CN118846811B - High-performance reverse osmosis membrane and preparation method thereof - Google Patents
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- B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
- B01D61/025—Reverse osmosis; Hyperfiltration
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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- B01D69/125—In situ manufacturing by polymerisation, polycondensation, cross-linking or chemical reaction
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Abstract
本发明涉及反渗透膜技术领域，具体涉及一种高性能反渗透膜及其制备方法。该高性能反渗透膜由该制备方法制备得到。该制备方法包括制备细菌纤维素层、在所述细菌纤维素层上制备聚酯层以及在所述聚酯层上制备聚酰胺功能层得到高性能反渗透膜。本发明能够制备出具有稳定高通量和高脱盐率性能的反渗透膜。
The present invention relates to the technical field of reverse osmosis membranes, and in particular to a high-performance reverse osmosis membrane and a preparation method thereof. The high-performance reverse osmosis membrane is prepared by the preparation method. The preparation method comprises preparing a bacterial cellulose layer, preparing a polyester layer on the bacterial cellulose layer, and preparing a polyamide functional layer on the polyester layer to obtain a high-performance reverse osmosis membrane. The present invention can prepare a reverse osmosis membrane with stable high flux and high desalination rate performance.
Description
Technical Field
The invention relates to the technical field of reverse osmosis membranes, in particular to a high-performance reverse osmosis membrane and a preparation method thereof.
Background
The reverse osmosis membrane has selective permeability, and can realize separation of solvent and solute in solution under the drive of pressure. Therefore, the reverse osmosis membrane has wide application in sea water desalination, pure water preparation, wastewater treatment, drinking water production and the like.
At present, reverse osmosis membranes which have both high flux and high desalination rate are being prepared in the industry, and stable reverse osmosis membrane performance is required. The Chinese patent application No. 202211533186.8 discloses a high-performance reverse osmosis membrane and a preparation method thereof, wherein a micron-sized prism structure is formed on the surface of a polysulfone base membrane in a cold pressing mode of a roller die, so that the flux of the reverse osmosis membrane is improved and the desalination rate is not sacrificed. However, the greatest problem of this method is that the surface pore size and porosity of the polysulfone-based membrane may be affected by physical cold pressing, thereby affecting the subsequent interfacial polymerization process, resulting in fluctuations in the flux and desalination rate performance of the reverse osmosis membrane.
In view of the above, there is a need to develop a high-performance reverse osmosis membrane and a preparation method thereof to solve the problem of unstable flux and desalination rate of the existing reverse osmosis membrane.
Disclosure of Invention
The invention aims to provide a high-performance reverse osmosis membrane and a preparation method thereof, and the specific technical scheme is as follows:
in a first aspect, the present invention provides a method for preparing a high performance reverse osmosis membrane comprising:
step S1, preparing a bacterial cellulose layer
Adding a cross-linking agent into the pretreated bacterial cellulose solution, and uniformly mixing to form a bacterial cellulose cross-linking system, scraping the bacterial cellulose cross-linking system on a carrier, and sequentially carrying out second standing treatment, water washing treatment and freeze drying treatment to obtain a bacterial cellulose layer, wherein the cross-linking agent comprises N, N-methylene bisacrylamide;
S2, preparing a polyester layer on the bacterial cellulose layer
Pouring a first aqueous phase solution onto the bacterial cellulose layer, standing for 0.5-3min, removing excessive water drops on the surface of the bacterial cellulose layer, pouring a first oil phase solution, and reacting for 1-5min to obtain a polyester prefabricated layer;
Hydrolyzing the polyester prefabricated layer by adopting alkali liquor to obtain a polyester layer;
S3, preparing a polyamide functional layer on the polyester layer to obtain the high-performance reverse osmosis membrane
Pouring a second aqueous phase solution onto the polyester layer, standing for 0.5-3min, removing excessive water drops on the surface of the polyester layer, pouring the second oil phase solution, reacting for 30-90s to obtain a polyamide functional layer, and drying to obtain the high-performance reverse osmosis membrane.
