CN112717707A - Preparation method of reverse osmosis membrane containing stable anti-fouling coating - Google Patents
Preparation method of reverse osmosis membrane containing stable anti-fouling coating Download PDFInfo
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Abstract
The invention belongs to the technical field of membrane separation, and discloses a preparation method of a reverse osmosis membrane containing a stable anti-fouling coating. The invention improves the problem of low binding force between the coating and the polyamide layer, and has the advantages of high membrane separation efficiency, good stability and the like.
Description
Technical Field
The invention relates to the technical field of membrane separation, in particular to a preparation method of a reverse osmosis membrane containing a stable anti-fouling coating.
Background
In recent years, the demand of people for fresh water resources is increasing due to the increase of population and the development of modern industry and agriculture, a large amount of fresh water resources are wasted due to the destruction of ecological environment and water pollution caused by human activities, and the shortage of water resources and water shortage are difficult problems which plague the world. Many countries are striving to produce more clean water, where desalination has become one of the effective ways to address water shortages. The method which can be used for seawater desalination comprises a distillation method, a crystallization method, a flash evaporation method, an ion exchange method and the like, and compared with other methods, the reverse osmosis membrane separation technology has wide application prospect in seawater desalination and sewage treatment due to the advantages of high efficiency, energy conservation, high automation degree, safety, stability and the like. However, the conventional reverse osmosis membrane is often scaled due to multiple actions between pollutants and the surface in the operation process, so that the permeation flux is greatly reduced, the energy consumption in the separation process is increased, the desalination cost is increased, and the practical application of the reverse osmosis membrane material in seawater desalination is hindered by membrane pollution.
In order to solve the problems, various methods can be adopted to prepare the high-performance anti-pollution reverse osmosis membrane. CN101130444 discloses a preparation method of a modified reverse osmosis membrane based on PVA coating, the hydrophilicity of PVA increases the contamination resistance of the reverse osmosis membrane, however, the PVA gradually dissolves and finally falls off during the washing process of the reverse osmosis membrane surface, and the membrane performance is reduced; CN107638805A discloses a preparation method of a graphene oxide/polyvinyl alcohol coating modified reverse osmosis membrane, wherein a cross-linking agent, serine and an acid catalyst are added into an aqueous solution of graphene oxide and polyvinyl alcohol, and then the mixed solution is coated on the surface of a nascent state reverse osmosis membrane to obtain the graphene oxide/polyvinyl alcohol coating modified reverse osmosis membrane.
Therefore, how to provide a reverse osmosis membrane containing a stable anti-fouling coating is a problem which needs to be solved by the technical personnel in the field.
Disclosure of Invention
In view of the above, the present invention provides a method for preparing a reverse osmosis membrane containing a stable anti-fouling coating.
In order to achieve the purpose, the invention adopts the following technical scheme:
a method for preparing a reverse osmosis membrane containing a stable anti-fouling coating comprises the following steps:
(1) preparation of polyamino polymer solution: weighing a certain amount of polyamino polymer, adding deionized water, and performing ultrasonic treatment for 30min to obtain a uniformly dispersed polyamino polymer solution for later use;
(2) activation of the polycarboxy Polymer: putting a certain amount of polycarboxy polymer into deionized water, adding 1-ethyl-3- (3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxysuccinimide, and reacting to obtain an activated polycarboxy polymer solution for later use;
(3) preparation of a solution containing metal ions: dispersing a certain amount of salt compounds containing metal ions in water, and performing ultrasonic treatment for 30min to obtain a solution containing metal ions for later use;
(4) preparation of aqueous phase solution: dissolving the water phase monomer in deionized water, placing in an ultrasonic instrument, and performing ultrasonic treatment for 10min to uniformly disperse the monomer to obtain a water phase solution for later use;
(5) preparation of oil phase solution: dissolving an oil phase monomer in an organic solvent, and stirring at constant temperature to obtain an oil phase solution for later use;
(6) preparing a modified reverse osmosis membrane: pouring the water phase solution on the surface of a reverse osmosis base membrane, standing, pouring out redundant solution, immersing the base membrane in the oil phase solution for reaction for a period of time, and putting the base membrane into an oven for heat treatment after the reaction is finished to obtain an initial PA membrane; and then pouring the polyamino polymer solution, the polycarboxyl polymer solution and the solution containing metal ions on the surface of the PA membrane in sequence, and depositing for a period of time to obtain the reverse osmosis membrane modified by the coating.
