CN112755817B - Composite nanofiltration membrane with high performance, preparation method and application thereof - Google Patents
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- 239000012528 membrane Substances 0.000 title claims abstract description 241
- 238000001728 nano-filtration Methods 0.000 title claims abstract description 115
- 239000002131 composite material Substances 0.000 title claims abstract description 100
- 238000002360 preparation method Methods 0.000 title claims abstract description 20
- 239000000178 monomer Substances 0.000 claims abstract description 123
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 109
- 238000000108 ultra-filtration Methods 0.000 claims abstract description 81
- 238000000926 separation method Methods 0.000 claims abstract description 52
- 229920000768 polyamine Polymers 0.000 claims abstract description 51
- 230000004907 flux Effects 0.000 claims abstract description 46
- 239000004952 Polyamide Substances 0.000 claims abstract description 36
- 229920002647 polyamide Polymers 0.000 claims abstract description 36
- 150000001263 acyl chlorides Chemical class 0.000 claims abstract description 33
- 238000006243 chemical reaction Methods 0.000 claims abstract description 32
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- 238000000034 method Methods 0.000 claims abstract description 23
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- GLUUGHFHXGJENI-UHFFFAOYSA-N Piperazine Chemical compound C1CNCCN1 GLUUGHFHXGJENI-UHFFFAOYSA-N 0.000 claims description 110
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 claims description 58
- 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 54
- -1 phosphoric acid diester compound Chemical class 0.000 claims description 40
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- LXEJRKJRKIFVNY-UHFFFAOYSA-N terephthaloyl chloride Chemical compound ClC(=O)C1=CC=C(C(Cl)=O)C=C1 LXEJRKJRKIFVNY-UHFFFAOYSA-N 0.000 claims description 7
- 238000004065 wastewater treatment Methods 0.000 claims description 7
- WZCQRUWWHSTZEM-UHFFFAOYSA-N 1,3-phenylenediamine Chemical compound NC1=CC=CC(N)=C1 WZCQRUWWHSTZEM-UHFFFAOYSA-N 0.000 claims description 6
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- XDTMQSROBMDMFD-UHFFFAOYSA-N Cyclohexane Chemical compound C1CCCCC1 XDTMQSROBMDMFD-UHFFFAOYSA-N 0.000 claims description 4
- 125000004177 diethyl group Chemical group [H]C([H])([H])C([H])([H])* 0.000 claims description 4
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- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 abstract description 12
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- 239000010408 film Substances 0.000 description 73
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- 239000011734 sodium Substances 0.000 description 17
- 150000004713 phosphodiesters Chemical class 0.000 description 16
- 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 14
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- YRIUSKIDOIARQF-UHFFFAOYSA-N dodecyl benzenesulfonate Chemical compound CCCCCCCCCCCCOS(=O)(=O)C1=CC=CC=C1 YRIUSKIDOIARQF-UHFFFAOYSA-N 0.000 description 1
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- HFQQZARZPUDIFP-UHFFFAOYSA-M sodium;2-dodecylbenzenesulfonate Chemical compound [Na+].CCCCCCCCCCCCC1=CC=CC=C1S([O-])(=O)=O HFQQZARZPUDIFP-UHFFFAOYSA-M 0.000 description 1
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- B01D—SEPARATION
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- B01D69/12—Composite membranes; Ultra-thin membranes
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- 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
- B01D65/00—Accessories or auxiliary operations, in general, for separation processes or apparatus using semi-permeable membranes
- B01D65/10—Testing of membranes or membrane apparatus; Detecting or repairing leaks
-
- 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
- B01D67/0079—Manufacture of membranes comprising organic and inorganic components
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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
- B01D69/10—Supported membranes; Membrane supports
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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
- B01D69/10—Supported membranes; Membrane supports
- B01D69/105—Support pretreatment
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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
- B01D69/125—In situ manufacturing by polymerisation, polycondensation, cross-linking or chemical reaction
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- 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
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2323/00—Details relating to membrane preparation
- B01D2323/50—Control of the membrane preparation process
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/20—Heavy metals or heavy metal compounds
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
- C02F2103/08—Seawater, e.g. for desalination
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
- C02F2103/34—Nature of the water, waste water, sewage or sludge to be treated from industrial activities not provided for in groups C02F2103/12 - C02F2103/32
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- 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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- Hydrology & Water Resources (AREA)
- Environmental & Geological Engineering (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Manufacturing & Machinery (AREA)
- Separation Using Semi-Permeable Membranes (AREA)
Abstract
The invention discloses a composite nanofiltration membrane with high performance, a preparation method and application thereof. The composite nanofiltration membrane comprises: the porous ultrafiltration support bottom membrane and the polyamide selective separation layer arranged on the porous ultrafiltration support bottom membrane are mainly formed by interfacial polymerization reaction of a polyamine monomer and a polyacyl chloride monomer under the regulation and control of a surfactant, wherein the surfactant comprises an oil-soluble anionic surfactant containing two hydrophobic carbon chains. The preparation method comprises the following steps: and (3) performing interfacial polymerization reaction on the polyamine monomer and the polybasic acyl chloride monomer under the regulation and control of a surfactant, so that a compact polyamide selective separation layer is formed on the surface of the porous ultrafiltration support base membrane, and then, performing aftertreatment to obtain the composite nanofiltration membrane. The high-performance composite nanofiltration membrane of the invention has excellent interception performance on divalent anions and cations, and the pure water flux is up to 16Lm ‑2 h ‑1 bar ‑1 The method has wide application prospect in the field of water treatment.
Description
Technical Field
The invention relates to a nanofiltration membrane, in particular to a high-performance film composite nanofiltration membrane and a preparation method thereof, and application of the film composite nanofiltration membrane, belonging to the technical fields of materials and water treatment.
Background
With the factors of global warming, population increase and economic exertion, the demands of human beings on water quality and water quantity are rapidly increased, and the problems of global water resource shortage, water pollution and the like potentially threaten the health and social development of human beings, so that the water resource problem needs to be solved. Compared with the traditional water treatment technology, such as distillation, electrodialysis, oxidation, flocculation and the like, the membrane separation technology has great application prospect in the water treatment field due to the advantages of high separation efficiency, low energy consumption, environmental protection and the like. The aperture of the nanofiltration membrane is between 0.5 and 2 and nm, and can cut off small molecular substances with the molecular weight of 200 to 2000 Da. Has high retention rate to most organic matters and multivalent salt ions in water, and lower retention rate to monovalent salt ions, thus having good separation selectivity to monovalent/multivalent salt, and having the advantages of high flux, high separation efficiency, low operation pressure, mild preparation conditions and the like. The typical nanofiltration membrane structure at present is a thin film composite membrane structure, and mainly consists of an ultrafiltration bottom membrane for providing mechanical support and a polyamide selective layer which is prepared on the ultrafiltration bottom membrane and has selective screening function and is prepared by interfacial polymerization reaction between polyamine and polybasic acyl chloride. The reaction between polyamine and polybasic acyl chloride is quick and difficult to control, and the traditional nanofiltration membrane prepared by the method has low interception of divalent positive ions and monovalent salt ions due to the fact that most of nanofiltration membranes are negatively charged, water flux is low, and meanwhile, the performance of the nanofiltration membrane is limited by the constant trade-off relationship between flux and interception. According to the report of the documents Polyamide nanofiltration membrane with highly uniform sub-nanometre pores for sub-1A precision separation, nature Communication, 11 2015 (2020), the formation of a monolayer network can be constructed by adding 1 Critical Micelle Concentration (CMC) of Sodium Dodecyl Sulfate (SDS) to a polyamine monomer solution, promoting the orderly diffusion of the polyamine monomer into an organic phase, and improving the crosslinking degree of a polyamide layer so as to enhance the separation efficiency. However, the high use concentration of SDS makes the possibility of introduction pollution in the discharge process, and simultaneously greatly increases the application cost, and the interception efficiency and flux of the nanofiltration membrane are improved at a value of 1CMC, but the 1CMC is not the optimal condition, and the performance of the nanofiltration membrane still has a great improvement space.
