A method for preparing modified PVDF ultrafiltration membrane

Abstract

The present invention relates to the field of membrane separation technology and provides a method for preparing a modified PVDF ultrafiltration membrane with bactericidal and antibacterial functions. The preparation method comprises: first preparing a modified titanium dioxide carrier loaded with AgO and FeOOH, then dispersing the carrier in a mixed solvent containing a polyhydroxy alcohol to obtain a modified titanium dioxide carrier dispersion, and finally immersing a hydroxyl-containing PVDF ultrafiltration membrane in the dispersion and drying to obtain the modified PVDF ultrafiltration membrane. The modified PVDF ultrafiltration membrane prepared by the present invention has good hydrophilicity, high mechanical strength, and bactericidal and antibacterial functions, and can be used in the field of water treatment.

Description

Technical Field

[0001] The present invention relates to the field of membrane separation technology, and in particular to a method for preparing a modified PVDF ultrafiltration membrane. The obtained ultrafiltration membrane has excellent photocatalytic activity and antibacterial performance, good mechanical properties and long service life. Background Art

[0002] Polymer separation membranes are materials used in modern high-efficiency separation, concentration, purification, and decontamination equipment. They are widely used in the chemical, environmental, food, biological, pharmaceutical, electronic, electric power, metallurgy, textile, and seawater desalination industries, playing a vital role in addressing contemporary energy, resource, and environmental pollution issues. Commonly used membrane materials include polyvinylidene fluoride (PVDF), polysulfone, and polyvinyl chloride.

[0003] Currently, when ultrafiltration membranes are used as reverse osmosis pretreatment to produce purified water, they can only adsorb proteins and tiny microorganisms in drinking water onto the membrane surface, preventing them from passing through, but they cannot kill them. This results in a high concentration of bacterial microorganisms in drinking water, which poses a serious threat to people's drinking water health. For example, CN102989329A discloses an Ag / TiO2-modified PVDF ultrafiltration membrane, its preparation method, and application. This membrane utilizes a one-pot process, directly adding nano-titanium dioxide particles and silver anion salts to a casting solution for cast film formation. While this membrane exhibits excellent antibacterial properties, the nano-titanium dioxide particles easily agglomerate, resulting in a low ultrafiltration strength and a reduced service life for the membrane. Summary of the Invention

[0004] In response to the shortcomings of the existing technology, the present invention provides a method for preparing a modified PVDF ultrafiltration membrane. The prepared modified PVDF ultrafiltration membrane has good hydrophilicity, high mechanical strength, and excellent photocatalytic activity and antibacterial properties. It can be used in the field of water treatment, especially in the purification of wastewater containing a large amount of iron ions, the preparation of household drinking pure water, and the purification of circulating water.

[0005] In order to achieve the above-mentioned purpose, the present invention adopts the following technical solutions.

[0006] In one aspect, the present invention provides a method for preparing a modified PVDF ultrafiltration membrane, comprising:

[0007] (1) Preparation of modified titanium dioxide carrier

[0008] A titanium dioxide support is added to an aqueous solution containing an iron source and a silver source, and the mixture is stirred to obtain a precursor solution; a sodium hydroxide solution is added to the precursor solution, the mixture is stirred, an oxidizing gas is introduced, the mixture is filtered, and the mixture is dried to obtain a modified titanium dioxide support loaded with AgO and FeOOH;

[0009] (2) Preparation of modified titanium dioxide carrier dispersion

[0010] The modified titanium dioxide carrier is added to a mixed solvent of polyhydroxy alcohol containing gelatin and water, and ultrasonically dispersed to obtain a modified titanium dioxide carrier dispersion;

[0011] (3) Preparation of modified PVDF ultrafiltration membrane

[0012] The modified titanium dioxide carrier dispersion liquid is immersed in the hydroxyl-containing PVDF ultrafiltration membrane, and then dried to obtain the modified PVDF ultrafiltration membrane.

