Pretreatment method for lithium-containing solution

Abstract

A pretreatment method for a lithium-containing solution, according to the present invention, comprises: an adsorption step of passing a lithium-containing solution through an adsorbent so as to obtain a lithium-adsorbed adsorbent; a washing step of passing a pretreatment solution containing divalent cations through the lithium-adsorbed adsorbent, so as to remove impurities; a desorption step of passing a medium through the lithium-adsorbed adsorbent so as to obtain a lithium-containing desorption solution; and a step of injecting the lithium-containing desorption solution into an electrodialysis device so as to obtain a lithium hydroxide aqueous solution.

Description

Pretreatment method for lithium-containing solutions

[0001] This application claims priority to Korean Patent Application No. 10-2024-0191458, and the contents of the said priority application specification are incorporated into this specification.

[0002] The present invention relates to a method for pre-treating a lithium-containing solution.

[0003] Lithium-ion batteries are an essential component in small devices such as mobile phones and laptops, and recently, the demand for them is also increasing as a power source for hybrid and electric vehicles. Consequently, the demand for lithium, a key raw material for lithium-ion batteries, is also surging.

[0004] Lithium, a key material for such lithium secondary batteries, is generally extracted from minerals, seawater, brine, etc. However, the lithium content in the Earth's crust is only 0.006%, and because of its high reactivity, it is not found in nature in the form of pure metal; generally, it is extracted in the form of lithium compounds such as Li2CO3 and LiOH·H2O rather than in the form of pure metal.

[0005] In addition, although seawater is abundant globally, its lithium content is low at 0.17 mg / L, which results in low efficiency for lithium extraction and high production costs compared to other lithium sources.

[0006] The most common method for extracting lithium is to evaporate water from brine and then add carbonates to extract lithium in the form of lithium carbonate. However, to extract lithium carbonate by adding carbonates, the brine must be concentrated to an economically viable level before proceeding with the extraction process; consequently, there is a problem in that brine sources capable of improving the economic feasibility of lithium extraction are scarce worldwide.

[0007] Therefore, there is an urgent need to develop technologies that can economically and efficiently recover lithium from lithium-containing solutions. As one such method, selective adsorption and desorption technologies for lithium using adsorbents are being researched.

[0008] The present invention aims to provide a method for pretreating a lithium-containing solution that enables the recovery of lithium more economically and effectively by including a pretreatment step in a technology for recovering lithium through the adsorption and desorption of lithium using an adsorbent.

[0009] The present invention provides a method for pretreating a lithium-containing solution, comprising: an adsorption step of passing a lithium-containing solution through an adsorbent to obtain an adsorbent on which lithium is adsorbed; a washing step of passing a pretreatment solution containing divalent cations through the adsorbent on which lithium is adsorbed to remove impurities; a desorption step of passing a medium through the adsorbent on which lithium is adsorbed to obtain a lithium-containing desorbent; and a step of introducing the lithium-containing desorbent into an electrodialysis device to obtain an aqueous lithium hydroxide solution.

[0010] The pretreatment method for a lithium-containing solution according to the present invention has the advantage of being able to delay the desorption of lithium from the adsorbent and reduce impurities in the lithium-containing desorption solution.

[0011] Figure 1 is a figure showing the concentration of lithium present in the pretreatment solution according to the embodiments and comparative examples of the present invention.

[0012] Hereinafter, embodiments of the present invention will be described in detail. However, these are presented as examples and are not intended to limit the present invention, and the present invention is defined only by the scope of the claims set forth below.

[0013] In the present invention, when a part is described as "comprising" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0014]

[0015] Pretreatment Method for Lithium-Containing Solutions

[0016] One aspect of the present invention relates to a method for pretreating a lithium-containing solution, comprising: an adsorption step of passing a lithium-containing solution through an adsorbent to obtain an adsorbent on which lithium is adsorbed; a washing step of passing a pretreatment solution containing divalent cations through the adsorbent on which lithium is adsorbed to remove impurities; a desorption step of passing a medium through the adsorbent on which lithium is adsorbed to obtain a lithium-containing desorbent; and a step of introducing the lithium-containing desorbent into an electrodialysis device to obtain an aqueous lithium hydroxide solution.

[0017]

[0018] The pretreatment method for a lithium-containing solution according to the present invention has the advantage of being able to recover lithium economically and efficiently from a lithium-containing solution by implementing a process of removing impurities using a pretreatment solution between the adsorption and desorption of lithium using an adsorbent and delaying the desorption of lithium.

