Pretreatment method of brine, brine pretreated using same, and recovery method of lithium, using same

Abstract

A pretreatment method for brine, according to the present invention, comprises the steps of: preparing brine containing one or more impurity ions selected from the group consisting of carbonate ions and bicarbonate ions; adjusting the pH of the brine to 5 or less; and injecting bubbles into the pH-adjusted brine so as to remove the impurity ions in the form of carbon dioxide.

Description

Method for pretreatment of brine, brine pretreated using the same, and method for recovering lithium using the same

[0001] The present invention relates to a method for pretreating brine, brine pretreated using the same, and a method for recovering lithium using the same.

[0002] 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.

[0003] 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.

[0004] 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 0.17 ppm, extracting lithium from seawater is very inefficient and has a problem of low economic feasibility.

[0005] 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.

[0006] 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 placed in evaporation ponds. This is then 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.

[0007] However, these conventional methods have the problem that they require a lot of energy and time for evaporation and concentration of brine, which significantly reduces productivity, and lithium is precipitated in the form of salt together with other impurities during the evaporation and concentration of brine, resulting in lithium loss, and their use is limited during the rainy season.

[0008] Recently, a method using an adsorbent has been proposed as one of the technologies for directly extracting lithium from brine containing lithium.

[0009] However, there are some problems as the adsorption performance deteriorates with repeated adsorption and desorption.

[0010] Therefore, there is a need to develop a method for easily recovering lithium from brine containing lithium.

[0011] The present invention seeks to provide a method for pretreatment of brine capable of suppressing deterioration in the performance of an adsorbent.

[0012] In addition, the present invention seeks to provide a brine having a low content of impurity ions, thereby suppressing deterioration in the performance of an adsorbent.

[0013] In addition, the present invention aims to provide a method for recovering lithium in which the performance degradation of the adsorbent is suppressed and lithium recovery is easy.

[0014] The present invention provides a method for pretreatment of brine, comprising the steps of: preparing brine containing one or more impurity ions selected from the group consisting of carbonate ions and bicarbonate ions; adjusting the pH of the brine to 5 or less; and injecting bubbles into the brine having the adjusted pH to remove the impurity ions in the form of carbon dioxide.

[0015] In addition, the present invention provides a brine having a concentration of at least one impurity ion selected from the group consisting of carbonate ions and bicarbonate ions of 0.48 g / L or less.

[0016] In addition, the present invention provides a method for recovering lithium, comprising the steps of: preparing a brine having a concentration of at least one impurity ion selected from the group consisting of carbonate ions and bicarbonate ions of 0.48 g / L or less; loading an Al-based adsorbent into a removal reactor; and adsorbing lithium ions while passing the brine through an adsorbent layer loaded into the reactor.

[0017] The pretreatment method of brine according to the present invention has the advantage of being able to suppress the deterioration of the performance of an adsorbent when an adsorbent is used by removing impurity ions contained in the brine.

[0018] In addition, the brine according to the present invention has a low content of impurity ions, and thus has the advantage of suppressing deterioration in the performance of the adsorbent when using the adsorbent.

[0019] In addition, the method for recovering lithium according to the present invention has the advantage of suppressing deterioration of the performance of the adsorbent and facilitating recovery of lithium.

[0020] Figure 1 is a diagram showing the change in lithium absorption / desorption amount according to the lithium absorption / desorption cycle process cycle of the examples and experimental examples of the present invention.

[0021] Figures 2 and 3 are diagrams showing changes in lithium adsorption amount according to the content of bicarbonate ions according to lithium adsorption / desorption recovery in examples and experimental examples of the present invention.

[0022] Figure 4 is a diagram illustrating a method for measuring the concentration of bicarbonate ions in a simulated brine according to a manufacturing example of the present invention using a back titration method.

[0023] 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. The present invention is defined solely by the scope of the claims set forth below.

[0024] In the present invention, when it is said that a member is located “on” another member, this includes not only cases where a member is in direct contact with another member, but also cases where another member is interposed between the two members.

[0025] 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.

