Superhydrophobic membrane for membrane distillation

Abstract

The present invention relates to a superhydrophobic membrane for membrane distillation, comprising a polymer base layer, a superhydrophobic layer and a nanocoating layer. The polymer base layer can be formed by electrospinning, phase separation, spray coating, blow spinning, roll coating or dip coating, and the superhydrophobic layer can be formed by electrospraying, chemical vapor deposition, physical vapor deposition, sputtering, atomic layer deposition, sol-gel coating, electrospinning, dip coating, spin coating, spray coating or plasma coating.

Description

Superhydrophobic membrane for membrane distillation

[0001] The present invention relates to a superhydrophobic membrane for membrane distillation, and more specifically, to a nanowire-coated superhydrophobic membrane for membrane distillation.

[0002] Membrane distillation (MD) is a technology that utilizes temperature differences to evaporate water, then transfer the vapor through a membrane and condense it to recover pure water. This technology operates at lower temperatures (e.g., 40-80°C) than conventional distillation methods and offers the advantage of producing high-purity water with low energy consumption.

[0003] Membrane distillation uses a hydrophobic (water-repellent) membrane to separate liquids and gases. On one side of the membrane (the feed side) is high-temperature water, while on the other side (the permeate side) is relatively cool water, an aqueous solution, or air. This temperature difference creates a partial vapor pressure difference between the two sides of the membrane. Water evaporates on the high-temperature side with the higher vapor pressure and passes through the membrane as vapor. The vapor then passes through the membrane and condenses on the low-temperature permeate side, where it is recovered as pure water. Furthermore, salts, organic matter, and microorganisms cannot pass directly through the membrane, so they are separated from the highly concentrated wastewater.

[0004] There are four main membrane distillation methods. First, direct contact membrane distillation (DCMD), the most common method, involves a membrane structure in which both sides of the membrane are in direct contact with liquid water. The vapor evaporated from the hot feedwater passes through the membrane and is condensed by direct contact with cooling water on the opposite side. This method offers the advantages of simple structure and easy condensation, but suffers from high heat loss and low energy efficiency. Second, air gap membrane distillation (AGMD) involves placing an air gap between the membrane and the condensing surface, allowing the vapor to pass through the air gap and condense on the cold surface. While this method has low heat loss and relatively high energy efficiency, the long vapor travel distance can slow the distillation rate. Third, sweep gas membrane distillation (SGMD) uses air (or an inert gas) to transport the vapor on the permeate side and then condense it externally. This method minimizes heat loss during the vapor condensation process and can maintain a high distillation rate, but the requirement for an external condenser can complicate the system. Finally, vacuum membrane distillation (VMD) creates a vacuum on the permeate side of the membrane to remove vapor, which is then condensed in an external condenser. This method can maintain a high distillation rate and operate at low temperatures, but the requirement for a vacuum system can increase operating costs.

[0005] A key advantage of membrane distillation technology is its ability to operate at low temperatures. Because it typically operates at relatively low temperatures, typically between 40 and 80°C, it can be combined with renewable energy sources like solar and waste heat. Furthermore, it can handle much higher salt concentrations than reverse osmosis (RO), ensuring high water quality. Its superior removal of salts, organic matter, and heavy metals makes it an ideal water purification technology. Furthermore, because it does not require high pressure, it offers lower maintenance costs compared to other water purification technologies like RO. Furthermore, its hydrophobic membrane reduces suspended solids and microbial adhesion, reducing membrane fouling.

[0006] Accordingly, membrane distillation technology is utilized in diverse fields, including seawater desalination, industrial wastewater treatment, the food and pharmaceutical industries, and the semiconductor and electronics industries. In seawater desalination, it is used to purify seawater into drinking water, while in industrial wastewater treatment, it is used to purify high-salinity and hazardous wastewater. Furthermore, in the food and pharmaceutical industries, it is used for concentration processes such as juice concentration and milk dehydration, and in the semiconductor and electronics industries, it is used for ultrapure water production.

[0007] However, membrane distillation technology also has several limitations. First, its high energy consumption is a major issue, and hybrid systems utilizing solar energy, waste heat, and other technologies are being developed to address this. Second, wetting can occur in hydrophobic membranes over time, and to prevent this, advanced hydrophobic membranes with strong chemical resistance are being developed. Third, scaling and fouling problems exist, but these can be mitigated through regular cleaning and high-quality pretreatment. Furthermore, its production rate is lower than that of traditional reverse osmosis processes, limiting its processing speed. Furthermore, the hydrophobic membranes may deteriorate over long periods of use. Consequently, membrane distillation membranes have not yet been commercialized due to their limited lifespan and low throughput. Therefore, the development of membranes with high throughput and high durability is urgently needed.

[0008] An object of the present invention to solve the above-mentioned problems is to provide a superhydrophobic membrane for membrane distillation having low operating temperature, high processing flow rate, high durability, long lifespan, low membrane fouling, suppressed wettability, and high salt removal effect.

[0009] Another object of the present invention to solve the above-mentioned problems is to provide a membrane distillation system including a superhydrophobic membrane for membrane distillation having low operating temperature, high processing flow rate, high durability, long life, low membrane fouling, suppressed wettability, and high salt removal effect.

[0010] Another object of the present invention to solve the above-mentioned problems is to provide a membrane distillation method having low operating temperature, high processing flow rate, high durability, long life, low membrane fouling, suppressed wettability, and high salt removal effect.

[0011] However, the problem to be solved by the present invention is not limited to this, and may be expanded in various ways without departing from the spirit and scope of the present invention.

[0012] A superhydrophobic membrane for membrane distillation according to one embodiment of the present invention for achieving the aforementioned purpose may include a polymer base layer, a superhydrophobic layer, and a nanocoating layer.

[0013] According to one aspect, the polymer base layer can be formed by a method of electrospinning, phase separation, spray coating, blow spinning, roll coating or dip coating.

[0014] According to one aspect, the superhydrophobic layer can be formed by a method of electrospraying, chemical vapor deposition (CVD), physical vapor deposition (PVD), sputtering, atomic layer deposition (ALD), sol-gel coating, electrospinning, dip coating, spin coating, spray coating, or plasma coating.

[0015] According to one aspect, the nanocoating layer can be formed by a method of chemical vapor deposition (CVD), physical vapor deposition (PVD), sputtering, atomic layer deposition (ALD), sol-gel coating, electrospinning, electrospraying, dip coating, spin coating, spray coating, or plasma coating.

[0016] According to one aspect, the polymer base layer may include one or more of Pellethane, thermoplastic polyurethane (TPU), polytetrafluoroethylene (PTFE), polypropylene (PP), polyvinylidene fluoride (PVDF), poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP), polydimethylsiloxane (PDMS), polyetheretherketone (PEEK), polyarylethersulfone (PAES), and fluorinated ethylene propylene (FEP).

[0017] According to one aspect, the superhydrophobic layer may include one or more of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), polydimethylsiloxane (PDMS), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), fluorinated ethylene propylene (FEP), polyhedral oligomer silsesquioxane (POSS), a mixture of PVDF-HFP and PDMS, and a mixture of PVDF-HFP and POSS.

