A composite nanofiltration membrane with high flux and high salt rejection, a preparation method and application thereof

Abstract

The application discloses a high-flux high-salt-rejection composite nanofiltration membrane, a preparation method and application thereof. The composite nanofiltration membrane comprises a porous support membrane and a polyamide separation layer combined on the porous support membrane; the opposite two side surfaces of the polyamide separation layer are provided with granular structures, so that a cavity structure is constructed between the polyamide separation layer and the porous support membrane. The high-flux high-salt-rejection composite nanofiltration membrane provided by the application has high flux, high selectivity and high salt rejection, and the preparation method is simple to adjust and control, and has a good application prospect in the field of water treatment or desalination.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of water treatment, and particularly relates to a composite nanofiltration membrane with high flux and high salt rejection rate, a preparation method thereof and application. BACKGROUND

[0002] With the rapid growth of population and economy, water pollution and water resource shortage have become a global challenge. Common treatment methods include adsorption, distillation, flocculation, and electrodialysis, etc., but these methods consume a large amount of energy and resources, and have low separation efficiency. Compared with existing desalination and wastewater treatment technologies, pressure-driven membrane separation technology has lower energy consumption and higher efficiency. In membrane separation technology, nanofiltration membranes can reject organic small molecules with a molecular weight greater than 200 and multivalent salt ions, and have great application prospects in the treatment field of desalination and wastewater treatment due to their high flux, low operating pressure, energy saving, etc. Most of the commercial nanofiltration membranes are thin film composite membranes, which mainly use ultrafiltration membranes as support layers and deposit a polyamide selective layer on the surface by interfacial polymerization with polyamine and polyacyl chloride as monomers. However, the flux and selectivity of this traditional nanofiltration membrane are relatively low, and the separation efficiency is still not high. In the composite nanofiltration membrane, the selective layer plays a decisive role in the separation flux and selectivity. According to the literature "Polyamide nanofiltration membrane with highly uniform sub-nanometre pores for sub-1 precision separation, Nature Communications, 2020, 11(1):2015.", etc., the interfacial polymerization process can be regulated to improve the flux and ion selectivity of the selective layer. Therefore, how to regulate the interfacial polymerization process, optimize the selective layer, and seek a new technology for preparing a composite nanofiltration membrane with high flux and high selectivity have been the long-term efforts of researchers in the industry. SUMMARY

[0003] The main purpose of the present application is to provide a composite nanofiltration membrane with high flux and high salt rejection rate, a preparation method thereof and application, to overcome the shortcomings of the prior art.

[0004] To achieve the foregoing purposes, the technical solutions adopted by the present application include:

[0005] The present application provides a composite nanofiltration membrane with high flux and high salt rejection rate, which comprises a porous support membrane and a polyamide separation layer combined on the porous support membrane; the opposite two sides of the polyamide separation layer both have a granular structure, thereby constructing a cavity structure between the polyamide separation layer and the porous support membrane.

[0006] The application also provides a preparation method of the composite nanofiltration membrane with high flux and high salt rejection rate, which comprises the following steps:

[0007] sufficiently wetting the surface of the porous support membrane with the polyamine aqueous solution with the first temperature to obtain a precursor membrane;

[0008] contacting the surface of the precursor membrane with the polyacyl chloride oil solution with the second temperature and performing an interfacial polymerization reaction to obtain the composite membrane;

[0009] performing an annealing treatment on the composite membrane to obtain the composite nanofiltration membrane;

[0010] wherein the first temperature is higher than the second temperature.

[0011] The application also provides a composite nanofiltration membrane with high flux and high salt rejection rate, which is prepared by the method.

[0012] The application also provides an application of the composite nanofiltration membrane with high flux and high salt rejection rate in the field of water treatment or desalination.

[0013] The application also provides a water treatment method, which comprises: performing nanofiltration treatment on the water body to be treated by using the composite nanofiltration membrane with high flux and high salt rejection rate.

