Super-hydrophobic mesh membrane loaded with super-hydrophilic particles, and preparation method and application thereof

Abstract

This invention provides a superhydrophobic mesh film loaded with superhydrophilic particles, its preparation method, and its application. The superhydrophobic mesh film comprises a mesh substrate and superhydrophilic particles loaded on the mesh substrate; the surface of the mesh substrate has a micro / nano rough structure with a roughness Ra greater than or equal to 100 nm and is modified for superhydrophobicity; the superhydrophilic particles are distributed on the surface of the mesh substrate and / or embedded in the pores of the mesh substrate, and the superhydrophilic particles include hydrophilic metal salt particles and / or hydrophilic metal-organic framework particles. This invention also provides a method for preparing the above-mentioned superhydrophobic mesh film loaded with superhydrophilic particles and its application in separating water-in-oil emulsions. The above-mentioned superhydrophobic mesh film loaded with superhydrophilic particles can efficiently trap emulsion water droplets, allowing continuous oil phase to pass through, thereby achieving water-in-oil emulsion separation.

Description

Technical Field

[0001] This invention relates to the field of water-in-oil emulsion separation technology, and in particular to a superhydrophobic membrane loaded with superhydrophilic particles, its preparation method and application. Background Technology

[0002] During oil and gas extraction, as the extraction depth increases, the water content in the extracted crude oil becomes excessively high, severely impacting fuel quality. For the transportation industry, excessively high water content in fuel can seriously affect the stable operation of engines. Studies show that if fuel contains 0.1% emulsified water, the emulsified water droplets will condense on the engine's metal surface, causing corrosion, a long-term cause of common engineering failures. Therefore, industrial processes urgently need oil-in-water emulsion separation to obtain ultra-high purity oil.

[0003] Biomimetic superwetting membranes can achieve water-in-oil emulsion separation by relying on their ultra-high oil-water selective permeability and the sieving effect of mesh size. However, during use, emulsion water droplets easily accumulate on the membrane surface to form a filter cake layer, and the flux reduction is not negligible. In addition, when the particle size of the emulsion water droplets is smaller than the mesh size of the biomimetic superwetting membrane, the emulsion water droplets will penetrate the membrane mesh, resulting in extremely poor separation efficiency. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a superhydrophobic membrane loaded with superhydrophilic particles, its preparation method, and its application. Even when the particle size of the emulsified water droplets is smaller than the mesh size of the membrane product, the superhydrophobic membrane loaded with superhydrophilic particles can efficiently trap the emulsified water droplets, allowing the continuous oil phase to pass through, thereby achieving water-in-oil emulsion separation.

[0005] To achieve the above objectives, the present invention provides a superhydrophobic mesh loaded with superhydrophilic particles, the superhydrophobic mesh comprising a mesh substrate and superhydrophilic particles loaded on the mesh substrate; the surface of the mesh substrate has a micro-nano rough structure, the roughness Ra of the micro-nano rough structure being greater than or equal to 100 nm, and the surface of the mesh substrate (including its micro-nano rough structure) is hydrophobically modified; the hydrophilic particles are distributed on the surface of the mesh substrate, and the superhydrophilic particles comprise metal salts or metal-organic frameworks (MOFs).

[0006] The superhydrophobic mesh membrane with superhydrophilic particles provided by this invention can be described as a superhydrophobic mesh membrane with superhydrophilic particles loaded on it. This superhydrophobic mesh membrane has a biomimetic water-collecting function similar to the back of a desert beetle. By loading hydrophilic metal salts or metal-organic framework particles onto the surface of the mesh substrate, it can induce the "capture-aggregation" of emulsion water droplets, avoiding the formation of a filter cake layer during the separation of water-in-oil emulsions. It can also prevent emulsion water droplets from penetrating the membrane pores when the droplet size is smaller than the mesh size of the biomimetic superwetting membrane. The hydrophilic metal salts or metal-organic framework particles are typically microscale particles with a particle size of 1-10 micrometers, such as bismuth molybdate or Cu-MOF (HKUST-1). The mesh substrate has a superhydrophobic surface, which allows continuous oil phase to pass through, thereby efficiently trapping emulsion water droplets and achieving water-in-oil emulsion separation.

[0007] In the aforementioned superhydrophobic membrane loaded with superhydrophilic particles, the superhydrophilic particles are generally hydrophilic metal salts or metal-organic framework particles. The static water contact angle of these superhydrophilic particles (hydrophilic metal salts or metal-organic framework particles) in air is 0°-10°, for example, specific values ​​such as 0°, 1°, 2°, 3°, 4°, 5°, 6°, 7°, 8°, 9°, 10°, and a range with any two of these specific values ​​as endpoints. Specifically, the hydrophilic metal salt particles may include one or more combinations of bismuth molybdate and bismuth tungstate, and the hydrophilic metal-organic framework particles may include one or more combinations of Cu-MOFs (e.g., HKUST-1), ZIF, UIO-66, and MIL.

