阅读说明：本技术 基于乳液浸渍的超疏水织物的制备方法及其在海水淡化中的应用 (Preparation method of super-hydrophobic fabric based on emulsion impregnation and application of super-hydrophobic fabric in seawater desalination ) 是由 高杰峰 肖薇 燕俊 汪玲 于 2021-08-03 设计创作，主要内容包括：基于乳液浸渍的超疏水织物的制备方法及其在海水淡化中的应用,涉及功能高分子材料的制备技术及海水淡化技术领域,将丙纶织物经pH值为8.5、浓度为0.2 wt.%的多巴胺水溶液浸渍6±0.5 h后,取得PDA改性的织物；将含量为8mg/mL的MXene水溶液和含量为2wt.%的聚二甲基硅氧烷的四氢呋喃溶液在超声辅助下混合,得水包油乳液；将PDA改性的织物经水包油乳液浸渍后干燥,得超疏水织物,用于被油污染的海水的油水分离中,该超疏水织物便可达到较好的分离效果,在应用于海水淡化时,能达到较好的淡化效果。(A preparation method of a super-hydrophobic fabric based on emulsion impregnation and application thereof in seawater desalination relate to the technical field of preparation technology of functional polymer materials and seawater desalination, and the PDA modified fabric is obtained after a polypropylene fabric is impregnated for 6 +/-0.5 hours by a dopamine aqueous solution with the pH value of 8.5 and the concentration of 0.2 wt.%; mixing MXene aqueous solution with the content of 8mg/mL and tetrahydrofuran solution with the content of 2wt.% of polydimethylsiloxane under the assistance of ultrasound to obtain oil-in-water emulsion; the PDA modified fabric is soaked in the oil-in-water emulsion and then dried to obtain the super-hydrophobic fabric, and the super-hydrophobic fabric is used for oil-water separation of oil-polluted seawater, so that the super-hydrophobic fabric can achieve a better separation effect and can achieve a better desalting effect when being applied to seawater desalting.)

1. The preparation method of the super-hydrophobic fabric based on emulsion impregnation is characterized by comprising the following steps:

1) soaking the polypropylene fabric in an aqueous solution of dopamine with the pH value of 8.5 and the concentration of 0.2 wt.% for 6 +/-0.5 h to obtain a PDA modified fabric;

2) mixing MXene aqueous solution with the content of 8mg/mL and tetrahydrofuran solution with the content of 2wt.% of polydimethylsiloxane under the assistance of ultrasound to obtain oil-in-water emulsion;

and (3) dipping the PDA modified fabric by the oil-in-water emulsion, taking out and drying to obtain the super-hydrophobic fabric.

2. The preparation method of claim 1, wherein the mass fractions of the MXene aqueous solution in the oil-in-water emulsion are respectively 25-75 wt.%.

3. The method as claimed in claim 1, wherein the PDA modified fabric is dipped in the oil-in-water emulsion for 10-30 min.

4. The method according to claim 1, wherein the drying treatment is carried out at 80 ℃ for 2 hours in the step 3).

5. The use of the superhydrophobic fabric obtained by the preparation method of claim 1 in seawater desalination.

6. Use according to claim 5, characterized in that the superhydrophobic fabric is used in oil-water separation of oil-contaminated seawater.

Technical Field

The invention relates to the technical field of preparation of functional polymer materials, and also relates to a seawater desalination technology.

Background

With the rapid development of modern industry, water pollution and shortages have become one of the most serious global challenges. The seawater resource is very rich, so the seawater desalination is an effective method for obtaining the fresh water resource. At present, the seawater desalination technology mainly comprises a freezing method, an electrodialysis method, a distillation method, a reverse osmosis method and an ammonium carbonate ion exchange method, and the reverse osmosis membrane method and the distillation method are more commercialized, but the energy consumption is large and the cost is high. As a green and renewable technology, solar-driven water evaporation provides an effective way for seawater desalination to realize water supply. The interface seawater evaporation is a renewable, environment-friendly and low-cost seawater desalination and wastewater treatment technology.