Therefore, how to optimize the polymerization system, a new technology for preparing the membrane composite nanofiltration membrane with high interception and high flux is sought, and the method has strong research significance and is also the direction of the researchers.
Disclosure of Invention
The invention mainly aims to provide a composite nanofiltration membrane with high separation and selection performance and high flux and a preparation method thereof, so as to overcome the defects in the prior art.
It is also an object of the present invention to provide the use of the composite nanofiltration membrane with high separation selectivity and high flux in the field of water treatment.
In order to achieve the purpose of the invention, the technical scheme adopted by the invention comprises the following steps:
the embodiment of the invention provides a composite nanofiltration membrane with high performance, which comprises the following components: the porous ultrafiltration support bottom membrane and the polyamide selective separation layer arranged on the porous ultrafiltration support bottom membrane are mainly formed by interfacial polymerization reaction of a polyamine monomer and a polyacyl chloride monomer under the regulation and control of a surfactant, wherein the surfactant comprises an oil-soluble anionic surfactant containing two hydrophobic carbon chains.
In some embodiments, the surfactant includes a phosphodiester compound, preferably including any one or a combination of two or more of dibutyl phosphate, didecyl phosphate, didodecyl phosphate, and the like, but is not limited thereto.
In some embodiments, the polyamide selective separation layers of the high performance composite nanofiltration membrane have a multivalent anion rejection rate of greater than 99%, preferably greater than 99.5%, and a multivalent cation rejection rate of greater than 90%, preferably greater than 98.5%; the interception rate of monovalent positive ions and monovalent negative ions is less than 35 percent.
Further, the flux of the composite nanofiltration membrane to pure water is 10 Lm -2 h -1 bar -1 Above, preferably at 16 Lm -2 h -1 bar -1 The above.
The embodiment of the invention also provides a preparation method of the composite nanofiltration membrane with high performance, which comprises the following steps:
separately providing an aqueous solution comprising a polyamine monomer, an organic solution comprising a polyacyl chloride monomer and a surfactant, wherein the surfactant comprises an oil-soluble anionic surfactant comprising two hydrophobic carbon chains;
the surface of the porous ultrafiltration support base film is used as the interface between the aqueous solution of the polyamine monomer and the organic solution, the polyamine monomer and the surfactant molecules are gathered at the interface through electrostatic interaction, and the polyamine monomer are subjected to interfacial polymerization under the regulation and control of the surfactant at the interface, so that a compact polyamide selective separation layer is formed on the surface of the porous ultrafiltration support base film, and then the porous ultrafiltration support base film is subjected to heat treatment, so that the composite nanofiltration film with high performance is obtained.
In some embodiments, the preparation method specifically includes:
adding the aqueous solution containing the polyamine monomer to the surface of the porous ultrafiltration support base membrane under the conditions of 50-70% of relative humidity and 20-30 ℃ of ambient temperature, and fully soaking for 10-150 s, preferably 60-90 s; and adding an organic solution containing a polybasic acyl chloride monomer and a surfactant on the surface of the porous ultrafiltration support base membrane, soaking the surface for 30-120 s, preferably 30-60 s, performing interfacial polymerization reaction on the polybasic amine monomer and the polybasic acyl chloride monomer at a two-phase interface for 30-60 s, and then placing the obtained composite nanofiltration membrane in an environment of 50-80 ℃ for heat treatment for 10-40 min to obtain the composite nanofiltration membrane with high performance.
The embodiment of the invention also provides the composite nanofiltration membrane with high performance prepared by the method.
The embodiment of the invention also provides application of the composite nanofiltration membrane with high performance in the fields of sea water desalination pretreatment, multivalent/monovalent salt separation or functional industrial wastewater treatment and the like.
Correspondingly, the embodiment of the invention also provides a separation method of heavy metal salt, which comprises the following steps:
providing the composite nanofiltration membrane with high performance;
And enabling a system containing heavy metal salt to pass through the composite nanofiltration membrane to separate the heavy metal salt.
Compared with the prior art, the invention has the beneficial effects that:
1) The high-performance film composite nanofiltration membrane provided by the invention adopts polyamine monomer aqueous solution as water phase and polybasic acyl chloride monomer/very low concentration phosphodiester fat-soluble mixed solution as oil phase to carry out interfacial polymerization, thus obtaining the film composite nanofiltration membrane with high performance, and greatly reducing the membrane aperture (r) p >0.270 nm), narrow pore size distribution, and greatly reduce molecular weight cut-off (MWCO)>150 Da) improves the crosslinking density of the polyamide separation layer, thereby improving the separation efficiency of divalent ions>99%）；
2) The high-performance film composite nanofiltration membrane provided by the invention has the advantages that the interception of the divalent ion salt solution with the concentration of 20mmol/L is more than 99%, and the flux to pure water is 16 Lm -2 h -1 bar -1 The membrane composite nanofiltration membrane with ultrahigh interception, high flux and low energy consumption has great application value in the aspects of desalination, chemical wastewater treatment, seawater desalination pretreatment, heavy metal solution separation and the like;
3) The preparation method of the high-performance film composite nanofiltration membrane provided by the invention is simple, the extremely low use concentration of the phosphodiester and the ultrahigh interception, high flux and effective separation of heavy metal salt of the nanofiltration membrane greatly reduce the energy consumption cost of desalination, wastewater treatment, heavy metal solution separation and the like, can realize wastewater desalination and recycling, can realize recycling of metal ions, is easy to realize amplified production in the process, and has high industrial application value.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required to be used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments described in the present invention, and other drawings may be obtained according to the drawings without inventive effort to those skilled in the art.
FIGS. 1 and 2 are graphs showing molecular weight cut-off and pore size distribution of the membrane surface after addition of very low concentration of phosphodiester to the organic phase and without interfacial polymerization in example 10 of the present invention;
FIG. 3 is an SEM image of the surface of a high performance composite nanofiltration membrane after interfacial polymerization with the addition of very low concentration of phosphodiester to the organic phase in example 10 of the present invention.
Detailed Description
In view of the deficiencies in the prior art, the present inventors have long studied and have found in great numbers that reducing the pore size of the polyamide layer to increase the degree of crosslinking and thus entrapment can be achieved by promoting the extent of reaction of the polyamine monomer with the polyacyl chloride monomer. It has been shown that the addition of surfactant SDS can form a monolayer at the interface of two phases, promoting the rapid and orderly diffusion of the polyamine monomer molecules into another phase and reaction with the polyacyl chloride monomer to form a polyamide layer, the hydrophobic carbon chains providing diffusion channels for this process. Based on this finding, the present inventors have proposed a method for preparing a high performance thin film composite nanofiltration membrane using very low concentration of phosphodiester containing two hydrophobic carbon chains.
The technical scheme, the implementation process, the principle and the like are further explained as follows.
As an aspect of the present invention, it relates to a composite nanofiltration membrane with high performance, comprising: the porous ultrafiltration support bottom membrane and the polyamide selective separation layer arranged on the porous ultrafiltration support bottom membrane are mainly formed by interfacial polymerization reaction of a polyamine monomer and a polyacyl chloride monomer under the regulation and control of a surfactant, wherein the surfactant comprises an oil-soluble anionic surfactant containing two hydrophobic carbon chains.
In some preferred embodiments, the surfactant includes a di-phosphate compound containing a double carbon chain, and for example, may preferably include any one or a combination of two or more of dibutyl phosphate, didecyl phosphate, didodecyl phosphate, and the like, but is not limited thereto. The phosphodiester compound is used as an oil-soluble anionic surfactant molecule containing a double carbon chain, is added into an organic phase to participate in a reaction, and can provide a sufficient channel for rapid transmission of monomers at a low concentration, so that a polyamide layer is promoted to form a compact selective separation layer on a bottom film, and the membrane has an ultrahigh rejection rate for divalent anions and cations.
