A carbon-titania nanomaterial doped filtration membrane with thin film nanocomposite interlayer for generating electrical energy from solar energy and a method of producing the same

Abstract

The present invention relates to thin film nanocomposite interlayer (TFNi) membranes, obtained by coating the interlayer between the microporous membrane and the selective permeation surface of a polymer TFC structure with a heterostructure of one-dimensional and two-dimensional titanium dioxide nanomaterials with P-N junction region characteristics, reduced by Ti-O-C bonds with carbon nanomaterials, and to a method (100) for the production of these membranes, the aim of which is to increase the filtration rate of polymer thin film composite (TFC) membranes conventionally used for filtration applications; to increase their filtration selectivity, to improve their anti-fouling performance; to increase their hydrophilic properties, and to enable the filtration membranes to simultaneously convert solar energy into usable electrical energy.

Description

Technical Field

[0001] This invention relates to thin-film nanocomposite sandwich (TFNi) membranes, which are obtained by coating a heterostructure of one-dimensional and two-dimensional titanium dioxide nanomaterials and carbon nanomaterials having PN junction region characteristics of mutual reduction via Ti-OC bonds onto a sandwich between a microporous membrane of polymer TFC structure and a selectively permeable surface. It also relates to methods for producing these membranes, with the aim of improving the filtration rate of polymer thin-film composite (TFC) membranes conventionally used for filtration applications; improving their filtration selectivity; enhancing their anti-clogging performance; improving their hydrophilicity; and enabling the filtration membrane to simultaneously convert solar energy into usable electrical energy. Background Technology

[0002] Analysis of existing technologies reveals that GO (graphene oxide) membranes, produced for energy harvesting in water treatment processes, utilize the movement of charged particles (anions and cations) in the water being treated to collect energy (gain an electric current in the membrane). Using the working mechanism described in the literature, the kinetic energy of the charged particles can be converted into electrical energy and harvested. However, these studies indicate that the moving anion and cation particles accumulate on the membrane surface through Coulomb interactions, leading to membrane fouling, thus requiring repeated cleaning of the membrane surface. It is known that fouled membranes reduce filtrate permeability and cause the membrane to lose its function. For charged particles in the water, which serve as the energy source, to pass through the membrane pores, the pore size must be larger than the hydrodynamic radius of the charged particles. Increasing the pore size also leads to reduced membrane selectivity. Therefore, unwanted particles and residues are expected to be present in the treated water during filtration. Low membrane selectivity and low filtrate permeability and short membrane lifetime due to fouling problems in energy-harvesting membranes operating on this principle have been identified as technical problems. Therefore, a new membrane design is needed to overcome these shortcomings.

[0003] According to the literature review, no membrane structure or membrane system has been found that is doped with heterostructures (prepared with one-dimensional and two-dimensional carbon nanomaterials and titanium dioxide nanomaterials, such as rGO-TiO2 nanowire heterostructures) and can simultaneously collect solar energy during water filtration.

[0004] Chinese patent document CN113694915, belonging to the prior art, discloses a method for preparing a titanium dioxide / graphene composite material. The preparation method includes the following steps: dispersing graphene oxide powder in water to obtain a graphene oxide dispersion; dispersing nano-titanium dioxide in water to obtain a titanium dioxide dispersion; providing a substrate; coating the substrate with the graphene oxide dispersion and the titanium dioxide dispersion, and drying it to obtain a composite material precursor; and irradiating the composite material precursor with ultraviolet light to reduce the graphene oxide in the composite material precursor to reduced graphene oxide, thereby obtaining the titanium dioxide / reduced graphene oxide composite material. Summary of the Invention

[0005] This invention relates to a thin-film nanocomposite sandwich (TFNi) membrane, which aims to reduce the cost of clean water by converting solar energy into electrical energy during daytime water treatment processes and by improving the filtration performance of conventional thin-film composite (TFC) membranes, thereby reducing the net electrical energy consumption of the filtration system. The membrane is composed of a polymer microporous support membrane as the first component, a carbon-titanium dioxide heterostructure with PN junction region characteristics as the second component, and a cross-linked polymer selective permeation surface as the third component. This invention also relates to a method for producing the membrane.

