CN114210213B - Preparation method of hollow nanofiltration membrane - Google Patents
Preparation method of hollow nanofiltration membrane Download PDFInfo
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- CN114210213B CN114210213B CN202111549170.1A CN202111549170A CN114210213B CN 114210213 B CN114210213 B CN 114210213B CN 202111549170 A CN202111549170 A CN 202111549170A CN 114210213 B CN114210213 B CN 114210213B
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- 239000012528 membrane Substances 0.000 title claims abstract description 223
- 238000001728 nano-filtration Methods 0.000 title claims abstract description 78
- 238000002360 preparation method Methods 0.000 title claims description 21
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 claims abstract description 86
- 239000008346 aqueous phase Substances 0.000 claims abstract description 65
- 239000012071 phase Substances 0.000 claims abstract description 56
- 238000010438 heat treatment Methods 0.000 claims abstract description 51
- 239000012510 hollow fiber Substances 0.000 claims abstract description 46
- 239000003223 protective agent Substances 0.000 claims abstract description 44
- 239000000178 monomer Substances 0.000 claims abstract description 40
- 238000000034 method Methods 0.000 claims abstract description 34
- 235000011187 glycerol Nutrition 0.000 claims abstract description 31
- 239000011148 porous material Substances 0.000 claims abstract description 27
- UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical compound [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 claims abstract description 23
- 239000001110 calcium chloride Substances 0.000 claims abstract description 23
- 229910001628 calcium chloride Inorganic materials 0.000 claims abstract description 23
- 150000001412 amines Chemical class 0.000 claims abstract description 19
- 238000006243 chemical reaction Methods 0.000 claims abstract description 17
- 238000011282 treatment Methods 0.000 claims abstract description 17
- 150000001263 acyl chlorides Chemical class 0.000 claims abstract description 12
- 238000002791 soaking Methods 0.000 claims abstract description 12
- 239000004952 Polyamide Substances 0.000 claims abstract description 11
- 229920002647 polyamide Polymers 0.000 claims abstract description 11
- 238000000108 ultra-filtration Methods 0.000 claims abstract description 10
- 125000004122 cyclic group Chemical group 0.000 claims abstract description 6
- 239000000243 solution Substances 0.000 claims description 100
- 239000002904 solvent Substances 0.000 claims description 80
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 56
- 239000007864 aqueous solution Substances 0.000 claims description 38
- 239000007788 liquid Substances 0.000 claims description 33
- 238000005266 casting Methods 0.000 claims description 31
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 claims description 27
- MTHSVFCYNBDYFN-UHFFFAOYSA-N diethylene glycol Chemical compound OCCOCCO MTHSVFCYNBDYFN-UHFFFAOYSA-N 0.000 claims description 23
- 229920002492 poly(sulfone) Polymers 0.000 claims description 22
- GLUUGHFHXGJENI-UHFFFAOYSA-N diethylenediamine Natural products C1CNCCN1 GLUUGHFHXGJENI-UHFFFAOYSA-N 0.000 claims description 19
- FXHOOIRPVKKKFG-UHFFFAOYSA-N N,N-Dimethylacetamide Chemical compound CN(C)C(C)=O FXHOOIRPVKKKFG-UHFFFAOYSA-N 0.000 claims description 18
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 15
- 238000005345 coagulation Methods 0.000 claims description 15
- 230000015271 coagulation Effects 0.000 claims description 15
- 229920000642 polymer Polymers 0.000 claims description 15
- 238000000926 separation method Methods 0.000 claims description 15
- UWCPYKQBIPYOLX-UHFFFAOYSA-N benzene-1,3,5-tricarbonyl chloride Chemical compound ClC(=O)C1=CC(C(Cl)=O)=CC(C(Cl)=O)=C1 UWCPYKQBIPYOLX-UHFFFAOYSA-N 0.000 claims description 11
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 claims description 9
- 239000004695 Polyether sulfone Substances 0.000 claims description 9
- 229920006393 polyether sulfone Polymers 0.000 claims description 9
- 239000003795 chemical substances by application Substances 0.000 claims description 8
- 230000001112 coagulating effect Effects 0.000 claims description 7
- 238000009987 spinning Methods 0.000 claims description 7
- 239000002202 Polyethylene glycol Substances 0.000 claims description 5
- FDQSRULYDNDXQB-UHFFFAOYSA-N benzene-1,3-dicarbonyl chloride Chemical compound ClC(=O)C1=CC=CC(C(Cl)=O)=C1 FDQSRULYDNDXQB-UHFFFAOYSA-N 0.000 claims description 5
- 229920001223 polyethylene glycol Polymers 0.000 claims description 5
- 229920000036 polyvinylpyrrolidone Polymers 0.000 claims description 5
- 239000001267 polyvinylpyrrolidone Substances 0.000 claims description 5
- 235000013855 polyvinylpyrrolidone Nutrition 0.000 claims description 5
- 125000004193 piperazinyl group Chemical group 0.000 claims description 3
- 238000004519 manufacturing process Methods 0.000 claims description 2
- 230000004907 flux Effects 0.000 abstract description 16
- 238000001035 drying Methods 0.000 abstract description 14
- 238000004804 winding Methods 0.000 description 29
- 230000000052 comparative effect Effects 0.000 description 12
- 230000008569 process Effects 0.000 description 11
- 238000012695 Interfacial polymerization Methods 0.000 description 10
- NGNBDVOYPDDBFK-UHFFFAOYSA-N 2-[2,4-di(pentan-2-yl)phenoxy]acetyl chloride Chemical compound CCCC(C)C1=CC=C(OCC(Cl)=O)C(C(C)CCC)=C1 NGNBDVOYPDDBFK-UHFFFAOYSA-N 0.000 description 9
- 239000000835 fiber Substances 0.000 description 8
- 238000002156 mixing Methods 0.000 description 7
- 229920002565 Polyethylene Glycol 400 Polymers 0.000 description 6
- JLFNLZLINWHATN-UHFFFAOYSA-N pentaethylene glycol Chemical compound OCCOCCOCCOCCOCCO JLFNLZLINWHATN-UHFFFAOYSA-N 0.000 description 6
- 238000010926 purge Methods 0.000 description 6
- 238000000746 purification Methods 0.000 description 6
- 238000003860 storage Methods 0.000 description 6
- -1 but not limited to Substances 0.000 description 5
- 239000010865 sewage Substances 0.000 description 4
- 238000010612 desalination reaction Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000008235 industrial water Substances 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 230000003020 moisturizing effect Effects 0.000 description 3
- 229920000768 polyamine Polymers 0.000 description 3
- 229920012266 Poly(ether sulfone) PES Polymers 0.000 description 2
- 239000004743 Polypropylene Substances 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000008233 hard water Substances 0.000 description 2
- 230000007246 mechanism Effects 0.000 description 2
- 238000001000 micrograph Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 229920001155 polypropylene Polymers 0.000 description 2
- 230000002195 synergetic effect Effects 0.000 description 2
- 239000002351 wastewater Substances 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- 239000002033 PVDF binder Substances 0.000 description 1
- 239000004697 Polyetherimide Substances 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- 239000004642 Polyimide Substances 0.000 description 1
- 150000001408 amides Chemical class 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000009395 breeding Methods 0.000 description 1
- 230000001488 breeding effect Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 238000011033 desalting Methods 0.000 description 1
- 230000035622 drinking Effects 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 150000002193 fatty amides Chemical class 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 238000007667 floating Methods 0.000 description 1
