Method for preparing fluorine-free hydrophobically modified w-mel or w-mfi zeolite molecular sieve membrane for oil-water separation

Abstract

The application provides a preparation method of a fluorine-free hydrophobic modified W-MEL or W-MFI zeolite molecular sieve membrane for oil-water separation, i.e. an in-situ crystallization method for preparing W-MEL and W-MFI type zeolite molecular sieve membranes. The method first pretreats a carrier with 3-aminopropyl triethoxysilane, then places the carrier in a reaction kettle, and performs high-temperature crystallization in a synthesis liquid to obtain W-MEL and W-MFI zeolite molecular sieve membranes with excellent performance. The research provides a simple synthesis method for novel W-MEL and W-MFI zeolite membrane materials, and innovatively proposes a fluorine-free hydrophobic modification strategy, so that the oil-water mixture can be effectively separated, and the method is applied to dye adsorption. The method provided by the application has strong operability, and has important industrial promotion and practical application value.

Description

Preparation method of fluorine-free hydrophobically modified W-MEL or W-MFI zeolite molecular sieve membranes for oil-water separation Technical Field

[0001] This invention belongs to the field of membrane separation technology, and relates to the preparation and application of fluorine-free hydrophobically modified W-MEL or W-MFI zeolite molecular sieve membranes, especially the in-situ crystallization preparation method of W-MEL or W-MFI zeolite molecular sieve membranes, the hydrophobic modification of fluorine-free systems, and their uses in oil-water separation and dye adsorption. Background Technology

[0002] Oil-water separation is a crucial industrial process for treating oily wastewater and water-containing oily liquids. Oily wastewater is generated in large quantities and across a wide range of industries, including petroleum, manufacturing, transportation, and food and beverage. Therefore, the treatment of oily wastewater and water-containing oily liquids is imperative, considering factors such as water reuse, oil recovery, and environmental remediation.

[0003] Conventional hydrophobic separation membranes are mainly prepared from fluorinated polymer materials. For example, in a composite hydrophobic membrane and its preparation method (CN202010002788.5), the inventors prepared a composite hydrophobic membrane by electrospinning a mixture of fluorinated copolymer and polyvinylidene fluoride, achieving a water contact angle of 153°. However, fluorinated materials are expensive, which does not align with the green and environmentally friendly development concept, and the adsorption of organic pollutants can affect the separation performance of organic membrane materials. Meanwhile, siloxanes in organosilanes possess reactive chemical properties, enabling hydrolysis and condensation to form a polysiloxane hydrophobic coating with a micron-sized structure. The resulting coating exhibits oxidation resistance and non-toxicity, making it an ideal material for constructing hydrophobic surfaces.

[0004] Zeolites are crystalline silicates or aluminosilicates, formed by silicon-oxygen tetrahedra or aluminum-oxygen tetrahedra linked by oxygen bridges. MFI and MEL zeolite frameworks belong to the pentasil family, possessing a 10-membered ring structure and similar pore sizes. Pure silica MFI and MEL zeolite frameworks are also known as Silicalite-1 and Silicalite-2, while aluminum-doped MFI and MEL zeolite frameworks are known as ZSM-5 and ZSM-11. Compared to their counterparts Silicalite-1 and Silicalite-2, ZSM-5 and ZSM-11 zeolites are more hydrophilic due to the presence of aluminum in their frameworks. The surface properties (hydrophobicity / hydrophilicity) of zeolite membranes play a crucial role in determining the ideal components for separation from oil-water mixtures. Hydrophilic zeolite membranes with a water contact angle less than 90° are used for separating water from oil-water mixtures. Conversely, hydrophobic zeolite membranes typically have a water contact angle greater than 120°, facilitating the separation of oil from oil-water mixtures. For example, an inorganic phase separation membrane and its application in oil-water separation (201210086896.0) describes how inventors grew a molecular sieve coating on a porous carrier to obtain a hydrophilic separation membrane with micro- and nano-sized structures. This hydrophilic membrane can separate oils in various harsh aquatic environments (strong acid environments, high ionic strength environments, and high temperature environments, etc.), making it suitable for treating oily wastewater. However, pollutants in aqueous oil solutions are mainly concentrated in the aqueous phase. Hydrophobic membranes are more resistant to pollution and can directly obtain the purified oil phase. Moreover, hydrophobic membranes have better chemical erosion resistance. To achieve efficient separation of oil-water mixtures, the hydrophobicity or hydrophilicity of zeolite membranes can be controlled to achieve even more efficient oil-water separation. In addition, by controlling the silica-alumina ratio (SAR) of zeolite, different chemical substances can be used to modify the membrane, and different heteroatoms can be incorporated into the zeolite framework. Introducing heteroatoms can not only adjust the surface properties of the zeolite membrane but also endow the zeolite framework with ideal characteristics. Summary of the Invention

