CN119345931A - A hydrophilic modified polysulfone hollow fiber nanofiltration membrane and its use - Google Patents
A hydrophilic modified polysulfone hollow fiber nanofiltration membrane and its use Download PDFInfo
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Abstract
一种亲水改性聚砜类中空纤维纳滤膜及其用途，属于高分子膜材料领域。包括以下步骤:1）将高分子成膜聚合物、亲水助剂，致孔剂及有机溶剂共混制成铸膜液；2）采用非溶剂诱导致相分离法制得中空纤维基膜；3）对中空基膜进行化学交联处理得到亲水改性聚砜类中空纤维纳滤膜。上述一种亲水改性聚砜类中空纤维纳滤膜，具有优异的亲水改性、渗透通量以及截留性和长期热稳定性，且制备方法简单、环保，生产成本低，有良好的工业应用前景。
A hydrophilic modified polysulfone hollow fiber nanofiltration membrane and its use, belonging to the field of polymer membrane materials. The method comprises the following steps: 1) blending a polymer membrane-forming polymer, a hydrophilic auxiliary agent, a porogen and an organic solvent to prepare a casting solution; 2) adopting a non-solvent induced phase separation method to prepare a hollow fiber base membrane; 3) chemically cross-linking the hollow base membrane to obtain a hydrophilic modified polysulfone hollow fiber nanofiltration membrane. The hydrophilic modified polysulfone hollow fiber nanofiltration membrane has excellent hydrophilic modification, permeation flux, interception and long-term thermal stability, and the preparation method is simple, environmentally friendly, and has low production cost, and has good industrial application prospects.
Description
Technical Field
The invention belongs to the field of polymer membrane materials, and particularly relates to a hydrophilic modified polysulfone hollow fiber nanofiltration membrane and application thereof.
Background
Water is critical to human health. However, the wastewater is gradually increased, and many wastewater contains more inorganic ions such as Cl -,SO4 2- ,Na+,Ca2+, and thus has higher conductivity. The nanofiltration membrane technology is a separation technology capable of realizing high-efficiency interception of 200-1000 daltons, has unique advantages for removing suspended matters, dissolved organic matters, heavy metal ions and the like in water, and is widely applied to the fields of high-salt wastewater treatment, pharmacy, chemical industry and the like.
Compared with the traditional roll nanofiltration membrane, the hollow fiber nanofiltration membrane has the advantages of good self-supporting property, high filling density, large specific surface area and wider water inlet flow passage. At present, the hollow fiber nanofiltration membrane has a plurality of types, but is usually prepared from polysulfone high polymer materials with stronger hydrophobicity, so that the application prospect is greatly influenced due to the problems of insufficient interception of hydrophobic substances and serious pollution. In addition, due to lower surface charge, many hollow fiber nanofiltration membranes have the problems of low rejection rate, poor permeability and the like.
Disclosure of Invention
Aiming at the problems existing in the prior art, the invention aims to design and provide a technical scheme of a hydrophilic modified polysulfone hollow fiber nanofiltration membrane and application thereof, wherein the hollow fiber nanofiltration membrane has excellent hydrophilic modification, permeation flux, retention and long-term thermal stability, the water contact angle of the hollow fiber nanofiltration membrane is 66.0+/-1.8 degrees, the permeation flux of pure water of the membrane is 33.2+/-1.1L ∙ m -2∙h-1（0.4MPa）,Na2SO4, the retention rate of the pure water of the membrane is up to 98.3+/-1.2 percent (0.4 MPa), the retention rate of 30 percent is less than or equal to 40 percent (0.4 MPa), and the optimal retention rate of the pure water of the membrane is up to 38.5+/-0.2 percent.
The hydrophilic modified polysulfone hollow fiber nanofiltration membrane is characterized by being prepared by the following steps:
1) Preparing a casting solution, namely mixing 15-25wt% of film-forming polymer, 4-12wt% of hydrophilic auxiliary agent and 6-13wt% of pore-forming agent into 50-75wt% of solvent according to the total mass of the casting solution, wherein the film-forming polymer is at least one of polysulfone materials, including PSF (polysulfone), PES (polyethersulfone), PPSU (polyphenylsulfone), SPSF (sulfonated polysulfone), SPES (sulfonated polyethersulfone), SPPSU (sulfonated polyphenylsulfone) and PES (preferably PES), the hydrophilic auxiliary agent is at least one of perfluorohexyl sulfonamide propyl triethoxysilane (PFSS) homologous compounds with a carbon chain length of 3-8, preferably PFSS, the carbon chain length directly influences the effect of pi-F between the auxiliary agent and the film-forming polymer, and is an important influence factor of a film structure;
2) Preparing a hollow base membrane by adopting a non-solvent induced phase separation method to prepare a hollow base membrane by using a casting membrane solution;
3) Preparing a hollow fiber nanofiltration membrane, namely performing chemical treatment on the hollow basal membrane to obtain the hydrophilic modified polysulfone hollow fiber nanofiltration membrane.
