A method of making a sorbent membrane sheet and membrane module

Abstract

This invention discloses a method for preparing adsorbent membrane sheets and membrane modules, belonging to the technical field of separation membrane materials for lithium extraction from salt lakes. This invention incorporates a special adsorbent for lithium extraction from salt lakes into a casting solution, supported by a high-strength, acid- and alkali-resistant nonwoven fabric. An adsorbent membrane sheet with both sieving and selective adsorption functions is prepared through a phase inversion process. The casting solution, by mass percentage, comprises: 8%–15% polyvinylidene fluoride, 30%–50% adsorbent, 1%–10% pore-forming agent, and 20%–50% solvent. The preparation steps include raw material pretreatment, casting solution preparation, adsorbent mixing, vacuum degassing, blade coating, air bath, gel bath, rinsing and shaping, and membrane module winding. The membrane sheet of this invention has high adsorption capacity, high flux, excellent mechanical strength and acid- and alkali resistance, and the adsorbent is not easily lost and is easily desorbed and regenerated. It can efficiently separate lithium ions in high magnesium-to-lithium ratio salt lake brine. The process is stable and controllable, suitable for continuous industrial production, and effectively solves the problems of high resistance, easy loss, and easy contamination of traditional powder adsorbents.

Description

Technical Field

[0001] This invention relates to the field of membrane separation technology, specifically to a method for preparing an adsorbent membrane sheet and membrane module for lithium extraction from salt lakes, which is particularly suitable for the selective separation and enrichment of lithium in salt lake brines with a high magnesium-to-lithium ratio, and belongs to the field of functional separation membrane material preparation technology. Background Technology

[0002] Membrane separation technology is a novel alternative separation technology. With the continuous development of membrane technology, it is increasingly being applied in both daily life and industrial production. Based on the size of the substances to be separated, membranes are classified into microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, and reverse osmosis membranes.

[0003] In existing technologies, adsorbent membrane materials used for lithium extraction from salt lakes generally suffer from the following technical bottlenecks: First, the adsorbent is unevenly dispersed in the membrane substrate, easily leading to agglomeration, which causes membrane pore blockage and reduced flux. Second, the membrane material has poor acid and alkali resistance, and is prone to swelling and degradation during long-term operation in salt lake brine, resulting in reduced mechanical strength. Third, the binding force between the adsorbent and the membrane substrate is insufficient, leading to severe adsorbent shedding during recycling and rapid decay of adsorption capacity. Fourth, the membrane preparation process is complex and requires harsh conditions, making it difficult to achieve large-scale, continuous production.

[0004] Therefore, there is an urgent need to develop an adsorbent membrane and membrane module with high adsorbent loading, excellent mechanical strength, resistance to acid and alkali corrosion, high flux, good selectivity, and simple preparation process. Summary of the Invention

[0005] The purpose of this invention is to address the technical shortcomings of existing lithium extraction adsorbents and membrane materials from salt lakes, such as high bed resistance, easy adsorbent loss, poor mechanical strength, weak acid and alkali resistance, and complex preparation processes. This invention provides a method for preparing adsorbent membrane sheets and membrane modules. By uniformly doping a special adsorbent for lithium extraction from salt lakes into a casting solution, and combining phase inversion membrane formation technology with high-strength acid and alkali resistant nonwoven fabric support technology, an adsorbent membrane sheet with high adsorption capacity, high flux, high mechanical strength, and excellent acid and alkali resistance is prepared. This membrane sheet is then further rolled into a membrane module, achieving efficient and selective separation and continuous enrichment of lithium ions in salt lake brine, and solving many technical problems in the application of traditional powder adsorbents.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution: A method for preparing an adsorbent membrane involves doping a lithium extraction adsorbent from salt lakes into a casting solution, uniformly coating the casting solution onto a high-strength, acid- and alkali-resistant nonwoven fabric, and then preparing the adsorbent membrane through a phase inversion process. The casting solution, by mass percentage, comprises the following components: 8%–15% polyvinylidene fluoride, 30%–50% lithium extraction adsorbent from salt lakes, 1%–10% pore-forming agent, and 20%–50% organic solvent.

[0007] As a preferred embodiment, the pore-forming agent is one or a mixture of polyethylene glycol, polyvinylpyrrolidone, and lithium chloride.

[0008] As a preferred embodiment, the organic solvent is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

[0009] As a preferred embodiment, the adsorbent for lithium extraction from salt lakes is one or a combination of aluminum-based adsorbents, manganese-based spinel oxide adsorbents, and titanium-based spinel oxide adsorbents.

