Ultrafiltration membrane for treating wastewater from phenylenediamine production and preparation method thereof

Abstract

The present invention belongs to the field of wastewater treatment technology, and specifically relates to an ultrafiltration membrane used for the treatment of wastewater from the production of phenylenediamine and a preparation method thereof. The present invention realizes layered and precise interception of pollutants of different molecular weights such as phenylenediamine, nitrobenzenes, and nitrophenols through an asymmetric gradient pore structure, efficiently intercepts characteristic pollutants, and improves the efficiency of pretreatment. By forming a hydration protective layer on the membrane surface through an amphiphilic block copolymer, the contact angle is reduced, the amount of protein adsorption is reduced, and the membrane pore size is dynamically adjusted with the pH of the wastewater through a functional monomer containing a disulfide bond, thereby realizing intelligent interception of pollutants of different molecular weights, effectively avoiding the clogging of the pores by large molecular pollutants, thereby maintaining an effective flux of the membrane and improving the stability of the membrane, achieving multiple advantages of efficient interception, anti-fouling, high stability, and long service life, and providing an advanced technical solution for the pretreatment of highly toxic organic wastewater.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment, and particularly relates to an ultrafiltration membrane used for treating wastewater from phenylenediamine production and a preparation method thereof. Background Art

[0002] Phenylenediamine production wastewater contains characteristic pollutants such as phenylenediamine, nitrobenzenes, and nitrophenols. These substances are highly biotoxic and difficult to biodegrade. Conventional biochemical treatment systems are extremely ineffective in removing them and may even inhibit microbial activity. Currently, LDO advanced oxidation technology is commonly used in industry to pretreat phenylenediamine wastewater. However, this process requires high temperature and pressure, resulting in high energy consumption. Furthermore, macromolecular organic matter in the wastewater easily forms intermediates during the oxidation process, resulting in increased mother liquor volume in the subsequent evaporation system and increased treatment costs.

[0003] Membrane filtration is a highly efficient, low-consumption, and easy-to-use solid-liquid separation technology. It uses pressure differential as a driving force to achieve excellent separation effects and has been widely used in many fields. Based on the filtration pore size, membrane filtration processes can be divided into microfiltration, ultrafiltration, nanofiltration, reverse osmosis, and others. Among them, ultrafiltration membranes can effectively separate particles and colloidal substances, forming an excellent barrier to achieve the effect of filtration and purification. Currently, the main materials for ultrafiltration membranes include cellulose acetate, cellulose acetate esters, polyethylene, polysulfones, and polyamides. Membrane assembly types include tubular, plate-type, roll-type, capillary, and others. In actual applications, multiple components can be assembled to increase the filtration area and facilitate maintenance. Ultrafiltration membranes are pressure-driven, asymmetric polymer membranes with pore sizes ranging from 2 to 50 nm. Operating pressures range from 100 to 1000 kPa, and molecular weight cutoffs range from approximately 1 to 500 kDa. The membrane structure generally consists of two layers: an upper functional layer with dense micropores and a lower support layer with large through-pores, primarily used to enhance membrane strength. Common ultrafiltration membranes used in practical engineering applications include hollow fiber membranes, organic tubular membranes, organic flat membranes, and ceramic membranes.

[0004] Ultrafiltration membranes have a small pore size and can effectively remove most particulate matter and colloids from wastewater through physical interception. However, while traditional ultrafiltration membrane technology is widely used in wastewater treatment, its retention capacity for hydrophobic organic compounds such as phenylenediamines is limited, and the membrane surface is easily contaminated by adsorption of pollutants, resulting in a rapid decrease in membrane flux and a short service life. Therefore, developing an ultrafiltration membrane with highly selective retention and anti-fouling properties for the characteristic pollutants in phenylenediamine wastewater is of great significance for improving wastewater pretreatment efficiency and reducing subsequent treatment loads. Summary of the Invention

[0005] The purpose of the present invention is to solve the existing problems and provide an ultrafiltration membrane for treating wastewater from phenylenediamine production and a preparation method thereof.