- 230000014509 gene expression Effects 0.000 description 1
- 229920006158 high molecular weight polymer Polymers 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000004615 ingredient Substances 0.000 description 1
- 244000144972 livestock Species 0.000 description 1
- 238000005374 membrane filtration Methods 0.000 description 1
- 239000004745 nonwoven fabric Substances 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 238000004806 packaging method and process Methods 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 229920001643 poly(ether ketone) Polymers 0.000 description 1
- 229920002239 polyacrylonitrile Polymers 0.000 description 1
- 229920001601 polyetherimide Polymers 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 229920001721 polyimide Polymers 0.000 description 1
- 239000002861 polymer material Substances 0.000 description 1
- 239000004810 polytetrafluoroethylene Substances 0.000 description 1
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 1
- 229920000915 polyvinyl chloride Polymers 0.000 description 1
- 239000004800 polyvinyl chloride Substances 0.000 description 1
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 1
- 230000008092 positive effect Effects 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 239000013535 sea water Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 238000009827 uniform distribution Methods 0.000 description 1
- 239000002912 waste gas Substances 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
- B01D71/06—Organic material
- B01D71/56—Polyamides, e.g. polyester-amides
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
- B01D67/0002—Organic membrane manufacture
- B01D67/0006—Organic membrane manufacture by chemical reactions
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/02—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor characterised by their properties
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/08—Hollow fibre membranes
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
- C02F1/442—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by nanofiltration
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A20/00—Water conservation; Efficient water supply; Efficient water use
- Y02A20/124—Water desalination
- Y02A20/131—Reverse-osmosis
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
- Nanotechnology (AREA)
- Life Sciences & Earth Sciences (AREA)
- Hydrology & Water Resources (AREA)
- Environmental & Geological Engineering (AREA)
- Water Supply & Treatment (AREA)
- Organic Chemistry (AREA)
- Manufacturing & Machinery (AREA)
- Separation Using Semi-Permeable Membranes (AREA)
Abstract
The invention discloses a method for preparing a hollow nanofiltration membrane, which comprises the following steps: soaking the hollow fiber base membrane by using an aqueous phase solution containing amine monomers and a pore-protecting agent under cyclic heating, carrying out contact reaction on the membrane and an oil phase solution containing acyl chloride monomers after the soaking treatment is finished, and then carrying out heat treatment to obtain the hollow nanofiltration membrane; wherein the pore-protecting agent comprises glycerin and optionally calcium chloride. The invention combines the pore-protecting agent with heating circulation to effectively protect the integrity of the membrane pore structure and the polyamide separating layer of the ultrafiltration base membrane in the drying process, thereby well maintaining the membrane flux and the removal rate.
Description
Technical Field
The invention belongs to the field of preparation and modification of polymer separation membranes, and particularly relates to a preparation method of a hollow nanofiltration membrane.
Background
The sewage reclamation has the double functions of water saving and emission reduction, and is a necessary strategy suitable for the problem of water shortage in China. Along with the continuous discharge of the national policy about sewage reclamation, the membrane separation technology becomes an indispensable part of the water resource circulation in the industrial field by the advantages of low energy consumption, small occupied area, precise separation and the like, and in recent years, along with the double driving of market cost and environmental protection policy, near zero emission becomes one of the more and more popular processes. Among these, nanofiltration membranes are gaining attention by their unique selective separation of small molecular organics and divalent salts, and are widely used in the industrial fields of hard water softening, dye concentration, purification, and the like.
The nanofiltration membrane structure commercialized at present is mainly a roll type membrane encapsulated by a flat membrane. Compared with the coiled nanofiltration membrane, the hollow nanofiltration membrane has the advantage of larger unit filling area, and the hollow nanofiltration membrane has a wider water inlet flow passage, so that the anti-pollution capability of the membrane is effectively improved.
The vast majority of processes for preparing nanofiltration membranes by interfacial polymerization include the steps of water phase soaking, residual water phase removing, oil phase soaking, excessive oil phase solvent removing, post-treatment, drying and winding. The excessive oil phase solvent is removed in a drying mode in industry generally, because the excessive oil phase solvent is removed in a drying mode, compared with other treatment modes, the method is more effective, the controllability is stronger in the industrialization process, the waste gas is easier to treat, and meanwhile, the further perfection of the interfacial polymerization process is promoted in the drying process, so that the positive effect on the improvement of the removal rate of the membrane is achieved. However, membrane pores of the ultrafiltration base membrane collapse easily due to water loss in the process of drying and removing excessive oil phase solvent, so that the membrane structure is changed, and further the flux and the surface structure are irreversibly changed.
Moreover, the process of drying and removing the excessive oil phase solvent has a significantly larger influence on the hollow fiber nanofiltration membrane than the flat nanofiltration membrane. The flat membrane usually contains supporting materials such as non-woven fabrics, the hollow fiber membrane can only be in a self-supporting structure, and the hollow fiber nanofiltration membrane prepared by an interfacial polymerization method can shrink in the process of drying and removing the oil phase solvent, so that a desalting layer cracks or is partially peeled off, the performance of the membrane is obviously reduced, and meanwhile, the cylindrical surface of the hollow fiber membrane is difficult to effectively keep the sufficient and uniform distribution of the polyamine aqueous solution on the surface of the membrane.
Therefore, there is a need in the art for a method for preparing a hollow fiber nanofiltration membrane with a membrane pore structure of an ultrafiltration base membrane which is not easy to change and a desalination layer which has high integrity in the preparation process.
Disclosure of Invention
The invention provides a preparation method of a hollow nanofiltration membrane. The invention combines the pore-protecting agent with heating circulation to effectively protect the integrity of the membrane pore structure and the polyamide separating layer of the ultrafiltration base membrane in the drying process, thereby well maintaining the membrane flux and the removal rate.