Preferably, in the above preparation method of a reverse osmosis membrane with a stable anti-fouling coating, in the step (1), the polyamino polymer is one or more of polyethyleneimine, polyacrylamide, polyacrylic acid, polylysine, polyamide-amine and polyarginine, and the polyamino polymer accounts for 0.05-0.5 wt% of the mass fraction of the water phase.
The beneficial effects of the above technical scheme are: the polyamino polymer is used as a part of the coating, wherein amino functional groups can react with unreacted acyl chloride groups on the surface of the membrane to form chemical bonds, the acting force of the chemical bonds is stronger than that of hydrogen bonds, physical adsorption and the like, so that the polyamino polymer can be firmly fixed on the surface of the membrane, namely the polyamino polymer can enhance the bonding force between the coating and a polyamide layer.
In addition, the mass fraction is determined according to the water flux, a plurality of initial reverse osmosis membranes are prepared, then polyamino polymer solutions with different mass fractions are poured on the surfaces of the membranes to obtain polyamino polymer modified reverse osmosis membranes, the modified reverse osmosis membranes and the initial reverse osmosis membranes are placed on a triple high-pressure flat membrane device for testing, the water fluxes of the initial reverse osmosis membranes and the modified reverse osmosis membranes are compared, the mass fraction corresponding to a sample with the water flux higher than that of the initial reverse osmosis membrane is selected, and in the test, the test shows that the polyamino polymer content is too low, the water flux is not obviously increased, the polyamino polymer content is too high, and the water flux is lower than that of the initial reverse osmosis membranes, so that the mass fraction of the polyamino polymer in the water phase is selected to be 0.05-0.5.
Preferably, in the above method for preparing a reverse osmosis membrane with a stable anti-fouling coating, in step (2), the polycarboxy polymer is one or more of polyaspartic acid, polylactic acid, polyacrylic acid, polymethacrylic acid and polyglutamic acid, and the polycarboxy polymer accounts for 0.1-1 wt% of the water phase.
The beneficial effects of the above technical scheme are: the carboxyl functional group of the polycarboxy polymer can react with the amino group of the polyamino polymer to form a chemical bond, namely an amido bond, and the polycarboxy polymer can be stably combined with the polyamino polymer, so that the formed coating can resist water washing.
Further the mass fraction is determined on the basis of the amount of polyamino polymer, in order to react as much amino groups and carboxyl groups on the polyamino polymer as possible, the mass ratio of polycarboxy polymer to polyamino polymer is chosen to be approximately 2: 1. the content of the polycarboxy polymer is too low, the yield of organic reaction is low, the complete reaction of amino carboxyl can not be ensured, and the waste of reagents is easily caused by too high content.
Preferably, in the above method for preparing a reverse osmosis membrane having a stable anti-fouling coating, the mass fraction of 1-ethyl-3- (3-dimethylaminopropyl) carbodiimide hydrochloride in the aqueous phase in step (2) is 0.2-2 wt%, and the mass fraction of N-hydroxysuccinimide in the aqueous phase is 0.125-1.25 wt%.
The beneficial effects of the above technical scheme are: 1-ethyl-3 (3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) are used for activating carboxyl groups of a polycarboxy polymer to improve the reactivity of the carboxyl groups and the amino groups, and the addition amount is determined according to the molar mass of the carboxyl groups in the carboxyl polymer, if the content is too small, the activation of all the carboxyl groups cannot be ensured, and if the content is too large, the waste of reagents is caused.
Preferably, in the preparation method of the reverse osmosis membrane with the stable anti-fouling coating, the reaction time of the step (2) is 15-120min, the reaction temperature is 25-60 ℃, and the reaction is carried out in a dark reaction.
The beneficial effects of the above technical scheme are: since EDC/NHS produces intermediate products during the activation of carboxyl groups, the reaction is selected to be protected from light in order to avoid the decomposition of the intermediate products under light.
