CN115364680B - Alkali-resistant nanofiltration membrane and preparation method and application thereof - Google Patents
Alkali-resistant nanofiltration membrane and preparation method and application thereof Download PDFInfo
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- 239000012528 membrane Substances 0.000 title claims abstract description 74
- 238000001728 nano-filtration Methods 0.000 title claims abstract description 48
- 239000003513 alkali Substances 0.000 title claims abstract description 42
- 238000002360 preparation method Methods 0.000 title claims abstract description 17
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 37
- 229920005610 lignin Polymers 0.000 claims abstract description 29
- 238000003756 stirring Methods 0.000 claims description 20
- GLUUGHFHXGJENI-UHFFFAOYSA-N Piperazine Chemical compound C1CNCCN1 GLUUGHFHXGJENI-UHFFFAOYSA-N 0.000 claims description 18
- 239000000243 solution Substances 0.000 claims description 17
- 238000005303 weighing Methods 0.000 claims description 16
- 239000012670 alkaline solution Substances 0.000 claims description 13
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 claims description 13
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 claims description 11
- 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
- 229910052938 sodium sulfate Inorganic materials 0.000 claims description 11
- 235000011152 sodium sulphate Nutrition 0.000 claims description 11
- 238000009210 therapy by ultrasound Methods 0.000 claims description 9
- 239000003960 organic solvent Substances 0.000 claims description 8
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 claims description 7
- 238000005266 casting Methods 0.000 claims description 7
- IAZDPXIOMUYVGZ-UHFFFAOYSA-N Dimethylsulphoxide Chemical compound CS(C)=O IAZDPXIOMUYVGZ-UHFFFAOYSA-N 0.000 claims description 6
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 claims description 6
- 239000011259 mixed solution Substances 0.000 claims description 6
- 239000000654 additive Substances 0.000 claims description 5
- 230000000996 additive effect Effects 0.000 claims description 5
- 239000004745 nonwoven fabric Substances 0.000 claims description 5
- 229920000642 polymer Polymers 0.000 claims description 5
- 239000004695 Polyether sulfone Substances 0.000 claims description 4
- 239000008367 deionised water Substances 0.000 claims description 4
- 229910021641 deionized water Inorganic materials 0.000 claims description 4
- 239000011521 glass Substances 0.000 claims description 4
- 238000000034 method Methods 0.000 claims description 4
- 239000002245 particle Substances 0.000 claims description 4
- 229920006393 polyether sulfone Polymers 0.000 claims description 4
- FXHOOIRPVKKKFG-UHFFFAOYSA-N N,N-Dimethylacetamide Chemical compound CN(C)C(C)=O FXHOOIRPVKKKFG-UHFFFAOYSA-N 0.000 claims description 3
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 claims description 3
- 238000001035 drying Methods 0.000 claims description 3
- 239000002033 PVDF binder Substances 0.000 claims description 2
- 239000004693 Polybenzimidazole Substances 0.000 claims description 2
- 239000002202 Polyethylene glycol Substances 0.000 claims description 2
- 239000004642 Polyimide Substances 0.000 claims description 2
- 239000004372 Polyvinyl alcohol Substances 0.000 claims description 2
- 239000004760 aramid Substances 0.000 claims description 2
- 229920003235 aromatic polyamide Polymers 0.000 claims description 2
- 230000015572 biosynthetic process Effects 0.000 claims description 2
- 230000008859 change Effects 0.000 claims description 2
- 238000010438 heat treatment Methods 0.000 claims description 2
- 230000014759 maintenance of location Effects 0.000 claims description 2
- 229920002492 poly(sulfone) Polymers 0.000 claims description 2
- 229920002239 polyacrylonitrile Polymers 0.000 claims description 2
- 229920002480 polybenzimidazole Polymers 0.000 claims description 2
- 229920001223 polyethylene glycol Polymers 0.000 claims description 2
- 229920001721 polyimide Polymers 0.000 claims description 2
- 229920013636 polyphenyl ether polymer Polymers 0.000 claims description 2
- 229920002451 polyvinyl alcohol Polymers 0.000 claims description 2
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 2
- 229920000036 polyvinylpyrrolidone Polymers 0.000 claims description 2
- 239000001267 polyvinylpyrrolidone Substances 0.000 claims description 2
- 235000013855 polyvinylpyrrolidone Nutrition 0.000 claims description 2
- 238000001556 precipitation Methods 0.000 claims description 2
- 238000007790 scraping Methods 0.000 claims description 2
- 230000003068 static effect Effects 0.000 claims description 2
- 238000004321 preservation Methods 0.000 claims 1
- 239000004952 Polyamide Substances 0.000 abstract description 18
- 229920002647 polyamide Polymers 0.000 abstract description 18
- 125000002887 hydroxy group Chemical group [H]O* 0.000 abstract description 3
- 125000003277 amino group Chemical group 0.000 abstract description 2
