阅读说明：本技术 一种分离性能可调控的高通量、耐污染超滤膜及其制备方法和应用 (High-flux pollution-resistant ultrafiltration membrane with adjustable separation performance and preparation method and application thereof ) 是由 黄征青 蔡威 于 2021-09-14 设计创作，主要内容包括：本发明公开了一种分离性能可调控的高通量、耐污染超滤膜及其制备方法和应用。所述分离性能可调控的高通量、耐污染超滤膜的膜材料是由氯甲基化聚砜或聚氯乙烯之一与带有伯胺或仲胺基团的改性剂反应制备得到。本发明解决了现有改性超滤膜吸附和去除小分子物质能力受pH值限制的问题,以及现有超滤膜通量小、抗污染能力弱的问题。本发明所制备的到的超滤膜的防污能力强、渗透通量高,并且能根据需要调控超滤膜的分离性能,具有较好的应用前景。(The invention discloses a high-flux pollution-resistant ultrafiltration membrane with adjustable separation performance, and a preparation method and application thereof. The membrane material of the high-flux pollution-resistant ultrafiltration membrane with adjustable separation performance is prepared by reacting one of chloromethylated polysulfone or polyvinyl chloride with a modifier with primary amine or secondary amine groups. The invention solves the problems that the adsorption and removal capacity of the existing modified ultrafiltration membrane is limited by the pH value, and the existing ultrafiltration membrane has small flux and weak pollution resistance. The ultrafiltration membrane prepared by the method has strong antifouling capacity and high permeation flux, can regulate and control the separation performance of the ultrafiltration membrane according to needs, and has good application prospect.)

1. The high-flux pollution-resistant ultrafiltration membrane with adjustable separation performance is characterized in that a membrane material of the high-flux pollution-resistant ultrafiltration membrane with adjustable separation performance is prepared by reacting one of chloromethylated polysulfone or polyvinyl chloride with a modifier with primary amine or secondary amine groups.

2. The method for preparing a high-flux pollution-resistant ultrafiltration membrane with controllable separation performance as claimed in claim 1, which is characterized by comprising the following steps:

(1) firstly, dissolving chloromethylated polysulfone or polyvinyl chloride in a solvent, then adding a modifier with primary amine or secondary amine groups, heating to 35-90 ℃, stirring for reaction, directly using a product after the reaction is finished or pouring the product after the reaction into water, filtering, washing and drying to obtain a hydrophilic modified polymer;

(2) dissolving a pore-foaming agent in a solvent, adding the hydrophilic modified polymer prepared in the step (1), stirring at 50-80 ℃ until the hydrophilic modified polymer is completely and uniformly mixed to obtain a membrane preparation solution, and then carrying out gel bath and membrane preparation by an immersion precipitation phase inversion method; or scraping the membrane on non-woven fabric or glass, and continuously soaking in water for at least 24h after the membrane is formed, thus obtaining the high-flux pollution-resistant ultrafiltration membrane with adjustable separation performance.

3. The preparation method of the high-flux pollution-resistant ultrafiltration membrane with the controllable separation performance as claimed in claim 2, wherein the chloromethylated polysulfone or polyvinyl chloride dissolved in the solvent in the step (1) is added in an amount of 0.01-0.20 g/mL;

in the membrane preparation liquid in the step (2), the pore-foaming agent accounts for 5-12 wt%, the hydrophilic modified polymer accounts for 15-23 wt%, and the solvent accounts for 65-80 wt%.

4. The method for preparing the high-flux pollution-resistant ultrafiltration membrane with controllable separation performance according to claim 2 or 3, wherein the molar ratio of chlorine atoms in the chloromethylated polysulfone or polyvinyl chloride and amine groups in the modifier in the step (1) is 1: 0.3-5;

and (2) the stirring reaction time in the step (1) is 5-24 h.

