High-temperature-resistant nanofiltration membrane and preparation method thereof

Abstract

The invention relates to the technical field of nanofiltration membranes, in particular to a high-temperature-resistant nanofiltration membrane and a preparation method thereof. The nanofiltration membrane is prepared by the method. The method comprises the following steps: preparing a nano layer; coating the surface of the porous support layer with a CHO-SiO2 nano particle solution with the required mass concentration to form a base membrane containing a nano layer; preparing a high-temperature-resistant nanofiltration membrane; immersing the base membrane into a water phase solution, taking out the base membrane after the first soaking treatment is completed, and air-drying water drops on the surface of the base membrane; secondly, soaking the base membrane into an oil phase solution, taking out the base membrane after the second soaking treatment is completed, and drying the base membrane to obtain the high-temperature-resistant nanofiltration membrane, the water-phase solution comprises polyamine, an acid absorbent, inorganic salt and a first organic solvent; the polyamine is a dibenzo N heterocyclic derivative; the oil phase solution comprises multi-element acyl chloride. The invention can solve the problem that the film is easy to fall off after being formed by directly introducing nanoparticles in the prior art.

Description

Technical Field

[0001] The invention relates to the technical field of nanofiltration membranes, and in particular to a high-temperature resistant nanofiltration membrane and a preparation method thereof. Background Art

[0002] In recent years, the demand for water purification at high temperatures (such as thermal desalination) has aroused great interest in high-temperature resistant nanofiltration membranes. Traditional nanofiltration membranes are generally limited to use at 50°C due to their inherent chemical structure and chemical properties. At present, some methods for preparing high-temperature resistant nanofiltration membranes are to introduce nanoparticles into the polysulfone layer and the polyamide layer, and improve the high-temperature resistance of the nanofiltration membrane by the high-temperature resistance of the nanoparticles. However, there is poor compatibility between nanoparticles and aqueous phase monomers, and they are easy to fall off after film formation, which restricts their large-scale application.

[0003] In summary, it is necessary to provide a high temperature resistant nanofiltration membrane and a preparation method thereof to solve the problem in the prior art that nanoparticles are easily detached after film formation when they are directly introduced. Summary of the invention

[0004] The object of the present invention is to provide a high temperature resistant nanofiltration membrane and a preparation method thereof. The specific technical scheme is as follows:

[0005] In a first aspect, the present invention provides a method for preparing a high temperature resistant nanofiltration membrane, comprising:

[0006] Step S1, preparing a nanolayer;

[0007] The required mass concentration of CHO-SiO 2 The nanoparticle solution is coated on the surface of the porous support layer to form a base film containing a nanolayer;

[0008] Step S2, preparing a high temperature resistant nanofiltration membrane;

[0009] First, the base membrane is immersed in an aqueous solution, and after the first immersion treatment is completed, the base membrane is taken out and the water droplets on the surface are air-dried; secondly, the base membrane is immersed in an oil solution, and after the second immersion treatment is completed, the base membrane is taken out and dried to obtain a high temperature resistant nanofiltration membrane;

[0010] The aqueous phase solution comprises a polyamine, an acid absorbent, an inorganic salt and a first organic solvent; the polyamine is a dibenzo-N heterocyclic derivative;

[0011] The oil phase solution includes polyacid chloride.

[0012] Optionally, the dibenzo-N-heterocyclic derivative includes at least one of 10H-phenothiazine-2,8-diamine, 10H-phenothiazine-2,8-diamine-5,5-dioxide, 10H-phenoxazine-2,8-diamine, 10H-phenoxazine-2,7-diamine-10-methyl and 3,6-diamino-9-acridone;

[0013] The mass concentration of the bisbenzoheterocyclic derivative in the aqueous solution is 0.5%-1%.

[0014] Optionally, the inorganic salt includes at least one of anhydrous potassium chloride, anhydrous potassium carbonate and anhydrous calcium chloride;

[0015] The mass concentration of the inorganic salt in the aqueous phase solution is 0.2%-0.5%.

[0016] Optionally, the acid absorbent includes at least one of sodium hydroxide, sodium carbonate and sodium bicarbonate;

[0017] The mass concentration of the acid absorbent in the aqueous solution is 0.2%-0.5%;

[0018] The aqueous phase solution further comprises a surfactant; the surfactant comprises at least one of dodecyl ammonium sulfate, sodium dodecylbenzene sulfonate, hexadecyl trimethyl ammonium bromide and benzalkonium chloride;

[0019] The mass concentration of the surfactant in the aqueous phase solution is 0.05%-0.1%.

