Acid and alkali resistant and pollution resistant regenerated cellulose ultrafiltration membrane as well as preparation method and application thereof

Abstract

The invention relates to the technical field of membrane separation, in particular to a regenerated cellulose ultrafiltration membrane with acid and alkali resistance and pollution resistance as well as a preparation method and application thereof, and aims to solve the problems of flux attenuation and short service life caused by poor chemical stability and easiness in oil pollution of an existing polymer ultrafiltration membrane under an extreme pH condition. The preparation method is characterized in that cotton linter or cotton pulp is taken as a raw material, cellulose is dissolved at low temperature by adopting a pre-cooled alkali / urea / thiourea aqueous solution system, after defoaming and membrane scraping, regeneration forming is performed in a specific coagulating bath, and finally the finished ultrafiltration membrane is obtained through freeze drying. The method is simple in process, green and environment-friendly. The prepared regenerated cellulose ultrafiltration membrane has the characteristics of excellent acid and alkali resistance (stable performance within the pH range of 1-14), high oil pollution resistance (the water flux recovery rate is greater than 90%), adjustable structure and performance (the average pore size is 12-76 nm) and the like, and is particularly suitable for treating industrial oily wastewater with complex components.

Description

Technical Field

[0001] This invention relates to the field of membrane separation technology, and in particular to a regenerated cellulose ultrafiltration membrane that is both acid and alkali resistant and antifouling, its preparation method, and its application in oil-water separation. Background Technology

[0002] In industrial production sectors such as petrochemicals, machining, and food manufacturing, large quantities of oily wastewater with complex compositions, often accompanied by extreme acidity or alkalinity, are commonly generated. Compared to microfiltration, which primarily removes suspended solids, and reverse osmosis and nanofiltration, which aim to desalinate, membrane separation technology, especially ultrafiltration, is widely recognized as one of the ideal choices for treating such wastewater, particularly recalcitrant emulsions, due to its nanoscale pore size, which can efficiently trap emulsified oil droplets while maintaining low operating energy consumption.

[0003] However, existing mainstream commercial ultrafiltration membrane materials (such as polysulfone PS, polyacrylonitrile PAN, and polyvinylidene fluoride PVDF) have two significant drawbacks: First, their polymer backbone is prone to chemical degradation under strong acid or strong alkali conditions, leading to membrane structure damage and severely limiting their long-term stability and application range in extreme pH environments; Second, the inherent hydrophobicity of these materials makes it easy for oil droplets to be adsorbed and clog the membrane pores, causing serious irreversible pollution, resulting in a sharp decline in flux, requiring frequent chemical cleaning, which greatly increases operating costs and shortens membrane life.

[0004] Regenerated cellulose (RC) materials, derived from natural polymers, have shown great potential in the preparation of antifouling separation membranes due to their excellent biocompatibility, biodegradability, and inherent hydrophilicity. However, traditional regenerated cellulose membrane preparation processes, such as the viscose method or the cuprammonium method, suffer from problems such as long process flows, severe environmental pollution, and generally small pore sizes and low water flux of the resulting membranes, making it difficult to meet the requirements of high-flux separation. In recent years, low-temperature green dissolution systems, represented by alkali / urea / thiourea aqueous solutions, have provided a new approach to replace the traditional highly polluting viscose and cuprammonium methods and achieve environmentally friendly processing of cellulose. However, regenerated cellulose membranes directly prepared by this system still suffer from problems such as low flux, insufficient mechanical strength, easy collapse of pore structure after drying, and a lack of systematic verification of their separation performance and stability under harsh actual environments (such as a wide pH range), which greatly limits their practical application in the treatment of industrial oily wastewater.

[0005] To overcome the aforementioned bottlenecks, the industry has tried various methods such as blending modification and surface grafting to improve the performance of traditional polymer films. However, these methods are often complex, and the long-term stability of the introduced modified components in harsh chemical environments is questionable. It is difficult to fundamentally solve the contradiction between the chemical resistance and anti-fouling properties of materials at the same time.

