casting solution, raw material composition, mixed matrix membrane, production method, wastewater treatment method

Abstract

This invention discloses a casting solution, a raw material composition, a mixed matrix membrane, a preparation method, and a wastewater treatment method. The raw material composition of the casting solution includes polysiloxane, a crosslinking agent, a solvent, modified polytetrafluoroethylene (PTFE) micropowder, and a catalyst; the modified PTFE micropowder contains PTFE micropowder and a silane coupling agent. The preparation method of the mixed matrix membrane includes the following steps: coating the surface of a base membrane with the casting solution obtained by reacting the raw material composition of the casting solution, and then curing it to obtain the mixed matrix membrane. The mixed matrix membrane of this invention can efficiently separate alcohol and ether pollutants from water-based paint wastewater, significantly reducing investment and operating costs compared to pure PDMS membranes, further achieving energy conservation, emission reduction, cost reduction, and efficiency improvement.

Description

Technical Field

[0001] This invention relates to the fields of environmental protection and membrane separation technology, specifically to a casting solution, a raw material composition, a mixed matrix membrane, a preparation method, and a wastewater treatment method. Background Technology

[0002] Wastewater from automotive painting workshops includes water-based waste solvents generated during the cleaning of spray guns and the pipelines transporting paint. These water-based waste solvents mainly contain complex components such as paint, organic solvents, surfactants, and curing agents, with a dichromate index (CODcr) content of approximately 300,000 to 800,000 mg / L.

[0003] For industrial wastewater generated in painting workshops, conventional treatment processes first use coagulation and sedimentation to remove paint, hardeners, and other components from the wastewater. The supernatant from the coagulation is then further treated using advanced oxidation technology to remove organic matter. The effluent then enters the plant's biological treatment system for further treatment to meet the discharge standards. Currently, existing treatment methods such as biological treatment, low-temperature evaporation technology, advanced oxidation technology, and reverse osmosis membrane methods suffer from various problems, including excessively high organic load, azeotropic mixing of water and organic matter, unstable operation, high cost, and insensitivity of membrane materials, preventing their practical engineering application.

[0004] Therefore, developing an efficient, environmentally friendly, economical, and stable process for treating water-based waste solvents has become a challenge for the environmental protection industry.

[0005] Pervaporation (PV) membrane separation technology is a novel membrane separation technology. This technology is used for the separation of liquid mixtures, and its outstanding advantage is that it can achieve separation tasks that are difficult to accomplish using traditional methods such as distillation, extraction, and adsorption with low energy consumption. Currently, pervaporation is mainly used for solvent dehydration, separation of organic solvents, and as a substitute for or partial substitute for distillation, with solvent dehydration already having been applied on a large scale industrially. The patent application number CN201920455502.1, "A Waterborne Coating Wastewater Treatment System," mentions the use of pervaporation to treat waterborne waste solvents. The treated effluent not only meets the requirements of biochemical treatment loads, but the concentrated liquid from membrane separation can also be reused in the production line, achieving the reduction and resource utilization of waterborne waste solvents. Currently, the functional layer of pervaporation membranes is mainly polymethylhydrosiloxane (PDMS). However, this type of membrane suffers from uneven dispersion and unstable membrane performance during preparation. Therefore, the use of inorganic particles, including zeolite, silica, carbon molecular sieve, MOF, etc., to modify PDMS has become a hot research direction, because these inorganic particles can not only enhance the hydrophobicity of the membrane surface, but also overcome the shortcomings of organic polymer membranes such as poor mechanical strength and chemical stability.

[0006] For example, patents CN101264429A, CN107081068A, CN107519770A, CN 110180414A, and CN 112999884A disclose the use of inorganic particles such as zeolite and silica to modify PDMS, further demonstrating that doping with hydrophobic materials can indeed improve the permeation flux of pervaporation composite membranes for treating organic matter. However, after the above-mentioned inorganic particles modify PDMS, the permeation membrane exhibits poor permeability to alcohol and ether solvents.

[0007] Polytetrafluoroethylene (PTFE) powder is an organic fluoropolymer and a common hydrophobic dopant. Patent CN104014259A discloses a method for preparing a hydrophobic separation membrane, wherein the hydrophobic monomers are fluorinated vinylidene, fluorinated acrylate, and fluorinated methacrylate, each containing 6-14 carbon atoms and 9-21 fluorine atoms. This study primarily investigates the membrane's hydrophobicity, rather than its preferential permeability to alcohols and ethers, and is not intended for the treatment of aqueous waste solvents. Patent CN117732277A discloses a high-flux superhydrophobic composite membrane and its preparation method. This involves preparing a microporous composite membrane with a micro-nano hierarchical structure using PTFE submicron particles and three-dimensional nanomaterials, and using it for vacuum membrane distillation to remove salt from water. This study primarily investigates the membrane's desalination performance, rather than its preferential permeability to alcohols and ethers, and is not intended for the treatment of aqueous waste solvents.

[0008] Therefore, how to provide a matrix membrane that can preferentially permeate alcohol and ether solvents in pervaporation membrane separation technology is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to overcome the defect that the matrix membrane preferentially permeates alcohol ether solvents in the existing pervaporation membrane separation technology, and to provide a casting solution, raw material composition, mixed matrix membrane, preparation method and wastewater treatment method.

