Phosphorus-containing aluminum lithium adsorbent and preparation method thereof

Abstract

The invention provides a preparation method of a phosphorus-containing aluminum lithium adsorbent. The preparation method comprises the following steps: S1, preparing a mixed solution of an aluminum salt and a lithium salt in a certain proportion; s2, preparing a mixed solution of alkali and phosphate according to a certain proportion; s3, dropwise adding the lithium-aluminum mixed solution into the mixed alkali liquor at a certain temperature, stirring and reacting, and controlling the pH value of a reaction endpoint to be 6; and S4, after the reaction is finished, stopping stirring, keeping the temperature for aging for a period of time, filtering, drying, cooling and grinding the turbid liquid to obtain the phosphorus-containing aluminum adsorbent precursor. And S5, adding the adsorbent precursor into warm pure water according to a certain feeding ratio, stirring and activating for a period of time, and filtering to obtain the phosphorus-containing aluminum adsorbent. Compared with a traditional aluminum adsorbent, high-valence phosphate ions are introduced between the adsorbent layers, so that the stability of the adsorbent is further improved, the adsorption capacity of the adsorbent is improved to a certain extent, and meanwhile, the defect that the aluminum adsorbent is not suitable for high-sulfate salt lake brine is overcome; the method has a great application prospect in the field of lithium extraction by an adsorption method.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion adsorbents, and in particular to a method for preparing a phosphorus-aluminum lithium adsorbent. Background Art

[0002] With the development of electric vehicles, renewable energy storage, and consumer electronics, demand for lithium is rapidly increasing. Lithium is a key raw material for lithium-ion batteries, and this market demand is driving the global search for efficient and low-cost lithium extraction technologies. Lithium resources primarily come from hard rock mines and salt lake brines. Compared to the higher mining costs of hard rock mines, lithium extraction from salt lake brines offers the advantages of abundant resources and lower costs, particularly in the salt lake regions of South America (such as Chile, Argentina, and Bolivia), which hold a significant portion of the global reserves. Although salt lake brines are rich in lithium, their chemical composition is complex and often contains high concentrations of impurity ions (such as sodium, magnesium, and sulfate). These impurities have similar properties to lithium ions, making them difficult to effectively separate using traditional chemical separation methods. Therefore, the development of highly selective and stable adsorption materials is crucial for lithium extraction. Aluminum-based lithium adsorbents have become important materials for lithium extraction due to their high adsorption capacity and excellent thermal and chemical stability. However, in highly sulfated salt lake brines, aluminum-based adsorbents are susceptible to sulfate, resulting in structural damage and reduced adsorption performance. To overcome this problem, the present invention introduces high-valent phosphate ions to enhance its stability and adsorption capacity. Summary of the Invention

[0003] The problem to be solved by the present invention is to propose an innovative solution to the shortcomings of the above-mentioned prior art, especially to provide a phosphorus-aluminum lithium adsorbent with strong stability and strong adsorption capacity and a preparation method thereof.

[0004] To solve the above problems, the solution adopted by the present invention is as follows: a phosphorus-aluminum lithium adsorbent, characterized in that the lithium adsorbent has a molecular formula of (1-3x)LiCl·xLi3PO4·Al2(OH)6∙yH2O.

