CN116116238A - High-flux anti-scaling nanofiltration membrane and preparation method and application thereof - Google Patents

High-flux anti-scaling nanofiltration membrane and preparation method and application thereof Download PDF

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CN116116238A
CN116116238A CN202310339138.3A CN202310339138A CN116116238A CN 116116238 A CN116116238 A CN 116116238A CN 202310339138 A CN202310339138 A CN 202310339138A CN 116116238 A CN116116238 A CN 116116238A
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solution
flux
chloride
membrane
scaling
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唐量
吴桐
张亦周
吴明红
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University of Shanghai for Science and Technology
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University of Shanghai for Science and Technology
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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
    • B01D69/02—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor characterised by their properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
    • B01D61/027—Nanofiltration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/12—Composite membranes; Ultra-thin membranes
    • B01D69/125—In situ manufacturing by polymerisation, polycondensation, cross-linking or chemical reaction
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/56—Polyamides, e.g. polyester-amides
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C02F1/442—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by nanofiltration
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A20/00—Water conservation; Efficient water supply; Efficient water use
    • Y02A20/124—Water desalination
    • Y02A20/131—Reverse-osmosis

Abstract

The invention provides a preparation method of a high-flux anti-scaling nanofiltration membrane, which comprises the following steps: 1) Adding polyamine monomer into water; 2) Adding a buffer solution into the polyamine solution, and adjusting the pH value to 4-12; 3) Taking an ultrafiltration bottom membrane, and fully infiltrating the ultrafiltration bottom membrane by adopting an interfacial polymerization aqueous phase solution; drying in the shade in the air to obtain a water phase ultrafiltration bottom membrane; 4) Fully infiltrating the surface of the aqueous phase ultrafiltration bottom membrane by adopting a polybasic acyl chloride solution, carrying out interfacial polymerization reaction on the polybasic amine monomer and the polybasic acyl chloride, thereby forming a polyamide ultrathin separating layer on the surface of the aqueous phase ultrafiltration bottom membrane, and carrying out annealing treatment to obtain a high-flux anti-scaling nanofiltration membrane; the polyacyl chloride solution comprises a polyacyl chloride and an organic solvent. According to the embodiment of the invention, the pH value of the buffer solution is changed, the ratio of the protonated piperazine is adjusted, and then the dynamic balance of the protonated piperazine and the unprotonated piperazine is established, so that the high-flux anti-scaling nanofiltration membrane is prepared.

Description

High-flux anti-scaling nanofiltration membrane and preparation method and application thereof
Technical Field
The invention relates to the technical field of water treatment, in particular to a method for improving the performance of a nanofiltration membrane applied to sewage treatment, and especially relates to a method for improving the flux and anti-scaling performance of the nanofiltration membrane.
Background
The sewage treatment and reuse is a method for improving the increment of water resources. The nanofiltration technology is used as a low-pressure driven membrane separation technology, can realize the efficient and selective removal of multivalent ions and small organic molecules, and has huge application value in the field of wastewater treatment due to the characteristics of simplicity, high efficiency, large treatment capacity, low treatment cost and the like. The nanofiltration membrane still has problems in the aspect of sewage treatment application at the present stage: firstly, because of uncontrollable interfacial polymerization reaction and nonuniform interfacial small molecular amine distribution, the membrane surface is easy to have defects, so that the membrane separation performance cannot be further improved; secondly, the membrane surface is severely scaled due to the high flux of the membrane and the selective interception of divalent ions.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a preparation method of a high-flux anti-scaling nanofiltration membrane.
In order to achieve the aim of the invention, the invention adopts the following technical scheme:
one aspect of the invention provides a method for preparing a high-flux, anti-scaling nanofiltration membrane, comprising the steps of:
1) Adding polyamine monomer into water to obtain polyamine solution;
2) Adding a buffer solution into the polyamine solution, and regulating the pH value to 4-12 to obtain an interfacial polymerization aqueous phase solution;
3) Taking an ultrafiltration bottom membrane, and fully infiltrating the ultrafiltration bottom membrane by adopting the interfacial polymerization aqueous phase solution; drying in the shade in the air to obtain a water phase ultrafiltration bottom membrane;
4) Fully infiltrating the surface of the aqueous phase ultrafiltration bottom membrane by adopting a polybasic acyl chloride solution, carrying out interfacial polymerization reaction on the polybasic amine monomer and the polybasic acyl chloride, thereby forming a polyamide ultrathin separating layer on the surface of the aqueous phase ultrafiltration bottom membrane, and carrying out annealing treatment to obtain a high-flux anti-scaling nanofiltration membrane;
the polyacyl chloride solution comprises a polyacyl chloride and an organic solvent.