[0005] This invention provides a method for preparing a fluorine-free hydrophobic modified W-MEL or W-MFI zeolite molecular sieve membrane for oil-water separation. This method involves high-temperature in-situ crystallization of a pretreated support to obtain a W-MEL or W-MFI zeolite molecular sieve membrane, and then subjecting the obtained W-MEL or W-MFI zeolite membrane to fluorine-free hydrophobic modification, thereby effectively separating oil-water mixtures and applying them to dye adsorption.

[0006] The production process of the fluorine-free hydrophobic modified W-MEL or W-MFI zeolite molecular sieve membrane involved in this invention is characterized by the following steps:

[0007] (1) Cleaning and pretreatment of porous carrier: The porous carrier was ultrasonically treated sequentially with sodium hydroxide solution, deionized water and ethanol to remove impurities. After the porous carrier was fully dried, it was pretreated by reflux in a mixed solution of 3-aminopropyltriethoxysilane / isopropanol, and then thoroughly cleaned and dried before use.

[0008] (2) Preparation of W-MEL or W-MFI synthesis solution: Tetrabutylammonium hydroxide or tetrapropylammonium hydroxide is used as silicon source and deionized water is mixed with tetrabutylammonium hydroxide or tetrapropylammonium hydroxide as organic structure directing agent. The mixture is stirred and aged to obtain a clear synthesis solution. Sodium tungstate is added after the synthesis solution is preheated. When preparing W-MEL synthesis solution, the organic structure directing agent is tetrabutylammonium hydroxide. When preparing W-MFI synthesis solution, the organic structure directing agent is tetrapropylammonium hydroxide.

[0009] (3) Crystallization and film formation: The porous support pretreated with 3-aminopropyltriethoxysilane is placed in a hydrothermal reactor, the synthesis solution is poured in, and the W-MEL or W-MFI zeolite molecular sieve membrane is obtained by high-temperature crystallization; the zeolite molecular sieve membrane is taken out from the hydrothermal reactor, washed with water, dried and calcined.

[0010] (4) Hydrophobic modification of W-MEL or W-MFI zeolite molecular sieve membranes: The prepared W-MEL or W-MFI zeolite molecular sieve membranes were hydrophobically modified using fluorine-free hydrophobic materials. The W-MEL or W-MFI zeolite molecular sieve membranes prepared in step (3) were immersed in a hydrophobic solution and then removed and thoroughly dried to obtain hydrophobic W-MEL or W-MFI zeolite molecular sieve membranes.

[0011] In the above technical solution of the present invention, in step (1), the porous carrier is made of alumina, zirconium oxide, mullite or metal mesh, and the metal mesh is preferably stainless steel wire mesh; the pore size of the porous carrier is 0.02-50 μm or 300-2000 mesh.

[0012] In the above technical solution of the present invention, in step (1), the porous carrier is in the shape of a tube, a plate, a hollow fiber or a porous channel carrier, preferably a plate.

[0013] In the above technical solution of the present invention, in step (1), the volume ratio of APTES:IPA:H2O in the porous carrier pretreatment solution is (0.01~0.1):(0.1~0.5):(0.1~1).

[0014] In the above technical solution of the present invention, in step (1), the pretreatment conditions of the porous carrier are: reflux at 50-90°C for 1-10 hours, preferably reflux at 60-90°C for 1-6 hours.

