CN110841491A - A kind of preparation method of high permeability and anti-pollution PVDF/PFSA-g-GO ultrafiltration membrane - Google Patents

Abstract

The invention relates to a preparation method of a high-permeability and anti-pollution PVDF/PFSA-g-GO ultrafiltration membrane, which is characterized in that a casting solution mainly composed of a PFSA-g-GO nano compound, PVDF, a solvent and a pore-foaming agent is coated on a support to form a membrane and then is immersed in water to carry out a phase conversion reaction to prepare the high-permeability and anti-pollution PVDF/PFSA-g-GO ultrafiltration membrane, wherein the PFSA-g-GO nano compound is prepared by esterification reaction of PFSA resin and GO nano particles, and the water flux of the PVDF/PFSA-g-GO ultrafiltration membrane is 388.3-593.7L/m²h, the retention rate is 87.4-96.7% (bovine serum albumin) and 72.3-79.6% (humic acid). The preparation method of the invention can simultaneously improve the water flux and the protein retention rate of the ultrafiltration membrane and effectively improveThe membrane has good hydrophilicity and pollution resistance, and the mechanical property of the membrane is excellent.

Description

A kind of preparation method of high permeability and anti-pollution PVDF/PFSA-g-GO ultrafiltration membrane

technical field

The invention belongs to the technical field of ultrafiltration membrane preparation, and relates to a preparation method of a PVDF/PFSA-g-GO ultrafiltration membrane with high permeability and anti-pollution.

Background technique

Ultrafiltration (UF) refers to the process of separating according to the molecular weight difference of the separated substances with the membrane as the separation medium under the promotion of static pressure difference. Ultrafiltration membranes are commonly used in the separation, concentration and purification of biological products, pharmaceuticals, food industries and wastewater treatment industries.

The hydrophilicity and permeability of PVDF (polyvinylidene fluoride) ultrafiltration membrane can be effectively solved by adding inorganic nanoparticles. However, there are still some problems, such as literature 1 (Preparation and characterization of poly(vinylidenefluoride) (PVDF) based ultrafiltration membranes using nanoγ-Al ₂ O ₃ . Journal of Membrane Science, 2011, 366(1): 97-103) by Adding γ-Al ₂ O ₃ to modify the PVDF ultrafiltration membrane, the hydrophilicity and anti-fouling properties of the membrane are improved, but the mechanical strength of the membrane is reduced; Literature 2 (The effects of mechanical and chemical modification of TiO ₂ , nanoparticles on the surfacechemistry ,structure and fouling performance of PES ultrafiltration membranes[J].Journal of Membranes Science 2011:378,73-84.) Using TiO ₂ to improve the anti-fouling performance of PVDF membranes, but its agglomeration in PVDF membranes reduces the The smoothness of the membrane surface and its mechanical strength. The agglomeration phenomenon is caused by the natural properties of nanoparticles such as small size and high specific surface free energy. Its occurrence will make the casting liquid system unstable, and the inorganic nanoparticles will be unevenly dispersed in the blended film, resulting in the morphology of the blended film. , the structure and properties are changed, and the properties of inorganic nanoparticles cannot be fully exerted. Therefore, it has become a research hotspot to find a blend modifier that can improve the hydrophilicity of the membrane without affecting other properties of the membrane.

