A multilayer oxidation-resistant composite film and a preparation method and application thereof

Abstract

This invention belongs to the field of membrane separation technology and advanced functional materials technology, and discloses a multilayer oxidation-resistant composite membrane, its preparation method, and its application. The multilayer oxidation-resistant composite membrane includes a support layer, an intermediate layer, and a separation layer arranged sequentially from bottom to top. The support layer provides mechanical strength; the intermediate layer smooths surface defects in the support layer, slows down oxidation of the support layer, and ensures uniform film formation in the separation layer; the separation layer contains two-dimensional nanochannels constructed from inorganic nanosheets and polymers, with a hydraulic diameter of 0.5~2 nm. This invention's multilayer composite structure combines the intrinsic oxidation resistance and rigidity of inorganic materials with the film-forming properties and modifiability of polymers, constructing dimensionally stable and precisely controllable nanochannels to achieve precise sieving of target molecules.

Description

Technical Field

[0001] This invention belongs to the field of membrane separation technology and advanced functional materials technology, and relates to a multilayer oxidation-resistant composite membrane, its preparation method and application. Background Technology

[0002] Hydrogen peroxide (H2O2) is a key wet electronic chemical in semiconductor manufacturing, high-end printed circuit board cleaning, and other fields, with extremely stringent requirements for its organic impurity content. According to the chemical industry standard "High-Purity Industrial Hydrogen Peroxide" (HG / T5736-2020), the total organic carbon (TOC) content of electronic-grade hydrogen peroxide must be controlled below 10 mg / L, depending on the grade. More stringent applications (such as the treatment of specific electronic device substrates) even require TOC ≤ 100 ppb (0.1 mg / L). Industrial-grade hydrogen peroxide is mainly produced by the anthraquinone process, which contains a large amount of organic carbon impurities (such as anthraquinones and esters) derived from the working solvent and degradation products. The TOC content is typically above 100 mg / L, requiring deep purification to meet the requirements for electronic-grade applications.

[0003] Currently, the main technologies for purifying organic carbon from hydrogen peroxide include distillation, adsorption, and membrane separation. Distillation is energy-intensive and carries safety risks. While adsorption methods (such as using activated carbon) can effectively adsorb organic matter, the large specific surface area of ​​activated carbon significantly catalyzes the decomposition of H2O2, resulting in product loss. Membrane separation technologies, especially nanofiltration (NF) and reverse osmosis (RO), have attracted much attention due to their low energy consumption and lack of phase change. However, the strong oxidizing properties of hydrogen peroxide pose a significant challenge to the chemical stability of membrane materials.

[0004] Commercially available polymer reverse osmosis / nanofiltration membranes (such as polyamide (PA) membranes and cellulose acetate (CA) membranes) are highly susceptible to oxidative degradation in hydrogen peroxide environments. Studies by Abejón et al. have shown that commercial polyamide membranes have extremely short effective lifespans when used for H2O2 ultrapurification, typically lasting only a few days, leading to frequent membrane module replacements and significantly increasing process costs. Ling et al. also confirmed that even in low-concentration (1700 mg / L) H2O2, the stability of polyamide membranes is affected by various factors; and in high-concentration (e.g., 30–35%) industrial-grade H2O2, performance degradation is even more severe. While cellulose acetate membranes are slightly better, their retention rates for impurities such as Na and B are poor, and they still experience peeling and swelling after long-term use.

[0005] In recent years, two-dimensional membrane materials, represented by graphene oxide (GO), have attracted attention due to their tunable interlayer channels and potential chemical stability. However, pure GO membranes are prone to interlayer swelling in aqueous solutions, especially hydrogen peroxide solutions, leading to increased channel size and a sharp decline in separation selectivity. Although stability can be enhanced through crosslinking or compositing with rigid materials, these studies have mainly focused on concentrating H2O2 from dilute solutions. Targeted removal of complex organic carbon impurities from industrial-grade H2O2, as well as long-term operational stability under industrial conditions such as high-pressure cross-flow filtration, have not been reported.