[0015] In the above technical solution of the present invention, in step (2), when synthesizing W-MEL zeolite molecular sieve membrane, the molar ratio of TEOS:TBAOH:Na2WO4·2H2O:H2O in the synthesis solution is 1:(0.1~0.35):(0.05~0.3):(20~120); when synthesizing W-MFI zeolite molecular sieve membrane, the molar ratio of TEOS:TPAOH:Na2WO4·2H2O:H2O in the synthesis solution is 1:(0.1~0.35):(0.05~0.3):(20~140).

[0016] In the above technical solution of the present invention, in step (2), the aging conditions are: stirring and aging at 20-50°C for 4-24 hours, preferably stirring and aging at 20-40°C for 4-20 hours.

[0017] In the above technical solution of the present invention, in step (2), the preheating conditions of the synthesis liquid are: preheating at 60-100°C for 6-16 hours, preferably preheating at 60-90°C for 6-12 hours.

[0018] In the above technical solution of the present invention, in step (3), the crystallization temperature is 70-180°C and the crystallization time is 1-50h, preferably the crystallization temperature is 100-180°C and the crystallization time is 6-30h.

[0019] In the above technical solution of the present invention, in step (3), the drying temperature is 40-100℃, the drying time is 10-36h, the calcination temperature is 400-500℃, the calcination time is 4-8h, and the heating / cooling rate is 0.5-1℃ / min.

[0020] In the above technical solution of the present invention, in step (4), the fluorine-free hydrophobic material can be hexadecyltrimethoxysilane or dodecyltrimethoxysilane. When synthesizing W-MEL zeolite molecular sieve membrane, hexadecyltrimethoxysilane is preferred; when synthesizing W-MFI zeolite molecular sieve membrane, dodecyltrimethoxysilane is preferred.

[0021] In the above technical solution of the present invention, in step (4), the molar ratio of HDTMS / DDTMS:C2H5OH:H2O in the hydrophobic aqueous solution is 1:(20-120):(10-65).

[0022] When using DDTMS, an acetic acid CH3COOH solution also needs to be added to the hydrophobic solution. The molar ratio of CH3COOH to DDTMS is 0.05-30:1, and the concentration of the CH3COOH solution is 0.5-6M.

[0023] In the above technical solution of the present invention, in step (4), the hydrophobic modification conditions are: soaking in a hydrophobic aqueous solution at 5-50°C for 1-12 hours, preferably soaking in a hydrophobic aqueous solution at 20-40°C for 1-10 hours.

[0024] This invention has the following advantages: it proposes a simple synthesis method for novel W-MEL or W-MFI zeolite membrane materials; the in-situ hydrothermally grown W-MEL or W-MFI zeolite molecular sieve membranes exhibit excellent water separation performance for oil-water mixtures (water-n-hexane mixture (50%-50%)), with the former achieving a separation efficiency of 99.4% and a water flux of 46247 L / (m³). 2 h); the latter has a separation efficiency >99% and a water flux of 20665 L / (m²). 2 In addition, the adsorption capacities for methylene blue dye were 440 and 840 mg / m³, respectively. 2 Subsequently, an innovative fluorine-free hydrophobic modification strategy was adopted, using fluorine-free materials to hydrophobically modify W-MEL or W-MFI zeolite molecular sieve membranes, achieving highly efficient separation of oil-water mixtures (dichloromethane-water mixture (50%-50%)). The W-MEL zeolite molecular sieve membrane achieved a separation efficiency exceeding 99.0%, with an oil flux as high as 61490 L / (m³). 2 h), the oil flux of the W-MEL zeolite molecular sieve membrane is 35460 L / (m). 2 h), the separation efficiency was 98.3%. After 20 oil-water separation cycles of a dichloromethane-water mixture (50%-50%), the separation efficiency of both hydrophobically modified zeolite molecular sieve membranes remained above 98%. This indicates that the W-MEL or W-MFI zeolite molecular sieve membranes prepared by the above method not only have high oil-water separation performance but also excellent stability. Attached Figure Description

[0025] Figure 1 is a flowchart of the preparation process of hydrophobically modified W-MEL or W-MFI zeolite molecular sieve membranes in the embodiments.