Optionally, in the step S1, the bacterial cellulose solution adopts the following raw material components in parts by weight, namely 4 parts of bacterial cellulose and 96 parts of dissolution system, wherein the dissolution system adopts the raw material components in percentage by weight, namely 12% of urea, 7% of sodium hydroxide and 81% of water, the pretreatment comprises a first standing treatment and a dissolution treatment which are sequentially carried out, the first standing treatment comprises standing the bacterial cellulose solution after being uniformly mixed for 15-60min, the dissolution treatment comprises firstly standing the bacterial cellulose solution for 1-2h at a temperature of-12 ℃ to-20 ℃, and then stirring and dissolving the bacterial cellulose solution after the freezing treatment.
Optionally, in step S1, the mass concentration of the cross-linking agent in the bacterial cellulose cross-linking system is 0.1% -0.8%, and the second standing treatment comprises standing the bacterial cellulose cross-linking system which is scraped on a carrier for 1-3h.
Optionally, in step S2, the monomers used in the first aqueous solution include epigallocatechin (CasNo:970-74-1, mdl: mfcd00075939, molecular formula: C 15H14O7), at least one of catechin and epicatechin, and the mass concentration of the monomers in the first aqueous solution is 2.8% -4.2%.
Optionally, the monomer adopted by the first oil phase solution comprises at least one of trimesoyl chloride, phthaloyl chloride, terephthaloyl chloride and isophthaloyl chloride, the solvent adopted by the first oil phase solution comprises at least one of n-hexane, isopar G, n-heptane and n-octane, and the mass concentration of the monomer of the first oil phase solution is 0.1% -0.3%.
Optionally, in step S2, the alkali solution comprises sodium hydroxide aqueous solution, and the hydrolysis treatment adopts hydrolysis conditions with pH value of 12 and hydrolysis time of 1-5min.
Optionally, in the step S3, the monomers adopted by the second aqueous phase solution comprise at least one of m-phenylenediamine, p-phenylenediamine and o-phenylenediamine, wherein the mass concentration of the monomers of the second aqueous phase solution is 2% -5%;
The second oil phase solution adopts at least one monomer selected from trimesoyl chloride, phthaloyl chloride, terephthaloyl chloride and isophthaloyl chloride, the second oil phase solution adopts at least one solvent selected from n-hexane, isopar G, n-heptane and n-octane, and the mass concentration of the monomer of the second oil phase solution is 0.08-0.2%.
Optionally, in step S3, the drying temperature used in the drying treatment is 50-60 ℃ and the drying time is 1-3min.
In a second aspect, the present invention provides a high performance reverse osmosis membrane prepared by the method for preparing a high performance reverse osmosis membrane.
Optionally, the thickness of the bacterial cellulose layer is 100-300 mu m, the thickness of the polyester layer is 200-400nm, and the thickness of the polyamide functional layer is 100-300nm.
The application of the technical scheme of the invention has at least the following beneficial effects:
(1) The preparation method of the high-performance reverse osmosis membrane provided by the invention comprises the steps of adopting hydroxyl groups in a bacterial cellulose solution and a polyester layer which is firmly combined on the bacterial cellulose layer after reacting with a first oil phase solution in the step S1, adopting an acryl double bond crosslinking reaction in N, N-methylene bisacrylamide to prepare the bacterial cellulose layer, having a porous three-dimensional nano fiber network skeleton structure, having high mechanical strength, being beneficial to improving the pressure resistance of the reverse osmosis membrane, simultaneously being beneficial to water molecule transmission, adopting an alkali solution in the step S2 to hydrolyze the polyester prefabricated layer, being beneficial to adjusting the aperture of the polyester layer to be large and small, being beneficial to subsequent polymerization, being beneficial to improving the water phase ratio of the carboxyl groups in the subsequent polymerization, being beneficial to the water phase ratio of the reverse osmosis membrane to be better than that of the reverse osmosis membrane through the first oil phase solution, being beneficial to form a second water phase solution, being beneficial to the reverse osmosis membrane, being beneficial to the water phase solution, being beneficial to the surface area being better than the second water phase solution, being beneficial to the surface area being beneficial to the enhancement of the reverse osmosis membrane, being beneficial to the step S2, being beneficial to the preparation of the reverse osmosis membrane, being beneficial to the water phase solution being better through the water phase solution, being beneficial to the surface area being better by adopting an alkaline solution in the step S2, and being beneficial to the water phase solution being beneficial to increase the water phase ratio of the reverse osmosis membrane, the pressure resistance of the bacterial cellulose layer is beneficial to ensuring the stability of the reverse osmosis membrane in the long-term use process of high flux and high desalination rate.
