CN115703046A - Preparation method of composite nanofiltration membrane and composite nanofiltration membrane - Google Patents
Preparation method of composite nanofiltration membrane and composite nanofiltration membrane Download PDFInfo
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- CN115703046A CN115703046A CN202110942138.3A CN202110942138A CN115703046A CN 115703046 A CN115703046 A CN 115703046A CN 202110942138 A CN202110942138 A CN 202110942138A CN 115703046 A CN115703046 A CN 115703046A
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02A20/124—Water desalination
- Y02A20/131—Reverse-osmosis
Abstract
The invention provides a preparation method of a composite nanofiltration membrane and the composite nanofiltration membrane prepared by the method, aiming at solving the problem of low water flux of the composite nanofiltration membrane. A preparation method of a composite nanofiltration membrane comprises the following steps: (1) Mixing polyamine monomer with water to prepare an aqueous phase solution; (2) Mixing a polybasic acyl chloride monomer with an organic solvent to prepare an oil phase solution; (3) Providing a base membrane, respectively immersing the base membrane into a water phase solution and an oil phase solution, performing interfacial polymerization reaction of the water phase and the oil phase on the surface of the base membrane, so as to generate a separation layer on the surface of the base membrane, and taking out to obtain a pretreated composite nanofiltration membrane; (4) And mixing an amino modifier with water to prepare a modified solution, and coating the surface of the pretreated composite nanofiltration membrane with the modified solution to obtain the composite nanofiltration membrane. According to the invention, a modified layer is constructed on the surface of the separation layer of the composite nanofiltration membrane, so that the water flux and the structural stability of the composite nanofiltration membrane can be effectively improved.
Description
Technical Field
The invention relates to a composite nanofiltration membrane, in particular to a preparation method of the composite nanofiltration membrane and the composite nanofiltration membrane.
Background
Nanofiltration membranes (NF) were first shown in the end of the 20 th century, the 70 s, and are one of the more rapidly developing membrane varieties internationally in recent years, and the separation performance thereof is intermediate between Reverse Osmosis (RO) and Ultrafiltration (UF). The composite nanofiltration membrane is mainly a composite membrane obtained by respectively optimizing a functional separation layer and a porous support layer in an interfacial polymerization mode, so that the performance of a nanofiltration membrane product is greatly improved. However, in actual production, the commercial traditional nanofiltration membrane still has the problems of unstable structure and low flux.
Disclosure of Invention
In order to solve the above problems, a first object of the present invention is to provide a method for preparing a composite nanofiltration membrane, thereby obtaining a composite nanofiltration membrane with stable structure and high flux; in order to achieve the above object, the present invention comprises the steps of:
(1) Mixing polyamine monomer, additive and water to prepare a water phase solution; (2) Mixing a polyacyl chloride monomer with an organic solvent to prepare an oil phase solution; (3) Providing a base membrane, respectively immersing the base membrane into a water phase solution and an oil phase solution (performing interfacial polymerization reaction of the water phase and the oil phase on the surface of the base membrane to generate a separation layer on the surface of the base membrane), and taking out to obtain a pretreated composite nanofiltration membrane; (4) And (2) mixing an amino modifier with water to prepare a modified solution, and coating the surface of the pretreated composite nanofiltration membrane with the modified solution to obtain the composite nanofiltration membrane.
According to the preparation method, a separation layer is formed on the surface of a base film through interfacial polymerization, then a modification solution is coated on the separation layer, and an amino group in the modification solution reacts with an acyl chloride group on the separation layer, so that a modification layer is constructed on the surface of the separation layer; through chemical bond connection between modified layer and the separation layer, not only stable in structure contains a large amount of hydroxyl groups on the modified layer moreover, can effectually improve the hydrophilicity of compound nanofiltration membrane, improves water flux greatly when can guarantee the salt rejection rate of compound nanofiltration membrane.
As an embodiment, the polyamine monomer in the step (1) is one or more of polyethyleneimine, piperazine, m-phenylenediamine, tetraethylenepentamine and polyvinylamine.
In one embodiment, the mass fraction of the polyamine monomer in the aqueous solution in the step (1) is 0.01 to 1.00% or 0.05 to 0.50%.