In particular, the present invention provides a method of preparing a hollow nanofiltration membrane, the method comprising: soaking the hollow fiber base membrane by using an aqueous phase solution containing amine monomers and a pore-protecting agent under cyclic heating, carrying out contact reaction on the membrane and an oil phase solution containing acyl chloride monomers after the soaking treatment is finished, and then carrying out heat treatment to obtain the hollow nanofiltration membrane; wherein the pore-protecting agent comprises glycerin and optionally calcium chloride.
In one or more embodiments, the pore-protecting agent is present in the aqueous solution in an amount of 5 to 40% by mass of the total mass of the aqueous solution.
In one or more embodiments, the mass of glycerol in the aqueous phase solution is 5-30%, preferably 15-25% of the total mass of the aqueous phase solution.
In one or more embodiments, the mass of calcium chloride in the aqueous phase solution is 0-15%, preferably 2-10% of the total mass of the aqueous phase solution.
In one or more embodiments, the hollow fiber-based membrane is immersed in the aqueous solution for a residence time of the hollow fiber-based membrane in the aqueous solution of 30 to 150 seconds, for example, 60 to 90 seconds.
In one or more embodiments, the temperature of the aqueous solution is 30-50 ℃, such as 40-45 ℃, when the hollow fiber base membrane is immersed in the aqueous solution.
In one or more embodiments, the hollow fiber base membrane is immersed in the aqueous solution in an amount of 20 to 100L/min, for example 30 to 60L/min, for the aqueous solution.
In one or more embodiments, the amine-based monomer is present in the aqueous solution in an amount of 0.15 to 2%, such as 0.2 to 0.5%, of the total mass of the aqueous solution.
In one or more embodiments, the amine-based monomer is piperazine.
In one or more embodiments, after the hollow fiber base membrane is soaked with the aqueous solution, droplets of the aqueous solution on the surface of the membrane are removed, and then the membrane is contacted with an oil phase solution containing an acid chloride monomer for reaction.
In one or more embodiments, the mass of the acid chloride-based monomer in the oil phase solution is 0.05 to 0.5%, such as 0.1 to 0.25%, of the total mass of the oil phase solution.
In one or more embodiments, the acid chloride-based monomer is selected from one or both of trimesoyl chloride and isophthaloyl chloride.
In one or more embodiments, the solvent of the oil phase solution is an isoparaffin.
In one or more embodiments, the membrane is contacted with the oil phase solution containing the acid chloride-based monomer for a period of time ranging from 20 to 120 seconds, such as from 30 to 120 seconds, from 30 to 45 seconds.
In one or more embodiments, the temperature of the heat treatment is 80-120 ℃, such as 90-110 ℃.
In one or more embodiments, the time of the heat treatment is from 30 to 150 seconds, such as from 30 to 120 seconds, from 80 to 90 seconds.
In one or more embodiments, the hollow fiber based membrane is a hollow fiber ultrafiltration membrane.
In one or more embodiments, the hollow fiber-based membrane is made of one or both of polysulfone and polyethersulfone.
In one or more embodiments, the hollow fiber-based membrane is prepared from a casting solution and a core solution by spinning, solidifying with a coagulation bath, and rinsing.
In one or more embodiments, the casting solution includes a high molecular polymer, a high molecular pore former, a non-solvent, and a solvent.
In one or more embodiments, the core liquid includes a non-solvent and optionally a solvent.
In one or more embodiments, the coagulation bath includes a non-solvent and optionally a solvent.
In one or more embodiments, the high molecular polymer is selected from one or both of polysulfone and polyethersulfone.
In one or more embodiments, the polymeric pore former is selected from one or both of polyethylene glycol and polyvinylpyrrolidone.
In one or more embodiments, the non-solvent is selected from one or more of water, ethanol, glycerol, and diethylene glycol.
In one or more embodiments, the solvent is selected from one or more of dimethylformamide, dimethylacetamide, and N-methylpyrrolidone.
In one or more embodiments, the casting solution has a high molecular weight polymer content of 15 to 30wt%, such as 17 to 22wt%, 18 to 20wt%, a high molecular weight pore former content of 1 to 10wt%, such as 1.5 to 8.2wt%, 7 to 8wt%, and a non-solvent content of 0.8 to 12.5wt%, such as 1.5 to 6.5wt%, and a solvent content of 55 to 82%, such as 57.3 to 80.7wt%, 70 to 75wt%, based on the total mass of the casting solution.
In one or more embodiments, the non-solvent is present in the core liquid in an amount of 20 to 100wt%, such as 25 to 100wt%, based on the total mass of the core liquid.
In one or more embodiments, the non-solvent is present in the coagulation bath in an amount of 80 to 100wt%, such as 95 to 100wt%, based on the total mass of the coagulation bath.
The invention also provides hollow nanofiltration membranes prepared by the method described in any of the embodiments herein.
The invention also provides nanofiltration devices comprising hollow nanofiltration membranes as described in any of the embodiments herein.
The invention also provides the use of a hollow nanofiltration membrane or nanofiltration device as described in any of the embodiments herein in domestic, agricultural or industrial water treatment.
The invention also provides the use of a pore-protecting agent in the preparation of a nanofiltration membrane with improved stability of the pore structure of the membrane and integrity of the polyamide separation layer, characterized in that the use comprises the step of contacting an aqueous solution comprising the pore-protecting agent with a base membrane, wherein the pore-protecting agent comprises glycerol and optionally calcium chloride.
In one or more embodiments, the pore-protecting agent is present in the aqueous solution in an amount of 5 to 40% by mass of the total mass of the aqueous solution.
In one or more embodiments, the mass of glycerol in the aqueous phase solution is 5-30%, preferably 15-25% of the total mass of the aqueous phase solution.
In one or more embodiments, the mass of calcium chloride is 0-15%, preferably 2-10% of the total mass of the aqueous phase solution.
In one or more embodiments, the aqueous phase solution is contacted with the base film for a time period of from 30 to 150 seconds, such as from 60 to 90 seconds.
In one or more embodiments, the aqueous phase solution is contacted with the base film at a temperature of from 30 to 50 ℃, such as from 40 to 45 ℃.
In one or more embodiments, the aqueous phase solution is contacted with the base film under circulation, preferably in an amount of 20 to 100L/min, for example 0 to 60L/min.
In some embodiments, the use is as described in the method of making hollow nanofiltration membranes according to any of the embodiments of the invention.
Drawings
FIG. 1 is an electron microscope image of the surface of a base film obtained by heat-treating the base film yarn of example 3 with an aqueous solution containing a pore-protecting agent directly after heat-treating the base film yarn by heat-cycling treatment to remove the residual aqueous phase on the surface of the film.
