OTES modified zsm-5 / pdms mixed matrix membrane and preparation method and application thereof

Abstract

The application relates to an OTES modified ZSM-5 / PDMS mixed matrix membrane and a preparation method and application thereof. The OTES modified ZSM-5 / PDMS mixed matrix membrane is characterized in that it comprises a base film and a separation layer which is combined on the surface of the base film, and the separation layer comprises raw materials of end-vinyl PDMS, a platinum group metal catalyst, a reaction inhibitor, OTES modified ZSM-5 molecular sieve and an organic solvent. Compared with the prior art, the PDMS-based composite membrane has the characteristics of high selectivity (high separation factor), high flux and rapid solidification, so as to meet the urgent needs of efficient and continuous treatment of industrial wastewater.

Description

Technical Field

[0001] This invention relates to the field of membrane separation technology, and in particular to an OTES-modified ZSM-5 / PDMS hybrid matrix membrane, its preparation method, and its application. Background Technology

[0002] Paint wastewater typically contains volatile organic solvents such as n-butyl acetate, which are toxic and easily cause environmental pollution, yet also have recycling value. Pervaporation (PV) technology, as a highly efficient membrane separation technology, demonstrates broad application prospects in the field of organic wastewater treatment and solvent recovery due to its advantages of low energy consumption, simple operation, and high separation efficiency.

[0003] Polydimethylsiloxane (PDMS) is a commonly used membrane material for pervaporation separation of organic aqueous solutions due to its excellent hydrophobicity, chemical stability, and high compatibility with organic solvents. However, pure PDMS membranes exhibit a significant "flux-selectivity trade-off," resulting in a low separation factor (approximately 450 for 0.3 wt% butyl acetate-water binary system) that fails to meet the requirements for high-efficiency separation.

[0004] To overcome the performance bottlenecks of pure polymer membranes, researchers have attempted to prepare hybrid matrix membranes by combining inorganic fillers with PDMS. ZSM-5 molecular sieve, as a highly hydrophobic aluminosilicate material, has a pore size that matches that of n-butyl acetate (6.1 Å), and its hydrophobicity is complementary to that of PDMS, making it an ideal hybrid filler. However, ZSM-5 molecular sieve has a high surface energy, and when directly combined with PDMS, it is prone to aggregation, leading to defects in the membrane structure. This not only fails to improve separation performance but may also reduce membrane stability and separation efficiency, limiting its application in hybrid matrix membranes.

[0005] For example, Liu Yanqing et al. (Reference 1) used zeolite ZSM-5 to modify PDMS material and PVDF as the support layer to prepare a PDMS / ZSM-5 / PVDF composite membrane for pervaporation separation of n-butyl acetate and ethyl acetate in water using a blade coating method. Although the introduction of ZSM-5 improved the hydrophobicity and thermal stability of the membrane to some extent, poor interfacial compatibility and agglomeration problems still existed in the actual treatment of low-concentration n-butyl acetate wastewater, making it difficult to meet the requirements of high-efficiency separation.

[0006] To further improve hydrophobicity, Song et al. (Reference 2) used OTES (n-octyltriethoxysilane) to hydrophobically modify ZSM-5 zeolite, then incorporated OTES@ZSM-5 into PDMS, and prepared a mixed matrix membrane (MMM) using PVDF as a support layer for pervaporation separation of organic pollutants in water. However, they used hydroxyl-terminated PDMS, which relies on a catalyst to initiate condensation crosslinking. Due to the lack of a reaction termination mechanism, the applicable period is extremely short, the crosslinking process is uncontrollable, and a drying and curing time of 16-36 hours is required. This makes it difficult to meet the real-time control requirements of industrial continuous coating processes for reaction progress, and the extended production cycle and increased equipment usage severely restrict large-scale application.

[0007] Regarding the use of hydroxyl-terminated PDMS to prepare composite membranes for the pervaporation separation of n-butyl acetate, Liu Yanqing et al. (Reference 1) disclosed a PDMS / ZSM-5 composite membrane. Using ZSM-5 molecular sieve with a Si / Al ratio of 80 as the packing material, at a loading of 10 wt%, the separation factor for n-butyl acetate in water was approximately 131, and the total flux was approximately 319 g·m⁻¹. -2 ·h -1 Mu Chunxia et al. (Reference 3) disclosed that doping 4 wt% nano-silica (SiO2) into PDMS increased the separation factor to 542, but the flux decreased accordingly to 240 g·m. -2 ·h -1 It also attempted to introduce ZIF-8, achieving approximately 275 g·m³ at a loading of 6 wt%. -2 ·h -1 The flux and separation factor of 462. Liu et al. (Reference 4) disclosed that by introducing OP-POSS, they achieved a flux of approximately 350 g·m⁻¹ at a loading of 6 wt%. -2 ·h -1 The flux and separation factor of 221. Although hydroxyl-terminated PDMS-based composite membranes can achieve the separation of n-butyl acetate to a certain extent, there is often an irreconcilable contradiction between high selectivity (high separation factor) and high throughput.

[0008] Therefore, there is an urgent need to develop a PDMS-based composite membrane that combines high selectivity (high separation factor) with high throughput and rapid curing properties to meet the pressing need for efficient and continuous treatment of industrial wastewater.

