CN115970520B - Preparation method of moth-eye structure bionic photocatalysis self-cleaning oil-water separation membrane - Google Patents
Preparation method of moth-eye structure bionic photocatalysis self-cleaning oil-water separation membrane Download PDFInfo
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W10/00—Technologies for wastewater treatment
- Y02W10/30—Wastewater or sewage treatment systems using renewable energies
- Y02W10/37—Wastewater or sewage treatment systems using renewable energies using solar energy
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Abstract
A preparation method of a moth-eye structure bionic photocatalysis self-cleaning oil-water separation film relates to a preparation method of a super-wettability and efficient oil-water separation film. The invention aims to solve the problems that most of dirt accumulation of the existing oil-water separation materials is difficult to remove, the oil-water separation efficiency is low and the application environment range is narrow. The method comprises the following steps: 1. preparing gel liquid; 2. preparing a moth eye bionic structure; 3. imprinting is carried out by a needle array mold; the prepared moth-eye structure bionic photocatalysis self-cleaning oil-water separation membrane has the light absorptivity of more than 95.2 percent, super-hydrophilicity and underwater super-oleophobic property, and can recover the super-hydrophilicity and the underwater super-oleophobic property after the pollution is invalid and the sunlight is irradiated for 0.5 to 1.0 h. The invention is used for preparing the moth-eye structure bionic photocatalysis self-cleaning oil-water separation membrane.
Description
Technical Field
The invention relates to a preparation method of an ultra-wettability and efficient oil-water separation membrane.
Background
Pollution of available water resources is a critical factor in damaging the environment and compromising human social safety. Therefore, efficient and convenient water pollution treatment technology is a focus of attention in the world today. In recent years, leakage of organic solvents is a common source of water contamination due to the increasing activity of the human offshore industry. However, existing conventional contaminant treatment methods, such as adsorption, flocculation, and chemical coagulation, are limited in practice by several factors. Most of these methods require the provision of energy input to be implemented, making them impractical for large scale industrial production in terms of cost, operability and ecological safety factors. In contrast, membrane separation technology has been widely used to treat water pollution problems caused by oily wastewater based on advantages of flexibility, low cost, and no need for external energy sources.
Currently, accumulation of fouling is an unavoidable key problem in the implementation of membrane separation technology. This is mainly because trace contaminants are affected by gravity, constantly deposited on the surface of the membrane during multiple uses, and eventually clog their internal passages, reducing permeate flow rate and separation efficiency. Super hydrophilic/underwater super evacuation membranes are ideal materials to solve this problem because of their good anti-fouling capabilities. However, although these membranes perform well in terms of stain resistance, the performance of these membranes can be impaired due to the accumulation of oil stains at the microstructure within the membranes over time and the multiple filtration of oily wastewater. Therefore, there is an urgent need to explore a film having excellent self-cleaning ability.
Photocatalytic degradation is an efficient and green technology and has many applications in environmental protection and new energy development. Compared with other traditional cleaning methods, the photocatalytic degradation has the advantages of low energy consumption, simple operation, no pollution and the like, and has been widely used in the study of the self-cleaning performance of the oil-water separation film. However, most of the existing photocatalytic degradation self-cleaning oil-water separation membranes only have the capability of degrading organic dyes. Meanwhile, the degradation speed is very slow, and the self-cleaning can be realized only under the illumination of fixed wavelength. This greatly limits its treatment of wastewater containing various organic substances and its application sites in practical processes. Therefore, it is imperative to develop an oil-water separation membrane which has high photocatalytic efficiency, can work under light of various wavelengths, and can degrade petroleum by photocatalysis.
Disclosure of Invention
The invention aims to solve the problems that most of dirt accumulation of oil-water separation materials is difficult to remove, the oil-water separation efficiency is low and the application environment range is narrow, and further provides a preparation method of the moth-eye structure bionic photocatalysis self-cleaning oil-water separation membrane.
A preparation method of a moth-eye structure bionic photocatalysis self-cleaning oil-water separation membrane is carried out according to the following steps:
1. Dissolving polyvinyl alcohol and tannic acid in ethanol water solution at the temperature of 80-90 ℃ to obtain a reaction system, adding magnetic titanium dioxide nano particles MTiO 2 into the reaction system at the temperature of 80-90 ℃ and fully mixing, then reducing the temperature to 70-75 ℃, dropwise adding MXene aqueous dispersion liquid, and uniformly stirring to obtain a gel liquid;
The volume ratio of the mass of the polyvinyl alcohol to the ethanol water solution is (0.6-0.8) g/40 mL; the volume ratio of the tannic acid to the ethanol water solution is (0.6-0.8) g/40 mL; the volume ratio of the mass of the magnetic titanium dioxide nano particle MTiO 2 to the ethanol water solution is (0.4-0.5) g to 40mL; the volume ratio of the MXene aqueous dispersion liquid to the ethanol aqueous solution is (2-2.5) 40;
2. Pouring the gel solution into a container with an iron wire mesh at the bottom, wherein the iron wire mesh is 1 cm-1.3 cm, drying, placing the dried gel solution and the container with the iron wire mesh at the bottom on a strong magnet, pouring magnetic titanium dioxide nano-particles MTiO 2 ethanol dispersion, controlling the poured magnetic titanium dioxide nano-particles MTiO 2 to form a moth-eye bionic structure on the surface of the gel solution through a magnetic control self-assembly method, and finally integrally drying to form a film and tearing down the lower iron wire mesh;
The concentration of the magnetic titanium dioxide nanoparticle MTiO 2 ethanol dispersion liquid is 0.2 g/mL-0.22 g/mL;
3. Imprinting the membrane prepared in the second step through a needle-shaped array die to obtain a porous channel, thereby obtaining the moth-eye structure bionic photocatalysis self-cleaning oil-water separation membrane;
The light absorptivity of the moth-eye structure bionic photocatalysis self-cleaning oil-water separation film is more than 95.2 percent;
The moth-eye structure bionic photocatalysis self-cleaning oil-water separation membrane has super hydrophilicity and underwater super oleophobicity, the water contact angle in the air is 0 degrees, the underwater oil contact angle is more than 150 degrees, and the separation efficiency is more than 99.85 percent when the oil-water mixed pollutant is treated;
When the pollution of the moth-eye structure bionic photocatalysis self-cleaning oil-water separation membrane fails, the moth-eye structure bionic photocatalysis self-cleaning oil-water separation membrane is irradiated for 0.5 to 1.0 hours under sunlight, and the super-hydrophilicity and underwater super-oleophobic performance can be recovered.