Optionally, the buffer solution adopts a conjugate acid-base pair, and the conjugate acid-base pair adopts weak acid and conjugate base thereof or weak base and conjugate acid thereof; the conjugated acid-base pair is selected from at least one of a phosphate system, a carbonate system, a borate system and a citrate system; the conjugated acid-base pair concentration in the interfacial polymerization aqueous phase solution is 0.001M-0.5M.
Optionally, the polyamine monomer is selected from at least one of piperazine, m-phenylenediamine, p-phenylenediamine, melamine, thiourea, polyethyleneimine, diethylenetriamine and N-aminoethylpiperazine.
Optionally, the organic solvent is selected from at least one of hexane, heptane, pentane, isopar G, toluene, ethyl acetate and benzene.
Optionally, the polybasic acyl chloride is at least one selected from 1,3, 5-trimesoyl chloride, terephthaloyl chloride, isophthaloyl chloride, nonyldiacid chloride, oxalyl chloride, 2', 4' -biphenyl tetra-formyl chloride.
Optionally, the ultrafiltration membrane material is selected from any one of polysulfone, polyethersulfone, polyvinylidene fluoride, polyacrylonitrile, polytetrafluoroethylene nylon, cellulose or cellulose derivative; the aperture of the holes contained in the ultrafiltration bottom membrane supporting layer is 0.01-2 mu m. The pore size of the polymer strongly influences interfacial polymerization reaction, and determines the storage amount of aqueous phase solution in the pore size. Optionally, the concentration of the polybasic acyl chloride in the polybasic acyl chloride solution is 0.25-7.5 mg/ml, the annealing treatment temperature is 20-80 ℃ and the annealing treatment time is 1-30 min.
Optionally, the polyamine monomer and the polybasic acyl chloride are subjected to interfacial polymerization reaction for 30-90 s under the condition that the interface is at the temperature of 20-35 ℃ and the relative humidity is 50-100%.
In another aspect, the invention provides a high flux, anti-fouling nanofiltration membrane made by any of the methods described above. The high-flux anti-scaling nanofiltration membrane comprises a polyamide ultrathin separation layer, wherein the thickness of the polyamide ultrathin separation layer is 8-30 nm, the polyamide ultrathin separation layer is positioned on the surface of the high-flux anti-scaling nanofiltration membrane, and the polyamide ultrathin separation layer has a smooth structure;
the pure water flux of the high flux anti-scaling nanofiltration membrane is 110 L.h -1 ·m -2 ·bar -1 The retention rate of the perfluoro caprylic acid reaches more than 88 percent; the retention rate of PEG600 reaches over 96 percent; on the premise of ensuring the high retention rate of specific substances, the water flux and the anti-scaling performance are greatly improved.
In a further aspect, the invention provides the application of the high-flux anti-scaling nanofiltration membrane in the field of water treatment, and the high-flux anti-scaling nanofiltration membrane is applied to sewage treatment.
Due to the adoption of the technical scheme, the method has at least the following beneficial effects:
1. the invention provides a method for improving flux and anti-scaling performance of a nanofiltration membrane, by which a high-flux anti-scaling nanofiltration membrane can be obtained.
2. The embodiment of the invention combines nanofiltration membrane structure and performance regulation means, and designs and optimizes the interfacial polymerization reaction rate and the small molecular amine diffusion rate: on one hand, the pH value of the water phase is adjusted to partially protonate the small molecular amine, so that a mixture balance solution is formed to regulate the diffusion rate of the small molecular amine at the interface; on the other hand, the neutralization effect of the buffer solution on the byproducts of the interfacial polymerization can ensure the continuous progress of the interfacial polymerization reaction, thereby forming a defect-free nanofiltration membrane.
3. In the preparation method of the embodiment of the invention, weak acid and conjugate base buffer solution thereof are added into aqueous phase solution, the ratio of protonated piperazine is adjusted by changing the pH value of the buffer solution, and then the dynamic balance of protonated piperazine and unprotonated piperazine is established, so as to achieve the purpose of regulating and controlling the diffusion of aqueous phase piperazine in the interfacial polymerization process, and the ultra-thin, high-flux, high-negative and anti-scaling nanofiltration membrane is prepared.
4. The preparation method provided by the embodiment of the invention regulates and controls the diffusion rate and interfacial polymerization reaction of piperazine, improves the surface defects, film thickness and electronegativity of the traditional nanofiltration membrane, solves the problems of complex traditional regulation and control methods, high cost, unsatisfactory effects and the like, is simple, low in cost, obvious and stable in regulation and control effect, is convenient for large-scale preparation, and has a relatively high industrial application value.
