strong acid during the conversion process. The dissolved phosphorus is substantially removed by a precipitant. However, because the present invention prevents or minimizes the dissolution of phosphorus from the lithium precipitate, lithium carbonate or lithium hydroxide can be produced by an economical, efficient, and simple method without the use of such a precipitant for dissolving phosphorus.

[0058] The present invention provides a method for preparing lithium hydroxide, which comprises using the lithium precipitate of the lithium extraction method according to the present invention.

[0059] The present invention provides a method for preparing lithium carbonate, which comprises using the lithium precipitate of the lithium extraction method according to the present invention.

[0060] Hereinafter, the present invention will be described in more detail with reference to embodiments.

[0061] (1) The method for extracting lithium according to the present invention comprises: +) and alkaline earth metal cations to produce a lithium precipitate containing magnesium, calcium, strontium and phosphorus, wherein the total concentration of alkaline earth metal cations in the first solution is above 100,000 mg / L.

[0062] In the first solution, lithium cations (Li + ) concentration may be 70 mg / L or more, preferably 100 mg / L or more, and more preferably 150 mg / L or more. In one embodiment, in the first solution, the lithium cation (Li + ) can be 3,000 mg / L or less, 700 mg / L or less, or 500 mg / L or less, for example, 70 mg / L, 80 mg / L, 90 mg / L, 100 mg / L, 110 mg / L, 120 mg / L, 130 mg / L, 140 mg / L, 150 mg / L, 160 mg / L, 170 mg / L, 180 mg / L, 190 mg / L, 200 mg / L, 210 mg / L, 220 mg / L, 230 mg / L, 240 mg / L, 250 mg / L, 260 mg / L, 270 mg / L, 280 mg / L, 290 mg / L, 300 mg / L, 310 mg / L, 320 mg / L, 330 mg / L, 3 00mg / L, 250mg / L, 300mg / L, 350mg / L, 400mg / L, 450mg / L, 500mg / L, 550mg / L, 600mg / L, 6 50mg / L, 700mg / L, 900mg / L, 1,000mg / L, 1,500mg / L, 2,000mg / L, 2,500mg / L, 3,000mg / L.

[0063] The total concentration of alkaline earth metal cations in the first solution is 100,000 mg / L or greater. However, even though the total concentration of alkaline earth metal cations in the first solution is 80,000 mg / L or greater, depending on the type or conditions of the first solution, the method for extracting lithium according to the present invention, the method for preparing lithium carbonate according to the present invention, or the method for preparing lithium hydroxide according to the present invention can also be used. Within the above range, a lithium precipitate having a relatively high lithium dissolution rate compared to lithium phosphate can be easily provided. Based on the chemical composition of the lithium precipitate, it is believed that impurities such as alkaline earth metal cations present in the first solution serve as a medium for generating the lithium precipitate, and the lithium cations dissolved in the first solution are extracted in the form of a lithium precipitate including alkaline earth metal cations and phosphorus.

[0064] Preferably, the total concentration of alkaline earth metal cations in the first solution may be 100,000 mg / L to 180,000 mg / L, most preferably 120,000 mg / L to 180,000 mg / L, such as 100,000 mg / L, 110,000 mg / L, 120,000 mg / L, 130,000 mg / L, 140,000 mg / L, 150,000 mg / L, 160,000 mg / L, 170,000 mg / L, 180,000 mg / L. Within the above range, a lithium precipitate having a relatively high lithium dissolution rate compared to lithium phosphate can be easily provided. In one embodiment, the magnesium cations (Mg 2+) in the first solution are 100,000 mg / L to 180,000 mg / L, most preferably 120,000 mg / L to 180,000 mg / L, such as 100,000 mg / L, 110,000 mg / L, 120,000 mg / L, 130,000 mg / L, 140,000 mg / L, 150,000 mg / L, 160,000 mg / L, 170,000 mg / L, 180,000 mg / L. 2+ ), calcium cation (Ca 2+ ) and strontium cations (Sr 2+ ) can be in the range of 100,000 mg / L to 180,000 mg / L, preferably 120,000 mg / L to 180,000 mg / L, for example 100,000 mg / L, 110,000 mg / L, 120,000 mg / L, 130,000 mg / L, 140,000 mg / L, 150,000 mg / L, 160,000 mg / L, 170,000 mg / L, 180,000 mg / L.