The hydrophilic modified polysulfone hollow fiber nanofiltration membrane is characterized in that in the step 1), 18-22wt% of a film forming polymer, 6-10wt% of a hydrophilic auxiliary agent, 8-11wt% of a pore-forming agent and 55-70wt% of a solvent are adopted.
The hydrophilic modified polysulfone hollow fiber nanofiltration membrane is characterized in that in the step 1), the pore-forming agent is at least one of polyethylene glycol (PEG) and polyvinylpyrrolidone (PVP) with different molecular weights, preferably at least one of PEG400, PEG600, PEG800, PEG1000, PEG1500, PVPK17, PVPK30 and PVPK90, and preferably PEG with molecular weight less than 600. The molecular weight of the porogen directly affects the size of the pore size. The pore-forming agent with smaller molecular weight is selected to form smaller pore diameter in the fiber more easily, so that the porosity is improved, the mechanical property of the membrane is improved, and the separation efficiency of the separation membrane is enhanced.
The hydrophilic modified polysulfone hollow fiber nanofiltration membrane is characterized in that in the step 1), the solvent is at least one of Dimethylacetamide (DMAC), dimethylformamide (DMF) and N-methylpyrrolidone (NMP). The kind of solvent can have important influence on the rheological property of the casting solution and the stability of the spinning process, and is a key factor influencing the phase inversion process and the pore structure.
The hydrophilic modified polysulfone hollow fiber nanofiltration membrane is characterized in that in the step 1), the water bath stirring temperature is 60-80 ℃, the stirring time is 2-4 h, the stirring speed is 150-250 r/min, the water bath stirring temperature is 65-70 ℃ preferably, the stirring time is 2.5-3 h, and the stirring speed is 200-220 r/min. The rheological property of the casting solution is controlled by regulating and controlling the stirring condition, so that the preparation process is ensured to be carried out smoothly.
The hydrophilic modified polysulfone hollow fiber nanofiltration membrane is characterized in that the specific method in the step 2) comprises the steps of leading casting solution into coagulation bath after passing through a spinneret containing core solution, obtaining a nascent fiber membrane, and rinsing the nascent fiber membrane to obtain a hollow fiber base membrane, wherein the core solution is deionized water, the coagulation bath is NaOH aqueous solution, the rinsing bath is deionized water, the coagulation bath temperature is 25-40 ℃, the rinsing bath temperature is 40-60 ℃, the preferred coagulation bath temperature is 30-35 ℃, and the rinsing bath temperature is 45-50 ℃. The aqueous NaOH solution has a pH of 7 to 10, preferably 9. The decomposition degree of the hydrophilic auxiliary agent is regulated and controlled by controlling the components, temperature and alkaline strength of the coagulating bath, so that the negative charge and the hydrophilicity of the surface of the membrane are optimized.
The hydrophilic modified polysulfone hollow fiber nanofiltration membrane is characterized in that the chemical treatment process in the step 3) is specifically that the hollow base membrane prepared in the step 2) is placed in glutaraldehyde aqueous solution at a certain temperature for chemical crosslinking for a certain time, the chemical crosslinking temperature is 30-40 ℃, preferably 35 ℃, and the mass fraction of the glutaraldehyde aqueous solution is 5-25wt%.
The chemical crosslinking time is 1.5 to 2.5 hours, preferably 2 hours.
The hydrophilic modified polysulfone hollow fiber nanofiltration membrane is applied to tap water labeling.
Compared with the prior art, the technical scheme of the invention has the following beneficial effects:
According to the invention, the PFSS homologous compound with good hydrophilic modification and electronegativity is blended with the polysulfone polymer, so that sulfonyl groups in the PFSS homologous compound are hydrolyzed and converted into electronegative sulfonic acid groups in an alkaline environment, and the electronegative hollow fiber nanofiltration membrane with excellent performance is prepared, and the hydrophilicity and electronegativity of the polysulfone membrane are obviously improved.
The invention uses the strong pi-F interaction between fluorocarbon chain carried by PFSS homologous compound and benzene ring in polysulfone polymer to strengthen the molecular coupling of the two, and forms a physical interpenetrating network structure by the good self-crosslinking reaction of PFSS homologous compound, thereby improving the structural stability of the separating layer in two directions.
The invention utilizes aldehyde solution to make sulfonic acid groups obtained by hydrolyzing PFSS homologous compounds on the surface of the membrane undergo partial cross-linking again, so as to promote densification of a separation layer on the surface of the membrane, form a nanofiltration layer, and show a certain selectivity on the interception performance of different inorganic salts, wherein the interception performance is R (Na 2SO4）＞R（MgSO4）＞R（MgCl2) > R (NaCl).
