CN110732248B

CN110732248B - Sulfonated polysulfone blended TB ultrafiltration membrane, preparation method and application thereof

Info

Publication number: CN110732248B
Application number: CN201910974164.7A
Authority: CN
Inventors: 唐海; 李南文; 张晨; 殷久龙
Original assignee: Anhui Polytechnic University
Current assignee: Anhui Polytechnic University
Priority date: 2019-10-14
Filing date: 2019-10-14
Publication date: 2021-08-10
Anticipated expiration: 2039-10-14
Also published as: CN110732248A

Abstract

The invention provides a sulfonated polysulfone blended TB ultrafiltration membrane, a preparation method and application thereof, wherein TB is taken as a base membrane material, sulfonated polysulfone with sulfonation degree of 5-20% is taken as a blended material, N-methyl-2-pyrrolidone is taken as a solvent, ethylene glycol monomethyl ether is taken as a pore-forming agent, deionized water is taken as a coagulation bath, and a non-solvent induced phase separation method is adopted to prepare the sulfonated polysulfone blended TB ultrafiltration membrane. Compared with the prior art, after the TB polymer and the sulfonated polysulfone are blended, the original neutral amine and sulfonic acid react to generate corresponding ammonium salt and sulfonate radical in the structure, so that the surface contact angle is reduced, the hydrophilicity is enhanced, the water flux is increased, and the anti-pollution capability of the membrane is obviously improved.

Description

Sulfonated polysulfone blended TB ultrafiltration membrane, preparation method and application thereof

Technical Field

The invention belongs to the field of ultrafiltration membranes, and particularly relates to a sulfonated polysulfone blended TB ultrafiltration membrane, and a preparation method and application thereof.

Background

The emulsified oil has stable physicochemical properties, and the emulsifier composition is increasingly complex with the molecular weight of the emulsified oil being smaller and smaller, which brings great difficulty and challenge to the treatment technology of the emulsified oil wastewater. The membrane separation technology is one of the methods for efficiently separating emulsified oil wastewater due to the characteristics of simple operation, good selectivity, no phase change, greenness, no pollution and the like. Research shows that the problems of easy membrane pollution, membrane flux attenuation, rejection rate reduction, membrane service life reduction, high operation cost and the like still exist when the organic membrane is directly used for treating oily wastewater due to low surface energy and strong hydrophobicity, so that the modification (surface modification, chemical modification, blending modification and the like) of the membrane material becomes a current research hotspot. The blend film-making is to blend different polymer materials by adopting a mechanical physical method to improve the performance of the original polymer, and the formation of a polymer blend system with special performance is an important direction.

According to the reports, on the aspect of commercial polyvinylidene fluoride (PVDF) and polyether sulfone (PES) membranes, a great deal of research (PFSA/PVDF, PAN/PVDF, PVDF/CA, PVDF-HFP/PTFE, graphene oxide/PVDF, SPSF/PES, PES and heteronaphthalene biphenyl co-polyether sulfone, PVDF/EVOH and the like) is carried out on the performance of membrane materials improved by blending, and the compatibility, coagulation bath, additives of a blending system and the influence of the additives on the membrane performance are found to ensure that the blending membrane not only retains the characteristics of the original PVDF base membrane material, but also effectively regulates the hydrophilicity and hydrophobicity, the membrane microporous structure and the performance of the membrane by blending, so that a new way is provided for the performance improvement of the membrane materials.

The polysulfone membrane has excellent heat resistance, ultraviolet resistance, oxidation resistance and good mechanical strength, but the separation membrane is limited in practical application due to strong hydrophobicity. Therefore, hydrophilic sulfonic acid groups are introduced into aromatic rings through sulfonation reaction to prepare Sulfonated Polysulfone (SPSF), so that the hydrophilicity is improved, and the flux and the anti-pollution performance of the sulfonated polysulfone are improved.

Based on blending of materials such as SPSF and PES, the compounding property, the shape and the performance of the blended membrane are obviously influenced by the addition of the SPSF; the latest Li et al report that PES/PSF mixed membranes are partially compatible to cause thermodynamic instability and transient delamination, the obtained membranes have finger-shaped structures, and PES/SPSF mixed systems can be fully mixed to cause thermodynamic stability and delayed delamination due to specific interaction between PES and SPSF polymers, so that the obtained membranes have sponge-like asymmetric gradient structures, and particularly, the surface separation behavior of SPSF and hydrophilic sulfonic acid groups promotes the migration of hydrophilic SPSf chains to the surface of the blended membranes through the process of mutual diffusion to enhance the hydrophilicity of the PES/SPSF blended membranes, and finally the PES/SPSF blended membranes have higher water permeability and better anti-pollution capacity.