[0006] In summary, current technologies lack membrane materials that can operate stably for extended periods in the highly oxidizing environment of industrial-grade hydrogen peroxide (concentration ≥30wt%), and can efficiently and selectively remove large organic molecular impurities (molecular weight 200~1000 Da, TOC reduced from >100 mg / L to ≤20 mg / L or even lower). Therefore, developing such materials has significant application value for achieving efficient, low-consumption, and safe purification of hydrogen peroxide. Summary of the Invention

[0007] This invention addresses the technical problems of traditional polymer membranes, such as poor chemical stability and short lifespan in strong oxidizing environments, and the tendency of two-dimensional materials to undergo interlayer swelling in hydrogen peroxide, leading to a sharp decline in separation selectivity. It provides a multilayer oxidation-resistant composite membrane, which combines the intrinsic oxidation resistance and rigidity of inorganic materials with the film-forming properties and modifiability of polymers through a multilayer composite structure design that combines rigidity and flexibility with multi-level protection. This constructs a dimensionally stable and precisely controllable nanochannel, enabling precise sieving of target molecules.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a multilayer oxidation-resistant composite membrane, comprising a support layer, an intermediate layer and a separation layer arranged sequentially from bottom to top; the support layer is used to provide mechanical strength; the intermediate layer is used to repair surface defects of the support layer, slow down oxidation of the support layer and make the separation layer uniformly formed; the separation layer contains two-dimensional nanochannels constructed from inorganic nanosheets and polymers, wherein the hydraulic diameter of the two-dimensional nanochannels is 0.5~2 nm.

[0010] In the above technical solution, the thickness of the support layer is 50~300 μm. The support layer of the present invention provides mechanical strength and has good resistance to strong oxidizing environments. It is preferred to use ultrafiltration / microfiltration membrane materials with a molecular weight cutoff of 50~100 kDa, such as polyvinylidene fluoride (PVDF), which has excellent oxidation resistance and chemical corrosion resistance and can be used stably under strong acid, strong alkali and various organic solvent conditions; polyethersulfone (PES) has high mechanical strength and uniform pore size distribution; polytetrafluoroethylene (PTFE) has the best intrinsic oxidation resistance, but the cost is relatively high.

[0011] In the above technical solution, the thickness of the intermediate layer is 50~200 nm, and the material of the intermediate layer is selected from polyvinyl alcohol (PVA), polydopamine (PDA), or polyethyleneimine (PEI). The intermediate layer of this invention is a cross-linked polymer thin layer, which can achieve interfacial adhesion and defect repair between the separation layer and the support layer, smooth the micropores on the surface of the support layer, provide a smooth interface, and ensure uniform film formation of the separation layer; it also further blocks the downward penetration of H2O2, slows down the oxidation of the support layer, and improves the overall stability.

[0012] In the above technical solution, the thickness of the separation layer is 50~500 nm. The separation layer of this invention is an organic-inorganic hybrid nanocomposite thin layer. Inorganic nanosheets are uniformly dispersed in a polymer matrix, with their sheet planes essentially parallel to the membrane surface. Stable covalent bond network structures are formed between the inorganic nanosheets and the polymer, and between polymer chain segments. The gaps between the inorganic nanosheets and the polymer chain segments together construct a uniformly sized, tortuous, and continuous two-dimensional nanochannel. By changing the mass ratio of inorganic nanosheets to polymer to adjust the degree of crosslinking, the theoretical hydraulic diameter of the two-dimensional nanochannel can be adjusted within the range of 0.5~2.0 nm. This size range lies between H2O2 molecules (kinetic diameter approximately 0.3 nm) and organic carbon impurity molecules (molecular weight 200~1000 Da), thereby achieving precise molecular sieving.