5. The method for preparing the high-flux pollution-resistant ultrafiltration membrane with controllable separation performance according to claim 2 or 3, wherein the solvent in the step (1) is at least one of dimethylformamide, dimethylacetamide, dimethylsulfoxide and N-methylpyrrolidone;

the modifier with primary amine or secondary amine groups in the step (1) is at least one of diethanolamine, aminobenzenesulfonic acid, sodium aminobenzenesulfonate, aminobenzoic acid, sodium aminobenzoate, L-aspartic acid, polyethyleneimine, diethylenetriamine and triethylene tetramine;

the drying in the step (1) is vacuum drying.

6. The method for preparing the high-flux pollution-resistant ultrafiltration membrane with controllable separation performance according to claim 2 or 3, wherein the pore-forming agent in the step (2) is at least one of lithium chloride, polyethylene glycol and polyvinylpyrrolidone;

the solvent in the step (2) is at least one of dimethylformamide, dimethylacetamide, dimethyl sulfoxide and N-methylpyrrolidone;

the liquid of the gel bath in the step (2) is water or aqueous solution containing solvent.

7. The use of the high flux, fouling resistant ultrafiltration membrane of claim 1 having controllable separation properties for removing at least one of anions, cations and macromolecular species from water.

8. The application according to claim 7, characterized in that it comprises the following steps:

(1) when removing anions in water, soaking or filtering the high-flux pollution-resistant ultrafiltration membrane with adjustable separation performance by adopting an acid solution, acidifying secondary amine or tertiary amine in the ultrafiltration membrane to convert the secondary amine or the tertiary amine into ammonium salt, and washing the ammonium salt; when the retention rate of the ultrafiltration membrane on anions can not meet the requirement, the membrane is regenerated by using the acidic solution again;

(2) when anions and cations are removed simultaneously, soaking the mixture by using hydrogen peroxide or washing the mixture after filtering the mixture; and adding salt into the filtrate when the membrane treated by the hydrogen peroxide is used for separating macromolecular substances.

9. The use according to claim 8, wherein the anion in steps (1) and (2) is at least one of hexavalent chromium, arsenic, borate and phosphate;

the acid solution in the step (1) is at least one of hydrochloric acid, nitric acid and sulfuric acid aqueous solution with the concentration of below 2 mol/L;

the cation in the step (2) is Pb²⁺、Cd²⁺、Hg²⁺、Cu²⁺、Al³⁺、Fe³⁺、Ca²⁺And Mg²⁺At least one of;

the concentration of the hydrogen peroxide in the step (2) is 1-5 wt%.

10. The use according to claim 8 or 9, wherein the macromolecular substance of step (2) is at least one of bovine serum albumin, egg white protein, whey protein, casein, collagen, plasma protein, soy protein, wheat protein and leaf protein;

the adding amount of the salt in the step (2) is 0.1-1 g/mL;

the salt in the step (2) is NaCl, KCl and Na₂SO₄And K₂SO₄At least one of (1).

Technical Field

The invention belongs to the technical field of membrane separation, and particularly relates to a high-flux pollution-resistant ultrafiltration membrane with adjustable separation performance, and a preparation method and application thereof.