[0013] According to the preparation method of the modified PVDF ultrafiltration membrane provided by the present invention, on the one hand, the titanium dioxide carrier is loaded with AgO and iron oxyhydroxide (FeOOH), and the AgO can slowly release Ag in water. 2+ , high-priced Ag 2+ It has strong bactericidal properties. AgO has a certain photocatalytic effect. After being excited by light, it produces electrons and holes. The presence of FeOOH can promote the photocatalytic process of AgO, thereby giving the ultrafiltration membrane excellent bactericidal and antibacterial properties. On the other hand, the modified titanium dioxide carrier is first dispersed in a mixed solvent containing gelatin and polyhydroxy alcohol. The polyhydroxy alcohol can form hydrogen bonds with titanium dioxide, thereby preventing the titanium dioxide carrier from agglomerating. Gelatin as a stabilizer can further enhance the formation stability of the dispersion. In addition, the PVDF ultrafiltration membrane is modified to make it rich in hydroxyl groups. The hydroxyl groups can also form hydrogen bonds with titanium dioxide, which can make the modified titanium dioxide carrier firmly bond to the PVDF matrix, have high mechanical strength and lasting bactericidal and antibacterial effects.

[0014] As a preferred embodiment of the present invention, the iron source is ferric nitrate; the silver source is silver nitrate.

[0015] As a preferred embodiment of the present invention, the concentration of the sodium hydroxide solution is 1-10%.

[0016] As a preferred embodiment of the present invention, the oxidizing gas is any one of O3, O2, O3 / O2 mixed gas, O3 / N2 mixed gas, and O2 / N2 mixed gas. By introducing the oxidizing gas, the iron hydroxide is oxidized to FeOOH, Ag + Oxidized to Ag 2+ .

[0017] As a preferred embodiment of the present invention, the time for introducing the oxidizing gas is 20 to 40 minutes, and the drying is vacuum drying at 40 to 80° C. for 4 to 8 hours.

[0018] As a preferred embodiment of the present invention, the mass of AgO is 5-15% of the mass of the titanium dioxide support, for example: 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, and so on.

[0019] As a preferred embodiment of the present invention, the mass of the FeOOH is 1-10% of the mass of the titanium dioxide support, for example: 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, and so on.

[0020] As a preferred embodiment of the present invention, the polyhydric alcohol is at least one of glycerol, 1,2-propylene glycol, 1,3-propylene glycol, ethylene glycol, diethylene glycol, polyethylene glycol 200, polyethylene glycol 400, and polyethylene glycol 600.

[0021] As a preferred embodiment of the present invention, the mass ratio of the polyhydric alcohol to water in the mixed solvent is 1:1-5. If the amount of polyhydric alcohol used is too small, the effect of preventing the modified titanium dioxide support from agglomerating is not ideal, and the stability of the resulting dispersion is poor; if the amount of polyhydric alcohol used is too large, it is not conducive to improving the impregnation efficiency.

[0022] In a preferred embodiment of the present invention, the gelatin accounts for 0.1-0.5% of the total mass of the mixed solvent (polyhydric alcohol and water). If the amount of gelatin is too much, the viscosity will be too high, which is not conducive to the dispersion of titanium dioxide and affects the impregnation efficiency; if the amount of gelatin is too little, the stabilization effect will be insignificant.

[0023] As a preferred embodiment of the present invention, in the dispersion, the mass fraction of the modified titanium dioxide carrier is 5-20%, more preferably 5-15%.

[0024] As a preferred embodiment of the present invention, the ultrasonic dispersion time is 30-60 minutes.

[0025] The hydroxyl-containing PVDF ultrafiltration membrane is obtained by modifying a PVDF ultrafiltration membrane. The PVDF ultrafiltration membrane can be prepared by any method known in the art. Preferably, the hydroxyl-containing PVDF ultrafiltration membrane has a porosity of 50-70% and a thickness of 100-300 μm.

[0026] As a preferred embodiment of the present invention, the impregnation is carried out at room temperature for 0.5-1 hour, and the impregnation can be assisted by vacuuming.

[0027] As a preferred embodiment of the present invention, the drying is vacuum drying at 60-100° C. for 4-12 hours.

[0028] On the other hand, the present invention provides a modified PVDF ultrafiltration membrane obtained by the above preparation method.

[0029] On the other hand, the present invention provides the use of modified PVDF ultrafiltration membrane in water treatment, especially the purification of wastewater containing a large amount of iron ions, the preparation of household drinking pure water and the purification of circulating water.