[0006] The present invention is achieved through the following technical solutions:

[0007] A method for preparing an ultrafiltration membrane for treating wastewater from phenylenediamine production comprises the following steps:

[0008] S1. Weigh corresponding weight portions of polyvinylidene fluoride (PVDF) 60-80 parts, modifier 5-15 parts, porogen 10-20 parts, TiO2@GO 2-5 parts, MIL-125-NH2 1-2 parts, Pluronic F127 4-6 parts, and polyvinyl pyrrolidone (PVP) 0.08-1.6 parts for later use;

[0009] S2, adding PVDF, modifier, and porogen into the solvent, stirring and dissolving at 50-80 °C to form a uniform polymer solution, then adding TiO2@GO, MIL-125-NH2, and Pluronic F127, and stirring to obtain a casting solution;

[0010] S3, after DMF / acetone was mixed at a volume ratio of 3:1, PVDF and PVA were added to the DMF / acetone mixture at a mass ratio of 7:3 to a concentration of 15-20%, and ultrasonic treatment was performed to obtain a nanofiber solution, and then a nanofiber layer with a thickness of 20-30 μm was prepared on the surface of a polyester non-woven fabric by electrospinning to obtain a support layer after spinning;

[0011] S4, immersing the support layer in the casting solution, scraping the film and treating it in a gradient coagulation bath to perform a phase inversion reaction;

[0012] S5, immersing the solidified film in a grafting solution after Ar plasma treatment, and then performing UV irradiation treatment;

[0013] S6. The grafted membrane is repeatedly rinsed with deionized water to remove residual initiator and unreacted monomer, and then dried at 50-60° C. for 22-26 hours to obtain a finished ultrafiltration membrane.

[0014] Furthermore, the modifier is polyvinyl alcohol (PVA) or chitosan;

[0015] The porogen is N-methylpyrrolidone (NMP).

[0016] Furthermore, the preparation method of the TiO2@GO is as follows: TiO2 nanoparticles are added to a graphene oxide (GO) aqueous dispersion at a ratio of TiO2:GO=1:0.5, hydrothermally reacted at 120-130°C for 5-6 hours, centrifuged, washed, and dried.

[0017] Furthermore, the synthesis method of MIL-125-NH2 is as follows: ZrCl4 and 2-amino terephthalic acid derivative are added to DMF (N,N-dimethylformamide) in a molar ratio of 1:1.2~1.5, stirred to fully dissolve, heated to 110~120°C, stirred at 200~300 r / min for 20~24 hours, and after the reaction is completed, centrifuged at 3000~4000 r / min for 15~20 minutes, and then dried and passed through a 100-mesh sieve.

[0018] Furthermore, the solvent in step S2 is N,N-dimethylacetamide (DMAC), and the amount of the solvent used is 3 to 5 times the total mass of the polymer;

[0019] The casting liquid is stirred at 50-60° C. for 4-5 hours to obtain the casting liquid.

[0020] Furthermore, the ultrasonic treatment time in step S3 is 30 to 40 minutes;

[0021] During electrospinning, the control voltage was 15 kV and the flow rate was 1 mL / h.

[0022] Furthermore, the specific operation of the gradient coagulation bath treatment after the scraping described in step S4 is as follows: controlling the coating thickness of the plating solution to 150-260 μm, immediately immersing in the first-level coagulation bath, transferring to the second level after 10 minutes, and transferring to the third level after 5 minutes to complete the phase inversion; the temperature of the first level is 25°C, and the coagulation bath is deionized water containing 10% ethanol; the temperature of the second level is 15°C, and the coagulation bath is deionized water containing 5% ethanol; the temperature of the third level is 5°C, and the coagulation bath is pure water.

[0023] Furthermore, a direct current electric field is applied in the coagulation bath. Specifically, stainless steel electrodes are placed on both sides of the coagulation bath, and a direct current electric field is applied with an electric field strength of ≥50 V / cm.

[0024] Furthermore, the power of the Ar plasma treatment in step S5 is 50 W, the pressure is 10 Pa, and the treatment time is 3 to 5 minutes;

[0025] The components and corresponding weight percentages in the grafting solution are: potassium persulfate 0.2%, acrylic acid 5%, disulfide-bonded functional monomer cystamine (C4H 12 N2S2) 1%, EDTA 0.1%, tetramethylethylenediamine 0.1%, and the balance is pure water.