The beneficial effects of the invention are as follows:
1. The oil-water separation film has a bionic moth-eye structure, the structure has a light trapping effect, when the surface of the oil-water separation film is illuminated, incident light can be reflected on the surface of the oil-water separation film for multiple times, and then the multistage absorption of the film on incident photons is realized, and the light absorptivity of the oil-water separation film is effectively improved by more than 95.2%. This facilitates photocatalytic degradation of the oil contaminants by the photocatalytic medium in the membrane.
2. The MXene-MTiO 2 composite material in the oil-water separation film has a large amount of charge transfer on the surface under sunlight irradiation, so that oxidation-reduction reaction is realized, and free electron pairs in the composite material are in an active state and are more easily excited. The photocatalytic degradation capability of the oil-water separation film on oil pollutants is effectively enhanced.
3. The oil-water separation film has an efficient photocatalysis self-cleaning function. After the solar water heater fails due to pollution, after the solar light with the intensity of 4.0kW/m 2 irradiates for 0.5 to 1.0h, the super-hydrophilicity and the underwater super-oleophobic performance of the solar water heater are recovered, so that the high-efficiency photocatalysis self-cleaning is realized.
4. The oil-water separation film has super-strong hydrophilicity (the contact angle of water in air is 0 DEG), and super-oleophobic property under water (the contact angle of various oil under water is more than 150 DEG and can reach 161 DEG at most). This makes it possible to realize efficient separation of oil-water pollutants with an oil-water separation efficiency as high as 99.85% or more.
5. The oil-water separation film has strong anti-fouling capability. When the oil-water separation circulation is carried out for not more than 64 times, the high-efficiency and rapid oil-water separation (the separation efficiency is more than 95 percent, and the water flux is more than 3900L/m 2 & h) can be ensured.
6. The oil-water separation membrane has underwater super-oleophobic property for various oil substances, so that the oil-water separation membrane can be used for efficiently separating various oil and water mixed pollutants.
Drawings
Fig. 1 is a schematic diagram of a bionic surface SEM of a bionic photocatalytic self-cleaning oil-water separation film with a moth-eye structure prepared in example 1, (a) a SEM photograph of a bionic prototype scale with a moth-eye cone structure of 10 μm, (b) a SEM photograph of a bionic scale with a moth-eye structure of 1 μm on the surface of the oil-water separation film, (c) a SEM photograph of a bionic prototype scale with a moth-eye cone structure of 100nm, and (d) a SEM photograph of a bionic scale with a moth-eye structure of 100nm on the surface of the oil-water separation film;
FIG. 2 is a light absorption diagram of an oil-water separation film in a wavelength range of 200nm to 2500nm, 1 is a bionic photocatalytic self-cleaning oil-water separation film with a moth-eye structure prepared in example 1, and 2 is an oil-water separation film prepared in comparative example 1;
FIG. 3 is a graph showing the comparison of water contact angle and underwater oil contact angle of an oil-water separation film;
FIG. 4 is a graph showing the oil-water separation efficiency of an oil-water separation membrane and the flow rate during the separation process;
Fig. 5 is a diagram of the oil-water separation process of the moth-eye structured bionic photocatalytic self-cleaning oil-water separation membrane prepared in example 1;
FIG. 6 is a graph showing the comparison of the contact angles of the moth-eye structured bionic photocatalytic self-cleaning oil-water separation membrane prepared in example 1 with the underwater oil of different oil-water mixtures;
FIG. 7 is a graph showing the comparison of the oil-water separation efficiency of the moth-eye structured bionic photocatalytic self-cleaning oil-water separation membrane prepared in example 1 for different oil-water mixtures and the flow rate during the separation process;
Fig. 8 is a diagram showing the separation characteristics of the moth-eye structured bionic photocatalytic self-cleaning oil-water separation membrane prepared in example 1 for separating an oil-water mixture at multiple cycles;
Fig. 9 is a graph showing the comparison of the contact angles of underwater oil after photocatalytic self-cleaning of the moth-eye structured bionic photocatalytic self-cleaning oil-water separation film prepared in example 1;
fig. 10 is a graph showing comparison of oil-water separation efficiency and flow rate in the separation process after photocatalytic self-cleaning of the moth-eye structured bionic photocatalytic self-cleaning oil-water separation membrane prepared in example 1.
