Super-hydrophilic self-cleaning separation membrane and preparation method thereof

Abstract

In order to solve the technical problems that the existing polymer separation membrane has poor anti-pollution performance and cannot be cleaned efficiently, the present application provides an ultrahydrophilic self-cleaning separation membrane and a preparation method thereof, specifically comprising: one, stirring amino malononitrile p-toluenesulfonic acid and manganese metal salt and adding them into an alkaline aqueous solution with a pH of 8.0-9.5 to obtain a mixed solution A; two, immersing a polymer membrane cleaned with alcohol and water step by step in the mixed solution A, and cleaning after coating; three, adding manganese metal salt into an alkaline aqueous solution with a pH of 8.0-9.5 to obtain a solution B; four, transferring the modified membrane obtained in the step two into the solution B, and cleaning after coating to obtain a modified membrane. The present application not only effectively gives the modified membrane ultrahydrophilicity, but also gives the modified membrane self-cleaning regeneration performance. The ultrahydrophilic self-cleaning modified membrane prepared by the present application can be widely applied in hydrophilic modification, oil-water separation, catalysis and other fields.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of polymer separation membranes, and particularly relates to a super-hydrophilic self-cleaning separation membrane and a preparation method thereof. BACKGROUND

[0002] Pressure-driven separation membrane processes play an increasingly important role in low-carbon wastewater treatment and water purification, which are closely related to the sustainable development of human society. Membrane fouling caused by the adsorption of pollutants at the separation membrane / water solution interface limits the effective and persistent operation of membrane modules and equipment. Therefore, developing effective membrane antifouling strategies is crucial to provide sufficient clean water. However, traditional membrane separation processes are severely limited by the ubiquitous membrane fouling and require energy or cost-intensive cleaning, which significantly increases production and maintenance costs. Self-cleaning membranes, which can repel and degrade pollutants with environmental stimuli (chemical, light, electricity, force, etc.), provide a great development prospect for membrane antifouling. However, there are still great challenges in how to construct a self-cleaning coating on widely used hydrophobic polymer membranes to prepare self-cleaning separation membranes. SUMMARY

[0003] In order to solve the technical problems of poor antifouling performance of existing polymer separation membranes and inability to perform efficient cleaning, the present application provides a super-hydrophilic self-cleaning separation membrane and a preparation method thereof.

[0004] A preparation method of a super-hydrophilic self-cleaning separation membrane, comprising the following steps:

[0005] I. Amino malonitrile p-toluenesulfonic acid and manganese metal salt are added to an alkaline aqueous solution with a pH of 8.0-9.5 while stirring to obtain a mixed solution A;

[0006] II. The polymer membrane washed with alcohol and water step by step is soaked in the mixed solution A, and then cleaned after coating;

[0007] III. Manganese metal salt is added to an alkaline aqueous solution with a pH of 8.0-9.5 to obtain solution B;

[0008] IV. The modified membrane obtained in step II is transferred to solution B, and then cleaned after coating to obtain a modified membrane.

[0009] The manganese metal salt in step I and step III is manganese sulfate, manganese nitrate or manganese chloride.

[0010] The concentration of manganese metal salt in the mixed solution A in step I is 1-5 mg / mL.

[0011] The concentration of manganese metal salt in solution B in step III is 2-10 mg / mL.

[0012] The concentration of the amino malononitrile p-toluenesulfonic acid in the mixed solution A in step one is 2-20 mg / mL.

[0013] The alkaline aqueous solution in step one and step three is a buffer solution prepared by mixing 0.1 mol / L of tris-hydroxymethyl aminomethane, 0.1 mol / L of hydrochloric acid and water in a volume ratio of 1:(0.28-0.32):(0.68-0.72).

[0014] The alcohol in step two is methanol, ethanol or isopropanol, etc.

[0015] The coating time in step two and step four is 12-48 h.

[0016] The polymer film in step two is a polyvinylidene fluoride film, a polypropylene film, a polytetrafluoroethylene film or a polyethylene film, etc.

[0017] The super-hydrophilic self-cleaning separation membrane prepared by the above method has MnO2 nanomaterials grown on the surface of the polymer film.