Graphene oxide (GO) has high dispersibility in water and good compatibility with polymer matrix due to its honeycomb-like six-layer planar structure and numerous hydrophilic groups. At present, many studies have used GO as an additive in the preparation and modification of PVDF ultrafiltration membranes to improve the performance of the membranes. Reference 3 (Application of sulfonicacid group functionalized graphene oxide to improve hydrophilicity, permeability, and antifouling of PVDF nanocomposite ultrafiltration membranes[J]. Journal of Membrane Science, 2016, 525:210-219.) added GO as an additive to PVDF membranes, The water flux of the membrane was increased by 1.6 times; Literature 4 (Optimized permeation and antifouling of PVDFhybrid ultrafiltration membranes: synergistic effect of dispersion and migration for fluorinated graphene oxide[J]. Journal of Nanoparticle Research, 2017, 19(3):114.) Blending fluorinated GO to modify PVDF improves the water flux and anti-fouling performance of the membrane; Literature 5 (Novel GO-blended PVDF ultrafiltration membranes[J]. Desalination, 2012, 299:50-54.) will 0.2 The GO/PVDF ultrafiltration membrane was prepared by blending wt% GO and PVDF. The study found that the water contact angle of the GO/PVDF ultrafiltration membrane decreased from 79° to 61°, and the flux recovery rate increased from 78% of pure PVDF membrane to 78%. 96%, and the pure water flux is more than 2 times that of pure PVDF membrane. Perfluorosulfonic acid (PFSA) because of its special structure, when in contact with water, PFSA resin undergoes spontaneous microphase separation, water molecules tightly surround the sulfonic acid group to form hydrophilic microdomains, and fluorocarbon polymers produce low surface energy microdomains, so PFSA can also be used to modify PVDF ultrafiltration membranes to improve membrane performance. Document 6 (Constructing dual-defense mechanisms on membrane surfaces by synergy of PFSA and SiO ₂ , nanoparticles for persistent antifouling performance[J]. Applied Surface Science, 2018, 440:113-124.) constructed PVDF/PFSA/SiO ₂ membranes, membranes The permeability and anti-fouling properties of the nanotubes were improved; Literature 7 (Influences of the structure parameters of multi-walled carbonnanotubes(MWNTs) on PVDF/PFSA/O-MWNTs hollow fiber ultrafiltration membranes[J]. Journal of Membrane Science, 2016, 499 : 179-190.) PVDF/PFSA/O-MWNTs fibrous membranes were prepared with PFSA as additive, and the membrane permeability was improved. However, the above treatment methods for GO and PFSA often face the defects of increased permeability and decreased anti-fouling performance. At the same time, the mechanical properties of the membrane are poor, and GO is prone to fall off during the long-term use of the membrane.

Therefore, it is of great significance to study a method to make PVDF ultrafiltration membranes have both high permeability, high anti-pollution performance, excellent mechanical properties and better durability through modification.

SUMMARY OF THE INVENTION

The object of the present invention is to solve the problem that the method for modifying PVDF ultrafiltration membrane in the prior art cannot make it have both high permeability, high anti-pollution performance, excellent mechanical performance and better durability, and provides a high Preparation method of permeable and anti-fouling PVDF/PFSA-g-GO ultrafiltration membrane.

For achieving the above object, the scheme that the present invention adopts is as follows:

A method for preparing a PVDF/PFSA-g-GO ultrafiltration membrane with high permeability and anti-pollution. The PVDF/PFSA-g-GO ultrafiltration membrane with high permeability and anti-pollution was prepared by immersing the film on the body and immersing it in water for phase inversion reaction. The PFSA-g-GO nanocomposite was esterified by PFSA resin and GO nanoparticles. The water flux of the PVDF/PFSA-g-GO ultrafiltration membrane prepared by the reaction was 388.3-593.7 L/m ² h, the rejection rate of bovine serum albumin (BSA) was 87.4-96.7%, and the humic acid ( The retention rate of HA) was 72.3-79.6%.

The method for preparing the PVDF/PFSA-g-GO ultrafiltration membrane by the phase inversion reaction of the present invention is a non-solvent induced phase separation method, also known as a wet method, the principle of which is to dissolve the polymer in a solvent to form a homogeneous solution. Then slowly add a reagent (called an extractant) that is more miscible with the solvent to extract the solvent to form a two-phase structure with the polymer as the continuous phase and the solvent as the dispersed phase, and then remove the solvent to obtain a polymer with a certain pore structure. When the PVDF ultrafiltration membrane is modified by adding PFSA-g-GO nanocomposite, the water flux and protein retention rate of the ultrafiltration membrane can be improved at the same time, which solves the deficiencies in the existing technology, namely ultrafiltration When the water flux of the membrane increases, the rejection rate decreases. On the contrary, when the rejection rate increases, the water flux decreases. The "seesaw" phenomenon of adding PFSA-g-GO nanocomposite to modify the PVDF ultrafiltration membrane can improve the performance of the ultrafiltration membrane. The water flux and protein retention rate are because: the PFSA-g-GO nanocomposite of the present invention is endowed with higher hydrophilicity due to the numerous hydrophilic groups on the surface of GO and the effect of -SO ₃ ^- in PFSA. , during the phase inversion process, the PFSA-g-GO nanocomposite with higher hydrophilicity as a nucleating agent can increase the gelation speed of the casting solution and change the pore structure of the membrane, and the hydrophilic PFSA-g -The strong interaction between the GO nanocomposite and the non-solvent will accelerate the diffusion between the solvent and the non-solvent during the phase separation process, forming larger irregular macropores, meanwhile, the hydrophilic PFSA-g-GO nanocomposite The addition of PFSA-g-GO nanocomposites enhances the thermodynamic instability of the casting solution, resulting in higher phase transition rates and more porous structures, both of which can lead to higher water fluxes; the addition of PFSA-g-GO nanocomposites Afterwards, compared with PVDF membranes with similar dense surface structure, the affinity between hydrophilic PFSA-g-GO and water (coagulation bath) increases with increasing amount of PFSA-g-GO nanocomposite. The larger, the number of pores on the surface of PVDF/PFSA-g-GO membrane gradually increases. In the case of high content of PFSA-g-GO nanocomposite in the casting solution, the diffusion rate between solvent and non-solvent increases, which will The surface layer is destroyed to form more pores, so the water flux increases. Although the number of pores on the membrane surface increases, the radius of the pores does not change much, and the hydrophilicity of the membrane increases, which can form a layer of water on the membrane surface. The chemical layer can effectively prevent a part of bovine serum albumin and humic acid from directly passing through the membrane pores, so the retention rate of the membrane is still high. In addition, the present invention uniformly disperses the PFSA-g-GO nanocomposite into the PVDF film, because the PFSA and GO in the PFSA-g-GO nanocomposite have an ester bond, and the PFSA-g-GO nanocomposite and PVDF The membrane has fluorine-fluorine interaction, thus improving the dispersion of the nanocomposite in the membrane, making it more compatible with PVDF membrane. In summary, the excellent properties of PFSA-g-GO nanocomposite can effectively improve the hydrophilicity and anti-fouling performance of the membrane (at the same time, it has higher water flux and protein rejection rate), and at the same time, compared with pure PVDF membrane , PVDF/PFSA-g-GO film has higher mechanical strength, and due to the graft modification of GO with PFSA, the PFSA-g-GO nanocomposite can exist stably in the film, and it is not easy to fall off, which improves the performance of the film. Long-term use performance.