In the device for interface seawater desalination by using solar energy, a water delivery channel pumps water upwards through capillary action, and a photo-thermal material is placed at the top of the device and used for absorbing solar energy and converting the solar energy into heat energy for heating the pumped seawater. In order to avoid heat loss, a material having low thermal conductivity is used as the heat insulating layer. Many efficient solar evaporation of seawater has been reported, and the long-term stable operation of high salinity seawater desalination becomes a non-negligible problem in practical applications. Meanwhile, in practical situations, some oily pollutants usually exist in the seawater, and adverse effects are generated in the seawater desalination process, so that the pretreatment of the oil-polluted seawater is very important. Document 1 (Y. Li, X. Jin, Y. ZHEN, W. Li, F. ZHEN, W. Wang, T. Lin, Z. Zhu, Tunable Water Delivery in Carbon-Coated Fabrics for High-Efficiency Solar Vapor Generation, ACS Applied Materials)&Interfaces, 11 (2019), 46938-(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) and then dip-coating the fabric with carbon black resulted in a fabric with different side wettabilities, which had good water transport capability, excellent broadband light absorption and low thermal conductivity. However, the evaporation rate of the fabric was 1.33kg m^-2h^-1The efficiency is 88.9%, which is only at a normal level, and evaporation performance when used for high salt concentration seawater is not mentioned herein. Document 2 (B. Zhu, H. Kou, Z. Liu, Z. Wang, D.K. Machara, M. Zhu, B. Wu, X. Liu, Z. Chen, Flexible and wave CNT-Embedded PAN Nonwoven Fabrics for Solar-Enabled evaluation and Desalination of Seawater, ACS Applied Materials)&Interfaces, 11 (2019)) prepares flexible washable polyacrylonitrile non-woven fabrics embedded with carbon nanotubes by simple electrostatic spinning, and the polyacrylonitrile non-woven fabrics have high evaporation rate when being used for seawater desalination. When the method is used for evaporating seawater with high salt concentration, solid salt is accumulated on the surface of the fabric, and the evaporation rate is reduced. The strategy to solve this problem is to remove the deposited salt by hand washing the fabric. The method achieves better effect, but the method for removing salt by hand washing is not convenient enough, and the long-term stable use is hindered.

MXene is a two-dimensional inorganic compound in material science, and has a two-dimensional layered structure of metal carbon/nitride (transition metal nitride/nitride), and the chemical general formula of MXene is M_n+1X_nTx, where (n = 1-3), M represents an early transition metal, such as Ti, Zr, V, Mo, etc.; x represents a C or N element, Tx is a surface group, typically-OH, -O, -F and-Cl. It is known as MXene because of its lamellar structure similar to Graphene. MXene materials were first discovered in 2011 by professor Yury Gogotsi, university of Derasel (Drexel) and professor Michel Barsoum. The MXene which is prepared by the earliest experiments and is the most studied MXene at present is Ti₃C₂Tx。

MXene consists of a transition metal carbide, nitride or carbonitride of several atomic layer thicknesses. It was originally reported in 2011 that MXene materials have metallic conductivity of transition metal carbides due to hydroxyl groups or terminal oxygen on their surface. The unique physicochemical properties of MXene make MXene have attracted extensive attention in several fields such as energy storage and conversion, sensors, multifunctional polymer composite materials and the like in recent years.

CN2020104436975 discloses a breathable and waterproof multi-response fabric sensor, and the method thereof is as follows: firstly, immersing the flexible elastic fabric into dopamine alkaline solution, and stirring to perform self-polymerization reaction of dopamine; and then, placing the elastic fabric modified by the polydopamine into MXene colloidal solution for soaking for a period of time, taking out and drying, repeating the soaking and drying processes, then placing the obtained elastic fabric with different MXene modification times into n-heptane solution of polydimethylsiloxane for soaking and modifying for a period of time, and curing to obtain the breathable and waterproof multi-response fabric sensor. The object sensor has the structural characteristics that: comprises a flexible elastic fabric substrate from inside to outside,

The interface layer is a polydopamine layer, the functional layer is an MXene network, and the protective layer is polydimethylsiloxane. The method for modifying MXene nanosheets on the dopamine-modified base fabric comprises the steps of placing the elastic fabric into MXene solution, soaking for a period of time, taking out, drying, and repeating for multiple times to obtain fabrics with different MXene modification times; the method for modifying the PDMS layer is to place the MXene modified fabric in the n-heptane solution of polydimethylsiloxane for dipping modification for a period of time and to cure to obtain the composite fabric.