[0019] Specifically, when undergoing a process to remove impurities using a pretreatment solution, such as a washing process, there is a phenomenon in which lithium contained in the adsorbent is desorbed initially. If lithium contained in the adsorbent is desorbed initially, there may be a problem in that the yield of the final lithium produced may be lowered. However, the pretreatment method for a lithium-containing solution according to the present invention has the excellent effect of removing impurities by washing with a pretreatment solution, and at the same time, the desorption of lithium is delayed during the washing step, and as lithium is desorbed during the subsequent desorption step, it has the excellent advantage of ultimately recovering lithium with excellent purity and yield.

[0020]

[0021] Adsorption step

[0022] A method for pretreating a lithium-containing solution according to the present invention comprises an adsorption step of passing the lithium-containing solution through an adsorbent to obtain an adsorbent on which lithium is adsorbed.

[0023] The above adsorption step refers to a step of adsorbing lithium from a lithium-containing solution. Specifically, the lithium-containing solution may be passed through an adsorbent to adsorb lithium onto the adsorbent.

[0024]

[0025] In one embodiment of the present invention, the lithium-containing solution may include LiCl.

[0026] In another embodiment of the present invention, the lithium concentration of the lithium-containing solution in the adsorption step may be 0.03 to 2.0 g / L.

[0027] When the lithium concentration of the above lithium-containing solution satisfies the above range, lithium adsorption on the adsorbent is easy, resulting in excellent adsorption efficiency and the advantage of increasing economic efficiency by reducing the need to operate multiple adsorption columns.

[0028] In addition, since lowering the time to reach the breakthrough point of the adsorbent reduces the need to operate multiple adsorption columns and thereby increases economic efficiency, it is desirable for the lithium concentration of the lithium-containing solution to satisfy the above range.

[0029]

[0030] The above adsorbent is intended to adsorb lithium dissolved in the above lithium-containing solution.

[0031] In another embodiment of the present invention, the adsorbent may be an aluminum-based adsorbent.

[0032] Specifically, the above adsorbent may include aluminum hydroxide.

[0033] When using the aluminum-based adsorbent containing the above aluminum hydroxide, the adsorption amount of lithium dissolved in the lithium-containing solution is high, and since there is almost no loss of aluminum in the desorption step described later, the adsorbent has a long lifespan, thus providing the advantage of excellent economic efficiency in the lithium extraction process.

[0034] The above aluminum-based adsorbent may be a molded body comprising adsorbent powder and a binder.

[0035] The above-mentioned adsorbent powder may be, for example, an adsorbent powder containing aluminum hydroxide. The advantages of using an adsorbent powder containing aluminum hydroxide are the same as those described above.

[0036] The above binder is intended to manufacture the adsorbent powder into a molded body of a suitable shape and serves to bind the adsorbent powders together.

[0037] The binder may include, for example, at least one of polyvinyl chloride (PVC), polysulfone, and polyaniline. Specifically, it is preferable that the binder include polyvinyl chloride (PVC), which can provide excellent bonding strength between adsorbent powders.

[0038]

[0039] Meanwhile, the step of passing a lithium-containing solution through an aluminum-based adsorbent to adsorb lithium onto the aluminum-based adsorbent may include, for example, the reaction of the following reaction scheme 1.

[0040] [Reaction Equation 1]

[0041] LiCl (1-x) .Al(OH)3.nH2O + xLiCl → LiCl.Al(OH)3.nH2O + (1-x)LiCl

[0042]

[0043] Washing step

[0044] The method for pretreatment of a lithium-containing solution according to the present invention includes a washing step of removing impurities by passing a pretreatment solution containing divalent cations through an adsorbent on which lithium is adsorbed as described above.

[0045] In summary, the pretreatment method for a lithium-containing solution according to the present invention performs a washing step after the adsorption step and before the desorption step. The washing step refers to a step of removing impurities by passing a pretreatment solution through an adsorbent on which lithium has been adsorbed.

[0046]

[0047] In another embodiment of the present invention, the pretreatment solution may inhibit the desorption of lithium adsorbed on the adsorbent during the washing step.

[0048]

[0049] In another embodiment of the present invention, the pretreatment solution may reduce the Na concentration of the lithium-containing desorption solution.

[0050]

[0051] The pretreatment solution according to the present invention contains divalent cations. When the pretreatment solution contains divalent cations, compared to when the pretreatment solution contains monovalent cations, there is an advantage that the concentration of impurities, specifically Na of the final lithium-containing desorption solution, is low.