[0026]

[0027] <Pretreatment method of brine>

[0028] One aspect of the present invention relates to a method for pretreating brine, comprising the steps of: preparing brine containing one or more impurity ions selected from the group consisting of carbonate ions and bicarbonate ions; adjusting the pH of the brine to 5 or lower; and injecting bubbles into the brine having the adjusted pH to remove the impurity ions in the form of carbon dioxide.

[0029] The method for pretreatment of brine according to the present invention has the advantage of suppressing the deterioration of the performance of the adsorbent by removing carbonate ions and / or bicarbonate ions that deteriorate the performance of the adsorbent.

[0030]

[0031] The pretreatment method of brine according to the present invention comprises carbonate ions (CO3 2- ) and bicarbonate ion (HCO3 - ) comprising a step of preparing a brine containing one or more impurity ions selected from the group consisting of;

[0032] The above brine may have a concentration of the impurity ion of, for example, greater than 0.48 g / L, but is not limited thereto.

[0033]

[0034] The pretreatment method of brine according to the present invention includes a step of adjusting the pH of the brine to 5 or less.

[0035]

[0036] In one embodiment of the present invention, the step of adjusting the pH of the brine to 5 or less can be performed by adding one or more acids selected from the group consisting of hydrochloric acid, concentrated sulfuric acid, and dilute sulfuric acid.

[0037] Specifically, the acid may be an acid containing hydrogen ions. When the acid containing hydrogen ions is added, the impurity ions are converted into the form of carbon dioxide (g) through the acid-base equilibrium according to the following reaction formula, thereby enabling the removal of the impurity ions.

[0038]

[0039] [Reaction Formula 1]

[0040] (CO2(g) + H2O (l) ) H2CO3(aq) H + (aq) + HCO3 - (aq) ··· pK a = 6.4

[0041] HCO3 - (aq) H + (aq) + CO3 - (aq) ··· pK a= 10.2

[0042] [Reaction Formula 2]

[0043] (CO2(g) + H2O (l) ) H2CO3(aq) H + (aq) + HCO3 - (aq) ··· pK a = 6.4

[0044] HCO3 - (aq) + H2O (l) CO3 - (aq) + H3O+ (aq) ··· pK a = 10.3

[0045]

[0046] In short, in the present invention, adjusting the pH to 5 or less means adding H to the brine. + It can be said that ion injection is taking place.

[0047]

[0048] The amount of the acid added may be added so as to adjust the pH of the brine to 5 or less, specifically 4 or less, and more specifically 3 or less.

[0049] In short, in another embodiment of the present invention, in the step of adjusting the pH of the brine to 5 or less, the pH can be adjusted to 4 or less.

[0050] In another embodiment of the present invention, in the step of adjusting the pH of the brine to 5 or less, the pH can be adjusted to 3 or less.

[0051] When the pH is lowered, the content of bicarbonate ions or carbonate ions remaining in the brine is lowered, which is preferable because it can suppress the decrease in lithium adsorption amount.

[0052]

[0053] The above dilute sulfuric acid may be derived from, but is not limited to, the BPED process.

[0054] In another embodiment of the present invention, the step of adjusting the pH of the brine to 5 or less can be performed by adding hydrochloric acid.

[0055] Since most of the anions that make up the above brine are in the form of Cl- ions, when other anions are added, bicarbonate ions or carbonate ions can be removed, but reactants are formed with other dissolved cations, and thus precipitates are generated during adsorption, which can reduce the permeability of the solution.

[0056] When using the above hydrochloric acid, it is particularly preferable because it has the advantage of suppressing side reactions compared to other acids.

[0057]

[0058] The pretreatment method of brine according to the present invention includes a step of removing impurity ions in the form of carbon dioxide by injecting bubbles into the brine with adjusted pH.

[0059] The injection of the above bubbles can be performed using a bubble generator.

[0060]

[0061] In another embodiment of the present invention, the bubbling may be performed for 1 to 10 minutes, preferably 1 to 6 minutes, and more preferably 1 to 3 minutes.

[0062] When the injection of the above bubbles is performed within the above time range, it is preferable that the carbon dioxide is sufficiently removed while shortening the process time.

