CN115382402B - Preparation method of composite membrane material - Google Patents

Preparation method of composite membrane material Download PDF

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CN115382402B
CN115382402B CN202110564744.6A CN202110564744A CN115382402B CN 115382402 B CN115382402 B CN 115382402B CN 202110564744 A CN202110564744 A CN 202110564744A CN 115382402 B CN115382402 B CN 115382402B
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solution
linking agent
membrane
polymer
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CN115382402A (en
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杜润红
杜发鑫
杜春良
闫伟
赵相山
洋汉军
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Tianjin Polytechnic University
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    • 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
    • B01D69/12—Composite membranes; Ultra-thin membranes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/22—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by diffusion
    • B01D53/228—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by diffusion characterised by specific membranes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/26—Drying gases or vapours
    • B01D53/268—Drying gases or vapours by diffusion
    • 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
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/36—Pervaporation; Membrane distillation; Liquid permeation
    • B01D61/362—Pervaporation
    • 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
    • B01D2257/00—Components to be removed
    • B01D2257/50—Carbon oxides
    • B01D2257/504—Carbon dioxide
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
    • B01D2257/80—Water
    • 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

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Water Supply & Treatment (AREA)
  • Nanotechnology (AREA)
  • Analytical Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Manufacturing & Machinery (AREA)
  • Separation Using Semi-Permeable Membranes (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Abstract

The invention provides a preparation method of a composite membrane material, which comprises the following steps: (1) Preparing a polymer containing tertiary amine groups and/or pyridine groups into a polymer solution; (2) Preparing a cross-linking agent into a cross-linking agent solution with the mass fraction of 0.01-2%; the cross-linking agent is selected from more than two halogenated olefins or more than two halogenated aromatic hydrocarbons; the halogenation is bromo and/or iodo; (3) Using an ultrafiltration membrane as a base membrane, transferring the prepared polymer solution onto the base membrane, and drying; and (3) contacting the dried film with a cross-linking agent solution for 0.5-30min, and drying to obtain the composite film material. The invention selects high-activity polybasic bromohydrocarbon or iodohydrocarbon as the cross-linking agent, can improve the reaction speed of tertiary amino and/or pyridine groups and halogenated hydrocarbon, greatly shortens the cross-linking time for preparing the film and improves the preparation efficiency of the composite film material.

Description

Preparation method of composite membrane material
Technical Field
The invention relates to a preparation method of a composite membrane material, and belongs to the technical field of preparation of polymer membrane materials.
Background
Nanofiltration membranes as a pressure-driven membrane have a separation layer with a pore size of 0.5-2nm and are charged, which makes it possible to have a relatively complex separation mechanism (including size sieving and charge rejection), and thus have many applications in dye removal, brine desalination, wastewater treatment, and drug purificationHas wide application. Negatively charged nanofiltration membranes are effective in trapping multivalent anions (SO 4 2- 、PO 4 3- 、CO 3 2- Etc.), anionic dyes, etc. negatively charged low molecular weight molecules; while positively charged nanofiltration membranes are more effective in trapping multivalent cations (Ca 2+ 、Mg 2+ 、Cr 3+ Etc.), cationic dyes, etc. positively charged low molecular weight molecules. Most commercial or literature reported nanofiltration membranes are usually negatively charged due to limitations of the preparation method or material, and their rejection of multivalent cations is poor. There is therefore an urgent need to develop positively charged nanofiltration membranes with excellent separation properties, which are of great importance for expanding the application of nanofiltration membranes.
The polymethyl methacrylate (PDMAEMA) is a water-soluble polymer which is easy to form a film, and tertiary amino in a molecular side chain of the polymer can be subjected to quaternization reaction with halogenated hydrocarbon to be converted into positively charged quaternary amino. When the halogenated hydrocarbon contains multiple reactive groups, the PDMAEMA can be crosslinked by a quaternization reaction.