[0018] According to one aspect, the nanocoating layer may include one or more of Parylene C, Parylene D, Parylene F, Parylene AF-4, polytetrafluoroethylene (PTFE), poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), fluorinated ethylene propylene (FEP), fluorinated silane, polydimethylsiloxane (PDMS), polyhedral oligomeric silsesquioxane (POSS), carbon nanotubes, graphene-based coatings, silica, a mixture of PVDF-HFP and PDMS, and a mixture of PVDF-HFP and POSS.

[0019] According to one aspect, the treatment flux of the superhydrophobic membrane for membrane distillation is 25 L / m 2 h to 40L / m 2 It could be h.

[0020] According to one aspect, the treatment flux when the superhydrophobic membrane for membrane distillation is stretched by 50% is 35 L / m 2 h to 50L / m 2 It could be h.

[0021] According to one aspect, the superhydrophobic layer may include microspheres.

[0022] According to one aspect, the nanocoating layer may include nanowires.

[0023] According to one aspect, the membrane distillation efficiency of the superhydrophobic membrane for membrane distillation can be 99.9% to 99.99%.

[0024] According to one aspect, the contact angle of the superhydrophobic membrane for membrane distillation may be 150 to 180°.

[0025] According to one aspect, the polymer base layer may be formed by electrospinning, the superhydrophobic layer may include microspheres formed by electrospraying, and the nanocoating layer may include nanowires formed by chemical vapor deposition.

[0026] According to one aspect, the polymer base layer may include a Pellethane base layer formed by electrospinning, the superhydrophobic layer may include microspheres of poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) and polydimethylsiloxane (PDMS) formed by electrospraying, and the nanocoating layer may include Parylene C nanowires formed by chemical vapor deposition.

[0027] In addition, a membrane distillation system according to one embodiment of the present invention for achieving the aforementioned purpose may include a superhydrophobic membrane for membrane distillation including a polymer base layer, a superhydrophobic layer, and a nanocoating layer.

[0028] In addition, a membrane distillation method including a superhydrophobic membrane for membrane distillation according to an embodiment of the present invention for achieving the above-described object includes a first step of positioning a feed channel having a higher temperature than a permeate channel on one side of the superhydrophobic membrane for membrane distillation and positioning a permeate channel having a lower temperature than the feed channel on the other side of the superhydrophobic membrane for membrane distillation; a second step of generating a partial vapor pressure difference due to a temperature difference between the feed channel and the permeate channel, so that water evaporates on the high-temperature feed channel side having a high vapor pressure and passes through the superhydrophobic membrane for membrane distillation in the form of vapor; and a third step of recovering vapor as water while condensing on the low-temperature permeate channel side having vapor passed through the superhydrophobic membrane for membrane distillation; wherein the superhydrophobic membrane for membrane distillation may include a polymer base layer, a superhydrophobic layer, and a nanocoating layer.

[0029] In addition, a method for manufacturing a superhydrophobic membrane for distillation according to one embodiment of the present invention for achieving the above-described purpose may include a first step of manufacturing a membrane by forming a polymer base layer through electrospinning; a second step of forming a superhydrophobic layer on both sides of the polymer base layer manufactured in the first step through electrospraying; and a third step of forming a nanocoating layer on both sides of the membrane manufactured in the second step, on which the superhydrophobic layer is formed on both sides of the polymer base layer.

[0030] The disclosed technology may have the following effects. However, this does not mean that a particular embodiment must include all or only the following effects, and thus the scope of the disclosed technology should not be construed as being limited thereby.

[0031] According to the superhydrophobic membrane for membrane distillation according to one embodiment of the present invention described above, it can exhibit low operating temperature, high processing flow rate, high durability, long lifespan, low membrane fouling, suppressed wettability, and high salt removal effect.

[0032] According to a membrane distillation system including a superhydrophobic membrane for membrane distillation according to an embodiment of the present invention described above, it can exhibit low operating temperature, high processing flow rate, high durability, long life, low membrane fouling, suppressed wettability, and high salt removal effect.

[0033] In addition, according to the membrane distillation method according to one embodiment of the present invention described above, it can exhibit low operating temperature, high processing flow rate, high durability, long life, low membrane fouling, suppressed wettability, and high salt removal effect.

[0034] In addition, according to the superhydrophobic membrane for membrane distillation of the present invention, membrane fouling is suppressed due to the nano-coating layer (e.g., Parylene C coating), and it has a high processing speed due to the superhydrophobicity and stable structure, and it has excellent durability by using a pellet material that can be mechanically stretched, and it is suitable for processing various solutions because the pore size can be controlled, and it can be operated even at a low heat source (about 60℃), so it can utilize energy such as waste heat and solar heat, and it is economical and environmentally friendly, and it maintains a membrane distillation efficiency of 99.9% or more, for example, 99.99% or more, and it has a higher salt removal effect than the RO method by maintaining performance even in a high-concentration salt solution, and it can be applied to solutions that are difficult to process with existing membranes, such as industrial wastewater and waste battery electrolyte, and it has improved superhydrophobicity compared to existing membranes, so that the evaporation speed is faster, and it can provide excellent processing flow rate and processing speed, and compared to using two or more membranes in the past, the membrane manufacturing time is shortened by applying one membrane. It has the effect of increasing the possibility of commercializing membrane distillation technology by shortening the time, simplifying the manufacturing process, and lowering the manufacturing cost compared to existing membranes.

[0035] Figure 1 shows the basic principle of membrane distillation (MD).

[0036] Figure 2 shows a conceptual diagram of the experimental setup of the present invention.

[0037] Figure 3 shows an image of the experimental setup of the present invention.

[0038] Figure 4 is a schematic diagram showing electrospinning (left), electrospraying (center), and perylene coating (right) during the manufacturing process of a superhydrophobic membrane for membrane distillation according to the present invention.

[0039] Figure 5a is a photograph showing electrospray at 95% RH.

[0040] Figure 5b is a photograph showing the appearance of 0.1 g of Parylene C coated after electrospraying at 50% RH.

[0041] Figure 5c is a photograph showing the appearance of 0.2 g of Parylene C coated after electrospraying at 50% RH.

[0042] Figure 5d shows the measured thickness of the nanowires for electrospraying at 95% RH, electrospraying at 50% RH followed by 0.1 g of Parylene C coating, and electrospraying at 50% RH followed by 0.2 g of Parylene C coating.

[0043] Figure 6a is a graph comparing the treatment flux per unit area for 24 hours between a superhydrophobic membrane for membrane distillation according to the present invention (gray) and a commercial PVDF membrane (black).

[0044] Figure 6b is a comparative graph of conductivity changes over 24 hours between a superhydrophobic membrane for membrane distillation according to the present invention (gray) and a commercial PVDF membrane (black).

[0045] Figure 7a is a graph comparing the treatment flux per area for 10 hours when the superhydrophobic membrane for membrane distillation according to the present invention is not mechanically stretched (triangles) and when it is mechanically stretched by 50% (circles).