- 230000004888 barrier function Effects 0.000 abstract description 2
- 229910052739 hydrogen Inorganic materials 0.000 abstract description 2
- 239000001257 hydrogen Substances 0.000 abstract description 2
- 230000007062 hydrolysis Effects 0.000 abstract description 2
- 238000006460 hydrolysis reaction Methods 0.000 abstract description 2
- 239000012071 phase Substances 0.000 description 42
- 230000004907 flux Effects 0.000 description 13
- 238000000926 separation method Methods 0.000 description 10
- 239000002351 wastewater Substances 0.000 description 6
- 239000012456 homogeneous solution Substances 0.000 description 5
- 239000008346 aqueous phase Substances 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- RPNUMPOLZDHAAY-UHFFFAOYSA-N Diethylenetriamine Chemical compound NCCNCCN RPNUMPOLZDHAAY-UHFFFAOYSA-N 0.000 description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 239000011148 porous material Substances 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- IKHGUXGNUITLKF-UHFFFAOYSA-N Acetaldehyde Chemical compound CC=O IKHGUXGNUITLKF-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- 238000004833 X-ray photoelectron spectroscopy Methods 0.000 description 2
- 238000005904 alkaline hydrolysis reaction Methods 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000004090 dissolution Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 230000007774 longterm Effects 0.000 description 2
- 229920005597 polymer membrane Polymers 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 238000002791 soaking Methods 0.000 description 2
- 238000003828 vacuum filtration Methods 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 238000004566 IR spectroscopy Methods 0.000 description 1
- 229920000877 Melamine resin Polymers 0.000 description 1
- 229920002396 Polyurea Polymers 0.000 description 1
- 238000000026 X-ray photoelectron spectrum Methods 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 238000005576 amination reaction Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 235000013361 beverage Nutrition 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 238000004132 cross linking Methods 0.000 description 1
- 239000004643 cyanate ester Substances 0.000 description 1
- 150000001913 cyanates Chemical class 0.000 description 1
- 230000002354 daily effect Effects 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- 238000010612 desalination reaction Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 230000003203 everyday effect Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000012065 filter cake Substances 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 229920002521 macromolecule Polymers 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- JDSHMPZPIAZGSV-UHFFFAOYSA-N melamine Chemical compound NC1=NC(N)=NC(N)=N1 JDSHMPZPIAZGSV-UHFFFAOYSA-N 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- 238000001000 micrograph Methods 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 235000015097 nutrients Nutrition 0.000 description 1
- 238000006116 polymerization reaction Methods 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000012827 research and development Methods 0.000 description 1
- 238000012216 screening Methods 0.000 description 1
- 239000013535 sea water Substances 0.000 description 1
- 239000010865 sewage Substances 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 239000006228 supernatant Substances 0.000 description 1
- 230000001988 toxicity Effects 0.000 description 1
- 231100000419 toxicity Toxicity 0.000 description 1
- 239000002023 wood Substances 0.000 description 1
Classifications
-
- 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
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
- B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
- B01D61/027—Nanofiltration
-
- 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
- B01D69/10—Supported membranes; Membrane supports
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2325/00—Details relating to properties of membranes
- B01D2325/22—Thermal or heat-resistance properties
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2325/00—Details relating to properties of membranes
- B01D2325/30—Chemical resistance
-
- 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)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Nanotechnology (AREA)
- Water Supply & Treatment (AREA)
- Manufacturing & Machinery (AREA)
- Separation Using Semi-Permeable Membranes (AREA)
Abstract
The invention discloses an alkali-resistant nanofiltration membrane, a preparation method and application thereof, wherein aminated lignin is added in a water phase, and the lignin contains a large amount of hydroxyl groups, so that hydrogen bonds are easily formed between the lignin and polyamide, amino groups and the like or between the lignin and the polyamide, thereby improving the heat stability of the integral polyamide, increasing the energy barrier of alkali hydrolysis and improving the alkali resistance of the integral polyamide.
