A pollution-resistant seawater desalination membrane and preparation method thereof

Abstract

The present invention relates to the technical field of separation membranes, and in particular to a pollution-resistant seawater desalination membrane and a preparation method thereof. The pollution-resistant seawater desalination membrane is prepared by the preparation method. The preparation method comprises forming a polyamide layer on a base layer through a first interfacial polymerization reaction; leaving unreacted acyl chloride groups on the polyamide layer; coating the polyamide layer with a pollution-resistant modified solution, wherein the pollution-resistant modified solution contains a nitrogen heterocyclic monomer with an amino group, and the nitrogen heterocyclic monomer with an amino group and the remaining unreacted acyl chloride groups on the polyamide layer undergo a second interfacial polymerization reaction to form a pollution-resistant seawater desalination membrane. The pollution-resistant seawater desalination membrane prepared by the present invention has high permeation flux, anti-pollution performance, and resistance to active chlorine oxidation.

Description

Technical Field

[0001] The invention relates to the technical field of separation membranes, and in particular to a pollution-resistant seawater desalination membrane and a preparation method thereof. Background Art

[0002] Desalinated water is an important incremental water source for water resources supply. It directly uses seawater desalination to produce fresh water, and has the advantages of excellent water quality, stable supply, and no influence of climate, time and space. Among them, reverse osmosis desalination technology is an important way to obtain desalinated water.

[0003] Compared with thermal desalination technology, reverse osmosis desalination technology has many advantages, but there are still some problems that need to be solved, such as low permeate flux, poor pollution resistance and inability to active chlorine oxidation. Among them, poor pollution resistance means that the reverse osmosis membrane is easily polluted by pollutants such as colloidal particles and organic matter in seawater. The polluted reverse osmosis membrane directly leads to a significant decrease in permeate flux and salt rejection rate, which greatly shortens its service life.

[0004] Therefore, it is necessary to develop a pollution-resistant seawater desalination membrane and a preparation method thereof to solve the problems of low permeate flux, poor pollution resistance and inability to resist active chlorine oxidation in the existing reverse osmosis seawater desalination technology. Summary of the invention

[0005] The object of the present invention is to provide a pollution-resistant seawater desalination membrane and a preparation method thereof. The specific technical scheme is as follows:

[0006] In a first aspect, the present invention provides a method for preparing a pollution-resistant seawater desalination membrane, comprising:

[0007] Step S1, forming a polyamide layer on the base layer through a first interfacial polymerization reaction; unreacted acyl chloride groups remain on the polyamide layer;

[0008] Step S2, coating the polyamide layer with a pollution-resistant modification solution, wherein the pollution-resistant modification solution contains a nitrogen heterocyclic monomer with an amino group, and the nitrogen heterocyclic monomer with an amino group reacts with the remaining unreacted acyl chloride groups on the polyamide layer through a second interfacial polymerization reaction to form a pollution-resistant seawater desalination membrane.

[0009] Optionally, in the pollution-resistant modified solution, the mass percentage of the nitrogen heterocyclic monomer with an amino group is 0.1%-5.0%; the coating amount of the pollution-resistant modified solution on the polyamide layer is controlled to be 50-150g / m 2 .

[0010] Optionally, in the pollution-resistant modified solution, the mass percentage of the nitrogen heterocyclic monomer with an amino group is 0.5%-3.0%.

[0011] Optionally, the nitrogen heterocyclic monomer with an amino group includes at least one of an aminoimidazole monomer, an aminopyrimidine monomer, an aminopyrazole monomer and an aminopyridazine monomer.

[0012] Optionally, the aminoimidazole monomer includes at least one of (1H-imidazole-4-yl)methylamine, histamine and 4-aminoimidazole;

[0013] The aminopyrimidine monomer includes at least one of 5-aminopyrimidine, 5-pyrimidinemethylamine and 2-(pyrimidin-5-yl)ethylamine;

[0014] The aminopyrazole monomer includes at least one of 3-aminopyrazole, 3-(aminomethyl)pyrazole and 2-(3-pyrazolyl)ethylamine;

[0015] The aminopyridazine monomer includes at least one of 4-aminopyridazine, 4-aminomethylpyridazine and 2-(pyridazine-4-yl)ethan-1-amine.

[0016] Optionally, the nitrogen heterocyclic monomer having an amino group includes at least one of 4-aminoimidazole, 5-aminopyrimidine, 3-aminopyrazole and 4-aminopyridazine.

[0017] Optionally, the solvent used in the pollution-resistant modified solution includes any one of n-hexane, n-heptane, n-decane and cyclohexane.