[0026] The UV irradiation treatment time is 20~40min.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] 1. The ultrafiltration membrane prepared by the present invention realizes layered and precise retention of pollutants with different molecular weights such as p-phenylenediamine, nitrobenzenes, and nitrophenols through an asymmetric gradient pore structure. The bionic lotus leaf micro-nanostructure is combined with super-hydrophilicity to promote the retention of hydrophobic p-phenylenediamine through the synergistic effect of physical screening and surface adsorption. The introduction of amino-modified MOFs materials increases the adsorption capacity of p-nitrophenol through coordination, effectively reduces the concentration of nitrophenols in wastewater, efficiently retains characteristic pollutants, and improves the efficiency of pretreatment.

[0029] 2. The present invention forms a hydrated protective layer on the membrane surface through amphiphilic block copolymers, reduces the contact angle, reduces the amount of protein adsorption, and thus effectively reduces the membrane fouling rate. In addition, the functional monomer containing disulfide bonds of the present invention allows the membrane pore size to be dynamically adjusted with the pH of the wastewater. A cross-linked network containing -SS- bonds is formed during UV-induced grafting. When the pH of the wastewater decreases (under acidic conditions), the disulfide bonds break and the membrane pores expand. When the pH increases (under alkaline conditions), the bonding is enhanced and the membrane pores shrink. Dynamic pore size adjustment realizes the intelligent retention of pollutants of different molecular weights, which can effectively prevent large molecular pollutants from clogging the pores, thereby maintaining an effective flux of the membrane and improving the stability of the membrane. Applying a DC electric field in the coagulation bath promotes the orientation of PVDF molecular chains, increases the β-crystalline phase content, enhances the solvent resistance of the membrane, and helps to improve the mechanical strength of the membrane.

[0030] 3. The present invention breaks through the technical bottleneck of low interception efficiency and easy pollution of traditional ultrafiltration membranes for difficult-to-degrade organic matter such as phenylenediamines, and achieves multiple advantages such as high efficiency interception, anti-fouling, high stability and long service life, providing an advanced technical solution for the pretreatment of highly toxic organic wastewater. DETAILED DESCRIPTION

[0031] In order to further explain the present invention, it is described below with reference to the following specific embodiments.

[0032] Table 1 Experimental reagents

[0033]

[0034] Note: Unless otherwise specified, the raw materials used in the present invention are all conventional products purchased from the market.

[0035] Example 1

[0036] A method for preparing an ultrafiltration membrane for treating wastewater from phenylenediamine production comprises the following steps:

[0037] S1. Weigh corresponding weight portions of polyvinylidene fluoride (PVDF) 60 parts, PVA 5 parts, NMP 10 parts, TiO2@GO 2 parts, MIL-125-NH2 1 part, Pluronic F127 4 parts, and PVP 0.08 parts for later use;

[0038] The TiO2@GO preparation method is as follows: TiO2 nanoparticles are added to a graphene oxide (GO) aqueous dispersion at a ratio of TiO2:GO = 1:0.5, hydrothermally reacted at 120°C for 5 hours, centrifuged, washed, and dried;

[0039] The synthesis method of MIL-125-NH2 is as follows: ZrCl4 and 2-amino terephthalic acid derivative are added to DMF (N,N-dimethylformamide) at a molar ratio of 1:1.2, stirred to fully dissolve, heated to 110°C, stirred at 200 rpm for 20 hours, and after the reaction is completed, centrifuged at 3000 rpm for 15 minutes, and then dried and passed through a 100-mesh sieve;

[0040] S2, PVDF, modifier, and porogen were added to DMAC, with the amount of solvent used being 3 times the total mass of the polymer, and stirred and dissolved at 50°C to form a uniform polymer solution. Then, TiO2@GO, MIL-125-NH2, and Pluronic F127 were added and stirred at 50°C for 4 h to obtain a casting solution;

[0041] S3, after DMF / acetone was mixed at a volume ratio of 3:1, PVDF and PVA were added to the DMF / acetone mixture at a mass ratio of 7:3 to a concentration of 15%, and ultrasonicated for 30 minutes to obtain a nanofiber solution, and then a nanofiber layer with a thickness of 20 μm was prepared on the surface of a polyester non-woven fabric by electrospinning to obtain a support layer after spinning;

