Saltwater pretreatment method, pretreated saltwater using the same, and lithium recovery method using the same

Abstract

The brine pretreatment method according to the present application is characterized in that the method comprises: a step of preparing 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 injecting gas bubbles into the pH-adjusted brine to remove the impurity ions in the form of carbon dioxide.

Description

Technical Field

[0001] This invention relates to a brine pretreatment method, the pretreated brine obtained therefrom, and a lithium recovery method using the same. Background Technology

[0002] Lithium compounds are widely used in various industrial fields such as secondary batteries, ceramics, glass, alloys, and pharmaceuticals. With the recent commercialization of electric vehicles and the increasing demand for energy storage, the demand for lithium materials is expected to grow significantly in the future.

[0003] The raw materials used to prepare lithium materials mainly include minerals, brine, and seawater. Among them, the minerals are spodumene, petalite, and lepidolite, etc. Although the lithium content is relatively high, about 1-1.5%, extracting lithium from the minerals requires a large number of processes, including flotation, high-temperature calcination, crushing, acid mixing, extraction, purification, concentration, and precipitation. Therefore, the recovery process is complex, the high energy consumption leads to high costs, and the use of acid in the lithium extraction process poses a serious environmental pollution problem.

[0004] In addition, it is known that the total amount dissolved in seawater is 2.5 × 10⁻⁶. 11 The current mainstream technology involves placing a recovery device containing an adsorbent into seawater to selectively adsorb lithium, followed by acid treatment to extract the lithium. However, since the lithium concentration in seawater is only 0.17 ppm, extracting lithium from seawater is very inefficient and economically unviable.

[0005] Due to these issues, lithium is currently mainly extracted from brine, which comes from natural salt lakes. More than 70% of the world's reserves are located in South America, including Argentina, Chile, and Bolivia.

[0006] Lithium in brine is mainly extracted in the form of lithium carbonate. In commercially available processes, the traditional method for extracting lithium from lithium-containing brine in the form of lithium carbonate is as follows: after drilling wells in natural salt lakes at altitudes above 3000m, the brine is pumped into evaporation ponds. After several months to about a year of natural evaporation, the lithium is concentrated to several to tens of times its original concentration. Then, impurities such as Mg, Ca, and B are removed through precipitation, and the amount of lithium carbonate precipitated exceeds its solubility, thereby achieving lithium recovery.

[0007] However, this traditional method consumes a lot of energy and time in the evaporation and concentration of brine, resulting in a significant decrease in productivity. In addition, lithium is lost as it precipitates as salt along with other impurities during the evaporation and concentration process. Furthermore, its use is limited during the rainy season.

[0008] Recently, an adsorbent-based method has been proposed as one of the techniques for directly extracting lithium from lithium-containing brine.

[0009] However, as the adsorption-desorption cycle is repeated, the adsorption performance decreases, leading to some problems.

[0010] Therefore, there is an urgent need to develop a method for easily recovering lithium from lithium-containing brine. Summary of the Invention

[0011] (a) Technical problems to be solved The present invention aims to provide a brine pretreatment method that can suppress the performance degradation of the adsorbent.

[0012] Furthermore, the present invention aims to provide a brine with a low content of impurity ions, thereby suppressing the decline in the performance of the adsorbent.

[0013] Furthermore, the present invention aims to provide a lithium recovery method that inhibits the performance degradation of the adsorbent and facilitates lithium recovery.

[0014] (II) Technical Solution The present invention provides a brine pretreatment method comprising: preparing a 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 below 5; and injecting air bubbles into the pH-adjusted brine to remove the impurity ions in the form of carbon dioxide.

[0015] Furthermore, the present invention provides a brine wherein the concentration of one or more impurity ions selected from the group consisting of carbonate ions and bicarbonate ions is less than 0.48 g / L.

[0016] Furthermore, the present invention provides a lithium recovery method comprising: preparing a brine solution with a concentration of 0.48 g / L or less of one or more impurity ions selected from the group consisting of carbonate ions and bicarbonate ions; loading an aluminum-based adsorbent into a removal reactor; and allowing the brine solution to flow through an adsorbent layer loaded into the reactor to adsorb lithium ions.