[0006] Therefore, based on the needs of green chemical industry and practical applications, developing a new type of regenerated cellulose ultrafiltration membrane that is simple to process and can simultaneously possess excellent acid and alkali resistance, high flux, high oil pollution resistance and good mechanical strength has become an urgent need to promote the large-scale and economical application of membrane technology in complex industrial wastewater, which also constitutes the fundamental starting point of this invention. Summary of the Invention

[0007] The purpose of this invention is to provide a regenerated cellulose ultrafiltration membrane that is both acid and alkali resistant and anti-fouling, as well as its preparation method and application. This membrane aims to solve the problems of poor chemical stability, susceptibility to oil contamination, flux decline, and short lifespan of existing polymer ultrafiltration membranes under extreme pH conditions.

[0008] The technical solution adopted in this invention is as follows: A method for preparing a regenerated cellulose ultrafiltration membrane that is both acid and alkali resistant and fouling resistant includes the following steps: Step 1: Quickly dissolve cotton linters or cotton pulp in an alkaline aqueous solution containing urea and / or thiourea that has been pre-cooled to -10℃ to -15℃, and stir at room temperature for 5 to 10 minutes to obtain a homogeneous casting solution with a cellulose mass fraction of 2.5 to 5 wt%. Step 2: First, remove the air bubbles from the casting solution obtained in Step 1, and then, at room temperature, scrape the degassed casting solution onto a clean substrate, controlling the wet film thickness to be 300~400 μm; Step 3: Quickly immerse the substrate coated with casting solution into the coagulation bath and leave it for 5-15 minutes to allow the cellulose to be fully regenerated and shaped. Then wash with deionized water until neutral to obtain a wet regenerated cellulose membrane. Step 4: Freeze-dry the wet regenerated cellulose membrane obtained in Step 3 to obtain the regenerated cellulose ultrafiltration membrane.

[0009] Further, in step 1, the degree of polymerization of the cotton linters or cotton pulp is 600-700; the alkaline aqueous solution containing urea and / or thiourea in step 1 is an aqueous solution with an alkali content of 2wt%~12wt%, a urea content of 0wt%~15wt%, and a thiourea content of 0wt%~6.5wt%, wherein the alkali is NaOH, LiOH, or KOH.

[0010] Further, the alkaline aqueous solution containing urea and / or thiourea is one of the following: An aqueous solution containing 4wt%~8wt% alkali, 8wt%~10wt% urea, and 4.5wt%~6.5wt% thiourea. An aqueous solution with an alkali content of 5wt%~7wt% and a urea content of 11wt%~15wt%; An aqueous solution with an alkali content of 9wt%~10wt% and a thiourea content of 4.5wt%~6.5wt%.

[0011] Furthermore, in step 2, the process of removing air bubbles involves centrifuging at 5000-8000 rpm for 5-15 minutes at 5-10℃.

[0012] Further, in step 3, the coagulation bath is an aqueous solution of any one of N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, or sulfuric acid, or deionized water.

[0013] Furthermore, the coagulation bath is a DMAc aqueous solution with a volume concentration of 30% to 100%, or a sulfuric acid aqueous solution with a mass concentration of 4-6 wt%.

[0014] Furthermore, the freeze-drying conditions described in step 4 are: temperature below -50°C, vacuum degree below 10 Pa, and drying time of 10 to 15 hours.

[0015] Furthermore, the dry thickness of the ultrafiltration membrane is 100~200 μm, and the average pore size is adjustable in the range of 12~76 nm.

[0016] The present invention also provides the application of the regenerated cellulose ultrafiltration membrane in the separation and treatment of acidic, alkaline or neutral oily wastewater.

[0017] Before using the regenerated cellulose ultrafiltration membrane prepared by this invention, which has excellent acid and alkali resistance and high oil pollution resistance, the membrane needs to be pre-pressed at 0.2 MPa for 30 minutes to allow its pressure to stabilize.

[0018] Compared with existing materials and technologies, the present invention has the following advantages: 1) The regenerated cellulose ultrafiltration membrane prepared by the preparation method proposed in this invention has excellent acid and alkali resistance. It can maintain structural and performance stability in a wide range of pH values ​​from 1 to 14 and is suitable for treating industrial oily wastewater with complex and varied composition.

[0019] 2) The regenerated cellulose ultrafiltration membrane prepared using this invention possesses excellent oil fouling resistance due to its inherent hydrophilic properties. After treating high-concentration oil emulsions, approximately 90% flux recovery can be achieved simply by water rinsing, significantly reducing operating and maintenance costs.