Detailed Description
The following detailed description of the present invention will be provided to facilitate understanding of the present invention, so that the above objects, features and advantages of the present invention will be more apparent. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, and to provide a preferred embodiment of the present invention. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete. The present invention may be embodied in many other forms than described herein and similarly modified by those skilled in the art without departing from the spirit of the invention, so that the invention is not limited to the specific embodiments disclosed below.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and/or" as used herein includes any and all combinations of one or more of the associated listed items.
The polyamide nanofiltration membrane is prepared by interfacial polymerization reaction of trimesoyl chloride and piperazine at an oil-water interface, and the interfacial polymerization comprises two steps: the first step is the diffusion of aqueous phase small molecule amine into the oil phase; the second step is the chemical reaction of the acid chloride group with the amino group. Diffusion of interfacial small molecular amines and too fast chemical reaction affect the uniformity and thickness of polyamide membranes, resulting in a failure to increase both permeability and selectivity. Therefore, the strategy for improving the permeation flux of the membrane composite nanofiltration membrane can be mainly divided into two aspects: firstly, regulating and controlling the diffusion rate of small molecular amine; and secondly, controlling the reaction rate of the interfacial polymerization reaction.
In view of the defects in the prior art, the inventor unexpectedly found that the structure and performance of the nanofiltration membrane can be regulated and controlled by adjusting the pH value of the water phase, and the diffusion rate of the small molecular amine at the interface can be regulated and controlled by adjusting the polymerization reaction rate of the interface and the diffusion rate of the small molecular amine on the one hand, the small molecular amine is partially protonated by adjusting the pH value of the water phase, so that a mixture balance solution is formed; on the other hand, the neutralization effect of the buffer solution on the byproducts of the interfacial polymerization can ensure the continuous progress of the interfacial polymerization reaction, thereby forming a defect-free nanofiltration membrane. Based on the finding, the inventor provides a technical scheme of the embodiment of the invention, namely the flux of the nanofiltration membrane is improved while the high performance of the nanofiltration membrane is ensured, meanwhile, the scaling risk of the nanofiltration membrane is reduced, and a preparation method of the nanofiltration membrane with high flux and scaling resistance and an application of the nanofiltration membrane prepared by the method in water treatment are provided. The technical scheme, implementation process, principle and the like are optionally explained as follows.
The embodiment of the invention provides a preparation method of a high-flux anti-scaling nanofiltration membrane, which comprises the following steps:
1) Adding polyamine monomer into water to obtain polyamine solution;
the polyamine monomer is at least one selected from piperazine, m-phenylenediamine, p-phenylenediamine, melamine, thiourea, polyethyleneimine, diethyl triamine and N-aminoethylpiperazine.
2) Adding a buffer solution into the polyamine solution, and regulating the pH value to 4-12 to obtain an interfacial polymerization aqueous phase solution;
the buffer solution adopts a conjugate acid-base pair, wherein the conjugate acid-base pair adopts weak acid and conjugate base thereof, or the conjugate acid-base pair adopts weak base and conjugate acid thereof;
the conjugated acid-base pair is selected from at least one of a phosphate system, a carbonate system, a borate system and a citrate system;
the conjugated acid-base pair concentration in the surface polymerization aqueous phase solution is 0.001M-0.5M.
3) Taking an ultrafiltration bottom membrane prepared in advance, and fully infiltrating the ultrafiltration bottom membrane with an interfacial polymerization aqueous phase solution for 10-120 s; drying in the shade in the air until no obvious liquid drops are on the surface, thus obtaining the aqueous phase ultrafiltration bottom membrane;
the ultrafiltration bottom membrane material is selected from any one of polysulfone, polyethersulfone, polyvinylidene fluoride, polyacrylonitrile, polytetrafluoroethylene nylon, cellulose or cellulose derivatives; the aperture of the holes contained in the ultrafiltration membrane supporting layer is 0.01-2 mu m. The pore size of the polymer strongly influences interfacial polymerization reaction, and determines the storage amount of aqueous phase solution in the pore size.