[0008] In the aforementioned superhydrophilic superhydrophobic mesh, the superhydrophilic particles have a particle size of 1-10 μm, such as specific values ​​of 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, and 10 μm, or a range with any two of these specific values ​​as endpoints. By using superhydrophilic particles of the above particle size, the superhydrophilic particles can be uniformly dispersed on the surface of the superhydrophobic mesh substrate, avoiding aggregation.

[0009] In the above-mentioned superhydrophobic mesh with superhydrophilic load, the mesh substrate has superhydrophobicity. In some specific embodiments, the static water contact angle of the mesh substrate in air is generally above 150°, such as above 151°, above 152°, above 153°, above 154°, above 155°, etc.

[0010] In the above-mentioned superhydrophobic mesh with superhydrophilic loading, the surface of the mesh substrate has a micro-nano rough structure with a roughness Ra value greater than or equal to 100 nm, and after hydrophobic modification, the surface of the mesh substrate can achieve a superhydrophobic effect.

[0011] In some specific implementations, the material of the micro-nano rough structure may include one or more of copper oxalate, copper phosphate, and copper hydroxide.

[0012] In some specific implementations, the morphology of the micro-nano rough structure may include one or more of nanosheets, nanowires, and bow-shaped micro-nano structures.

[0013] In the aforementioned superhydrophobic mesh loaded with superhydrophilic particles, the mesh substrate has a mesh structure. In some specific embodiments, the pore size of the mesh substrate (without superhydrophilic particles) having a micro-nano roughened surface structure and being hydrophobically modified is 5μm-20μm, for example, specific values ​​such as 5μm, 10μm, 15μm, 20μm, etc., and a range with any two of the above specific values ​​as endpoints.

[0014] The present invention also provides a method for preparing the above-mentioned superhydrophobic membrane loaded with superhydrophilic particles, the method comprising:

[0015] Micro-nano rough structures are formed on the surface of a metal substrate, and then the metal substrate with micro-nano rough structures is mixed with a hydrophobic modifier for hydrophobic modification to obtain a mesh substrate.

[0016] A solution of superhydrophilic particles is loaded onto the surface of the mesh substrate by surface coating and then dried to obtain the superhydrophobic mesh film loaded with superhydrophilic particles.

[0017] According to a specific embodiment of the present invention, the above-described preparation method may further include a pretreatment of the metal substrate before forming the micro / nano rough structure. The pretreatment process may include: pretreating the metal substrate with an organic solvent and an inorganic acid to remove surface lipid contaminants and an oxide layer. The organic solvent includes one or more combinations of acetone, isopropanol, and ethanol; the inorganic acid includes hydrochloric acid.

[0018] In the above preparation method, the present invention does not impose special restrictions on the material of the metal substrate or the process for forming the micro / nano rough structure, as long as the metal substrate can be formed into a micro / nano rough structure through a certain process, and the roughness Ra value is greater than or equal to 100 nm, and then it can be modified to have a superhydrophobic surface. In some specific embodiments, the metal substrate may include copper mesh and / or stainless steel mesh, wherein the copper mesh has good electrical conductivity, mechanical and chemical stability.

[0019] In the above preparation method, the process of forming micro-nano rough structures may include etching and / or oxidation.

[0020] In the above preparation method, the etching agent used for etching may include oxalic acid, for example, an oxalic acid solution of 0.5-0.8 mol / L can be used; accordingly, copper oxalate nanosheets can be formed after etching the copper mesh. Copper oxalate nanosheets can form a rough structure on the surface of the metal substrate, increase the hydrophobicity of the surface of the metal substrate, and have good antioxidant properties and can be used as an antioxidant layer.

[0021] In some specific embodiments, when oxalic acid is used as the etchant, the etching temperature is 60-80°C, for example, specific values ​​such as 60°C, 65°C, 70°C, 75°C, and 80°C, and a range with any two of the above specific values ​​as endpoints; the etching time is 5 days or more, and more specifically, 7 days or more. A longer etching time can promote the deposition of a more abundant and denser antioxidant layer on the surface of the metal substrate.

[0022] In the above preparation method, the oxidant used in the oxidation process may include ammonium persulfate and sodium hydroxide. When the metal substrate is a copper mesh, the oxidation produces a rough structure of copper hydroxide nanowires. The oxidation temperature is 25-30℃, for example, specific values ​​such as 25℃, 26℃, 27℃, 28℃, 29℃, 30℃, etc., and any two of the above specific values ​​as endpoints; the oxidation time is 10-30 minutes, for example, specific values ​​such as 10 minutes, 12 minutes, 14 minutes, 16 minutes, 18 minutes, 20 minutes, 22 minutes, 24 minutes, 26 minutes, 28 minutes, 30 minutes, etc., and any two of the above specific values ​​as endpoints.

[0023] In the above preparation method, the oxidant used in the oxidation may also include ammonium persulfate and disodium hydrogen phosphate. When the metal substrate is a copper mesh, the oxidation produces a rough structure of copper phosphate nanosheets. The oxidation temperature is 25-30℃, for example, specific values ​​such as 25℃, 26℃, 27℃, 28℃, 29℃, 30℃, etc., and any two of the above specific values ​​as endpoints; the oxidation time is 24-36 hours, for example, specific values ​​such as 24 hours, 28 hours, 32 hours, 36 hours, etc., and any two of the above specific values ​​as endpoints.

