A lithium ion adsorbent, preparation method thereof and lithium ion extraction method

Abstract

The present invention discloses a lithium ion adsorbent, a preparation method thereof and a method for extracting lithium ions, and belongs to the technical field of lithium ion enrichment and recovery. The preparation method of the lithium ion adsorbent of the present invention adds titanium tetrachloride for hydrolysis to generate titanium oxide anions, and uses the titanium oxide anions as the crystal nuclei for the co-precipitation reaction between lithium ions and aluminum ions or aluminate ions, thereby synthesizing titanium oxide doped lithium aluminum LDH. When the present invention adopts the co-precipitation reaction between lithium ions and aluminum ions or aluminate ions, titanium tetrachloride is innovatively added to hydrolyze the titanium tetrachloride to generate titanium oxide anions, and the generated titanium oxide anions are used as the crystal nuclei for the co-precipitation reaction, thereby synthesizing titanium oxide doped lithium aluminum LDH, and effectively improving the specific surface area of ​​the obtained lithium aluminum LDH, refining its lamellar structure, and thereby improving the adsorption capacity of lithium aluminum LDH for lithium ions.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium ion enrichment and recovery, and more specifically, relates to a lithium ion adsorbent, a preparation method thereof, and a method for extracting lithium ions. Background Art

[0002] In nature, lithium resources are primarily found in brine, particularly salt lake brines, which account for over 80% of all lithium reserves. Therefore, extracting lithium ions from brine and seawater has become a hot topic among researchers. Several methods exist for extracting lithium from salt lake brines, including membrane separation, precipitation, solvent extraction, adsorption, and electrochemical methods. Adsorption offers significant environmental and economic advantages over other methods, particularly for extracting lithium from low-grade brines or seawater. The key to this approach is the preparation of adsorbents with superior properties, including high selectivity, high adsorption capacity, and large specific surface area.

[0003] At present, the lithium adsorbents reported in research are mainly divided into three types, namely lithium manganese oxide (Li-Mn-O), titanate (Li-Ti-O) and lithium aluminum layered double hydroxide (Li / Al-LDHs). Li / Al-LDHs has the advantages of simple preparation process, mild synthesis conditions, high lithium selectivity and low cost. Although the adsorption capacity is lower than that of lithium manganese oxide and titanate adsorbents, lithium aluminum LDH can be eluted without loss with a neutral solution. If the analytical conditions are well controlled, it can maintain good structural stability and adsorption capacity in multiple cycles. It has been proven to be a very promising adsorbent material. The expression of lithium aluminum LDH adsorbent is generally: LiX·mAl(OH)3·nH2O(Li / Al-LDH), where X represents anion (common anion is Cl - OH - ). In the process of lithium adsorption, Li + Due to the size matching, they preferentially enter the Al-O octahedral cavities, while the remaining ions cannot be adsorbed into the pores due to the steric hindrance effect. + High selective adsorption. During the desorption process, neutral water can remove the Li + Elution. The adsorption-desorption process can be expressed as:

[0004]

[0005] At present, there are two methods for preparing aluminum salt lithium adsorbents. One is to insert LiCl between the layers; the other is to insert LiOH between the layers. Most of the reported patents are to insert LiCl between the layers to synthesize LiCl·mAl(OH)3·nH2O. For example, Chinese patents CN108993376A, CN110354796A, and CN114570338A all disclose a method for preparing LiCl·aAl(OH)3·nH2O aluminum salt adsorbent. The literature Zhong J, Lin S, Yu J, Desalination, 2021, 505: 114983 used a co-precipitation method to prepare a LiCl·aAl(OH)3·nH2O aluminum salt adsorbent with a specific surface area of ​​161m 2 / g of Li / Al-LDHs, for Li + The adsorption capacity is 7.27 mg / g; the specific surface area of ​​LDHs-A synthesized by Zhou H, Li J, Xu L, et al, Materials Letters, 2023, 340: 134159 is 58.30 m 2 / g, for Li + The adsorption capacity is 6.69 mg / g; Chen J, Lin S, Yu J, Journal of hazardous materials, 2020, 388: 122101 magnetic lithium-aluminum layered double hydroxides (MLDHs) with an average specific surface area of ​​103.5 prepared by a staged chemical co-precipitation method have a good adsorption capacity for Li + The adsorption capacity is 6.00 mg / g. By comparing and analyzing the latest research results in the past three years, it can be seen that there is still room for improvement in the specific surface area and adsorption capacity of lithium adsorbents. Summary of the Invention

