Surface-modified membrane, manufacturing method therefor, and membrane contactor including same

Abstract

Provided are a surface-modified membrane, a surface-modified membrane manufacturing method for manufacturing same, and a membrane contactor comprising same, the surface-modified membrane comprising: a porous membrane comprising a polymer; a highly oxidized graphene oxide supported on at least a portion of the surface of the porous membrane and having an oxygen content of 40-60 wt%; and a surface-modified layer formed on at least a portion of the surface of the highly oxidized graphene oxide and comprising fluorine-containing silane.

Description

Surface-modified membrane, method for manufacturing the same, and membrane contactor including the same

[0001] The present invention relates to a surface-modified membrane capable of exhibiting superhydrophobicity, a method for manufacturing the same, and a membrane contactor including the same.

[0002] As industrial development and population growth occur globally, the use of fossil fuels has increased rapidly. Consequently, nitrogen oxides (NOx), sulfur oxides (SOx), and carbon dioxide (CO2) emitted from combustion flue gases are threatening human survival through environmental pollution, such as acid rain, smog, and global warming. In particular, NOx and SOx are drawing attention as causes of respiratory diseases as they are converted into ultrafine dust through photochemical reactions in the atmosphere. Common methods for removing various air pollutants from flue gases include scrubber-type packed towers, spray towers, and bubble towers. However, existing methods struggle to improve removal efficiency or reduce device size, and they suffer from numerous problems, such as fluid flooding and channeling within the equipment.

[0003] As a means to solve these problems, membrane contactor processes based on membranes and absorbents have attracted attention as an attractive method for gas separation researchers. The membrane contactor process has the advantage of not causing phenomena such as fluid flooding and drift, and can maximize removal efficiency due to a higher volumetric mass transfer coefficient than conventional technologies. In addition, it is modular, allowing for flexible adjustment of processing capacity and miniaturization. However, there are significant difficulties in commercialization due to membrane wetting, which causes a degradation in gas removal performance during long-term process operation.

[0004] Specifically, when the pores of the membrane become wetted by the absorbent during membrane contactor process operation, the mass transfer resistance increases rapidly, causing a significant decrease in gas separation efficiency. Therefore, in order to maintain high efficiency performance for a long time, the wetting of the membrane pores must be prevented during operation.

[0005] To improve the wetting phenomenon of membrane pores, methods include increasing the surface tension of the absorbent according to the Laplace-Young equation or enhancing the hydrophobicity of the membrane to increase the contact angle. In other words, improving the hydrophobicity of the membrane can improve the wetting phenomenon of the membrane contactor, thereby increasing long-term performance stability. Therefore, continuous research is required to improve hydrophobicity by modifying the membrane surface.

[0006] Accordingly, there have been attempts to hydrophobize the membrane to improve the wetting phenomenon of the membrane, but the contact angle has not increased sufficiently, which is insufficient to provide long-term performance stability.

[0007] The objective of the present invention is to provide a surface-modified membrane having a stable structure and exhibiting high superhydrophobicity. Additionally, the objective of the present invention is to provide a surface-modified membrane capable of minimizing membrane wetting and increasing the replacement cycle.

[0008] In addition, the objective of the present invention is to provide a surface-modified membrane that is more economical and exhibits high-quality superhydrophobicity, comprising highly oxidized graphene oxide produced by a one-pot reaction.

[0009] In addition, the objective of the present invention is to provide a method for manufacturing a surface-modified membrane exhibiting the above characteristics, which can reduce manufacturing time and cost and increase process efficiency by manufacturing highly oxidized graphene oxide by a one-pot reaction.

[0010] The objects of the present invention are not limited to those mentioned above, and other unmentioned objects and advantages of the present invention may be understood from the following description and will be more clearly understood by the embodiments of the present invention. Furthermore, it will be readily apparent that the objects and advantages of the present invention can be realized by the means and combinations thereof set forth in the claims.

[0011] A surface-modified membrane may be provided, comprising: a porous membrane comprising a polymer according to the present invention; a highly oxidized graphene oxide supported on at least a portion of the surface of the porous membrane and having an oxygen content of 40% to 60% by weight; and a surface modification layer formed on at least a portion of the surface of the highly oxidized graphene oxide and comprising a fluorine-containing silane.

[0012] The surface water contact angle of the above surface-modified membrane may be greater than 150°.

[0013] The surface-modified membrane may have an elevated water contact angle of 35° or more compared to the surface water contact angle of the porous membrane containing the polymer.

[0014] The adsorption energy of the fluorine-containing silane and the highly oxidized graphene oxide may be -4 eV to -5.5 eV.

[0015] The above polymer may include at least one selected from the group consisting of polypropylene, polyethylene, polyester, polyamide, polyimide, polyvinyl chloride, polyurethane, polysulfone, polyetheretherketone, polypropylene oxide, and combinations thereof.