Preferably, in the above preparation method of the reverse osmosis membrane with the stable anti-fouling coating, in the step (3), the salt compound is one or more of ferrous chloride, ferric nitrate, cupric chloride, cupric nitrate, zinc sulfate, copper sulfate, manganese sulfate and aluminum chloride, and the salt compound accounts for 0.5-3 wt% of the aqueous phase solution.
The beneficial effects of the above technical scheme are: the metal ions can generate coordination with N atoms in amido bonds, carboxyl groups of the polycarboxyl polymer and amino groups in the polyamino polymer, and the binding force between the polycarboxyl polymer and the polyamino polymer is increased.
Preferably, in the above preparation method of a reverse osmosis membrane with a stable anti-fouling coating, the oil phase monomer is 1,3, 5-benzenetricarboxychloride, 1, 3-benzenedicarbonyl chloride, bridged bicyclic tricyclic tetracarbonyl or biphenyl hexacarbonyl; the organic solvent is one or more of n-hexane, heptane, cyclohexane or Isopar-G, and the oil phase monomer accounts for 0.1-0.5 wt% of the organic solvent; the water phase monomer is one or more of m-phenylenediamine, 1,3, 5-triaminobenzene, melamine or piperazine, and the mass fraction of the water phase monomer in deionized water is 2 wt%.
The beneficial effects of the above technical scheme are: the oil phase monomer and the water phase monomer form a polyamide layer, and the interception performance of the reverse osmosis membrane is determined by the polyamide layer.
Preferably, in the above method for preparing a reverse osmosis membrane with a stable anti-fouling coating, in step (6), the material of the reverse osmosis base membrane comprises polysulfone, polyethersulfone, polyacrylonitrile, cellulose acetate, and polyamide, and the pore size of the reverse osmosis base membrane is 0.001-0.002 μm.
The beneficial effects of the above technical scheme are: the reverse osmosis basal membrane provides certain mechanical strength for the reverse osmosis membrane and plays a supporting role.
Preferably, in the above method for preparing a reverse osmosis membrane with a stable anti-fouling coating, the reaction time for immersing the membrane into the oil phase solution in the step (6) is 30s-5 min; the temperature of the heat treatment is 50-120 ℃, and the time is 1-30 min; the deposition time of the polyamino polymer solution on the surface of the initial reverse osmosis membrane is 3-60min, the deposition time of the polycarboxy polymer solution on the surface of the initial reverse osmosis membrane is 12-24h, and the deposition time of the solution containing the metal ions on the surface of the initial reverse osmosis membrane is 0.5-12 h.
The beneficial effects of the above technical scheme are: the surface appearance of the reverse osmosis membrane can be changed by the reaction time of the oil phase solution; the cross-linking structure in the polyamide layer can be changed at different temperatures and heat treatment times, and the interception and permeability of the reverse osmosis membrane are influenced; the deposition time varies, and the amount of polyamino polymer grafted to the surface of the membrane, the amount of polycarboxy polymer reacted with the polyamino polymer, and the amount of metal ion coordination will vary.