[0020] Optionally, the first organic solvent includes at least one of N,N′-dimethylacetamide, N,N′-dimethylformamide, dimethyl sulfoxide and tetrahydrofuran;

[0021] The volume ratio of water to the first organic solvent used in the aqueous phase solution is 1:1-4:1.

[0022] Optionally, the oil phase solution further comprises a second organic solvent; the second organic solvent comprises at least one of n-hexane, cyclohexane, n-heptane and Isopar G;

[0023] The polyacid chloride comprises at least one of trimesoyl chloride, terephthaloyl chloride, phthaloyl chloride and 1,2,4,5-benzene tetracarboxylic acid chloride;

[0024] The mass concentration of the polyacid chloride in the oil phase solution is 0.1%-0.3%.

[0025] Optionally, the soaking time used in the first soaking treatment and the second soaking treatment is 30-120s;

[0026] The drying process adopts a drying temperature of 50-80° C. and a drying time of 1-5 min.

[0027] Optionally, the method for preparing the high temperature resistant nanofiltration membrane further includes a non-woven fabric base layer; the non-woven fabric base layer is arranged on a side of the porous support layer away from the nanolayer; and the porous support layer is a hydrophilic porous support layer.

[0028] Optionally, the CHO-SiO 2 The mass concentration of the nanoparticle solution is 0.1%-1%;

[0029] The coating time used in the coating is 60-300s.

[0030] In a second aspect, the present invention provides a high temperature resistant nanofiltration membrane, which is prepared by using the method for preparing the high temperature resistant nanofiltration membrane.

[0031] The application of the technical solution of the present invention has at least the following beneficial effects:

[0032] (1) The present invention provides a method for preparing a high temperature resistant nanofiltration membrane, which can solve the problem of the prior art that nanoparticles are easily detached after film formation when they are directly introduced. Specifically, the present invention first adopts aldehyde-rich silicon dioxide CHO-SiO 2 The nanoparticles are coated on the surface of the porous support layer to form a base film containing a nanolayer; secondly, the nitrogen atom on the secondary amine of the dibenzo-N heterocyclic derivative is used as a nucleophilic reagent to attack the aldehyde-rich silica CHO-SiO 2 The carbon atoms on the carbonyl group in the nanoparticles form intermediate products, which undergo Stork enamine synthesis reaction through dehydration with inorganic salts to generate enamines. This strengthens the bonding effect between the nanolayer and the polyamide layer, and solves the problem of easy shedding after film formation caused by directly introducing nanoparticles. At the same time, based on the high temperature resistance of the nanolayer itself, the polyamide layer formed on the nanolayer requires higher breaking energy due to the strong rigidity and large steric effect of the dibenzo structure, thereby effectively improving the stability of the nanofiltration membrane at high temperatures. In addition, the electron-withdrawing heteroatoms on the middle ring of the dibenzo N-heterocyclic derivatives can reduce the electron cloud density of the amino group connected to the benzene ring, making the amino group more susceptible to attack by the partially positively charged acyl group, thereby promoting the amidation interfacial polymerization reaction between the amino group on the benzene ring and the acyl chloride, and improving the cross-linking degree of the polyamide layer. The increased cross-linking degree helps the polyamide to form a denser multilayer network structure, thereby improving its structural deformation resistance under high temperature conditions and achieving high temperature resistance. An acid absorbent is used to neutralize the hydrogen ions produced in the interfacial polymerization reaction, promote the interfacial polymerization reaction, and maintain the stability of the pH of the system. Furthermore, the multilayer network structure formed by cross-linking can effectively penetrate into the porous support layer, ensuring the stability of the overall structure of the high temperature resistant nanofiltration membrane.

[0033] (2) The high-temperature resistant nanofiltration membrane prepared by the present invention has high-temperature resistance and can be effectively used to intercept high-valent anion salts in saline liquid under high-temperature environment, and has good application prospects in high-temperature liquid treatment. DETAILED DESCRIPTION

[0034] The technical solutions in the present invention will be described clearly and completely below in conjunction with 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. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention belong to the scope of protection of the present invention.