[0009] References: Reference 1: Liu Yanqing, Hu Tingting, Lu Luoyi, Wang Wei, Zou Yun, Tong Zhangfa. Preparation of PDMS / ZSM-5 membrane and its pervaporation separation of n-butyl acetate and ethyl acetate in water. Journal of Chemical Industry and Engineering (China) [J], 2020, 71(2): 843-853. Document 2: Song, X.; Song, Reference 3: Mu Chunxia. Study on the modified preparation of PDMS / PVDF composite membrane and its separation of n-butyl acetate in water [D]. Guangxi University, 2017. Document 4: Liu Y, Hu T, Zhao J, et al.Synthesis and application of PDMS / OP-POSS membrane for the pervaporative recovery of n-butyl acetate and ethylacetate from aqueous media[J]. Journal of Membrane Science, 2019,591(C):117324-117324. Summary of the Invention

[0010] The purpose of this invention is to overcome the shortcomings of the prior art by providing an OTES-modified ZSM-5 / PDMS hybrid matrix membrane, its preparation method, and its application.

[0011] The objective of this invention can be achieved through the following technical solutions: One of the technical solutions of the present invention is to provide an OTES-modified ZSM-5 / PDMS hybrid matrix membrane, which includes a base membrane and a separation layer composited on the surface of the base membrane. The separation layer includes raw materials comprising the following components: terminal vinyl PDMS, platinum group metal catalyst, reaction inhibitor, OTES-modified ZSM-5 molecular sieve, and a first organic solvent.

[0012] Furthermore, the ratio of the terminal vinyl PDMS, catalyst, reaction inhibitor, OTES-modified ZSM-5 molecular sieve and the first organic solvent is 100g: 1~5mL: 1~5mL: 5~20g: 250~450g.

[0013] Furthermore, the base membrane comprises a hydrophobic microfiltration membrane composed of one or more of polytetrafluoroethylene, polyvinylidene fluoride, polypropylene, or polyethersulfone. The terminal vinyl PDMS is one or more combinations of α,ω-divinyl PDMS and PDMS with vinyl side chains; The platinum group metal catalyst is Pt2(C8H) 18 OSi2)3, chloroplatinic acid, or platinum-vinylsiloxane complex; The reaction inhibitor is one or more combinations of 1-ethynylcyclohexanol, 3,5-dimethyl-1-hexyn-3-ol, and 2-methyl-3-butyn-2-ol. The first organic solvent is one or more combinations of n-heptane, toluene, cyclohexane, xylene, or n-hexane.

[0014] Furthermore, the base film has an average pore size of 5-15 nanometers and a thickness of 160-190 μm.

[0015] Furthermore, the kinematic viscosity of the terminal vinyl PDMS at 25°C is 45000~55000 mPa·s.

[0016] Further, the preparation process of the OTES-modified ZSM-5 molecular sieve is as follows: after removing the template agent from the ZSM-5 molecular sieve, the template-removed ZSM-5 molecular sieve, OTES, and a second organic solvent are mixed and stirred to carry out a hydrolysis reaction. After the reaction, the mixture is centrifuged, the precipitate is washed, and then dried to obtain the OTES-modified ZSM-5 molecular sieve. OTES undergoes a hydrolysis reaction with water in the solution to generate a hydroxyl-containing silane intermediate. This intermediate undergoes a condensation reaction with the hydroxyl groups on the surface of ZSM-5 to form stable Si-O-Si chemical bonds. Simultaneously, the n-octyl long chain in the OTES molecule is branched onto the surface of ZSM-5. The modification mechanism is that the n-octyl long chain of the OTES molecule has good compatibility with the PDMS molecular chain, and can improve the interfacial bonding force between ZSM-5 and the vinyl-terminated PDMS matrix through molecular chain entanglement, effectively inhibiting the aggregation of ZSM-5 during the composite process. At the same time, the n-octyl long chain can reduce the surface energy of ZSM-5, further improving the hydrophobicity of the molecular sieve and composite membrane, and enhancing the selective adsorption of organic components.

[0017] Furthermore, the process for removing the template agent from the ZSM-5 molecular sieve is as follows: the ZSM-5 molecular sieve is heated to 500-700℃ at a heating rate of 2-5℃ / min, kept at that temperature for 3-5 hours, and then cooled to room temperature to obtain the ZSM-5 molecular sieve with the template agent removed.

[0018] Furthermore, the ZSM-5 molecular sieve has a silica-to-alumina ratio of 500-2000 and an average particle size of 1000-2000 nm; The mass ratio of ZSM-5 molecular sieve (for removing template agent), OTES, and the second organic solvent is 1~5:1:30~50; The second organic solvent is one or more combinations of n-heptane, toluene, cyclohexane, xylene, or n-hexane; The hydrolysis reaction is carried out at a temperature of 25~35℃.

[0019] Furthermore, the hydrolysis reaction is carried out at a speed of 200-800 rpm, preferably 400-600 rpm, for a time of 5-10 hours; The precipitate is washed with an organic solvent, which is one or more of n-heptane, toluene, cyclohexane, xylene or n-hexane, and the number of washing cycles is 3 to 10. The drying temperature is 50~90℃, and the time is 10~24h.

[0020] The second technical solution of the present invention is to provide a method for preparing an OTES-modified ZSM-5 / PDMS hybrid matrix membrane. The method involves mixing and stirring terminal vinyl PDMS, OTES-modified ZSM-5 molecular sieve, a first organic solvent and a platinum group metal catalyst, pre-crosslinking until the viscosity of the system reaches a certain value, and then adding a reaction inhibitor to terminate the crosslinking reaction to obtain a uniformly dispersed coating liquid. The coating liquid is then coated onto the surface of a base membrane, crosslinked and cooled to obtain an OTES-modified ZSM-5 / PDMS hybrid matrix membrane.