[0014] Compared with the prior art, the application has the following beneficial effects:

[0015] (1) The interfacial polymerization control method of the composite nanofiltration membrane provided by the application, by preheating the polyamine monomer aqueous solution and the high polymer support base membrane, and then contacting the polyacyl chloride oil monomer solution in the room temperature environment, due to heat exchange, the interfacial temperature changes dramatically, and experiences rapid rise and fall, so that the separation layer structure generated by the interfacial polymerization reaction between the polyamine and the polyacyl chloride is coarse and granular, which is beneficial to create more water transmission channels, thereby improving the water flux in the water treatment process; at the same time, the initial temperature of the interfacial polymerization is increased, so that the selectivity of the separation layer is improved, thereby improving the ion rejection rate in the water treatment process;

[0016] (2) The composite nanofiltration membrane with high flux and high salt rejection rate provided by the application has a water flux of up to 108 Lm -2 h -1 at 6 bar operating pressure, and the salt solution with a concentration of 1000 ppm has a salt rejection rate of up to 93%, and the composite nanofiltration membrane with high flux, high selectivity and low energy consumption has great application value in desalination and wastewater treatment;

[0017] (3) The preparation method of the high-flux high-salt-rejection composite nanofiltration membrane provided by the application is relatively simple, the high flux and high rejection of multivalent ions can reduce the energy consumption cost of desalination and wastewater treatment, hard water softening and wastewater desalination can be realized, metal ions can be reused, and the application has industrial application value. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments described in the present application, and other drawings can also be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0019] Figure 1 is the temperature change curve of the dynamic temperature control interfacial polymerization interface and the temperature change curve of the conventional interfacial polymerization in the embodiment 2 of the present application;

[0020] Figures 2a-2b is the SEM diagram of the upper surface and the lower surface of the separation layer in the high-flux high-salt-rejection composite nanofiltration membrane prepared in the embodiment 2 of the present application;

[0021] Figures 3a-3b is the salt rejection and salt flux diagram of the composite nanofiltration membrane prepared in the embodiment 2 of the present application and the nanofiltration membrane prepared by the conventional interfacial polymerization. DETAILED DESCRIPTION

[0022] In view of the defects of the prior art, the present inventors have long-term research and a large number of practices, and have proposed the technical solutions of the present application, which mainly are that the support base membrane and the aqueous monomer solution are preheated, and then transferred to a low-temperature environment to perform interfacial polymerization reaction with the oil phase monomer solution, and the temperature of the oil phase monomer solution is consistent with the temperature of the low-temperature environment. Due to the heat exchange between the hot support base membrane and the aqueous monomer solution and the low-temperature environment and the oil phase monomer solution, the temperature of the water / oil interface is a dynamic change process, which experiences rapid temperature rise and rapid temperature drop, and then the upper and lower surfaces of the generated separation layer have granular structures. These granular structures can reduce the contact area between the separation layer and the support base membrane, and construct a large number of cavity structures between the support base membrane and the separation layer to provide additional water transmission channels for the nanofiltration membrane in the filtration process, and improve the membrane separation flux. At the same time, the short-term interface temperature rise promotes the film formation reaction, improves the compactness of the separation layer, and the generated nanofiltration membrane has higher salt rejection.

[0023] The technical solutions of the present application will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts fall within the scope of the present application.

[0024] Specifically, as one aspect of the technical solutions of the present application, the high-flux high-salt-rejection composite nanofiltration membrane includes a porous support membrane and a polyamide separation layer combined on the porous support membrane; the opposite two side surfaces of the polyamide separation layer both have a granular structure, thereby constructing a cavity structure between the polyamide separation layer and the porous support membrane.

[0025] In some preferred embodiments, the roughness Ra of the opposite two side surfaces of the polyamide separation layer is about 7.8 nm.

[0026] In some preferred embodiments, the thickness of the polyamide separation layer is 10-100 nm.

[0027] In some preferred embodiments, the porous support membrane includes an ultrafiltration membrane.

[0028] Further, the ultrafiltration membrane includes any one or a combination of polyether sulfone ultrafiltration membrane, polyacrylonitrile ultrafiltration membrane, and polysulfone ultrafiltration membrane, and is not limited thereto.

[0029] Further, the pore size of the pores in the porous support membrane is 5-100 nm.

[0030] In some preferred embodiments, the flux of the composite nanofiltration membrane to a salt solution with a concentration of 1000 ppm under an operating pressure of 6 bar is 108 Lm -2 h -1 The above has a rejection rate of more than 93%.