Description
Technical Field
The invention belongs to the technical field of membrane separation, and particularly relates to an alkali-resistant nanofiltration membrane and a preparation method thereof.
Background
The continuous development of modern chemical industry, food industry, beverage industry and pharmaceutical industry generates a large amount of wastewater, and the wastewater needs to be further treated to be discharged, and meanwhile, the wastewater contains partial nutrient components or metal ions and needs to be recycled. The membrane separation technology is a modern separation technology based on one or more of pore size screening, dielectric repulsion and steric hindrance as a main separation mechanism, and has received wide attention due to low cost, high efficiency and environmental friendliness.
Nanofiltration membranes are important separation membranes in water treatment, and are widely applied to sea water desalination, dye industry and multi-salt wastewater due to their excellent separation performance. In many productions, a certain amount of alkali is required to adjust the alkalinity, so that the alkalinity of the discharged wastewater is extremely high, which requires that the separation membrane has a certain alkali resistance. The traditional nanofiltration membrane selection layer mainly consists of polyamide, the operation pH is generally below 12, and the nanofiltration membrane is easy to be subjected to alkaline hydrolysis under the highly alkaline condition, and the carbon-based skeleton structure is damaged, so that the separation performance is reduced, so that the research and development of the alkaline-resistant polyamide nanofiltration membrane has great significance and wide application prospect;
The pure polyamide structure has insufficient alkali resistance, so that the problem of low treatment efficiency exists when the polyamide is applied to complex alkaline wastewater. Therefore, other alkali-resistant materials need to be applied to prepare nanofiltration membrane selection layers for application in complex alkaline water systems. In recent years, researchers prepare acid and alkali resistant nanofiltration membranes by using cyanate esters, melamine, polyurea and other substances, and can still maintain excellent stability under long-term operation. However, in the process of using the materials with stronger toxicity, the problem of incomplete reaction is difficult to avoid, the materials are embedded in the membrane and possibly fall off from the membrane along with the time, flow into water quality, and cause secondary pollution to the water quality.
Disclosure of Invention
This section is intended to outline some aspects of embodiments of the application and to briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section as well as in the description of the application and in the title of the application, which may not be used to limit the scope of the application.
The present invention has been made in view of the above and/or problems occurring in the prior art.
Therefore, the invention aims to overcome the defects in the prior art and provide the alkali-resistant nanofiltration membrane.
In order to solve the technical problems, the invention provides the following technical scheme: the separating layer of the nanofiltration membrane has a bubble structure and long-term alkali resistance, and the supporting layer is a pure high-molecular porous polymer membrane or a high-molecular porous polymer membrane lined by non-woven fabrics.
As a preferable scheme of the alkali-resistant nanofiltration membrane, the alkali-resistant nanofiltration membrane comprises the following components: the nanofiltration membrane is characterized in that the main body of the nanofiltration membrane is nano aminated lignin particles, and the nano aminated lignin particles are crosslinked by a compact polyamide layer, so that the separation layer structure is more compact and stable. The pore size is less than 100nm, preferably less than 50nm, more preferably less than 10nm.
As a preferable scheme of the alkali-resistant nanofiltration membrane, the alkali-resistant nanofiltration membrane comprises the following components: the alkali-resistant filter membrane can stably run for more than 168 hours under the condition of pH 13.