FIG. 2 is an electron microscope image of the surface of the base film of example 3 after heat-treating the base film yarn directly with the aqueous solution containing no pore-protecting agent after heat-cycling treatment to remove the residual aqueous phase on the surface of the film.
Detailed Description
So that those skilled in the art can appreciate the features and effects of the present invention, a general description and definition of the terms and expressions set forth in the specification and claims follows. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs, and in the event of a conflict, the present specification shall control.
The theory or mechanism described and disclosed herein, whether right or wrong, is not meant to limit the scope of the invention in any way, i.e., the present disclosure may be practiced without limitation to any particular theory or mechanism.
Herein, "comprising," "including," "containing," and similar terms are intended to cover the meaning of "consisting essentially of … …" and "consisting of … …," e.g., "a consisting essentially of B and C" and "a consisting of B and C" should be considered to have been disclosed herein when "a comprises B and C" is disclosed herein.
In this document, all features such as values, amounts, and concentrations that are defined as ranges of values or percentages are for brevity and convenience only. Accordingly, the description of a numerical range or percentage range should be considered to cover and specifically disclose all possible sub-ranges and individual values (including integers and fractions) within the range.
Herein, unless otherwise specified, percentages refer to mass percentages, and proportions refer to mass ratios.
Herein, when embodiments or examples are described, it should be understood that they are not intended to limit the invention to these embodiments or examples. On the contrary, all alternatives, modifications, and equivalents of the methods and materials described herein are intended to be included within the scope of the invention as defined by the appended claims.
In this context, not all possible combinations of the individual technical features in the individual embodiments or examples are described in order to simplify the description. Accordingly, as long as there is no contradiction between the combinations of these technical features, any combination of the technical features in the respective embodiments or examples is possible, and all possible combinations should be considered as being within the scope of the present specification.
The invention discovers that the stability of the membrane pore structure of the base membrane and the integrity of the desalination layer can be improved in the process of drying and removing excessive oil phase solvent of the nanofiltration membrane by adding glycerol and optional calcium chloride into the aqueous phase solution and circularly heating the base membrane when the base membrane contacts the aqueous phase solution, thereby improving the flux and the removal rate of the nanofiltration membrane. The glycerol not only can play a role of a solvent, but also can form a more uniform water film on the surface of the membrane, and simultaneously has a good moisturizing effect, so that the membrane pore structure of the base membrane is effectively protected in the drying process, and the integrity of the primary polyamide separation layer is further protected. The calcium chloride also has a moisturizing effect and can protect the membrane pore structure of the base membrane. The base film structure is protected, so that the rear end post-treatment temperature can be increased, redundant oil phase is removed better, meanwhile, the perfection of interfacial polymerization reaction is improved, and the removal rate of the nanofiltration film is improved.
Base film
The base membrane suitable for use in the present invention may be an ultrafiltration membrane. The structure of the base membrane may be a flat plate membrane or a hollow fiber membrane, particularly a hollow fiber membrane.
The material of the base membrane suitable for the present invention is not particularly limited, and may be various polymers known to be used as a nanofiltration membrane base membrane, including, but not limited to, polyethylene, polypropylene, polysulfone (PSF), sulfonated polysulfone, polyethersulfone (PES), sulfonated polyethersulfone, polypropylene, polyacrylonitrile, polyvinylidene fluoride, polytetrafluoroethylene, polyvinylchloride, polysulfone amide, polyetherketone, poly fatty amide, polyimide, polyetherimide, etc. In some preferred embodiments, the base membrane used in the present invention is made of one or both of polysulfone and polyethersulfone.
The base film may be prepared using methods known in the art. In some embodiments, the present invention uses a hollow fiber membrane made from a casting solution and a core solution by spinning, solidifying with a coagulation bath, and rinsing as a base membrane. For example, the casting solution is passed through a spinneret containing a core solution and then introduced into a coagulation bath to be solidified, whereby a nascent fiber membrane is obtained, and the nascent fiber membrane is rinsed to obtain a hollow fiber membrane.
The casting solution of the base film may include or consist of a high molecular polymer, a high molecular pore-forming agent, a non-solvent, and a solvent.
In the present invention, the high molecular polymer may be any of the aforementioned polymers known to be useful as nanofiltration membrane base membranes, in particular one or both selected from polysulfone and polyethersulfone.
In the present invention, the polymer pore-forming agent may be one or both selected from polyethylene glycol (PEG) and polyvinylpyrrolidone (PVP). Examples of polyethylene glycol as a pore-forming agent include PEG400, PEG2000, and the like. Examples of polyvinylpyrrolidone as a pore former include PVPK17, PVPK30, PVPK90, and the like.
In the present invention, a solvent and a non-solvent have meanings known in the art, the solvent means a liquid having good solubility to a polymer, and the non-solvent means a liquid having poor solubility to the polymer. The non-solvent in the casting solution may be one or more selected from water, ethanol, glycerol and diethylene glycol. The solvent in the casting solution may be one or more selected from Dimethylformamide (DMF), dimethylacetamide (DMAc), and N-methylpyrrolidone (NMP).
The content of the high molecular polymer in the casting solution may be 15 to 30wt%, for example 17 to 22wt%, 18 to 20wt%, based on the total mass of the casting solution. The content of the polymeric pore-forming agent may be 1 to 10wt%, for example 1.5 to 8.2wt%, 5 to 8wt%, 7wt%, 7.8wt%. The non-solvent may be present in an amount of 0.8 to 12.5wt%, for example 1 to 10wt%, 1.5wt%, 1.8wt%, 6.4wt%, 6.5wt%. The solvent may be present in an amount of 55 to 82wt%, such as 57.3 to 80.7wt%, 70 to 75wt%, 72.5wt% based on the total mass of the casting solution.
And uniformly mixing the components of the casting solution to obtain the casting solution. For example, the polymer pore-forming agent, the solvent and the non-solvent may be mixed under heating, and vacuum defoamed after being uniformly mixed to obtain the casting solution. Mixing may be performed by stirring. The heating temperature may be 60-90 ℃.
The core liquid used to prepare the hollow fiber membranes includes or consists of a non-solvent and an optional solvent.
The non-solvent in the core liquid may be one or more selected from water, ethanol, glycerol and diethylene glycol. The solvent in the core liquid may be one or more selected from dimethylformamide, dimethylacetamide and N-methylpyrrolidone. The non-solvent content in the core liquid may be 20 to 100wt%, for example 25wt%, 30wt%, 50wt%, 100wt%, based on the total mass of the core liquid.