[0021] Further, using vinyl-terminated PDMS as the polymer matrix, OTES-modified ZSM-5 molecular sieve, a first organic solvent, and a platinum group metal catalyst were added. The mixture was stirred at 25-35°C and 600-1000 rpm for pre-crosslinking until the system viscosity reached 150-350 mPa·s. Then, a reaction inhibitor was added to terminate the crosslinking reaction, resulting in a uniformly dispersed coating solution. The mixture was stirred for 20-60 min and then sonicated for 20-30 min. The coating solution was then coated onto the surface of the base film with the doctor blade height controlled at 25-10000 μm. The mixture was crosslinked at a constant temperature of 100-150°C for 8-20 min and then cooled to room temperature to obtain an OTES-modified ZSM-5 / PDMS mixed matrix film.

[0022] The third technical solution of the present invention is to provide an application of an OTES-modified ZSM-5 / PDMS mixed matrix membrane, characterized in that the OTES-modified ZSM-5 / PDMS mixed matrix membrane is used to pervaporate and separate n-butyl acetate from the n-butyl acetate-water mixed system.

[0023] Furthermore, the process parameters for pervaporation separation are as follows: the concentration of n-butyl acetate in the n-butyl acetate-water system is 0.3wt%~0.7wt%, the feed temperature is 30~70℃, the feed flow rate is 1~5L / min, the vacuum degree on the permeation side is ≤2kPa, and the permeation vapor is collected by a liquid nitrogen cold trap on the permeation side.

[0024] Compared with the prior art, the present invention has the following advantages: (1) The aggregation problem has been effectively solved: After OTES modification, the n-octyl long chain grafted on the surface of ZSM-5 is entangled with the PDMS molecular chain, and the interfacial compatibility is significantly improved. SEM characterization shows that the modified ZSM-5 is uniformly dispersed in the PDMS matrix without obvious aggregation, and the membrane structure is dense and defect-free.

[0025] (2) Significantly enhanced hydrophobicity: After OTES modification, the water contact angle of ZSM-5 increased from about 31° to more than 133°. The water contact angle of the mixed matrix membrane increased to 108°~110° compared with the pure PDMS membrane (about 106°), effectively inhibiting water permeation.

[0026] (3) Breakthrough in separation performance: In the system of 0.3wt% n-butyl acetate + 99.7wt% water, the mixed matrix membrane with a loading of 20wt% showed the best performance, with a n-butyl acetate separation factor of 884, which is 96.44% higher than that of the pure PDMS membrane of the same thickness; the flux of organic components increased from 195.13gh of the pure membrane. -1 .m -2 Increased to 235.81gh -1 .m -2 The water flux increased from 143.9 gh for the pure membrane. -1 .m -2 Reduced to 88.9gh -1 .m -2 Furthermore, compared to existing composite membranes prepared using hydroxyl-terminated PDMS, this invention achieves synergistic optimization of selectivity and flux.

[0027] (4) Significant industrialization potential: This invention uses a combination of vinyl-terminated PDMS and platinum group metal catalysts. The preparation process adopts a simple blade coating-crosslinking process. In particular, the drying and crosslinking time is shorter than that of conventional hydroxyl-terminated PDMS. In the laboratory, it was found that a 500-micron coating thickness can be completely dried in about 8 to 20 minutes at 120°C. At the same time, the membrane performance is stable and can be adapted to paint wastewater systems with different concentration ranges, making it suitable for large-scale industrial applications. Attached Figure Description

[0028] Figure 1 (a) FTIR images of ZSM-5 molecular sieve before and after modification, (b) FTIR images of the wavenumber region of 3200~3700, and (c) a magnified schematic diagram of b. Figure 2 XRD patterns of ZSM-5 molecular sieve before and after modification; Figure 3 SEM images of ZSM-5 molecular sieve before and after modification: (a) before modification, (b) after modification. Figure 4 The diagram shows the water contact angles of ZSM-5 molecular sieve before and after modification. Figure 5 SEM images of the membranes in Examples 1-4 and Comparative Example 1: (a) Surface image of pure PDMS membrane, (a') Cross-sectional image of pure PDMS membrane, (b) Surface image of membrane with 5 wt% loading, (b') Cross-sectional image of membrane with 5 wt% loading, (c) Surface image of membrane with 10 wt% loading, (c') Cross-sectional image of membrane with 10 wt% loading, (d) Surface image of membrane with 15 wt% loading, (d') Cross-sectional image of membrane with 15 wt% loading, (e) Surface image of membrane with 20 wt% loading, (e') Cross-sectional image of membrane with 20 wt% loading. Figure 6 This is a schematic diagram of a pervaporation device; Figure 7 A comparison of the contact angles of modified ZSM-5 mixed matrix membranes with different loadings and pure PDMS membranes (loading 0); Figure 8 A comparison of the pervaporation performance of mixed matrix membranes with different loadings.

[0029] Explanation of markings in the diagram: 1-Heating liquid storage tank, 2-Circulating water pump, 3-Temperature probe, 4-Rotameter, 5-Membrane module, 6-Vacuum pressure probe, 7-Vacuum buffer tank, 8-Liquid collection bottle, 9-Liquid nitrogen cold trap, 10-Vacuum pump, 11-Mechanical ball valve. Detailed Implementation

[0030] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments. All other embodiments obtained by those skilled in the art based on the given embodiments without creative effort are within the scope of protection of this application.

[0031] Unless otherwise specified, the reagents, methods, instruments and equipment used in this invention are conventional reagents, methods, instruments and equipment in the art.