As an embodiment, in the step (1), an additive is added during the mixing of the polyamine monomer and the water, wherein in the step (1), the additive comprises a surfactant and/or an acid-binding agent, and the surfactant is one or more of sodium dodecyl benzene sulfonate, sodium dodecyl sulfate and tetrabutylammonium bromide; the acid-binding agent is one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate and triethylamine.
As an embodiment, the mass fraction of the surfactant in the aqueous phase solution is 0.01 to 1.00%; or 0.05-0.50%.
As an embodiment, the mass fraction of the acid-binding agent in the aqueous phase solution is 0.01-1.00%; or 0.05-0.50%.
In one embodiment, the polybasic acyl chloride monomer in the step (2) is one or more of trimesoyl chloride, isophthaloyl chloride and terephthaloyl chloride.
In one embodiment, the organic solvent in step (2) is one or more selected from n-hexane, cyclohexane, isoparaffin, and n-heptane.
As an embodiment, the isoparaffin is one or more of Isopar C, isopar E, isopar G, isopar H, isopar L, isopar M, isopar V.
In one embodiment, the mass fraction of the polybasic acyl chloride monomer in the oil phase solution in the step (2) is 0.01 to 1.00% or 0.05 to 0.50%.
As an embodiment, the raw material of the base membrane in the step (3) is one or more of polysulfone, polyethersulfone, polytetrafluoroethylene and polyvinylidene fluoride.
The sequence of immersing the basement membrane into the water phase solution and the oil phase solution is not limited, and the basement membrane can be immersed into the water phase solution firstly and then immersed into the oil phase solution; or immersing the substrate into the oil-phase solution first and then the water-phase solution. The water used in the aqueous phase solution of the present invention may be either deionized or pure water, preferably with a conductivity of <10 μ s/cm.
As an implementation mode, firstly, immersing the base membrane into the water phase solution for 1-10 minutes, then taking out, drying in an oven at 30-50 ℃ for 2-10 minutes, then immersing the base membrane into the oil phase solution for 1-10 minutes, and then taking out to obtain the pretreated composite nanofiltration membrane. The water phase attached to the surface of the base film and the oil solution generate interfacial polymerization reaction to form a separation layer on the surface of the base film.
The interfacial polymerization reaction is as follows:
wherein PIP is piperazine
TMC is trimesoyl chloride
As an embodiment, the pretreatment composite nanofiltration membrane is immersed in the modification solution, is taken out after being immersed for 1 to 10 minutes, so that the surface of the pretreatment composite nanofiltration membrane is coated with the modification solution, and then is placed in an oven to be dried, wherein the temperature of the oven is 50 to 130 ℃ or 70 to 120 ℃; the drying time is 1-30 minutes or 2-15 minutes. And (3) reacting amino groups in the modified solution with acyl chloride groups on the separation layer of the pretreated composite nanofiltration membrane to form a modified layer on the surface of the separation layer of the composite nanofiltration membrane, wherein the reaction speed is higher when the temperature of the oven is higher, but the separation layer is damaged when the temperature is too high, namely higher than 130 ℃.
The reaction process of the pretreated composite nanofiltration membrane and the modified solution is as follows:
wherein Tris is Tris (hydroxymethyl) aminomethane
In one embodiment, the amino modifier in step (4) is one or more of tris, 1, 3-bis ((tris) methylamino) propane, and 3-aminopropyl phosphoric acid. The amino modifier adopted by the invention not only contains amino groups capable of reacting with acyl chloride groups, so that the modified layer is connected to the surface of the separation layer of the composite nanofiltration membrane through chemical bonds, and the modified layer is connected to the separation layer through chemical bonds. In addition, the amino modifier adopted by the invention also contains hydroxyl groups, and the existence of the hydroxyl groups improves the hydrophilicity of the composite nanofiltration membrane; on the basis that the modified layer is connected with the separation layer, the modified layer also contains a large amount of hydroxyl groups, so that the salt rejection rate of the composite nanofiltration membrane is ensured, and the water flux of the composite nanofiltration membrane is improved.
In one embodiment, the amino modifier in the modifying solution in the step (4) is 0.10 to 5.00% by mass or 0.50 to 5.00% by mass.
