A method for preparing lithium aluminum adsorbent from brine with low magnesium-to-lithium ratio

Abstract

The present invention discloses a method for preparing a lithium aluminum adsorbent from a low magnesium-lithium ratio brine. The method comprises: subjecting a lithium aluminum mixed salt solution, an inorganic alkaline solution and a modifier to a coprecipitation nucleation reaction under a pH value of 5 to 7 to obtain a lithium aluminum adsorbent crystal nucleus; wherein the lithium aluminum mixed salt solution is prepared from a low magnesium-lithium ratio brine, and the low magnesium-lithium ratio brine includes an adsorption lithium-rich brine and / or a membrane lithium-rich brine; the magnesium-lithium ratio in the adsorption lithium-rich brine is 3 to 5:1, and the magnesium-lithium ratio in the membrane lithium-rich brine is 0.1 to 0.5:1; and, subjecting the lithium aluminum adsorbent crystal nucleus to an aging treatment to obtain a lithium aluminum adsorbent. The present invention directly prepares an aluminum-based adsorbent using a low magnesium-lithium ratio brine as a raw material, which not only reduces the preparation cost of the aluminum-based adsorbent, but also expands the development and extraction methods of salt lake lithium resources; and the prepared lithium aluminum adsorbent material has a high adsorption capacity.

Description

Technical Field

[0001] The invention belongs to the technical field of comprehensive utilization of salt lake resources, and specifically relates to a method for preparing a lithium aluminum adsorbent from brine with a low magnesium-to-lithium ratio. Background Art

[0002] Lithium is the lightest metal element in nature. It has unique physical and chemical properties such as high specific heat, high electrical conductivity and strong chemical activity. Lithium and its compounds are closely related to people's lives and are known as "energy metals that promote world progress". In recent years, with the rapid development of new energy vehicles, the demand for lithium batteries and lithium power batteries has increased, and the demand for lithium has also increased sharply. In nature, lithium resources are mainly found in solid ores and liquid brines. Global lithium resources are limited and concentrated. The cost of extracting lithium from ores remains high and is limited by the scale of mining. It is difficult to meet the fast-growing demand for low-cost lithium batteries. The important position of brine lithium resources in the development of lithium resources in the world has been established for nearly 40 years. Therefore, lithium extraction from salt lakes has received more and more attention. The notable feature of Qinghai salt lake brine is its high magnesium / lithium ratio. The magnesium / lithium mass ratio of the Qarhan Salt Lake, which was developed earlier and to a higher degree, is as high as 1837, while that of the Da Qaidam Salt Lake is 114. The magnesium / lithium ratio of the brine in the East and West Taijinai Salt Lakes is 40-60, which is dozens or even thousands of times that of foreign countries. The presence of a large amount of magnesium makes it more difficult to separate and extract lithium.

[0003] At present, the main technologies for extracting lithium from salt lake brine include precipitation, solvent extraction, adsorption, calcination, electrodialysis, nanofiltration and solar pond. The adsorption method has greater advantages than other methods from the perspective of environment and economy, especially in the extraction of lithium from low-grade brine or seawater. The adsorption method uses an adsorbent that selectively adsorbs lithium ions to adsorb lithium ions, and then elutes the lithium ions to achieve the purpose of separating lithium ions from other impurity ions. The key is to develop an adsorbent with excellent performance, which requires the adsorbent to have extremely high selectivity for lithium. In addition, the adsorbent preparation method is simple, with high utilization rate, fast exchange rate, suitable for large-scale operation, and no pollution to water bodies. The adsorption method has the advantages of simple process, high recovery rate, good selectivity and environmental friendliness.