Du et al first coated a Polysulfone (PSF) support layer with a 2% aqueous solution of PDMAEMA, dried for 30min, then immersed in a 0.5% p-dichlorobenzyl/n-heptane solution for 5h, and interface crosslinked at room temperature to prepare a positively charged nanofiltration membrane. However, this preparation process has a crosslinking time as long as 5h [ ref: properties of poly (N, N-dimethylaminoethyl methacrylate)/polysulfone positively charged composite nanofiltration membrane, journal of membrane science,2004,239 (2): 183-188 ].
Zhang et al prepared positively charged hollow fiber nanofiltration membranes by immersing PSF hollow fiber membranes in 1wt% PDMAEMA aqueous solution for 1h, then taking out and drying for 20min, and immersing them in 1wt% p-dichlorobenzyl/n-heptane solution for crosslinking for 5h [ reference: positively charged hollow-fiber composite nanofiltration membrane prepared by quaternization crosslinking, journal of Applied Polymer Science,2013,129 (5): 2806-2812 ]. Xiao et al prepared positively charged nanofiltration membranes by immersing PSF in 10g/L of an aqueous solution of dimethylaminoethyl acrylate (DMAEMA) monomer, graft polymerizing a PDMAEMA layer on the PSF membrane surface by uv induction, drying, immersing in 30ml of 1.5% p-dichlorobenzyl/ethanol solution, and interface crosslinking reacting at room temperature for 20 hours [ reference: li X L, zhu L P, xu Y, et al A novel positively charged nanofiltration membrane prepared from N, N-dimethylaminoethyl methacrylate by quaternization cross-linking [ J ]. Journal of Membrane Science,2011,374 (1-2): 33-42 ].
The crosslinking time in the method for preparing the PDMAEMA positively charged nanofiltration membrane is as long as 5-20 hours, so that the preparation efficiency of the nanofiltration membrane is greatly reduced, and the development of the nanofiltration membrane to industrial production is limited.
The retention rate of the polymethyl methacrylate positively charged nanofiltration membrane on divalent salt can reach more than 90 percent, and the polymethyl methacrylate positively charged nanofiltration membrane has oxidation resistance and free chlorine resistance. However, the crosslinking reaction time of the nanofiltration membrane in the preparation process is as long as 5-20 hours, so that the production efficiency of the nanofiltration membrane is greatly reduced, and the industrialized application of the positively charged nanofiltration membrane is limited.
Disclosure of Invention
The invention aims to solve the technical problems that the positively charged nanofiltration membrane is excessively long in crosslinking time in the preparation process, and is not beneficial to industrialized application.
In order to solve the technical problems, the technical scheme of the invention is that a preparation method of a composite membrane material is provided, which comprises the following steps:
(1) Preparing a polymer containing tertiary amine groups and/or pyridine groups into a polymer solution;
(2) Preparing a cross-linking agent into a cross-linking agent solution with the mass fraction of 0.01-2%; the cross-linking agent is selected from more than two halogenated olefins or more than two halogenated aromatic hydrocarbons; the halogenation is bromo and/or iodo;
(3) Using an ultrafiltration membrane as a base membrane, transferring the prepared polymer solution onto the base membrane, and drying; and (3) contacting the dried film with a cross-linking agent solution for 0.5-30min, and drying to obtain the composite film material.
Preferably, the mass fraction of polymer in the polymer solution of step (1) is 0.01-4%; more preferably 0.2 to 3wt%; further preferably 0.5 to 2wt%.
Preferably, the concentration of the crosslinker solution is from 0.1 to 1% by weight.
Preferably, in step (3), the base film is immersed in the prepared polymer solution by a dip coating method.
Preferably, in the step (3), the drying is selected to be air-drying or oven-drying.
Preferably, the halogenated aromatic hydrocarbon is selected from aromatic hydrocarbons having two or more halomethyl groups substituted on a benzene ring, and the halogen atom in the halomethyl groups is a bromine atom and/or an iodine atom.