The invention further aims to overcome the defects in the prior art and provide a preparation method of the alkali-resistant nanofiltration membrane.
In order to solve the technical problems, the invention provides the following technical scheme: dissolving a high molecular polymer and a pore-forming additive in an organic solvent according to a certain proportion, heating and stirring to form a homogeneous mixed solution, namely casting film solution; after static defoaming (12-24 h) treatment of the casting solution, scraping the casting solution on a glass plate or non-woven fabric by using a micron-sized scraper, wherein the non-woven fabric is required to be tiled and fixed on the glass plate, stays in air for 0-30 s, and then is immersed in deionized water for phase change film formation for 3-5 min to form a supporting layer; adding a certain amount of piperazine into an alkaline solution (pH is 10-12) of amination wood to form a homogeneous solution, namely a water phase; a certain amount of trimesic acid chloride (TMC) is dissolved in normal hexane to form a homogeneous solution, namely an oil phase; immersing the supporting layer which is wiped by dust-free paper into the water phase for a certain time, taking out the supporting layer, and drying superfluous water drops on the surface by a blower; and finally pouring a certain amount of oil phase into the support layer immersed in the water phase, taking out the membrane after a certain time, and immersing the membrane into deionized water for storage after the surface organic solvent is volatilized.
As a preferable scheme of the preparation method of the alkali-resistant nanofiltration membrane, the invention comprises the following steps: the casting solution is a homogeneous solution formed by a high molecular polymer, a pore-forming additive and an organic solvent; or a homogeneous solution formed by high molecular polymerization and an organic solvent, wherein the dissolution temperature is 60-90 ℃ and the time is 12-24 h.
As a preferable scheme of the preparation method of the alkali-resistant nanofiltration membrane, the invention comprises the following steps: the high polymer is one or more of polyethersulfone, polysulfone, polyacrylonitrile, polyimide, polybenzimidazole, polyphenyl ether, aromatic polyamide, polyvinylidene fluoride and the like; the pore-forming additive is one or more of polyvinylpyrrolidone, polyethylene glycol, polyvinyl alcohol, glycerol and the like; the organic solvent is one or more of N, N-Dimethylformamide (DMF), N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), etc.
As a preferable scheme of the preparation method of the alkali-resistant nanofiltration membrane, the invention comprises the following steps: the thickness of the scraper is one of 50 μm, 100 μm, 150 μm and 250 μm; the supporting layer has certain interception to partial macromolecular substances
As a preferable scheme of the preparation method of the alkali-resistant nanofiltration membrane, the invention comprises the following steps: preparation of the aqueous phase: dissolving aminated lignin and piperazine in an alkali solution with pH of 12, magnetically stirring for 1-3 h, and then carrying out ultrasonic treatment for 1-2 h;
preparation of an oil phase: dissolving trimesic acid chloride in normal hexane, and magnetically stirring for 1-3 h to form a homogeneous solution; pouring the water phase onto the supporting layer for 2min; pouring the oil phase onto the support layer for a residence time of 1min
It is a further object of the present invention to overcome the deficiencies of the prior art and to provide an application of an alkali resistant nanofiltration membrane.
In order to solve the technical problems, the invention provides the following technical scheme: application of nanofiltration membrane in food industry, chemical industry, sewage treatment or biochemical industry
The invention has the beneficial effects that:
(1) According to the invention, aminated lignin is added into the aqueous phase, and a large amount of hydroxyl groups are contained in the lignin, so that hydrogen bonds are easily formed between the lignin and polyamide, amino groups and the like or between the lignin and the polyamide, the thermal stability of the whole polyamide is improved, the energy barrier of alkaline hydrolysis is increased, and the alkali resistance of the polyamide is improved.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the description of the embodiments will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art. Wherein:
FIG. 1 is an X-ray photoelectron spectrum of aminated lignin prepared in example 3 of the present invention and lignin as a raw material.
FIG. 2 is an infrared total reflection spectrum of the films prepared in examples 1, 2, and 3 of the present invention and pure PES film.
