Method of recovering lithium

Abstract

A method of recovering lithium, according to one embodiment of the present invention, may comprise the steps of: preparing a solution containing lithium; injecting a Ca-containing additive into the solution containing lithium so as to precipitate a magnesium-containing precipitate; and separating out the precipitated precipitate so as to obtain a filtrate.

Description

How to recover lithium

[0001] The present invention relates to a method for recovering lithium.

[0002]

[0003] Lithium compounds are used for a variety of purposes across various industries, including secondary batteries, ceramics, glass, alloys, and pharmaceuticals. With the recent commercialization of electric vehicles and the increasing need for power storage, demand for lithium materials is expected to grow significantly in the future.

[0004] Raw materials for manufacturing lithium materials include minerals, brine, and seawater. Among these, ores, such as spodumene, petalite, and lepidolite, contain relatively high lithium contents of about 1 to 1.5%. However, extracting lithium from minerals requires many processes such as flotation, high-temperature calcination, crushing, acid mixing, extraction, purification, concentration, and precipitation, making the recovery process complex, costly due to high energy consumption, and severe environmental pollution due to the use of acid in the lithium extraction process.

[0005] Additionally, seawater contains a total of 2.5×10 11 It is known that lithium is dissolved in seawater, and the main technology is to selectively adsorb lithium by inserting a recovery device containing an adsorbent into seawater and then extract lithium by acid treatment. However, since the concentration of lithium contained in seawater is only 0.1 to 0.2 ppm, extracting lithium from seawater is very inefficient and has a problem of low economic feasibility.

[0006] Due to these problems, lithium is currently extracted primarily from brine, which comes from natural salt lakes, and more than 70% of the world's reserves are distributed in South America, including Argentina, Chile, and Bolivia.

[0007] Lithium contained in brine is mainly extracted in the form of lithium carbonate. In a commercialized process, to extract lithium carbonate from lithium-containing brine, a well is drilled in a natural salt lake at an altitude of 3,000 m or higher, the brine is pumped out, and the brine is then trapped in evaporation ponds, naturally evaporated over a long period of several months to a year to concentrate the lithium several to several dozen times, and then impurities such as Mg, Ca, and B are precipitated and removed, and the lithium is recovered by causing an amount exceeding the solubility of lithium carbonate to precipitate.

[0008] These brine solutions contain a higher concentration of divalent cation impurities than lithium. These impurities precipitate together with the lithium when the lithium is extracted as a solid, so a purification process is required to remove them before lithium extraction. However, this purification process poses a problem: lithium precipitates as a salt along with other impurities, resulting in lithium loss.

[0009] In general, in the process of removing Mg among the above impurities, an alkaline substance containing Ca is used as an inexpensive raw material, and in this process, both Mg and SO4 can be removed.

[0010] Mg 2+ + SO4 2- + Ca 2+ + 2OH - → Mg(OH)2(↓) + CaSO4(↓)

[0011]

[0012] To recover Li from brine, Ca is also an impurity that must be removed. Insufficient Ca input during the Mg removal process can lead to ineffective removal of Mg and SO4. Excessive Ca input can lead to increased residual Ca in the brine, increasing the load on the subsequent Ca removal process and reducing the final Li yield due to Li loss.

[0013] Therefore, there is a need to develop a method for recovering lithium that can improve Li purity and production efficiency by minimizing lithium precipitation and effectively removing Mg during the purification process in brine.

[0014]

[0015] One object of the present invention relates to a method for recovering lithium from brine, and more specifically, to provide a method for recovering lithium from brine capable of reducing the loss of lithium in the process of removing impurities by controlling the calcium concentration in concentrated brine into which a calcium-containing additive for removing magnesium has been added.

[0016]

[0017] A method for recovering lithium from brine according to one embodiment of the present invention comprises the steps of: preparing a solution containing lithium; adding a Ca-containing additive to the solution containing lithium to precipitate a magnesium-containing precipitate; and separating the precipitated precipitate to obtain a filtrate; wherein the concentration of Mg in the filtrate is 0.1 g / L or less.

[0018] The Ca concentration of the above residue can satisfy the following relationship 1.

[0019] [Relationship 1]

[0020] [Ca _f ] = a×[Ca _i ] + b×[B] +c×[SO4] + d1×[Ca _ad ] + d2×[Ca _ad ] 2 + d3×[Ca _ad ] 3

[0021] In the above relational expression 1,

[0022] [Ca _f ] is the Ca concentration (mol / L) in the filtrate,

[0023] [Ca _i ] is the Ca concentration (mol / L) in a solution containing lithium,

[0024] [B] is the concentration of B (mol / L) in a solution containing lithium,

[0025] [SO4] is the SO4 concentration (mol / L) in a solution containing lithium,

[0026] [Ca _ad ] is the amount (mol) of calcium-containing additive added to a lithium-containing solution divided by the volume (L) of the solution.