[0006] One object of the present invention is to improve the filtration rate of conventional thin film composite (TFC) membranes and provide these membranes with anti-clogging properties by utilizing hydrophilic titanium dioxide nanomaterials in a carbon-titanium dioxide heterostructure (i.e., a second component between the first and third components in a layered membrane structure).

[0007] Another object of the present invention is to provide conductive properties to conventional thin film composite (TFC) films by utilizing carbon nanomaterials in a carbon-titanium dioxide heterostructure (i.e., the second component between the first and third components in a layered film structure, which have conductivity in a hexagonal structure through π bonds between carbon atoms that are sp² hybridized).

[0008] Another objective of this invention is to utilize the PN junction region, which exists when p-type semiconductor carbon nanomaterials and n-type semiconductor titanium dioxide nanomaterials are bonded together by Ti-OC bonds in a carbon-titanium dioxide heterostructure (i.e., the second component between the first and third components in a layered film structure), to provide conventional thin film composite (TFC) films with the ability to generate electricity from solar energy.

[0009] Another object of the present invention is to provide conventional thin film composite (TFC) membranes with the ability to separate different contaminants from the filter medium using the same materials by utilizing the ability to chemically modify the surfaces of carbon and titanium dioxide nanomaterials used in carbon-titanium dioxide heterostructures (i.e., the second component between the first and third components in a layered membrane structure).

[0010] Detailed description of the invention The "a filter membrane doped with carbon-titanium dioxide nanomaterials with a thin-film nanocomposite layer for generating electricity from solar energy and its production method thereof," which was developed to achieve the purpose of this invention, is shown in the accompanying drawings, wherein: Figure 1 This is a flowchart of the method of the present invention.

[0011] Figure 2It is the Fourier transform infrared spectrum of the reduced graphene oxide and titanium dioxide heterostructure.

[0012] Figure 3 This is a scanning electron microscope image of the heterostructure of reduced graphene oxide and titanium dioxide nanowires.

[0013] The method (100) for obtaining the membrane of the present invention capable of harvesting electrical energy from solar energy during the filtration process includes the following steps: - A heterostructure with PN junction region characteristics was obtained by using carbon nanomaterials and titanium dioxide nanomaterials (101). - Production of polymer microporous support membrane (102); - A heterostructure with PN junction region characteristics is coated onto the surface of a polymer microporous support membrane (103); and - Selective permeable surfaces (104) are produced by interfacial polymerization on the surface of a polymer microporous support membrane with a heterostructure having PN junction region characteristics.

[0014] In step (101) of the method (100) of the present invention, which involves obtaining a heterostructure (second component) with PN junction region characteristics using carbon nanomaterials and titanium dioxide nanomaterials, preferably 10 to 1000 mg of carbon nanomaterials and titanium dioxide nanomaterials powder, preferably in a ratio of 0.1% to 99.9% w / w, are weighed and added to a Teflon-lined stainless steel reactor. Preferably, 1 to 100 mL of deionized water is added, and the mixture is stirred at a preferred speed of 100 to 1000 rpm for 0.5 to 7 hours using a magnetic stirrer. After the magnetic stirring process, the magnetic stir bar is removed from the Teflon liner, the lid of the stainless steel reactor is closed, and the reactor is placed in an atmospheric pressure furnace. Preferably, the furnace is heated to a temperature between 100°C and 500°C at a preferred heating rate of 1°C / min to 50°C / min, and the simultaneous hydrothermal reduction is allowed to occur, preferably for 1 to 72 hours. During this stage, the hydrogen and hydroxyl groups on the surfaces of the carbon nanomaterials and titanium dioxide nanomaterials undergo hydrolysis, forming a carbon-titanium dioxide heterostructure through new Ti-OC bonds. After this process, the furnace is shut off and the reactor is cooled to room temperature. The cooled reactor is removed from the furnace, and the heterostructure, with a dark gray wet foam interior inside a Teflon liner, is dried in a drying oven, preferably at a temperature between 25°C and 200°C, for 1 to 72 hours. The dried structure is then heat-treated in an atmospheric pressure furnace, preferably in an open atmosphere, an argon atmosphere, or a nitrogen atmosphere, preferably at 200°C to 950°C, for 0.5 to 48 hours. During this stage, electron-withdrawing (p-type) carboxyl groups, carbonyl groups, and sp³-bonded hydroxyl, ether, and epoxy groups in the defect regions of the carbon nanostructure become more dominant than electron-donating (n-type) sp²-bonded hydroxyl, ether, and epoxy groups, causing the carbon nanomaterials in the heterostructure to exhibit p-type semiconductor properties. The temperature used in this stage does not change the semiconductor properties of titanium dioxide as an n-type semiconductor. Therefore, after this stage, a carbon-titanium dioxide heterostructure with PN junction region characteristics is obtained in the form of a black solid powder.

