Li-type cation exchanger, exchange membrane and preparation method

Abstract

The invention discloses a preparation method of a Li-type cation exchanger. The preparation method comprises the following steps: pickling natural zeolite, washing, drying, roasting and simultaneously carrying out lithium ion replacement or carrying out lithium replacement by using a lithium ion solution after roasting, and washing and drying. The Li type cation exchanger is obtained by the preparation method. The preparation method of the Li type cation exchange membrane comprises the following steps: preparing sulfonated polyethersulfone; the method comprises the following steps: dispersing a Li-type cation exchanger in polyvinylpyrrolidone, heating to 60 DEG C, keeping the temperature, adding sulfonated polyethersulfone into the polyvinylpyrrolidone, and stirring to react; uniformly casting the reacted solution on a flat plate to form a thin film with the thickness of 100-140 microns; carrying out coagulating bath treatment on the film in deionized water for 8-12 minutes; deionized water is used for removing N-methyl pyrrolidone in the film subjected to coagulating bath treatment; and finally air-drying the film. The ion exchanger provided by the invention can efficiently and selectively remove potassium ions in a lithium chloride solution, and overcomes the problem of introduction of new pollutants in the prior art.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of ion exchangers, in particular to a Li-type cation exchanger, an exchange membrane and a preparation method. BACKGROUND

[0002] Lithium is an important strategic resource, which has a wide range of applications in batteries, ceramics, glass, lubricants, refrigerants, etc.

[0003] In many industrial production processes and lithium extraction from salt lake brine, lithium salts are often contaminated by impurity ions such as potassium ions. The presence of potassium ions not only affects the purity of lithium salt products and reduces their quality, but also can cause a series of problems in subsequent processing. For example, in the preparation process of battery-grade lithium carbonate, potassium ions can interfere with the crystallization process of lithium salts, resulting in unstable product quality and affecting the performance and service life of the battery.

[0004] Currently, there are various methods for removing potassium ions from lithium salt solutions, but these methods generally have problems such as high cost, complex operation, and introduction of new impurities. For example, the aluminum potassium sulfate precipitation method reported in patent CN102010991A requires the introduction of aluminum ions, the jarosite method reported in patent CN113387374A requires the introduction of iron ions and has harsh reaction conditions, and the isopropyl alcohol extraction method reported in US patent US4274834 has high cost and high risk. Ion exchange method is a potential technology for removing potassium ions due to its high efficiency and economy.

[0005] However, there are few reports on Li-type cation exchangers for selectively removing potassium ions from lithium salts. For example, the Na-type ion exchanger described in patent CN102730722A releases sodium ions while removing potassium ions. Therefore, it is of great practical significance to develop a cation exchanger with high potassium ion selectivity. SUMMARY

[0006] In view of the above-mentioned defects of the prior art, the purpose of the present application is to provide a Li-type cation exchanger and a film forming method thereof, which can efficiently and selectively remove potassium ions from lithium chloride solution, overcoming the problem of introducing new pollutants in the prior art.

[0007] The purpose of the present application is achieved by the following technical solution:

[0008] The preparation method of the Li-type cation exchanger comprises the following steps:

[0009] The natural clinoptilolite is acid washed to remove impurities and replace the internal cations with hydrogen ions;

[0010] The acid-washed clinoptilolite is washed, dried and then calcined to activate the clinoptilolite.

[0011] After calcination, the clinoptilolite is washed and dried,

[0012] After drying, the clinoptilolite is soaked in a lithium chloride solution to replace lithium ions into the clinoptilolite;

[0013] After replacement, the clinoptilolite is washed and dried to obtain a Li-type cation exchanger.

[0014] Further, the natural clinoptilolite is pickled with a hydrochloric acid solution, and the clinoptilolite is soaked in the hydrochloric acid solution and stirred during the soaking process; the soaking time of the natural clinoptilolite in the hydrochloric acid solution at room temperature is 4-5 hours, and the concentration of the hydrochloric acid solution is 2-12 wt%.

