CN110841491A - Preparation method of high-permeability and anti-pollution PVDF/PFSA-g-GO ultrafiltration membrane - Google Patents
Preparation method of high-permeability and anti-pollution PVDF/PFSA-g-GO ultrafiltration membrane Download PDFInfo
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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
Technical Field
The invention belongs to the technical field of ultrafiltration membrane preparation, and relates to a preparation method of a high-permeability and anti-pollution PVDF/PFSA-g-GO ultrafiltration membrane.
Background
Ultrafiltration (UF) refers to a process of separating according to the difference of molecular weights of substances to be separated by using a membrane as a separation medium under the pushing 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 the permeability of the PVDF (polyvinylidene fluoride) ultrafiltration membrane can be effectively solved by adding inorganic nano particles. However, there still exist some problems such as document 1(Preparation and characterization of poly (vinylidene fluoride) (PVDF) based ultrafiltration membranes using nano γ -Al2O3Journal of Membrane Science,2011,366(1):97-103) by addition of γ -Al2O3The modified PVDF ultrafiltration membrane has improved hydrophilicity and pollution resistance, but the mechanical strength of the membrane is reduced; document 2(The efffect 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) with TiO2The pollution resistance of the PVDF film is improved, but the agglomeration phenomenon of the PVDF film reduces the smoothness of the film surface and the mechanical strength of the film surface. The agglomeration phenomenon is caused by natural properties of small size, high specific surface free energy and the like of the nano particles, and the agglomeration phenomenon can cause the instability of a casting solution system and the nonuniform dispersion of inorganic nano particles in a blend film, so that the morphology, the structure and the performance of the blend film are changed, and the performance of the inorganic nano particles can not be fully exerted. Therefore, it has become a focus of research to find a blending modifier which can improve the hydrophilicity of the membrane and does not affect other properties of the membrane.
Graphene Oxide (GO) has a honeycomb-like six-layer planar structure and numerous hydrophilic groups, and thus has a structure in waterHigh dispersivity and good compatibility with polymer matrix. At present, much research is carried out on GO serving as an additive to be applied to preparation and modification of a PVDF ultrafiltration membrane so as to improve the performance of the membrane. Document 3(Application of sulfonated group functionalized graphene oxide to improved hydrophilicity, and anti-hydrophilicity of PVDF nanocomposite ultrafiltration membranes [ J]Journal of Membrane Science 2016,525: 210-; document 4(Optimized Transmission and differentiation of PVDFhygral ultrafiltration membranes: synthetic effect of dispersion and differentiation for fluorinated graphene oxide [ J)]Journal of Nanoparticle Research,2017, 19(3): 114) blending fluorinated GO with modified PVDF improves the water flux and anti-fouling properties of the membrane; document 5(Novel GO-blended PVDF ultrafiltration membranes [ J ]]Desalinization, 2012,299:50-54.) GO/PVDF ultrafiltration membranes were prepared by blending 0.2 wt% GO with PVDF and found that the GO/PVDF ultrafiltration membrane water contact angle decreased from 79 ° to 61 °, the flux recovery increased from 78% to 96% for pure PVDF membrane, and the pure water flux was more than 2 times the pure PVDF membrane flux. Perfluorosulfonic acid (PFSA) due to its specific structure, PFSA resin undergoes spontaneous microphase separation when in contact with water, water molecules form hydrophilic domains tightly surrounding sulfonic acid groups, and fluorocarbon polymers create low surface energy domains, so PFSA can also be used to modify PVDF ultrafiltration membranes to improve membrane performance. Document 6 (structuring dual-default mechanisms on membrane surfaces of PFSAand SiO by synthesis of PFSAand SiO)2,nanoparticles for persistent antifouling performance[J]Applied surface science,2018,440:113-2The membrane has improved permeability and anti-pollution performance; document 7 (influements of the structural parameters of Multi-walled carbon nanotubes (MWNTs) on PVDF/PFSA/O-MWNTs hole fiber extraction membranes [ J]Journal of Membrane Science 2016,499: 179. 190.) PVDF/PFSA/O-MWNTs fiber membranes were prepared using PFSA as an additive, the permeability of the membranes being improved. However, the above treatments for GO and PFSA tend to face contamination resistance while permeability increasesThe defect that can descend, the mechanical properties of membrane are relatively poor simultaneously, GO takes place to drop easily in the long-time use of membrane.
