A modified poly(m-phenylene isophthalamide) membrane with oil-water separation properties, its preparation method and application

Abstract

This invention relates to a modified poly(m-phenylene isophthalamide) membrane with oil-water separation properties, its preparation method, and its applications. The method includes the following steps: S1, triethanolamine, hexadecyltrimethylammonium bromide, sodium salicylate, and tetraethyl orthosilicate are sequentially added to deionized water and mixed to obtain silica particles; S2, the silica particles are mixed with tannic acid and polyethyleneimine to obtain tannic acid and polyethyleneimine-modified silica particles; S3, the tannic acid and polyethyleneimine-modified silica particles are mixed with poly(m-phenylene isophthalamide) to prepare a casting solution; S4, the casting solution is coated onto a substrate to obtain the modified poly(m-phenylene isophthalamide) membrane. Compared with existing technologies, this invention has a simple preparation process, good production process stability, and the prepared SiO2@TA-PEI modified PMIA membrane has high water flux and good oil-water emulsion retention effect, effectively separating oil-water emulsions and showing potential application value in oily wastewater treatment.

Description

Technical Field

[0001] This invention relates to the field of membrane separation technology, and in particular to a modified poly(m-phenylene isophthalamide) membrane with oil-water separation properties, its preparation method, and its application. Background Technology

[0002] Oily wastewater is an important area of ​​industrial and domestic wastewater treatment. Among various forms of oil, oil-water emulsions (especially emulsions stabilized by surfactants) are the most difficult to separate due to their excellent stability and tiny droplet size (<20μm). Compared with traditional degreasing, flotation, and chemical flocculation separation methods, membrane separation technology is considered a promising method for separating oil-water emulsions due to its advantages such as high separation efficiency, low cost, ease of operation, and no secondary pollution.

[0003] Poly(m-phenylene isophthalamide) membranes are synthetic high-performance fibers with good thermal stability, chemical corrosion resistance, and excellent mechanical properties. Due to the large number of amide groups in the PMIA membrane molecular structure, it possesses high surface free energy, thus being considered an excellent hydrophilic membrane material. The "hydration layer" on the surface of hydrophilic membranes can effectively mitigate oil contamination during oil-water separation, achieving good separation results. Chinese patent CN107158960A discloses a method for preparing a high-flux and anti-fouling poly(m-phenylene isophthalamide) nanofiltration membrane, which uses the synergistic effect of graphene oxide and sulfonated polyether ether ketone to improve the flux and anti-fouling performance of the poly(m-phenylene isophthalamide) nanofiltration membrane. However, it still struggles to solve the problem of difficult oil-water emulsion separation. Summary of the Invention

[0004] The purpose of this invention is to overcome the defects of the prior art by providing a modified poly(m-phenylene isophthalamide) membrane with oil-water separation performance, its preparation method and application, to solve the problem of difficult separation of oil-water emulsions.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] On one hand, the present invention provides a method for preparing a modified poly(m-phenylene isophthalamide) membrane with oil-water separation properties, comprising the following steps:

[0007] S1. Triethanolamine (TEA), hexadecyltrimethylammonium bromide (CTAB), sodium salicylate (NaSal), and tetraethyl orthosilicate (TEOS) were added to deionized water in sequence and mixed. The mixture was stirred evenly, then centrifuged, the supernatant was removed, the lower precipitate was taken, and finally the precipitate was calcined to obtain silicon dioxide (SiO2) particles.

[0008] S2. The SiO2 particles obtained in S1 are mixed with tannic acid (TA) and polyethyleneimine (PEI) and stirred with ultrasound. Then, the mixture is centrifuged, the supernatant is removed, the lower precipitate is taken, and finally the precipitate is vacuum dried to obtain SiO2@TA-PEI particles.

[0009] S3. The SiO2@TA-PEI particles obtained in S2 are mixed with poly(m-phenylene isophthalamide) (PMIA) to prepare a casting solution.

[0010] S4. The casting solution is scraped onto the substrate and then placed in a gel bath for phase separation to obtain a modified PMIA film containing SiO2@TA-PEI particles.

