CN113694746A

CN113694746A - Self-cleaning hydrophilic membrane and preparation method thereof

Info

Publication number: CN113694746A
Application number: CN202110916594.0A
Authority: CN
Inventors: 熊竹; 杨洋; 曹阿坤
Original assignee: Guangzhou University
Current assignee: Guangzhou University
Priority date: 2021-08-10
Filing date: 2021-08-10
Publication date: 2021-11-26

Abstract

The invention discloses a self-cleaning hydrophilic membrane and a preparation method thereof, and relates to the technical field of nano materials. The preparation method comprises the following steps: (1) adding dopamine hydrochloride and polyethyleneimine into a buffer solution to prepare a cross-linked modified solution; (2) putting the hydrophilic membrane into the crosslinking modified solution obtained in the step (1), and oscillating to obtain a crosslinking modified hydrophilic membrane; (3) and (3) putting the cross-linked modified hydrophilic membrane obtained in the step (2) into an iron salt solution, slowly adding a dilute acid solution, and standing to obtain the self-cleaning hydrophilic membrane. The preparation method is simple in process, and the prepared self-cleaning hydrophilic membrane improves the stability of a hydrophilic hierarchical micro-nano structure on the surface of the membrane, enhances a hydration layer, reduces the adhesion of oil and reduces the pore diameter of the membrane. The cross-flow separation process has excellent long-acting separation performance on emulsion, namely stable permeation flux, high water yield and high separation efficiency.

Description

Self-cleaning hydrophilic membrane and preparation method thereof

Technical Field

The invention relates to the technical field of nano materials, in particular to a self-cleaning hydrophilic membrane and a preparation method thereof.

Background

In recent years, treatment of a large amount of emulsified oily wastewater generated in petrochemical, textile, leather, steel processing, metal finishing, food and other industries has been a great challenge, and research and development of a water recovery process with high efficiency, energy saving and low cost in these fields are urgently needed. Generally, emulsified oil droplets varying in size from several micrometers to several tens of micrometers are very stable in water, resulting in high chemical oxygen demand and poor biodegradability in biochemical treatment processes. In addition, degrading the oil that should be recycled in the water is a waste of resources. Therefore, the oil-water separation can reduce the pressure of the treatment of the oily wastewater and improve the economic benefit to the maximum extent by recovering the oil.

To achieve this goal, superhydrophilic polymer membranes can be developed that combine surface chemical modification and surface roughness structures to provide a relatively simple process for treating various emulsified oily wastewater. The polymer with super-wettability has controllable pore size, and can couple the demulsification and size screening effects of a hydration layer so as to efficiently separate various intractable emulsified wastewater. Currently, the most serious problem limiting the application of super-wetting polymer membranes is the long-term separation stability of oily wastewater.

The super-wetting polymer membrane has special binding force to water, and can form a hydration layer on the surface of the membrane to prevent emulsified oil drops from permeating through the membrane. The polymer membrane surface with the hydrophilic chemical composite material and the rough hierarchical structure can be used for constructing an enhanced hydration layer on the surface, shows better underwater super-oleophobic property and is hopeful to be applied to emulsion separation. However, such rough polymer membrane surface textures are highly susceptible to shear damage under actual cross-flow operation, and in addition, cross-direction shear may also alter the chemical properties of the membrane surface. Continuous cross-flow pressure actuation can expose the underlying polymer membrane surface and disrupt the surface hydration layer, resulting in the immobilization of emulsified oil droplets on the rough membrane surface. Thus, for a rough superhydrophilic polymer membrane, long-lasting oil removal of the emulsion is still difficult to achieve.

To address this problem, a large number of rigid nanoparticles are embedded into the rough nano/microstructure of the membrane surface by the micropore restriction effect, which can create a robust super-wetting surface that can withstand harsh physical and chemical insults. However, the durability of such organic-inorganic hybrid membranes is still unsatisfactory. In addition, because the membrane surface is inevitably polluted by oil, no matter how the hydration layer is enhanced on the membrane surface, the oil drops are still difficult to prevent from permanently permeating or infiltrating the super-hydrophilic membrane, so that the construction of the super-hydrophilic membrane with the activity antifouling and self-cleaning performances can become a more effective and more environment-friendly method for separating the emulsified wastewater.