[0027] a is a rational number between 120 and 140,

[0028] b is a rational number between 22 and 26,

[0029] c is a rational number between -90 and -75,

[0030] d1 is a rational number in the range 155 to 175,

[0031] d2 is a rational number in the range -1333 to -1200,

[0032] d3 is a rational number in the range 3450 to 3850.

[0033] The above Ca-containing additive can be added in an amount of 1.1 to 1.5 equivalents (eq / mol) based on the equivalent weight of magnesium ions.

[0034] The above Ca-containing additive may include at least one selected from calcium hydroxide (Ca(OH)2), calcium carbonate (CaCO3), and calcium oxide (CaO), and specifically, the Ca-containing additive may be calcium hydroxide (Ca(OH)2).

[0035] The solution containing the lithium to which the Ca-containing additive has been added has a pH of 10.5 to 12.0.

[0036] The concentration ratio of Ca to Li in the above filtrate ([Ca] / [Li]) is 1.05 or less, the Li concentration in the above filtrate is 1.5 to 8.0 g / L, and the Ca concentration is 1.0 to 6.0 g / L.

[0037] In the step of preparing the above lithium-containing solution, the lithium concentration in the lithium-containing solution may be 1.0 to 10.0 g / L.

[0038] In the step of adding a Ca-containing additive to the lithium-containing solution to precipitate a magnesium-containing precipitate, wherein the lithium concentration in the lithium-containing solution is 1.0 to 2.0 g / L, an alkali metal hydroxide may be further added.

[0039] The molar ratio of the above alkali metal hydroxide and Ca of the Ca-containing additive to be added is 3:8.5 to 7:6.5.

[0040] In the step of preparing the above lithium-containing solution, the concentration of the magnesium component in the lithium-containing solution is 2.0 to 25.0 g / L.

[0041] In the step of preparing the above lithium-containing solution, the concentration of sulfate (SO4) in the lithium-containing solution is 2.5 to 30.0 g / L.

[0042] The method may further include a step of separating the precipitated precipitate to obtain a filtrate; and a step of adding an impurity removing agent to the filtrate to remove impurities.

[0043] The step of removing impurities by adding an impurity removing agent to the above-mentioned filtrate may include a step of precipitating a precipitate containing calcium by adding a calcium removing agent.

[0044] In the step of precipitating a precipitate containing calcium by adding the above calcium remover, the lithium loss rate of the filtrate may be 5 wt% or less.

[0045] The above calcium remover may include at least one selected from sodium hydroxide (NaOH), sodium carbonate (Na2CO3), calcium hydroxide (Ca(OH)2), sodium sulfate (Na2SO4), and potassium hydroxide (KOH).

[0046] The above calcium remover can be added in an amount of 0.2 to 1.2 equivalents (eq / mol) based on the equivalent weight of calcium ions.

[0047] The pH of the lithium-containing solution into which the Ca-containing additive is added can satisfy the following relationship 2.

[0048] [Relationship 2]

[0049] pH _f = e×[pH _i ] + g×[B] + h×f([Mg],Y) + i1×[Ca _ad ] + i2×[Ca _ad ] 2 + i3×[Ca _ad ] 3

[0050] In the above equation 2, f([Mg],Y) is a function of the pH of the filtrate and the Mg concentration (g / L) in the lithium-containing solution, 8.5+3*tanh[Mg / 2]+exp(pH _f -10) can be expressed as,

[0051] pH _f is the pH of the residue,

[0052] pH _i is the pH of the solution containing lithium,

[0053] [Mg] is the Mg concentration in the filtrate (mol / L),

[0054] [MOH] is the OH concentration (mol / L) of alkali metal hydroxide contained in the filtrate,

[0055] [B] is the concentration of B (mol / L) in a solution containing lithium,

[0056] [Ca _ad ] is the Ca concentration (mol / L) of the calcium-containing additive added to the lithium-containing solution,

[0057] e is a rational number between 3.2710 and 3.2730,

[0058] g is a rational number between 2.2980 and 2.3000,

[0059] h is a rational number between -0.8510 and -0.8520,

[0060] i1 is a rational number between 4.1030 and 4.1050,

[0061] i2 is a rational number between -0.7935 and -0.7920,

[0062] i3 is a rational number between 0.0560 and 0.0580.

[0063] Above [Ca _f ], [Ca _i ], [B] and [SO4] can be considered to adjust the amount of Ca-containing additive added.

[0064]

[0065] According to one embodiment of the present invention, there is an advantage in that the removal rate of magnesium impurities in brine can be improved.

[0066] According to one embodiment of the present invention, there is an advantage in that the recovery rate and purity of lithium recovered from brine can be improved.

[0067]

[0068]

[0069] In this specification, the terms first, second, and third, etc. are used to describe various parts, components, regions, layers, and / or sections, but are not limited thereto. These terms are used only to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, a first part, component, region, layer, or section described below may be referred to as a second part, component, region, layer, or section without departing from the scope of the present invention.