[0024] In the above preparation method, the metal substrate used as raw material generally has a mesh. In some specific embodiments, the mesh diameter of the metal substrate is less than or equal to 50 μm, for example, it can be 20 μm-50 μm, specifically it can be 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, etc., and a range with any two of the above specific values ​​as endpoints; the mesh count of the metal substrate can be 300 or more, and more specifically, 400 or more.

[0025] In the above preparation method, the surface modified with the hydrophobic modifier can exhibit superhydrophobicity, meaning that the static water contact angle in air can reach 150° or higher. The hydrophobic modifier may include one or a combination of two or more of n-dodecyl mercaptan, hexadecyltrimethoxysilane (HDTMS), and stearic acid. In some specific embodiments, the hydrophobic modifier may be a 3-5 mmol / L solution of n-dodecyl mercaptan, and the solvent for this solution may include ethanol. The hydrophobic modifier may be a 2% (v / v) solution of hexadecyltrimethoxysilane.

[0026] In the above preparation method, when the hydrophobic modifier is n-dodecyl mercaptan, the hydrophobic modification temperature can be 25-30℃, for example, specific values ​​such as 25℃, 26℃, 27℃, 28℃, 29℃, 30℃, etc., and a range with any two of the above specific values ​​as endpoints; the hydrophobic modification time can be 10min-30min, for example, specific values ​​such as 10min, 15min, 20min, 25min, 30min, etc., and a range with any two of the above specific values ​​as endpoints.

[0027] In the above preparation method, when the hydrophobic modifier is hexadecyltrimethoxysilane, the hydrophobic modification temperature can be 50-80℃, for example, specific values ​​such as 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, and any two of the above specific values ​​as endpoints; the hydrophobic modification time can be 2h-3h, for example, specific values ​​such as 2h, 2.5h, 3h, and any two of the above specific values ​​as endpoints.

[0028] In the above preparation method, when the hydrophobic modifier is stearic acid, the hydrophobic modification temperature can be 25-30℃, for example, specific values ​​such as 25℃, 26℃, 27℃, 28℃, 29℃, 30℃, etc., and a range with any two of the above specific values ​​as endpoints; the hydrophobic modification time can be 3h-5h, for example, specific values ​​such as 3h, 3.5h, 4h, 4.5h, 5h, etc., and a range with any two of the above specific values ​​as endpoints.

[0029] The metal salt particles or metal-organic framework particles used in this invention are hydrophilic, have high water stability, and have a particle size of 1-10 μm. In some specific embodiments, the metal salt particles include one or more combinations of bismuth molybdate and bismuth tungstate; the metal-organic framework particles include one or more combinations of Cu-MOFs (e.g., HKUST-1), ZIF, UIO-66, and MIL.

[0030] In the above preparation method, when the superhydrophilic particles are metal salt particles, the preparation method of the metal salt particles includes: reacting an inorganic metal source in an alcohol solvent to obtain metal salt particles.

[0031] In some specific implementations, the inorganic metal source includes a combination of a molybdenum source and a bismuth source, or a combination of a tungsten source and a bismuth source.

[0032] In some specific implementations, the reaction temperature can be 170-190°C, for example, specific values ​​such as 170°C, 175°C, 180°C, 185°C, 190°C, and a range with any two of the above specific values ​​as endpoints.

[0033] In some specific implementations, the reaction time can be adjusted according to the reaction temperature, as long as the generated metal salt particles have a suitable particle size. Specifically, the reaction time can be 12h-24h.

[0034] In some specific embodiments, the alcohol solvent includes ethylene glycol and anhydrous ethanol. The volume ratio of ethylene glycol to anhydrous ethanol can be 1:3.

[0035] In some specific embodiments, the above preparation method uses a solvothermal method to synthesize metal salt particles, and the obtained metal salt particles can be bismuth molybdate particles with a particle size of 1-10 μm. In some specific embodiments, the morphology of the metal salt particles can be spherical.

[0036] In the above preparation method, when the superhydrophilic particles are metal-organic framework particles, the preparation method of the metal-organic framework particles includes: mixing a coordinating metal source and an organic ligand to obtain a precursor solution, and crystallizing the precursor solution to obtain metal-organic framework particles.

[0037] In the above preparation method, the coordination metal source may include one or a combination of two or more of the following: copper source, cobalt source, iron source, zinc source, and zirconium source.

[0038] In the above preparation method, the organic ligand may include pyromellitic acid H3BTC and / or 2-methylimidazole.

[0039] In the above preparation method, the molar ratio of the coordinating metal source to the organic ligand is generally 5-10:3.5-5.

[0040] In the above preparation method, the crystallization temperature is 100-120℃, for example, specific values ​​such as 100℃, 105℃, 110℃, 115℃, 120℃, etc., and a range with any two of the above specific values ​​as endpoints; the crystallization time is 12h-36h, for example, specific values ​​such as 12h, 18h, 24h, 30h, 36h, etc., and a range with any two of the above specific values ​​as endpoints.

[0041] In some specific implementations, the surface coating method includes spraying.