[0063]

[0064] Meanwhile, adsorption, one of the technologies for directly extracting lithium from brine containing lithium, is [LiX] 0-1　 [Al(OH) 3　 ] 2　 (X: Cl - , SO4 2- , OH - , NO3 -Anions such as Cl, preferably - Al compounds such as (Im) are used.

[0065]

[0066] Without wishing to be limited by theory, traditional two-dimensional layered aluminum hydroxide (hereinafter referred to as 'lithium aluminum intercalate' or 'LDH') facilitates the insertion of anions between the layers, and the diffusion of positively charged lithium cations into the hexagonal cavities formed within the two-dimensional layered structure easily accommodates the size of lithium.

[0067] LiCl inside LDH cannot escape from the structure at a certain rate without causing a structural change in LDH. LDH with LiCl escaped has a high salt concentration, and when it comes into contact with a lithium solution containing LiCl, it quickly fills the space left by the escaped LiCl. LDH with LiCl escaped has a high salt concentration, and when it comes into contact with a lithium solution containing LiCl, it quickly fills the space left by the escaped LiCl. The degree to which the vacant space is filled is greater as the LiCl concentration of the lithium solution and the salt concentration are higher.

[0068] When LDH comes into contact with water with low salt concentration and low LiCl concentration, LiCl inside the LDH escapes to the outside, and the degree to which LiCl escapes to the outside is inversely proportional to the salt concentration and the LiCl concentration.

[0069] When LDH comes into contact with water with extremely low salt and LiCl concentrations, the LDH structure collapses as excessive LiCl is released from the LDH.

[0070] When LDH with a collapsed structure comes into contact with a high-concentration LiCl solution, it regenerates into an LDH structure by absorbing LiCl, and this rate is slower than the rate at which LDH with a normal structure absorbs LiCl.

[0071] Therefore, when carbonate ions and / or bicarbonate ions are present in the brine, LDH forms an ionic equilibrium state in the LDH structure layer when the bicarbonate and / or carbonate ions come into contact with the adsorbent and acts to block the adsorption site with a strong bond within the structure, which may result in a decrease in adsorption performance.

[0072] The pretreatment method of brine according to the present invention can suppress the deterioration of the performance of the adsorbent by removing carbonate ions and / or bicarbonate ions that deteriorate the performance of the adsorbent.

[0073]

[0074] <Pretreated brine>

[0075] Another aspect of the present invention relates to a brine having a concentration of at least one impurity ion selected from the group consisting of carbonate ions and bicarbonate ions of 0.48 g / L or less.

[0076] Another aspect of the present invention relates to brine pretreated by the above-described brine pretreatment method.

[0077] In short, the brine having a concentration of at least one impurity ion selected from the group consisting of carbonate ions and bicarbonate ions of 0.48 g / L or less according to the present invention is pretreated by the pretreatment method of the brine described above.

[0078]

[0079] Since the brine according to the present invention has a very low concentration of one or more impurity ions selected from the group consisting of carbonate ions and bicarbonate ions, when lithium is recovered using the brine as an adsorbent, there is an advantage in that the performance of the adsorbent is suppressed and lithium can be easily recovered.

[0080] Specifically, the brine according to the present invention may have a concentration of the impurity ion of 0.30 g / L or less, more specifically 0.10 g / L or less.

[0081]

[0082] In another embodiment of the present invention, the brine may have a lithium ion concentration of 10 mg / L, preferably 70 mg / L or more, and more preferably 100 mg / L or more.

[0083] When the concentration of the lithium ions satisfies the above range, the adsorption speed is fast in the process of recovering lithium, which is advantageous in that it improves productivity and has excellent economic efficiency.

[0084]

[0085] <Method of recovering lithium>

[0086] Another aspect of the present invention relates to a method for recovering lithium, comprising the steps of: preparing a brine having a concentration of at least one impurity ion selected from the group consisting of carbonate ions and bicarbonate ions of 0.48 g / L or less; loading an Al-based adsorbent into a removal reactor; and adsorbing lithium ions while passing the brine through an adsorbent layer loaded into the reactor.

[0087] The step of preparing brine having a concentration of at least one impurity ion selected from the group consisting of carbonate ions and bicarbonate ions of 0.48 g / L or less may be a step of using the brine pretreatment method described above.