[0031] Further, the salt solution includes Na2SO4, MgCl2, etc.

[0032] The composite nanofiltration membrane with high flux, high rejection rate, and low energy consumption in the present application has great application value in desalination and wastewater treatment.

[0033] Another aspect of the embodiments of the present application further provides a preparation method of a high-flux high-salt-rejection composite nanofiltration membrane, which includes:

[0034] immersing the surface of the porous support membrane with the first temperature in the aqueous polyamine solution with the first temperature to obtain a precursor membrane;

[0035] contacting a surface of the precursor film having a first temperature with a polyacid chloride oil phase solution having a second temperature and performing an interfacial polymerization reaction to produce a composite membrane;

[0036] annealing the composite membrane to produce the composite nanofiltration membrane;

[0037] wherein the first temperature is higher than the second temperature.

[0038] In some preferred embodiments, the preparation method specifically comprises:

[0039] In an environment with an ambient temperature of 15-40℃ and a relative humidity of 20-80%, the porous support membrane and the polyamine aqueous phase solution are preheated to a first temperature of 35-85℃ and contacted and infiltrated for 10-240s, and then the obtained porous support membrane is immersed in a polyacid chloride oil phase solution having a second temperature of 25-30℃ to perform an interfacial polymerization reaction, thereby obtaining the composite nanofiltration membrane with high flux and high salt rejection rate; wherein the ambient temperature is lower than the first temperature.

[0040] Further, the contacting and infiltrating time is 30-240s.

[0041] Further, the interfacial polymerization reaction time is 10-150s.

[0042] In some preferred embodiments, the annealing temperature is 20-90℃.

[0043] In some preferred embodiments, the annealing time is 5-30min.

[0044] In some preferred embodiments, the polyamine aqueous phase solution comprises a polyamine monomer and water.

[0045] Further, the concentration of the polyamine monomer in the polyamine aqueous phase solution is 0.5-15g / L. The polyamine monomer includes any one or a combination of two or more of piperazine, polyethyleneimine, and polyamide-amine dendrimer, and is not limited thereto.

[0046] In some preferred embodiments, the polyacid chloride oil phase solution comprises a polyacid chloride and an organic solvent.

[0047] Further, the concentration of the polyacid chloride in the polyacid chloride oil phase solution is 0.5-30g / L.

[0048] Further, the polyacid chloride includes any one or a combination of two or more of trimesoyl chloride, isophthaloyl chloride, and phthaloyl chloride, and is not limited thereto.

[0049] Further, the organic solvent includes any one of n-hexane, cyclohexane, benzene, or a combination of two or more thereof, and is not limited thereto.

[0050] In some preferred embodiments, the polyamide separation layer has a thickness of 10-100 nm.

[0051] In some preferred embodiments, the porous support membrane includes an ultrafiltration membrane.

[0052] Further, the ultrafiltration membrane includes any one of a polyethersulfone ultrafiltration membrane, a polyacrylonitrile ultrafiltration membrane, a polysulfone ultrafiltration membrane, or a combination of two or more thereof, and is not limited thereto.

[0053] Further, the porous ultrafiltration support membrane is made of polyethersulfone.

[0054] Further, the porous support membrane has a pore size of 5-100 nm.

[0055] The preparation method provided in the present application adjusts the preparation process by preheating the support base membrane and the aqueous monomer solution, and then transferring them to a low-temperature environment to perform interfacial polymerization reaction with the oil-phase monomer solution. The temperature of the oil-phase monomer solution is consistent with that of the low-temperature environment. Due to the heat exchange between the hot support base membrane and the aqueous monomer solution and the low-temperature environment and the oil-phase monomer solution, the temperature of the water / oil interface is a dynamic change process, which experiences rapid temperature rise and rapid temperature drop, thereby causing the upper and lower surfaces of the generated separation layer to have granular structures. These granular structures can reduce the contact area between the separation layer and the support base membrane, and construct a large number of cavity structures between the support base membrane and the separation layer to provide additional water transmission channels for the nanofiltration membrane in the filtration process, thereby improving the membrane separation flux. At the same time, the short-term temperature rise of the interface promotes the film formation reaction, improves the compactness of the separation layer, and generates a nanofiltration membrane with a higher salt rejection rate. In addition, the interfacial polymerization film formation reaction adjustment method proposed in the present application is simple, closely matches the existing interfacial polymerization preparation process, and has important application value in the fields of preparing high-performance thin-film composite nanofiltration membranes, thin-film composite organic nanofiltration membranes, and thin-film composite reverse osmosis membranes, etc.