(2) The monomer adopted in the first aqueous phase solution comprises at least one of epigallocatechin, catechin and epicatechin, has antibacterial and bacteriostatic properties, is a cheap and easily available environment-friendly natural hydrophilic substance, has rich hydrophilic groups, can form hydrogen bonds with hydroxyl groups of bacterial cellulose on one hand, and can react with the monomer in the first oil phase solution on the other hand to form a polyester layer. In addition, catechin monomers have antibacterial and bacteriostatic properties.
(3) The high-performance reverse osmosis membrane prepared by the invention has the average water flux reaching 109-121LMH and the average desalination rate higher than 99.4 percent.
In addition to the objects, features and advantages described above, the present invention has other objects, features and advantages. The present invention will be described in further detail with reference to the drawings.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the application. In the drawings:
FIG. 1 is a schematic view of the structure of a high performance reverse osmosis membrane prepared in example 1 of the present invention;
FIG. 2 is a field emission scanning electron microscope (FEMS) of the high performance reverse osmosis membrane prepared in example 1 of the present invention;
Wherein, 1, bacterial cellulose layer, 2, polyester layer, 3, polyamide functional layer.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which are derived by a person skilled in the art based on the embodiments of the invention, fall within the scope of protection of the invention.
Example 1:
a method for preparing a high performance reverse osmosis membrane comprising:
Step S1, preparation of bacterial cellulose layer 1
Adding a cross-linking agent into the pretreated bacterial cellulose solution, and uniformly mixing to form a bacterial cellulose cross-linking system, scraping the bacterial cellulose cross-linking system on a carrier, and sequentially carrying out second standing treatment, water washing treatment (washing to be neutral by pure water) and freeze drying treatment to obtain a bacterial cellulose layer 1, wherein the cross-linking agent is N, N-methylene bisacrylamide;
step S2, preparing a polyester layer 2 on the bacterial cellulose layer 1
Pouring a first aqueous phase solution onto the bacterial cellulose layer 1, standing for 1min, removing excessive water drops on the surface of the bacterial cellulose layer 1, pouring a first oil phase solution, and reacting for 3min to obtain a polyester prefabricated layer;
hydrolyzing the polyester prefabricated layer by adopting alkali liquor to obtain a polyester layer 2;
s3, preparing a polyamide functional layer 3 on the polyester layer 2 to obtain the high-performance reverse osmosis membrane
Pouring a second aqueous phase solution onto the polyester layer 2, standing for 1min, removing excessive water drops on the surface of the polyester layer 2, pouring a second oil phase solution, reacting for 30s to obtain a polyamide functional layer 3, and drying to obtain a high-performance reverse osmosis membrane;
In the step S1, the bacterial cellulose solution adopts the following raw material components in parts by weight, namely 4 parts of bacterial cellulose and 96 parts of dissolution system, wherein the dissolution system adopts the raw material components in percentage by mass, namely 12% of urea, 7% of sodium hydroxide and 81% of water, the pretreatment comprises a first standing treatment and a dissolution treatment which are sequentially carried out, the first standing treatment comprises standing the bacterial cellulose solution after uniform mixing for 30min, the dissolution treatment comprises firstly standing the bacterial cellulose solution for 2h under the condition of-12 ℃, and then stirring and dissolving the bacterial cellulose solution after the freezing treatment.
In the step S1, the mass concentration of the cross-linking agent in the bacterial cellulose cross-linking system is 0.3%, and the second standing treatment comprises the step of standing the bacterial cellulose cross-linking system which is scraped on a carrier for 2 hours.