Disclosure of Invention

In order to overcome the disadvantages of time consuming and high cost of the prior art, the first object of the present invention is to propose a method for preparing a superhydrophobic fabric based on emulsion impregnation.

The invention comprises the following steps:

1) soaking the polypropylene fabric in an aqueous solution of dopamine with the pH value of 8.5 and the concentration of 0.2 wt.% for 6 +/-0.5 h to obtain a PDA modified fabric;

2) mixing MXene aqueous solution with the content of 8mg/mL and tetrahydrofuran solution with the content of 2wt.% of polydimethylsiloxane under the assistance of ultrasound to obtain oil-in-water emulsion;

and (3) dipping the PDA modified fabric by the oil-in-water emulsion, taking out and drying to obtain the super-hydrophobic fabric.

According to the invention, the flexible commercial polypropylene fabric is used as a substrate and is soaked in a dopamine solution, so that the dopamine autopolymerization surface modification treatment of the polypropylene fabric is realized, and the hydrophilic dopamine modified fabric PF is obtained. And then, obtaining the super-hydrophobic fabric coated with MXene and PDMS layers through the step 3).

The present invention differs from CN2020104436975 mainly in the method of modifying MXene nanoplatelets and Polydimethylsiloxane (PDMS) layers on dopamine modified fabric.

The method for modifying the MXene nanosheet and the PDMS layer on the dopamine-modified fabric does not need to dip for multiple times, and the PDMS/MXene-modified fabric can be obtained by dipping the MXene nanosheet and the PDMS layer into a uniform emulsion formed by MXene water dispersion and polydimethylsiloxane Tetrahydrofuran (THF) solution in one step, taking out and drying the uniform emulsion.

As the mass fraction of the aqueous phase of MXene in the emulsion increases, more and more nanosheets are accumulated on the surface of the fiber, the MXene is used as an excellent photo-thermal material, the absorbance of the material is increased by more nanosheets, and the photo-thermal conversion capability is enhanced. For its application to desalination of sea water, i.e. to absorb more energy from sunlight into heat energy for heating the sea water at the interface, the efficiency of desalination of sea water is increased. And the mass fraction of the oil phase is reduced, so that the thickness of the PDMS layer is reduced, the surface roughness of the material is increased, and the hydrophobic property is more excellent. This also means that the material has better thermal insulation properties and salt rejection properties for use in the evaporation of seawater.

The PDA modified fabric is soaked in the oil-in-water emulsion for 10-30 min. As the impregnation time increases, more and more MXene nanosheets in the emulsion attach to the fiber surface, which is beneficial for light absorption; in addition, the amount of PDMS layer coated on the fiber is also increasing. When the dipping time is short, the MXene nanosheets cannot be completely wrapped by the PDMS layer, the protection effect on the MXene nanosheets is weak, and the MXene is easy to oxidize; when the immersion time is too long, the thickness of the PDMS layer increases, the surface roughness decreases, and the hydrophobic property becomes weak.

In step 3), the drying treatment was carried out at 80 ℃ for 2 hours. At 80 ℃, the solvent of the oil phase in the emulsion is volatilized, and the PDMS molecular chain is crosslinked into a complete polymer network under the action of the curing agent. At the same time, the solvent in the water phase is volatilized, and the crosslinking and drying are finished after two hours.

The invention also aims to provide the application of the super-hydrophobic fabric obtained by the preparation method in seawater desalination.

The super-hydrophobic fabric is used for oil-water separation of oil-polluted seawater, and the super-hydrophobic fabric can achieve a good separation effect; when the method is applied to seawater desalination, a better desalination effect can be achieved.

The super-hydrophobic PMPF can be used for oil-water separation firstly, so that higher separation efficiency can be obtained, and a better separation effect is achieved. In the seawater desalination apparatus, hydrophilic PF is used as a water transport channel, superhydrophobic PMPF is used as a light absorption layer, and polystyrene PS foam having low thermal conductivity is used as a heat insulation layer. The test shows that the material has excellent photo-thermal performance and super-hydrophobicity, is excellent in seawater desalination test performance, and can stably work in high-salinity solution.