[0013] In the above technical solution, the inorganic nanosheets are selected from one or more two-dimensional materials such as hexagonal boron nitride nanosheets (h-BN), graphene oxide (GO) nanosheets, molybdenum disulfide (MoS2) nanosheets, and mica nanosheets. The gaps between the layers help to construct two-dimensional nanochannels, and their cross-linking with polymers can effectively regulate the interlayer spacing, thereby improving the selectivity for hydrogen peroxide molecules and organic carbon molecules.

[0014] In the above technical solution, the hexagonal boron nitride nanosheets are amination-modified hexagonal boron nitride nanosheets. h-BN is intrinsically resistant to oxidation and possesses extremely high chemical inertness, maintaining structural stability in a strongly oxidizing H₂O₂ environment. It also exhibits excellent mechanical strength and modifiability, serving as a rigid framework to effectively suppress film swelling. After amination modification, -NH₂ is introduced onto the surface, allowing it to react with crosslinking agents to form covalent bonds. For example, hexagonal boron nitride nanosheets (h-BN) with a thickness of 10–50 nm can be reduced to a thickness of 0.8–2.5 nm after grinding and amination modification.

[0015] In the above technical solution, the polymer is selected from one or more of cellulose acetate (CA), sulfonated polyether ether ketone (SPEEK), polyimide (PI), polyetherimide (PEI), polybenzimidazole (PBI), cellulose triacetate (CTA), cellulose acetate butyrate (CBA), cellulose acetate propionate (CAP), and polyvinylidene fluoride (PVDF). Cellulose acetate (CA), sulfonated polyether ether ketone (SPEEK), and polyimide (PI) are preferred. Cellulose acetate (CA) is more preferred, as CA has superior intrinsic oxidation resistance compared to polyamides and can maintain a stable chemical structure in an H2O2 environment. Simultaneously, CA possesses abundant active functional groups and excellent film-forming properties. The residual hydroxyl groups (-OH) on the CA chain can react with crosslinking agents and aminated nanosheets to form a stable covalent crosslinking network. CA is soluble in common solvents such as N-methylpyrrolidone (NMP) and N,N-dimethylacetamide (DMAc), making it easy to prepare ultrathin functional layers through methods such as blade coating and phase inversion.

[0016] Secondly, the present invention provides a method for preparing the above-mentioned multilayer oxidation-resistant composite film, comprising the following steps:

[0017] 1) An aqueous dispersion of inorganic nanosheets is mixed with an organic solution of polymer and then covalently crosslinked to obtain a casting solution;

[0018] 2) Immerse the support layer material in an aqueous solution of the intermediate layer material to form an intermediate layer on the support layer;

[0019] 3) The casting solution is coated onto the intermediate layer, and then the wet film is immersed in a deionized water coagulation bath for phase transformation and molding. After washing and drying, a multilayer oxidation-resistant composite film is obtained.

[0020] In the above technical solution, the mass ratio of the inorganic nanosheets to the polymer is 1~4:6~9.

[0021] It is worth noting that when using aminated hexagonal boron nitride nanosheets and polymers to prepare the casting solution, a crosslinking agent needs to be added for a covalent chemical crosslinking reaction (reaction temperature 45~55℃). After phase inversion molding, the wet film needs to be immersed in an ethanol solution containing the crosslinking agent for secondary crosslinking to form a stable covalent network structure. The aforementioned crosslinking agent is selected from one of the following: polyamines (such as ethylenediamine, polyethyleneimine), polyepoxides, polyaldehydes (such as glutaraldehyde), thiourea and their derivatives. When using graphene oxide (GO) nanosheets and polymers to prepare the casting solution, no crosslinking agent is needed. The hydroxyl and sulfonic acid groups on the polymer chains form a stable hydrogen bond-ion association structure with the oxygen-containing functional groups on the GO surface, while simultaneously promoting covalent crosslinking between polymer segments, thus forming a size-stable covalent network structure.