[0035] Embodiment 1:

[0036] A method for preparing a high temperature resistant nanofiltration membrane, comprising:

[0037] Step S1, preparing a nanolayer;

[0038] The required mass concentration of CHO-SiO 2 The nanoparticle solution is coated on the surface of the porous support layer to form a base film containing a nanolayer;

[0039] The preparation method of the porous supporting layer is as follows:

[0040] Weigh 200 g of polysulfone and 20 g of PEG-600 and disperse them in 780 g of N,N′-dimethylformamide, stir at 70° C. until completely dissolved, and vacuum degassing to obtain a polymer solution. Use a spatula to coat the polymer solution on a non-woven fabric, and then solidify it in a coagulation bath to form a polysulfone support layer, i.e., a porous support layer, which is refrigerated in a freezer at 5° C. for use;

[0041] Step S2, preparing a high temperature resistant nanofiltration membrane;

[0042] First, the basement membrane is immersed in an aqueous solution, and after the first immersion treatment is completed, the basement membrane is taken out and the water droplets on the surface thereof are air-dried; secondly, the basement membrane is immersed in an oily solution, and after the second immersion treatment is completed, the basement membrane is taken out and placed in an oven for drying treatment to obtain a high temperature resistant nanofiltration membrane;

[0043] The aqueous phase solution includes a polyamine, an acid absorbent, an inorganic salt and a first organic solvent; the polyamine is a dibenzo-N heterocyclic derivative, specifically 10H-phenothiazine-2,8-diamine;

[0044] The oil phase solution includes polyacid chloride, and the polyacid chloride is specifically trimesoyl chloride.

[0045] The mass concentration of the bisbenzoheterocyclic derivative in the aqueous solution is 0.5%-1%, specifically 0.8%.

[0046] The inorganic salt is anhydrous potassium chloride to prevent other impurities from being introduced into the inorganic salt;

[0047] The mass concentration of the inorganic salt in the aqueous phase solution is 0.2%-0.5%, specifically 0.5%.

[0048] The acid absorbent is sodium hydroxide;

[0049] The mass concentration of the acid absorbent in the aqueous phase solution is 0.2%-0.5%, specifically 0.3%;

[0050] The aqueous phase solution also includes a surfactant; the surfactant is ammonium dodecyl sulfate;

[0051] The mass concentration of the surfactant in the aqueous phase solution is 0.05%-0.1%, specifically 0.05%.

[0052] The first organic solvent is dimethyl sulfoxide; the first organic solvent is water-soluble and is used to dissolve dibenzo-N-heterocyclic derivatives.

[0053] The volume ratio of water to the first organic solvent used in the aqueous phase solution is 4:1.

[0054] The oil phase solution also includes a second organic solvent; the second organic solvent is n-hexane;

[0055] The mass concentration of the polyacid chloride in the oil phase solution is 0.1%-0.3%, specifically 0.1%.

[0056] The soaking time used in the first soaking treatment and the second soaking treatment is 60s;

[0057] The drying temperature used in the drying process is 70° C. and the drying time is 5 min.

[0058] The CHO-SiO 2 Nanoparticle solution (solute is CHO-SiO 2 The mass concentration of nanoparticles (purchased) is 0.1%-1%, specifically 0.5%;

[0059] The coating time used in the coating is 120s.

[0060] Embodiment 2:

[0061] Different from Example 1, the dibenzo-N-heterocyclic derivative is 10H-phenothiazine-2,8-diamine-5,5-dioxide.

[0062] Embodiment 3:

[0063] Different from Example 1, the dibenzo-N-heterocyclic derivative is 10H-phenoxazine-2,8-diamine.

[0064] Embodiment 4:

[0065] Different from Example 1, the dibenzo-N-heterocyclic derivative is 10H-phenoxazine-2,7-diamine-10-methyl.

[0066] Embodiment 5:

[0067] Different from Example 1, the dibenzo-N-heterocyclic derivative is 3,6-diamino-9-acridone.

[0068] Embodiment 6:

[0069] The difference from Example 1 is that the mass concentration of the dibenzo-N-heterocyclic derivative in the aqueous solution is 0.5%; the CHO-SiO 2 The mass concentration of the nanoparticle solution was 0.1%.

[0070] Embodiment 7:

[0071] The difference from Example 1 is that the mass concentration of the dibenzo-N-heterocyclic derivative in the aqueous solution is 1%; the CHO-SiO 2 The mass concentration of the nanoparticle solution was 1%.

[0072] Comparative Example 1:

[0073] Different from Example 1, the polyamine is piperazine.

[0074] Comparative Example 2:

[0075] The difference from Example 1 is that the preparation of the nano layer is omitted.

[0076] Comparative Example 3:

[0077] The difference from Example 1 is that the polyamine is dapsone.

[0078] Comparative Example 4:

[0079] Different from Example 1, the polyamine is 2,8-dibenzothiophene diamine.