According to the technical scheme, compared with the prior art, the invention discloses a preparation method of a reverse osmosis membrane containing a stable anti-fouling coating, which comprises the steps of firstly constructing a first heavy network by using amidation reaction between a polyamino polymer, unreacted acyl chloride groups on the surface of the membrane and an activated polycarboxy polymer, and then constructing a second heavy network by using coordination among metal ions, amino groups and carboxyl groups, so that a stable anti-fouling coating is formed on the surface of the reverse osmosis membrane, and the membrane is endowed with excellent long-term anti-fouling performance; the flux of the coated reverse osmosis membrane is 16.7-45.8% higher than that of the initial membrane, and the prepared reverse osmosis membrane has good resistance to bovine serum albumin and sodium alginate in a pollution test for 36 hours. The invention improves the problem of low binding force between the coating and the polyamide layer, and has the advantages of high membrane separation efficiency, good stability and the like.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
FIG. 1 is a surface SEM image of a reverse osmosis membrane obtained in comparative example and example: (a) comparative example 1; (b) example 1; (c) example 2; (d) example 3; (e) example 4; (f) example 5.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
0.1g of polyaspartic acid was added to 100ml of water, 0.2g of 1-ethyl-3- (3-dimethylaminopropyl) carbodiimide hydrochloride and 0.125g of N-hydroxysuccinimide were added, and the mixture was stirred sufficiently to carry out a reaction at 25 ℃ for 15 minutes in the absence of light. 0.05g of PEI was placed in 100ml of distilled water and sonicated for 10min to completely disperse it. 0.5g of copper chloride is weighed into 100ml of distilled water to prepare a copper chloride solution with the mass fraction of 0.5 wt%. 2.0g of m-phenylenediamine, 2.3g of camphorsulfonic acid and 1.1g of triethylamine are put into 100ml of distilled water, poured on the surface of a basement membrane after being completely dissolved, kept stand for 5min and then poured to remove the redundant solution. 0.1g of 1,3, 5-benzene trimethyl acyl chloride is dissolved in 100g of n-hexane, after the dissolution is finished, the solution is poured on the surface of a basement membrane for reaction, the reaction time is 40s, and after the reaction is finished, the prepared PA membrane is subjected to heat treatment for 5min at the temperature of 70 ℃. And then sequentially pouring the PEI solution, the activated PASP solution and the copper chloride solution onto the surface of the membrane for reaction for 10min, 12h and 30min to obtain the modified reverse osmosis membrane.
Example 2
0.2g of polyaspartic acid was added to 100ml of water, 0.4g of 1-ethyl-3- (3-dimethylaminopropyl) carbodiimide hydrochloride and 0.25g of N-hydroxysuccinimide were added, and the mixture was stirred sufficiently to carry out a reaction at 30 ℃ for 30 minutes in the absence of light. 0.1g of PEI was placed in 100ml of distilled water and sonicated for 10min to completely disperse it. 1g of ferric chloride is weighed and placed in 100ml of distilled water to prepare ferric chloride solution with the mass fraction of 1 wt%. 2.0g of m-phenylenediamine, 2.3g of camphorsulfonic acid and 1.1g of triethylamine are put into 100ml of distilled water, poured on the surface of a basement membrane after being completely dissolved, kept stand for 10min and then poured to remove the redundant solution. 0.1g of 1,3, 5-benzene trimethyl acyl chloride is dissolved in 100g of n-hexane, after the dissolution is finished, the solution is poured on the surface of a basement membrane for reaction, the reaction time is 50s, and after the reaction is finished, the prepared PA membrane is subjected to heat treatment for 5min at the temperature of 80 ℃. And then sequentially pouring the PEI solution, the activated PASP solution and the ferric chloride solution onto the surface of the membrane for reaction for 20min, 15h and 2h to obtain the modified reverse osmosis membrane.
Example 3
0.5g of polyaspartic acid was added to 100ml of water, 1.0g of 1-ethyl-3- (3-dimethylaminopropyl) carbodiimide hydrochloride and 0.625g of N-hydroxysuccinimide were added, and the mixture was stirred sufficiently to carry out a reaction at 40 ℃ for 60 minutes in the absence of light. 0.25g of PEI was placed in 100ml of distilled water and sonicated for 10min to completely disperse it. 1.5g of zinc sulfate is weighed and placed in 100ml of distilled water to prepare a zinc sulfate solution with the mass fraction of 1.5 wt%. 2.0g of m-phenylenediamine, 2.3g of camphorsulfonic acid and 1.1g of triethylamine are put into 100ml of distilled water, poured on the surface of a basement membrane after being completely dissolved, kept stand for 5min and then poured to remove the redundant solution. 0.25g of 1,3, 5-benzene trimethyl acyl chloride is dissolved in 100g of n-hexane, after the dissolution is finished, the solution is poured on the surface of a basement membrane for reaction, the reaction time is 60s, and after the reaction is finished, the prepared PA membrane is subjected to heat treatment for 5min at the temperature of 90 ℃. And then pouring the PEI solution, the activated PASP solution and the zinc sulfate solution into the surface of the membrane in sequence for reacting for 40min, 18h and 2h to obtain the modified reverse osmosis membrane.
