Mica composite nanofiltration membrane, preparation method and application
By combining polyethyleneimine with mica nanosheets, a three-dimensional network structure of mica composite nanofiltration membrane is formed, which solves the problem of easy swelling of nanofiltration membranes, achieves efficient separation of dyes and salts, and improves membrane stability and separation efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CENT SOUTH UNIV
- Filing Date
- 2025-09-25
- Publication Date
- 2026-06-30
AI Technical Summary
Existing nanofiltration membranes are prone to swelling during long-term aqueous phase separation, which leads to a decrease in separation selectivity and fails to meet the separation requirements of high-salt dye wastewater.
A composite nanosheet dispersion was formed by mixing a polyethyleneimine solution with a mica nanosheet dispersion and then ultrasonically treating it. This dispersion was then deposited on a porous substrate membrane to form a mica composite nanofiltration membrane with a three-dimensional network structure, which suppressed the swelling process and maintained the stability of the interlayer spacing.
This improved the porosity and pore connectivity of the mica composite nanofiltration membrane, enabling efficient separation of dyes and salts, maintaining long-term operational stability, reducing costs, and meeting the high-performance requirements of nanofiltration membranes.
Smart Images
Figure CN121314402B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of dye desalination nanofiltration membrane technology, and particularly relates to mica composite nanofiltration membrane, preparation method and application. Background Technology
[0002] A large amount of complex high-salt wastewater exists in chemical production. Due to its high salt and high organic content, it is extremely difficult to treat. Conventional chemical and physical treatment methods are limited by the high organic content and have poor treatment effects, while biological treatment methods fail due to the high salt content. Therefore, an advanced separation technology is needed to efficiently separate salt and organic matter in wastewater, which has become a technical problem that researchers in this field urgently need to solve.
[0003] Two-dimensional laminar flow membranes constructed from layered materials (such as graphene and clay minerals) provide a solution for the aforementioned separation requirements. However, in practical applications, especially during long-term aqueous phase separation, these membrane materials often face uncontrollable swelling due to their excessive hydrophilicity, leading to a sharp decline in separation selectivity and an inability to maintain stable membrane performance over long periods, severely restricting their industrial application. Existing technologies provide a method for preparing ultrafiltration membranes doped with two-dimensional mica, which involves doping mica sheets into a polymer matrix to create a mixed matrix membrane, effectively improving membrane flux and mechanical strength. However, the ultrafiltration membranes prepared by the above methods have separation precision concentrated in the microfiltration / ultrafiltration range, with pore sizes much larger than dye molecules and salt ions, failing to meet the nanofiltration-level separation requirements of high-salt dye wastewater. Therefore, this invention provides a mica composite nanofiltration membrane, its preparation method, and its applications. Summary of the Invention
[0004] The main objective of this invention is to provide a mica composite nanofiltration membrane, its preparation method, and its application, aiming to solve the technical problems of easy swelling and poor long-term aqueous phase stability of nanofiltration membranes in the prior art.
[0005] To achieve the above objectives, the present invention provides a method for preparing a mica composite nanofiltration membrane, comprising the following steps:
[0006] A composite nanosheet dispersion was obtained by mixing a polyethyleneimine solution with a mica nanosheet dispersion and carrying out a composite reaction.
[0007] The composite nanosheet dispersion is permeated through a porous substrate membrane under negative pressure, causing the composite nanosheets in the dispersion to be deposited on the porous substrate membrane, thus obtaining the mica composite nanofiltration membrane.
[0008] According to the embodiments of this application, the above-mentioned composite reaction includes:
[0009] A polyethyleneimine solution was added to the mica nanosheet dispersion and subjected to ultrasonic treatment at room temperature to carry out a composite reaction.
[0010] The ultrasonic treatment power is 300~500W, and the ultrasonic treatment duration is 5~30min.
[0011] According to an embodiment of this application, the mass ratio of mica nanosheets in the mica nanosheet dispersion to polyethyleneimine in the polyethyleneimine solution is (3:1) to (1:3).
[0012] According to an embodiment of this application, the mica nanosheet dispersion comprises mica nanosheets and water.