[0042] During electrospinning, the control voltage was 15 kV and the flow rate was 1 mL / h;

[0043] S4, immersing the support layer in the casting solution, scraping the film and treating it in a gradient coagulation bath to perform a phase inversion reaction;

[0044] Specifically, the coating thickness of the coating solution is controlled to be 150 μm, and the coating is immediately immersed in the first-stage coagulation bath. After 10 minutes, it is transferred to the second stage, and after 5 minutes, it is transferred to the third stage to complete the phase inversion. The temperature of the first stage is 25°C, and the coagulation bath is deionized water containing 10% ethanol; the temperature of the second stage is 15°C, and the coagulation bath is deionized water containing 5% ethanol; the temperature of the third stage is 5°C, and the coagulation bath is pure water;

[0045] Applying a DC electric field in the coagulation bath, specifically placing stainless steel electrodes on both sides of the coagulation bath, applying a DC electric field with an electric field strength of ≥50 V / cm;

[0046] S5, immersing the solidified film in a grafting solution after Ar plasma treatment, and then subjecting it to UV irradiation for 20 minutes;

[0047] The power of Ar plasma treatment was 50 W, the pressure was 10 Pa, and the treatment time was 3 min;

[0048] The components and corresponding weight percentages in the grafting solution are: potassium persulfate 0.2%, acrylic acid 5%, disulfide-bonded functional monomer cystamine (C4H 12 N2S2) 1%, EDTA 0.1%, tetramethylethylenediamine 0.1%, the balance is pure water;

[0049] S6. The grafted membrane was repeatedly rinsed with deionized water to remove the residual initiator and unreacted monomers, and then dried at 50° C. for 22 hours to obtain a finished ultrafiltration membrane.

[0050] Example 2

[0051] A method for preparing an ultrafiltration membrane for treating wastewater from phenylenediamine production comprises the following steps:

[0052] S1. Weigh corresponding weight portions of polyvinylidene fluoride (PVDF) 70 parts, PVA 10 parts, NMP 15 parts, TiO2@GO 3 parts, MIL-125-NH2 1.5-2 parts, Pluronic F127 5 parts, and PVP 1.2 parts for later use;

[0053] The TiO2@GO preparation method is as follows: TiO2 nanoparticles are added to a graphene oxide (GO) aqueous dispersion at a ratio of TiO2:GO = 1:0.5, hydrothermally reacted at 125°C for 5.5 hours, centrifuged, washed, and dried;

[0054] The synthesis method of MIL-125-NH2 is as follows: ZrCl4 and 2-amino terephthalic acid derivative are added to DMF (N,N-dimethylformamide) at a molar ratio of 1:1.3, stirred to fully dissolve, heated to 115°C, stirred at 250 rpm for 22 hours, and after the reaction is completed, centrifuged at 3500 rpm for 17 minutes, and then dried and passed through a 100-mesh sieve;

[0055] S2, PVDF, modifier, and porogen were added to DMAC, with the amount of solvent used being 4 times the total mass of the polymer, and stirred and dissolved at 60°C to form a uniform polymer solution. Then, TiO2@GO, MIL-125-NH2, and Pluronic F127 were added and stirred at 55°C for 4.5 h to obtain a casting solution;

[0056] S3, after DMF / acetone was mixed at a volume ratio of 3:1, PVDF and PVA were added to the DMF / acetone mixture at a mass ratio of 7:3 to a concentration of 17%, and ultrasonicated for 35 minutes to obtain a nanofiber solution, and then a nanofiber layer with a thickness of 25 μm was prepared on the surface of a polyester non-woven fabric by electrospinning to obtain a support layer after spinning;

[0057] During electrospinning, the control voltage was 15 kV and the flow rate was 1 mL / h;

[0058] S4, immersing the support layer in the casting solution, scraping the film and treating it in a gradient coagulation bath to perform a phase inversion reaction;

[0059] Specifically, the coating thickness of the coating solution is controlled to be 200 μm, and the coating is immediately immersed in the first-stage coagulation bath. After 10 minutes, it is transferred to the second stage, and after 5 minutes, it is transferred to the third stage to complete the phase inversion. The temperature of the first stage is 25°C, and the coagulation bath is deionized water containing 10% ethanol; the temperature of the second stage is 15°C, and the coagulation bath is deionized water containing 5% ethanol; the temperature of the third stage is 5°C, and the coagulation bath is pure water;