The step-shaped compound is obtained by the polycondensation reaction of o-tolidine and dimethoxymethane

Base (TB) polymers, since in their main chain

The base repeating unit has a V-shaped rigid knotThe structure causes the twisted structure of the molecular chain, prevents the accumulation of the high molecular chain and can be provided with micropores.

Disclosure of Invention

The sulfonated polysulfone blended TB ultrafiltration membrane provided by the invention has good hydrophilic performance and a more compact structure.

The invention also provides a preparation method of the sulfonated polysulfone blended TB ultrafiltration membrane, and the method comprises the following steps

Base (TB) is a base membrane material, Sulfonated Polysulfone (SPSF) with 5-20% of sulfonation Degree (DS) is a blending material, N-methyl-2-pyrrolidone (NMP) is a solvent, ethylene glycol monomethyl Ether (EGM) is used as a pore-forming agent, deionized water is used as a coagulation bath, and a non-solvent induced phase separation method (NIPS) is adopted to prepare the sulfonated polysulfone blending TB ultrafiltration membrane.

The invention also provides application of the sulfonated polysulfone blended TB ultrafiltration membrane for treating oily wastewater, the retention rate of emulsified oil drops can reach above 98.52%, and most of emulsified oil dissolved in water is removed and tends to 199.1L/m²H, FRR up to 61.4%.

The specific technical scheme of the invention is as follows:

a preparation method of a sulfonated polysulfone blended TB ultrafiltration membrane comprises the following steps:

1) will be provided with

Mixing a base polymer, sulfonated polysulfone, N-methyl-2-pyrrolidone and ethylene glycol monomethyl ether, and then sealing, stirring and dissolving to obtain a membrane casting solution;

2) defoaming;

3) the sulfonated polysulfone blended TB ultrafiltration membrane is prepared by adopting a non-solvent-water induced gel phase inversion method.

In step 1)

The preparation method of the base polymer comprises the following steps: according to M.Carta, R.Malpass-Evans, M.Croad, Y.Rogan, M.Lee, I.Rose, N.B.McKeown, The synthesis of micropous polymers useg Troger's base formation, Polymer. chem.5(2014) 5267-5272.

Further, in step 1)

The preparation method of the base polymer comprises the following specific steps: 20g of 4,4 '-diamino-3, 3' -dimethylbiphenyl and 35.84g of dimethanol formal are added into a 500mL round-bottom flask and mechanically stirred, 160mL of trifluoroethylene is slowly added in a dropwise manner under the condition of an ice water bath, and stirring is continued for 30min under the condition of the ice water bath after the dropwise addition is finished. Then reacting for 96h at room temperature. Precipitating the obtained solution in ammonia water, washing with deionized water, dissolving the precipitate in chloroform, precipitating in methanol, washing with methanol solution, and vacuum drying.

The sulfonation degree DS of the sulfonated polysulfone in the step 1) is 5-20%. The SPSF with high sulfonation degree is proved to be unfavorable to be used as a blending modified material through earlier experiments.

Further, as described in step 1)

The mass ratio of the base polymer, the sulfonated polysulfone, the N-methyl-2-pyrrolidone and the ethylene glycol monomethyl ether is 0.8-1:0.02-0.2:4-5: 1.

Stirring and dissolving the mixture obtained in the step 1) at the rotating speed of 2500r/min at the temperature of 25 +/-2 ℃.

The defoaming in the step 2) refers to defoaming in a vacuum drying oven at 60 ℃ for 1 hour.

The step 3) is specifically as follows: pouring the membrane casting solution treated in the step 2) into a membrane scraping device, spreading the membrane casting solution on a glass plate, standing, and immersing the glass plate spread with the membrane casting solution into water to prepare the ultrafiltration membrane by adopting a non-solvent induced phase inversion method.

And 3) cooling the defoamed casting solution to 25 +/-2 ℃, and pouring into a film scraping device.

The standing in the step 3) refers to standing for 1-30s at room temperature to achieve the aim of pre-evaporation.

The temperature of water used for immersing in the water in the step 3) is 25 +/-2 ℃;

the thickness of the prepared sulfonated polysulfone and TB blended ultrafiltration membrane is controlled to be 100 mu m.

Preferably, the membrane prepared in step 3) is washed.

The sulfonated polysulfone blended TB ultrafiltration membrane provided by the invention is prepared by adopting the method.

The sulfonated polysulfone blended TB ultrafiltration membrane provided by the invention is used for treating oily wastewater.