[0011] Furthermore, in S1, the mass ratio of triethanolamine, hexadecyltrimethylammonium bromide, sodium salicylate, and tetraethyl orthosilicate is (0.1-3):(0.1-10):(0.1-10):(20-30).

[0012] Preferably, in S1, the mass ratio of triethanolamine, hexadecyltrimethylammonium bromide, sodium salicylate, and tetraethyl orthosilicate is (0.3-0.5):(1.5-2.5):3:(23-28).

[0013] Furthermore, in S1, the calcination temperature is 400–600°C, and the calcination time is 1.5–20 h.

[0014] Furthermore, in S1, the stirring method is magnetic stirring.

[0015] Furthermore, in S2, the mass ratio of the silica particles, tannic acid, and polyethyleneimine is (0.1-10):(0.1-10):(0.1-10).

[0016] Preferably, in S2, the mass ratio of the silica particles, tannic acid, and polyethyleneimine is (1-1.2):(1.8-2):(1.6-2).

[0017] Furthermore, in S2, the centrifugation rate is 5000-8000 rpm.

[0018] Furthermore, in S2, the temperature of the vacuum drying is 40–100°C.

[0019] Furthermore, in S3, the specific process of preparing the casting solution is as follows: SiO2@TA-PEI particles, co-solvent and PMIA are added to N,N-dimethylacetamide (DMAC) and stirred evenly to obtain the casting solution.

[0020] Furthermore, in S3, the mass ratio of SiO2@TA-PEI particles, co-solvent, and PMIA is (0.1~2):(0.1~5):(15~25).

[0021] Preferably, in S3, the mass ratio of SiO2@TA-PEI particles, co-solvent, and PMIA is (0.1-0.5):2:(9-10).

[0022] Furthermore, in S3, the co-solvent is lithium chloride.

[0023] Furthermore, in S3, the stirring temperature is 30–80°C, and the stirring time is 8–48 h.

[0024] Furthermore, in S4, the coating thickness of the casting liquid on the substrate is 100–300 μm.

[0025] Furthermore, in S4, the gel bath is carried out in deionized water, and the temperature of the gel bath is 10–40°C.

[0026] On the other hand, the present invention also provides a modified poly(m-phenylene isophthalamide) membrane with oil-water separation properties, which is prepared by the preparation method described above.

[0027] On the other hand, the present invention also provides an application of a modified poly(m-phenylene isophthalamide) membrane with oil-water separation properties.

[0028] Specifically, it can be used in the field of oil-water separation of oily wastewater.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The method of preparing SiO2@TA-PEI modified PMIA film of the present invention is simple and easy to operate, with a short process cycle, no energy consumption required, low cost, and good production process stability.

[0031] (2) The SiO2@TA-PEI modified PMIA membrane prepared in this invention not only has good permeability, but also a pure water flux of up to 330 L·(h) -1 ·m -2 Furthermore, the membrane maintains its oil-water separation performance even after immersion in common solvents for 12 hours, demonstrating excellent stability. In addition, the membrane exhibits good hydrophilicity and antifouling properties, with a contact angle of 37° measured in air, making it difficult for oil droplets to adhere to the membrane surface. This significantly improves the separation efficiency of oil-water emulsions, reaching over 95%. Therefore, this membrane has significant application potential in oily wastewater treatment, effectively separating oil-water emulsions and providing a highly efficient and stable solution for oil-water separation technology. Attached Figure Description

[0032] Figure 1 This is a SEM image of SiO2@TA-PEI obtained in Example 1 of the present invention;

[0033] Figure 2 These are comparison images of the oil-water emulsion before and after separation in Example 1 of the present invention.

[0034] Figure 3 The images show a microscopic comparison of the oil-water emulsion before and after separation in Example 1 of the present invention: (a) before separation, (b) after separation. Detailed Implementation

[0035] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. Any preparation methods, materials, structures, or compositional ratios not explicitly described in this technical solution are considered common technical features disclosed in the prior art.