[0026] Figure 2 shows the scanning electron microscope (SEM) images of the synthesized W-MEL zeolite molecular sieve membrane in the examples, and the SEM images of W-MEL zeolite grown on stainless steel wire mesh of different sizes, where (a, b, c) are 300 mesh; (d, e, f) are 500 mesh; (g, h, i) are 1000 mesh; and (j, k, l) are 2000 mesh.

[0027] Figure 3 shows the scanning electron microscope (SEM) images of the synthesized W-MFI zeolite molecular sieve membrane in the examples, and the SEM images of W-MFI zeolite grown on stainless steel wire mesh of different sizes, where (a, b, c) are 300 mesh; (d, e, f) are 500 mesh; (g, h, i) are 1000 mesh; and (j, k, l) are 2000 mesh.

[0028] Figure 4 shows the X-ray diffraction (XRD) patterns of unmodified W-MFI (a) and W-MEL (b) zeolite molecular sieve membranes grown on stainless steel wire meshes of different sizes; and the Fourier transform infrared (FT-IR) spectra of hydrophobically modified W-MFI (c) and W-MEL (d) zeolite molecular sieve membranes modified with HDTMS and DDTMS.

[0029] Figure 5 shows the water contact angle diagrams for W-MFI and W-MEL, where (a) W-MFI; (b) W-MFI-DDTMS; (c) W-MFI-HDTMS; (d) W-MEL; (e) W-MEL-DDTMS; and (f) W-MEL-HDTMS. Detailed Implementation

[0030] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0031] Example 1

[0032] (1) Cleaning and pretreatment of porous carrier: The 500-mesh stainless steel wire mesh carrier was ultrasonically treated (200V / 50Hz / 600W) for one hour in sequence with 1mol / L sodium hydroxide solution, deionized water and ethanol to remove impurities on the carrier. After the carrier was fully dried, it was pretreated with a mixed solution of 0.08APTES:0.12IPA:0.8H2O by volume and refluxed at 70℃ for 3 hours. After that, it was taken out, thoroughly cleaned and dried for later use.

[0033] (2) When synthesizing W-MEL zeolite molecular sieve membranes, the synthesis solution was prepared with a molar ratio of 1 TEOS:0.35 TBAOH:0.2 Na2WO4·2H2O:120H2O; when synthesizing W-MFI zeolite molecular sieve membranes, the synthesis solution was prepared with a molar ratio of 1 TEOS:0.15 TPAOH:0.15 Na2WO4·2H2O:135H2O. The silicon source, organic structure directing agent, and deionized water were mixed and aged at 25°C for 4 hours until clear. The solution was preheated at 90°C for 6 hours, and then sodium tungstate was added.

[0034] (3) Place the stainless steel wire mesh pretreated with APTES in a hydrothermal reactor, pour in the synthesis solution, and crystallize at 120℃ for 24h to obtain W-MEL or W-MFI zeolite molecular sieve membranes; take the membrane out of the hydrothermal reactor, wash it with water, dry it at 60℃ for 12h, and then calcine it in a muffle furnace at 500℃ for 4h. The heating / cooling rate of the muffle furnace is 1℃ / min.

[0035] (4) Hydrophobic modification of W-MEL or W-MFI zeolite molecular sieve membranes: For the hydrophobic modification of W-MEL molecular sieve membranes, a hydrophobic solution with a molar ratio of 1:80C2H5OH:10H2O was used; for the hydrophobic modification of W-MFI molecular sieve membranes, a hydrophobic solution with a molar ratio of 1:90C2H5OH:10H2O:15CH3COOH (1M) was used. First, the solution was stirred at 65℃ for 1 h to promote the hydrolysis of HDTMS / DDTMS to obtain a hydrophobic solution. Then, the prepared W-MEL and W-MFI zeolite molecular sieve membranes were soaked in the hydrophobic solution at 30℃ for 3 hours and thoroughly dried before use.