More specifically, the invention provides a membrane composite nanofiltration membrane which has high separation selectivity and high flux and is regulated by a phosphoric acid diester containing a double carbon chain, and the membrane composite nanofiltration membrane comprises a porous support bottom membrane for providing mechanical support and a polyamide selective separation layer which is formed by interfacial polymerization of polyamine and a polybasic acyl chloride monomer solution containing the phosphoric acid diester and has selective separation function on the porous support bottom membrane, wherein the polybasic acyl chloride monomer and a phosphoric acid diester molecule are accumulated at an interface through electrostatic interaction.
Further, the polyamide selective separation layer is mainly prepared by interfacial polymerization reaction of a polyamine monomer solution and a polybasic acyl chloride monomer solution added with a phosphodiester molecule, wherein the phosphodiester contains two hydrophobic carbon chains, and the performance of the nanofiltration membrane can be effectively improved under low concentration.
In some embodiments, the polybasic acid chloride monomer may include any one or a combination of two or more of trimesoyl chloride, isophthaloyl chloride, adipoyl chloride, terephthaloyl chloride, and the like, but is not limited thereto.
In some embodiments, the polyamine monomer may include one or a combination of two or more of piperazine, polyethyleneimine, m-phenylenediamine, diethylenetriamine, etc., but is not limited thereto.
In some embodiments, the polyamide selective separation layer has a thickness of 30-70 nm.
In some embodiments, the porous ultrafiltration support base membrane may be any one or a combination of two or more of a polyethersulfone ultrafiltration membrane, a polyacrylonitrile ultrafiltration membrane, a polysulfone ultrafiltration membrane, a sulfonated polysulfone ultrafiltration membrane, and a polyvinylidene chloride ultrafiltration membrane, and is preferably a polyethersulfone ultrafiltration membrane, but is not limited thereto.
Further, the pore diameter of the pores contained in the porous ultrafiltration support bottom membrane is 5-100 nm.
In some embodiments, the pore size of the pores contained in the polyamide selective separation layer of the composite nanofiltration membrane is above 0.270 nm, preferably 0.270-0.300 nm.
In some embodiments, the molecular weight cut-off (MWCO) of the polyamide selective separation layer is above 150 Da, preferably 150-260 Da.
Further, the high-performance film composite nanofiltration membrane comprises a porous support bottom membrane and a polyamide selective separation layer with the aperture of 0.27-0.30 nm.
The high-performance film composite nanofiltration membrane provided by the invention greatly reduces the membrane aperture (r) p >0.270 nm), narrow pore size distribution, and greatly reduce molecular weight cut-off (MWCO)>150 Da) improves the crosslinking density of the polyamide separation layer, thereby improving the separation efficiency of divalent ions >99%）。
In some embodiments, the porous ultrafiltration support backing membrane is further provided with a nonwoven substrate, i.e., alternatively, the ultrafiltration porous support backing membrane may be nonwoven-backed or nonwoven-backed.
In some embodiments, the polyamide selective separation layers of the high performance composite nanofiltration membrane have a multivalent anion rejection rate of greater than 99%, preferably greater than 99.5%, and a multivalent cation rejection rate of greater than 90%, preferably greater than 98.5%; the interception rate of monovalent positive ions and monovalent negative ions is less than 35 percent.
Further, the polyamide selective separation layer pair SO 4 2- The ion rejection rate is as high as 99.11-99.85%, and the polyamide is prepared by the methodAmine Selective separation layer pair Mg 2+ The ion retention rate is as high as 99.12-99.78%, and the polyamide selective separation layer is used for separating Ca 2+ The rejection rate of ions is as high as 93.88-98.95%.
In some embodiments, the flux of the membrane composite nanofiltration membrane prepared by adding the phosphodiester in the organic phase to pure water is 10 Lm -2 h -1 bar -1 Above, preferably at 16 Lm -2 h -1 bar -1 The above; compared with the nanofiltration membrane prepared by not adding the phosphodiester in the organic phase, the pure water flux of the nanofiltration membrane is 5 Lm -2 h -1 bar -1 The pure water flux was 3 times or more that of the unmodified one. The ultra-high interception, high flux and low energy consumption film composite nanofiltration membrane has great application value in the aspects of desalination, chemical wastewater treatment, sea water desalination pretreatment, heavy metal solution separation and the like.
Further, the high-performance film composite nanofiltration membrane can intercept the salt solution containing the multivalent anions with the concentration of 20mmol/L to be more than 99 percent, preferably more than 99.5 percent; the retention rate of the salt solution containing the multivalent positive ions with the concentration of 20mmol/L is more than 90 percent, preferably more than 98.5 percent; the interception rate of monovalent positive ions and monovalent negative ions is less than 35 percent.
Therefore, the film composite nanofiltration membrane has ultrahigh interception of divalent ions and multivalent positive and negative ions>99 percent and high pure water flux>16 Lm -2 h -1 bar -1 ) Greatly reduces the molecular weight cut-off (MWCO)>150 Da）。
In conclusion, the high-performance film composite nanofiltration membrane provided by the invention has ultrahigh rejection on salt and has high pure water permeation flux. The high-performance film composite nanofiltration membrane provided by the invention adopts polyamine monomer solution as a water phase and polybasic acyl chloride/extremely low concentration phosphoric acid diester solution as an organic phase to carry out interfacial polymerization, and the phosphoric acid diester provides a double channel for the diffusion of piperazine, so that the film composite nanofiltration membrane with ultrahigh interception and high flux is obtained, the pore diameter is greatly reduced, the pore diameter distribution is narrowed, and the density of a separation selection layer is improved.
As another aspect of the technical scheme of the present invention, it also relates to a preparation method of a composite nanofiltration membrane with high performance, which comprises:
Separately providing an aqueous solution comprising a polyamine monomer, an organic solution comprising a polyacyl chloride monomer and a surfactant, wherein the surfactant comprises an oil-soluble anionic surfactant comprising two hydrophobic carbon chains;
the surface of the porous ultrafiltration support base film is used as the interface between the aqueous solution of the polyamine monomer and the organic solution, the polyamine monomer and the surfactant molecules are gathered at the interface through electrostatic interaction, and the polyamine monomer are subjected to interfacial polymerization under the regulation and control of the surfactant at the interface, so that a compact polyamide selective separation layer is formed on the surface of the porous ultrafiltration support base film, and then the porous ultrafiltration support base film is subjected to aftertreatment, so that the composite nanofiltration film with high performance is obtained.
In some preferred embodiments, the surfactant includes a di-phosphate compound containing a double carbon chain, and for example, may preferably include any one or a combination of two or more of dibutyl phosphate, didecyl phosphate, didodecyl phosphate, and the like, but is not limited thereto. The phosphodiester compound is dissolved in an organic solvent, and can provide a double channel for the diffusion of polyamine monomers in the interfacial polymerization process.
The preparation principle of the composite nanofiltration membrane with high performance of the invention may be as follows: the phosphodiester solution added to the organic solution comprising the polybasic acyl chloride monomer/phosphodiester mixture has two hydrophobic carbon chains, and the carbon chain lengths of the several phosphodiesters involved are different; the phosphodiester molecules are dissolved in an organic solvent, so that a double channel can be provided for the diffusion of polyamine monomers in the interfacial polymerization process; the porous ultrafiltration support bottom membrane is used as a water-oil phase interface of a polyamine monomer aqueous solution and a mixed organic solution containing a polybasic acyl chloride monomer/phosphoric acid diester, and the polyamine monomer in the water phase solution and the polybasic acyl chloride monomer in the mixed organic solution containing the polybasic acyl chloride monomer/phosphoric acid diester are subjected to interfacial polymerization reaction on the surface of the membrane, so that a polyamide selective separation layer is formed, meanwhile, hydroxyl contained in a phosphoric acid diester molecule and the polyamine monomer are attracted through electrostatic interaction, and double chains contained in the phosphoric acid diester can provide an effective channel for the diffusion of the polyamine monomer under low concentration, so that the high-performance film composite nanofiltration membrane is obtained.