[0056] Another aspect of the embodiments of the present application also provides a high-flux high-salt-rejection composite nanofiltration membrane prepared by the aforementioned method.

[0057] Another aspect of the embodiments of the present application also provides the application of the aforementioned high-flux high-salt-rejection composite nanofiltration membrane in the field of water treatment.

[0058] For example, desalination treatment.

[0059] Another aspect of the embodiment of the present application also provides a water treatment method, which comprises: using the aforementioned high-flux high-salt rejection composite nanofiltration membrane to perform nanofiltration treatment on a water body to be treated.

[0060] The experimental materials used in the following examples are commercially available from conventional biochemical reagent companies, unless otherwise specified.

[0061] By means of the aforementioned technical solution, the present application uses a polyamine monomer aqueous solution and a polyacyl chloride monomer to perform preheating interfacial polymerization, thereby obtaining a high-flux high-salt rejection composite nanofiltration membrane, improving the separation flux and the rejection rate, and having a relatively simple preparation method. The high-flux high-desalination performance reduces the desalination energy consumption cost, can realize wastewater purification and salt recycling, and has industrial application value.

[0062] The technical solution of the present application will be explained and described in more detail below in combination with several preferred embodiments and the accompanying drawings. The specific embodiments described below are only used to further illustrate and explain the present application, and are not a limitation on the present application. In the following described embodiments, the ultrafiltration membrane is taken as an example of a polyether sulfone membrane, the polyamine monomer is taken as an example of piperazine, the organic solvent is taken as an example of n-hexane, and the polyacyl chloride monomer is taken as an example of trimesoyl chloride. Some simple improvements based on the method of the present application should be within the protection scope of the claims.

[0063] Embodiment 1

[0064] Piperazine is dissolved in water to prepare a PIP aqueous solution with a concentration of 2.5 g / L, which is used to preheat a polyether sulfone ultrafiltration membrane to 45℃ in a PIP aqueous solution under the conditions of a temperature of 25℃ and a relative humidity of 50%, and then the polyether sulfone ultrafiltration membrane is immersed in the PIP aqueous solution for 60 s, during which the temperature is kept at 45℃, to prepare a precursor membrane. Then the temperature of the precursor membrane is kept at 45℃, and the surface of the precursor membrane is immersed in a trimesoyl chloride n-hexane solution with a concentration of 2 g / L and a temperature of 25℃, and after 30 s of reaction, a composite membrane is obtained, and then the composite membrane is immersed in n-hexane to wash away the excess trimesoyl chloride. Finally, the composite membrane is heated at 60℃ for 30 min, immersed in deionized water, and then stored, to prepare a high-flux high-salt rejection composite nanofiltration membrane.

[0065] After testing, the high-flux high-salt rejection composite nanofiltration membrane prepared in this embodiment is tested with a 1000 ppm MgSO4 aqueous solution, the test temperature is 25℃, the operating pressure is 6 bar, the flux is 149 Lm -2 h -1 , and the rejection rate is 93.7%.

[0066] Embodiment 2

[0067] PIP water solution with a concentration of 2.5 g / L was prepared by dissolving piperazine in water, and was used to preheat the polyethersulfone ultrafiltration membrane to 65℃ in the condition of 25℃ and 50% relative humidity, and then the surface of the polyethersulfone ultrafiltration membrane was immersed in the PIP water solution for 60 s, during which the temperature was kept at 65℃, to obtain a precursor membrane; then the temperature of the precursor membrane was kept at 65℃, and the surface of the precursor membrane was immersed in a trimesoyl chloride n-hexane solution with a concentration of 2 g / L at 30℃ for 30 s, to obtain a composite membrane, and then the composite membrane was immersed in n-hexane to wash away the excess trimesoyl chloride. Finally, the composite membrane was heated at 60℃ for 30 min, was immersed in deionized water, and was stored, to obtain a composite nanofiltration membrane with high flux and high salt rejection rate.