[0018] The present application utilizes dip coating to obtain a super-hydrophilic self-cleaning separation membrane. First, an active intermediate layer is prepared by biomimetic coating, and then a MnO2 modified composite membrane is prepared by inducing hydrolysis of a metal salt solution. The modified membrane is effectively endowed with super-hydrophilicity and self-cleaning and regeneration properties. The super-hydrophilic self-cleaning modified membrane prepared by the present application can be widely applied in the fields of hydrophilic modification, oil-water separation, catalysis, etc. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is a digital photo of the polyvinylidene fluoride film original film in Example 1;

[0020] Figure 2 It is a digital photo of the polyvinylidene fluoride super-hydrophilic self-cleaning film prepared in Example 1;

[0021] Figure 3 It is a picture of the contact angle of the polyvinylidene fluoride film with water in Example 1;

[0022] Figure 4 It is a picture of the contact angle of the super-hydrophilic self-cleaning film prepared in Example 1 with water;

[0023] Figure 5 It is a scanning electron microscope photo of the polyvinylidene fluoride film in Example 1;

[0024] Figure 6 It is a scanning electron microscope photo of the super-hydrophilic self-cleaning film prepared in Example 1;

[0025] Figure 7 It is a scanning electron microscope photo of the control group modified film prepared in Example 1;

[0026] Figure 8 Transmission electron microscope photo of the super-hydrophilic self-cleaning membrane prepared in Example 1;

[0027] Figure 9 Effect photo of the super-hydrophilic self-cleaning membrane prepared in Example 1 in hydrogen peroxide solution;

[0028] Figure 10 Flux change graph of the super-hydrophilic self-cleaning membrane prepared in Example 1 with cleaning time. DETAILED DESCRIPTION

[0029] The technical scheme of the present application is not limited to the following specific embodiments, and the following examples are used to verify the beneficial effects of the present application.

[0030] A preparation method of a super-hydrophilic self-cleaning separation membrane, comprising the following steps:

[0031] I. Amino propandinitrile p-toluenesulfonic acid and manganese metal salt are added into an alkaline aqueous solution with pH of 8.0-9.5 under stirring to obtain a mixed solution A, the concentration of manganese metal salt in the mixed solution A is 1-5 mg / mL, the manganese metal salt is manganese sulfate, manganese nitrate or manganese chloride, the concentration of amino propandinitrile p-toluenesulfonic acid in the mixed solution A is 2-20 mg / mL, and the alkaline aqueous solution is a buffer solution prepared by mixing 0.1 mol / L of tris-hydroxymethyl aminomethane, 0.1 mol / L of hydrochloric acid and water in a volume ratio of 1:(0.28-0.32):(0.68-0.72);

[0032] II. The polymer membrane cleaned with alcohol and water is immersed in the mixed solution A, and then cleaned after coating, wherein the alcohol is methanol, ethanol or isopropyl alcohol, the coating time is 12-48 h, and the polymer membrane is polyvinylidene fluoride membrane, polypropylene membrane, polytetrafluoroethylene membrane or polyethylene membrane, etc.;

[0033] III. Manganese metal salt is added into an alkaline aqueous solution with pH of 8.0-9.5 to obtain a solution B, the concentration of manganese metal salt in the solution B is 2-10 mg / mL, the manganese metal salt is manganese sulfate, manganese nitrate or manganese chloride, and the alkaline aqueous solution is a buffer solution prepared by mixing 0.1 mol / L of tris-hydroxymethyl aminomethane, 0.1 mol / L of hydrochloric acid and water in a volume ratio of 1:(0.28-0.32):(0.68-0.72);

[0034] IV. The modified membrane obtained in step II is transferred into the solution B, and then cleaned after coating to obtain a modified membrane, and the coating time is 12-48 h.

[0035] Example 1:

[0036] The preparation method of the super-hydrophilic self-cleaning separation membrane in the embodiment is specifically prepared according to the following steps:

[0037] I. Amino propandinitrile p-toluenesulfonic acid and manganese sulfate are added into an alkaline aqueous solution with a pH of 8.5 under stirring to obtain a mixed solution A, wherein the final concentration of amino propandinitrile p-toluenesulfonic acid is 5 mg / mL, the final concentration of manganese sulfate is 2.5 mg / mL, and the alkaline aqueous solution is a buffer solution prepared by mixing 0.1 mol / L tris-hydroxymethyl aminomethane, 0.1 mol / L hydrochloric acid and water at a volume ratio of 1:0.3:0.7;

[0038] II. The polyvinylidene fluoride membrane cleaned with ethanol and water is immersed in the mixed solution A, and modified for 24 hours, and then cleaned with deionized water;

[0039] III. Manganese sulfate is added into an alkaline aqueous solution with a pH of 8.5 to obtain a solution B, wherein the final concentration of manganese sulfate in the solution B is 5 mg / mL;

[0040] IV. The modified membrane obtained in step II is transferred into the solution B, and modified for 24 hours, and then cleaned with deionized water to obtain a final modified membrane.