Preferably, the crosslinking agent is selected from aromatic hydrocarbons having three or more halomethyl groups substituted on the aromatic ring. More preferably, the aromatic ring is a benzene ring.
Preferably, the halogenated olefin is selected from olefins substituted with two or more halomethyl groups on a carbon-carbon double bond, the halogen atoms in the halomethyl groups being bromine atoms and/or iodine atoms.
Preferably, the carbon atoms in the halomethyl groups are each directly attached to a carbon atom of an olefinic double bond.
Preferably, the cross-linking agent is 1, 4-dibromo-2, 3-bis (bromomethyl) -2-butene, 1, 6-dibromo-2, 4-dihexylene, 1, 4-dibromo-2-methyl-2-butene, 1, 4-dibromo-2-bromomethyl-2-butene, 1, 4-dibromo-2, 3-methyl-2-butene, 1, 4-diiodo-2-butene, 1, 2-bis (dibromomethyl) benzene, 1, 4-bis (dibromomethyl) benzene, 4' -dibromomethyl biphenyl, 1,2,4, 5-tetrakis (bromomethyl) benzene, 1, 2-bis (bromomethyl) benzene, 1, 3-bis (bromomethyl) benzene, 1, 4-bis (bromomethyl) benzene, 1, 2-bis (iodomethyl) benzene, 1, 3-bis (iodomethyl) benzene, 1, 4-bis (diiodomethyl) benzene, 1,3, 5-tribromomethyl-benzene, 1, 3-bis (bromomethyl) benzene.
Preferably, the polymer is the product of the polymerization of vinyl monomers containing tertiary amine groups or pyridine groups. More preferably, the vinyl monomer containing tertiary amine groups is selected from any one or more of dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, dimethylaminoethyl acrylate, diethylaminoethyl acrylate, dimethylaminopropyl methacrylamide, dimethylaminopropyl acrylamide, 4-vinylpyridine, 2-vinylpyridine and vinylimidazole.
Preferably, the ultrafiltration membrane is one of polysulfone ultrafiltration membrane, polyethersulfone ultrafiltration membrane, polyvinylidene fluoride ultrafiltration membrane, polyacrylonitrile ultrafiltration membrane, polyamide ultrafiltration membrane and cellulose ultrafiltration membrane.
Preferably, the polymer solution of step (1) is an alcoholic and/or aqueous solution, preferably an ethanol solution; and/or the crosslinker solution of step (2) is an alkane or haloalkane solution, preferably n-hexane or cyclohexane solution.
Preferably, the crosslinking time of the crosslinking agent selected in the present invention is 1 to 15 minutes, preferably 1 to 5 minutes.
In the pyridine group contained in the polymer, the nitrogen element of the pyridine group can also carry out the crosslinking reaction with the crosslinking agent, so the invention is not limited to the polymer containing tertiary amino groups, and the polymer containing the pyridine group has the prospect of being used as a composite membrane material.
The prepared composite membrane material can be used for nanofiltration membranes, pervaporation dehydration membranes, carbon dioxide separation membranes and gas dehumidification membranes; particularly, when the membrane material obtained by the invention is used as a positively charged nanofiltration membrane, the application is wider.
In the invention, the halomethyl is substituted by more than 1 halogen atom on the methyl; preferably substituted by 1 halogen atom, in particular-CH 2 X, wherein X represents a halogen atom. In the present invention, X is Br or I.
In the present invention, "binary or more halo" means "substituted with two or more halogen atoms"; "ternary or higher halo" means "substituted with three or more halogen atoms". In the present invention, wt% means mass%.
Compared with the prior art, the invention has the beneficial effects that: the invention selects high-activity polybasic bromohydrocarbon or iodohydrocarbon as the cross-linking agent, can improve the reaction speed of tertiary amino or pyridyl and halohydrocarbon, shortens the cross-linking time of membrane preparation from 5-20 hours to 0.5-30 minutes, improves the preparation efficiency of composite membrane materials (especially positively charged nanofiltration membranes), and promotes the progress of the composite membrane materials to industrialization.