[0016] The above fluorine-containing silane may include at least one selected from the group consisting of perfluorodecyltriethoxysilane, ethyltrimethoxysilane, hexamethyldisilane, methoxytrimethylsilane, triethylethoxysilane, dimethyldecoxysilane, trimethylchlorosilane, methyltrimethoxysilane, and combinations thereof.

[0017] In addition, a method for manufacturing a surface-modified membrane may be provided, comprising the steps of: manufacturing a hydrophilized porous membrane by treating a porous membrane containing a polymer according to the present invention with a hydrophilic coating; manufacturing a porous membrane supported with highly oxidized graphene oxide having an oxygen content of 40% to 60% by weight by supporting highly oxidized graphene oxide synthesized by a one-pot reaction on at least a portion of the surface of the hydrophilic porous membrane; and manufacturing a fluorinated surface-modified membrane by surface treating the porous membrane supported with highly oxidized graphene oxide with a surface modification solution containing a fluorine-containing silane to form a surface modification layer containing a fluorine-containing silane formed on at least a portion of the surface of the highly oxidized graphene oxide.

[0018] The highly oxidized graphene oxide synthesized by the above one-pot reaction can be synthesized by forming a graphene sheet from graphite through anodic exfoliation and electrochemically oxidizing the graphene sheet.

[0019] The above electrochemical oxidation can be performed in an electrolyte solution containing an acid and an oxidizing agent.

[0020] The above electrochemical oxidation can be performed at a current density of 0.125 A / cm² to 0.3125 A / cm².

[0021] In addition, a membrane contactor for use in at least one separation process selected from the group consisting of sulfur oxides (SOx), nitrogen oxides (NOx), carbon dioxide (CO2) and combinations thereof, comprising the surface-modified membrane according to the present invention.

[0022] The surface-modified membrane according to the present invention has a stable structure and can exhibit high superhydrophobicity. Accordingly, the surface-modified membrane according to the present invention can minimize membrane wetting and increase the replacement cycle.

[0023] In addition, the surface-modified membrane according to the present invention may include highly oxidized graphene oxide produced by a one-pot reaction, thereby exhibiting more economical and high-quality superhydrophobicity.

[0024] In addition, the method for manufacturing a surface-modified membrane according to the present invention can produce highly oxidized graphene oxide by a one-pot reaction, thereby reducing manufacturing time and cost, increasing process efficiency, and can produce a surface-modified membrane exhibiting the above characteristics.

[0025] In addition to the effects described above, the specific effects of the present invention are described together with the specific details for implementing the invention below.

[0026] FIGS. 1 to 3 schematically illustrate a method for manufacturing a surface-modified membrane according to one embodiment of the present invention.

[0027] Figure 4 is a graph showing the water contact angle of the membrane according to the example and comparative example.

[0028] In FIG. 5, (A) shows the adsorption energy of Comparative Example 2, and (B) shows the adsorption energy of Example 1.

[0029] The aforementioned objectives, features, and advantages are described in detail below with reference to the attached drawings, thereby enabling those skilled in the art to easily implement the technical concept of the present invention. In describing the present invention, detailed descriptions of known technologies related to the present invention are omitted if it is determined that such descriptions would unnecessarily obscure the essence of the invention. Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the attached drawings. In the drawings, the same reference numerals are used to indicate the same or similar components.

[0030] In the following, the statement that any configuration is placed on the "upper (or lower)" of a component or on the "upper (or lower)" of a component may mean not only that any configuration is placed in contact with the upper (or lower) surface of said component, but also that another configuration may be interposed between said component and any configuration placed on (or below) said component.

[0031] Hereinafter, a surface-modified membrane according to some embodiments of the present invention and a method for manufacturing the same will be described.

[0032]

[0033] One embodiment of the present invention provides a surface-modified membrane comprising: a porous membrane comprising a polymer; a highly oxidized graphene oxide supported on at least a portion of the surface of the porous membrane and having an oxygen content of 40% to 60% by weight; and a surface modification layer comprising a fluorine-containing silane formed on at least a portion of the surface of the highly oxidized graphene oxide.

[0034] The surface-modified membrane described above comprises highly oxidized graphene oxide, has a stable structure, and can exhibit superhydrophobicity. Accordingly, membrane wetting can be minimized and the replacement cycle can be increased. This will be examined in detail below.

[0035]

[0036] The surface-modified membrane described above comprises a porous membrane containing a polymer. To prevent membrane wetting during the operation of a membrane contactor or the like, it is possible to manufacture the membrane using a fluorine-containing compound exhibiting strong hydrophobicity. However, since fluorine-containing compounds exhibiting strong hydrophobicity, such as fluorine-containing membranes (PTFE, PVDF, etc.), are expensive materials, using them is uneconomical. Therefore, in order to manufacture a hydrophobic membrane economically, a porous membrane comprising a polymer coated with a fluorine-containing silane material is included.