As a preferred solution:

The above-mentioned preparation method of a highly permeable and anti-pollution PVDF/PFSA-g-GO ultrafiltration membrane, the specific steps are as follows:

(1) After mixing the PFSA-g-GO nanocomposite, PVDF, solvent and porogen, and stirring at a temperature of 20-25 °C for 48-60 h to obtain a casting solution, the whole process of preparing the casting solution is It is carried out at close to room temperature. Stirring for 48-60 hours can make the obtained casting solution more uniform. If the casting solution is not uniform, it will affect the structure, water flux, retention rate and surface roughness of the membrane. Among them, The mass ratio of solvent to PFSA-g-GO nanocomposite is 80-809:1, the mass ratio of solvent to PVDF is 5.00-5.06:1, and the total mass of substances in the casting liquid formula is a fixed value. When the addition amount of PFSA-g-GO nanocomposite is fixed, changing the addition amount of PFSA-g-GO nanocomposite will change the corresponding amount of solvent, and the increase of PFSA-g-GO nanocomposite content will affect the structure, Water flux, retention rate and surface roughness, etc.; the mass content of porogen in the casting solution is 3% to 5%; if the content of porogen is too high, the surface layer of the prepared membrane is thin, resulting in high permeability of the membrane, and the The retention rate is correspondingly small;

(2) Coat the casting liquid on the support to form a film, control the thickness of the film to be 0.15-0.2 mm, and immerse the film in water for a phase inversion reaction to obtain PVDF/PFSA-g-GO ultrafiltration with high permeability and anti-pollution This method only needs to be immersed in water for a period of time, and the film is formed by means of the diffusion of solvent and non-solvent, which can be completed at room temperature.

The above-mentioned preparation method of a highly permeable and anti-pollution PVDF/PFSA-g-GO ultrafiltration membrane, the solvent is DMAc, the support is a glass plate, and the porogen is polyethylene glycol (PEG) or polyethylene Pyrrolidone K30 (PVP).

In the above-mentioned preparation method of a high-permeability and anti-pollution PVDF/PFSA-g-GO ultrafiltration membrane, the porogen is polyvinylpyrrolidone K30 (PVP).

The above-mentioned preparation method of a high-permeability and anti-pollution PVDF/PFSA-g-GO ultrafiltration membrane, the GO nanoparticles are obtained by the improved Hummers method of natural graphite powder;

The preparation of the GO nanoparticles includes the following steps:

(1) 4.0～5.0g graphite and sodium nitrate whose mass ratio is 1:1～2:1 are successively added 70mL98% concentrated sulfuric acid solution and stirred under the temperature condition of 0～5 ℃, then add 8～10g permanganic acid Potassium and keep the temperature below 20°C;

(2) transferring the above-mentioned reactant to a temperature of 30-40° C. for 0.5-1 h to form a thick substance;

(3) After adding 600-700 mL of water to react for 15-20 min, slowly add 20-25 mL of hydrogen peroxide solution with a mass fraction of 30%;

(4) The obtained solution was centrifuged and washed with 250-350 mL of an aqueous hydrochloric acid solution with a volume ratio of 1:10-1:14, followed by ultrasonication, centrifugation, dialysis, and finally freeze-drying to obtain GO nanoparticles.