[0088] In short, the step of preparing a brine having a concentration of at least one impurity ion selected from the group consisting of carbonate ions and bicarbonate ions of 0.48 g / L or less may include the steps of: preparing a brine containing at least one impurity ion selected from the group consisting of carbonate ions and bicarbonate ions; adjusting the pH of the brine to 5 or less; and injecting bubbles into the brine having the pH adjusted to remove the impurity ions in the form of carbon dioxide.

[0089] Specifically, the brine may have a concentration of one or more impurity ions selected from the group consisting of carbonate ions and bicarbonate ions of 0.30 g / L or less, more specifically, 0.10 g / L or less.

[0090]

[0091] In another embodiment of the present invention, the brine may have a lithium ion concentration of 10 mg / L or more, preferably 70 mg / L or more, and more preferably 100 mg / L or more.

[0092] When the concentration of the lithium ions satisfies the above range, it is preferable because it has the advantage of a fast adsorption rate, improved productivity, and excellent economic efficiency.

[0093]

[0094] A method for recovering lithium according to the present invention comprises the steps of: loading an Al-based adsorbent into a removal reactor; and adsorbing lithium ions while passing the brine through an adsorbent layer loaded into the reactor.

[0095] In another embodiment of the present invention, the Al-based adsorbent may be a molded body comprising adsorbent powder and a binder.

[0096] The above adsorbent powder may be, for example, an adsorbent powder containing aluminum hydroxide.

[0097] The above binder is used to manufacture the adsorbent powder into a molded body of an appropriate shape, and can serve to bind the adsorbent powders together.

[0098] The above binder may include, for example, at least one selected from the group consisting of polyvinyl chloride (PVC), polysulfone, and polyaniline.

[0099] Preferably, the binder may include polyvinyl chloride (PVC) that can provide excellent binding force between the adsorbent powders.

[0100] The above-mentioned molded body may contain the binder in an amount of 5 to 30 wt%, preferably 10 to 15 wt%, based on the total weight of the adsorbent powder.

[0101] When the content of the above binder satisfies the above range, it is preferable that the amount of the adsorbent powder be appropriate so as to maximize the amount of lithium adsorbed.

[0102]

[0103] In another embodiment of the present invention, the Al-based adsorbent may include aluminum hydroxide.

[0104] When the above Al-based adsorbent contains aluminum hydroxide, it is preferable because it can increase the amount of lithium adsorbed and has the advantage of a long lifespan of the adsorbent due to little aluminum loss during the desorption process.

[0105]

[0106] The adsorption and desorption reaction of lithium by the above Al-based adsorbent is as follows.

[0107]

[0108] [Reaction Formula 3]

[0109] (a + b)Li + + aCl - + bHCO3 - + (1 - x)LiCl·2[Al(OH)3]

[0110] aLiCl·2[Al(OH)3] + bLiHCO3·2[Al(OH)3]

[0111] (x ≥ a + b)

[0112]

[0113] The step of adsorbing lithium ions while passing the brine through the adsorbent layer loaded into the reactor can be performed at a temperature in the range of 5 to 100°C, preferably in the range of 30 to 80°C.

[0114] When the adsorption temperature satisfies the above range, it is preferable because the adsorption performance of lithium can be improved.

[0115] The step of adsorbing lithium ions while passing the brine through the adsorbent layer loaded into the reactor can be performed for 30 minutes to 10 hours, preferably 30 minutes to 8 hours, and more preferably 30 minutes to 6 hours.

[0116] When the step of adsorbing lithium ions while passing the brine through the adsorbent layer loaded into the reactor is performed within the above time range, the overall process time is shortened while the lithium adsorption performance is excellent, which is preferable.

[0117]

[0118] The method for recovering lithium according to the present invention may further include a step of obtaining a lithium-containing desorption liquid from the Al-based adsorbent to which the lithium ions are adsorbed.

[0119] For example, a lithium-containing desorption liquid can be obtained by passing distilled water through the Al-based adsorbent on which the lithium ions are adsorbed, but is not limited thereto.

