A method for extracting lithium from carbonate brine

Abstract

The application belongs to the technical field of lithium extraction from brine, and particularly relates to a lithium extraction method applied to carbonate brine. The method comprises the following steps: removing more than 90% of carbonate ions in the brine to obtain primary product water; converting the residual carbonate ions in the primary product water into bicarbonate ions to obtain secondary product water; and using a solid aluminum adsorbent to perform lithium extraction and impurity removal operation on the secondary product water. After more than 90% of the carbonate ions in the brine are removed by conventional means, acid is added to the primary product water to convert the carbonate ions into bicarbonate ions, so as to alleviate the poisoning of the adsorbent. The aluminum adsorbent used in the application is solid and has no internal pores. All active sites of the solid aluminum adsorbent are exposed, the acid-base environment of the adsorbent is consistent with the product water environment, the pH can be accurately controlled, the conversion of bicarbonate ions into carbonate ions in the aluminum hydroxide liquid film is avoided from the source, and the adsorbent is prevented from being poisoned by carbonates.

Description

Technical Field

[0001] This invention belongs to the field of lithium extraction technology from brine, specifically relating to a method for lithium extraction from carbonate brine. Background Technology

[0002] Aluminum-based lithium adsorbents have been industrially applied for lithium extraction from brine, and their working mechanism differs fundamentally from ion exchange. Traditional adsorption methods for lithium extraction utilize particulate adsorbents in adsorption towers for lithium ion adsorption and desorption. Aluminum-based adsorption is widely used for lithium extraction from potassium-precipitated brine, but it is generally considered unsuitable for direct lithium extraction from carbonate-containing brines. Aluminum-based adsorption uses fresh water for desorption, and the entire process does not involve strong acids or bases, making it easier to maintain the structural stability of the adsorbent over long periods and control the impurity content of the product liquid in the adsorption stage. It is currently the most widely used intensive process for brine lithium extraction. However, traditional aluminum-based adsorbents are easily blocked by large-radius anions, leading to poisoning. Specifically, in the process of lithium extraction from brines containing high-valence anions (such as sulfate), the adsorption capacity of the aluminum-based adsorbent decreases significantly due to its use in the brine, especially with a significant increase in the salt-to-lithium ratio of the desorbate and a significant decrease in the lithium concentration. Carbonates, borates, arsenates, and sulfates all negatively impact the continuous and stable operation of aluminum-based adsorbents.

[0003] Existing technologies for extracting lithium from carbonate brines generally involve evaporating and concentrating the brine, followed by freezing to precipitate carbonate or sulfate ions, thereby reducing their content. For example, invention patent CN103553088A discloses a method for preparing lithium-boron salt ore from mixed brine using natural energy. This method includes: evaporating and freezing carbonate brine until the Li content is less than or equal to 2.5 g / L or the lithium carbonate content in the precipitated solid ore is less than or equal to 0.5% to obtain brine A; and collecting the mixed alkali produced during the freezing process; evaporating and freezing sulfate brine until the Mg content is greater than or equal to 10 g / L to obtain brine B; and... Water A and brine B are mixed and reacted to obtain brine C; brine C is evaporated to a sulfate concentration of 5 g / L to 40 g / L to obtain brine D; brine D is frozen and then nitrated to obtain brine E; brine E is evaporated to a certain extent to obtain brine F; brine F is naturally evaporated to precipitate potassium halite and brine G; brine G is mixed and reacted with high-magnesium brine to obtain brine H; brine H is reacted with mirabilite to obtain brine I; brine I is evaporated and concentrated to precipitate lithium sulfate ore and brine J; brine J is mixed with fresh water or sulfate-type raw brine in a certain proportion and evaporated to precipitate boron ore.

[0004] For example, the invention patent with announcement number CN112142076B discloses a method for extracting lithium from brine by adsorption. This method uses sulfate-type brine or sulfate-containing salt lake brine as raw material. The content and ratio of sulfate ions in the brine are adjusted by adding fresh water, selecting brine or selecting compounds. Alternatively, the sulfate-containing salt lake brine is evaporated and concentrated, and then frozen to reduce the sulfate content in the brine to below 7 g / L and the ratio of sulfate content to total anion content in the solution to below 4.7 wt%.