[0018] Optionally, in step S2, before the second interfacial polymerization reaction, the anti-pollution modified solution coated on the polyamide layer needs to be subjected to a vibration dispersion treatment, with the vibration frequency being 20-50 Hz and the vibration time being 5-30 s;

[0019] The method further comprises step S3 of drying the prepared pollution-resistant seawater desalination membrane; the drying temperature used in the drying treatment is 60-90° C. and the drying time is 2-8 minutes.

[0020] Optionally, in step S1, the base layer includes a non-woven fabric layer and a polysulfone support layer stacked in sequence;

[0021] A polyamide layer is formed on the polysulfone supporting layer through a first interfacial polymerization reaction.

[0022] In a second aspect, the present invention provides a pollution-resistant seawater desalination membrane, which is prepared by using the method for preparing the pollution-resistant seawater desalination membrane.

[0023] The application of the technical solution of the present invention has at least the following beneficial effects:

[0024] (1) The present invention provides a pollution-resistant seawater desalination membrane and a preparation method thereof, and the prepared pollution-resistant seawater desalination membrane has high permeation flux, anti-pollution performance and resistance to active chlorine oxidation. Specifically, the nitrogen heterocyclic monomer with an amino group used in the pollution-resistant modified solution can react with the remaining unreacted acyl chloride groups on the polyamide layer through a second interfacial polymerization reaction to form a pollution-resistant seawater desalination membrane, greatly reducing the unreacted acyl chloride groups, avoiding the hydrolysis of the unreacted acyl chloride groups into carboxylic acid groups, resulting in the negative charge on the membrane surface. The charge on the membrane surface of the formed pollution-resistant seawater desalination membrane tends to be more neutral, and the anti-pollution performance of pollutants with positive and negative charges is increased; at the same time, the nitrogen heterocyclic monomer is firmly attached to the surface of the polyamide layer, and it is difficult to fall off in long-term use and complex environments, thereby improving the stability and durability of the pollution-resistant seawater desalination membrane. In addition, the membrane surface of the pollution-resistant seawater desalination membrane formed by the second interfacial polymerization reaction is smooth, and the roughness is significantly reduced, which can effectively reduce the attachment of pollutants on the membrane surface, improve the pollution resistance of the membrane surface, and is easy to remove during the cleaning process. Furthermore, the N- in the nitrogen heterocyclic monomer can react with active chlorine first, reducing the attack and damage of active chlorine on the polyamide layer, and improving the resistance of the pollution-resistant seawater desalination membrane to active chlorine oxidation. In addition, the introduction of nitrogen heterocyclic monomers improves the hydrophilicity of the surface of the pollution-resistant seawater desalination membrane. The increase in hydrophilicity makes it easier for water molecules to diffuse on the membrane surface, reducing transmission resistance, thereby increasing the water penetration rate and further increasing the permeation flux.

[0025] (2) Before the second interfacial polymerization reaction, the anti-fouling modified solution coated on the polyamide layer needs to be subjected to a vibration dispersion treatment, with the vibration frequency being 20-50 Hz and the vibration time being 5-30 s, which helps to fully contact the nitrogen heterocyclic monomer with the amino group with the remaining unreacted acyl chloride groups on the polyamide layer, thereby ensuring that the second interfacial polymerization reaction is sufficient, and further improving the anti-fouling performance of the anti-fouling seawater desalination membrane.

[0026] (3) The nitrogen heterocyclic monomer with an amino group used in the present invention is a bulk industrial product with a low price. The preparation method protected by the present invention can realize industrial production and has practicality.

[0027] In addition to the above-described purposes, features and advantages, the present invention has other purposes, features and advantages. The present invention will be further described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0029] Figure 1is an atomic force microscope height image of the pollution-resistant seawater desalination membrane prepared in Example 7 of the present invention;

[0030] Figure 2 This is an atomic force microscope height map of the pollution-resistant seawater desalination membrane prepared in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0031] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0032] Embodiment 1:

[0033] See also Figure 1 , a method for preparing a pollution-resistant seawater desalination membrane, comprising:

[0034] Step S1, forming a polyamide layer on the base layer through a first interfacial polymerization reaction; unreacted acyl chloride groups remain on the polyamide layer;

[0035] Step S2, uniformly coating the anti-pollution modification solution on the polyamide layer, wherein the coating amount of the anti-pollution modification solution on the polyamide layer is controlled to be 100 g / m 2 The pollution-resistant modified solution contains a nitrogen heterocyclic monomer with an amino group, and the nitrogen heterocyclic monomer with an amino group and the remaining unreacted acyl chloride groups on the polyamide layer undergo a second interfacial polymerization reaction to form a pollution-resistant seawater desalination membrane.