The coagulation bath for solidifying the casting solution ejected from the spinneret includes or consists of a non-solvent and an optional solvent.
The non-solvent in the coagulation bath may be one or more selected from water, ethanol, glycerol and diethylene glycol. The solvent in the coagulation bath may be one or more selected from dimethylformamide, dimethylacetamide and N-methylpyrrolidone. The non-solvent content in the coagulation bath may be 80-100wt%, such as 85wt%, 90wt%, 95wt%, 100wt%, based on the total mass of the coagulation bath.
The temperature of the coagulation bath may be 30-65 c, such as 45-60 c,
the rinse liquid used to rinse the as-spun fibrous membrane may be water. The temperature of the rinsing may be 60-90 ℃, for example 70-80 ℃.
The prepared hollow fiber membrane can be received on a winding drum for standby.
Nanofiltration membrane
The nanofiltration membrane is prepared by contacting an aqueous phase solution containing amine monomers and a pore-protecting agent with a base membrane under cyclic heating, then carrying out contact reaction on the membrane and an oil phase solution containing acyl chloride monomers, and then carrying out heat treatment. When the hollow fiber membrane is used as a base membrane, the prepared nanofiltration membrane is a hollow fiber nanofiltration membrane (hollow nanofiltration membrane for short).
The invention combines the pore-protecting agent with the heating circulation mode, and the pore-protecting agent in the aqueous phase solution plays a synergistic effect with the heating circulation mode, so that the membrane pore structure of the base membrane (such as a hollow fiber ultrafiltration membrane) is effectively protected, the perfection of interfacial polymerization reaction is improved, the membrane pore structure of the base membrane is effectively protected, the integrity of a nascent polyamide separation layer is improved, and the flux and the removal rate of the nanofiltration membrane are improved.
The method for preparing the hollow fiber nanofiltration membrane comprises the following steps: soaking the hollow fiber base membrane by using an aqueous phase solution containing amine monomers and a pore-protecting agent under cyclic heating, carrying out contact reaction on the membrane and an oil phase solution containing acyl chloride monomers after the soaking treatment is finished, and then carrying out heat treatment to obtain the hollow nanofiltration membrane; wherein the pore-protecting agent comprises glycerin and optionally calcium chloride.
The aqueous phase solution of the invention comprises or consists of an amine monomer, a pore-protecting agent and water.
In the present invention, the pore-protecting agent comprises glycerin, optionally calcium chloride. In the aqueous solution, the mass of the pore-protecting agent is preferably 5 to 40%, more preferably 10 to 25%, for example 15%, 20%, 22.5%, 25% of the total mass of the aqueous solution. The mass of glycerol in the aqueous solution is preferably 5-30%, more preferably 10-25%, such as 15%, 20%, 25% of the total mass of the aqueous solution. In the aqueous phase solution, the mass of the calcium chloride is preferably 0-15% of the total mass of the aqueous phase solution. When the pore-protecting agent comprises calcium chloride, the mass of calcium chloride is preferably 2-10%, for example 2.5%, 5%, 7.5%. The glycerol in the pore-protecting agent is a good solvent of amine monomers, and meanwhile, the overall viscosity of the water phase can be improved, so that the adhesion of the water phase on the surface of the base film is increased, the interfacial polymerization efficiency is improved, and meanwhile, the glycerol also has a good moisture-preserving effect, the film pore structure of the base film is effectively protected in the drying process, and the integrity of a primary polyamide separation layer is further protected. The calcium chloride also has a moisturizing effect and can protect the membrane pore structure of the base membrane.
The amine monomers suitable for use in the present invention may be various amine monomers known to be useful in polyamide separation layers of nanofiltration membranes. The amine monomer is usually a polyamine containing two or more-NH' s 2 or-NH-groups. In some embodiments, the amine-based monomer used in the present invention is piperazine (PIP). The mass of amine monomer in the aqueous solution may be 0.15-2%, such as 0.2%, 0.25%, 0.28%, 0.3%, 0.5%, 1% of the total mass of the aqueous solution.
In the present invention, the contact time of the aqueous phase solution with the base film is preferably 30 to 150 seconds, for example, 60 to 90 seconds. The aqueous solution may be contacted with the base film by immersing the base film in the aqueous solution.
The invention adopts a heating circulation mode to contact the aqueous phase solution with the base film. Herein, the heating cycle means that the aqueous phase is circulated in a water tank by a pump and the aqueous phase is maintained at a certain temperature by heating. The circulation amount of the aqueous phase solution is preferably 20 to 100L/min, for example 30L/min, 60L/min, when the heating is circulated; the temperature is preferably 30-50deg.C, such as 40deg.C, 45deg.C.
The hollow fiber-based membrane may be introduced into the aqueous phase solution in such a manner that the hollow fiber-based membrane is set on a constant tension pay-off machine for unwinding.
After the hollow fiber base membrane is soaked by using the aqueous solution, the residual aqueous solution drops on the surface of the membrane can be removed, and then the membrane is contacted and reacted with the oil phase solution containing the acyl chloride monomer. An annular air knife can be used to remove the residual aqueous solution droplets on the membrane surface.
The oil phase solution of the invention comprises or consists of acyl chloride monomers and an oil phase solvent.
The acid chloride-based monomer suitable for the present invention may be various acid chloride-based monomers known to be used for polyamide separation layers of nanofiltration membranes. The amine monomer is typically a polyacyl chloride containing two or more-COCl groups. In some embodiments, the acid chloride-based monomer used in the present invention is one or both selected from trimesoyl chloride (TMC) and isophthaloyl chloride (IPC). In the oil phase solution, the mass of the acid chloride monomer may be 0.05-0.5% of the total mass of the oil phase solution, for example 0.1%, 0.15%, 0.2%, 0.22%, 0.25%. The oil phase solvent suitable for the present invention may be an organic solvent commonly used for dissolving acid chloride-based monomers. In some embodiments, the oil phase solvent is an isoparaffin. Examples of isoparaffins include IsoPar G, isoPar E, isoPar L, and the like.
The time of contact of the membrane with the oil phase solution may be in the range of 20 to 120s, for example 30 to 120s, 30 to 45s. The contact between the two can be achieved by immersing the membrane in an oil phase solution.
After contact with the oil phase, the membrane is heat treated to remove excess oil phase solvent from the membrane and promote further perfection of the interfacial polymerization process. The heat treatment may be performed by a drying method. The temperature of the heat treatment may be 80-120 ℃, for example 90-110 ℃. The heat treatment time may be 30 to 150s, for example 30 to 120s, 80 to 90s.