The hydrophilic modified polysulfone hollow fiber nanofiltration membrane has high heavy metal ion interception efficiency, can intercept Cu 2+ and Co 2+ to 97.5% and 96.2% respectively, and can be used for tap water standard extraction.
The preparation method disclosed by the invention is simple and environment-friendly in operation process, effectively avoids complex operation and use of expensive materials in the membrane preparation process, is convenient for large-scale production in practical application, and has good industrial application prospect.
Drawings
FIG. 1 is a graph showing the results of surface contact angle tests of hydrophilic modified polysulfone-based hollow fiber base membranes and nanofiltration membranes prepared in examples and comparative examples;
FIG. 2 is a graph showing the results of pure water flux tests of the hydrophilic modified polysulfone-based hollow fiber base membranes and nanofiltration membranes prepared in the examples and comparative examples;
FIG. 3 is a graph showing the results of the test of the retention performance of each inorganic salt solution of the hydrophilic modified polysulfone hollow fiber nanofiltration membranes prepared in each example and comparative example;
FIG. 4 is a graph showing the test results of the retention performance of the hydrophilic modified polysulfone hollow fiber nanofiltration membrane prepared in experimental example 1 and example 1 on heavy metal ions;
FIG. 5 is a graph showing the results of long-term stability test of flux and Na 2SO4 and NaCl interception efficiency of the hydrophilically modified polysulfone hollow fiber nanofiltration membrane prepared in example 1.
Detailed Description
The invention will be further illustrated by means of specific examples. It should be understood that these examples are illustrative only and are not intended to limit the scope of the invention. The methods and reagents used in the examples are, unless otherwise indicated, conventional in the art.
Example 1
1) Preparing casting solution, namely mixing 20wt% of PES,12wt% of PFSS and 13wt% of PEG (Mr: 400) into 55wt% of DMAC according to the total mass of the casting solution, heating and stirring in a 60 ℃ water bath for 2.5h, wherein the stirring speed is 200r/min, uniformly mixing, and defoaming to obtain the casting solution;
2) Preparing a hollow base membrane, namely leading the casting solution obtained in the step 1) into a NaOH solution with the pH value of 9 at the temperature of 25 ℃ after passing through a spinning nozzle containing water core solution, so as to obtain a nascent fiber membrane, and obtaining the base membrane after the nascent fiber membrane is subjected to rinsing bath at the temperature of 50 ℃;
3) Preparing a hollow fiber nanofiltration membrane, namely placing the hollow base membrane prepared in the step 2) into a glutaraldehyde aqueous solution at the temperature of 35 ℃ for 2 hours for chemical crosslinking, and obtaining the hollow fiber nanofiltration membrane. The resulting film product was designated M-1.
The mass fraction of the glutaraldehyde aqueous solution is 20wt%.
4) Membrane filament test 8 groups of hollow base membrane and hollow fiber nanofiltration membrane filaments were tested, and the average contact angle, pure water flux and inorganic salt rejection rate were as shown in fig. 1 to 3, respectively.
Example 2
1) Preparing a casting solution, namely mixing 25wt% of PES,12wt% of PFSS and 13wt% of PVP into 50wt% of NMP according to the total mass of the casting solution, heating and stirring in a 55 ℃ water bath for 3 hours at a stirring speed of 200r/min, uniformly mixing, and defoaming to obtain the casting solution;
2) Preparing a hollow base membrane, namely leading the casting solution obtained in the step 1) into a NaOH solution with the pH value of 9 at 30 ℃ after passing through a spinneret containing water core solution to obtain a nascent fiber membrane, and obtaining the base membrane after the nascent fiber membrane is subjected to rinsing bath at 50 ℃;
3) Preparing a hollow fiber nanofiltration membrane, namely placing the hollow base membrane prepared in the step 2) into a glutaraldehyde aqueous solution at the temperature of 35 ℃ for 2 hours for chemical crosslinking, and obtaining the hollow fiber nanofiltration membrane. The resulting film product was designated M-2.
The mass fraction of the glutaraldehyde aqueous solution is 22wt%.
4) Membrane filament test 8 groups of hollow base membrane and hollow fiber nanofiltration membrane filaments were tested, and the average contact angle, pure water flux and inorganic salt rejection rate were as shown in fig. 1 to 3, respectively.