[0020] 3) By adjusting process parameters such as the type and content of the casting solution mixture and the composition of the coagulation bath, this invention can flexibly and precisely adjust the pore size, flux and rejection rate of the membrane, thereby preparing a series of ultrafiltration membrane products suitable for different separation scenarios.

[0021] 4) The anion exchange membrane prepared by this invention has a simple preparation process and simple synthesis steps, and is easy to industrialize. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the self-made membrane performance evaluation device. 1-Raw material tank, 2-Mechanical pump, 3-Buffer tank, 4-Pressure gauge 1, 5-Membrane module unit, 6-Permeate receiving tank, 7-Pressure gauge 2, 8-Pressure regulating valve, 9-Flow meter. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions will be further described clearly and completely below through embodiments. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0024] The regenerated cellulose ultrafiltration membrane prepared by the method of this invention possesses both excellent acid and alkali resistance and high resistance to oil contamination. Based on the intrinsic chemical stability and inherent hydrophilicity of cellulose materials, this membrane can be used for a long time in harsh environments with pH 1-14 and effectively resists oil adhesion. Most of its flux can be restored with simple water washing, making it particularly suitable for treating complex industrial oily wastewater. Furthermore, the preparation process is green and environmentally friendly.

[0025] The following samples were involved: cotton pulp: Shandong Yinying Chemical Fiber Co., Ltd.; cotton linters: Tangshan Sanyou Xingda Chemical Fiber Co., Ltd. Sodium hydroxide (granular): Sinopharm Chemical Reagent Co., Ltd.; Potassium hydroxide: Hangzhou Xiaoshan Chemical Reagent Factory; Lithium hydroxide: Aladdin Reagent Co., Ltd.; N,N-Dimethylacetamide (99.5%): Anaiji Chemical; N-Methylpyrrolidone (99.0%): Shanghai Titan Chemical Co., Ltd.; Dimethyl sulfoxide: Shanghai Titan Chemical Co., Ltd.; Bovine serum albumin: Aladdin Reagent Co., Ltd.; Edible oil: Kerry Oils & Grains Co., Ltd.; Potassium dihydrogen phosphate: Huzhou Husheng Chemical Reagent Co., Ltd.; Urea: Sinopharm Chemical Reagent Co., Ltd.; Thiourea: Xilong Chemical Co., Ltd.

[0026] The room temperature described in this embodiment of the invention is around 25°C.

[0027] Example 1: Preparation of an ultrafiltration membrane (1) Weigh 4g of cotton linters with a degree of polymerization of 600 and quickly dissolve them in 96 mL of 4.6wt%LiOH / 10wt%urea / 4.5wt%thiourea aqueous solution that has been pre-cooled to -10℃ to -15℃. Stir at room temperature for 5 to 10 minutes to obtain a homogeneous casting solution A with a cellulose mass fraction of 4 wt%. (2) Centrifuge solution A at 8000 rpm for 10 minutes at 10℃ to remove bubbles; then at room temperature, scrape the degassed casting solution onto a clean substrate, pour the degassed casting solution onto a clean, dry glass plate, and quickly scrape the film with a self-made scraper, controlling the film thickness to 360 μm. (3) The glass plate was quickly immersed in a 5wt% H2SO4 aqueous solution and left for 5 min, then rinsed with plenty of deionized water until neutral. The prepared membrane was stored in a deionized water coagulation bath to obtain a wet regenerated cellulose membrane; (4) The obtained wet regenerated cellulose membrane was placed in a vacuum freeze dryer and dried under the conditions of -50°C and 2 Pa for 12 hours to obtain a dry cellulose membrane, which was denoted as RC-LTU.

[0028] Example 2: Preparation of an ultrafiltration membrane (1) Weigh 4g of cotton linters with a degree of polymerization of 600 and quickly dissolve them in 96 mL of 8wt% NaOH / 8wt% urea / 6.5wt% thiourea aqueous solution that has been pre-cooled to -10℃ to -15℃. Stir at room temperature for 5 to 10 minutes to obtain a homogeneous casting solution A with a cellulose mass fraction of 4 wt%. (2) Centrifuge solution A at 8000 rpm for 10 minutes at 10℃ to remove bubbles; then at room temperature, scrape the degassed casting solution onto a clean substrate, pour the degassed casting solution onto a clean, dry glass plate, and quickly scrape the film with a self-made scraper, controlling the film thickness to 360 μm. (3) The glass plate was quickly immersed in a 5wt% H2SO4 aqueous solution and left for 5 min, then rinsed with plenty of deionized water until neutral. The prepared membrane was stored in a deionized water coagulation bath to obtain a wet regenerated cellulose membrane; (4) The obtained wet regenerated cellulose membrane was placed in a vacuum freeze dryer and dried under the conditions of -50℃ and 2 Pa for 12 hours to obtain a dry cellulose membrane, which was denoted as RC-NTU.