The preparation method of a high-permeability and anti-pollution PVDF/PFSA-g-GO ultrafiltration membrane as described above, the preparation process of PFSA-g-GO nanocomposite is as follows: firstly dissolving GO nanoparticles in DMSO (or DMF) to obtain a solution with a concentration of 0.02-0.04 g·mL ^-1 , and then adding an activator, a catalyst and a PFSA solution to the solution to obtain a mixture, and then reacting the mixture at a temperature of 40-50 ° C for 60-72 h , increasing the temperature of the reaction is conducive to speeding up the reaction, but considering the tolerance range of the catalyst, activator and material used, the temperature should not be too high, and the reaction time is set here, which is conducive to the full reaction of PFSA and GO, so as to obtain the The desired PFSA-g-GO nanocomposite was obtained, and finally the PFSA-g-GO nanocomposite was obtained by post-treatment (centrifugation, acetone washing, 80-95 °C ethanol aqueous solution washing, and drying). Under the action of activators and catalysts, the carboxyl group (-COOH) on GO nanoparticles was esterified with the hydroxyl group (-OH) in PFSA, realizing the modification of GO nanoparticles with PFSA, and obtaining PFSA-g-GO nanoparticles Complex.

The preparation method of a kind of high-permeability and anti-pollution PVDF/PFSA-g-GO ultrafiltration membrane as mentioned above, the activator is thionyl chloride, 1-(3-dimethylaminopropyl)-3-ethyl Carbodiimide hydrochloride (EDC) or N,N'-dicyclohexylcarbodiimide (DCC); the catalyst is 4-dimethylaminopyridine (DMAP) or N-hydroxysuccinimide (NHS).

The above-mentioned preparation method of a high-permeability and anti-pollution PVDF/PFSA-g-GO ultrafiltration membrane, the activator is N,N'-dicyclohexylcarbodiimide (DCC); the catalyst is 4-dicyclohexylcarbodiimide (DCC) methylaminopyridine (DMAP).

The above-mentioned preparation method of a highly permeable and anti-pollution PVDF/PFSA-g-GO ultrafiltration membrane, the concentration of the PFSA solution (specifically the DMSO solution of PFSA) is 0.01～0.1g·mL ^-1 ; the activator The mass ratio to GO nanoparticles is 46-50:1, the mass ratio of catalyst to PFSA is 17-20:50-59, and the mass ratio of activator to catalyst is 13.5-135.3:1.

Beneficial effects:

(1) The preparation method of a high-permeability and anti-pollution PVDF/PFSA-g-GO ultrafiltration membrane of the present invention is simple and easy to implement and has low cost;

(2) The preparation method of a high-permeability and anti-pollution PVDF/PFSA-g-GO ultrafiltration membrane of the present invention can simultaneously improve the water flux and protein retention rate of the ultrafiltration membrane, and effectively improve the hydrophilicity of the membrane and anti-fouling performance, and the mechanical properties of the membrane will not decline;

(3) According to the preparation method of a high-permeability and anti-pollution PVDF/PFSA-g-GO ultrafiltration membrane of the present invention, due to the graft modification of GO by PFSA, the PFSA-g-GO nanocomposite can exist stably In the film, it is not easy to fall off, which improves the long-term use performance of the film;

(4) The preparation method of a high-permeability and anti-pollution PVDF/PFSA-g-GO ultrafiltration membrane of the present invention can be widely used in the fields of chemical industry, medicine, seawater desalination and sewage regeneration, and has good application prospects .

Description of drawings

Fig. 1 is the XRD spectrum of GO nanoparticles and graphite prepared in the embodiment of the present invention, wherein, (a) is graphite, (b) is GO nanoparticles;

Fig. 2 is the infrared spectrum of GO, PFSA, PFSA-g-GO nanocomposite in the embodiment of the present invention;

Fig. 3 is the infrared spectrum of PVDF, PVDF/PFSA-g-GO ultrafiltration membrane in the embodiment of the present invention;

Fig. 4 is the XRD spectrum of PVDF/PFSA-g-GO ultrafiltration membrane in the embodiment of the present invention;

Fig. 5 is the scanning electron microscope (SEM) figure of the upper surface of ultrafiltration membrane in the embodiment of the present invention;

Fig. 6 cross-sectional scanning electron microscope (SEM) figure of ultrafiltration membrane in the embodiment of the present invention;

Fig. 7 is the atomic force microscope (AFM) figure of ultrafiltration membrane in the embodiment of the present invention;

Fig. 8 is the contact angle diagram of ultrafiltration membrane in the embodiment of the present invention;

Fig. 9 is the water flux and rejection rate diagram of ultrafiltration membrane in the embodiment of the present invention;

Fig. 10 is the anti-protein pollution diagram of ultrafiltration membrane in the embodiment of the present invention;

Fig. 11 is the Young's modulus and tensile strength diagram of ultrafiltration membrane in the embodiment of the present invention;

FIG. 12 is a stress-strain curve diagram of an ultrafiltration membrane in an embodiment of the present invention.