Compared with the prior art, the invention has the following advantages:

1. the super-hydrophobic fabric provided by the invention has the advantages of simple preparation process, mild and controllable reaction conditions, low energy consumption, no pollution, suitability for large-scale manufacturing and wide application prospect.

2. The super-hydrophobic fabric prepared by the method has the light absorption rate of 95 percent, excellent super-hydrophobic property and a contact angle of 152 degrees.

3. The super-hydrophobic fabric prepared by the invention can be used in the fields of seawater desalination and sewage treatment. When the method is used for oil-water separation, the separation efficiency can reach 95 percent. When the fabric is applied to seawater desalination, the evaporation rate can reach 1.526 kg m^-2 h^-1The efficiency was 93.3%.

Drawings

FIG. 1 is a scanning electron microscope image of the composite fabric when the mass fraction of MXene aqueous solution (8 mg/mL) in the emulsion is 75wt.% and the soaking time is 30 min.

FIG. 2 is a scanning electron microscope image of the composite fabric when the mass fraction of MXene aqueous solution (8 mg/mL) in the emulsion is 50wt.% and the soaking time is 30 min.

FIG. 3 is a scanning electron microscope image of the composite fabric when the mass fraction of MXene aqueous solution (8 mg/mL) in the emulsion is 25wt.% and the soaking time is 30 min.

FIG. 4 is a scanning electron microscope image of the surface of the composite fabric when the mass fraction of MXene aqueous solution in the emulsion is 75 wt% and the soaking time is 10 min.

Fig. 5 is a scanning electron micrograph of dopamine-modified fabric.

Fig. 6 is a scanning electron microscope image of the composite fabric when the mass fraction of MXene aqueous solution (8 mg/mL) in the emulsion is 100 wt.%.

FIG. 7 is a graph showing the relationship between the contact angle and the mass fraction of MXene aqueous solution in different emulsions when the emulsion immersion time is 30 min.

Fig. 8 is a graph of the change of the contact angle and different soaking time when the mass fraction of the MXene aqueous solution in the emulsion is 75 wt.%.

Fig. 9 is the contact angle of PMPF-75% surface water, acid (pH =1), and basic (pH =13) solutions of different tensile lengths.

FIG. 10 is the contact angle of PMPF-75% aqueous solution at different times of irradiation and sonication.

FIG. 11 is the PMPF-75% aqueous contact angle at different cyclic abrasions.

Fig. 12 is a graph comparing the light absorption rate of the composite fabric of MXene aqueous solution mass fractions in different emulsions when the emulsion soaking time is 30 min.

FIG. 13 is a graph of the temperature of the sample of the composite fabric as a function of time under illumination by a sunlight intensity simulated light source.

Fig. 14 is a diagram of an apparatus for oil-water separation (when the density of oil is greater than that of water) of the superhydrophobic composite fabric of example 1.

Fig. 15 is a cycle test graph of the separation flux and separation efficiency of the superhydrophobic composite fabric of example 1 for oil-water separation (when the density of oil is greater than that of water).

Fig. 16 is a diagram of an apparatus for oil-water separation (when the density of oil is less than that of water) of the superhydrophobic composite fabric of example 1.

Fig. 17 is a cycle test graph of the separation flux of the superhydrophobic composite fabric of example 1 for oil-water separation (when the density of oil is less than that of water).

Fig. 18 is a diagram of a simulated seawater evaporation device.

FIG. 19 shows the evaporation rate of the composite fabric when the composite fabric is used for a seawater desalination test when the mass fraction of MXene aqueous solution in different emulsions is 30 min.

FIG. 20 shows Na contained in the fresh water collected after desalination of sea water in example 1⁺、K⁺、Mg²⁺、Ca²⁺The concentration is compared with the concentration regulation of each ion in drinking water by the world health organization.

FIG. 21 shows the evaporation rates of the NaCl solutions of different concentrations used in example 1 and comparative example 2.

Figure 22 is the evaporation rate for comparative example 2 for the evaporation cycle of 20% wt.% NaCl solution.

FIG. 23 is a scanning electron micrograph of PMPF-75% taken after multiple high concentration evaporations.