Therefore, the research on a method for modifying the PVDF ultrafiltration membrane to have high permeability, high pollution resistance, excellent mechanical property and better durability is of great significance.
Disclosure of Invention
The invention aims to solve the problem that a PVDF ultrafiltration membrane in the prior art cannot be modified by a method for modifying the PVDF ultrafiltration membrane so that the PVDF ultrafiltration membrane has high permeability, high pollution resistance, excellent mechanical property and better durability, and provides a preparation method of the PVDF/PFSA-g-GO ultrafiltration membrane with high permeability and pollution resistance.
In order to achieve the purpose, the invention adopts the following scheme:
a preparation method of a high-permeability and anti-pollution PVDF/PFSA-g-GO ultrafiltration membrane comprises the steps of coating a casting solution mainly composed of a PFSA-g-GO nano compound, PVDF, a solvent and a pore-foaming agent on a support to form a membrane, and immersing the membrane into water to perform a phase inversion 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 performing an esterification reaction on 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 Bovine Serum Albumin (BSA) is 87.4-96.7%, and the retention rate of Humic Acid (HA) is 72.3-79.6%.
The method for preparing the PVDF/PFSA-g-GO ultrafiltration membrane by the phase inversion reaction is a non-solvent induced phase separation method, also called a wet method, and the method is characterized in that a polymer is dissolved in a solvent to form a homogeneous solution, then a reagent (called an extractant) with stronger intersolubility with the solvent is slowly added to extract the solvent to form a two-phase structure with the polymer as a continuous phase and the solvent as a dispersed phase, and the solvent is removed to obtain the polymer with a certain pore structure; when the PVDF ultrafiltration membrane is modified by adding the PFSA-g-GO nano compound, the water flux and the protein retention rate of the ultrafiltration membrane can be simultaneously improved, and the defects in the prior art are overcome, namely the retention rate is reduced when the water flux of the ultrafiltration membrane is increased, and conversely the water flux is reduced when the retention rate is increasedThe phenomenon of plate is that the water flux and the protein retention rate of the ultrafiltration membrane can be improved by adding the PFSA-g-GO nano compound to modify the PVDF ultrafiltration membrane because: the PFSA-g-GO nano composite is prepared by the preparation method of the PFSA-g-GO nano composite, wherein a plurality of hydrophilic groups on the surface of GO and-SO in PFSA3 -The PFSA-g-GO nano-composite with higher hydrophilicity is used as a nucleating agent in the phase transformation process, so that the gel speed of the membrane casting solution can be increased, the pore structure of the membrane can be changed, the strong interaction between the hydrophilic PFSA-g-GO nano-composite and a non-solvent can accelerate the diffusion between the solvent and the non-solvent in the phase separation process, larger irregular macropores are formed, meanwhile, the thermodynamic instability of the membrane casting solution can be enhanced by adding the hydrophilic PFSA-g-GO nano-composite, so that higher phase transition rate and a more porous structure are caused, and higher water flux can be caused by the phenomena; after the PFSA-g-GO nano-composite is added, compared with a PVDF membrane, the composite has a similar compact surface structure, the affinity between hydrophilic PFSA-g-GO and water (a coagulating bath) is increasingly greater with the increase of the amount of the PFSA-g-GO nano-composite, the number of pores on the surface of the PVDF/PFSA-g-GO membrane is gradually increased, and under the condition that the content of the PFSA-g-GO nano-composite in a casting membrane solution is high, the diffusion rate between a solvent and a non-solvent is increased, so that a surface layer is damaged, more pores are formed, the water flux is increased, although the number of pores on the surface of the membrane is increased, the radius change of the pores is not large, the hydrophilicity of the membrane is increased, a hydration layer can be formed on the surface of the membrane, and a part of bovine serum albumin and humic acid can be effectively prevented from directly passing through the pores of the membrane, the rejection of the membrane is still high. In addition, the PFSA-g-GO nano composite is uniformly dispersed into the PVDF membrane, and because the PFSA and the GO in the PFSA-g-GO nano composite have ester bond interaction and the PFSA-g-GO nano composite and the PVDF membrane have fluorine-fluorine interaction, the dispersion of the nano composite in the membrane is improved, and the nano composite has better compatibility with the PVDF membrane. In conclusion, by utilizing the excellent performance of the PFSA-g-GO nano composite, the hydrophilicity and the anti-pollution performance of the membrane (higher water flux and protein rejection rate) are effectively improved, and simultaneously, compared with a pure PVDF membrane, the mechanical strength of the PVDF/PFSA-g-GO membrane is higherMoreover, as the GO is subjected to graft modification by the PFSA, the PFSA-g-GO nano compound can stably exist in the membrane, is not easy to fall off, and improves the long-time service performance of the membrane.