[0032] In the following examples, ZSM-5 molecular sieve, with a silica-to-alumina ratio of 1500 and a molecular sieve bulk density of 0.5 g·cm⁻³, was purchased from Nanjing Chemical (Tianjin) Catalyst Co., Ltd.; n-Heptane (CAS No. 142-82-5) was purchased from Shanghai Shenze Chemical Technology Co., Ltd.; OTES (CAS No. 2943-75-1) was purchased from Shanghai Naicheng Biotechnology Co., Ltd.; and α,ω-divinyl PDMS, with a dynamic viscosity of 50000±5000 mPa·s and a density of 1.00 g·cm⁻³, was used. -3Purchased from China Siliconware Precision Materials Co., Ltd.; Pt2(C8H 18 OSi2)3 original concentration 1000mg / L, purchased from China Siliconware Precision Materials Co., Ltd.; MA8700 high-efficiency inhibitor (1-ethynylcyclohexanol), purchased from China Siliconware Precision Materials Co., Ltd.; PTFE hydrophobic base membrane (support material is non-woven fabric), pore size 10 nm, thickness 160-190 μm, purchased from Jiumu Filtration Technology Co., Ltd.; n-butyl acetate, CAS No. 123-86-4, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0033] An OTES-modified ZSM-5 / PDMS hybrid matrix membrane comprises a base membrane and a separation layer composited on the surface of the base membrane. The separation layer comprises raw materials with the following components: terminal vinyl PDMS, platinum group metal catalyst, reaction inhibitor, OTES-modified ZSM-5 molecular sieve, and a first organic solvent.

[0034] In some specific embodiments, the ratio of the terminal vinyl PDMS, catalyst, reaction inhibitor, OTES-modified ZSM-5 molecular sieve and the first organic solvent is 100g: 1~5mL: 1~5mL: 5~20g: 250~450g.

[0035] In some specific embodiments, the base membrane comprises a hydrophobic microfiltration membrane composed of one or more of polytetrafluoroethylene, polyvinylidene fluoride, polypropylene, or polyethersulfone. The terminal vinyl PDMS is one or more combinations of α,ω-divinyl PDMS and PDMS with vinyl side chains; The platinum group metal catalyst is Pt2(C8H) 18 OSi2)3, chloroplatinic acid, or platinum-vinylsiloxane complex; The reaction inhibitor is one or more combinations of 1-ethynylcyclohexanol, 3,5-dimethyl-1-hexyn-3-ol, and 2-methyl-3-butyn-2-ol. The first organic solvent is one or more combinations of n-heptane, toluene, cyclohexane, xylene, or n-hexane.

[0036] In some specific embodiments, the base film has an average pore size of 5-15 nanometers and a thickness of 160-190 μm.

[0037] In some specific embodiments, the kinematic viscosity of the terminal vinyl PDMS at 25°C is 45000~55000 mPa·s.

[0038] In some specific embodiments, the preparation process of the OTES-modified ZSM-5 molecular sieve is as follows: after removing the template agent from the ZSM-5 molecular sieve, the template-removed ZSM-5 molecular sieve, OTES, and a second organic solvent are mixed and stirred to carry out a hydrolysis reaction. After the reaction is completed, the mixture is centrifuged, the precipitate is washed, and then dried to obtain the OTES-modified ZSM-5 molecular sieve. OTES undergoes a hydrolysis reaction with water in the solution to generate a hydroxyl-containing silane intermediate. This intermediate undergoes a condensation reaction with the hydroxyl groups on the surface of ZSM-5 to form stable Si-O-Si chemical bonds. Simultaneously, the n-octyl long chain in the OTES molecule is branched onto the surface of ZSM-5. The modification mechanism is that the n-octyl long chain of the OTES molecule has good compatibility with the PDMS molecular chain, and can improve the interfacial bonding force between ZSM-5 and the vinyl-terminated PDMS matrix through molecular chain entanglement, effectively inhibiting the aggregation of ZSM-5 during the composite process. At the same time, the n-octyl long chain can reduce the surface energy of ZSM-5, further improving the hydrophobicity of the molecular sieve and the composite membrane, and enhancing the selective adsorption of organic components.

[0039] In some specific embodiments, the removal process of the template agent of the ZSM-5 molecular sieve is as follows: the ZSM-5 molecular sieve is heated to 500-700°C at a heating rate of 2-5°C / min, kept at the temperature for 3-5 hours, and then cooled to room temperature to obtain the ZSM-5 molecular sieve with the template agent removed.

[0040] In some specific embodiments, the ZSM-5 molecular sieve has a silica-to-alumina ratio of 500 to 2000 and an average particle size of 1000 to 2000 nm. The mass ratio of ZSM-5 molecular sieve (for removing template agent), OTES, and the second organic solvent is 1~5:1:30~50; The second organic solvent is one or more combinations of n-heptane, toluene, cyclohexane, xylene, or n-hexane; The hydrolysis reaction is carried out at a temperature of 25~35℃.

[0041] In some specific embodiments, the hydrolysis reaction is carried out at a rotation speed of 200-800 rpm, preferably 400-600 rpm, for a duration of 5-10 hours. The precipitate is washed with an organic solvent, which is one or more of n-heptane, toluene, cyclohexane, xylene or n-hexane, and the number of washing cycles is 3 to 10. The drying temperature is 50~90℃, and the time is 10~24h.