[0005] The presence of carbonates or bicarbonates in the brine can poison aluminum-based lithium adsorbents, making it impossible to meet the requirements for stable lithium extraction from carbonate brine using aluminum-based adsorption methods. Summary of the Invention

[0006] The purpose of this invention is to address the above-mentioned problems by providing a lithium extraction method for carbonate brine. This method can overcome the problem of carbonate or bicarbonate poisoning caused by aluminum-based adsorbents and significantly improve lithium extraction efficiency.

[0007] The specific technical solution of the present invention is as follows:

[0008] A method for lithium extraction from carbonate brine includes the following steps:

[0009] (1) Remove more than 90% of carbonate ions from the brine to obtain primary product water;

[0010] (2) Convert the residual carbonate ions in the primary product water into bicarbonate ions to obtain secondary product water;

[0011] (3) Solid aluminum-based adsorbents are used to perform lithium extraction and impurity removal operations on secondary product water.

[0012] Through extensive research, the inventors discovered that aluminum-based adsorbents exhibit significant differences in tolerance to anions with different large ionic radii. Specifically, their tolerance to monovalent anions is significantly better than that to divalent anions. In carbonate-containing brine, aluminum-based adsorbents show significantly lower tolerance to carbonate ions than to bicarbonate ions. Therefore, this invention, after removing more than 90% of carbonate ions from the brine using conventional methods, adds acid to the primary permeate to convert carbonate ions into bicarbonate ions, thereby mitigating adsorbent poisoning.

[0013] Furthermore, traditional aluminum-based adsorbents are all porous granular adsorbents, and are used by filling them into adsorption towers. This makes precise pH control of all aluminum hydroxide interfaces impossible, easily leading to aluminum hydroxide carbonate poisoning during production. Therefore, the aluminum-based adsorbent used in this invention is solid and without internal pores. All active sites of this solid aluminum-based adsorbent are exposed, making it easier to maintain a consistent acid-base environment with the product water environment, facilitating precise pH control and preventing the conversion of bicarbonate ions to carbonate ions in the aluminum hydroxide liquid film from the source, thus avoiding carbonate poisoning of the adsorbent.

[0014] In the above-mentioned lithium extraction method applied to carbonate brine, in step (1), nanofiltration, chemical precipitation, or adsorption is used to remove carbonate ions from the brine.

[0015] Preferably, the present invention utilizes nanofiltration to remove 90%-99% of carbonate ions from brine to obtain primary product water.

[0016] Since this invention will completely remove carbonate ions through acid adjustment, there is no need to remove carbonate ions from the original brine through brine evaporation and concentration, freezing, etc. Nanofiltration treatment can meet the requirements of the subsequent first-stage permeate. The permeate yield of nanofiltration pretreatment is 30-70%, and only one stage of nanofiltration pretreatment is required.

[0017] In the above-mentioned lithium extraction method applied to carbonate brine, in step (2), carbonate ions are converted into bicarbonate ions by adjusting the pH value of the primary product water to 4.0-6.5.

[0018] Generally, adjusting the pH of the primary product water to acidic will achieve the conversion of carbonate ions to bicarbonate ions; however, the pH of the primary product water should not be too low (below 4.0) to avoid chemical dissolution of aluminum hydroxide and unnecessary losses.

[0019] In the above-mentioned lithium extraction method applied to carbonate brine, at least one of sulfuric acid, hydrochloric acid, and nitric acid is used to adjust the pH value of the primary product water.

[0020] This invention uses sulfuric acid, hydrochloric acid, nitric acid, etc., to adjust acidity and convert the small amount of carbonate ions remaining in the primary product water into bicarbonate ions. Although the sulfuric acid used in the acid adjustment process introduces high-valence anions such as sulfate ions, the concentration of these sulfate ions is only one-hundredth to one-thousandth of the original sulfate ion concentration in the brine, and the amount introduced is extremely small. Furthermore, the solid aluminum-based powder adsorbent used in this invention eliminates concerns about large-radius anions clogging the adsorbent channels and causing adsorbent poisoning.

