An ultrafiltration membrane for advanced water treatment and its preparation method

Abstract

The present invention discloses an ultrafiltration membrane for advanced water treatment and a preparation method thereof, relating to the technical field of ultrafiltration membranes; the ultrafiltration membrane is obtained by blending 15-20 parts of block polysulfone particles, 3-5 parts of polyvinylpyrrolidone, 2-5 parts of sulfonated Ag-MOF, 6-10 parts of quaternized cellulose nanocrystals and 70-80 parts of N-methylpyrrolidone; wherein the block polysulfone particles are obtained by co-polycondensation of phenolphthalein, 4,4'-dichlorodiphenyl sulfone and polyethylene glycol; the introduction of sulfonated Ag-MOF and quaternized cellulose nanocrystals synergistically improves the anti-pollution performance of the prepared ultrafiltration membrane and prolongs the service life.

Description

Technical Field

[0001] The invention relates to the technical field of ultrafiltration membranes, in particular to an ultrafiltration membrane for deep water treatment and a preparation method thereof. Background Art

[0002] With the acceleration of urbanization and the growth of population, the discharge of water treatment, especially sewage treatment, has gradually increased year by year. Although traditional sewage treatment processes, such as activated sludge method and oxidation ditch, can effectively remove most organic matter and suspended solids, their effluent quality is usually difficult to meet the increasingly stringent emission standards or the needs of water reuse. Residual pollutants in domestic sewage (such as colloids, pathogenic microorganisms, trace organic matter and some soluble pollutants) have become the key bottleneck restricting the improvement of water quality. In such an environment, deep treatment technology has gradually become a hot spot for research and application, and ultrafiltration membranes use a pore size range of 1-100 nm to remove suspended solids, colloids, bacteria and macromolecular organic matter in water through physical interception. Due to its high-efficiency separation performance, it has become one of the core means in the field of deep treatment.

[0003] However, in domestic sewage treatment, although ultrafiltration membrane technology is highly efficient, it still faces multiple challenges. Among them, membrane fouling seriously affects the selectivity, permeability and service life of ultrafiltration membranes. Therefore, finding ultrafiltration membrane materials with more optimized performance is still a key issue in membrane applications. Summary of the invention

[0004] The object of the present invention is to provide an ultrafiltration membrane for deep water treatment and a preparation method thereof, so as to solve the problems raised in the prior art.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A method for preparing an ultrafiltration membrane for deep water treatment comprises the following steps:

[0007] Step 1: After drying and removing water from phenolphthalein, 4,4'-dichlorodiphenyl sulfone, anhydrous potassium carbonate and polyethylene glycol respectively, phenolphthalein, 4,4'-dichlorodiphenyl sulfone and anhydrous potassium carbonate are mixed, toluene and dimethylacetamide are added, and the mixture is heated to 140° C. and stirred for reaction for 6-10 hours until no water is taken out, and the mixture is heated to 160-180° C. to remove toluene, and the mixture is continued to react for 8 hours, and the mixture is cooled to 150° C., polyethylene glycol is added, and the mixture is continued to react for 1-2 hours, and the mixture is poured into pure water for sedimentation, and dilute hydrochloric acid is added dropwise, and the solid is filtered out and then crushed, and then washed and dried to obtain segmented polysulfone particles;

[0008] Step 2: Mix the block polysulfone particles prepared in Step 1 with polyvinylpyrrolidone, sulfonated Ag-MOF, quaternized cellulose nanocrystals, and N-methylpyrrolidone, stir at 40 - 60 °C for 6 - 8 h, and then degas under vacuum for 1 h to obtain a casting solution; pour the casting solution onto a clean glass plate, use a doctor blade with a gap of 100 - 150 μm to scrape into a flat film, after standing for 15 - 30 s, immerse it in pure water until the nascent film falls off, and replace the pure water every 6 - 8 h to obtain the final ultrafiltration membrane.

[0009] Among them, the ultrafiltration membrane in Step 2 includes the following raw materials in parts by mass: 15 - 20 parts of block polysulfone particles, 3 - 5 parts of polyvinylpyrrolidone, 2 - 5 parts of sulfonated Ag-MOF, 6 - 10 parts of quaternized cellulose nanocrystals, and 70 - 80 parts of N-methylpyrrolidone.