[0010] The mixed matrix membrane of this invention disperses PTFE micropowder with a silane coupling agent (e.g., an ethanol solution of a silane coupling agent) to prepare a hydrophobic modified PTFE micropowder that preferentially permeates alcohol ethers. By doping the modified PTFE micropowder, a strongly hydrophobic, high-flux permeable mixed matrix membrane that preferentially permeates alcohol ethers can be prepared. This mixed matrix membrane can efficiently separate alcohol ether pollutants from water-based paint wastewater. Compared with pure PDMS membranes, it can greatly reduce investment and operating costs, further achieving energy conservation, emission reduction, cost reduction and efficiency improvement.

[0011] This invention provides a raw material composition for casting liquid, which includes polysiloxane, crosslinking agent, solvent, modified polytetrafluoroethylene micro powder, and catalyst;

[0012] The modified polytetrafluoroethylene micro powder contains polytetrafluoroethylene micro powder and a silane coupling agent.

[0013] In this invention, the type of polysiloxane can be a type of polysiloxane conventional in the art, such as hydroxyl-terminated polysiloxane.

[0014] In some embodiments of the present invention, the polysiloxane is a polymethylsiloxane, such as polydimethylsiloxane.

[0015] In some embodiments of the present invention, the polysiloxane is a hydroxyl-terminated polymethylsiloxane, or, for example, a hydroxyl-terminated polydimethylsiloxane.

[0016] In some embodiments of the present invention, the molecular weight of the polysiloxane is 1,000 to 100,000, for example, 10,000.

[0017] In some embodiments of the present invention, the polysiloxane was purchased from Jiangxi Xinghuo Factory.

[0018] In this invention, the crosslinking agent can be a conventional crosslinking agent in the art that can crosslink polysiloxanes, such as one or more of tetraethyl orthosilicate (TEOS), methyltrimethoxysilane, and vinyltriethoxysilane, and also, for example, tetraethyl orthosilicate.

[0019] In this invention, the solvent can be a conventional volatile solvent in the art, capable of dissolving the polysiloxane and the crosslinking agent without participating in the polymerization reaction, such as one or more of n-heptane, toluene, and n-hexane, or n-heptane.

[0020] In this invention, the polytetrafluoroethylene in the polytetrafluoroethylene micro powder can be conventional polytetrafluoroethylene in the art, such as polytetrafluoroethylene with a molecular weight of 10,000 to 100,000, polytetrafluoroethylene with a molecular weight of 50,000 to 100,000, or polytetrafluoroethylene with a molecular weight of 50,000.

[0021] In some embodiments of the present invention, the polytetrafluoroethylene is purchased from Dongguan Zhanyang Polymer Materials Co., Ltd.

[0022] In this invention, the average particle size of the polytetrafluoroethylene micro powder can be a conventional average particle size in the art, for example, 1~10μm, or even 2μm.

[0023] In this invention, the silane coupling agent can be one or more of the conventional silane coupling agents in the art, such as KH-570, KH560 and KH550, preferably KH570, i.e. γ-methacryloyloxypropyltrimethoxysilane.

[0024] In this invention, the mass ratio of the polytetrafluoroethylene micro powder to the silane coupling agent can be 10:(0.25~5.0), for example 10:1, 10:3 or 10:5.

[0025] In this invention, the silane coupling agent in the modified polytetrafluoroethylene micro powder modifies the surface of the polytetrafluoroethylene micro powder, thereby enabling the polytetrafluoroethylene to be uniformly dispersed.

[0026] In some embodiments of the present invention, the preparation method of the modified polytetrafluoroethylene micro powder includes the following steps:

[0027] The modified polytetrafluoroethylene (PTFE) micropowder is prepared by mixing and modifying the dispersion containing the PTFE micropowder and the silane coupling agent.

[0028] The pH of the dispersion containing the polytetrafluoroethylene micropowder can be 8-10, for example, 9.

[0029] The pH of the dispersion containing the polytetrafluoroethylene micropowder can be adjusted using a pH adjuster, such as ammonia.

[0030] The solvent in the dispersion containing the polytetrafluoroethylene micropowder can be a conventional solvent in the art, such as ethanol, or ethanol with a volume fraction of 50%.

[0031] In the preparation method of the modified polytetrafluoroethylene micro powder, the dispersion containing the polytetrafluoroethylene micro powder can be prepared by conventional methods in the art, such as mixing the polytetrafluoroethylene micro powder and a solvent and then dispersing it by ultrasound.

[0032] The ultrasonic dispersion time can be 10-20 minutes, for example, 15 minutes.

[0033] In the preparation method of the modified polytetrafluoroethylene micro powder, the mixing process can be a conventional process in the art, such as adding the silane coupling agent dropwise to the dispersion containing the polytetrafluoroethylene micro powder under stirring conditions.

[0034] The stirring can be done using a pneumatic stirrer.

[0035] The stirring can be carried out under constant temperature conditions.

[0036] The stirring temperature can be 20~30℃, for example 25℃.

[0037] In the method for preparing the modified polytetrafluoroethylene micro powder, the silane coupling agent may exist in the form of a solution containing the silane coupling agent, such as an ethanol solution containing the silane coupling agent.

[0038] In the solution containing the silane coupling agent, the mass concentration of the silane coupling agent can be 1-5%, for example 3%.

[0039] In the preparation method of the modified polytetrafluoroethylene micro powder, the modification process can be a conventional process in the art, such as modification under rapid stirring conditions, modification at 800~1200 r / min, or modification at 1000 r / min.

[0040] In the preparation method of the modified polytetrafluoroethylene micro powder, the modification temperature can be 20~30℃, for example 25℃.

[0041] In the preparation method of the modified polytetrafluoroethylene micro powder, the modification time can be 1~5 h, for example 3~5 h, or even 3 h.

[0042] The preparation method of the modified polytetrafluoroethylene micro powder may further include steps such as centrifugation and drying after modification.