In some embodiments, the preparation method specifically includes:
adding the aqueous solution containing the polyamine monomer to the surface of the porous ultrafiltration support base membrane under the conditions of 50-70% of relative humidity and 20-30 ℃ of ambient temperature, and fully soaking for 10-150 s, preferably 60-90 s; and adding an organic solution containing a surfactant such as a polybasic acyl chloride monomer and an acid diester molecule to the surface of the porous ultrafiltration support base membrane, soaking the surface for 30-120 s, preferably 30-60 s, carrying out interfacial polymerization reaction on the polybasic amine monomer and the polybasic acyl chloride monomer at a two-phase interface for 30-60 s, providing a double channel for the diffusion of the polybasic amine monomer from an aqueous phase to an organic phase by the acid diester molecule, and then placing the obtained composite nanofiltration membrane in an environment of 50-80 ℃ for heat treatment for 10-40 min to obtain the high-performance thin film composite nanofiltration membrane.
In some embodiments, the method of making comprises: the oil-soluble phosphate diester compound anionic surfactant is dissolved in an organic solvent which is not mutually soluble with water to prepare a solution of the phosphate diester compound.
In some embodiments, the concentration of the phosphodiester compound in the solution of the phosphodiester compound is 0.01 g/L to 1g/L, preferably 0.04 g/L to 0.1 g/L.
Further, the organic solvent used for dissolving the phosphodiester molecule may be any one or a combination of two or more of n-hexane, benzene, toluene, cyclohexane, and the like, but is not limited thereto.
In some embodiments, the method of making comprises: the organic solution containing the polyacyl chloride monomer and the surfactant (namely the polyacyl chloride/phosphoric acid diester mixed organic solution) is prepared by dissolving the polyacyl chloride monomer in a solution of a water-insoluble phosphoric acid diester compound (namely a phosphoric acid diester solution).
Further, the concentration of the polybasic acyl chloride monomer in the organic solution (namely the polybasic acyl chloride/phosphoric acid diester mixed organic solution) is 1 g/L-10 g/L, preferably 1 g/L-5 g/L.
Further, the polybasic acyl chloride monomer in the organic solution includes any one or a combination of more than two of trimesoyl chloride, isophthaloyl chloride, adipoyl chloride, terephthaloyl chloride and the like, but is not limited thereto.
Further, the organic phase solution comprises an organic solvent, a polybasic acyl chloride monomer and a phosphoric acid diester compound.
In some embodiments, the polyamine monomer in the aqueous solution containing the polyamine monomer includes one or a combination of two or more of piperazine, polyethyleneimine, m-phenylenediamine, diethylenetriamine, etc., but is not limited thereto.
In some embodiments, the concentration of the polyamine monomer in the aqueous solution comprising the polyamine monomer is 0.5 g/L to 10 g/L.
In some embodiments, the porous ultrafiltration support base membrane may be any one or a combination of two or more of a polyethersulfone ultrafiltration membrane, a polyacrylonitrile ultrafiltration membrane, a polysulfone ultrafiltration membrane, a sulfonated polysulfone ultrafiltration membrane, and a polyvinylidene chloride ultrafiltration membrane, and is preferably a polyethersulfone ultrafiltration membrane, but is not limited thereto.
Further, the pore diameter of the pores contained in the porous ultrafiltration support bottom membrane is 5-100 nm.
In some embodiments, the porous ultrafiltration support backing membrane is further provided with a nonwoven substrate, i.e., alternatively, the ultrafiltration porous support backing membrane may be nonwoven-backed or nonwoven-backed.
Wherein, as one of more specific embodiments, the preparation method specifically may include the following steps:
Carrying out interfacial polymerization under the conditions of 20-30 ℃ and 50-70% of relative humidity: the polyamine monomer is dissolved in pure water which is not mutually dissolved with the organic phase, the concentration is 0.5 g/L-10 g/L, the polyacyl chloride monomer is dissolved in fat-soluble phosphodiester solution with the concentration of 0.01 g/L-1 g/L, and the concentration is 1 g/L-5 g/L;
removing residual water stains on the surface of the porous ultrafiltration support base film, dripping aqueous solution of polyamine monomer on the surface of the porous ultrafiltration support base film, fully soaking the surface for 30-150 s, then sucking the polyamine monomer solution remained on the surface to be dry until no visible water stains, dripping the polybasic acyl chloride monomer/phosphoric acid diester mixed solution on the surface of the film, fully soaking the surface of the film in the polybasic acyl chloride monomer/phosphoric acid diester mixed solution for 10-120 s, carrying out interfacial polymerization reaction on the polyamine monomer and the polybasic acyl chloride monomer at the two-phase interface for 30-60 s, soaking the porous ultrafiltration base film in an organic solvent, washing away redundant unreacted acyl chloride monomer, then placing the film composite nanofiltration film in an environment of 50-80 ℃ for heat treatment for 10-40 min, and finally placing the film composite nanofiltration film in deionized water for storage to obtain the high-performance film composite nanofiltration film.
In conclusion, the preparation method of the high-performance film composite nanofiltration membrane provided by the invention is simple, the cost is greatly reduced due to the extremely low use concentration of the phosphodiester, the energy consumption cost of desalination, wastewater treatment, heavy metal solution separation and the like is greatly reduced due to the ultrahigh interception, high flux and effective separation of the heavy metal salt of the nanofiltration membrane, the desalination and recycling of wastewater can be realized, the recycling of metal ions can be realized, the process is easy to realize the large-scale production, and the method has high industrial application value.
Furthermore, the preparation method of the high-performance composite nanofiltration membrane is simpler, the cost of the used medicines and materials is low, the low energy consumption is ensured by the low pressure during operation, the high flux is achieved, meanwhile, the high interception efficiency of divalent cations and anions is achieved, and the high-performance composite nanofiltration membrane has wide application prospects in the field of water treatment.
As another aspect of the technical scheme of the invention, the invention also relates to the membrane composite nanofiltration membrane with ultrahigh interception performance and high flux, which is prepared by the method.
Further, the high-performance composite nanofiltration membrane has the concentration of Na of 20 mmol/L 2 SO 4 、MgSO 4 And MgCl 2 The retention rate of the solution is up to more than 99.5 percent, and CaCl is simultaneously treated 2 The retention rate of the catalyst is as high as 98.95%, and the catalyst shows the effect on divalent anions and cations Excellent interception performance, and pure water flux up to 16 Lm -2 h -1 bar -1 The above.
Another aspect of the embodiment of the invention also provides the application of the membrane composite nanofiltration membrane with ultrahigh interception performance and high flux in the field of water treatment.
Further, the high-performance film composite nanofiltration membrane is applied to the fields of sea water desalination pretreatment, monovalent/multivalent salt separation, functional industrial wastewater treatment and the like.
Accordingly, another aspect of the present invention also provides a method for separating a heavy metal salt, comprising:
providing the composite nanofiltration membrane with high performance;
and enabling a system containing heavy metal salt to pass through the composite nanofiltration membrane to separate the heavy metal salt.
The technical scheme of the invention is explained in more detail below with reference to a plurality of preferred embodiments and attached drawings. The following specific examples are given for the purpose of further illustration and explanation of the present invention and are not intended to be limiting thereof; in the examples described below, the ultrafiltration membrane is exemplified by a polyethersulfone ultrafiltration membrane, the diester phosphate molecules are exemplified by dibutyl phosphate, didecyl phosphate and didodecyl phosphate, the polyamine monomers are exemplified by piperazine, the organic solvent is exemplified by n-hexane, and the polyacyl chloride monomers are exemplified by trimesic chloride; some simple modifications of the method according to the invention are intended to be within the scope of the claims. A step of
Example 1
Dissolving piperazine (PIP) in pure water solution to prepare piperazine water solution with the concentration of 2.5 g/L; dibutyl phosphate molecules were prepared in a 0.6. 0.6 g/L solution using n-hexane solvent, and then adipoyl chloride monomer was dissolved in the dibutyl phosphate solution to prepare a 2. 2 g/L acid chloride solution. After immersing the sulfonated polysulfone ultrafiltration membrane on the surface of 100. 100 s with 2.5g/L piperazine solution at a temperature of 25 ℃ and a relative humidity of 60%, the membrane surface solution was blotted to be free of visible water stains, the membrane surface was immersed in adipoyl chloride/dibutyl phosphate solution with a concentration of 2 g/L for reaction of 30 s, and the membrane was immersed in n-hexane for 30 s to wash away the adipoyl chloride monomer remaining on the surface. Finally, the film is put into an oven, and is soaked in deionized water and stored in a refrigerator after being heat treated for 40 min at 50 ℃.