[0010] In Step 1, the dosage ratio of phenolphthalein, 4,4'-dichlorodiphenyl sulfone, and polyethylene glycol is 1 mol : 1 mol : 25 - 80 g.

[0011] The preparation steps of sulfonated Ag-MOF are as follows: Place dopamine hydrochloride in a Tris buffer solution with a pH of 8.5, add Ag-MOF and ultrasonicate for 10 min, then stir and react for 4 - 6 h, centrifuge, wash, and dry. Then transfer it to pure water and ultrasonicate for 20 min, add 3-mercapto-1-propanesulfonic acid sodium salt, raise the temperature to 50 - 60 °C and stir and react for 24 h, then centrifuge and separate, wash and dry to obtain it.

[0012] Preferably, the mass ratio of Ag-MOF, dopamine hydrochloride, and 3-mercapto-1-propanesulfonic acid sodium salt is 1:1:(0.6 - 1.5).

[0013] The preparation steps of quaternized cellulose nanocrystals are as follows:

[0014] Step s1: Take cellulose nanocrystals, place them in a nitric acid solution, oscillate and activate for 6 h, then freeze-dry. After mixing with sodium periodate and placing them in pure water, stir and react for 3 h, then add ethylene glycol, centrifuge and wash with water. After mixing with cysteine, raise the temperature to 40 °C under nitrogen protection and stir for 5 h to obtain mercapto-functionalized cellulose nanocrystals for standby;

[0015] Step s2: Dissolve dimethylaminoethyl methacrylate in N,N'-dimethylformamide, add dodecyl bromide, stir and react for 48 h under a nitrogen atmosphere, add anhydrous ether for repeated precipitation and purification to obtain a quaternary ammonium salt monomer for standby;

[0016] Step s3: Place the mercapto-functionalized cellulose nanocrystals prepared in Step s1 in dimethyl sulfoxide, add the quaternary ammonium salt monomer prepared in Step s2 and 2,2-dimethylolpropionic acid, introduce nitrogen, react under ultraviolet light for 10 h, then centrifuge, wash, and freeze-dry to obtain quaternized cellulose nanocrystals.

[0017] Preferably, in step s1, the mass ratio of cellulose nanocrystals to sodium periodate and cysteine ​​is 1:(0.6-1):(1-2); and in step s2, the volume ratio of dimethylaminoethyl methacrylate to dodecane bromide is (4-5):6.

[0018] Preferably, in step s3, the mass ratio of the thiolated cellulose nanocrystals to the quaternary ammonium salt monomer is 1:1; the mass fraction of 2,2-dihydroxymethylpropionic acid is 1.5%-2% of the thiolated cellulose nanocrystals.

[0019] An ultrafiltration membrane for deep water treatment is prepared by the above preparation method.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. The present invention uses block polysulfone particles and polyvinyl pyrrolidone, sulfonated Ag-MOF, quaternized cellulose nanocrystals, and N-methylpyrrolidone to mix to obtain a casting solution, and scrapes to obtain an ultrafiltration membrane; wherein the block polysulfone particles are obtained by co-condensation of phenolphthalein, 4,4'-dichlorodiphenyl sulfone, and polyethylene glycol, and the polyethylene glycol has good biocompatibility and hydrophilicity, effectively improves the hydrophilicity of the ultrafiltration membrane, and increases the porosity and permeability of the membrane; the sulfonated Ag-MOF uses a silver metal-organic framework, which has excellent antibacterial properties, and utilizes the mikrophore of polydopamine and thiol to obtain a membrane casting solution; By introducing sulfonic acid groups, hydrophilic groups, on the surface of Ag-MOF, the compatibility of Ag-MOF and ultrafiltration membrane is improved, the stability of Ag-MOF and membrane matrix is ​​improved, the shedding is slowed down and the service life is increased; cellulose nanocrystals have good hydrophilicity and adsorption. By introducing thiol and quaternary ammonium salt monomers to produce click reactions, quaternization is achieved, the dispersibility and compatibility of CNC in ultrafiltration membrane are improved, and cellulose is created again. Use value, at the same time, quaternary ammonium salts are introduced to give the membrane surface good hydrophilicity, and improve the anti-fouling performance of ultrafiltration membrane during water treatment.