[0065] In one embodiment, the lithium cations (Li + The total concentration of lithium cations (Li) and alkaline earth metal cations may be 100,100 mg / L or more and 300,000 mg / L or less. Within the above range, a precipitate having a relatively high lithium dissolution rate compared to lithium phosphate can be easily provided. Preferably, the lithium cations (Li + The total concentration of ) and alkaline earth metal cations can be from 100,100 mg / L to 250,000 mg / L, most preferably from 100,100 mg / L to 200,000 mg / L, for example 100,100 mg / L, 110,000 mg / L, 120,000 mg / L, 130,000 mg / L, 140,000 mg / L, 150,000 mg / L, 160,000 mg / L, 170,000 mg / L, mg / L, 180,000mg / L, 190,000mg / L, 200,000mg / L, 210,000mg / L, 220,000mg / L, 230,000mg / L, 240 ,000mg / L, 250,000mg / L, 260,000mg / L, 270,000mg / L, 280,000mg / L, 290,000mg / L, 300,000mg / L.

[0066] In one embodiment, the lithium cations (Li + ), magnesium cation (Mg 2+ ), calcium cation (Ca 2 + ) and strontium cations (Sr 2+ ) can be a total concentration of 100,100 mg / L or more and 300,000 mg / L or less, more preferably 100,100 mg / L to 250,000 mg / L, most preferably 100,100 mg / L to 200,000 mg / L, for example 100,100 mg / L, 110,000 mg / L, 120,000 mg / L, 130,000 mg / L, 140,000 mg / L, 150,000 mg / L, 160,000 mg / L, g / L, 170,000 mg / L, 180,000 mg / L, 190,000 mg / L, 200,000 mg / L, 210,000 mg / L, 220,000 mg / L, 230,000 mg / L, 240,000 mg / L, 250,000 mg / L, 260,000 mg / L, 270,000 mg / L, 280,000 mg / L, 290,000 mg / L, and 300,000 mg / L. Within the above range, a lithium precipitate having a considerably higher lithium dissolution rate than lithium phosphate can be easily provided.

[0067] The alkaline earth metal cations in the first solution may be beryllium cations (Be 2+ ), magnesium cation (Mg 2+ ), calcium cation (Ca 2+ ), strontium cation (Sr 2+ ), barium cation (Ba 2+ ) and radium cations (Ra 2+ In one embodiment, the alkaline earth metal cation in the first solution may be a magnesium cation (Mg 2+ ), calcium cation (Ca 2+ ) and strontium cations (Sr 2 + ). When magnesium cation (Mg 2+ ), calcium cation (Ca 2+ ) and strontium cations (Sr 2+ ) are included as alkaline earth metal cations, the method for extracting lithium according to the present invention can be well applied.

[0068] The first solution may further comprise an alkali metal cation. The alkali metal cation may be an alkali metal cation other than lithium, and may be, for example, a sodium cation (Na + ), potassium cation (K +), rubidium cation (Rb + ), cesium cation (Cs + ) and francium cations (Fr + In one embodiment, the alkali metal cation may be a sodium cation (Na + ) and potassium cation (K + ) in one or more. When containing sodium cations (Na + ) and potassium cation (K + ) are included, the method for extracting lithium according to the present invention can be well applied.