FIG. 24 is a scanning electron micrograph of PMPF-100% taken after multiple high concentration evaporations.

Fig. 25 shows the resistance change of the sample when the mass fraction of the aqueous MXene solution (8 mg/mL) in the emulsion is 75wt.% and the soaking time is 10, 30, 50, 70 min.

Detailed Description

Example 1

(1) Soaking the polypropylene fabric in an alkaline solution of dopamine with the concentration of 0.2 wt.% for 6 hours, taking out and cleaning the polypropylene fabric, and drying the polypropylene fabric in an oven to obtain the PDA modified fabric.

Soaking the PDA modified fabric in an oil-in-water emulsion formed by 8mg/mL of MXene aqueous solution and 2 wt% of polydimethylsiloxane tetrahydrofuran solution (the mass ratio is 3: 1) for 30 minutes, so that the mass fraction of the MXene aqueous solution in the oil-in-water emulsion is 75 wt%. Taking out and drying at 80 ℃ to obtain the PMPF-75% of the fabric.

The microstructure of PMPF-75% of the prepared fabric was observed by scanning electron microscope as shown in FIG. 1.

(2) Contact angle test:

the fabric was tested for contact angle PMPF-75% using an OCA20 contact angle measuring apparatus.

5 mu L of distilled water is dripped on the surface of the fabric, and the test is carried out for 5 times to ensure the accuracy of the result, and the average value is obtained, and the test result is shown in figure 7. The contact angle of the fabric is 151.9 degrees, and the super-hydrophobic property is achieved.

(3) Hydrophobic stability test:

PMPF-75% was stretched to different lengths and tested for contact angle with surface water, acid (pH =1) and alkaline (pH =13) solutions, the test results are shown in fig. 9; when the sample tensile length is increased to 100%, the contact angle is only slightly decreased by 3.8 °, and the excellent hydrophobic properties are maintained. And the contact angle of the acidic solution with the sample surface pH =1 substantially coincides with the contact angle of the neutral solution. But the contact angle of samples of different tensile lengths in basic solution (pH =14) dropped to about 140 °, about 8 ° lower than neutral and acidic solutions, probably due to the weaker chemical resistance of PDMS in basic solution. Overall, however, the contact angle did not change much regardless of the stretched length, indicating that superhydrophobicity was maintained even though the fabric was stretched or deformed to a great extent. This results from the hierarchical structure and rough surface that is reconstructed during the stretching process.

Testing the contact angle of the aqueous solution of PMPF-75% of the fabric under different times of solar irradiation and ultrasonic treatment, wherein the test result is shown in figure 10; after the composite fabric is subjected to the irradiation treatment for 300 minutes, the WCA of the fabric is reduced by only 1.9 degrees, which shows that the PDMS layer has stronger ultraviolet irradiation resistance, because of the cross-linked network structure of the PDMS. After long-time ultrasonic washing, the contact angle can still be kept at about 150 degrees, and strong interface bonding capability between the MXene nanosheets and the PDMS layer is displayed.

PMPF-75% of the fabric, loaded with a 50g weight, was placed on sandpaper and then dragged horizontally for 2cm for one cycle, and the contact angle of the sample was measured every 5 cycles, the results of which are shown in FIG. 11. From the contact angle of PMPF-75% in water at different cyclic abrasions in FIG. 11, it can be seen that: the contact angle of the sample varied from 150.2 ° -145.3 ° upon the 50 cycle friction test, exhibiting excellent abrasion resistance due to excellent interfacial interactions between the sample PDMS layer, MXene layer, and the fabric fibers.

From the above tests, it can be known that the superhydrophobic performance of the sample is stable.

(4) And (3) testing the absorbance:

PMPF-75% of the fabric was tested for light absorbance using a UV/VIS/NIR spectrometer (Perkinelmer, Lambda 750S), the results of which are shown in FIG. 12; PMPF-75% of the fabric has light absorptivity up to 97%.

Photothermal Performance test, PMPF-75% of the fabric was placed under a simulated xenon light source (PLS-SXE300UV) with an optical power density set at 1 kW/m²Recording the temperature of the sample by using an infrared imager, wherein the test result is shown in figure 13; it is known that the photothermal conversion ability of the composite fabric is excellent.