[0022] Thirdly, the present invention provides an application of the above-mentioned multilayer oxidation-resistant composite membrane in industrial-grade hydrogen peroxide purification.

[0023] In use, the multilayer oxidation-resistant composite membrane of this invention has a separation layer on the feed liquid side and a support layer on the permeate side. Under pressure, industrial-grade hydrogen peroxide solution first contacts the separation layer, where nanochannels (0.5~2.0 nm) allow small molecules (including water and hydrogen peroxide) with a kinetic diameter of about 0.3 nm to pass through preferentially, while organic carbon impurities with a molecular weight of 200~1000 Da are effectively retained on the membrane surface. After passing through the separation layer, hydrogen peroxide and water molecules flow out through the intermediate layer and the support layer to form a purified permeate, thereby achieving efficient removal of organic carbon impurities.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] 1. Excellent oxidation resistance and structural anti-swelling properties. By introducing intrinsically oxidation-resistant inorganic nanosheets as a framework and forming a covalent cross-linked network with polymers, the composite membrane can operate stably for a long time in a high-concentration (≥30wt%) hydrogen peroxide strong oxidizing environment, inhibiting the oxidative degradation and interlayer swelling of the membrane material, significantly extending its service life, and solving the problem of rapid failure of existing membrane materials.

[0026] 2. Highly efficient and precise molecular sieving capability. Utilizing inorganic nanosheets to construct tunable (0.5~2.0 nm), tortuous, and continuous two-dimensional nanochannels within a polymer matrix enables precise sieving of target molecules. While maintaining high permeability for water and hydrogen peroxide molecules (-0.3 nm), it achieves high rejection rates (>95%) for organic carbon impurities in industrial-grade hydrogen peroxide (such as anthraquinones, molecular weight 306 Da), ensuring that the purified product meets electronic-grade standards (e.g., SEMIC8, TOC ≤ 20 mg / L) and minimizing product loss (H2O2 loss rate < 2%).

[0027] 3. Excellent industrial application and process compatibility. The multilayer composite membrane has a reasonable structural design, and its preparation method is highly compatible with existing mature nanofiltration membrane production processes. It can be easily scaled up to prepare large-area industrial components through methods such as blade coating and spin coating. It can be directly applied to pressure-driven cross-flow filtration processes, providing an efficient, low-consumption, and safe solution for the deep purification of industrial-grade hydrogen peroxide. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of the multilayer oxidation-resistant composite film material of the present invention.

[0029] Figure 2 This is a schematic diagram illustrating the separation mechanism of organic carbon impurities in hydrogen peroxide by the multilayer oxidation-resistant composite membrane material of the present invention.

[0030] Figure 3 This is a SEM image of the BN-CA membrane prepared in Example 1 of the present invention.

[0031] Figure 4 The XRD patterns of the BN-CA membrane prepared in Example 1 of this invention before and after immersion in 30 wt% H2O2 are shown.

[0032] Figure 5 The FTIR spectra of the BN-CA membrane prepared in Example 1 of this invention before and after immersion in 30 wt% H2O2 for 7 days are shown.

[0033] Figure 6 The images show the appearance of the BN-CA membrane and the commercial PA membrane prepared in Example 1 of this invention after being immersed in 30 wt% H2O2 for 7 days.

[0034] Figure 7 The image shows the AFM pattern of the GO nanosheets prepared in Example 2 of this invention.

[0035] Figure 8 This is a SEM image of the GO / SPEEK membrane prepared in Example 2 of the present invention.

[0036] Figure 9 The XRD patterns of the GO / SPEEK membrane prepared in Example 2 of this invention before and after immersion in 30 wt% H2O2 are shown.

[0037] Figure 10 This is an image showing the appearance of the GO / SPEEK membrane prepared in Example 2 of the present invention after 120 h of operation. Detailed Implementation

[0038] The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of protection of the present invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the test methods in the following embodiments are conventional methods.