[0069] In one embodiment, the total concentration of alkali metal cations in the first solution can be 20,000 mg / L or more, for example, 20,000 mg / L to 50,000 mg / L or 20,000 mg / L to 40,000 mg / L, for example, 20,000 mg / L, 21,000 mg / L, 22,000 mg / L, 23,000 mg / L, 24,000 mg / L, 25,000 mg / L, 26,000 mg / L, 27,000 mg / L, 28,000 mg / L, 29,000 mg / L, 30,000 mg / L, 31,000 mg / L, 32,000 mg / L, 33,000 mg / L, 34,000 mg / L, 35,000 mg / L, 36,000 mg / L, 37,000 mg / L, 38,000 mg / L, 39,000 mg / L, 40,000 mg / L, 41,000 mg / L, 42,000 mg / L, 43,000 mg / L, 44,000 mg / L, 45,000 mg / L, 46,000 mg / L, 47,000 mg / L, 48,000 mg / L, 49,000 mg / L, 50,000 mg / L, 51,000 mg / L, 52,000 mg / L, 53,000 mg / L, 54,000 mg / L 0mg / L, 32,000mg / L, 33,000mg / L, 34,000mg / L, 35,000mg / L, 36,000mg / L, 37,000mg / L, 38,000mg / L, 39,000mg / L, 40,000mg / L, 41 ,000mg / L, 42,000mg / L, 43,000mg / L, 44,000mg / L, 45,000mg / L, 46,000mg / L, 47,000mg / L, 48,000mg / L, 49,000mg / L, 50,000mg / L.

[0070] The first solution may further comprise cations or anions derived from one or more of iron, manganese, cobalt, boron, silicon, aluminum, chlorine, and sulfur. In one embodiment, the first solution may comprise sulfur-derived anions. When sulfur-derived anions are included, the method for extracting lithium according to the present invention is particularly useful.

[0071] The total concentration of lithium cations, alkaline earth metal cations and alkali metal cations in the first solution may exceed 100,000 mg / L. Within the above range, a precipitate having a relatively high lithium dissolution rate compared to lithium phosphate can be easily provided. Preferably, the lithium cations (Li +), the total concentration of alkaline earth metal cations and alkali metal cations can be 150,000 mg / L to 300,000 mg / L, more preferably 150,000 mg / L to 250,000 mg / L, most preferably 150,000 mg / L to 200,000 mg / L, for example 110,000 mg / L, 120,000 mg / L, 130,000 mg / L, 140,000 mg / L, 150,000 mg / L, 160,000 mg / L g / L, 170,000 mg / L, 180,000 mg / L, 190,000 mg / L, 200,000 mg / L, 210,000 mg / L, 220,000 mg / L, 230,000 mg / L, 240,000 mg / L, 250,000 mg / L, 260,000 mg / L, 270,000 mg / L, 280,000 mg / L, 290,000 mg / L, 300,000 mg / L. In one embodiment, the lithium cation (Li + ), magnesium cation (Mg 2+ ), calcium cation (Ca 2+ ), strontium cation (Sr 2+ ), sodium cation (Na + ) and potassium cation (K + ) can be 150,000 mg / L or more, preferably 150,000 mg / L to 300,000 mg / L, more preferably 150,000 mg / L to 250,000 mg / L, most preferably 150,000 mg / L to 200,000 mg / L, for example 150,000 mg / L, 160,000 mg / L, 170,000 mg / L, 180,000 mg / L, g / L, 190,000mg / L, 200,000mg / L, 210,000mg / L, 220,000mg / L, 230,000mg / L, 240,000mg / L, 250,000mg / L, 260,000mg / L, 270,000mg / L, 280,000mg / L, 290,000mg / L, 300,000mg / L.

[0072] The phosphorus source material may be one or more selected from phosphorus, phosphoric acid, phosphates, hydrogen phosphates, and phosphorus-containing solutions. Specific examples of phosphates include potassium phosphate, sodium phosphate, ammonium phosphate (specifically, ammonium phosphate may be (NR4)3PO4, wherein R may independently be hydrogen, deuterium, or a substituted or unsubstituted C1 to C10 alkyl group), etc. More specifically, the phosphate may be monopotassium phosphate, dipotassium phosphate, tripotassium phosphate, monosodium phosphate, disodium phosphate, trisodium phosphate, aluminum phosphate, zinc phosphate, ammonium polyphosphate, sodium hexametaphosphate, monocalcium phosphate, dicalcium phosphate, tricalcium phosphate, etc.