Example 3
Preparing a casting solution, namely mixing 18wt% of PSF,10wt% of PFSS and 13wt% of PEG (Mr=600) based on the total mass of the casting solution, adding the mixture into 69wt% of NMP, heating and stirring in a 60 ℃ water bath for 3 hours, wherein the stirring speed is 200r/min, uniformly mixing, and defoaming to obtain the casting solution;
2) Preparing a hollow base membrane, namely leading the casting solution obtained in the step 1) into a NaOH solution with the pH value of 9 at the temperature of 32 ℃ after passing through a spinning nozzle containing water core solution, so as to obtain a nascent fiber membrane, and obtaining the base membrane after the nascent fiber membrane is subjected to rinsing bath at the temperature of 45 ℃;
3) Preparing a hollow fiber nanofiltration membrane, namely placing the hollow base membrane prepared in the step 2) into a glutaraldehyde aqueous solution at the temperature of 35 ℃ for 2 hours for chemical crosslinking, and obtaining the hollow fiber nanofiltration membrane. The resulting film product was designated M-3.
The mass fraction of the glutaraldehyde aqueous solution is 25wt%.
4) Membrane filament test 8 groups of hollow base membrane and hollow fiber nanofiltration membrane filaments were tested, and the average contact angle, pure water flux and inorganic salt rejection rate were as shown in fig. 1 to 3, respectively.
Example 4
Preparing casting solution, namely mixing 23wt% of PPSF,8wt% of PFSS and 7wt% of PEG (Mr=600) into 62wt% of NMP according to the total mass of the casting solution, heating and stirring for 3 hours in a 50 ℃ water bath, wherein the stirring speed is 200r/min, mixing uniformly, and defoaming to obtain the casting solution;
2) Preparing a hollow base membrane, namely leading the casting solution obtained in the step 1) into NaOH solution with the pH value of 9 at 35 ℃ after passing through a spinning nozzle containing water core solution to obtain a nascent fiber membrane, and obtaining the base membrane after the nascent fiber membrane is subjected to a rinsing bath at 47 ℃;
3) Preparing a hollow fiber nanofiltration membrane, namely placing the hollow base membrane prepared in the step 2) into a glutaraldehyde aqueous solution at the temperature of 35 ℃ for 2 hours for chemical crosslinking, and obtaining the hollow fiber nanofiltration membrane. The resulting film product was designated M-4.
The mass fraction of the glutaraldehyde aqueous solution is 15wt%.
4) Membrane filament test 8 groups of hollow base membrane and hollow fiber nanofiltration membrane filaments were tested, and the average contact angle, pure water flux and inorganic salt rejection rate were as shown in fig. 1 to 3, respectively.
Comparative examples 1 to 2
1) Preparing casting solution, namely mixing 20wt% of PES, a certain amount of PFSS and 13wt% of PEG (Mr: 400) into DMAC according to the total mass of the casting solution, heating and stirring for 4 hours in a water bath at 60 ℃, mixing uniformly at the stirring speed of 200r/min, and defoaming to obtain the casting solution;
the PFSS content was 0 (comparative example 1), 12% by weight (comparative example 2), respectively.
The DMAC content was 77wt% (comparative example 1), 56wt% (comparative example 2), respectively.
Preparing a hollow base film, namely leading the casting film liquid obtained in the step 1) into a coagulating bath at 25 ℃ after passing through a spinning nozzle containing water core liquid to obtain a primary fiber film, and obtaining the base film after the primary fiber film is rinsed at 50 ℃;
The coagulation baths were respectively aqueous NaOH solutions (comparative example 1) at PH 9, and aqueous solutions (comparative example 2).
Preparing a hollow fiber nanofiltration membrane, namely placing the hollow base membrane prepared in the step 2) into a crosslinking bath at 35 ℃ for 2 hours for chemical crosslinking, and obtaining the hollow fiber nanofiltration membrane. The film products obtained in comparative examples 1-2 were labeled C-1, C-2, respectively.
The crosslinking baths were each an aqueous glutaraldehyde solution (comparative example 1) and a pure water solution (comparative example 2) at a mass fraction of 20 wt%.
4) Membrane filament test 8 groups of hollow base membrane and hollow fiber nanofiltration membrane filaments were tested, and the average contact angle, pure water flux and inorganic salt rejection rate were as shown in fig. 1 to 3, respectively.
Comparative example 1 differs from example 1 in that the casting solution of example 1 contains the hydrophilic adjuvant PFSS and the casting solution of comparative example 1 does not contain PFSS. The results show that the hollow base membrane and hollow fiber nanofiltration membrane of example 1 have better flux, hydrophilicity and Na 2SO4,MgSO4 retention efficiencies than the corresponding membrane samples of comparative example 1, as compared to comparative example 1. And each index measured in example 1 showed a more stable state than comparative example 1.