[0030] Compared with the prior art, the present invention has the following technical effects:

[0031] (1) In the preparation method of the modified PVDF ultrafiltration membrane provided by the present invention, on the one hand, the titanium dioxide carrier is loaded with AgO and iron oxyhydroxide (FeOOH), and the AgO can slowly release Ag in water. 2+ , high-priced Ag 2+ It has strong bactericidal properties. AgO has a certain photocatalytic effect. After being excited by light, it produces electrons and holes. The presence of FeOOH can promote the photocatalytic process of AgO, thereby giving the ultrafiltration membrane excellent bactericidal and antibacterial properties. On the other hand, the modified titanium dioxide carrier is first dispersed in a mixed solvent containing polyhydroxy alcohol. The polyhydroxy alcohol can form hydrogen bonds with titanium dioxide, thereby preventing the titanium dioxide carrier from agglomerating and forming a stable dispersion. The PVDF ultrafiltration membrane is then modified to make it rich in hydroxyl groups. The hydroxyl groups can also form hydrogen bonds with titanium dioxide, which can make the modified titanium dioxide carrier firmly bonded to the PVDF matrix, with high mechanical strength and long-lasting bactericidal and antibacterial effects.

[0032] (2) The modified PVDF ultrafiltration membrane prepared by the present invention has good hydrophilicity, high mechanical strength and excellent bactericidal performance, and can kill bacterial microorganisms in drinking water to ensure the safety of residents' water use. DETAILED DESCRIPTION

[0033] Unless otherwise specified, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the art to which this invention belongs. All patents and publications related to this invention are incorporated herein by reference in their entirety. The terms "comprising" or "including" are open-ended expressions, meaning that they include the contents specified in the present invention but do not exclude other aspects.

[0034] The following describes in detail a method for preparing a modified PVDF ultrafiltration membrane according to an embodiment of the present invention.

[0035] 1. Preparation of hydroxyl-containing PVDF ultrafiltration membrane

[0036] The preparation method of the hydroxyl-containing PVDF can be referred to CN107626216A. The details are as follows:

[0037] The PVDF ultrafiltration membrane is first treated with alkali solution, and then the PVDF ultrafiltration membrane treated with alkali solution is reacted in an isopropanol solution of sodium borohydride in sequence. After the reaction is completed, the membrane is filtered and dried to obtain a hydroxyl-containing PVDF ultrafiltration membrane.

[0038] Specifically, the alkali solution is a lithium hydroxide aqueous solution with a mass fraction of 3%; the reaction conditions of the alkali solution treatment are: stirring and reacting at 25-60° C. for 36-72 hours.

[0039] Specifically, the mass fraction of the sodium borohydride isopropanol solution is 0.1-1.5%, more preferably 0.2%; the reduction reaction conditions in the sodium borohydride isopropanol solution are: stirring the reaction at room temperature for 18-36 hours.

[0040] According to some embodiments provided by the present invention, the preparation of the hydroxyl-containing PVDF ultrafiltration membrane specifically includes: immersing the PVDF ultrafiltration membrane in a 3% by mass lithium hydroxide aqueous solution, stirring at 60°C for 48 hours, and then rinsing with water (2000 mL) and isopropanol (2000 mL), respectively; then adding the rinsed PVDF ultrafiltration membrane to a 0.2% by mass sodium borohydride isopropanol solution, stirring the reaction at room temperature for 24 hours, filtering, and drying to obtain a hydroxyl-containing PVDF ultrafiltration membrane.

[0041] 2. Preparation of modified titanium dioxide carrier

[0042] adding a titanium dioxide carrier to an aqueous solution containing an iron source and a silver source, stirring and mixing, and obtaining a precursor solution;

[0043] Alkali solution is added to the precursor solution, stirred, an oxidizing gas is introduced, filtered, and dried to obtain a modified titanium dioxide support loaded with AgO and FeOOH.

[0044] As a preferred embodiment of the present invention, the iron source is ferric nitrate; the silver source is silver nitrate.

[0045] As a preferred embodiment of the present invention, the mass fraction of the sodium hydroxide solution is 1-10%, for example, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc. The sodium hydroxide solution is not particularly limited, and its amount can be sufficient to fully react with the iron source and the silver source.

[0046] As a preferred embodiment of the present invention, the oxidizing gas is any one of O3, O2, O3 / O2 mixed gas, O3 / N2 mixed gas, and O2 / N2 mixed gas. By introducing the oxidizing gas, the iron hydroxide is oxidized to FeOOH, Ag + Oxidized to Ag 2+ .

[0047] As a preferred embodiment of the present invention, the time for introducing the oxidizing gas is 20 to 40 minutes, and the drying is vacuum drying at 40 to 80° C. for 4 to 8 hours.

[0048] As a preferred embodiment of the present invention, the mass of AgO is 5-15% of the mass of the titanium dioxide support, for example: 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, and so on.

[0049] As a preferred embodiment of the present invention, the mass of the FeOOH is 1-10% of the mass of the titanium dioxide support, for example: 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, and so on.