[0052] When the Na concentration of the above lithium-containing desorption solution is low, there is an advantage in that the current efficiency can be increased in the lithium hydroxide conversion process described later, specifically the LiOH BPED process of LiCl. In addition, when the lithium hydroxide solution obtained in the above BPED process is crystallized, Na is not precipitated together with the lithium hydroxide product but can remain in the solution, that is, the crystallization filtrate.

[0053] I do not wish to be limited by theory, but for example, the above pretreatment solution as a divalent cation, Ca 2+ , Mg 2+In cases including the like, the above Ca 2+ and Mg 2+ Since adsorption itself does not occur, it can be easily removed, so the Ca of the above lithium-containing desorption solution 2+ , Mg 2+ The concentration of can be maintained at a low level. In addition, there is the advantage of reducing the Na concentration in the lithium-containing desorption solution.

[0054] When a monovalent cation is used as the above pretreatment solution, the content of the monovalent cation in the lithium-containing desorption solution may be 0.02 to 0.2 g / L.

[0055] On the other hand, when a divalent cation is used as the above pretreatment solution, the content of monovalent cation in the lithium-containing desorption solution may be within 50 mg / L.

[0056]

[0057] In another embodiment of the present invention, the pretreatment solution may include one or more salts selected from the group consisting of calcium and magnesium.

[0058] The calcium and magnesium mentioned above possess appropriate reactivity compared to other divalent cations, making process control easy and allowing for the suppression of excessive side reactions. Additionally, since they are more environmentally friendly and harmless to the human body compared to other divalent cations, thereby minimizing the impact on workers and the environment, it is desirable for the pretreatment solution to contain one or more salts selected from the group consisting of calcium and magnesium. Furthermore, using a pretreatment solution containing calcium and magnesium offers the advantage of maintaining low calcium and magnesium content even during concentration, as subsequent removal is easy.

[0059] In another embodiment of the present invention, the pretreatment solution may include one or more selected from the group consisting of CaCl2 and MgCl2.

[0060] Specifically, the above pretreatment solution is Cl as an anion corresponding to lithium. - It may include.

[0061] Since Li in the adsorption / desorption solution using an Al-based adsorbent may be present in the form of LiCl, and there is a possibility that the said anion may act as an impurity during pretreatment using other anions, the said anion is Cl - It is desirable that it is.

[0062]

[0063] In another embodiment of the present invention, the concentration of Total Dissolved Solids (TDS) in the pretreatment solution may be in the range of 0.5 to 3.0 mol / L.

[0064] In this case, total dissolved solids refers to the concentration calculated by including all salts, regardless of the type of salt.

[0065] If the concentration of total dissolved solids falls below the above range, lithium may be desorbed, which may impair the lithium recovery rate and prevent the efficient removal of impurities.

[0066] In addition, if the concentration of total dissolved solids exceeds the above range, salt may act as an impurity. In particular, considering that the solubility of magnesium chloride (CaCl2), which accounts for more than 50 wt% of the total weight of total dissolved solids, is approximately 0.556 mol / L (approx. 54.3 g / L, @20℃, Anhydrous), the solution becomes saturated, leading to the formation of precipitates. This creates a problem where it is difficult to perform the impurity removal process and may increase the load on subsequent processes. Therefore, it is desirable for the total dissolved solids included in the pretreatment solution to satisfy the above range.

[0067]

[0068] The above pretreatment solution may further contain lithium. If the above lithium is further included, the influence of other impurities can be reduced, and if the said pretreatment solution is mixed with raw brine and extracted again, the loss of lithium may not be significant.

[0069] While we do not wish to be limited by theory, the concentration of Li lost to the initial washing solution—in other words, the pretreatment solution—varies depending on the Li concentration of the brine. Therefore, if the Li concentration of the brine is very high, it may be somewhat difficult to re-extract by mixing the pretreatment solution with the brine. This is because if the Li concentration is too low relative to the brine, there is a problem with the concentration becoming too low. However, in the case of oilfield or geothermal brine where the brine concentration is low, the Li concentration of the pretreatment solution is higher relative to the brine, making it possible to mix and use them. Specifically, additional factors to consider when mixing with the brine are the Ca and Mg concentrations of the brine. If the concentrations of Ca and Mg in the pretreatment solution become higher relative to the brine, it can increase the overall influx of impurities when mixed; therefore, unlike Li, the concentrations of Ca and Mg must be lower relative to the brine in this case. In short, by considering the lithium, Ca, and Mg concentrations of the brine, the corresponding pretreatment solution can be mixed with the brine for re-extraction.