[0013] The solid-liquid ratio of mica nanosheets to water in the mica nanosheet dispersion is (5mg:1mL) to (1mg:5mL).
[0014] According to an embodiment of this application, the method further includes: depositing composite nanosheets on the porous substrate membrane, followed by vacuum drying.
[0015] The vacuum drying process involves a vacuum degree of 0.1~1 Pa, a drying temperature of 50~80℃, and a drying time of 3~8 hours.
[0016] According to embodiments of this application, the porous substrate membrane includes one of polyethersulfone membrane, polyvinylidene fluoride membrane, polycarbonate membrane, cellulose acetate membrane, nylon membrane, and alumina membrane.
[0017] According to embodiments of this application, the ratio of composite nanosheets to the porous substrate membrane in the composite nanosheet dispersion is 0.35~5 μg / cm³. 2 .
[0018] According to embodiments of this application, the mica nanosheets are derived from mica-like minerals.
[0019] The mica minerals mentioned include one or more of muscovite, phlogopite, and biotite.
[0020] The thickness of the mica nanosheets is 2~5nm.
[0021] The present invention also provides a mica composite nanofiltration membrane, which is prepared by the above-described method for preparing mica composite nanofiltration membrane.
[0022] The present invention also provides an application of a mica composite nanofiltration membrane in dye separation and / or salt separation.
[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0024] The aforementioned mica composite nanofiltration membrane, its preparation method, and its application utilize polyethyleneimine, which possesses excellent adsorption and film-forming properties. By mixing a polyethyleneimine solution with a mica nanosheet dispersion, the three-dimensional network structure formed through the cross-linking of polyethyleneimine encapsulates the mica nanosheets, preventing water molecule penetration and thus inhibiting the swelling process. Furthermore, the three-dimensional network structure formed by the cross-linking of polyethyleneimine provides support between the mica nanosheets. Even under long-term immersion, the relative positions between the mica nanosheets are maintained, thereby stabilizing the interlayer spacing. This overcomes the problem of easy swelling inherent in conventional nanofiltration membranes.
[0025] This invention involves permeating a composite nanosheet dispersion through a porous substrate membrane under negative pressure, resulting in the uniform deposition of the composite nanosheets on the membrane. This facilitates the formation of a dense and uniformly performing mica composite nanofiltration membrane, improving its porosity and pore connectivity. Through the synergistic effect of each step, the flux and separation efficiency of the mica composite nanofiltration membrane are effectively enhanced. It maintains long-term operational stability in the nanofiltration of dye-aqueous solutions, achieving highly efficient separation of dyes and salts.
[0026] Moreover, the preparation method of this invention is simple, convenient, and inexpensive. The resulting mica composite nanofiltration membrane can efficiently achieve nanofiltration separation, meeting the high performance requirements of nanofiltration membranes in various fields. It has high economic efficiency and practicality. Attached Figure Description
[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.
[0028] Figure 1 The image shows the nanofiltration effect of the mica composite nanofiltration membrane prepared in Example 1 of this invention in a water system with various dyes, including Evans blue.
[0029] Figure 2 The image shows the nanofiltration effect of the mica nanofiltration membrane prepared in Comparative Example 1 of this invention in a water system with various dyes, including Evans Blue.
[0030] Figure 3 The images show the SEM and EDS images of the mica composite nanofiltration membrane prepared in Example 1 of this invention.
[0031] Figure 4 This is a schematic diagram showing the separation factor and permeation flux of Congo red dye and salt on the mica composite membrane prepared in Example 1 of the present invention.
[0032] The realization of the objective, functional characteristics and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation
[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0034] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.
[0035] To achieve the above objectives, the present invention provides a method for preparing a mica composite nanofiltration membrane, comprising the following steps:
[0036] S1: Mix polyethyleneimine solution with mica nanosheet dispersion to carry out composite reaction, and obtain composite nanosheet dispersion.