[0015] Further, the calcination temperature is 150-400 degrees Celsius, and the calcination time is 50-70 minutes; after calcination, the clinoptilolite is cooled to room temperature and then washed.

[0016] Further, the concentration of the lithium chloride solution is 15 wt%, and the solution is shaken at 45-55 degrees Celsius for 6-12 hours; during the replacement process, the solution is replaced with a new 15 wt% lithium chloride solution every 100-140 minutes.

[0017] The Li-type cation exchanger is prepared by the following steps:

[0018] The natural clinoptilolite is pickled to remove impurities and replace internal cations with hydrogen ions;

[0019] The pickled clinoptilolite is washed and dried;

[0020] The dried clinoptilolite is mixed with lithium chloride powder, and the mixture is uniformly mixed and then calcined to replace lithium ions into the clinoptilolite; the mass ratio of the clinoptilolite to the lithium chloride powder is 1:0.5-2; the calcination temperature is 150-400 degrees Celsius, and the calcination time is 50-70 minutes;

[0021] After calcination, the clinoptilolite is cooled to room temperature and then washed and dried to obtain a Li-type cation exchanger.

[0022] Further, the natural clinoptilolite is pickled with a hydrochloric acid solution, and the clinoptilolite is soaked in the hydrochloric acid solution and stirred during the soaking process; the soaking time of the natural clinoptilolite in the hydrochloric acid solution at room temperature is 4-5 hours, and the concentration of the hydrochloric acid solution is 2-12 wt%.

[0023] The Li-type cation exchanger comprises a Li-type cation exchanger prepared by any of the above preparation methods.

[0024] A method for preparing a Li-type cation exchange membrane, comprising the following steps:

[0025] Preparation or taking of sulfonated polyether sulfone;

[0026] The Li-type cation exchanger prepared by the method of any one of claims 1-6 is dispersed in polyvinylpyrrolidone;

[0027] The polyvinylpyrrolidone with the dispersed Li-type cation exchanger is heated to 60 degrees Celsius, and then sulfonated polyether sulfone is added and stirred to react; the ratio of the Li-type cation exchanger, the polyvinylpyrrolidone, and the sulfonated polyether sulfone is 1:0.8-1.2:16-24

[0028] The reacted solution is uniformly cast on a flat plate to form a thin film with a thickness of 100-140 um;

[0029] The thin film is subjected to a coagulation bath treatment for 8-12 minutes in deionized water to induce phase inversion;

[0030] Deionized water is used to remove N-methylpyrrolidone in the thin film after the coagulation bath treatment;

[0031] The thin film is air-dried to obtain a Li-type cation exchange membrane.

[0032] Further, the preparation of the sulfonated polyether sulfone comprises the following steps:

[0033] 8-12 g of polyether sulfone is dissolved in 90-110 mL of concentrated sulfuric acid, and stirred at 80 degrees Celsius for 48 hours;

[0034] The sulfonation reaction of the reaction mixture is quenched using ice water;

[0035] The sulfonated polyether sulfone precipitated in the ice water is washed with deionized water;

[0036] The washed sulfonated polyether sulfone is rinsed with isopropyl alcohol for 50-70 minutes, and then dried at room temperature to obtain the sulfonated polyether sulfone.

[0037] Further, the polyvinylpyrrolidone with the added Li-type cation exchanger is ultrasonically treated for 25-35 minutes before being heated to 60 degrees Celsius;

[0038] The sulfonated polyether sulfone is added to the polyvinylpyrrolidone with the dispersed Li-type cation exchanger in 3-5 batches, and the reaction time is controlled to be 10-14 hours.

[0039] Thanks to the above technical solutions, the present application has the following advantages:

[0040] 1. The present application effectively removes impurities in the pore channel of natural clinoptilolite by a specific acid leaching process, significantly increases the specific surface area of the zeolite, provides more active sites for ion exchange, and thus improves the adsorption capacity and efficiency of the ion exchanger for potassium ions.

[0041] 2. The LiCl solution impregnation modification process and the "one-step" calcination-lithium replacement process can successfully prepare Li-type cation exchangers with excellent performance, and the preparation conditions are relatively loose and have a wide range of applications.