The invention also aims to provide the composite nanofiltration membrane prepared by the preparation method.
The invention has the technical effects that:
the invention utilizes the reaction of amino groups in the modified solution and acyl chloride groups on the separation layer on the surface of the pretreated nanofiltration membrane, thereby constructing a modified layer on the surface of the separation layer of the composite nanofiltration membrane, and the modified layer is connected with the separation layer through chemical bonds, so that the structure is stable. The other end of the modified layer contains a large number of hydroxyl groups, the hydrophilicity of the composite nanofiltration membrane can be effectively enhanced by the hydroxyl groups, and the desalination rate cannot be influenced due to the fact that the structure of the separation layer is not damaged, but the separation layer is reinforced, and the water flux of the composite nanofiltration membrane can be obviously improved on the premise that the desalination rate is guaranteed. And the whole preparation process is simple, the reaction condition is mild, the performance is stable, the industrial implementation is easy, and the method has a good industrial application prospect.
Drawings
FIG. 1 is a schematic representation of the water contact angle of comparative example 1 (before modification) of the present invention;
FIG. 2 is a schematic diagram showing the water contact angle of example 1 (after modification) of the present invention;
Detailed Description
The following specific examples describe the present invention in detail, however, the present invention is not limited to the following examples.
The prepared composite nanofiltration membranes are pre-pressed for half an hour by pure water under 0.3MPa, and the pure water flux of the membranes is respectively tested by the pure water and 2g/L MgSO 4 The electrolyte solution of (2) was tested for salt rejection at 25 ℃.
The calculation formula of the pure water flux is shown in (1).
Wherein A pi DL (A-active membrane area, m) 2 (ii) a D-average diameter of membrane filaments, m; l-the effective length of the membrane filaments, m); t-time required for collecting Q volume of produced fluid, h; q-volume of product fluid collected over time t, L.
And (3) repeatedly measuring the composite nanofiltration membrane for 3 times, and taking an average value to obtain the pure water flux of the composite nanofiltration membrane.
The salt rejection calculation method is shown in (2).
Wherein R is the salt rejection of the membrane, C f -the conductivity of the stock solution,. Mu.S/cm; c p Conductivity of the produced water,. Mu.S/cm.
And (3) repeatedly measuring the composite nanofiltration membrane for 3 times, and taking an average value to obtain the desalination rate of the composite nanofiltration membrane.
Comparative example 1
Preparing the composite nanofiltration membrane according to a conventional method:
(1) Mixing 0.25g of piperazine, 0.1g of sodium dodecyl sulfate, 0.075g of triethylamine and 100g of deionized water, and uniformly stirring to obtain an aqueous phase solution;
(2) 0.15g of trimesoyl chloride and 100g of normal hexane are mixed and uniformly stirred to obtain an oil phase solution;
(3) Immersing a polysulfone ultrafiltration basement membrane into the water phase solution, and taking out after immersing for 5 minutes to obtain a coated basement membrane;
(4) Drying the base membrane coated in the step (3) in an oven at 30 ℃ for 5 minutes, then immersing the base membrane in the oil phase solution for 2 minutes, and taking out the base membrane to obtain a pretreated composite nanofiltration membrane; and then drying the membrane in an oven at 120 ℃ for 5 minutes to obtain the composite nanofiltration membrane.
And (3) testing results: testing the obtained composite nanofiltration membrane at 25 deg.C and 0.3Mpa to obtain pure water flux of 33L/m 2 h, for 2g/L MgSO 4 The retention of (a) was 95%.
Example 1:
the difference from the comparative example 1 is that after the pretreated composite nanofiltration membrane is obtained, the pretreated composite nanofiltration membrane is modified, and the specific steps comprise:
(1) Mixing 1g of tris (hydroxymethyl) aminomethane with 99g of water and uniformly stirring to obtain a modified solution;
(2) And (3) immersing the pretreated composite nanofiltration membrane into the modified solution for 5 minutes, drying in an oven at 80 ℃ for 15 minutes, and taking out to obtain the composite nanofiltration membrane.