Detailed Description
The present invention will be further described with reference to examples and comparative examples.
Example 1
The embodiment provides a preparation method of a positively charged composite nanofiltration membrane, which comprises the following steps:
(1) And (3) polymer synthesis: selecting dimethylaminoethyl methacrylate (product purity 99%, 1000ppm MEHQ stabilizer; manufacturer: shanghai Ala Biotechnology Co., ltd.) monomer as raw material, adsorbing with neutral alumina chromatography to remove polymerization inhibitor, and bulk polymerizing with azobisisobutyronitrile as initiator to obtain dimethylaminoethyl methacrylate (PDMAEMA);
(2) 1,3, 5-tris (bromomethyl) benzene (product purity: 98%; manufacturer: shanghai Meilin Biochemical technologies Co., ltd.) was dissolved in cyclohexane (product purity: AR; manufacturer: tianjin, density European chemical Co., ltd.) as a crosslinking agent to obtain a 0.5wt% 1,3, 5-tris (bromomethyl) benzene-cyclohexane solution;
(3) And (3) film preparation: preparing 1wt% ethanol (product purity: AR; manufacturer: tianjin Fengsha chemical reagent technology Co., ltd.) solution from the synthesized PDMAEMA, using a polyether sulfone ultrafiltration flat membrane with a molecular weight cut-off of 5 ten thousand as a base membrane, immersing the base membrane in the prepared ethanol solution of PDMAEMA for 3 minutes, taking out, and air-drying;
(4) Interface crosslinking: and (3) immersing the dried film with the PDMAEMA polymer layer in the 1,3, 5-tri (bromomethyl) benzene-cyclohexane solution prepared in the step (2) for 3 minutes, taking out and drying to obtain the composite nanofiltration film.
Performance test: the obtained composite nanofiltration membrane has a concentration of 1000mg/L MgSO at room temperature 4 The aqueous solution was tested for salt removal and water flux at 0.8MPa and 25℃and the results are shown in Table 1.
Example 2
This example is identical to the procedure of example 1, except that: the cross-linking agent is 1,3, 5-tri (iodomethyl) benzene (product purity: 95%; manufacturer: aituochi Co., ltd.).
Under the same test conditions as in example 1, the performance data are shown in Table 1.
Example 3
This example is identical to the procedure of example 1, except that: the cross-linking agent is 1, 4-bis (bromomethyl) benzene (product purity: 97%; manufacturer: shanghai Michlin Biochemical technology Co., ltd.).
Under the same test conditions as in example 1, the performance data are shown in Table 1.
Example 4
This example is identical to the procedure of example 1, except that: the cross-linking agent is cis-1, 4-dibromo-2-butene (product purity: 95%; manufacturer: shanghai Yi En chemical technology Co., ltd.).
Under the same test conditions as in example 1, the performance data are shown in Table 1.
Example 5
This example is identical to the procedure of example 1, except that: the cross-linking agent is trans-1, 4-dibromo-2-butene (product purity: 97%; manufacturer: shanghai Michlin Biochemical technology Co., ltd.).
Under the same test conditions as in example 1, the performance data are shown in Table 1.
Comparative example 1
This comparative example is identical to the procedure of example 1, except that: the cross-linking agent is 1, 2-diiodoethane (product purity: 98%; manufacturer: shanghai Micin Biochemical technology Co., ltd.).
Under the same test conditions as in example 1, the performance data are shown in Table 1.
Comparative example 2
This comparative example is identical to the procedure of example 1, except that: the cross-linking agent is 1, 4-dibromobutane (product purity: 98%; manufacturer: shanghai Michlin Biochemical technology Co., ltd.).
Under the same test conditions as in example 1, the performance data are shown in Table 1.
Comparative example 3
This comparative example is identical to the procedure of example 1, except that: the cross-linking agent is 1, 4-diiodobutane (product purity: 95%; manufacturer: shanghai Micin Biochemical technology Co., ltd.).