FIG. 3 is a graph showing changes in flux and sodium sulfate retention when nanofiltration membranes prepared in examples 1 and 3 of the present invention were immersed for eight days at pH 13.
FIG. 4 is a front scanning electron microscope image of the nanofiltration membrane prepared in example 3 of the present invention.
Detailed Description
In order that the above-recited objects, features and advantages of the present invention will become more apparent, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced in other ways other than those described herein, and persons skilled in the art will readily appreciate that the present invention is not limited to the specific embodiments disclosed below.
Further, reference herein to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic can be included in at least one implementation of the invention. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments.
Example 1
Weighing 0.5g of piperazine, dissolving in 50g of alkaline solution (pH 12), magnetically stirring for 1h, and performing ultrasonic treatment for 1.5h to prepare an aqueous phase; weighing 0.05g TMC to dissolve in 50g normal hexane, stirring for 1h to dissolve completely, and preparing an oil phase for later use;
Firstly pouring the water phase into the supporting layer, standing for 2min, taking out the membrane, sucking the redundant water phase by using dust-free paper, then pouring a certain oil phase into the supporting layer, standing for 1min, taking out the membrane, naturally airing, and completing the alkali-resistant nanofiltration preparation.
And (3) performing alkali resistance test on the prepared nanofiltration membrane under the condition of pH 13. As in M0 in FIG. 3, it was found that the first and second days were respectively 6.2 and 8.0LMH/bar, and the third day was as high as 35LMH/bar, with a corresponding sodium sulfate cut-off of 95% to 8% from the original, indicating that the surface polyamide structure was severely damaged.
Example 2
Weighing 0.5g of aminated lignin, dissolving in 50g of alkaline solution (pH 12), magnetically stirring for 1h, and performing ultrasonic treatment for 1.5h to prepare an aqueous phase; weighing 0.05g TMC to dissolve in 50g normal hexane, stirring for 1h to dissolve completely, and preparing an oil phase for later use;
Firstly pouring the water phase into the supporting layer, standing for 2min, taking out the membrane, sucking the redundant water phase by using dust-free paper, then pouring a certain oil phase into the supporting layer, standing for 1min, taking out the membrane, naturally airing, and completing the alkali-resistant nanofiltration preparation.
The flux and interception of sodium sulfate are measured by the prepared nanofiltration membrane, and the flux is up to 353LMH/bar, and the interception of sodium sulfate is 0%. In comparison with the pure PES-based membrane, the flux was only slightly varied, indicating that the surface was not sufficiently polyamide to form a dense separation layer.
Example 3
The invention provides a preparation method of an alkali-resistant nanofiltration membrane, which comprises the following steps:
(1) Preparation of aminated lignin: 5g of dealkalized lignin is weighed and dissolved in 50ml of 0.4mol/l sodium hydroxide, and the solution is heated and dissolved in an oil bath so that the solution is dark black and has no precipitate, and then 2ml of Diethylenetriamine (DETA) is added for continuous dissolution for 30min. After the oil bath temperature was stabilized and dissolved at 90℃for 10 minutes, 2ml of an acetaldehyde solution (37%) was gradually injected by a dropping method using a syringe, the reaction solution was taken out after 4 to 6 hours of reaction, cooled to room temperature, pH was adjusted to a brown color (pH 3 to 5) with HCl, and after standing to precipitate the reaction solution until a supernatant liquid appeared, vacuum filtration was performed, and the pore diameter of the filter paper was 0.4. Mu.m. And the cake layer was washed three times with deionized and ethanol to remove excess DETA and other soluble impurities. And taking out the filter cake and drying (60 ℃) for 12 hours after the vacuum filtration is finished, and standing by.
(2) Weighing 0.25g of aminated lignin and 0.75g of piperazine, dissolving in 50g of alkaline solution (pH 12), magnetically stirring for 1h, and performing ultrasonic treatment for 1.5h until no particle precipitation occurs, and preparing into a water phase; weighing 0.05g TMC to dissolve in 50g normal hexane, stirring for 1h to dissolve completely, and preparing an oil phase for later use;
(3) Firstly pouring the water phase into the supporting layer, standing for 2min, taking out the membrane, sucking the redundant water phase by using dust-free paper, then pouring a certain oil phase into the supporting layer, standing for 1min, taking out the membrane, naturally airing, and completing the alkali-resistant nanofiltration preparation.