[0070]

[0071] In another embodiment of the present invention, the pretreatment solution may contain lithium at a concentration of 0.02 to 3.0 g / L throughout the entire pretreatment solution.

[0072] With respect to the amount of lithium adsorbed on the adsorbent, the amount of lithium contained in the pretreatment solution after passing through the adsorbent may be in the range of 0.1 to 10.0 weight%, and specifically, may be in the range of 0.5 to 8.0 weight%, 1.0 to 6.0 weight%, 1.0 to 4.0 weight%, or 1.0 to 2.5 weight%.

[0073] Specifically, the amount of lithium contained in the pretreatment solution after passing through the adsorbent can refer to the amount of lithium lost due to the initial washing solution, in other words, the pretreatment solution; in short, the pretreatment method for a lithium-containing solution according to the present invention has the advantage of minimizing the amount of lithium lost due to the pretreatment solution.

[0074]

[0075] This means that the above pretreatment solution inhibits the desorption of lithium adsorbed on the adsorbent during the washing step.

[0076]

[0077] Detachment step

[0078] The pretreatment method for a lithium-containing solution according to the present invention comprises a desorption step of obtaining a lithium-containing desorbent by passing a medium through the aforementioned adsorbent on which lithium is adsorbed.

[0079] Specifically, a lithium-containing desorbent can be obtained by passing a medium, such as distilled water or an aqueous solution containing a lithium salt, through the aluminum adsorbent on which the lithium is adsorbed.

[0080] At this time, the amount of medium passed through the aluminum adsorbent on which the lithium is adsorbed can be 10 to 50 BV, specifically 15 to 40 BV, based on the bed volume (BV) of the adsorbent column.

[0081]

[0082] In the total lithium-containing desorbent obtained by passing a medium through an adsorbent, the lithium concentration in the desorbent after 80 volume% of the desorbent has passed through may be 0.4 g / L or less.

[0083] Lithium hydroxide can be recovered through a desorption solution with a high lithium concentration obtained through the above desorption step, but is not limited thereto. Specifically, the lithium-containing desorption solution can be used in the process up to the step of passing a medium with an amount of 10 BV after the washing step in which impurities are removed, and preferably, the lithium-containing desorption solution can be used up to the step of passing a medium with an amount of 7 BV or 5 BV, but may vary depending on the shape of the desorption curve.

[0084] Regarding the amount of lithium present in the adsorbent after the above adsorption step, the amount of lithium obtained in the above desorption step may be in the range of 90.0 to 99.9 wt%, and specifically, in the range of 95.0 to 99.9 wt%.

[0085]

[0086] In the case where the washing step according to the present invention is not included, the amount of lithium lost with respect to the amount of lithium present in the adsorbent after the adsorption step may be in the range of 10.0 to 50.0 wt%, and specifically, in the range of 25.0 to 45.0 wt% or 30.0 to 40.0 wt%. The reason for such lithium loss is that a lithium-containing desorption solution containing a high concentration of impurities may be difficult to use in the lithium recovery process. It is preferable that the concentration of impurities (salts excluding lithium) be lower, and specifically, in the case of a lithium-containing desorption solution containing impurities (salts excluding lithium) at a concentration of 20 g / L, 15 g / L, or 10 g / L or less, the recovery rate of lithium hydroxide obtained after proceeding with the subsequent process described below may be excellent.

[0087]

[0088] The step of obtaining a lithium-containing desorbent by passing a medium through the above-mentioned aluminum adsorbent on which lithium is adsorbed may include, for example, the reaction of Reaction Scheme 2 below.

[0089] [Reaction Equation 2]

[0090] LiCl·Al(OH)3·nH2O → LiCl (1-x) ·Al(OH)3·nH2O + xLiCl

[0091]

[0092] The medium used in the above desorption step may be an aqueous solution containing a lithium salt, specifically, the medium may be an aqueous solution containing lithium chloride. In this case, the concentration of lithium in the obtained desorption solution may be increased. This improvement in the lithium concentration in the desorption solution can reduce the load on the downstream concentration process.

[0093] Specifically, the lithium concentration in the medium may be in the range of 0.05 to 1.50 g / L, and more specifically, 0.10 to 1.00 g / L, 0.10 to 0.80 g / L, or 0.10 to 0.40 g / L.

[0094] When the lithium concentration in the medium satisfies the above range, it is desirable to suppress the phenomenon in which lithium (Li) contained in the aluminum adsorbent is lost and causes damage to the LDH (Layered Double Hydroxide) structure, and to suppress the phenomenon in which adsorption rather than desorption occurs.