[0039] like Figure 1 The structure shown in this invention, a multilayer oxidation-resistant composite membrane material, comprises a support layer, an intermediate layer, and a separation layer arranged sequentially from bottom to top. The support layer provides mechanical strength and has a thickness of 50–300 μm. The intermediate layer, located between the separation layer and the support layer, serves as an adhesive, defect repair, and antioxidant barrier, and has a thickness of 50–200 nm. The separation layer, a key layer imparting selectivity and stability to the membrane, has a thickness of 50–500 nm.

[0040] like Figure 2 The separation mechanism illustrated involves a separation layer containing two-dimensional nanochannels constructed from inorganic nanosheets and polymers. These nanochannels have a hydraulic diameter of 0.5–2 nm. This size range falls between H₂O₂ molecules (kinetic diameter approximately 0.3 nm) and organic carbon impurity molecules (molecular weight 200–1000 Da), enabling precise molecular sieving. Under pressure, industrial-grade hydrogen peroxide solution first contacts the separation layer. The nanochannels (0.5–2.0 nm) allow small molecules (including water and hydrogen peroxide) with a kinetic diameter of approximately 0.3 nm to preferentially permeate, while organic carbon impurities with a molecular weight of 200–1000 Da are effectively retained on the membrane surface. Hydrogen peroxide and water molecules permeate through the separation layer, then through the intermediate and support layers, flowing out to form a purified permeate, thus achieving highly efficient removal of organic carbon impurities.

[0041] Example 1 h-BN / CA Oxidation-Resistant Composite Nanofiltration Membrane

[0042] (1) Preparation of aminated h-BN nanosheets:

[0043] 1 g of hexagonal boron nitride (h-BN) powder (Suzhou Napo Materials Technology Co., Ltd., purity ≥99%, powder particle size 1~2 μm, nanosheet thickness 20~50 nm) and 10 g of urea were added to a ball mill jar containing 200 mL of water and ball milled at 400 rpm for 24 h. After centrifugation and washing with water, an aminated h-BN nanosheet dispersion (concentration approximately 1 mg / mL) was obtained. The modified nanosheets had a thickness of 1.5~2.5 nm and a lateral size of 200~500 nm.

[0044] (2) Preparation of casting solution:

[0045] 0.3 g of cellulose acetate (CA, CA-398-30) was dissolved in 98 g of N-methylpyrrolidone (NMP) and stirred until completely dissolved to obtain a CA / NMP solution. 50 mL of the above h-BN nanosheet dispersion (containing 50 mg of h-BN) was slowly added to the CA / NMP solution while stirring. 0.01 g of crosslinking agent glutaraldehyde and 0.01 mL of concentrated hydrochloric acid (catalyst) were added, and the mixture was stirred at 50°C for 6 h to obtain a uniform casting solution.

[0046] (3) Base film treatment:

[0047] A commercial polyethersulfone (PES) ultrafiltration membrane (molecular weight cutoff 50 kDa) was used as the support layer (10 cm long, 10 cm wide, and 150 μm thick). It was immersed in an aqueous solution containing 2 wt% polyethyleneimine for 10 min, and then heat-treated at 80°C for 30 min to form an intermediate layer on the surface of the support layer.

[0048] (4) Preparation of composite membrane:

[0049] The casting solution was coated onto the pre-treated PES substrate using a blade coating method with a blade gap of 140 μm. The wet membrane was immediately immersed in a deionized water coagulation bath for phase inversion and molding. Subsequently, the wet membrane was removed and immersed in an ethanol solution containing 5 wt% ethylenediamine for 2 h for secondary crosslinking. Finally, it was thoroughly washed with deionized water to obtain the h-BN / CA composite nanofiltration membrane (denoted as BN-CA membrane).

[0050] Structural characterization and performance testing of BN-CA membranes:

[0051] 1. Structural characterization

[0052] Figure 3 The SEM image shows that the separation layer thickness in the BN-CA membrane is approximately 200 nm. Figure 3 a) h-BN nanosheets are uniformly dispersed in the CA matrix ( Figure 3 b).