Detailed ways

The present invention will be further described below in conjunction with specific embodiments. It should be understood that these examples are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

Example 1

The specific steps of the preparation method of PFSA-g-GO nanocomposite are as follows:

(1) GO nanoparticles are prepared from natural graphite powder by the modified Hummers method. The XRD and infrared spectra of the prepared GO nanoparticles are shown in Figures 1-2. In Figure 1, (a) is graphite, (b) ) are GO nanoparticles;

(2) Preparation of PFSA-g-GO nanocomposites: First, GO nanoparticles were dissolved in DMSO (solvent) to obtain a solution with a concentration (c1) of 0.003 g·mL-1, and then N,N' was added to the solution. - Dicyclohexylcarbodiimide (DCC) (activator), 4-dimethylaminopyridine (DMAP) (catalyst) and PFSA in DMSO to obtain a mixture, which was then subjected to a temperature (T1) of 50°C The reaction was carried out for 72 h (t1), and finally centrifuged, washed with acetone, washed with an aqueous ethanol solution at a temperature (T2) of 95 °C, and dried to obtain PFSA-g-GO nanocomposite. The infrared spectrum of PFSA-g-GO nanocomposite is shown in Figure 2. Among them, the concentration (c2) of the DMSO solution of PFSA is 0.01 g·mL-1; the mass ratio (W1) of N,N'-dicyclohexylcarbodiimide (DCC) to GO nanoparticles (W1) is 46:1 , the mass ratio (W2) of N,N'-dicyclohexylcarbodiimide (DCC) to 4-dimethylaminopyridine (DMAP) is 135.3:1, the mass of 4-dimethylaminopyridine (DMAP) to PFSA The ratio (W3) was 17:50.

Examples 2 to 5

The preparation method of PFSA-g-GO nanocomposite, its specific steps are basically the same as Example 1, the difference lies in the reaction parameters, as shown in Table 1, wherein, EDC is 1-(3-dimethylaminopropyl)- 3-ethylcarbodiimide hydrochloride, NHS is N-hydroxysuccinimide.

Table 1

Example 2 Example 3 Example 4 Example 5 c1 g·mL^-1 0.003 0.003 0.004 0.003 solvent DMSO DMSO DMSO DMF activator DCC thionyl chloride EDC DCC catalyst DMAP NHS DMAP NHS T1 °C 45 40 48 50 t1 h 65 60 70 72 T2 °C 95 85 80 85 c2 g·mL^-1 0.025 0.05 0.1 0.025 W1 48:1 50:1 46:1 48:1 W2 56.5:1 29.4:1 13.5:1 56.5:1 W3 19:54 20:59 17:50 19:54

Example 6

A preparation method of a high-permeability and anti-pollution PVDF/PFSA-g-GO ultrafiltration membrane, the specific steps are as follows:

(1) After mixing the PFSA-g-GO nanocomposite prepared in Example 1, PVDF, DMAc and polyvinylpyrrolidone K30, and stirring at a temperature of 23 °C for 60 h to obtain a casting solution, wherein DMSO and PFSA- The mass ratio of g-GO nanocomposite is 161:1, the mass ratio of DMSO to PVDF is 5.03:1, and the mass content of polyvinylpyrrolidone K30 in the casting solution is 3%;

(2) coating the casting liquid on the glass plate to form a film, the thickness of the control film is 0.15mm, and the film is immersed in water and a phase inversion reaction occurs to obtain a PVDF/PFSA-g-GO ultrafiltration membrane with high permeability and anti-pollution;

The PVDF/PFSA-g-GO ultrafiltration membrane, the membrane serial number is M3, and its performance indicators are shown in Table 3.