The calculation formula of the membrane flux (J) is as follows: j=v/(t×a); wherein J- -membrane flux (ml/cm 2. Multidot.s); v- -sample volume (ml); t- -sample time(s); a- -membrane effective area (cm 2);
As can be seen from fig. 1, the prepared aminated lignin powder was subjected to X-ray photoelectron spectroscopy (XPS) analysis with dealkalized lignin, and a peak of nitrogen element (at 400 eV) was found to be 5% in the powder; the nanofiltration membrane prepared was subjected to infrared spectroscopy (model Nicolet iS 50) analysis, and found to have a characteristic peak at 3670cm -1, which iS a characteristic peak for hydroxyl groups, and a peak at 1640cm -1, which iS a characteristic peak for polyamide, indicating the presence of a polyamide structure and successful crosslinking into aminated lignin (fig. 2); the prepared nanofiltration membrane is subjected to alkali resistance experiment tests, as shown in M1 in FIG. 3, and after being soaked for eight days under the condition of pH 13, the flux is 7.0LMH/bar, and the interception of sodium sulfate is maintained at 90%, which shows that the crosslinked polyamide structure can still be kept relatively intact without serious damage caused by alkali hydrolysis.
Example 4
The aminated lignin was prepared in the same manner as in example 3.
Weighing 0.125g of aminated lignin and 0.5g of piperazine, dissolving in 50g of alkaline solution (pH 12), magnetically stirring for 1h, and then performing ultrasonic treatment for 1.5h to completely homogenize the mixed solution to prepare a water phase; weighing 0.05g of TMC, dissolving in 50g of n-hexane, stirring for 1h, and preparing an oil phase for later use;
Pouring the water phase onto the supporting layer, standing for 2min, taking out the membrane, sucking the excessive water phase with dust-free paper, pouring a certain oil phase onto the supporting layer, standing for 1min, taking out the membrane, and naturally airing to prepare the alkali-resistant nanofiltration membrane.
The prepared nanofiltration membrane is soaked in an alkaline solution with pH of 13 for 7 days, and the interception and flux conditions of the test membrane to 1000ppm sodium sulfate are observed every day. The results of the test found that the flux of the membrane was 9.2LMH/bar at day seven, with a rejection of 89% for sodium sulfate.
Example 5
The aminated lignin was prepared in the same manner as in example 3.
Weighing 0.25g of aminated lignin and 0.5g of piperazine, dissolving in 50g of alkaline solution (pH 12), magnetically stirring for 1h, and then performing ultrasonic treatment for 1.5h to completely homogenize the mixed solution to prepare a water phase; weighing 0.05g TMC, dissolving in 50g normal hexane, stirring for 1h, and preparing an oil phase for later use;
Pouring the water phase onto the supporting layer, standing for 2min, taking out the membrane, sucking the excessive water phase with dust-free paper, pouring a certain oil phase onto the supporting layer, standing for 1min, taking out the membrane, naturally airing, and preparing the alkali-resistant nanofiltration.
The nanofiltration membrane was prepared in an alkaline solution at pH 13 and the membrane was tested daily for flux and rejection of 1000ppm sodium sulfate, the results showed: the flux was varied from 6.7LMH/bar on the first day to 7.2LMH/bar on the seventh day, with the rejection varying from 95% to 90%.
Example 6
The aminated lignin was prepared in the same manner as in example 3.