[0037] In a porous membrane comprising the above polymer, the polymer may include at least one selected from the group consisting of polypropylene, polyethylene, polyester, polyamide, polyimide, polyvinyl chloride, polyurethane, polysulfone, polyetheretherketone, polypropylene oxide, and combinations thereof. A porous membrane comprising the above polymer can be more economical, have a simple processing process, and exhibit high chemical stability. In one embodiment, the porous membrane may be a polypropylene porous membrane, and accordingly, can simultaneously exhibit excellent physical properties such as tensile strength and impact strength, and excellent processability.

[0038] On the other hand, porous membranes containing polymers inherently lack hydrophobicity, and wetting may occur during prolonged operation in membrane contactors. Furthermore, since porous membranes containing polymers have almost no reactivity, it is difficult to combine them with hydrophobic materials.

[0039] Accordingly, the porous membrane containing the above polymer can be used as a hydrophilized porous membrane by inducing an oxidation reaction using a hydrophilic treatment solution containing an oxidizing agent to generate hydroxyl groups (-OH) on the surface of the polymer membrane. As a result, it can be made to react with other substances. For example, the hydrophilic treatment solution may be a piranha solution. The piranha solution may be a solution prepared by mixing concentrated sulfuric acid and hydrogen peroxide, an oxidizing agent, in a weight ratio of 3:1 to 7:1.

[0040]

[0041] The surface-modified membrane comprises highly oxidized graphene oxide (HOGO) supported on at least a portion of the surface of the porous membrane.

[0042] To impart hydrophobicity to the membrane, one might consider directly surface-modifying the surface of the porous membrane with a hydrophobic fluorine-containing silane, or supporting silica (SiO2) having a -SiO- structure similar to the fluorine-containing silane between the porous membrane and the fluorine-containing silane. However, in all of the above cases, despite modifying the surface of the membrane with a highly hydrophobic fluorine-containing silane, the high superhydrophobicity intended by the present invention was not exhibited.

[0043] The inventors, through diligent research, prepared a surface-modified membrane comprising a porous membrane surface containing the polymer, wherein highly oxidized graphene oxide particles are supported on at least a portion of the surface of the porous membrane, and a surface modification layer containing a fluorine-containing silane is supported on at least a portion of the surface of the highly oxidized graphene oxide. The surface-modified membrane exhibits structural stability among its constituents, forms stable bonds, and allows for the effective immobilization of hydrophobic fluorine-containing silanes. Furthermore, it exhibits significantly high superhydrophobicity and can provide long-term performance stability when used in a membrane contactor.

[0044] Graphene oxide refers to graphene containing oxygen-containing functional groups, formed when oxygen is inserted between carbon bonds as graphene is oxidized. The oxygen-containing functional groups may be, for example, at least one substituent selected from the group consisting of hydroxyl groups, epoxy groups, carboxyl groups, carbonyl groups, aldehyde groups, ester groups, alkoxy groups, ether groups, acetal groups, and ketone groups. Graphene oxide can form various bonding structures by including such diverse functional groups, which can contribute to structural stability.

[0045] The highly oxidized graphene oxide mentioned above refers to graphene oxide in which graphene is oxidized to a high proportion. Specifically, the highly oxidized graphene oxide refers to graphene oxide with a high number of oxygen-containing functional groups attached, meaning graphene oxide in which the oxygen content contained by said functional groups is 40% to 60% by weight. The highly oxidized graphene oxide may be synthesized by the one-pot reaction described below. The highly oxidized graphene oxide formed in this way can enhance electrical interactions with fluorine-containing silanes and provide anchoring sites with fluorine-containing silanes, thereby enabling stronger binding of more fluorine-containing silanes. Furthermore, the highly oxidized graphene oxide can be uniformly supported on the porous membrane in the form of particles.

[0046] The adhesion energy between the porous membrane containing the above polymer and the highly oxidized graphene oxide supported on at least a portion of the surface of the porous membrane is -0.05 eV / Å. 2 Up to -0.2 eV / Å 2 It is possible. Accordingly, the highly oxidized graphene oxide can exhibit excellent bonding strength with the porous membrane containing the polymer, thereby further enhancing hydrophilicity. It can also exhibit significantly improved structural stability. Furthermore, through an enhanced crosslinking reaction with the fluorine-containing silane formed on one side of the highly oxidized graphene oxide, the surface modification layer containing the fluorine-containing silane can be effectively fixed.