[0036] Table 1 lists the specifications and manufacturers of the materials and reagents used in the following embodiments. Unless otherwise specified, all other raw materials or processing techniques are commercially available materials or conventional techniques in the field.

[0037] Table 1 Materials and Reagents

[0038]

[0039] The permeation and retention properties of a modified PMIA membrane were studied using pressurized membrane separation technology. Specifically, under a certain pressure, small-molecule solutes and solvents pass through the membrane with a specific pore size, while large-molecule solutes are retained.

[0040] An oil-water emulsion was prepared by blending oil components (n-hexadecane, n-heptane, n-hexane, and cyclohexane), deionized water, and a surfactant (Tween 80). The volume ratio of water to oil components was 99:1, and the Tween 80 concentration was 10 mg / L after a 10-fold dilution. The emulsion was ultrasonically dispersed at room temperature for 30 min and stirred for 8 h to obtain a stable oil-water emulsion. A specific volume of the emulsion was then poured into a vacuum filtration apparatus. The separation process began after the system pressure reached 0.1 MPa and was operated at room temperature.

[0041] Finally, the separation efficiency R is calculated using equation (1), and the permeation flux J (L·m) is calculated using equation (2). -2 ·h -1 ),as follows:

[0042]

[0043] Where R is the separation efficiency, and M1 and M2 are the weight of the filtered permeate and the mass (g) of the feed liquid, respectively.

[0044]

[0045] Where Q is the permeation volume, T is the time it takes for the oil-water emulsion to pass through the membrane, and A is the effective filtration area of ​​the sample.

[0046] Example 1

[0047] This embodiment is used to prepare a modified poly(m-phenylene isophthalamide) membrane with oil-water separation properties. The specific preparation method is as follows:

[0048] S1. At room temperature, 0.3 g TEA was added to 100 mL of deionized water and magnetically stirred for 2.5 h. Then, 2.5 g CTAB and 3 g NaSal were added to the solution, and the mixture was stirred for another 2.5 h. Next, 30 mL TEOS was added to the above solution, and the mixture was stirred at 80 °C for another 2.5 h. After standing for 30 min, the mixture was centrifuged at 8000 rpm for 30 min. The supernatant was discarded, and the lower precipitate was collected. The precipitate was dried at 50 °C for 48 h, and finally calcined in a muffle furnace at 550 °C for 5 h to obtain SiO2 particles.

[0049] S2. Weigh 1.8g of TA and place it in a 250mL beaker. Add 120mL of deionized water and stir for 1.5h to completely dissolve the TA, obtaining solution A. Take 1g of SiO2 particles and place them in 80mL of deionized water, then pour them into solution A. Stir for 1.5h to obtain a TA-SiO2 suspension. Weigh 1.6g of PEI and pour it into 40mL of deionized water. Stir for 1.5h, then quickly pour in hydrochloric acid solution to adjust the pH to 8. Stir for 2h, then pour the resulting solution into the above TA-SiO2 suspension and continue stirring for 12h. Let it stand for 30min. Centrifuge at 8000rpm for 25min, remove the lower precipitate, place the precipitate in a crucible, and vacuum dry in a 60℃ oven for 12h to finally obtain SiO2@TA-PEI particles, which are then ground into powder.

[0050] S3. Dissolve 0.1g SiO2@TA-PEI particles, 2g lithium chloride, and 9.25g PMIA in 80mL DMAc and stir at 80℃ for 24h until fully dissolved to prepare the casting solution.

[0051] S4. The casting solution is coated onto a glass plate to a thickness of 250 μm. The glass plate with the coating solution is then immersed in a coagulation bath of deionized water at 20 °C for phase separation to obtain a modified PMIA membrane containing SiO2@TA-PEI particles, denoted as M1 membrane.

[0052] The water flux and oil-water emulsion rejection rate of the M1 membrane prepared in Example 1 were tested. The water flux was 330 L·(h) -1 ·m-2 The oil-water separation performance of the M1 membrane was tested using 100g of oil-water emulsion (oil to water volume ratio of 1:9), and the oil rejection rate was 95%.