In fact, many non-toxic active nanoparticles, such as iron, titanium and manganese-based metal oxides, have been widely used as heterogeneous activators to generate reactive oxygen species to enable non-selective oxidation of organic contaminants in water. The super-hydrophilic film is provided with the active nano particles, so that the micro/nano structure of the surface can be enhanced, and the surface can be endowed with self-cleaning performance. The rough composite membrane with strong super-hydrophilicity, underwater super-lipophobicity and self-cleaning property is expected to realize long-term separation of oily wastewater.

Disclosure of Invention

Based on the above, the invention aims to overcome the defects of the prior art and provide a self-cleaning hydrophilic membrane and a preparation method thereof.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

the invention provides a preparation method of a self-cleaning hydrophilic membrane, which comprises the following steps:

(1) adding dopamine hydrochloride and polyethyleneimine into a buffer solution to obtain a cross-linked modified solution;

(2) putting the hydrophilic membrane into the crosslinking modified solution obtained in the step (1), and oscillating to obtain a crosslinking modified hydrophilic membrane;

(3) and (3) putting the cross-linked modified hydrophilic membrane obtained in the step (2) into an iron salt solution, adding an acid solution, and standing to obtain the self-cleaning hydrophilic membrane.

The inventor finds that iron ions in an iron salt solution can perform a complexing reaction on a crosslinking modified layer of the crosslinking modified hydrophilic membrane, and then the complexed iron ions perform a hydrolysis reaction through the addition of an acid solution to generate iron oxyhydroxide in situ on the crosslinking modified hydrophilic membrane. The hydrophilic membrane compounded with the hydroxyl ferric oxide improves the stability of a hydrophilic hierarchical micro-nano structure on the surface of the membrane, enhances a hydration layer, reduces the adhesion of oil and reduces the aperture of the membrane.

Preferably, the ferric salt solution in the step (3) is ferric trichloride solution, ferric sulfate solution or ferric nitrate solution; the concentration of iron ions in the iron salt solution is 0.005-0.015 mol/L; the acid solution in the step (3) is hydrochloric acid, sulfuric acid or nitric acid, and the concentration of hydrogen ions in the acid solution is 0.005-0.015 mol/L.

The inventor finds that when the concentration of hydrogen ions in the acid solution is in the range of 0.005-0.015mol/L, the solution acidity and the hydrolysis process of iron salt are mild and easy to control.

Preferably, the volume ratio of the ferric salt solution to the diluted acid solution is 5:1-1: 5.

The inventor finds that the hydrolysis reaction of the ferric salt can be better carried out when the volume ratio of the ferric salt solution to the dilute acid solution is in the range of 5:1-1: 5. If the iron salt is excessive, the solution is too acidic, the hydrolysis speed is accelerated, and a large amount of ferric hydroxide precipitate can be generated in the solution. If the diluted acid is excessive, the solution is too acidic, and the ferric salt solution cannot be hydrolyzed.

Preferably, the buffer solution of step (1) comprises tris (hydroxymethyl) aminomethane, the concentration of tris (hydroxymethyl) aminomethane is 50mmol/L, and the pH of the buffer solution is 8.5.

The inventors have found through studies that the amounts of sodium hydroxide and hydrochloric acid required to adjust the solution to an appropriate pH and the time taken to adjust the pH are reasonable when the concentration of tris is 50 mmol/L. When the concentration of the tris is too low, the prepared buffer solution has poor buffering effect, and the pH value is difficult to maintain relatively stable in a long-time reaction process. If the concentration of tris is too high, the amount of sodium hydroxide and hydrochloric acid required to adjust the solution to the appropriate pH and the time taken to adjust are long, and the pH of the buffer solution is not changed for a while after the reaction time is over, wasting the reagent.

The inventor finds that when the pH value of the buffer solution is 8.5, the control of the crosslinking reaction of dopamine hydrochloride and polyethyleneimine is most favorable, and a stable and uniform crosslinked layer is formed on the membrane.