[0042] 3. The Li-type cation exchanger after film formation has excellent performance and shows good selectivity for potassium ions in LiCl solution, preferentially adsorbs K + in the simulated salt lake brine solution system, and shows high potassium ion removal efficiency.

[0043] 4. The raw material natural zeolite used in the present application has a wide source and low cost, the film formation process is simple, suitable for large-scale industrial production, and has good economic and social benefits.

[0044] Other advantages, objects, and features of the present application will be set forth in part in the following specification, and in part will become apparent to those skilled in the art from a consideration of the following description, or can be learned from practice of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 is a schematic diagram of the device structure for testing the exchange film of Example 1, Example 2, and Example 3. DETAILED DESCRIPTION

[0046] The present application will be further described below in conjunction with examples.

[0047] Example 1:

[0048] Step 1: Preparation of Li-type cation exchanger

[0049] 1) Weigh 200g of commercially available natural clinoptilolite with a particle size of about 300-400 mesh, wash it with deionized water three times, then soak it in 500mL of freshly prepared 6wt% hydrochloric acid, stir at room temperature for 5h, filter, and wash with deionized water, then dry for use.

[0050] During the acid leaching process, the HCl solution can react with calcium, magnesium, iron and other metal oxides or amorphous impurities in the pore channel of natural clinoptilolite, and dissolve and remove these impurities. At the same time, the acid leaching process can replace the cations (such as Na + , Ca 2+ ) in the zeolite with H +This process not only increases the specific surface area and porosity of the zeolite, but also creates more favorable conditions for the subsequent ion exchange reaction.

[0051] In the present embodiment, a 6wt% hydrochloric acid solution is preferred; from the N2adsorption characterization results, the hydrochloric acid concentration is too low (less than 2wt%), and the impurity treatment is insufficient; the hydrochloric acid concentration is too high (more than 12wt%), and the specific surface area of the zeolite after acid leaching is significantly reduced, which is attributed to the partial collapse of the zeolite framework. Specifically, the effects of different hydrochloric acid concentrations on the specific surface area of the zeolite are shown in Table 1.

[0052] Table 1. Specific surface area of zeolite samples after acid leaching treatment

[0053] HCl concentration 0 wt% 2 wt% 4 wt% 6 wt% 8 wt% 10 wt% 12 wt% Zeolite specific surface area (m 2 / g) 26 41 55 73 70 62 35

[0054] 2) The zeolite sample after acid leaching treatment is placed in a muffle furnace and calcined at 300 degrees Celsius for 1h. After cooling to room temperature, it is washed with deionized water and dried for use.

[0055] High-temperature calcination activates the natural zeolite by dehydration, further increases the specific surface area, and widens the pore channels. The calcination temperature is preferably 300 degrees Celsius; when the temperature is lower than 300 degrees Celsius, the dehydration activation is insufficient; when the temperature is higher than 300 degrees Celsius, the zeolite framework gradually collapses, and the specific surface area decreases sharply. Specifically, the effects of different calcination temperatures on the specific surface area of the zeolite are shown in Table 2.

[0056] Table 2. Specific surface area of zeolite samples after calcination treatment

[0057] Baking temperature 摄氏度 ​ 150 200 250 300 350 400 Zeolite specific surface area (m 2 / g) 81 93 110 129 90 62

[0058] 3) The calcined zeolite sample is soaked in 500mL of a 15wt% lithium chloride solution, shaken at 50 degrees Celsius for 10h, and the fresh 15wt% lithium chloride solution is replaced every 2h.

[0059] EDS (Energy Dispersive X-ray Spectroscopy) characterization results show that the lithium content reaches saturation after 10h, and the lithium replacement is insufficient below 10h. Specifically, the effects of different lithium ion replacement times on the main element content in the zeolite after replacement are shown in Table 3.