[0004] In patent CN106507704B, powdered aluminum hydroxide or aluminum oxide is made into balls with an organic adhesive or an inorganic adhesive, and then a lithium compound and an alkaline compound are dissolved in water, and the spherical aluminum hydroxide or aluminum oxide prepared above are added to react to form LiX.2Al(OH)3 microcrystals, and after the reaction is completed, the crystals are separated and washed to obtain a lithium adsorbent; in patent CN108854935A, aluminum hydroxide is mixed with a lithium salt, the mixture is activated, the activated compound is aged, and the pH value of the aged compound is adjusted to 3-7 to obtain a compound with adjusted pH value; the above compound is separated and dried to obtain the lithium adsorbent; In CN108993376A, aluminum salt and lithium salt are mixed and dissolved in deionized water, ultrasonically mixed, and then the mixed solution is added dropwise to the alkaline solution, or the alkaline solution is added dropwise to the mixed solution, or the mixed solution and the alkaline solution are added dropwise to the reactor in parallel, pH is controlled, aging, hydrothermal reaction, filtration and washing, vacuum drying, water washing and drying are performed to obtain the aluminum salt lithium adsorbent; in patent CN101829538A, an organic lithium salt or lithium salt solid is reacted with active aluminum hydroxide obtained by hydrolysis to prepare an aluminum adsorbent. The raw materials used in the preparation of the above-mentioned aluminum adsorbent are inorganic salts or organic lithium salts of lithium such as lithium chloride and organic lithium, which have high cost, long process flow, difficult separation and low adsorption capacity. Summary of the invention

[0005] The main purpose of the present invention is to provide a method for preparing a lithium aluminum adsorbent from brine with a low magnesium-to-lithium ratio, so as to overcome the shortcomings of the prior art.

[0006] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention includes:

[0007] The embodiment of the present invention provides a method for preparing a lithium aluminum adsorbent from brine with a low magnesium-to-lithium ratio, which comprises:

[0008] A lithium aluminum mixed salt solution, an inorganic alkaline solution and a modifier are subjected to a coprecipitation nucleation reaction under a pH value of 5 to 7 to obtain a lithium aluminum adsorbent crystal nucleus; wherein the lithium aluminum mixed salt solution is prepared from a low magnesium-to-lithium ratio brine, and the low magnesium-to-lithium ratio brine includes a lithium-rich brine extracted by an adsorption method and / or a lithium-rich brine extracted by a membrane method; the magnesium-to-lithium ratio of the lithium-rich brine extracted by the adsorption method is 3 to 5:1, and the magnesium-to-lithium ratio of the lithium-rich brine extracted by the membrane method is 0.1 to 0.5:1;

[0009] And, the lithium aluminum adsorbent crystal nucleus is aged at 40° C. to 80° C. to obtain the lithium aluminum adsorbent.

[0010] An embodiment of the present invention also provides a lithium aluminum adsorbent prepared by the aforementioned method, wherein the chemical formula of the lithium aluminum adsorbent is (LiClAl2(OH)6)·nH2O, n=1-10; the capacity of the lithium aluminum adsorbent is 11-15 mg / g.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention uses lithium-rich brine extracted by adsorption method with low magnesium-lithium ratio and / or lithium-rich brine extracted by membrane method as raw materials, adopts coprecipitation method to prepare lithium-aluminum adsorbent and separates and extracts lithium resources in salt lake at the same time, simplifies the steps of solid lithium salt dissolution and filtration when preparing aluminum adsorbent with inorganic lithium salt such as lithium chloride or organic lithium salt as raw materials, reduces the process flow, reduces the cost, improves the product dispersibility, increases the filtration speed of lithium-aluminum adsorbent, and the filtration speed refers to the shorter filtration time under the same conditions, improves the cycle stability of lithium adsorption material, reduces the dissolution loss rate of adsorption material to below 0.001%, combines the comprehensive utilization of salt lake resources with functional utilization, and improves the utilization efficiency of lithium resources. Combines the comprehensive utilization of salt lake resources with functional utilization, and improves the utilization efficiency of lithium resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0013] Figure 1 is the XRD pattern of the lithium aluminum adsorbent prepared in Example 1 of the present invention;

[0014] Figure 2 It is the XRD diagram of the material prepared in Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0015] In view of the defects of the prior art, the inventors of this case have proposed the technical solution of the present invention after long-term research and extensive practice. The present invention directly prepares lithium-aluminum adsorbent using lithium-rich brine extracted by adsorption method and / or lithium-rich brine extracted by membrane method as raw materials, which solves the technical problems of preparing lithium chloride or lithium carbonate from salt lake lithium resources and then preparing aluminum-based adsorbents from lithium salts, such as complex process and high cost, while improving the utilization efficiency of salt lake lithium resources.