The invention is provided with

Base (TB) is a base membrane material, Sulfonated Polysulfone (SPSF) with 20 percent of sulfonation Degree (DS) is a blending material, N-methyl-2-pyrrolidone (NMP) is a solvent, ethylene glycol monomethyl Ether (EGM) is used as a pore-forming agent, deionized water is used as a coagulating bath, a non-solvent induced phase separation method (NIPS) is adopted to prepare the sulfonated polysulfone blended TB ultrafiltration membrane, and the mass transfer speed of the solvent and the non-solvent in two-way diffusion is high, so that the membrane pores are easy to form.

Compared with the prior art, the invention

After the base polymer and the sulfonated polysulfone are blended, corresponding ammonium salt and sulfonate radical are generated due to the reaction of original neutral amine and sulfonic acid on the structure, the surface contact angle is reduced, the hydrophilicity is enhanced, the water flux is increased, the pollution resistance of the membrane is obviously improved, and further the sulfonated polysulfone blended TB ultrafiltration membrane (SPSF/TB blended membrane for short) is completely changed into a gradient sponge pore structure in shape and structure, and the polymer cross-linking presents a unique network structure due to the formation of organic macromolecular salt in larger blending ratio. SPSF/TB Water flux J compared to pure TB films_WCReach 274.92-343.21L/m²H (operating pressure of 0.1MPa), the flux recovery value FRR reaches 61.11% -67.45%, and is respectively improved by 42.88% -78.37% and 67.4% -84.8%. In addition, the potential application of the SPSF/TB blended membrane in water treatment is explored, the retention rate of the emulsified oil under the better condition can reach more than 98.52%, and the water flux after 3 cycles tends to 199.1L/m²H, FRR up to 61.6%.

Drawings

FIG. 1 is a photograph of the contact angle of the film prepared in comparative example 1;

FIG. 2 is a photograph of the contact angle of the SPSF/TB blend film prepared in example 1;

FIG. 3 is a photograph of the contact angle of the SPSF/TB blend film prepared in example 2;

FIG. 4 is a photograph of the contact angle of the SPSF/TB blend film prepared in example 3;

FIG. 5 is a photograph of the contact angle of the SPSF/TB blend film prepared in example 4;

FIG. 6 is a photograph of the contact angle of the SPSF/TB blend film prepared in example 5;

FIG. 7 is a schematic diagram of the reaction of sulfonated polysulfone blended TB ultrafiltration membrane of the present invention;

FIG. 8 is a contact angle of the films prepared in comparative example 1 and examples 1-5;

FIG. 9 is a graph showing the adsorption of BSA onto membranes prepared in comparative example 1 and examples 1 to 5;

FIG. 10 is a graph of the porosity of membranes prepared in comparative example 1 and examples 1-5;

FIG. 11 is a graph of the surface porosity parameters of the membranes prepared in comparative example 1 and examples 1-5;

FIG. 12 is a SEM image of the plane of the membrane prepared in comparative example 1;

FIG. 13 is a SEM image in plan view of the SPSF/TB blended film prepared in example 1;

FIG. 14 is a SEM image in plan view of the SPSF/TB blended film prepared in example 2;

FIG. 15 is a SEM image in plan view of the SPSF/TB blended film prepared in example 3;

FIG. 16 is a SEM image in plan view of the SPSF/TB blended film prepared in example 4;

FIG. 17 is a SEM image in plan of an SPSF/TB blended film made in example 5;

FIG. 18 is a SEM image of a cross-section of a membrane prepared in comparative example 1;

FIG. 19 is a SEM cross-section of an SPSF/TB blended film prepared in example 1;

FIG. 20 is a SEM cross-section of an SPSF/TB blended film prepared in example 2;

FIG. 21 is a SEM cross-section of an SPSF/TB blended film prepared in example 3;

FIG. 22 is a SEM cross-section of an SPSF/TB blended film made in example 4;

FIG. 23 is a SEM cross-section of an SPSF/TB blended film prepared in example 5;

FIG. 24 is an SEM magnified cross-sectional view of the membrane prepared in comparative example 1;

FIG. 25 is an SEM magnified cross-section view of the SPSF/TB blended film prepared in example 4;

FIG. 26 is an SEM magnified cross-section view of the SPSF/TB blended film prepared in example 5;

FIG. 27 is a graph showing the water flux of membranes prepared in comparative example 1 and examples 1 to 5;

FIG. 28 is a graph of the BSA retention of membranes prepared in comparative example 1 and examples 1-5;

FIG. 29 is a graph showing the flux recovery rates of membranes prepared in comparative example 1 and examples 1 to 5;

FIG. 30 is a graph showing the trend of water flux with time for the membranes prepared in comparative example 1 and examples 1 to 5;

FIG. 31 is a particle size distribution of oily wastewater treated by the membrane prepared in comparative example 1 and examples 1 to 5;

FIG. 32 is a graph showing the tendency of flux of the membrane for treating oil-containing wastewater with time, which is prepared in comparative example 1 and examples 1 to 5.