Comparative example 2 differs from example 1 in that the coagulation bath of example 1 is an aqueous NaOH solution having a pH of 9, the crosslinking bath is a 20wt% glutaraldehyde solution, and both the coagulation bath and the crosslinking bath of comparative example are pure water solutions, i.e., comparative example 2 employs pure water coagulation without chemical crosslinking operation. The results show that the flux, hydrophilic modification and each inorganic salt entrapment efficiency of the hollow base membrane and hollow fiber nanofiltration membrane in comparative example 2 are all smaller than the corresponding indexes of the corresponding membrane samples in example 1 and comparative example 1. And is inferior to example 1 in terms of its characteristics to comparative example 1. The addition of the hydrophilic auxiliary PFSS and the combined process of alkaline hydrolysis-assisted and glutaraldehyde solution chemical treatment are both beneficial to improving the membrane separation performance.
Comparative example 3
1) Preparing casting solution, namely mixing 20wt% of PES,12wt% of PFSS and 8wt% of PEG (Mr: 400) into 60wt% of DMAC according to the total mass of the casting solution, heating and stirring for 4 hours in a water bath at 60 ℃, wherein the stirring speed is 200r/min, uniformly mixing, and defoaming to obtain the casting solution;
2) Preparing a hollow base membrane, namely leading the casting solution obtained in the step 1) into a NaOH solution with the pH value of 9 at the temperature of 25 ℃ after passing through a spinning nozzle containing water core solution, so as to obtain a nascent fiber membrane, and obtaining the base membrane after the nascent fiber membrane is subjected to rinsing bath at the temperature of 50 ℃;
3) Preparing a hollow fiber nanofiltration membrane, namely placing the hollow base membrane prepared in the step 2) into a glutaraldehyde aqueous solution at the temperature of 35 ℃ for 2 hours for chemical crosslinking, and obtaining the hollow fiber nanofiltration membrane. The resulting film product was designated C-3.
The mass fraction of the glutaraldehyde aqueous solution is 20wt%.
4) Membrane filament test 8 groups of hollow base membrane and hollow fiber nanofiltration membrane filaments were tested, and the average contact angle, pure water flux and inorganic salt rejection rate were as shown in fig. 1 to 3, respectively.
Comparative example 3 differs from example 1 in that the porogen PEG content in example 1 was 13wt% and in comparative example 3 the porogen PEG content was 8wt%. The results show that the hollow base membrane and hollow fiber nanofiltration membrane of example 1 have better flux, hydrophilic modification and each inorganic salt rejection efficiency than the corresponding membrane sample of comparative example 1, compared to comparative example 3.
Comparative examples 4 to 5
1) Preparing casting solution, namely mixing 20wt% of PES,12wt% of hydrophilic auxiliary agent and 13wt% of PEG (Mr: 400) into 55wt% of DMAC according to the total mass of the casting solution, heating and stirring for 4 hours in a 60 ℃ water bath, wherein the stirring speed is 200r/min, mixing uniformly, and defoaming to obtain the casting solution;
the hydrophilic auxiliary agents are perfluoro butyl sulfonamide propyl triethoxysilane and perfluoro heptyl sulfonamide propyl triethoxysilane respectively.
2) Preparing a hollow base membrane, namely leading the casting solution obtained in the step 1) into a NaOH solution with the pH value of 9 at the temperature of 25 ℃ after passing through a spinning nozzle containing water core solution, so as to obtain a nascent fiber membrane, and obtaining the base membrane after the nascent fiber membrane is subjected to rinsing bath at the temperature of 50 ℃;
3) Preparing a hollow fiber nanofiltration membrane, namely placing the hollow base membrane prepared in the step 2) into a glutaraldehyde aqueous solution at the temperature of 35 ℃ for 2 hours for chemical crosslinking, and obtaining the hollow fiber nanofiltration membrane. The film products obtained in comparative examples 4-5 were labeled C-4, C-5.
The mass fraction of the glutaraldehyde aqueous solution is 20wt%.
4) Membrane filament test 8 groups of hollow base membrane and hollow fiber nanofiltration membrane filaments were tested, and the average contact angle, pure water flux and inorganic salt rejection rate results of comparative examples 4 to 5 are shown in fig. 1 to 3, respectively.
Comparative examples 4 and 5 differ from example 1 in that the hydrophilic adjuvants in example 1 are PFSS and in comparative examples 4 and 5 are perfluorobutyl sulfonamide propyl triethoxysilane and perfluoroheptyl sulfonamide propyl triethoxysilane, respectively. The results show that the NaCl cut-off of example 1 far exceeds that of comparative examples 4 and 5.