[0046] Figure 7b is a comparative graph of conductivity changes over 10 hours in the case where the superhydrophobic membrane for membrane distillation according to the present invention is not mechanically stretched (triangles) and in the case where it is mechanically stretched by 50% (circles).

[0047] Figure 8 shows contact angle measurement data of a commercial PVDF membrane (left), a membrane that has been electrosprayed (center), and a superhydrophobic membrane for membrane distillation according to the present invention with Parylene C coating (right).

[0048] Figure 9 is a schematic diagram showing the principle by which superhydrophobic properties are maintained in a flexible structure.

[0049] Figure 10a is an SEM image (magnifications of 200, 1000, 2000, 5000, 10000) of the membrane surface after a 24-hour membrane distillation test of a membrane without Parylene C coating.

[0050] FIG. 10b is an SEM image (magnifications of 200, 1000, 2000, 5000, and 10000) of the membrane surface of a superhydrophobic membrane for membrane distillation according to the present invention with Parylene C coating completed after a 24-hour membrane distillation test.

[0051] Figure 11a is an SEM image of a superhydrophobic membrane for membrane distillation according to the present invention when no mechanical tension is applied.

[0052] Figure 11b is a SEM image of a superhydrophobic membrane for membrane distillation according to the present invention when it is mechanically stretched 100% along the x-axis.

[0053] The present invention can be modified in various ways and has various embodiments, and specific embodiments are illustrated in the drawings and described in detail.

[0054] However, this is not intended to limit the present invention to a specific embodiment, but should be understood to include all modifications, equivalents, or substitutes included in the spirit and technical scope of the present invention.

[0055] While terms such as "first" and "second" may be used to describe various components, these components should not be limited by these terms. These terms are used solely to distinguish one component from another. For example, without departing from the scope of the present invention, a first component may be referred to as a "second component," and similarly, a second component may also be referred to as a "first component." The term "and / or" includes any combination of multiple related items described herein or any item among multiple related items described herein.

[0056] When a component is referred to as being "connected" or "connected" to another component, it should be understood that it may be directly connected or connected to that other component, but that there may be other components intervening. Conversely, when a component is referred to as being "directly connected" or "connected" to another component, it should be understood that there are no other components intervening.

[0057] The terminology used in this application is only used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, it should be understood that the terms "comprise" or "have" indicate the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0058] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and will not be interpreted in an idealized or overly formal sense unless explicitly defined herein.

[0059] Hereinafter, with reference to the attached drawings, preferred embodiments of the present invention will be described in more detail. In order to facilitate an overall understanding in describing the present invention, identical reference numerals will be used for identical components in the drawings, and redundant descriptions of identical components will be omitted.

[0060]

[0061] Membrane distillation (MD) is a separation process using a semi-permeable membrane that allows only vapor to pass through a liquid by utilizing a temperature difference. This technology can operate at a lower temperature (40-80℃) than general distillation, and has the advantage of being environmentally friendly and economical in that it can utilize low-temperature heat sources such as waste heat or solar heat. The present invention discloses a superhydrophobic membrane for membrane distillation and a membrane distillation method that can remove salt with high efficiency and high purity from water having a concentration similar to seawater (3.5%). In the case of NaCl, Na in water + ions and Cl - Since they exist as ions and each ion is a monovalent ion with an extremely small ion size, the removal rate in general membrane methods such as microfiltration, ultrafiltration, and nanofiltration is very low. In addition, reverse osmosis shows a limit of treatment salt concentration of about 10% due to membrane fouling caused by increased salt concentration in the influent and an increase in required pressure due to increased osmotic pressure. Specifically, seawater reverse osmosis (SWRO) shows a limit of treatment salt concentration of about 6-7%, and disc tube reverse osmosis (DTRO) shows a limit of treatment salt concentration of about 10%. Therefore, research and development on membrane distillation is needed as a complementary alternative technology to solve the current RO concentrated water problem.

[0062] Existing commercial membranes have limitations, such as relatively low superhydrophobicity and limited throughput. Conversely, high-performance membranes developed in laboratories, while offering excellent superhydrophobicity, suffer from poor durability, hindering long-term use. To address these issues, the present invention developed a membrane that simultaneously combines high superhydrophobicity, durability, and superior throughput. Furthermore, compared to existing commercial polytetrafluoroethylene (PTFE) membranes, this membrane offers the advantage of lower manufacturing costs, thereby aiming to accelerate the commercialization of membrane distillation technology.

[0063]

[0064] Hereinafter, the configuration and structure of the superhydrophobic membrane for membrane distillation according to the present invention are described, but are not limited thereto.

[0065] According to one aspect, the superhydrophobic membrane for membrane distillation according to the present invention includes a multilayer structure, and may include, but is not limited to, a polymer base layer, a superhydrophobic layer, and a nanocoating layer, and may further include other layers.

[0066]

[0067] The polymer base layer according to the present invention may not have superhydrophobicity, but is preferably mechanically stretchable. Examples of the polymer base layer according to the present invention include, but are not limited to, Pellethane, thermoplastic polyurethane (TPU), polytetrafluoroethylene (PTFE), polypropylene (PP), polyvinylidene fluoride (PVDF), poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP), polydimethylsiloxane (PDMS), polyetheretherketone (PEEK), polyarylethersulfone (PAES), fluorinated ethylene propylene (FEP), and the like. The polymer base layer according to the present invention may be formed by, but is not limited to, electrospinning, phase separation, spray coating, blow spinning, roll coating, dip coating, and the like. The thickness of the polymer base layer according to the present invention may be 50 to 500 μm, preferably 50 to 300, or 50 to 200 μm.

[0068] In one aspect, the polymer base layer according to the present invention can be formed by electrospinning. Electrospinning is a technology that converts a polymer solution or melt into nanofibers using a high-voltage electric field. First, a voltage of several kilovolts to several tens of kilovolts is applied to a syringe or nozzle, forming an electric field with a grounded collecting plate on the opposite side. As the electric field increases, an electrostatic force acts on the surface of the solution, forming a Taylor cone that balances the surface tension. When the voltage exceeds a certain level, the solution is ejected as a thin, thread-like electrospinning jet, which is elongated and thinned by the electric field and air resistance. During this process, the solvent in the solution evaporates, leaving behind fibers, and the melt cools and solidifies. The nanofibers thus generated are collected on the collecting plate and can be arranged randomly or in a specific direction.

[0069]

[0070] The superhydrophobic layer according to the present invention is designed to prevent water droplets from blocking the pores of the membrane so that only vapor can pass through the membrane. The superhydrophobic layer according to the present invention may include, but is not limited to, poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), polydimethylsiloxane (PDMS), PTFE, PVDF, FEP, polyhedral oligomeric silsesquioxane (POSS), a mixture of PVDF-HFP and PDMS, a mixture of PVDF-HFP and POSS, and the like. The superhydrophobic layer according to the present invention may be formed in the form of, but is not limited to, a laminate, a microsphere, a nanowire, a nanofiber, a colloid assembly, a thin film coating, and the like. The superhydrophobic layer according to the present invention can be formed by a method such as chemical vapor deposition (CVD), physical vapor deposition (PVD), sputtering, atomic layer deposition (ALD), sol-gel coating, electrospinning, electrospraying, dip coating, spin coating, spray coating, plasma coating, etc., but is not limited thereto.