Through testing, the high-performance film composite nanofiltration membrane prepared in the embodiment uses 20mmol/L Na respectively under the conditions that the testing temperature is 25 ℃ and the operating pressure is 4 bar 2 SO 4 、MgSO 4 、MgCl 2 And CaCl 2 The aqueous solution was tested with rejection rates of 99.11%, 99.12%, 92.84% and 84.15%, pure water flux of 14.86 Lm -2 h -1 bar -1 。
Example 2
M-phenylenediamine is dissolved in pure water solution to prepare m-phenylenediamine water solution with the concentration of 5 g/L; dibutyl phosphate molecules were prepared into a solution with a concentration of 0.2. 0.2 g/L using an n-hexane solvent, and then trimesoyl chloride (TMC) monomers were dissolved using a dibutyl phosphate solution to prepare an acid chloride solution with a concentration of 3 g/L. After impregnating the polyethersulfone ultrafiltration bottom membrane with 5g/L m-phenylenediamine solution at 25.5 ℃ and a relative humidity of 55% on the surface of the bottom membrane for 90 s, sucking the solution on the surface of the membrane to be free of visible water, impregnating the surface of the membrane with 3 g/L trimesic chloride/dibutyl phosphate solution for 30 s, and immersing the membrane in n-hexane for 30 s to wash away residual trimesic chloride monomer on the surface. Finally, the film is put into an oven, and is soaked in deionized water and stored in a refrigerator after being heat treated for 30 min at 60 ℃.
Through testing, the high-performance film composite nanofiltration membrane prepared in the embodiment uses 20mmol/L Na respectively under the conditions that the testing temperature is 25 ℃ and the operating pressure is 4 bar 2 SO 4 、MgSO 4 、MgCl 2 And CaCl 2 The aqueous solution was tested for rejection of 99.47%, 99.27%, 92.46% and 80.34% and pure water flux of 16.98 Lm -2 h -1 bar -1 。
Example 3
Dissolving piperazine (PIP) in pure water solution to prepare a piperazine water solution with the concentration of 7 g/L; dibutyl phosphate molecules were prepared into a solution with a concentration of 0.1 g/L using an n-hexane solvent, and then isophthaloyl dichloride monomers were dissolved using a dibutyl phosphate solution to prepare an acid chloride solution with a concentration of 2 g/L. After impregnating the surface of a polyethersulfone ultrafiltration bottom membrane with a piperazine solution of 7 g/L for 1min at a temperature of 20 ℃ and a relative humidity of 70%, the surface solution of the membrane is sucked dry until no visible water stain exists, the surface of the membrane is then impregnated with an isophthaloyl chloride/dibutyl phosphate solution with a concentration of 2 g/L for reaction of 30 s, and then the membrane is soaked in n-hexane for 30 s to wash off residual isophthaloyl chloride monomers on the surface. Finally, the film is put into an oven, and is soaked in deionized water and stored in a refrigerator after being heat treated for 10 min at 80 ℃.
Through testing, the high-performance film composite nanofiltration membrane prepared in the embodiment uses 20mmol/L Na respectively under the conditions that the testing temperature is 25 ℃ and the operating pressure is 4 bar 2 SO 4 、MgSO 4 、MgCl 2 And CaCl 2 The aqueous solution was tested with rejection rates of 99.67%, 99.53%, 95.45% and 86.36% and pure water flux of 14.15 Lm -2 h -1 bar -1 。
Example 4
Dissolving piperazine (PIP) in pure water solution to prepare 8 g/L piperazine water solution; the dibutyl phosphate molecule was prepared into a solution with a concentration of 3 g/L using a cyclohexane solvent, and then the terephthaloyl chloride monomer was dissolved with the dibutyl phosphate solution to prepare an acid chloride solution with a concentration of 3 g/L. At a temperature of 23 ℃ and a relative humidity of 70%, the polyacrylonitrile ultrafiltration bottom membrane is soaked with 8 g/L piperazine solution for 1min, the surface solution of the membrane is dried until no visible water stain exists, then the surface of the membrane is soaked with 3 g/L terephthaloyl chloride/dibutyl phosphate solution for 30 s, and then the membrane is soaked in n-hexane for 30 s to wash away residual terephthaloyl chloride monomers on the surface. Finally, the film is put into an oven, and is soaked in deionized water and stored in a refrigerator after being heat treated for 10 min at 60 ℃.
Through testing, the high-performance film composite nanofiltration membrane prepared in the embodiment uses 20mmol/L Na respectively under the conditions that the testing temperature is 25 ℃ and the operating pressure is 4 bar 2 SO 4 、MgSO 4 、MgCl 2 And CaCl 2 The aqueous solution was tested with retention rates of 99.69%, 99.62%, 94.05% and 79.15% and pure water flux of 13.21 Lm -2 h -1 bar -1 。
Example 5
Dissolving piperazine (PIP) in pure water solution to prepare piperazine water solution with the concentration of 2.5 g/L; dibutyl phosphate molecules were prepared into a solution with a concentration of 0.08 g/L using an n-hexane solvent, and then trimesoyl chloride (TMC) monomers were dissolved using a dibutyl phosphate solution to prepare an acid chloride solution with a concentration of 2 g/L. After the polyethersulfone ultrafiltration bottom membrane was immersed in a piperazine solution of 2.5g/L at a temperature of 25℃and a relative humidity of 60% on the surface of 60. 60 s, the solution on the surface of the membrane was blotted to be free of visible water, the surface of the membrane was immersed in a trimesic acid chloride/dibutyl phosphate solution of a concentration of 2 g/L for reaction of 30 s, and then the membrane was immersed in n-hexane for 30 s to wash away residual trimesic acid chloride monomer on the surface. Finally, the film is put into an oven, and is soaked in deionized water and stored in a refrigerator after being heat treated for 30 min at 60 ℃.
Through testing, the high-performance film composite nanofiltration membrane prepared in the embodiment uses 20mmol/L Na respectively under the conditions that the testing temperature is 25 ℃ and the operating pressure is 4 bar 2 SO 4 、MgSO 4 、MgCl 2 And CaCl 2 The aqueous solutions were tested for rejection of 99.59%, 99.62%, 96.92% and 88.87% and pure water flux of 13.21 Lm -2 h -1 bar -1 。
Example 6
Dissolving piperazine (PIP) in pure water solution to prepare piperazine water solution with the concentration of 0.5 g/L; dibutyl phosphate molecules were prepared into a 0.06. 0.06 g/L solution with a benzene solvent, and then trimesoyl chloride (TMC) monomers were dissolved with the dibutyl phosphate solution to prepare a 2 g/L acid chloride solution. After the polyethersulfone ultrafiltration bottom membrane was immersed in a piperazine solution of 0.5g/L at a temperature of 27℃and a relative humidity of 60% on the surface of 60. 60 s, the solution on the surface of the membrane was blotted to be free of visible water, the surface of the membrane was immersed in a trimesic acid chloride/dibutyl phosphate solution of a concentration of 2 g/L for reaction of 30 s, and then the membrane was immersed in n-hexane for 30 s to wash away residual trimesic acid chloride monomer on the surface. Finally, the film is put into an oven, and is soaked in deionized water and stored in a refrigerator after being heat treated at 70 ℃ for 25 min.