[0015] exist Figure 1 The Fourier transform infrared spectra obtained confirm that Ti-OC bonds were formed in the reduced graphene oxide and titanium dioxide nanowire heterostructure obtained after the hydrothermal reduction process, using graphene oxide as the carbon nanomaterial and titanium dioxide nanowires as the titanium dioxide nanomaterial.

[0016] exist Figure 2The images obtained from the scanning electron microscope confirm that the reduced graphene oxide and titanium dioxide nanowire heterostructure with PN junction region characteristics, obtained after hydrothermal reduction and thermal sintering processes using graphene oxide as carbon nanomaterial and titanium dioxide nanowire as titanium dioxide nanomaterial, are uniformly dispersed and there are no other unwanted residues in the structure.

[0017] In step (102) of the method (100) of the present invention for producing a polymer microporous support membrane, a hydrophilic polymer, preferably in the form of polysulfone, or a hydrophobic polymer, preferably in the form of polyvinylidene fluoride, in powder / granule form, is dissolved in an inorganic solvent (preferably in the form of pure water) or an organic solvent (preferably in the form of dimethylformamide) at a concentration preferably from 1% to 40% w / w in an autoclaved glass bottle, preferably for 1 to 24 hours using a magnetic stirrer. An inorganic liquid (preferably in the form of pure water) or an organic liquid (in the form of dimethylformamide) that is not a solvent for the polymer used and is immiscible with the solvent is added to a glass chemical bath. The polymer solution is poured onto a flat glass surface that can be placed in the chemical bath and coated to the desired thickness using a doctor blade coater. The glass surface coated with the polymer and its solvent is quickly placed into the chemical bath, and the solvent of the polymer is replaced by a non-solvent chemical liquid in the medium. During the phase transition polymerization process that occurs at this stage, a polymer microporous support membrane is formed on the glass surface. To completely remove the solvent from the formed membrane, the produced membrane is washed several times with the non-solvent chemical liquid used, and the chemical liquid remaining in the drying oven or at room temperature is evaporated. After the evaporation process, a polymer microporous supported membrane (first component) is obtained.

[0018] In step (103) of the method (100) of the present invention, which involves coating a heterostructure with PN junction region characteristics onto the surface of a polymer microporous support membrane, the heterostructure composed of the produced carbon-titanium dioxide nanomaterials is mixed with a high-purity solvent (preferably ethanol, methanol, or pure water) in an autoclaved glass bottle at room temperature using a magnetic stirrer for 1 to 24 hours. The resulting dispersion is then coated onto the surface of the polymer microporous support membrane by methods such as spin coating, spraying, or drop coating. After the coating process, the solvent is evaporated in a drying oven, preferably at a temperature between 25°C and 100°C, for several hours. The coating and evaporation processes can be repeated depending on the desired amount of nanomaterial per unit surface area. After the evaporation process, a polymer microporous support membrane coated with a heterostructure having PN junction region characteristics is obtained.