[0016] The technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0017] Specifically, as one aspect of the technical solution of the present invention, a method for preparing a lithium aluminum adsorbent from a low magnesium-to-lithium ratio brine comprises:

[0018] A lithium aluminum mixed salt solution, an inorganic alkaline solution and a modifier are subjected to a coprecipitation nucleation reaction under a pH value of 5 to 7 to obtain a lithium aluminum adsorbent crystal nucleus; wherein the lithium aluminum mixed salt solution is prepared from a low magnesium-to-lithium ratio brine, and the low magnesium-to-lithium ratio brine includes a lithium-rich brine extracted by an adsorption method and / or a lithium-rich brine extracted by a membrane method; the magnesium-to-lithium ratio of the lithium-rich brine extracted by the adsorption method is 3 to 5:1, and the magnesium-to-lithium ratio of the lithium-rich brine extracted by the membrane method is 0.1 to 0.5:1;

[0019] And, the lithium aluminum adsorbent crystal nucleus is aged at 40° C. to 80° C. to obtain the lithium aluminum adsorbent.

[0020] The present invention adopts a modifier to change the surface characteristics of the crystal nucleus, increase the specific surface area of ​​the product, reduce the agglomeration phenomenon in the nucleation process, reduce the particle size of the crystal nucleus, and improve the filtering performance of the product.

[0021] Specifically, the present invention adopts an adsorption method to extract lithium from lithium-rich brine and / or a membrane method to extract lithium from lithium-rich brine to prepare a lithium-aluminum mixed salt solution, which is then mixed with a sodium hydroxide solution and a modifier at the same time, and a co-precipitation reaction is carried out under certain pH and temperature conditions. A solid lithium-aluminum adsorbent is obtained through the steps of nucleation, aging, filtration, washing, and drying.

[0022] In some preferred embodiments, the method specifically comprises:

[0023] Mixing low magnesium-to-lithium ratio brine with aluminum salt to form the lithium-aluminum mixed salt solution;

[0024] And, the lithium aluminum mixed salt solution and the inorganic base solution are mixed at a speed of 0.5 to 10 mL / min, and the modifier is added at the same time, and a coprecipitation nucleation reaction occurs under the conditions of pH 5.5 to 6 and temperature 25° C. to 80° C. to form the lithium aluminum adsorbent crystal nucleus.

[0025] In some preferred embodiments, the adsorption method is used to extract Li from lithium-rich brine. + The concentration is 3~7.5g / L.

[0026] In some preferred embodiments, the membrane method for extracting lithium from lithium-rich brine + The concentration is 12~20g / L.

[0027] In some preferred embodiments, the molar concentration ratio of aluminum element to lithium element in the lithium-aluminum mixed salt solution is 1 to 5:1.

[0028] Furthermore, the molar concentration ratio of aluminum element to lithium element in the lithium-aluminum mixed salt solution is 1.5 to 3.5:1.

[0029] In some preferred embodiments, the aluminum salt includes aluminum chloride and / or aluminum sulfate, but is not limited thereto.

[0030] In some preferred embodiments, the inorganic alkali solution includes sodium hydroxide solution and / or potassium hydroxide solution, and the concentration of the sodium hydroxide solution is 2 to 12 mol / L.

[0031] Furthermore, the concentration of the sodium hydroxide solution is 5 to 10 mol / L.

[0032] In some preferred embodiments, the modifier includes hydroxyethyl cellulose and / or carboxymethyl cellulose, but is not limited thereto.

[0033] In some preferred embodiments, the amount of the modifier used is 0.05% to 2 wt% of the mixed salt in the lithium aluminum mixed salt solution.

[0034] In some preferred embodiments, the temperature of the coprecipitation nucleation reaction is 40°C to 70°C.

[0035] In some preferred embodiments, the aging treatment time is 1 to 12 hours.

[0036] In some preferred embodiments, the aging treatment comprises hydrothermal aging.

[0037] In some preferred embodiments, the method further comprises: after the aging treatment is completed, filtering, washing and drying the obtained product.

[0038] Furthermore, the washing treatment is carried out at a temperature of 5-20°C.

[0039] Furthermore, the washing liquid used in the washing treatment includes any one of methanol, ethanol, and deionized water, or a combination of two or more thereof, but is not limited thereto.

[0040] Furthermore, the washing process is performed 1 to 3 times.