[0005] A method for preparing a phosphorus-aluminum lithium adsorbent, characterized by comprising the following steps: S1. An aluminum salt and a lithium salt are mixed in a molar ratio of 2: (1-1.2) and pure water is configured according to their total mass of 1: (3-10) to obtain a lithium-aluminum mixed solution, wherein the aluminum salt is one or more of aluminum chloride hexahydrate, aluminum sulfate, aluminum nitrate, and aluminum acetate, and the lithium salt is one or more of lithium chloride, lithium sulfate, and lithium nitrate; S2. Prepare an alkaline solution having a concentration of 5 to 10 mol / L and a phosphate solution having a concentration of 0.1-0.5 mol / L, and mix them to obtain a mixed alkali solution, wherein the alkaline solution is a solution of sodium hydroxide, potassium hydroxide, or one or more of ammonia, and the phosphate solution is a solution of sodium phosphate dodecahydrate, potassium phosphate, or one or more of sodium hydrogen phosphate; S3. Maintaining the temperature at 80-90°C, slowly add the lithium-aluminum mixed solution to the mixed alkali solution while stirring the reaction and controlling the reaction endpoint pH = 6; The reaction equation is: 6NaOH + 2AlCl3+LiCl+xNa3PO4·12H2O+(y-12)H2O ═ (1-3x)LiCl∙·xLi3PO4·Al2(OH)6∙yH2O + (3x+6)NaCl; S4. After the reaction is completed, stirring is stopped and the temperature is maintained for aging. After the aging is completed, the mixture is filtered, dried, cooled, and then ground to obtain a phosphorus-containing aluminum adsorbent precursor; S5. Add the adsorbent precursor to pure water at 40-60°C for stirring and activation, and filter to obtain a phosphorus-aluminum adsorbent. Reaction equation: (1-3x)LiCl·xLi3PO4·Al2(OH)6∙yH2O+H2O=(1-3x-a)LiCl∙(xb)Li3PO4·Al2(OH)6∙yH2O +a LiCl+b Li3PO4.

[0006] Furthermore, the preparation method of the phosphorus-aluminum lithium adsorbent is characterized in that the drying process in step S4 is to place the filtered precipitate in a drying oven and dry it at a temperature of 65-80° C. for 10-20 hours.

[0007] Furthermore, the preparation method of the phosphorus-aluminum lithium adsorbent is characterized in that the activation process refers to adding the adsorbent precursor to constant temperature pure water for mechanical stirring activation, the constant temperature pure water temperature is 40-60°C, the mechanical stirring rate is 200-500r / min, the feed ratio is 20-60mL / g, and the activation time is 0.5-1h.

[0008] The technical effects of the present invention are as follows: This method further improves the electrostatic attraction between layers by introducing high-valent phosphate ions between adsorbent layers, making the structure more stable. At the same time, since the ionic radius of phosphate ions is larger than that of chloride ions, the interlayer spacing is widened, which further improves the adsorption capacity. It also has excellent performance in high-sulfate salt lake brine and has great application prospects in the field of lithium extraction by adsorption. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1These are the test results of adsorbent cycle adsorption, water washing and desorption. DETAILED DESCRIPTION

[0010] The present invention will be further described in detail below with reference to the accompanying drawings. Example

[0011] Take 482.9g of AlCl3·6H2O (analytical grade) and 42.39g of LiCl (analytical grade) and add them to 1L of deionized water, stir and dissolve for later use; take 240g of NaOH (analytical grade) and 40g of Na3PO4·12H2O (analytical grade) and add them to 1L of deionized water, stir and dissolve for later use; set the reaction temperature of the oil bath pot to 85℃, add the lithium aluminum mixed salt solution to the mixed alkali solution through a peristaltic pump, the pump speed flow rate is 20ml / L, the stirring speed is 300r / min, and the reaction pH is controlled to be about 6. After the reaction is completed, stop stirring, maintain the temperature, and age for 2h. After the reaction is completed, filter, dry the filter cake at 75℃ for 18h, grind to obtain an adsorbent precursor, take 10g of the adsorbent precursor, add it to 500ml of constant temperature water at 40℃, mechanically stir at 300r / min, activate for 30min, and obtain a phosphorus-containing lithium adsorbent after filtration. Example