[0071] In one aspect, the superhydrophobic layer according to the present invention can be formed by electrospraying. Electrospray is a technology that uses a strong electric field to atomize a liquid into fine droplets. When a high voltage (several kV to tens of kV) is applied to a nozzle, an electrostatic force acts on the surface of the solution, forming a Taylor cone. As the electric field becomes stronger, the solution is ejected in the form of a thin jet, which is then broken up into fine droplets by surface tension and electrostatic repulsion. These droplets can become smaller as the solvent evaporates, or they can be uniformly distributed on the surface while maintaining a charged state.

[0072] The superhydrophobic layer according to the present invention may preferably include a microsphere shape including PVDF-HFP and PDMS. In addition, the shape of the microsphere according to the present invention may be spherical, cylindrical, tubular, rod-shaped, etc., but is not limited thereto. The thickness of the superhydrophobic layer according to the present invention may be 1 to 50 μm, preferably 5 to 40, or 10 to 30 μm. In addition, the diameter of the microsphere according to the present invention may be 500 nm to 10 μm, preferably 800 nm to 5 μm, or 1 to 5 μm, or 1 to 3 μm.

[0073] Meanwhile, the microspheres according to the present invention can play a role in increasing the efficiency of membrane distillation by forming many microscopic air pockets on the surface of the membrane, thereby changing the surface of the membrane into a superhydrophobic one and increasing the contact area of ​​the surface of the membrane with water.

[0074]

[0075] The nanocoating layer according to the present invention can be formed into a nanowire structure by nanocoating to enhance the adhesion stability of the microspheres. The nanocoating layer according to the present invention may include, but is not limited to, Parylene C, Parylene D, Parylene F, Parylene AF-4, PTFE, PVDF-HFP, FEP, fluorinated silane, PDMS, POSS, carbon nanotubes, graphene-based coating, silica, a mixture of PVDF-HFP and PDMS, a mixture of PVDF-HFP and POSS, etc. The nanocoating layer according to the present invention can be formed by a method such as chemical vapor deposition (CVD), physical vapor deposition (PVD), sputtering, atomic layer deposition (ALD), sol-gel coating, electrospinning, electrospraying, dip coating, spin coating, spray coating, plasma coating, etc., but is not limited thereto.

[0076] In one aspect, the nanocoating layer according to the present invention can be formed using a chemical vapor deposition method. Chemical vapor deposition (CVD) is a technique for forming a thin film by injecting a gaseous precursor (reactive gas) into a reaction chamber and heating the substrate to induce a chemical reaction. The precursor gas decomposes on the substrate surface or reacts with another gas to deposit the desired material, and any unwanted byproducts are removed in gaseous form.

[0077]

[0078] The nanocoating layer according to the present invention may include forming a nanowire structure by coating with Parylene C, preferably by a chemical vapor deposition method. While existing microsphere-based superhydrophobic membranes had structural instability as a problem, the present invention further maintains the structure by additionally coating with Parylene C on the microsphere-based superhydrophobic membrane. In addition, Parylene C also plays a role in improving the processing speed by increasing the contact area with water. The thickness of the nanocoating layer according to the present invention may be 30 nm to 500 nm, preferably 50 nm to 400 nm, or 80 nm to 200 nm. When the nanocoating layer is in the form of nanowires, the diameter of the nanowires may be 30 nm to 500 nm, preferably 50 nm to 400 nm, or 80 nm to 200 nm.

[0079]

[0080] According to one aspect, the total thickness of the superhydrophobic membrane for membrane distillation according to the present invention may be 50 to 600 μm, preferably 80 to 500 μm, or 100 to 300 μm, or 100 to 200 μm.

[0081] According to one aspect, the contact angle of the superhydrophobic membrane for membrane distillation according to the present invention is 150 to 180°, preferably 155 to 170°, and more preferably 158 to 165°.

[0082] According to one aspect, the treatment flux of the superhydrophobic membrane for membrane distillation according to the present invention is 25 L / m 2 h to 40L / m 2 h may be, but is not limited to,

[0083] According to one aspect, when the superhydrophobic membrane for membrane distillation according to the present invention is stretched by 50%, the treatment flux is 35 L / m. 2 h to 50L / m2 h may be, but is not limited to,

[0084] According to one aspect, the membrane distillation efficiency (separation efficiency) of the superhydrophobic membrane for membrane distillation according to the present invention may be 99.9% to 99.99%, but is not limited thereto.

[0085]

[0086] According to one aspect, a superhydrophobic membrane for membrane distillation according to the present invention may include pellets as a polymer base layer, microspheres including PVDF-HFP and PDMS as a superhydrophobic layer, and a Parylene C coating as a nanocoating layer.

[0087] According to one aspect, the polymer base layer of the superhydrophobic membrane for membrane distillation according to the present invention may be formed by electrospinning, the superhydrophobic layer may include microspheres formed by electrospraying, and the nanocoating layer may include nanowires formed by chemical vapor deposition.

[0088] According to one aspect, the polymer base layer of the superhydrophobic membrane for membrane distillation according to the present invention may include a Pellethane base layer formed by electrospinning, the superhydrophobic layer may include microspheres of poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) and polydimethylsiloxane (PDMS) formed by electrospraying, and the nanocoating layer may include Parylene C nanowires formed by chemical vapor deposition.

[0089]

[0090] The superhydrophobic membrane for membrane distillation according to the present invention has several distinct advantages compared to conventional membranes. By forming a microsphere structure on the membrane surface, water is prevented from directly contacting the pelletan membrane in a liquid state, allowing only gasified water vapor to pass through the pores of the membrane. Furthermore, since a larger membrane surface area allows a greater amount of water to be converted into gas, the microsphere and nanowire structures maximize the contact area with water, thereby increasing the processing speed. In the membrane distillation (MD) process, a greater temperature difference between the two sides results in a higher driving force. Parylene C, with its excellent insulating properties, reduces the thermal conductivity of the membrane according to the present invention, suppresses the decrease in temperature gradient, and thus increases distillation efficiency. Furthermore, the Parylene C coating inhibits microsphere shedding and scaling, including PVDF-HFP and PDMS. And since the seams of the fibers of the pellet, which is the polymer base layer of the superhydrophobic membrane for membrane distillation according to the present invention, are cross-linked with each other, and furthermore, since it has the rigid properties of the Parylene C nanowires, the mechanical strength of the superhydrophobic membrane for membrane distillation according to the present invention can be improved by more than twice. As a result, even if the thickness of the membrane is reduced by half compared to the existing one, the LEP (liquid entry pressure, the minimum pressure required for a liquid to pass through the membrane) value can be higher. Furthermore, due to the reduced thickness of the membrane, the resistance to the movement of water vapor is reduced, so that a higher permeation rate can be achieved, and since it is wrapped with a material (Parylene C coating) that is highly biocompatible and has a low diffusion coefficient, the possibility of residual organic solvent diffusion, which was a problem of the existing electrospun membrane, can be reduced.