[0022] 2. The block polysulfone particles, sulfonated Ag-MOF and quaternized cellulose nanocrystals in the raw materials of the product of the present invention are self-developed products, and the product quality is effectively controlled during the production process. DETAILED DESCRIPTION

[0023] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making any creative work shall fall within the scope of protection of the present invention.

[0024] In the experiment, the molecular weight of polyethylene glycol was 2000Da; polyvinyl pyrrolidone K30 and Ag-MOF were purchased from Xi'an Qiyue Biology with the product number of Q-0340346; phenolphthalein, 4,4'-dichlorodiphenyl sulfone, anhydrous potassium carbonate and polyethylene glycol all needed to be dried and dehydrated before being put into use;

[0025] The preparation steps of sulfonated Ag-MOF are as follows: Place 1 g of hydrochloric acid dopamine in 100 mL of Tris buffer solution with a pH of 8.5 and a concentration of 10 mM. After adding 1 g of Ag-MOF and ultrasonically treating for 10 min, stir and react for 4 h, then centrifuge, wash, and dry. Then transfer it to pure water and ultrasonically treat for 20 min. Add 1 g of 3-mercapto-1-propanesulfonic acid sodium salt, heat to 50 °C, stir and react for 24 h, then centrifuge and separate, wash, and dry to obtain it;

[0026] Example 1: Provide a preparation method of an ultrafiltration membrane for advanced water treatment. The specific steps are as follows:

[0027] Step 1: Mix 9.547 g of phenolphthalein, 8.620 g of 4,4'-dichlorodiphenyl sulfone, and 5.526 g of anhydrous potassium carbonate, then add 20 mL of toluene and 100 g of dimethylacetamide, heat to 140 °C, stir and react for 6 h until no water is carried out. Heat to 160 °C to remove toluene, then continue to react for 8 h. Cool to 150 °C, add 1.753 g of polyethylene glycol, continue to react for 2 h, then pour it into pure water for sedimentation, add dilute hydrochloric acid dropwise until the pH is 1, filter out the solid matter, crush it, wash, and dry to obtain block polyethersulfone particles;

[0028] Step 2: Mix 18 g of the block polyethersulfone particles prepared in Step 1, 3 g of polyvinylpyrrolidone, 4 g of sulfonated Ag-MOF, 8 g of quaternized cellulose nanocrystals, and 72 g of N-methylpyrrolidone, stir at 40 °C for 8 h, then vacuum degas for 1 h to obtain a casting solution. Pour the casting solution onto a clean glass plate, use a doctor blade with a gap of 150 μm to scrape it into a flat membrane. After standing for 30 s, immerse it in pure water until the nascent membrane falls off, and change the pure water every 8 h to obtain the final ultrafiltration membrane.

[0029] Among them, the preparation steps of quaternized cellulose nanocrystals are as follows:

[0030] Step s1: Take 5 g of cellulose nanocrystals, place them in 100 mL of nitric acid solution with a concentration of 0.5 mol / L, oscillate and activate for 6 h, then freeze-dry. Mix with 5 g of sodium periodate, place it in pure water, stir and react for 3 h, then add 8 mL of ethylene glycol, centrifuge and wash with water. Mix with 5 g of cysteine, heat to 40 °C under nitrogen protection, and stir for 5 h to obtain thiolated cellulose nanocrystals for standby;

[0031] Step s2: Dissolve 10 mL of dimethylaminoethyl methacrylate in 25 mL of N,N'-dimethylformamide, add 15 mL of bromododecane, stir and react for 48 h under a nitrogen atmosphere, add anhydrous ether for repeated precipitation and purification to obtain a quaternary ammonium salt monomer for standby;

[0032] Step s3: Place the thiolated cellulose nanocrystals prepared in step s1 of 5 g into 100 mL of dimethyl sulfoxide, add the quaternary ammonium salt monomer prepared in step s2 of 5 g and 0.075 g of 2,2-dimethylolpropionic acid, introduce nitrogen, react under ultraviolet light for 10 h, then centrifuge, wash, and freeze-dry to obtain quaternized cellulose nanocrystals.