(5) And (3) oil-water separation testing:

placing PMPF-75% of the fabric in a self-made oil-water separation device, pouring 20mL of Sudan IV dyed dichloromethane and 20mL of methylene blue dyed seawater into a filter cup, and recording the separation timetAnd separated volumeVAnd the rate and efficiency of oil-water separation, the apparatus and the separation result are calculated by the following formulas as shown in fig. 14 and 15.

In the above formula, the first and second carbon atoms are,Vthe volume (L) of the oil obtained after separation,Sis a separation area (m)²)，tThe separation time (h) is given. V₀Is the volume of the initial oil.

The test shows that PMPF-75% of the fabric has good separation effect.

(6) Testing the seawater desalination performance:

firstly, building a seawater desalination device: the fabric PMPF-75% was placed on a polystyrene foam wrapped with a hydrophilic fabric, which was then placed on simulated seawater. The device is schematically shown in FIG. 18.

In the process of seawater desalination test, the device is placed under a simulated xenon lamp light source, and the power density of the light source is 1 kW/m². And connecting the balance with a computer, and recording the mass change of the seawater. Rate of evaporationVAnd efficiencyηThe calculation formula of (c) is shown below. The test results are shown in FIG. 19. Testing Na in fresh water obtained after desalination⁺、K⁺、Mg²⁺、Ca²⁺The concentration, the test results are shown in FIG. 20.

In the above formula, ΔmIs the sea water quality variable quantity (kg),Sis the area (m) of the light absorber²)， tThe evaporation time (h) is given.

QeThe energy required for the evaporation of the water,Qinis the incident solar illumination energy.HeIs liquid-gas phase change enthalpy, m is the mass change quantity of subtracting natural evaporation,tis the time of the evaporation and is,Sis the area of illumination. WhereinCoptIn order to be the optical density,qis standard solar radiation intensity (1 kW m)^-2) (ii) a Tests show that the composite fabric can be applied to efficient solar interface seawater evaporation.

The PMPF-75% of the fabric was applied to NaCl solutions of different concentrations to test the evaporation performance of the material in high salinity seawater, and the test results are shown in FIG. 21.

Scanning electron micrographs of the samples after multiple cycles of testing, see FIG. 23, can reveal that no significant salt clumps were present between the PMPF-75% fibers of the fabric and the fibers. Therefore, the potential of the super-hydrophobic fabric for seawater desalination in high-salt-concentration seawater can be deduced.

Example 2

(1) Soaking the polypropylene fabric in an alkaline solution of dopamine with the concentration of 0.2 wt.% for 6 hours, taking out and cleaning the polypropylene fabric, and drying the polypropylene fabric in an oven to obtain the PDA modified fabric.

Soaking the PDA modified fabric in an oil-in-water emulsion (mass ratio of 1: 1) formed by 8mg/mL of MXene aqueous solution and 2 wt% of tetrahydrofuran solution of polydimethylsiloxane for 30 minutes, wherein the mass fraction of the MXene aqueous solution in the oil-in-water emulsion is 50 wt%. Taking out and drying at 80 ℃ to obtain the PMPF-50% of the fabric.

The microscopic morphology of PMPF-50% of the prepared fabric was observed by scanning electron microscopy as shown in FIG. 2.

(2) Contact angle test:

testing the PMPF-50% contact angle of the fabric by using an OCA20 contact angle measuring instrument, dripping 5 mu L of distilled water on the PMPF-50% surface of the fabric, testing for 5 times to ensure the accuracy of the result, and averaging to obtain a test result shown in FIG. 7; the contact angle of PMPF-50% of the fabric was 147 ℃ slightly lower than the superhydrophobic standard (150 ℃).

(3) And (3) testing the absorbance:

PMPF-50% light absorbance of the fabric was measured using UV/VIS/NIR spectrometer (Perkinelmer, Lambda 750S), the results of which are shown in FIG. 12; PMPF-50% of the fabric has better light absorptivity.

(4) Testing the photo-thermal performance:

the fabric PMPF-50% was placed under a simulated xenon light source (PLS-SXE300UV) with an optical power density set at 1 kW/m²Recording the temperature of the sample by using an infrared imager, wherein the test result is shown in figure 13; PMPF-50% of the fabric was found to have slightly inferior photothermal conversion.