[0021] In the above-mentioned lithium extraction method applied to carbonate brine, in step (3), the particle size of the solid aluminum adsorbent is between 50 and 200 micrometers.

[0022] This invention strictly controls the particle size of the solid aluminum adsorbent to be between 50 and 200 micrometers, which on the one hand enables industrial solid-liquid separation, and on the other hand ensures that the solid aluminum adsorbent has sufficient adsorption capacity.

[0023] The present invention has found that the smaller the particle size of the solid aluminum adsorbent, the higher its adsorption capacity. Therefore, as a preferred embodiment, more than 50 wt% of the solid aluminum adsorbent has a particle size of less than or equal to 100 micrometers.

[0024] In the above-mentioned lithium extraction method applied to carbonate brine, the solid aluminum-based adsorbent is prepared by the following method:

[0025] The active ingredient LiCl·Al(OH)3·nH2O is fully pulverized, added to a binder and molded, and then enters a crushing-molding cycle until the final aluminum-based lithium adsorbent has a dense structure without internal pores.

[0026] In the above-mentioned lithium extraction method applied to carbonate brine, step (3) includes the following:

[0027] (a) The secondary permeate water is thoroughly mixed with a solid aluminum-based adsorbent and then vacuum filtered to obtain a filter cake;

[0028] (b) Use a washing brine to remove impurities from the filter cake;

[0029] (c) Lithium ions in the filter cake are eluted with a desorption solution to obtain a lithium eluent.

[0030] In the above-mentioned lithium extraction method applied to carbonate brine, fresh water with a pH of 4.5-5.0 is used as the washing solution; and fresh water with a pH of 4.0-6.5 is used as the desorption solution.

[0031] Since the pH value of the water environment in which the adsorbent is located may rise due to various reasons in each stage of the lithium extraction and impurity removal process, in order to ensure that the bicarbonate ions in the water environment in which the adsorbent is located do not convert into carbonate ions, this invention sets the pH value of the washing salt solution and the desorption solution to a relatively low 4.0-6.5, so that the adsorbent always operates in an acidic water environment.

[0032] Compared with the prior art, the advantages of the present invention are as follows:

[0033] (1) Through extensive research, the inventors discovered that aluminum-based adsorbents have significant differences in tolerance to anions with different large ionic radii. Specifically, they are significantly more tolerant to monovalent anions than to divalent anions. In carbonate-containing brine, aluminum-based adsorbents are significantly less tolerant to carbonate ions than to bicarbonate ions. Therefore, after removing more than 90% of carbonate ions from the brine using conventional methods, this invention adds acid to the primary product water to convert carbonate ions into bicarbonate ions, thereby reducing the poisoning of the adsorbent.

[0034] (2) The aluminum adsorbent used in this invention is solid and has no internal channels. All active sites of this solid aluminum adsorbent are exposed, and its acid and alkaline environment is easy to keep in line with the product water environment, which facilitates precise pH control and avoids the conversion of bicarbonate ions to carbonate ions in the aluminum hydroxide liquid film from the source, thus avoiding carbonate poisoning of the adsorbent.

[0035] (3) The solid aluminum adsorbent used in this invention has a particle size between 50 and 200 micrometers. This particle size of solid aluminum adsorbent can achieve industrial solid-liquid separation on the one hand, and ensure sufficient adsorption capacity on the other hand.

[0036] (4) Since the pH value of the water environment in which the adsorbent is located may rise due to various reasons in each stage of the lithium extraction and impurity removal process, in order to ensure that the bicarbonate ions in the water environment in which the adsorbent is located will not be converted into carbonate ions, the present invention sets the pH value of the washing salt solution and the desorption solution to a relatively low 4.0-6.5 so that the adsorbent always operates in an acidic water environment. Attached Figure Description

[0037] Figure 1 This is an electron microscope image of the solid aluminum-based adsorbent used in the lithium extraction method of carbonate brine according to the present invention. Detailed Implementation