[0042] In the above preparation method, the spraying process disperses superhydrophilic particles on the surface of the mesh substrate. The precursor solution used for spraying comprises superhydrophilic particles, ethanol (as a solvent), and epoxy resin. The concentration of superhydrophilic particles in the precursor solution is 5-20 mg / mL, for example, specific values ​​such as 5 mg / mL, 10 mg / mL, 15 mg / mL, 20 mg / mL, etc., and a range with any two of the above specific values ​​as endpoints; the mass concentration of epoxy resin in the precursor solution is 5%. The single spraying time does not exceed 10 seconds, and the epoxy resin is cured at room temperature (25-30℃). By controlling the concentration of epoxy resin, spraying time, curing conditions, etc., it is possible to use epoxy resin to uniformly distribute superhydrophilic particles while avoiding the epoxy resin affecting the hydrophilicity and hydrophobicity of the superhydrophilic particles and the mesh substrate.

[0043] This invention also provides the application of the above-mentioned superhydrophobic membrane loaded with superhydrophilic particles in water-in-oil emulsion separation. In the above-mentioned superhydrophobic membrane loaded with superhydrophilic particles, the superhydrophilic particles exhibit good water absorption and water stability; the mesh substrate is superhydrophobic, and the surface of the mesh substrate has pores, which can efficiently trap emulsion water droplets. During the water-in-oil emulsion separation process, the superhydrophilic particles can "capture and aggregate" emulsion water droplets, and the pores of the mesh substrate also help to efficiently trap emulsion water droplets, thereby preventing emulsion water droplets with a particle size smaller than the membrane pore size from penetrating the membrane pores, and also preventing the trapped emulsion water droplets from accumulating on the membrane surface to form a filter cake layer.

[0044] In some specific embodiments, this invention utilizes a copper mesh with micro / nano rough structures of copper oxalate, copper phosphate, and copper hydroxide on its surface for superhydrophobic modification. Compared to other hydrophobic films, copper oxalate, copper phosphate, and copper hydroxide possess excellent antioxidant capabilities, and the nanosheets, nanowires, and bow-shaped nanostructures have larger sizes and surface areas. Therefore, the copper mesh surface exhibits greater roughness, with Ra values ​​all greater than or equal to 100 nm. According to the Wenzel model, the greater the surface roughness of a solid, the stronger its hydrophobicity. Therefore, the modified mesh substrate prepared by this invention will possess more stable and stronger superhydrophobicity compared to other hydrophobic films. This excellent superhydrophobicity is beneficial for more efficient retention of emulsion water droplets during water-in-oil emulsion separation.

[0045] The beneficial effects of this invention include:

[0046] (1) This invention utilizes a metal substrate with a micro-nano rough structure on its surface to perform superhydrophobic modification to form a mesh substrate. The micro-nano rough structure can increase the specific surface area of ​​the metal substrate, thereby increasing the surface roughness and hydrophobicity of the formed mesh substrate. Compared with conventional hydrophobic films, the mesh substrate of this invention has more stable and stronger superhydrophobicity. Good superhydrophobicity is beneficial for more efficient interception of emulsion water droplets during the separation of water-in-oil emulsions.

[0047] (2) This invention draws inspiration from the dorsal structure of desert beetles, distributing superhydrophilic particles on a superhydrophobic surface. During the separation of water-in-oil emulsions, these superhydrophilic particles can "capture and aggregate" emulsion droplets, thereby preventing emulsion droplets with a diameter smaller than the membrane pore size from penetrating the membrane pores and also preventing the trapped emulsion droplets from accumulating on the membrane surface to form a filter cake layer. Compared to existing superhydrophobic oil-water separation membranes that rely entirely on pore size sieving for emulsion separation, the superhydrophobic membrane with superhydrophilic particles provided by this invention can improve the retention efficiency of emulsion droplets during the separation of water-in-oil emulsions, enhance emulsion separation, and prevent filter cake layer contamination. Attached Figure Description

[0048] Figure 1 To prepare the water contact angle of the bismuth molybdate particle powder in Example 1.

[0049] Figure 2 The water contact angle of the Fe-doped MOF (HKUST-1) particle powder prepared in Example 2.

[0050] Figure 3 The images show the SEM images and contact angle diagrams of the HDTMS-modified copper oxalate nanosheets superhydrophobic copper mesh obtained in step (b) of Example 1.

[0051] Figure 4 Atomic force microscopy (AFM) results of copper nanosheets obtained in step (a) of Example 1.

[0052] Figure 5 The image shows a SEM image of the superhydrophobic membrane loaded with superhydrophilic particles obtained in Example 1.

[0053] Figure 6 The images show the SEM images and contact angle diagrams of the HDTMS-modified copper phosphate nanosheets superhydrophobic copper mesh obtained in step (c) of Example 2.

[0054] Figure 7 SEM images and contact angle diagrams of the copper hydroxide nanowire mesh obtained in step (b) and the HDTMS-modified copper hydroxide nanowire superhydrophobic copper mesh obtained in step (c) of Example 3.