Detailed Description
The first embodiment is as follows: the preparation method of the moth-eye structure bionic photocatalysis self-cleaning oil-water separation membrane is carried out according to the following steps:
1. Dissolving polyvinyl alcohol and tannic acid in ethanol water solution at the temperature of 80-90 ℃ to obtain a reaction system, adding magnetic titanium dioxide nano particles MTiO 2 into the reaction system at the temperature of 80-90 ℃ and fully mixing, then reducing the temperature to 70-75 ℃, dropwise adding MXene aqueous dispersion liquid, and uniformly stirring to obtain a gel liquid;
The volume ratio of the mass of the polyvinyl alcohol to the ethanol water solution is (0.6-0.8) g/40 mL; the volume ratio of the tannic acid to the ethanol water solution is (0.6-0.8) g/40 mL; the volume ratio of the mass of the magnetic titanium dioxide nano particle MTiO 2 to the ethanol water solution is (0.4-0.5) g to 40mL; the volume ratio of the MXene aqueous dispersion liquid to the ethanol aqueous solution is (2-2.5) 40;
2. Pouring the gel solution into a container with an iron wire mesh at the bottom, wherein the iron wire mesh is 1 cm-1.3 cm, drying, placing the dried gel solution and the container with the iron wire mesh at the bottom on a strong magnet, pouring magnetic titanium dioxide nano-particles MTiO 2 ethanol dispersion, controlling the poured magnetic titanium dioxide nano-particles MTiO 2 to form a moth-eye bionic structure on the surface of the gel solution through a magnetic control self-assembly method, and finally integrally drying to form a film and tearing down the lower iron wire mesh;
The concentration of the magnetic titanium dioxide nanoparticle MTiO 2 ethanol dispersion liquid is 0.2 g/mL-0.22 g/mL;
3. Imprinting the membrane prepared in the second step through a needle-shaped array die to obtain a porous channel, thereby obtaining the moth-eye structure bionic photocatalysis self-cleaning oil-water separation membrane;
The light absorptivity of the moth-eye structure bionic photocatalysis self-cleaning oil-water separation film is more than 95.2 percent;
The moth-eye structure bionic photocatalysis self-cleaning oil-water separation membrane has super hydrophilicity and underwater super oleophobicity, the water contact angle in the air is 0 degrees, the underwater oil contact angle is more than 150 degrees, and the separation efficiency is more than 99.85 percent when the oil-water mixed pollutant is treated;
When the pollution of the moth-eye structure bionic photocatalysis self-cleaning oil-water separation membrane fails, the moth-eye structure bionic photocatalysis self-cleaning oil-water separation membrane is irradiated for 0.5 to 1.0 hours under sunlight, and the super-hydrophilicity and underwater super-oleophobic performance can be recovered.
The embodiment is based on the emerging materials MXene and MTiO 2, a moth-eye bionic structure is built through a magnetic control self-assembly method, and meanwhile, an oil-water separation film capable of efficiently separating oil from water can be achieved, a light trapping effect is achieved through multiple reflections of light incident on the surface of the film, and therefore efficient light absorption is achieved. Meanwhile, when MXene and MTiO 2 contained in the oil-water separation film are irradiated by sunlight, oxidation-reduction reaction occurs at the interface of titanium dioxide and ferroferric oxide particles, and a large amount of charge transfer exists. These promote the capture of photo-generated electrons and holes by oxygen and water molecules dissolved in the oil-water contaminants, thereby generating superoxide radicals and highly reactive hydroxyl radicals. The super-oxygen free radical and the high-activity hydroxyl and pollutant molecules act to decompose the super-oxygen free radical into nontoxic carbon dioxide and water, and finally the photocatalytic self-cleaning of the oil-water separation film is realized, namely, after the oil-water separation film is subjected to multiple oil-water separation processes, the oil-water separation film can realize photocatalytic degradation on oil pollutants remained on the surface after short-time sunlight irradiation so as to recover to an initial state, and the high-efficiency photocatalytic self-cleaning function is realized.
Principle of:
The moth-eye structure bionic photocatalysis self-cleaning oil-water separation membrane prepared by the embodiment can realize efficient oil-water separation and multiple recycling times, and is mainly beneficial to super-hydrophilicity (water contact angle is 0 degree in air) and underwater super-oleophobicity (various underwater oil contact angles are all larger than 150 degrees and can reach 161 degrees at most). This allows for efficient contaminant separation by inducing water phase permeation while blocking oil phase permeation when it is treating oil-water mixed contaminants. Meanwhile, the excellent anti-fouling capability of the oil-water separator can ensure efficient and rapid oil-water separation when the oil-water separation cycle is carried out for not more than 64 times.
The self-cleaning oil-water separation film with the moth-eye structure and the self-cleaning method can realize self-cleaning by photocatalysis, which is mainly characterized in that electrons in a Valence Band (VB) of MTiO 2 -MXene are excited under the irradiation of visible light, and electron-hole pairs (e -/h+) are generated by absorbing the light energy of photons (hv), and the photons are then transited to a Conduction Band (CB) of the self-cleaning oil-water separation film. Dissociation of a large number of photogenerated electron-hole pairs reduces electrons distributed around MTiO 2 MXene, which further promotes high-speed transport of free electrons within the nanoparticle and accelerates the movement of the photogenerated electrons. The photo-generated electrons are able to capture oxygen dissolved in the oil-water mixture, thereby generating superoxide radical O 2 ·-. It has strong oxidizing power to organic macromolecules dispersed in solution. In addition, the photogenerated holes induce water molecules to form highly reactive hydroxyl groups (· OH) by oxidation. Finally ·OH、O2 ·- and h + attack the contaminant molecules, causing them to break down into non-toxic carbon dioxide and water. The photocatalytic degradation equation is as follows:
MTiO2-MXene+hv→h++e-
e-+O2→O2 ·-
h++H2O→·OH+H+
O2 ·-+·OH+h++pollutants→CO2+H2O。
The function of this embodiment wire netting:
(1) The moth-eye array structure is prevented from being too dense, and the moth-eye array structure is prevented from being damaged during imprinting. Meanwhile, the excessively dense moth-eye array structure is unfavorable for the light trapping effect. (2) The stripping is facilitated, and the gel liquid can adhere to the bottom of the container in the drying process, so that the stripping is not facilitated. Thus, placement of the expanded metal facilitates demolding.