Example 4
0.2g of polyglutamic acid was added to 100ml of water, and 0.4g of 1-ethyl-3- (3-dimethylaminopropyl) carbodiimide hydrochloride and 0.25g of N-hydroxysuccinimide were added thereto, and the mixture was sufficiently stirred to carry out a reaction at 50 ℃ for 90 minutes in the absence of light. 0.1g of polylysine is placed in 100ml of distilled water and is subjected to ultrasonic treatment for 10min to completely disperse the polylysine. 1g of ferric chloride is weighed and placed in 100ml of distilled water to prepare ferric chloride solution with the mass fraction of 1 wt%. 2.0g of m-phenylenediamine, 2.3g of camphorsulfonic acid and 1.1g of triethylamine are put into 100ml of distilled water, poured on the surface of a basement membrane after being completely dissolved, kept stand for 5min and then poured to remove the redundant solution. 0.1g of 1,3, 5-benzene trimethyl acyl chloride is dissolved in 100g of n-hexane, after the dissolution is finished, the solution is poured on the surface of a basement membrane for reaction, the reaction time is 100s, and after the reaction is finished, the prepared PA membrane is subjected to heat treatment for 3min at the temperature of 90 ℃. And then sequentially pouring the PEI solution, the activated PASP and the ferric chloride solution onto the surface of the membrane for reaction for 50min, 20h and 4h to obtain the modified reverse osmosis membrane.
Example 5
1.0g of polyglutamic acid was added to 100ml of water, 2g of 1-ethyl-3- (3-dimethylaminopropyl) carbodiimide hydrochloride and 1.25g of N-hydroxysuccinimide were added thereto, and the mixture was stirred sufficiently to carry out a reaction at 60 ℃ for 120min in the absence of light. 0.5g of polylysine is placed in 100ml of distilled water and is subjected to ultrasonic treatment for 10min to completely disperse the polylysine. 3g of ferric chloride is weighed and placed in 100ml of distilled water to prepare ferric chloride solution with the mass fraction of 3 wt%. 2.0g of m-phenylenediamine, 2.3g of camphorsulfonic acid and 1.1g of triethylamine are put into 100ml of distilled water, poured on the surface of a basement membrane after being completely dissolved, kept stand for 5min and then poured to remove the redundant solution. 0.5g of 1,3, 5-benzene trimethyl acyl chloride is dissolved in 100g of n-hexane, after the dissolution is finished, the solution is poured on the surface of a basement membrane for reaction, the reaction time is 150s, and after the reaction is finished, the prepared PA membrane is subjected to heat treatment for 3min at the temperature of 90 ℃. And then sequentially pouring the PEI solution, the activated PASP and the ferric chloride solution onto the surface of the membrane for reaction for 60min, 24h and 6h to obtain the modified reverse osmosis membrane.
Comparative example 1
2.0g of m-phenylenediamine, 2.3g of camphorsulfonic acid and 1.1g of triethylamine are put into 100ml of distilled water, poured on the surface of a basement membrane after being completely dissolved, kept stand for 5min and then poured to remove the redundant solution. And (2) putting 0.15g of 1,3, 5-benzene trimethyl acyl chloride in 100g of n-hexane, pouring the mixture on the surface of the base membrane for reaction after the dissolution is finished, wherein the reaction time is 30s, and after the reaction is finished, carrying out heat treatment on the prepared PA membrane for 3min at the temperature of 60 ℃ to obtain the reverse osmosis membrane.
As can be seen from fig. 1, the surfaces of the example and comparative example films each show a typical peak-valley structure, which is a typical characteristic of the surface active layer of the aromatic polyamide composite film. Although the characteristic morphology of a polyamide structure is kept on the surface of the membrane in the embodiment, compared with a 'wood ear' structure with a full and smooth polyamide layer on the surface of an initial reverse osmosis membrane, modified 'wood ear' blades are mutually bonded, which shows that the polymer is attached to the surface of a peak-valley structure and is crosslinked.
In addition, the flux and the salt rejection of the reverse osmosis membranes prepared in examples 1 to 5 and comparative example 1 were measured, and the measurement results are shown in table 1.