(5) Testing the seawater desalination performance:

firstly, building a seawater desalination device: the fabric PMPF-50% was placed on a polystyrene foam wrapped with a hydrophilic fabric, which was then placed on simulated seawater. The device is schematically shown in FIG. 18.

In the process of seawater desalination test, the device is placed under a simulated xenon lamp light source, and the power density of the light source is 1 kW/m². And connecting the balance with a computer, and recording the mass change of the seawater. The test results are shown in FIG. 19.

Example 3

(1) Soaking the polypropylene fabric in an alkaline solution of dopamine with the concentration of 0.2 wt.% for 6 hours, taking out and cleaning the polypropylene fabric, and drying the polypropylene fabric in an oven to obtain the PDA modified fabric.

Soaking the PDA modified fabric in an emulsion (the mass ratio is 1: 3) formed by 8mg/mL of MXene aqueous solution and 2wt.% of polydimethylsiloxane tetrahydrofuran solution for 30 minutes, so that the mass fraction of the MXene aqueous solution in the emulsion is 25 wt.%. After being taken out, the fabric is dried at 80 ℃ to obtain PMPF-25 percent of the fabric.

The microscopic morphology of the PMPF-25% of the prepared fabric was observed by scanning electron microscopy as shown in FIG. 3.

(2) Contact angle test:

dripping 5 μ L of distilled water on PMPF-25% surface of fabric by using OCA20 contact angle measuring instrument to measure PMPF-25% contact angle, and measuring for 5 times to obtain average value with the result shown in FIG. 7; after contact angle test, PMPF-25% of the fabric can not meet the super-hydrophobic requirement, and the contact angle is only 132 degrees.

(3) And (3) testing the absorbance:

the PMPF-25% absorbance of the fabric was measured using a UV/VIS/NIR spectrometer (Perkinelmer, Lambda 750S), the results of which are shown in FIG. 12; PMPF-25% of the fabric has better light absorptivity.

(4) Testing the photo-thermal performance:

the fabric PMPF-25% was placed under a simulated xenon light source (PLS-SXE300UV) with an optical power density set at 1 kW/m²Recording the temperature of the sample by using an infrared imager, wherein the test result is shown in figure 13; PMPF-25% of the fabric was found to have slightly inferior photothermal conversion.

(5) Testing the seawater desalination performance:

firstly, building a seawater desalination device: the fabric PMPF-25% was placed on a polystyrene foam wrapped with a hydrophilic fabric, which was then placed on simulated seawater. The device is schematically shown in FIG. 18.

In the process of seawater desalination test, the device is placed under a simulated xenon lamp light source, and the power density of the light source is 1 kW/m². And connecting the balance with a computer, and recording the mass change of the seawater. The test results are shown in FIG. 19.

Example 4

(1) Soaking the polypropylene fabric in an alkaline solution of dopamine with the concentration of 0.2 wt.% for 6 hours, taking out and cleaning the polypropylene fabric, and drying the polypropylene fabric in an oven to obtain the PDA modified fabric.

(2) Soaking the PDA modified fabric in an emulsion (the mass ratio is 3: 1) formed by 8mg/mL of MXene aqueous solution and 2wt.% of polydimethylsiloxane tetrahydrofuran solution for 10 minutes, so that the mass fraction of the MXene aqueous solution in the emulsion is 75 wt.%. Taking out and drying at 80 ℃ to obtain the fabric with high light absorption rate and super-hydrophobicity.

The microscopic morphology of the resulting high light absorbance and superhydrophobic fabric was observed with a scanning electron microscope as shown in fig. 4.

(2) Contact angle test:

the contact angle of the fabric with high light absorptivity and super-hydrophobicity is tested by using an OCA20 contact angle measuring instrument, 5 mu L of distilled water is dripped on the surface of the fabric, and in order to ensure the accuracy of the result, the test is carried out for 5 times, the average value is taken, and the test result is shown in figure 8.

(3) And (3) resistance testing:

testing resistance of the dried test sample with TH2684A insulation resistance tester for 5 times, and taking average value R₀The resistance was then recorded as R every 24 h. The test results are shown in FIG. 9.