[0041] The digital photos of the polyvinylidene fluoride membrane and the prepared super-hydrophilic self-cleaning membrane in the embodiment are shown in Figure 1 and Figure 2 It can be seen from Figure 2 that the prepared super-hydrophilic composite membrane is black and the color is relatively uniform.

[0042] The contact angle picture of the commercially available polyvinylidene fluoride membrane with water is shown in Figure 3 , and the contact angle picture of the prepared super-hydrophilic self-cleaning membrane with water in the embodiment is shown in Figure 4 . It can be seen from Figure 3 that the contact angle of the polymer-based membrane with water is about 120°, indicating that the membrane has hydrophobicity. It can be seen from Figure 4 that the contact angle of the prepared super-hydrophilic self-cleaning membrane with water is almost 0°, indicating that the membrane has super-hydrophilicity.

[0043] The scanning electron microscope photo of the commercially available polyvinylidene fluoride membrane is shown in Figure 5 , the scanning electron microscope photo of the prepared super-hydrophilic self-cleaning membrane in the embodiment is shown in Figure 6 , and the scanning electron microscope photo of the modified membrane of the control group without adding manganese sulfate in step I is shown in Figure 7 . It can be seen from Figure 5 that the porous polymer-based membrane material surface is relatively smooth. It can be seen from Figure 6 that a lot of nanoparticles are uniformly grown on the material surface of the prepared super-hydrophilic self-cleaning membrane. Figure 7It can be seen that the nanoparticles grown on the surface of the modified film in the control group without the addition of manganese sulfate in step one are very uneven.

[0044] The transmission electron microscope image of the superhydrophilic self-cleaning membrane prepared in this embodiment is shown below. Figure 8 As shown, by Figure 8 It can be seen that MnO2 nanomaterials were grown on the surface of the prepared superhydrophilic self-cleaning membrane material.

[0045] The effect of the superhydrophilic self-cleaning membrane prepared in this embodiment in hydrogen peroxide solution is shown in the following photograph. Figure 9 As shown, by Figure 9 It is known that the prepared superhydrophilic self-cleaning membrane can catalyze the decomposition of hydrogen peroxide to produce oxygen and other active substances.

[0046] The superhydrophilic self-cleaning membrane prepared in this embodiment, after filtering wastewater for a period of time, is cleaned with deionized water or dilute hydrogen peroxide solution, and its flux recovery effect is as follows: Figure 10 As shown, by Figure 10 It can be seen that, compared with the cleaning effect of pure water, the modified membrane has self-cleaning properties and can achieve self-cleaning and regeneration under the stimulation of dilute hydrogen peroxide solution.

[0047] Example 2:

[0048] The preparation method of the superhydrophilic self-cleaning separation membrane in this embodiment is specifically prepared according to the following steps:

[0049] 1. While stirring, aminomalononitrile, p-toluenesulfonic acid, and manganese sulfate are added to an alkaline aqueous solution with a pH of 8.5 to obtain mixed solution A; wherein the final concentration of aminomalononitrile, p-toluenesulfonic acid is 10 mg / mL; the final concentration of manganese sulfate is 5 mg / mL; the alkaline aqueous solution is a buffer solution prepared by mixing 0.1 mol / L tris(hydroxymethyl)aminomethane, 0.1 mol / L hydrochloric acid, and water in a volume ratio of 1:0.3:0.7.

[0050] 2. The polyvinylidene fluoride membrane, after being gradually cleaned with ethanol and water, is immersed in mixed solution A and coated for 12 hours for modification.

[0051] 3. Add manganese sulfate to an alkaline aqueous solution with a pH of 8.5 to obtain solution B; wherein the final concentration of manganese sulfate in solution B is 5 mg / mL;

[0052] 4. After cleaning the modified membrane obtained in step 2, transfer it to solution B, coat it for 48 hours, and then clean it with deionized water to obtain the final modified membrane.