[0050] 3. Preparation of modified titanium dioxide carrier dispersion

[0051] The modified titanium dioxide carrier is added into a mixed solvent of polyhydroxy alcohol containing gelatin and water, and ultrasonically dispersed to obtain a modified titanium dioxide carrier dispersion.

[0052] As a preferred embodiment of the present invention, the polyhydric alcohol is at least one of glycerol, 1,2-propylene glycol, 1,3-propylene glycol, ethylene glycol, diethylene glycol, polyethylene glycol 200, polyethylene glycol 400, and polyethylene glycol 600.

[0053] As a preferred embodiment of the present invention, in the mixed solvent, the mass ratio of the polyhydric alcohol to water is 1:1-5, for example: 1:1, 1:2, 1:3, 1:4, 1:5, and the like.

[0054] As a preferred embodiment of the present invention, the gelatin accounts for 0.1-0.5% of the total mass of the mixed solvent, for example: 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, and so on.

[0055] As a preferred embodiment of the present invention, the mass fraction of the modified titanium dioxide in the dispersion is 5-20%, more preferably 5-15%, for example: 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, and the like.

[0056] As a preferred embodiment of the present invention, the ultrasonic dispersion time is 30-60 minutes.

[0057] 4. Preparation of modified PVDF ultrafiltration membrane

[0058] The modified titanium dioxide carrier dispersion liquid is immersed in the hydroxyl-containing PVDF ultrafiltration membrane, and then dried to obtain the modified PVDF ultrafiltration membrane.

[0059] As a preferred embodiment of the present invention, the impregnation is carried out at room temperature for 0.5-1 hour, and the impregnation can be assisted by vacuuming.

[0060] As a preferred embodiment of the present invention, the drying is vacuum drying at 60-100° C. for 4-12 hours.

[0061] In some embodiments, the drying is vacuum drying at 60-80° C. for 4-8 hours.

[0062] The embodiments of the present invention will be described in detail below with reference to the examples, but it will be understood by those skilled in the art that the following examples are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. In the examples, if no specific conditions are specified, the conditions described in the specification sheets or conventional conditions or the conditions recommended by the manufacturer are followed. If the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially.

[0063] Example 1

[0064] The method for preparing the modified PVDF ultrafiltration membrane provided in this embodiment comprises the following steps:

[0065] (1) Preparation of modified titanium dioxide support

[0066] In the obtained titanium dioxide support, the mass of AgO accounts for 10% of the mass of the titanium dioxide support, and the mass of FeOOH accounts for 5% of the mass of the titanium dioxide support.

[0067] According to the above proportions, Fe(NO3)3 and AgNO3 were weighed and dissolved in water, and stirred for 30 minutes; then the titanium dioxide carrier was added and stirred at room temperature for 1.5 hours to obtain a precursor solution;

[0068] Add 8% NaOH solution by mass to the precursor solution and stir for 15 minutes; then introduce O2 / N2 mixed gas and continue stirring for 30 minutes, filter and wash, and vacuum dry at 60°C for 4 hours to obtain a modified titanium dioxide support loaded with AgO and FeOOH.

[0069] (2) Preparation of modified titanium dioxide carrier dispersion

[0070] The modified titanium dioxide carrier was added to a mixed solvent of ethylene glycol and water containing gelatin, and ultrasonically dispersed for 40 minutes to obtain a modified titanium dioxide carrier dispersion with a mass fraction of 10%, wherein the mass ratio of the ethylene glycol to water was 1:1, and the gelatin accounted for 0.1% of the total mass of the mixed solvent.

[0071] (3) Preparation of modified PVDF ultrafiltration membrane

[0072] The hydroxyl-containing PVDF ultrafiltration membrane was immersed in the modified titanium dioxide carrier dispersion at room temperature for 40 minutes, and then vacuum-dried at 80° C. for 6 hours to obtain a modified PVDF ultrafiltration membrane.

[0073] Example 2

[0074] The preparation method of the modified PVDF ultrafiltration membrane provided in this embodiment is different from that in Example 1 in that:

[0075] (1) Preparation of modified titanium dioxide support

[0076] The preparation method is the same as that of Example 1. In the obtained modified titanium dioxide support, the mass of AgO is 10% of the mass of the titanium dioxide support, and the mass of FeOOH is 10% of the mass of the titanium dioxide support.