[0053] Figure 4 The XRD pattern shown indicates that the interlayer spacing of the dry BN-CA film is 0.85 nm. Figure 4 a) After immersion in 30% H2O2 (25℃) for 7 days, the interlayer spacing only increased to 0.92 nm. Figure 4 (b) shows excellent resistance to swelling.

[0054] 2. Separation performance

[0055] The separation performance of the BN-CA membrane for a simulated 30% H₂O₂ solution containing 100 mg / L anthraquinone-2-sulfonate sodium (AQS, molecular weight 306 Da) was tested using a cross-flow filtration device at 20 bar and 25°C. The initial pure water flux was 45 L·m⁻¹. -2 ·h -1 The results showed that the BN-CA membrane had a rejection rate of 98.5% for AQS, and the permeation flux of the H2O2 solution was 28 L·m. -2 ·h -1 The H2O2 loss rate was calculated to be <1.5% based on titration analysis.

[0056] 3. Long-term stability

[0057] Under the conditions described in 2) above, the membrane was operated continuously for 168 hours (7 days). The results showed that the BN-CA membrane maintained an AQS rejection rate above 97%, with a permeate flux decrease of <15%. In contrast, a commercial polyamide reverse osmosis membrane (BW30) tested under the same conditions showed a sharp increase in flux within the first 24 hours (membrane degradation), and its AQS rejection rate decreased from >99% to less than 70% within 72 hours.

[0058] 4. Antioxidant Acceleration Test

[0059] The BN-CA membrane sample was immersed in a 30 wt% H2O2 solution at 40°C. Figure 5 The FTIR spectrum shown indicates that the CA characteristic peak of the BN-CA film did not show significant attenuation after 7 days. Figure 6 The appearance diagram shows that after 7 days, there were no visible changes on the surface of the BN-CA membrane, while the surface of the commercial PA membrane in comparison had turned yellowish-brown and become brittle.

[0060] Example 2: GO / SPEEK Oxidation-Resistant Composite Nanofiltration Membrane

[0061] (1) Preparation of graphene oxide (GO) dispersion:

[0062] Graphene oxide was prepared using a modified Hummers method. Solid GO was repeatedly washed with water until neutral, then dispersed in deionized water and ultrasonically treated for 1 h to obtain an aqueous GO dispersion with a mass concentration of approximately 2 mg / mL.

[0063] Figure 7 The AFM test results show that the thickness of the GO nanosheets is mainly distributed in the range of 0.8~1.2 nm, and the lateral size is 0.5~2 μm.

[0064] (2) Preparation of SPEEK solution:

[0065] Commercial polyether ether ketone (PEEK) was sulfonated to obtain SPEEK with a sulfonation degree of approximately 60%. 0.6 g of SPEEK was dissolved in 9.4 g of N,N-dimethylacetamide (DMAc), and the solution was stirred at 60 °C for 12 h to form a homogeneous polymer solution with a mass fraction of 6 wt%.

[0066] (3) Preparation of GO / SPEEK casting solution:

[0067] 75 mL of the above GO dispersion was slowly added to the SPEEK solution, and the mass ratio of GO to SPEEK was controlled at 2:8. The mixture was stirred under magnetic stirring for 6 h to ensure that the GO nanosheets were fully dispersed in the SPEEK matrix.

[0068] The mixed solution was subjected to thermally induced crosslinking treatment at 80°C for 4 h to form a stable hydrogen bond-ion association structure between the sulfonic acid groups in the SPEEK molecular chain and the oxygen-containing functional groups on the GO surface, while promoting covalent crosslinking between polymer chain segments and constructing a size-stable covalent network structure.