[0017] (III) Beneficial Effects The brine pretreatment method according to the present invention has the advantage of suppressing the decline in adsorbent performance when using adsorbents by removing impurity ions contained in the brine.

[0018] Furthermore, the brine according to the present invention has the advantage of suppressing the decline in adsorbent performance when using an adsorbent due to its low content of impurity ions.

[0019] Furthermore, the lithium recovery method according to the present invention has the advantages of being able to suppress the performance degradation of the adsorbent and being easy to recover lithium. Attached Figure Description

[0020] Figure 1 This is a schematic diagram illustrating the change in lithium adsorption / desorption capacity with the lithium adsorption / desorption cycle process in the embodiments and experimental examples of the present invention.

[0021] Figure 2 and Figure 3 This is a schematic diagram showing the changes in lithium adsorption capacity with the number of lithium adsorption / desorption cycles and bicarbonate ion content in the embodiments and experimental examples of the present invention.

[0022] Figure 4 This is a schematic diagram of a method for measuring the concentration of bicarbonate ions in simulated saline solution using back titration according to a preparation example of the present invention. Detailed Implementation

[0023] Embodiments of the present invention will be described in detail below. However, the following embodiments are merely illustrative, and the present invention is not limited to these embodiments; rather, it is defined only by the scope of the claims.

[0024] In this invention, when it is said that a component is located "on" another component, this includes not only the case where one component is in direct contact with another component, but also the case where another component is interposed between the two components.

[0025] In this invention, when a part is referred to as "containing" a certain constituent element, unless otherwise specifically stated to the contrary, it means that other constituent elements may be included, but does not exclude other constituent elements.

[0026] <Saline Pretreatment Methods> One aspect of the present invention relates to a brine pretreatment method, comprising: preparing a 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 below 5; and injecting air bubbles into the pH-adjusted brine to remove the impurity ions in the form of carbon dioxide.

[0027] The brine pretreatment method according to the present invention has the advantage of suppressing the decline in adsorbent performance by removing carbonate ions and / or bicarbonate ions that reduce the performance of the adsorbent.

[0028] According to the brine pretreatment method of the present invention, it comprises preparing brine containing carbonate ions (CO3-) selected from the salt water. 2-) and bicarbonate ions (HCO3) - The steps of preparing a saline solution containing one or more impurity ions from a group consisting of )

[0029] For the saline solution, the concentration of impurity ions may exceed 0.48 g / L, but is not limited thereto.

[0030] According to the brine pretreatment method of the present invention, the brine is further comprising the step of adjusting the pH of the brine to below 5.

[0031] In one embodiment of the present invention, the step of adjusting the pH of the brine to below 5 can be performed by adding one or more acids selected from the group consisting of hydrochloric acid, concentrated sulfuric acid, and dilute sulfuric acid.

[0032] Specifically, the acid can be an acid containing hydrogen ions. When the acid containing hydrogen ions is added, the impurity ions are converted into carbon dioxide (g) through an acid-base balance according to the following reaction formula, thereby removing the impurity ions.

[0033] [Reaction Formula 1] CO2 g ) + H2O ( l ) H2CO3( aq ) H + ( aq ) + HCO3 - ( aq ) ··· p K a = 6.4 HCO3 - ( aq ) H + ( aq ) + CO3 - ( aq ) ··· p K a = 10.2 [Reaction 2] CO2 g ) + H2O ( l ) H2CO3( aq ) H + ( aq ) + HCO3 - ( aq ) ··· p K a = 6.4 HCO3- ( aq ) + H2O (l) CO3 - ( aq ) + H3O+ ( aq ) ··· p K a = 10.3 In short, in this invention, adjusting the pH to below 5 can refer to adding H+ to the saline solution. + ion.

[0034] The amount of acid added can be such that the pH of the saline solution is adjusted to below 5, specifically below 4, and more specifically below 3.

[0035] In short, in another embodiment of the present invention, in the step of adjusting the pH of the saline solution to below 5, the pH can be adjusted to below 4.

[0036] In another embodiment of the present invention, in the step of adjusting the pH of the brine to below 5, the pH can be adjusted to below 3.