[0037] In some embodiments, a polyethyleneimine solution is added to a mica nanosheet dispersion. Ultrasonic treatment is then performed at room temperature to promote the composite reaction. The high-frequency vibration of ultrasound further disperses the mica nanosheets in the dispersion, ensuring uniform distribution within the polyethyleneimine solution, resulting in a uniform and stable composite nanosheet dispersion. The excellent composite of polyethyleneimine and mica nanosheets, along with the uniform distribution of the mica nanosheets, gives the resulting mica composite nanofiltration membrane higher strength and toughness, enabling it to withstand greater pressure and tension, reducing rupture, and making it suitable for complex operating environments and conditions, thus extending its service life.
[0038] In some embodiments, mica nanosheets, with their well-developed layered structure, can form denser and more uniform filtration channels when combined with polyethyleneimine. This results in a mica composite nanofiltration membrane with enhanced impurity interception capacity and higher selectivity, enabling more effective separation of substances of different sizes and properties, such as better removal of small molecule organic matter and heavy metal ions in water treatment. Simultaneously, the uniform filtration channels reduce the risk of membrane clogging, maintain stable filtration flux, and lower maintenance costs.
[0039] In some embodiments, polyethyleneimine is a polymer containing a large number of amino (-NH2) and imino (-NH-) groups. These amino and imino groups are highly reactive and can chemically react with mica nanosheets in a mica nanosheet dispersion to form a cross-linked network. This network can encapsulate the mica nanosheets, enhancing the interaction between them and the overall structural stability. Furthermore, the cross-linked network structure formed by polyethyleneimine can restrict the free movement of the mica nanosheets. When the mica composite nanofiltration membrane is exposed to an aqueous solution, the cross-linked network formed by the composite reaction can prevent water molecule penetration, thereby inhibiting the swelling process.
[0040] In this invention, the method for preparing mica nanosheet dispersions from mica-like minerals is the lithium nitrate molten salt method. The steps include:
[0041] First, mica-type mineral raw materials are subjected to high-temperature calcination and acid activation treatment in sequence to obtain activated clay minerals.
[0042] The activated clay mineral, organic intercalating agent, and water are then mixed and intercalated under supercritical carbon dioxide conditions to obtain intercalated clay mineral.
[0043] Finally, the intercalated clay minerals were dispersed in water, ultrasonically exfoliated, and centrifuged to collect the upper dispersion, which is the mica nanosheet dispersion.
[0044] In this invention, mica mineral raw materials are calcined in air at 600-750°C for 4-6 hours, and then mixed evenly with nitric acid (3-5 mol / L) at a mass ratio of 1:(4-8) in a three-necked flask. The mixture is then placed in a heating mantle and heated at 80-100°C for 3-6 hours to obtain activated mica powder. The activated mica powder, hexadecyltrimethylammonium bromide, and water are then mixed, with the mass ratio of activated mica powder to hexadecyltrimethylammonium bromide being 1:(2-3), and the mass ratio of the mixture of activated mica powder and hexadecyltrimethylammonium bromide to water being 1:(20-25). An intercalation reaction is carried out in a supercritical carbon dioxide apparatus. The reaction temperature of the supercritical carbon dioxide apparatus is 30-60°C, the reaction pressure is 10-15 MPa, and the reaction time is 10-12 hours to obtain intercalated mica powder. Intercalated mica powder was dispersed in water, and after ultrasonic exfoliation and centrifugation, the upper dispersion was collected to obtain a mica nanosheet dispersion.
[0045] S2: The composite nanosheet dispersion is passed through a porous base membrane under negative pressure, so that the composite nanosheets in the composite nanosheet dispersion are deposited on the porous base membrane to obtain the mica composite nanofiltration membrane.
[0046] In some embodiments, the composite nanosheets are solid products obtained from the composite reaction. The uniformly dispersed composite nanosheet dispersion prepared in step S1 is passed through a porous substrate membrane by vacuum filtration to ensure uniform deposition of the composite nanosheets on the substrate membrane, forming a uniform mica composite nanofiltration membrane structure. This ensures consistent filtration performance and avoids filtration efficiency reduction or breakage due to local defects.