The beneficial effects of this embodiment are:
1. The oil-water separation film has a bionic moth-eye structure, the structure has a light trapping effect, when the surface of the oil-water separation film is illuminated, incident light can be reflected on the surface of the oil-water separation film for multiple times, and then the multistage absorption of the film on incident photons is realized, and the light absorptivity of the oil-water separation film is effectively improved by more than 95.2%. This facilitates photocatalytic degradation of the oil contaminants by the photocatalytic medium in the membrane.
2. The MXene-MTiO 2 composite material in the oil-water separation film has a large amount of charge transfer on the surface under sunlight irradiation, so that oxidation-reduction reaction is realized, and free electron pairs in the composite material are in an active state and are more easily excited. The photocatalytic degradation capability of the oil-water separation film on oil pollutants is effectively enhanced.
3. The oil-water separation film has an efficient photocatalysis self-cleaning function. After the solar water heater fails due to pollution, after the solar light with the intensity of 4.0kW/m 2 irradiates for 0.5 to 1.0h, the super-hydrophilicity and the underwater super-oleophobic performance of the solar water heater are recovered, so that the high-efficiency photocatalysis self-cleaning is realized.
4. The oil-water separation film has super-strong hydrophilicity (the contact angle of water in air is 0 DEG), and super-oleophobic property under water (the contact angle of various oil under water is more than 150 DEG and can reach 161 DEG at most). This makes it possible to realize efficient separation of oil-water pollutants with an oil-water separation efficiency as high as 99.85% or more.
5. The oil-water separation film has strong anti-fouling capability. When the oil-water separation circulation is carried out for not more than 64 times, the high-efficiency and rapid oil-water separation (the separation efficiency is more than 95 percent, and the water flux is more than 3900L/m 2 & h) can be ensured.
6. The oil-water separation membrane has underwater super-oleophobic property for various oil substances, so that the oil-water separation membrane can be used for efficiently separating various oil and water mixed pollutants.
The second embodiment is as follows: the first difference between this embodiment and the specific embodiment is that: the full mixing in the first step is specifically that a magnetic stirrer is used for stirring for 1 to 1.2 hours under the condition that the rotating speed is 800 to 1200 r/min; the stirring in the first step is carried out for 0.8 to 1 hour under the condition that the rotating speed is 600 to 900 r/min. The other is the same as in the first embodiment.
And a third specific embodiment: this embodiment differs from one or both of the embodiments in that: the molecular weight of the polyvinyl alcohol in the first step is 1750+/-50, the molecular weight of the tannic acid is 1701+/-50, and the purity is AR grade. The other is the same as the first or second embodiment.
The specific embodiment IV is as follows: this embodiment differs from one of the first to third embodiments in that: the volume ratio of water to absolute ethyl alcohol in the ethyl alcohol aqueous solution in the first step is 1 (1-1.2). The other embodiments are the same as those of the first to third embodiments.
Fifth embodiment: this embodiment differs from one to four embodiments in that: the magnetic titanium dioxide nano particles MTiO 2 in the first step and the second step are hydrophilic, and the main components are TiO 2 and Fe 3O4. The other embodiments are the same as those of the first to fourth embodiments.
Specific embodiment six: this embodiment differs from one of the first to fifth embodiments in that: the MXene aqueous dispersion in the first step is a single-layer Ti 3C2Tx aqueous dispersion, the concentration is 5 mg/mL-6 mg/mL, and the purity of the single-layer Ti 3C2Tx is more than 99.9%. The other embodiments are the same as those of the first to fifth embodiments.
Seventh embodiment: this embodiment differs from one of the first to sixth embodiments in that: the wire netting in the second step is the wire netting after pretreatment, and the aperture of the wire netting is 0.12 mm-0.15 mm; the pretreatment is specifically carried out according to the following steps: immersing the wire netting in acetic acid with the mass percentage of 10-12% for 5-6 h, sequentially placing the wire netting in acetone and absolute ethyl alcohol under the condition of the power of 80-100W, respectively ultrasonically cleaning for 10-20 min, then flushing for 3-4 times by using deionized water, and finally introducing nitrogen for drying. The other embodiments are the same as those of the first to sixth embodiments.
Eighth embodiment: this embodiment differs from one of the first to seventh embodiments in that: the dosage of the magnetic titanium dioxide nanoparticle MTiO 2 ethanol dispersion liquid in the second step is (0.5-0.6) mL/cm 2. The other is the same as in embodiments one to seven.
Detailed description nine: this embodiment differs from one to eight of the embodiments in that: and step two, the strong magnet is a neodymium magnet. The others are the same as in embodiments one to eight.
Detailed description ten: this embodiment differs from one of the embodiments one to nine in that: and step three, the needle diameter in the needle array mould is 0.2 mm-0.3 mm. The others are the same as in embodiments one to nine.