[0091]

[0092] Meanwhile, the microsphere structures manufactured previously had very irregular and complex shapes, and SEM analysis confirmed the presence of very thin nanowire structures of less than 50 nm. However, the existing PVDF-HFP-based nanowire structures formed extremely thinly had the limitation of being too thin to function as structural support. To compensate for this, research was conducted to increase the thickness to the level of 100 nm using the electrospraying technique in an ultra-high humidity (over 95% RH) environment. However, this method was difficult to apply in practice due to reproducibility and facility issues.

[0093] In order to solve these reproducibility problems and equipment problems in ultra-high humidity environments, in the present invention, very thin nanowires were formed through electrospray in a general laboratory environment (50% RH level), and then Parylene C was vapor deposited to increase the thickness of the nanowires to several hundred nm, for example, 100 to 500 nm. This enabled the nanowires to serve as a structural support and prevent the microspheres and nanostructures from falling off. In addition, Parylene C increases the contact area with water, further improving the processing speed. The membrane manufactured in this way secured durability in which the microsphere structure did not fall off even under external force, and showed stability in which the structure was maintained even after long-term use.

[0094]

[0095] One embodiment of membrane distillation according to the present invention will be described with reference to FIG. 1 as follows. On the left side of the membrane is a feed channel containing high-temperature seawater, and on the right side is a permeate channel containing relatively low-temperature freshwater. Due to this temperature difference, a partial vapor pressure difference occurs on both sides of the membrane, and water evaporates on the high-temperature side with high vapor pressure and passes through the membrane in the form of vapor. Afterwards, the vapor passes through the membrane and is condensed on the low-temperature permeate side, where it is recovered as pure water.

[0096]

[0097] An embodiment of membrane distillation according to the present invention will be described with reference to FIGS. 2 and 3. A thermometer is used to maintain a constant temperature in a feed tank. A hot plate serves to increase and maintain the temperature of the feed tank. A gear pump is used to circulate the fluid. A log computer measures and records data from an electronic balance. The electronic balance is a device for measuring the weight change in a permeate tank. A heat exchanger maintains a constant temperature using cooling water from a chiller before the fluid from the permeate tank is fed into a membrane module. A conductivity meter is used to continuously measure the conductivity of the permeate tank. The chiller maintains a constant cooling temperature in the permeate tank. Finally, the membrane module serves to allow the feed stream and permeate stream to flow alternately across the membrane.

[0098] According to one aspect, a membrane distillation method including a superhydrophobic membrane for membrane distillation according to the present invention comprises: a first step of positioning a feed channel having a higher temperature than a permeate channel on one side of the superhydrophobic membrane for membrane distillation and positioning a permeate channel having a lower temperature than the feed channel on the other side of the superhydrophobic membrane for membrane distillation; a second step of generating a partial vapor pressure difference due to a temperature difference between the feed channel and the permeate channel, so that water evaporates on the high-temperature feed channel side having a high vapor pressure and passes through the superhydrophobic membrane for membrane distillation in the form of vapor; and a third step of recovering vapor as water while condensing on the low-temperature permeate channel side having vapor passed through the superhydrophobic membrane for membrane distillation; wherein the superhydrophobic membrane for membrane distillation may include a polymer base layer, a superhydrophobic layer, and a nanocoating layer.

[0099]

[0100] Hereinafter, the manufacturing process of the superhydrophobic membrane for membrane distillation according to the present invention will be described with reference to examples.

[0101]

[0102] 1. Example 1: Membrane fabrication through electrospinning of polymer solution

[0103]

[0104] (1) Example 1-1: Preparation of polymer solution for membrane production

[0105] Prepare Pellethane 2363-80AE from Lubrizol, dimethylformamide (DMF) from Samchun Chemicals, South Korea, and tetrahydrofuran (THF) from Samchun Chemicals, South Korea.

[0106] A solution containing 10 wt% of Pelletane 2363-80AE and THF and DMF organic solvents in a volume ratio of 6:4 was mixed well using a stirrer for more than one day.

[0107]

[0108] (2) Example 1-2: Electrospinning of polymer solution for membrane production

[0109] After the well-mixed polymer solution is placed in a syringe, it is mounted on a syringe pump, and an aluminum plate is placed on the bottom, and the distance between the syringe needle tip and the aluminum plate is adjusted to about 20 cm. Then, a ground wire is connected to the aluminum plate, and a positive high-voltage wire is fixed to the syringe tip. After that, the syringe pump is operated at a flow rate of 1 ml / h and a voltage is applied by setting the high-voltage source to 9 kV. When the voltage exceeding the surface tension of the Taylor cone is applied, very small fibers with a thickness of several micrometers are continuously and randomly spun onto the aluminum plate. This is called electrospinning. After continuing electrospinning for about 2 hours, the aluminum plate is taken outside, covered with a lid, and dried for one day. The thickness of the electrospun membrane manufactured in this way was about 100 μm.

[0110]

[0111] 2. Example 2: Microsphere spraying through electrospray of polymer solution

[0112]

[0113] (1) Example 2-1: Preparation of polymer solution for manufacturing microspheres

[0114] Prepare PDMS. PDMS is a commercial product, Sylgard®184 from Dow Corning Corporation. Polydimethylsiloxane (PDMS, Sylgard®184, Dow Corning Corporation, USA) included in Sylgard®184 and a curing set (Dow Corning Corporation, USA) are mixed in a weight ratio of 10:1 (hereinafter referred to as “PDMS”), and then placed in a vacuum chamber to remove air bubbles.

[0115] Prepare poly(vinylidene fluoride-co-hexafluoropropylene), PVDF-HFP, molecular weight (MW): 455 kDa, Sigma-Aldrich (USA).

[0116] [PDMS: PVDF-HFP: THF: DMF] were mixed in a weight ratio of [2.5:2.5:47.5:47.5], a magnetic stirrer was added, and the mixture was heated to 60°C on a hot plate while stirring at 800 rpm for one day.

[0117]

[0118] (2) Example 2-2: Electrospraying of polymer solution for microsphere production

[0119] After placing the polymer solution in a syringe, connect the ground line to the aluminum plate and the positive high-voltage line to the syringe tip as in Example 1, and then apply a high-voltage source of 13 kV at a distance of approximately 20 cm between the tip and the aluminum plate.

[0120] The membrane manufactured in Example 1-2 was sprayed in a non-continuous fiber format, a process known as electrospraying. After approximately one hour of electrospraying, the membrane was brought outside, covered with an aluminum plate, and allowed to dry for a day. The electrosprayed microsphere layer (superhydrophobic layer) manufactured in this manner had a thickness of approximately 20 μm.

[0121]

[0122] (3) Example 2-3: Electrospraying of polymer solution on the back surface

[0123] The electrosprayed membrane manufactured in Example 2-2 was turned over, fixed with the back side facing upward, and the electrospraying of Example 2-2 was performed once more, followed by drying for one day in the same manner. The thickness of the electrosprayed microsphere layer (superhydrophobic layer) manufactured in this way was approximately 20 μm, and the diameter of the microspheres was approximately 1.5 μm.