[0077] Example 3

[0078] The preparation method of the modified PVDF ultrafiltration membrane provided in this embodiment is different from that in Example 1 in that:

[0079] (1) Preparation of modified titanium dioxide support

[0080] The preparation method is the same as that of Example 1. In the obtained modified titanium dioxide support, the mass of AgO is 10% of the mass of the titanium dioxide support, and the mass of FeOOH is 1% of the mass of the titanium dioxide support.

[0081] Example 4

[0082] The preparation method of the modified PVDF ultrafiltration membrane provided in this embodiment is different from that in Example 1 in that:

[0083] (1) Preparation of modified titanium dioxide support

[0084] The preparation method is the same as that of Example 1. In the obtained modified titanium dioxide support, the mass of AgO is 5% of the mass of the titanium dioxide support, and the mass of FeOOH is 5% of the mass of the titanium dioxide support.

[0085] Example 5

[0086] The preparation method of the modified PVDF ultrafiltration membrane provided in this embodiment is different from that in Example 1 in that:

[0087] (1) Preparation of modified titanium dioxide support

[0088] The preparation method is the same as that of Example 1. In the obtained modified titanium dioxide support, the mass of AgO is 15% of the mass of the titanium dioxide support, and the mass of FeOOH is 5% of the mass of the titanium dioxide support.

[0089] Example 6

[0090] The preparation method of the modified PVDF ultrafiltration membrane provided in this embodiment is different from that in Example 1 in that:

[0091] (2) Preparation of modified titanium dioxide carrier dispersion

[0092] The modified titanium dioxide carrier was added to a mixed solvent of ethylene glycol and water containing gelatin, and ultrasonically dispersed for 40 minutes to obtain a modified titanium dioxide carrier dispersion with a mass fraction of 10%. The mass ratio of the ethylene glycol to water was 1:5, and the gelatin accounted for 0.5% of the total mass of the mixed solvent.

[0093] Comparative Example 1

[0094] The preparation method of the modified PVDF ultrafiltration membrane provided in this comparative example is different from that in Example 1 in that:

[0095] (3) Preparation of modified PVDF ultrafiltration membrane

[0096] The PVDF ultrafiltration membrane was immersed in the modified titanium dioxide carrier dispersion at room temperature for 40 minutes, and then vacuum-dried at 80° C. for 6 hours to obtain a modified PVDF ultrafiltration membrane.

[0097] Comparative Example 2

[0098] This comparative example provides a method for preparing a modified PVDF ultrafiltration membrane, which differs from Example 1 in that:

[0099] (2) Preparation of modified titanium dioxide carrier dispersion

[0100] The modified titanium dioxide carrier was added to a mixed solvent of ethylene glycol and water, and ultrasonically dispersed for 40 minutes to obtain a modified titanium dioxide carrier dispersion with a mass fraction of 10%, wherein the mass ratio of ethylene glycol to water was 1:1.

[0101] Comparative Example 3

[0102] This comparative example provides a method for preparing a modified PVDF ultrafiltration membrane, which differs from Example 1 in that:

[0103] (2) Preparation of modified titanium dioxide carrier dispersion

[0104] The modified titanium dioxide carrier was added to water containing gelatin and ultrasonically dispersed for 40 minutes to obtain a modified titanium dioxide carrier dispersion with a mass fraction of 10%, wherein the gelatin accounted for 0.1% of the mass of the water.

[0105] Performance Testing

[0106] 1. Water flux test

[0107] After the prepared composite ultrafiltration membrane was placed in deionized water for a period of time, a circular membrane piece with a diameter of 7.5 cm was cut and placed in a YL-300 ultrafiltration cup. It was pre-pressed at a pressure of 0.1 MPa for 40 minutes until the water flux was basically stable, and then measured at a pressure of 0.1 MPa. The test results are shown in Table 1.

[0108] 2. Anti-pollution performance test

[0109] The test was conducted using a UV-Vis-Infrared spectrophotometer at 0.1 MPa using an external pressure measurement method. 1 g / L of bovine serum albumin with a molecular weight of 80,000 was used as the test object. The retention rate of the ultrafiltration membrane was determined by measuring the residual amount of bovine serum albumin on the membrane. Among them C p is the concentration of bovine serum albumin in the influent, C f is the concentration of bovine serum albumin in purified water. The test results are shown in Table 1.

[0110] 3. Hydrophilic performance test

[0111] The contact angle between the prepared ultrafiltration membrane and water was tested using a contact angle tester. The test results are shown in Table 1.

[0112] 4. Tensile strength

[0113] The tensile strength of the prepared ultrafiltration membrane was tested using a universal material tensile testing machine. The test results are shown in Table 1.