[0033] Example 2: Provide a preparation method for an ultrafiltration membrane for advanced water treatment, and the specific steps are as follows:

[0034] Step 1: Take 9.548 g of phenolphthalein, 8.612 g of 4,4'-dichlorodiphenyl sulfone, and 5.525 g of anhydrous potassium carbonate, mix them, add 20 mL of toluene and 100 g of dimethylacetamide, heat to 140 °C and stir to react for 6 h until no water is carried out, heat to 160 °C to remove toluene, continue to react for 8 h, cool to 150 °C, add 0.844 g of polyethylene glycol and continue to react for 2 h, then pour into pure water for sedimentation, dropwise add dilute hydrochloric acid until the pH is 1, filter out the solid matter, crush it, wash and dry to obtain block polysulfone particles;

[0035] Step 2: Mix 15 g of the block polysulfone particles prepared in step 1, 3 g of polyvinylpyrrolidone, 3 g of sulfonated Ag-MOF, 6 g of quaternized cellulose nanocrystals, and 78 g of N-methylpyrrolidone, stir at 40 °C for 8 h and then vacuum degas for 1 h to obtain a casting solution; pour the casting solution onto a clean glass plate, use a doctor blade with a gap of 150 μm to scrape into a flat membrane, let it stand for 30 s, then immerse it in pure water until the nascent membrane falls off, and change the pure water every 8 h to obtain the final ultrafiltration membrane.

[0036] Among them, the preparation steps of the quaternized cellulose nanocrystals are as follows:

[0037] Step s1: Take 5 g of cellulose nanocrystals, place them in 100 mL of a 0.5 mol / L nitric acid solution, oscillate and activate for 6 h, then freeze-dry. After mixing with 5 g of sodium periodate and placing them in pure water, stir and react for 3 h, add 8 mL of ethylene glycol, centrifuge and wash with water, mix with 5 g of cysteine, and under nitrogen protection, heat to 40 °C and stir for 5 h to obtain thiolated cellulose nanocrystals for standby;

[0038] Step s2: Dissolve 10 mL of dimethylaminoethyl methacrylate in 25 mL of N,N'-dimethylformamide, add 15 mL of bromododecane, stir and react under a nitrogen atmosphere for 48 h, add anhydrous ether for repeated precipitation and purification to obtain the quaternary ammonium salt monomer for standby;

[0039] Step s3: Place the thiolated cellulose nanocrystals prepared in step s1 of 5 g into 100 mL of dimethyl sulfoxide, add 5 g of the quaternary ammonium salt monomer prepared in step s2 and 0.075 g of 2,2-dimethylolpropionic acid, introduce nitrogen, react under an ultraviolet lamp for 10 h, then centrifuge, wash, and freeze-dry to obtain quaternized cellulose nanocrystals.

[0040] Example 3: Provide a preparation method of an ultrafiltration membrane for advanced water treatment, and the specific steps are as follows:

[0041] Step 1: Mix 9.549 g of phenolphthalein, 8.617 g of 4,4'-dichlorodiphenyl sulfone, and 5.529 g of anhydrous potassium carbonate, add 20 mL of toluene and 100 g of dimethylacetamide, heat to 140 °C and stir to react for 6 h until no water is carried out, warm to 160 °C to remove toluene, continue to react for 8 h, cool to 150 °C, add 2.398 g of polyethylene glycol and continue to react for 2 h, then pour into pure water for sedimentation, add dilute hydrochloric acid dropwise until the pH is 1, filter out the solid matter, crush, wash, and dry to obtain block polysulfone particles;

[0042] Step 2: Mix 20 g of the block polysulfone particles prepared in step 1, 5 g of polyvinylpyrrolidone, 5 g of sulfonated Ag-MOF, 10 g of quaternized cellulose nanocrystals, and 80 g of N-methylpyrrolidone, stir at 40 °C for 8 h and then degas under vacuum for 1 h to obtain a casting solution; pour the casting solution onto a clean glass plate, use a doctor blade with a gap of 150 μm to scrape into a flat membrane, let stand for 30 s, then immerse in pure water until the nascent membrane falls off, and change the pure water every 8 h to obtain the final ultrafiltration membrane.