[0124]

[0125] 3. Example 3: Fixing the membrane to the support

[0126] After lifting the membrane manufactured in Example 2-3, a hollow square-shaped support made of acrylic material created through CAD work is used to fix the outer tape-wrapped portion of the membrane to the support, and the membrane portion is positioned so that both sides are exposed to the air.

[0127]

[0128] 4. Example 4: Membrane coating

[0129] Grind 0.1 g and 0.2 g of Parylene C respectively and place them in a Parylene coater, then place the support with the membrane manufactured in Example 3 attached into a vaporizer device, and operate the vaporizer to rotate it so that the coating is evenly applied for about 2 hours.

[0130]

[0131] 5. Example 5: Confirmation of membrane manufacturing and membrane distillation effect

[0132]

[0133] (1) Example 5-1: Confirmation of manufacturing a superhydrophobic membrane for membrane distillation according to the present invention

[0134] FIG. 5a is a photograph showing the formation of nanowires through electrospraying at 95% RH, which is a conventional method; FIG. 5b is a photograph showing the appearance of coating 0.1 g of Parylene C after electrospraying at 50% RH; FIG. 5c is a photograph showing the appearance of coating 0.2 g of Parylene C after electrospraying at 50% RH; and FIG. 5d shows the measured values ​​of the thickness of nanowires in the cases of electrospraying at 95% RH, electrospraying at 50% RH, coating 0.1 g of Parylene C, and electrospraying at 50% RH, and coating 0.2 g of Parylene C.

[0135] Compared to nanowire formation using high humidity (95% RH), when forming nanowires using Parylene C, it was confirmed that relatively thick nanowires were formed, with the thickness of the nanowires being approximately twice as thick when 0.1 g of Parylene C was used and approximately 3.5 times thicker when 0.2 g was used. In addition, vapor deposition was also performed at the joint between the pellet fiber and the microsphere, increasing the bonding strength and resulting in higher durability compared to the conventional method.

[0136]

[0137] (2) Example 5-2: Measurement of treatment flow rate and conductivity of membrane distillation using a superhydrophobic membrane for membrane distillation according to the present invention

[0138] The membrane distillation experiment was conducted to measure the treatment flux and conductivity using the membrane manufactured in Example 4. The effective area of ​​the membrane was 8 cm 2was set to . The temperature of the supply tank was maintained at 60℃, and the temperature of the permeate tank was maintained at 20℃. The flow rate of the supply fluid was set to 250ml / min by controlling it with an accuracy of 0.1ml / min through a gear pump. In addition, the flow rate of the permeate fluid was set to 200ml / min.

[0139]

[0140] The water on the feed side has a salinity of about 3.5 wt%, which is the same as the world average salinity of seawater (3.5 wt%). The performance of the Pellethane-based superhydrophobic membrane for distillation according to the present invention (gray) and the commercial PVDF membrane (black) were compared for 24 hours. As a result, as shown in Fig. 6a, the Pellethane-based superhydrophobic membrane for distillation according to the present invention had a permeability of 25 L / m for 24 hours. 2 It was confirmed that a high treatment flow rate of h or more was maintained. The data is the result of analyzing the values ​​measured every minute and averaging them at 10-minute intervals. On the other hand, as shown in Fig. 6a, the commercial PVDF membrane used was a membrane manufactured by GVS's Phase Inversion method with a pore size of 0.45 μm, and the average treatment flow rate for 24 hours was approximately 15 L / m. 2 The processing flow rate at h level was recorded.

[0141] Also, the most reliable way to determine whether the membrane is functioning properly in the membrane distillation (MD) process is to measure the conductivity of the water in the permeate tank. The raw water on the feed side has a salinity of 3.5 wt%, which, when converted to conductivity, is about 53 mS / cm (= 53,000 μS / cm). If even a trace amount of salt passes through the membrane, the conductivity value on the permeate side increases, allowing the selective permeation performance of the membrane to be directly evaluated. The water on the permeate side was deionized water (DI Water), and the initial conductivity value was very low at about 2 μS / cm. For reference, the conductivity of typical tap water is about 200 μS / cm.

[0142] As a result of the experiment, as shown in Fig. 6b, the superhydrophobic membrane for pellet-based membrane distillation according to the present invention was measured to have a final conductivity value of about 4 μS / cm after 24 hours, and recorded a salt rejection rate of over 99.99%. On the other hand, as shown in Fig. 6b, the conductivity of the commercial PVDF membrane on the permeate side began to increase after about 17 hours, and it was confirmed that it increased to about 8 μS / cm after 24 hours. Through this, the salt rejection rate of the commercial PVDF membrane was found to be 99.98%, and it was confirmed that the superhydrophobic membrane for pellet-based membrane distillation according to the present invention has higher salt rejection performance and stable long-term sustainability.

[0143] [Calculation Formula 1]

[0144] Treatment flux = (increased weight of permeate tank for 1 hour) [kg / h] / (area of ​​membrane) [m 2 ]

[0145] [Calculation Formula 2]

[0146] Salt rejection rate (R[%]) = (1 - (conductivity on the permeate side) / (conductivity on the supply side)) x 100

[0147]

[0148] (3) Example 5-3: Measurement of the treatment flow rate and conductivity of membrane distillation when the superhydrophobic membrane for membrane distillation according to the present invention is tensioned.

[0149] A membrane distillation experiment was conducted for 10 hours to compare the case of no tension and the case of tensioning by 50% in the x-direction for a superhydrophobic membrane for membrane distillation manufactured according to the present invention (pelletan electrospinning for 60 minutes, microsphere electrospraying for 120 minutes, and coating with 0.2 g of Parylene C). Each experimental data was measured at 1-minute intervals, averaged over 10-minute units, and graphed.

[0150] As a result of the experiment, as shown in Fig. 7a, the processing flux of the untensioned membrane (triangle) was approximately 24 L / m 2 h, and the membrane (circle) stretched by 50% is approximately 38 L / m 2 It was confirmed that the membrane flux increased by approximately 58% through mechanical tension. This confirmed that the membrane flux can be significantly improved through mechanical tension.

[0151] Furthermore, as shown in Fig. 7b, the stability of the membrane was evaluated through conductivity measurements. While the initial conductivity value for the 50% stretched membrane (circled) was somewhat high, a similar pattern of conductivity value increase was observed over the same experimental time. Considering the measurement deviation that occurred during the experimental process, this indicates that stable performance was maintained within the margin of error. Therefore, it was confirmed that the membrane formed through mechanical stretching can effectively increase the processing flow rate while maintaining a level of stability equivalent to that of the conventional membrane.

[0152]

[0153] (4) Example 5-4: Contact angle measurement of superhydrophobic membrane for membrane distillation according to the present invention

[0154] A common method for assessing the hydrophobicity of a membrane involves dropping a droplet onto its surface and measuring the contact angle. To this end, a Smart Drop device was used to compare and measure the contact angles of a commercial PVDF membrane, a conventional electrosprayed membrane, and a superhydrophobic membrane for membrane distillation according to the present invention coated with Parylene C.