[0068] Tested, the high flux and high salt rejection rate composite nanofiltration membrane prepared in this embodiment was tested by using 1000 ppm MgSO4 aqueous solution, the test temperature was 25℃, the operation pressure was 6 bar, the flux was 175 Lm -2 h -1 , and the rejection rate was 95.8%.

[0069] Performance characterization: Figure 1 is the interface temperature change curve of the dynamic temperature control interfacial polymerization in this embodiment; the SEMs of the upper surface and the lower surface of the separation layer of the high flux and high salt rejection rate composite nanofiltration membrane prepared in this embodiment are shown in Figure 2a , Figure 2b ; and Figures 3a-3b is the salt rejection and salt flux diagram of the composite nanofiltration membrane prepared in this embodiment and the nanofiltration membrane prepared by conventional interfacial polymerization.

[0070] Example 3

[0071] PIP water solution with a concentration of 2.5 g / L was prepared by dissolving piperazine in water, and was used to preheat the polyethersulfone ultrafiltration membrane to 85℃ in the condition of 25℃ and 50% relative humidity, and then the surface of the polyethersulfone ultrafiltration membrane was immersed in the PIP water solution for 60 s, during which the temperature was kept at 85℃, to obtain a precursor membrane; then the temperature of the precursor membrane was kept at 85℃, and the surface of the precursor membrane was immersed in a trimesoyl chloride n-hexane solution with a concentration of 2 g / L at 27℃ for 30 s, to obtain a composite membrane, and then the composite membrane was immersed in n-hexane to wash away the excess trimesoyl chloride. Finally, the composite membrane was heated at 60℃ for 30 min, was immersed in deionized water, and was stored, to obtain a composite nanofiltration membrane with high flux and high salt rejection rate.

[0072] Tested, the high flux and high salt rejection rate composite nanofiltration membrane prepared in this embodiment was tested by using 1000 ppm MgSO4 aqueous solution, the test temperature was 25℃, the operation pressure was 6 bar, the flux was 109 Lm -2 h-1 The rejection rate was 96.8%.

[0073] It should be noted that the high-flux composite nanofiltration membranes obtained in the above examples were tested by using cross-flow mode. The salt rejection rate was calculated according to the ratio of the concentration of the permeate liquid to the concentration of the feed liquid, and the calculation formula was:

[0074]

[0075] The flux was calculated according to the volume of liquid filtered per square meter of membrane area per hour, and was normalized to one atmosphere:

[0076]

[0077] Comparative Example 1

[0078] A polyamide composite nanofiltration membrane was obtained by interfacial polymerization on the surface of a polysulfone ultrafiltration membrane using piperazine (2.5 g / L) and trimesoyl chloride (2 g / L) as monomers. The operation mode for membrane formation was the same as the operation steps of the examples except that the support layer and the aqueous monomer solution were not preheated. The temperature of the aqueous monomer solution and the oil monomer solution was the same. However, the flux and rejection rate of this traditional composite nanofiltration membrane were very low.

[0079] After testing, the composite nanofiltration membrane prepared in this comparative example was tested with 1000 ppm MgSO4 aqueous solution, the test temperature was 25°C, the operating pressure was 6 bar, and the flux was 54 Lm -2 h -1 The rejection rate was 82.9%.

[0080] Comparative Example 2

[0081] Piperazine was dissolved in water to prepare a PIP aqueous solution with a concentration of 2.5 g / L, which was used to preheat the polyether sulfone ultrafiltration membrane to 45°C with the PIP aqueous solution under the conditions of a temperature of 25°C and a relative humidity of 50%. Then the polyether sulfone ultrafiltration membrane surface was immersed in the PIP aqueous solution for 60 s, maintaining 45°C during the process. Then the membrane surface was immersed in a trimesoyl chloride n-hexane solution with a concentration of 2 g / L at a temperature of 45°C, and the reaction was maintained at 45°C for 30 s. Then the membrane was immersed in n-hexane to wash away the excess trimesoyl chloride. Finally, the membrane was heated at 60°C for 30 min, immersed in deionized water, and then stored to obtain the composite nanofiltration membrane.