Preferably, in the crosslinking modification solution in the step (1), the mass ratio of dopamine hydrochloride to polyethyleneimine is 1: 1.

the inventor finds that the mass ratio of dopamine hydrochloride to polyethyleneimine is 1: 1, dopamine hydrochloride and polyethyleneimine can theoretically perform complete condensation reaction. If the dopamine hydrochloride is excessive, self-polymerization reaction is carried out, and uneven polydopamine microspheres are generated. If the polyethyleneimine is excessive, it will adhere to the membrane. In any case, an unnecessary uneven film surface structure is formed.

Preferably, the hydrophilic membrane in the step (2) is one of a hydrophilic polytetrafluoroethylene membrane, a hydrophilic polyvinylidene fluoride membrane, a hydrophilic polycarbonate membrane, a hydrophilic polyvinyl chloride membrane, a hydrophilic polysulfone membrane, a hydrophilic polyacrylonitrile membrane, a hydrophilic polyamide membrane, a hydrophilic polyvinyl alcohol membrane, and a hydrophilic acrylic acid membrane.

Preferably, in the step (2), the area-to-volume ratio of the hydrophilic membrane to the crosslinking modification solution is 0.1-0.02cm²and/mL, the time for the hydrophilic membrane to oscillate in the crosslinking modification solution is 6-24 hours.

Preferably, in the step (3), the volume ratio of the diameter of the cross-linked modified hydrophilic membrane to the ferric salt solution is 0.1-0.02cm/mL, and the time for the cross-linked modified hydrophilic membrane to stand in the ferric salt solution and the dilute acid solution is 12-36 hours.

In addition, the application provides the self-cleaning hydrophilic membrane prepared by the preparation method.

Further, the application provides an application of the self-cleaning hydrophilic membrane in the field of water treatment.

Compared with the prior art, the invention has the beneficial effects that:

the self-cleaning hydrophilic membrane improves the stability of a hydrophilic hierarchical micro-nano structure on the surface of the membrane, enhances a hydration layer, reduces the adhesion of oil and reduces the pore diameter of the membrane. The cross-flow separation process has excellent long-acting separation performance on emulsion, namely stable permeation flux, high water yield and high separation efficiency. In addition, the photocatalytic layer compounded on the surface of the membrane shows high photo-Fenton reaction activity under the irradiation of ultraviolet light and the existence of hydrogen peroxide, so that the membrane has a self-cleaning function and can efficiently clean stubborn oil drops on the surface of the membrane. After photocatalytic cleaning, the oil-contaminated membrane can recover long-acting separation performance, so that more oily wastewater can be treated before the membrane is replaced.

The invention has simple process, improves the compactness of the membrane material, improves the oleophobic property of the membrane material, enhances the stability of the membrane material, improves the separation performance of emulsion, widens the potential application field of the super-wetting membrane in the treatment of oily wastewater, and provides new insight for combining strong filtration and self-cleaning to reduce membrane pollution.

Drawings

FIG. 1 is a scanning electron microscope image of a hydrophilic polyvinylidene fluoride membrane, a cross-linked modified hydrophilic membrane prepared in comparative example 1, and a self-cleaning hydrophilic membrane prepared in example 1;

FIG. 2 is a scanning electron microscope image of the self-cleaning hydrophilic film prepared in example 1;

FIG. 3 is an underwater oil adhesion diagram of a hydrophilic polyvinylidene fluoride membrane, a cross-linked modified hydrophilic membrane prepared in comparative example 1, and a self-cleaning hydrophilic membrane prepared in example 1;

FIG. 4 is a graph showing the pore size distribution of a hydrophilic polyvinylidene fluoride membrane, a cross-linked modified hydrophilic membrane prepared in comparative example 1, and a self-cleaning hydrophilic membrane prepared in example 1;

FIG. 5 is an electron paramagnetic resonance plot of a hydrophilic polyvinylidene fluoride membrane, a cross-linked modified hydrophilic membrane prepared in comparative example 1, and a self-cleaning hydrophilic membrane prepared in example 1;

FIG. 6 is a single separation test chart of a hydrophilic polyvinylidene fluoride membrane, a cross-linked modified hydrophilic membrane prepared in comparative example 1, and a self-cleaning hydrophilic membrane prepared in example 1;

fig. 7 is a graph showing cyclic separation tests of a hydrophilic polyvinylidene fluoride membrane, a cross-linked modified hydrophilic membrane prepared in comparative example 1, and a self-cleaning hydrophilic membrane prepared in example 1.