Due to the short emulsion impregnation time, the MXene nanosheets cannot be completely coated by the PDMS layer, so that part of MXene is seriously oxidized.

Comparative example 1:

(1) soaking the polypropylene fabric in a dopamine alkaline solution with the concentration of 0.2 wt.% for 6 hours, taking out and cleaning the polypropylene fabric, and drying the polypropylene fabric in an oven to obtain the dopamine modified fabric PF.

The microstructure of the dopamine modified fabric PF was observed with a scanning electron microscope as shown in FIG. 5.

(2) And (3) testing the absorbance:

the optical absorption of the dopamine modified fabric PF was tested using a UV/VIS/NIR spectrometer (PerkinElmer, Lambda 750S), the test results are shown in fig. 12; the light absorption of the dopamine modified fabric PF is low.

(3) Testing the photo-thermal performance:

the dopamine-modified fabric PF was placed under a simulated xenon lamp light source (PLS-SXE300UV) with the optical power density set at 1 kW/m²Recording the temperature of the sample by an infrared imager, and testingThe results are shown in FIG. 13. It is known that the photo-thermal conversion capability of the dopamine-modified fabric PF is poor.

Comparative example 2:

soaking the polypropylene fabric in an alkaline solution of dopamine with the concentration of 0.2 wt.% for 6 hours, taking out and cleaning the polypropylene fabric, and drying the polypropylene fabric in an oven to obtain the PDA modified fabric.

Soaking the PDA modified fabric in 2wt.% tetrahydrofuran solution of polydimethylsiloxane (namely 0wt.% of MXene aqueous solution in the emulsion) for 30 minutes, taking out and drying at 80 ℃ to obtain the composite fabric.

The composite fabric does not contain the photothermal material MXene, so the composite fabric has light color, low light absorption rate and poor photothermal conversion capability, and cannot be used as a photothermal material for seawater desalination.

Comparative example 3:

(1) soaking the polypropylene fabric in an alkaline solution of dopamine with the concentration of 0.2 wt.% for 6 hours, taking out and cleaning the polypropylene fabric, and drying the polypropylene fabric in an oven to obtain the PDA modified fabric.

The PDA modified fabric was soaked in 8mg/mL aqueous MXene solution for 30 minutes (mass fraction of aqueous phase in emulsion 100 wt.%). After being taken out, the fabric is dried at 80 ℃ to obtain the PMPF-100 percent.

The microstructure of PMPF-100% of the prepared fabric was observed by scanning electron microscope as shown in FIG. 6.

(2) The contact angle is tested by the contact angle test,

the contact angle of PMPF-100% of the fabric is tested by using an OCA20 contact angle measuring instrument, 5 microliter of distilled water is dripped on the surface of PMPF-100% of the fabric, and in order to ensure the accuracy of the result, the test is carried out for 5 times, the average value is taken, the test result is shown in figure 7, and the PMPF-100% of the fabric has good hydrophilic performance.

(3) Testing the seawater desalination performance:

firstly, building a seawater desalination device: the fabric PMPF-100% was placed on polystyrene foam wrapped with hydrophilic fabric, which was then placed on simulated seawater. The device is schematically shown in FIG. 18.

In the process of seawater desalination test, the device is placed under a simulated xenon lamp light source, and the power density of the light source is 1 kW/m². And connecting the balance with a computer, and recording the mass change of the seawater. The test results are shown in FIG. 19. PMPF-100% of the fabric had a higher evaporation rate when used in the evaporation test.

The PMPF-100% of the fabric was applied to NaCl solutions of different concentrations to test the evaporation performance of the material in high salinity seawater, and the test results are shown in FIG. 21. It is known that PMPF-100% used in the evaporation of high salt concentration seawater has a large decrease in evaporation performance due to the deposition of salt inside and on the surface of the hydrophilic photothermal layer, which affects the water transport and light absorption.

The evaporation performance of the fabric PMPF-100% was tested by applying it to a 20% wt.% NaCl solution in a cyclic manner, the test results are shown in FIG. 22, and the evaporation rate was greatly reduced after 10 cycles.

The scanning electron microscope image of the sample after multiple cycles is shown in fig. 24, and a large number of salt blocks appear between fibers of the fabric, so that the original appearance of the fabric is damaged to a great extent.