As a preferable scheme:
the preparation method of the PVDF/PFSA-g-GO ultrafiltration membrane with high permeability and pollution resistance comprises the following specific steps:
(1) mixing a PFSA-g-GO nano compound, PVDF, a solvent and a pore-forming agent, stirring for 48-60 hours at a temperature of 20-25 ℃ to obtain a casting solution, wherein the whole process of preparing the casting solution is carried out at a temperature close to room temperature, the obtained casting solution can be more uniform by stirring for 48-60 hours, and if the casting solution is not uniform, the structure, water flux, rejection rate, surface roughness and the like of a membrane can be influenced, 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, the total mass of substances in the formula of the casting solution is a fixed value, under the condition that the addition amounts of the PVDF and PVP are fixed, the addition amount of the PFSA-g-GO nano compound is changed, the corresponding amount of the solvent is changed along with the change, the content of the PFSA-g-GO nano compound is increased, the structure, water flux, rejection rate, surface roughness and the like of the membrane are affected; the mass content of the pore-foaming agent in the membrane casting solution is 3-5 percent; the content of the pore-foaming agent is too high, the surface layer of the prepared membrane is thin, the permeability of the membrane is high, and the retention rate of the membrane is correspondingly small;
(2) coating the casting membrane solution on a support to form a membrane, wherein the thickness of the membrane is 0.15-0.2 mm, immersing the membrane in water to perform a phase inversion reaction to obtain the high-permeability and anti-pollution PVDF/PFSA-g-GO ultrafiltration membrane, immersing the membrane in water for a period of time to form the membrane by means of the diffusion effect of a solvent and a non-solvent, and finishing at normal temperature.
According to the preparation method of the PVDF/PFSA-g-GO ultrafiltration membrane with high permeability and pollution resistance, the solvent is DMAc, the support body is a glass plate, and the pore-forming agent is polyethylene glycol (PEG) or polyvinylpyrrolidone K30 (PVP).
The preparation method of the PVDF/PFSA-g-GO ultrafiltration membrane with high permeability and pollution resistance is characterized in that the pore-forming agent is polyvinylpyrrolidone K30 (PVP).
According to the preparation method of the PVDF/PFSA-g-GO ultrafiltration membrane with high permeability and pollution resistance, GO nano particles are prepared from natural graphite powder by an improved Hummers method;
the preparation of the GO nanoparticles comprises the following steps:
(1) sequentially adding 4.0-5.0 g of graphite and sodium nitrate in a mass ratio of 1: 1-2: 1 into 70mL of 98% concentrated sulfuric acid solution, stirring at the temperature of 0-5 ℃, then adding 8-10 g of potassium permanganate, and keeping the temperature below 20 ℃;
(2) transferring the reactants to a temperature of 30-40 ℃ and reacting for 0.5-1 h to form a thick substance;
(3) adding 600-700 mL of water, reacting for 15-20 min, and slowly adding 20-25 mL of hydrogen peroxide solution with the mass fraction of 30%;
(4) and centrifuging the obtained solution, washing the solution with 250-350 mL of hydrochloric acid aqueous solution with the volume ratio of 1: 10-1: 14, performing ultrasonic treatment, centrifuging, dialyzing, and finally performing freeze drying to obtain GO nano particles.