[0047] The highly oxidized graphene oxide has a two-dimensional structure and can be supported in the form of a flat sheet. Thus, unlike materials such as silica, it exhibits a large specific surface area and can increase the surface area for modification of fluorine-containing silanes. The highly oxidized graphene oxide can be supported in a stacked state of one or more layers, and the highly oxidized graphene oxide only needs to have a certain size. The size is not particularly limited.

[0048] The highly oxidized graphene oxide can hydrogen bond with a porous membrane containing the polymer. Also, the highly oxidized graphene oxide can covalently bond with a fluorine-containing silane.

[0049]

[0050] The surface-modified membrane is formed on at least a portion of the surface of the highly oxidized graphene oxide and comprises a surface modification layer comprising a fluorine-containing silane. By including the surface modification layer comprising the fluorine-containing silane, the surface energy can be lowered and a high water contact angle can be exhibited.

[0051] The above fluorine-containing silane may include at least one selected from the group consisting of perfluorodecyltriethoxysilane, ethyltrimethoxysilane, hexamethyldisilane, methoxytrimethylsilane, triethylethoxysilane, dimethyldecoxysilane, trimethylchlorosilane, methyltrimethoxysilane, and combinations thereof.

[0052] The above fluorine-containing silane may be coated on the surface of the porous membrane supported with the above-degraded graphene oxide, more specifically, on part or all of the surface of the above-degraded graphene oxide to form a surface modification layer. Although the surface modification layer is described as a “layer,” this refers to a coating layer and may be discontinuously distributed on the surface of the porous membrane supported with the above-degraded graphene oxide.

[0053] The adsorption energy of the fluorine-containing silane and the highly oxidized graphene oxide may be -4 eV to -5.5 eV. The highly oxidized graphene oxide can exhibit strong adsorption power by having an adsorption energy within the above range with the fluorine-containing silane.

[0054]

[0055] The surface water contact angle of the above surface-modified membrane may exceed 150°. Although there have been many attempts to exhibit hydrophobicity by surface treatment with conventional fluorine-containing silanes, it has been practically difficult to achieve a water contact angle exceeding 150°.

[0056] As previously described, the surface-modified membrane has excellent bonding strength between materials and a stable structure, allowing it to have a water contact angle of more than 150°. Thus, it can exhibit superhydrophobicity even while containing a porous membrane containing a polymer. Accordingly, the surface-modified membrane can improve the durability of the membrane, minimize membrane wetting, and increase the replacement cycle. Furthermore, it can be applied to various applications requiring superhydrophobicity.

[0057] For example, if the surface water contact angle of the surface-modified membrane is less than 150°, there may be a problem where membrane wetting occurs as the service period lengthens, resulting in a shorter replacement cycle. The surface water contact angle of the surface-modified membrane may be greater than 150°, 152° or more, 155° or more, 156° or more, and 160° or less, but is not limited thereto.

[0058] The surface-modified membrane described above may exhibit an elevated water contact angle of 35° or more compared to the surface water contact angle of a porous membrane containing a polymer. Accordingly, it is possible to minimize membrane wetting and increase the replacement cycle while using a more economical porous membrane containing a polymer. For example, the surface-modified membrane may exhibit an elevated water contact angle of 30° or more, 35° or more, and 45° or less, or 40° or less compared to the surface water contact angle of a porous membrane containing a polymer.

[0059]

[0060] Another embodiment of the present invention provides a method for manufacturing the surface-modified membrane. FIGS. 1 to 3 schematically illustrate a method for manufacturing a surface-modified membrane according to one embodiment of the present invention, comprising the steps of: (1) manufacturing a hydrophilized porous membrane (PP-OH) by treating a porous membrane (PP) containing a polymer with a hydrophilic coating; and (2) manufacturing a porous membrane (HOGO / PP-OH) supported with highly oxidized graphene oxide (HOGO) synthesized by a one-pot reaction on at least a portion of the surface of the hydrophilic porous membrane, such that the highly oxidized graphene oxide has an oxygen content of 40% to 60% by weight. The present invention provides a method for manufacturing a surface-modified membrane (F-SiO3 / HOGO / PP-OH), comprising the step (3) of surface-treating the porous membrane supported with the highly oxidized graphene oxide with a surface-modifying solution containing a fluorine-containing silane to form a surface-modifying layer containing a fluorine-containing silane formed on at least a portion of the surface of the highly oxidized graphene oxide, thereby manufacturing a fluorinated surface-modified membrane (F-SiO3 / HOGO / PP-OH). By the above manufacturing method, the surface-modified membrane described above can be manufactured. Details regarding the surface-modified membrane are as described above unless specifically described below. Below, the manufacturing method will be examined in detail.