Detailed Description

To better illustrate the objects, aspects and advantages of the present invention, the present invention will be further described with reference to the accompanying drawings and specific embodiments.

Comparative example 1

In an embodiment of the present application, a method for preparing a self-cleaning hydrophilic film includes the following steps:

(1) adding 200mg of dopamine hydrochloride and 200mg of polyethyleneimine into 100mL of buffer solution to prepare a crosslinking modified solution, wherein the buffer solution is prepared from tris (hydroxymethyl) aminomethane, the volume concentration of the tris (hydroxymethyl) aminomethane is 50mmol/L, and the pH value of the prepared buffer solution is 8.5;

(2) putting the hydrophilic membrane into the crosslinking modified solution obtained in the step (1), and oscillating to obtain the crosslinking modified hydrophilic membrane, wherein the hydrophilic membrane is hydrophilic polyvinylidene fluoride, and the area (square centimeter) of the hydrophilic membrane and the crosslinking modified solution is as follows: volume (ml) ═ 1: 20, the time for shaking the hydrophilic membrane in the crosslinking modification solution was 12 hours.

Example 1

(2) putting the hydrophilic membrane into the crosslinking modified solution obtained in the step (1), and oscillating to obtain the crosslinking modified hydrophilic membrane, wherein the hydrophilic membrane is hydrophilic polyvinylidene fluoride, and the area (square centimeter) of the hydrophilic membrane and the crosslinking modified solution is as follows: volume (ml) ═ 1: 20, oscillating the hydrophilic membrane in the crosslinking modified solution for 12 hours;

(3) preparing an iron salt solution and a dilute acid solution, wherein the iron salt solution is prepared from ferric chloride, the concentration of iron ions in the iron salt solution is 0.01mol/L, the dilute acid solution is prepared from hydrochloric acid, and the concentration of the dilute acid solution is 0.01 mol/L;

(4) putting the cross-linked modified hydrophilic membrane obtained in the step (2) into the ferric salt solution obtained in the step (3), slowly adding the dilute acid solution obtained in the step (3), standing to obtain the self-cleaning hydrophilic membrane, wherein the ratio of the diameter (centimeter) of the cross-linked modified hydrophilic membrane to the volume (milliliter) of the ferric salt solution is 1: 20, the ratio of the volume of ferric salt solution (in ml) to the volume of dilute acid solution (in ml) is 2: 1, standing the crosslinking modified hydrophilic membrane in the ferric salt solution for 24 hours.

Example 2

(2) putting the hydrophilic membrane into the crosslinking modified solution obtained in the step (1), and oscillating to obtain the crosslinking modified hydrophilic membrane, wherein the hydrophilic membrane is hydrophilic polyvinylidene fluoride, and the area (square centimeter) of the hydrophilic membrane and the crosslinking modified solution is as follows: volume (ml) ═ 1: 10, oscillating the hydrophilic membrane in the crosslinking modified solution for 6 hours;

(3) preparing ferric salt solution and dilute acid solution, wherein the ferric salt solution is prepared by ferric sulfate, the concentration of ferric ions in the ferric salt solution is 0.005mol/L, the dilute acid solution is prepared by sulfuric acid, and H in the dilute acid solution⁺The concentration of (A) is 0.005 mol/L;

(4) putting the cross-linked modified hydrophilic membrane obtained in the step (2) into the ferric salt solution obtained in the step (3), slowly adding the dilute acid solution obtained in the step (3), standing to obtain the self-cleaning hydrophilic membrane, wherein the ratio of the diameter (centimeter) of the cross-linked modified hydrophilic membrane to the volume (milliliter) of the ferric salt solution is 1: 10, the ratio of the volume of ferric salt solution (in ml) to the volume of dilute acid solution (in ml) is 5:1, standing the crosslinking modified hydrophilic membrane in the ferric salt solution for 24 hours.