According to the preparation method of the PVDF/PFSA-g-GO ultrafiltration membrane with high permeability and pollution resistance, the preparation process of the PFSA-g-GO nano composite is as follows: firstly, GO nano particles are dissolved in DMSO (dimethyl sulfoxide (DMF) to obtain the concentration of 0.02-0.04 g/mL)-1Adding an activator, 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 ℃, increasing the reaction temperature, and facilitating the reaction, but considering the tolerance range of the used catalyst, activator and material, the temperature is not too high, the reaction time is set to be longer, so that the PFSA and GO are fully reacted, and thus the required PFSA-g-GO nano-composite is obtained, and finally, the PFSA-g-GO nano-composite is obtained through post-treatment (centrifugation, acetone washing, washing with an ethanol water solution at the temperature of 80-95 ℃ and drying). Under the action of an activator and a catalyst, carboxyl (-COOH) on GO nano particles and hydroxyl (-OH) in PFSA generate esterification reaction, so that the GO nano particles are modified by the PFSA, and the PFSA-g-GO nano compound is obtained.
A process for the preparation of a highly permeable and stain resistant PVDF/PFSA-g-GO ultrafiltration membrane as described above, the activating agent being thionyl chloride, 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride (EDC) or N, N' -Dicyclohexylcarbodiimide (DCC); the catalyst is 4-Dimethylaminopyridine (DMAP) or N-hydroxysuccinimide (NHS).
A highly permeable and contamination resistant PVDF/PFSA-g-GO ultrafiltration membrane is prepared as described above, the activating agent is N, N' -Dicyclohexylcarbodiimide (DCC); the catalyst was 4-Dimethylaminopyridine (DMAP).
According to the preparation method of the PVDF/PFSA-g-GO ultrafiltration membrane with high permeability and pollution resistance, the concentration of the PFSA solution (specifically the DMSO solution of PFSA) 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.
Has the advantages that:
(1) the preparation method of the PVDF/PFSA-g-GO ultrafiltration membrane with high permeability and pollution resistance is simple and easy to implement and low in cost;
(2) the preparation method of the PVDF/PFSA-g-GO ultrafiltration membrane with high permeability and pollution resistance can simultaneously improve the water flux and the protein rejection rate of the ultrafiltration membrane, effectively improve the hydrophilicity and the pollution resistance of the membrane, and prevent the mechanical property of the membrane from being reduced;
(3) according to the preparation method of the PVDF/PFSA-g-GO ultrafiltration membrane with high permeability and pollution resistance, the GO is subjected to graft modification by PFSA, so that the PFSA-g-GO nano compound can stably exist in the membrane, is not easy to fall off, and the long-term service performance of the membrane is improved;
(4) the preparation method of the PVDF/PFSA-g-GO ultrafiltration membrane with high permeability and pollution resistance can be widely applied to the fields of chemical industry, medicine, seawater desalination and sewage regeneration treatment, and has good application prospect.
Drawings
Fig. 1 is an XRD spectrum of GO nanoparticles and graphite prepared according to an embodiment of the present invention, where (a) is graphite and (b) is GO nanoparticles;
FIG. 2 is an infrared spectrum of GO, PFSA-g-GO nanocomposites in an example of the present invention;
FIG. 3 is an infrared spectrum of a PVDF, PVDF/PFSA-g-GO ultrafiltration membrane in an example of the present invention;
FIG. 4 is an XRD spectrum of a PVDF/PFSA-g-GO ultrafiltration membrane in an example of the present invention;
FIG. 5 is a Scanning Electron Microscope (SEM) top view of an ultrafiltration membrane in an embodiment of the invention;
FIG. 6 is a Scanning Electron Microscope (SEM) cross-sectional view of an ultrafiltration membrane in an embodiment of the present invention;
FIG. 7 is an Atomic Force Microscope (AFM) image of an ultrafiltration membrane in an embodiment of the present invention;
FIG. 8 is a graph of the contact angle of an ultrafiltration membrane in an example of the present invention;
FIG. 9 is a graph of water flux and rejection for an ultrafiltration membrane in an example of the invention;
FIG. 10 is a graph showing the resistance of an ultrafiltration membrane to protein contamination according to an embodiment of the present invention;
FIG. 11 is a graph of Young's modulus versus tensile strength for an ultrafiltration membrane in an example of the present invention;
fig. 12 is a stress-strain graph of an ultrafiltration membrane in an example of the invention.