[0120] Specifically, the amount of distilled water passed through the Al-based adsorbent may be 0.5 to 10 times, preferably 1 to 5 times, and more preferably 1 to 3 times the volume of the Al-based adsorbent based on the volume of the Al-based adsorbent.

[0121] When the amount of the distilled water satisfies the above range, the desorption of lithium is excellent, and the phenomenon of the desorbed lithium being diluted and the concentration of lithium contained in the lithium-containing desorption liquid decreasing can be suppressed, which is preferable.

[0122] The concentration of lithium contained in the above lithium removal solution may be 0.5 to 2.0 g / L, specifically 0.8 to 1.5 g / L. When the lithium concentration satisfies the above range, the lithium recovery rate is improved, which is preferable.

[0123]

[0124] The lithium recovery method according to the present invention may further include, but is not limited to, a step of concentrating the lithium-containing desorbent to obtain a lithium-containing concentrate. The step of obtaining the lithium-containing concentrate may be performed using an electrodialyzer or the like, but is not limited thereto.

[0125]

[0126] Hereinafter, preferred embodiments and comparative examples of the present invention are described. However, the following examples are only preferred embodiments of the present invention, and the present invention is not limited to the following examples.

[0127]

[0128] Manufacturing example: HCO3 - Preparation of simulated brine containing

[0129] Bicarbonate ions (HCO3) in brine - ) In order to evaluate the effect of the adsorbent on the lithium adsorption / desorption performance, simulated brine A and B containing bicarbonate ions according to the composition shown in Table 1 below were prepared. For brine C, Diabillos from Rodinia Lithium was used.

[0130] At this time, the concentration of bicarbonate ions was measured using the back titration method.

[0131] The concentration of bicarbonate ions in simulated brine A to C was measured using the acid-base back titration method according to the following reaction scheme 4, and the results are shown in Table 2 and Figure 4.

[0132] Specifically, the acid-base back titration method is a method that uses the neutralization reaction of acid and base to first react an unknown sample with an excess of acid (primary standard solution) (step 1), and then titrates the remaining acid with a base of known concentration (secondary standard solution) to determine the concentration of the sample (step 2).

[0133]

[0134] [Reaction Formula 4]

[0135] (Step 1) HCO3 - (aq) + nHCl(aq) → H2O(l) + CO2(g) + Cl - (aq) + (n-1)HCl(aq) (n > 1)

[0136] (Step2) (n-1)HCl(aq) + mNaOH(aq) → (n-1)H2O(l) + (n-1)NaCl(aq) + (m-n+1)NaOH(aq)

[0137]

[0138] (Step 1) As a result, 1 mL of 0.500 M HCl was added to 25 mL of each of brine A to C and stirred for 0.5 to 1 hour. Afterwards, the concentration of bicarbonate ions in the simulated brine was measured by titration using the acid treatment solution and 0.0503 M NaOH, and the results are shown in Table 2 below. At this time, C HCO3- represents the content of bicarbonate ions in brine A to C, C * HCO3- represents the content of bicarbonate ions after titration.

[0139]

[0140] (g / L)LiNaKMgCaBSHCO3 - pHSaline A0.4944.65.41.850.770.582.380.007Saline B0.4944.65.41.850.770.582.380.487Saline C0.4944.65.41.850.770.582.380.967

[0141]

[0142] HCl added(mmol)NaOH @ ep (mmol)HCl reacted(mmol)C HCO3- (g / L)C * HCO3- (g / L)Saline A (0 ppm HCO3 - )0.5000.4220.0780.190 (±.0017)-Brine B (480 ppm HCO3 - )0.5000.2140.2860.697 (±.0039)0.507Saline C (960 ppm HCO3 - )0.5000.0300.4701.148 (±.0018)0.958

[0143]

[0144] Example

[0145] The pH of brine C was adjusted by adding hydrochloric acid until the pH became 3 or lower. Afterwards, bubbling was performed using a bubble injector to obtain brine C' with bicarbonate ions removed in the form of carbon dioxide.