[0061]

[0062] First, the method includes the step (1) of preparing a hydrophilized porous membrane by treating a porous membrane containing a polymer with a hydrophilic coating. Specifically, the porous membrane containing a polymer can be hydrophilized by immersing it in a hydrophilic treatment solution containing an oxidizing agent and an acid, for example, a piranha solution, and performing a hydroxylation reaction to attach hydroxyl groups (-OH) to the surface of the membrane.

[0063] The above oxidizing agent may include one or more selected from the group consisting of potassium chlorate (KClO3), potassium dichromate (K2Cr2O7), hydrogen peroxide (H2O2), and potassium permanganate (KMnO4), and, for example, may include potassium chlorate (KClO3).

[0064] The above acid may include one or more selected from the group consisting of sulfuric acid, hydrochloric acid, nitric acid, perchloric acid, hydrobrominated acid, and hydroiodized acid, and, for example, may include sulfuric acid.

[0065]

[0066] Subsequently, the method comprises the step (2) of supporting highly oxidized graphene oxide, synthesized by a one-pot reaction, on at least a portion of the surface of the hydrophilic porous membrane to produce a porous membrane supported with highly oxidized graphene oxide having an oxygen content of 40% to 60% by weight. By synthesizing the highly oxidized graphene oxide supported on the surface of the hydrophilic porous membrane by a one-pot reaction, a high yield can be obtained in a short time, thereby reducing manufacturing time and cost. It can provide improved practicality and efficiency.

[0067] The highly oxidized graphene oxide synthesized by the above one-pot reaction may be synthesized by forming a graphene sheet from graphite through anodic exfoliation and electrochemically oxidizing the graphene sheet.

[0068] Specifically, a graphene sheet can be formed through anodic exfoliation by applying an electric current to a graphite electrode under an electrolyte solution containing an acid. The acid may include, for example, one or more selected from the group consisting of sulfuric acid, hydrochloric acid, nitric acid, perchloric acid, hydrobrominated acid, and hydroiodized acid, and may include, for example, sulfuric acid and phosphoric acid.

[0069] The above-mentioned exfoliated graphene sheet can be electrochemically oxidized by applying an electric current under an electrolyte solution to synthesize graphene oxide.

[0070] For example, the electrochemical oxidation may be performed in an electrolyte solution containing an acid and an oxidizing agent. In this case, the acid may be at least one selected from sulfuric acid, phosphoric acid, perchloric acid, nitric acid, or boric acid. For example, it may include sulfuric acid and phosphoric acid. And, the oxidizing agent may include one or more selected from the group consisting of potassium chlorate (KClO3), potassium dichromate (K2Cr2O7), hydrogen peroxide (H2O2), and potassium permanganate (KMnO4), for example, it may include potassium permanganate.

[0071] For example, the electrochemical oxidation described above can be performed using Platinum-coated titanium dimension stable electrodes (DSE).

[0072] The degree of oxidation of the highly oxidized graphene oxide can be controlled by adjusting the current density and / or the time for applying the current. The highly oxidized graphene oxide can be oxidized by a current density of 0.125 A / cm² to 0.3125 A / cm². Additionally, oxidation can be achieved by applying the current density for 30 minutes to 480 minutes. If the current density and / or the time for applying the current falls outside the above range, there may be issues such as the graphene not being oxidized uniformly, or the degree of oxidation being insufficient or excessive.

[0073] The above oxidation can be stopped by adding a chemical element, for example, H2O2.

[0074]

[0075] As described above, highly oxidized graphene oxide synthesized by a one-pot reaction is supported on at least a portion of the surface of the hydrophilized porous membrane to produce a porous membrane supported with highly oxidized graphene oxide (3).

[0076] For example, the above steps can be performed by a sol-gel process. A sol is a state in which solid particles are dispersed colloidally in a liquid phase, and a gel refers to a state in which the components of the sol form a network or polymer chains connected to each other by specific chemical or physical bonds, thereby losing fluidity. The gel state includes cases where the solid phase forms a network and the liquid phase is fixed within the network.

[0077] The sol-gel method is a technique that allows for control to realize specific physical properties at every stage until the sol gels, and can be described as a method for manufacturing materials through the formation of a sol, gelation, and removal of a solvent.

[0078] Since the sol-gel method allows the reactants to start in a liquid phase, reaction control is easy, chemical uniformity can be maintained, and various types of final products can be manufactured.

[0079] Since graphene oxide is insoluble in water, organic solvents are used as cosolvents. It undergoes hydrolysis and condensation reactions in solution to form an oligomeric precursor sol, followed by a sol-gel reaction in which it becomes a three-dimensional network gel through further condensation reactions. As particles in the solution form bonds and connect through hydrolysis and condensation to form a three-dimensional network structure, the viscosity of the solution rises sharply, and it loses fluidity as it passes the gel point. This process is called gelation.