Detailed Description
The invention will be further illustrated with reference to specific embodiments. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, it should be understood that various changes and modifications can be made by those skilled in the art after reading the teachings of the present invention, and such equivalents also fall within the scope of the appended claims.
Example 1
The preparation method of the PFSA-g-GO nano composite comprises the following specific steps:
(1) the GO nano particles are prepared from natural graphite powder by an improved Hummers method, XRD and infrared spectrograms of the prepared GO nano particles are shown in figures 1-2, wherein in figure 1, (a) is graphite, and (b) is the GO nano particles;
(2) preparation of PFSA-g-GO nanocomposite: firstly, dissolving GO nano particles in DMSO (solvent) to obtain a solution with the concentration (c1) of 0.003 g.mL < -1 >, adding N, N' -Dicyclohexylcarbodiimide (DCC) (activating agent), 4-Dimethylaminopyridine (DMAP) (catalyst) and a DMSO solution of PFSA to the solution to obtain a mixture, reacting the mixture at the temperature (T1) of 50 ℃ for 72h (T1), and finally, centrifuging, washing with acetone, washing with an ethanol aqueous solution at the temperature (T2) of 95 ℃, and drying to obtain a PFSA-g-GO nano compound, wherein the infrared spectrum of the PFSA-g-GO nano compound is shown in figure 2; wherein the concentration of the DMSO solution of PFSA (c2) is 0.01 g.mL-1; the mass ratio of N, N '-Dicyclohexylcarbodiimide (DCC) to GO nanoparticles (W1) was 46:1, the mass ratio of N, N' -Dicyclohexylcarbodiimide (DCC) to 4-Dimethylaminopyridine (DMAP) was 135.3:1 (W2), and the mass ratio of 4-Dimethylaminopyridine (DMAP) to PFSA was 17:50 (W3).
Examples 2 to 5
The preparation method of the PFSA-g-GO nano-composite has the same specific steps as the example 1, except that the reaction parameters are shown in the table 1, wherein EDC is 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride, and 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(s) | DMSO | DMSO | DMSO | DMF | ||
| Activating agent | DCC | Thionyl chloride | EDC | DCC | ||
| Catalyst and process for preparing same | DMAP | NHS | DMAP | NHS | ||
| T1 | ℃ | 45 | 40 | 48 | 50 | |
| | h | 65 | 60 | 70 | 72 | |
| T2 | ℃ | 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 comprises the following specific steps:
(1) mixing the PFSA-g-GO nano-composite prepared in the example 1, PVDF, DMAc and polyvinylpyrrolidone K30, and stirring for 60 hours at the temperature of 23 ℃ to obtain a casting solution, wherein the mass ratio of DMSO to the PFSA-g-GO nano-composite 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 solution on a glass plate to form a membrane, controlling the thickness of the membrane to be 0.15mm, and immersing the membrane in water to perform phase conversion reaction to obtain a high-permeability and anti-pollution PVDF/PFSA-g-GO ultrafiltration membrane;
the PVDF/PFSA-g-GO ultrafiltration membrane has the membrane number of M3, and the performance indexes 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 comprises the following specific steps:
(1) mixing the PFSA-g-GO nano-composite prepared in the example X, PVDF, DMAc and a pore-forming agent, and stirring for 48-60 h (T2) at the temperature of 20-25 ℃ at T3 to obtain a membrane casting solution, wherein the mass ratio of DMSO to the PFSA-g-GO nano-composite (W4) is 80-809: 1, the mass ratio of DMSO to PVDF (W5) is 5.00-5.06: 1, and the mass content (W) of the pore-forming agent in the membrane casting solution is 3-5%;
(2) coating the casting solution on a glass plate to form a film, controlling the thickness (d) of the film to be 0.15-0.2 mm, and immersing the film in water to perform a phase conversion reaction to obtain a high-permeability and anti-pollution PVDF/PFSA-g-GO ultrafiltration film;
specific preparation parameters of examples 7 to 14 are shown in table 2, wherein PEG is polyethylene glycol, and PVP is polyvinylpyrrolidone K30;
the performance indexes of the PVDF/PFSA-g-GO ultrafiltration membranes prepared in the embodiments 7-14 are shown in Table 3, wherein the retention rate of BSA is the retention rate of bovine serum albumin, and the retention rate of HA is the retention rate of humic acid; the serial numbers of the ultrafiltration membranes are sequentially M4-M11, and the specific corresponding relationship is shown in Table 3;
in addition, M4 is selected for infrared testing, and the testing result is shown in FIG. 3;
selecting M4 and M7-M9 to carry out XRD test, wherein the test result is shown in figure 4;