[0114] 5. Antibacterial performance test

[0115] Escherichia coli was used as an indicator bacteria to culture the filtrate of the prepared membrane. The number of Escherichia coli in the filtrate was calculated by the plate count method, and the antibacterial rate was calculated. The test results are shown in Table 1.

[0116] Table 1

[0117]

[0118] As can be seen from the data in Table 1, the modified PVDF ultrafiltration membrane obtained in the embodiment of the present invention has good hydrophilicity, large water flux, high rejection rate, good anti-pollution performance, and excellent antibacterial and mechanical properties. In Comparative Example 1, since the PVDF ultrafiltration membrane does not contain hydroxyl groups, its binding force with the titanium dioxide carrier is poor, and the hydrophilicity and mechanical properties of the obtained ultrafiltration membrane are reduced to a certain extent. It can be seen from Comparative Examples 2 and 3 that when gelatin or polyhydroxy alcohol is not added to the modified titanium dioxide carrier dispersion, the modified titanium dioxide carrier is easily agglomerated and unevenly distributed in the modified PVDF ultrafiltration membrane, resulting in a significant decrease in hydrophilicity and mechanical properties.

[0119] In the description of this specification, the reference terms "some embodiments", "other embodiments", "embodiments", "examples", etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0120] Although the embodiments and examples of the present invention have been shown and described above, it will be understood that the above embodiments and examples are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments and examples within the scope of the present invention.

Claims

1. A method for preparing a modified PVDF ultrafiltration membrane, characterized in that: include: (1) Preparation of modified titanium dioxide carrier A titanium dioxide support is added to an aqueous solution containing an iron source and a silver source, and the mixture is stirred to obtain a precursor solution; a sodium hydroxide solution is added to the precursor solution, the mixture is stirred, an oxidizing gas is introduced, the mixture is filtered, and the mixture is dried to obtain a modified titanium dioxide support loaded with AgO and FeOOH; (2) Preparation of modified titanium dioxide carrier dispersion The modified titanium dioxide carrier is added to a mixed solvent of polyhydroxy alcohol containing gelatin and water, and ultrasonically dispersed to obtain a modified titanium dioxide carrier dispersion; (3) Preparation of modified PVDF ultrafiltration membrane The modified titanium dioxide carrier dispersion liquid is immersed in the hydroxyl-containing PVDF ultrafiltration membrane, and then dried to obtain the modified PVDF ultrafiltration membrane.

2. The method for preparing a modified PVDF ultrafiltration membrane according to claim 1, wherein The iron source is ferric nitrate, the silver source is silver nitrate; the oxidizing gas is any one of O3, O2, O3 / O2 mixed gas, O3 / N2 mixed gas, and O2 / N2 mixed gas.

3. The method for preparing a modified PVDF ultrafiltration membrane according to claim 1, wherein The time for introducing the oxidizing gas is 20 to 40 minutes, and the drying is vacuum drying at 40 to 80° C. for 4 to 8 hours.

4. The method for preparing a modified PVDF ultrafiltration membrane according to claim 1, wherein The mass of the AgO is 5-15% of the mass of the titanium dioxide support, and the mass of the FeOOH is 1-10% of the mass of the titanium dioxide support.

5. The method for preparing a modified PVDF ultrafiltration membrane according to claim 1, wherein The polyhydric alcohol is at least one of glycerol, 1,2-propylene glycol, 1,3-propylene glycol, ethylene glycol, diethylene glycol, polyethylene glycol 200, polyethylene glycol 400, and polyethylene glycol 600.

6. The method for preparing a modified PVDF ultrafiltration membrane according to claim 1, wherein In the mixed solvent, the mass ratio of the polyhydroxy alcohol to water is 1:1-5; and the gelatin accounts for 0.1-0.5% of the total mass of the mixed solvent.

7. The method for preparing a modified PVDF ultrafiltration membrane according to claim 1, wherein The mass fraction of the modified titanium dioxide carrier dispersion is 5-20%.

8. The method for preparing a modified PVDF ultrafiltration membrane according to claim 1, wherein The impregnation is carried out at room temperature for 0.5-1 hour; and the drying is carried out at 60-100° C. in vacuum for 4-12 hours.

9. The modified PVDF ultrafiltration membrane obtained according to the preparation method according to any one of claims 1 to 8.

10. Use of the modified PVDF ultrafiltration membrane according to claim 9 in water treatment.

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