[0037] When the pH decreases, the content of bicarbonate ions or carbonate ions remaining in the brine decreases, thereby suppressing the reduction of lithium adsorption, which is therefore preferred.

[0038] The dilute sulfuric acid may also be derived from the BPED process, but is not limited to this.

[0039] In another embodiment of the invention, the step of adjusting the pH to below 5 can be performed by adding hydrochloric acid.

[0040] Since most of the anions constituting the brine are in the form of Cl- ions, when other anions are added, although bicarbonate or carbonate ions can be removed, they also react with other dissolved cations to form precipitates, which may reduce the permeability of the solution during adsorption.

[0041] When the hydrochloric acid is used, it has the advantage of suppressing side reactions compared to other acids, and is therefore particularly preferred.

[0042] According to the brine pretreatment method of the present invention, the step of injecting air bubbles into the pH-adjusted brine to remove the impurity ions in the form of carbon dioxide is included.

[0043] The injection of the bubbles can be performed using a bubble generator.

[0044] In another embodiment of the invention, the bubbles can be continuously injected for 1 to 10 minutes, preferably 1 to 6 minutes, and more preferably 1 to 3 minutes.

[0045] When the injection of the bubbles is carried out within the specified time range, the process time can be shortened while the carbon dioxide is sufficiently removed, which is therefore preferred.

[0046] On the other hand, adsorption technology, as one of the techniques for directly extracting lithium from lithium-containing brine, utilizes aluminum-based compounds such as [LiX]. 0-1 [Al(OH)3]2(X is Cl) - SO4 2- OH - NO3 - Anions, preferably Cl - )wait.

[0047] While not wishing to be limited by theory, conventional two-dimensional layered aluminum hydroxide (hereinafter referred to as "lithium aluminum interlayer compound" or "LDH") can promote the intercalation of anions between layers and allow positively charged lithium cations to diffuse into the hexagonal cavities formed within the two-dimensional layered structure, which are large enough to accommodate the size of lithium cations.

[0048] The LiCl inside the LDH cannot be extracted to the outside of the structure in a certain proportion without inducing structural changes. The LDH in the LiCl-extracted state has a high salt concentration, and when it comes into contact with a lithium solution containing LiCl, the vacancy is rapidly filled. The degree of vacancy filling increases with both the LiCl concentration and the salt concentration in the lithium solution when the LDH in the LiCl-extracted state fills the vacancy.

[0049] When in contact with water with low salt and low LiCl concentration, LiCl inside the LDH is released to the outside, and the degree to which LiCl is released to the outside is inversely proportional to the salt concentration and LiCl concentration.

[0050] When in contact with water with extremely low salt and LiCl concentrations, the LDH structure collapses as excessive LiCl is released from the LDH.

[0051] When a structurally collapsed LDH comes into contact with a high-concentration LiCl solution, it absorbs LiCl and regenerates back into an LDH structure. This process is slower than that of a normally structured LDH.

[0052] Therefore, for LDH, when carbonate and / or bicarbonate ions are present in the brine, the bicarbonate and / or carbonate ions come into contact with the adsorbent and form an ionic equilibrium state within the LDH structural layer. The strong binding force within the structure acts to block the adsorption sites, which may lead to a decrease in adsorption performance.

[0053] According to the brine pretreatment method of the present invention, the performance degradation of the adsorbent can be suppressed by removing carbonate ions and / or bicarbonate ions that reduce the performance of the adsorbent.

[0054] Pretreated brine Another aspect of the present invention relates to a brine wherein the concentration of one or more impurity ions selected from the group consisting of carbonate ions and bicarbonate ions is less than 0.48 g / L.

[0055] Another aspect of the present invention relates to a brine, which is a brine pretreated by the aforementioned brine pretreatment method.

[0056] In short, the brine according to the present invention, wherein the concentration of one or more impurity ions selected from the group consisting of carbonate ions and bicarbonate ions is less than 0.48 g / L, is a brine pretreated by the aforementioned brine pretreatment method.

[0057] The brine according to the present invention has the advantage of being able to suppress the decline of adsorbent performance and easily recover lithium when lithium is recovered using an adsorbent, since the concentration of one or more impurity ions selected from the group consisting of carbonate ions and bicarbonate ions is extremely low.