[0055] Figure 8 The image shows the atomic force microscopy (AFM) test results of the copper hydroxide nanowire mesh obtained in step (b) of Example 3.

[0056] Figure 9 SEM images and contact angle diagrams of the dodecyl mercaptan-modified copper oxalate superhydrophobic copper mesh obtained in Comparative Example 1.

[0057] Figure 10 The images are SEM images of the superhydrophobic mesh with loaded MOF particles obtained in Comparative Example 1 at different magnifications. Detailed Implementation

[0058] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0059] The present invention will be further described below with reference to the accompanying drawings to facilitate understanding by those skilled in the art. The characterization methods involved in the following experiments are as follows: morphological characterization of the samples was performed using a Hitachi REGULUS-8230 field emission scanning electron microscope (Fe-SEM, Hitachi Instrument, Tokyo, Japan); the water contact angle (WCA) was evaluated using a JC2000 goniometer (Shanghai Zhongchen Digital Equipment Co., Ltd., China); and the surface roughness of the samples was characterized using a Bruker Dimension ICON atomic force microscope (AFM, Bruker, Germany). The water content in the filtrate was tested using an AKF-1 Karl Fischer moisture titrator (Shanghai Hegong Scientific Instruments Co., Ltd.).

[0060] Preparation Example 1

[0061] This preparation example provides metal salt (bismuth molybdate) particles, the preparation method of which includes:

[0062] 0.97 g of bismuth nitrate and 0.24 g of sodium molybdate were dissolved separately in 10 L of ethylene glycol. The solutions were then mixed using magnetic stirring, while 60 L of anhydrous ethanol was slowly added to form a reaction solution. This reaction solution was then transferred to a polytetrafluoroethylene hydrothermal reactor and reacted at 180 °C for 24 hours. The product after the reaction was completed was collected and washed alternately with deionized water and anhydrous ethanol to remove unreacted reaction solution. After drying, the resulting bismuth molybdate microspheres were obtained. The particle size of the bismuth molybdate microspheres was 1-2 μm. Figure 1 The static water contact angle of the bismuth molybdate microspheres in air is shown to be 6°.

[0063] Preparation Example 2

[0064] This preparation example provides an Fe-doped MOF (HKUST-1) particle, the preparation method of which includes:

[0065] 3.5 mmol H3BTC, 5 mmol Cu(NO3)2·3H2O, and 0.26 mmol FeCl3·6H2O were dissolved separately in 25 mL of ethanol / deionized water (V:V = 1:1) solution using magnetic stirring. The solutions were then mixed and stirred for 1 h to obtain the precursor solution. The prepared precursor solution was transferred to a stainless steel high-pressure reactor lined with polytetrafluoroethylene and reacted at 110 °C for 18 h. After the reaction, the sample was collected and washed repeatedly by centrifugation with ethanol / deionized water (V:V = 1:1) solution to remove unreacted precursor solution. The sample was then dried in a vacuum drying oven at 60 °C to obtain iron-doped HKUST-1MOF particles. Figure 2 The static water contact angle of the iron-doped HKUST-1MOF particles in air is 0°.

[0066] Example 1

[0067] This embodiment provides a superhydrophobic membrane loaded with superhydrophilic particles, the preparation method of which includes:

[0068] (a) Preparation of a rough structure of copper oxalate nanosheets on a copper mesh surface: A copper mesh (pore size 20-50 μm) was pretreated with an organic solvent (at least one of acetone, isopropanol, and ethanol) and an inorganic acid (hydrochloric acid) to remove surface lipid contaminants and oxide layers. Then, copper oxalate nanosheets were grown in situ on the copper mesh skeleton surface through chemical etching: the etching solution was a 1 mol / L oxalic acid solution. The chemical etching process involved immersing the pretreated copper mesh in the oxalic acid etching solution and reacting at 70°C for 7 days, resulting in the deposition of dense copper oxalate nanosheets on the copper mesh surface, forming a rough structure. After the chemical etching reaction was completed, the sample was washed with a large amount of deionized water and then dried in a constant temperature (60°C) forced-air drying oven to obtain a copper mesh with copper oxalate nanosheets on its surface.

[0069] (b) Preparation of superhydrophobic copper mesh substrate: A copper mesh with a rough copper oxalate nanosheet structure on its surface was immersed in a mixed solution of ethanol and water containing hexadecyltrimethoxysilane (by volume, the mixed solution contained 80% ethanol, 18% water, and 2% hexadecyltrimethoxysilane). The reaction was carried out at 60°C for 2 hours. After the reaction, the mesh was rinsed with a large amount of deionized water to remove the physically adsorbed reactants on the surface. Finally, it was dried in a constant temperature drying oven at 60°C to obtain the superhydrophobic copper mesh substrate.

[0070] (c) Preparation of a superhydrophobic membrane loaded with superhydrophilic particles: A superhydrophobic membrane loaded with metal salt particles was prepared by a spray coating process. The precursor solution used for spray coating was a suspension formed by bismuth molybdate microspheres, ethanol, and epoxy resin as described in Preparation Example 1. The concentration of bismuth molybdate microspheres in the suspension was 10 mg / mL, and the mass concentration of epoxy resin was 5%. The well-dispersed precursor solution was placed in a spray gun and sprayed onto the superhydrophobic surface, and cured at 25°C for 2 hours to obtain the superhydrophobic membrane loaded with superhydrophilic particles.

