A pspeek / cof composite membrane for reverse electrodialysis technology and a method for preparing the same

Abstract

The application discloses a PSPEEK / COF composite membrane for reverse electrodialysis technology and a preparation method thereof, and belongs to the technical field of renewable energy extraction. First, sulfonated polyether ether ketone material is synthesized by using ether ether ketone and concentrated sulfuric acid, then a porous sulfonated polyether ether ketone casting solution is prepared by adding a solvent and polyethylene glycol 400, then a COF membrane is formed above the PSPEEK casting solution by using an interfacial polymerization method, finally, the PSPEEK / COF composite membrane is obtained by removing the solvent and polyethylene glycol 400. The COF membrane with inherent pore transmission channels is prepared first, and the COF membrane is used for selectively conducting cations. The mechanical stability of the COF membrane is improved by combining the COF membrane with the PSPEEK substrate. The prepared membrane has high salt difference power generation performance and long service life.

Description

Technical Field

[0001] This invention belongs to the field of renewable energy extraction technology, and relates to a PSPEEK / COF composite membrane for reverse electrodialysis technology and its preparation method. Background Technology

[0002] Salinity gradient energy, along with tidal energy, wave energy, ocean thermal energy, ocean current energy, and marine bioenergy, is a type of renewable green energy from the ocean. Compared to other ocean energy sources, salinity gradient energy has the advantage of being less restricted by climate conditions, but it is also one of the least developed and utilized renewable energy sources among ocean energy sources. Salinity gradient energy is referred to as "blue energy" by many Western scholars, and it mainly exists at the junction of rivers and the sea. In addition, salinity gradient energy can also be utilized in salt lakes and underground salt mines in freshwater-rich areas because these places have a salt gradient difference between freshwater and saltwater. The principle of salinity gradient energy power generation is that when two salt solutions of different concentrations are mixed, salt ions in the concentrated solution spontaneously diffuse into the dilute solution until the concentrations are equal, releasing energy in the process. Therefore, salinity gradient energy power generation utilizes the chemical potential difference between seawater and freshwater, or between two types of seawater with different salinity concentrations, and converts it into usable electrical energy; it is a type of ocean energy that exists in a chemical form.

[0003] Reverse electrodialysis is widely used in the extraction of marine salinity gradient energy due to its simple equipment, low membrane fouling, and low energy consumption. The separator, as a key component of the battery, has two main functions: separating the feed solution into concentrate and desalination chambers; and directionally conducting cations to generate a potential difference. An ideal membrane in reverse electrodialysis should have the following characteristics: 1) rapid ion conduction with high ion conductivity; 2) effective prevention of multivalent ion permeation, achieving high monovalent ion selectivity; 3) high chemical stability in strong salinity environments; and 4) low commercialization cost. David A. Vermaas's article, "Influence of multivalent ions on renewable energy generation in reverse electrodialysis," primarily used commercially available membranes originally designed for electrodialysis. However, these membranes have low ion conductivity and lack monovalent ion selectivity, resulting in low power generation performance. Therefore, the development of high-performance battery separators is needed. Porous polymer membranes possess high ion permeability and good stability in high-salt solutions, but their limited ion selectivity restricts their application in the field of battery separators. Therefore, designing and developing high-performance composite membranes has become a key research area.

[0004] Covalent organic frameworks (COFs) possess high specific surface area, uniform and stable pore channels, tunable pore size (reported to be 0.5-4.7 nm), and excellent stability. Highly oriented crystallinity and ordered pore structure endow COFs with significant advantages in membrane separation. The inherent channel structure of COFs not only enables rapid ion transport but also allows for selective ion permeation due to differences in ion hydration sizes; however, their poor mechanical stability remains a challenge. Therefore, utilizing composite membrane support structures to improve the mechanical stability of COF membranes is of significant research importance. Summary of the Invention

[0005] This invention aims to improve the power generation performance of reverse electrodialysis technology and provides a PSPEEK / COF composite membrane that utilizes the pore size of COF to conduct Na+. + And prevent Mg 2+ A cation exchange membrane with high power generation performance and stable structure was prepared by permeation.

[0006] The technical solution of the present invention:

[0007] A PSPEEK / COF composite membrane for reverse electrodialysis technology is prepared by interfacial polymerization. The PSPEEK / COF composite membrane consists of two parts: an upper COF membrane and a lower porous sulfonated polyether ether ketone (PSPEEK) membrane. The COF membrane is TpPa-SO3H, and its structure is as follows:

[0008]

[0009] PSPEEK membranes are obtained by adding polyethylene glycol 400 as a porogen to sulfonated polyether ether ketone (SPEEK) polymer before film formation, and then removing the polyethylene glycol 400 after film formation. The structures of PSPEEK and SPEEK are as follows:

[0010]

[0011] Where the value of x is 70 <x<80。

[0012] The thickness of the PSPEEK membrane is 88–92 μm.