[0070] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the present invention. As used herein, the singular forms "singular" and "comprising" include plural forms as well, unless the context clearly dictates otherwise. The word "comprising" as used herein specifies a particular feature, region, integer, step, operation, element, and / or component, but does not exclude the presence or addition of other features, regions, integers, steps, operations, elements, and / or components.

[0071] When a part is referred to as being "on" or "over" another part, it can be directly on or over the other part, or there may be other parts intervening. Conversely, when a part is referred to as being "directly on" another part, there are no other parts intervening.

[0072] Although not defined otherwise, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention pertains. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with the relevant technical literature and the present disclosure, and are not to be construed as ideal or overly formal unless otherwise defined.

[0073] When a part of the present invention is said to "include" a certain component, this does not mean that other components are excluded, but rather that other components may be included, unless otherwise specifically stated.

[0074] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0075]

[0076] One embodiment of the present invention relates to a method for recovering lithium.

[0077] A method for recovering lithium according to one embodiment of the present invention may include the steps of: preparing a solution containing lithium; adding a Ca-containing additive to the solution containing lithium to precipitate a magnesium-containing precipitate; and separating the precipitated precipitate to obtain a filtrate.

[0078] Meanwhile, the Ca concentration in the above-mentioned solution can satisfy the following relationship 1.

[0079] [Relationship 1]

[0080] [Ca _f ] = a×[Ca _i ] + b×[B] +c×[SO4] + d1×[Ca _ad ] + d2×[Ca _ad ] 2 + d3×[Ca _ad ] 3

[0081] In the above relational expression 1,

[0082] [Ca _f ] is the Ca concentration (mol / L) in the filtrate,

[0083] [Ca _i ] is the Ca concentration (mol / L) in a solution containing lithium,

[0084] [B] is the concentration of B (mol / L) in a solution containing lithium,

[0085] [SO4] is the SO4 concentration (mol / L) in a solution containing lithium,

[0086] [Ca _ad ] is the amount (mol) of calcium-containing additive added to a lithium-containing solution divided by the solution volume (L).

[0087] a is a factor obtained from a graph of the calcium concentration in the lithium-containing solution after addition of the calcium-containing additive according to the calcium concentration in the initial lithium-containing solution. a is a rational number in the range of 120 to 140, more preferably in the range of 130 to 133, and even more preferably in the range of 131 to 131.5.

[0088] b is a factor obtained from a graph of the calcium concentration in the lithium-containing solution after addition of the calcium-containing additive according to the boron concentration in the initial lithium-containing solution. The b is a rational number in the range of 22 to 26, more preferably in the range of 23.5 to 24.5, and even more preferably in the range of 24.0 to 24.1.

[0089] c is a factor obtained from a graph of the calcium concentration in a lithium-containing solution after addition of a calcium-containing additive according to the concentration of sulfate groups (SO4) in the initial lithium-containing solution. The c is in the range of -90 to -75, more preferably in the range of -83 to -80, and more preferably a rational number of -82.0 to -81.5.

[0090] d1 to d3 are factors obtained from a graph of the calcium concentration in a lithium-containing solution after adding a calcium-containing additive according to the Ca concentration of the calcium-containing additive added to the lithium-containing solution. Since the change in each element in the solution according to the amount of calcium-containing additive does not satisfy a simple linear proportional relationship, a quadratic term (d2) that can consider the change in the slope in the graph and a cubic term (d3) that can consider the asymmetry were added to satisfy a nonlinear relationship. Although these can be utilized to consider more multidimensional variables, d1 to d3 were introduced as the minimum variables.

[0091] The above d1 is a rational number in the range of 155 to 175.

[0092] The above d2 is a rational number in the range of -1333 to -1200,

[0093] The above d3 is a rational number in the range of 3450 to 3850.

[0094] In the above relational expression 1,

[0095] The concentration of sulfate (SO4) in the solution containing the lithium may be 0.025 to 0.3 mol / L, and specifically, 0.15 to 0.25 mol / L.

[0096] [Ca _f ] is the Ca concentration (mol / L) in the filtrate,

[0097] The concentration of Ca in the above lithium-containing solution [Ca _i ] may be 0.0025 to 0.025 mol / L, and specifically may be 0.0025 to 0.0125 mol / L.

[0098] The B concentration [B] in the above lithium-containing solution may be 0.05 to 0.4 mol / L, and specifically 0.1 to 0.3.0 mol / L.

[0099] The Ca concentration of the calcium-containing additive in the lithium-containing solution containing the calcium-containing additive [Ca _ad ] can be 0.4 to 0.6 mol / L, and specifically can be 0.45 to 0.55 mol / L.

[0100] In one embodiment of the present invention, the [Ca _f ], [Ca _i ], [B] and [SO4] can be analyzed in a short period of time, and the amount of Ca-containing additive added can be adjusted by considering the above measured values. Specifically, [Ca in equation 1 _f ] can adjust the amount of Ca-containing additive required to maintain the level desired in the present invention.