[0043] The drying temperature can be 60~80℃.

[0044] In a preferred embodiment of the present invention, the method for preparing the modified polytetrafluoroethylene micropowder includes the following steps:

[0045] Polytetrafluoroethylene (PTFE) micropowder was dispersed in an ethanol-ammonia solution and ultrasonically dispersed. Then, an ethanol solution of silane coupling agent was added dropwise, and the mixture was rapidly stirred at 1000 r / min for modification. After washing, centrifugation, and drying, the modified PTFE micropowder was obtained.

[0046] In this invention, the average particle size of the modified polytetrafluoroethylene micropowder can be 1~10μm.

[0047] In this invention, the catalyst can be a type of catalyst commonly used in the art for the reaction of polysiloxanes and crosslinking agents, such as dibutyltin dilaurate.

[0048] In this invention, the amount of polysiloxane used can be the amount of polysiloxane commonly used in the art, for example, the mass ratio of polysiloxane to crosslinking agent is 10:(0.75~1.25), or for example, 10:1.

[0049] In this invention, the amount of catalyst used can be the conventional amount of catalyst used in the art, for example, the mass ratio of the catalyst to the crosslinking agent is (0.3~1.0):1, for example (0.3~0.5):1, or for example 0.5:1.

[0050] In this invention, the amount of solvent used can be the amount of solvent conventional in the art, for example, the mass ratio of the solvent to the crosslinking agent is (20~100):1, for example (20~50):1, or even 50:1.

[0051] In some embodiments of the present invention, the mass ratio of the modified polytetrafluoroethylene micro powder to the crosslinking agent may be (1~5):1, for example (2~5):1, or even 2:1, 3:1, or 4:1.

[0052] In one embodiment of the present invention, the mass ratio of the polysiloxane, the crosslinking agent, the catalyst, the solvent, and the modified polytetrafluoroethylene micro powder is 10:1:(0.3~0.5):(20~50):(2~5), for example 10:1:0.5:50:2, 10:1:0.5:50:3, or 10:1:0.5:50:4.

[0053] The present invention also provides a modified polytetrafluoroethylene micro powder, which is composed of polytetrafluoroethylene micro powder and a silane coupling agent.

[0054] The polytetrafluoroethylene micro powder can be as described above.

[0055] The silane coupling agent can be as described above.

[0056] The preparation method of the modified polytetrafluoroethylene micro powder can be as described above.

[0057] The present invention also provides a method for preparing a casting solution, which includes the following steps: reacting the raw material composition of the casting solution to obtain the casting solution.

[0058] In a preferred embodiment of the present invention, the method for preparing the casting solution includes the following steps:

[0059] The polysiloxane, the crosslinking agent, the solvent, and the modified polytetrafluoroethylene micro powder are mixed for the first time to obtain mixture A;

[0060] The mixture A and the catalyst are mixed a second time to obtain mixture B;

[0061] The mixture B is reacted to obtain the casting solution.

[0062] In this invention, the terms "first time" and "second time" have no special meaning; they only indicate the order in which they were mixed.

[0063] In this invention, the first mixing can be carried out under stirring conditions.

[0064] The stirring speed for the first mixing step can be 800~1000 r / min, for example, 800 r / min.

[0065] The stirring time for the first mixing can be 1 to 5 hours, for example 3 to 5 hours, or even 3 hours.

[0066] In this invention, the reaction time can be 10-30 min, for example 15-30 min, or even 15 min.

[0067] In this invention, the reaction temperature can be 20~30℃, for example 25℃.

[0068] In this invention, the endpoint of the reaction can be when the viscosity of the casting solution reaches 30~50 mPa·s, for example 40 mPa·s.

[0069] In this invention, the viscosity of the casting solution can be 30~50 mPa·s, for example 40 mPa·s.

[0070] In this invention, the viscosity can be measured using a Hammerson Viscolite XL7-100B portable viscometer.

[0071] In this invention, the casting solution is generally subjected to degassing post-treatment.

[0072] The degassing post-treatment method may be to let it stand for 0.5 to 1 hour, for example, 0.5 hours.

[0073] In this invention, in the raw material composition of the casting solution, under the action of the catalyst, the polysiloxane and the crosslinking agent undergo a crosslinking reaction, and the product is generally a low surface energy PDMS.

[0074] The present invention also provides a casting solution, which is prepared by the above method.

[0075] The present invention also provides a method for preparing a hybrid matrix membrane, comprising the following steps:

[0076] The casting solution is coated onto the surface of the base film and cured to obtain the hybrid matrix film.

[0077] The coating thickness of the casting solution can be 5~300 μm, for example 150 μm.

[0078] The coating method can be a conventional coating method in the art, such as blade coating.

[0079] The base membrane material can be a conventional material in the art that can provide support, such as fluorine materials, polyvinylidene fluoride (PVDF), or PVDF membrane purchased from Shenzhen Jiaquan Membrane Filter Equipment Co., Ltd.

[0080] The curing temperature can be 60~100℃, for example 80℃.

[0081] The curing time can be 2 to 10 hours, for example 6 to 10 hours, or even 6 hours.

[0082] Before curing, the casting solution can be left to stand at room temperature for 1 to 2 hours, for example, 2 hours, after being coated onto the base film layer.

[0083] The present invention also provides a hybrid matrix membrane prepared by the above method.

[0084] The present invention also provides a hybrid matrix membrane comprising a functional layer and a base film layer, wherein the functional layer comprises polysiloxane A and polytetrafluoroethylene micropowder and a silane coupling agent dispersed in the polysiloxane A;

[0085] The polysiloxane A is prepared by cross-linking reaction of polysiloxane and cross-linking agent.