[0047] The aforementioned method for preparing mica composite nanofiltration membranes utilizes polyethyleneimine, which possesses excellent adsorption and film-forming properties. By mixing a polyethyleneimine solution with a mica nanosheet dispersion, the three-dimensional network structure formed through the cross-linking of polyethyleneimine encapsulates the mica nanosheets, preventing water molecule penetration and thus inhibiting the swelling process. Furthermore, the three-dimensional network structure formed by the cross-linking of polyethyleneimine provides support between the mica nanosheets. Even under prolonged immersion, the relative positions of the mica nanosheets are maintained, thereby stabilizing the interlayer spacing. This overcomes the problem of easy swelling inherent in conventional nanofiltration membranes.
[0048] The composite nanosheet dispersion is permeated through a porous substrate membrane under negative pressure, resulting in uniform deposition of the composite nanosheets on the membrane. This facilitates the formation of a dense and uniformly performing mica composite nanofiltration membrane, improving its porosity and pore connectivity. Through the synergistic effect of each step, the flux and separation efficiency of the mica composite nanofiltration membrane are effectively enhanced. Long-term operational stability is maintained in the nanofiltration of dye-aqueous solutions, achieving highly efficient separation of dyes and salts.
[0049] Moreover, the preparation method of this invention is simple, convenient, and inexpensive. The resulting mica composite nanofiltration membrane can efficiently achieve nanofiltration separation, meeting the high performance requirements of nanofiltration membranes in various fields. It has high economic efficiency and practicality.
[0050] In some embodiments, the power of the ultrasonic treatment is 300~400W, and the duration of the ultrasonic treatment is 5~20min, more specifically 10~20min.
[0051] In some embodiments, the mass ratio of mica nanosheets in the mica nanosheet dispersion to polyethyleneimine in the polyethyleneimine solution is (3:1) to (1:3).
[0052] In some embodiments, the mass ratio of mica nanosheets in the mica nanosheet dispersion to polyethyleneimine in the polyethyleneimine solution is 1:(1~3). By adding more polyethyleneimine, the flexibility and antifouling properties of the mica composite nanofiltration membrane can be improved.
[0053] In some embodiments, the mass ratio of mica nanosheets in the mica nanosheet dispersion to polyethyleneimine in the polyethyleneimine solution is (1~3):1. Increasing the mass of the mica nanosheets improves the mechanical strength and density of the mica composite nanofiltration membrane.
[0054] In some embodiments, the mass ratio of mica nanosheets in the mica nanosheet dispersion to polyethyleneimine in the polyethyleneimine solution is (0.8~1.2):(0.8~1.2), or (1.8~2.2):(0.8~1.2), or (0.8~1.2):(1.8~2.2).
[0055] In some embodiments, the mica nanosheet dispersion comprises mica nanosheets and water. The solid-liquid ratio of the mica nanosheets to water in the mica nanosheet dispersion is (5 mg: 1 mL) to (1 mg: 5 mL).
[0056] In some embodiments, the solid-liquid ratio of mica nanosheets to water in the mica nanosheet dispersion is 5 mg: (1 mL to 5 mL).
[0057] In some embodiments, the solid-liquid ratio of mica nanosheets to water in the mica nanosheet dispersion is 1 mg: (1 mL to 5 mL).
[0058] In some embodiments, water is used as a solvent to disperse mica nanosheets. By adjusting the solid-liquid ratio of mica nanosheets to water, the dispersion effect of mica nanosheets in water can be optimized, thereby enhancing the stability of the mica composite nanofiltration membrane.
[0059] In some embodiments, the mass of mica nanosheets in the mica nanosheet dispersion is constant, the volume of water is constant, and the polyethyleneimine solution is added according to the mass ratio of mica nanosheets in the mica nanosheet dispersion to polyethyleneimine in the polyethyleneimine solution being (3:1) to (1:3).
[0060] In some embodiments, step S2 further includes: depositing composite nanosheets on the porous substrate membrane, followed by vacuum drying.
[0061] The vacuum drying process involves a vacuum degree of 0.1~1 Pa, a drying temperature of 50~80℃, and a drying time of 3~8 hours.
[0062] In some embodiments, the vacuum degree of vacuum drying is 0.1~0.6 Pa, the drying temperature is 65~80℃, and the drying time is 3~6 h. Vacuum drying can effectively remove moisture from the mica composite nanofiltration membrane, preventing performance degradation due to residual moisture during subsequent use. Vacuum drying can also promote the tight bonding between composite nanosheets, improving the density of the mica composite nanofiltration membrane, thereby enhancing filtration performance, selectivity, and separation efficiency.