[0082] After testing, the composite nanofiltration membrane prepared in this example was tested with 1000 ppm MgSO4 aqueous solution, the test temperature was 25°C, the operating pressure was 6 bar, and the flux was 65 Lm -2 h -1 The rejection rate was 98.8%.

[0083] Comparative Example 3

[0084] PIP aqueous solution with a concentration of 2.5 g / L was prepared by dissolving piperazine in water. The polyethersulfone ultrafiltration membrane was preheated to 65 °C with the PIP aqueous solution under the conditions of 25 °C and 50% relative humidity. Then the surface of the polyethersulfone ultrafiltration membrane was immersed in the PIP aqueous solution for 60 s, and the temperature was kept at 65 °C. Subsequently, the membrane surface was immersed in a solution of trimesoyl chloride in n-hexane with a concentration of 2 g / L at 65 °C. After 30 s, the excess trimesoyl chloride was washed away by immersing the membrane in n-hexane. Finally, the membrane was heated at 60 °C for 30 min, soaked in deionized water, and stored to obtain the composite nanofiltration membrane.

[0085] The composite nanofiltration membrane prepared in this example was tested with 1000 ppm MgSO4 aqueous solution, the test temperature was 25 °C, the operating pressure was 6 bar, and the flux was 33 Lm -2 h -1 , and the rejection rate was 98.8%.

[0086] Comparative Example 4

[0087] PIP aqueous solution with a concentration of 2.5 g / L was prepared by dissolving piperazine in water. The polyethersulfone ultrafiltration membrane was preheated to 85 °C with the PIP aqueous solution under the conditions of 25 °C and 50% relative humidity. Then the surface of the polyethersulfone ultrafiltration membrane was immersed in the PIP aqueous solution for 60 s, and the temperature was kept at 85 °C. Subsequently, the membrane surface was immersed in a solution of trimesoyl chloride in n-hexane with a concentration of 2 g / L at 65 °C. After 30 s, the excess trimesoyl chloride was washed away by immersing the membrane in n-hexane. Finally, the membrane was heated at 60 °C for 30 min, soaked in deionized water, and stored to obtain the composite nanofiltration membrane.

[0088] The composite nanofiltration membrane prepared in this example was tested with 1000 ppm MgSO4 aqueous solution, the test temperature was 25 °C, the operating pressure was 6 bar, and the flux was 16.2 Lm -2 h -1 , and the rejection rate was 99.0%.

[0089] Example 4

[0090] The polyethyleneimine is dissolved in water to prepare a polyethyleneimine aqueous solution with a concentration of 0.5 g / L, which is used to preheat a polyacrylonitrile ultrafiltration membrane to 35℃ and a polyethyleneimine aqueous solution to 35℃ under the conditions of a temperature of 15℃ and a relative humidity of 20%, and then the surface of the polyethersulfone ultrafiltration membrane is infiltrated with the polyethyleneimine aqueous solution for 240 s while maintaining the temperature at 35℃, to prepare a precursor membrane; then the temperature of the precursor membrane is maintained at 35℃, and the surface of the precursor membrane is immersed in a m-phthaloyl chloride n-hexane solution with a concentration of 0.5 g / L and a temperature of 25℃, and the reaction is allowed to proceed for 150 s, to obtain a composite membrane, and then the composite membrane is immersed in n-hexane to wash away the excess m-phthaloyl chloride. Finally, the composite membrane is heated at 20℃ for 30 min, immersed in deionized water, and then stored, to prepare a composite nanofiltration membrane with high flux and high salt rejection.

[0091] Example 5

[0092] The polyamide-amine dendrimer is dissolved in water to prepare a polyamide-amine dendrimer aqueous solution with a concentration of 15 g / L, which is used to preheat a polysulfone ultrafiltration membrane to 85℃ and a polyamide-amine dendrimer aqueous solution to 85℃ under the conditions of a temperature of 40℃ and a relative humidity of 80%, and then the surface of the polyethersulfone ultrafiltration membrane is infiltrated with the polyamide-amine dendrimer aqueous solution for 10 s while maintaining the temperature at 85℃, to prepare a precursor membrane; then the temperature of the precursor membrane is maintained at 85℃, and the surface of the precursor membrane is immersed in an o-phthaloyl chloride n-hexane solution with a concentration of 30 g / L and a temperature of 30℃, and the reaction is allowed to proceed for 10 s, to obtain a composite membrane, and then the composite membrane is immersed in n-hexane to wash away the excess o-phthaloyl chloride. Finally, the composite membrane is heated at 90℃ for 5 min, immersed in deionized water, and then stored, to prepare a composite nanofiltration membrane with high flux and high salt rejection.