[0058] Specifically, for the brine according to the present invention, the concentration of the impurity ions can be less than 0.30 g / L, more specifically less than 0.10 g / L.

[0059] In another embodiment of the present invention, the lithium ion concentration in the brine can be 10 mg / L or more, preferably 70 mg / L or more, and more preferably 100 mg / L or more.

[0060] When the concentration of lithium ions meets the specified range, the adsorption rate during lithium recovery is fast, which has the advantages of improving productivity and excellent economic efficiency, and is therefore preferred.

[0061] <Lithium Recovery Methods> Another aspect of the present invention relates to a lithium recovery method, comprising: preparing a brine solution with a concentration of less than 0.48 g / L of one or more impurity ions selected from the group consisting of carbonate ions and bicarbonate ions; loading an aluminum-based adsorbent into a removal reactor; and allowing the brine solution to flow through an adsorbent layer loaded into the reactor to adsorb lithium ions.

[0062] The step of preparing a brine solution with a concentration of less than 0.48 g / L of one or more impurity ions selected from the group consisting of carbonate and bicarbonate ions can be performed using the aforementioned brine pretreatment method.

[0063] In short, the step of preparing a saline solution with a concentration of 0.48 g / L or less for one or more impurity ions selected from the group consisting of carbonate ions and bicarbonate ions may include: preparing a saline solution containing one or more impurity ions selected from the group consisting of carbonate ions and bicarbonate ions; adjusting the pH of the saline solution to 5 or less; and injecting air bubbles into the pH-adjusted saline solution to remove the impurity ions in the form of carbon dioxide.

[0064] Specifically, for the brine, the concentration of one or more impurity ions selected from the group consisting of carbonate ions and bicarbonate ions can be less than 0.30 g / L, and more specifically, less than 0.10 g / L.

[0065] In another embodiment of the present invention, the concentration of lithium ions in the brine can be 10 mg / L or more, preferably 70 mg / L or more, and more preferably 100 mg / L or more.

[0066] When the concentration of lithium ions meets the specified range, the adsorption rate is fast, which has the advantages of improving productivity and excellent economic efficiency, and is therefore preferred.

[0067] The lithium recovery method according to the present invention includes the steps of: loading an aluminum-based adsorbent into a removal reactor; and flowing the brine through an adsorbent layer loaded in the reactor to adsorb lithium ions.

[0068] In another embodiment of the present invention, the aluminum-based adsorbent may be a molded body comprising adsorbent powder and a binder.

[0069] The adsorbent powder may be, for example, an adsorbent powder containing aluminum hydroxide.

[0070] The adhesive is used to prepare the adsorbent powder into a molded body of appropriate shape, and can play the role of binding the adsorbent powder together.

[0071] The adhesive may, for example, contain one or more of the following: polyvinyl chloride (PVC), polysulfone, and polyaniline.

[0072] Preferably, the adhesive may comprise polyvinyl chloride (PVC) capable of providing excellent bonding between the adsorbent powders.

[0073] For the molded body, based on the total weight of the adsorbent powder, it may contain 5 to 30% by weight of the binder, preferably 10 to 15% by weight of the binder.

[0074] When the content of the binder meets the specified range, the amount of the adsorbent powder is appropriate, thereby maximizing the amount of lithium adsorbed, which is therefore preferred.

[0075] In another embodiment of the present invention, the aluminum-based adsorbent may comprise aluminum hydroxide.

[0076] When the aluminum-based adsorbent contains aluminum hydroxide, it can increase the adsorption capacity of lithium and has almost no aluminum loss in the desorption process, thus having the advantage of a long adsorbent lifespan, making it a preferred choice.

[0077] The lithium adsorption-desorption reaction induced by the aluminum-based adsorbent is shown below.

[0078] [Reaction 3] (a + b)Li + + aCl - + bHCO3 - + (1 - x)LiCl·2[Al(OH)3] aLiCl·2[Al(OH)3] + bLiHCO3·2[Al(OH)3] (x ≥ a + b) The step of passing the brine through an adsorbent layer packed in the reactor to adsorb lithium ions can be carried out at a temperature of 5 to 100°C, preferably 30 to 80°C.