[0043] Among them, the preparation steps of the quaternized cellulose nanocrystals are as follows:

[0044] Step s1: Take 5 g of cellulose nanocrystals, place them in 100 mL of a nitric acid solution with a concentration of 0.5 mol / L, oscillate and activate for 6 h, then freeze-dry, mix with 5 g of sodium periodate, place in pure water, stir and react for 3 h, add 8 mL of ethylene glycol, centrifuge and wash with water, mix with 5 g of cysteine, and under nitrogen protection, heat to 40 °C and stir for 5 h to obtain thiolated cellulose nanocrystals for standby;

[0045] Step s2: Dissolve 10 mL of dimethylaminoethyl methacrylate in 25 mL of N,N'-dimethylformamide, add 15 mL of bromododecane, stir and react for 48 h under a nitrogen atmosphere, add anhydrous ether for repeated precipitation and purification to obtain a quaternary ammonium salt monomer for standby;

[0046] Step s3: 5 g of the thiolated cellulose nanocrystals prepared in step s1 are placed in 100 mL of dimethyl sulfoxide, 5 g of the quaternary ammonium salt monomer prepared in step s2 and 0.075 g of 2,2-dihydroxymethylpropionic acid are added, nitrogen is introduced, and the mixture is reacted under ultraviolet light for 10 h. The mixture is then centrifuged, washed, and freeze-dried to obtain quaternary cellulose nanocrystals.

[0047] Comparative Example 1: As a control experiment of Example 1, the segmented polysulfone particles were not subjected to polyethylene glycol blocking, and the specific steps were as follows:

[0048] Step 1: 9.544 g of phenolphthalein, 8.618 g of 4,4'-dichlorodiphenyl sulfone, and 5.528 g of anhydrous potassium carbonate were mixed, and 20 mL of toluene and 100 g of dimethylacetamide were added, and the mixture was heated to 140° C. and stirred for 6 h until no water was taken out, and the mixture was heated to 160° C. to remove toluene, and the mixture was reacted for 8 h, and the mixture was poured into pure water for sedimentation, and dilute hydrochloric acid was added dropwise until the pH was 1, and the solid was filtered out and crushed, and then washed and dried to obtain polysulfone particles;

[0049] Step 2: Mix 18 g of the polysulfone particles prepared in step 1 with 3 g of polyvinyl pyrrolidone, 4 g of sulfonated Ag-MOF, 8 g of quaternized cellulose nanocrystals, and 72 g of N-methylpyrrolidone, stir at 40 °C for 8 h, and then vacuum degas for 1 h to obtain a casting solution; pour the casting solution onto a clean glass plate, and use a scraper with a gap of 150 μm to scrape it into a flat membrane. After standing for 30 seconds, immerse it in pure water until the primary membrane falls off, and replace the pure water every 8 hours to obtain the final ultrafiltration membrane.

[0050] The preparation steps of quaternized cellulose nanocrystals are as follows:

[0051] Step s1: 5 g of cellulose nanocrystals were placed in 100 mL of 0.5 mol / L nitric acid solution for oscillation activation for 6 h, then freeze-dried, mixed with 5 g of sodium periodate, placed in pure water, stirred for reaction for 3 h, added with 8 mL of ethylene glycol, centrifuged and washed with water, mixed with 5 g of cysteine, heated to 40° C. under nitrogen protection and stirred for 5 h to obtain thiolated cellulose nanocrystals for later use;

[0052] Step s2: dissolving 10 mL of dimethylaminoethyl methacrylate in 25 mL of N,N'-dimethylformamide, adding 15 mL of dodecane bromide, stirring and reacting for 48 h under a nitrogen atmosphere, adding anhydrous ether to repeat precipitation and purification to obtain a quaternary ammonium salt monomer for later use;

[0053] Step s3: 5 g of the thiolated cellulose nanocrystals prepared in step s1 are placed in 100 mL of dimethyl sulfoxide, 5 g of the quaternary ammonium salt monomer prepared in step s2 and 0.075 g of 2,2-dihydroxymethylpropionic acid are added, nitrogen is introduced, and the mixture is reacted under ultraviolet light for 10 h. The mixture is then centrifuged, washed, and freeze-dried to obtain quaternary cellulose nanocrystals.