[0073] The phosphorus source material may be included in an amount of 1 to 4 moles based on 1 mole of lithium cations in the first solution. Within the above range, the effects of the present invention can be easily achieved.

[0074] The lithium precipitate can be produced by adding a phosphorus source to the first solution and stirring at room temperature for 1 to 24 hours. As a result, a lithium precipitate containing lithium, magnesium, calcium, strontium, and phosphorus can be easily produced, and the lithium extraction rate can be very high. In this case, "room temperature" does not refer to a specific temperature, but rather to a temperature without added energy. Therefore, the room temperature may vary depending on the location and time. For example, the room temperature may be 20°C to 30°C. Preferably, the stirring time may be 1 to 12 hours. Within the above range, the lithium extraction rate can be quite high.

[0075] In one embodiment, this step may be performed such that the lithium extraction rate according to the following Equation 1 is 70% or more, for example, 70% to 100%.

[0076] [Equation 1]

[0077] Lithium extraction rate = A / B × 100

[0078] (In Equation 1,

[0079] A = concentration of lithium cations in the first solution - concentration of lithium cations in the filtrate obtained when producing lithium precipitate (unit: mg / L),

[0080] B = concentration of lithium cations in the first solution (unit: mg / L)

[0081] See also Figures 2A to 2C , the first solution is a transparent solution. On the other hand, the first solution obtained after adding the phosphorus source material to the first transparent solution and reacting it is a white opaque slurry. The opaque slurry can then be filtered to produce a lithium precipitate in the form of a white solid.

[0082] The lithium precipitate can be separated from the slurry by typical methods, such as filtration from the first solution.

[0083] The lithium precipitate comprises lithium, magnesium, calcium, strontium and phosphorus. In one embodiment, the lithium precipitate may further comprise one or more of sodium, potassium, chlorine and sulfur.

[0084] (2) The method for extracting lithium according to the present invention may further include adding 5 to 20 times the weight of the lithium precipitate and 80 to 100°C of water, stirring the slurry for 12 to 60 hours, and then filtering the slurry to obtain a second solution, wherein the second solution may contain lithium cations (Li +Within the above-mentioned ranges of water content, water temperature, and stirring time, the dissolution of lithium cations in the lithium precipitate can be promoted. Preferably, this step can be performed by adding 7 to 18 times the weight of the lithium precipitate in water at 85° C. to 95° C., stirring the slurry for 12 to 60 hours, and then filtering the slurry.

[0085] The concentration of lithium cations in the second solution can be greater than 200 mg / L, for example, greater than 500 mg / L, greater than 1000 mg / L, less than 10000 mg / L, less than 5000 mg / L, or less than 3000 mg / L, for example, 500 mg / L, 600 mg / L, 700 mg / L, 800 mg / L, 900 mg / L, 1000 mg / L, 2000 mg / L, 3000 mg / L, 4000 mg / L, 5000 mg / L, 6000 mg / L, 7000 mg / L, 8000 mg / L, 9000 mg / L, 10000 mg / L.

[0086] This step can facilitate the subsequent preparation of lithium carbonate or lithium hydroxide by selectively dissolving lithium cations from the lithium precipitate due to the high solubility of lithium cations in the lithium precipitate.

[0087] In one embodiment, when stirred in 90° C. water in an amount 15 times the weight of the precipitate for 12 to 60 hours, the lithium precipitate may have a lithium dissolution rate of 25% or more, e.g., 50% or more, 60% or more, 60% to 100%. Within the above range, lithium hydroxide or lithium carbonate can be easily prepared from the lithium precipitate. The lithium dissolution rate can be calculated according to the following equation 2:

[0088] [Equation 2]

[0089] Lithium dissolution rate = A / B × 100

[0090] (In Equation 2, B = the total concentration of lithium cations contained in the lithium precipitate (unit: mg / L),

[0091] A = total concentration of lithium cations in a filtrate obtained by stirring a lithium precipitate in 90°C water in an amount 15 times the weight of the lithium precipitate for 60 hours and filtering the slurry (unit: mg / L).