[0101]

[0102] In one embodiment of the present invention, in removing magnesium impurities from a solution containing lithium, by controlling the concentrations of Ca, B, SO4 in the solution, the additional Ca concentration according to the addition of additives, and the concentration of additives, magnesium and other impurities can be effectively removed while minimizing the loss of lithium, thereby improving the recovery rate and purity of the lithium finally recovered.

[0103]

[0104] A method for recovering lithium according to the present invention comprises the step of preparing a solution containing lithium.

[0105] In the present invention, the lithium-containing solution is an aqueous solution containing lithium, a lithium-containing liquid that is extracted from underground through a pump or introduced into a process in a form that is dissolved on its own, exists in the form of groundwater within the earth's crust, or is introduced underground due to industrial needs (e.g., introduced underground in an oil extraction process or introduced underground for geothermal power generation), and is not limited to brine in a salt lake area, geothermal brine, oil field brine (oil well brine), etc.

[0106] Specifically, the lithium-containing solution may be a saline solution. More specifically, the lithium-containing solution may be a concentrated saline solution.

[0107] The above concentrated brine contains lithium and may have a pH ranging from, but not limited to, 5.0 to 7.0.

[0108] The method for obtaining the above-mentioned concentrated brine is not limited in the present invention.

[0109] The concentration of lithium component in the above lithium-containing solution may be 0.5 to 20.0 g / L, specifically 1.0 to 10.0 g / L, and more specifically 1.5 to 4.0 g / L.

[0110] The concentration of the magnesium component in the above lithium-containing solution may be 2.0 to 25.0 g / L, and specifically 5.0 to 12 g / L.

[0111] The concentration of sulfate (SO4) in the solution containing the lithium may be 2.5 to 30.0 g / L, and specifically, 15 to 25 g / L.

[0112] The concentration of the boron component in the solution containing the lithium may be 0.5 to 10.0 g / L, and specifically, 1.1 to 3.0 g / L.

[0113] In the step of adding a Ca-containing additive to the above lithium-containing solution to precipitate a magnesium-containing precipitate, at least one selected from calcium hydroxide (Ca(OH)2), calcium carbonate (CaCO3), and calcium oxide (CaO) may be included.

[0114] In one embodiment of the present invention, the Ca-containing additive may be calcium hydroxide (Ca(OH)2). When calcium hydroxide is used as the additional additive, there is an advantage in that, in addition to removing magnesium through the form of Mg(OH)2 by introducing hydroxide ions and establishing pH conditions for removing metal impurities as carbonates, calcium ions meet with sulfate ions to precipitate, and even when further concentrated, lithium sulfate precipitation does not occur, but instead meets with borate ions to form a compound, thereby lowering the B concentration.

[0115] When the above Ca-containing additive is added to a solution containing lithium, it is preferable because it can suppress lithium precipitation while improving the removal efficiency of magnesium.

[0116] The above Ca-containing additive can be added in an amount of 1.0 to 1.6 equivalents (eq / mol) based on the equivalent weight of magnesium ions, and specifically, can be added in an amount of 1.1 to 1.3 equivalents (eq / mol).

[0117] If the Ca-containing additive is below the equivalent range, the magnesium removal rate is low, and if it exceeds the equivalent range, Ca is added in excess, which not only increases the calcium removal load in the subsequent calcium and other impurity removal step, but also increases the amount of lithium precipitation, resulting in a problem of a decrease in the lithium recovery rate in the entire process.

[0118] Meanwhile, when the concentration of lithium component in the solution containing lithium is 2.0 g / L or less, an alkali metal hydroxide may be added in addition to the Ca-containing additive, and the alkali metal hydroxide may be specifically sodium hydroxide (NaOH).

[0119] The molar ratio of the sodium hydroxide and Ca of the Ca-containing additive (NaOH:Ca) may be 1:3 to 1:1, and specifically 1:2 to 1:1.2.

[0120] In the present invention, by additionally adding sodium hydroxide at the above molar ratio, the concentration ratio of calcium concentration and lithium concentration in the filtrate after magnesium removal ([Ca] / [Li]) is controlled to the range targeted by the present invention, so that calcium can be effectively removed while lithium precipitation can be suppressed in the subsequent step of removing impurities such as calcium, which is preferable.

[0121]

[0122] The concentration ratio of Ca to Li in the above-mentioned solution ([Ca] / [Li]) may be 1.05 or less, and specifically, 1.0 or less.

[0123] The Li concentration in the above filtrate may be 1.5 to 8.0 g / L, and the Ca concentration in the above filtrate may be 1.0 to 6.0 g / L.

[0124] In the present invention, by controlling the Ca concentration, Li concentration and their concentration ratio in the filtrate within the above range, it is preferable to effectively remove calcium and suppress lithium precipitation in the subsequent calcium and other impurity removal step.

[0125]

[0126] In one embodiment of the present invention, the step of adding a Ca-containing additive to the lithium-containing solution to precipitate a magnesium-containing precipitate may include a step of controlling the temperature of the lithium-containing solution to 50°C or higher, specifically, 50 to 95°C.