[0060] Table 3. Relative content of main elements in the original zeolite and the zeolite sample after lithium replacement detected by EDS

[0061] Element content (%) O Si Al Na K Mg Ca Li Other elements Natural zeolite as is 67.33 20.26 7.12 1.77 0.96 0.99 1.09 0 0.48 Replacement 6 h 65.88 23.75 6.65 1.01 0.25 1.21 0.98 0.05 0.22 Replacement 8 h 65.97 23.86 6.66 1.00 0.21 1.29 0.93 0.08 0.30 Replacement 10 h 66.11 23.92 6.70 0.87 0.15 1.13 0.81 0.10 0.21 Replacement 12 h 66.08 23.95 6.64 0.85 0.16 1.11 0.82 0.10 0.29

[0062] 4) The zeolite sample after lithium replacement is washed with deionized water and dried to obtain a Li-type cationic ion exchanger-1, i.e., a Li-type cationic ion exchanger (Zeolite(Li+)-1-300).

[0063] Second step, preparation of Li-type cation exchange membrane

[0064] 1) 5 g of Li-type cation exchanger (Zeolite(Li+-1-300) and 5 g of polyvinylpyrrolidone (PVP) were dispersed in 70 g of NMP, and ultrasonic treatment was performed for 30 min.

[0065] 2) Heating to 60 degrees Celsius, adding sulfonated polyether sulfone (SPES) in four batches, 5 g each batch, stirring for 12 h.

[0066] 3) The viscous solution was uniformly cast onto a glass plate using a doctor blade to form a thin film with a thickness of about 120 μm, and then immersed in a deionized water coagulation bath at room temperature for 10 min to induce phase inversion.

[0067] 4) The thin film was continuously soaked in deionized water for 24 h to remove residual N-methylpyrrolidone (NMP), and then air dried to obtain a Li-type cation exchange membrane (denoted as: SPES@Zeolite(Li + )-1-300).

[0068] Example 2:

[0069] First step, preparation of Li-type cation exchanger

[0070] 1) 200 g of commercially available natural clinoptilolite with a particle size of about 300-400 mesh was washed with deionized water three times, then soaked in 500 mL of freshly prepared 6 wt% hydrochloric acid, stirred at room temperature for 5 h, suction filtered, and washed thoroughly with deionized water, and dried for use.

[0071] 2) 50 g of acid-leached clinoptilolite was mixed uniformly with 50 g of LiCl powder, and placed in a muffle furnace for calcination at 300 degrees Celsius for 1 h.

[0072] After mixing the acid-leached zeolite sample with lithium chloride powder and heat treatment, the calcination activation and lithium replacement were completed in one step. The mass ratio of the zeolite sample to lithium chloride powder is preferably 1:1. When the mass ratio of the zeolite sample to lithium chloride powder is 2:1, the lithium replacement is not sufficient. Specifically, after calcination of different zeolite samples with lithium chloride powder at a temperature of 300 degrees Celsius, the main element contents in the zeolite samples are shown in Table 4.

[0073] Table 4. Relative content of main elements in zeolite samples after calcination-lithium replacement detected by EDS

[0074] Element content (%) O Si Al Na K Mg Ca Li Other elements Mass ratio 2:1 65.61 23.99 6.55 0.97 0.25 1.19 1.08 0.07 0.29 Mass ratio 1 :1 65.63 24.52 6.41 0.91 0.13 1.09 0.75 0.11 0.45 Mass ratio 1 :2 65.71 24.56 6.39 0.89 0.11 1.03 0.76 0.11 0.44

[0075] Note: The mass ratio in Table 4 represents the mass ratio of the zeolite sample to lithium chloride powder

[0076] 3) The zeolite sample after calcination and lithium replacement was washed thoroughly with deionized water, and dried to obtain Li-type cation exchanger-2, i.e. Li-type cation exchanger (Zeolite(Li+)-2-1).

[0077] Second step, preparation of Li-type cation exchange membrane

[0078] 1) 5 g of Li-type cation exchanger (Zeolite(Li+)-2-1) and 5 g of polyvinylpyrrolidone (PVP) were dispersed in 70 g of N-methylpyrrolidone (NMP) and ultrasonically treated for 30 min.

[0079] 2) The temperature was raised to 60 degrees Celsius, and sulfonated polyether sulfone (SPES) was added in four batches, 5 g each, and stirred for 12 h.