[0092] In one embodiment, when stirred in 90°C water in an amount 15 times the weight of the lithium precipitate for 12 to 60 hours, the phosphorus dissolution rate of the lithium precipitate can be less than 0.2%. Within the above range, when the lithium precipitate solution is used to prepare lithium carbonate, it is not necessary to use a phosphorus anion precipitant to remove phosphorus anions. The phosphorus dissolution rate can be calculated according to the following equation 3:

[0093] [Equation 3]

[0094] Phosphorus dissolution rate = A / B × 100

[0095] (In Equation 3,

[0096] B = total concentration of phosphorus anions in the lithium precipitate (unit: mg / L),

[0097] A = total concentration of phosphorus anions in a filtrate obtained by stirring a lithium precipitate in water at 90° C. in an amount 15 times the weight of the lithium precipitate for 60 hours and filtering the slurry (unit: mg / L).

[0098] Although there is no particular limitation on B in Equation 2, B can be calculated from the total concentration of lithium cations in a solution obtained by completely dissolving the lithium precipitate in a room temperature hydrochloric acid aqueous solution 15 times the weight of the lithium precipitate (the concentration of hydrochloric acid in the hydrochloric acid aqueous solution is 9 wt % to 15 wt %).

[0099] Although there is no particular limitation on B in Equation 3, B can be calculated from the total concentration of phosphorus anions in a solution obtained by completely dissolving the lithium precipitate in a room temperature hydrochloric acid aqueous solution 15 times the weight of the lithium precipitate (the concentration of hydrochloric acid in the hydrochloric acid aqueous solution is 9 wt % to 15 wt %).

[0100] In one embodiment, when stirred in 90° C. water in an amount 15 times the weight of the lithium precipitate for 36 to 60 hours, the lithium precipitate may have a lithium dissolution rate of 90% or more, for example, 98 to 100%. Within this range, lithium hydroxide or lithium carbonate can be easily prepared from the lithium precipitate.

[0101] (3) The method for extracting lithium according to the present invention may further include adding 0.1% to 5% by weight of dilute hydrochloric acid, such as a dilute hydrochloric acid aqueous solution, at room temperature, which is 5 to 20 times the weight of the lithium precipitate, to the lithium precipitate, stirring the slurry for 1 to 5 hours, and then filtering the slurry to obtain a third solution, wherein the third solution may contain lithium cations. The concentration of lithium cations in the third solution may be 200 mg / L or greater. Lithium hydroxide or lithium carbonate may be prepared from the third solution.

[0102] (4) The method for preparing lithium carbonate according to the present invention comprises using the lithium precipitate of the lithium extraction method according to the present invention.

[0103] The method for preparing lithium carbonate according to the present invention may include: obtaining a lithium precipitate according to the lithium extraction method of the present invention (step 1); adding water at 80° C. to 100° C., which is 5 to 20 times the weight of the lithium precipitate, to the lithium precipitate, stirring the slurry for 12 to 60 hours, and then filtering the slurry to obtain a slurry containing lithium cations (Li + ) of the second solution (step 2); and carbonating the second solution to prepare lithium carbonate (step 3).

[0104] Steps 1 and 2 are substantially the same as described above. Therefore, only step 3 will be described below.

[0105] Step 3 is the step of preparing Quilonum Retard by carbonating the second solution. Carbonating can be carried out by adding carbonate in the second solution or by using carbonating gas (carbonating gas). Carbonate can be sodium carbonate (Na2CO3). Using carbonate or carbonating gas to prepare Quilonum Retard can be carried out by typical method known in the art.

[0106] In one embodiment, the method for preparing lithium carbonate according to the present invention may not include the use of acid or acidic aqueous solution.