[0127] When the temperature of the lithium-containing solution is within the above range, there is an advantage in that the expected lithium recovery rate can be increased without changing the lithium concentration while simultaneously effectively removing impurities such as boron. In addition, it is preferable because the solubility of calcium precipitates, such as calcium carbonate, decreases within the solubility of lithium compounds in the lithium-containing solution.

[0128] In one embodiment of the present invention, the step of adding a Ca-containing additive to the lithium-containing solution to precipitate a magnesium-containing precipitate may include the step of adding a solution having a lower lithium concentration than the lithium-containing solution to the lithium-containing solution.

[0129] When a solution having a lower lithium concentration than the lithium-containing solution is added to the lithium-containing solution, the lithium recovery rate can be increased by lowering the lithium concentration in the lithium-containing solution, which is preferable.

[0130] A solution having a lower lithium concentration than the above lithium-containing solution may be, but is not limited to, a calcium-free raw material solution, a liquid solution in a lithium-containing process having a low concentration, or fresh water.

[0131]

[0132] In one embodiment of the present invention, in the step of adding a Ca-containing additive to the lithium-containing solution to precipitate a magnesium-containing precipitate, the lithium-containing solution to which the Ca-containing additive has been added may have a pH of 10.0 to 12.5, and specifically, 10.5 to 12.0.

[0133] When the pH of the lithium-containing solution with the Ca-containing additive added satisfies the above range, not only is the magnesium removal rate excellent, but the concentration ratio of calcium and lithium ([Ca] / [Li]) in the lithium-containing solution from which magnesium has been removed can be controlled to the range targeted by the present invention, thereby improving the final lithium recovery rate. In addition, it is preferable because the filtration speed can be improved during solid-liquid separation in the step of obtaining a filtrate by separating the precipitated precipitate, which will be described later. In addition, it is preferable because the precipitate produced has an appropriate particle size, so that filtration is easy.

[0134]

[0135] If the pH of the lithium-containing solution containing the Ca-containing additive is below the above range, the magnesium removal efficiency is low, which reduces the purity of the final recovered lithium. If the pH exceeds the above range, the precipitate separation efficiency is reduced, which may lead to an increase in costs. In addition, the Ca content increases, which increases the load in the subsequent calcium and other impurity removal step, and the amount of lithium precipitation increases, which reduces the lithium recovery rate.

[0136]

[0137] In one embodiment of the present invention, the pH of the lithium-containing solution into which the Ca-containing additive is added can satisfy the following relationship 2.

[0138] [Relationship 2]

[0139] pH _f = e×[pH _i ] + g×[B] + h×f([Mg],Y) + i1×[Ca _ad ] + i2×[Ca _ad ] 2 + i3×[Ca _ad ] 3

[0140] In the above relational expression 2,

[0141] f([Mg],Y) is a function of the pH of the filtrate and the Mg concentration (g / L) in the lithium-containing solution, which is 8.5+3*tanh[Mg / 2]+exp(pH _f -10) can be expressed as,

[0142] pH _f is the pH of the residue,

[0143] pH _i is the pH of the solution containing lithium,

[0144] [Mg] is the Mg concentration in the filtrate (mol / L),

[0145] [MOH] is the OH concentration (mol / L) of alkali metal hydroxide contained in the filtrate,

[0146] [B] is the concentration of B (mol / L) in a solution containing lithium,

[0147] [Ca _ad ] is the value obtained by dividing the Ca concentration (mol / L) of the calcium-containing additive added to the lithium-containing solution by the solution volume (L).

[0148] e is a rational number between 3.2710 and 3.2730, specifically between 3.2715 and 3.2725,

[0149] g is a rational number between 2.2980 and 2.3000, specifically between 2.2985 and 2.2995,

[0150] h is a rational number between -0.8510 and -0.8520, specifically between -0.8505 and -0.8515,

[0151] i1 is a rational number between 4.1030 and 4.1050, specifically between 4.1038 and 4.1044,

[0152] i2 is a rational number between -0.7935 and -0.7920, specifically between -0.7932 and -0.7926,

[0153] i3 is a rational number between 0.0560 and 0.0580, specifically between 0.0566 and 0.0572.

[0154] The above e, g, h and i1 to i3 are factors obtained from a graph of the calcium concentration in the lithium-containing solution after addition of the calcium-containing additive according to the calcium concentration in the initial lithium-containing solution.

[0155]

[0156] In one embodiment of the present invention, the method may further include a step of separating the precipitated precipitate to obtain a filtrate; and then, a step of removing impurities by adding an impurity removing agent to the filtrate.

[0157] The step of removing impurities by adding an impurity removing agent to the above-mentioned filtrate may be a step of precipitating a precipitate containing calcium by adding a calcium removing agent.