[0060] Applying a DC electric field in the coagulation bath, specifically placing stainless steel electrodes on both sides of the coagulation bath, applying a DC electric field with an electric field strength of ≥50 V / cm;

[0061] S5, immersing the solidified film in a grafting solution after Ar plasma treatment, and then subjecting it to UV irradiation for 30 minutes;

[0062] The power of Ar plasma treatment was 50 W, the pressure was 10 Pa, and the treatment time was 4 min;

[0063] The components and corresponding weight percentages in the grafting solution are: potassium persulfate 0.2%, acrylic acid 5%, disulfide-bonded functional monomer cystamine (C4H 12 N2S2) 1%, EDTA 0.1%, tetramethylethylenediamine 0.1%, the balance is pure water;

[0064] S6. The grafted membrane was repeatedly rinsed with deionized water to remove the residual initiator and unreacted monomers, and then dried at 55° C. for 24 hours to obtain a finished ultrafiltration membrane.

[0065] Example 3

[0066] A method for preparing an ultrafiltration membrane for treating wastewater from phenylenediamine production comprises the following steps:

[0067] S1. Weigh corresponding weight portions of polyvinylidene fluoride (PVDF) 80 parts, PVA 15 parts, NMP 20 parts, TiO2@GO 5 parts, MIL-125-NH2 2 parts, Pluronic F127 6 parts, and PVP 1.6 parts for later use;

[0068] The TiO2@GO preparation method is as follows: TiO2 nanoparticles are added to a graphene oxide (GO) aqueous dispersion at a ratio of TiO2:GO = 1:0.5, hydrothermally reacted at 130°C for 6 hours, centrifuged, washed, and dried;

[0069] The synthesis method of MIL-125-NH2 is as follows: ZrCl4 and 2-amino terephthalic acid derivative are added to DMF (N,N-dimethylformamide) at a molar ratio of 1:1.5, stirred to fully dissolve, heated to 120°C, stirred at 300 rpm for 24 hours, and after the reaction is completed, centrifuged at 4000 rpm for 20 minutes, and then dried and passed through a 100-mesh sieve;

[0070] S2, PVDF, modifier, and porogen were added to DMAC, with the amount of solvent used being 5 times the total mass of the polymer, and stirred and dissolved at 80°C to form a uniform polymer solution. Then, TiO2@GO, MIL-125-NH2, and Pluronic F127 were added and stirred at 60°C for 5 h to obtain a casting solution;

[0071] S3, after mixing DMF / acetone in a volume ratio of 3:1, PVDF and PVA were added to the DMF / acetone mixture in a mass ratio of 7:3 to a concentration of 20%, and ultrasonically treated for 40 minutes to obtain a nanofiber solution, and then a nanofiber layer with a thickness of 30 μm was prepared on the surface of a polyester non-woven fabric by electrospinning to obtain a support layer after spinning;

[0072] During electrospinning, the control voltage was 15 kV and the flow rate was 1 mL / h;

[0073] S4, immersing the support layer in the casting solution, scraping the film and treating it in a gradient coagulation bath to perform a phase inversion reaction;

[0074] Specifically, the coating thickness of the coating solution is controlled to be 260 μm, and the coating is immediately immersed in the first-stage coagulation bath. After 10 minutes, it is transferred to the second stage, and after 5 minutes, it is transferred to the third stage to complete the phase inversion. The temperature of the first stage is 25°C, and the coagulation bath is deionized water containing 10% ethanol; the second stage is 15°C, and the coagulation bath is deionized water containing 5% ethanol; the third stage is 5°C, and the coagulation bath is pure water;

[0075] Applying a DC electric field in the coagulation bath, specifically placing stainless steel electrodes on both sides of the coagulation bath, applying a DC electric field with an electric field strength of ≥50 V / cm;

[0076] S5, immersing the solidified film in a grafting solution after Ar plasma treatment, and then subjecting it to UV irradiation for 40 minutes;

[0077] The power of Ar plasma treatment was 50 W, the pressure was 10 Pa, and the treatment time was 5 min;

[0078] The components and corresponding weight percentages in the grafting solution are: potassium persulfate 0.2%, acrylic acid 5%, disulfide-bonded functional monomer cystamine (C4H 12 N2S2) 1%, EDTA 0.1%, tetramethylethylenediamine 0.1%, the balance is pure water;

[0079] S6. The grafted membrane was repeatedly rinsed with deionized water to remove the residual initiator and unreacted monomers, and then dried at 60° C. for 26 h to obtain a finished ultrafiltration membrane.