The following examples are used to verify the benefits of the present invention:
Example 1:
A preparation method of a moth-eye structure bionic photocatalysis self-cleaning oil-water separation membrane is carried out according to the following steps:
1. Dissolving 0.7g of polyvinyl alcohol and 0.7g of tannic acid in 40mL of ethanol water solution at the temperature of 90 ℃ to obtain a reaction system, adding 0.4g of magnetic titanium dioxide nano particles MTiO 2 into the reaction system at the temperature of 90 ℃, stirring for 1h at the rotating speed of 1000r/min by using a magnetic stirrer, then reducing the temperature to 75 ℃, dropwise adding 2mLMXene aqueous dispersion liquid, and stirring for 0.8h at the rotating speed of 700r/min to obtain a gel solution;
2. pouring the gel solution into an evaporation pan with an iron wire net at the bottom, wherein the evaporation pan is over 1cm of the iron wire net, drying for 4 hours in a vacuum drying oven with the temperature of 60 ℃, placing the dried gel solution and a container with the iron wire net at the bottom on a strong magnet, pouring magnetic titanium dioxide nano-particle MTiO 2 ethanol dispersion liquid, controlling the poured magnetic titanium dioxide nano-particle MTiO 2 to form a moth-eye bionic structure on the surface of the gel solution through a magnetic control self-assembly method, integrally drying in the vacuum drying oven with the temperature of 55 ℃, and tearing down the lower iron wire net to obtain a film with the thickness of 0.25 mm;
The concentration of the magnetic titanium dioxide nanoparticle MTiO 2 ethanol dispersion liquid is 0.2g/mL;
3. imprinting the membrane prepared in the second step through a needle-shaped array die to obtain a porous channel, and finally obtaining the moth-eye structure bionic photocatalysis self-cleaning oil-water separation membrane;
The molecular weight of the polyvinyl alcohol in the first step is 1750+/-50, the molecular weight of the tannic acid is 1701+/-50, and the purity is AR grade.
The volume ratio of water to absolute ethyl alcohol in the ethyl alcohol aqueous solution in the first step is 1:1.
The magnetic titanium dioxide nano-particles MTiO 2 in the first and second steps are hydrophilic, and the main components are TiO 2 and Fe 3O4, which are purchased from Nanjing pioneer nanotechnology Co., ltd., number: XF245, particle size: 1.2.+ -. 0.2 μm.
The MXene aqueous dispersion in the first step is a single-layer Ti 3C2Tx aqueous dispersion, the concentration is 5mg/mL, and the purity of the single-layer Ti 3C2Tx is more than 99.9%.
The diameter of the evaporation pan in the second step is 50mm; the wire netting in the second step is a pretreated wire netting, the wire netting is round with the diameter of 40mm, the aperture of 0.15mm, and the diameter of the wire netting is 10 microns; the pretreatment is specifically carried out according to the following steps: immersing the wire netting in acetic acid with the mass percentage of 10% for 5 hours, sequentially placing the wire netting in acetone and absolute ethyl alcohol under the condition of the power of 80W, respectively ultrasonically cleaning the wire netting for 10 minutes, then flushing the wire netting with deionized water for 3 times, and finally introducing nitrogen for drying.
The dosage of the magnetic titanium dioxide nanoparticle MTiO 2 ethanol dispersion liquid in the second step is 0.5mL/cm 2;
The strong magnet in the second step is a neodymium magnet, and the dimensions are 50mm×50mm×20mm (length×width×height).
The needle array mould in the third step is a3×3 needle array, the diameter of the needle is 0.2mm, the height is 2.5mm, and the mould size is 25×25mm.
Comparative example 1:
Dissolving 0.7g of polyvinyl alcohol and 0.7g of tannic acid in 40mL of ethanol water solution at the temperature of 90 ℃, drying the solution into a film with the thickness of 0.25mm in a vacuum drying oven at the temperature of 60 ℃, and embossing the film through a needle-shaped array die to obtain a porous channel to obtain an oil-water separation film; the molecular weight of the polyvinyl alcohol is 1750+/-50, the molecular weight of the tannic acid is 1701+/-50, and the purities are all AR grades; the volume ratio of water to absolute ethyl alcohol in the ethyl alcohol aqueous solution is 1:1; the needle array die is a 3X 3 needle array, the diameter of the needle is 0.2mm, the height is 2.5mm, and the size of the die is 25X 25mm.
Comparative example 2:
Dissolving 0.7g of polyvinyl alcohol and 0.7g of tannic acid in 40mL of ethanol water solution at the temperature of 90 ℃ to obtain a reaction system, adding 0.4g of titanium dioxide nano-particle TiO 2 into the reaction system at the temperature of 90 ℃, stirring for 1h by using a magnetic stirrer at the rotating speed of 1000r/min, drying in a vacuum drying oven at the temperature of 60 ℃ to obtain a film with the thickness of 0.25mm, and embossing the film through a needle array die to obtain a porous channel to obtain an oil-water separation film; the molecular weight of the polyvinyl alcohol is 1750+/-50, the molecular weight of the tannic acid is 1701+/-50, and the purities are all AR grades; the volume ratio of water to absolute ethyl alcohol in the ethyl alcohol aqueous solution is 1:1; the titanium dioxide nano-particle TiO 2 is hydrophilic and has the particle size of 30nm plus or minus 5nm; the needle array die is a 3X 3 needle array, the diameter of the needle is 0.2mm, the height is 2.5mm, and the size of the die is 25X 25mm.
Comparative example 3:
Dissolving 0.7g of polyvinyl alcohol and 0.7g of tannic acid in 40mL of ethanol water solution at the temperature of 90 ℃ to obtain a reaction system, adding 0.4g of magnetic titanium dioxide nano particles MTiO 2 into the reaction system at the temperature of 90 ℃, stirring for 1h by using a magnetic stirrer at the rotating speed of 1000r/min, drying in a vacuum drying oven at the temperature of 60 ℃ to obtain a film with the thickness of 0.25mm, and embossing the film by a needle array die to obtain a porous channel to obtain an oil-water separation film; the molecular weight of the polyvinyl alcohol is 1750+/-50, the molecular weight of the tannic acid is 1701+/-50, and the purities are all AR grades; the volume ratio of water to absolute ethyl alcohol in the ethyl alcohol aqueous solution is 1:1; the magnetic titanium dioxide nanoparticle MTiO 2 is hydrophilic, and comprises main components of TiO 2 and Fe 3O4, and is purchased from Nanjing pioneer nanotechnology Co., ltd., number: XF245, particle size: 1.2+/-0.2 mu m; the needle array die is a 3X 3 needle array, the diameter of the needle is 0.2mm, the height is 2.5mm, and the size of the die is 25X 25mm.