[0041] Furthermore, the drying process is carried out at a temperature of 30°C to 70°C and for a time of 12 to 48 hours.

[0042] In some specific embodiments, the process steps for preparing a lithium aluminum adsorbent using a low magnesium-to-lithium ratio brine in the present invention are: preparing an aluminum salt solution and a sodium hydroxide solution, adding the aluminum salt solution and the sodium hydroxide solution dropwise at the same time, and adding a modifier, co-precipitating under certain pH and temperature conditions, and obtaining a solid lithium aluminum adsorbent through nucleation, aging, filtering, washing, drying and other steps, specifically:

[0043] (1) preparing a lithium aluminum mixed salt solution and a sodium hydroxide solution, and simultaneously dropping the lithium aluminum mixed salt solution and the sodium hydroxide solution at a certain flow rate (adding a modifier at the same time) to perform a coprecipitation reaction to form a lithium aluminum adsorbent crystal nucleus, i.e., a nucleation process of the adsorbent;

[0044] (2) After the coprecipitation reaction is nucleated, the solid-liquid separation is carried out after aging under stirring and at a certain temperature to obtain a lithium aluminum adsorbent filter cake;

[0045] (3) After solid-liquid separation, the filter cake is washed and dried to obtain a white solid lithium aluminum adsorbent product.

[0046] In some more specific embodiments, the method for preparing a lithium aluminum adsorbent from a low magnesium to lithium ratio brine comprises:

[0047] (1) preparing a lithium aluminum mixed salt solution and a sodium hydroxide solution, and simultaneously dropping the lithium aluminum mixed salt solution and the sodium hydroxide solution at a certain flow rate to perform a coprecipitation reaction to form lithium aluminum adsorbent crystal nuclei, i.e., a lithium aluminum nucleation process. + The concentration is 3-7.5 g / L, and the magnesium-lithium ratio is 3-5; the membrane method for extracting lithium-rich brine, wherein Li + The concentration is 12-20g / L, and the magnesium-lithium ratio is 0.1-0.5; the molar concentration of aluminum in the lithium-aluminum mixed salt solution is 1-5 times, preferably 1.5-3.5 times, of the molar concentration of lithium in the lithium-rich brine extracted by the adsorption method, and the hydroxide concentration in the sodium hydroxide solution is 2-12mol / L, preferably 5-10mol / L. The precipitation reaction is to drop the lithium-aluminum mixed salt solution and the alkaline solution at a rate of 0.5-10mL / min for co-precipitation reaction, and add a modifier during the co-precipitation reaction to increase the specific surface area of ​​the product, and the specific surface area increases by 10%-30% compared with when no addition is made. The reaction is a constant pH method, maintaining the pH at 5-7, preferably 5.5-6; the reaction temperature is 25℃-80℃, preferably 40℃-70℃. The aluminum salt is aluminum chloride. The modifier is one or both of hydroxyethyl cellulose and carboxymethyl cellulose.

[0048] (2) After the coprecipitation reaction is nucleated, the solid-liquid separation is carried out after aging under stirring and at a certain temperature to obtain a lithium aluminum adsorbent product filter cake; the aging process is hydrothermal aging, the aging temperature is 40° C. to 80° C., and the aging time is 1 to 12 hours.

[0049] (3) After solid-liquid separation, the filter cake is washed and dried to obtain a white solid lithium aluminum adsorbent product, whose chemical formula is (LiClAl2(OH)6)·nH2O, n=1-10; the drying temperature is 30°C-70°C, the drying time is 12-48h, the washing is 1-3 times of pulp washing, the washing liquid is one or a mixed washing liquid of methanol, ethanol, and deionized water, the washing temperature is 5-20°C, and the obtained lithium aluminum adsorbent has a capacity of 11-15 mg / g.

[0050] Another aspect of an embodiment of the present invention further provides a lithium aluminum adsorbent prepared by the aforementioned method, wherein the chemical formula of the lithium aluminum adsorbent is (LiClAl2(OH)6)·nH2O, n=1 to 10; the capacity of the lithium aluminum adsorbent is 11 to 15 mg / g.

[0051] Furthermore, the lithium aluminum adsorbent has a special selectivity for lithium and has a high selectivity only for lithium.