[0095]

[0096] In another embodiment of the present invention, the lithium-containing desorption solution may have a Na concentration of 300 mg / L or less.

[0097] In short, the lithium-containing desorption solution has the advantage of being able to maintain impurities, specifically Na concentration, at a low level.

[0098] Specifically, it is preferable that the lithium-containing desorption solution using the above divalent cation has a Na concentration of 300 mg / L or less. In short, it is desirable that the impurities in the final lithium hydroxide aqueous solution, specifically the Na concentration, are low so that a high-purity LHM (Lithium Hydroxide Material) can be obtained without undergoing an additional recrystallization step.

[0099]

[0100] The concentration of lithium contained in the lithium-containing desorption solution obtained by the above method may be 0.1 g / L to 3.0 g / L, or 0.2 g / L to 3.0 g / L, and more specifically, 0.5 g / L to 2.5 g / L.

[0101] When the lithium concentration of the above lithium-containing desorption solution is high, it implies that the amount of water to be removed in the subsequent concentration step is reduced, thereby significantly improving the process burden of the downstream process. In this case, the downstream process refers to the concentration step, which may mean the step of feeding the solution into an electrodialysis device.

[0102]

[0103] The method for pretreating a lithium-containing solution according to the present invention may further include a step of concentrating the total desorbed solution obtained through the desorbed step.

[0104] Specifically, the concentration step may include a concentration process of the desorbent using reverse osmosis and electrodialysis, through which the target lithium concentration can be determined according to the characteristics of the intermediate to be extracted. If additional concentration is required beyond the above methods, the lithium concentration can be raised to the desired level through a concentration step using reduced pressure / evaporation.

[0105]

[0106] The above lithium-containing desorption solution may further perform a step of removing impurities, but is not limited thereto. For example, it may further include a step of removing impurities from the lithium-containing desorption solution using an ion exchange resin, etc.

[0107]

[0108] Step to obtain an aqueous lithium hydroxide solution

[0109] The method for pretreatment of a lithium-containing solution according to the present invention comprises the step of introducing the lithium-containing desorption solution into an electrodialysis device to obtain an aqueous lithium hydroxide solution.

[0110] Specifically, the pretreatment method for a lithium-containing solution according to the present invention is particularly useful when an aqueous lithium hydroxide solution is obtained by introducing it into an electrodialysis device.

[0111] Generally, when a pretreatment solution containing monovalent cations is used, when a lithium-containing desorption solution is introduced into an electrodialysis device to obtain an aqueous lithium hydroxide solution, a problem may arise in which the monovalent cations increase proportionally to the lithium concentration of the lithium-containing desorption solution as they pass through the ion exchange membrane within the electrodialysis device along with lithium ions.

[0112] However, since the pretreatment method for a lithium-containing solution according to the present invention uses a pretreatment solution containing divalent cations, divalent cations can be removed during the impurity removal process, thereby suppressing the problem of monovalent cations, such as sodium, increasing proportionally with the lithium concentration in the electrodialysis device.

[0113] Although it is not desired to be limited by theory, as the concentration of total dissolved solids in the pretreatment solution decreases, a phenomenon may occur in which a large amount of lithium adsorbed on the adsorbent is desorbed and exists in the washing solution at a high concentration. However, since the desorption delay effect of lithium due to the concentration of dissolved solids occurs when using a pretreatment solution containing divalent cations, there is an advantage in obtaining a high-purity aqueous lithium hydroxide solution without undergoing a recrystallization step.

[0114]

[0115] Preferred embodiments and comparative examples of the present invention are described below. However, the following examples are merely preferred embodiments of the present invention, and the present invention is not limited to the following examples.

[0116]

[0117] Experimental Example 1: Experiment to Confirm Washing Effect and Lithium Desorption Retardation Effect Using Monovalent Chlorides

[0118] Experiments were conducted to verify the cleaning (initial 2BV) effect and lithium desorption delay effect according to 1,2 chlorides.

[0119] The brine used was the brine with the composition shown in Table 1 below.

[0120] Saline composition LiKNaCaMgB Concentration value (mg / L) 75650049000217003000270

[0121] Adsorption step

[0122] 4 L of brine having the composition according to Table 1 above was passed through an adsorbent containing aluminum hydroxide.

[0123]

[0124] Washing step

[0125] As a pretreatment solution, NaCl, KCl, CaCl2, and MgCl2 were each mixed with distilled water to prepare aqueous solutions having concentrations according to Table 2 below.