[0071] Figure 3 This shows the SEM image and contact angle diagram of the superhydrophobic copper mesh obtained in step (b) of this embodiment. From... Figure 3 As can be seen, after HDTMS hydrophobic modification, the copper mesh surface possesses a rough structure of copper oxalate nanosheets. Contact angle testing shows that the water contact angle in the air on the surface of the HDTMS-modified copper mesh is 154.1°, confirming its superhydrophobicity. The pore size of the superhydrophobic copper mesh from step (b) is 5 μm.

[0072] Figure 4 The atomic force microscopy (AFM) test results of the copper oxalate nanosheet copper mesh obtained in step (a) of this embodiment show that the surface roughness Ra value of the obtained copper oxalate nanosheet copper mesh is 161 nm, which is greater than the limit of 100 nm for hydrophobic modification roughness.

[0073] The surface microstructure of the superhydrophobic membrane loaded with superhydrophilic particles prepared in Example 1 was observed by SEM, as follows: Figure 5 As shown, the prepared bismuth molybdate microspheres are randomly dispersed on the surface of HDTMS-modified copper oxalate mesh. The size of the bismuth molybdate microspheres is 1-2 μm. The random dispersion of the microspheres helps to expand the effective range of the superhydrophilic particles, enabling the "capture-aggregation" of more emulsified water droplets, thereby achieving more efficient demulsification.

[0074] Example 2

[0075] This embodiment provides a superhydrophobic membrane loaded with superhydrophilic particles, the preparation method of which includes:

[0076] (a) Perform copper mesh pretreatment using the same steps as in Example 1;

[0077] (b) The copper mesh is then oxidized to form a rough structure. The oxidation process includes immersing the pretreated copper mesh in 40 mL of an aqueous solution containing 0.2 mol / L ammonium persulfate and 0.8 mol / L disodium hydrogen phosphate, and reacting at 25 °C for 36 hours. The copper phosphate nanosheets generated by the reaction form a micro-nano rough structure on the surface of the copper mesh.

[0078] (c) The copper mesh after the above reaction is modified to be superhydrophobic in the same way as step (b) in Example 1;

[0079] (d) Using the same method as step (c) of Example 1, superhydrophilic particles are loaded onto the superhydrophobic modified copper mesh to obtain a superhydrophobic mesh film loaded with superhydrophilic particles.

[0080] The superhydrophobic membrane prepared in step (c) of Example 2 was characterized by SEM and its contact angle was tested. Figure 6 The prepared superhydrophobic mesh exhibits a rough structure of copper phosphate nanosheets, with the modified superhydrophobic copper mesh having a pore size of less than 10 μm and greater than or equal to 5 μm. Contact angle testing results show that the contact angle with water in air is 154.7°, confirming its superhydrophobicity.

[0081] Example 3

[0082] This embodiment provides a superhydrophobic membrane loaded with superhydrophilic particles, the preparation method of which includes:

[0083] (a) Perform copper mesh pretreatment using the same steps as in Example 1;

[0084] (b) The pretreated copper mesh was oxidized to form a rough structure. The oxidation process was as follows: the pretreated copper mesh was immersed in 100 mL of an aqueous solution containing 2.97 g of ammonium persulfate and 10 g of sodium hydroxide, and reacted at 25 °C for 30 minutes. The copper hydroxide nanowires generated by the reaction formed a micro-nano rough structure on the surface of the copper mesh.

[0085] (c) The copper mesh after the above reaction is modified to be superhydrophobic in the same way as step (b) in Example 1;

[0086] (d) Using the same method as step (c) of Example 1, superhydrophilic particles are loaded onto the superhydrophobic modified copper mesh to obtain a superhydrophobic mesh film loaded with superhydrophilic particles.

[0087] The superhydrophobic membrane prepared in Example 3 was characterized by SEM and its contact angle was tested. Figure 7 In the image, 'a' is the SEM image of the product from step (b). Figure 7 In the image, b is the SEM image of the product from step (c). Figure 7 In the figure, 'c' represents the static water contact angle test diagram of the product from step (c) in air. For example... Figure 7 As shown, after the oxidation reaction, the copper mesh surface possesses a rough Cu(OH)₂ nanowire structure. Even after hydrophobic modification with hexadecyltrimethoxysilane, the rough Cu(OH)₂ nanowire structure is still retained, and the contact angle test result is 153.2°, confirming its superhydrophobicity. The pore size of the superhydrophobic copper mesh in step (c) is 5-10 μm.

[0088] Figure 8 The atomic force microscopy (AFM) test results of the Cu(OH)2 nanowire copper mesh obtained in step (b) of the above embodiment show that the surface roughness Ra value of the obtained Cu(OH)2 nanowire copper mesh is 148 nm, which is greater than the limit of 100 nm for hydrophobic modification roughness.