Comparative examples 6 to 7
1) Preparing casting solution, namely mixing 20wt% of PES,12wt% of PFSS and 13wt% of PEG (Mr: 400) into 55wt% of DMAC according to the total mass of the casting solution, heating and stirring for 4 hours in a 60 ℃ water bath, wherein the stirring speed is 200r/min, mixing uniformly, and defoaming to obtain the casting solution;
2) Preparing a hollow base membrane, namely leading the casting solution obtained in the step 1) into a NaOH solution with the pH value of 9 at the temperature of 25 ℃ after passing through a spinning nozzle containing water core solution, so as to obtain a nascent fiber membrane, and obtaining the base membrane after the nascent fiber membrane is subjected to rinsing bath at the temperature of 50 ℃;
3) Preparing a hollow fiber nanofiltration membrane, namely placing the hollow base membrane prepared in the step 2) into a glutaraldehyde aqueous solution at the temperature of 35 ℃ for 2 hours for chemical crosslinking, and obtaining the hollow fiber nanofiltration membrane. The film products obtained in comparative examples 6 and 7 were designated C-6 and C-7, respectively.
The mass fractions of the glutaraldehyde aqueous solutions were 1wt% (comparative example 6), 30wt% (comparative example 7), respectively.
4) Membrane filament test 8 groups of hollow base membrane and hollow fiber nanofiltration membrane filaments were tested, and the average contact angle, pure water flux and inorganic salt rejection rate results of comparative examples 6 to 7 are shown in fig. 1 to 3, respectively.
Comparative examples 6 and 7 are different from example 1 in that the mass fraction of glutaraldehyde aqueous solution in example 1 is 20wt% and that in comparative examples 6 and 7, the mass fraction of glutaraldehyde aqueous solution is 5wt% and 30wt%, respectively. The results show that the hollow fiber nanofiltration membrane of example 1 has a flux and NaCl retention of between comparative examples 6 and 7, and is characterized in that the flux is superior to example 7 and the retention is superior to example 6.
The beneficial effects of the application are further demonstrated by corresponding test data below.
Test 1 film surface Water contact Angle test
The water contact angles of the hollow base membranes and the hollow fiber nanofiltration membranes prepared in each example and comparative example were tested to characterize the changes in hydrophilic modification of the membranes, and the results are shown in fig. 1. The water contact angle values of the surfaces of the prepared base films and nanofiltration films are shown in Table 1. The results show that the surface water contact angles of the nanofiltration membranes prepared in examples 1-4 are 66.8+ -1.3 DEG, 67.1+ -1.5 DEG, 63.5+ -1.0 DEG and 68.4+ -1.3 DEG respectively, and the surface water contact angles of the nanofiltration membranes prepared in comparative examples 1-7 are 82.3+ -4.1 DEG, 74.2+ -3.2 DEG, 73.4+ -2.4 DEG, 66.4+ -3.0 DEG, 67.5+ -2.8 DEG, 65.1+ -2.2 DEG and 63.2+ -3.2 DEG respectively. From this, it is clear that the addition of hydrophilic auxiliaries such as PFSS and the like in examples 1 to 4 and comparative examples 2 to 7 effectively improves the hydrophilicity of the film surface and remarkably reduces the water contact angle by the double chemical treatment process of NaOH and glutaraldehyde aqueous solution.
Table 1 test table of water contact angle and pure water flux on surfaces of hollow base membrane and nanofiltration membrane of each group
Test 2 pure water flux test
The hollow base membranes and the hollow fiber nanofiltration membranes prepared in the above examples and comparative examples were pre-pressed with pure water at room temperature under a pressure of 4bar for 30min to achieve a stable flux, and then a pure water flux test was performed under a pressure of 4 bar. The calculation formula is as follows:
P=v/(a×t), V represents the permeation volume, m 3, a represents the effective area of the membrane, m 2, t represents the filtration time, s, and the results are shown in fig. 2 and table 1. The result shows that the hollow fiber nanofiltration membrane prepared by adopting the recording scheme of the invention has higher pure water flux, and the flux of each membrane exceeds 28L ∙ m -2∙h-1. Wherein the pure water fluxes of the membrane samples of examples 1 to 4 were 33.2±1.1L∙m-2∙h-1、28.9±2.6L∙m-2∙h-1、31.3±2.3L∙m-2∙h-1、28.2±1.9L∙m-2∙h-1, and the pure water fluxes of comparative examples 1 to 7 were 17.3±2.2L∙m-2∙h-1、24.7±2.3L∙m-2∙h-1、20.6±3.1L∙m-2∙h-1、23.6±1.4L∙m-2∙h-1、19.4±2.2L∙m-2∙h-1,37.2±1.2L∙m-2∙h-1 and 15.5.+ -. 2.2L ∙ m -2∙h-1, respectively.
Further analysis shows that the addition of PFSS and the homologous compounds thereof and the treatment of NaOH solution effectively improve the hydrophilicity of the hollow fiber nanofiltration membrane, so that the water flux of the hollow fiber nanofiltration membrane is improved, and the membrane water flux is gradually increased along with the increase of the PFSS content from 0 to 12 weight percent. In addition, in the chemical treatment process, the mass fraction of glutaraldehyde solution is increased, so that the chemical crosslinking degree is enhanced, the density of the membrane surface is improved, and the membrane flux is reduced.