[0012] Take 482.9g of AlCl3·6H2O (analytical grade) and 46.629g of LiCl (analytical grade) and add them to 1L of deionized water, stir and dissolve for later use; take 240g of NaOH (analytical grade) and 40g of Na3PO4·12H2O (analytical grade) and add them to 1L of deionized water, stir and dissolve for later use; set the reaction temperature of the oil bath pot to 85℃, add the lithium aluminum mixed salt solution to the mixed alkali solution through a peristaltic pump, the pump speed flow rate is 15ml / L, the stirring speed is 300r / min, and the reaction pH is controlled to be about 6.5. After the reaction is completed, stop stirring, maintain the temperature, and age for 3h. After the reaction is completed, filter, dry the filter cake at 75℃ for 18h, grind to obtain an adsorbent precursor, take 20g of the adsorbent precursor, add it to 1L of constant temperature water at 40℃, mechanically stir at 300r / min, activate for 1h, and obtain a phosphorus-containing lithium adsorbent after filtration. Example

[0013] Take 482.9g of AlCl3·6H2O (analytical grade) and 42.39g of LiCl (analytical grade) and add them to 1L of deionized water, stir and dissolve for later use; take 240g of NaOH (analytical grade) and 76g of Na3PO4·12H2O (analytical grade) and add them to 1L of deionized water, stir and dissolve for later use; set the reaction temperature of the oil bath pot to 85℃, add the lithium aluminum mixed salt solution to the mixed alkali solution through a peristaltic pump, the pump speed flow rate is 25ml / L, the stirring speed is 500r / min, and the reaction pH is controlled to be about 6. After the reaction is completed, stop stirring, maintain the temperature, and age for 4h. After the reaction is completed, filter, dry the filter cake at 65℃ for 15h, grind to obtain an adsorbent precursor, take 10g of the adsorbent precursor, add it to 500ml of constant temperature water at 40℃, mechanically stir at 300r / min, activate for 30min, and obtain a phosphorus-containing lithium adsorbent after filtration.

[0014] Comparative Example 1 The only difference is that Na3PO4·12H2O is not added, and the rest of the operations are the same as those in Implementation Case 1.

[0015] Comparative Example 2 The remaining operations were the same as those in Example 2 except that Na3PO4·12H2O was not added.

[0016] Comparative Implementation Case 3 The only difference is that Na3PO4·12H2O is not added, and the rest of the operations are the same as those in Implementation Case 3.

[0017] Experiment 1 Table 1 shows the specific composition of a chloride salt lake: Ion name Li+ Na+ K+ Mg2+ Cl- Content (g / L) 0.22 86.2 7.21 23.6 219 The brine was used to test the performance of the adsorbents prepared in each embodiment. The adsorption experimental conditions were as follows: adsorption at a brine-to-adsorbent ratio of 80 mL / g, stirring in a static beaker for 30 min, and a rotation speed of 250 r / min; filtration, washing the saturated adsorbent with water, and desorption. The washing experimental conditions were as follows: the adsorbent was placed in a suction filtration device and rinsed with 1 L of 5°C deionized water to ensure that the effluent TDS was less than 100 mg / L. The desorption experimental conditions were as follows: desorption at a deionized water-to-adsorbent ratio of 100 ml / g, the water temperature was constant at 50°C, and the static beaker was stirred for 30 min and a rotation speed of 250 r / min; filtration; the lithium ion concentration in the supernatant was determined, and the adsorption capacity, adsorption rate, and resolution were calculated. The experimental conclusions are shown in Table 2.

[0018] Table 2 Adsorption results of the above experiments: From the data in the table, it can be found that compared with the undoped lithium adsorbent, the adsorption capacity of the adsorbent is greatly improved after doping with phosphate ions, and the average adsorption capacity is increased by about 80%, indicating that the embedding of phosphate ions is the key to significantly improving the adsorption capacity of aluminum-based lithium adsorbents.