[0126] After passing 0.2 L of pretreatment solution according to the examples and comparative examples in Table 2 below, the concentration of lithium present in the pretreatment solution was measured, and the results are shown in Figure 1.

[0127]

[0128] Classification Pretreatment Solution Concentration Example 1 CaCl 230g / L Example 2 MgCl 230g / L Comparative Example 1 NaCl 5g / L Comparative Example 2 NaCl 30g / L Comparative Example 3 KCl 30g / L

[0129] Referring to Figure 1, it can be seen that in the case of Comparative Example 1, the detachment delay effect was not observed due to the low TDS (Total Dissolved Solids).

[0130] It can be seen that Examples 1 and 2 have an excellent lithium detachment delay effect.

[0131] In the case of Comparative Examples 2 and 3, it can be seen that the lithium desorption delay effect appears similar to that of Examples 1 and 2 in the initial stage (~2 BV), but since Ca and Mg are removed in the impurity removal process regardless of the washing conditions used thereafter, the concentrations of Ca and Mg can be maintained at a low level.

[0132] Therefore, in the case of Examples 1 and 2, it can be seen that the Na concentration in the lithium-containing desorption solution can be further reduced, making it useful as a BPED application feed.

[0133]

[0134] Experimental Example 2: Confirmation of changes in the composition of concentrated brine

[0135] In Experimental Example 1, after washing with the pretreatment solution according to Comparative Example 2, Examples 1 and 2, desorption was performed using the desorption solution, concentrated, and the composition of the concentrated desorption solution (concentrate) was checked, and the results are shown in Tables 3 to 5 below, respectively.

[0136] Specifically, after washing in the same manner as in Experimental Example 1 above, 4 L of DLE Eluent with a composition according to Tables 3 to 5 per volume was passed through the lithium-adsorbed adsorbent to obtain a lithium-containing desorption solution.

[0137] Specifically, a lithium-containing desorption solution was obtained by performing a desorption step at 40 BV under desorption conditions of 40°C temperature and a flow rate of 30 mL / min in a DLE Eluent. Subsequently, the lithium-containing desorption solution was concentrated by reverse osmosis to obtain a concentrate, and then impurities were removed using an ion exchange resin, after which its composition was confirmed.

[0138]

[0139] Element (mg / L)DLE EluentNa 60mg / LNa 80mg / LNa 100mg / LNa 120mg / LLi60512,55512,55512,55512,555K5.4106.5106.5106.5106.6Na60~1201,1861,5811,9 762,372Ca37.50.1120.1130.1130.114Mg20.0020.0020.0020.002B14.8279.7279.8279.9280.0

[0140] Element(mg / L)DLE EluentCa 20mg / LCa 40mg / LCa 60mg / LCa 80mg / LCa 100mg / LCa 120mg / LLi40012,59312,79713,00313,20913,41513,621K5.4160.7160.6160.6160.5160.5160.4Na20596.8596.5596.3596.2596.0595.9Ca (Variable)20~1200.1110.1150.1180.1220.1250.129Mg20.0020.0020.0020.0020.0020.002B14.8407.9405.4405.6405.7406.0406.1

[0141] Element(mg / L)DLE EluentMg 20mg / LMg 40mg / LMg 60mg / LMg 80mg / LMg 100mg / LMg 120mg / LLi40013,06513,39213,71714,04314,36714,690K5.4160.5160.3160.1159.9159.7 159.6Na20595.9595.2594.5593.7593.0592.3Ca37.50.1190.1250.1300.1360.1420.149Mg (Variable)20~1200.0020.0020.0020.0020.0020.002B14.8409.8410.4410.5410.7410.7410.7

[0142] Referring to Tables 3 to 5 above, it can be seen that when a pretreatment solution containing NaCl is used, the Na concentration in the lithium-containing desorption solution is very high.

[0143] On the other hand, it can be seen that when a pretreatment solution containing CaCl2 and MgCl2 is used, the Na concentration in the lithium-containing desorption solution is maintained at 600 mg / L or less.

[0144] In addition, it can be seen that the concentrations of Ca and Mg are kept low even when using a pretreatment solution containing CaCl2 and MgCl2. This is because the divalent cations Ca and Mg can be kept low during the impurity removal process.

[0145] However, when using a pretreatment solution containing CaCl2 and MgCl2, the lithium peak height is lowered during desorption, which has the effect of slightly lowering the lithium concentration in the desorption solution (see Fig. 1), but as a result, there is an excellent advantage in that the lithium concentration before BPED application is at a level of 12 to 14 g / L and the Na concentration can be 600 mg / L or less.