Test 3 inorganic salt entrapment efficiency test
The hollow fiber nanofiltration membranes prepared in each example and comparative example were pre-pressed with pure water at room temperature under a pressure of 4bar for 30min to achieve a stable flux, and then 1g/L of sodium chloride, magnesium chloride, sodium sulfate, magnesium sulfate was filtered, and the selective permeability of each hollow fiber nanofiltration membrane was characterized by the removal rate of salts in four solutions, and the rejection rate of the membranes was calculated as follows:
R= [1- (KP/KR) ]. Times.100%, wherein KP and KR respectively represent the conductivity values of salt solutions in permeate and stock solutions, and the results are shown in FIG. 3 and Table 2. It is observed that, compared with comparative example 1 without hydrophilic auxiliary agent and comparative example 2 without NaOH hydrolysis and glutaraldehyde chemical crosslinking, the retention efficiency of each hydrophilically modified hollow fiber nanofiltration membrane is greatly improved, the retention efficiency of Na 2SO4 and MgSO 4 is more than 90%, and the retention efficiency of NaCl is up to 40%. This is because the chemical manipulation of the hydrophilic auxiliary and hydrolytic crosslinking is advantageous for improving the electronegativity of the membrane surface. In addition, the interception performance of each nanofiltration membrane has good selectivity, and the interception performance is expressed as R (Na 2SO4）＞R（MgSO4）＞R（MgCl2) > R (NaCl). Therefore, the hydrophilic modified polysulfone hollow fiber nanofiltration membrane prepared by the invention is a charged membrane with excellent selectivity.
Table 2 inorganic salt rejection test table for each group of film samples
Test 4 heavy metal ion entrapment efficiency
The nanofiltration membrane prepared in example 1 was subjected to a heavy metal ion filtration experiment according to the method of experiment 3, and the test results are shown in fig. 4. FIG. 4 shows that the interception of Cu 2+ and Co 2+ by the hydrophilic modified polysulfone hollow fiber nanofiltration membrane prepared by the invention can reach 97.5% and 96.2%, respectively, and the hydrophilic modified polysulfone hollow fiber nanofiltration membrane has good heavy metal ion separation performance.
Test 5 Long term thermal stability test
The performance stability of the hollow fiber nanofiltration membrane is verified through a long-term filtration experiment. The performance stability of the prepared hydrophilic modified polysulfone hollow fiber nanofiltration membrane is characterized by taking the example 1 as a representative and carrying out a long-term filtration experiment. Specifically, deionized water, na 2SO4 (1 g/L) and NaCl (1 g/L) were used as feed solutions, respectively, and membrane permeation and salt rejection were measured every 2 hours at 4bar for 84 hours. The results are shown in FIG. 5 and Table 3. As can be seen, the membrane shows a high and stable Na 2SO4 rejection (98.0%) and a relatively low NaCl rejection (35.3%). The water permeation flux of the hollow fiber nanofiltration membrane prepared by the invention is reduced from 32.8L ∙ m -2∙h-1 to 31.1L ∙ m -2∙h-1 within 84h, the high-efficiency and durable long-term separation process is realized, and the high selectivity to Na 2SO4 and NaCl is shown, so that the high-efficiency and durable long-term separation process is shown to have excellent performance stability and structural stability.
TABLE 3M-1 Long-term stability test table of sample Water flux and salt rejection
| Time (h) | Water flux (L ∙ m -2∙h-1) | Na 2SO4 retention (%) | NaCl retention (%) |
| 8 | 32.8±1.2 | 98.9±0.9 | 36.5±1.7 |
| 16 | 32.4±1.8 | 99.0±1.7 | 35.1±1.8 |
| 24 | 32.1±1.6 | 97.9±2.0 | 37.0±1.2 |
| 32 | 32.3±2.1 | 99.0±2.1 | 36.5±1.6 |
| 40 | 31.6±1.5 | 99.8±3.4 | 34.7±2.0 |
| 48 | 32.2±1.5 | 98.9±3.7 | 35.5±2.1 |
| 56 | 31.5±1.3 | 97.9±1.9 | 35.4±1.7 |
| 64 | 31.7±1.3 | 98.9±2.5 | 35.0±2.1 |
| 72 | 31.5±1.2 | 98.8±3.5 | 36.8±1.5 |
| 80 | 31.1±2.5 | 98.9±1.0 | 34.6±1.5 |
The foregoing description of the embodiments of the present application has been presented in conjunction with the drawings, but the foregoing embodiment is merely a preferred embodiment of the present application, and is merely for illustrating the technical concept and features of the present application, and is not intended to limit the scope of the present application, as equivalent replacement or modification of the present application is not limited thereto.