[0079] When the adsorption temperature meets the specified range, the adsorption performance of lithium can be improved, and therefore it is preferred.

[0080] The step of allowing the brine to flow through the adsorbent layer loaded in the reactor to adsorb lithium ions can be carried out for 30 minutes to 10 hours, preferably 30 minutes to 8 hours, and more preferably 30 minutes to 6 hours.

[0081] When the step of flowing the brine through the adsorbent layer loaded in the reactor to adsorb lithium ions is carried out within the time range, the total process time can be shortened and excellent lithium adsorption performance is achieved, making it a preferred method.

[0082] The lithium recovery method according to the present invention may further include the step of obtaining a lithium-containing desorption solution from the aluminum-based adsorbent adsorbed with lithium ions.

[0083] For example, a lithium-containing desorption solution can be obtained by passing distilled water through the aluminum-based adsorbent that has adsorbed lithium ions, but it is not limited thereto.

[0084] Specifically, based on the volume of the aluminum-based adsorbent, the amount of distilled water flowing through the aluminum-based adsorbent can be 0.5 to 10 times, preferably 1 to 5 times, and more preferably 1 to 3 times the volume of the aluminum-based adsorbent.

[0085] When the amount of distilled water meets the specified range, the lithium desorption effect is excellent, and the phenomenon that the lithium concentration in the lithium-containing desorption solution is reduced due to the dilution of the desorbed lithium can be suppressed, which is therefore preferred.

[0086] The lithium concentration in the lithium desorption solution can be from 0.5 to 2.0 g / L, specifically from 0.8 to 1.5 g / L. When the lithium concentration meets this range, the lithium recovery rate becomes excellent, and this is therefore preferred.

[0087] The lithium recovery method according to the present invention may further include a step of concentrating the lithium-containing desorption solution to obtain a lithium-containing concentrate, but is not limited thereto. The step of obtaining the lithium-containing concentrate can be performed using an electrodialysis unit or the like, but is also not limited thereto.

[0088] Preferred embodiments and comparative examples of the present invention are described below. However, the following embodiments are merely one of the preferred embodiments of the present invention, and the present invention is not limited to the following embodiments.

[0089] Preparation example: containing HCO3 - Preparation of simulated saline To evaluate the presence of bicarbonate (HCO3-) ions in salt water - The effect of the adsorption on the lithium adsorption-desorption performance of the adsorbent was investigated. Simulated brine A and B containing bicarbonate ions were prepared based on the components in Table 1. For brine C, Diabillos from Rodinia Lithium was used.

[0090] At this point, the concentration of bicarbonate ions was measured using back titration.

[0091] The concentrations of bicarbonate ions in simulated saline solutions A through C were measured using an acid-base back titration method based on reaction equation 4 below. The results are shown in Table 2 and below. Figure 4 middle.

[0092] Specifically, the acid-base back titration method is as follows: using the neutralization reaction of acid and base, the unknown sample is first reacted with an excess of acid (first standard solution) (step 1), and then the remaining acid is titrated with a base of known concentration (second standard solution) to determine the concentration of the sample (step 2).

[0093] [Reaction 4] (Step 1) HCO3 - (aq) + nHCl(aq) → H2O(l) + CO2(g) + Cl - (aq) + (n-1)HCl(aq) (n>1) (Step 2)(n-1)HCl(aq) + mNaOH(aq) → (n-1)H2O(l) + (n-1)NaCl(aq) + (m-n+1)NaOH(aq) As step 1, 1 mL of 0.500 M HCl was added to each of 25 mL saline solutions A through C, and the mixture was stirred for approximately 0.5–1 hour. Subsequently, titration was performed using an acid-treated solution and 0.0503 M NaOH to measure the concentration of bicarbonate ions in the simulated saline solution. The results are shown in Table 2 below. At this point, C… HCO3- This indicates the bicarbonate ion content in salt solutions A through C, where C is the bicarbonate ion content. * HCO3- This indicates the content of bicarbonate ions after titration.