[0155] As shown in Fig. 8, the experimental results confirmed that the superhydrophobic membrane for membrane distillation according to the present invention with Parylene C coating exhibited higher hydrophobicity than a commercial PVDF membrane. In particular, even after Parylene C coating was performed, the contact angle did not decrease and was 160.54°, confirming that the superhydrophobicity was stably maintained. Through this, it was confirmed that the Parylene C coating contributed to maintaining the stability of the existing structure without lowering the hydrophobicity of the membrane.

[0156] Meanwhile, Fig. 9 illustrates the principle of maintaining superhydrophobic properties in a flexible structure. Referring to the left drawing of Fig. 9, a non-elastic superhydrophobic layer is formed on an elastic layer. A water droplet rests on the superhydrophobic layer, minimizing the contact area with the surface while maintaining a high contact angle. This structure implements superhydrophobic properties by coating a non-elastic layer on an elastic base layer.

[0157] Referring to the right drawing of Fig. 9, when the elastic base layer is deformed or stretched, microscale cracks are formed in the inelastic superhydrophobic layer thereon. However, superhydrophobicity is maintained even when cracks are formed due to the hierarchical structure. Even when microscopic cracks occur, the nano- and micro-structures of the surface are maintained, still forming a high contact angle, so that water droplets do not spread. In other words, even if the surface is deformed due to the stretching of the superhydrophobic membrane for membrane distillation according to the present invention, superhydrophobicity can be maintained as long as the nano- and micro-patterns are maintained.

[0158]

[0159] (5) Example 5-5: Confirmation of the membrane surface after membrane distillation of the superhydrophobic membrane for membrane distillation according to the present invention

[0160] SEM images of the membrane surface after a 24-hour membrane distillation test were obtained for a membrane not coated with Parylene C (Fig. 10a) and a superhydrophobic membrane for membrane distillation according to the present invention with Parylene C coating (Fig. 10b).

[0161] In the case of membranes not coated with Parylene C, it was observed that microsphere structure detachment and salt-induced scaling occurred on the membrane surface. On the other hand, in the superhydrophobic membrane for membrane distillation according to the present invention with Parylene C coating, neither microsphere detachment nor scaling was observed. Through this, it was confirmed that the Parylene C coating plays a role in improving the structural stability of the membrane and effectively preventing salt-induced fouling.

[0162]

[0163] (6) Example 5-6: Confirmation of the membrane surface after tensioning of the superhydrophobic membrane for membrane distillation according to the present invention

[0164] Fig. 11a is a SEM image of a superhydrophobic membrane for membrane distillation according to the present invention when no mechanical stretching is applied, and Fig. 11b is a SEM image of a superhydrophobic membrane for membrane distillation according to the present invention when the superhydrophobic membrane for membrane distillation is mechanically stretched 100% along the x-axis. As shown in Fig. 11b, it can be confirmed that the pore size of the superhydrophobic membrane for membrane distillation according to the present invention increases when mechanical stretching is applied, and it can also be confirmed that the shape of the pores is an oval that is elongated in one direction rather than a circle.

[0165] The increase in permeability per unit area when mechanically stretched is attributed to an increase in pore size. Generally, the principle applies that permeability is improved when the pore shape is closer to an elongated oval than a circular one. Therefore, the 58% increase in permeability per unit area when 50% stretching was applied in Example 5-3 is also believed to be due to changes in pore shape.

[0166]

[0167] The high-performance superhydrophobic membrane for membrane distillation according to the present invention has several advantages over existing commercial membranes and can be applied in various industries. The usable duration of conventional membrane distillation membranes was limited to 5 hours or less due to the problem of easy shedding of the microsphere structure. In addition, the existing method using electrospray in an ultra-high humidity (over 95% RH) environment was limited to a maximum of 10 hours or less due to the irregular formation of nanowires and the stability issue of the equipment that can maintain a constant ultra-high humidity. However, the high-performance superhydrophobic membrane for membrane distillation according to the present invention has advanced the structure of the mechanically stretchable membrane and the superhydrophobic layer one step further and added Parylene C, which has excellent biocompatibility, as a coating layer, thereby resolving the instability, which was the biggest problem of the existing structure, and ensuring stability against the release of residual organic solvents. Furthermore, Parylene C is a material with very low reactivity. Long-term testing has shown that there is virtually no salt contamination on the membrane surface. This plays a crucial role in maintaining long-term stability during the membrane distillation process. Furthermore, the polymer base layer used in the present invention, Pelletane, is an elastic material capable of stretching by over 100%. Mechanically stretching it allows for control of pore size, enabling the achievement of higher processing fluxes. These characteristics are expected to further expand the membrane's flexibility and applicability.

[0168] Moreover, unlike the previous method that required two overlapping membranes, a single membrane can achieve sufficient performance, shortening the manufacturing time and simplifying the manufacturing process. Furthermore, the superhydrophobic membrane for membrane distillation according to the present invention has been confirmed to have secured chemical resistance and to have the effects of increasing treatment flow rate and enhancing durability.

[0169] These improvements confirmed high stability even during membrane distillation (MD) processes lasting more than 24 hours. Furthermore, the nanowires coated with Parylene C were not only thicker and more durable, but also showed that the microsphere structure was protected by a protective layer, preventing it from easily detaching even when the membrane was subjected to external forces. These results are significant in that they play a crucial role in enhancing the mechanical stability of the structure and maintaining structural consistency over long-term use.

[0170]

[0171] Furthermore, since the membrane distillation method according to the present invention can use a low heat source of about 60℃, it can utilize surplus heat sources such as factory waste heat, geothermal heat, and solar power generation, and since it is a distillation method, it provides a high separation efficiency (membrane distillation efficiency) of 99.9% or more, or 99.99% or more. In the case of the reverse osmosis (RO) method, which is the most widely used among the existing water filtration or desalination methods, the efficiency drops sharply even when the salinity is only about 10 wt%, and a serious contamination problem occurs as pressure is applied toward the membrane. However, the superhydrophobic membrane for membrane distillation according to the present invention was maintained without durability problems even in a membrane distillation test for more than 24 hours, and the membrane distillation efficiency was 25 L / m per hour. 2 The processing capacity of h was recorded. In addition, the purity of the treated water was maintained at 99.99% even after 24 hours, demonstrating superior separation efficiency compared to conventional RO.

[0172] Additionally, the superhydrophobic membrane for membrane distillation according to the present invention can be applied to a variety of solutions because its pore size can be controlled through mechanical stretching. Furthermore, Parylene C possesses inert properties, making it resistant to most organic solvents, acids, and bases, excluding THF. These properties make it highly likely to be applied to membrane distillation processes for solutions difficult to treat with existing membranes, such as industrial wastewater and spent battery electrolyte.