[0063] In some embodiments, the porous substrate membrane includes one of polyethersulfone membrane, polyvinylidene fluoride membrane, polycarbonate membrane, cellulose acetate membrane, nylon membrane, and alumina membrane.
[0064] In some embodiments, the pore size of the porous base membrane is 0.2~0.6μm.
[0065] In some embodiments, the pore size of the porous base membrane is 0.22~0.45μm.
[0066] In some embodiments, the porous substrate membrane comprises a polyvinylidene fluoride membrane.
[0067] In some embodiments, the ratio of composite nanosheets to the porous substrate membrane in the composite nanosheet dispersion is 0.35~5 μg / cm³. 2 .
[0068] In some embodiments, the ratio of composite nanosheets to the porous substrate membrane in the composite nanosheet dispersion is 0.35~2 μg / cm³. 2 .
[0069] In some embodiments, the ratio of composite nanosheets to the porous substrate membrane in the composite nanosheet dispersion is 0.4~0.8 μg / cm³. 2 .
[0070] In some embodiments, the mica nanosheets are derived from mica-like minerals.
[0071] The mica minerals mentioned include one or more of muscovite, phlogopite, and biotite.
[0072] The thickness of the mica nanosheets is 2~5nm.
[0073] In some embodiments, the mica minerals include one or more of muscovite and biotite.
[0074] In some embodiments, the mica-like minerals include muscovite.
[0075] In some embodiments, the mica nanosheets have a thickness of 3-5 nm. Thinner nanosheets have a higher specific surface area, providing more active sites and enhancing the adsorption and filtration performance of the mica composite nanofiltration membrane.
[0076] In some embodiments, the average diameter of the mica nanosheets is 600-800 nm.
[0077] The present invention also provides a mica composite nanofiltration membrane, which is prepared by the above-described method for preparing mica composite nanofiltration membrane.
[0078] The present invention also provides the application of mica composite nanofiltration membranes in dye separation and / or salt separation.
[0079] In some embodiments, the prepared mica composite nanofiltration membrane is used in the nanofiltration separation of Congo red dye and sodium chloride salt. The sodium chloride concentration is 40-60 ppm, and the Congo red concentration is 10-30 ppm, which enables efficient separation of the dye and salt.
[0080] In some embodiments, the prepared mica composite nanofiltration membrane is used to measure the rejection rate of dyes with different molecular weights. The dyes with different molecular weights include Evans Blue (EB), Methyl Blue (MB), Congo Red (CR), Chrome Black T (CBT), Methylene Blue, Methyl Orange (MO), and Methyl Red (MR). The prepared mica composite nanofiltration membrane exhibits good dye rejection performance and high water flux.
[0081] In some embodiments, the prepared mica composite nanofiltration membrane has high flux and high rejection rate, enabling efficient interception and selective separation of dye molecules and / or salt ions, thus improving separation efficiency and selectivity. It also reduces multi-stage filtration and processing steps, lowers energy consumption and cost, and improves processing efficiency.
[0082] To further illustrate the present invention, the following examples are provided:
[0083] Example 1
[0084] 1. A method for preparing a mica composite nanofiltration membrane, comprising the following steps:
[0085] S1: Mix the polyethyleneimine solution with the mica nanosheet dispersion to carry out a composite reaction. The ultrasonic treatment power during the mixing is 400W and the ultrasonic treatment time is 10min to obtain the composite nanosheet dispersion.
[0086] The mica nanosheets are muscovite nanosheets, and the mica nanosheet dispersion consists of muscovite nanosheets and water, with a muscovite nanosheet concentration of 3 g / L. The thickness of the mica nanosheets is 3-5 nm, and the average diameter is 600-800 nm, mainly concentrated around 750 nm. The mass ratio of mica nanosheets in the mica nanosheet dispersion to polyethyleneimine in the polyethyleneimine solution is 1:1.
[0087] S2: The composite nanosheet dispersion is passed through a porous base membrane under negative pressure, so that the composite nanosheets in the composite nanosheet dispersion are deposited on the porous base membrane. After vacuum drying, a mica composite nanofiltration membrane is obtained.