[0053] Example 3:

[0054] The preparation method of the superhydrophilic self-cleaning separation membrane in this embodiment is specifically prepared according to the following steps:

[0055] I. Amino propandinitrile p-toluenesulfonic acid and manganese sulfate were added into the alkaline aqueous solution with pH of 8.5 under stirring to obtain a mixed solution A; wherein the final concentration of amino propandinitrile p-toluenesulfonic acid was 10 mg / mL; the final concentration of manganese sulfate was 5 mg / mL; the alkaline aqueous solution was a buffer solution prepared by 0.1 mol / L of tris-hydroxymethyl aminomethane, 0.1 mol / L of hydrochloric acid and water in a volume ratio of 1:0.3:0.7;

[0056] II. The polypropylene film cleaned by ethanol and water step by step was immersed in the mixed solution A to coat and modify for 24 h;

[0057] III. Manganese sulfate was added into the alkaline aqueous solution with pH of 8.5 to obtain a solution B; wherein the final concentration of manganese sulfate in the solution B was 10 mg / mL;

[0058] IV. The modified film obtained in step II was cleaned and transferred into the solution B to coat and modify for 12 h, and then cleaned by deionized water to obtain the final modified film.

[0059] Example 4:

[0060] The preparation method of the super-hydrophilic self-cleaning separation film in the example was prepared according to the following steps:

[0061] I. Amino propandinitrile p-toluenesulfonic acid and manganese sulfate were added into the alkaline aqueous solution with pH of 8.5 under stirring to obtain a mixed solution A; wherein the final concentration of amino propandinitrile p-toluenesulfonic acid was 20 mg / mL; the final concentration of manganese sulfate was 5 mg / mL; the alkaline aqueous solution was a buffer solution prepared by 0.1 mol / L of tris-hydroxymethyl aminomethane, 0.1 mol / L of hydrochloric acid and water in a volume ratio of 1:0.3:0.7;

[0062] II. The polypropylene film cleaned by ethanol and water step by step was immersed in the mixed solution A to coat and modify for 12 h;

[0063] III. Manganese sulfate was added into the alkaline aqueous solution with pH of 9.0 to obtain a solution B; wherein the final concentration of manganese sulfate in the solution B was 10 mg / mL;

[0064] IV. The modified film obtained in step II was cleaned and transferred into the solution B to coat and modify for 24 h, and then cleaned by deionized water to obtain the final modified film.

[0065] Example 5:

[0066] The preparation method of the super-hydrophilic self-cleaning separation film in the example was prepared according to the following steps:

[0067] I. Amino propandinitrile p-toluenesulfonic acid and manganese sulfate are added into the alkaline aqueous solution with pH of 8.5 under stirring to obtain a mixed solution A; the final concentration of amino propandinitrile p-toluenesulfonic acid is 20 mg / mL; the final concentration of manganese sulfate is 5 mg / mL; the alkaline aqueous solution is a buffer solution prepared by 0.1 mol / L of tris-hydroxymethyl aminomethane, 0.1 mol / L of hydrochloric acid and water in a proportion of 1:0.3:0.7 by volume ratio;

[0068] II. The polytetrafluoroethylene film cleaned by ethanol and water step by step is soaked in the mixed solution A to coat and modify for 12 hours;

[0069] III. Manganese sulfate is added into the alkaline aqueous solution with pH of 8.5 to obtain a solution B; the final concentration of manganese sulfate in the solution B is 7.5 mg / mL;

[0070] IV. The modified film obtained in step II is cleaned and transferred into the solution B to coat and modify for 24 hours, and then cleaned by deionized water to obtain the final modified film.

[0071] Example 6:

[0072] The preparation method of the super-hydrophilic self-cleaning separation film in the example is prepared according to the following steps:

[0073] I. Amino propandinitrile p-toluenesulfonic acid and manganese sulfate are added into the alkaline aqueous solution with pH of 8.5 under stirring to obtain a mixed solution A; the final concentration of amino propandinitrile p-toluenesulfonic acid is 5 mg / mL; the final concentration of manganese sulfate is 2.5 mg / mL; the alkaline aqueous solution is a buffer solution prepared by 0.1 mol / L of tris-hydroxymethyl aminomethane, 0.1 mol / L of hydrochloric acid and water in a proportion of 1:0.3:0.7 by volume ratio;

[0074] II. The polytetrafluoroethylene film cleaned by ethanol and water step by step is soaked in the mixed solution A to coat and modify for 24 hours;

[0075] III. Manganese sulfate is added into the alkaline aqueous solution with pH of 8.0 to obtain a solution B; the final concentration of manganese sulfate in the solution B is 5 mg / mL;

[0076] IV. The modified film obtained in step II is cleaned and transferred into the solution B to coat and modify for 36 hours, and then cleaned by deionized water to obtain the final modified film.