[0010] As a preferred embodiment, the high-strength acid and alkali resistant nonwoven fabric is one of polyester nonwoven fabric, polypropylene nonwoven fabric, and polytetrafluoroethylene nonwoven fabric.

[0011] A method for preparing an adsorbent membrane, specifically including the following steps: S1: Raw material pretreatment: Polyvinylidene fluoride, pore-forming agent, and special adsorbent for lithium extraction from salt lakes are dried and pretreated in an oven at 105℃. S2: Preparation of casting solution: Pretreated polyvinylidene fluoride and pore-forming agent are added to an organic solvent and dissolved completely under stirring conditions of 60℃~70℃ and 200r / min to obtain casting solution; S3: Preparation of adsorbent preparation solution: Add the casting liquid to the kneader, add the pretreated adsorbent powder, stir and mix evenly to obtain the adsorbent preparation solution; S4: Degassing treatment: Degas the adsorbent preparation solution at 30℃~80℃ and vacuum degree -0.09MPa for 12h~24h; S5: Film Formation by Scraping: The degassed adsorbent preparation solution is uniformly scraped onto the nonwoven fabric at a speed of 1m / s~8m / s; S6: Air bath treatment: Place the coated nonwoven fabric in an air bath at room temperature for 5s~60s; S7: Gel bath treatment: After air bath, the membrane is subjected to phase separation gel bath in deionized water at 0℃~20℃ for 5min~15min; S8: Rinsing and Shaping: Rinse the membrane after gel bath in deionized water at 40℃~80℃ for 20min~60min, and dry to obtain the adsorbent membrane.

[0012] As a preferred embodiment, the gap between the doctor blade and the nonwoven fabric in S5 is 200μm~300μm, preferably 250μm; the coating speed is preferably 5m / s.

[0013] As a preferred option, the ambient temperature in S6 is 25℃~30℃, and the air bath time is preferably 5s~10s.

[0014] A method for preparing an adsorbent membrane module involves cutting the prepared adsorbent membrane sheet, rolling it up with a grid and a flow guide cloth around a central tube as the axis, and then sealing, curing, assembling, and testing to obtain a spiral-wound adsorbent membrane module.

[0015] An adsorbent membrane includes a nonwoven fabric support layer and an adsorbent separation layer, wherein the adsorbent separation layer is loaded with a special adsorbent for lithium extraction from salt lakes, and the lithium ion adsorption capacity is 178 mg / m² to 280 mg / m².

[0016] Compared with the prior art, the beneficial effects of the present invention are: 1. By adding a pore-forming agent to the membrane, a continuous pore structure is formed through a phase inversion process, resulting in high porosity and significantly improved flux. At the same time, the membrane also has a screening and filtration function, which can effectively intercept suspended particulate matter, colloids and other impurities in salt lake brine, reduce the risk of membrane fouling and extend the service life of the membrane.

[0017] 2. The adsorbent is uniformly doped into the membrane substrate and tightly bonded to the polyvinylidene fluoride substrate. There is no adsorbent loss or breakage during the adsorption-elution cycle, the adsorbent utilization rate is close to 100%, and the operating cost is low.

[0018] 3. High-strength acid and alkali resistant non-woven fabric is used as the support substrate, and polyvinylidene fluoride is used as the membrane matrix material. The overall membrane has high mechanical strength, is resistant to strong acid, strong alkali and high salt corrosion, and can adapt to the complex working environment of salt lake brine. The membrane is not easily damaged or swollen and has a long service life.

[0019] 4. The adsorbent membrane of the present invention has a loading of up to 30%~50% for lithium extraction from salt lakes. It uses titanium-based and manganese-based spinel-type inorganic adsorbents, which have specific selective adsorption capacity for lithium ions. The lithium ion adsorption capacity can reach 178mg / m²~280mg / m², which can achieve efficient and selective separation of lithium ions in salt lake brines with high magnesium-to-lithium ratio and high magnesium-to-lithium separation coefficient. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the adsorbent membrane of the present invention.

[0021] Figure 2 This describes the preparation process of the adsorbent membrane of the present invention.