The separation performance of the reverse osmosis membrane was evaluated by two indexes of salt rejection (SR,%) and water flux (J, Lm-2h-1, LMH).
Firstly, fixing a reverse osmosis membrane in a membrane pool of triple high-pressure flat membrane test equipment, wherein the effective test area of each membrane pool is 60cm2And the flow channel is 1mm high, then the mixture is pre-pressed under 5MPa by using deionized water, and then 3000mL of 2000ppm sodium chloride aqueous solution is prepared as a feeding liquid to be tested under 1.6MPa, and the temperature of the feeding liquid is kept at 25 ℃ during pre-pressing and testing, and the flow rate is kept at 3.6L/min; collecting water at a permeation end, weighing the water at intervals of specific time (delta t) (m), and calculating by a formula (2-1), wherein A is the effective area of the membrane pool, so that the mass of the water passing through the unit membrane area in unit time, namely the water flux, can be obtained, and all water flux data need to be recorded after the flux is stable. The sodium chloride is strong electrolyte, so that the conductivity of the aqueous solution of the sodium chloride can be tested to represent the concentration of the sodium chloride, the aqueous solution of the feed liquid and the penetrating fluid is tested to obtain the conductivity data of the feed liquid and the penetrating fluid, the calculation is carried out according to a formula (2-2), and the salt rejection rate of the reverse osmosis membrane can be obtained, wherein CpAnd CfConductivity of permeate and feed respectively.
TABLE 1
| Water flux (L.m)-2·h-1) | Salt rejection (%) | |
| Comparative example 1 | 48 | 98 |
| Example 1 | 59 | 97.9 |
| Example 2 | 70 | 98.9 |
| Example 3 | 69 | 97.8 |
| Example 4 | 56 | 98.5 |
| Example 5 | 60 | 98.8 |
As can be seen from table 1, the water flux was greater for all examples than for the comparative example, indicating that the introduction of the coating did not increase the mass transfer resistance of water molecules. The reason for the improved permeability may be that the formation of a hydrated layer on the surface increases the driving force of water molecules through the reverse osmosis membrane due to the excellent hydrophilicity of the coating layer.
The salt rejection rate can indicate the internal structure of the polyamide layer, the polyamide selective layer is relatively compact, so that the high salt rejection rate can be maintained, and when the polyamino polymer is grafted on the surface, the formation of a cross-linked selective layer can be interfered, so that the rejection of the salt is changed; in addition, unreacted carboxyl functionality of the polycarboxy polymer can also affect salt rejection.
In examples 1 to 5, some of the salt rejection was lower than in the case of the comparative example, and the reason for the reduction in salt rejection may be due to: the polycarboxyl polymer on the surface of the coating still has unreacted carboxyl functional groups, and the negatively charged functional groups are easy to generate electrostatic interaction with sodium ions, so that the transmission of the sodium ions is promoted, and the salt rejection rate of the reverse osmosis membrane is reduced. But even though the partial salt rejection is relatively low, the rejection is still comparable to the comparative example, and the reverse osmosis performance is not affected.
The invention also tests and records the flux loss and flux recovery data of examples 1-5 and comparative example 1 after 36h of bovine serum albumin contamination, and specifically refers to table 2.
And a cross current permeation experiment is adopted to research the anti-fouling performance of the initial reverse osmosis membrane and the modified reverse osmosis membrane. BSA (600ppm) is added into a NaCl aqueous solution with 2000ppm to serve as a pollutant solution for simulating the pollution of protein pollutants to a reverse osmosis membrane under actual conditions, and the whole experiment is the same as a water flux salt rejection rate test system. The specific experimental steps are as follows: all membrane samples were pre-stressed for 30min to stabilize the filtration system, and then the membrane samples were filtered in 2000ppm NaCl aqueous solution for 1h to obtain a stable pure water flux (Jo), followed by an anti-fouling filtration test: a. the NaCl aqueous solution in the feeding cylinder is replaced by the pollutant feeding solution, the circulation filtration is carried out for 10 hours, and the water flux (Jt) of the membrane under the pollution condition is measured in real time; b. the pollutant solution in the cylinder is replaced by pure water and the membrane is washed for 1 h; c. the aqueous NaCl solution was poured into the feed cylinder again, and the pure water flux (Jr) recovered by filtration for 1 hour was measured. For the membrane surface modification experiments, the above anti-fouling filtration experiments were cycled three times in order to evaluate the anti-fouling stability of the grafts on the membrane surface.