[0069] (4) Base film treatment:

[0070] A commercial PVDF ultrafiltration membrane (molecular weight cutoff 100 kDa) was used as the support layer (10 cm long, 10 cm wide, and 120 μm thick). It was immersed in a solution containing 2 mg / mL dopamine (pH=8.5) for 2 h to self-polymerize. After removal, it was heat-treated at 80°C for 30 min to form an intermediate layer on the support layer.

[0071] (5) Preparation of composite membranes:

[0072] The GO / SPEEK casting solution was uniformly coated onto the treated substrate membrane surface using a blade coating method with a blade gap of 120 μm. The wet membrane was then placed in a deionized water coagulation bath for phase inversion. After film formation, the membrane was thoroughly washed with water to obtain the GO / SPEEK oxidation-resistant composite nanofiltration membrane, denoted as GO-SPEEK membrane.

[0073] Structural characterization and performance testing of GO / SPEEK membranes:

[0074] 1. Structural and stability characterization

[0075] Figure 8 The SEM cross-section shown indicates that the thickness of the functional separation layer of the GO-SPEEK membrane is approximately 150–180 nm, and it bonds well with the support layer. Figure 8 a) The film is continuous and dense, and the GO nanosheets are uniformly dispersed in the SPEEK matrix. Figure 8 b).

[0076] Figure 9The XRD test results show that the average interlayer spacing of the dry GO-SPEEK membrane is about 0.90 nm. After immersing the GO / SPEEK membrane sample in 30 wt% H2O2 solution (25℃) for 7 days, the interlayer spacing only increased to 0.98 nm, showing significantly better anti-swelling performance than the pure GO membrane.

[0077] 2. Separation performance

[0078] In a cross-flow filtration apparatus, the separation performance of the GO-SPEEK membrane for a simulated solution of 30 wt% H₂O₂ containing 100 mg / L sodium anthraquinone-2-sulfonate (AQS, molecular weight 306 Da) was tested at 15 bar and 25 °C. The initial pure water flux was 45 L·m⁻¹. -2 ·h -1 The results showed that the GO-SPEEK membrane had a rejection rate of 96.2% for AQS; the steady-state permeation flux of the H2O2 solution was approximately 24 L·m. -2 ·h -1 Titration analysis showed that the H2O2 loss rate was less than 2%.

[0079] 3. Oxidation resistance and long-term operational stability

[0080] The GO-SPEEK membrane was operated continuously for 120 hours under the above conditions. The results showed that the AQS rejection rate of the GO-SPEEK membrane remained above 95% throughout; the permeate flux decline rate was less than 18%; and no obvious cracks, delamination, or color changes were observed on the surface of the GO-SPEEK membrane. Figure 10 In contrast, the pure SPEEK membrane without GO showed a significant decrease in flux and selectivity degradation after 48 h of operation.

[0081] Comparative Example 1: h-BN / CA composite nanofiltration membrane without intermediate layer

[0082] (1) The preparation of aminated h-BN nanosheets is exactly the same as in Example 1.

[0083] (2) The preparation of the casting solution is exactly the same as in Example 1.

[0084] (3) A commercial polyethersulfone (PES) ultrafiltration membrane was used as the support layer (10 cm long, 10 cm wide, and 120 μm thick), without polydopamine coating, and was used directly as the base membrane.

[0085] (4) The casting solution was directly coated onto the PES base film without an intermediate layer using a blade coating method with a blade gap of 140 μm. The wet film was immediately immersed in a deionized water coagulation bath to form the film. The subsequent secondary crosslinking and washing steps were the same as in Example 1.

[0086] The results of structural and performance tests comparing Example 1 and Comparative Example 1 are shown in the table below:

[0087]

[0088] Example 3: Purification effect of composite membrane on industrial-grade hydrogen peroxide

[0089] An industrial-grade hydrogen peroxide solution (H2O2 concentration 30%, TOC: 120 mg / L) provided by a chemical plant was used to conduct a cross-flow nanofiltration experiment using the BN-CA membrane prepared in Example 1 (operating pressure 15 bar, temperature 20℃). The permeate was collected for analysis.