Comparative example 4:
Dissolving 0.7g of polyvinyl alcohol and 0.7g of tannic acid in 40mL of ethanol water solution at the temperature of 90 ℃ to obtain a reaction system, stirring for 1h at the rotating speed of 1000r/min by using a magnetic stirrer, then dropping 2mLMXene aqueous dispersion at the temperature of 75 ℃, stirring for 0.8h at the rotating speed of 700r/min, finally drying in a vacuum drying oven at the temperature of 60 ℃ to obtain a film with the thickness of 0.25mm, and embossing the film by using a needle-shaped array die to obtain a porous channel to obtain the oil-water separation film; the molecular weight of the polyvinyl alcohol is 1750+/-50, the molecular weight of the tannic acid is 1701+/-50, and the purities are all AR grades; the volume ratio of water to absolute ethyl alcohol in the ethyl alcohol aqueous solution is 1:1; the MXene aqueous dispersion is a single-layer Ti 3C2Tx aqueous dispersion, the concentration is 5mg/mL, and the purity of the single-layer Ti 3C2Tx is more than 99.9%; the needle array die is a 3X 3 needle array, the diameter of the needle is 0.2mm, the height is 2.5mm, and the size of the die is 25X 25mm.
The method comprises the following steps of (1) SEM test of a moth-eye structure bionic photocatalysis self-cleaning oil-water separation membrane:
Fig. 1 is a schematic diagram of a bionic surface SEM of a bionic photocatalytic self-cleaning oil-water separation film with a moth-eye structure prepared in example 1, (a) a SEM photograph of a bionic prototype scale with a moth-eye cone structure of 10 μm, (b) a SEM photograph of a bionic scale with a moth-eye structure of 1 μm on the surface of an oil-water separation film, (c) a SEM photograph of a bionic prototype scale with a moth-eye cone structure of 100nm, and (d) a SEM photograph of a bionic scale with a moth-eye structure of 100nm on the surface of an oil-water separation film. As can be seen from figures (a) and (c), the moth eye is composed of a plurality of hexagonal structures, while the interior of the hexagon is composed of a series of cone-shaped structures. The cone-shaped structures have light trapping effect and can effectively absorb external photons, so that moth eyes have high light absorptivity. While figures (b) and (d) show the distribution of MTiO 2 nanoparticles on the surface of the oil-water separation film, and the sample was observed to have a cone-like structure on the surface of the composite film at a 60 ° tilt angle by scanning electron microscopy, the cone-like structure being similar to the microstructure of the inside of the moth eye. The structures have the light trapping effect, can realize multiple reflections on light rays incident on the surface of the film and promote multi-stage absorption of photons, so that the light absorption efficiency of the film is greatly enhanced, and the photocatalysis effect of the film is further improved.
FIG. 2 is a light absorption diagram of an oil-water separation film in a wavelength range of 200nm to 2500nm, 1 is a bionic photocatalytic self-cleaning oil-water separation film with a moth-eye structure prepared in example 1, and 2 is an oil-water separation film prepared in comparative example 1; it can be seen that the light absorptivity of the oil-water separation film is improved from 14.2% to 95.6% by introducing the MXene, the MTiO 2 and the moth-eye bionic structure.
And (II) identifying the oil-water separation characteristics of the moth-eye structure bionic photocatalysis self-cleaning oil-water separation film:
(1) Contact angle test of moth-eye structure bionic photocatalysis self-cleaning oil-water separation film:
The bionic photocatalytic self-cleaning oil-water separation film with the moth-eye structure prepared in example 1 and the oil-water separation films prepared in comparative examples 1, 2, 3 and 4 were flatly placed on a contact angle measuring instrument, and then 2 microliter water drops were slowly attached to the surfaces of the different films, and the contact angle of water was measured by using the contact angle measuring instrument. The contact angle of the water oil is measured by a contact angle measuring instrument, and the result is shown in figure 3, and figure 3 is a comparison graph of the water contact angle and the underwater oil contact angle of the oil-water separation film; from the graph, the moth-eye structure bionic photocatalysis self-cleaning oil-water separation membrane has the lowest water contact angle of 0 degree. Proved by the super-hydrophilicity of the photo-catalytic self-cleaning oil-water separation membrane with the moth-eye structure. The moth-eye structure bionic photocatalytic self-cleaning oil-water separation membrane has a maximum underwater oil contact angle of 161 degrees, and proves that the moth-eye structure imitates the underwater super-oleophobicity of the photocatalytic self-cleaning oil-water separation membrane.