[0036] The crystal structures of the W-MEL and W-MFI zeolite molecular sieve membranes were confirmed by X-ray diffraction analysis as shown in Figure 4. The hydrophobically modified W-MEL and W-MFI zeolite molecular sieve membranes prepared in this example were used to separate dichloromethane from a dichloromethane-water mixture (50%-50%). The former had an oil flux of 61490 L / (m³). 2 h), separation efficiency 99.2%, the latter oil flux is 35460 L / (m 2 h), the separation efficiency was 98.3%. This is because the W-MEL and W-MFI zeolite molecular sieve membranes modified with HDTMS / DDTMS have more long carbon chains, and the water contact angle of the hydrophobically modified zeolite membranes is greater than 140°, which can obtain better hydrophobicity.

[0037] Example 2

[0038] In step (4) of Example 1, HDTMS in the preparation of the W-MEL zeolite molecular sieve membrane was replaced with DDTMS, and a hydrophobic aqueous solution with a molar ratio of 1 DDTMS:90C2H5OH:10H2O:15CH3COOH (1M) was used. Other synthesis conditions remained the same as those for the W-MEL zeolite molecular sieve membrane in Example 1, resulting in a W-MEL zeolite molecular sieve membrane with a water contact angle of 146.2°. This membrane was used to separate dichloromethane from a dichloromethane-water mixture (50%-50%), with an oil flux of 50233 L / (m³). 2 h), separation efficiency 99.2%.

[0039] Example 3

[0040] In step (1) of Example 1, the 500-mesh stainless steel wire mesh was replaced with a 300-mesh stainless steel wire mesh. The prepared W-MEL zeolite molecular sieve membrane was used to separate dichloromethane from a dichloromethane-water mixture (50%-50%), wherein the oil flux was 85700 L / (m²). 2 h), separation efficiency 98.3%.

[0041] Example 4

[0042] In step (1) of Example 1, the 500-mesh stainless steel wire mesh was replaced with a 1000-mesh stainless steel wire mesh. The prepared W-MEL zeolite molecular sieve membrane was used to separate dichloromethane from a dichloromethane-water mixture (50%-50%), wherein the oil flux was 39280 L / (m²). 2 h), separation efficiency 99.3%.

[0043] Example 5

[0044] In step (1) of Example 1, the 500-mesh stainless steel wire mesh was replaced with a 2000-mesh stainless steel wire mesh. The prepared W-MEL zeolite molecular sieve membrane was used to separate dichloromethane from a dichloromethane-water mixture (50%-50%), wherein the oil flux was 23290 L / (m²). 2 h), with a separation efficiency greater than 99.2%.

[0045] Example 6

[0046] Step (4) in Example 1 is omitted, that is, the W-MEL and W-MFI zeolite molecular sieve membranes are not hydrophobically modified, and the other synthesis conditions are the same as in Example 1.

[0047] Unmodified W-MEL and W-MFI zeolite molecular sieve membranes exhibit strong hydrophilicity, with water contact angles of 0° and 61.2°, respectively, making them suitable for separating water from oil-water mixtures such as water-n-hexane or water-petroleum ether. When the unmodified W-MEL zeolite molecular sieve membrane was used for the separation of a water-n-hexane (50%-50%) mixture, the water flux reached 46247 L / (m²). 2 The separation efficiency was 99.4%; when this membrane was used to separate water from a water-petroleum ether (50%-50%) mixture, the water flux was 37462 L / (m³). 2 h), the separation efficiency is greater than 99%. Simultaneously, when this membrane was used to adsorb methylene blue dye at a concentration of 50 ppm and a pH of 9.8, the adsorption capacity reached 440 mg / m³. 2 Furthermore, unmodified W-MFI zeolite molecular sieve membranes were used for water-n-hexane (50%-50%) conversion with a water flux of 20665 L / (m³). 2 The membrane exhibits a separation efficiency greater than 99% (h); when used to separate water from a water-petroleum ether (50%-50%) mixture, the water flux is 15070 L / (m). 2 h), the separation efficiency is greater than 99%. The two unmodified zeolite molecular sieve membranes mentioned above were used to adsorb methylene blue dye at a concentration of 50 ppm and a pH of 9.8, with adsorption capacities of 440 and 840 mg / m³, respectively. 2 .