And (3) testing results: testing the obtained composite nanofiltration membrane at 25 deg.C and 0.3Mpa to obtain pure water flux of 55L/m 2 h, for 2g/L MgSO 4 The retention of (a) was 97%.
Example 2:
the difference from the comparative example 1 is that after the pretreated composite nanofiltration membrane is obtained, the composite nanofiltration membrane is modified, and the specific steps comprise:
(1) Mixing and uniformly stirring 5g of 1, 3-bis ((trihydroxymethyl) methylamino) propane and 95g of water to obtain a modified solution;
(2) And (3) immersing the pretreated composite nanofiltration membrane into the modified solution for 10 minutes, then placing the solution into an oven at 100 ℃ for drying for 10 minutes, and taking out the solution to obtain the composite nanofiltration membrane.
And (3) testing results: testing the obtained composite nanofiltration membrane at 25 deg.C and 0.3Mpa to obtain pure water flux of 48L/m 2 h, for 2g/L MgSO 4 The retention of (a) was 96%.
Example 3:
the difference from the comparative example 1 is that after the pretreated composite nanofiltration membrane is obtained, the composite nanofiltration membrane is modified, and the specific steps comprise:
(1) Mixing 0.5g of 3-aminopropyl phosphoric acid and 99.5g of water, and uniformly stirring to obtain a modified solution;
(2) And (3) immersing the pretreated composite nanofiltration membrane into the modified solution for 1 minute, then placing the solution into an oven at 120 ℃ for drying for 5 minutes, and taking out the solution to obtain the composite nanofiltration membrane.
And (3) testing results: testing the obtained composite nanofiltration membrane at 25 deg.C and 0.3Mpa to obtain pure water flux of 51L/m 2 h, for 2g/L MgSO 4 The retention of (a) was 96%.
Example 4:
the difference from the comparative example 1 is that after the pretreated composite nanofiltration membrane is obtained, the composite nanofiltration membrane is modified, and the specific steps comprise:
(1) 0.1g of 1, 3-bis ((trimethylol) methylamino) propane was mixed with 99.9g of water and stirred uniformly to obtain a modified solution;
(2) And (3) immersing the pretreated composite nanofiltration membrane into the modified solution for 1 minute, drying in an oven at 120 ℃ for 5 minutes, and taking out to obtain the composite nanofiltration membrane.
And (3) testing results: testing the obtained composite nanofiltration membrane at 25 deg.C and 0.3Mpa to obtain pure water flux of 46L/m 2 h, for 2g/L MgSO 4 The retention of (a) was 97%.
Example 5:
the point different from comparative example 1 is that the amount of piperazine was changed from 0.25g to 0.01g, and the amount of trimesoyl chloride was changed from 0.15g to 0.5g of isophthaloyl dichloride; after the pretreated composite nanofiltration membrane is obtained, the pretreated composite nanofiltration membrane is modified, and the method specifically comprises the following steps:
(1) Mixing 0.1g of 3-aminopropyl phosphoric acid and 99.9g of water, and uniformly stirring to obtain a modified solution;
(2) And (3) immersing the pretreated composite nanofiltration membrane into the modified solution for 1 minute, drying in an oven at 120 ℃ for 5 minutes, and taking out to obtain the composite nanofiltration membrane.
And (3) testing results: testing the obtained composite nanofiltration membrane at 25 deg.C and 0.3Mpa to obtain pure water flux of 53L/m 2 h, for 2g/L MgSO 4 The retention of (a) was 96%.
Example 6:
the difference from comparative example 1 is that the amount of piperazine was changed from 0.25g to 1g, and the amount of trimesoyl chloride was changed from 0.15g to 0.05g of terephthaloyl chloride; after the pretreated composite nanofiltration membrane is obtained, the composite nanofiltration membrane is modified, and the method specifically comprises the following steps:
(1) 0.5g of 1, 3-bis ((trimethylol) methylamino) propane was mixed with 99.5g of water and stirred uniformly to obtain a modified solution;
(2) And (3) immersing the pretreated composite nanofiltration membrane into the modified solution for 1 minute, drying in an oven at 120 ℃ for 5 minutes, and taking out to obtain the composite nanofiltration membrane.