[0029] Example 3: Preparation of an ultrafiltration membrane (1) Weigh 4g of cotton linters with a degree of polymerization of 600 and quickly dissolve them in 96 mL of 7wt% NaOH / 12wt% urea aqueous solution that has been pre-cooled to -10℃ to -15℃. Stir at room temperature for 5 to 10 minutes to obtain a homogeneous casting solution A with a cellulose mass fraction of 4 wt%. (2) Centrifuge solution A at 8000 rpm for 10 minutes at 10℃ to remove bubbles; then at room temperature, scrape the degassed casting solution onto a clean substrate, pour the degassed casting solution onto a clean, dry glass plate, and quickly scrape the film with a self-made scraper, controlling the film thickness to 360 μm. (3) The glass plate was quickly immersed in a 5wt% H2SO4 aqueous solution and left for 5 min, then rinsed with plenty of deionized water until neutral. The prepared membrane was stored in a deionized water coagulation bath to obtain a wet regenerated cellulose membrane; (4) The obtained wet regenerated cellulose membrane was placed in a vacuum freeze dryer and dried under the conditions of -50℃ and 2 Pa for 12 hours to obtain a dry cellulose membrane, which was denoted as RC-NU.

[0030] Example 4: Preparation of an ultrafiltration membrane (1) Weigh 4g of cotton linters with a degree of polymerization of 600 and quickly dissolve them in 96 mL of 9.5wt% NaOH / 4.5wt% thiourea aqueous solution that has been pre-cooled to -10℃ to -15℃. Stir at room temperature for 5 to 10 minutes to obtain a homogeneous casting solution A with a cellulose mass fraction of 4 wt%. (2) Centrifuge solution A at 8000 rpm for 10 minutes at 10℃ to remove bubbles; then at room temperature, scrape the degassed casting solution onto a clean substrate, pour the degassed casting solution onto a clean, dry glass plate, and quickly scrape the film with a self-made scraper, controlling the film thickness to 360 μm. (3) The glass plate was quickly immersed in a 5wt% H2SO4 aqueous solution and left for 5 min, then rinsed with plenty of deionized water until neutral. The prepared membrane was stored in a deionized water coagulation bath to obtain a wet regenerated cellulose membrane; (4) The obtained wet regenerated cellulose membrane was placed in a vacuum freeze dryer and dried under the conditions of -50℃ and 2 Pa for 12 hours to obtain a dry cellulose membrane, which was denoted as RC-NT.

[0031] Example 5: Preparation of an ultrafiltration membrane (1) Weigh 4g of cotton linters with a degree of polymerization of 600 and quickly dissolve them in 96 mL of 5wt% LiOH / 12wt% urea aqueous solution that has been pre-cooled to -10℃ to -15℃. Stir at room temperature for 5 to 10 minutes to obtain a homogeneous casting solution A with a cellulose mass fraction of 4 wt%. (2) Centrifuge solution A at 8000 rpm for 10 minutes at 10℃ to remove bubbles; then at room temperature, scrape the degassed casting solution onto a clean substrate, pour the degassed casting solution onto a clean, dry glass plate, and quickly scrape the film with a self-made scraper, controlling the film thickness to 360 μm. (3) The glass plate was quickly immersed in a 5wt% H2SO4 aqueous solution and left for 5 min, then rinsed with plenty of deionized water until neutral. The prepared membrane was stored in a deionized water coagulation bath to obtain a wet regenerated cellulose membrane; (4) The obtained wet regenerated cellulose membrane was placed in a vacuum freeze dryer and dried under the conditions of -50℃ and 2 Pa for 12 hours to obtain a dry cellulose membrane, denoted as RC-LU.

[0032] The performance of the prepared regenerated cellulose ultrafiltration membrane was then tested: Test 1: Membrane thickness, membrane surface resistance, and ion exchange capacity data are shown in Table 1.