Through testing, the high-performance film composite nanofiltration membrane prepared in the embodiment uses 20mmol/L Na respectively under the conditions that the testing temperature is 25 ℃ and the operating pressure is 4 bar 2 SO 4 、MgSO 4 、MgCl 2 And CaCl 2 The aqueous solutions were tested for rejection of 99.66%, 99.71%, 90.73% and 74.98% and pure water flux of 10.38 Lm -2 h -1 bar -1 。
Example 7
Dissolving piperazine (PIP) in pure water solution to prepare piperazine water solution with the concentration of 2.5 g/L; dibutyl phosphate molecules were prepared into a solution with a concentration of 0.04 g/L using an n-hexane solvent, and then trimesoyl chloride (TMC) monomers were dissolved using a dibutyl phosphate solution to prepare an acid chloride solution with a concentration of 1 g/L. After the polyethersulfone ultrafiltration bottom membrane was immersed in a piperazine solution of 2.5g/L at a temperature of 30℃and a relative humidity of 70% on the surface of 60. 60 s, the solution on the membrane surface was blotted to be free of visible water, the membrane surface was immersed in a trimesic acid chloride/dibutyl phosphate solution of a concentration of 1 g/L for reaction of 120. 120 s, and then the membrane was immersed in n-hexane for 30. 30 s to wash away residual trimesic acid chloride monomer on the surface. Finally, the film is put into an oven, and is soaked in deionized water and stored in a refrigerator after being heat treated for 30 min at 60 ℃.
Through testing, the high-performance film composite nanofiltration membrane prepared in the embodiment uses 20mmol/L Na respectively under the conditions that the testing temperature is 25 ℃ and the operating pressure is 4 bar 2 SO 4 、MgSO 4 、MgCl 2 And CaCl 2 The aqueous solutions were tested for rejection of 99.54%, 99.30%, 87.94% and 73.63% and pure water flux of 16.98 Lm -2 h -1 bar -1 。
Example 8
Dissolving diethyl triamine in pure water solution to prepare diethyl triamine water solution with the concentration of 10 g/L; the didecyl phosphate molecules were prepared into a solution with a concentration of 0.2. 0.2 g/L using an n-hexane solvent, and then trimesoyl chloride (TMC) monomers were dissolved using the didecyl phosphate solution to prepare an acid chloride solution with a concentration of 5. 5 g/L. After the polyvinylidene chloride ultrafiltration bottom film is soaked on the surface 10 s by using 10g/L of diethylenetriamine solution at the temperature of 24 ℃ and the relative humidity of 65%, the solution on the surface of the film is sucked to be free of visible water, then the surface of the film is soaked on the surface by using 5 g/L of trimesic chloride/dibutyl phosphate solution for reaction 60 s, and then the film is soaked in n-hexane for 30 s to wash off residual trimesic chloride monomer on the surface. Finally, the film is put into an oven, heat treated for 30 min at 55 ℃, soaked in deionized water and stored in a refrigerator.
Through testing, the high-performance film composite nanofiltration membrane prepared in the embodiment uses 20mmol/L Na respectively under the conditions that the testing temperature is 25 ℃ and the operating pressure is 4 bar 2 SO 4 、MgSO 4 、MgCl 2 And CaCl 2 The aqueous solutions were tested for retention rates of 98.39%, 98.23%, 97.06% and 83.19% and pure water flux of 12.98 Lm -2 h -1 bar -1 。
Example 9
Dissolving piperazine (PIP) in pure water solution to prepare piperazine water solution with the concentration of 2.5 g/L; the didecyl phosphate molecules were prepared into a 0.1. 0.1 g/L solution with n-hexane solvent, and then trimesoyl chloride (TMC) monomers were dissolved with the didecyl phosphate solution to prepare a 2 g/L acid chloride solution. After the polyethersulfone ultrafiltration bottom membrane was immersed in a piperazine solution of 2.5g/L at a temperature of 25℃and a relative humidity of 55% for a surface of 150. 150 s, the membrane surface solution was blotted dry to no visible water stain, the membrane surface was immersed in a trimesic acid chloride/dibutyl phosphate solution of a concentration of 2 g/L for a reaction of 30. 30 s, and then the membrane was immersed in n-hexane for 30. 30 s to wash away residual trimesic acid chloride monomer on the surface. Finally, the film is put into an oven, and is soaked in deionized water and stored in a refrigerator after being heat treated at 60 ℃ for 40 min.
Through testing, the high-performance film composite nanofiltration membrane prepared in the embodiment uses 20mmol/L Na respectively under the conditions that the testing temperature is 25 ℃ and the operating pressure is 4 bar 2 SO 4 、MgSO 4 、MgCl 2 And CaCl 2 The aqueous solution was tested for retention rates of 98.66%, 98.96%, 98.39% and 93.88% and pure water flux of 11.17 Lm -2 h -1 bar -1 。
Example 10
Dissolving piperazine (PIP) in pure water solution to prepare piperazine water solution with the concentration of 2.5 g/L; the didecyl phosphate molecules were prepared with n-hexane solvent to a concentration of 0.08 g/L (about 0.5 CMC) and then didecyl phosphate solution was used to dissolve trimesoyl chloride (TMC) monomer to a concentration of 2 g/L. After the polyethersulfone ultrafiltration bottom membrane was immersed in a piperazine solution of 2.5g/L at a temperature of 25℃and a relative humidity of 60% on the surface of 60. 60 s, the solution on the surface of the membrane was blotted to be free of visible water, the surface of the membrane was immersed in a trimesic acid chloride/dibutyl phosphate solution of a concentration of 2 g/L for reaction of 30 s, and then the membrane was immersed in n-hexane for 30 s to wash away residual trimesic acid chloride monomer on the surface. Finally, the film is put into an oven, and is soaked in deionized water and stored in a refrigerator after being heat treated for 30 min at 60 ℃.
Through testing, the high-performance film composite nanofiltration membrane prepared in the embodiment uses 20mmol/L Na respectively under the conditions that the testing temperature is 25 ℃ and the operating pressure is 4 bar 2 SO 4 、MgSO 4 、MgCl 2 And CaCl 2 The aqueous solution was tested with rejection rates of 99.85%, 99.78%, 99.57% and 98.95% and pure water flux of 16.38Lm -2 h -1 bar -1 。
Through testing, in the embodiment, MWCO and pore size distribution diagrams of the surface of the membrane after the didecyl phosphate is added and the membrane is not added for interfacial polymerization are respectively shown in fig. 1 and fig. 2, and as can be seen from fig. 1 and fig. 2, the pore size distribution of the nanofiltration membrane is obviously narrowed and the molecular weight cut-off is greatly reduced after the didecyl phosphate is added for interfacial polymerization. FIG. 3 is a SEM image of the surface morphology of the thin film composite nanofiltration after the addition of didecyl phosphate.
Example 11
Dissolving piperazine (PIP) in pure water solution to prepare piperazine water solution with the concentration of 2.5 g/L; the didecyl phosphate molecules were prepared into a solution with a concentration of 0.06. 0.06 g/L using a toluene solvent, and then trimesoyl chloride (TMC) monomers were dissolved using the didecyl phosphate solution to prepare an acid chloride solution with a concentration of 10 g/L. After impregnating the polysulfone ultrafiltration backing membrane with 2.5g/L piperazine solution at 28℃and 60% relative humidity on the surface 60 and s, the membrane surface solution was blotted dry to no visible water spots, the membrane surface was then impregnated with trimesic acid chloride/dibutyl phosphate solution at a concentration of 10g/L for reaction 100 s, and the membrane was then immersed in n-hexane for 30 s to wash away residual trimesic acid chloride monomer on the surface. Finally, the film is put into an oven, and is soaked in deionized water and stored in a refrigerator after being heat treated for 30 min at 75 ℃.