Weighing 0.375g of aminated lignin and 0.5g of piperazine, dissolving in 50g of alkaline solution (pH 12), magnetically stirring for 1h, and then performing ultrasonic treatment for 1.5h to completely homogenize the mixed solution to prepare a water phase; weighing 0.05g TMC, dissolving in n-hexane, stirring for 1h, and preparing an oil phase for later use;
Pouring the water phase onto the supporting layer, standing for 2min, taking out the membrane, sucking the excessive water phase with dust-free paper, pouring a certain oil phase onto the supporting layer, standing for 1min, taking out the membrane, naturally airing, and preparing the alkali-resistant nanofiltration. The flux of the nanofiltration membrane was measured to vary from 5.8LMH/bar to 6.7LMH/bar for the seventh day, and the rejection of 1000ppm sodium sulfate was measured to vary from 92% to 89% by soaking in an alkaline solution at pH 13 for seven days.
Example 7
The aminated lignin was prepared in the same manner as in example 3.
Weighing 0.5g of aminated lignin and 0.5g of piperazine, dissolving in 50g of alkaline solution (pH 12), magnetically stirring for 1h, and then performing ultrasonic treatment for 1.5h to completely homogenize the mixed solution to prepare a water phase; weighing 0.05g TMC, dissolving in 50g normal hexane, stirring for 1h, and preparing an oil phase for later use;
Pouring the water phase onto the supporting layer, standing for 2min, taking out the membrane, sucking the excessive water phase with dust-free paper, pouring a certain oil phase onto the supporting layer, standing for 1min, taking out the membrane, naturally airing, and preparing the alkali-resistant nanofiltration. The flux of the nanofiltration membrane was measured to vary from 6.7LMH/bar to 6.9LMH/bar for the seventh day, with a rejection of 1000ppm sodium sulfate ranging from 93% to 88% by soaking in an alkaline solution at pH 13 for seven days.
It should be noted that the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the same, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solution of the present invention may be modified or substituted without departing from the spirit and scope of the technical solution of the present invention, which is intended to be covered in the scope of the claims of the present invention.
Claims (3)
1. The preparation method of the alkali-resistant nanofiltration membrane is characterized by comprising the following steps of:
dissolving a high molecular polymer and a pore-forming additive in an organic solvent according to a certain amount, heating and stirring to form a homogeneous mixed solution, namely a casting solution;
After the static defoaming treatment of the casting solution for 12-24 hours, scraping the casting solution on a glass plate or non-woven fabric by using a micron-sized scraper, wherein the non-woven fabric is required to be tiled and fixed on the glass plate, stays in air for 0-30 seconds, then is immersed in deionized water for phase change film formation for 3-5 minutes, and forms a supporting layer;
weighing 0.25g of aminated lignin and 0.75g of piperazine, dissolving in 50g of alkaline solution with pH of 12, magnetically stirring for 1h, and performing ultrasonic treatment for 1.5h until no particle precipitation occurs, and preparing into a water phase;
weighing 0.05g of trimesic acid chloride, dissolving in 50g of n-hexane, stirring for 1h to dissolve completely, and preparing an oil phase for later use;
immersing the supporting layer which is wiped by dust-free paper into the water phase for a certain time, taking out the supporting layer, and drying superfluous water drops on the surface by a blower;
finally pouring a certain amount of oil phase into the support layer immersed in the water phase, taking out the membrane after a certain time, immersing the membrane into deionized water for preservation after the surface organic solvent is volatilized, and obtaining the alkali-resistant nanofiltration membrane;
wherein, the alkali-resistant nanofiltration membrane can stably run for more than 168 hours under the condition of pH 13, and the retention rate of sodium sulfate is maintained at 90 percent.
2. The method for preparing the alkali-resistant nanofiltration membrane according to claim 1, comprising the following steps: the high polymer is one or more of polyethersulfone, polysulfone, polyacrylonitrile, polyimide, polybenzimidazole, polyphenyl ether, aromatic polyamide and polyvinylidene fluoride; the pore-forming additive is one or more of polyvinylpyrrolidone, polyethylene glycol, polyvinyl alcohol and glycerol; the organic solvent is one or more of N, N-dimethylformamide, N-dimethylacetamide, N-methylpyrrolidone and dimethyl sulfoxide.
3. The method for preparing the alkali-resistant nanofiltration membrane according to claim 1, comprising the following steps: the thickness of the scraper is one of 50 μm, 100 μm, 150 μm and 250 μm.
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