Example 3

(2) putting the hydrophilic membrane into the crosslinking modified solution obtained in the step (1), and oscillating to obtain the crosslinking modified hydrophilic membrane, wherein the hydrophilic membrane is hydrophilic polyvinylidene fluoride, and the area (square centimeter) of the hydrophilic membrane and the crosslinking modified solution is as follows: volume (ml) ═ 1: 50, the oscillation time of the hydrophilic membrane in the crosslinking modified solution is 24 hours;

(3) preparing ferric salt solution and dilute acid solution, wherein the ferric salt solution is prepared by ferric sulfate, the concentration of ferric ions in the ferric salt solution is 0.015mol/L, the dilute acid solution is prepared by sulfuric acid, and H in the dilute acid solution is⁺The concentration of (2) is 0.015 mol/L;

(4) putting the cross-linked modified hydrophilic membrane obtained in the step (2) into the ferric salt solution obtained in the step (3), slowly adding the dilute acid solution obtained in the step (3), standing to obtain the self-cleaning hydrophilic membrane, wherein the ratio of the diameter (centimeter) of the cross-linked modified hydrophilic membrane to the volume (milliliter) of the ferric salt solution is 1: 50, the ratio of the volume of ferric salt solution (in ml) to the volume of dilute acid solution (in ml) is 1: and 5, standing the crosslinking modified hydrophilic membrane in the ferric salt solution for 36 hours.

Evaluation of Performance

Test example 1 scanning Electron microscope test

Scanning electron microscope tests were performed on the hydrophilic polyvinylidene fluoride membrane, the cross-linked modified hydrophilic membrane prepared in comparative example 1, and the self-cleaning hydrophilic membrane prepared in example 1. FIG. 1a1 and FIG. 1a show the results of scanning electron micrographs of the hydrophilic polyvinylidene fluoride membrane; FIGS. 1c1 and 1c are SEM images of the crosslinked modified hydrophilic film prepared in comparative example 1, and FIGS. 1e1, 1e and 2 are SEM images of the self-cleaning hydrophilic film prepared in example 2.

Through comparison, the pore diameter of the surface of the cross-linked modified hydrophilic membrane (V-array SHPVDF @ PDA/PEI) prepared in the comparative example 1 is not obviously changed compared with the pores on the surface of the hydrophilic polyvinylidene fluoride membrane (V-array SHPVDF), and the macropores of the self-cleaning hydrophilic membrane (V-array SHPVDF @ PDA/PEI-g-FeOOH) prepared in the example 1 are obviously reduced, and a rod-shaped micro-nano structure appears in the pore channel.

Test example 2 Underwater oil adhesion and pore size distribution test

The hydrophilic polyvinylidene fluoride membrane, the cross-linked modified hydrophilic membrane prepared in comparative example 1, and the self-cleaning hydrophilic membrane prepared in example 1 were subjected to an underwater oil adhesion test. As shown in FIG. 3, it can be seen that the underwater oil adhesion of the hydrophilic polyvinylidene fluoride membrane (V-array SHPVDF), the cross-linked modified hydrophilic membrane prepared in comparative example 1 (V-array SHPVDF @ PDA/PEI) and the self-cleaning hydrophilic membrane prepared in example 1 (V-array SHPVDF @ PDA/PEI-g-FeOOH) is gradually reduced, which indicates that the oil-applying force of the three membranes is gradually reduced, reflecting the enhanced oil repellency of the membranes.

The pore size distribution test was performed on the hydrophilic polyvinylidene fluoride membrane, the cross-linked modified hydrophilic membrane prepared in comparative example 1, and the self-cleaning hydrophilic membrane prepared in example 1. As shown in FIG. 4, it can be found that the pore size distributions of the hydrophilic polyvinylidene fluoride membrane (V-array SHPVDF) and the crosslinked modified hydrophilic membrane (V-array SHPVDF @ PDA/PEI) prepared in comparative example 1 are substantially consistent, while the pore size distribution of the self-cleaning hydrophilic membrane (V-array SHPVDF @ PDA/PEI-g-FeOOH) prepared in example 1 is greatly increased, which proves that the pore size of the self-cleaning hydrophilic membrane prepared in example 1 is obviously reduced, and the separation performance is improved.