[0158] Specifically, when compared to the filtrate before adding the calcium remover, the lithium loss rate of the filtrate may be 5% or less, specifically 3% or less.

[0159] The above calcium remover may include at least one selected from sodium hydroxide (NaOH), sodium carbonate (Na2CO3), calcium hydroxide (Ca(OH)2), sodium sulfate (Na2SO4), and potassium hydroxide (KOH).

[0160] The above lithium can be recovered by separating the solid phase and the liquid phase into a filtrate through a depressurized filtration method after the reaction in which the above precipitate is precipitated is completed, and then recovering the lithium from the filtrate.

[0161] For example, the above filtrate can be recovered in the form of lithium carbonate or lithium phosphate by carbonating or phosphorylating, but is not limited thereto.

[0162]

[0163] The method for recovering lithium according to the present invention has the advantage of effectively removing magnesium impurities in a lithium-containing solution and simultaneously minimizing lithium loss, thereby improving the lithium recovery rate and purity by quantifying the residual calcium concentration in the solution after magnesium removal using equation 1.

[0164] Hereinafter, embodiments of the present invention will be described in more detail through examples. However, the following examples are merely preferred embodiments of the present invention, and the present invention is not limited to the following examples.

[0165]

[0166] (Manufacturing example using Ca(OH)2)

[0167] The composition of the lithium-containing solution before adding Ca(OH)2 as a magnesium remover and the composition of the filtrate after precipitating magnesium using Ca(OH)2 are shown in Table 1. At this time, the filtrate was obtained by the following method.

[0168] Ca(OH)2 powder was added to 200 ml of concentrated brine as a solution containing lithium in an equivalent amount shown in Table 1 for the magnesium content, and stirred at 200 RPM for 2 hours to precipitate a precipitate.

[0169] After the sediment was precipitated, calcium was removed by separating it into solid and liquid phases using a pressurized solid-liquid separation device, and the components of the filtrate from which magnesium was removed were analyzed, and the results are shown in Table 1 below.

[0170] Component analysis was performed using an ICP analyzer.

[0171]

[0172] Reaction Equivalent Ratio (Ca(OH)2 / Mg before reaction) After removal of magnesium, filtrate Relationship 1 Relationship 2 pH Composition (g / L) Residual Mg (g / L) Residual Ca(g / L)pHCa / LiLiSCaBMgPreparation Example 1Composition 16.653.90011.210.2372.6619.0931.001.4912.4019.270.6082.4529.73Preparation Example 21.150.3793.1229.550.7883.0189.50Preparation Example 31.300.0003.89410.940.9833.87110.78Preparation Example 41.450.0003.95111.781.0203.92711.53Preparation Example 5Composition 26.684.27011.810.2612.835 9.6021.001.2452.6129.790.6092.57810.26 Manufacturing Example 61.150.1563.34810.270.7763.50310.38 Manufacturing Example 71.300.0003.78211.190.8973.91211.74 Manufacturing Example 81.450.0004.04411.870.9694.09511.86 Manufacturing Example 9 Composition 36.703.86811.380.2392.7259.2021.002.0221.6989.580.4291.7139.95 Manufacturing Example 101.150.924 2.1839.800.5342.1209.42 Manufacturing Example 111.300.0093.20810.720.8053.08110.20 Manufacturing Example 121.450.0003.80711.800.9493.84912.32 Manufacturing Example 13 Composition 46.604.06811.660.2482.7759.3481.001.3051.9399.350.4761.9799.41 Manufacturing Example 141.150.3642.7579.680.6622.62310.15 Manufacturing Example 151.300.0003.84510.850. 9163.70110.54 Manufacturing Example 161.450.0003.82511.490.9283.64411.86 Manufacturing Example 17 Composition 56.231.5765.7490.4521.0393.3841.000.9781.1889.510.7511.1659.17 Manufacturing Example 181.150.4761.4859.670.9381.4959.63 Manufacturing Example 191.300.0532.06410.171.3022.09310.28 Manufacturing Example 201.450.0002.23011.301.4072.33510.95 Manufacturing Example 21 Composition 66.921.7425.9720.4021.1653.6321.000.9491.1859.530.6771.2349.12 Manufacturing Example 221.150.4131.5069.720.8591.4429.26 Manufacturing Example 231.300.0281.68710.320.9681. 73310.64 Manufacturing Example 241.450.0001.91411.321.0991.86311.86 Manufacturing Example 25 Composition 74.855.42718.0150.2043.52111.831.001.7782.4679.360.4552.4579.50 Manufacturing Example 261.150.4573.1879.3 80.5873.1769.27 Manufacturing Example 271.300.0004.08010.410.7523.83110.14 Manufacturing Example 281.450.0004.45811.070.8214.42010.73 Manufacturing Example 29 Composition 84.636.80322.8980.1734.4414.831.002.088 2.6599.170.3912.5598.83 Manufacturing Example 301.150.4243.3249.940.4893.3139.54 Manufacturing Example 311.300.0004.29210.590.6313.96310.49 Manufacturing Example 321.450.0004.59311.900.6754.51111.68.