selecting the upper surfaces and the sections of M4-M9 to respectively perform Scanning Electron Microscope (SEM) tests, wherein the test results are shown in FIGS. 5 and 6;
selecting M4 and M9 to perform an Atomic Force Microscope (AFM) test, wherein the test result is shown in FIG. 7, and the data are shown in Table 4, wherein Ra is the average surface roughness, and RMS is the root mean square surface roughness;
selecting M4 and M7-M9 to carry out contact angle test, wherein the test result is shown in figure 8;
selecting M4-M9 to carry out water flux and retention rate tests, wherein the test results are shown in FIG. 9;
m4 was selected for the protein fouling resistance test, the results are shown in fig. 10, and the data are shown in table 6, wherein the water flux recovery (FRR) is used to evaluate the antifouling performance of the UF membrane, and the test method is as follows: first, the pure water flux (J) of the membrane was measuredw) The permeation media was then changed to 0.5g/L BSA in water for the same membrane; after 30 minutes of filtration, the membrane was removed from the membrane module and washed with deionized water for 5 minutes under the action of ultrasonic waves; the cleaned membrane was then mounted in a membrane module and the pure water flux was measured again and recorded as Jw1(ii) a The same "water flux-BSA filter-water flux" procedure was then repeated, referred to as the "second cycle"; FRR is calculated using the following formula:
selecting M4 and M7-M9 to carry out Young modulus and tensile strength tests, wherein the test results are shown in FIG. 11, and the obtained data are shown in Table 5;
the stress and elongation tests were performed on M4 and M7-M9, and the results are shown in FIG. 12.
TABLE 2
Comparative example 1
The steps of the preparation method of the PVDF ultrafiltration membrane are basically the same as those of the embodiment 7, except that the PFSA-g-GO nano compound is not added, the performance test of the prepared ultrafiltration membrane is shown in the table 3-6, and the serial number of the ultrafiltration membrane is M0.
Comparative example 2
The steps of the preparation method of the PVDF/GO ultrafiltration membrane are basically the same as those of the embodiment 7, the difference is that the added PFSA-g-GO nano composite is replaced by GO nano particles, the performance test of the prepared ultrafiltration membrane is shown in tables 3-6, and the serial number of the ultrafiltration membrane is M1.
Comparative example 3
The steps of a preparation method of a PVDF/PFSA ultrafiltration membrane are basically the same as those of the embodiment 7, the difference is that PFSA-g-GO nano composite added is replaced by PFSA, PFSA infrared spectrum is shown in figure 2, the performance test of the prepared ultrafiltration membrane is shown in tables 3-6, and the serial number of the ultrafiltration membrane is M2;
the infrared spectrum and XRD test of M0 are selected, and the results are shown in figures 3 and 4;
selecting the upper surfaces and the sections of M0-M2 to respectively perform Scanning Electron Microscope (SEM) tests, wherein the test results are shown in FIGS. 5 and 6;
m0 and M1 were selected for Atomic Force Microscope (AFM) testing, the results are shown in FIG. 7, and the data are shown in Table 4;
selecting M0 to perform a contact angle test, wherein the test result is shown in FIG. 8;
selecting M0-M2 to carry out water flux and retention rate tests, wherein the test results are shown in FIG. 9;
selecting M0-M2 to carry out a protein contamination resistance test, wherein the test result is shown in figure 10, and the data are shown in table 6;
selecting M0-M2 to test the Young modulus and the tensile strength, wherein the test result is shown in figure 11, and the obtained data are shown in a table 5;
selecting M0-M2 to perform stress and elongation tests, wherein the test results are shown in FIG. 12;