4) Fully infiltrating the surface of the aqueous phase ultrafiltration bottom membrane by adopting a polybasic acyl chloride solution, carrying out interfacial polymerization reaction on the polybasic amine monomer and the polybasic acyl chloride for 30-90 s under the condition that the interface is at the temperature of 20-35 ℃ and the relative humidity is 50-100%, so as to form a polyamide ultrathin separation layer on the surface of the aqueous phase ultrafiltration bottom membrane, and then carrying out annealing treatment, wherein the annealing treatment temperature is 20-80 ℃ and the annealing treatment time is 1-30 min; thereby obtaining a high-flux anti-scaling nanofiltration membrane;
the polybasic acyl chloride solution comprises polybasic acyl chloride and an organic solvent;
the polybasic acyl chloride is at least one selected from 1,3, 5-trimesoyl chloride, terephthaloyl chloride, isophthaloyl chloride, nonyldiacid chloride, oxalyl chloride and 2,2', 4' -biphenyl tetra-formyl chloride; the concentration of the polybasic acyl chloride in the polybasic acyl chloride solution is 0.25-7.5 mg/ml;
the organic solvent is at least one selected from hexane, heptane, pentane, isopar G, toluene, ethyl acetate and benzene.
The high-flux anti-scaling nanofiltration membrane comprises a polyamide ultrathin separation layer, wherein the thickness of the polyamide ultrathin separation layer is 8-30 nm, the polyamide ultrathin separation layer is positioned on the surface of the high-flux anti-scaling nanofiltration membrane, and the polyamide ultrathin separation layer has a smooth structure;
the pure water flux of the high flux anti-scaling nanofiltration membrane is 110 L.h -1 ·m -2 ·bar -1 The retention rate of the perfluoro caprylic acid reaches more than 88 percent; the retention rate of PEG600 reaches over 96 percent; on the premise of ensuring the high retention rate of specific substances, the water flux and the anti-scaling performance are greatly improved.
The high-flux anti-scaling nanofiltration membrane prepared by the embodiment of the invention can be applied to sewage treatment.
The following are specific examples
Example 1
Regulation of piperazine (2.5 mg/ml) and NaH 2 (PO 4 ) 3 (0.1M) mixing the aqueous solution to pH 7.36, soaking the polysulfone composite bottom film with the solution for 120s, then sucking the surface solution to dryness, then soaking the surface of the composite bottom film in 1,3, 5-trimesoyl chloride hexane solution with concentration of 2mg/ml, taking out after reacting for 60s at 25 ℃ and relative humidity of 80%, cleaning the film with normal hexane, and then placing the film at 60 ℃ and heating for 1min to obtain the high-flux nanofiltration film, wherein SEM and AFM analysis shows that the nanofiltration film surface has a smooth structure, TEM shows that the thickness of the separation layer is 15nm, and zeta potential at pH7 is 50mV.
The nanofiltration membrane prepared by the method is tested by cross flow of an aqueous solution, the testing temperature is 25 ℃, the reflux is firstly carried out for 30min under the pressure of 4bar, then the testing is carried out under the pressure of 2bar, and the flux is 30 L.h -1 ·m -2 ·bar -1 The method comprises the steps of carrying out a first treatment on the surface of the With 1000ppm Na 2 SO 4 The cross-flow test of the aqueous solution, the test temperature is 25 ℃, the test is carried out under the pressure of 2bar, and the retention rate is 96%; with 1000ppm MgSO 4 The cross-flow test of the aqueous solution, the test temperature is 25 ℃, the test is carried out under the pressure of 2bar, and the retention rate is 67%; with 1000ppm MgCl 2 The cross-flow test of the aqueous solution, the test temperature is 25 ℃, the test is carried out under the pressure of 2bar, and the retention rate is 22%; with 1000ppm CaCl 2 The cross-flow test of the aqueous solution, the test temperature is 25 ℃, the test is carried out under the pressure of 2bar, and the retention rate is 16%; cross-flow test was carried out with 1000ppm NaCl aqueous solution at 25℃and at a pressure of 2bar with a retention of 25%.
Comparative example 1
After piperazine (2.5 mg/ml) aqueous solution is soaked in polysulfone composite bottom film for 120s, the surface solution is sucked dry, then the composite bottom film is soaked in 1,3, 5-trimesoyl chloride hexane solution with the concentration of 2mg/ml, the solution is reacted for 60s at the temperature of 25 ℃ and the relative humidity of 80%, the solution is taken out, the obtained film is washed by normal hexane, the film is placed at the temperature of 60 ℃ and heated for 1min, and a nanofiltration film is obtained, wherein TEM shows the thickness of a separation layer of 65nm, and the zeta potential at the pH7 is minus 30mV.