Detailed Description

The reagents used in the present invention: o-tolidine (C)₁₄H₁₆N₂98.0%,), trifluoroacetic acid (TFA, 99.0%), N-methyl-2-pyrrolidone (NMP,>99.0%) and ethylene glycol monomethyl ether (EGM, 99.0%) were purchased from shanghai alatin biochemistry; dimethoxymethane (C)₃H₈O₂98.0%) purchased from alfa aesar chemical); ammonia monohydrate (NH. H O, 99.0%), chloroform (CHCl)₃，>99.0%) and methanol (CH)₃OH, 99.7%) were purchased from the national drug group; bovine serum albumin (BSA, molecular weight 67kDa) was purchased from tianjin zhengjiang; the sulfonated polysulfone raw material is purchased from Tianjin inkstone.

The apparatus used in the present invention: a table type film coating machine (HLK GM3125D, automation of Suzhou holy reclamation), a film pressing machine (ZYIA, automation of Suzhou holy reclamation), a double-beam ultraviolet visible light spectrophotometer (TU-1901, general purpose for Beijing Pujingyu), a digital display constant temperature multi-head magnetic stirrer (HJ-6A, Jetta Jerrel), a vacuum drying box (DZF-6050, Jetta Jerrel), a scanning electron microscope (S-4800, Hitachi Japan), a contact angle measuring instrument (OSA60, German Lauda), a Mark laser particle size analyzer (MS-2000, British Mark), and a COD digestion instrument (5B-1FV8, Lianhua science and technology).

Example 1

4,4 '-diamino-3, 3' -dimethylbiphenyl (20g,94mmol) and dimethanol formal (35.84g, 470mmol) were added to a 500mL round bottom flask, mechanically stirred, trifluoroacetic acid (160mL) was slowly added dropwise in an ice-water bath, and stirring was continued for 30min in an ice-water bath after the addition was completed. Then reacting for 96h at room temperature. Precipitating the obtained solution in ammonia water, washing with deionized water, dissolving the precipitate in chloroform, precipitating in methanol, washing with methanol solution, and vacuum drying to obtain the final product

A base polymer.

1) 1.455g

Placing a base polymer, 0.045g of sulfonated polysulfone with 20% sulfonation degree, 7g of N-methyl-2-pyrrolidone and 1.5g of ethylene glycol monomethyl ether in a conical flask, adding a rotor, tightly plugging a bottle cap, wrapping a bottle mouth with a preservative film, and then carrying out magnetic stirring at 25 +/-2 ℃ for 12 hours to prepare a uniform and stable casting solution;

2) defoaming: placing the coating liquid prepared in the step 1) into a vacuum drying oven to be defoamed for 1h at 60 ℃;

3) film scraping: and adjusting a micrometer on the film scraping device to accurately control the distance between the scraper and the glass plate to be 100 micrometers, then uniformly pouring the casting film liquid near the scraper, sliding the scraper at a constant speed to spread the casting film liquid on the glass plate, standing in the air for 10s for pre-evaporation, quickly immersing the glass plate into water at 25 +/-2 ℃ to convert into a film, and then automatically peeling the film from the glass plate.

4) Cleaning or soaking the membrane prepared in the step 3) with deionized water for 30min to completely remove residual organic solvent, thus obtaining the membrane. And then placing the membrane in another pot of distilled water to be soaked for 24h for storage, and waiting for next performance test.

Examples 2-5 and comparative example 1 preparation of sulfonated polysulfone blended TB Ultrafiltration Membrane Using the same procedure as in example 1 except that

The ratio of the base polymer to the sulfonated polysulfone is specifically shown in the following table 1:

TABLE 1 formulation of different casting solutions

The membranes prepared in examples 1 to 5 and comparative example 1 were subjected to the determination and characterization:

1) contact angle: the contact angle was measured randomly at 5 points on one film and averaged.

2) BSA adsorption performance: a small amount of regularly shaped membrane pieces were soaked in a buffer solution (PBS, pH 7.4) for 3.0 hours, then further soaked in 10mL of 0.5g/L BSA solution for 3.0 hours, the membrane pieces were taken out, the membrane surfaces were washed with the buffer solution and diluted to 50mL, the BSA concentrations (278nm) before and after washing were measured by UV-vis, and the membrane piece adsorption rate Q was calculated according to formula (1).