And (3) testing results: testing the obtained composite nanofiltration membrane at 25 deg.C and 0.3Mpa to obtain pure water flux of 48L/m 2 h, for 2g/L MgSO 4 The retention of (a) was 96%.
To summarize
As can be seen from the comparison results of the examples 1 to 6 and the comparative example 1, the water flux of the modified composite nanofiltration membrane is obviously improved, and the desalination rate is also improved to a certain extent (the desalination stability is good).
Table 1: influence of modification treatment on water flux and desalination rate of composite nanofiltration membrane
The water contact angle detection comparison is carried out by selecting the embodiment 1 and the comparative example 1, as shown in fig. 1 and 2, the water contact angle of the composite nanofiltration membrane after modification is obviously reduced, the water contact angle is reduced from 71 degrees before modification (comparative example 1) to 23 degrees after modification (embodiment 1), and the hydrophilicity is obviously improved.
The foregoing is only a few specific embodiments of the invention. The protection scope of the present invention is subject to the protection scope of the claims.
Claims (11)
1. The preparation method of the composite nanofiltration membrane is characterized by comprising the following steps of:
(1) Mixing polyamine monomer with water to prepare an aqueous phase solution;
(2) Mixing a polybasic acyl chloride monomer with an organic solvent to prepare an oil phase solution;
(3) Providing a base membrane, respectively immersing the base membrane into a water phase solution and an oil phase solution, and taking out to obtain a pretreated composite nanofiltration membrane;
(4) And (2) mixing an amino modifier with water to prepare a modified solution, and coating the surface of the pretreated composite nanofiltration membrane with the modified solution to obtain the composite nanofiltration membrane.
2. The method for preparing a composite nanofiltration membrane according to claim 1, wherein the polyamine monomer in the step (1) is one or more of polyethyleneimine, piperazine, m-phenylenediamine, tetraethylenepentamine and polyvinylamine.
3. The method of claim 1, wherein in step (1), an additive is added during the mixing of the polyamine monomer and water, wherein the additive comprises a surfactant and/or an acid-binding agent, and the surfactant is one or more of sodium dodecyl benzene sulfonate, sodium dodecyl sulfate and tetrabutylammonium bromide; the acid-binding agent is one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate and triethylamine.
4. The method for preparing a composite nanofiltration membrane according to claim 1, wherein the mass fraction of the polyamine monomer in the aqueous solution in the step (1) is 0.01-1.00%.
5. The method for preparing a composite nanofiltration membrane according to claim 1, wherein in the step (2), the polyacyl chloride monomer is one or more of trimesoyl chloride, isophthaloyl chloride and terephthaloyl chloride.
6. The method for preparing a composite nanofiltration membrane according to claim 1, wherein the organic solvent in the step (2) is one or more of n-hexane, cyclohexane, isoparaffin, and n-heptane.
7. The method for preparing a composite nanofiltration membrane according to claim 1, wherein the mass fraction of the polybasic acid chloride monomer in the oil phase solution in the step (2) is 0.05-0.50%.
8. The method for preparing a composite nanofiltration membrane according to claim 1, wherein the raw material of the base membrane in the step (3) is one or more of polysulfone, polyethersulfone, polytetrafluoroethylene and polyvinylidene fluoride.
9. The method for preparing a composite nanofiltration membrane according to claim 1, wherein the amino modifier in step (4) is one or more of tris, 1, 3-bis ((tris) methylamino) propane, and 3-aminopropyl phosphoric acid.
10. The method for preparing a composite nanofiltration membrane according to claim 1, wherein the mass fraction of the amino modifier in the modification solution in the step (4) is 0.10-5.00%.
11. A composite nanofiltration membrane prepared by the preparation method of any one of claims 1 to 10.
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| CN116459684A (en) * | 2023-06-19 | 2023-07-21 | 蓝星（杭州）膜工业有限公司 | Composite membrane and preparation method and application thereof |
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| CN116459684A (en) * | 2023-06-19 | 2023-07-21 | 蓝星（杭州）膜工业有限公司 | Composite membrane and preparation method and application thereof |
| CN116459684B (en) * | 2023-06-19 | 2023-09-05 | 蓝星（杭州）膜工业有限公司 | Composite membrane and preparation method and application thereof |
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