[0080] A coating solution containing highly oxidized graphene oxide further comprises a solvent, and said solvent may include at least one selected from the group consisting of ethanol, methanol, acetone, ethyl acetate, and combinations thereof. The coating solution may further comprise ammonia water. The coating solution may comprise 10 to 20 parts by weight of the ammonia water and 1 to 10 parts by weight of the highly oxidized graphene oxide per 100 parts by weight of the solvent, and preferably may comprise 14 to 18 parts by weight of the ammonia water and 2 to 6 parts by weight of the highly oxidized graphene oxide per 100 parts by weight of the solvent.

[0081] If the highly oxidized graphene oxide is less than 1 part by weight per 100 parts by weight of the solvent in the above coating solution, the hydrophobic effect may be insufficient, and if it exceeds 10 parts by weight, the viscosity of the coating solution increases and some clumping and precipitation may occur, making coating difficult.

[0082]

[0083] The method includes the step of surface treating the porous membrane supported with the above-mentioned highly oxidized graphene oxide with a surface modification solution containing a fluorine-containing silane to form a surface modification layer containing a fluorine-containing silane, which is formed on at least a portion of the surface of the above-mentioned highly oxidized graphene oxide.

[0084] The above-mentioned fluorine-containing silane is as described above, and the surface modification solution further comprises a solvent, and the solvent may include at least one selected from the group consisting of ethanol, methanol, acetone, ethyl acetate, and combinations thereof. The surface modification solution may further comprise ammonia water.

[0085] The surface modification solution may comprise 1 to 10 parts by weight of the ammonia water and 0.1 to 15 parts by weight of the fluorine-containing silane per 100 parts by weight of the solvent, and preferably may comprise 3 to 5 parts by weight of the ammonia water and 0.5 to 5 parts by weight of the fluorine-containing silane per 100 parts by weight of the solvent.

[0086] If the fluorine-containing silane is less than 0.1 parts by weight per 100 parts by weight of the solvent in the above surface modification solution, the surface modification effect is negligible and the effect of increasing hydrophobicity and durability does not appear, which is undesirable, and if it exceeds 15 parts by weight, the viscosity of the surface modification solution increases, and clumping and clogging of the membrane pores due to excessive coating may occur.

[0087] The above fluorine-containing silane can exhibit excellent bonding strength by forming a network structure through an enhanced cross-linking reaction with the highly oxidized graphene oxide supported on the porous membrane supported with the highly oxidized graphene oxide.

[0088]

[0089] The method for manufacturing the surface-modified membrane described above may further include a drying and stabilization step of drying and stabilizing the surface-modified membrane, which includes a surface-modified layer containing the fluorine-containing silane, at 80°C to 90°C.

[0090]

[0091] The above method for manufacturing a surface-modified membrane can be environmentally friendly as it does not use solvents such as toluene, xylene, and hexane, which are highly volatile and harmful to the human body.

[0092] The surface water contact angle of the surface modified membrane manufactured by the above method for manufacturing the surface modified membrane can be greater than 150°, exhibiting superhydrophobicity.

[0093]

[0094] Another embodiment of the present invention provides a membrane contactor for use in at least one separation process selected from the group consisting of sulfur oxides (SOx), nitrogen oxides (NOx), carbon dioxide (CO2) and combinations thereof, comprising the surface-modified membrane described above.

[0095] The above membrane contactor comprises the aforementioned surface-modified membrane and can be used in at least one separation process selected from the group consisting of sulfur oxides (SOx), nitrogen oxides (NOx), carbon dioxide (CO2), and combinations thereof. In addition, membrane wetting can be minimized and the replacement cycle can be increased.

[0096]

[0097] (Example)

[0098] Example 1

[0099] Preparation Example 1-1: Preparation of a hydrophilized porous membrane (PP-OH) (S1)

[0100] A piranha solution was prepared by mixing 80 wt% sulfuric acid and 20 wt% water (H2O) at room temperature, and then adding 0.75 wt% potassium chlorate (KClO3) as an oxidizing agent. A 5 cm (width) × 5 cm (length) porous polypropylene membrane was immersed in the piranha solution, which is a hydrophilic treatment solution, for 10 minutes to hydrophilize the surface of the polypropylene porous membrane. Then, the surface of the polypropylene porous membrane was washed with water and dried in a vacuum oven at 40°C for 2 hours to produce a hydrophilized polypropylene porous membrane (PP-OH).