[0036] In the pollution-resistant modified solution, the mass percentage of the nitrogen heterocyclic monomer with an amino group is 1.0%. Specifically, 1 gram of 4-aminoimidazole is added to 99 grams of n-hexane and stirred until completely dissolved to obtain the pollution-resistant modified solution.

[0037] In step S2, before the second interfacial polymerization reaction is carried out, the anti-pollution modified solution coated on the polyamide layer needs to be subjected to a vibration dispersion treatment, with a vibration frequency of 50 Hz and a vibration time of 20 s.

[0038] The method further comprises step S3 of drying the prepared pollution-resistant seawater desalination membrane; the drying temperature used in the drying treatment is 80° C. and the drying time is 3 minutes.

[0039] In step S1, the base layer includes a non-woven fabric layer and a polysulfone support layer stacked in sequence;

[0040] The preparation process of the polysulfone support layer is specifically as follows: 100 grams of polysulfone resin (PSF) and 400 grams of N,N-dimethylformamide (DMF) are weighed and mixed to prepare a 500-gram solution; the mixture is stirred at 75° C. for 8 hours to prepare a uniformly dispersed casting solution; the casting solution is filtered and vacuum degassed, and then evenly coated on a non-woven fabric on a scraper, with a wet film thickness of 200 μm. After evaporation for 3 seconds at room temperature, the film is immersed in ultrapure water at 15° C. to gel and solidify into a film, and then the film is completely solidified by water at room temperature, and finally the film is treated in water at 75° C. for 3 minutes to obtain a polysulfone support layer;

[0041] A polyamide layer is prepared on a polysulfone support layer through a first interfacial polymerization reaction, specifically: firstly, the polysulfone support layer is contacted with a polyamine aqueous solution for 30 seconds, and excess solution is removed with a rubber roller to form a polyamine solution layer on the surface of the polysulfone support layer; then, the obtained polysulfone support layer is contacted with an acyl chloride oil phase solution for 20 seconds, and the residual oil phase solution on the surface is removed to form a polyamide layer; wherein: 400 grams of m-phenylenediamine, 88 grams of triethylamine, 184 grams of camphorsulfonic acid and 8 grams of sodium dodecylsulfonate are weighed and dissolved in 7320 grams of deionized water, and stirred evenly to obtain a polyamine aqueous solution; 30 grams of trimesoyl chloride is dissolved in 9970 grams of n-hexane, and stirred evenly to obtain an acyl chloride oil phase solution.

[0042] Embodiment 2:

[0043] Different from Example 1, in the pollution-resistant modified solution, the mass percentage of the nitrogen heterocyclic monomer with an amino group is 2.0%. Specifically, 2 grams of 4-aminoimidazole is weighed and added to 98 grams of n-hexane, and stirred until completely dissolved to obtain the pollution-resistant modified solution.

[0044] Embodiment 3:

[0045] Different from Example 1, in the pollution-resistant modified solution, the mass percentage of the nitrogen heterocyclic monomer with an amino group is 3.0%. Specifically, 3 grams of 4-aminoimidazole is weighed and added to 97 grams of n-hexane, and stirred until completely dissolved to obtain the pollution-resistant modified solution.

[0046] Embodiment 4:

[0047] The difference from Example 1 is that 4-aminoimidazole is replaced by 5-aminopyrimidine.

[0048] Embodiment 5:

[0049] The difference from Example 2 is that 4-aminoimidazole is replaced by 5-aminopyrimidine.

[0050] Embodiment 6:

[0051] The difference from Example 3 is that 4-aminoimidazole is replaced by 5-aminopyrimidine.

[0052] Embodiment 7:

[0053] The difference from Example 1 is that 4-aminoimidazole is replaced by 3-aminopyrazole.

[0054] Embodiment 8:

[0055] The difference from Example 2 is that 4-aminoimidazole is replaced by 3-aminopyrazole.

[0056] Embodiment 9:

[0057] The difference from Example 3 is that 4-aminoimidazole is replaced by 3-aminopyrazole.

[0058] Embodiment 10:

[0059] The difference from Example 1 is that 4-aminoimidazole is replaced by 4-aminopyridazine.

[0060] Embodiment 11:

[0061] The difference from Example 2 is that 4-aminoimidazole is replaced by 4-aminopyridazine.

[0062] Embodiment 12:

[0063] The difference from Example 3 is that 4-aminoimidazole is replaced by 4-aminopyridazine.

[0064] Embodiment 13:

[0065] The difference from Example 1 is that in the pollution-resistant modified solution, the mass percentage of the nitrogen heterocyclic monomer with an amino group is 0.5%. Specifically, 0.5 g of 4-aminoimidazole is weighed and added to 99.5 g of n-hexane, and stirred until completely dissolved to obtain the pollution-resistant modified solution.