Under the same test conditions as in example 1, the performance data are shown in Table 1.
Comparative example 4
This comparative example is identical to the procedure of example 1, except that: the cross-linking agent is cis-1, 4-dichloro-2-butene (product purity: 95%; manufacturer: shanghai Micin Biochemical technology Co., ltd.).
Under the same test conditions as in example 1, the performance data are shown in Table 1.
Comparative example 5
This comparative example is identical to the procedure of example 1, except that: the cross-linking agent is trans-1, 4-dichloro-2-butene (product purity: 95%; manufacturer: shanghai Michlin Biochemical technology Co., ltd.).
Under the same test conditions as in example 1, the performance data are shown in Table 1.
Comparative example 6
This comparative example is identical to the procedure of example 1, except that: the cross-linking agent is 1, 4-bis (chloromethyl) benzene (product purity: 98%; manufacturer: shanghai Micin Biochemical technology Co., ltd.).
Under the same test conditions as in example 1, the performance data are shown in Table 1.
Comparative example 7
This comparative example is identical to the procedure of example 1, except that: the cross-linking agent is 1,3, 5-tri (chloromethyl) benzene (product purity: 98%; manufacturer: zhengzhou Convergence chemical Co., ltd.).
Under the same test conditions as in example 1, the performance data are shown in Table 1.
TABLE 1 influence of different crosslinkers on nanofiltration membrane flux and rejection
Data analysis for examples 1-5 and comparative examples 1-7: the film forming conditions in examples 1 to 5 and comparative examples 1 to 7 differ only in the choice of the crosslinking agent. Other main parameters were the same as follows: PDMAEMA concentration 1.0% (wt), cross-linking agent concentration 0.5% (wt), cross-linking time 3min, film forming time 3min.
As can be seen from the data in Table 1, the retention rate of 1, 4-dibromo-2-butene, 1, 4-di (bromomethyl) benzene, 1,3, 5-tri (iodomethyl) benzene was 70% or more, relative to MgSO 4 Has higher interception effect. And 1, 2-diiodoethane, 1, 4-dibromobutane, 1, 4-diiodobutane, 1, 4-dichloro-2-butene, 1, 4-di (chloromethyl) benzene, 1,3, 5-tri (chloromethyl) benzene pair MgSO 4 The retention rate of the catalyst is lower than 37 percent, and the catalyst is extremely low in retention rate of divalent salt and is not suitable for removing divalent salt ions. From examples 4 and 5, comparative examples 4 and 5, it can be seen that the retention rate of the nanofiltration membrane prepared by using dibromo-olefine as the cross-linking agent is significantly higher than that of the nanofiltration membrane prepared by using dichloro-olefine as the cross-linking agent, because the reactivity of dibromo-olefine is higher than that of dichloro-olefine. From examples 1,2, 3, comparative examples 6 and 7 show that the retention rate of the nanofiltration membrane prepared by using 1, 4-di (chloromethyl) benzene and 1,3, 5-tri (chloromethyl) benzene as the cross-linking agent is significantly lower than that of the nanofiltration membrane prepared by using 1, 4-di (bromomethyl) benzene, 1,3, 5-tri (bromomethyl) benzene and 1,3, 5-tri (iodomethyl) benzene as the cross-linking agent in the same cross-linking time, because the reactivity of bromine/iodoaromatic hydrocarbon is higher than that of the chloroaromatic hydrocarbon, and the cross-linking degree of the nanofiltration membrane prepared by using bromomethyl aromatic hydrocarbon and iodomethyl aromatic hydrocarbon is higher than that of the chloromethylaromatic hydrocarbon. In addition, the dissociation energy of the C-I bond is 218kJ/mol, the dissociation energy of the C-Br bond is 285kJ/mol, the dissociation energy of the C-Cl bond is 339kJ/mol, the dissociation energy of the C-I, C-Br and the C-Cl are sequentially increased, the polarizability of the C-I, C-Br and the C-Cl is sequentially reduced, and the dissociation energy and the polarizability of the C-X carbon halogen bond are shown as I - 、Br - 、Cl - The higher the leaving ability, the easier the quaternization reaction proceeds, so that the iodinated hydrocarbon, the brominated hydrocarbonThe reactivity of chlorinated hydrocarbon is reduced in turn, so that the crosslinking degree of the PDMAEMA is reduced in turn, and the performances of the PDMAEMA nanofiltration membrane are the reduction of the interception rate and the improvement of the flux.