[0019] Experiment 2 Table 3 shows the specific composition of a sulfate salt lake: Ion name Li+ Na+ K+ Mg2+ Ca2+ SO42- Cl- Content (g / L) 0.41 95.2 6.42 7.26 0.28 70.6 150.2 The performance of the adsorbents prepared in each embodiment was tested using this brine. The adsorption experimental conditions were as follows: adsorption at a brine-to-adsorbent ratio of 80 mL / g, stirring in a static beaker for 30 min at a speed of 250 r / min; filtration, determination of the lithium ion concentration in the clear liquid, calculation of the adsorption capacity, and washing and desorption of the saturated adsorbent. The washing experimental conditions were as follows: the adsorbent was placed in a suction filtration device and rinsed with 1 L of 5°C deionized water to ensure that the outlet TDS was less than 100 mg / L. The desorption experimental conditions were as follows: desorption at a deionized water-to-adsorbent ratio of 100 ml / g, constant water temperature of 50°C, stirring in a static beaker for 30 min at a speed of 250 r / min; filtration, and the above adsorption, washing, and desorption processes were repeated 10 times for a cycle test experiment. The experimental conclusions are shown in the table. Figure 1 .

[0020] By observing the data in the table, it can be found that compared with the undoped lithium adsorbent, the adsorbent doped with phosphate ions can still maintain a high adsorption capacity when adsorbing high-sulfate brine, and through cyclic testing, it can be found that the phosphorus-aluminum adsorbent is immune to the interference of sulfate ions, and the adsorption capacity can still maintain a high level after multiple cycles, indicating that this adsorbent can be applied to high-sulfate salt lake brine and has great application prospects in the field of lithium extraction from salt lakes.

Claims

1. A phosphorus-aluminum lithium adsorbent, characterized in that: The molecular formula of the lithium adsorbent is (1-3x)LiCl·xLi3PO4·Al2(OH)6∙yH2O.

2. A method for preparing a phosphorus-aluminum lithium adsorbent, characterized in that: The steps include: S1. An aluminum salt and a lithium salt are mixed in a molar ratio of 2: (1-1.2) and pure water is configured according to their total mass of 1: (3-10) to obtain a lithium-aluminum mixed solution, wherein the aluminum salt is one or more of aluminum chloride hexahydrate, aluminum sulfate, aluminum nitrate, and aluminum acetate, and the lithium salt is one or more of lithium chloride, lithium sulfate, and lithium nitrate; S2. Prepare an alkaline solution having a concentration of 5 to 10 mol / L and a phosphate solution having a concentration of 0.1-0.5 mol / L, and mix them to obtain a mixed alkali solution, wherein the alkaline solution is a solution of sodium hydroxide, potassium hydroxide, or one or more of ammonia, and the phosphate solution is a solution of sodium phosphate dodecahydrate, potassium phosphate, or one or more of sodium hydrogen phosphate; S3. Maintaining the temperature at 80-90°C, slowly add the lithium-aluminum mixed solution to the mixed alkali solution while stirring the reaction and controlling the reaction endpoint pH = 6; The reaction equation is: 6NaOH + 2AlCl3+LiCl+xNa3PO4·12H2O+(y-12)H2O ═(1-3x)LiCl∙·xLi3PO4·Al2(OH)6∙yH2O + (3x+6)NaCl; S4. After the reaction is completed, stirring is stopped and the temperature is maintained for aging. After the aging is completed, the mixture is filtered, dried, cooled, and then ground to obtain a phosphorus-containing aluminum adsorbent precursor; S5. Add the adsorbent precursor to pure water at 40-60°C for stirring and activation, and filter to obtain a phosphorus-aluminum adsorbent. Reaction equation: (1-3x)LiCl·xLi3PO4·Al2(OH)6∙yH2O+H2O=(1-3x-a)LiCl∙(xb)Li3PO4·Al2(OH)6∙yH2O +a LiCl+b Li3PO4.

3. The method for preparing the phosphorus-aluminum lithium adsorbent according to claim 2, characterized in that: The drying process in step S4 is to place the filtered precipitate in a drying oven and dry it at a temperature of 65-80° C. for 10-20 hours.

4. The method for preparing the phosphorus-aluminum lithium adsorbent according to claim 2, wherein: The activation process is to add the adsorbent precursor into constant temperature pure water for mechanical stirring activation, the constant temperature pure water temperature is 40-60°C, the mechanical stirring rate is 200-500r / min, the feed ratio is 20-60mL / g, and the activation time is 0.5-1h.

Images