[0146]

[0147] Experimental Example 3: Verification of changes in Na concentration according to BPED input conditions

[0148] In order to verify the change in Na concentration of the final lithium hydroxide aqueous solution obtained according to the BPED input conditions, a lithium-containing desorption solution having conditions according to Tables 6 to 10 below was prepared.

[0149] Afterward, each lithium-containing desorption solution was introduced into a BPED process under the same conditions to obtain an aqueous lithium hydroxide solution, and the change in Na concentration was checked, and the results are shown in Tables 6 to 10, respectively.

[0150]

[0151] Case 1 Li(g / L) Na(g / L) Li Concentration Ratio Na Concentration Ratio Na / Li Concentration Ratio BPED Before 5.0 30.17 1.9 81.8 80.95 BPED After 9.9 80.32

[0152] Case 2 Li(g / L) Na(g / L) Li Concentration Ratio Na Concentration Ratio Na / Li Concentration Ratio BPED Before 9.3 20.1 22.0 91.6 70.80 BPED After 19.4 80.20

[0153] Case 3 Li(g / L) Na(g / L) Li Concentration Ratio Na Concentration Ratio Na / Li Concentration Ratio Before BPED 5.0 ​​30.1 7 2.9 4 2.5 30.8 6 After BPED 14.8 10.4 3

[0154] Case 4Li(g / L)Na(g / L)Li Concentration RatioNa Concentration RatioNa / Li Concentration Ratio Before BPED 10.730.840.991041.05 After BPED 10.580.87

[0155] Case 5 Li(g / L) Na(g / L) Li Concentration Ratio Na Concentration Ratio Na / Li Concentration Ratio Before BPED 5.9 70.4 41.8 62.1 31.1 4 After BPED 11.1 20.9 4

[0156] Referring to Tables 6 to 10 above, it can be seen that the initial Na concentration level also exhibits similar behavior between 0.8 and 1.14 times depending on the degree of Li concentration in the lithium-containing desorption solution introduced into the BPED process.

[0157] Through this, the concentration of Na confirmed under lithium concentration conditions of about 12 to 15 g / L obtained through the initial DLE desorption, concentration, and impurity removal process can be expected to have a similar level of Na concentration as an impurity value even if the solution is converted from a LiCl solution to a LiOH solution through the BPED process.

[0158]

[0159] Experimental Example 4: Confirmation of changes in impurity concentration in LHM during BPED conversion and concentration / crystallization

[0160] Confirmation of changes in impurity concentration within LHM

[0161] In order to investigate the change in the concentration of impurities in LHM during BPED conversion and concentration / crystallization of the lithium-containing desorption solution according to washing conditions, an additional crystallization step was performed.

[0162] Specifically, in the same manner as Experimental Example 2, the pretreatment solutions according to Comparative Example 2, Example 1, and Example 2 were each used for washing, and then a lithium-containing desorption solution was obtained using a desorption solution having the composition according to Tables 11 to 13 below, and after concentrating and removing impurities from this solution, the obtained concentrate was introduced into BPED, and the lithium hydroxide aqueous solution prepared through BPED conversion was introduced into a crystallizer to proceed with crystallization.

[0163] The crystallization conditions were set to a crystallization rate of 90%, a water content of 5% entering the LHM solid phase, and an impurity removal rate of 92% through washing, with 60% removed in the Thickener and 80% in the Centrifuge.

[0164] The composition of the LHM prepared in this way is shown in Tables 11 and 12 below. Specifically, Table 11 shows the results using the pretreatment solution according to Comparative Example 2 in the washing step, and Table 12 shows the results using the pretreatment solution according to Examples 1 and 2.

[0165] Generally, when washing with 15 to 30 g / L of NaCl, the Na concentration in the lithium-containing desorption solution is at the level of 120 mg / L, and when washing with 10 g / L, the Na concentration is at the level of 80 mg / L.

[0166] Referring to Table 11, the Na concentration in the LHM produced under the above conditions is 100 ppm or higher, so it cannot be applied to battery grade. Therefore, in this case, there is a problem in that a two-stage crystallizer is required to redissolve the crude LHM and then recrystallize it into pure LHM.