Background

The ultrafiltration is a membrane separation technology, and has the advantages of convenient operation, no pollution, high efficiency, energy saving, small occupied area and the like. At present, ultrafiltration is not only applied to separation, concentration and purification in the fields of biology, medicine, food and the like, but also widely applied to various industries and fields of drinking water treatment, wastewater treatment, ultrapure water preparation, hemodialysis and the like. The ultrafiltration technology is used for treating tap water in recent years, can effectively remove pathogenic microorganisms in water, and has good removal effect on harmful bacteria and viruses in water; compared with the traditional tap water treatment process, the ultrafiltration membrane technology has the following advantages: the effluent quality is reliable and the safety is high; the removal rate of colloid such as iron, manganese, aluminum and the like is 90-95 percent; the ultrafiltration membrane is convenient to combine with other units, good in controllability, short in construction period and low in cost. Although tap water produced by the ultrafiltration membrane technology has the advantages of high water quality safety, economy, high efficiency, environmental friendliness and the like, harmful small molecular substances such as bromate, chromate, perchlorate, anionic surfactant and the like in water cannot be removed, and the application of the ultrafiltration membrane in drinking water treatment is greatly limited. Meanwhile, ultrafiltration membrane pollution is a main obstacle for limiting the application of the ultrafiltration membrane, and the preparation of a high-flux and pollution-resistant ultrafiltration membrane is a fundamental way for solving the problems of ultrafiltration membrane pollution, high cost and the like. With the expansion of the application field and range, some new requirements are also in need. For example, in some emergency situations (heavy metal pollution caused by external factors such as flood water), the ultrafiltration membrane used in the household water purifier or the waterworks needs to have a function of coping with the emergency situations (i.e., the separation performance is regulated as required).

The membrane may be hydrophilically modified by a graft method, a blend method, or the like. There have been some reports in the literature that ultrafiltration membranes having an adsorption ability for hexavalent chromium ions can be prepared by blending polymers containing amine groups or quaternary ammonium salts. (Zhukan Yao, Shiyuan Du, Yin Zhuang, Baoku Zhu, Liping Zhu, Angelin Ebanezzar John. positional charged membrane for removing low registration Cr (VI) in profiling Process. Journal of Water Process Engineering 8(2015) 99-107 Zhikan Yao, Yili, Yue Cui, Ke Zheng, Baoku Zhu, Hong Xu, Liping Zhu. rectangular amine coating mapping membrane with pH-dependent mapping and Cr (VI) registration pH-mapping slurry, coating mapping slurry-355. mapping slurry-coating, coating slurry-coating slurry-coating slurry-coating slurry, coating slurry, coating slurry, 2017,134, 45198). The research shows that: the ultrafiltration membrane containing the quaternary ammonium salt polymer has good adsorption and removal capacity on hexavalent chromium ions, and the applicable pH value range is wide; the polymer film containing tertiary amine has better adsorption and removal capability only under acidic condition, and has poor adsorption and removal capability under neutral condition. However, most of water in nature is neutral or weakly alkaline, and thus the application of water is limited. Although the ultrafiltration membrane containing quaternary ammonium salt has strong removal capability to hexavalent chromium ions and the like because of strong positive charge, the pollution resistance of the ultrafiltration membrane is also poor because pollutants in water are mostly substances with negative charges. For example, Wang et al, which employs polysulfone for quaternary amination grafting modification and hybridization with graphene oxide, can prepare ultrafiltration membranes with good high flux contamination resistance, and the results also show that positively charged membranes are prone to adsorb contaminants such as BAS, Wei Wang, Liang Wang, Bin ZHao, ZHaohui ZHang, Xiaoming Xia, Huifang Yang, Yu Xue, Na Chang. The above documents only investigate the use of ultrafiltration membranes under acidic conditions and do not relate to the use under neutral conditions, and it is generally believed that the use under neutral conditions after the acidification treatment may soon be ineffective because bound hydrogen ions are easily lost.

Disclosure of Invention

Aiming at the technical defects of the existing ultrafiltration membrane, the invention aims to provide a high-flux pollution-resistant ultrafiltration membrane with adjustable separation performance, a preparation method and application thereof, so as to solve the problems that the capacity of the existing modified ultrafiltration membrane for adsorbing and removing small molecular substances is limited by a pH value, and the existing ultrafiltration membrane has small flux and weak pollution resistance.

The purpose of the invention is realized by the following technical scheme:

a high-flux pollution-resistant ultrafiltration membrane with adjustable separation performance is prepared by reacting one of chloromethylated polysulfone or polyvinyl chloride with a modifier with primary amine or secondary amine groups.