[0054] Comparative Example 2: As a control experiment for Example 1, sulfonated Ag-MOF was not added to the prepared ultrafiltration membrane. The specific steps are as follows:

[0055] Step 1: Take 9.55 g of phenolphthalein, 8.62 g of 4,4'-dichlorodiphenyl sulfone, and 5.53 g of anhydrous potassium carbonate, mix them, add 20 mL of toluene and 100 g of dimethylacetamide, heat to 140 °C and stir for 6 h until no water is carried out. After heating to 160 °C to remove toluene, continue the reaction for 8 h. Cool to 150 °C, add 1.75 g of polyethylene glycol and continue the reaction for 2 h, then pour into pure water for sedimentation. Dropwise add dilute hydrochloric acid until the pH is 1, filter out the solid, crush it, wash and dry to obtain block polyethersulfone particles.

[0056] Step 2: Mix 18 g of the block polyethersulfone particles prepared in Step 1, 3 g of polyvinylpyrrolidone, 8 g of quaternized cellulose nanocrystals, and 72 g of N-methylpyrrolidone, stir at 40 °C for 8 h, and then degas under vacuum for 1 h to obtain a casting solution. Pour the casting solution onto a clean glass plate, use a doctor blade with a gap of 150 μm to scrape into a flat membrane. After standing for 30 s, immerse it in pure water until the nascent membrane falls off, and change the pure water every 8 h to obtain the final ultrafiltration membrane.

[0057] Among them, the preparation steps of the quaternized cellulose nanocrystals are as follows:

[0058] Step s1: Take 5 g of cellulose nanocrystals, place them in 100 mL of a 0.5 mol / L nitric acid solution, oscillate and activate for 6 h, then freeze-dry. Mix with 5 g of sodium periodate, place in pure water, stir and react for 3 h, add 8 mL of ethylene glycol, centrifuge and wash with water. Mix with 5 g of cysteine, heat to 40 °C under nitrogen protection and stir for 5 h to obtain thiolated cellulose nanocrystals for standby.

[0059] Step s2: Dissolve 10 mL of dimethylaminoethyl methacrylate in 25 mL of N,N'-dimethylformamide, add 15 mL of bromododecane, stir and react for 48 h under a nitrogen atmosphere, add anhydrous ether for repeated precipitation and purification to obtain a quaternary ammonium salt monomer for standby.

[0060] Step s3: Place 5 g of the thiolated cellulose nanocrystals prepared in Step s1 in 100 mL of dimethyl sulfoxide, add 5 g of the quaternary ammonium salt monomer prepared in Step s2 and 0.075 g of 2,2-bis(hydroxymethyl)propionic acid, introduce nitrogen, react under ultraviolet light for 10 h, then centrifuge, wash and freeze-dry to obtain quaternized cellulose nanocrystals.

[0061] Comparative Example 3: As a control experiment for Example 1, quaternized cellulose nanocrystals were not added to the prepared ultrafiltration membrane. The specific steps are as follows:

[0062] Step 1: Take 9.55 g of phenolphthalein, 8.62 g of 4,4'-dichlorodiphenyl sulfone, and 5.53 g of anhydrous potassium carbonate, mix them, add 20 mL of toluene and 100 g of dimethylacetamide, heat to 140 °C, stir and react for 6 h until no water is carried out. After heating to 160 °C to remove toluene, continue the reaction for 8 h. Cool down to 150 °C, add 1.75 g of polyethylene glycol and continue the reaction for 2 h. Then pour it into pure water for sedimentation, add dilute hydrochloric acid dropwise until the pH is 1. Filter out the solid, crush it, wash and dry to obtain block polysulfone particles;