[0033] Table 1 Comparison of the performance of the RC membranes used .

[0034] Test 2: The structure of the membrane performance evaluation instrument self-made in this application is as follows: Figure 1 As shown, the system includes a feed tank 1, a mechanical pump 2, a buffer tank 3, a pressure gauge 4, a membrane module 5, a permeate receiving tank 6, a pressure gauge 7, a pressure regulating valve 8, and a flow meter 9. The ultrafiltration membrane is installed in the membrane module 5. The feed tank 1, mechanical pump 2, and buffer tank 3 are sequentially connected to the inlet of the membrane module 5 via pipelines. Pressure gauge 4 is installed on the inlet pipeline of the membrane module 5. The permeate from the membrane module 5 flows into the permeate receiving tank 6. The outlet of the membrane module 5 is sequentially connected to the pressure regulating valve 8, the flow meter 9, and the feed tank 1 via pipelines. Pressure gauge 7 is installed on the inlet pipeline of the pressure regulating valve 8.

[0035] To evaluate the oil-water separation performance of the prepared regenerated cellulose ultrafiltration membrane, a self-made membrane performance evaluation instrument was used. Figure 1 Membrane separation performance was determined using a cross-flow method. A certain amount of edible oil was added to deionized water, and then stirred for 30 minutes using a mechanical stirrer (speed greater than 3000 rpm) to obtain 800 mg L / min. -1 Oil-in-water emulsion. The effective area of ​​the membrane used was 19.63 cm². 2 The membrane was first pre-pressed with pure water at 0.2 MPa for 30 min. After stabilization, the pure water flux was measured at 0.1 MPa to obtain the initial membrane water flux J1. Then, the water flux of the oil-in-water emulsion was measured to obtain the membrane water flux J2. The membrane was then rinsed with deionized water for 10 min, and the pure water flux J3 (i.e., the water flux after rinsing the membrane with deionized water) was measured again. The separation test of the oil-in-water emulsion should continue until the membrane flux decreased and stabilized. The membrane's oil-water separation performance was evaluated using the membrane's rejection rate (R) for oil-water emulsions, and the flux recovery rate (FRR) and flux decay rate (FDR) were used to evaluate the membrane's resistance to oil fouling. Before measuring the membrane's rejection rate for oil-water emulsions, the permeate was extracted with n-hexane, with each sample extracted three times.

[0036] The formula for calculating the flux recovery rate (FRR) is: .

[0037] The formula for calculating flux decay rate (FDR) is: .

[0038] In the formula, FRR is the water flux recovery rate; FDR is the flux decay rate; J1 is the initial water flux of the membrane; and J3 is the water flux after cleaning the membrane with deionized water. The results are shown in Table 2.

[0039] Table 2 Oil-water separation performance of RC membrane .

[0040] Test 3: To evaluate the acid and alkali resistance of the prepared regenerated cellulose ultrafiltration membrane, the membrane was immersed in deionized water solutions with pH values ​​of 1, 7, and 14 at room temperature. After one week of immersion, a self-made membrane performance evaluation instrument was used. Figure 1 The membrane separation performance was determined using a cross-flow method. The effective area of ​​the membrane used was 19.63 cm². 2 Before testing, the membrane was pre-pressurized with pure water at 0.2 MPa for 30 min to obtain the initial membrane water flux J1. Once the pressure stabilized, the membrane water flux and the rejection rate of the oil-in-water emulsion were measured at 0.1 MPa to obtain the membrane water flux J2. The separation test of the oil-in-water emulsion should continue until the membrane flux decreased and stabilized. Then, the retention rates of pure water flux, membrane area, and mass under different pH conditions were compared as indicators to evaluate the membrane's acid and alkali resistance. The concentration of the oil-in-water emulsion used was 800 mg / L. −1 (Prepared by dissolving edible oil in deionized water), the aqueous solutions with pH of 1 and 14 were adjusted with sulfuric acid and sodium hydroxide, respectively, and were denoted as RC-LTU-H2SO4 and RC-LTU-NaOH.

[0041] The formula for calculating the area retention rate (α) is: .

[0042] The formula for calculating the quality retention rate (β) is: .