[0080] Comparative Example 1

[0081] Compared with Example 2, this comparative example 1 replaces TiO2@GO with TiO2 nanoparticles, and the remaining steps are the same as those in Example 2.

[0082] Comparative Example 2

[0083] Compared with Example 2, this comparative example 2 omitted MIL-125-NH2, and the remaining steps were the same as those in Example 2.

[0084] Comparative Example 3

[0085] Compared with Example 2, this comparative example 3 omits step S3, and replaces the support layer in step S4 with polyester non-woven fabric. The remaining steps are the same as those in Example 2.

[0086] Comparative Example 4

[0087] Compared with Example 2, this comparative example 4 replaces step S4 with the following steps, and the remaining steps are the same as those in Example 2.

[0088] The casting liquid was evenly coated on the support layer to control the film thickness to 200 μm, and immediately immersed in a coagulation bath for phase inversion reaction. The coagulation bath was a 10% mass fraction ethanol aqueous solution at a temperature of 25° C. and a coagulation time of 45 min.

[0089] Comparative Example 5

[0090] Compared with Example 2, the DC electric field treatment in step S4 is omitted in Comparative Example 5, and the remaining steps are the same as those in Example 2.

[0091] Comparative Example 6

[0092] Compared with Example 2, the Ar plasma treatment in step S5 is omitted in Comparative Example 6, and the remaining steps are the same as those in Example 2.

[0093] Performance Testing

[0094] 1. Pure water flux and retention rate test

[0095] The pure water flux test method is: pure water flux test at 25℃ for 30min under 0.1MPa pressure;

[0096] The retention rate test method is: 100 mg / L phenylenediamine / nitrobenzene / nitrophenol solution, HPLC analysis of the inlet and outlet concentrations, and then calculate the retention rate.

[0097] The specific test results are shown in Table 2 below.

[0098] Table 2

[0099]

[0100] 2. Anti-pollution performance test

[0101] 2.1 Static adsorption test

[0102] Each group of membrane samples was immersed in 500 mg / L bovine serum albumin solution for 24 h, and the protein adsorption capacity was measured.

[0103] 2.2 Dynamic pollution test

[0104] The simulated wastewater containing 50 mg / L phenylenediamine and 10 mg / L humic acid was continuously filtered for 24 h and then rinsed with pure water for 30 min. The flux recovery rate (FRR) was then tested.

[0105] The specific test results are shown in Table 3 below.

[0106] Table 3

[0107]

[0108] It can be seen from Table 2 and Table 3 above that the pure water flux of the ultrafiltration membrane prepared by the method of the present invention is ≥180m 2 h·MPa, the retention rates of phenylenediamine, nitrobenzene, and nitrophenol are ≥95%, ≥92%, and ≥90%, respectively, and the protein adsorption capacity is as low as 5±0.5 mg / m 2 , continuously filtered simulated wastewater containing 50 mg / L phenylenediamine + 10 mg / L humic acid for 24 hours, and after rinsing with pure water for 30 minutes, the flux recovery rate was as high as 92±1%. It has high retention rate, high flux, high stability and high anti-fouling ability, and can treat phenylenediamine wastewater in a long-lasting and effective manner.