[0038] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0039] Example 1

[0040] This embodiment provides a method for lithium extraction from carbonate brine, the specific steps of which are as follows:

[0041] (1) Take brine, and after removing particulate matter from the brine in a sand filter tank, use a first-stage nanofiltration to remove 90%-99% of carbonate ions from the brine to obtain first-stage product water;

[0042] (2) Add sulfuric acid to the primary product water to adjust the pH to 6.5. The residual carbonate ions in the primary product water are converted into bicarbonate ions to obtain the secondary product water:

[0043] (3) Solid aluminum-based adsorbents were used to perform lithium extraction and impurity removal operations on the secondary product water;

[0044] Specifically, it includes:

[0045] (a) The secondary permeate water is thoroughly mixed with a solid aluminum-based adsorbent and then vacuum filtered to obtain a filter cake;

[0046] This solid aluminum-based adsorbent was prepared by the following method:

[0047] S1 pulverizes the active component LiCl·Al(OH)3·nH2O of the aluminum-based lithium adsorbent into micro powder with a particle size of less than 35 micrometers;

[0048] S2 prepares a dispersion by dispersing chlorinated polyvinyl chloride in trichloroethylene at a mass concentration of 30%;

[0049] S3 adds a dispersion to the micro powder, wherein the amount of chlorinated polyvinyl chloride added is 5% of the mass of the aluminum-based lithium adsorbent. The powder is then bonded and granulated by a spheroidizing granulator and dried to obtain a powder with a particle size of 80-140 micrometers.

[0050] S4. Repeat steps S1 and S3 until no internal channels are visible under an electron microscope (e.g., ...). Figure 1 (as shown), and then solid aluminum-based adsorbents with a particle size of 100 micrometers were screened out by cyclone sieve;

[0051] (b) Use a washing brine to remove impurities from the filter cake;

[0052] Fresh water with a pH of 6.5 was used as the washing salt solution;

[0053] (c) Lithium ions in the filter cake are eluted with a desorption solution to obtain a lithium eluent;

[0054] Fresh water with a pH of 5.0 was used as the desorption solution;

[0055] The above-mentioned lithium extraction and impurity removal operations can be carried out on a filter press as described in patent CN202010646187.8;

[0056] (d) The obtained desorption solution is concentrated by reverse osmosis. The concentrated water is used as lithium-rich eluent, and the deionized water is acidified and used as desorption solution. The lithium-rich eluent is then concentrated, impurity removed, and lithium evaporation and precipitation are performed to obtain lithium carbonate product.

[0057] Example 2

[0058] This embodiment is basically the same as that of embodiment 1, except that in step (2), hydrochloric acid is added to the primary product water to adjust the pH value to 5.0; in step (b), fresh water with a pH of 4.5 is used as the washing solution; and in step (c), fresh water with a pH of 6.5 is used as the desorption solution.

[0059] Example 3

[0060] This embodiment is basically the same as that of embodiment 1, except that: in step (2), nitric acid is added to the primary permeate to adjust the pH value to 4.0; in step (b), fresh water with a pH of 5.0 is used as the washing brine; and in step (c), fresh water with a pH of 4.0 is used as the desorption solution.

[0061] Table 1 shows the pH values ​​of the influent and effluent in each stage of the lithium extraction and impurity removal operation in Examples 1-3.

[0062] Table 1. pH values ​​of influent and effluent at each stage of lithium extraction and impurity removal operation.

[0063] Adsorption process Salt washing process Desorption phase Inlet water pH 4.0-6.5 4.0-6.5 4.0-6.5 effluent pH value 5.5-6.5 6-6.8 6-6.5

[0064] Examples 4-6

[0065] This embodiment is basically the same as that of embodiment 1, except that the particle size of the solid aluminum adsorbent used in step (3) is 50 micrometers, 150 micrometers and 200 micrometers respectively.

[0066] Comparative Example 1

[0067] This comparative example is basically the same as Example 1, except that: the pH value of the primary product water is not adjusted in step (2); and the washing brine and desorption solution used in step (3) are fresh water with a neutral pH.