In the step S2, the monomer adopted by the first aqueous phase solution is epigallocatechin, and the mass concentration of the monomer of the first aqueous phase solution is 3.5%.
The monomer adopted by the first oil phase solution is trimesoyl chloride, the solvent adopted by the first oil phase solution is normal hexane, and the mass concentration of the monomer of the first oil phase solution is 0.2%.
In the step S2, the alkali liquor is sodium hydroxide aqueous solution, the hydrolysis condition adopted in the hydrolysis treatment is that the pH value is 12, and the hydrolysis time is 2min.
In the step S3, the monomer adopted by the second aqueous phase solution is m-phenylenediamine, and the mass concentration of the monomer of the second aqueous phase solution is 3.2%;
The monomer adopted by the second oil phase solution is trimesoyl chloride, the solvent adopted by the second oil phase solution is normal hexane, and the mass concentration of the monomer of the second oil phase solution is 0.12%.
In step S3, the drying temperature used in the drying treatment is 60 ℃ and the drying time is 1min.
Example 2:
Unlike example 1, the hydrolysis time was 1min.
Example 3:
unlike example 1, the hydrolysis time was 5min.
Comparative example 1:
unlike example 1, the hydrolysis time was 0.5min.
Comparative example 2:
Unlike example 1, the hydrolysis time was 6min.
Comparative example 3:
1) Preparing a porous support membrane, namely preparing an 18wt% polysulfone solution, filtering to remove impurities, uniformly coating the polymer solution on a commodity PET non-woven fabric (120 mu m) by using a scraper after vacuum degassing, then converting the solution into a membrane by using a pure water coagulation bath phase at 15 ℃, and cleaning to obtain the porous support membrane.
2) The preparation of the polyamide functional layer 3 comprises the steps of pouring 3.2wt% of m-phenylenediamine aqueous solution on the surface of a porous support membrane for 1min, removing superfluous aqueous solution on the surface, pouring 0.12wt% of trimesoyl chloride-n-hexane organic solution for interfacial polymerization for 30 seconds, and drying in a 60 ℃ oven for 1min to obtain the high-performance reverse osmosis composite membrane.
Diaphragm performance test:
10 membranes of equal size prepared in examples 1-3 and comparative examples 1-3 were placed on a cross-flow membrane detection table, respectively, and the test was run under conditions of an operating pressure of 150 lbf/square inch, a raw water of 1500ppm NaCl aqueous solution, a temperature of 25℃and a pH of 7-8, and the water flux of the reverse osmosis membranes was calculated according to formulas a and b, respectively And desalination rate. The test results are shown in Table 1.
Calculating a formula a:;
wherein the water flux Refers to a unit time under certain operating conditionsInner transmission unit membrane areaIs the volume of water of (2)Water fluxIn units of (A);Is permeate volume (in L); Is the effective surface area of the reverse osmosis membrane (unit is m 2); The water permeation time (unit is h).
Calculation formula b:;
Wherein, Represents the removal rate of the solute, namely the desalination rate (%),、Respectively represents the concentration of the permeate and the concentration of the raw water after the raw water passes through the reverse osmosis membrane.
Pressure resistance test:
after testing the initial average water flux and initial average desalination rate of the reverse osmosis membrane, the operating pressure was adjusted to 600 lbf/square inch (4 times the original operating pressure) and operated under the same conditions for 180 minutes. And then the operation pressure is regulated to the normal test pressure for testing, and the average water flux and the average desalination rate of the reverse osmosis membrane after high pressure are respectively calculated according to the formula a and the formula b. The test results are shown in Table 1.
Polyester layer 2 molecular weight cut-off test:
The degree of hydrolysis was quantified by testing the molecular weight cut-off of polyester layer 2 prepared in examples 1-3 and comparative examples 1-2. The test adopts 100mg/L of aqueous solutions of PEG-1000, PEG-2000, PEG-4000, PEG-6000, PEG10000 and PEG20000 as test solutions, the TOC values of the original test solution and the filtrate are respectively tested by a total organic carbon analyzer (TOC), the retention rate of the polyester layer 2 is calculated, and a fitted curve is used to obtain the molecular weight when the retention rate is 90 percent as the retention molecular weight of the polyester layer 2. The test results are shown in Table 1.