Experimental example 3 Electron paramagnetic resonance test

The cross-linked modified hydrophilic membrane prepared in comparative example 1 and the self-cleaning hydrophilic membrane prepared in example 1 were subjected to electron paramagnetic resonance testing. As shown in FIG. 5, it was found that the crosslinked modified hydrophilic membrane (V-array SHPVDF @ PDA/PEI) prepared in comparative example 1 could not excite hydrogen peroxide to generate a radical signal regardless of the presence of UV light. However, the self-cleaning hydrophilic membrane (V-array SHPVDF @ PDA/PEI-g-FeOOH) prepared in example 1 can effectively excite hydrogen peroxide to generate a strong radical signal under the condition of ultraviolet illumination.

Test example 4 emulsion separation and cycle Performance test

The test process comprises the following steps:

emulsion separation tests were performed on a hydrophilic polyvinylidene fluoride membrane, a cross-linked modified hydrophilic membrane prepared in comparative example 1, and a self-cleaning hydrophilic membrane prepared in examples 1 to 3 at 0.1MPa using an emulsion prepared with 1% volume fraction of petroleum (containing 1 ‰ surfactant) as a test solution. The emulsion separation involves a test procedure that is two-part: the first part was a pure water flux test for 30 minutes and the second part was an emulsion separation test for 1440 minutes (for hydrophilic polyvinylidene fluoride membranes, an emulsion separation test for 120 minutes was performed).

The cross-linked modified hydrophilic membrane prepared in comparative example 1 and the self-cleaning hydrophilic membrane prepared in examples 1 to 3 were subjected to a cycle performance test using an emulsion (containing 1 ‰ surfactant) prepared from 1% volume fraction of petroleum as a test solution under 0.1 MPa. The cycle performance test included three cycles of the test procedure, wherein the first cycle was the test procedure included in the emulsion separation as described above, and the second and third cycles included a pure water flux test for 30 minutes and an emulsion separation test for 720 minutes, respectively. For the cross-linked modified hydrophilic membrane prepared in the comparative example 1, pollutants on the surface of the membrane are removed in a stirring and water washing mode for 30 minutes after each circulation is finished, and then the next circulation performance test is carried out; the self-cleaning hydrophilic membranes prepared in examples 1-3 were photocatalyzed by 30 minutes after each cycle (membranes soaked in a solution containing 0.1% H)₂O₂In aqueous solution, uv illumination) to remove contaminants from the surface of the membrane, and then performing the next cycle performance test.

And (3) test results:

TABLE 1 Single and Cyclic separation Performance of hydrophilic membranes prepared in comparative example 1 and examples 1-3

The hydrophilic membranes prepared in examples 1 to 3 and comparative example 1 were subjected to emulsion separation and cycle performance tests, and the results of the tests are shown in table 1.

And, fig. 6 is a result of an emulsion separation test performed on the hydrophilic polyvinylidene fluoride membrane, the cross-linked modified hydrophilic membrane prepared in comparative example 1, and the self-cleaning hydrophilic membrane prepared in example 1, wherein fig. 6a shows flux of the membrane separation emulsion, and fig. 6b shows COD removal rate of the membrane separation emulsion. It was found that there was no significant difference in pure water flux. When an emulsion separation test was performed, it was found that the flux and removal rate of the hydrophilic polyvinylidene fluoride membrane (V-array SHPVDF) were extremely fast in decay rate. The flux of the crosslinked modified hydrophilic membrane (V-array SHPVDF @ PDA/PEI) prepared in comparative example 1 and the self-cleaning hydrophilic membrane (V-array SHPVDF @ PDA/PEI-g-FeOOH) prepared in example 1 decreased slowly and stabilized at 30L/m after 240 minutes²H, in addition, the crosslinked modified hydrophilic membrane (V-array) prepared in comparative example 1

SHPVDF @ PDA/PEI) and self-cleaning hydrophilic membrane (V-array) prepared in example 1

SHPVDF @ PDA/PEI-g-FeOOH) also maintains the COD removal rate of the emulsion above 90%, but the removal rate of the self-cleaning hydrophilic membrane (V-array SHPVDF @ PDA/PEI-g-FeOOH) prepared in example 1 is maintained above 95% and is more stable, which indicates that the anti-pollution performance of the membrane is stronger.