[0167]

[0168] Solid ppm Na 60mg / L Na 80mg / L Na 100mg / L Na 120mg / LLHM 1.00E+06 1.00E+06 1.00E+06 1.00E+06 6Ca(OH)2 1.90 2.012.09 2.19Mg(OH)2 0.07 0.07 0.07 0.07 Impurities Na 10 6.75 135.90 162.78 187.85K 9.59 9.15 8.77 8.44Ca 0.08 0.09 0.09 0.09Mg 0.000.000.000.00B 25.18 24.06 23.06 22.18

[0169] The concentration of residual Na impurities in the LHM product obtained through BPED and LHM crystallization is 50 to 60 ppm, achieved by maintaining the Na concentration in the lithium-containing desorption solution at 20 mg / L using CaCl2 and MgCl2 (see Table 12 below).

[0170]

[0171] Example 1 Example 2 Solid ppm Ca 20 mg / LCa 120 mg / LMg 20 mg / LMg 120 mg / LLHM 1.00E+06 1.00E+06 1.00E+06 1.00E+06 1.00E+06 6Ca(OH)2 1.80 1.99 1.88 2.19Mg(OH)2 0.07 0.07 0.07 0.06Impurities Na 5 9.125 4.625 6.965 0.45K 15.92 14.70 15.34 13.59Ca 0.08 0.09 0.08 0.10Mg 0.000.000.000.00B 4 0.40 37.223 9.173 4.98

[0172] In other words, it can be seen that the concentration of Na impurities can be reduced to less than one-third of the level of the data obtained through the existing 30g / L NaCl washing conditions in Table 10 above (Na 120mg / L condition result: Na 187.85ppm).

[0173] Through this, it is expected that the lithium hydroxide aqueous solution prepared by the pretreatment method of the lithium-containing solution according to the present invention will enable the production of battery-grade LHM through one-stage LHM crystallization and washing without a recrystallization step.

[0174]

[0175] The present invention is not limited to the above embodiments and can be manufactured in various different forms, and those skilled in the art will understand that the invention can be implemented in other specific forms without changing the technical concept or essential features of the invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

Claims

1. An adsorption step of passing a lithium-containing solution through an adsorbent to obtain an adsorbent on which lithium is adsorbed; A washing step of removing impurities by passing a pretreatment solution containing divalent cations through the above lithium-adsorbed adsorbent; A desorption step of obtaining a lithium-containing desorption solution by passing a medium through the adsorbent on which the lithium is adsorbed; and The method comprising the step of introducing the above lithium-containing desorption solution into an electrodialysis device to obtain an aqueous lithium hydroxide solution; Pretreatment method for lithium-containing solutions.

2. In Paragraph 1, A method for pretreating a lithium-containing solution in which the above pretreatment solution inhibits the desorption of lithium adsorbed on the adsorbent during the washing step.

3. In Paragraph 1, The above pretreatment solution is a method for pretreating a lithium-containing solution that reduces the Na concentration of the lithium-containing desorption solution.

4. In Paragraph 1, A method for pretreating a lithium-containing solution, wherein the above-mentioned pretreatment solution comprises one or more salts selected from the group consisting of calcium and magnesium.

5. In Paragraph 4, A method for pretreating a lithium-containing solution, wherein the above-mentioned pretreatment solution comprises one or more selected from the group consisting of CaCl2 and MgCl2.

6. In Paragraph 1, A method for pretreating a lithium-containing solution in which the above-mentioned pretreatment solution has a total dissolved solids concentration of 0.5 to 3.0 mol / L.

7. In Paragraph 1, The above lithium-containing desorption solution is a pretreatment method for a lithium-containing solution having a Na concentration of 300 mg / L or less.

8. In Paragraph 1, A method for pretreating a lithium-containing solution, wherein the above-mentioned pretreatment solution contains lithium at a concentration of 0.02 to 3.0 g / L in the entire pretreatment solution.

9. In Paragraph 1, A method for pretreating a lithium-containing solution in which the lithium concentration of the lithium-containing solution in the above adsorption step is 0.03 to 2.0 g / L.

10. In Paragraph 1, A method for pretreating a lithium-containing solution in which the lithium concentration of the medium used in the above desorption step is 0.05 to 1.50 g / L.

11. In Paragraph 1, Regarding the amount of lithium present in the adsorbent after the above adsorption step, A method for pretreating a lithium-containing solution in which the amount of lithium contained in the pretreatment solution after the washing step is 0.1 to 10.0 weight%.

12. In Paragraph 1, A method for pre-treating a lithium-containing solution in which the above-mentioned adsorbent is an aluminum-based adsorbent.

13. In Paragraph 1, A method for pretreating a lithium-containing solution in which the above lithium-containing solution contains LiCl.

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