[0088] The porous substrate membrane is made of polyvinylidene fluoride (PVDF) with a pore size of 0.22 μm. The ratio of composite nanosheets to porous substrate membrane in the composite nanosheet dispersion is 0.5 μg / cm³. 2 The vacuum degree in the vacuum drying process is 0.1 Pa, the drying temperature is 60℃, and the drying time is 3 hours.
[0089] 2. Filtration test of Evans blue aqueous solution:
[0090] The mica composite nanofiltration membrane from Example 1 was tested for filtration with Evans blue aqueous solution (pressure 0.05 MPa), with an Evans blue solution concentration of 20 mg / L and a volume of 1 L. The results showed a flux of 93.5 L HMB and a rejection rate of 99.2%.
[0091] Example 2
[0092] 1. A method for preparing a mica composite nanofiltration membrane, comprising the following steps:
[0093] Compared to Example 1, the mass ratio of mica nanosheets in the mica nanosheet dispersion to polyethyleneimine in the polyethyleneimine solution was changed. Other preparation steps were the same as in Example 1.
[0094] The mass ratio of mica nanosheets in the mica nanosheet dispersion to polyethyleneimine in the polyethyleneimine solution is 2:1.
[0095] 2. Filtration test of Evans blue aqueous solution:
[0096] The mica composite nanofiltration membrane from Example 2 was tested for filtration with Evans blue aqueous solution (pressure 0.05 MPa), with an Evans blue solution concentration of 20 mg / L and a volume of 1 L. The tested flux was 88.1 L HMB, and the rejection rate was 93.6%.
[0097] Example 3
[0098] 1. A method for preparing a mica composite nanofiltration membrane, comprising the following steps:
[0099] Compared to Example 1, the mass ratio of mica nanosheets in the mica nanosheet dispersion to polyethyleneimine in the polyethyleneimine solution was changed. Other preparation steps were the same as in Example 1.
[0100] The mass ratio of mica nanosheets in the mica nanosheet dispersion to polyethyleneimine in the polyethyleneimine solution is 1:2.
[0101] 2. Filtration test of Evans blue aqueous solution:
[0102] The mica composite nanofiltration membrane from Example 3 was tested for filtration with Evans blue aqueous solution (pressure 0.05 MPa), with an Evans blue solution concentration of 20 mg / L and a volume of 1 L. The test results showed a flux of 76.5 L HMB and a rejection rate of 95.3%.
[0103] Example 4
[0104] 1. A method for preparing a mica composite nanofiltration membrane, comprising the following steps:
[0105] Compared to Example 1, the mica nanosheets were changed. Other preparation steps were the same as in Example 1.
[0106] Among them, the mica nanosheets are biotite nanosheets.
[0107] 2. Filtration test of Evans blue aqueous solution:
[0108] The mica composite nanofiltration membrane from Example 4 was tested for filtration with Evans blue aqueous solution (pressure 0.05 MPa), with an Evans blue solution concentration of 20 mg / L and a volume of 1 L. The results showed a flux of 84.3 L HMB and a rejection rate of 98.34%.
[0109] Comparative Example 1
[0110] 1. A method for preparing a mica composite nanofiltration membrane, comprising the following steps:
[0111] S1: Provides mica nanosheet dispersion.
[0112] Among them, the mica nanosheets are muscovite nanosheets, the mica nanosheet dispersion is muscovite nanosheets and water, and the concentration of muscovite nanosheets is 3g / L; the thickness of the mica nanosheets is 3~5nm, the average diameter is 600~800nm, mainly concentrated at around 750nm.
[0113] S2: The mica nanosheet dispersion is passed through a porous base membrane under negative pressure, so that the mica nanosheets in the mica nanosheet dispersion are deposited on the porous base membrane. After vacuum drying, a nanofiltration membrane loaded with mica nanosheets is obtained.
[0114] The porous substrate membrane is made of polyvinylidene fluoride (PVDF) with a pore size of 0.22 μm. The ratio of mica nanosheets to the porous substrate membrane in the mica nanosheet dispersion is 0.5 μg / cm³. 2 The vacuum degree of vacuum drying is 0.1 Pa, the drying temperature is 60℃, and the drying time is 3 hours.