Formula C₁And C₂Respectively, the concentration of BSA after raw and washing is mg/L, A is the effective area of the membrane and the unit is cm²，V₁＝10mL，V₂＝50mL；

3) And (3) film structure: freeze-drying the prepared membrane, quenching in liquid nitrogen, spraying gold on the cross section, and observing the shape of the cross section of the membrane by using an SEM (scanning Electron microscope); and analyzing the SEM picture by using image J to obtain the porosity and the pore size distribution of the surface of the membrane.

4) Porosity: soaking the membraneTaking out the mixture in distilled water at room temperature for 24 hours, filtering excessive water by using filter paper, and weighing the mass w of the mixture₁Drying the mixture in a vacuum drying oven at 60 ℃ for 24h, and then weighing the mass w₂Calculated according to equation (2):

in the formula w₁Is the wet film weight, w₂Is the dry film weight, p_wIs the density of water (1.0 g/cm)³)，V(m³) Is the membrane volume (thickness x membrane area);

5) flux: prepressing for 15min at 0.15MPa by using a dead-end filtering device, then measuring the pure water flux of the membrane at 0.1MPa, and calculating according to the formula (3):

wherein m is the permeate mass (g), A (m)²) Is the effective membrane area, and ρ is the permeate density (1.0 g/cm)³) And Δ t (h) is the transit time.

6) Retention rate: the pure water was replaced with 0.5g/L BSA solution and filtered at 0.1MPa for 60min, the absorbance of the filtrate and stock solution was measured, and the membrane rejection was calculated according to formula (4).

Wherein, C_fIs the concentration of the BSA stock solution, C_pIs the concentration of the BSA solution after permeation.

7) Anti-pollution performance: after the BSA raw material solution with the concentration of 0.5g/L runs for 1 hour, the raw material solution is replaced by distilled water, and the membrane is washed for 10min at low pressure and high speed; measuring the Water flux (J) of the membranes_WCThe method is the same as above), repeating 3 cycles; the Flux Recovery Ratio (FRR) was calculated according to equation (5).

8) Treating oily wastewater: the flux and retention rate measuring method is consistent with the ultrafiltration experiment; COD digestion instrument and Malvern diffraction particle size distribution are used to determine the COD concentration of raw water and effluent and the particle size distribution of oil droplets (the retention rate is calculated by converting COD standard curve into the concentration of oily wastewater).

Through the experiment, the hydrophilic result of the sulfonated polysulfone blended TB ultrafiltration membrane prepared by the method is as follows:

the physical and chemical properties of the blend film are closely related to the compatibility and proportion of the polymers in the blend system, and the structure and the performance of the blend film after being formed are also determined. Fig. 1-6 and 8 are photographs of contact angles and changes of contact angles of SPSF/TB blend films prepared in examples 1-5 and pure TB films prepared in comparative example 1, respectively. As seen from the figure, the contact angle of the blended film generally shows a descending trend along with the increase of the content of the SPSF, the contact angle of the TB film is (100.3 +/-4.07) °, and the SPSF/TB⁵、SPSF/TB¹⁰And SPSF/TB¹⁵The contact angles are respectively (77.08 + -3.05) °, (71.49 + -5.46) °and (64.93 + -5.89) °, and are respectively reduced by 22.4-35.3% compared with TB original film. Since the static water contact angle can reflect the hydrophilic and hydrophobic properties of the membrane surface and indirectly reflect the chemical composition of the membrane surface, this is because

Sulfonic acid group-SO after base and SPSF are compounded₃The H and the N on the TB alkali ring are combined into a salt by ionic bonds generated by mutual attraction of positive and negative charges, and the original neutral amine and sulfonic acid are changed into corresponding ammonium salt and sulfonate (see figure 7) structurally, so that the hydrophilicity of the blended membrane is obviously improved. Further analysis was made with respect to the adsorption performance of the blended membrane to BSA, and the results are shown in fig. 9. Compared with TB raw material, the adsorption capacity of the material to BSA is 173.53ug/cm²Compared with the blend membrane SPSF/TB accessed to the SPSF⁵、SPSF/TB¹⁰And SPSF/TB¹⁵The adsorption performance to BSA is low (83.24-117.55 ug/cm)²) The hydrophilic sulfonate, ammonium salt and sulfonic acid group on the surface of the membrane can adsorb a large amount of water molecules to form a hydration layer, and the hydration layer can prevent BSA (bovine serum albumin) from contacting the surface of the membrane, further inhibit the adsorption of the BSA on the surface of the membrane and reduce the adsorption quantity of the BSA。