[0022] Figure 3 This is a schematic diagram of the anatomical structure of the adsorbent membrane assembly of the present invention. Detailed Implementation

[0023] The technical solution of this application will be further described and illustrated below through embodiments. Example

[0024] A method for preparing an adsorbent membrane sheet and membrane module, comprising the following specific steps: 1) Raw material pretreatment: Polyvinylidene fluoride, polyvinylpyrrolidone, and titanium adsorbent were placed in an oven at 105℃ for 2 hours to dry and pretreat, removing moisture and volatile impurities; 2) Preparation of casting solution: Take 12% polyvinylidene fluoride and 3% polyvinylpyrrolidone by mass percentage and add them to 45% N-methylpyrrolidone. Stir at 65℃ and 200 r / min for 12 h until completely dissolved to form a uniform casting solution. 3) Preparation of adsorbent preparation solution: Add the casting liquid to the kneader, add 40% titanium adsorbent powder, stir and mix thoroughly to form the adsorbent preparation solution; 4) Degassing treatment: The adsorbent preparation solution was placed in a double-layer vacuum degassing tank with a vacuum degree of -0.09MPa and a heating layer temperature of 80℃ for 24 hours. 5) Film formation by scraping: Adjust the gap between the scraper and the polyester nonwoven fabric to 250μm, control the coating speed to 5m / s, and uniformly scrape the adsorbent preparation liquid onto the surface of the nonwoven fabric. 6) Air bath treatment: Air bath at 28℃ for 10 seconds; 7) Gel bath treatment: Transfer to 18℃ deionized water for gel bath for 10 min; 8) Rinsing and setting: Rinse in 60℃ deionized water for 30 minutes; 9) Drying and winding: Dry at room temperature and in a ventilated environment, then wind up to obtain the adsorbent membrane; 10) Membrane module preparation: After cutting the membrane sheet, roll it up with the flow guide cloth and grid, seal and cure it, and assemble it to obtain the spiral-wound adsorbent membrane module.

[0025] The adsorbent membrane prepared in this embodiment was tested for performance. The lithium ion adsorption capacity was 280 mg / m², the membrane flux was high, the acid and alkali resistance was excellent, and the adsorption capacity did not decrease significantly after 100 cycles. Example

[0026] A method for preparing an adsorbent membrane sheet and membrane module, comprising the following specific steps: 1) Raw material pretreatment: Polyvinylidene fluoride, polyvinylpyrrolidone, and titanium adsorbent were placed in an oven at 105℃ and dried for 2 hours. 2) Preparation of casting solution: Take 15% polyvinylidene fluoride and 3% polyvinylpyrrolidone by mass percentage and add them to 50% N-methylpyrrolidone. Stir at 70℃ and 200 r / min for 18 h until completely dissolved. 3) Preparation of adsorbent preparation solution: Add the casting solution to the kneader, add 32% titanium adsorbent powder, and stir thoroughly to mix evenly; 4) Degassing treatment: Vacuum degree -0.09MPa, heating layer temperature 80℃, degassing for 24h; 5) Film formation by blade coating: blade gap 250μm, coating speed 5m / s; 6) Air bath treatment: Air bath at 28℃ for 5 seconds; 7) Gel bath treatment: Transfer to 16℃ deionized water for a gel bath for 15 min; 8) Rinsing and setting: Rinse in 60℃ deionized water for 40 minutes; 9) Drying and winding, and membrane module preparation are the same as in Example 1.

[0027] The adsorbent membrane prepared in this embodiment has a lithium ion adsorption capacity of 178 mg / m², excellent mechanical strength, and good anti-fouling performance. Example

[0028] A method for preparing an adsorbent membrane sheet and membrane module, comprising the following specific steps: 1) Raw material pretreatment: Polyvinylidene fluoride, polyvinylpyrrolidone, and titanium adsorbent were placed in an oven at 105℃ and dried for 2 hours. 2) Preparation of casting solution: Take 15% polyvinylidene fluoride and 2% polyvinylpyrrolidone by mass percentage and add them to 45% N-methylpyrrolidone. Stir at 70℃ and 200 r / min for 18 h until completely dissolved. 3) Preparation of adsorbent preparation solution: Add the casting solution to the kneader, add 38% titanium adsorbent powder, and stir thoroughly to mix evenly; 4) Degassing treatment: Vacuum degree -0.09MPa, heating layer temperature 80℃, degassing for 24h; 5) Film formation by blade coating: blade gap 250μm, coating speed 5m / s; 6) Air bath treatment: Air bath at 28℃ for 5 seconds; 7) Gel bath treatment: Transfer to 16℃ deionized water for a gel bath for 15 min; 8) Rinsing and setting: Rinse in 60℃ deionized water for 40 minutes; 9) Drying and winding, and membrane module preparation are the same as in Example 1.

[0029] The adsorbent membrane prepared in this embodiment has a lithium ion adsorption capacity of 226 mg / m², exhibiting excellent overall performance and is suitable for industrial applications.