[0090] The results showed that the TOC content in the permeate decreased to below 15 mg / L, meeting the TOC limit requirements for high-purity hydrogen peroxide products of the corresponding grade in HG / T 5736-2020. The H2O2 concentration was measured to be 29.7%, with a retention rate of approximately 99.0% relative to the feed concentration. After 120 hours of membrane operation, there was no significant performance degradation.

[0091] The above embodiments demonstrate that the oxidation-resistant composite membrane material provided by the present invention exhibits excellent long-term stability, high-efficiency selective separation capability, and low hydrogen peroxide loss rate in a highly oxidizing hydrogen peroxide environment, making it fully suitable for the deep purification process of industrial-grade hydrogen peroxide solutions.

[0092] The embodiments described above are merely preferred embodiments of the present invention and are only used to explain the present invention. They are not intended to limit the scope of the present invention. For those skilled in the art, other implementation methods can be easily made by substitution or modification based on the technical content disclosed in this specification. Therefore, all changes and improvements made on the principle of the present invention should be included within the scope of the patent application of the present invention.

Claims

1. A multilayer oxidation-resistant composite film, characterized in that, It includes a support layer, an intermediate layer and a separation layer arranged sequentially from bottom to top; the support layer is used to provide mechanical strength; the intermediate layer is used to repair surface defects of the support layer, slow down the oxidation of the support layer and make the separation layer form a uniform film; the separation layer contains two-dimensional nanochannels constructed from inorganic nanosheets and polymers, and the hydraulic diameter of the two-dimensional nanochannels is 0.5~2 nm.

2. The multilayer oxidation-resistant composite film according to claim 1, characterized in that, The thickness of the support layer is 50~300 μm, and the material of the support layer is selected from one of polyvinylidene fluoride, polyethersulfone, and polytetrafluoroethylene.

3. The multilayer oxidation-resistant composite film according to claim 1, characterized in that, The thickness of the intermediate layer is 50~200 nm, and the material of the intermediate layer is selected from polyvinyl alcohol, polydopamine or polyethyleneimine.

4. The multilayer oxidation-resistant composite film according to claim 1, characterized in that, The thickness of the separation layer is 50~500 nm.

5. A multilayer oxidation-resistant composite film according to claim 1 or 4, characterized in that, The inorganic nanosheets are selected from one or more of hexagonal boron nitride nanosheets, graphene oxide nanosheets, molybdenum disulfide nanosheets, and mica nanosheets.

6. The multilayer oxidation-resistant composite film according to claim 5, characterized in that, The hexagonal boron nitride nanosheets are amination-modified hexagonal boron nitride nanosheets.

7. A multilayer oxidation-resistant composite film according to claim 1 or 4, characterized in that, The polymer is selected from one or more of cellulose acetate, sulfonated polyether ether ketone, polyimide, polyether imide, polybenzimidazole, cellulose triacetate, cellulose acetate butyrate, cellulose acetate propionate, and polyvinylidene fluoride.

8. A method for preparing a multilayer oxidation-resistant composite film according to any one of claims 1 to 7, characterized in that, Includes the following steps: 1) An aqueous dispersion of inorganic nanosheets is mixed with an organic solution of polymer and then covalently crosslinked to obtain a casting solution; 2) Immerse the support layer material in an aqueous solution of the intermediate layer material to form an intermediate layer on the support layer; 3) The casting solution is coated onto the intermediate layer, and then the wet film is immersed in a deionized water coagulation bath for phase transformation and molding. After washing and drying, a multilayer oxidation-resistant composite film is obtained.

9. The preparation method according to claim 8, characterized in that, The mass ratio of the inorganic nanosheets to the polymer is 1~4:6~9.

10. The application of the multilayer oxidation-resistant composite membrane according to any one of claims 1 to 7 in industrial-grade hydrogen peroxide purification.

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