(2) Oil-water separation characteristic test of moth-eye structure bionic photocatalysis self-cleaning oil-water separation film:
N-hexane-water mixture (the volume ratio of n-hexane to water is 1:1, and water is marked by blue ink) is respectively prepared by the method of example 1 to prepare a moth-eye structure bionic photocatalytic self-cleaning oil-water separation membrane and the oil-water separation membranes prepared by the method of comparative examples 1,2, 3 and 4, and fig. 5 is a diagram of an oil-water separation process of the moth-eye structure bionic photocatalytic self-cleaning oil-water separation membrane prepared by the method of example 1; the specific process is as follows: super-hydrophilicity/underwater super-oleophobicity based on moth-eye structure bionic photocatalysis self-cleaning oil-water separation membrane, and high-efficiency oil-water separation is realized. When the membrane contacts with the oil-water mixture, the oil phase cannot permeate the oil-water separation membrane and the water phase can permeate the oil phase, so that the oil phase is effectively separated above the oil-water separation membrane, and water is collected below the oil-water separation membrane through the oil-water separation membrane. First, the collected oil-water mixture is poured into a glass pipe fixed above an oil-water separation film by a beaker, and oil of the oil-water mixture can be collected by forming an oil column in the glass pipe because the oil cannot pass through the oil-water separation film. Then, since water can pass through the oil-water separation membrane, it can be collected in the conical flask below the oil-water separation membrane.
By measuring the oil amount (V 1) in the oil-water mixture before separation and the oil amount (V 2) in the oil-water mixture collected in the conical flask after separation, the separation efficiency (SE%) of the oil-water separation film was calculated as follows: SE% = (1-V 2/V1) ×100% and the flow rate during separation (Flux, unit Lm -2h-1) is calculated from the volume of filtered water (V, unit L), membrane contact area (a, unit m 2) and separation time (t, unit h) via the formula:
FIG. 4 is a graph showing the oil-water separation efficiency of an oil-water separation membrane and the flow rate during the separation process; from the graph, the moth-eye structure bionic photocatalytic self-cleaning oil-water separation membrane prepared in the embodiment 1 has extremely high oil-water separation efficiency of 99.85% and relatively high oil-water separation speed 6815.85Lm -2h-1.
Thirdly, identifying oil-water separation characteristics of the moth-eye structure bionic photocatalysis self-cleaning oil-water separation membrane under different oil-water mixture environments:
N-hexane in experiment (two) was treated with different kinds of oils: gasoline, soybean oil, gear oil, dimethylbenzene and aniline are replaced, and the oil-water separation characteristic of the moth-eye structure bionic photocatalysis self-cleaning oil-water separation membrane is tested according to an experimental (II) contact angle test and an oil-water separation characteristic test method. FIG. 6 is a graph showing the comparison of the contact angles of the moth-eye structured bionic photocatalytic self-cleaning oil-water separation membrane prepared in example 1 with the underwater oil of different oil-water mixtures; from the figure, the bionic photocatalytic self-cleaning oil-water separation film with the moth-eye structure prepared in the embodiment 1 has the underwater contact angles of more than 150 degrees for various oils and has the underwater super-oleophobicity for various oils. FIG. 7 is a graph showing the comparison of the oil-water separation efficiency of the moth-eye structured bionic photocatalytic self-cleaning oil-water separation membrane prepared in example 1 for different oil-water mixtures and the flow rate during the separation process; from the figure, the oil-water separation film has higher separation efficiency (> 99%) and higher separation speed (> 5783.8Lm -2h-1) for various oil-water mixtures.
Fourthly, identifying the oil-water separation characteristics of the moth-eye structure bionic photocatalysis self-cleaning oil-water separation membrane under multiple oil-water separation cycle experiments:
And (3) carrying out repeated cyclic separation on the cyclohexane-water mixture according to an experimental (II) oil-water separation method, and respectively counting the separation efficiency, the underwater oil contact angle and the flow velocity after single cycle. Fig. 8 is a diagram showing the separation characteristics of the moth-eye structured bionic photocatalytic self-cleaning oil-water separation membrane prepared in example 1 for separating an oil-water mixture at multiple cycles. It can be seen that underwater oleophobic properties (underwater oil contact angle higher than 130 °) are maintained over a plurality of cycles. Meanwhile, the oil-water separation device can achieve good oil-water separation effect in a plurality of circulation, the oil-water separation efficiency in 64 circulation is higher than 95%, and the separation speed is higher than 3900Lm -2h-1.
And (V) identifying the photocatalysis self-cleaning property of the moth-eye structure bionic photocatalysis self-cleaning oil-water separation membrane:
The experiment (IV) is conducted through more than 64 cycles, the bionic photocatalysis self-cleaning oil-water separation film with a moth-eye structure, which is invalid when the pollution degree is too high (the oil-water separation efficiency is lower than 95 percent and the separation speed is lower than 3900Lm -2h-1), is placed under a xenon lamp with the light intensity of 4.0kW/m 2, is irradiated by simulated sunlight to degrade and clean photocatalytic pollutants, and the oil-water separation film can be recovered to an initial state after a period of irradiation, so that efficient oil-water separation can be continued. Fig. 9 is a graph showing comparison of the contact angle of the oil and water under water after the photocatalytic self-cleaning of the moth-eye structure bionic photocatalytic self-cleaning oil-water separation film prepared in example 1, and the oil and water contact angle of the oil-water separation film is recovered to 160 degrees after 1 hour of irradiation, so that the super oleophobic property under water can be recovered. FIG. 10 is a graph showing the comparison of the oil-water separation efficiency and the flow rate in the separation process after the photocatalytic self-cleaning of the moth-eye structured bionic photocatalytic self-cleaning oil-water separation membrane prepared in example 1; from the graph, after the simulated sunlight irradiation for 0.5 hour, the separation efficiency of the oil-water separation film is recovered to 99.23%, and the flow rate is recovered to 6740.68Lm -2h-1 (about 98.9% of the initial flow rate of the oil-water separation film). After 2 hours of simulated sunlight irradiation, the separation efficiency of the oil-water separation film is recovered to 99.82%, and the flow rate is recovered to 6814.29Lm -2h-1 (about 99.98% of the initial flow rate of the oil-water separation film). The service life of the oil-water separation membrane is further prolonged effectively, and the simple and convenient in-situ solar catalysis self-cleaning function is realized.