[0109] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for preparing an ultrafiltration membrane for treating wastewater from phenylenediamine production, characterized in that: The steps include: S1. Weigh corresponding weight portions of PVDF (60-80 parts), modifier (5-15 parts), porogen (10-20 parts), TiO2@GO (2-5 parts), MIL-125-NH2 (1-2 parts), Pluronic F127 (4-6 parts), and PVP (0.08-1.6 parts) for later use. S2, adding PVDF, modifier, and porogen into the solvent, stirring and dissolving to form a uniform polymer solution, then adding TiO2@GO, MIL-125-NH2, and Pluronic F127, stirring to obtain a casting solution; S3, after mixing DMF / acetone at a volume ratio of 3:1, PVDF and PVA were added to the DMF / acetone mixture at a mass ratio of 7:3 to a concentration of 15-20%, and ultrasonically treated to obtain a nanofiber solution, and then a nanofiber layer was prepared on the surface of a polyester non-woven fabric by electrospinning to obtain a spun support layer; S4, immersing the support layer in the casting solution, scraping the film and treating it in a gradient coagulation bath to perform a phase inversion reaction; The specific operation of the gradient coagulation bath treatment after the scraping is as follows: the coating thickness of the coating solution is controlled to be 150-260 μm, and the film is immediately immersed in the first-level coagulation bath. After 10 minutes, it is transferred to the second level, and after 5 minutes, it is transferred to the third level to complete the phase inversion. The temperature of the first level is 25°C, and the coagulation bath is deionized water containing 10% ethanol; the temperature of the second level is 15°C, and the coagulation bath is deionized water containing 5% ethanol; the temperature of the third level is 5°C, and the coagulation bath is pure water; S5, immersing the solidified film in a grafting solution after Ar plasma treatment, and then performing UV irradiation treatment; S6. The grafted membrane is repeatedly rinsed with deionized water to remove the residual initiator and unreacted monomers, and then dried to obtain a finished ultrafiltration membrane.

2. The method for preparing an ultrafiltration membrane for treating wastewater from phenylenediamine production according to claim 1, wherein: The modifier is polyvinyl alcohol or chitosan; The porogen is N-methylpyrrolidone.

3. The method for preparing an ultrafiltration membrane for treating wastewater from phenylenediamine production according to claim 1, wherein: The preparation method of the TiO2@GO is as follows: TiO2 nanoparticles are added to a graphene oxide aqueous dispersion at a ratio of TiO2:GO=1:0.5, hydrothermally reacted at 120-130°C for 5-6 hours, and then centrifuged, washed, and dried.

4. The method for preparing an ultrafiltration membrane for treating wastewater from phenylenediamine production according to claim 1, wherein: The synthesis method of MIL-125-NH2 is as follows: ZrCl4 and 2-amino terephthalic acid derivative are added to N,N-dimethylformamide in a molar ratio of 1:1.2~1.5, stirred to fully dissolve, heated to 110~120°C, stirred at 200~300 r / min for 20~24 hours, and after the reaction is completed, centrifuged at 3000~4000 r / min for 15~20 minutes, and then dried and passed through a 100-mesh sieve.

5. The method for preparing an ultrafiltration membrane for treating wastewater from phenylenediamine production according to claim 1, wherein: The solvent in step S2 is N,N-dimethylacetamide, and the amount of the solvent used is 3 to 5 times the total mass of the polymer; The casting liquid is stirred at 50-60° C. for 4-5 hours to obtain the casting liquid.

6. The method for preparing an ultrafiltration membrane for treating wastewater from phenylenediamine production according to claim 1, wherein: The ultrasonic treatment time in step S3 is 30-40 min; During electrospinning, the control voltage was 15 kV and the flow rate was 1 mL / h.

7. The method for preparing an ultrafiltration membrane for treating wastewater from phenylenediamine production according to claim 1, wherein: A DC electric field is applied in the coagulation bath. Specifically, stainless steel electrodes are placed on both sides of the coagulation bath and a DC electric field is applied with an electric field strength of ≥50 V / cm.

8. The method for preparing an ultrafiltration membrane for treating wastewater from phenylenediamine production according to claim 1, wherein: The Ar plasma treatment in step S5 is performed at a power of 50 W, a pressure of 10 Pa, and a treatment time of 3 to 5 minutes; The components and corresponding weight percentages in the grafting solution are: potassium persulfate 0.2%, acrylic acid 5%, disulfide-bonding functional monomer cystamine 1%, EDTA 0.1%, tetramethylethylenediamine 0.1%, and the balance is pure water; The UV irradiation treatment time is 20~40min.

9. An ultrafiltration membrane for treating wastewater from phenylenediamine production, characterized in that: The compound is prepared by the preparation method according to any one of claims 1 to 8.

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