[0048] Example 7

[0049] The synthesis solution formulation of the W-MFI zeolite molecular sieve membrane in step (2) of Example 1 was modified to a molar ratio of 1 TEOS:0.35 TPAOH:0.15 Na2WO4·2H2O:135 H2O. Other synthesis conditions remained the same as those for the W-MFI zeolite molecular sieve membrane in Example 1. The prepared W-MFI zeolite molecular sieve membrane was used to separate dichloromethane from a dichloromethane-water mixture (50%-50%), with an oil flux of 24517 L / (m³). 2 h), separation efficiency 98.5%.

[0050] Example 8

[0051] The synthesis solution formulation of the W-MEL zeolite molecular sieve membrane in step (2) of Example 1 and the crystallization conditions in step (3) were changed. A synthesis solution was prepared with a molar ratio of 1 TEOS: 0.1 TBAOH: 0.2 Na2WO4·2H2O: 120H2O. A stainless steel wire mesh pretreated with APTES was placed in a hydrothermal reactor, and the synthesis solution was poured in and crystallized at 140°C for 30 hours. Other conditions remained the same as those for the preparation of the W-MEL zeolite molecular sieve membrane in Example 1. The prepared W-MEL zeolite molecular sieve membrane was used to separate dichloromethane from a dichloromethane-water mixture (50%-50%), where the oil flux was 57582 L / (m³). 2 h), separation efficiency 99.1%.

[0052] Example 9

[0053] The crystallization temperature in step (3) of Example 1 was changed from 120°C to 180°C. Other synthesis conditions remained the same as in Example 1. The prepared W-MEL or W-MFI zeolite molecular sieve membranes were used to separate dichloromethane from a dichloromethane-water mixture (50%-50%). The former had an oil flux of 52855 L / (m³). 2 The separation efficiency was 99.5%; the oil flux of the latter was 23187 L / (m³). 2 h), separation efficiency 98.5%.

[0054] Example 10

[0055] The volume ratio of the pretreatment mixed solution in step (1) of Example 1 was changed to 0.08APTES:0.5IPA:0.8H2O, and the solution was refluxed at 90°C for 1 hour for pretreatment. Other synthesis conditions remained the same as in Example 1. The prepared W-MEL or W-MFI zeolite molecular sieve membranes were used to separate dichloromethane from a dichloromethane-water mixture (50%-50%). The former had an oil flux of 59485 L / (m³). 2 The separation efficiency was 99.0%; the oil flux of the latter was 30977 L / (m³). 2h), separation efficiency 98.2%.

Claims

1. A method for preparing fluorine-free hydrophobically modified W-MEL or W-MFI zeolite molecular sieve membranes for oil-water separation, characterized in that, The steps are as follows: (1) Cleaning and pretreatment of porous carrier: Sonic treatment of porous carrier with sodium hydroxide solution, deionized water and ethanol in sequence to remove impurities on porous carrier; After the porous carrier is fully dried, it is pretreated by reflux in 3-aminopropyltriethoxysilane / isopropanol mixed solution, and then fully cleaned and dried for use; (2) Preparation of W-MEL or W-MFI synthesis solution: Tetrabutylammonium hydroxide or tetrapropylammonium hydroxide is used as silicon source, and tetrabutylammonium hydroxide or tetrapropylammonium hydroxide is used as organic structure directing agent. The silicon source, organic structure directing agent and deionized water are mixed, stirred and aged to obtain a clear synthesis solution. Sodium tungstate is added after the synthesis solution is preheated; when preparing W-MEL synthesis solution, the organic structure directing agent is tetrabutylammonium hydroxide; when preparing W-MFI synthesis solution, the organic structure directing agent is tetrapropylammonium hydroxide. Ammonium hydroxide; (3) Crystallization film formation: The porous carrier pretreated with 3-aminopropyltriethoxysilane is placed in a hydrothermal reactor, the synthesis liquid is poured in, and the W-MEL or W-MFI zeolite molecular sieve membrane is obtained by high-temperature crystallization; the zeolite molecular sieve membrane is taken out from the hydrothermal reactor, washed with water, dried and calcined; (4) Hydrophobic modification of W-MEL or W-MFI zeolite molecular sieve membrane: The prepared W-MEL or W-MFI zeolite molecular sieve membrane is hydrophobically modified with a fluorine-free hydrophobic material; the W-MEL or W-MFI zeolite molecular sieve membrane prepared in step (3) is soaked in a hydrophobic solution and then taken out and fully dried to obtain a hydrophobic W-MEL or W-MFI zeolite molecular sieve membrane; the fluorine-free hydrophobic material is hexadecyltrimethoxysilane or dodecyltrimethoxysilane.