[0080] Comparative Example 5:

[0081] Different from Example 1, the polyamine is 2,8-dibenzothiophene diamine-5,5-dioxide.

[0082] Comparative Example 6:

[0083] The difference from Example 1 is that the mass concentration of the dibenzo-N-heterocyclic derivative in the aqueous solution is 0.3%.

[0084] Comparative Example 7:

[0085] The difference from Example 1 is that the mass concentration of the dibenzo-N-heterocyclic derivative in the aqueous solution is 1.2%.

[0086] Comparative Example 8:

[0087] Different from Example 1, the CHO-SiO 2 The mass concentration of the nanoparticle solution was 0.05%.

[0088] Comparative Example 9:

[0089] Different from Example 1, the CHO-SiO 2 The mass concentration of the nanoparticle solution was 0.15%.

[0090] The high temperature resistant nanofiltration membranes prepared in Examples 1-7 and Comparative Examples 1-9 were sampled for normal temperature test and high temperature resistance test, and the test results are shown in Table 1. The experimental method is as follows:

[0091] Three membranes were taken for each sample, and the test results of the normal temperature test and the high temperature test were averaged. Specifically, each membrane was tested on a cross-flow membrane test bench, first tested at normal temperature, i.e., tested under test condition ①, and then tested under high temperature test, i.e., tested under test condition ②. Among them, test condition ① is: MgSO 4 Aqueous solution 2000ppm, operating pressure 100psi, test temperature 25℃ and pH 6.8; test conditions ② are: MgSO 4 Aqueous solution 2000 ppm, operating pressure 100 psi, test temperature 80°C and pH 6.8.

[0092] Table 1 High temperature resistance test results

[0093]

[0094]

[0095] From the data in Table 1, we know that:

[0096] Compared with comparative examples 1-9, the membranes prepared in examples 1-7 of the present invention have suitable water flux and significant high temperature resistance effect.

[0097] In Comparative Example 1, the conventional piperazine aqueous phase amine monomer is used, and the prepared membrane has a high rejection rate for divalent anions at room temperature; however, since the boat conformation of the piperazine monomer is prone to bond breaking at high temperatures, the rejection rate drops sharply. However, in Example 1, the use of dibenzo-N heterocyclic derivatives as aqueous phase monomers has a significant effect on improving the high temperature resistance of the nanofiltration membrane.

[0098] In Comparative Example 2, the retention rate of the membrane prepared without the nanolayer is significantly reduced at high temperature, while in Example 1, the use of the nanolayer has a significant effect on improving the high temperature resistance of the nanofiltration membrane.

[0099] Compared with the non-N-heterocyclic dianiline derivatives used in Comparative Examples 3-5, the dibenzo-N-heterocyclic derivatives used in Examples 1-5 of the present invention have a significant effect on improving the high temperature resistance of the nanofiltration membrane. Specifically, the nitrogen atom on the secondary amine of the dibenzo-N-heterocyclic derivative is used as a nucleophilic reagent to attack the aldehyde-rich silica CHO-SiO 2 The carbon atoms on the carbonyl groups in the nanoparticles form intermediate products, which undergo Stork enamine synthesis reaction to generate enamines after dehydration by inorganic salts, which strengthens the bonding effect between the nanolayer and the polyamide layer; at the same time, on the basis of the high temperature resistance of the nanolayer itself, the polyamide layer formed on the nanolayer requires higher breaking energy due to the strong rigidity and large steric effect of the dibenzo structure, thus effectively improving the stability of the nanofiltration membrane at high temperatures. In addition, the electron-withdrawing heteroatoms on the intermediate ring of the dibenzo-N heterocyclic derivatives can reduce the electron cloud density of the amino groups connected to the benzene ring, making the amino groups more susceptible to attack by the partially positively charged acyl groups, thereby promoting the amidation interfacial polymerization reaction between the amino groups on the benzene ring and the acyl chloride, and improving the crosslinking degree of the polyamide layer. The increased crosslinking degree helps the polyamide to form a denser multilayer network structure, thereby improving its structural deformation resistance under high temperature conditions and achieving high temperature resistance.