Blending film SEM structure: FIGS. 12-26 are plan and cross-sectional SEM images of different ratios of SPSF/TB blended membranes prepared in examples 1-5 and comparative example 1. As shown in the figure, the influence of the SPSF content on the membrane structure is obvious, the surface of the pure TB membrane is relatively flat and compact, a large number of micropores are formed on the surface of the SPSF/TB blended membrane, and the pore diameter of the micropores tends to gradually increase along with the increase of the mass fraction of the SPSF in the membrane casting solution. The porosity of the TB film and the SPSF/TB blended film measured by a soaking method are shown in FIG. 10, and it can be seen that the porosity is increased along with the increase of SPSF compared with TB, and compared with 43.85% of the pure TB film prepared in comparative example 1, the porosity of the films prepared in examples 1-5 reaches 60.44% -82.88%; analyzing the SEM image of the membrane surface by image J software to obtain the porosity P of the membrane surface_s(%) and mean surface pore size r_s(nm), the results are shown in FIG. 11. As can be seen from the graph, as the mass ratio of the SPSF in the casting solution is increased, the porosity and the average surface pore diameter are increased, and the porosity is increased along with the increase of the SPSF, compared with TB (3.41%/13.5 nm), the membranes prepared in examples 1 to 5 reach 6.72 to 13.48%/26.49 nm to 67.10nm, and the change trend of the test is consistent with the SEM observation result. During the membrane forming process of the ultrafiltration membrane, a compact skin layer is formed firstly. When the blending degree is increased, the contents of sulfonic acid groups, ammonium salts and sulfonic acid groups with strong hydrophilicity are increased, the hydrophilicity of a polymer body is increased, the chemical potential difference between a casting solution and a non-solvent is reduced, higher non-solvent concentration is needed when a skin layer is subjected to phase separation, the density of a lean phase core of the polymer is increased, the number and the density of pores on the surface of the membrane are increased, and the pore diameter and the porosity are also increased.

In the aspect of section, all membrane sections show asymmetric porous structures, pure TB has the tendency of transition from finger-shaped pores to sponge pores, during the phase inversion process, the pure TB is instantly solidified into a compact sponge-like structure in contact with a coagulating bath, part of small pores continuously grow to form large cavities, the SPSF/TB blended membrane completely becomes a gradient sponge network pore structure, and the section sponge pores are more dense along with the increase of SPSF, particularly the SPSF/TB¹⁰、SPSF/TB¹⁵The salt of the organic macromolecule causes the polymer to be crosslinked, and the organic macromolecule presents uniquenessThe network structure of (2). Research shows that the mutual mass transfer speed of the solvent and the non-solvent has great influence on the structure of the membrane, and the membrane forming process and the membrane structure are mainly controlled by the dynamic mass transfer of the system. The diffusion of the solvent in the water bath is limited due to the large interaction between the polymer chains in the precipitation process of the TB in the coagulating bath, so that a compact film is formed; the compatibility of SPSF and TB is good, after salt exchange, the hydrophilicity of the membrane casting solution is stronger, more non-solvent enters the membrane casting solution, so that the mass transfer speed between the solvent and the non-solvent in the phase conversion process is delayed, the membrane casting solution generates delayed phase splitting in the phase conversion process, a supporting layer structure of the membrane is easy to convert to a spongy hole, a small amount of water gradually immerses into a polymer, and then the supporting layer structure is dispersed in the membrane casting solution to form a large number of micropores, so that the interaction between TB polymer chains is weakened, respective agglomeration occurs, the membrane casting solution is instantly cured, the micropores are fixed when the micropores do not grow up, and the porosity of the SPSF/TB blend membrane is improved.