Claims (9)
1. The preparation method of the moth-eye structure bionic photocatalysis self-cleaning oil-water separation membrane is characterized by comprising the following steps of:
1. Dissolving polyvinyl alcohol and tannic acid in ethanol water solution at the temperature of 80-90 ℃ to obtain a reaction system, adding magnetic titanium dioxide nano particles MTiO 2 into the reaction system at the temperature of 80-90 ℃ and fully mixing, then reducing the temperature to 70-75 ℃, dropwise adding MXene aqueous dispersion liquid, and uniformly stirring to obtain a gel liquid;
The volume ratio of the mass of the polyvinyl alcohol to the ethanol water solution is (0.6-0.8) g/40 mL; the volume ratio of the tannic acid to the ethanol water solution is (0.6-0.8) g/40 mL; the volume ratio of the mass of the magnetic titanium dioxide nano particle MTiO 2 to the ethanol water solution is (0.4-0.5) g to 40mL; the volume ratio of the MXene aqueous dispersion liquid to the ethanol aqueous solution is (2-2.5) 40;
2. Pouring the gel solution into a container with an iron wire mesh at the bottom, wherein the iron wire mesh is 1 cm-1.3 cm, drying, placing the dried gel solution and the container with the iron wire mesh at the bottom on a strong magnet, pouring magnetic titanium dioxide nano-particles MTiO 2 ethanol dispersion, controlling the poured magnetic titanium dioxide nano-particles MTiO 2 to form a moth-eye bionic structure on the surface of the gel solution through a magnetic control self-assembly method, and finally integrally drying to form a film and tearing down the lower iron wire mesh;
The concentration of the magnetic titanium dioxide nanoparticle MTiO 2 ethanol dispersion liquid is 0.2 g/mL-0.22 g/mL;
3. Imprinting the membrane prepared in the second step through a needle-shaped array die to obtain a porous channel, thereby obtaining the moth-eye structure bionic photocatalysis self-cleaning oil-water separation membrane;
The light absorptivity of the moth-eye structure bionic photocatalysis self-cleaning oil-water separation film is more than 95.2 percent;
The moth-eye structure bionic photocatalysis self-cleaning oil-water separation membrane has super hydrophilicity and underwater super oleophobicity, the water contact angle in the air is 0 degrees, the underwater oil contact angle is more than 150 degrees, and the separation efficiency is more than 99.85 percent when the oil-water mixed pollutant is treated;
When the pollution of the moth-eye structure bionic photocatalysis self-cleaning oil-water separation membrane fails, the moth-eye structure bionic photocatalysis self-cleaning oil-water separation membrane irradiates for 0.5 to 1.0h under sunlight, and the super-hydrophilicity and underwater super-oleophobic performance can be recovered;
The magnetic titanium dioxide nano particles MTiO 2 in the first step and the second step are hydrophilic, and the main components are TiO 2 and Fe 3O4.
2. The preparation method of the moth-eye structure bionic photocatalytic self-cleaning oil-water separation membrane according to claim 1, which is characterized in that the full mixing in the first step is specifically stirring for 1-1.2 h by using a magnetic stirrer under the condition that the rotating speed is 800-1200 r/min; the stirring in the first step is carried out for 0.8 to 1 hour under the condition that the rotating speed is 600 to 900 r/min.
3. The method for preparing the moth-eye structured bionic photocatalytic self-cleaning oil-water separation membrane according to claim 1, wherein the molecular weight of the polyvinyl alcohol in the first step is 1750+/-50, the molecular weight of the tannic acid is 1701+/-50, and the purity is AR grade.
4. The method for preparing the moth-eye structured bionic photocatalytic self-cleaning oil-water separation membrane according to claim 2, wherein the volume ratio of water to absolute ethyl alcohol in the ethyl alcohol aqueous solution in the step one is 1 (1-1.2).
5. The preparation method of the moth-eye structured bionic photocatalytic self-cleaning oil-water separation membrane according to claim 1, wherein the MXene aqueous dispersion in the first step is a single-layer Ti 3C2Tx aqueous dispersion with the concentration of 5 mg/mL-6 mg/mL, and the purity of the single-layer Ti 3C2Tx is more than 99.9%.
6. The preparation method of the moth-eye structured bionic photocatalytic self-cleaning oil-water separation membrane is characterized in that the wire mesh in the second step is a pretreated wire mesh, and the diameter of the wire mesh is 0.12-0.15 mm; the pretreatment is specifically carried out according to the following steps: immersing the wire netting in acetic acid with the mass percentage of 10-12% for 5-6 h, sequentially placing the wire netting in acetone and absolute ethyl alcohol under the condition of the power of 80-100W, respectively ultrasonically cleaning for 10-20 min, then flushing for 3-4 times by using deionized water, and finally introducing nitrogen for drying.
7. The method for preparing the moth-eye structured bionic photocatalytic self-cleaning oil-water separation membrane according to claim 1, wherein the dosage of the magnetic titanium dioxide nanoparticle MTiO 2 ethanol dispersion in the second step is (0.5-0.6) mL/cm 2.
8. The method for preparing the moth-eye structured bionic photocatalytic self-cleaning oil-water separation membrane according to claim 7, wherein the strong magnet in the second step is a neodymium magnet.
9. The method for preparing the moth-eye structured bionic photocatalytic self-cleaning oil-water separation membrane according to claim 1, wherein the needle diameter in the needle array die in the step three is 0.2-0.3 mm.
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