Examples 7 to 14

A preparation method of a high-permeability and anti-pollution PVDF/PFSA-g-GO ultrafiltration membrane, the specific steps are as follows:

(1) After mixing the PFSA-g-GO nanocomposite prepared in Example X, PVDF, DMAc and porogen, and stirring at a temperature (T3) of 20-25 °C for 48-60 h (t2) to obtain a cast iron The film solution, wherein the mass ratio (W4) of DMSO and PFSA-g-GO nanocomposite is 80-809:1, and the mass ratio (W5) of DMSO and PVDF is 5.00-5.06:1, and the casting solution is porosity. The mass content (W) of the agent is 3% to 5%;

(2) Coat the casting liquid on the glass plate to form a film, control the thickness (d) of the film to be 0.15-0.2 mm, and immerse the film in water to undergo a phase inversion reaction to obtain a highly permeable and anti-pollution PVDF/PFSA-g- GO ultrafiltration membrane;

The specific preparation parameters of Examples 7-14 are shown in Table 2, wherein, PEG is polyethylene glycol, and PVP is polyvinylpyrrolidone K30;

The performance indicators of the PVDF/PFSA-g-GO ultrafiltration membranes prepared in Examples 7 to 14 are shown in Table 3, wherein the BSA retention rate is the retention rate of bovine serum albumin, and the HA retention rate is the retention rate of humic acid; The serial numbers of the ultrafiltration membranes are M4-M11 in sequence, and the specific correspondence is shown in Table 3;

In addition, M4 is selected for infrared test, and the test result is shown in Figure 3;

M4, M7-M9 were selected for XRD test, and the test results are shown in Figure 4;

The upper surface and cross section of M4-M9 were selected for scanning electron microscopy (SEM) tests, and the test results are shown in Figure 5 and Figure 6;

M4 and M9 were selected for atomic force microscopy (AFM) test, the test results are shown in Figure 7, and the data are shown in Table 4, where Ra is the average surface roughness, and RMS is the root mean square surface roughness;

M4, M7-M9 were selected for the contact angle test, and the test results are shown in Figure 8;

Select M4-M9 for water flux and retention rate tests, and the test results are shown in Figure 9;

M4 was selected for the anti-fouling test. The results of the test are shown in Figure 10 and the data are shown in Table 6. Among them, the water flux recovery rate (FRR) is used to evaluate the anti-fouling performance of the UF membrane. The test method is as follows: First, measure the The pure water flux ( _Jw ) of the membrane, then the permeate medium was changed to 0.5 g/L BSA aqueous solution for the same membrane; after filtration for 30 min, the membrane was removed from the membrane module and deionized under ultrasonic Washed with water for 5 minutes; then, the cleaned membrane was installed in the membrane module, and the pure water flux was measured again, recorded as J _w1 ; then the same "water flux-BSA filtration-water flux" procedure was repeated, called "Second Loop"; FRR is calculated using the following formula:

M4, M7-M9 were selected for Young's modulus and tensile strength test, the test results are shown in Figure 11, and the obtained data are shown in Table 5;

M4, M7-M9 were selected for stress and elongation tests, and the test results are shown in Figure 12.

Table 2

Comparative Example 1

A preparation method of PVDF ultrafiltration membrane, the steps are basically the same as those in Example 7, the difference is that PFSA-g-GO nanocomposite is not added. The filter serial number is M0.

Comparative Example 2

A preparation method of PVDF/GO ultrafiltration membrane, the steps are basically the same as in Example 7, the difference is that the added PFSA-g-GO nanocomposite is replaced with GO nanoparticles, and the performance of the ultrafiltration membrane obtained The test is shown in Tables 3 to 6, and the serial number of the ultrafiltration membrane is M1.

Comparative Example 3

A preparation method of PVDF/PFSA ultrafiltration membrane, the steps are basically the same as those in Example 7, the difference is that the added PFSA-g-GO nanocomposite is replaced with PFSA, and the infrared spectrum of PFSA is shown in Figure 2. The performance test of the obtained ultrafiltration membrane is shown in Tables 3 to 6, and the serial number of the ultrafiltration membrane is M2;

Select M0 for infrared spectrum and XRD test, the results are shown in Figure 3 and Figure 4;

The upper surface and cross-section of M0-M2 were selected for scanning electron microscope (SEM) test respectively, and the test results are shown in Figure 5 and Figure 6;

Select M0 and M1 for atomic force microscope (AFM) test, the test results are shown in Figure 7, and the data are shown in Table 4;

M0 was selected for the contact angle test, and the test results are shown in Figure 8;

Select M0-M2 to test the water flux and retention rate, and the test results are shown in Figure 9;

M0-M2 was selected for anti-protein contamination test, the results of the test are shown in Figure 10, and the data are shown in Table 6;

Select M0-M2 for Young's modulus and tensile strength test, the test results are shown in Figure 11, and the obtained data are shown in Table 5;