The two values of flux loss rate (DRt) and water Flux Recovery Rate (FRR) are commonly used to quantitatively analyze the anti-fouling performance of a membrane sample, and are commonly calculated as follows:
FRR＝Jr/Jo×100％
DRt＝(1–Jt/Jo)×100％
here, Jo is the initial pure water flux of the membrane sample, Jt is the water flux of the membrane sample after 10h (or 30h) of testing, and Jr is the water flux of the contaminated membrane sample after being washed with pure water. Generally, lower DRt values and higher FRR values indicate better fouling resistance of the reverse osmosis membrane.
TABLE 2
The present invention also tested and recorded the flux loss and flux recovery data after 36h of sodium alginate contamination for examples 1-5 and comparative example 1, see table 3 for details.
And cross-flow permeation experiments are adopted to research the anti-fouling performance of the initial membrane and the modified membrane. SA (200ppm) is added into a NaCl aqueous solution with the concentration of 2000ppm to serve as a pollutant solution for simulating the pollution of polysaccharide pollutants on a reverse osmosis membrane under actual conditions, and the whole experiment is the same as a water flux salt rejection rate test system. The specific experimental steps are as follows: all membrane samples were pre-stressed for 30min to stabilize the filtration system, and then the membrane samples were filtered in 2000ppm NaCl aqueous solution for 1h to obtain stable pure water flux (Jo), followed by an anti-fouling filtration test: a. replacing the NaCl aqueous solution in the feeding cylinder by a pollutant feeding solution, circularly filtering for 10 hours, and immediately measuring the water flux (Jt) of the membrane under the pollution condition; b. the pollutant solution in the cylinder is replaced by pure water and the membrane is washed for 1 h; c. the aqueous NaCl solution was poured into the feed cylinder again, and the pure water flux (Jr) recovered by filtration for 1 hour was measured. For the membrane surface modification experiments, the above anti-fouling filtration experiments were cycled three times in order to evaluate the anti-fouling stability of the grafts on the membrane surface.
2. The two values of flux loss rate (DRt) and water Flux Recovery Rate (FRR) are commonly used to quantitatively analyze the anti-fouling performance of a membrane sample, and are commonly calculated as follows:
FRR＝Jr/Jo×100％
DRt＝(1–Jt/Jo)×100％
here, Jo is the initial pure water flux of the membrane sample, Jt is the water flux of the membrane sample after 10h (or 30h) of testing, and Jr is the water flux of the contaminated membrane sample after being washed with pure water. Generally, lower DRt values and higher FRR values indicate better fouling resistance of the reverse osmosis membrane.
TABLE 3
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. For the scheme disclosed by the embodiment, the scheme corresponds to the method disclosed by the embodiment, so that the description is simple, and the relevant points can be referred to the method part for description.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. A preparation method of a reverse osmosis membrane containing a stable anti-fouling coating is characterized by comprising the following steps:
(1) preparation of polyamino polymer solution: weighing a certain amount of polyamino polymer, adding deionized water, and performing ultrasonic treatment for 30min to obtain a uniformly dispersed polyamino polymer solution for later use;
(2) activation of the polycarboxy Polymer: putting a certain amount of polycarboxy polymer into deionized water, adding 1-ethyl-3- (3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxysuccinimide, and reacting to obtain an activated polycarboxy polymer solution for later use;
(3) preparation of a solution containing metal ions: dispersing a certain amount of salt compounds containing metal ions in water, and performing ultrasonic treatment for 30min to obtain a solution containing metal ions for later use;
(4) preparation of aqueous phase solution: dissolving the water phase monomer in deionized water, placing in an ultrasonic instrument, and performing ultrasonic treatment for 10min to uniformly disperse the monomer to obtain a water phase solution for later use;
(5) preparation of oil phase solution: dissolving an oil phase monomer in an organic solvent, and stirring at constant temperature to obtain an oil phase solution for later use;
(6) preparing a modified reverse osmosis membrane: pouring the water phase solution on the surface of a reverse osmosis base membrane, standing, pouring out redundant solution, immersing the base membrane in the oil phase solution for reaction for a period of time, and putting the base membrane into an oven for heat treatment after the reaction is finished to obtain an initial reverse osmosis membrane; and then pouring the polyamino polymer solution, the polycarboxyl polymer solution and the solution containing metal ions on the surface of the initial reverse osmosis membrane in sequence, and depositing for a period of time to obtain the reverse osmosis membrane with the modified coating.