[0042] A method for preparing an OTES-modified ZSM-5 / PDMS hybrid matrix membrane involves mixing and stirring terminal vinyl PDMS, OTES-modified ZSM-5 molecular sieve, a first organic solvent, and a platinum group metal catalyst. After pre-crosslinking until the system viscosity reaches a certain value, a reaction inhibitor is added to terminate the crosslinking reaction, resulting in a uniformly dispersed coating solution. The coating solution is then coated onto the surface of a base membrane, crosslinked, and cooled to obtain the OTES-modified ZSM-5 / PDMS hybrid matrix membrane.

[0043] In some specific embodiments, vinyl-terminated PDMS is used as the polymer matrix, and OTES-modified ZSM-5 molecular sieve, a first organic solvent, and a platinum group metal catalyst are added. The mixture is stirred at 25-35°C and 600-1000 rpm. After pre-crosslinking until the system viscosity reaches 150-350 mPa·s, a reaction inhibitor is added to terminate the crosslinking reaction, resulting in a uniformly dispersed coating solution. The mixture is stirred for 20-60 min and then sonicated for 20-30 min. The coating solution is then coated onto the surface of the base film with the scraper height controlled at 25-10000 μm. The mixture is crosslinked at a constant temperature of 100-150°C for 8-20 min and then cooled to room temperature to obtain an OTES-modified ZSM-5 / PDMS mixed matrix film.

[0044] An application of an OTES-modified ZSM-5 / PDMS mixed matrix membrane, characterized in that the OTES-modified ZSM-5 / PDMS mixed matrix membrane is used to pervaporate and separate n-butyl acetate from a n-butyl acetate-water mixed system.

[0045] In some specific embodiments, the process parameters for pervaporation separation are as follows: the concentration of n-butyl acetate in the n-butyl acetate-water system is 0.3wt%~0.7wt%, the feed temperature is 30~70℃, the feed flow rate is 1~5L / min, the vacuum degree on the permeation side is ≤2kPa, and the permeation vapor is collected by a liquid nitrogen cold trap on the permeation side.

[0046] Each of the above embodiments can be implemented individually or in any combination of two or more.

[0047] The following description uses specific examples to illustrate the point.

[0048] Example 1 The preparation process of an OTES-modified ZSM-5 / PDMS hybrid matrix membrane includes the following steps: (1) Removal of ZSM-5 molecular sieve template agent (tetrapropylammonium hydroxide): 10g of ZSM-5 molecular sieve was weighed into an alumina crucible and placed in a muffle furnace. The furnace was heated to 600℃ at a heating rate of 2℃ / min and held at that temperature for 4 hours. The mixture was then allowed to cool naturally to room temperature to obtain ZSM-5 molecular sieve with the template agent removed. The ZSM-5 molecular sieve had a silica-to-alumina ratio of 1500 and an average particle size of 1500nm.

[0049] (2) Preparation of OTES-modified ZSM-5 molecular sieve: 5g of template-removed ZSM-5 molecular sieve was weighed and dispersed in 250g of n-heptane solution, and ultrasonically dispersed for 10min to obtain a uniformly dispersed ZSM-5 suspension. 2.5g of OTES was added dropwise to the suspension, and the mixture was placed in a 30℃ constant temperature water bath and magnetically stirred at 800rpm for 8h for hydrolysis. After the reaction, the mixture was centrifuged at 10000rpm for 10min, and the precipitate was collected. The precipitate was washed five times with n-heptane to remove unreacted OTES and byproducts. The precipitate was then placed in a vacuum drying oven and dried at 80℃ for 12h to obtain OTES-modified ZSM-5 molecular sieve.

[0050] FTIR spectral results as follows Figure 1 As shown. In the FTIR spectrum of unmodified ZSM-5, at 1100 cm⁻¹ -1 and 800 cm -1 The characteristic peak at 450 cm⁻¹ corresponds to the asymmetric and symmetric stretching vibrations of the -Si-O-Si- bond. -1 The vibration at 3400 cm⁻¹ is a bending vibration of the -Si-O-Si- bond. -1 The broad characteristic peaks in the vicinity are attributed to the stretching and bending vibrations of -OH. After OTES silanization modification, a new characteristic peak appears in the spectrum at 2850 cm⁻¹. -1 and 2929 cm -1 The symmetric and asymmetric stretching vibrations of the CH bonds in the OTES molecule were observed, confirming the successful grafting of the OTES molecule. Simultaneously, the modified 3400 cm⁻¹... -1 The intensity of the -OH vibration peak at 1100 cm⁻¹ decreased significantly, indicating that the hydroxyl groups on the ZSM-5 surface reacted with and were consumed by hydrolyzed OTES. -1 800 cm -1 and 450 cm -1 The increased intensity of the -Si-O-Si- characteristic peak indicates the formation of new -Si-O-Si- bonds on the ZSM-5 surface. These results confirm the formation of stable chemical bonds between the OTES silane molecules and ZSM-5, indicating successful modification.

[0051] Figure 2By comparing the XRD patterns of the samples before and after modification, it was found that the positions of the characteristic peaks did not change, indicating that the OTES modification only occurred on the surface and inside the pores of the molecular sieve and did not affect its core framework structure.

[0052] Figure 3 The results show that the OTES-modified material retains its original basic shape, which means that the modified layer is very thin and does not affect the morphological characteristics of the particles.

[0053] Figure 4 In the study, water was used as the probe liquid. Compared with the unmodified sample, the hydrophobicity of the modified ZSM-5 was significantly improved, which directly confirms that OTES modification is an effective means to enhance the hydrophobicity of ZSM-5-based materials.