[0063] Step 2: Mix 18 g of the block polysulfone particles prepared in Step 1, 3 g of polyvinylpyrrolidone, 4 g of sulfonated Ag-MOF, and 72 g of N-methylpyrrolidone, stir at 40 °C for 8 h, and then perform vacuum degassing for 1 h to obtain a casting solution. Pour the casting solution onto a clean glass plate, use a doctor blade with a gap of 150 μm to scrape it into a flat film. After standing for 30 s, immerse it in pure water until the nascent membrane falls off, and change the pure water every 8 h to obtain the final ultrafiltration membrane.

[0064] Detection test

[0065] 1. Contact angle test experiment: Take the ultrafiltration membranes prepared in Examples 1-3 and Comparative Examples 1-3, place them on the test bench of a water contact angle tester, drop 4 μL of water droplets on the surface of the ultrafiltration membrane at room temperature, take a photo and measure the angle between the water droplet section and the membrane surface. Each ultrafiltration membrane is tested 5 times at different water droplet positions, calculate the average value, and record it in Table 1.

[0066] 2. Ultrafiltration membrane circulation experiment: Use a cross-flow filtration device to test the ultrafiltration membranes prepared in Examples 1-3 and Comparative Examples 1-3:

[0067] (1) Pre-press the ultrafiltration membrane with pure water before testing, pre-press at 0.15 MPa for 30 min;

[0068] (2) Adjust the pressure to 0.10 MPa, record the volume of pure water permeated every 10 min, and continuously record the cumulative volume for 1 h;

[0069] (3) Replace pure water with 0.1 g / L BAS solution, perform the same operation as above, record the volume of BAS solution permeated every 10 min, continuously record the cumulative volume for 1 h, then collect the filtrate and the contaminated solution, and use a UV-visible spectrophotometer to measure the absorbance of each at a wavelength of 280 nm;

[0070] (4) After rinsing the front and back sides of the ultrafiltration membrane with pure water, continue to work for 1 h according to (2), and record the volume of pure water permeated;

[0071] Calculate the fluxes J (L / m 2 ·h) of pure water and BAS solution with the cumulative volume of the permeate;

[0072] Calculate the rejection rate R (%) of the ultrafiltration membrane using the permeate concentration of BAS in (3) and the original solution concentration.

[0073] Calculate the flux recovery rate FRR (%) using the pure water flux in (2) and the pure water flux in (4).

[0074] Calculate the irreversible fouling parameter R using the pure water fluxes and the BAS fluxes in two runs. ir (%).

[0075] Table 1

[0076]

[0077] Conclusion: From the above data, it can be seen that the ultrafiltration membrane prepared in Example 1 has good hydrophilicity and excellent anti-fouling performance; in Comparative Example 1, the block of polyethylene glycol was not carried out for Example 1, which had an obvious impact on the hydrophilicity of the membrane, and the anti-fouling performance also decreased accordingly; in Comparative Example 2, sulfonated Ag-MOF was not added, which had a slight impact on the hydrophilicity and anti-fouling performance; in Comparative Example 3, quaternized CNC was not added, which significantly affected the anti-fouling performance of the ultrafiltration membrane. It can be seen that quaternized CNC effectively improves the anti-fouling performance of the ultrafiltration membrane.