[0086] In some embodiments of the present invention, the polytetrafluoroethylene micro powder and the silane coupling agent may be as described above.

[0087] In some embodiments of the present invention, the polysiloxane may be as described above.

[0088] In some embodiments of the present invention, the functional layer is formed by curing the casting liquid.

[0089] The curing temperature can be 60~100℃, for example 80℃.

[0090] The curing time can be 2 to 10 hours, for example 6 to 10 hours, or even 6 hours.

[0091] Before curing, the casting solution can be left to stand at room temperature for 1 to 2 hours, for example, 2 hours, after being coated on the support layer.

[0092] The material of the base membrane layer can be a conventional material in the art that can provide support, such as polyvinylidene fluoride (PVDF), or a polyvinylidene fluoride membrane purchased from Shenzhen Jiaquan Membrane Filter Equipment Co., Ltd.

[0093] The present invention also provides a pervaporation membrane assembly comprising the aforementioned mixed matrix membrane.

[0094] In a preferred embodiment of the present invention, the pervaporation membrane assembly sequentially includes a first cover plate, a first graphite gasket, a first mixed matrix membrane, a stainless steel support plate, a non-woven fabric, a second mixed matrix membrane, a second graphite gasket, and a second cover plate.

[0095] In a preferred embodiment of the present invention, a stainless steel flow guide layer is further included between the mixed matrix membrane and the stainless steel support plate.

[0096] In a preferred embodiment of the present invention, in the pervaporation membrane assembly, the effective area of ​​the mixed matrix membrane is 0.1~15 m². 2 For example, 0.13m 2 .

[0097] In this invention, the effective area refers to the area that can produce an actual treatment effect during the wastewater treatment process.

[0098] The present invention also provides a pervaporation apparatus, which includes a pervaporation system, the pervaporation system including the pervaporation membrane assembly.

[0099] In a preferred embodiment of the present invention, the pervaporation device includes a feed tank, a circulating pump, the pervaporation membrane assembly, a condensation system, and a vacuum pump.

[0100] In a preferred embodiment of the present invention, the liquid tank is placed in a heating device, such as a water bath.

[0101] In a preferred embodiment of the present invention, the condensation system may include a condensation tank and a cooling tank.

[0102] The volume of the liquid tank can be 5 to 1000 L.

[0103] The circulating pump can provide a stable flow rate on the feed liquid side, with a flow rate range of 1~10 L / min, for example 5 L / min.

[0104] The total membrane area that can be packed into the pervaporation system can range from 0.1 to 15 m². 2 Between, for example, 0.1m 2 .

[0105] The pervaporation system is typically maintained at a temperature of 40-80°C, for example, 65°C.

[0106] The condensation system can maintain a constant temperature in the permeate heat exchanger, with a pressure range generally between -10 and 0°C, for example, -5°C.

[0107] The vacuum pump can provide a constant pressure on the feed liquid permeation side, with a pressure range of 200~1000 Pa, for example, between 200~800 Pa, or even 800 Pa.

[0108] The present invention also provides a method for treating wastewater, which includes the following steps:

[0109] The wastewater is treated using the pervaporation device.

[0110] In this invention, the wastewater may be an aqueous waste solvent or an aqueous ink cleaning waste liquid.

[0111] The CODcr in the wastewater can be between 150,000 and 200,000 mg / L, for example, 178,000 mg / L or 192,000 mg / L.

[0112] The content of ethylene glycol monobutyl ether in the aqueous waste solvent can be 6.5~7.5 wt%, where the percentage refers to the mass percentage.

[0113] The total organic matter content in the aqueous waste solvent can be 13.5~15.5 wt%, where the percentage refers to the mass percentage.

[0114] The isopropanol content in the water-based ink cleaning waste liquid can be 7.5~10 wt%, where the percentage refers to the mass percentage.

[0115] The total organic matter content in the water-based ink cleaning waste liquid is 12.5~14.5wt%, where the percentage refers to the mass percentage.

[0116] In this invention, the terminology is explained as follows:

[0117] Polytetrafluoroethylene (PTFE)

[0118] Polymethylhydrosiloxane (PDMS)

[0119] KH-570: γ-methacryloyloxypropyltrimethoxysilane;

[0120] Tetraethyl orthosilicate (TEOS)

[0121] Polyvinylidene fluoride (PVDF)

[0122] Dibutyltin dilaurate T-12, abbreviated as DBTDL;

[0123] Dichromate index: dichromate oxidizability, abbreviated as CODcr.

[0124] Permeation flux: The amount of substance that permeates per unit membrane area per unit time during membrane separation.

[0125] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0126] The reagents and raw materials used in this invention are all commercially available.

[0127] The positive and progressive effects of this invention are as follows:

[0128] (1) This invention is the first to prepare a strongly hydrophobic, high-flux preferentially permeable alcohol ether pervaporation mixed matrix membrane by doping modified PTFE micro powder, and apply it to the treatment of water-based waste solvents in automotive coating. It can solve the problem of disposal of such high-concentration organic hazardous waste in a low-cost, high-stability and high-efficiency manner, and can better realize its low-carbon reduction and resource utilization benefits.

[0129] (2) In this invention, a pervaporation mixed matrix membrane is prepared by using doped modified PTFE micro powder. SEM shows that the PTFE micro powder is evenly distributed on the membrane surface and can form a relatively dense separation layer on the membrane surface, which can prevent water from passing through and preferentially allow alcohols and ethers to pass through. Moreover, the preparation method is simple and inexpensive, providing a valuable reference for subsequent scale-up production.