[0052] The present invention uses sulfate-type and chloride-type high-magnesium-to-lithium ratio salt lake brine and old brine as raw materials to directly prepare aluminum-based adsorbents, which not only reduces the preparation cost of the aluminum-based adsorbents, but also expands the development and extraction methods of salt lake lithium resources, and improves the utilization rate of salt lake lithium resources; at the same time, the present invention uses sulfate-type and chloride-type high-magnesium-to-lithium ratio salt lake brine and old brine as raw materials, adopts a co-precipitation method to prepare aluminum-based lithium adsorbents, and simultaneously separates and extracts lithium resources in the salt lake, thereby combining the comprehensive utilization of salt lake resources with functional utilization, and improving resource utilization efficiency.

[0053] Another aspect of the embodiments of the present invention further provides the use of the aforementioned lithium aluminum adsorbent in extracting lithium from salt lakes.

[0054] The technical solution of the present invention is further described in detail below in conjunction with several preferred embodiments. This embodiment is implemented on the premise of the technical solution of the invention, and a detailed implementation method and specific operation process are given, but the protection scope of the present invention is not limited to the following embodiments.

[0055] Unless otherwise specified, the experimental materials used in the following examples can be purchased from conventional biochemical reagent companies.

[0056] Example 1

[0057] The lithium-rich brine used in this example is from a salt lake in Qinghai. + The concentration is 3g / L and the magnesium to lithium ratio is 3:1.

[0058] 104.35 aluminum chloride hexahydrate was weighed and dissolved in 1L of lithium-rich brine extracted by adsorption method to prepare a lithium aluminum mixed salt solution, 2L of 2mol / L sodium hydroxide solution was prepared, and the lithium aluminum mixed salt solution and the sodium hydroxide solution were added dropwise at a rate of 10mL / min for coprecipitation reaction. The reaction temperature was 25°C, and the pH was controlled at 5. At the same time, 0.1% hydroxyethyl cellulose was added to synthesize a slurry containing lithium aluminum adsorbent crystal nuclei; the prepared lithium aluminum adsorbent crystal nucleus slurry was hydrothermally aged at 40°C for 1h and filtered, the filter cake was slurried once with deionized water at 5°C, and the lithium aluminum adsorbent product was dried at 30°C for 48h to obtain a lithium aluminum adsorbent, and the adsorbent was used for the old brine (Li +The concentration is 0.4g / L) and the adsorption capacity is 11mg / g. The adsorbent dissolution rate is 0.0003%. The lithium in the old brine of the Qarhan Salt Lake can be reduced from 0.4g / L to below 4ppm. The lithium extraction efficiency is 99.00%. The adsorption capacity is 11mg / g. The XRD pattern of the lithium aluminum adsorbent prepared in this embodiment is shown in FIG. Figure 1 shown.

[0059] For comparison, when hydroxyethyl cellulose was not added, the product obtained was recorded as product A. Compared with product A, the lithium aluminum adsorbent prepared in Example 1 had a specific surface area increased by 10%.

[0060] Example 2

[0061] The lithium-rich brine used in this example is from a salt lake in Qinghai. + The concentration is 7.5g / L and the magnesium to lithium ratio is 5:1.

[0062] 391.31g of aluminum sulfate was weighed and dissolved in 1L of lithium-rich brine extracted by adsorption method to prepare a lithium-aluminum mixed salt solution, 2L of 12mol / L sodium hydroxide solution was prepared, and the lithium-aluminum mixed salt solution and the sodium hydroxide solution were added dropwise at a rate of 0.5mL / min for coprecipitation reaction. The reaction temperature was 80°C, and the pH was controlled at 7. At the same time, 2% carboxymethyl cellulose was added to synthesize a slurry containing lithium-aluminum adsorbent crystal nuclei; the prepared lithium-aluminum adsorbent crystal nucleus slurry was hydrothermally aged at 80°C for 12h and filtered, the filter cake was washed once with deionized water at 20°C, then washed with ethanol for the second time, and then washed with deionized water for the third time at 20°C, and the lithium-aluminum adsorbent product was dried at 70°C for 12h to obtain a lithium-aluminum adsorbent, and the adsorbent was used for the old brine (Li + The concentration is 0.550g / L) for lithium extraction, with an adsorption capacity of 13mg / g and an adsorbent dissolution rate of 0.0006%. The lithium in the old brine of the Qarhan Salt Lake can be reduced from 0.55g / L to below 10ppm, and the lithium extraction efficiency is 98.18%.