[0080] 3) The viscous solution was uniformly cast onto a glass plate using a doctor blade to form a thin film with a thickness of about 120 pm, and then immersed in a deionized water coagulation bath at room temperature for 10 min to induce phase inversion.

[0081] 4) The thin film was continuously immersed in deionized water for 24 h to remove residual N-methylpyrrolidone (NMP), and then air-dried to obtain a Li-type cation exchange membrane (denoted as: SPES@Zeolite(Li + )-2-1).

[0082] Example 3:

[0083] The exchange membrane was prepared according to the exchange membrane preparation method of the present application using a commercially available natural clinoptilolite without any treatment.

[0084] 1) 5 g of commercially available natural clinoptilolite with a particle size of about 300-400 mesh and 5 g of PVP were dispersed in 70 g of N-methylpyrrolidone (NMP) and ultrasonically treated for 30 min.

[0085] 2) The temperature was raised to 60 degrees Celsius, and sulfonated polyether sulfone (SPES) was added in four batches, 5 g each, and stirred for 12 h.

[0086] 3) The viscous solution was uniformly cast onto a glass plate using a doctor blade to form a thin film with a thickness of about 120 pm, and then immersed in a deionized water coagulation bath at room temperature for 10 min to induce phase inversion.

[0087] 4) The thin film was continuously immersed in deionized water for 24 h to remove residual N-methylpyrrolidone (NMP), and then air-dried to obtain a Li-type cation exchange membrane (denoted as: SPES@Zeolite(Li

[0088] The exchange membranes obtained in Examples 1-3 were tested for performance.

[0089] First step, preparation of test solution

[0090] Analytical grade lithium chloride, sodium chloride, potassium chloride and magnesium chloride were used to prepare simulated salt lake brine, wherein the Li content was 1200 ppm, the Na content was 250 ppm, the K content was 300 ppm and the Mg content was 150 ppm.

[0091] Step 2: Make an ion exchange device

[0092] like Figure 1 As shown, the apparatus consists of a mother liquor tank, a booster pump, a pressure gauge, a shut-off valve, a membrane module with an inner diameter of 8.0 cm, and a filtrate tank. Simulated salt lake brine was passed through the membrane module at a constant flow rate of 0.1 L / h, with the operating pressure and temperature maintained at 0.1 MPa and 25 degrees Celsius, respectively.

[0093] Step 3: Test Method

[0094] The potassium removal effect was analyzed by monitoring the metal ion concentrations at the inlet and outlet of the mixed matrix membrane.

[0095] The exchange membranes obtained in Examples 1-3 were placed in an ion exchange device and experiments were carried out. The experimental results are shown in Table 5.

[0096] Table 5. ICP-AES test results

[0097] Cation exchanger Li (ppm) K (ppm) Na (ppm) Mg (ppm) SPES@Zeolite 1125 264 237 146 SPES@Zeolite(Li + -1-300]]> 1301 28 241 143 SPES@Zeolite(Li + )-2-1]]> 1333 21 244 141

[0098] As can be clearly seen from Table 5, the Li-type cation exchange membranes prepared using Examples 1 and 2 significantly reduced the potassium ion content in the solution by 89.39% and 92.05%, respectively, compared to conventional exchange membranes. Furthermore, compared to conventional exchange membranes, the lithium, sodium, and magnesium ions in the solutions treated with Examples 1 and 2 did not significantly increase, meaning no significant increase in impurity ions was introduced.

[0099] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for preparing a Li-type cation exchanger, characterized in that: The following steps are involved: The natural clinoptilolite is acid-washed to remove its impurities and replace the internal cations with hydrogen ions; The acid-washed clinoptilolite is washed and dried, and then calcined to dehydrate and activate the clinoptilolite; The calcined clinoptilolite is washed and then dried. The dried clinoptilolite is immersed in a lithium chloride solution to replace lithium ions into the clinoptilolite; The replaced clinoptilolite is washed and dried to obtain a Li-type cation exchanger.