From examples 3, 4 and 5, comparative example 2 shows that the retention rate of nanofiltration membranes prepared by the same halogen atoms in different chemical environments is greatly different, and the retention rate of nanofiltration membranes prepared by comparative example 2 using 1, 4-dibromobutane as a cross-linking agent is obviously lower than that of nanofiltration membranes prepared by examples 3, 4 and 5 using 1, 2-dibromo-2-butene and 1, 4-bis (bromomethyl) benzene as cross-linking agents. This is because the haloalkane reactivity is lower than the reactivity of the haloalkene and benzyl halide: the methylene in the benzyl halide and the benzene ring form delta-pi conjugation, so that the activity of halogen atoms is stronger, and the quaternary amination reaction is facilitated; the methylene group in the bromomethyl group in the 1, 2-dibromo-2-butene forms delta-pi conjugation with the double bond, so that the reactivity of the 1, 2-dibromo-2-butene is higher than that of the 1, 4-dibromobutane.
As can be seen from the comparison of example 1 and example 3,1, 3, 5-tris (bromomethyl) benzene with three bromomethyl substituents has more active groups and higher activity than 1, 4-p-dibromobenzyl with two bromomethyl substituents, and thus the nanofiltration membrane prepared in the same crosslinking time has higher crosslinking degree and retention rate.
Example 6
This example is identical to the procedure of example 4, except that: the crosslinking time was 15 minutes.
Under the same test conditions as in example 1, the performance data are shown in tables 2 and 3.
Example 7
This example is identical to the procedure of example 4, except that: the crosslinking time was 30 minutes.
Under the same test conditions as in example 1, the performance data are shown in Table 3.
Example 8
This example is identical to the procedure of example 5, except that: the crosslinking time was 15 minutes.
Under the same test conditions as in example 1, the performance data are shown in tables 2 and 3.
Example 9
This example is identical to the procedure of example 5, except that: the crosslinking time was 30 minutes.
Under the same test conditions as in example 1, the performance data are shown in Table 3.
Example 10
This example is identical to the procedure of example 3, except that: the crosslinking time was 15 minutes.
Under the same test conditions as in example 1, the performance data are shown in tables 2 and 3.
Example 11
This example is identical to the procedure of example 3, except that: the crosslinking time was 30 minutes.
Under the same test conditions as in example 1, the performance data are shown in Table 3.
Comparative example 8
This example is identical to the procedure of comparative example 4, except that: the crosslinking time was 15 minutes.
Under the same test conditions as in example 1, the performance data are shown in Table 2.
Comparative example 9
This comparative example is identical to the procedure of comparative example 5, except that: the crosslinking time was 15 minutes.
Under the same test conditions as in example 1, the performance data are shown in Table 2.
Comparative example 10
This comparative example is identical to the procedure of comparative example 6, except that: the crosslinking time was 15 minutes.
Under the same test conditions as in example 1, the performance data are shown in Table 2.