The preparation method of the high-flux pollution-resistant ultrafiltration membrane with adjustable separation performance comprises the following steps:

(1) firstly, dissolving chloromethylated polysulfone or polyvinyl chloride in a solvent, then adding a modifier with primary amine or secondary amine groups, heating to 35-90 ℃, stirring for reaction, directly using a product after the reaction is finished or pouring the product after the reaction into water, filtering, washing and drying to obtain a hydrophilic modified polymer;

(2) dissolving a pore-foaming agent in a solvent, adding the hydrophilic modified polymer prepared in the step (1), stirring at 50-80 ℃ until the hydrophilic modified polymer is completely and uniformly mixed to obtain a membrane preparation solution, and then carrying out gel bath and membrane preparation by an immersion precipitation phase inversion method; or scraping the membrane on non-woven fabric or glass, and continuously soaking in water for at least 24h after the membrane is formed, thus obtaining the high-flux pollution-resistant ultrafiltration membrane with adjustable separation performance.

Preferably, the chloromethylated polysulfone in the step (1) is prepared according to the method disclosed in the following documents: silvia Ioan, Anca Filimon, Ecaterna Avram. infiluence of the development of the simulation on the Solution Properties of chlorinated polymeric Science, journal of Applied Polymer Science,101, 524-.

Preferably, the chloromethylated polysulfone or polyvinyl chloride dissolved in the solvent in the step (1) is added in an amount of 0.01-0.20 g/mL.

Preferably, the molar ratio of the chlorine atom in the chloromethylated polysulfone or polyvinyl chloride in the step (1) to the amine group in the modifier is 1: 0.3-5.

Preferably, the stirring reaction time in the step (1) is 5-24 h.

Preferably, the solvent in step (1) is at least one of dimethylformamide, dimethylacetamide, dimethylsulfoxide and N-methylpyrrolidone.

Preferably, the modifier with primary amine or secondary amine group in the step (1) is at least one of diethanolamine, aminobenzenesulfonic acid, sodium aminobenzenesulfonate, aminobenzoic acid, sodium aminobenzoate, L-aspartic acid, polyethyleneimine, diethylenetriamine and triethylenetetramine.

Preferably, the drying in step (1) is vacuum drying.

Preferably, the pore-foaming agent in step (2) is at least one of lithium chloride, polyethylene glycol and polyvinylpyrrolidone.

Preferably, the solvent in step (2) is at least one of dimethylformamide, dimethylacetamide, dimethylsulfoxide and N-methylpyrrolidone.

Preferably, in the membrane-making solution in the step (2), the pore-forming agent accounts for 5-12 wt%, the hydrophilic modified polymer accounts for 15-23 wt%, and the solvent accounts for 65-80 wt%.

Preferably, the liquid of the gel bath in step (2) is water or an aqueous solution containing a solvent.

The application of the high-flux pollution-resistant ultrafiltration membrane with adjustable separation performance in removing at least one of anions, cations and macromolecular substances in water.

Preferably, the application comprises the following steps:

(1) when removing anions in water, soaking or filtering the high-flux pollution-resistant ultrafiltration membrane with adjustable separation performance by adopting an acid solution, acidifying secondary amine or tertiary amine in the ultrafiltration membrane to convert the secondary amine or the tertiary amine into ammonium salt, and washing the ammonium salt; when the retention rate of the ultrafiltration membrane on anions can not meet the requirement, the membrane is regenerated by using the acidic solution again;

(2) when anions and cations are removed simultaneously, soaking the mixture by using hydrogen peroxide or washing the mixture after filtering the mixture; when the membrane treated by the hydrogen peroxide is used for separating some macromolecular substances, salt is added into the filtrate, so that the retention rate of the membrane on the macromolecular substances (such as protein molecules) can be further regulated and controlled.

Preferably, the anion in steps (1) and (2) is at least one of hexavalent chromium ion, arsenic ion, borate ion and phosphate ion.

Preferably, the acidic solution in the step (1) is at least one of hydrochloric acid, nitric acid and sulfuric acid aqueous solution with the concentration of less than 2 mol/L.