Select M0-M2 for stress and elongation test, and the test results are shown in Figure 12;

Comparing Example 7 with Comparative Example 1, it can be seen that the total porosity and average pore size of the ultrafiltration membrane in Comparative Example 1 are smaller than those of Example 7. The addition of the composite, the hydrophilic PFSA-g-GO nanocomposite can accelerate the phase separation and the formation of the polymer-pore phase during the membrane formation process, so the total porosity and average pore size of the membrane are larger than those in Comparative Example 1. Filter membrane; the water flux and HA rejection are less than Example 7 because the strong interaction between the hydrophilic PFSA-g-GO nanocomposite and the non-solvent water would accelerate the solvent-non-solvent phase separation process In addition, the addition of the hydrophilic PFSA-g-GO nanocomposite will enhance the thermodynamic instability of the casting solution, resulting in a higher phase transition rate and more More porous structure, increasing the number of pores on the membrane surface, and improving the hydrophilicity of the membrane surface, these phenomena can lead to higher water flux; although the number of pores on the membrane surface increases, the pore radius does not change much , and the hydrophilicity of the membrane increases, a hydration layer can be formed on the surface of the membrane, which can effectively prevent a part of BSA and HA from directly passing through the membrane pores, so the retention of the membrane is still better; the surface roughness is larger than Example 7 , this is because the membrane surface roughness is reduced after the membrane is modified by PFSA-g-GO nanocomposite, and the PFSA-g-GO nanocomposite has better dispersibility in the membrane, making the membrane surface becomes smooth and reduces the surface roughness of M4 in Example 7; the mechanical strength is worse than that of Example 7 because GO is an excellent nanofiller for enhancing the mechanical properties of the membrane, however, the GO content is too high. When high, it is easy to stack and aggregate during the film formation process, which affects the mechanical properties of the film. The graft modification of GO with PFSA, due to the existence of the PFSA resin in the PFSA-g-GO nanocomposite, interacts with PVDF and GO. PFSA-g-GO nanocomposite is stably dispersed in the membrane, thereby enhancing the mechanical properties of the membrane; the antifouling property is worse than Example 7, because when the hydrophilic PFSA-g-GO nanocomposite is When added as a filler, the higher hydrophilicity and smoothness of the UF membrane surface of Example 7, which can inhibit the adsorption and deposition of protein molecules on the membrane surface during filtration, and improve the antifouling property;

Comparing Example 7 with Comparative Example 2, it can be seen that the HA rejection rate and BSA rejection rate of the ultrafiltration membrane in Comparative Example 2 are smaller than those in Example 7, because there is hydrophilic -SO ^3- in PFSA, so The PFSA-g-GO nanocomposite is more hydrophilic than pure GO. The M4 membrane of Example 7 has better hydrophilicity, and the hydrophilicity of the membrane increases, and a hydration layer can be formed on the surface of the membrane. Effectively prevent a part of BSA and HA from directly passing through the membrane pores, so the retention of the membrane is better; the surface roughness is larger than that of Example 7, because the graft modification of the GO surface by the membrane PFSA can reduce the agglomeration of GO, and Due to the fluorine-fluorine interaction between PFSA and PVDF, the PFSA-g-GO nanocomposite has better compatibility with PVDF, and can be dispersed in the film better and more stably, making the surface of M4 of Example 7 smoother; The fouling resistance is worse than that of Example 7, because the increased hydrophilicity of the membrane and the smoother surface can reduce the accumulation of pollutants on the membrane surface, so the membrane has better anti-fouling properties;

Comparing Example 7 with Comparative Example 3, it can be seen that the water flux, HA rejection rate and BSA rejection rate of the ultrafiltration membrane in Comparative Example 3 are smaller than those in Example 7, because GO contains many hydrophilic membranes. Therefore, the PFSA-g-GO nanocomposite is more hydrophilic than pure PFSA, and can form a hydration layer on the membrane surface, which can effectively prevent a part of BSA and HA from directly passing through the membrane pores, so the retention of the membrane Still better; the fouling resistance is worse than Example 7 because the membrane is more resistant to fouling due to the increased hydrophilicity of the membrane.

table 3

Table 4 serial number Membrane serial number Ra(nm) RMS(nm) Comparative Example 1 M0 33.540 58.197 Comparative Example 2 M1 29.854 32.814 Example 7 M4 22.072 27.562 Example 12 M9 25.251 15.251

table 5

serial number Membrane serial number Young's modulus (MPa) Tensile strength (MPa) Comparative Example 1 M0 52.34 1.26 Comparative Example 2 M1 74.87 1.56 Comparative Example 3 M2 65.18 1.3 Example 7 M4 71.78 1.58 Example 10 M7 60.22 1.29 Example 11 M8 69.18 1.51 Example 12 M9 76.88 1.76