[0130] (3) Compared with the existing pure PDMS membranes used in engineering applications, the pervaporation mixed matrix membrane prepared by doped modified PTFE micro powder provided in this invention can increase the permeation flux by 35-45%, greatly reducing equipment investment and operating costs, and resulting in significant economic benefits. Attached Figure Description

[0131] Figure 1 This is a scanning electron microscope (SEM) image of the surface of the pervaporated mixed matrix membrane in Example 2.

[0132] Figure 2 These are schematic diagrams of the membrane module structures in Examples 1-3 and Comparative Examples 1-2.

[0133] Figure 3 The diagram shows the pervaporation process in Examples 1-3 and Comparative Examples 1-2.

[0134] in:

[0135] 201: Flow guiding layer; 202: Graphite gasket; 203: Pervaporation membrane; 204: Stainless steel support plate with non-woven fabric.

[0136] 1: Feed tank, 2: Heating device, 3: Water inlet pump, 4: Membrane module, 5: Condensate tank, 6: Cooling tank, 7: Vacuum pump. Detailed Implementation

[0137] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0138] The terminology is explained below:

[0139] Polytetrafluoroethylene (PTFE)

[0140] Polymethylhydrosiloxane (PDMS)

[0141] KH-570: γ-methacryloyloxypropyltrimethoxysilane;

[0142] Tetraethyl orthosilicate (TEOS)

[0143] Polyvinylidene fluoride (PVDF)

[0144] Dibutyltin dilaurate T-12, abbreviated as DBTDL;

[0145] Dichromate index: dichromate oxidizability, abbreviated as CODcr.

[0146] Permeation flux: The amount of substance that permeates per unit membrane area per unit time during membrane separation.

[0147] The properties and sources of each raw material in the following examples and comparative examples are described below:

[0148] Polymethylsiloxane: hydroxyl-terminated polydimethylsiloxane with a molecular weight of 10,000, purchased from Jiangxi Xinghuo Factory;

[0149] Polytetrafluoroethylene: molecular weight 50,000, purchased from Dongguan Zhanyang Polymer Materials Co., Ltd.

[0150] Polyvinylidene fluoride membrane: Finished membrane, purchased from Shenzhen Jiaquan Membrane Filtration Equipment Co., Ltd.;

[0151] Molecular sieve: Mesoporous molecular sieve SBA-15;

[0152] Zeolite: MFI type zeolite.

[0153] Viscosity was measured using a Heimerson Viscolite XL7-100B portable viscometer.

[0154] Example 1

[0155] (1) Disperse polytetrafluoroethylene powder (average particle size of powder is 2 μm) in a 50% (50% refers to the volume concentration of ethanol) ethanol-ammonia solution at pH=9, and ultrasonically disperse for 15 min. Then, stir with a pneumatic stirrer under constant temperature (25℃), and slowly add an ethanol solution containing 3% (percentage refers to mass concentration) KH-570 (mass ratio of polytetrafluoroethylene powder to KH-570 is 10:1). Stir rapidly (1000 r / min) under constant temperature (25℃) for 3 h. Then, centrifuge the mixture, vacuum dry (60~80℃), and grind it to obtain modified polytetrafluoroethylene micro powder (average particle size of powder is 1~10 μm).

[0156] (2) Mix 10 parts PDMS, 1 part TEOS, 50 parts n-heptane and 2 parts modified polytetrafluoroethylene (PTFE) micro powder, stir at 800 r / min for 3 h, add 0.5 parts DBTDL, continue stirring at 800 r / min for 15 min (the reaction temperature is 25℃) until the reaction viscosity reaches 40 mpa.s, stop stirring, and let stand for 0.5 h to remove bubbles for later use;

[0157] (3) Pour the casting solution in (2) evenly onto the PVDF ultrafiltration membrane, and coat it with a certain thickness (wet membrane) on the surface of the base membrane using a scraper. Control the coating thickness to be 150 μm to obtain a liquid coating. Let it stand at room temperature for 2 hours, and then transfer it to an oven and heat it at 80°C for 6 hours to obtain a PDMS / PVDF pervaporation mixed matrix membrane doped with polytetrafluoroethylene micropowder.

[0158] (4) Take 0.13m 2 (Effective size of a single membrane: 0.205*0.16m, structure as follows) Figure 2 The hybrid matrix membrane module (shown) was used in a test device to treat pretreated water-based waste solvent from an automobile factory and water-based ink cleaning waste from a printing factory. The CODcr of the feed liquid was between 150,000 and 200,000 mg / L. The pervaporation operation parameters were: feed temperature 65℃, vacuum degree on the gas phase side 800 Pa, condensation temperature -5℃, and flow rate on the feed liquid side 5L / min.

[0159] Example 2

[0160] (1) Disperse polytetrafluoroethylene powder (average particle size of powder is 2 μm) in a 50% (50% refers to the volume concentration of ethanol) ethanol-ammonia solution at pH=9, and ultrasonically disperse for 15 min. Then, stir with a pneumatic stirrer under constant temperature (25℃), and slowly add an ethanol solution containing 3% (percentage refers to the mass concentration) of KH-570 (mass ratio of polytetrafluoroethylene powder to KH-570 is 10:3). Stir rapidly (1000 r / min) under constant temperature (25℃) for 3 h. Then, centrifuge the mixture, vacuum dry (60~80℃), and grind it to obtain modified polytetrafluoroethylene micro powder (average particle size of powder is 1~10 μm).