In some embodiments, the invention is based on interfacial polymerization technology, firstly, preparing ultrafiltration base film by using high polymer material, after collecting the base film on a winding drum, feeding the winding drum through a constant tension unwinder, firstly, feeding membrane wires into an aqueous phase tank containing a pore-protecting agent, wherein the aqueous phase tank is in a heating circulation mode to promote the aqueous phase to enter the membrane more quickly, removing surface floating water of the membrane wires through an annular air knife, then entering an oil phase reaction tank, and then winding the membrane wires into a film after a certain temperature oven.
The invention includes nanofiltration membranes, particularly hollow nanofiltration membranes, produced by the method of any of the preceding embodiments.
The invention also includes the use of a pore protecting agent as described herein for the preparation of nanofiltration membranes with improved stability of the pore structure of the membrane and/or improved integrity of the polyamide separation layer. The application includes the step of contacting an aqueous phase solution containing the pore-protecting agent with a base membrane of a nanofiltration membrane. The types and amounts of pore-protecting agent and other ingredients in the aqueous solution are as described in any of the embodiments herein. The manner and conditions of contacting the aqueous phase solution with the base film are as described in any of the embodiments herein. Preferably, the application comprises the step of contacting the aqueous phase solution containing the pore-protecting agent with the base membrane of the nanofiltration membrane under heating cycle conditions. The application may further include the step of contacting the base film contacted with the aqueous phase solution with an oil phase solution and subsequently performing a heat treatment. The oil phase solution, the manner and conditions of contact with the oil phase solution, and the conditions of heat treatment may be as described in any of the embodiments herein.
Nanofiltration device and application
The nanofiltration membrane of the invention can be assembled with a housing or other components into a nanofiltration device using conventional packaging and the like. The nanofiltration membrane of the invention has improved flux and removal rate, and thus has improved water treatment effect. The invention comprises the application of the nanofiltration membrane and the nanofiltration device in water treatment in the fields of household, agriculture, industry and the like. The application in the household water treatment can be, for example, a water dispenser filter element, a tap filter element, a water purifier, a water softener, a direct drinking machine, a household full house water purification system and the like. The application in agricultural water treatment may be, for example, agricultural feed water, livestock breeding water purification plants, agricultural sewage/wastewater purification, etc. The industrial water treatment can be applied to the industrial fields such as sea water desalination, hard water softening, industrial sewage/wastewater purification, industrial water supply, reclaimed water recycling, solid-liquid separation, oil-water separation, dye concentration, purification and the like.
The invention has the following beneficial effects:
1. according to the invention, the self-supporting hollow fiber membrane is subjected to pore-protecting treatment in a mode of mixing pore-protecting agent in water phase, and finally is subjected to heat treatment, so that the shrinkage phenomenon of the membrane pores is obviously reduced, the membrane flux can be well maintained, and meanwhile, the influence on interfacial polymerization reaction is small;
2. the glycerol in the pore-protecting agent is a good solvent of polyamine, and can also improve the overall viscosity of the water phase, so that the adhesion of the water phase on the surface of the base film is increased, and the effective rate of interfacial polymerization is improved;
3. according to the invention, the pore-protecting agent is promoted to enter the membrane pores more quickly in a heating circulation disturbance mode, and the membrane pore structure is maintained not to collapse in the subsequent heat treatment process.
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) Preparation of a base film: based on the total mass of the casting solution, adding 72.5% of solvent DMAc into a reaction kettle, heating to 80 ℃, then sequentially adding 18% of Polysulfone (PSF), 5.5% of PVPK30, 2.2% of PEG400 and 1.8% of pure water, uniformly mixing, and transferring to a storage kettle for vacuum defoaming. The casting film liquid is led into a pure water/DMAc (100/0) coagulating tank at 45 ℃ after passing through a spinning jet containing pure water/DMAc (100/0) core liquid, and the nascent fiber film is collected by a winding machine after passing through a rinsing tank at 80 ℃ and is used on a winding drum.
(2) Preparation of nanofiltration membranes: and (3) placing the membrane wire on the winding drum on a constant tension paying-off machine for unwinding, immersing the membrane wire in a water phase solvent circulation tank containing 0.2% of PIP, 20% of glycerol and 2.5% of calcium chloride for 90s, wherein the temperature of the circulation tank is 40 ℃, the circulation flow is 30L/min, then purging by an annular air knife to remove residual water phase liquid drops on the surface of the membrane, immersing the membrane in an IsoPar G solvent containing 0.15% of TMC for 30s, and then carrying out heat treatment on the membrane wire in an oven at 105 ℃ for 90s and winding to obtain a hollow nanofiltration membrane product.
(3) Film wire test: the PSF hollow nanofiltration membrane has a silk flux of 41.3L/m 2 h, a removal rate of 93.6% (test conditions: 0.4MPa,25 ℃,2000ppm MgSO) 4 )。
Example 2
(1) Preparation of a base film: based on the total mass of the casting solution, 68.2% of solvent DMF is added into a reaction kettle to be heated to 80 ℃, then 20% of polyether sulfone (PES), 1.5% of PVPK90, 3.5% of PVPK30, 2.0% of PEG400 and 4.8% of diethylene glycol are sequentially added, and the mixture is transferred into a storage kettle to be defoamed in vacuum after being uniformly mixed. The casting film liquid is led into a pure water/DMF (100/0) coagulating tank at 50 ℃ after passing through a spinneret containing diethylene glycol/DMF (30/70) core liquid, and the nascent fiber film is wound into filaments by a winding machine after passing through a rinsing tank at 75 ℃ and the filaments are used on a winding drum.
(2) Preparation of nanofiltration membranes: and (3) placing the membrane wire on the winding drum on a constant tension paying-off machine for unwinding, immersing the membrane wire in a water phase solvent circulation tank containing 0.5% of PIP and 25% of glycerol for 60s, wherein the temperature of the circulation tank is 45 ℃, the circulation flow is 60L/min, then purging and removing residual water phase liquid drops on the surface of the membrane by an annular air knife, immersing the membrane in an IsoPar E solvent containing 0.22% of TMC for 45s, and carrying out heat treatment on the membrane wire in an oven at 90 ℃ for 80s, and then winding to obtain the hollow nanofiltration membrane product.