[0006] 1. Problem to be solved

[0007] The object of the present invention is to provide a lithium ion adsorbent, a preparation method thereof and a method for extracting lithium ions, so as to solve the problem that the specific surface area of ​​existing aluminum-lithium LDH products for lithium ion adsorption is relatively small and the adsorption capacity for lithium ions needs to be further improved.

[0008] 2. Technical solution

[0009] In order to solve the above problems, the technical solutions adopted by the present invention are as follows:

[0010] The present invention provides a preparation method of a lithium ion adsorbent, wherein titanium tetrachloride is added and hydrolyzed to generate titanyl anions, which are used as crystal nuclei for a coprecipitation reaction between lithium ions and aluminum ions or aluminate ions, thereby synthesizing titanium oxide-doped lithium aluminum hydroxide (LDH).

[0011] The present invention innovatively adds titanium tetrachloride when a co-precipitation reaction occurs between lithium ions and aluminum ions or aluminate ions, causing the titanium tetrachloride to be hydrolyzed to generate titanium oxide anions. The generated titanium oxide anions are used as crystal nuclei for the co-precipitation reaction, thereby synthesizing titanium oxide-doped lithium aluminum hydrate (LDH). The specific surface area of ​​the obtained lithium aluminum hydrate (LDH) is effectively increased, its lamellar structure is refined, and the adsorption capacity of the lithium aluminum hydrate (LDH) for lithium ions is thereby increased.

[0012] Furthermore, the concentration of titanium tetrachloride is not greater than 2 mol / L. It should be noted that the concentration control of titanium tetrachloride in the aqueous solution is crucial in this application. By strictly controlling the concentration of titanium tetrachloride, it is possible to ensure that titanium tetrachloride is hydrolyzed according to the following formulas (1)-(3) to generate titanium oxide anions (Ti n O 4n ) 4n- The titanium oxide anion (Ti n O 4n ) 4n- It can serve as the crystal nucleus of the coprecipitation reaction and participate in the reaction during the aluminum and lithium coprecipitation process to generate amorphous titanium oxide, as shown in the following formulas (4) and (5). The generated titanium oxide not only serves as the core wrapped inside the lamellar aluminum-lithium LDH, but is also doped between the layers of the LDH.

[0013] TiCl4+nH2O→H2(Ti(OH) n Cl 6-n )+(n-2)HCl↑ (1)

[0014] H2(Ti(OH) n Cl 6-n )+(6-n)H2O→(Ti(OH) n H2O 6-n )Cl 4-n +2HCl↑ (2)

[0015] (Ti(OH) n H2O 6-n ) (4-n)+ →(Ti n (OH) 2n (H2O) 2n ) 2n+ →(Ti n O 4n ) 4n- (3)

[0016]

[0017] (Ti n O 4n )4n- +Li + +2Al 3+ +8OH - +(2n+X)H2O

[0018] =2nTiO2·[LiAl2(OH)6]OH·XH2O+(4n+1)OH - (5)

[0019] Furthermore, the ratio of the molar amount of Ti atoms to the total molar amount of Ti and Al in the lithium ion adsorbent is 0.05-0.5. When the doping amount of titanium atoms is low, the effect is not significant. As the doping ratio increases, the specific surface area and adsorption efficiency of the adsorbent can be continuously improved. However, when the doping ratio exceeds 0.5, the adsorption efficiency of the resulting adsorbent no longer continues to improve.