[0053] Figure 1 The image shows a SEM image of SiO2@TA-PEI prepared in Example 1. As can be seen from the image, SiO2@TA-PEI consists of regular and uniform spherical particles with a diameter of less than 100 nm.

[0054] Figure 2 The figure shows a comparison of the oil-water emulsion before and after retention. As can be seen from the figure, the modified PMIA membrane has a good retention effect. Therefore, this modification scheme significantly improves the hydrophilicity and oil-water separation ability of the PMIA membrane. The modified PMIA membrane has good application prospects in the treatment of oily wastewater.

[0055] Figure 3 These are microscopic comparison images of the oil-water emulsion before and after separation in Example 1. The oil-water emulsions before and after separation were photographed under an optical microscope. Figure 3 (a) is a microscopic image before separation. Figure 3 (b) is a microscopic image after separation. It can be seen that the modified PMIA membrane can effectively trap oil droplets, and the liquid obtained after trapping has almost no oil droplets.

[0056] Example 2

[0057] This embodiment is used to prepare a modified poly(m-phenylene isophthalamide) membrane with oil-water separation properties. The specific preparation method is as follows:

[0058] S1. At room temperature, 0.5 g TEA was added to 100 mL of deionized water and magnetically stirred for 2.5 h. Then, 1.5 g CTAB and 3 g NaSal were added to the solution, and the mixture was stirred for another 2.5 h. Next, 25 mL TEOS was added to the above solution, and the mixture was stirred at 80 °C for another 2.5 h. After standing for 30 min, the mixture was centrifuged at 8000 rpm for 30 min. The supernatant was discarded, and the lower precipitate was collected. The precipitate was dried at 50 °C for 48 h, and finally calcined in a muffle furnace at 550 °C for 5 h to obtain SiO2 particles.

[0059] S2. Weigh 1.8g of TA and place it in a 250mL beaker. Add 120mL of deionized water and stir for 1.5h to completely dissolve the TA, obtaining solution A. Take 1g of SiO2 particles and place them in 80mL of deionized water, then pour them into solution A. Stir for 1.5h to obtain a TA-SiO2 suspension. Weigh 1.6g of PEI and pour it into 40mL of deionized water. Stir for 1.5h, then quickly pour in hydrochloric acid solution to adjust the pH to 8. Stir for 2h, then pour the resulting solution into the above TA-SiO2 suspension and continue stirring for 12h. Let it stand for 30min. Centrifuge at 8000rpm for 25min, remove the lower precipitate, place the precipitate in a crucible, and vacuum dry in a 60℃ oven for 12h to finally obtain SiO2@TA-PEI particles, which are then ground into powder.

[0060] S3. Dissolve 0.1g SiO2@TA-PEI particles, 2g lithium chloride, and 9.25g PMIA in 80mL DMAc and stir at 80℃ for 24h until fully dissolved to prepare the casting solution.

[0061] S4. The casting solution is coated onto a glass plate to a thickness of 250 μm. The glass plate with the coating solution is then immersed in a coagulation bath composed of deionized water at 20 °C for phase separation to obtain a modified PMIA membrane containing SiO2@TA-PEI particles, denoted as M2 membrane.

[0062] The water flux of M2 is 298 L·(h) -1 ·m -2 The oil retention rate was 87%.

[0063] Example 3

[0064] This embodiment is used to prepare a modified poly(m-phenylene isophthalamide) membrane with oil-water separation properties. The specific preparation method is as follows:

[0065] S1. At room temperature, 0.3 g TEA was added to 100 mL of deionized water and magnetically stirred for 2.5 h. Then, 2.5 g CTAB and 3 g NaSal were added to the solution, and the mixture was stirred for another 2.5 h. Next, 30 mL TEOS was added to the above solution, and the mixture was stirred at 80 °C for another 2.5 h. After standing for 30 min, the mixture was centrifuged at 8000 rpm for 30 min. The supernatant was discarded, and the lower precipitate was collected. The precipitate was dried at 50 °C for 48 h, and finally calcined in a muffle furnace at 550 °C for 5 h to obtain SiO2 particles.