[0107] (5) The method for preparing lithium hydroxide according to the present invention includes using the lithium precipitate of the lithium extraction method according to the present invention.

[0108] The method for preparing lithium hydroxide according to the present invention may include: obtaining a lithium precipitate according to the lithium extraction method of the present invention (step 1); adding water at 80° C. to 100° C., which is 5 to 20 times the weight of the lithium precipitate, to the lithium precipitate, stirring the slurry for 12 to 60 hours, and then filtering the slurry to obtain a slurry containing lithium cations (Li + ) of the second solution (step 2); and adding a precipitating agent for precipitating phosphate anions to the second solution to prepare lithium hydroxide (step 3).

[0109] Steps 1 and 2 are substantially the same as described above. Therefore, only step 3 will be described below.

[0110] Step 3 is a step of adding a precipitant for precipitating phosphate anions to the second solution to prepare lithium hydroxide. The precipitant can be an oxide or hydroxide of an alkaline earth metal including Ca, Sr, Ba, Ra, Be or Mg, such as calcium hydroxide.

[0111] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the following embodiments are only provided for illustrating the present invention, and the present invention is not limited thereto.

[0112] [Example 1]

[0113] As shown in Table 1 below, a brine-derived lithium solution containing impurities was prepared as a first solution.

[0114] [Table 1]

[0115] chemical composition <![CDATA[Li + ]]> <![CDATA[Mg 2+ ]]> <![CDATA[Ca 2+ ]]> <![CDATA[Sr 2+ ]]> <![CDATA[Na + ]]> <![CDATA[K + ]]> S Content (mg / L) 346 21,770 128,571 2,275 7,482 16,730 16

[0116] Based on 1 mole of lithium cations in the first solution, 2 moles of Na3PO4 were added to the first solution and the reaction was stirred at room temperature for 1 to 24 hours. After the reaction was complete, the resulting solution was filtered to separate the lithium precipitate in the form of a solid filter cake, and the filtrate was collected. The concentrations of lithium, magnesium, calcium, and strontium in the filtrate were measured using an atomic emission spectrometer (ICP-AES), and the results are shown in Table 2.

[0117] [Table 2]

[0118]

[0119]

[0120] In Table 2, the lithium extraction rate was calculated by the formula (concentration of lithium cations in the first solution - concentration of lithium cations in the filtrate) x 100 / (concentration of lithium cations in the first solution).

[0121] As shown in Table 2, after 24 hours of reaction, 279 mg / L (equivalent to approximately 81% of the 346 mg / L of lithium cations dissolved in the first solution) was confirmed to have precipitated as lithium precipitate, resulting in only 67 mg / L remaining in the reaction filtrate. This result demonstrates that lithium cations were successfully extracted from the first solution containing a large amount of impurities.

[0122] The concentration of lithium dissolved in the first solution and the lithium extraction rate shown in Table 2 are plotted as a function of reaction time. Figure 1 In. Reference Figure 1 It can be confirmed that the lithium cation concentration in the filtrate (left Y axis) gradually decreases with the reaction time (X axis), and accordingly, the lithium extraction rate gradually increases.

[0123] The precipitate was dried at 105° C. for 24 hours, and the chemical composition of the obtained lithium precipitate was measured by ICP-AES. The weight percentage of each component in the lithium precipitate is shown in Table 3.

[0124] [Table 3]

[0125] chemical composition <![CDATA[Li + ]]> <![CDATA[Mg 2+ ]]> <![CDATA[Ca 2+ ]]> <![CDATA[Sr 2+ ]]> P Content (mg / L) 3.7 2.69 12.24 0.28 10.4

[0126] As shown in Table 3, it can be clearly seen that lithium can be successfully extracted by using the impurities as a medium to produce lithium precipitates in the first solution.

[0127] [Example 2]

[0128] The lithium precipitate shown in Table 3 was mixed with 90°C water (15 times the weight of the lithium precipitate), stirred for 12 to 60 hours, and then filtered to obtain a filtrate as a second solution. The chemical components of the second solution were analyzed by ICP-AES, and the results are shown in Table 4.