The nanofiltration membrane prepared by the method is tested by cross-flow of aqueous solution at 25 ℃ under the pressure of 4bar for 30min, and then is subjected to 2Tested at bar pressure, flux 8 L.h -1 ·m -2 ·bar -1 The method comprises the steps of carrying out a first treatment on the surface of the With 1000ppm Na 2 SO 4 The cross-flow test of the aqueous solution, the test temperature is 25 ℃, the test is carried out under the pressure of 2bar, and the retention rate is 95%; with 1000ppm MgSO 4 The cross-flow test of the aqueous solution, the test temperature is 25 ℃, the test is carried out under the pressure of 2bar, and the retention rate is 93%; with 1000ppm MgCl 2 The cross-flow test of the aqueous solution, the test temperature is 25 ℃, the test is carried out under the pressure of 2bar, and the retention rate is 81%; with 1000ppm CaCl 2 The cross-flow test of the aqueous solution, the test temperature is 25 ℃, the test is carried out under the pressure of 2bar, and the retention rate is 72%; cross-flow test was carried out with 1000ppm NaCl aqueous solution at 25℃and at a pressure of 2bar with a retention of 26%.
Comparative example 2
Comparative example 2 was identical to the other conditions of example 1, with the only difference: comparative example 2 the pH of the aqueous piperazine (2.5 mg/ml) solution was adjusted to 7.36 by hydrochloric acid without addition of buffer solution; experiments find that the interception performance is poor.
The nanofiltration membrane prepared in comparative example 2 was tested with an aqueous solution cross-flow at 25℃under reflux for 30min at a pressure of 4bar and then at a flux of 29 L.h at a pressure of 2bar -1 ·m -2 ·bar -1 The method comprises the steps of carrying out a first treatment on the surface of the With 1000ppm Na 2 SO 4 The cross-flow test of the aqueous solution, the test temperature is 25 ℃, the test is carried out under the pressure of 2bar, and the retention rate is 68%; with 1000ppm MgSO 4 The cross-flow test of the aqueous solution, the test temperature is 25 ℃, the test is carried out under the pressure of 2bar, and the retention rate is 45%; with 1000ppm MgCl 2 The cross-flow test of the aqueous solution, the test temperature is 25 ℃, the test is carried out under the pressure of 2bar, and the retention rate is 14%; with 1000ppm CaCl 2 The cross-flow test of the aqueous solution, the test temperature is 25 ℃, the test is carried out under the pressure of 2bar, and the retention rate is 9%; cross-flow test was carried out with 1000ppm NaCl aqueous solution at a temperature of 25℃and a pressure of 2bar, with a rejection of 13%.
Anti-fouling experiment
An anti-fouling experiment was performed on example 1 and comparative example 1, comprising the following steps: firstly, respectively placing nanofiltration membranes prepared in the two embodiments in NF cross-flow units, and firstly refluxing for 30min under the pressure of 4bar for compaction; the cross-flow speed and the feeding solution temperature are respectively 21.4cm/s and 25.0+/-0.5 ℃; a mixed solution composed of 30mM calcium chloride, 20mM sodium sulfate and 10mM sodium chloride was prepared, the pH of the mixed solution was adjusted to 7.0.+ -. 0.1, the solution was thoroughly mixed, and the mixture was refluxed for 1 hour. The pressure was adjusted to the appropriate pressure and the initial permeate flux of the two membranes was 85LMH. The reaction was carried out at a cycle temperature of 15.0cm/s and 25.0.+ -. 0.5 ℃ for 12 hours.
After 12h, the flux of the nanofiltration membrane prepared in comparative example 1 was reduced by 21% and the flux of the nanofiltration membrane prepared in example 1 was reduced by 6%. The nanofiltration membrane prepared in example 1 has little flux drop, which indicates that the fouling resistance is good.
Example 2
Regulation of piperazine (2.5 mg/ml) and Na 2 CO 3 /NaCHO 3 (0.1M) mixing the aqueous solution to pH11.0 with
The solution is used for soaking a polyether sulfone composite bottom membrane for 120 seconds, then the surface solution is sucked to dryness, then the surface of the composite bottom membrane is soaked in a 1,3, 5-trimesoyl chloride hexane solution with the concentration of 2mg/ml, the solution is taken out after being reacted for 60 seconds under the condition that the temperature is 25 ℃ and the relative humidity is 80%, the membrane is cleaned by normal hexane, and then the membrane is placed at the temperature of 60 ℃ and heated for 1 minute, so that the high flux nanofiltration membrane is obtained.