[0066] S2. Weigh 2g of TA and place it in a 250mL beaker. Add 120mL of deionized water and stir for 1.5h to completely dissolve the TA, obtaining solution A. Take 1.2g of SiO2 particles and place them in 80mL of deionized water, then pour them into solution A. Stir for 1.5h to obtain a TA-SiO2 suspension. Weigh 2g of PEI and pour it into 50mL of deionized water. Stir for 1.5h, then quickly pour in hydrochloric acid solution to adjust the pH to 8. Stir for 2h, then pour the resulting solution into the above TA-SiO2 suspension and continue stirring for 12h. Let it stand for 30min. Centrifuge at 8000rpm for 25min, remove the lower precipitate, place the precipitate in a crucible, and vacuum dry in a 60℃ oven for 12h to finally obtain SiO2@TA-PEI particles, which are then ground into powder.

[0067] S3. Dissolve 0.1g SiO2@TA-PEI particles, 2g lithium chloride, and 9.25g PMIA in 80mL DMAc and stir at 80℃ for 24h until fully dissolved to prepare the casting solution.

[0068] S4. The casting solution is coated onto a glass plate to a thickness of 250 μm. The glass plate with the coating solution is then immersed in a coagulation bath of deionized water at 20 °C for phase separation to obtain a modified PMIA membrane containing SiO2@TA-PEI particles, denoted as M3 membrane.

[0069] The water flux of M3 is 309 L·(h) -1 ·m -2 The oil retention rate was 91%.

[0070] Example 4

[0071] This embodiment is used to prepare a modified poly(m-phenylene isophthalamide) membrane with oil-water separation properties. The specific preparation method is as follows:

[0072] S1. At room temperature, 0.3 g TEA was added to 100 mL of deionized water and magnetically stirred for 2.5 h. Then, 2.5 g CTAB and 3 g NaSal were added to the solution, and the mixture was stirred for another 2.5 h. Next, 30 mL TEOS was added to the above solution, and the mixture was stirred at 80 °C for another 2.5 h. After standing for 30 min, the mixture was centrifuged at 8000 rpm for 30 min. The supernatant was discarded, and the lower precipitate was collected. The precipitate was dried at 50 °C for 48 h, and finally calcined in a muffle furnace at 550 °C for 5 h to obtain SiO2 particles.

[0073] S2. Weigh 1.8g of TA and place it in a 250mL beaker. Add 120mL of deionized water and stir for 1.5h to completely dissolve the TA, obtaining solution A. Take 1g of SiO2 particles and place them in 80mL of deionized water, then pour them into solution A. Stir for 1.5h to obtain a TA-SiO2 suspension. Weigh 1.6g of PEI and pour it into 40mL of deionized water. Stir for 1.5h, then quickly pour in hydrochloric acid solution to adjust the pH to 8. Stir for 2h, then pour the resulting solution into the above TA-SiO2 suspension and continue stirring for 12h. Let it stand for 30min. Centrifuge at 8000rpm for 25min, remove the lower precipitate, place the precipitate in a crucible, and vacuum dry in a 60℃ oven for 12h to finally obtain SiO2@TA-PEI particles, which are then ground into powder.

[0074] S3. Dissolve 0.5g SiO2@TA-PEI particles, 2g lithium chloride, and 10g PMIA in 80mL DMAc and stir at 80℃ for 24h until fully dissolved to prepare the casting solution.

[0075] S4. The casting solution is coated onto a glass plate to a thickness of 250 μm. The glass plate with the coating solution is then immersed in a coagulation bath composed of deionized water at 20 °C for phase separation to obtain a modified PMIA membrane containing SiO2@TA-PEI particles, denoted as M4 membrane.

[0076] The water flux of M4 is 315 L·(h) -1 ·m -2 The oil retention rate was 92%.