[0101]

[0102] Preparation Example 1-2: Synthesis and support of highly oxidized graphene oxide (S2)

[0103] (1-2-1) Synthesis of highly oxidized graphene oxide (HOGO) (S2-1)

[0104] An electrolyte solution was prepared by mixing 90 wt% sulfuric acid (H2SO4) and 10 wt% phosphoric acid (H3PO4). In the electrolyte solution, a current density of 0.125 A / cm² was applied to two graphite electrodes to exfoliate graphene sheets through anodic exfoliation. Then, highly oxidized graphene oxide particles with an oxygen content of 40 wt% to 60 wt% were synthesized by oxidizing the graphene sheets for 120 minutes at a current density of 0.2425 A / cm² using Platinum-coated titanium dimension stable electrodes (DSE). Subsequently, the reaction was terminated using cold water and 30% H2O2, centrifuged, washed with deionized water and ethanol, and dried.

[0105] (1-2-2) Preparation of porous membrane (HOGO / PP-OH) supported with highly oxidized graphene oxide (S2-2)

[0106] A mixed solution was prepared by mixing 83 wt% of ethanol with 13.5 wt% of ammonia solution (NH3OH) for 10 minutes. A mixture was prepared by immersing the hydrophilized porous membrane (PP-OH) according to Preparation Example 1-1 in the prepared mixed solution for 30 minutes. Then, a coating solution was prepared by mixing 3.5 wt% of highly oxidized graphene oxide particles according to 1-2-1 into the mixed solution. The coating solution containing the highly oxidized graphene oxide particles was slowly injected dropwise into the mixture immersed in the hydrophilized porous membrane (PP-OH), while stirring at 200 RPM for 4 hours. Then, the immersed membrane was removed, the surface of the membrane was washed with ethanol, and then dried in a 60°C oven for 3 hours to produce a hydrophilized polypropylene porous membrane (HOGO / PP-OH) supported with highly oxidized graphene oxide particles.

[0107]

[0108] Preparation Example 1-3: Preparation of a fluorinated surface-modified membrane (F-SiO3 / HOGO / PP-OH) (S3)

[0109] A surface modification solution was prepared by mixing 4 wt% of ammonia water with 95 wt% of ethanol for 15 minutes, and then adding 1 wt% of 1H,1H,2H,2H- perfluorodecyltriethoxysilane (PFDTS). Then, a porous membrane (HOGO / PP-OH) loaded with highly oxidized graphene oxide according to Preparation Example 1-2 was immersed in the surface modification solution for 12 hours. Afterward, the immersed membrane was removed, the surface of the membrane was washed with ethanol, and then dried in an 80°C oven for 2 hours to produce a superhydrophobic surface-modified PP membrane (F-SiO3 / HOGO / PP-OH).

[0110]

[0111] Comparative Example 1: Surface-unmodified polypropylene porous membrane (pristine PP)

[0112] Instead of the surface-modified membrane of Example 1, a porous membrane made of 5 (width) × 5 (length) polypropylene material was used as Comparative Example 1.

[0113]

[0114] Comparative Example 2: F-SiO3 / Graphene / PP-OH

[0115] Instead of the highly oxidized graphene oxide (HOGO) of Example 1, graphene was supported on a hydrophilized polypropylene porous membrane. Then, a surface-modified PP membrane (F-SiO3 / Graphene / PP-OH) was prepared in the same manner as in Example 1, except that surface modification was performed by adding 1H,1H,2H,2H- perfluorodecyltriethoxysilane (PFDTS).

[0116]

[0117] evaluation

[0118] Experimental Example 1: Contact angle (°)

[0119] Table 1 and Figure 2 below show the contact angles of the membranes according to Preparation Examples 1-1 and 1-3 prepared in Example 1 and Comparative Example 1. The contact angles were measured by dropping 1.5 μL of distilled water onto the surfaces of Preparation Examples 1-1 and 1-3 of Example 1 and Comparative Example 1, and measuring the contact angle between each surface and the water droplet using a Kruss DSA 25 instrument.

[0120]

[0121] Comparative Example 1 (pristine PP) Example 1 Preparation Example 1-1 (PP-OH) Preparation Example 1-3 (F-SiO3 / HOGO / PP-OH) Contact Angle (°) 121.4 107.3 156.8

[0122] Referring to Table 1 and Figure 2 above, the contact angle is an indicator of the degree of hydrophobicity of the surface. The contact angle of Comparative Example 1 (pristine PP) was 121.4°, but the surface-modified membrane of Example 1 (F-SiO3 / GO / PP-OH) was found to exhibit superhydrophobicity exceeding 150° with a contact angle of 156.8°.

[0123] Experimental Example 2: Adsorption Energy

[0124] The adsorption energies of the fluorinated surface-modified membrane of Example 1 (F-SiO3 / HOGO / PP-OH) and the fluorinated surface-modified membrane of Comparative Example 2 (F-SiO3 / Graphene / PP-OH) were measured. The results are shown in Figure 3 and Table 2 below.