Claims (10)
1. A hydrophilic modified polysulfone hollow fiber nanofiltration membrane is characterized by being prepared by the following steps:
1) Preparing a casting solution, namely mixing 15-25wt% of film-forming polymer, 4-12wt% of hydrophilic auxiliary agent and 6-13wt% of pore-forming agent into 50-75wt% of solvent according to the total mass of the casting solution, wherein the film-forming polymer is at least one of polysulfone materials, the hydrophilic auxiliary agent is at least one of perfluorohexyl sulfonamide propyl triethoxysilane homologous compounds with the carbon chain length of 3-8, heating and stirring in a water bath, uniformly mixing, and defoaming to obtain the casting solution;
2) Preparing a hollow base membrane by adopting a non-solvent induced phase separation method to prepare a hollow base membrane by using a casting membrane solution;
3) Preparing a hollow fiber nanofiltration membrane, namely performing chemical treatment on the hollow basal membrane to obtain the hydrophilic modified polysulfone hollow fiber nanofiltration membrane.
2. The hydrophilic modified polysulfone hollow fiber nanofiltration membrane as defined in claim 1, wherein in step 1), the membrane-forming polymer is 18-22wt%, the hydrophilic auxiliary agent is 6-10wt%, the pore-forming agent is 8-11wt% and the solvent is 55-70wt%.
3. The hydrophilic modified hollow fiber nanofiltration membrane of polysulfone type as recited in claim 1, wherein in step 1), the membrane-forming polymer is at least one of polysulfone, polyethersulfone, polyphenylsulfone, sulfonated polysulfone, sulfonated polyethersulfone, and sulfonated polyphenylsulfone.
4. The hydrophilic modified polysulfone hollow fiber nanofiltration membrane of claim 1, wherein in step 1), the pore-forming agent is at least one of polyethylene glycol and polyvinylpyrrolidone with different molecular weights, preferably at least one of PEG400, PEG600, PEG800, PEG1000, PEG1500, PVPK17, PVPK30 and PVPK 90.
5. The hydrophilically-modified polysulfone hollow fiber nanofiltration membrane as defined in claim 1, wherein in step 1), the solvent is at least one of dimethylacetamide, dimethylformamide and N-methylpyrrolidone.
6. The hydrophilic modified polysulfone hollow fiber nanofiltration membrane as defined in claim 1, wherein in the step 1), the stirring temperature in water bath is 60-80 ℃, the stirring time is 2-4h, the stirring speed is 150-250r/min, the stirring temperature in water bath is 65-70 ℃ and the stirring time is 2.5-3h, and the stirring speed is 200-220r/min.
7. A hydrophilic modified polysulfone hollow fiber nanofiltration membrane as defined in claim 1, wherein the specific method in step 2) is that the casting solution is introduced into a coagulating bath for phase inversion and primary hydrolytic crosslinking after passing through a spinneret containing a core solution, the primary fiber membrane is rinsed to obtain a hollow fiber base membrane, the core solution is deionized water, the coagulating bath is a NaOH aqueous solution, the rinsing bath is deionized water, the coagulating bath temperature is 25-40 ℃, the rinsing bath temperature is 40-60 ℃, the preferred coagulating bath temperature is 30-35 ℃, the rinsing bath temperature is 45-50 ℃, and the PH value of the NaOH aqueous solution is 7-10, and the preferred pH value is 9.
8. A hydrophilically modified polysulfone hollow fiber nanofiltration membrane as claimed in claim 1, wherein the chemical treatment process in step 3) is specifically that the hollow base membrane prepared in step 2) is placed in glutaraldehyde aqueous solution at a certain temperature for chemical crosslinking for a certain period of time, the chemical crosslinking temperature is 30-40 ℃, preferably 35 ℃, and the chemical crosslinking time is 1.5-2.5 hours, preferably 2 hours.
9. A hydrophilically modified polysulfone hollow fiber nanofiltration membrane as defined in claim 8, wherein the glutaraldehyde solution has a mass fraction of 5-25wt%.
10. The application of the hydrophilic modified polysulfone hollow fiber nanofiltration membrane in the labeling of tap water industry as claimed in claim 1.
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| CN105561805A (en) * | 2014-10-17 | 2016-05-11 | 中国石油化工股份有限公司 | Composite nanofiltration membrane as well as preparation method and application thereof |
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| CN118454483A (en) * | 2024-03-28 | 2024-08-09 | 浙江工业大学 | A Cu-AMO composite membrane for degradation of quinolone antibiotics and its application |
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| US20030226799A1 (en) * | 2002-06-07 | 2003-12-11 | John Charkoudian | Microporous membrane substrate having caustic stable, low protein binding surface |
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