[0043] In the formula, α is the area retention rate; β is the mass retention rate; S a With M a These represent the area and mass of the initial membrane, respectively; S b With M b The figures show the area and mass of the membrane after immersion in acid or alkali, respectively. The results are shown in Table 3.

[0044] Table 3 Properties of RC-LTU membranes after acid and alkali treatment .

[0045] The present invention has been specifically demonstrated and described through the above preferred embodiments. However, those skilled in the art should understand that various changes in form and detail may be made to the present invention without departing from the spirit and scope of the invention as defined in the appended claims, and all such changes shall be within the scope of protection of the present invention.

Claims

1. A method for preparing a regenerated cellulose ultrafiltration membrane that combines acid and alkali resistance with antifouling properties, characterized in that, Includes the following steps: Step 1: Quickly dissolve cotton linters or cotton pulp in an alkaline aqueous solution containing urea and / or thiourea that has been pre-cooled to -10℃ to -15℃, and stir at room temperature for 5 to 10 minutes to obtain a homogeneous casting solution with a cellulose mass fraction of 2.5 to 5 wt%. Step 2: First, remove the air bubbles from the casting solution obtained in Step 1, and then, at room temperature, scrape the degassed casting solution onto a clean substrate, controlling the wet film thickness to be 300~400 μm; Step 3: Quickly immerse the substrate coated with casting solution into the coagulation bath and leave it for 5-15 minutes to allow the cellulose to be fully regenerated and shaped. Then wash with deionized water until neutral to obtain a wet regenerated cellulose membrane. Step 4: Freeze-dry the wet regenerated cellulose membrane obtained in Step 3 to obtain the regenerated cellulose ultrafiltration membrane.

2. The method for preparing a regenerated cellulose ultrafiltration membrane with both acid and alkali resistance and anti-fouling properties as described in claim 1, characterized in that, In step 1, the degree of polymerization of the cotton linters or cotton pulp is 600-700; the alkaline aqueous solution containing urea and / or thiourea in step 1 is an aqueous solution with an alkali content of 2wt%~12wt%, a urea content of 0wt%~15wt%, and a thiourea content of 0wt%~6.5wt%, wherein the alkali is NaOH, LiOH, or KOH.

3. The method for preparing a regenerated cellulose ultrafiltration membrane with both acid and alkali resistance and anti-fouling properties as described in claim 2, characterized in that, The alkaline aqueous solution containing urea and / or thiourea is one of the following: An aqueous solution containing 4wt%~8wt% alkali, 8wt%~10wt% urea, and 4.5wt%~6.5wt% thiourea. An aqueous solution with an alkali content of 5wt%~7wt% and a urea content of 11wt%~15wt%; An aqueous solution with an alkali content of 9wt%~10wt% and a thiourea content of 4.5wt%~6.5wt%.

4. The method for preparing a regenerated cellulose ultrafiltration membrane with both acid and alkali resistance and anti-fouling properties as described in claim 1, characterized in that, In step 2, the process of removing air bubbles involves centrifuging at 5000-8000 rpm for 5-15 minutes at 5-10℃.

5. The method for preparing a regenerated cellulose ultrafiltration membrane with both acid and alkali resistance and anti-fouling properties as described in claim 1, characterized in that, In step 3, the coagulation bath is an aqueous solution of any one of N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, or sulfuric acid, or deionized water.

6. The method for preparing a regenerated cellulose ultrafiltration membrane with both acid and alkali resistance and anti-fouling properties as described in claim 5, characterized in that, The coagulation bath is a DMAc aqueous solution with a volume concentration of 30% to 100%, or a sulfuric acid aqueous solution with a mass concentration of 4-6 wt%.

7. The method for preparing a regenerated cellulose ultrafiltration membrane with both acid and alkali resistance and antifouling properties as described in claim 1, characterized in that, The freeze-drying conditions described in step 4 are: temperature below -50℃, vacuum degree below 10 Pa, and drying time of 10 to 15 hours.

8. A regenerated cellulose ultrafiltration membrane prepared by the method according to any one of claims 1-7, characterized in that, The dry thickness of the ultrafiltration membrane is 100~200 μm, and the average pore size is adjustable in the range of 12~76 nm.

9. The application of the regenerated cellulose ultrafiltration membrane with acid and alkali resistance and anti-fouling properties as described in claim 8 in the separation and treatment of acidic, alkaline or neutral oily wastewater.

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