[0054] (3) Preparation of OTES-modified ZSM-5 / PDMS hybrid matrix membrane: Weigh 10g of α,ω-divinyl PDMS into a flask, add 30g of n-heptane, and stir at 30℃ and 800rpm for 10min to fully dissolve the α,ω-divinyl PDMS. Add 2g of OTES-modified ZSM-5 molecular sieve, continue stirring for 30min, and then ultrasonically disperse for 30min to ensure uniform dispersion of the molecular sieve. Add 2mL of catalyst Pt2(C8H2O) diluted 10 times with n-heptane to the system. 18 OSi2)3, continue stirring until the viscosity of the coating solution reaches 300 mPa·s (measured by rotational viscometer), then immediately add 2 mL of MA8700 inhibitor (1-ethynylcyclohexanol) to terminate the crosslinking reaction, and obtain a uniformly dispersed coating solution. Continue stirring for 30 min and then sonicate for 30 min.

[0055] A PTFE base membrane was fixed on the platen of an automatic coating machine, and the above coating solution was evenly coated onto the surface of the base membrane using a doctor blade, controlling the coating thickness to be 500 μm. The coated membrane was placed in a 120℃ constant temperature oven for crosslinking reaction for 10 min, and then naturally cooled to room temperature to obtain an OTES-modified ZSM-5@PDMS mixed matrix membrane with a loading of 20 wt%. The loading of 20 wt% represents the ratio of the mass of the modified molecular sieve to the mass of α,ω-divinyl PDMS.

[0056] Figure 5 SEM cross-sectional images of the mixed matrix membrane confirmed the uniform distribution of OTES-modified ZSM-5 / PDMS.

[0057] An application of an OTES-modified ZSM-5 / PDMS mixed matrix membrane involves loading the OTES-modified ZSM-5 / PDMS mixed matrix membrane into a pervaporation device to separate n-butyl acetate from the n-butyl acetate-water system via pervaporation.

[0058] Prepare a simulated paint wastewater system: 0.3wt% n-butyl acetate + 99.7wt% water, total mass 2kg.

[0059] The prepared 20wt% OTES-modified ZSM-5@PDMS mixed matrix membrane was installed in a pervaporation membrane module, with an effective membrane area of ​​132.73 cm². 2 .

[0060] Pervaporation devices are conventional in the field, except for replacing the substrate membrane. Pervaporation devices, such as... Figure 6 As shown, the system includes a heated feed tank 1, a circulating water pump 2, a temperature probe 3, a rotor flowmeter 4, a membrane module 5, a vacuum pressure probe 6, a vacuum buffer tank 7, a feed collection bottle 8, a liquid nitrogen cold trap 9, a vacuum pump 10, and a mechanical ball valve 11. The arrows indicate the direction of liquid flow. The feed flow of the entire system can be summarized as follows: the feed in the heated feed tank 1 flows through the circulating water pump 2 and the rotor flowmeter 4, then enters the membrane module 5 to contact the membrane separation layer, and flows back to the feed tank 1. This cycle ensures that the feed within the membrane module 5 is in a dynamic equilibrium state. The n-butyl acetate molecules dissolved in the membrane, in gaseous form, enter the vacuum buffer tank 7 under the negative pressure provided by the vacuum pump 10, then pass through the feed collection bottle 8, and are converted from gaseous to solid form in the liquid nitrogen cold trap 9 before falling back into the feed collection bottle for collection.

[0061] The membrane installation method is as follows: Cut a circular OTES-modified ZSM-5 / PDMS mixed matrix membrane with a diameter of 13cm, place it flat in the membrane module 5 position (i.e., the black part in the figure), ensuring that the separation layer is facing upwards and the non-woven fabric side is facing downwards. Then connect the upper and lower parts of the membrane module 5 with nuts and clamp the membrane.

[0062] The separation process parameters were set as follows: feed temperature 50℃, feed flow rate 5L / min, and permeate side vacuum ≤2kPa. After stable operation, the permeate vapor was collected from the permeate side within 1 hour using a liquid nitrogen cold trap, weighed, and the concentration of n-butyl acetate in the permeate was determined by gas chromatography.

[0063] Calculate membrane performance parameters; total flux 324.71 g·m³. -2 ·h -1 The flux of n-butyl acetate was 235.81 g·m³. -2 ·h --1 Water flux 88.9 g·m -2 ·h -1 , Separation factor of n-butyl acetate 884.

[0064] Example 2 Compared with Example 1, most of the contents are the same, except that the amount of OTES-modified ZSM-5 molecular sieve added is adjusted to 0.5g, which yields an OTES-modified ZSM-5@PDMS mixed matrix membrane with a loading of 5%.

[0065] Example 3 Compared with Example 1, most of the contents are the same, except that the amount of OTES-modified ZSM-5 molecular sieve added is adjusted to 1g, which yields an OTES-modified ZSM-5@PDMS mixed matrix membrane with a loading of 10%.

[0066] Example 4 Compared with Example 1, most of the contents are the same, except that the amount of OTES-modified ZSM-5 molecular sieve added is adjusted to 1.5g, which yields an OTES-modified ZSM-5@PDMS mixed matrix membrane with a loading of 15%.

[0067] Example 5 The majority of the components are the same as in Example 1, except that the simulated paint wastewater system is: 0.5 wt% n-butyl acetate + 99.5 wt% water.

[0068] Example 6 The majority of the components are the same as in Example 1, except that the simulated paint wastewater system is: 0.7wt% n-butyl acetate + 99.3wt% water.