[0115] 2. Filtration test of Evans blue aqueous solution:
[0116] The nanofiltration membrane loaded with mica nanosheets in Comparative Example 1 was tested for filtration with Evans blue aqueous solution (pressure 0.05 MPa). The Evans blue solution concentration was 20 mg / L, and the volume was 1 L. The test results showed a flux of 83.6 L HMB and a rejection rate of 90.3%.
[0117] Comparative Example 2
[0118] 1. A method for preparing a mica composite nanofiltration membrane, comprising the following steps:
[0119] Compared to Example 1, the mica nanosheets were changed. Other preparation steps were the same as in Example 1.
[0120] Among them, the mica nanosheets are sericite nanosheets.
[0121] 2. Filtration test of Evans blue aqueous solution:
[0122] The mica composite nanofiltration membrane in Comparative Example 2 was tested for filtration with Evans blue aqueous solution (pressure 0.05 MPa). The Evans blue solution concentration was 20 mg / L, and the volume was 1 L. The test results showed a flux of 71.4 L HMB and a rejection rate of 89.3%.
[0123] Figure 1 The image shows the nanofiltration effect of the mica composite nanofiltration membrane prepared in Example 1 of this invention in a water system with various dyes, including Evans blue. Figure 2 The image shows the nanofiltration effect of the mica nanofiltration membrane prepared in Comparative Example 1 of this invention in a water system with various dyes, including Evans Blue. Figure 3 The images show the SEM and EDS images of the mica composite nanofiltration membrane prepared in Example 1 of this invention. Figure 4 This is a schematic diagram showing the separation factor and permeation flux of Congo red dye and salt on the mica composite membrane prepared in Example 1 of the present invention.
[0124] from Figure 1It can be seen that, using the mica composite nanofiltration membrane prepared in Example 1, the retention rates of dyes with different molecular weights were measured. Evans Blue (EB), Methyl Blue (MB), Congo Red (CR), Chrome Black T (CBT), and Methylene Blue (MBT) all showed retention rates higher than 98%, while the retention rates of Methyl Orange (MO) and Methyl Red (MR) also exceeded 40%. This indicates that the mass ratio of mica nanosheets in the mica nanosheet dispersion to polyethyleneimine in the polyethyleneimine solution is 1:1. The ratio of composite nanosheets to porous substrate membrane in the composite nanosheet dispersion is 0.5 μg / cm³. 2 The resulting mica composite nanofiltration membrane exhibits excellent dye rejection performance and high water flux.
[0125] from Figure 2 As can be seen from the data, when measuring the retention rates of dyes with different molecular weights using the mica nanofiltration membrane prepared in Comparative Example 1, the retention rates of Evans Blue (EB), Methyl Blue (MB), Congo Red (CR), and Chrome Black T (CBT) were all below 91%, while the retention rate of Methyl Orange (MO) was also below 30%. This highlights the importance of mixing the polyethyleneimine solution with the mica nanosheet dispersion for a composite reaction. Without the addition of the polyethyleneimine solution, the mica nanosheets themselves lack chemical bonds and readily swell in water, resulting in a low retention rate. This causes dye permeation, making it impossible to separate the dye from the salt, thus leading to a poor performance of the resulting mica nanofiltration membrane.
[0126] from Figure 3 It can be seen that the surface of the mica composite nanofiltration membrane prepared by this invention is intact and without defects, and the nitrogen, silicon and aluminum elements are evenly distributed, indicating the successful composite between mica nanosheets and polyethyleneimine.
[0127] The mica composite nanofiltration membrane prepared in Example 1 was subjected to nanofiltration separation tests of Congo red dye and sodium chloride salt, wherein the sodium chloride concentration was 50 ppm and the Congo red concentration was 20 ppm. Figure 4 As can be seen, the dye separation factor reaches approximately 118, which enables efficient separation of dyes and salts.