[0019] In step (104) of the method (100) of the present invention, a selectively permeable surface (third component) is produced by interfacial polymerization on the surface of a polymer microporous support membrane coated with a heterostructure having PN junction region characteristics. An inorganic solution, preferably based on water, ethanol, or methanol, in the form of m-phenylenediamine (MDPA), triethylamine (TEA), and camphor sulfonic acid (CSA), with weight / volume percentages (w / v%) of 2.0%, 1.0%, and 2.0%, is stirred in an autoclaved glass bottle, preferably at 25°C to 150°C, for 1 to 720 minutes using a magnetic stirrer. The prepared inorganic solution is transferred to a glass chemical bath. The polymer support membrane coated with the heterostructure having PN junction region characteristics is carefully placed into the chemical bath, and the inorganic solution in the chemical bath is allowed to be absorbed by the coated polymer structure, preferably for 1 to 60 minutes. In the subsequent process, an organic solution containing 0.01% to 7% trimesoyl chloride (TMC) by weight / volume in Isopar G (an isoparaffin solvent oil produced by ExxonMobil) is stirred with a magnetic stirrer in another autoclaved glass bottle at a temperature preferably between 25°C and 150°C. The membrane, having absorbed the inorganic monomer solution, is removed from the chemical bath and allowed to stand for several minutes to allow excess solvent remaining on the surface to evaporate. The resulting organic initiator solution is slowly poured onto the upper surface of the membrane, which is still saturated with respect to the monomer solution and coated with a heterogeneous structure exhibiting PN junction region characteristics. At this stage, interfacial polymerization of the selectively permeable surface occurs. After a few minutes, excess solvent in the resulting TFNi membrane structure is removed from the structure by washing, preferably with an inorganic or organic solvent. This washing process can be repeated several times. The TFNi membrane obtained after washing is dried in a drying oven, preferably at a temperature between 25°C and 230°C, preferably for 1 to 72 hours. After this stage, the production of the selectively permeable surface is complete.

[0020] The present invention also relates to a membrane doped with a carbon-titanium dioxide heterostructure having PN junction region characteristics, capable of converting solar energy into electrical energy during filtration, and obtained by following the steps of the method (100) described above. The TFNi membrane of the present invention is obtained by following the steps of the method described above.

[0021] The titanium dioxide nanomaterial component used in the heterostructure is preferably in a one-dimensional or two-dimensional morphology; it comprises any one or more of amorphous, anatase, rutile, and brookite crystal structures; and its surface contains hydrogen and hydroxyl groups. The carbon nanomaterial component used in the heterostructure consists of carbon atoms with sp² hybridization in a hexagonal structure, and its surface preferably contains functional groups, such as hydroxyl, carboxyl, and amino groups, that allow it to disperse in an aqueous medium.

[0022] To improve the filtration selectivity and conductivity of the final product, the carbon nanomaterial component and the titanium dioxide nanomaterial component in the heterostructure are mixed in an aqueous medium using a magnetic stirrer, vortex mixer, ultrasonic generator, or any similar method, preferably at a ratio of 0.1% to 99.9% w / w. To improve the filtration rate of the final product and provide anti-clogging performance, the titanium dioxide nanomaterial component and the carbon nanomaterial component in the heterostructure are mixed in an aqueous medium using a magnetic stirrer, vortex mixer, ultrasonic generator, or any similar method, preferably at a ratio of 0.1% to 99.9% w / w. To provide the final product with PN junction region characteristics capable of converting solar energy into electrical energy during the filtration process, the carbon nanomaterial and titanium dioxide nanomaterial components are chemically bonded through Ti-OC bonds to form a heterostructure through a simultaneous hydrothermal reduction process in a Teflon-lined stainless steel reactor, preferably between 100°C and 500°C, preferably for 1 to 72 hours. To provide the final product with PN junction region characteristics capable of converting solar energy into electrical energy during the filtration process, a heterostructure is sintered in a furnace, preferably at a temperature between 200°C and 950°C, for a preferred time of 1 to 48 hours, causing the semiconductor carbon nanomaterial component chemically bonded to the n-type semiconductor titanium dioxide nanomaterial component to differentiate into a p-type semiconductor. The carbon-titanium dioxide nanomaterial heterostructure with PN junction region characteristics is coated between a microporous support membrane (preferably hydrophilic in the form of polysulfone or hydrophobic in the form of polyvinylidene fluoride) and a selective permeation membrane (preferably hydrophilic in the form of polyamide or hydrophobic in the form of polydimethylsiloxane).