[0069] Comparative Example 1 The application of a pure PDMS matrix membrane in a butyl acetate-water system includes the following steps: The OTES-modified ZSM-5 / PDMS mixed matrix membrane was loaded into a pervaporation device to perform pervaporation separation on the n-butyl acetate-water system. Prepare a simulated paint wastewater system: 0.3wt% n-butyl acetate + 99.7wt% water, total mass 2kg.

[0070] A pure PDMS matrix membrane was installed in a pervaporation membrane module, with an effective membrane area of ​​132.73 cm². 2 The pervaporation apparatus is identical to the pervaporation apparatus in Example 1, except that the membrane used is a pure PDMS polymer membrane.

[0071] The separation process parameters were set as follows: feed temperature 50℃, feed flow rate 5L / min, and permeate side vacuum ≤2kPa. After stable operation, the permeate vapor was collected from the permeate side within 1 hour using a liquid nitrogen cold trap, weighed, and the concentration of n-butyl acetate in the permeate was determined by gas chromatography.

[0072] Calculate membrane performance parameters; total flux 339.03 g·m³. -2 ·h -1 The flux of n-butyl acetate was 195.13 g·m³. -2 ·h --1 Water flux 143.9 g·m -2 ·h -1, n-Butyl acetate separation factor 450.

[0073] The comparison results between Example 1 and Comparative Example 1 show that, compared with the pure PDMS membrane, the mixed matrix membrane prepared in Example 1 of this invention has a 96.44% higher separation factor of n-butyl acetate, a 61.78% lower water flux, and a significantly enhanced selectivity of organic components, effectively breaking through the performance bottleneck of the pure PDMS membrane.

[0074] Comparative Example 2 Compared with Example 1, most of the contents are the same, except that the amount of OTES-modified ZSM-5 molecular sieve added is adjusted to 2.5g, which yields an OTES-modified ZSM-5@PDMS mixed matrix membrane with a loading of 25%.

[0075] Comparative Example 3 Compared with Example 1, most of the contents are the same, except that the amount of OTES-modified ZSM-5 molecular sieve added is adjusted to 3g, which yields an OTES-modified ZSM-5@PDMS mixed matrix membrane with a loading of 30%.

[0076] Comparative Example 4 Compared with Example 1, most of the contents are the same, except that the amount of OTES-modified ZSM-5 molecular sieve added is adjusted to 3.5g, which yields an OTES-modified ZSM-5@PDMS mixed matrix membrane with a loading of 35%.

[0077] The membrane performance parameters of the OTES-modified ZSM-5 molecular sieves of Examples 1-4 and Comparative Examples 2-4, and the pure PDMS matrix membrane (i.e., with a loading of 0) of Comparative Example 1 are shown in Table 1 and... Figure 6 , 7 As shown.

[0078] Table 1. Membrane performance parameters of OTES-modified ZSM-5 molecular sieves in Examples 1-4 and Comparative Examples 2-4 Figure 7 The changes in the water contact angle of the membranes with increasing ZSM-5@OTES loading are shown. Overall, the water contact angle of the mixed matrix membranes is greater than the average measured water contact angle of the pure polymer membranes (101.99°). Furthermore, the contact angle of the mixed matrix membranes increases slowly with increasing loading, with the membrane at 20 wt% loading showing an average water contact angle of 109.72°. This indicates that incorporating OTES-modified ZSM-5 can improve the hydrophobicity of the PDMS membrane. However, the contact angles of the four different loadings of the mixed matrix membranes are all smaller than those of ZSM-5@OTES. Figure 5 Analysis suggests that the polymer encapsulates the molecular sieve, and the observed improvement in hydrophobicity is mainly due to the increased surface roughness of the membrane.

[0079] Figure 8 The results showed that with increasing loading, the separation factor of the organic components of the mixed matrix membrane continuously increased, while the water flux decreased significantly. The best overall performance was achieved at a loading of 20 wt%, with a separation factor of 884.04 for n-butyl acetate and a total flux of 235.81 gh. -1 .m -2 Within the 0-20 wt% loading range, the separation factor of n-butyl acetate continuously increased, mainly due to the decrease in water flux and the increase in n-butyl acetate flux (as can be seen from the component flux data). This is because the uniformly distributed highly hydrophobic ZSM-5 zeolite within the composite membrane successfully inhibited the diffusion of water molecules within the membrane, releasing more intramembrane transport channels for n-butyl acetate molecules. However, as the loaded molecular sieve increased from 20 wt% to 35 wt%, the separation factor began to show a downward trend, combined with... Figure 5 We can observe (in the blue circle) that at a 20 wt% zeolite loading, localized agglomeration is already visible on the membrane cross-section. This indicates that further increasing the zeolite loading will exacerbate the agglomeration. Therefore, the decrease is mainly due to excessive zeolite loading, which leads to localized agglomeration of zeolite inside the membrane, hindering the rapid passage of organic molecules through the membrane. Simultaneously, localized defects allow water molecules to more easily pass through the membrane (as also reflected in the component flux data), thus affecting the membrane's separation performance.

[0080] Comparative Example 5 The majority of the components are the same as in Example 1, except that the simulated paint wastewater system is: 0.15wt% n-butyl acetate + 99.85wt% water.

[0081] Table 2 compares the separation performance of simulated paint wastewater with different n-butyl acetate feed concentrations (Examples 1, 5, 6 and Comparative Example 5).

[0082] Table 2 Comparison of simulated paint wastewater separation performance with different n-butyl acetate feed concentrations As shown in Table 2, the mixed matrix membrane prepared in Example 1 of this invention exhibits optimal performance in separating a feed system of 0.3 wt% n-butyl acetate + 99.7 wt% water, with a separation factor of 884.04 for n-butyl acetate and a total flux of 235.81 gh. - 1 .m -2 .