[0020] Furthermore, the specific surface area of ​​the obtained lithium ion adsorbent is 170-190m 2 ·g -1 .

[0021] Furthermore, lithium hydroxide, lithium chloride, lithium nitrate or lithium sulfate is used as the lithium source, and sodium aluminate solution, aluminum chloride, aluminum nitrate or aluminum sulfate is used as the aluminum source of aluminum ions.

[0022] Furthermore, the mixing temperature of the reaction mixture is 25-80°C, and the crystallization temperature is 70-150°C. After the reaction is completed, the adsorption material is obtained by vacuum filtration, boiling water washing, and drying at 60-90°C.

[0023] The present invention also provides a lithium ion adsorbent, which is prepared by the preparation method of the present invention.

[0024] The present invention also provides a method for extracting lithium ions, using the lithium ion adsorbent prepared by the present invention to adsorb lithium from a lithium-containing solution. The lithium-containing solution can be salt lake brine, lithium precipitation mother liquor, or sodium aluminate solution from aluminum production processes, providing a wider range of extraction systems.

[0025] In summary, compared with the prior art, the present invention can achieve the following beneficial effects:

[0026] (1) The present invention prepares aluminum lithium LDH by adding a certain amount of titanium tetrachloride for hydrolysis during the co-precipitation reaction between lithium ions and aluminum ions or aluminate ions, and uses the hydrolysis product titanium oxide complex anion as the crystal nucleus of the co-precipitation reaction, thereby synthesizing titanium oxide-doped aluminum lithium LDH with a larger specific surface area and improving the adsorption capacity of aluminum lithium LDH for lithium ions.

[0027] (2) The present invention optimizes and controls the concentration of titanium tetrachloride, thereby ensuring that it can be hydrolyzed to generate titanium oxide anions (Ti n O 4n ) 4n- , thereby ensuring that titanium oxide-doped aluminum lithium LDH with a larger specific surface area can be finally synthesized; at the same time, the present application optimizes and controls the titanium-aluminum doping ratio, which is conducive to further ensuring the doping effect and minimizing the amount of titanium added. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a comparison chart of the XRD analysis results of the lithium ion adsorbents synthesized in Examples 1-5 and Comparative Example 1;

[0029] Figure 2-Figure 5 They are comparative example 1, examples 1-3, and the structural morphologies of the prepared lithium ion adsorbents;

[0030] Figure 6 This is the XPS analysis result of the lithium ion adsorbent prepared in Example 3;

[0031] Figure 7 This is the XPS analysis result of the lithium ion adsorbent prepared in Example 5;

[0032] Figure 8 This is a comparison chart of the XRD analysis results of the lithium ion adsorbents synthesized in Examples 6-9 and Comparative Example 1;

[0033] Figure 9 The structural morphology of the lithium ion adsorbent prepared in Comparative Example 1 and Examples 6-8. DETAILED DESCRIPTION

[0034] The main feature of the present invention is to unify the hydrolysis process of titanium tetrachloride and the coprecipitation process of lithium ions and aluminum ions, and prepare TiO2@AlLi-LDH by coprecipitation. At the same time, by controlling the concentration of titanium tetrachloride, it can be hydrolyzed to form titanium oxide anions (Ti n O 4n ) 4n- , so that on the one hand it can be used as the crystal nucleus of the coprecipitation reaction to synthesize TiO2-doped AlLi-LDH with a large specific surface area, and on the other hand it makes the reaction process more controllable and easy to modify the product. It should be noted that in this application, the lithium source can be lithium chloride, lithium nitrate or lithium sulfate, the aluminum source can be aluminum chloride, aluminum nitrate or aluminum sulfate, the alkali solution can be NaOH, LiOH, KOH, ammonia water, etc., or the lithium source and sodium aluminate solution can be directly used for coprecipitation reaction, but the specific types of lithium source and aluminum source are not subject to the above restrictions. Due to limited space here, only some substances are used as examples for illustration below.