[0161] (2) Mix 10 parts PDMS, 1 part TEOS, 50 parts n-heptane and 3 parts modified polytetrafluoroethylene (PTFE) micro powder, stir at 800 r / min for 3 h, add 0.5 parts DBTDL, continue stirring at 800 r / min for 15 min (the reaction temperature is 25℃) until the reaction viscosity reaches 40 mpa.s, stop stirring, and let stand for 0.5 h to remove bubbles for later use;

[0162] (3) Pour the casting solution in (2) evenly onto the PVDF ultrafiltration membrane, and coat it with a certain thickness (wet membrane) on the surface of the base membrane using a scraper. Control the coating thickness to be 150 μm to obtain a liquid coating. Let it stand at room temperature for 2 hours, and then transfer it to an oven and heat it at 80°C for 6 hours to obtain a PDMS / PVDF pervaporation mixed matrix membrane doped with polytetrafluoroethylene micropowder.

[0163] (4) Take 0.13m 2 (Effective size of a single membrane: 0.205*0.16m, structure as follows) Figure 2 The PDMS / PVDF pervaporation hybrid matrix membrane module doped with polytetrafluoroethylene micropowder (as shown) was used to treat pretreated water-based waste solvent from an automobile factory and water-based ink cleaning waste liquid from a printing factory on a test device. The CODcr of the feed liquid was between 150,000 and 200,000 mg / L. The pervaporation operation parameters were: feed temperature 65℃, vacuum degree on the gas phase side 800 Pa, condensation temperature -5℃, and flow rate on the feed liquid side 5L / min.

[0164] Example 3

[0165] (1) Disperse polytetrafluoroethylene powder (average particle size of powder is 2 μm) in a 50% (50% refers to the volume concentration of ethanol) ethanol-ammonia solution at pH=9, and ultrasonically disperse for 15 min. Then, stir with a pneumatic stirrer under constant temperature (25℃), and slowly add an ethanol solution containing 3% (percentage refers to the mass concentration) of KH-570 (the mass ratio of polytetrafluoroethylene powder to KH-570 is 10:5). Stir rapidly (1000 r / min) under constant temperature (25℃) for 3 h. Then, centrifuge the mixture, vacuum dry (60~80℃), and grind it to obtain modified polytetrafluoroethylene micro powder (average particle size of powder is 1~10 μm).

[0166] (2) Mix 10 parts PDMS, 1 part TEOS, 50 parts n-heptane and 4 parts modified polytetrafluoroethylene (PTFE) micro powder, stir at 800 r / min for 3 h, add 0.5 parts DBTDL, continue stirring at 800 r / min for 15 min (the reaction temperature is 25℃) until the reaction viscosity reaches 40 mpa.s, stop stirring, and let stand for 0.5 h to remove bubbles for later use;

[0167] (3) Pour the casting solution from (2) evenly onto the PVDF ultrafiltration membrane, and coat it with a certain thickness (wet membrane) on the surface of the base membrane using a scraper. Control the coating thickness to be 150 μm to obtain a liquid coating. Let it stand at room temperature for 2 hours, and then transfer it to an oven and heat it at 80°C for 6 hours to obtain a PDMS / PVDF pervaporation mixed matrix membrane doped with polytetrafluoroethylene micropowder.

[0168] (4) Take 0.13m 2 (Effective size of a single membrane: 0.205*0.16m, structure as follows) Figure 2 (As shown) A PDMS / PVDF pervaporation hybrid matrix membrane module doped with polytetrafluoroethylene micropowder was used to treat pretreated water-based waste solvent from an automobile factory and water-based ink cleaning waste liquid from a printing factory on a test device. The CODcr of the feed liquid was between 150,000 and 200,000 mg / L. The pervaporation operation parameters were: feed temperature 65℃, vacuum degree on the gas phase side 800 Pa, condensation temperature -5℃, and flow rate on the feed liquid side 5L / min.

[0169] Comparative Example 1

[0170] (1) Mix 10 parts PDMS, 1 part TEOS, 50 parts n-heptane and 3 parts mesoporous molecular sieve SBA-15, stir at 800 r / min for 3 h, add 0.5 parts DBTDL, continue stirring at 800 r / min for 15 min (the reaction temperature is 25℃) until the reaction viscosity reaches 40 mpa.s, stop stirring, and let stand for 0.5 h to remove bubbles for later use;

[0171] (2) Pour the casting solution from (1) evenly onto the PVDF ultrafiltration membrane, and coat it with a doctor blade to a certain thickness (wet membrane) on the surface of the base membrane. Control the coating thickness to be 150 μm to obtain a liquid coating. Let it stand at room temperature for 2 hours, and then transfer it to an oven and heat it at 80°C for 6 hours to obtain a PDMS / PVDF pervaporation membrane.

[0172] (3) Take 0.13m 2 (Effective size of a single membrane: 0.205*0.16m, structure as follows) Figure 2 The PDMS / PVDF pervaporation membrane module (shown) was used in a test device to treat pretreated water-based waste solvent from an automobile factory and water-based ink cleaning waste from a printing factory. The CODcr of the feed liquid was between 150,000 and 200,000 mg / L. The pervaporation operation parameters were: feed temperature 65℃, vacuum degree on the gas phase side 800 Pa, condensation temperature -5℃, and flow rate on the feed liquid side 5L / min. Comparative Example 2

[0173] (1) Mix 10 parts PDMS, 1 part TEOS, 50 parts n-heptane and 3 parts MFI zeolite, stir at 800 r / min for 3 h, add 0.5 parts DBTDL, continue stirring at 800 r / min for 15 min (the reaction temperature is 25℃) until the reaction viscosity reaches 40 mpa.s, stop stirring, let stand for 0.5 h to remove bubbles and set aside;

[0174] Steps (2) and (3) are the same as steps (2) and (3) in Comparative Example 1.