[0023] Within these basic conceptual frameworks, various embodiments of the present invention, “a filter membrane doped with carbon-titanium dioxide nanomaterials having a thin-film nanocomposite interlayer for generating electrical energy from solar energy and a method thereof,” can be developed; the invention is not limited to the examples disclosed herein and is essentially as claimed.

Claims

1. A method (100) for obtaining a membrane capable of harvesting electrical energy from solar energy during filtration, characterized in that, The method includes the following steps: - A heterostructure with PN junction region characteristics was obtained by using carbon nanomaterials and titanium dioxide nanomaterials (101). - Production of polymer microporous support membrane (102); - A heterostructure with PN junction region characteristics is coated onto the surface of a polymer microporous support membrane (103); and - Selective permeable surfaces (104) are produced by interfacial polymerization on the surface of a polymer microporous support membrane with a heterostructure having PN junction region characteristics.

2. The method (100) according to claim 1, characterized in that, In step (101) of obtaining a heterostructure with PN junction region characteristics by using carbon nanomaterials and titanium dioxide nanomaterials, a total amount of 10 to 1000 mg of carbon nanomaterials and titanium dioxide nanomaterials powder in a ratio of 0.1% to 99.9% w / w is weighed and added to a Teflon-lined stainless steel reactor, and then stirred with 1 to 100 mL of deionized water.

3. The method (100) according to claim 2, characterized in that, In step (101) of obtaining a heterostructure with PN junction region characteristics by using carbon nanomaterials and titanium dioxide nanomaterials, after the stirring process, the lid of the stainless steel reactor is closed and placed in an atmospheric pressure furnace; the furnace is heated to a temperature between 100°C and 500°C at a heating rate of 1°C / min to 50°C / min; and while waiting for simultaneous hydrothermal reduction to occur for 1 to 72 hours, the hydrogen and hydroxyl groups on the surface of the carbon nanomaterials and titanium dioxide nanomaterials are hydrolyzed and a carbon-titanium dioxide heterostructure is formed through new Ti-OC bonds.

4. The method (100) according to claim 2 or 3, characterized in that, In step (101) of obtaining a heterostructure with PN junction region characteristics by using carbon nanomaterials and titanium dioxide nanomaterials, after forming the carbon-titanium dioxide heterostructure, the furnace is closed and the reactor is cooled to room temperature; the cooled reactor is removed from the furnace, and the heterostructure in the form of dark gray wet foam inside the Teflon liner is dried in a drying oven heated to a temperature between 25°C and 200°C for 1 to 72 hours; the dried structure is heat-treated in an atmospheric pressure furnace at 200°C to 950°C for 0.5 to 48 hours in an open atmosphere, an argon atmosphere, or a nitrogen atmosphere; and during this stage, electron-withdrawing (p-type) carboxyl groups, carbonyl groups, and sp³-bonded hydroxyl groups, ether groups, and epoxy groups in the defect region of the carbon nanostructure become more dominant than electron-donating (n-type) sp²-bonded hydroxyl groups, ether groups, and epoxy groups, causing the carbon nanomaterials in the heterostructure to exhibit p-type semiconductor characteristics; and a carbon-titanium dioxide heterostructure with PN junction region characteristics in the form of a black solid powder is obtained.

5. The method (100) according to claim 1, characterized in that, In step (102) of producing the polymer microporous support membrane, a hydrophilic polymer in the form of polysulfone or a hydrophobic polymer in the form of polyvinylidene fluoride in powder / particle form is dissolved in an inorganic solvent in the form of pure water or an organic solvent in the form of dimethylformamide at a concentration of 1% to 40% w / w in an autoclaved glass bottle for 1 to 24 hours using a magnetic stirrer.

6. The method (100) according to claim 5, characterized in that, In step (102) of producing the polymer microporous support membrane, an inorganic liquid in the form of pure water or an organic liquid in the form of dimethylformamide, which is not a solvent for the polymer used and is not miscible with the solvent, is added to a glass chemical bath; the polymer solution is poured onto a flat glass surface that can be placed in the chemical bath and coated to the required thickness using a doctor blade coater.