2. The method for preparing a fluorine-free hydrophobically modified W-MEL or W-MFI zeolite molecular sieve membrane for oil-water separation according to claim 1, characterized in that, In step (1), the porous carrier is made of alumina, zirconium oxide, mullite or metal mesh; the pore size of the porous carrier is 0.02 ~ 50 μm or 300 ~ 2000 mesh; the shape of the porous carrier is tubular, flat, hollow fiber or porous channel carrier.

3. The method for preparing the fluorine-free hydrophobically modified W-MEL or W-MFI zeolite molecular sieve membrane for oil-water separation according to claim 1, characterized in that, In step (1), the volume ratio of APTES:IPA:H2O in the porous carrier pretreatment solution is (0.01 ~ 0.1):(0.1 ~ 0.5):(0.1 ~ 1); the porous carrier pretreatment conditions are: reflux at 50 ~ 90 ℃ for 1 ~ 10 h.

4. The method for preparing a fluorine-free hydrophobically modified W-MEL or W-MFI zeolite molecular sieve membrane for oil-water separation according to claim 1, characterized in that, In step (2), when synthesizing W-MEL zeolite molecular sieve membrane, the molar ratio of TEOS:TBAOH:Na2WO4·2H2O:H2O in the synthesis solution is 1:(0.1 ~ 0.35):(0.05 ~ 0.3):(20 ~ 120); when synthesizing W-MFI zeolite molecular sieve membrane, the molar ratio of TEOS:TPAOH:Na2WO4·2H2O:H2O in the synthesis solution is 1:(0.1 ~ 0.35):(0.05 ~ 0.3):(20 ~ 140).

5. The method for preparing a fluorine-free hydrophobically modified W-MEL or W-MFI zeolite molecular sieve membrane for oil-water separation according to claim 1, characterized in that, In step (2), the aging conditions are: stirring and aging at 20 ~ 50 ℃ for 4 ~ 24 h; the preheating conditions for the synthesis liquid are: preheating at 60 ~ 100 ℃ for 6 ~ 16 h.

6. The method for preparing a fluorine-free hydrophobically modified W-MEL or W-MFI zeolite molecular sieve membrane for oil-water separation according to claim 1, characterized in that, In step (3), the crystallization temperature is 70~180℃ and the crystallization time is 1~50h.

7. The method for preparing a fluorine-free hydrophobically modified W-MEL or W-MFI zeolite molecular sieve membrane for oil-water separation according to claim 1, characterized in that, In step (3), the drying temperature is 40~100℃, the drying time is 10~36h, the calcination temperature is 400~500℃, the calcination time is 4~8h, and the heating / cooling rate is 0.5~1℃ / min.

8. The method for preparing a fluorine-free hydrophobically modified W-MEL or W-MFI zeolite molecular sieve membrane for oil-water separation according to claim 1, characterized in that, In step (4), the molar ratio of HDTMS / DDTMS:C2H5OH:H2O in the hydrophobic aqueous solution is 1:(20 ~ 120):(10 ~ 65).

9. The method for preparing a fluorine-free hydrophobically modified W-MEL or W-MFI zeolite molecular sieve membrane for oil-water separation according to claim 8, characterized in that, When using DDTMS, an acetic acid CH3COOH solution also needs to be added to the hydrophobic solution. The molar ratio of CH3COOH to DDTMS is 0.05-30:1, and the concentration of the CH3COOH solution is 0.5-6M.

10. The method for preparing a fluorine-free hydrophobically modified W-MEL or W-MFI zeolite molecular sieve membrane for oil-water separation according to claim 1, characterized in that, In step (4), the hydrophobic modification conditions are: soaking in a hydrophobic solution at 5 ~ 50 ℃ for 1 ~ 12 h.

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