[0068] Comparative Example 2

[0069] This comparative example is basically the same as Example 1, except that the washing salt solution and desorption solution used in step (3) are fresh water with a neutral pH.

[0070] Comparative Examples 3-5

[0071] This comparative example is basically the same as Example 1, except that the particle sizes of the solid aluminum adsorbent used in step (3) are 500 micrometers, 1000 micrometers and 2000 micrometers respectively.

[0072] Comparative Example 6

[0073] This comparative example is basically the same as Example 1, except that: in step (3), a common porous aluminum-based powder adsorbent is used, and the particle size of the adsorbent is 200 micrometers.

[0074] The brine from a carbonate-type salt lake was selected. The specific composition of the brine is shown in Table 2, and the total salinity is approximately 40 g / L. Lithium was extracted using the methods described in Examples 1-6 and Comparative Examples 1-6, and the following tests were performed:

[0075] (a) Ion composition test of primary produced water

[0076] The ionic composition of the primary permeate from Examples 1-3 was tested; the test results are shown in Table 2.

[0077] Table 2. Ionic composition of raw brine and primary product water in Examples 1-3

[0078]

[0079] (Ion concentration unit is mg / L)

[0080] As shown in Table 2, in Examples 1-3, the carbonate ion content of the primary product water was 0.077-0.117 mg / L and the sulfate ion content was 0.072-0.089 mg / L, which is much lower than the carbonate ion content (1.536 mg / L) and sulfate ion content (2.568 mg / L) in the original brine. This indicates that 90%-99% of the carbonate and sulfate ions in the original brine can be removed in one nanofiltration, reducing the pressure on subsequent steps.

[0081] (II) Ionic composition test of lithium eluent

[0082] The lithium eluents of Examples 1-3 and Comparative Examples 1-2 and 6 were tested for ionic composition; the test results are shown in Table 3.

[0083] Table 3. Ionic composition of original brine and lithium eluent in Examples 1-3 and Comparative Examples 1-2 and 6.

[0084]

[0085] (Ion concentration unit is mg / L)

[0086] As shown in Table 3, no HCO3 was detected in the lithium eluents of Examples 1-3. - CO3 2- and SO4 2- This is because, on the one hand, the acidification treatment performed in step (2) reduces the CO3 content in the primary permeate. 2- All were converted to HCO3 - The washing salt solution and desorption solution used in step (3) are both acidic, thus preventing the release of HCO3. - Reversed to CO3 2- The possibility of HCO3; while the solid aluminum adsorbent used in Examples 1-3 - and SO4 2-All of them have extremely high tolerance. These large-radius anions are separated from the adsorbent after step (a) adsorption separation and step (b) salt washing, so that there are no large-radius anions left in the lithium eluent after desorption, and the lithium ion concentration is greatly increased.

[0087] In contrast, Examples 1-2 did not undergo acidification treatment, or the pH of the water environment increased during the washing and desorption processes, leading to a decrease in HCO3. - Reversed to CO3 2- Both of these factors contribute to a decrease in the tolerance of solid aluminum-based adsorbents to these large-radius anions. In Comparative Example 6, although acid adjustment was performed and the adsorbent remained in an acidic environment, its porous structure still caused anion blockage, ultimately leading to adsorbent poisoning and a relatively lower lithium ion concentration in the lithium eluent.

[0088] (III) Testing of lithium concentration in brine effluent after adsorption, lithium concentration in lithium eluent, adsorption capacity, and lithium recovery rate

[0089] For each embodiment and comparative example, 50 rounds of adsorption-desorption experiments were conducted. The lithium concentration in the brine and the lithium eluent after the 50th adsorption were measured, and the lithium recovery rate was calculated. The test results are shown in Table 4.

[0090] Table 4. Test results of lithium concentration in brine effluent after adsorption, lithium concentration in lithium eluent, and lithium recovery rate in the adsorption section for Examples 1-6 and Comparative Examples 1-6.