7. The method (100) according to claim 5 or 6, characterized in that, In step (102) of producing the polymer microporous support membrane, a glass surface coated with the polymer and its solvent is rapidly placed into a chemical bath and the solvent of the polymer is replaced by a non-solvent chemical liquid in the medium; and during the phase transformation polymerization process that occurs in this replacement stage, a polymer microporous support membrane is formed on the glass surface.

8. The method (100) according to any one of claims 5 to 7, characterized in that, In step (102) of producing a polymer microporous support membrane, in order to completely remove the solvent from the formed membrane, the produced membrane is washed several times with the non-solvent chemical liquid used, and the chemical liquid remaining in the drying oven or at room temperature is evaporated; and after the evaporation process, a polymer microporous support membrane is obtained.

9. The method (100) according to claim 1, characterized in that, In step (103), the heterostructure having PN junction region characteristics is coated onto the surface of the polymer microporous support membrane. A dispersion is obtained by mixing the heterostructure composed of the produced carbon-titanium dioxide nanomaterial with a high-purity solvent in the form of ethanol, methanol or pure water in an autoclaved glass bottle at room temperature for 1 to 24 hours using a magnetic stirrer. The resulting dispersion is then coated onto the surface of the polymer microporous support membrane by methods such as spin coating, spraying, or drop coating.

10. The method (100) according to claim 9, characterized in that, In step (103), after coating the heterostructure with PN junction region characteristics onto the surface of the polymer microporous support membrane, the solvent used is evaporated in a drying oven at a temperature between 25°C and 100°C for several hours; after the evaporation process, a polymer microporous support membrane with a heterostructure having PN junction region characteristics is obtained.

11. The method (100) according to claim 1, characterized in that, In step (104), selectively permeable surfaces are produced by interfacial polymerization on the surface of a polymer microporous support membrane with a heterostructure having PN junction region characteristics. In this step, an inorganic solution based on water, ethanol, or methanol, in the form of m-phenylenediamine (MDPA), triethylamine (TEA), and camphor sulfonic acid (CSA) in weight / volume percentage (w / v%) ratios of 2.0%, 1.0%, and 2.0%, respectively, is stirred in an autoclaved glass bottle at 25°C to 150°C for 1 to 720 minutes using a magnetic stirrer.

12. The method (100) according to claim 11, characterized in that, In step (104), selective permeable surfaces are produced by interfacial polymerization on the surface of a polymer microporous support membrane coated with a heterostructure having PN junction region characteristics. The prepared inorganic solution is transferred to a glass chemical bath. The polymer support membrane coated with a heterostructure having PN junction region characteristics is carefully placed into the chemical bath, and the inorganic solution in the chemical bath is allowed to be absorbed by the coated polymer structure for 1 to 60 minutes.

13. The method (100) according to claim 11 or 12, characterized in that, In step (104), selectively permeable surfaces are produced by interfacial polymerization on the surface of a polymer microporous support membrane with a heterostructure having PN junction region characteristics. An organic solution of trimesoyl chloride (TMC) containing 0.01% to 7% by weight / volume in Isopar G is stirred with a magnetic stirrer in another autoclaved glass bottle at a temperature between 25°C and 150°C. The membrane that has absorbed the inorganic monomer solution is removed from the chemical bath and left for a few minutes to allow excess solvent remaining on the surface to evaporate.

14. The method (100) according to any one of claims 11 to 13, characterized in that, In step (104), the selective permeable surface is produced by interfacial polymerization on the surface of a polymer microporous support membrane coated with a heterostructure having PN junction region characteristics. The resulting organic initiator solution is slowly poured onto the upper surface of the membrane coated with the heterostructure having PN junction region characteristics, which is still saturated with respect to the monomer solution. At this stage, interfacial polymerization of the selective permeable surface occurs. After a few minutes, excess solvent in the resulting TFNi membrane structure is removed from the structure by washing with an inorganic or organic solvent. The selective permeable surface is produced after the TFNi membrane obtained after washing is dried in a drying oven at a temperature between 25°C and 230°C for preferably 1 to 72 hours.

15. A TFNi film obtained by following the steps of the above method (100) and doped with a carbon-titanium dioxide heterostructure having PN junction region characteristics, which is capable of converting solar energy into electrical energy during filtration.

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