[0077] Comparative Example 1

[0078] This embodiment is used to prepare a poly(m-phenylene isophthalamide) membrane that does not contain SiO2@TA-PEI particles. The specific preparation method is as follows:

[0079] S1. Dissolve 2g of lithium chloride and 9.25g of PMIA in 80mL of DMAc and stir at 80℃ for 24h until fully dissolved to prepare the casting solution.

[0080] S2. The casting solution is coated onto a glass plate to a thickness of 250 μm. The glass plate with the coating solution is then immersed in a coagulation bath composed of deionized water at 20 °C for phase separation to obtain an unmodified PMIA membrane, denoted as M0 membrane.

[0081] The water flux of M0 is 276 L·(h) -1 ·m -2 The oil rejection rate is 20%.

[0082] As can be seen from the test results in Examples 1-4 and Comparative Example 1, the modified PMIA membrane containing SiO2@TA-PEI particles exhibits superior permeability and better water-oil separation performance compared with the unmodified PMIA membrane.

[0083] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing a modified poly(m-phenylene isophthalamide) membrane with oil-water separation properties, characterized in that, Includes the following steps: S1. Triethanolamine, hexadecyltrimethylammonium bromide, sodium salicylate, and tetraethyl orthosilicate are added sequentially to deionized water and mixed. After calcination, silica particles are obtained. S2. Mix the silica particles obtained in S1 with tannic acid and polyethyleneimine to obtain silica particles modified with tannic acid and polyethyleneimine. S3. The tannic acid and polyethyleneimine-modified silica particles obtained in S2 are mixed with poly(m-phenylene isophthalamide) to prepare a casting solution. S4. The casting solution is scraped onto the substrate and then placed in a gel bath for phase separation to obtain a modified poly(m-phenylene isophthalamide) membrane.

2. The method for preparing a modified poly(m-phenylene isophthalamide) membrane with oil-water separation properties according to claim 1, characterized in that, In S1, the mass ratio of triethanolamine, hexadecyltrimethylammonium bromide, sodium salicylate, and tetraethyl orthosilicate is (0.1-3):(0.1-10):(0.1-10):(20-30), the calcination temperature is 400-600℃, and the calcination time is 1.5-20h.

3. The method for preparing a modified poly(m-phenylene isophthalamide) membrane with oil-water separation properties according to claim 1, characterized in that, In S2, the mass ratio of the silica particles, tannic acid, and polyethyleneimine is (0.1-10):(0.1-10):(0.1-10).

4. The method for preparing a modified poly(m-phenylene isophthalamide) membrane with oil-water separation properties according to claim 1, characterized in that, In S3, the specific process of preparing the casting solution is as follows: Tannic acid, polyethyleneimine-modified silica particles, co-solvent, and poly(m-phenylene isophthalamide) are added to N,N-dimethylacetamide and stirred evenly to obtain the casting solution.

5. The method for preparing a modified poly(m-phenylene isophthalamide) membrane with oil-water separation properties according to claim 4, characterized in that, The mass ratio of the tannic acid and polyethyleneimine-modified silica particles, the co-solvent, and poly(m-phenylene isophthalamide) is (0.1–2):(0.1–5):(15–25), and the co-solvent is lithium chloride.

6. The method for preparing a modified poly(m-phenylene isophthalamide) membrane with oil-water separation properties according to claim 4, characterized in that, The stirring temperature is 30–80°C, and the stirring time is 8–48 hours.

7. The method for preparing a modified poly(m-phenylene isophthalamide) membrane with oil-water separation properties according to claim 1, characterized in that, In S4, the coating thickness of the casting liquid on the substrate is 100-300 μm.

8. The method for preparing a modified poly(m-phenylene isophthalamide) membrane with oil-water separation properties according to claim 1, characterized in that, In S4, the gel bath is carried out in deionized water, and the temperature of the gel bath is 10-40°C.

9. A modified poly(m-phenylene isophthalamide) membrane with oil-water separation properties, characterized in that, Prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the modified poly(m-phenylene isophthalamide) membrane with oil-water separation performance as described in claim 9 in oil-water separation.

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