[0063] For comparison, when no carboxymethyl cellulose was added, the product obtained was recorded as product B. Compared with product B, the lithium aluminum adsorbent prepared in Example 2 had a specific surface area increased by 30%.

[0064] Example 3

[0065] The lithium-rich brine used in this example is from a salt lake in Qinghai. + The concentration is 12g / L, and the magnesium-lithium ratio is 0.1:1.

[0066] 1043.49 aluminum chloride hexahydrate was weighed and dissolved in 1L of lithium-rich brine by membrane lithium extraction to prepare a lithium aluminum mixed salt solution, 2L of 2mol / L potassium hydroxide solution was prepared, and the lithium aluminum mixed salt solution and sodium hydroxide solution were added dropwise at a rate of 10mL / min for coprecipitation reaction. The reaction temperature was 25°C, and the pH was controlled at 6. At the same time, 0.5% hydroxyethyl cellulose was added to synthesize a slurry containing lithium aluminum adsorbent crystal nuclei; the prepared lithium aluminum adsorbent crystal nucleus slurry was hydrothermally aged at 40°C for 1h and filtered, the filter cake was slurried once with deionized water at 5°C, and the lithium aluminum adsorbent product was dried at 30°C for 48h to obtain a lithium aluminum adsorbent, which was used for the old brine (Li + The concentration is 3.5g / L) and the adsorption capacity is 15mg / g. The adsorbent dissolution rate is 0.0002%. The lithium in the old brine of Yiliping Salt Lake can be reduced from 3.5g / L to below 20ppm, and the lithium extraction efficiency is 99.43%.

[0067] For comparison, when hydroxyethyl cellulose was not added, the product obtained was recorded as product C. Compared with product C, the lithium aluminum adsorbent prepared in Example 3 had a specific surface area increased by 10%.

[0068] Example 4

[0069] The lithium-rich brine used in this example is from a salt lake in Qinghai. + The concentration is 20g / L, and the magnesium-lithium ratio is 0.5:1.

[0070] 347.83g of aluminum chloride hexahydrate was weighed and dissolved in 1L of lithium-rich brine extracted by membrane method to prepare a lithium-aluminum mixed salt solution, 2L of 12mol / L sodium hydroxide solution was prepared, and the lithium-aluminum mixed salt solution and the sodium hydroxide solution were added dropwise at a rate of 0.5mL / min for coprecipitation reaction. The reaction temperature was 80°C, and the pH was controlled at 5.5. At the same time, 1% carboxymethyl cellulose was added to synthesize a slurry containing lithium-aluminum adsorbent crystal nuclei; the prepared lithium-aluminum adsorbent crystal nucleus slurry was hydrothermally aged at 80°C for 12h and filtered, the filter cake was washed once with deionized water at 20°C, then washed with ethanol for a second time, and then washed with deionized water for a third time at 20°C, and the lithium-aluminum adsorbent product was dried at 70°C for 12h to obtain a lithium-aluminum adsorbent, which was used for raw brine (Li + The concentration is 50ppm) and the adsorption capacity is 13mg / g. The adsorbent dissolution rate is 0.001%. The lithium in the old brine of the Qarhan Salt Lake can be reduced from 50 to below 3ppm, and the lithium extraction efficiency is 94.00%.

[0071] For comparison, when no carboxymethyl cellulose was added, the product obtained was recorded as product D. Compared with product D, the lithium aluminum adsorbent prepared in Example 4 had a specific surface area increased by 30%.

[0072] Comparative Example 1

[0073] The method is the same as Example 1, except that the lithium aluminum mixed salt solution is directly added to the inorganic alkaline solution. Because the reaction system is strongly alkaline, the aluminum salt will produce aluminum ions, and the output of the obtained lithium aluminum adsorbent is small, the yield is low, and the adsorption capacity is low.

[0074] Comparative Example 2

[0075] The method is the same as in Example 1, except that the pH value of the coprecipitation reaction is 3. Since the pH is too low, the lithium aluminum adsorption material cannot be generated. The XRD pattern of the prepared material is shown in FIG. Figure 2 shown.