comparing example 7 with comparative example 1, it can be seen that the ultrafiltration membrane of comparative example 1 is smaller in both total porosity and average pore size than example 7, because the hydrophilic PFSA-g-GO nanocomposite can accelerate phase separation and formation of a polymer-pore phase during membrane formation with the addition of the PFSA-g-GO nanocomposite in example 7, and thus the total porosity and average pore size of the membrane are larger than the ultrafiltration membrane of comparative example 1; the water flux and the HA rejection rate are less than those of example 7, because the strong interaction between the hydrophilic PFSA-g-GO nanocomposite and the non-solvent water accelerates the diffusion between the solvent and the non-solvent during the phase separation process, forming larger irregular macropores, and meanwhile, the addition of the hydrophilic PFSA-g-GO nanocomposite enhances the thermodynamic instability of the casting solution, resulting in higher phase change rate and more pore structures, increasing the number of pores on the membrane surface, and improving the hydrophilicity of the membrane surface, which can result in higher water flux; although the number of the pores on the surface of the membrane is increased, the radius of the pores is not changed greatly, the hydrophilicity of the membrane is increased, a hydration layer can be formed on the surface of the membrane, and a part of BSA and HA can be effectively prevented from directly passing through the pores of the membrane, so that the interception of the membrane is still good; the surface roughness is larger than that of example 7, because the membrane reduces the surface roughness after being modified by blending PFSA-g-GO nano compound, and the PFSA-g-GO nano compound has better dispersibility in the membrane, so that the surface of the membrane becomes smooth, and the surface roughness of M4 in example 7 is reduced; the mechanical strength is poorer than that of example 7, because GO is an excellent nano filler for enhancing the mechanical property of the membrane, however, when the content of GO is too high, the GO is easy to accumulate and aggregate in the membrane forming process, the mechanical property of the membrane is influenced, the GO is subjected to graft modification by PFSA, and the PFSA-g-GO nano composite material is stably dispersed in the membrane due to the interaction of PFSA resin existing in the PFSA-g-GO nano composite material and PVDF and GO, so that the mechanical property of the membrane is enhanced; the antifouling property is worse than that of example 7 because of higher hydrophilicity and smoothness of the UF membrane surface of example 7 when a hydrophilic PFSA-g-GO nanocomposite is added as a filler, which can inhibit adsorption and deposition of protein molecules on the membrane surface during filtration, improving the antifouling property;
comparing example 7 with comparative example 2, it can be seen that the HA rejection and BSA rejection of the ultrafiltration membrane of comparative example 2 are less than those of example 7 because of the hydrophilic-SO in PFSA3-Therefore, the PFSA-g-GO nano composite material HAs higher hydrophilicity than pure GO, the M4 membrane of the embodiment 7 HAs better hydrophilicity, the hydrophilicity of the membrane is increased, a hydration layer can be formed on the surface of the membrane, and a part of BSA and HA can be effectively prevented from directly passing through the membrane pores, so that the interception of the membrane is better; the surface roughness is larger than that of example 7, because the membrane PFSA is used for grafting modification on the GO surface, the agglomeration of GO can be reduced, and because the PFSA and PVDF have fluorine-fluorine interaction, the PFSA-g-GO nano composite material has better compatibility with the PVDF and can be better and more stably dispersed in the membrane, so that the surface of M4 of example 7 is smoother; the antifouling property is worse than that of example 7 because the increase of hydrophilicity and the smoother surface of the membrane can reduce the accumulation of the contaminants on the membrane surface, and thus, the antifouling property of the membrane is better;
comparing example 7 with comparative example 3, it can be seen that the water flux, HA rejection and BSA rejection of the ultrafiltration membrane in comparative example 3 are less than those of example 7, because GO contains numerous hydrophilic groups, so that PFSA-g-GO nanocomposite is more hydrophilic than pure PFSA, a hydration layer can be formed on the membrane surface, and a part of BSA and HA can be effectively prevented from directly passing through the membrane pores, so that the rejection of the membrane is still good; the anti-fouling property was worse than that of example 7 because the anti-fouling property of the membrane was better due to the increase of the hydrophilicity of the membrane.
TABLE 3
TABLE 4
| Serial number | Number of membrane | 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 | Number of membrane | 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 | Number of membrane | 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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