[0093] In addition, the inventors of the present case also refer to the manners of Examples 1-3, and conduct tests on other raw materials and conditions listed in the specification, and also have good performance.

[0094] In addition, the inventors of the present case also refer to the aforementioned examples, and conduct tests on other raw materials, process operations, and process conditions described in the specification, and all obtain relatively ideal results.

[0095] It should be understood that the technical solutions of the present application are not limited to the specific implementation cases described above, and any technical modification made according to the technical solutions of the present application without departing from the purpose of the present application and the scope protected by the claims falls within the protection scope of the present application.

Claims

1. A composite nanofiltration membrane with high flux and high salt rejection, characterized in that, The composite nanofiltration membrane comprises a porous support membrane and a polyamide separation layer combined on the porous support membrane; opposite two side surfaces of the polyamide separation layer each have a granular structure, thereby constructing a cavity structure between the polyamide separation layer and the porous support membrane. The preparation method of the composite nanofiltration membrane comprises the following steps: The porous support membrane and the polyamine aqueous solution are preheated to a first temperature and contacted and infiltrated for 10-240 s in an environment with an ambient temperature of 15-40 ℃ and a relative humidity of 20-80%, to obtain a precursor membrane; The precursor membrane with the first temperature is immersed in a polyacyl chloride oil phase solution with a second temperature to perform an interfacial polymerization reaction, thereby obtaining a composite membrane; The composite membrane is subjected to annealing treatment, to obtain the composite nanofiltration membrane. The first temperature is 35-85 ℃, and the second temperature is 25-30 ℃.

2. The composite nanofiltration membrane according to claim 1, wherein: The thickness of the polyamide separation layer is 10-100 nm.

3. The composite nanofiltration membrane of claim 1, wherein: The porous support membrane comprises an ultrafiltration membrane.

4. The composite nanofiltration membrane according to claim 3, wherein: The ultrafiltration membrane comprises any one or a combination of polyether sulfone ultrafiltration membranes, polyacrylonitrile ultrafiltration membranes and polysulfone ultrafiltration membranes.

5. The composite nanofiltration membrane according to claim 3, wherein: The pore size of the pores in the porous support membrane is 5-100 nm.

6. The composite nanofiltration membrane according to claim 1, wherein: The composite nanofiltration membrane has a flux of 108 Lm -2 h -1 The above has a rejection rate of 93% or more.

7. The composite nanofiltration membrane according to claim 1, wherein: The contacting and infiltrating time is 30-240 s.

8. The composite nanofiltration membrane according to claim 1, wherein: The interfacial polymerization reaction time is 10-150 s.

9. The composite nanofiltration membrane according to claim 1, wherein: The annealing treatment temperature is 20-90 ℃, and / or the annealing treatment time is 5-30 min.

10. The composite nanofiltration membrane according to claim 1, wherein: The polyamine aqueous solution comprises a polyamine monomer and water; the concentration of the polyamine monomer in the polyamine aqueous solution is 0.5-15 g / L; and the polyamine monomer comprises any one or a combination of more than two of piperazine, polyethyleneimine and polyamide-amine dendrimer.

11. The composite nanofiltration membrane according to claim 1, wherein: The polyacyl chloride oil phase solution comprises a polyacyl chloride and an organic solvent; the concentration of the polyacyl chloride in the polyacyl chloride oil phase solution is 0.5-30 g / L; the polyacyl chloride comprises any one or a combination of more than two of trimesoyl chloride, isophthaloyl chloride and phthaloyl chloride; and the organic solvent comprises any one or a combination of more than two of n-hexane, cyclohexane and benzene.

12. Application of the high-flux high-salt-rejection composite nanofiltration membrane in the field of water treatment.

13. A method of water treatment, characterized by, The method comprises: The high-flux high-salt-rejection composite nanofiltration membrane is used for nanofiltration treatment of a water body to be treated.

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