[0173] In conclusion, the superhydrophobic membrane for membrane distillation according to the present invention addresses the existing issues of durability and stability, while maintaining high processing speed and separation efficiency (membrane distillation efficiency). This technology is expected to overcome the limitations that have hindered the commercialization of existing membrane distillation technologies and significantly expand their potential for practical application across industries.

[0174]

[0175] Although the present invention has been described with reference to the drawings and embodiments, it does not mean that the scope of protection of the present invention is limited by the drawings or embodiments, and it will be understood that a person skilled in the art can modify and change the present invention in various ways without departing from the spirit and scope of the present invention as described in the following claims.

[0176] Although the present invention described above is described based on a series of functional blocks, it is not limited to the above-described embodiments and the attached drawings, and it will be apparent to those skilled in the art to which the present invention pertains that various substitutions, modifications, and changes are possible within a scope that does not depart from the technical spirit of the present invention.

[0177] The combination of the above-described embodiments is not limited to the above-described embodiments, and various combinations may be provided in addition to the above-described embodiments depending on implementation and / or needs.

[0178] In the above-described embodiments, the methods are described based on a flowchart as a series of steps or blocks. However, the present invention is not limited to the order of the steps, and some steps may occur in a different order or simultaneously with other steps described above. Furthermore, those skilled in the art will understand that the steps depicted in the flowchart are not exclusive, and other steps may be included, or one or more steps in the flowchart may be deleted without affecting the scope of the present invention.

[0179] The above-described embodiments include examples of various aspects. While not all possible combinations to illustrate the various aspects can be described, those skilled in the art will recognize that other combinations are possible. Accordingly, the present invention is intended to encompass all other alterations, modifications, and variations within the scope of the following claims.

Claims

1. A superhydrophobic membrane for membrane distillation comprising a polymer base layer, a superhydrophobic layer, and a nanocoating layer.

2. In paragraph 1, A superhydrophobic membrane for membrane distillation, wherein the polymer base layer is formed by a method such as electrospinning, phase separation, spray coating, blow spinning, roll coating or dip coating.

3. In paragraph 1, A superhydrophobic membrane for membrane distillation, wherein the superhydrophobic layer is formed by a method such as electrospraying, chemical vapor deposition (CVD), physical vapor deposition (PVD), sputtering, atomic layer deposition (ALD), sol-gel coating, electrospinning, dip coating, spin coating, spray coating or plasma coating.

4. In paragraph 1, A superhydrophobic membrane for membrane distillation, wherein the nanocoating layer is formed by a method of chemical vapor deposition (CVD), physical vapor deposition (PVD), sputtering, atomic layer deposition (ALD), sol-gel coating, electrospinning, electrospraying, dip coating, spin coating, spray coating or plasma coating.

5. In paragraph 1, A superhydrophobic membrane for membrane distillation, wherein the polymer base layer comprises at least one of Pellethane, thermoplastic polyurethane (TPU), polytetrafluoroethylene (PTFE), polypropylene (PP), polyvinylidene fluoride (PVDF), poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP), polydimethylsiloxane (PDMS), polyetheretherketone (PEEK), polyarylethersulfone (PAES), and fluorinated ethylene propylene (FEP).

6. In paragraph 1, A superhydrophobic membrane for membrane distillation, wherein the superhydrophobic layer comprises at least one of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), polydimethylsiloxane (PDMS), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), fluorinated ethylene propylene (FEP), polyhedral oligomer silsesquioxane (POSS), a mixture of PVDF-HFP and PDMS, and a mixture of PVDF-HFP and POSS.

7. In paragraph 1, A superhydrophobic membrane for membrane distillation, wherein the nanocoating layer comprises at least one of Parylene C, Parylene D, Parylene F, Parylene AF-4, polytetrafluoroethylene (PTFE), poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), fluorinated ethylene propylene (FEP), fluorinated silane, polydimethylsiloxane (PDMS), polyhedral oligomer silsesquioxane (POSS), carbon nanotubes, graphene-based coating, silica, a mixture of PVDF-HFP and PDMS, and a mixture of PVDF-HFP and POSS.

8. In paragraph 1, The treatment flux of the above superhydrophobic membrane for membrane distillation is 25 L / m 2 h to 40L / m 2 h, superhydrophobic membrane for membrane distillation.

9. In paragraph 1, When the above superhydrophobic membrane for membrane distillation is stretched by 50%, the processing flux is 35 L / m 2 h to 50L / m 2 h, superhydrophobic membrane for membrane distillation.

10. In paragraph 3, A superhydrophobic membrane for membrane distillation, wherein the superhydrophobic layer comprises microspheres.

11. In paragraph 4, A superhydrophobic membrane for membrane distillation, wherein the nanocoating layer comprises nanowires.

12. In paragraph 1, A superhydrophobic membrane for membrane distillation, wherein the membrane distillation efficiency of the superhydrophobic membrane for membrane distillation is 99.9% to 99.99%.

13. In paragraph 1, A superhydrophobic membrane for membrane distillation, wherein the contact angle of the superhydrophobic membrane for membrane distillation is 150 to 180°.

14. In paragraph 1, The above polymer base layer is formed by electrospinning, The superhydrophobic layer comprises microspheres formed by electrospraying, A superhydrophobic membrane for membrane distillation, wherein the nanocoating layer comprises nanowires formed by chemical vapor deposition.

15. In paragraph 14, The above polymer base layer includes a Pellethane base layer formed by electrospinning, The superhydrophobic layer comprises microspheres of poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) and polydimethylsiloxane (PDMS) formed by electrospraying, A superhydrophobic membrane for membrane distillation, wherein the nanocoating layer comprises Parylene C nanowires formed by chemical vapor deposition.

16. A membrane distillation system comprising a superhydrophobic membrane for membrane distillation comprising a polymer base layer, a superhydrophobic layer, and a nanocoating layer.

17. A membrane distillation method including a superhydrophobic membrane for membrane distillation, A first step of positioning a feed channel having a higher temperature than a permeate channel on one side of the superhydrophobic membrane for membrane distillation, and positioning a permeate channel having a lower temperature than the feed channel on the other side of the superhydrophobic membrane for membrane distillation; A second step in which water evaporates from the high-temperature supply channel side with high vapor pressure by generating a partial vapor pressure difference due to a temperature difference between the supply channel and the permeation channel, and passes through the superhydrophobic membrane for membrane distillation in the form of vapor; and A third step in which the vapor passing through the superhydrophobic membrane for distillation is condensed on the low-temperature permeation channel side and recovered as water; Including, A membrane distillation method, wherein the superhydrophobic membrane for the above membrane distillation comprises a polymer base layer, a superhydrophobic layer, and a nanocoating layer.

18. A method for manufacturing a superhydrophobic membrane for membrane distillation, A first step of manufacturing a membrane by forming a polymer base layer through electrospinning; A second step of forming a superhydrophobic layer on both sides of the polymer base layer manufactured in the first step through electrospray; A third step of forming a nanocoating layer on both sides of the membrane having a superhydrophobic layer formed on both sides of the polymer base layer manufactured in the second step; A method for manufacturing a superhydrophobic membrane for membrane distillation, comprising:

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