(3) Film wire test: PES hollow nanofiltration membrane wire flux is 34.1L/m 2 h, a removal rate of 95.2% (test conditions: 0.4MPa,25 ℃,2000ppm MgSO) 4 )。
Example 3
(1) Preparation of a base film: based on the total mass of the casting solution, 66.8% of solvent NMP is added into a reaction kettle to be heated to 80 ℃, then 19% of PSF, 3.8% of PVPK17, 4.0% of PEG2000 and 6.4% of glycerol are sequentially added, and the mixture is transferred to a storage kettle to be defoamed in vacuum after being uniformly mixed. The casting solution is led into a pure water/NMP (95/5) coagulating tank at 60 ℃ after passing through a spinneret containing glycerol/NMP (25/75) core solution, and the nascent fiber film is wound into filaments by a winding machine after passing through a rinsing tank at 70 ℃ and the filaments are used on a winding drum.
(2) Preparation of nanofiltration membranes: and (3) placing the membrane wire on the winding drum on a constant tension paying-off machine for unwinding, firstly immersing the membrane wire in a water phase solvent circulation tank containing 0.28% of PIP, 15% of glycerol and 7.5% of calcium chloride for 60s, wherein the temperature of the circulation tank is 45 ℃, the circulation flow is 60L/min, then purging by an annular air knife to remove residual water phase liquid drops on the surface of the membrane, immersing the membrane in an IsoPar E solvent containing 0.22% of TMC for 45s, and then carrying out heat treatment on the membrane wire in a baking oven at 100 ℃ for 80s, and then winding to obtain the hollow nanofiltration membrane product.
(3) Film wire test: the PSF hollow nanofiltration membrane silk flux is 52.1L/m 2 h, removal rate of 89.6% (test conditions: 0.4MPa,25 ℃,2000ppm MgSO) 4 )。
An electron microscopic image of the surface of the base film obtained by heat treatment directly without immersing in an oil phase after removing the residual aqueous phase of the film surface according to steps (1) and (2) in example 3 is shown in fig. 1. As can be seen from fig. 1, the membrane pore structure of the base membrane is relatively uniform and intact.
An electron microscopic image of the surface of the base film obtained by following steps (1) and (2) in example 3, but without adding pore-protecting agent glycerin and calcium chloride to the aqueous phase, and directly performing heat treatment without immersing the oil phase after removing the residual aqueous phase on the surface of the film, is shown in fig. 2. As can be seen from comparing fig. 1 and fig. 2, the film pore structure of the base film collapses without adding the pore-protecting agent Kong Jishi, and the film pore is not uniform and the number is significantly reduced.
Comparative example 1
(1) Preparation of a base film: based on the total mass of the casting solution, adding 72.5% of solvent DMAc into a reaction kettle, heating to 80 ℃, then sequentially adding 18% of PSF, 5.5% of PVPK30, 2.2% of PEG400 and 1.8% of pure water, uniformly mixing, and transferring to a storage kettle for vacuum defoaming. The casting film liquid is led into a pure water/DMAc (100/0) coagulating tank at 45 ℃ after passing through a spinning jet containing pure water/DMAc (100/0) core liquid, and the nascent fiber film is collected by a winding machine after passing through a rinsing tank at 80 ℃ and is used on a winding drum.
(2) Preparation of nanofiltration membranes: and (3) placing the membrane wire on the winding drum on a constant tension paying-off machine for unwinding, immersing the membrane wire in a water phase solvent circulation tank containing 0.2% PIP for 90s, wherein the temperature of the circulation tank is 40 ℃, the circulation flow is 30L/min, then purging and removing residual water phase liquid drops on the surface of the membrane by an annular air knife, immersing the membrane in an IsoPar G solvent containing 0.15% TMC for 30s, heat-treating the membrane wire in an oven at 105 ℃ for 90s, and winding to obtain the hollow nanofiltration membrane product.
(3) Film wire test: the PSF hollow nanofiltration membrane silk flux is 19.6L/m 2 h, a removal rate of 85.2% (test conditions: 0.4MPa,25 ℃,2000ppm MgSO) 4 )。
Comparative example 2
(1) Preparation of a base film: based on the total mass of the casting solution, adding 72.5% of solvent DMAc into a reaction kettle, heating to 80 ℃, then sequentially adding 18% of PSF, 5.5% of PVPK30, 2.2% of PEG400 and 1.8% of pure water, uniformly mixing, and transferring to a storage kettle for vacuum defoaming. The casting film liquid is led into a pure water/DMAc (100/0) coagulating tank at 45 ℃ after passing through a spinning jet containing pure water/DMAc (100/0) core liquid, and the nascent fiber film is collected by a winding machine after passing through a rinsing tank at 80 ℃ and is used on a winding drum.
(2) Preparation of nanofiltration membranes: and (3) placing the membrane wire on the winding drum on a constant tension paying-off machine for unwinding, immersing the membrane wire in an aqueous phase solvent tank containing 0.2% of PIP, 20% of glycerol and 2.5% of calcium chloride for 90s, wherein the tank temperature is 25 ℃, no circulation is realized, then purging and removing residual aqueous phase liquid drops on the surface of the membrane by an annular air knife, immersing the membrane in an IsoPar G solvent containing 0.15% of TMC for 30s, and then carrying out heat treatment on the membrane wire in an oven at 105 ℃ for 90s, and then winding to obtain the hollow nanofiltration membrane product.
(3) Film wire test: PSF hollow nanofiltration membrane silk flux is 28.4L/m 2 h, a removal rate of 88.1% (test conditions: 0.4MPa,25 ℃,2000ppm MgSO) 4 )。
Comparative example 3
(1) Preparation of a base film: based on the total mass of the casting solution, adding 72.5% of solvent DMAc into a reaction kettle, heating to 80 ℃, then sequentially adding 18% of PSF, 5.5% of PVPK30, 2.2% of PEG400 and 1.8% of pure water, uniformly mixing, and transferring to a storage kettle for vacuum defoaming. The casting film liquid is led into a pure water/DMAc (100/0) coagulating tank at 45 ℃ after passing through a spinning jet containing pure water/DMAc (100/0) core liquid, and the nascent fiber film is collected by a winding machine after passing through a rinsing tank at 80 ℃ and is used on a winding drum.
(2) Preparation of nanofiltration membranes: and (3) placing the membrane wire on the winding drum on a constant tension paying-off machine for unwinding, immersing the membrane wire in an aqueous phase solvent tank containing 0.2% PIP for 90s, wherein the tank temperature is 25 ℃, no circulation exists, then purging and removing residual aqueous phase liquid drops on the surface of the membrane by an annular air knife, immersing the membrane in an IsoPar G solvent containing 0.15% TMC for 30s, heat-treating the membrane wire in an oven at 105 ℃ for 90s, and winding to obtain the hollow nanofiltration membrane product.