[0035] Example 1

[0036] The preparation method of the lithium ion adsorbent of this embodiment comprises the following steps:

[0037] Step 1: Prepare a mixed solution of titanium chloride, aluminum chloride, and lithium chloride, wherein the concentration of lithium chloride is 0.5 mol / L and the concentration of aluminum chloride is 0.9 mol / L. Add titanium tetrachloride to the mixed solution, and the concentration of titanium tetrachloride is 0.047 mol / L, that is, the titanium doping ratio (the ratio of the molar amount of titanium atoms to the total molar amount of titanium and aluminum atoms) is 0.05;

[0038] Step 2: prepare sodium hydroxide solution with a concentration of 7 mol / L;

[0039] Step 3: Prepare 100 ml of a mixed solution of titanium chloride, aluminum chloride, and lithium chloride and 50 ml of a sodium hydroxide solution. Use a constant flow pump to mix the two solutions to prepare titanium aluminum lithium LDH. The mixing temperature is 25° C. and the crystallization temperature is 70° C.

[0040] Step 4: After the reaction is completed, the mixture is vacuum filtered, washed with boiling water, and dried at 60° C. to obtain the adsorption material.

[0041] Examples 2-5

[0042] The preparation methods of the lithium ion adsorbents of Examples 2-5 are basically the same as those of Example 1, with the main difference being that the titanium doping ratio is different from that of Example 1. The titanium doping ratios in Examples 2-4 are 0.1, 0.2, 0.3, and 0.5, respectively (the concentration of titanium tetrachloride is different from that of Example 1).

[0043] Comparative Example 1

[0044] The preparation method of the lithium ion adsorbent of this comparative example is basically the same as that of Example 1, with the main difference being that titanium chloride is not added to the reaction mixture of this comparative example.

[0045] Performance Testing

[0046] A solution with a lithium ion concentration of 1 g / L was prepared, and adsorption experiments were carried out on the solution using the adsorbents prepared in Examples 1-5 and Comparative Example 1, respectively. The adsorption time was 30 min-1440 min. The XRD analysis results before and after adsorption were as follows: Figure 1 As shown, according to the XRD analysis results, the physical composition of the adsorbent prepared in Examples 1-5 is mainly Li2CO3·Al(OH)3·xH2O. This is because hydroxide ions are converted into carbonate ions during the drying process, and as the addition amount increases, the grains are refined, resulting in the continuous broadening of the product XRD characteristic peak, but the phase type remains unchanged.

[0047] As shown in Table 1 below, the adsorbent in Comparative Example 1 has a 1h adsorption capacity of 2.1 mg / g for lithium ions. As the titanium doping amount increases, the adsorption capacity of the adsorbent for lithium ions gradually increases. When the titanium doping amount is 50%, the adsorption capacity of the adsorbent for lithium ions can reach 9.9 mg / g for 1h. When the titanium doping amount is greater than 50%, the adsorption capacity of the adsorbent for lithium ions increases less. Therefore, the titanium doping amount is preferably 20%-50%. In addition, as the titanium doping ratio in the adsorbent increases, the overall structure and the layer structure of the obtained adsorbent are effectively refined (which can be combined with the attached Figure 2-5 ).

[0048] Table 1 Comparative data of adsorption results of the adsorbents prepared in Examples 1-5 and Comparative Example 1

[0049]

[0050] like Figure 6 and Figure 7 Shown are the XPS analysis spectra of the adsorbents in Example 3 and Example 5, respectively. The results show that Ti-O exists in the prepared adsorbent, and the higher the titanium doping ratio, the higher the Ti-O content, which indirectly proves that TiO2 is not only wrapped in the core of the adsorbent in an amorphous form, but also exists between the adsorbent layers.