[0129] To determine the lithium and phosphorus concentrations when the lithium precipitate shown in Table 3 was completely dissolved, the lithium precipitate shown in Table 3 was mixed with a 9 wt% aqueous hydrochloric acid solution (15 times the weight of the lithium precipitate) and stirred. ICP-AES analysis revealed that the lithium and phosphorus concentrations in the aqueous solution were 1,879 mg / L and 5,897 mg / L, respectively. This result confirmed that when the lithium precipitate was completely dissolved in 90°C water at an amount 15 times the weight of the lithium precipitate, the lithium and phosphorus concentrations were 1,879 mg / L and 5,897 mg / L, respectively. These concentrations were compared with the concentrations of the second solution stirred for 12 to 60 hours. Based on these comparisons, the dissolution rates of lithium and phosphorus were calculated according to Equation 2.

[0130] As shown in Table 4, it was confirmed that when the precipitate was mixed with 90°C water (15 times the weight of the precipitate) and then stirred for 60 hours, 98.2% of the lithium contained in the lithium precipitate, that is, nearly all of the lithium in the lithium precipitate, dissolved. On the other hand, it was confirmed that, unlike when the lithium precipitate was mixed with hydrochloric acid and stirred, when the lithium precipitate was mixed with 90°C water (15 times the weight of the lithium precipitate) and stirred for 60 hours, almost no phosphorus contained in the lithium precipitate dissolved. These results indicate that when lithium carbonate is prepared using a solution of the lithium precipitate, it is not necessary to use a phosphorus anion precipitant to remove phosphorus anions. Furthermore, it can be easily seen that when the lithium precipitate is dissolved using a weak acid diluted with a large amount of water, lithium can be dissolved without dissolving phosphorus, even at room temperature.

[0131] [Table 4]

[0132]

[0133] [Comparative Example]

[0134] like Figure 3 As shown in the results of X-ray diffraction analysis, single-phase lithium phosphate (Li3PO4) was prepared. Lithium phosphate is a poorly soluble compound with a solubility of 0.39 g / L. The lithium phosphate was mixed with 15 times the weight of water to prepare an aqueous lithium phosphate solution. The aqueous solution was stirred at 90°C for 12 to 60 hours and then filtered. The chemical composition of the resulting filtrate was analyzed by ICP-AES, and the results are shown in Table 5.

[0135] To determine the lithium concentration when the lithium phosphate is completely dissolved, the lithium phosphate was mixed with a 9% hydrochloric acid aqueous solution (15 times the weight of the lithium phosphate) and stirred. ICP-AES analysis revealed a lithium concentration of 9,739 mg / L in the aqueous solution. This result confirms that when the lithium phosphate is completely dissolved in 90°C water (15 times the weight of the lithium phosphate), the lithium concentration is 9,739 mg / L.

[0136] These concentration values ​​were compared with the concentration values ​​of the second solution stirred for 12 hours to 60 hours. Based on these comparisons, the dissolution rate of lithium was calculated according to Equation 2. The results are shown in Tables 5 and Figure 4 middle.

[0137] [Table 5]

[0138]

[0139] As mentioned above, lithium phosphate is a typical insoluble substance with a solubility in water of 0.39 g / L. As shown in Table 5, even if lithium phosphate is stirred in water for 60 hours, its lithium dissolution rate is very low, only 0.2%. This is significantly different from the high dissolution rate of 98.2% of the lithium precipitate under similar conditions. These experimental results clearly show that the lithium precipitate of the present invention is a substance whose physical and chemical properties are completely different from those of insoluble lithium phosphate (Li3PO4). Therefore, it can be seen from Example 2 and the comparative example that the lithium precipitate extracted from the lithium solution according to the present invention is not the commonly known insoluble lithium phosphate with a solubility of 0.39 g / L. In addition, as shown in Tables 5 and Figure 4 As shown, the lithium dissolution behaviors of lithium precipitates and lithium phosphate in aqueous solution are significantly different.