[0175] Example 1

[0176] (1) Take the pervaporated mixed matrix membrane from step (3) of Example 2 and observe its surface scanning electron microscope (SEM) image, as follows. Figure 1 As shown in the figure, SEM reveals that the modified PTFE micropowder (i.e., modified polytetrafluoroethylene micropowder) in Example 2 is uniformly distributed on the membrane surface, forming a relatively dense separation layer on the membrane surface, which can prevent water from passing through and preferentially allow alcohol ethers to pass through.

[0177] (2) Take the pervaporation mixed matrix membrane modules from Examples 1-3 and Comparative Examples 1-2 and treat water-based waste solvent and water-based ink cleaning waste liquid respectively. The CODcr of these feed liquids are all between 150,000 and 200,000 mg / L. The pervaporation operation process parameters are: feed temperature is 65℃, vacuum degree on the gas phase side is 800 Pa, condensation temperature is -5℃, and flow rate on the feed liquid side is 5L / min.

[0178] A schematic diagram of the pervaporation process is shown below. Figure 3 As shown.

[0179] The raw materials tested were water-based waste solvents generated during the color-changing process in the painting workshop of an automobile factory and high-concentration water-based ink cleaning waste liquid generated during the printing and packaging process.

[0180] The aqueous waste solvent contained 6.5-7.5 wt% ethylene glycol monobutyl ether and 13.5-15.5 wt% total organic matter. The CODcr of the influent was 178,000 mg / L.

[0181] The isopropanol content in the water-based ink cleaning wastewater was 7.5~10 wt%, the total organic matter content was 12.5~14.5 wt%, and the CODcr of the influent was 192000 mg / L.

[0182] Table 1. Comparison of the effects of the examples and comparative examples on the treatment of water-based waste solvents and water-based ink cleaning waste liquids.

[0183]

[0184] As shown in Table 1, compared with Comparative Examples 1-2, the pervaporation mixed matrix membranes prepared by doping modified PTFE micropowder in Examples 1-3 significantly improved the permeation flux of alcohol ether solvents and could efficiently separate alcohol ether pollutants in water-based paint waste. It can be seen that the PDMS membrane modified by inorganic particle molecular sieves, zeolites, etc. has poor permeability to alcohol ether solvents.

Claims

1. A method for preparing a casting solution, characterized in that, It includes the following steps: reacting the raw material composition of the casting solution to obtain the casting solution; The raw material composition of the casting solution includes polysiloxane, crosslinking agent, solvent, modified polytetrafluoroethylene micro powder, and catalyst; The mass ratio of the polysiloxane, the crosslinking agent, the catalyst, the solvent, and the modified polytetrafluoroethylene micro powder is 10:1:(0.3~0.5):(20~50):(2~5). (1) The modified polytetrafluoroethylene micro powder contains polytetrafluoroethylene micro powder and silane coupling agent. The polytetrafluoroethylene in the polytetrafluoroethylene micro powder is polytetrafluoroethylene with a molecular weight of 10,000 to 100,000. The type of silane coupling agent is one or more of KH-570, KH560 and KH550. The preparation method of the modified polytetrafluoroethylene micro powder includes the following steps: The modified polytetrafluoroethylene (PTFE) micro powder is prepared by mixing and modifying the dispersion containing the PTFE micro powder and the silane coupling agent; the pH of the dispersion containing the PTFE micro powder is 8-10. In the preparation method of the modified polytetrafluoroethylene micro powder, the mixing process is as follows: under stirring conditions, the silane coupling agent is added dropwise to the dispersion containing the polytetrafluoroethylene micro powder; the silane coupling agent exists in the form of a solution containing the silane coupling agent, and the mass concentration of the silane coupling agent in the solution is 1~5%; (2) The preparation method of the casting solution includes the following steps: The polysiloxane, the crosslinking agent, the solvent, and the modified polytetrafluoroethylene micro powder are mixed for the first time to obtain mixture A; The mixture A and the catalyst are mixed a second time to obtain mixture B; The mixture B is reacted to obtain the casting solution.