Preferably, the cation in step (2) is Pb²⁺、Cd²⁺、Hg²⁺、Cu²⁺、Al³⁺、Fe³⁺、Ca²⁺And Mg²⁺At least one of (1).

Preferably, the concentration of the hydrogen peroxide in the step (2) is 1-5 wt%.

Preferably, the macromolecular substance in step (2) is at least one of bovine serum albumin, egg albumin, whey protein, casein, collagen, plasma protein, soy protein, wheat protein and leaf protein.

Preferably, the addition amount of the salt in the step (2) is 0.1-1 g/mL.

Preferably, the salt in step (2) is NaCl, KCl, Na₂SO₄And K₂SO₄At least one of (1).

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

according to the invention, a polymer material is subjected to graft modification by using a compound containing primary amine or secondary amine with strong hydrophilicity, and an ultrafiltration membrane with high permeation flux and good pollution resistance is prepared by using a phase inversion method or a membrane scraping method. The ultrafiltration membrane can meet the daily application requirements, in some emergency (or certain application requirements), the separation performance of the membrane can be changed by simply pretreating the membrane, and meanwhile, the influence on the permeation flux, the mechanical property, the thermal stability, the chemical stability and the like of the membrane is small, so that the aim of regulating and controlling the separation performance of the ultrafiltration membrane according to the requirements can be realized.

Drawings

FIG. 1 is a stress-strain curve of a PSF film, a CM-PSF film, a T-PSF film, and an AT-PSF film.

FIG. 2 is a DSC chart of a PSF film, a CM-PSF film, a T-PSF film and an AT-PSF film.

FIG. 3 is a cross-sectional SEM image and a surface SEM image of a PSF film, a CM-PSF film, a T-PSF film, and an AT-PSF film.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Example 1

A preparation method of a high-flux pollution-resistant ultrafiltration membrane with adjustable separation performance comprises the following steps:

(1) a1000 mL three-necked flask was charged with 20.0g Polysulfone (PSF), 600mL CH₂Cl₂After the mixture was completely dissolved, 12g of paraformaldehyde and 50mL of trimethylchlorosilane (CH) were added₃)₃SiCl, nitrogen, then 0.56mLSnCl₄Reacting at 35 ℃ for 60h, then adding absolute ethyl alcohol for precipitation, filtering, washing, and drying in vacuum at 50 ℃ to constant weight to obtain chloromethyl polysulphone (CM-PSF).

(2) 30.0g of CM-PSF and 300mL of Dimethylformamide (DMF) are sequentially added into a 500mL three-neck flask, after complete dissolution, 12mL of diethanolamine is dropwise added, stirring is carried out for 24h at 50 ℃, the product is precipitated and washed by deionized water, and vacuum drying is carried out at 50 ℃ until the weight is constant, so that the obtained product is polysulfone (T-PSF) with tertiary amine groups.

(3) Adding polyethylene glycol PEG600 into DMF, dissolving, adding polysulfone (T-PSF) with tertiary amino, heating and stirring at 60 ℃ for 24 hours to obtain a casting solution containing 10 wt% of PEG600 and 17 wt% of modified polysulfone (T-PSF). Standing and defoaming the membrane liquid at the room temperature for 2 hours, pouring the membrane casting liquid on a glass plate, scraping the membrane by using a membrane scraper, placing the membrane casting liquid in air for 30s, soaking the membrane casting liquid in deionized water, demoulding for 15 minutes, and soaking the membrane in the deionized water for more than 24 hours to obtain the product, wherein the product is recorded as a T-PSF membrane.

And (3) soaking the T-PSF membrane in 0.5mol/L hydrochloric acid for 3h, taking out the T-PSF membrane, washing the T-PSF membrane with deionized water for multiple times, and then placing the T-PSF membrane in deionized water for storage, wherein the T-PSF membrane is an acidified ultrafiltration membrane (AT-PSF membrane).