Table 6

serial number Membrane serial number First cycle FRR (%) Second cycle FRR (%) Comparative Example 1 M0 80.2% 64.6% Comparative Example 2 M1 88.9% 78.6% Comparative Example 3 M2 83.1% 72% Example 7 M4 90.8% 82.3%

Claims (9)

1. High permeability and resistanceThe preparation method of the polluted PVDF/PFSA-g-GO ultrafiltration membrane is characterized by comprising the following steps: coating a casting solution mainly comprising a PFSA-g-GO nano compound, PVDF, a solvent and a pore-foaming agent on a support to form a film, and then immersing the film into water to perform a phase conversion reaction to prepare the high-permeability and anti-pollution PVDF/PFSA-g-GO ultrafiltration membrane, wherein the PFSA-g-GO nano compound is prepared by esterification reaction of PFSA resin and GO nano particles, and the water flux of the PVDF/PFSA-g-GO ultrafiltration membrane is 388.3-593.7L/m²h, the retention rate of the humic acid-containing composite material on bovine serum albumin is 87.4-96.7%, and the retention rate of the humic acid-containing composite material on humic acid is 72.3-79.6%.

2. The preparation method of the high-permeability and anti-pollution PVDF/PFSA-g-GO ultrafiltration membrane according to claim 1, which is characterized by comprising the following specific steps:

(1) mixing the PFSA-g-GO nano compound, PVDF, a solvent and a pore-forming agent, and stirring for 48-60 hours at the temperature of 20-25 ℃ to obtain a membrane casting solution, wherein the mass ratio of the solvent to the PFSA-g-GO nano compound is 80-809: 1, the mass ratio of the solvent to the PVDF is 5.00-5.06: 1, and the mass content of the pore-forming agent in the membrane casting solution is 3% -5%;

(2) coating the membrane casting solution on a support to form a membrane, controlling the thickness of the membrane to be 0.15-0.2 mm, and immersing the membrane in water to perform a phase conversion reaction to obtain the high-permeability and anti-pollution PVDF/PFSA-g-GO ultrafiltration membrane.

3. The method for preparing the PVDF/PFSA-g-GO ultrafiltration membrane with high permeability and pollution resistance as claimed in claim 2, wherein the solvent is DMAc, the support is a glass plate, and the pore-forming agent is polyethylene glycol or polyvinylpyrrolidone K30.

4. The method for preparing the PVDF/PFSA-g-GO ultrafiltration membrane with high permeability and pollution resistance as claimed in claim 3, wherein the pore-forming agent is polyvinylpyrrolidone K30.

5. The method for preparing the PVDF/PFSA-g-GO ultrafiltration membrane with high permeability and pollution resistance as claimed in claim 1, wherein GO nano-particles are prepared from natural graphite powder by a modified Hummers method.

6. The preparation method of the high-permeability and anti-pollution PVDF/PFSA-g-GO ultrafiltration membrane as claimed in claim 5, wherein the PFSA-g-GO nano-composite is prepared by the following steps: firstly, GO nano particles are dissolved in DMSO to obtain the concentration of 0.02-0.04 g.mL^-1Adding an activating agent, a catalyst and a PFSA solution into the solution to obtain a mixture, reacting the mixture for 60-72 hours at the temperature of 40-50 ℃, and finally performing post-treatment to obtain the PFSA-g-GO nano composite.

7. The method for preparing the PVDF/PFSA-g-GO ultrafiltration membrane with high permeability and pollution resistance as claimed in claim 6, wherein the activating agent is thionyl chloride, 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride or N, N' -dicyclohexylcarbodiimide; the catalyst is 4-dimethylamino pyridine or N-hydroxysuccinimide.

8. The method for preparing the PVDF/PFSA-g-GO ultrafiltration membrane with high permeability and pollution resistance as claimed in claim 7, wherein the activating agent is N, N' -dicyclohexylcarbodiimide; the catalyst is 4-dimethylamino pyridine.

9. The preparation method of the PVDF/PFSA-g-GO ultrafiltration membrane with high permeability and pollution resistance as claimed in claim 6, wherein the concentration of PFSA solution is 0.01-0.1 g-mL^-1(ii) a The mass ratio of the activator to the GO nano particles is 46-50: 1, the mass ratio of the catalyst to the PFSA is 17-20: 50-59, and the mass ratio of the activator to the catalyst is 13.5-135.3: 1.

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