[0089] Comparative Example 1

[0090] This comparative example provides a superhydrophobic membrane loaded with MOF particles, the preparation method of which includes:

[0091] (a) A rough structure of copper oxalate nanosheets was prepared on the surface of the copper mesh by the same method as step (a) in Example 1, and a copper mesh with copper oxalate nanosheets on the surface was obtained.

[0092] (b) Preparation of superhydrophobic copper mesh substrate: A copper mesh with a rough copper oxalate nanosheet structure on its surface was immersed in a 5 mmol / L n-dodecyl mercaptan (NDM) / ethanol solution and reacted at room temperature for 30 minutes to modify the copper mesh surface with low surface energy substances. After the reaction, the mesh was rinsed with plenty of deionized water to remove the physically adsorbed reactants. Finally, it was dried in a constant temperature drying oven at 60°C to obtain the superhydrophobic copper mesh.

[0093] (c) Preparation of MOF-loaded superhydrophobic mesh: A MOF-loaded superhydrophobic mesh was prepared using a spin-coating process. The precursor solution used in the spin-coating process was a suspension of iron-doped HKUST-1 and ethanol from Preparation Example 2, with a concentration of 30 mg / mL of iron-doped HKUST-1 in the suspension. The prepared iron-doped HKUST-1 / ethanol suspension (1 mL) was dropped onto the surface of the superhydrophobic copper mesh obtained in step (b) and rotated at 1000 rpm for 10 seconds. The spin-coated copper mesh was then dried by rotating at 3000 rpm to remove residual solvent from the surface. The final membrane was a locally loaded MOF superhydrophobic mesh.

[0094] Figure 9 This shows the SEM image and contact angle diagram of the superhydrophobic copper mesh obtained in step (b) of this comparative example. Figure 9 It can be seen that after hydrophobic modification, the copper oxalate nanosheets on the copper mesh surface are transformed into a bow-shaped micro-nano rough structure, with a significant change in the morphology of the rough structure. The contact angle test result is 152.3°, which is lower than the contact angle of the superhydrophobic mesh obtained in Examples 1 to 3. The surface micromorphology of the locally loaded MOFs superhydrophobic mesh prepared in Comparative Example 1 was observed by SEM, as follows... Figure 10 As shown, iron-doped HKUST-1 particles with regular octahedrons are tightly packed in the porous structure of the copper mesh.

[0095] Test Example 1

[0096] This test example provides an oil (kerosene)-in-water emulsion separation experiment of the superhydrophobic membrane loaded with superhydrophilic particles obtained in Example 1 and the superhydrophobic membrane partially loaded with MOFs obtained in Comparative Example 1.

[0097] Water-in-oil emulsion separation was performed by gravity separation. The superhydrophobic membrane with superhydrophilic particles loaded in Example 1 and the superhydrophobic membrane with partially loaded MOFs obtained in Comparative Example 1 were respectively fixed to flange openings. The feed solution was added from the top of the flange, and the filtrate was collected from the bottom. Various types of kerosene and water were magnetically mixed at a volume ratio of 99:1, and 0.1 g / L Span-80 was added to the mixture. The stirring time was maintained for at least 12 hours to ensure that the prepared water-in-oil emulsion remained stable for at least 24 hours. The particle size of the emulsified water droplets in the water-in-oil emulsion was 500 nm-5 μm. The membrane product of Example 1 had a pore size of 5-10 μm, and the membrane product of Comparative Example 1 had a pore size of 1-5 μm.

[0098] When the emulsion feedstock comes into contact with the copper mesh surface, the continuous oil phase rapidly permeates, while the dispersed emulsified water droplets are efficiently retained by the oil film and then demulsified by the "capture-aggregation" of the superhydrophilic particles, ultimately achieving water-in-oil emulsion separation. The separation results are shown in Table 1.

[0099] The residual water content in the filtrate in Table 1 was determined directly, and the separation flux was calculated using the following formula:

[0100] Flux = Filtrate volume / (Membrane area × Unit time). Where filtrate volume is in L (liters) and membrane area is in m² (meters). 2 The unit of time is h; the unit of flux is L·m⁻²·h⁻¹.

[0101] Table 1

[0102]

[0103] As shown in Table 1, the separation flux of the superhydrophobic membrane loaded with superhydrophilic particles obtained in Example 1 for separating water-in-oil emulsions was 1034.2 L·m⁻²·h⁻¹, and the residual water content in the filtrate was 49.7 ppm. In contrast, the separation flux of the superhydrophobic membrane partially loaded with MOFs obtained in Comparative Example 1 was 832.2 L·m⁻²·h⁻¹, and the residual water content in the filtrate was 80.5 ppm. Clearly, the superhydrophobic membrane loaded with superhydrophilic particles obtained in Example 1 has a higher separation flux and higher separation efficiency; that is, distributing superhydrophilic particles on the surface of a superhydrophobic copper mesh is more conducive to obtaining better water-in-oil emulsion separation results.