2. The method for preparing a Li-type cation exchanger according to claim 1, wherein The natural clinoptilolite is pickled using a hydrochloric acid solution. During the pickling process, the clinoptilolite is immersed in the hydrochloric acid solution and stirred during the immersion process. The natural clinoptilolite is immersed in the hydrochloric acid solution for 4-5 hours at room temperature. The concentration of the hydrochloric acid solution is 2-12 wt%.

3. The method for preparing a Li-type cation exchanger according to claim 1, wherein The calcination temperature is 150-400 degrees Celsius, and the calcination time is 50-70 minutes. After the calcination, the clinoptilolite is cooled to room temperature and then washed.

4. The method for preparing a Li-type cation exchanger according to claim 1, wherein The lithium chloride solution has a concentration of 15 wt % and is shaken at 45-55 degrees Celsius for 6-12 hours; during the replacement process, a new 15 wt % lithium chloride solution is replaced every 100-140 minutes.

5. A method for preparing a Li-type cation exchanger, characterized in that: The following steps are involved: The natural clinoptilolite is acid-washed to remove its impurities and replace the internal cations with hydrogen ions; washing and drying the acid-washed clinoptilolite; The dried clinoptilolite is mixed with lithium chloride powder, and then calcined to replace lithium ions into the clinoptilolite; The mass ratio of clinoptilolite to lithium chloride powder is 1:0.5-2; the calcination temperature is 150-400 degrees Celsius, and the calcination time is 50-70 minutes; After the calcination, the clinoptilolite is cooled to room temperature and then washed and dried to obtain a Li-type cation exchanger.

6. The method for preparing a Li-type cation exchanger according to claim 5, wherein: The natural clinoptilolite is pickled using a hydrochloric acid solution. During the pickling process, the clinoptilolite is immersed in the hydrochloric acid solution and stirred during the immersion process. The natural clinoptilolite is immersed in the hydrochloric acid solution for 4-5 hours at room temperature. The concentration of the hydrochloric acid solution is 2-12 wt%.

7. Li-type cation exchanger, characterized in that The invention comprises a Li-type cation exchanger prepared by the preparation method according to any one of claims 1 to 6.

8. A method for preparing a Li-type cation exchange membrane, characterized in that: The following steps are involved: preparing or taking sulfonated polyethersulfone; Dispersing the Li-type cation exchanger prepared by the preparation method of any one of claims 1 to 6 in polyvinyl pyrrolidone; The polyvinyl pyrrolidone dispersed with the Li-type cation exchanger is heated to 60 degrees Celsius and maintained, and then sulfonated polyethersulfone is added and stirred for reaction; the ratio of Li-type cation exchanger, polyvinyl pyrrolidone, and sulfonated polyethersulfone is 1:0.8-1.2:16-24 The reacted solution is evenly cast onto a flat plate to form a film with a thickness of 100-140 μm; The film was subjected to a coagulation bath treatment in deionized water for 8–12 min to induce phase inversion; Deionized water was used to remove N-methylpyrrolidone from the film after coagulation bath treatment; The film was air-dried to obtain a Li-type cation exchange membrane.

9. The method for preparing a Li-type cation exchange membrane according to claim 8, wherein: The preparation of sulfonated polyethersulfone comprises the following steps: Dissolve 8-12 g of polyethersulfone in 90-110 mL of concentrated sulfuric acid and stir at 80 degrees Celsius for 48 hours; The sulfonation reaction of the reaction mixture was quenched with ice water; The sulfonated polyethersulfone precipitated in ice water was washed with deionized water; The washed sulfonated polyethersulfone was rinsed in isopropyl alcohol for 50-70 minutes and then dried at room temperature to obtain the sulfonated polyethersulfone.

10. The method for preparing a Li-type cation exchange membrane according to claim 8, wherein: The polyvinylpyrrolidone with the Li-type cation exchanger was then ultrasonically treated for 25-35 minutes before being heated to 60°C. Sulfonated polyethersulfone is added into polyvinylpyrrolidone dispersed with Li-type cation exchanger in equal amounts in 3-5 batches, and the reaction time is controlled within 10-14 hours.

Images