2. The method for preparing a reverse osmosis membrane with a stable anti-fouling coating according to claim 1, wherein the polyamino polymer in step (1) is one or more of polyethyleneimine, polyacrylamide, polyacrylic acid, polylysine, polyamide-amine and polyarginine, and the polyamino polymer accounts for 0.05-0.5 wt% of deionized water.
3. The method for preparing a reverse osmosis membrane with a stable anti-fouling coating according to claim 1, wherein the polycarboxy polymer in the step (2) is one or more of polyaspartic acid, polylactic acid, polyacrylic acid, polymethacrylic acid and polyglutamic acid, and the polycarboxy polymer accounts for 0.1-1 wt% of deionized water.
4. The method for preparing a reverse osmosis membrane with a stable anti-fouling coating according to claim 1, wherein in the step (2), the mass fraction of 1-ethyl-3- (3-dimethylaminopropyl) carbonyldiimide hydrochloride in deionized water is 0.2-2 wt%, and the mass fraction of N-hydroxysuccinimide in deionized water is 0.125-1.25 wt%.
5. The preparation method of a reverse osmosis membrane containing a stable anti-fouling coating according to claim 1, characterized in that the reaction time of the step (2) is 15-120min, the reaction temperature is 25-60 ℃, and the reaction is carried out in a dark place.
6. The method for preparing a reverse osmosis membrane with a stable anti-fouling coating according to claim 1, wherein the salt compound in step (3) is one or more of ferrous chloride, ferric nitrate, cupric chloride, cupric nitrate, zinc sulfate, copper sulfate, manganese sulfate and aluminum chloride, and the salt compound accounts for 0.5-3 wt% of the aqueous solution.
7. The method for preparing a reverse osmosis membrane with a stable anti-fouling coating according to claim 1, wherein the aqueous phase monomer is one or more of m-phenylenediamine, 1,3, 5-triaminobenzene, melamine or piperazine, and the mass fraction of the aqueous phase monomer in deionized water is 2 wt%;
the oil phase monomer is 1,3, 5-benzene trimethyl acyl chloride, 1, 3-benzene diacid chloride, bridged bicyclic tricyclic tetracarbonyl or biphenyl hexacarbonyl; the organic solvent is one or more of n-hexane, heptane, cyclohexane or Isopar-G; and the oil phase monomer accounts for 0.1-0.5 wt% of the organic solvent.
8. The method for preparing a reverse osmosis membrane with a stable anti-fouling coating according to claim 1, wherein in the step (6), the material of the reverse osmosis base membrane comprises polysulfone, polyethersulfone, polyacrylonitrile, cellulose acetate and polyamide, and the pore size of the reverse osmosis base membrane is 0.001-0.002 μm.
9. The preparation method of a reverse osmosis membrane containing a stable anti-fouling coating according to claim 1, wherein the reaction time for immersing the membrane into the oil phase solution in the step (6) is 30s-5 min; the temperature of the heat treatment is 50-120 ℃, and the time is 1-30 min; the deposition time of the polyamino polymer solution on the surface of the initial reverse osmosis membrane is 3-60min, the deposition time of the polycarboxy polymer solution on the surface of the initial reverse osmosis membrane is 12-24h, and the deposition time of the solution containing the metal ions on the surface of the initial reverse osmosis membrane is 0.5-12 h.
10. A reverse osmosis membrane comprising a stable anti-fouling coating prepared by the process of any one of claims 1 to 9.
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