Table 1 test results
As can be seen from Table 1, the average water flux of examples 1-3 is significantly higher than that of comparative example 3, on the one hand, the porous three-dimensional nanofiber network skeleton structure formed by crosslinking bacterial cellulose and a crosslinking agent is favorable for water molecule transmission in step S1, on the other hand, the polyester layer prepared in step S2 is relatively thinner, has smaller water mass transfer resistance and is favorable for flux improvement compared with the polysulfone layer formed by conventional phase inversion, and simultaneously, carboxyl and hydroxyl formed by hydrolysis treatment of the polyester pre-prepared layer are convenient for hydrophilicity improvement in step S2 by alkali liquor, and the reaction with the second aqueous phase solution in step S3 is more vigorous by hydrogen bond adsorption, so that a large-leaf-shaped polyamide functional layer structure is favorable for formation, the specific surface area is increased, and the water flux of the reverse osmosis composite membrane is improved. Thus, the synergistic effect of steps S1 to S3 is such that the average water flux of examples 1-3 is significantly higher than that of comparative example 3. In addition, in the pressure resistance test, the performances of the examples 1-3 are basically maintained unchanged, and the average water flux of the comparative example 3 is obviously reduced, because the porous three-dimensional nanofiber network skeleton structure formed by crosslinking bacterial cellulose and the crosslinking agent has high mechanical strength, the pressure resistance of the reverse osmosis membrane is improved, and the stability of the high flux performance of the reverse osmosis membrane is ensured.
As is clear from comparative example 1 and comparative example 1, the average water flux of comparative example 1 decreases because the hydrolysis time is short, and the polyester layer 2 formed is relatively denser on the one hand, and the content of hydrophilic groups after hydrolysis is reduced, and the adsorbed metaphenylene diamine is relatively reduced, resulting in a decrease in the specific surface area of the polyamide layer formed, and therefore, the average water flux decreases.
As is clear from comparative examples 1 and 2, comparative example 2 has a relatively low average salt rejection rate, which is due to the long hydrolysis time, the polyester layer 2 is damaged more, and the bacterial cellulose layer 1 may be partially exposed, and the polyamide functional layer 3 formed later is more likely to have defective spots, particularly, is likely to be broken under high pressure, because the bacterial cellulose layer 1 is coarser than the polyester layer 2, and thus the average salt rejection rate is lowered.
From the test of the molecular weight cut-off of the polyester layers 2 prepared in examples 1 to 3 and comparative examples 1 to 2, it was revealed that the longer the hydrolysis time, the larger the molecular weight cut-off of the polyester layer 2, which indicates that the pore size of the polyester layer 2 can be adjusted to an appropriate size by controlling the appropriate hydrolysis time. Adjusting the pore size of the polyester layer 2 to a proper size is convenient for optimizing the preparation of the subsequent polyamide functional layer 3, and ensures that the reverse osmosis membrane has good desalination rate and water flux.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A method for preparing a high performance reverse osmosis membrane, comprising:
step S1, preparing a bacterial cellulose layer
Adding a cross-linking agent into the pretreated bacterial cellulose solution, and uniformly mixing to form a bacterial cellulose cross-linking system, scraping the bacterial cellulose cross-linking system on a carrier, and sequentially carrying out second standing treatment, water washing treatment and freeze drying treatment to obtain a bacterial cellulose layer, wherein the cross-linking agent comprises N, N-methylene bisacrylamide;
S2, preparing a polyester layer on the bacterial cellulose layer
Pouring a first aqueous phase solution onto the bacterial cellulose layer, standing for 0.5-3min, removing excessive water drops on the surface of the bacterial cellulose layer, pouring a first oil phase solution, and reacting for 1-5min to obtain a polyester prefabricated layer;
The hydrolysis treatment is carried out on the polyester prefabricated layer by adopting alkali liquor to obtain a polyester layer, wherein the hydrolysis condition adopted in the hydrolysis treatment is that the pH value is 12, and the hydrolysis time is 1-5min;
S3, preparing a polyamide functional layer on the polyester layer to obtain the high-performance reverse osmosis membrane
Pouring a second aqueous phase solution onto the polyester layer, standing for 0.5-3min, removing excessive water drops on the surface of the polyester layer, pouring the second oil phase solution, reacting for 30-90s to obtain a polyamide functional layer, and drying to obtain the high-performance reverse osmosis membrane.