Fig. 7 is a result of cycle performance test of the cross-linked modified hydrophilic membrane prepared in comparative example 1 and the self-cleaning hydrophilic membrane prepared in example 1, in which fig. 7b shows the flux of the membrane separation emulsion at the second cycle, fig. 7c shows the COD removal rate of the membrane separation emulsion at the second cycle, fig. 7d shows the flux of the membrane separation emulsion at the third cycle, and fig. 7e shows the COD removal rate of the membrane separation emulsion at the third cycle. In the cycle performance test, it was found that the flux of the emulsion separated by the crosslinked modified hydrophilic membrane (V-array SHPVDF @ PDA/PEI) prepared in comparative example 1 was slightly smaller than that of the emulsion separated by the self-cleaning hydrophilic membrane (V-array SHPVDF @ PDA/PEI-g-FeOOH) prepared in example 1, and the COD removal rate of the emulsion was lower than that of the crosslinked modified hydrophilic membrane (V-array SHPVDF @ PDA/PEI) prepared in comparative example 1 and was less stable than that of the self-cleaning hydrophilic membrane (V-array SHPVDF @ PDA/PEI-g-FeOOH) prepared in example 1.

Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the protection scope of the present invention, and although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A preparation method of a self-cleaning hydrophilic membrane is characterized by comprising the following steps:

(3) and (3) putting the cross-linked modified hydrophilic membrane obtained in the step (2) into an iron salt solution, then adding an acid solution, and standing to obtain the self-cleaning hydrophilic membrane.

2. The method for preparing a self-cleaning hydrophilic membrane according to claim 1, wherein the ferric salt solution of step (3) is ferric trichloride solution, ferric sulfate solution or ferric nitrate solution; the concentration of iron ions in the iron salt solution is 0.005-0.015 mol/L; the acid solution in the step (3) is hydrochloric acid, sulfuric acid or nitric acid, and the concentration of hydrogen ions in the acid solution is 0.005-0.015 mol/L.

3. The method for preparing a self-cleaning hydrophilic membrane as claimed in claim 1, wherein the volume ratio of the ferric salt solution to the acid solution is 5:1 to 1: 5.

4. The method of claim 1, wherein the buffer solution of step (1) comprises tris (hydroxymethyl) aminomethane, the concentration of tris is 50mmol/L, and the pH of the buffer solution is 8.5.

5. The method for preparing a self-cleaning hydrophilic membrane according to claim 1, wherein in the crosslinking modification solution in the step (1), the mass ratio of the dopamine hydrochloride to the polyethyleneimine is 1: 1.

6. the method for preparing a self-cleaning hydrophilic membrane according to claim 1, wherein the hydrophilic membrane in step (2) is one of a hydrophilic polytetrafluoroethylene membrane, a hydrophilic polyvinylidene fluoride membrane, a hydrophilic polycarbonate membrane, a hydrophilic polyvinyl chloride membrane, a hydrophilic polysulfone membrane, a hydrophilic polyacrylonitrile membrane, a hydrophilic polyamide membrane, a hydrophilic polyvinyl alcohol membrane, and a hydrophilic acrylic acid membrane.

7. The method for preparing a self-cleaning hydrophilic membrane as claimed in claim 1, wherein in the step (2), the ratio of the area of the hydrophilic membrane to the volume of the crosslinking modification solution is 0.1-0.02cm²and/mL, the time for the hydrophilic membrane to oscillate in the crosslinking modification solution is 6-24 hours.

8. The method for preparing a self-cleaning hydrophilic membrane as claimed in claim 1, wherein in the step (3), the ratio of the diameter of the cross-linked modified hydrophilic membrane to the volume of the iron salt solution is 0.1-0.02cm/mL, and the time for which the cross-linked modified hydrophilic membrane is left to stand is 12-36 hours.

9. A self-cleaning hydrophilic membrane prepared by the preparation method according to any one of claims 1 to 8.

10. Use of a self-cleaning hydrophilic membrane as claimed in claim 9 in the field of water treatment.