(3) Film wire test: PSF hollow nanofiltration membrane silk flux is 20.5L/m 2 h, removal rate of 83.7% (test conditions: 0.4MPa,25 ℃,2000ppm MgSO) 4 )。
The results of performance tests of the hollow fiber nanofiltration membranes of examples 1 to 3 and comparative examples 1 to 3 are shown in Table 1.
Table 1: performance of the hollow fiber nanofiltration membranes of examples 1 to 3 and comparative examples 1 to 3 (test conditions: 0.4MPa,25 ℃,2000ppm MgSO) 4 )
As can be seen from Table 1, the hollow fiber nanofiltration membrane prepared by the method of the invention has high flux and removal rate. Comparative example 1 differs from example 1 in that the aqueous phase does not contain a pore-protecting agent, and comparative example 2 differs from example 1 in that no heating cycle is used when the aqueous phase is immersed, and as a result, it is shown that the flux and removal rate of nanofiltration membranes of comparative examples 1 and 2 are inferior to those of example 1. Comparative example 3 used a conventional process in which the aqueous phase contained no pore-protecting agent and no heating cycle was used. The results showed that the throughput and removal rate of comparative example 1 were substantially unchanged compared to comparative example 3, and the throughput and removal rate of comparative example 2 were slightly improved (by about 38% and 5%, respectively), and the throughput and removal rate of example 1 were very excellent (by about 100% and 12%, respectively). The above results reflect that the present invention effectively protects the membrane pore structure of the ultrafiltration base membrane and the integrity of the polyamide separation layer during the drying process by using a pore-protecting agent in combination with a heating cycle, and indicate that the addition of both the pore-protecting agent and the heating cycle has a synergistic effect in improving the flux and removal rate of the nanofiltration membrane.
Claims (10)
1. A method of making a hollow nanofiltration membrane, the method comprising: soaking the hollow fiber base membrane by using an aqueous phase solution containing amine monomers and a pore-protecting agent under cyclic heating, carrying out contact reaction on the membrane and an oil phase solution containing acyl chloride monomers after the soaking treatment is finished, and then carrying out heat treatment to obtain the hollow nanofiltration membrane; wherein the pore-protecting agent comprises glycerin and optionally calcium chloride;
in the aqueous phase solution, the mass of the pore-protecting agent is 5-40% of the total mass of the aqueous phase solution, the mass of the glycerol is 5-30% of the total mass of the aqueous phase solution, and the mass of the calcium chloride is 0-15% of the total mass of the aqueous phase solution;
when the hollow fiber base membrane is soaked by using the aqueous phase solution, the residence time of the hollow fiber base membrane in the aqueous phase solution is 30-150s, the temperature of the aqueous phase solution is 30-50 ℃, and the circulation amount of the aqueous phase solution is 20-100L/min;
the amine monomer is piperazine;
the acyl chloride monomer is selected from one or two of trimesoyl chloride and isophthaloyl chloride;
the hollow fiber base membrane is made of one or two selected from polysulfone and polyethersulfone.
2. The method of claim 1, wherein the mass of glycerol in the aqueous solution is 15-25% of the total mass of the aqueous solution.
3. The method of claim 1, wherein the mass of calcium chloride in the aqueous solution is 2-10% of the total mass of the aqueous solution.
4. The method of claim 1, wherein the method has one or more of the following features:
in the aqueous phase solution, the mass of the amine monomer is 0.15-2% of the total mass of the aqueous phase solution;
in the oil phase solution, the mass of the acyl chloride monomer is 0.05-0.5% of the total mass of the oil phase solution;
the solvent of the oil phase solution is isoparaffin;
the contact time of the membrane and the oil phase solution containing the acyl chloride monomer is 20-120s;
the heat treatment temperature is 80-120 deg.C, and the heat treatment time is 30-150s.
5. The method of claim 1, wherein,
the hollow fiber base membrane is a hollow fiber ultrafiltration membrane; and/or
The hollow fiber base membrane is prepared by spinning casting solution and core solution, solidifying by coagulating bath solution and rinsing.
6. The method of claim 5, wherein the method has one or more of the following features:
the casting film liquid comprises a high molecular polymer, a high molecular pore-forming agent, a non-solvent and a solvent;
the core liquid comprises a non-solvent and optionally a solvent;
the coagulation bath includes a non-solvent and optionally a solvent.
7. The method of claim 6, wherein the method has one or more of the following features:
the high molecular polymer is selected from one or two of polysulfone and polyethersulfone;
the high molecular pore-forming agent is one or two selected from polyethylene glycol and polyvinylpyrrolidone;
the non-solvent is selected from one or more of water, ethanol, glycerol and diethylene glycol;
the solvent is selected from one or more of dimethylformamide, dimethylacetamide and N-methylpyrrolidone;
the casting film liquid comprises, by weight, 15-30% of high molecular polymer, 1-10% of high molecular pore-forming agent, 0.8-12.5% of non-solvent and 55-82% of solvent;
the content of the non-solvent in the core liquid is 20-100wt% based on the total mass of the core liquid;
the non-solvent content in the coagulation bath is 80-100wt% based on the total mass of the coagulation bath.
8. Use of a pore protecting agent in the preparation of a hollow nanofiltration membrane with improved stability of the pore structure of the hollow fiber-based membrane and improved integrity of the polyamide separation layer, characterized in that the use comprises: soaking the hollow fiber base membrane by using an aqueous phase solution containing amine monomers and a pore-protecting agent under cyclic heating, carrying out contact reaction on the membrane and an oil phase solution containing acyl chloride monomers after the soaking treatment is finished, and then carrying out heat treatment to obtain the hollow nanofiltration membrane; wherein the pore-protecting agent comprises glycerin and optionally calcium chloride;
in the aqueous phase solution, the mass of the pore-protecting agent is 5-40% of the total mass of the aqueous phase solution, the mass of the glycerol is 5-30% of the total mass of the aqueous phase solution, and the mass of the calcium chloride is 0-15% of the total mass of the aqueous phase solution;
when the hollow fiber base membrane is soaked by using an aqueous phase solution, the residence time of the hollow fiber base membrane in the aqueous phase solution is 30-150s, the circulation amount of the aqueous phase solution is 20-100L/min, and the temperature of the aqueous phase solution is 30-50 ℃;
the amine monomer is piperazine;
the acyl chloride monomer is selected from one or two of trimesoyl chloride and isophthaloyl chloride;
the hollow fiber base membrane is made of one or two selected from polysulfone and polyethersulfone.
9. The use according to claim 8, wherein the mass of glycerol in the aqueous solution is 15-25% of the total mass of the aqueous solution.
10. The use according to claim 8, wherein the mass of calcium chloride in the aqueous solution is 2-10% of the total mass of the aqueous solution.
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