2. The method for preparing a high-performance reverse osmosis membrane according to claim 1, wherein in the step S1, the bacterial cellulose solution comprises the following raw material components, by weight, 4 parts of bacterial cellulose and 96 parts of dissolution system, the dissolution system comprises the following raw material components, by mass, 12% of urea, 7% of sodium hydroxide and 81% of water, the pretreatment comprises a first standing treatment and a dissolution treatment which are sequentially carried out, the first standing treatment comprises the steps of standing the bacterial cellulose solution after uniform mixing for 15-60min, the dissolution treatment comprises the steps of firstly standing the bacterial cellulose solution for 1-2h at a temperature of-12 ℃ to-20 ℃, and then stirring and dissolving the bacterial cellulose solution after the freezing treatment.
3. The method according to claim 1, wherein in step S1, the mass concentration of the crosslinking agent in the bacterial cellulose crosslinking system is 0.1 to 0.8%, and the second standing treatment comprises standing the bacterial cellulose crosslinking system blade-coated on the carrier for 1 to 3 hours.
4. The method according to claim 1, wherein in the step S2, the monomers used in the first aqueous solution include at least one of epigallocatechin, catechin and epicatechin, and the mass concentration of the monomers in the first aqueous solution is 2.8% -4.2%.
5. The method for preparing a high-performance reverse osmosis membrane according to claim 1, wherein the monomers adopted by the first oil phase solution comprise at least one of trimesoyl chloride, phthaloyl chloride, terephthaloyl chloride and isophthaloyl chloride, the solvents adopted by the first oil phase solution comprise at least one of n-hexane, isopar G, n-heptane and n-octane, and the mass concentration of the monomers in the first oil phase solution is 0.1% -0.3%.
6. The method for preparing a high performance reverse osmosis membrane according to claim 1, wherein in step S2, the alkaline solution comprises aqueous sodium hydroxide solution.
7. The method for preparing a high-performance reverse osmosis membrane according to claim 1, wherein in the step S3, the monomers used in the second aqueous phase solution include at least one of m-phenylenediamine, p-phenylenediamine and o-phenylenediamine, and the mass concentration of the monomers in the second aqueous phase solution is 2% -5%;
The second oil phase solution adopts at least one monomer selected from trimesoyl chloride, phthaloyl chloride, terephthaloyl chloride and isophthaloyl chloride, the second oil phase solution adopts at least one solvent selected from n-hexane, isopar G, n-heptane and n-octane, and the mass concentration of the monomer of the second oil phase solution is 0.08-0.2%.
8. The method for preparing a high-performance reverse osmosis membrane according to claim 1, wherein in step S3, the drying temperature used for the drying treatment is 50-60 ℃ and the drying time is 1-3min.
9. A high performance reverse osmosis membrane prepared by the method of any one of claims 1-8.
10. The high performance reverse osmosis membrane according to claim 9, wherein the bacterial cellulose layer has a thickness of 100-300 μm, the polyester layer has a thickness of 200-400nm, and the polyamide functional layer has a thickness of 100-300nm.
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| AU2020101861A4 (en) * | 2019-12-04 | 2020-09-24 | Qilu University Of Technology | Bacterial cellulose-poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block copolymer composite membrane and manufacturing method thereof |
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| AU2020101861A4 (en) * | 2019-12-04 | 2020-09-24 | Qilu University Of Technology | Bacterial cellulose-poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block copolymer composite membrane and manufacturing method thereof |
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