Through testing, the high-performance film composite nanofiltration membrane prepared in the embodiment uses 20mmol/L Na respectively under the conditions that the testing temperature is 25 ℃ and the operating pressure is 4 bar 2 SO 4 、MgSO 4 、MgCl 2 And CaCl 2 The aqueous solution was tested with rejection rates of 99.7%, 99.85%, 98.29% and 95.54% and pure water flux of 13.43 Lm -2 h -1 bar -1 。
Example 12
Dissolving piperazine (PIP) in pure water solution to prepare piperazine water solution with the concentration of 0.5 g/L; the didecyl phosphate molecules were prepared into a solution with a concentration of 0.01g/L using a n-hexane solvent, and then trimesoyl chloride (TMC) monomers were dissolved using the didecyl phosphate solution to prepare an acid chloride solution with a concentration of 2 g/L. After impregnating the surface of the polyvinylidene chloride ultrafiltration base membrane with a piperazine solution of 0.5 g/L at a temperature of 25.0 ℃ and a relative humidity of 50% for 80 s, the surface solution of the membrane is sucked dry until no visible water stain exists, the surface of the membrane is subjected to an impregnating reaction with a trimesic acid chloride/dibutyl phosphate solution of a concentration of 2 g/L for 30 s, and then the membrane is immersed in n-hexane for 30 s to wash away residual trimesic acid chloride monomers on the surface. Finally, the film is put into an oven, and is soaked in deionized water and stored in a refrigerator after being heat treated for 30 min at 60 ℃.
Through testing, the high-performance film composite nanofiltration membrane prepared in the embodiment uses 20mmol/L Na respectively under the conditions that the testing temperature is 25 ℃ and the operating pressure is 4 bar 2 SO 4 、MgSO 4 、MgCl 2 And CaCl 2 The aqueous solution was tested with rejection rates of 99.8%, 99.9%, 98.45% and 95.91% and pure water flux of 14.51 Lm -2 h -1 bar -1 。
Example 13
Dissolving polyethyleneimine in pure water solution to prepare polyethyleneimine water solution with the concentration of 2.5 g/L; didodecyl phosphate molecules were prepared into a 1 g/L solution with n-hexane solvent, and then trimesoyl chloride (TMC) monomers were dissolved with the didodecyl phosphate solution to prepare a 4 g/L acid chloride solution. At the temperature of 25.0 ℃ and relative humidity of 60%, the polyethersulfone ultrafiltration bottom membrane is soaked in a polyethyleneimine solution with the concentration of 2.5g/L for 1min, the solution on the surface of the membrane is dried until no visible water stain exists, then the surface of the membrane is soaked in a trimesic acid chloride/dibutyl phosphate solution with the concentration of 4 g/L for reaction for 30 s, and then the membrane is soaked in n-hexane for 30 s to wash out residual trimesic acid chloride monomer on the surface. Finally, the film is put into an oven, and is soaked in deionized water and stored in a refrigerator after being heat treated for 30 min at 60 ℃.
Through testing, the high-performance film composite nanofiltration membrane prepared in the embodiment uses 20mmol/L Na respectively under the conditions that the testing temperature is 25 ℃ and the operating pressure is 4 bar 2 SO 4 、MgSO 4 、MgCl 2 And CaCl 2 The aqueous solution was tested with rejection rates of 98.17%, 98.83%, 96.66% and 90.55% and pure water flux of 15.57 Lm -2 h -1 bar -1 。
Example 14
Dissolving piperazine (PIP) in pure water solution to prepare piperazine water solution with the concentration of 2.5 g/L; didodecyl phosphate molecules were prepared into a solution with a concentration of 0.08g/L using an n-hexane solvent, and then trimesoyl chloride (TMC) monomers were dissolved using the didodecyl phosphate solution to prepare an acid chloride solution with a concentration of 2 g/L. After the polyethersulfone ultrafiltration bottom membrane is soaked on the surface for 1min with 2.5g/L piperazine solution at the temperature of 25 ℃ and the relative humidity of 60%, the solution on the surface of the membrane is sucked to be dry until no visible water stain exists, then the surface of the membrane is soaked with 2 g/L trimesic chloride/dibutyl phosphate solution for reaction for 30 s, and then the membrane is soaked in n-hexane for 30 s to wash off residual trimesic chloride monomer on the surface. Finally, the film is put into an oven, and is soaked in deionized water and stored in a refrigerator after being heat treated for 30 min at 60 ℃.
Through tests, the high-performance film composite nanofiltration membrane prepared in the embodiment is prepared in the following wayThe test temperature was 25℃and the operating pressure was 4 bar, each with 20mmol/L Na 2 SO 4 、MgSO 4 、MgCl 2 And CaCl 2 The aqueous solutions were tested for retention rates of 99.72%, 99.9%, 99.18% and 97.88% and pure water flux of 19.59Lm -2 h -1 bar -1 。
It should be noted that: the high-performance composite nanofiltration membranes obtained in the above examples were tested by using a cross-flow mode. The retention rate of salt is calculated according to the ratio of the concentration of permeate to the concentration of feed liquid, and the calculation formula is as follows:
Pure water flux is based on the volume of liquid filtered per hour per square meter of membrane area and normalized to unit atmospheric pressure:
comparative example 1
The polyether sulfone ultrafiltration membrane is used as a support base membrane, piperazine (2.5 g/L) and trimesoyl chloride (2 g/L) are respectively used as polyamine monomers and polybasic acyl chloride monomers on the surface of the support base membrane for interfacial polymerization reaction to obtain the polyamide film composite nanofiltration membrane. However, the traditional nanofiltration membrane has low flux and low interception of salt, and can not achieve the purpose of separating and recycling the salt far enough, and is more easily polluted.
Through testing, the film composite nanofiltration membrane prepared in the comparative example uses 20mmol/L Na respectively under the conditions that the testing temperature is 25 ℃ and the operating pressure is 4 bar 2 SO 4 、MgSO 4 、MgCl 2 And CaCl 2 The aqueous solutions were tested for retention rates of 96.33%, 75.28%, 41.81% and 26.67% and pure water flux of 5.66Lm -2 h -1 bar -1 And the membrane has large pore diameter, wide pore diameter distribution and large molecular weight cut-off (392 Da).
Control 2 (aqueous phase surfactant: SDBS, sodium dodecylbenzenesulfonate)
Preparing a solution with the concentration of 1CMC from sodium dodecyl benzene sulfonate molecules by deionized water, and then dissolving piperazine (PIP) monomers by using the sodium dodecyl benzene sulfonate solution to prepare a piperazine/sodium dodecyl benzene sulfonate solution with the concentration of 2.5 g/l; trimesoyl chloride (TMC) monomer was dissolved in deionized water to prepare an acyl chloride solution at a concentration of 2 g//. After the polyethersulfone ultrafiltration bottom membrane is soaked with 2.5g/L piperazine/dodecyl benzene sulfonate solution for 1min at the temperature of 25 ℃ and the relative humidity of 60%, the solution on the surface of the membrane is sucked to be free of visible water stains, then the surface of the membrane is soaked with trimesic acid chloride/dibutyl phosphate solution with the concentration of 2 g/L for reaction for 30 s, and then the membrane is soaked in n-hexane for 30 s to wash off residual trimesic acid chloride monomer on the surface. Finally, the film is put into an oven, and is soaked in deionized water and stored in a refrigerator after being heat treated for 30 min at 60 ℃.
Through testing, the high-performance film composite nanofiltration membrane prepared in the embodiment uses 20mmol/L Na respectively under the conditions that the testing temperature is 25 ℃ and the operating pressure is 4 bar 2 SO 4 、MgSO 4 、MgCl 2 And CaCl 2 The aqueous solution was tested with rejection rates of 96.56%, 94.07%, 90.34% and 85.15% and pure water flux of 6.37 Lm -2 h -1 bar -1 。
The various aspects, embodiments, features and examples of the invention are to be considered in all respects as illustrative and not intended to limit the invention, the scope of which is defined solely by the claims. Other embodiments, modifications, and uses will be apparent to those skilled in the art without departing from the spirit and scope of the claimed invention.