[0083] Although the present invention has been described in detail above with general descriptions, specific embodiments, and experiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. An OTES-modified ZSM-5 / PDMS hybrid matrix membrane, characterized in that, It includes a base membrane and a separation layer composited on the surface of the base membrane. The separation layer comprises raw materials with the following components: terminal vinyl PDMS, platinum group metal catalyst, reaction inhibitor, OTES-modified ZSM-5 molecular sieve, and a first organic solvent.

2. The OTES-modified ZSM-5 / PDMS hybrid matrix membrane according to claim 1, characterized in that, The ratio of the terminal vinyl PDMS, catalyst, reaction inhibitor, OTES-modified ZSM-5 molecular sieve and the first organic solvent is 100g: 1~5mL: 1~5mL: 5~20g: 250~450g.

3. The OTES-modified ZSM-5 / PDMS hybrid matrix membrane according to claim 1, characterized in that, The base membrane includes a hydrophobic microfiltration membrane composed of one or more of polytetrafluoroethylene, polyvinylidene fluoride, and polypropylene. The terminal vinyl PDMS is one or more combinations of α,ω-divinyl PDMS and PDMS with vinyl side chains; The platinum group metal catalyst is Pt2(C8H) 18 OSi2)3, chloroplatinic acid, or platinum-vinylsiloxane complex; The reaction inhibitor is one or more combinations of 1-ethynylcyclohexanol, 3,5-dimethyl-1-hexyn-3-ol, and 2-methyl-3-butyn-2-ol. The first organic solvent is one or more combinations of n-heptane, toluene, cyclohexane, xylene, or n-hexane.

4. The OTES-modified ZSM-5 / PDMS hybrid matrix membrane according to claim 1, characterized in that, The preparation process of the OTES-modified ZSM-5 molecular sieve is as follows: after removing the template agent of ZSM-5 molecular sieve, the template agent-removed ZSM-5 molecular sieve, OTES and a second organic solvent are mixed and stirred to carry out a hydrolysis reaction. After the reaction is completed, the mixture is centrifuged, the precipitate is washed and dried to obtain the OTES-modified ZSM-5 molecular sieve.

5. The OTES-modified ZSM-5 / PDMS hybrid matrix membrane according to claim 4, characterized in that, The process for removing the template agent from the ZSM-5 molecular sieve is as follows: the ZSM-5 molecular sieve is heated to 500-700℃ at a heating rate of 2-5℃ / min, kept at that temperature for 3-5 hours, and then cooled to room temperature to obtain the ZSM-5 molecular sieve with the template agent removed.

6. The OTES-modified ZSM-5 / PDMS hybrid matrix membrane according to claim 4, characterized in that, The ZSM-5 molecular sieve has a silica-to-alumina ratio of 500-2000 and an average particle size of 1000-2000 nm. The mass ratio of ZSM-5 molecular sieve (for removing template agent), OTES, and the second organic solvent is 1~5:1:30~50; The second organic solvent is one or more combinations of n-heptane, toluene, cyclohexane, xylene, or n-hexane; The hydrolysis reaction is carried out at a temperature of 25~35℃.

7. A method for preparing an OTES-modified ZSM-5 / PDMS hybrid matrix membrane as described in any one of claims 1 to 6, characterized in that, End-vinyl PDMS, OTES-modified ZSM-5 molecular sieve, first organic solvent and platinum group metal catalyst are mixed and stirred, and pre-crosslinked until the viscosity of the system reaches a certain value. Then, a reaction inhibitor is added to terminate the crosslinking reaction, and a uniformly dispersed coating liquid is obtained. The coating liquid is scraped onto the surface of the base film, crosslinked and cooled to obtain an OTES-modified ZSM-5 / PDMS mixed matrix film.

8. The method for preparing an OTES-modified ZSM-5 / PDMS hybrid matrix membrane according to claim 7, characterized in that, Using vinyl-terminated PDMS as the polymer matrix, OTES-modified ZSM-5 molecular sieve, a first organic solvent, and a platinum group metal catalyst were added. The mixture was stirred at 25-35℃ and 600-1000rpm for pre-crosslinking until the system viscosity reached 150-350mPa·s. Then, a reaction inhibitor was added to terminate the crosslinking reaction, resulting in a uniformly dispersed coating solution. The mixture was stirred for 20-60 minutes and then sonicated for 20-30 minutes. The coating solution was then coated onto the surface of the base film with the doctor blade height controlled at 25-10000μm. The mixture was crosslinked at a constant temperature of 100-150℃ for 8-20 minutes and then cooled to room temperature to obtain an OTES-modified ZSM-5 / PDMS mixed matrix film.

9. An application of the OTES-modified ZSM-5 / PDMS hybrid matrix membrane as described in any one of claims 1 to 6, characterized in that, The OTES-modified ZSM-5 / PDMS hybrid matrix membrane is used to pervaporate and separate n-butyl acetate from the n-butyl acetate-water mixture.

10. The application according to claim 9, characterized in that, The process parameters for pervaporation separation are as follows: the concentration of n-butyl acetate in the n-butyl acetate-water system is 0.3wt%~0.7wt%, the feed temperature is 30~70℃, the feed flow rate is 1~5L / min, the vacuum degree on the permeation side is ≤2kPa, and the permeation vapor is collected by a liquid nitrogen cold trap on the permeation side.

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