[0125] Specifically, the adsorption energy was simulated using Castep within the Materials Studio program. The adsorption energy of Example 1 (Figure 3 (B)) can be derived by calculating the value obtained by subtracting the sum of the enthalpy energy of the fluorine-containing silane (F-SiO3) and the enthalpy energy of the surface-modified membrane (HOGO / PP-OH) excluding the fluorine-containing silane from the enthalpy energy of the surface-modified membrane (F-SiO3 / HOGO / PP-OH), as shown in Equation 1 below.

[0126] [Equation 1] Adsorption energy = Enthalpy energy of F-SiO3 / HOGO / PP-OH - (Enthalpy energy of F-SiO3 + Enthalpy energy of HOGO / PP-OH)

[0127]

[0128] The adsorption energy of Comparative Example 2 ((A) in Fig. 3) can be derived by calculating according to Equation 2 below.

[0129] [Equation 2] Adsorption energy = Enthalpy energy of F-SiO3 / Graphene / PP-OH - (Enthalpy energy of F-SiO3 + Enthalpy energy of Graphene / PP-OH)

[0130]

[0131] Example 1 Comparative Example 2 Adsorption Energy (eV) -5.27 -3.05

[0132] As shown in Table 2 above, a lower adsorption strength is considered better, and since Example 1 exhibits a high adsorption strength, it can be seen that surface modification has been maximized. Although the present invention has been described above with reference to the illustrated drawings, the present invention is not limited by the embodiments and drawings disclosed in this specification, and it is obvious that various modifications can be made by a person skilled in the art within the scope of the technical concept of the present invention. Furthermore, even if the effects of the configuration of the present invention were not explicitly described while explaining the embodiments of the present invention above, it is natural to acknowledge that the effects predictable by said configuration should also be recognized.

Claims

1. A porous membrane containing a polymer; Highly oxidized graphene oxide supported on at least a portion of the surface of the porous membrane and having an oxygen content of 40% to 60% by weight; and A surface modification layer formed on at least a portion of the surface of the above-mentioned highly oxidized graphene oxide and comprising a fluorine-containing silane; Surface-modified membrane.

2. In Paragraph 1, The surface water contact angle of the above surface-modified membrane is greater than 150° Surface-modified membrane.

3. In Paragraph 1, The surface-modified membrane has an elevated water contact angle of 35° or more compared to the surface water contact angle of the porous membrane containing the polymer. Surface-modified membrane.

4. In Paragraph 1, The adsorption energy of the fluorine-containing silane and the highly oxidized graphene oxide is -4 eV to -5.5 eV Surface-modified membrane.

5. In Paragraph 1, The above polymer comprises at least one selected from the group consisting of polypropylene, polyethylene, polyester, polyamide, polyimide, polyvinyl chloride, polyurethane, polysulfone, polyetheretherketone, polypropylene oxide, and combinations thereof. Surface-modified membrane.

6. In Paragraph 1, The above fluorine-containing silane comprises at least one selected from the group consisting of perfluorodecyltriethoxysilane, ethyltrimethoxysilane, hexamethyldisilane, methoxytrimethylsilane, triethylethoxysilane, dimethyldecoxysilane, trimethylchlorosilane, methyltrimethoxysilane, and combinations thereof. Surface-modified membrane.

7. A step of manufacturing a hydrophilized porous membrane by treating a porous membrane containing a polymer with a hydrophilic coating; A step of supporting highly oxidized graphene oxide synthesized by a one-pot reaction on at least a portion of the surface of the hydrophilic porous membrane to produce a porous membrane supported with highly oxidized graphene oxide having an oxygen content of 40% to 60% by weight; and A step of preparing a fluorinated surface-modified membrane by surface-treating the porous membrane supported with the above-mentioned highly oxidized graphene oxide with a surface-modifying solution containing a fluorine-containing silane to form a surface-modifying layer containing a fluorine-containing silane formed on at least a portion of the surface of the above-mentioned highly oxidized graphene oxide. Method for manufacturing a surface-modified membrane.

8. In Paragraph 7, The highly oxidized graphene oxide synthesized by the above one-pot reaction is synthesized by forming a graphene sheet from graphite through anodic exfoliation and electrochemically oxidizing the graphene sheet. Method for manufacturing a surface-modified membrane.

9. In Paragraph 8, The above electrochemical oxidation is performed in an electrolyte solution containing an acid and an oxidizing agent. Method for manufacturing a surface-modified membrane.

10. In Paragraph 8, The above electrochemical oxidation is performed at a current density of 0.125 A / cm² to 0.3125 A / cm² Method for manufacturing a surface-modified membrane.

11. A surface-modified membrane according to paragraph 1, comprising A membrane contactor for use in at least one separation process selected from the group consisting of sulfur oxides (SOx), nitrogen oxides (NOx), carbon dioxide (CO2) and combinations thereof.

Images