The use of headings and chapters in this disclosure is not meant to limit the disclosure; each section may apply to any aspect, embodiment, or feature of the present invention.
Throughout this disclosure, where a composition is described as having, comprising, or including a particular component, or where a process is described as having, comprising, or including a particular process step, it is contemplated that the composition of the teachings of the present invention also consist essentially of, or consist of, the recited component, and that the process of the teachings of the present invention also consist essentially of, or consist of, the recited process step.
Unless specifically stated otherwise, the use of the terms "comprising (include, includes, including)", "having (has, has or has)" should generally be understood to be open-ended and not limiting.
It should be understood that the order of steps or order in which a particular action is performed is not critical, as long as the present teachings remain operable. Furthermore, two or more steps or actions may be performed simultaneously.
In addition, the present inventors have also conducted experiments with other materials and conditions listed in the present specification, etc. in the manner of example 1-example 14, and have also produced a high-performance thin film composite nanofiltration membrane having both ultra-high rejection and high flux of positive and negative divalent ions.
While the invention has been described with reference to an illustrative embodiment, it will be understood by those skilled in the art that various other changes, omissions and/or additions may be made and substantial equivalents may be substituted for elements thereof without departing from the spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. Moreover, unless specifically stated any use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another.
Claims (14)
1. A composite nanofiltration membrane having high performance, comprising: the porous ultrafiltration support bottom film and a polyamide selective separation layer arranged on the porous ultrafiltration support bottom film, wherein the polyamide selective separation layer is formed by interfacial polymerization reaction of an aqueous solution containing a polyamine monomer and an organic solution containing a polybasic acyl chloride monomer and a phosphoric acid diester compound under the regulation and control of the phosphoric acid diester compound, and the phosphoric acid diester compound comprises any one or more than two of dibutyl phosphate, didecyl phosphate and didodecyl phosphate;
the organic solvent in the organic solution comprises any one or more than two of normal hexane, benzene, toluene and cyclohexane, and the concentration of the phosphoric acid diester compound is 0.01-g/L to 1g/L;
the polybasic acyl chloride monomer comprises any one or more than two of trimesoyl chloride, isophthaloyl dichloride, adipoyl chloride and terephthaloyl dichloride;
the polyamine monomer comprises one or more than two of piperazine, polyethyleneimine, m-phenylenediamine and diethyl triamine;
the retention rate of the polyamide selective separation layer of the composite nanofiltration membrane with high performance on multivalent anions is more than 99%, and the retention rate on multivalent cations is more than 90%; the interception rate of monovalent positive ions and monovalent negative ions is less than 35 percent;
The flux of the composite nanofiltration membrane to pure water is 10 Lm -2 h -1 bar -1 The above;
the aperture of the holes contained in the polyamide selective separating layer of the composite nanofiltration membrane is above 0.270 and nm, and the molecular weight cut-off is above 150 and Da.
2. The composite nanofiltration membrane with high performance according to claim 1, wherein: the thickness of the polyamide selective separation layer is 30-70 nm;
the porous ultrafiltration support bottom membrane is made of a polyethersulfone ultrafiltration membrane, a polyacrylonitrile ultrafiltration membrane, a polysulfone ultrafiltration membrane, a sulfonated polysulfone ultrafiltration membrane or a polyvinylidene chloride ultrafiltration membrane;
the pore diameter of the pores contained in the porous ultrafiltration support bottom membrane is 5-100 nm;
the porous ultrafiltration support bottom membrane is also provided with a non-woven fabric substrate.
3. The composite nanofiltration membrane with high performance according to claim 1, wherein: the polyamide selective separation layer with the high-performance composite nanofiltration membrane has the interception rate of multivalent anions of more than 99.5 percent and the interception rate of multivalent cations of more than 98.5 percent.
4. The composite nanofiltration membrane with high performance according to claim 1, wherein: the polyamide selective separation layer pair SO 4 2- The retention rate of ions is 99.11-99.85%, and the ion retention rate is as high as Mg 2+ The retention rate of ions is 99.12-99.78%, and Ca is as follows 2+ The rejection rate of ions is 93.88-98.95%.
5. The composite nanofiltration membrane with high performance according to claim 1, wherein: the flux of the composite nanofiltration membrane to pure water is 16 Lm -2 h -1 bar -1 The above.
6. The composite nanofiltration membrane with high performance according to claim 1, wherein: the aperture of the holes contained in the polyamide selective separation layer of the composite nanofiltration membrane is 0.270-0.300 nm, and the molecular weight cut-off is 150-260 Da.
7. The preparation method of the composite nanofiltration membrane with high performance is characterized by comprising the following steps:
respectively providing an aqueous solution containing a polyamine monomer and an organic solution containing a polybasic acyl chloride monomer and a phosphate diester compound, wherein the phosphate diester compound comprises any one or more than two of dibutyl phosphate, didecyl phosphate and didodecyl phosphate, and the concentration of the phosphate diester compound is 0.01-g/L to 1g/L;
the organic solvent in the organic solution comprises any one or more than two of normal hexane, benzene, toluene and cyclohexane;
the surface of a porous ultrafiltration support base film is used as a reaction interface between aqueous solution of the polyamine monomer and the organic solution, the polyamine monomer and the phosphoric acid diester compound molecules are gathered at the reaction interface through electrostatic interaction, and the polyamine monomer are subjected to interfacial polymerization under the regulation and control of the phosphoric acid diester compound at the reaction interface, so that a compact polyamide selective separation layer is formed on the surface of the porous ultrafiltration support base film, and then heat treatment is carried out, so that the composite nanofiltration film with high performance is obtained.
8. The preparation method according to claim 7, characterized by comprising: the solution of the phosphoric acid diester compound is prepared by dissolving the phosphoric acid diester compound in an organic solvent which is not miscible with water.
9. The method for preparing the organic light emitting diode compound according to claim 8, wherein the concentration of the organic light emitting diode compound in the solution of the organic light emitting diode compound is 0.04 g/L to 0.1 g/L.
10. The preparation method according to claim 8, characterized by comprising: dissolving a polybasic acyl chloride monomer into a solution of a water-insoluble phosphoric acid diester compound to prepare an organic solution containing the polybasic acyl chloride monomer and the phosphoric acid diester compound; the concentration of the polybasic acyl chloride monomer in the organic solution is 1 g/L-10 g/L, and the polybasic acyl chloride monomer comprises any one or more than two of trimesoyl chloride, isophthaloyl chloride, adipoyl chloride and terephthaloyl chloride.
11. The preparation method according to claim 7 or 8, characterized in that: the polyamine monomer in the aqueous solution containing the polyamine monomer comprises one or more than two of piperazine, polyethyleneimine, m-phenylenediamine and diethyl triamine; the concentration of the polyamine monomer in the aqueous solution containing the polyamine monomer is 0.5 g/L-10 g/L;
The porous ultrafiltration support bottom membrane is made of a polyethersulfone ultrafiltration membrane, a polyacrylonitrile ultrafiltration membrane, a polysulfone ultrafiltration membrane, a sulfonated polysulfone ultrafiltration membrane or a polyvinylidene chloride ultrafiltration membrane; the pore diameter of the pores contained in the porous ultrafiltration support bottom membrane is 5-100 nm; the porous ultrafiltration support bottom membrane is also provided with a non-woven fabric substrate.
12. A composite nanofiltration membrane with high performance produced by the method of any one of claims 7-11.
13. Use of a composite nanofiltration membrane with high performance according to any one of claims 1-6, 12 in the field of desalination pretreatment, multivalent/monovalent salt separation or functional industrial wastewater treatment.
14. A method for separating a heavy metal salt, comprising:
providing a composite nanofiltration membrane of any one of claims 1-6, 12 having high performance;
and enabling a system containing heavy metal salt to pass through the composite nanofiltration membrane to separate the heavy metal salt.
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