[0013] A method for preparing a PSPEEK / COF composite membrane for reverse electrodialysis technology, comprising the following steps:

[0014] First, SPEEK material is synthesized using polyetheretherketone (PEEK) and concentrated sulfuric acid. Then, solvent and polyethylene glycol 400 are added and stirred until homogeneous. Next, 2,5-diaminobenzenesulfonic acid (Pa-SO3H) is added to the casting solution to dissolve the material. Then, a solvent containing trialdehyde pyrogallol (Tp) is added to the top of the casting solution to form a COF membrane. The solvent is then removed. Finally, the composite membrane is immersed in water to remove the polyethylene glycol, thus obtaining the composite membrane. Due to the channel structure of the COF membrane, the porous sulfonated polyetheretherketone membrane (PSPEEK) can simultaneously possess high ion conductivity and selectivity, significantly improving the power generation performance of reverse electrodialysis technology.

[0015] (1) Preparation of PSPEEK casting solution: Prepare reaction solution according to the ratio of 1g PEEK to 10ml concentrated sulfuric acid, and precipitate SPEEK material with ice water; after drying, add dimethyl sulfoxide (DMSO) solvent to SPEEK to completely dissolve it, add polyethylene glycol 400 according to the mass ratio of SPEEK: polyethylene glycol 400 = 1:2.5, stir evenly to obtain colorless and transparent PSPEEK casting solution, seal and store for later use;

[0016] (2) Preparation of PSPEEK / COF composite membrane: At room temperature, 2,5-diaminobenzenesulfonic acid (Pa-SO3H) was added to the PSPEEK casting solution and stirred until it was completely dissolved to obtain a transparent solution; then solvent A containing trialdehyde phloroglucinol (Tp) was added above the PSPEEK casting solution. After 24 hours, a COF membrane was formed at the interface. The solvent A was removed by heating, and then the temperature was raised to 80℃ to remove DMSO. Finally, the membrane was cooled to room temperature and immersed in deionized water for 24 hours to completely remove polyethylene glycol 400 to obtain the PSPEEK / COF composite membrane.

[0017] Solvent A is one of n-hexane and n-octane;

[0018] The molar ratio of Tp:Pa-SO3H is 2:3;

[0019] The drying conditions in step (1) are: temperature of 60-80℃ and time of more than 12 hours.

[0020] The stirring time in step (1) is more than 12 hours.

[0021] The drying time for removing dimethyl sulfoxide in step (2) is 36 to 48 hours.

[0022] The temperature for removing solvent A in step (2) is 40-50°C, and the time is 2-6 hours.

[0023] The beneficial effects of the present invention are as follows: The present invention prepares a sulfonic acid COF composite membrane, which can be used for salinity gradient power generation, has high ion conductivity, high chemical stability, and a longer service life. Detailed Implementation

[0024] The present invention will be further described in detail below with reference to specific implementation examples, but the implementation of the present invention is not limited thereto.

[0025] Example 1

[0026] Preparation of PSPEEK casting solution: 10g of PEEK was placed in a single-necked flask and 100ml of concentrated sulfuric acid was added to dissolve it completely. After mechanical stirring at 60℃ for 2 hours, SPEEK material was precipitated with ice water. After drying, 1.25g of SPEEK was placed in a 100ml beaker, and 50ml of dimethyl sulfoxide (DMSO) was added. The mixture was magnetically stirred until completely dissolved, and then 2.5g of polyethylene glycol 400 was added and stirring was continued for 6 hours to obtain a uniform PSPEEK casting solution.

[0027] Preparation of PSPEEK / COF composite membrane: At room temperature, 0.12 mmol of 2,5-diaminobenzenesulfonic acid (Pa-SO3H) was added to 12 ml of PSPEEK casting solution and stirred until completely dissolved to obtain a transparent solution; then 0.08 mmol of trialdehyde phloroglucinol (Tp) was dissolved in 8 ml of n-hexane, and the resulting solution was slowly poured on top of the PSPEEK casting solution. After 24 h, a COF membrane was formed at the interface. The temperature was raised to 50 °C to remove n-hexane, and then raised to 80 °C to remove DMSO. Finally, the membrane was cooled to room temperature and immersed in deionized water for 24 h to completely remove polyethylene glycol 400, resulting in the PSPEEK / COF-1 composite membrane.

[0028] Example 2

[0029] Preparation of PSPEEK casting solution: Same as in Example 1

[0030] Preparation of PSPEEK / COF composite membrane: At room temperature, 0.18 mmol of 2,5-diaminobenzenesulfonic acid (Pa-SO3H) was added to 12 ml of PSPEEK casting solution and stirred until completely dissolved to obtain a transparent solution; then 0.12 mmol of trialdehyde phloroglucinol (Tp) was dissolved in 8 ml of n-hexane, and the resulting solution was slowly poured on top of the PSPEEK casting solution. After 24 h, a COF membrane was formed at the interface. The temperature was raised to 50 °C to remove n-hexane, and then raised to 80 °C to remove DMSO. Finally, the membrane was cooled to room temperature and immersed in deionized water for 24 h to completely remove polyethylene glycol 400, resulting in the PSPEEK / COF-2 composite membrane.