[0128] The aforementioned mica composite nanofiltration membrane, its preparation method, and its application utilize polyethyleneimine, which possesses excellent adsorption and film-forming properties. A polyethyleneimine solution is mixed with a mica nanosheet dispersion. The three-dimensional network structure formed by the cross-linking of polyethyleneimine encapsulates the mica nanosheets, preventing water molecule penetration and thus inhibiting the swelling process. Furthermore, the three-dimensional network structure formed by the cross-linking of polyethyleneimine provides support between the mica nanosheets. Even under long-term immersion, the relative positions between the mica nanosheets are maintained, thereby stabilizing the interlayer spacing. This overcomes the problem of easy swelling inherent in conventional nanofiltration membranes.
[0129] Permeation of the composite nanosheet dispersion through a porous substrate membrane under negative pressure allows for uniform deposition of the composite nanosheets on the membrane, facilitating the formation of a dense and uniformly performing mica composite nanofiltration membrane. This process improves the membrane's porosity and pore connectivity. Through the synergistic effect of each step, the flux and separation efficiency of the mica composite nanofiltration membrane are effectively enhanced. Long-term operational stability is maintained in the nanofiltration of dye-aqueous solutions, achieving highly efficient separation of dyes and salts.
[0130] Moreover, the preparation method of this invention is simple, convenient to operate, and low in cost. The resulting mica composite nanofiltration membrane can be applied in the field of efficient separation of dyes and salts. It can efficiently achieve nanofiltration separation, meet the high performance requirements of nanofiltration membranes in different fields, and has high economic efficiency and practicality.
[0131] In summary, the above-described technical solutions of the present invention are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made using the contents of the present invention's specification and drawings under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.
Claims
1. A method for preparing a mica composite nanofiltration membrane, characterized in that, Including the following steps: S1: Mix polyethyleneimine solution with mica nanosheet dispersion to carry out composite reaction and obtain composite nanosheet dispersion; S2: The composite nanosheet dispersion is permeated through a porous base membrane under negative pressure, so that the composite nanosheets in the composite nanosheet dispersion are deposited on the porous base membrane to obtain the mica composite nanofiltration membrane. The mass ratio of mica nanosheets in the mica nanosheet dispersion to polyethyleneimine in the polyethyleneimine solution is (3:1) to (1:3); The mica nanosheets are derived from mica-type minerals; The mica minerals mentioned include one or more of muscovite and biotite.
2. The method for preparing the mica composite nanofiltration membrane according to claim 1, characterized in that, The complex reaction in step S1 includes: A polyethyleneimine solution was added to the mica nanosheet dispersion, and the mixture was subjected to ultrasonic treatment to carry out a composite reaction. The ultrasonic treatment power is 300~500W, and the ultrasonic treatment duration is 5~30min.
3. The method for preparing the mica composite nanofiltration membrane according to claim 1, characterized in that, The mica nanosheet dispersion comprises mica nanosheets and water; The solid-liquid ratio of mica nanosheets to water in the mica nanosheet dispersion is (5mg:1mL) to (1mg:5mL).
4. The method for preparing the mica composite nanofiltration membrane according to claim 1, characterized in that, Step S2 also includes: depositing composite nanosheets on the porous substrate membrane, followed by vacuum drying. The vacuum drying process involves a vacuum degree of 0.1~1 Pa, a drying temperature of 50~80℃, and a drying time of 3~8 hours.
5. The method for preparing the mica composite nanofiltration membrane according to claim 1, characterized in that, The porous substrate membrane includes one of the following: polyethersulfone membrane, polyvinylidene fluoride membrane, polycarbonate membrane, cellulose acetate membrane, nylon membrane, and alumina membrane.
6. The method for preparing the mica composite nanofiltration membrane according to claim 1, characterized in that, The ratio of composite nanosheets to the porous substrate membrane in the composite nanosheet dispersion is 0.35~5 μg / cm³. 2 .
7. The method for preparing the mica composite nanofiltration membrane according to claim 1, characterized in that, The thickness of the mica nanosheets is 2~5nm.
8. A mica composite nanofiltration membrane, characterized in that, The mica composite nanofiltration membrane is prepared using the method described in any one of claims 1 to 7.
9. The application of the mica composite nanofiltration membrane as described in claim 8 in dye separation and / or salt separation.