2. The method for preparing the casting solution as described in claim 1, characterized in that, The method for preparing the casting solution satisfies one or more of the following conditions: (1) The polysiloxane is polymethylsiloxane or hydroxyl-terminated polysiloxane; (2) The molecular weight of the polysiloxane is 1,000 to 100,000; (3) The crosslinking agent is one or more of tetraethyl orthosilicate, methyltrimethoxysilane, and vinyltriethoxysilane: (4) The solvent is one or more of n-heptane, toluene, and n-hexane; (5) The polytetrafluoroethylene in the polytetrafluoroethylene micro powder has a molecular weight of 50,000 to 100,000; (6) The average particle size of the polytetrafluoroethylene micro powder is 1~10μm; (7) The mass ratio of the polytetrafluoroethylene micro powder to the silane coupling agent is 10:(0.25~5.0). (8) The pH of the dispersion containing the polytetrafluoroethylene micro powder is 9; (9) The pH of the dispersion containing the polytetrafluoroethylene micro powder is adjusted using ammonia water; (10) The solvent in the dispersion containing the polytetrafluoroethylene micro powder is ethanol with a volume fraction of 50%; (11) In the preparation method of the modified polytetrafluoroethylene micro powder, the preparation method of the dispersion containing the polytetrafluoroethylene micro powder is: after mixing the polytetrafluoroethylene micro powder and the solvent, it is obtained by ultrasonic dispersion; (12) In the preparation method of the modified polytetrafluoroethylene micro powder, during the mixing process: the stirring temperature is 20~30℃; (13) In the method for preparing the modified polytetrafluoroethylene micro powder, the mass concentration of the silane coupling agent in the solution containing the silane coupling agent is 3%; (14) In the preparation method of the modified polytetrafluoroethylene micro powder, the modification process is as follows: modification is carried out at 800~1200 r / min. (15) In the preparation method of the modified polytetrafluoroethylene micro powder, the modification temperature is 20~30℃; (16) In the preparation method of the modified polytetrafluoroethylene micro powder, the modification time is 1~5 h; (17) The average particle size of the modified polytetrafluoroethylene micro powder is 1~10μm; (18) The catalyst is dibutyltin dilaurate; (19) The mass ratio of the catalyst to the crosslinking agent is 0.5:1; (20) The mass ratio of the solvent to the crosslinking agent is 50:1; (21) The mass ratio of the modified polytetrafluoroethylene micro powder to the crosslinking agent is 2:1, 3:1, or 4:1; (22) The stirring speed for the first mixing is 800~1000 r / min; (23) The stirring time for the first mixing is 1 to 5 hours; (24) The reaction time is 10~30 min; (25) The reaction temperature is 20~30℃; (26) The endpoint of the reaction is when the viscosity of the casting solution reaches 30-50 mPa·s; and (27) The type of silane coupling agent is KH-570.

3. The method for preparing the casting solution as described in claim 2, characterized in that, The method for preparing the casting solution satisfies one or more of the following conditions: (1) The molecular weight of the polysiloxane is 10,000; (2) The crosslinking agent is tetraethyl orthosilicate; (3) The solvent is n-heptane; (4) The average particle size of the polytetrafluoroethylene micro powder is 2 μm; (5) The mass ratio of the polytetrafluoroethylene micro powder to the silane coupling agent is 10:1, 10:3 or 10:5; (6) The ultrasonic dispersion time is 10~20 min; (7) In the preparation method of the modified polytetrafluoroethylene micro powder, the modification process is as follows: modification at 1000 r / min. (8) In the preparation method of the modified polytetrafluoroethylene micro powder, the modification time is 3~5 h; (9) The mass ratio of the polysiloxane, the crosslinking agent, the catalyst, the solvent, and the modified polytetrafluoroethylene micro powder is 10:1:0.5:50:2, 10:1:0.5:50:3, or 10:1:0.5:50:4; (10) The stirring time for the first mixing is 3-5 h; (11) The reaction time is 15-30 min; and (12) The endpoint of the reaction is when the viscosity of the casting solution reaches 40 mPa·s.

4. A casting solution, characterized in that, It is prepared by the method of any one of claims 1-3.

5. A method for preparing a hybrid matrix membrane, characterized in that, It includes the following steps: The casting solution described in claim 4 is coated onto the surface of the base film and cured to obtain the mixed matrix film.

6. The method for preparing the hybrid matrix membrane as described in claim 5, characterized in that, The coating thickness of the casting solution is 5~300 μm.

7. The method for preparing the hybrid matrix membrane as described in claim 5, characterized in that, The coating thickness of the casting solution is 150 μm.

8. The method for preparing a hybrid matrix membrane as described in claim 5, characterized in that, The coating method is blade coating.

9. The method for preparing a hybrid matrix membrane as described in claim 5, characterized in that, The base film is made of fluorine.

10. The method for preparing the hybrid matrix membrane as described in claim 5, characterized in that, The base membrane is made of polyvinylidene fluoride.

11. The method for preparing a hybrid matrix membrane as described in claim 5, characterized in that, The curing temperature is 60~100℃.

12. The method for preparing a hybrid matrix membrane as described in claim 5, characterized in that, The curing time is 2 to 10 hours.

13. The method for preparing a hybrid matrix membrane as described in claim 5, characterized in that, The curing time is 6~10 hours.

14. A hybrid matrix membrane, characterized in that, The mixed matrix membrane was prepared by the method described in any one of claims 5-13.

15. A pervaporation membrane module, characterized in that, It includes the hybrid matrix membrane as described in claim 14.

16. The pervaporation membrane assembly as described in claim 15, characterized in that, The pervaporation membrane assembly sequentially includes a first cover plate, a first graphite gasket, a first mixed matrix membrane, a stainless steel support plate, a non-woven fabric, a second mixed matrix membrane, a second graphite gasket, and a second cover plate.

17. The pervaporation membrane assembly as claimed in claim 16, characterized in that, A stainless steel flow guide layer is also included between the hybrid matrix membrane and the stainless steel support plate.

18. The pervaporation membrane assembly as claimed in claim 15, characterized in that, In the aforementioned pervaporation membrane assembly, the effective area of ​​the mixed matrix membrane is 0.1~15 m². 2 .

19. The pervaporation membrane assembly as described in claim 15, characterized in that, In the aforementioned pervaporation membrane assembly, the effective area of ​​the mixed matrix membrane is 0.13 m². 2 .

20. A pervaporation device, characterized in that, It includes a pervaporation system, which includes a pervaporation membrane assembly as described in any one of claims 15-19.

21. The pervaporation apparatus as described in claim 20, characterized in that, The pervaporation device includes a feed tank, a circulating pump, the pervaporation membrane assembly, a condensation system, and a vacuum pump.

22. A method for treating wastewater, characterized in that, It includes the following steps: Wastewater is treated using a pervaporation membrane module as described in any one of claims 15-19 or a pervaporation device as described in claim 20 or 21.

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