The nanofiltration membrane prepared by the method is tested by cross flow of an aqueous solution, the testing temperature is 25 ℃, the reflux is firstly carried out for 30min under the pressure of 4bar, then the testing is carried out under the pressure of 2bar, and the flux is 47 L.h -1 ·m -2 ·bar -1 The method comprises the steps of carrying out a first treatment on the surface of the With 1000ppm Na 2 SO 4 The cross-flow test of the aqueous solution, the test temperature is 25 ℃, the test is carried out under the pressure of 2bar, and the retention rate is 98.2%; with 1000ppm MgSO 4 The cross-flow test of the aqueous solution, the test temperature is 25 ℃, the test is carried out under the pressure of 2bar, and the retention rate is 92.8%; with 1000ppm MgCl 2 The cross-flow test of the aqueous solution, the test temperature is 25 ℃, the test is carried out under the pressure of 2bar, and the retention rate is 15.8%; with 1000ppm CaCl 2 The cross-flow test of the aqueous solution, the test temperature is 25 ℃, the test is carried out under the pressure of 2bar, and the retention rate is 8%; cross-flow test was carried out with 1000ppm NaCl aqueous solution at 25℃and at a pressure of 2bar with a retention of 18%.
Example 3
Regulation of piperazine (2.5 mg/ml) and Na, respectively 2 H(PO 4 ) 3 (0.1M) mixing the pH value of the aqueous solution to 8.0 and 6.5, soaking the polysulfone composite bottom film with the solution for 120 seconds, sucking the surface solution, soaking the surface of the composite bottom film in 1,3, 5-trimesoyl chloride hexane solution with the concentration of 2mg/ml, reacting for 60 seconds at the temperature of 25 ℃ and the relative humidity of 80%, taking out, cleaning the film with normal hexane, and heating the film at the temperature of 60 ℃ for 1 minute to obtain the high-flux nanofiltration film, wherein the TEM of the nanofiltration film (pH 8.0) shows the separation layer thickness of 30nm, the zeta potential of-55 mV at the pH7, and the TEM of the nanofiltration film (pH 6.5) shows the separation layer thickness of 9nm, and the zeta potential of-65 mV at the pH 7.
The nanofiltration membrane prepared above was tested by cross-flow with an aqueous solution at a temperature of 25℃and under a pressure of 4bar for 30min. The pure water flux of the nanofiltration membrane prepared at the pH value of 8.0 is 78 L.h -1 ·m -2 ·bar -1 The method comprises the steps of carrying out a first treatment on the surface of the With 1000ppm Na 2 SO 4 The cross flow test of the water solution, the test temperature is 25 ℃, the test is carried out under the pressure of 2bar, and the retention rate of the nanofiltration membrane is 85.5%; cross-flow test with 1ppm of perfluorooctanoic acid water solution, test temperature 25 deg.c, test under 2bar pressure, retention rate 89%; cross-flow testing was performed with 1000ppm PEG600 aqueous solution at 25℃under a pressure of 2bar with a retention of 97%. The pure water flux of the nanofiltration membrane prepared at the pH value of 6.5 is 111.3 L.h -1 ·m -2 ·bar -1 The method comprises the steps of carrying out a first treatment on the surface of the With 1000ppm Na 2 SO 4 The cross flow test of the water solution, the test temperature is 25 ℃, the test is carried out under the pressure of 2bar, and the retention rate of the nanofiltration membrane is 71.5%; cross-flow test with 1ppm of perfluorooctanoic acid water solution, test temperature 25 deg.c, test under 2bar pressure, retention rate 88%; cross-flow testing was performed with 1000ppm PEG600 aqueous solution at 25℃under a pressure of 2bar with a rejection of 96%.
Comparative example 3
After piperazine (2.5 mg/ml) aqueous solution is soaked in polyethersulfone composite base film for 120s, the surface solution is sucked dry, then the composite base film is soaked in 1,3, 5-trimesoyl chloride hexane solution with the concentration of 2mg/ml, the solution is reacted for 60s at the temperature of 25 ℃ and the relative humidity of 80%, the solution is taken out, the obtained film is washed by normal hexane, and the film is placed at the temperature of 60 ℃ and heated for 1min, so as to obtain the nanofiltration film, wherein the TEM of the nanofiltration film shows the separation layer thickness of 63nm, and the zeta potential at the pH7 is minus 28mV.