[0076] Comparative Example 3

[0077] The method is the same as Example 1, except that the pH value of the coprecipitation nucleation reaction is 9, and the product generated at this time is mainly magnesium aluminum hydrotalcite, and a pure phase lithium aluminum adsorbent material cannot be obtained.

[0078] In addition, the inventors of this case also referred to the aforementioned embodiments and conducted experiments with other raw materials, process operations, and process conditions described in this specification, and obtained relatively ideal results.

[0079] It should be understood that the technical solution of the present invention is not limited to the above-mentioned specific implementation cases. Any technical deformation made according to the technical solution of the present invention without departing from the scope of protection of the purpose of the present invention and the claims shall fall within the protection scope of the present invention.

Claims

1. A method for preparing a lithium aluminum adsorbent from brine with a low magnesium-to-lithium ratio, characterized in that include: Mixing low magnesium-to-lithium ratio brine with aluminum salt to form a lithium-aluminum mixed salt solution; then mixing the lithium-aluminum mixed salt solution with an inorganic alkali solution at a rate of 0.5-10 mL / min, adding a modifier at the same time, and performing a coprecipitation nucleation reaction under the conditions of pH value of 5-5.5 and temperature of 25°C-80°C to obtain lithium-aluminum adsorbent crystal nuclei; wherein the low magnesium-to-lithium ratio brine is selected from lithium-rich brine extracted by adsorption method and / or lithium-rich brine extracted by membrane method; the magnesium-to-lithium ratio in the lithium-rich brine extracted by adsorption method is 3-5:1, and the magnesium-to-lithium ratio in the lithium-rich brine extracted by membrane method is 0.1-0.5:1; the modifier is selected from hydroxyethyl cellulose and / or carboxymethyl cellulose; and subjecting the lithium aluminum adsorbent crystal nucleus to an aging treatment at 40° C. to 80° C. to obtain a lithium aluminum adsorbent; The chemical formula of the lithium aluminum adsorbent is (LiClAl2(OH)6)·nH2O, n=1-10; the capacity of the lithium aluminum adsorbent is 11-15 mg / g; and the dissolution rate of the lithium aluminum adsorbent is below 0.001%.

2. The method according to claim 1, characterized in that: The adsorption method is used to extract Li from lithium-rich brine + The concentration is 3~7.5g / L.

3. The method according to claim 1, characterized in that: The membrane method for extracting lithium from lithium-rich brine + The concentration is 12~20g / L.

4. The method according to claim 1, characterized in that: The molar concentration ratio of aluminum element to lithium element in the lithium aluminum mixed salt solution is 1 to 5:

1.

5. The method according to claim 4, characterized in that: The molar concentration ratio of aluminum element to lithium element in the lithium aluminum mixed salt solution is 1.5 to 3.5:

1.

6. The method according to claim 1, characterized in that: The aluminum salt is selected from aluminum chloride and / or aluminum sulfate.

7. The method according to claim 1, characterized in that: The inorganic alkali solution is selected from sodium hydroxide solution and / or potassium hydroxide solution, and the concentration of the sodium hydroxide solution is 2-12 mol / L.

8. The method according to claim 7, characterized in that: The concentration of the sodium hydroxide solution is 5-10 mol / L.

9. The method according to claim 1, characterized in that: The amount of the modifier used is 0.05% to 2wt% of the mixed salt in the lithium aluminum mixed salt solution.

10. The method according to claim 1, characterized in that: The temperature of the coprecipitation nucleation reaction is 40°C to 70°C.

11. The method according to claim 1, characterized in that: The aging treatment time is 1 to 12 hours.

12. The method according to claim 1, characterized in that: The aging treatment method is selected from hydrothermal aging.

13. The method according to claim 1, characterized in that Also includes: After the aging treatment is completed, the obtained product is filtered, washed and dried.

14. The method according to claim 13, characterized in that: The temperature of the washing treatment is 5-20° C.; the number of times of the washing treatment is 1 to 3 times; the washing liquid used in the washing treatment is selected from any one of methanol, ethanol, and deionized water, or a combination of two or more thereof.

15. The method according to claim 13, characterized in that: The drying process is carried out at a temperature of 30° C. to 70° C. and for a time of 12 to 48 hours.

16. A lithium aluminum adsorbent prepared by the method of any one of claims 1 to 15.

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