[0094] Table 1 Table 2 Example Hydrochloric acid is added to brine C until the pH reaches below 3 to adjust the pH. Then, air bubbles are injected using a bubble injector to remove bicarbonate ions present as carbon dioxide, thus obtaining brine C'.

[0095] Table 3 Experimental Example: Performance Evaluation of Adsorbents Based on Bicarbonate Ion ion content The performance of the adsorbent based on bicarbonate ions was evaluated, and the results are shown in... Figures 1 to 3 middle.

[0096] Specifically, 600 mL of saline solution A to C and C' are respectively passed through a packed column (reactor) filled with 60 g of LAH (lithium aluminum hydroxide) adsorbent.

[0097] Subsequently, 30 L / volume of distilled water is passed through the adsorbent containing lithium to obtain a lithium-containing desorption solution.

[0098] The adsorbent from which lithium was separated was repeatedly subjected to adsorption and desorption using the same saline solution, and the amount of lithium adsorbed was measured according to the number of adsorption and desorption cycles.

[0099] Figure 1 The results of Li adsorption amounts in saline solutions A to C and C' based on the number of adsorption-desorption cycles are shown. Figure 2 and Figure 3 The results for saline solutions B and C based on the number of adsorption / desorption cycles are shown respectively. At this point, Figure 2 and Figure 3 The reference point is set as the Li adsorption site that is filled during the first adsorption.

[0100] In addition, HCO3 in saline solutions B and C was measured. - Theoretical and measured values ​​of HCO3 in column experiments - The adsorption amount is shown in Table 4 below.

[0101] Table 4 Reference Figures 1 to 3 As shown in Table 4, the content of bicarbonate ions in the brine affects the adsorption performance of the adsorbent.

[0102] This invention is not limited to the embodiments described above, and can be prepared in various different ways. Those skilled in the art should understand that this invention can be implemented in other specific ways without changing the technical concept or essential features of the invention. Therefore, it should be understood that the above embodiments are exemplary in all respects and not restrictive.

Claims

1. A method for brine pretreatment, comprising: The steps for preparing a salt solution containing one or more impurity ions selected from the group consisting of carbonate ions and bicarbonate ions. The step of adjusting the pH of the saline solution to below 5; and The step of injecting air bubbles into the pH-adjusted brine to remove the impurity ions in the form of carbon dioxide.

2. The brine pretreatment method according to claim 1, wherein, The step of adjusting the pH of the brine to below 5 is performed by adding one or more acids selected from the group consisting of hydrochloric acid, concentrated sulfuric acid, and dilute sulfuric acid.

3. The brine pretreatment method according to claim 2, wherein, The step of adjusting the pH of the brine to below 5 is performed by adding hydrochloric acid.

4. The brine pretreatment method according to claim 1, wherein, In the step of adjusting the pH of the saline solution to below 5, the pH is adjusted to below 4.

5. The brine pretreatment method according to claim 4, wherein, In the step of adjusting the pH of the saline solution to below 5, the pH is adjusted to below 3.

6. The brine pretreatment method according to claim 1, wherein, The bubbles are continuously injected for 1 to 10 minutes.

7. A salt solution, wherein, The concentration of one or more impurity ions selected from the group consisting of carbonate ions and bicarbonate ions is less than 0.48 g / L.

8. The brine according to claim 7, wherein, The concentration of lithium ions is above 10 mg / L.

9. A salt solution, wherein, The brine is brine pretreated by the brine pretreatment method according to any one of claims 1 to 6.

10. A lithium recovery method, comprising: The steps for preparing a saline solution with a concentration of less than 0.48 g / L of one or more impurity ions selected from the group consisting of carbonate ions and bicarbonate ions. The step of loading aluminum-based adsorbent into the removal reactor; and The step of passing the brine through an adsorbent layer packed in the reactor to adsorb lithium ions.

11. The lithium recovery method according to claim 10, wherein, The lithium ion concentration of the brine is above 10 mg / L.

12. The lithium recovery method according to claim 10, wherein, The aluminum-based adsorbent is a molded body comprising adsorbent powder and a binder.

13. The lithium recovery method according to claim 10, wherein, The aluminum-based adsorbent contains aluminum hydroxide.

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