[0146]

[0147] (g / L)LiNaKMgCaBSHCO3 - pH saline C'0.4944.65.41.850.770.582.380.007

[0148]

[0149] Experimental Example: Evaluation of Adsorbent Performance According to Bicarbonate Ions

[0150] The performance of the adsorbent according to the bicarbonate ion was evaluated, and the results are shown in Figures 1 to 3.

[0151] Specifically, 600 mL each of brine A to C and C' was passed through a column (reactor) filled with 60 g of LAH (lithium aluminum hydroxide) adsorbent.

[0152] Afterwards, 30 L of distilled water per volume was passed through the adsorbent on which the lithium was adsorbed to obtain a lithium-containing desorption liquid.

[0153] Adsorption and desorption were repeated using the same brine for each of the above adsorbents from which lithium was separated, and the amount of lithium adsorbed was measured according to the number of adsorption and desorption cycles.

[0154] The results of Li adsorption according to the number of adsorption / desorption times of brine A to C and C' are shown in Fig. 1, and the results according to the number of adsorption / desorption times of brine B and C are shown in Figs. 2 and 3, respectively. At this time, the reference point of Figs. 2 and 3 was set as the Li adsorption site filled during the first adsorption.

[0155] Also, HCO3 in brine B and C - Theoretical value, measured value and HCO3 in column experiment - The adsorption amount was measured and the results are shown in Table 4 below.

[0156]

[0157] HCO3 in brine - (g / L)HCO3 in column experiment - (mmol)Theoretical value (Theo.)Measured value (Mea.)Served amount / cycleAdsorbed amount / cycleSaline B0.480.507122.9 (ave.)Saline C0.960.958224.9 (ave.)

[0158]

[0159] Referring to Figures 1 to 3 and Table 4, it can be seen that the content of bicarbonate ions in brine affects the adsorption performance of the adsorbent.

[0160]

[0161] The present invention is not limited to the above-described embodiments, but can be manufactured in a variety of different forms. Those skilled in the art will appreciate that the present invention can be implemented in other specific forms without altering the technical spirit or essential characteristics of the present invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

Claims

1. A step of preparing a brine containing one or more impurity ions selected from the group consisting of carbonate ions and bicarbonate ions; A step of adjusting the pH of the brine to 5 or less; and A step of removing the impurity ions in the form of carbon dioxide by injecting bubbles into the brine with adjusted pH; A method for pretreatment of brine comprising:

2. In paragraph 1, The step of adjusting the pH of the brine to 5 or less; A method for pretreatment of brine, which is performed by adding one or more acids selected from the group consisting of hydrochloric acid, concentrated sulfuric acid, and dilute sulfuric acid.

3. In paragraph 2, A method for pretreatment of brine, wherein the step of adjusting the pH of the brine to 5 or less is performed by adding hydrochloric acid.

4. In paragraph 1, In the step of adjusting the pH of the brine to 5 or less; A method for pretreatment of brine, wherein the pH is adjusted to 4 or lower.

5. In paragraph 4, In the step of adjusting the pH of the brine to 5 or less; A method for pretreatment of brine, wherein the pH is adjusted to 3 or less.

6. In paragraph 1, A method for pretreatment of brine, wherein the bubbles are injected for 1 to 10 minutes.

7. Salt water having a concentration of one or more impurity ions selected from the group consisting of carbonate ions and bicarbonate ions of 0.48 g / L or less.

8. In paragraph 7, Salt water having a lithium ion concentration of 10 mg / L or more.

9. Brine pretreated by a brine pretreatment method according to any one of clauses 1 to 6.

10. A step of preparing a brine having a concentration of one or more impurity ions selected from the group consisting of carbonate ions and bicarbonate ions of 0.48 g / L or less; Step of loading the Al-based adsorbent into the removal reactor; and A step of adsorbing lithium ions while passing the brine through an adsorbent layer loaded into the reactor; A method for recovering lithium comprising:

11. In paragraph 10, A method for recovering lithium, wherein the brine has a lithium ion concentration of 10 mg / L or more.

12. In paragraph 10, A method for recovering lithium, wherein the above Al-based adsorbent is a molded body comprising adsorbent powder and a binder.

13. In paragraph 10, A method for recovering lithium, wherein the above Al-based adsorbent contains aluminum hydroxide.

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