Water flux and rejection rate of the blend membrane: the pore size and hydrophilicity directly affect the water flux and rejection rate of the ultrafiltration membrane. The water flux and the retention rate of the SPSF/TB blended membranes with different proportions are respectively shown in figures 27-28, the change of the membrane performance is consistent with the change of the membrane structure, the water flux of the membranes is in an ascending trend along with the increase of the SPSF mass ratio, and the water flux J of the membranes prepared in examples 1-5_WCFrom 274.92L/m²H increases to 343.21L/m²H (operating pressure 0.1MPa), compared with pure TB film (192.41L/m)²H) from 42.88% to 78.37% higher, because as the SPSF content increases, the membrane surface pores tend to increase due to diffusion of the SPSF into the coagulation bath. The aperture of the membrane is increased, and meanwhile, the hydrophilic property of the surface of the ultrafiltration membrane is improved by the access of the sulfonic acid group, so that the water flux of the membrane is obviously increased. From the change curve of the retention rate of the SPSF/TB blended membrane to BSA, the retention rate of the SPSF/TB blended membrane to BSA is kept high, the whole change range is small, TB is 77.03%, and the SPSF/TB blended membrane is increased and then slightly reduced and is between 68.24% and 87.52%. Further analysis was carried out when SPSF/TB³To SPSF/TB⁵The retention of BSA increased, from 79.67% to 87.52%; when SPSF/TB⁵To SPSF/TB¹⁵The retention of BSA was determined by the SPSF/TB co-operationThe increase of the mixing ratio is reduced from 87.52% to 68.24%. The rejection rate of ultrafiltration membranes is largely influenced by the size of the surface pore size and the electrostatic effect of the membrane surface charge on the attraction or repulsion of contaminants, when SPSF/TB³To SPSF/TB⁵The influence of hydrophilicity on the membrane rejection is dominant, SPSF/TB³And SPSF/TB⁵The hydrophobic protein molecules are blocked outside membrane pores by electrostatic repulsion of hydrophilic sulfonic groups when a protein aqueous solution passes through the ultrafiltration membrane, and the resistance of the protein molecules passing through the ultrafiltration membrane is greatly increased, so that the rejection rate is increased. When the blending ratio is increased continuously, the increase of the surface pore diameter and the surface pore density of the blended membrane is obvious, so that protein molecules penetrate through the mixed blended membrane in the filtering process, the retention effect of BSA is influenced, and the retention rate is reduced.

Anti-pollution property of the membrane: the membrane flux recovery (FRR) is an important indicator for characterizing the anti-fouling performance of a membrane. It is believed that the higher the flux recovery, the greater the anti-fouling performance of the membrane. Fig. 29 shows the flux recovery rates of different blend membranes after contamination with BSA solution, and it can be seen from the graph that the flux recovery rate FRR of the pure TB membrane is 36.49%, while the flux recovery rate of the blend SPSF/TB membrane is significantly improved, and the flux recovery rate FRR of the blend SPSF/TB membranes of different proportions prepared in examples 1 to 5 reaches 61.11% to 67.45%, which is improved by 67.4% to 66.5%. Presumably, the hydrophilic functional groups on the surface of the SPSF/TB mixed membrane can extend into the solution, so that water molecules can be adsorbed more easily, a hydration layer is formed on the surface of the membrane, the hydrophobic effect of BSA molecules and the SPSF/TB membrane can be reduced, the deposition of the BSA molecules on the surface of the membrane is further avoided, and the contact between the surface of the membrane and pollutants is prevented, so that the anti-pollution performance of the membrane is improved. To investigate the anti-fouling performance of the blended membranes during dynamic filtration fouling, a 3-cycle run was performed. Fig. 30 is a plot of flux versus time for TB membranes and blended membranes at different SPSF ratios. As can be seen from the figure, the BSA flux and the water flux of the TB membrane both significantly decline. In the early stages of contaminated operation, TB and SPSF/TB³、SPSF/TB¹⁵The flux obtained respectively is from 201.5L/m²·h，319.63–385.63L/m²H acuteDown to 67.2 and 151.2-198.17L/m²H, the water flux of the TB membrane only reached 33.34% of the pure water flux of the clean membrane, and the BSA flux also dropped 54.01%. Compared with the SPSF/TB blend membrane, after 3 periods of running, the water flux and the BSA flux of the blend membrane only reach 42.3-57.2% and 34.31% -54.91% of the pure water flux of the clean membrane, and the BSA aqueous solution flux of the blend membrane is lower than the pure water flux because the BSA belongs to macromolecular protein, the mobility of the aqueous solution is poor, the dynamic resistance of the BSA when the BSA passes through the membrane is higher, so that the flux of the BSA aqueous solution is lower than the pure water flux, simultaneously, a filter cake is blocked, and the protein macromolecules cover the surface of the ultrafiltration membrane and also prevent BSA molecules from passing through.

Treating oily wastewater: in order to explore the potential application of the SPSF/TB blend membrane in water treatment, the filtration performance of the TB and the SPSF/TB blend membrane in the separation process of emulsified oil wastewater is researched. FIG. 31 shows the retention rate of the SPSF/TB blend membrane for treating oily wastewater (R in the figure)_COD) And particle size distribution. The figure shows that the blended membrane has better emulsified oil retention performance than a TB original membrane, the water quality of the filtered fluid is clear and transparent, and the existence of emulsified oil drops can not be observed by naked eyes. Measuring the calculated retention rate of emulsified oil drops, SPSF/TB by using a COD digestion method⁵,SPSF/TB¹⁵98.52% and 95.16% respectively. From the oil droplet particle size test analysis before and after the circulation, it can be seen that: the blend membrane has good retention effect on emulsified oil, and most of the emulsified oil dissolved in water is removed. The average pore diameter of the blend membrane is 33nm, while the oil diameter of most of the emulsified oil is 120 μm which is far larger than the pore diameter of the blend membrane, so the treatment effect is obvious. The two figures are combined to show that the blended membrane has better flux recovery rate when treating the oily wastewater, and the water flux is not changed greatly and tends to 199.1L/m after the oily wastewater is polluted for many times²H, FRR up to 61.4%.