[0031] Example 3

[0032] Preparation of PSPEEK casting solution: Same as in Example 1

[0033] Preparation of PSPEEK / COF composite membrane: At room temperature, 0.24 mmol of 2,5-diaminobenzenesulfonic acid (Pa-SO3H) was added to 12 ml of PSPEEK casting solution and stirred until completely dissolved to obtain a transparent solution; then 0.16 mmol of trialdehyde phloroglucinol (Tp) was dissolved in 8 ml of n-hexane, and the resulting solution was slowly poured on top of the PSPEEK casting solution. After 24 h, a COF membrane was formed at the interface. The temperature was raised to 50 °C to remove n-hexane, and then raised to 80 °C to remove DMSO. Finally, the membrane was cooled to room temperature and immersed in deionized water for 24 h to completely remove polyethylene glycol 400, resulting in the PSPEEK / COF-3 composite membrane.

[0034] Example 4

[0035] Preparation of PSPEEK casting solution: Same as in Example 1

[0036] Preparation of PSPEEK / COF composite membrane: At room temperature, 0.36 mmol of 2,5-diaminobenzenesulfonic acid (Pa-SO3H) was added to 12 ml of PSPEEK casting solution and stirred until completely dissolved to obtain a transparent solution; then 0.24 mmol of trialdehyde phloroglucinol (Tp) was dissolved in 8 ml of n-hexane, and the resulting solution was slowly poured on top of the PSPEEK casting solution. After 24 h, a COF membrane was formed at the interface. The temperature was raised to 50 °C to remove n-hexane, and then raised to 80 °C to remove DMSO. Finally, the membrane was cooled to room temperature and immersed in deionized water for 24 h to completely remove polyethylene glycol 400, resulting in the PSPEEK / COF-4 composite membrane.

[0037] The maximum power density of the COF composite membrane for salinity gradient power generation prepared by this invention is shown in Table 1:

[0038] Table 1. Thickness and maximum power density of the COF composite membrane for salinity gradient power generation prepared according to the present invention.

[0039] composition COF film thickness PSPEEK film thickness Maximum power density Example 1 PSPEEK / COF-1 7μm 91μm <![CDATA[0.63W / m 2 ]]> Example 2 PSPEEK / COF-2 11μm 89μm <![CDATA[1.04W / m 2 ]]> Example 3 PSPEEK / COF-3 14μm 90μm <![CDATA[0.97W / m 2 ]]> Example 4 PSPEEK / COF-4 20μm 90μm <![CDATA[0.86W / m 2 ]]>

Claims

1. A method for preparing a PSPEEK / COF composite membrane for reverse electrodialysis technology, wherein the PSPEEK / COF composite membrane for reverse electrodialysis technology is prepared by interfacial polymerization; characterized in that, The PSPEEK / COF composite membrane consists of two parts: an upper COF membrane and a lower porous sulfonated polyether ether ketone (PSPEEK) membrane; the COF membrane is TpPa-SO3H, and its structure is as follows: PSPEEK membranes are obtained by adding polyethylene glycol 400 as a porogen to sulfonated polyether ether ketone (PEEEK) polymer before film formation, and then removing the PPEEK 400 after film formation. The structures of PSPEEK and SPEEK are as follows: Where the value of x is 70 <x<80; The thickness of the PSPEEK membrane is 88~92 μm; The specific steps are as follows: (1) Preparation of PSPEEK casting solution: Prepare reaction solution according to the ratio of 1g PEEK to 10ml concentrated sulfuric acid, and precipitate SPEEK material with ice water; after drying, add dimethyl sulfoxide to SPEEK to completely dissolve it, add polyethylene glycol 400 according to the mass ratio of SPEEK: polyethylene glycol 400 = 1:2.5, stir evenly to obtain colorless and transparent PSPEEK casting solution, seal and store for later use; (2) Preparation of PSPEEK / COF composite membrane: At room temperature, 2,5-diaminobenzenesulfonic acid Pa-SO3H was added to the PSPEEK casting solution and stirred until it was completely dissolved to obtain a transparent solution; then solvent A containing trialdehyde phloroglucinol Tp was added to the PSPEEK casting solution. After 24 hours, a COF membrane was formed at the interface. The solvent A was removed by heating, and then the temperature was raised to 80 °C to remove dimethyl sulfoxide. Finally, the membrane was cooled to room temperature and immersed in deionized water for 24 hours to completely remove polyethylene glycol 400 to obtain the PSPEEK / COF composite membrane. Solvent A is one of n-hexane and n-octane; The molar ratio of Tp:Pa-SO3H is 2:

3.

2. The preparation method according to claim 1, characterized in that, The drying conditions in step (1) are: temperature of 60~80℃ and time of more than 12 hours.

3. The preparation method according to claim 1, characterized in that, The stirring time in step (1) is more than 12 hours.

4. The preparation method according to claim 1, characterized in that, The temperature for removing solvent A in step (2) is 40~50 ℃ and the time is 2~6 hours.

5. The preparation method according to claim 1, characterized in that, The drying time for removing dimethyl sulfoxide in step (2) is 36 to 48 hours.

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