Comparative example 1

A preparation method of a PSF film comprises the following steps:

adding polyethylene glycol PEG600 into DMF, dissolving, adding PSF, heating and stirring at 60 ℃ for 24 hours to obtain a casting solution containing 10 wt% of PEG600 and 17 wt% of PSF. Standing and defoaming the membrane liquid at the room temperature for 2 hours, pouring the membrane casting liquid on a glass plate, scraping the membrane by using a membrane scraper, placing the membrane casting liquid in air for 30s, soaking the membrane casting liquid in deionized water, demoulding for 15 minutes, and soaking the membrane in the deionized water for more than 24 hours, wherein the product is recorded as a PSF membrane.

The properties of the above T-PSF film and AT-PSF film are compared in Table 1.

Table 1 film property comparison table

Table 1 the test conditions for the properties are as follows:

filtration experiments of pure water and aqueous BSA (bovine serum albumin) solutions:

under the conditions of constant temperature of 25 + -1 deg.C and operation pressure (transmembrane pressure) of 100kPa, a crossflow filtration apparatus (active membrane area of 19.84 cm)²) The initial pure water flow rate (Jw0) was detected. An aqueous BSA solution having a concentration of 150mg/L was added to the above-mentioned filtration apparatus. After 5 minutes of circulation without any pressure, the pressure was adjusted to 0.10 MPa. The permeate and reflux were collected to determine the first 3 minutes of excretion and the last 3 minutes of excretion. The volume of permeate was measured every 3 minutes to calculate the flow of the aqueous BSA solution. Both the permeate and the reflux are recycled to the feed tank. The test temperature was maintained at 25. + -. 1 ℃. The amount of BSA in the reflux and permeate was measured at 280nm with a UV-visible spectrophotometer (Shimadzu UVmini-1280).

Filtration experiment of hexavalent chromium solution: a volume of 2.0L of a 1.0mg/L Cr (VI) solution was used as the feed solution (pH of solution 7.02). The pressure was adjusted to 0.10 MPa. 10mL of the permeate and 10mL of the reflux were collected, and the chromate concentration was determined by 1, 5-diphenylcarbide method using an ultraviolet-visible spectrometer.

The flux of the BSA solution is a parameter that reflects the fouling resistance of the membrane. The greater the flux of the BSA solution, the greater the fouling resistance of the membrane.

From table 1 it can be derived: after acidification treatment, the tertiary amine group is combined with hydrogen ions to be charged, the pore diameter of the membrane is slightly reduced, and the permeation flux is slightly reduced; meanwhile, the retention rate and flux recovery rate of the membrane to bovine serum albumin are slightly reduced due to the positive charge. After the acidification treatment, hydrogen ions are combined with tertiary amine to enable the film to have positive charges, hexavalent chromium ions can be adsorbed due to the electrostatic attraction effect, the retention rate of the hexavalent chromium ions by the acidification film is improved to 100% from 8.5% of the hexavalent chromium ions by the acidification film, the retention rate of the hexavalent chromium ions can be kept to 100% after the acidification film runs for 30 minutes, and the retention rate is reduced to 50.8% after the acidification film runs for 90 minutes due to the fact that the adsorption gradually reaches saturation. The above-mentioned acidified film was stored in deionized water until use, and the above-mentioned experimental results show that hydrogen ions bonded to tertiary amines are strongly bonded by hydrogen bonding and do not run off during storage or use.

Comparative example 2

A preparation method of a CM-PSF film comprises the following steps:

adding polyethylene glycol PEG600 into DMF, dissolving, adding CM-PSF, heating and stirring at 60 ℃ for 24 hours to obtain a casting solution containing 10 wt% of PEG600 and 17 wt% of CM-PSF. Standing and defoaming the membrane liquid at the room temperature for 2 hours, pouring the membrane casting liquid on a glass plate, scraping the membrane by using a membrane scraper, placing the membrane casting liquid in air for 30s, soaking the membrane casting liquid in deionized water, demoulding for 15 minutes, and soaking the membrane in the deionized water for more than 24 hours, wherein the product is recorded as a CM-PSF membrane.