[0100] Compared with Comparative Examples 6-9, the present invention adopts an appropriate amount of CHO-SiO 2 Nanoparticles and dibenzo-N-heterocyclic derivatives have a significant effect on improving the high temperature resistance of nanofiltration membranes. In Comparative Example 6, too low a dosage of dibenzo-N-heterocyclic derivatives was used, and in Comparative Example 8, too low a dosage of CHO-SiO 2 The nanoparticles will cause the high temperature resistance of the prepared membrane to be significantly reduced; in Comparative Example 7, an excessive amount of dibenzo-N heterocyclic derivatives is used, and in Comparative Example 9, an excessive amount of CHO-SiO 2 Nanoparticles do not significantly improve the high temperature resistance of nanofiltration membranes, but instead increase production costs.

[0101] 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 high temperature resistant nanofiltration membrane, characterized in that: include: Step S1, preparing a nanolayer; coating a CHO-SiO2 nanoparticle solution of a desired mass concentration on the surface of the porous support layer to form a base film containing a nanolayer; Step S2, preparing a high temperature resistant nanofiltration membrane; First, the base membrane is immersed in an aqueous solution, and after the first immersion treatment is completed, the base membrane is taken out and the water droplets on the surface are air-dried; secondly, the base membrane is immersed in an oil solution, and after the second immersion treatment is completed, the base membrane is taken out and dried to obtain a high temperature resistant nanofiltration membrane; The aqueous phase solution comprises a polyamine, an acid absorbent, an inorganic salt and a first organic solvent; the polyamine is a dibenzo-N heterocyclic derivative; The oil phase solution includes polyacid chloride.

2. The method for preparing a high temperature resistant nanofiltration membrane according to claim 1, characterized in that: The bisbenzoheterocyclic derivatives include at least one of 10H-phenothiazine-2,8-diamine, 10H-phenothiazine-2,8-diamine-5,5-dioxide, 10H-phenoxazine-2,8-diamine, 10H-phenoxazine-2,7-diamine-10-methyl and 3,6-diamino-9-acridone; The mass concentration of the bisbenzoheterocyclic derivative in the aqueous solution is 0.5%-1%.

3. The method for preparing a high temperature resistant nanofiltration membrane according to claim 1, characterized in that: The inorganic salt includes at least one of anhydrous potassium chloride, anhydrous potassium carbonate and anhydrous calcium chloride; The mass concentration of the inorganic salt in the aqueous phase solution is 0.2%-0.5%.

4. The method for preparing a high temperature resistant nanofiltration membrane according to claim 1, characterized in that: The acid absorbent comprises at least one of sodium hydroxide, sodium carbonate and sodium bicarbonate; The mass concentration of the acid absorbent in the aqueous solution is 0.2%-0.5%; The aqueous phase solution further comprises a surfactant; the surfactant comprises at least one of dodecyl ammonium sulfate, sodium dodecylbenzene sulfonate, hexadecyl trimethyl ammonium bromide and benzalkonium chloride; The mass concentration of the surfactant in the aqueous phase solution is 0.05%-0.1%.

5. The method for preparing a high temperature resistant nanofiltration membrane according to claim 1, characterized in that: The first organic solvent includes at least one of N,N′-dimethylacetamide, N,N′-dimethylformamide, dimethyl sulfoxide and tetrahydrofuran; The volume ratio of water to the first organic solvent used in the aqueous phase solution is 1:1-4:

1.

6. The method for preparing a high temperature resistant nanofiltration membrane according to claim 1, characterized in that: The oil phase solution further comprises a second organic solvent; the second organic solvent comprises at least one of n-hexane, cyclohexane, n-heptane and Isopar G; The polyacid chloride comprises at least one of trimesoyl chloride, terephthaloyl chloride, phthaloyl chloride and 1,2,4,5-benzene tetracarboxylic acid chloride; The mass concentration of the polyacid chloride in the oil phase solution is 0.1%-0.3%.

7. The method for preparing a high temperature resistant nanofiltration membrane according to claim 1, characterized in that: The soaking time used in the first soaking treatment and the second soaking treatment is 30-120s; The drying process adopts a drying temperature of 50-80° C. and a drying time of 1-5 min.

8. The method for preparing a high temperature resistant nanofiltration membrane according to claim 1, characterized in that: It also includes a non-woven fabric base layer; the non-woven fabric base layer is arranged on the side of the porous support layer away from the nano layer; the porous support layer is a hydrophilic porous support layer.

9. The method for preparing a high temperature resistant nanofiltration membrane according to any one of claims 1 to 8, characterized in that: The mass concentration of the CHO-SiO2 nanoparticle solution is 0.1%-1%; The coating time used in the coating is 60-300s.

10. A high temperature resistant nanofiltration membrane, characterized in that: The high temperature resistant nanofiltration membrane is prepared by the preparation method of claim 9.

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