[0104] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, alterations, and equivalent transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A superhydrophobic mesh loaded with superhydrophilic particles, the superhydrophobic mesh comprising a mesh substrate and superhydrophilic particles loaded on the mesh substrate; the surface of the mesh substrate has a micro-nano rough structure, the roughness Ra of the micro-nano rough structure being greater than or equal to 100 nm, and the surface of the mesh substrate being hydrophobically modified. The superhydrophilic particles are distributed on the surface of the mesh substrate, and the superhydrophilic particles include hydrophilic metal salt particles and / or hydrophilic metal-organic framework particles.

2. The superhydrophobic membrane loaded with superhydrophilic particles according to claim 1, wherein, The superhydrophilic particles have a static water contact angle of 0°-10° in air.

3. The superhydrophobic membrane loaded with superhydrophilic particles according to claim 1, wherein, The superhydrophilic particles have a particle size of 1-10 μm.

4. The superhydrophobic membrane loaded with superhydrophilic particles according to any one of claims 1-3, wherein, The hydrophilic metal salt particles include bismuth molybdate and / or bismuth tungstate.

5. The superhydrophobic membrane loaded with superhydrophilic particles according to any one of claims 1-3, wherein, The hydrophilic metal-organic framework particles include one or more of Cu-MOFs, ZIF, UIO-66, and MIL.

6. The superhydrophobic membrane loaded with superhydrophilic particles according to claim 1, wherein, The mesh substrate has a static water contact angle of over 150° in air.

7. The superhydrophobic membrane loaded with superhydrophilic particles according to claim 1, wherein, The micro-nano rough structure on the surface of the mesh substrate is made of one or more of copper oxalate, copper phosphate, and copper hydroxide. The morphology of the micro-nano rough structure includes one or more combinations of nanosheets, nanowires, and bow-shaped micro-nano structures.

8. The superhydrophobic membrane loaded with superhydrophilic particles according to claim 1, wherein, The pore size of the mesh substrate without superhydrophilic particles is 5μm-20μm.

9. A method for preparing a superhydrophobic membrane loaded with superhydrophilic particles according to any one of claims 1-8, the method comprising: Micro-nano rough structures are formed on the surface of a metal substrate, and then the metal substrate with micro-nano rough structures is mixed with a hydrophobic modifier for hydrophobic modification to obtain a mesh substrate. A solution of superhydrophilic particles is loaded onto the surface of the mesh substrate by surface coating and then dried to obtain the superhydrophobic mesh film loaded with superhydrophilic particles.

10. The preparation method according to claim 9, wherein, The metal substrate includes copper mesh and / or stainless steel mesh; And / or, the metal substrate has a mesh, the mesh aperture of the metal substrate being 20μm-50μm.

11. The preparation method according to claim 9, wherein, The process of forming micro-nano rough structures on the surface of the metal substrate includes etching and / or oxidation. The etching agent used in the etching includes oxalic acid. The oxidation agent used in the oxidation includes a combination of ammonium persulfate and sodium hydroxide or a combination of ammonium persulfate and disodium hydrogen phosphate. The etching temperature is 60-80℃, and the etching time is more than 5 days; The oxidation temperature is 25-30℃; When the oxidant comprises a combination of ammonium persulfate and sodium hydroxide, the oxidation time is 10-30 minutes; When the oxidant comprises a combination of ammonium persulfate and disodium hydrogen phosphate, the oxidation time is 24-36 hours.

12. The preparation method according to claim 9, wherein, The hydrophobic modifier includes one or more of n-dodecyl mercaptan, hexadecyltrimethoxysilane, and stearic acid.

13. The preparation method according to claim 9, wherein, When the hydrophobic modifier is n-dodecyl mercaptan, the hydrophobic modification temperature is 25-30℃ and the hydrophobic modification time is 10-30 min. When the hydrophobic modifier is hexadecyltrimethoxysilane, the hydrophobic modification temperature is 50-80℃ and the hydrophobic modification time is 2-3 hours. When the hydrophobic modifier is stearic acid, the hydrophobic modification temperature is 25-30℃ and the hydrophobic modification time is 3-5 hours.

14. The preparation method according to claim 9, wherein, When the superhydrophilic particles are metal salt particles, the preparation method of the metal salt particles includes: reacting an inorganic metal source in an alcohol solvent to obtain metal salt particles; The inorganic metal source includes a combination of a molybdenum source and a bismuth source, or a combination of a tungsten source and a bismuth source; The reaction temperature is 170-190℃, and the reaction time is 12-24h.

15. The preparation method according to claim 9, wherein, When the superhydrophilic particles are metal-organic framework particles, the preparation method of the metal-organic framework particles includes: mixing a coordinating metal source and an organic ligand to obtain a precursor solution, and crystallizing the precursor solution to obtain metal-organic framework particles.

16. The preparation method according to claim 15, wherein, The coordination metal source includes one or more of copper, cobalt, iron, zinc, and zirconium sources, and the organic ligand includes pyromellitic acid and / or 2-methylimidazole. The molar ratio of the coordinating metal source to the organic ligand is 5-10:3.5-5.

17. The preparation method according to claim 15, wherein, The crystallization temperature is 100-120℃, and the crystallization time is 12h-36h.

18. The application of the superhydrophobic membrane loaded with superhydrophilic particles as described in any one of claims 1-8 in the separation of water-in-oil emulsions.

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