FIG. 1 is a stress-strain curve of a PSF film, a CM-PSF film, a T-PSF film, and an AT-PSF film. As can be seen from fig. 1: the PSF film had the lowest tensile strength of 1.4048 mpa, but the highest elongation at break of 39%. The CM-PSF film possessed the highest tensile strength of 1.7026MPa and an elongation at break of 14.4%. The tensile strength of the T-PSF film was 1.4032MPa, and the elongation at break was 14.3%. Further, the AT-PSF film had mechanical properties similar to those of the T-PSF film (tensile strength of 1.4942MPa, elongation AT break of 12.4%). In general, the PSF film has a tensile strength of 60MPa and an elongation at break of less than 5%. CM-PSF exhibits lower rigidity than PSF because the backbone may be broken when the chloromethylation reaction occurs. In addition, highly functionalized films exhibit lower stretch. The tensile strength of the CM-PSF film with a degree of chloromethylation of 75% was 44MPa and the elongation at break was 3.5%, while the tensile strength of the CM-PSF film with a degree of chloromethylation of 143% was 12MPa and the elongation was 2.6%. The inventors believe that the starting material polysulfone may have a broad molecular weight distribution. Low molecular weight polysulfones act as plasticizers, reducing tensile strength and increasing elongation at break. The chloromethylation reaction, which may occur mainly in low molecular weight polysulfones, does not destroy the backbone, which increases the tensile strength and is associated with a decrease in the elongation at break.

FIG. 2 is a DSC chart of the PSF film, CM-PSF film, T-PSF film and AT-PSF film, as can be seen from FIG. 2: the glass transition temperature (Tg) of the PSF film was 182.71 ℃. This value is close to the value reported elsewhere (190-. In addition, the glass transition temperature (Tg) of the PSF film in the literature is 142 ℃. The glass transition temperature of the CM-PSF film dropped to 173 deg.C, while the glass transition temperature of the T-PSF film further dropped to 158.24 deg.C. This phenomenon has been reported in the literature. The glass transition temperature of the CM-PSF decreased from 183 ℃ to 158 ℃ depending on the degree of grafting. The higher the degree of grafting, the lower the glass transition temperature. Of course, the change in glass transition temperature also indicates the success of the graft modification. However, the glass transition temperature of AT-PSF increased from 158.24 ℃ corresponding to T-PSF to 180.02 ℃ close to the glass transition temperature of the PSF film.

FIG. 3 is a cross-sectional SEM image and a surface SEM image of a PSF film, a CM-PSF film, a T-PSF film and an AT-PSF film, wherein (a) corresponds to a PSF cross-section; (c) corresponding to the CM-PSF section; (e) corresponding to the T-PSF section; (g) corresponding to the cross section of the AT-PSF; (b) corresponding to the PSF surface; (d) corresponding to a CM-PSF surface; (f) corresponding to the T-PSF surface; (h) corresponding to the AT-PSF surface; as can be seen from fig. 3: all modified films were more porous in both surface and cross-section than the original PSF film. The morphology of the membrane can be explained by a phase inversion soaking process, including liquid-liquid phase separation and solidification of the polymer-rich phase. Membranes prepared from PEG/DMF/water systems are formed by a transient demixing mechanism because DMF containing casting fluids have a high mutual affinity for water, which facilitates the formation of finger-shaped pores. After the polysulfone is modified, the affinity of the high molecular material and PEG is stronger, and the solubility in DMF is higher. The high affinity of the modified polysulfone for water promotes the influx of non-solvent when immersed in a coagulation bath. More polymer-rich phase and more polymer-poor phase will appear on the surface of the casting liquor and water, which favors the formation of more pores.