[0078] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of an ultrafiltration membrane for advanced water treatment, characterized in that, It includes the following steps: Step 1: After drying and removing water from phenolphthalein, 4,4'-dichlorodiphenyl sulfone, anhydrous potassium carbonate and polyethylene glycol respectively, take phenolphthalein, 4,4'-dichlorodiphenyl sulfone and anhydrous potassium carbonate and mix them, then add toluene and dimethylacetamide, heat to 140 °C and stir for reaction for 6 - 10 h until no water is carried out, heat to 160 - 180 °C to remove toluene, continue the reaction for 8 h, cool to 150 °C, add polyethylene glycol and continue the reaction for 1 - 2 h, then pour into pure water for sedimentation, add dilute hydrochloric acid dropwise, filter out the solid and crush it, wash and dry to obtain block polysulfone particles; Step 2: Mix the block polysulfone particles prepared in Step 1 with polyvinylpyrrolidone, sulfonated Ag-MOF, quaternized cellulose nanocrystals and N-methylpyrrolidone, stir at 40 - 60 °C for 6 - 8 h and then degas under vacuum for 1 h to obtain a casting solution; pour the casting solution onto a clean glass plate, use a doctor blade with a gap of 100 - 150 μm to scrape into a flat film, stand for 15 - 30 s, then immerse in pure water until the nascent film falls off, and change the pure water every 6 - 8 h to obtain the final ultrafiltration membrane; In Step 1, the dosage ratio of phenolphthalein, 4,4'-dichlorodiphenyl sulfone and polyethylene glycol is 1 mol : 1 mol : 25 - 80 g; The ultrafiltration membrane in Step 2 includes the following raw materials in parts by mass: 15 - 20 parts of block polysulfone particles, 3 - 5 parts of polyvinylpyrrolidone, 2 - 5 parts of sulfonated Ag-MOF, 6 - 10 parts of quaternized cellulose nanocrystals and 70 - 80 parts of N-methylpyrrolidone; The preparation steps of quaternized cellulose nanocrystals are as follows: Step s1: Take cellulose nanocrystals, place them in a nitric acid solution and oscillate for activation for 6 h, then freeze-dry, mix with sodium periodate and place in pure water, stir and react for 3 h, then add ethylene glycol, centrifuge and wash with water, mix with cysteine, heat to 40 °C under nitrogen protection and stir for 5 h to obtain mercapto-functionalized cellulose nanocrystals for standby; Step s2: Dissolve dimethylaminoethyl methacrylate in N,N'-dimethylformamide, add dodecyl bromide, stir and react for 48 h under a nitrogen atmosphere, add anhydrous ethyl ether for repeated precipitation and purification to obtain a quaternary ammonium salt monomer for standby; Step s3: Place the mercapto-functionalized cellulose nanocrystals prepared in Step s1 in dimethyl sulfoxide, add the quaternary ammonium salt monomer prepared in Step s2 and 2,2-dimethylolpropionic acid, introduce nitrogen, react under an ultraviolet lamp for 10 h, then centrifuge, wash and freeze-dry to obtain quaternized cellulose nanocrystals.

2. The preparation method of an ultrafiltration membrane for advanced water treatment according to claim 1, characterized in that, The preparation steps of sulfonated Ag-MOF are as follows: Place hydrochloric acid dopamine in a Tris buffer solution with a pH of 8.5, add Ag-MOF and ultrasonicate for 10 min, then stir and react for 4 - 6 h, centrifuge and wash and dry, then transfer to pure water and ultrasonicate for 20 min, add 3-mercapto-1-propanesulfonic acid sodium salt, heat to 50 - 60 °C and stir and react for 24 h, then centrifuge and separate, wash and dry to obtain it.

3. The preparation method of an ultrafiltration membrane for advanced water treatment according to claim 2, characterized in that, The mass ratio of Ag-MOF, hydrochloric acid dopamine and 3-mercapto-1-propanesulfonic acid sodium salt is 1:1:(0.6 - 1.5).

4. The preparation method of an ultrafiltration membrane for advanced water treatment according to claim 1, wherein, In step s1, the mass ratio of cellulose nanocrystals, sodium periodate, and cysteine is 1:(0.6 - 1):(1 - 2); in step s2, the volume ratio of dimethylaminoethyl methacrylate and dodecyl bromide is (4 - 5):

6.

5. The preparation method of an ultrafiltration membrane for advanced water treatment according to claim 1, characterized in that, In step s3, the mass ratio of thiolated cellulose nanocrystals and quaternary ammonium salt monomer is 1:1; the mass portion of 2,2 - bis(hydroxymethyl)propionic acid is 1.5% - 2% of the thiolated cellulose nanocrystals.

6. An ultrafiltration membrane for advanced water treatment, characterized in that, Prepared by the preparation method according to any one of claims 1 - 5.

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