[0030] The above-mentioned test method involves injecting the adsorbent solution into the adsorbent membrane module at a certain flow rate, taking samples for analysis, and determining the working capacity of the adsorbent membrane based on the analysis results. The adsorption capacity is calculated using the following formula: Adsorption capacity A = (C0 - C1) / S, where C0 is the initial ion concentration in the solution, C1 is the ion concentration in the solution at the end of adsorption, and S is the effective membrane area.

[0031] This invention is not limited to the above embodiments. Based on the technical solutions disclosed in this invention, those skilled in the art can make some substitutions and modifications to some of the technical features without creative effort, and all such substitutions and modifications are within the protection scope of this invention.

Claims

1. A method for preparing an adsorbent membrane, characterized in that: A lithium-extraction adsorbent specifically designed for salt lake extraction is incorporated into a casting solution, which is then uniformly coated onto a high-strength, acid- and alkali-resistant nonwoven fabric. An adsorbent membrane is prepared via a phase inversion process. The casting solution comprises, by mass percentage, the following components: 8%–15% polyvinylidene fluoride, 30%–50% lithium-extraction adsorbent specifically designed for salt lake extraction, 1%–10% pore-forming agent, and 20%–50% organic solvent.

2. The method for preparing an adsorbent membrane according to claim 1, characterized in that: The pore-forming agent is one or more of polyethylene glycol, polyvinylpyrrolidone, and lithium chloride.

3. The method for preparing an adsorbent membrane according to claim 1, characterized in that: The organic solvent is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

4. The method for preparing an adsorbent membrane according to claim 1, characterized in that: The adsorbent for lithium extraction from salt lakes is one or a combination of aluminum-based adsorbents, manganese-based spinel oxide adsorbents, and titanium-based spinel oxide adsorbents.

5. The method for preparing an adsorbent membrane according to claim 1, characterized in that: The high-strength acid and alkali resistant nonwoven fabric is one of polyester nonwoven fabric, polypropylene nonwoven fabric, and polytetrafluoroethylene nonwoven fabric.

6. The method for preparing an adsorbent membrane according to claim 1, characterized in that: Specifically, the following steps are included: S1: Raw material pretreatment: Polyvinylidene fluoride, pore-forming agent, and special adsorbent for lithium extraction from salt lakes are dried and pretreated in an oven at 105℃. S2: Preparation of casting solution: Pretreated polyvinylidene fluoride and pore-forming agent are added to an organic solvent and dissolved completely under stirring conditions of 60℃~70℃ and 200r / min to obtain casting solution; S3: Preparation of adsorbent preparation solution: Add the casting liquid to the kneader, add the pretreated adsorbent powder, stir and mix evenly to obtain the adsorbent preparation solution; S4: Degassing treatment: Degas the adsorbent preparation solution at 30℃~80℃ and vacuum degree -0.09MPa for 12h~24h; S5: Film Formation by Scraping: The degassed adsorbent preparation solution is uniformly scraped onto the nonwoven fabric at a speed of 1m / s~8m / s; S6: Air bath treatment: Place the coated nonwoven fabric in an air bath at room temperature for 5s~60s; S7: Gel bath treatment: After air bath, the membrane is subjected to phase separation gel bath in deionized water at 0℃~20℃ for 5min~15min; S8: Rinsing and Shaping: Rinse the membrane after gel bath in deionized water at 40℃~80℃ for 20min~60min, and dry to obtain the adsorbent membrane.

7. The method for preparing an adsorbent membrane according to claim 6, characterized in that: In S5, the gap between the doctor blade and the nonwoven fabric is 200μm~300μm, preferably 250μm; the coating speed is preferably 5m / s.

8. The method for preparing an adsorbent membrane according to claim 6, characterized in that: The ambient temperature in S6 is 25℃~30℃, and the air bath time is preferably 5s~10s.

9. A method for preparing an adsorbent membrane module, characterized in that, After cutting the adsorbent membrane sheet prepared by any one of claims 1 to 8, it is rolled up with the grid and the flow guide cloth around the central tube as the axis, and then sealed, cured, assembled and tested to obtain the spiral-wound adsorbent membrane assembly.

10. An adsorbent membrane, characterized in that, Prepared by any one of the preparation methods described in claims 1 to 8, comprising a nonwoven fabric support layer and an adsorbent separation layer, wherein the adsorbent separation layer is loaded with a special adsorbent for lithium extraction from salt lakes, and the lithium ion adsorption capacity is 178 mg / m² to 280 mg / m².

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