[0173] Referring to Table 1 above, it can be confirmed that as the equivalent ratio of Ca(OH)2 and magnesium in the solution before reaction (Ca(OH)2 / Mg before reaction) increases, the magnesium removal rate tends to increase.

[0174] In the case of Manufacturing Examples 1 to 16 where the lithium concentration in the solution before reaction is approximately 4.0 / L, it can be confirmed that the concentration ratio of Ca and Li in the filtrate is 1.05 or less in all cases where the equivalent ratio (Ca(OH)2 / Mg before reaction) is 1.00, 1.15, 1.30, or 1.45.

[0175] In addition, in the case of Manufacturing Examples 1 to 16, when the equivalent ratio (Ca(OH)2 / Mg before reaction) was 1.30 or 1.45, the residual Mg concentration in the filtrate was found to be less than 0.1 g / L, but when the equivalent ratio (Ca(OH)2 / Mg before reaction) was 1.00 and 1.15, the residual Mg concentration in the filtrate was confirmed to be less than 0.1 g / L.

[0176]

[0177] Meanwhile, in the case of Manufacturing Examples 17 to 24 where the lithium concentration in the solution before the reaction was less than 2.0 g / L, the residual Mg concentration in the filtrate was found to be less than 0.1 g / L when the equivalent ratio (Ca(OH)2 / Mg before the reaction) was 1.45, but the residual Mg concentration in the filtrate was found to be greater than 0.1 g / L when the equivalent ratio (Ca(OH)2 / Mg before the reaction) was 1.00, 1.15, and 1.30.

[0178] In addition, in the case of Manufacturing Examples 17 to 24, it was found that as the equivalence ratio (Ca(OH)2 / Mg before reaction) increased, the concentration ratio of Ca and Li in the filtrate (Ca / Li) increased.

[0179] As a result, in the case of a lithium-containing solution with a low concentration, the Ca(OH)2 equivalent required for Mg removal is relatively large, which results in a relatively high concentration ratio of Ca and Li (Ca / Li) in the filtrate from which Mg has been removed.

[0180]

[0181] (Manufacturing example using Ca(OH)2 and NaOH)

[0182] Using the same method as the manufacturing example using the above Ca(OH)2, a magnesium removal experiment was conducted by adding NaOH in addition to Ca(OH)2 as a magnesium removal agent using composition 5 in Table 1. At this time, the equivalence ratio ((Ca(OH)2+NaOH) / Mg before reaction)) was set to 1.35.

[0183] The analysis results are shown in Table 2 below.

[0184] Molar ratio before reaction NaOH / Ca(OH)2 After removing magnesium, equation 1, equation 2, composition (g / L) Mg(g / L) Ca(g / L) pH Ca / Li LiSCaBMg, manufacturing example 33, composition 5 1.57, 6 5.74, 9 0.45, 2 1.03, 9 3.38, 4 0:100, 000, 2.44, 2 1.33, 1.39, 4 2.50, 4 10.86, manufacturing example 34, 2:90, 000, 2.03, 3 11.44, 1.16, 11.94, 1 10.73, manufacturing example 35, 4:80, 000, 1.70, 6 11.57, 0.97, 5 1.66, 2 11.12, manufacturing example 36, 6:70, 000, 1.45, 1 1.68, 0.83, 0 1.53, 6 11.29

[0185] Referring to Table 2 above, when the molar ratio of NaOH and Ca(OH)2 is 1:2 and 6:7, it was confirmed that the concentration ratio of Ca and Li (Ca / Li) in the filtrate from which Mg was removed was less than 1.0, and it can be confirmed that this also reproduces the value of 1.75 g / L, which is the Li concentration of the filtrate, in equation 1.

[0186]

[0187] Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications can be made within the scope of the patent claims, the detailed description of the invention, and the attached drawings, and it is obvious that this also falls within the scope of the present invention.

[0188] Accordingly, the actual scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. Step of preparing a solution containing lithium; A step of adding a Ca-containing additive to the above lithium-containing solution to precipitate a magnesium-containing precipitate; and A step of separating the precipitated sediment to obtain a residue; The Mg concentration in the residue is less than 0.1 g / L, The Ca concentration of the above solution satisfies the following relationship 1: How to recover lithium: [Relationship 1] [That _f ] = a×[Ca _i ] + b×[B] +c×[SO4] + d1×[Ca _ad ] + d2×[Ca _ad ] 2 + d3×[Ca _ad ] 3 In the above relational expression 1, [Ca _f ] is the Ca concentration in the residue (mol / L), [Ca _i ] is the Ca concentration (mol / L) in a solution containing lithium, [B] is the concentration of B in the solution containing lithium (mol / L), [SO4] is the SO4 concentration (mol / L) in a solution containing lithium, [Ca _ad ] is the amount (mol) of calcium-containing additive added to a solution containing lithium divided by the volume (L) of the solution. a is a rational number between 120 and 140, b is a rational number between 22 and 26, c is a rational number between -90 and -75, d1 is a rational number in the range 155 to 175, d2 is a rational number in the range -1333 to -1200, d3 is a rational number in the range of 3450 to 3850.