[0066] Embodiment 14:

[0067] The difference from Example 1 is that in the pollution-resistant modified solution, the mass percentage of the nitrogen heterocyclic monomer with an amino group is 3.0%. Specifically, 0.5 g of 4-aminoimidazole and 2.5 g of 4-aminopyridazine are weighed and added to 97 g of n-hexane, and stirred until completely dissolved to obtain the pollution-resistant modified solution.

[0068] Comparative Example 1:

[0069] Different from the embodiment 7, step S2 is not provided.

[0070] Comparative Example 2:

[0071] Different from Example 7, no vibration dispersion treatment was performed.

[0072] Comparative Example 3:

[0073] Different from Example 7, the temperature of the second interfacial polymerization reaction is 50°C.

[0074] Comparative Example 4:

[0075] Different from Example 7, the temperature of the second interfacial polymerization reaction is 100°C.

[0076] The pollution-resistant seawater desalination membranes prepared in Examples 1-14 and Comparative Examples 1-4 were sampled for basic tests and pollution-resistant tests. Specifically:

[0077] In the first stage, the membrane was taken for basic testing on a cross-flow membrane test bench. Basic testing was carried out in a 32000ppm NaCl aqueous solution, at an operating pressure of 800psi, a temperature of 25°C and a pH of 7.5 to determine the benchmarks of permeation flux and desalination rate.

[0078] In the second stage, the membrane was taken to a cross-flow membrane test station for pollution resistance test. The membrane pollution resistance test was carried out in a 32000ppm NaCl and 200ppm sodium alginate contaminated aqueous solution, 800psi constant pressure, 25℃ temperature, and pH 7.5. The membrane flux was examined after 180min of test time.

[0079] In the third stage, after the pollution resistance test is completed, the membrane is flushed with pure water at a flow rate of 5L / min under low pressure for 30min.

[0080] In the fourth stage, the membrane permeation flux test was conducted again under the standard conditions of the first stage.

[0081] The flux attenuation rate and recovery rate are calculated by the following formula. The test results are shown in Table 1.

[0082] Flux attenuation rate (%) = [1-(permeation flux of the second stage / permeation flux of the first stage)] × 100%

[0083] Flux recovery rate (%) = (permeation flux in the fourth stage / permeation flux in the first stage) × 100%

[0084] The test results of the basic test and the pollution resistance test of the pollution-resistant seawater desalination membranes prepared in Examples 1-14 and Comparative Examples 1-2 are shown in Table 1.

[0085] Table 1 Test results of basic test and pollution resistance test

[0086]

[0087]

[0088] The pollution-resistant seawater desalination membranes prepared in Example 2, Example 4, Example 7, Example 10 and Comparative Example 1 were sampled for basic tests and active chlorine oxidation resistance tests. Specifically:

[0089] In the first stage, the membrane was taken to a cross-flow membrane test bench for basic testing. Basic testing was carried out in a 32000ppm NaCl aqueous solution, at an operating pressure of 800psi, a temperature of 25°C and a pH value of 7.5 to determine the benchmarks of the permeation flux and the desalination rate, that is, to obtain the initial permeation flux and initial desalination rate data.

[0090] In the second stage, the membrane was tested for its resistance to active chlorine oxidation on a cross-flow membrane test bench. The membrane was tested for its resistance to active chlorine oxidation in a 32000ppm NaCl and 100ppm sodium hypochlorite solution, at a constant pressure of 800psi, a temperature of 25°C and a pH value of 7.5. The test time was 48 hours.

[0091] In the third stage, after the active chlorine oxidation resistance test is completed, the membrane is flushed with pure water at a flow rate of 5L / min under low pressure for 30 minutes.

[0092] In the fourth stage, the membrane permeation flux test and the desalination rate test were carried out again under the standard conditions of the first stage to obtain the permeation flux and desalination rate data after resistance to active chlorine oxidation.

[0093] The test results of the basic test and the active chlorine oxidation resistance test of the pollution-resistant seawater desalination membranes prepared in Example 2, Example 4, Example 7, Example 10 and Comparative Example 1 are shown in Table 2.