[0077] Example 7:

[0078] The preparation method of the super-hydrophilic self-cleaning separation film in the example is prepared according to the following steps:

[0079] I. Amino propandinitrile p-toluenesulfonic acid and manganese nitrate are added into an alkaline aqueous solution with pH of 8.5 under stirring to obtain a mixed solution A; the final concentration of amino propandinitrile p-toluenesulfonic acid is 10 mg / mL; the final concentration of manganese nitrate is 5 mg / mL; the alkaline aqueous solution is a buffer solution prepared by 0.1 mol / L of tris-hydroxymethyl aminomethane, 0.1 mol / L of hydrochloric acid and water in a proportion of 1:0.3:0.7 by volume ratio;

[0080] II. The polyethylene film cleaned with ethanol and water step by step is soaked in the mixed solution A to coat and modify for 24 h;

[0081] III. Manganese nitrate is added into an alkaline aqueous solution with pH of 8.0 to obtain a solution B; the final concentration of manganese nitrate in the solution B is 5 mg / mL;

[0082] IV. The modified film obtained in step II is cleaned and transferred into the solution B to coat and modify for 48 h, and then cleaned with deionized water to obtain a final modified film.

[0083] Example 8:

[0084] The preparation method of the super-hydrophilic self-cleaning separation film in the example is prepared according to the following steps:

[0085] I. Amino propandinitrile p-toluenesulfonic acid and manganese chloride are added into an alkaline aqueous solution with pH of 8.5 under stirring to obtain a mixed solution A; the final concentration of amino propandinitrile p-toluenesulfonic acid is 5 mg / mL; the final concentration of manganese chloride is 2.5 mg / mL; the alkaline aqueous solution is a buffer solution prepared by 0.1 mol / L of tris-hydroxymethyl aminomethane, 0.1 mol / L of hydrochloric acid and water in a proportion of 1:0.3:0.7 by volume ratio;

[0086] II. The polyethylene film cleaned with ethanol and water step by step is soaked in the mixed solution A to coat and modify for 24 h;

[0087] III. Manganese chloride is added into an alkaline aqueous solution with pH of 8.5 to obtain a solution B; the final concentration of manganese chloride in the solution B is 10 mg / mL;

[0088] IV. The modified film obtained in step II is cleaned and transferred into the solution B to coat and modify for 24 h, and then cleaned with deionized water to obtain a final modified film.

Claims

1. A method for preparing a super-hydrophilic self-cleaning separation membrane, comprising the following steps: I. adding amino malonitrile p-toluenesulfonic acid and manganese metal salt into an alkaline aqueous solution with pH of 8.0-9.5 while stirring to obtain a mixed solution A; II. immersing a polymer membrane washed with alcohol and water into the mixed solution A, and then washing after coating; III. adding manganese metal salt into an alkaline aqueous solution with pH of 8.0-9.5 to obtain a solution B; IV. transferring the modified membrane obtained in step II into the solution B, and then washing after coating to obtain a modified membrane.

2. The method of claim 1, wherein the superhydrophilic self-cleaning separation membrane is prepared by the steps of: The manganese metal salt in step I and step III is manganese sulfate, manganese nitrate or manganese chloride.

3. The method of claim 1, wherein the superhydrophilic self-cleaning separation membrane is prepared by the steps of: The concentration of manganese metal salt in the mixed solution A in step I is 1-5 mg / mL.

4. The method of claim 1, wherein the superhydrophilic self-cleaning separation membrane is prepared by the steps of: The concentration of manganese metal salt in the solution B in step III is 2-10 mg / mL.

5. The method of claim 1, wherein the superhydrophilic self-cleaning separation membrane is prepared by the steps of: The concentration of amino malonitrile p-toluenesulfonic acid in the mixed solution A in step I is 2-20 mg / mL.

6. The method of claim 1, wherein the superhydrophilic self-cleaning separation membrane is prepared by the steps of: The alkaline aqueous solution in step I and step III is a buffer solution prepared by mixing 0.1 mol / L tris-hydroxymethyl aminomethane, 0.1 mol / L hydrochloric acid and water in a volume ratio of 1: (0.28-0.32) : (0.68-0.72).

7. The method of claim 1, wherein the superhydrophilic self-cleaning separation membrane is prepared by the steps of: The coating time in step II and step IV is 12-48 h.

8. The method of claim 1, wherein the superhydrophilic self-cleaning separation membrane is prepared by the steps of: The polymer membrane in step II is a polyvinylidene fluoride membrane, a polypropylene membrane, a polytetrafluoroethylene membrane or a polyethylene membrane. 9.A super-hydrophilic self-cleaning separation membrane prepared by the method according to any one of claims 1-8.

10. The superhydrophilic self-cleaning separation membrane according to claim 9, wherein, MnO2 nanomaterials grow on the surface of the polymer membrane.

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