2. In paragraph 1, The above Ca-containing additive is added in an amount of 1.1 to 1.50 equivalents (eq / mol) based on the equivalent weight of magnesium ions. Method of recovering lithium.

3. In paragraph 1, The above Ca-containing additive includes at least one selected from calcium hydroxide (Ca(OH)2), calcium carbonate (CaCO3), and calcium oxide (CaO). Method of recovering lithium.

4. In paragraph 3, The above Ca-containing additive is calcium hydroxide (Ca(OH)2). Method of recovering lithium.

5. In paragraph 1, The solution containing the lithium to which the Ca-containing additive is added has a pH of 10.5 to 12.

0. Method of recovering lithium.

6. In paragraph 1, The concentration ratio of Ca to Li in the above solution ([Ca] / [Li]) is 1.05 or less. Method of recovering lithium.

7. In paragraph 1, The Li concentration in the above residue is 1.5 to 8.0 g / L, Method of recovering lithium.

8. In paragraph 1, The Ca concentration in the above solution is 1.0 to 6.0 g / L. Method of recovering lithium.

9. In paragraph 1, In the step of preparing the above lithium-containing solution, The lithium concentration in the solution containing the lithium is 1.0 to 10.0 g / L, Method of recovering lithium.

10. In paragraph 9, In the step of preparing the above lithium-containing solution, The lithium concentration in the solution containing the lithium is 1.0 to 2.0 g / L, In the step of adding a Ca-containing additive to the above lithium-containing solution to precipitate a magnesium-containing precipitate, Adding more alkali metal hydroxide, Method of recovering lithium.

11. In paragraph 10, The molar ratio of Ca of the above alkali metal hydroxide and the Ca-containing additive to be added is 3:8.5 to 7:6.

5. Method of recovering lithium.

12. In paragraph 1, In the step of preparing the above lithium-containing solution, The concentration of magnesium component in the solution containing lithium is 2.0 to 25.0 g / L, Method of recovering lithium.

13. In paragraph 1, In the step of preparing the above lithium-containing solution, The concentration of sulfate group (SO4) in the solution containing the lithium is 2.5 to 30.0 g / L. Method of recovering lithium.

14. In paragraph 1, A step of separating the above precipitated precipitate to obtain a residue; thereafter, It further includes a step of removing impurities by adding an impurity removing agent to the above-mentioned residue; Method of recovering lithium.

15. In paragraph 14, The step of removing impurities by adding an impurity removing agent to the above-mentioned residue; A step of precipitating a precipitate containing calcium by adding a calcium remover, Method of recovering lithium.

16. In paragraph 15, In the step of precipitating a precipitate containing calcium by adding the above calcium remover, The lithium loss rate of the above residue is 5 wt% or less. Method of recovering lithium.

17. In paragraph 15, The above calcium remover comprises at least one selected from sodium hydroxide (NaOH), sodium carbonate (Na2CO3), calcium hydroxide (Ca(OH)2), sodium sulfate (Na2SO4), and potassium hydroxide (KOH). Method of recovering lithium.

18. In paragraph 15, The above calcium remover is added in an amount of 0.2 to 1.2 equivalents (eq / mol) based on the equivalent amount of calcium ions. Method of recovering lithium.

19. In paragraph 1, The pH of the solution containing the lithium to which the Ca-containing additive has been added satisfies the following equation 2: How to recover lithium: [Relationship 2] pH _f = e×[pH _i ] + g×[B] + h× f([Mg],Y) + i1×[Ca _ad ] + i2×[Ca _ad ] 2 + i3×[Ca _ad ] 3 In the above relational expression 2, f([Mg],Y) is a function of the pH of the filtrate and the Mg concentration (g / L) in the lithium-containing solution, 8.5+3*tanh[Mg / 2]+exp(pH _f -10) can be expressed as, pH _f is the pH of the residue, pH _i is the pH of the solution containing lithium, [Mg] is the Mg concentration in the residue (mol / L), [MOH] is the OH concentration (mol / L) of alkali metal hydroxide contained in the residue. [B] is the concentration of B in the solution containing lithium (mol / L), [Ca _ad ] is the Ca concentration (mol / L) of the calcium-containing additive added to the solution containing lithium, e is a rational number between 3.2710 and 3.2730, g is a rational number between 2.2980 and 2.3000, h is a rational number between -0.8510 and -0.8520, i1 is a rational number between 4.1030 and 4.1050, i2 is a rational number between -0.7935 and -0.7920, i3 is a rational number between 0.0560 and 0.0580.

20. In paragraph 1, Above [Ca _f ], [Ca _i ], [B] and [SO4] are measured to adjust the amount of Ca-containing additives added. Method of recovering lithium.