[0051] Example 6

[0052] The preparation method of the lithium ion adsorbent of this embodiment comprises the following steps:

[0053] Step 1: prepare a mixed solution of sodium aluminate and sodium hydroxide, wherein the molecular ratio of the sodium aluminate solution is 1.3, the concentration of sodium hydroxide is 3.5 mol / L, and the concentration of aluminum in the solution is 0.9 mol / L;

[0054] Step 2: Prepare a mixed solution of lithium chloride and titanium chloride, wherein the concentration of lithium chloride is 0.5 mol / L and the concentration of titanium chloride is 0.047 mol / L;

[0055] Step 3: Use a constant flow pump to mix equal volumes of the two solutions to prepare titanium aluminum lithium LDH. The mixing temperature is 80°C and the crystallization temperature is 150°C, that is, the titanium doping ratio (the ratio of the molar amount of titanium atoms to the total molar amount of titanium and aluminum atoms) is 0.1; Step 4: After the reaction is completed, vacuum filtration, boiling water washing, and drying at 90°C can obtain the adsorption material.

[0056] Examples 7-10

[0057] The preparation methods of the lithium ion adsorbents of Examples 7-10 are basically the same as those of Example 6, with the main difference being that the titanium doping ratio is different from that of Example 6. The titanium doping ratios in Examples 7-10 are 0.1, 0.2, 0.3 and 0.5, respectively.

[0058] like Figure 8 The figure shows the comparison of XRD analysis results of the lithium ion adsorbents synthesized in Examples 6-9 and Comparative Example 1. Figure 9 The structural morphology of the lithium ion adsorbents prepared in Comparative Example 1 and Examples 6-8 is shown. The adsorbents prepared in Examples 6-10 have similar adsorption properties for lithium ions to the adsorbents prepared in Examples 1-5.

Claims

1. A method for preparing a lithium ion adsorbent, characterized in that: Titanium tetrachloride is added and hydrolyzed to generate titanyl anions, which are used as crystal nuclei for coprecipitation reaction between lithium ions and aluminum ions or aluminate ions, thereby synthesizing titanium oxide-doped lithium aluminum LDH; the concentration of the titanium tetrachloride is not greater than 2 mol / L.

2. The method for preparing a lithium ion adsorbent according to claim 1, wherein: The titanium oxide in the obtained titanium oxide doped aluminum lithium LDH is in an amorphous state, wrapped in the interior of the lamellar aluminum lithium LDH and doped between the LDH layers.

3. The method for preparing a lithium ion adsorbent according to claim 2, wherein: The ratio of the molar amount of Ti atoms in the lithium ion adsorbent to the total molar amount of Ti and Al is 0.05-0.

5.

4. The method for preparing a lithium ion adsorbent according to any one of claims 1 to 3, characterized in that: The specific surface area of ​​the obtained lithium ion adsorbent is 170-190m 2 ·g -1 .

5. The method for preparing a lithium ion adsorbent according to any one of claims 1 to 3, characterized in that: Lithium hydroxide, lithium chloride, lithium nitrate or lithium sulfate is used as a lithium source, and sodium aluminate, aluminum chloride, aluminum nitrate or aluminum sulfate is used as an aluminum source of aluminate ions or aluminum ions.

6. The method for preparing a lithium ion adsorbent according to any one of claims 1 to 3, characterized in that: The mixing temperature of the reaction mixture in the coprecipitation reaction is 25-80° C., and the reaction crystallization temperature is 70-150° C. After the reaction is completed, the adsorption material is obtained by vacuum filtration, boiling water washing, and drying at 60-90° C.

7. A lithium ion adsorbent prepared by the preparation method according to any one of claims 1 to 6.

8. A method for extracting lithium ions, characterized in that: The lithium ion adsorbent prepared by the preparation method according to any one of claims 1 to 6 is used to adsorb lithium in a lithium-containing solution.

9. The method for extracting lithium ions according to claim 8, characterized in that: The lithium-containing solution is salt lake brine, lithium precipitation mother liquor or sodium aluminate solution in the aluminum industry production process.

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