[0140] The present invention is not limited to the embodiments described herein, but may be implemented in other forms, and those skilled in the art will understand that the present invention may be implemented in other specific forms without changing the technical spirit or basic characteristics of the present invention. Therefore, it should be understood that the above embodiments are merely illustrative in all aspects and are not restrictive.

Claims

1. A method for extracting lithium, comprising: The phosphorus source is added to the lithium cation (Li + ) and alkaline earth metal cations to produce a lithium precipitate containing magnesium, calcium, strontium and phosphorus, wherein the total concentration of the alkaline earth metal cations in the first solution is 100,000 mg / L to 180,000 mg / L, wherein the phosphorus source is one or more selected from phosphoric acid, phosphates and hydrogen phosphates, Wherein in the first solution, the alkaline earth metal cation is a magnesium cation (Mg 2+ ), calcium cation (Ca 2+ ) and strontium cations (Sr 2+ ), Based on 1 mole of lithium cations in the first solution, 1 mole to 4 moles of the phosphorus source are included. The lithium precipitate has a lithium dissolution rate of 25% or more calculated according to the following equation 2: [Equation 2] Lithium dissolution rate = A / B × 100 In Equation 2, B = the total concentration of lithium cations contained in the lithium precipitate, unit: mg / L, A = total concentration of lithium cations in a filtrate obtained by stirring the lithium precipitate in 90°C water in an amount 15 times the weight of the lithium precipitate for 60 hours and filtering the slurry, unit: mg / L. 2 . The method according to claim 1 , wherein the lithium precipitate has a lithium dissolution rate of more than 60% calculated according to Equation 2. The method according to claim 1 , wherein the first solution further contains alkali metal cations.

4. The method according to claim 3, wherein the alkali metal cation is a sodium cation (Na + ) and potassium cation (K + ) 5. The method of claim 3, wherein the first solution further comprises cations or anions derived from one or more of iron, manganese, cobalt, boron, silicon, aluminum, chlorine, and sulfur.

6. The method according to any one of claims 1 to 5, wherein the first solution is derived from any one of brine, underground hot water, seawater, minerals and spent batteries. 7 . The method according to claim 1 , wherein the concentration of lithium cations in the first solution is 70 mg / L or more.

8. The method of any one of claims 1 to 5, wherein the lithium precipitate further comprises one or more of sodium, potassium, chlorine, and sulfur.

9. The method according to any one of claims 1 to 5, wherein the lithium cations (Li + ) and alkaline earth metal cations is above 100,100 mg / L.

10. The method of any one of claims 1 to 5, wherein the total concentration of lithium cations, alkaline earth metal cations, and alkali metal cations in the first solution exceeds 100,000 mg / L.

11. The method according to any one of claims 1 to 5, further comprising adding 5 to 20 times the weight of the lithium precipitate as water at 80° C. to 100° C. to the lithium precipitate, stirring the slurry of the lithium precipitate for 12 to 60 hours, and then filtering the slurry to obtain a second solution, wherein the second solution contains lithium cations. 12 . The method according to claim 11 , wherein the concentration of lithium cations in the second solution is 200 mg / L or more.

13. The method according to any one of claims 1 to 5, further comprising adding 0.1 wt % to 5 wt % of dilute hydrochloric acid, which is 5 to 20 times the weight of the lithium precipitate, to the lithium precipitate at room temperature, stirring the slurry of the lithium precipitate for 1 to 5 hours, and then filtering to obtain a third solution, wherein the third solution contains lithium cations. The method according to claim 13 , wherein the concentration of lithium cations in the third solution is 200 mg / L or more.

15. The method of claim 11, further comprising producing lithium hydroxide or lithium carbonate from the second solution.

16. A method for preparing lithium carbonate, comprising using the precipitate of the method for extracting lithium according to any one of claims 1 to 15.

17. A method for preparing lithium hydroxide, comprising using the precipitate of the method for extracting lithium according to any one of claims 1 to 15.

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