TABLE 2 Effect of increasing crosslinking time on nanofiltration membrane flux and rejection
Examples 6, 8, 10, comparative examples 8-10 analysis:
the data analysis in Table 1 shows that bromomethyl is more reactive than chloromethyl and that the crosslinking agent with ternary halomethyl is more reactive than the crosslinking agent with binary halomethyl. The data in Table 2 shows that high rejection nanofiltration membranes can also be prepared with increased crosslinking times for binary bromomethyl olefins or aromatic hydrocarbons. Examples 3, 4,5, 6, 8 and 10 and comparative examples 4,5, 6 and 8-10 show that the retention rate of nanofiltration membranes prepared by using 1, 4-dibromo-2-butene and 1, 4-bis (bromomethyl) benzene as cross-linking agents is higher than that of nanofiltration membranes prepared by using 1, 4-dichloro-2-butene and 1, 4-bis (chloromethyl) benzene as cross-linking agents after the cross-linking time is increased from 3 minutes to 15 minutes. As can be seen from examples 1,6, 8 and 10, the retention rate of the nanofiltration membrane prepared by using 1, 4-dibromo-2-butene and 1, 4-di (bromomethyl) benzene as the cross-linking agents for 15 minutes was similar to that of the nanofiltration membrane prepared by using 1,3, 5-tri (bromomethyl) benzene as the cross-linking agents for 3 minutes. The disubstituted bromine/iodine halohydrocarbon with the similar structure is used as a cross-linking agent, so that the nanofiltration membrane with high retention rate can be prepared in a short time.
TABLE 3 influence of different crosslinking times on nanofiltration membrane flux and rejection
Examples 6-11 data analysis: as can be seen from examples 3-5 and 6-11, the preparation of positively charged nanofiltration membranes with high retention rate can be realized by crosslinking with high-activity dihalohydrocarbon in a short time, the crosslinking time is increased from 3min to 15min, the retention rate is increased from 72% to 92% or more, and the membrane is used for MgSO 4 The divalent salt ions have high retention rate, and the retention rate of the nanofiltration membrane prepared by continuously increasing the crosslinking time is only increased from 92% to 95%, so that the influence of the continuous increase of the crosslinking time on the performance of the nanofiltration membrane is not obvious. The PDMAEMA nanofiltration membrane prepared by using dibromo/iodo-olefin or aromatic hydrocarbon cross-linking agent within a cross-linking time of 15min has high retention rate on bivalent salt ions.

Claims (7)

1. The preparation method of the composite membrane material is characterized by comprising the following steps of:
(1) Preparing a polymer containing tertiary amine groups and/or pyridine groups into a polymer solution;
(2) Preparing a cross-linking agent into a cross-linking agent solution with the mass fraction of 0.01-2%;
the cross-linking agent is 1,3, 5-tri (bromomethyl) benzene, 1,3, 5-tri (iodomethyl) benzene, 1, 4-di (bromomethyl) benzene or 1, 4-dibromo-2-butene;
(3) Using an ultrafiltration membrane as a base membrane, transferring the prepared polymer solution onto the base membrane, and drying; and (3) contacting the dried film with a cross-linking agent solution for 0.5-30min, and drying to obtain the composite film material.
2. The method according to claim 1, wherein in the step (3), the base film is immersed in the prepared polymer solution by a dip coating method.
3. The process according to claim 1 or 2, wherein the mass fraction of polymer in the polymer solution of step (1) is 0.01-4%.
4. The method according to claim 1 or 2, wherein in the step (1), the polymer is a product obtained by polymerizing a vinyl monomer having a tertiary amine group or a pyridine group.
5. The method according to claim 1 or 2, wherein the ultrafiltration membrane is one of polysulfone ultrafiltration membrane, polyethersulfone ultrafiltration membrane, polyvinylidene fluoride ultrafiltration membrane, polyacrylonitrile ultrafiltration membrane, polyamide ultrafiltration membrane, and cellulose ultrafiltration membrane.
6. The process according to claim 1 or 2, wherein the polymer solution of step (1) is an alcoholic solution and/or an aqueous solution; and/or the cross-linking agent solution in the step (2) is alkane or halogenated alkane solution.
7. The method of claim 6, wherein the polymer solution is an ethanol solution; the cross-linking agent solution is normal hexane or cyclohexane solution.
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