The invention takes TB as a basement membrane material and SPSF as a blending material, and adopts a non-solvent induced phase separation method to prepare the SPSF/TB blending ultrafiltration membrane. Due to the fact that

After base and SPSF are compounded, the base and the SPSF are subjected to sulfonic acid group-SO₃Of H and TB basesThe N on the ring is combined into salt by ionic bonds generated by mutual attraction of positive and negative charges, the original neutral amine and sulfonic acid are structurally changed into corresponding ammonium salt and sulfonate, the surface contact angle is reduced along with the increase of the mass ratio of SPSF, and the hydrophilic performance of the PES membrane is greatly improved;

moreover, SEM shows that the form structure of the blended membrane becomes more compact, the SPSF/TB blended membrane completely becomes sponge pores, and the cross section of the sponge pores is more dense with the increase of SPSF, particularly the SPSF/TB¹⁰、SPSF/TB¹⁵Due to the formation of organic macromolecular salt, the polymer is crosslinked, and a unique network structure is presented; the test result of the blended membrane shows that the membrane graph gradually increases along with the increase of the SPSF content, and the water flux shows a trend of greatly increasing. SPSF/TB prepared in examples 1-5 compared to neat TB film³、SPSF/TB⁵、SPSF/TB⁷、SPSF/TB¹⁰、SPSF/TB¹⁵Water flux J_WCReach 274.92-343.21L/m²H. The increase of the SPSF content has little influence on the retention rate of BSA, and is kept between 68.24 and 87.52 percent.

Under the better condition of SPSF/TB, the flux recovery rate value FRR reaches 61.11-67.45%, is respectively improved by 42.88-78.37% and 67.4-84.8%, and the anti-pollution capability of the TB membrane is obviously improved. Further exploring the potential application of the SPSF/TB blend membrane in water treatment, finding that the retention rate of the SPSF/TB blend membrane on emulsified oil drops can reach above 98.52%, and most of emulsified oil dissolved in water is removed and tends to 199.1L/m²H, FRR up to 61.4%.

Claims

1. A preparation method of a sulfonated polysulfone blended TB ultrafiltration membrane is characterized by comprising the following steps:

1) mixing Trhyger's base polymer, sulfonated polysulfone, N-methyl-2-pyrrolidone and ethylene glycol monomethyl ether, and then sealing, stirring and dissolving to obtain a casting solution;

2) defoaming;

3) preparing a sulfonated polysulfone blended TB ultrafiltration membrane by adopting a non-solvent-water induced gel phase inversion method;

the sulfonation degree DS of the sulfonated polysulfone in the step 1) is 5-20%.

2. The manufacturing method according to claim 1, wherein the mass ratio of the Tr baby's base polymer, the sulfonated polysulfone, the N-methyl-2-pyrrolidone and the ethylene glycol monomethyl ether in the step 1) is 0.8-1:0.02-0.2:4-5: 1.

3. The method according to claim 1 or 2, wherein the defoaming in the step 2) is performed by placing the mixture in a vacuum drying oven at 60 ℃ for 1 hour.

4. The preparation method according to claim 1 or 2, wherein step 3) is specifically: pouring the membrane casting solution treated in the step 2) into a membrane scraping device, spreading the membrane casting solution on a glass plate, standing, and immersing the glass plate spread with the membrane casting solution into water to prepare the ultrafiltration membrane by adopting a non-solvent induced phase inversion method.

5. The method according to claim 4, wherein the standing in step 3) is performed at room temperature for 1 to 30 seconds.

6. The method for preparing according to claim 4, wherein the temperature of water used for the immersion in the step 3) is 25 ± 2 ℃.

7. The method for preparing according to claim 5, wherein the temperature of water used for the immersion in the step 3) is 25 ± 2 ℃.

8. The preparation method according to claim 5, wherein the thickness of the prepared sulfonated polysulfone blended TB ultrafiltration membrane is controlled to be 100 μm.

9. A sulfonated polysulfone blended TB ultrafiltration membrane prepared by the preparation method of any one of claims 1-8.

10. The application of the sulfonated polysulfone blended TB ultrafiltration membrane prepared by the preparation method of any one of claims 1-8 is characterized in that the sulfonated polysulfone blended TB ultrafiltration membrane is used for treating oily wastewater.