[0091]

[0092] As shown in Table 4, in Examples 1-6 of this invention, since there are no carbonate ions in the secondary permeate that would cause adsorbent poisoning, and the solid aluminum-based adsorbent used fundamentally eliminates adsorbent poisoning, lithium ions can specifically intercalate and deintercalate between the aluminum hydroxide layers. This manifests in two ways: firstly, the adsorption capacity of the adsorbent is significantly improved. When the secondary permeate is mixed with the solid aluminum-based adsorbent for adsorption, most of the lithium ions in the secondary permeate are absorbed by the adsorbent, resulting in a relatively lower lithium concentration in the brine effluent after adsorption (as low as 17 ppm); secondly, the lithium ion concentration in the lithium eluent obtained after desorption is significantly increased, and the lithium recovery rate reaches over 80% (as high as 97.0%). In contrast, when carbonate ions affecting adsorbent performance are present in the aquatic environment where the adsorbent is located (Comparative Examples 1-2) and when a porous adsorbent is used (Comparative Example 6), the adsorbent is poisoned to varying degrees, leading to an increase in the lithium ion concentration in the brine effluent after adsorption and a decrease in the lithium recovery rate.

[0093] As can be seen from Table 4, the adsorption capacity of the solid aluminum-based adsorbent gradually decreases as the particle size of the adsorbent gradually increases (50 μm in Example 4, 100 μm in Example 1, 150 μm in Example 5, 200 μm in Example 6, 500 μm in Comparative Example 3, 1000 μm in Comparative Example 4, and 2000 μm in Comparative Example 5). It can be seen that when the particle size is within 200 μm, the solid aluminum-based adsorbent has a better adsorption capacity; and the smaller the particle size of the aluminum-based lithium adsorbent, the higher the adsorption capacity. This suggests that in practical applications using solid aluminum-based adsorbents, ensuring that more than 50 wt% of the solid aluminum-based adsorbent powder has a particle size of less than or equal to 100 μm is more conducive to the adsorption process.

[0094] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

[0095] Although this document uses a great deal of terminology, its use is solely for the convenience of describing and explaining the essence of the invention, and interpreting it as any additional limitation would be contrary to the spirit of the invention.

Claims

1. A method for lithium extraction from carbonate brine, characterized in that: Includes the following steps: (1) Remove more than 90% of carbonate ions from the brine to obtain primary product water; (2) Convert the carbonate ions remaining in the primary product water into bicarbonate ions to obtain secondary product water; (3) Use solid aluminum adsorbents without internal pores to perform lithium extraction and impurity removal operations on secondary product water; The particle size of the solid aluminum-based adsorbent is between 50 and 200 micrometers; By mass percentage, the particle size of solid aluminum adsorbents exceeding 50 wt% is less than or equal to 100 micrometers; The solid aluminum-based adsorbent is prepared by the following method: The active ingredient LiCl·Al(OH)3·nH2O is fully pulverized, added to a binder and molded, and then enters a crushing-molding cycle until the final aluminum-based lithium adsorbent has a dense structure without internal pores. The lithium extraction and impurity removal process includes: (a) The secondary permeate water is thoroughly mixed with a solid aluminum-based adsorbent, and then vacuum filtered to obtain a filter cake; (b) Use washing salt solution to remove impurities from the filter cake; (c) Lithium ions in the filter cake are eluted with a desorption solution to obtain a lithium eluent.

2. The lithium extraction method applied to carbonate brine as described in claim 1, characterized in that: In step (1), nanofiltration, chemical precipitation or adsorption methods are used to remove carbonate ions from the brine.

3. The lithium extraction method applied to carbonate brine as described in claim 1, characterized in that: In step (2), carbonate ions are converted into bicarbonate ions by adjusting the pH of the primary permeate to 4.0-6.

5.

4. The lithium extraction method applied to carbonate brine as described in claim 3, characterized in that: The pH value of the primary product water is adjusted using at least one of sulfuric acid, hydrochloric acid, and nitric acid.

5. The lithium extraction method applied to carbonate brine as described in claim 1, characterized in that: Fresh water with a pH of 4.0-6.5 was used as the washing salt solution.

6. The lithium extraction method applied to carbonate brine as described in claim 1, characterized in that: Fresh water with a pH of 4.0-6.5 was used as the desorption solution.

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