The nanofiltration membrane prepared by the method is tested by cross flow of an aqueous solution, the testing temperature is 25 ℃, the reflux is carried out for 30min under the pressure of 4bar, and then the testing is carried out under the pressure of 2bar, and the flux is 18 L.h -1 ·m -2 ·bar -1 The method comprises the steps of carrying out a first treatment on the surface of the With 1000ppm Na 2 SO 4 The cross-flow test of the aqueous solution, the test temperature is 25 ℃, the test is carried out under the pressure of 2bar, and the retention rate is 98%; with 1000ppm MgSO 4 The cross-flow test of the aqueous solution, the test temperature is 25 ℃, the test is carried out under the pressure of 2bar, and the retention rate is 98%; with 1000ppm MgCl 2 The cross flow test of the aqueous solution, the test temperature is 25 ℃, the test is carried out under the pressure of 2bar, and the retention rate is 89%; with 1000ppm CaCl 2 The cross-flow test of the aqueous solution, the test temperature is 25 ℃, the test is carried out under the pressure of 2bar, and the retention rate is 80%; the cross flow test is carried out by using 1000ppm NaCl water solution, the test temperature is 25 ℃, the test is carried out under the pressure of 2bar, and the retention rate is 22%; cross-flow test with 1ppm of perfluorooctanoic acid water solution, test temperature 25 deg.c, test under 2bar pressure, retention rate 90%; cross-flow testing was performed with 1000ppm PEG600 aqueous solution at 25℃under a pressure of 2bar with a rejection of 99%.
From the above, the following conclusions can be drawn:
the composite bottom films adopted in the embodiment 1 and the comparative embodiment 1 are polysulfone composite bottom films, the embodiment adopts conjugate acid-base pairs, and the interface polymerization reaction is regulated and controlled by regulating the diffusion and trans-interface migration rate of piperazine in the interface polymerization process, so that the thickness, the micropore structure and the surface physicochemical properties of a nanofiltration separation layer are influenced, and an ultrathin, high-flux, high-negative and anti-scaling nanofiltration film is prepared, and the performance and the anti-scaling capacity of the nanofiltration film are improved; the comparative example 1 does not adopt conjugate acid-base pair, the nanofiltration membrane is of an asymmetric compact structure, the pore distribution is uneven, and the flux is low.
In example 2 and comparative example 3, polyethersulfone was used as the base membrane, and the flux of example 2 (pH 11.0) was 47 L.h -1 ·m -2 ·bar -1 For Na 2 SO 4 And MgSO 4 The retention rates of (2) are 98.2% and 92.8%, respectively; compared with comparative example 3, the flux is greatly improved, and meanwhile, the Na is kept higher 2 SO 4 And MgSO 4 Is a high retention rate.
In example 3 and comparative example 3, polyethersulfone was used as the base membrane, and the pure water flux of the nanofiltration membrane of example 3 (pH 8.0) was 78 L.h -1 ·m -2 ·bar -1 The method comprises the steps of carrying out a first treatment on the surface of the EXAMPLE 3 (pH 6.5) nanofiltration membrane pure water flux was 111.3 L.h -1 ·m -2 ·bar -1 The method comprises the steps of carrying out a first treatment on the surface of the The retention rate of the perfluorooctanoic acid is 89% and 88% respectively; the retention rate of PEG600 was 97% and 96%, respectively; greatly improves the water flux on the premise of ensuring the high retention rate of the specific substances.
The embodiment of the invention has the beneficial effects that:
1. the interfacial polymerization is divided into a water phase and an oil phase, in the embodiment of the invention, the water phase is a mixed aqueous solution composed of polyamine and conjugate acid-base pairs, and the oil phase is an organic solvent for dissolving polybasic acyl chloride; the interfacial polymerization is carried out on the polyamine diffused from the oil phase and the water phase, and under the combined action of the oil phase and the water phase, the ultra-thin high-negative electricity polyamide nanofiltration membrane is formed.
2. Action of conjugate acid base pair: firstly, the phenomenon of uneven reaction caused by the change of the interfacial pH in the interfacial polymerization process can be improved, and the inventor finds that the aqueous phase solution cannot form a complete polyamide membrane under low pH, and the conjugate acid-base pair can stabilize the pH in the interfacial process, so that the continuous interfacial polymerization reaction is ensured to be carried out, and a complete nanofiltration membrane is formed; secondly, regulating the pH value of the buffer solution through conjugate acid and alkali, and regulating the duty ratio of the protonated small molecular amine, so as to regulate the trans-interface migration rate of the small molecular amine; thirdly, because of the electrostatic interaction between the conjugate acid-base pair and piperazine, hydrogen on polyamine and oxygen on the conjugate acid-base pair form hydrogen bonds, and the diffusion rate of polyamine molecules to an oil phase can be reduced, so that interfacial polymerization reaction is affected.