Example 2

A preparation method of a high-flux pollution-resistant ultrafiltration membrane with adjustable separation performance comprises the following steps:

adding 15.0g of chloromethylated polysulfone into a 250mL three-necked flask in sequence (the preparation method is the same as that of example 1), adding 74g N-methyl pyrrolidone, stirring at 60 ℃, dropwise adding 5.0g of polyethyleneimine after complete dissolution, stirring at 60 ℃ for 24 hours, then adding 6g of polyvinylpyrrolidone into the mixture, stirring until a transparent solution is formed, standing and defoaming for 2 hours to obtain a casting solution, pouring the casting solution on a glass plate, scraping the film by using a film scraper, standing in the air for 15 seconds, soaking the casting solution in deionized water, and after 15 minutes of demolding, soaking the film in deionized water for more than 24 hours.

And (3) testing conditions are as follows: the temperature is 25 +/-1 ℃, the operation pressure (transmembrane pressure) is 100kPa, and the concentration of BSA for experiments is 150 mg/L; the concentrations of the calcium chloride and sodium sulfate aqueous solutions are both 200 mg/L.

The pure water flux of the resulting membrane was 280L.m^-2.h^-1The retention rate of BSA is 93.8%, the recovery rate of permeation flux is 89%, and the retention rate of copper ions is 82%; after being circularly filtered by 3 weight percent of hydrogen peroxide for 15 minutes, the pure water flux of the membrane is 242L.m^{- 2}.h^-1The retention rate of BSA is 100%, the flux recovery of the membrane reaches 98%, and the retention rates of calcium chloride and sodium sulfate reach 45% and 48% respectively.

Example 3

A preparation method of a high-flux pollution-resistant ultrafiltration membrane with adjustable separation performance comprises the following steps:

(1) dissolving 5g of sulfanilic acid in 250mL of dimethyl sulfoxide, adding 50mL of triethylamine, uniformly stirring, adding 5g of polyvinyl chloride, stirring and reacting at 60-65 ℃ for 24 hours under the protection of nitrogen, pouring reactants into a mixed solution of ice water and methanol (volume ratio is 1:2) for precipitation, filtering the precipitate, washing with water and drying to obtain the modified polyvinyl chloride; the triethylamine is equivalent to a base, is used for neutralizing hydrogen ions in sulfanilic acid, plays a role in protecting, reduces side reactions, and allows chlorine on a methyl group to react with only amino groups but not with sulfonic acid groups.

(2) Weighing 6g of polyethylene glycol 1000 and 4g of anhydrous lithium chloride, adding into an iodine measuring flask, adding 74g of dimethylacetamide, stirring for dissolving, adding 16g of the modified polyvinyl chloride, stirring at 60 ℃ until the modified polyvinyl chloride is completely dissolved, standing for defoaming, scraping a film on a non-woven fabric, evaporating in air for 1 minute, putting into water for forming a film, and then putting into deionized water for soaking for 24 hours.

And (3) testing conditions are as follows: the temperature is 25 +/-1 ℃, the operation pressure (transmembrane pressure) is 100kPa, and the concentration BSA of the experimental feed solution is 150 mg/L; the concentration of the copper sulfate solution is 200 mg/L; the concentration of the potassium dichromate aqueous solution is 10 mg/L.

The pure water flux of the obtained membrane was 670L.m^-2.h^-1The retention rate of BSA is 67.8%, the recovery rate of permeation flux is 91%, and the retention rate of copper ions is 76%; after being circulated for 15 minutes by using 0.1M hydrochloric acid aqueous solution, the membrane is washed by water, and the pure water flux of the membrane is 520L.m^-2.h^-1The BSA retention rate is 96%, the flux of the membrane is recovered to 95%, and 10ppm of potassium dichromate aqueous solution is filtered, so that the electrolyte can be completely retained.

The above-described embodiments of the present invention should not be construed as limiting the scope of the present invention. Any other corresponding changes and modifications made according to the technical idea of the present invention should be included in the protection scope of the claims of the present invention.