[0094] Table 2 Test results of basic test and active chlorine oxidation resistance test

[0095]

[0096] It is known from the data in Table 1 that, compared with Comparative Examples 1-2, the present invention adopts Examples 1-14 to control the amount, vibration frequency and vibration time of the nitrogen heterocyclic monomer with an amino group in combination to prepare a pollution-resistant seawater desalination membrane with anti-pollution performance, and can also show good permeation flux and desalination rate. Wherein, step S2 is not adopted in Comparative Example 1, so that the prepared pollution-resistant seawater desalination membrane does not have anti-pollution performance. In Comparative Example 2, vibration dispersion treatment is not adopted, so that the anti-pollution performance of the prepared pollution-resistant seawater desalination membrane is significantly reduced. This is because the nitrogen heterocyclic monomer with an amino group fails to fully contact the remaining unreacted acyl chloride group on the polyamide layer, resulting in insufficient second interfacial polymerization reaction, which reduces the anti-pollution performance of the pollution-resistant seawater desalination membrane.

[0097] From the data in Table 2, it can be seen that compared with Comparative Example 1, the present invention can prepare pollution-resistant seawater desalination membranes with resistance to active chlorine oxidation using Examples 2, 4, 7 and 10. This is because the N- in the nitrogen heterocyclic monomer introduced by the present invention can react preferentially with active chlorine, reduce the attack and damage of active chlorine on the polyamide layer, and improve the resistance to active chlorine oxidation of the pollution-resistant seawater desalination membrane; while in Comparative Example 1, no nitrogen heterocyclic monomer is introduced. During the active chlorine oxidation process, the electron-withdrawing effect of the carbonyl makes the N on the amide susceptible to active chlorine attack and produces N-Cl, and then the irreversible chlorination on the aromatic ring is formed by Orton rearrangement, and the hydrogen bonds between the cross-linked aromatic polyamide chains are severely damaged, which eventually leads to the breakage of the amide bond and the decrease in the cross-linking degree of the polyamide layer, thereby causing the desalination rate to decrease and the permeation flux to increase.

[0098] See also Figure 1-Figure 2 The roughness of the pollution-resistant seawater desalination membrane prepared in comparative example 1 is 112 nm, and the roughness of the pollution-resistant seawater desalination membrane prepared in example 7 of the present invention is 71.6 nm, which is significantly lower. This shows that setting step S2 is helpful to form a pollution-resistant seawater desalination membrane with a smooth surface.

[0099] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a pollution-resistant seawater desalination membrane, characterized in that: include: Step S1, forming a polyamide layer on the base layer through a first interfacial polymerization reaction; Remaining unreacted acyl chloride groups on the polyamide layer; Step S2, coating the polyamide layer with a pollution-resistant modification solution, wherein the pollution-resistant modification solution contains a nitrogen heterocyclic monomer with an amino group, and the nitrogen heterocyclic monomer with an amino group reacts with the remaining unreacted acyl chloride groups on the polyamide layer through a second interfacial polymerization reaction to form a pollution-resistant seawater desalination membrane; The nitrogen heterocyclic monomer with an amino group includes at least one of 4-aminoimidazole, 5-aminopyrimidine, 3-aminopyrazole and 4-aminopyridazine.

2. The method for preparing a pollution-resistant seawater desalination membrane according to claim 1, characterized in that: In the anti-pollution modification solution, the mass percentage of the nitrogen heterocyclic monomer with an amino group is 0.1%-5.0%; the coating amount of the anti-pollution modification solution on the polyamide layer is controlled to be 50-150g / m 2 .

3. The method for preparing the pollution-resistant seawater desalination membrane according to claim 2, characterized in that: In the pollution-resistant modified solution, the mass percentage of the nitrogen heterocyclic monomer with an amino group is 0.5%-3.0%.

4. The method for preparing a pollution-resistant seawater desalination membrane according to claim 1, characterized in that: The solvent used in the anti-pollution modification solution includes any one of n-hexane, n-heptane, n-decane and cyclohexane.

5. The method for preparing a pollution-resistant seawater desalination membrane according to claim 1, characterized in that: In step S2, before the second interfacial polymerization reaction is carried out, the anti-pollution modified solution coated on the polyamide layer needs to be subjected to a vibration dispersion treatment, with a vibration frequency of 20-50 Hz and a vibration time of 5-30 s; The method further comprises step S3 of drying the prepared pollution-resistant seawater desalination membrane; the drying temperature used in the drying treatment is 60-90° C. and the drying time is 2-8 minutes.

6. The method for preparing a pollution-resistant seawater desalination membrane according to claim 1, characterized in that: In step S1, the base layer includes a non-woven fabric layer and a polysulfone support layer stacked in sequence; A polyamide layer is formed on the polysulfone supporting layer through a first interfacial polymerization reaction.

7. A pollution-resistant seawater desalination membrane, characterized in that: The desalination membrane is prepared by the method for preparing the pollution-resistant seawater desalination membrane according to any one of claims 1 to 6.

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