Claims (10)

1. The preparation method of the high-flux anti-scaling nanofiltration membrane is characterized by comprising the following steps of:
1) Adding polyamine monomer into water to obtain polyamine solution;
2) Adding a buffer solution into the polyamine solution, and regulating the pH value to 4-12 to obtain an interfacial polymerization aqueous phase solution;
3) Taking an ultrafiltration bottom membrane, and fully infiltrating the ultrafiltration bottom membrane by adopting the interfacial polymerization aqueous phase solution; drying in the shade in the air to obtain a water phase ultrafiltration bottom membrane;
4) Fully infiltrating the surface of the aqueous phase ultrafiltration bottom membrane by adopting a polybasic acyl chloride solution, carrying out interfacial polymerization reaction on the polybasic amine monomer and the polybasic acyl chloride, thereby forming a polyamide ultrathin separating layer on the surface of the aqueous phase ultrafiltration bottom membrane, and carrying out annealing treatment to obtain a high-flux anti-scaling nanofiltration membrane;
the polyacyl chloride solution comprises a polyacyl chloride and an organic solvent.
2. The preparation method according to claim 1, wherein the buffer solution adopts a conjugate acid-base pair, and the conjugate acid-base pair adopts weak acid and conjugate base thereof or weak base and conjugate acid thereof; the conjugated acid-base pair is selected from at least one of a phosphate system, a carbonate system, a borate system and a citrate system; the conjugated acid-base pair concentration in the interfacial polymerization aqueous phase solution is 0.001M-0.5M.
3. The method according to claim 1, wherein the polyamine monomer is at least one selected from piperazine, m-phenylenediamine, p-phenylenediamine, melamine, thiourea, polyethyleneimine, diethylenetriamine and N-aminoethylpiperazine.
4. The method according to claim 1, wherein the organic solvent is at least one selected from the group consisting of hexane, heptane, pentane, isopar G, toluene, ethyl acetate, and benzene.
5. The method according to claim 1, wherein the polybasic acyl chloride is at least one selected from the group consisting of 1,3, 5-trimesoyl chloride, terephthaloyl chloride, isophthaloyl chloride, nonyldiacid chloride, oxalyl chloride, 2', 4' -biphenyltetracarboxylic acid chloride.
6. The method according to claim 1, wherein the ultrafiltration membrane material is selected from any one of polysulfone, polyethersulfone, polyvinylidene fluoride, polyacrylonitrile, polytetrafluoroethylene nylon, cellulose or cellulose derivative; the aperture of the holes contained in the ultrafiltration bottom membrane supporting layer is 0.01-2 mu m.
7. The method according to claim 1, wherein the concentration of the polyacyl chloride in the polyacyl chloride solution is 0.25 to 7.5mg/ml, and the annealing treatment is performed at a temperature of 20 to 80 ℃ for 1 to 30 minutes.
8. The method according to claim 1, wherein the polyamine monomer and the polyacyl chloride undergo interfacial polymerization at an interface temperature of 20 to 35 ℃ and a relative humidity of 50 to 100% for 30 to 90 seconds.
9. The high-flux anti-scaling nanofiltration membrane prepared by adopting the method of any one of claims 1-8, which is characterized in that the high-flux anti-scaling nanofiltration membrane comprises a polyamide ultrathin separation layer, the thickness of the polyamide ultrathin separation layer is 8-30 nm, the polyamide ultrathin separation layer is positioned on the surface of the high-flux anti-scaling nanofiltration membrane, and the polyamide ultrathin separation layer has a smooth structure;
the pure water flux of the high flux anti-scaling nanofiltration membrane is 110 L.h -1 ·m -2 ·bar -1 The retention rate of the perfluoro caprylic acid reaches more than 88 percent; the retention rate of PEG600 reaches over 96 percent; on the premise of ensuring the high retention rate of specific substances, the water flux and the anti-scaling performance are greatly improved.
10. Use of a high flux, anti-fouling nanofiltration membrane according to claim 9 for water treatment, wherein the high flux, anti-fouling nanofiltration membrane is used for wastewater treatment.
CN202310339138.3A 2023-04-01 2023-04-01 High-flux anti-scaling nanofiltration membrane and preparation method and application thereof Pending CN116116238A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117797665A (en) * 2024-03-01 2024-04-02 中山大学 Glutamic acid modified separation membrane and preparation method and application thereof

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117797665A (en) * 2024-03-01 2024-04-02 中山大学 Glutamic acid modified separation membrane and preparation method and application thereof
CN117797665B (en) * 2024-03-01 2024-05-07 中山大学 Glutamic acid modified separation membrane and preparation method and application thereof

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