Preparation method and application of bismuth oxy-sulfide-hydrogel-melamine photothermal evaporator with "solarization cloth structure"

Abstract

A preparation method and application of a bismuth oxy-sulfide-hydrogel-melamine photothermal evaporator with a "solarization cloth structure", wherein dithiothreitol and bismuth nitrate are dissolved in an organic solvent, a surfactant ligand is added, and then an aqueous sodium hydroxide solution is added; after the reaction is completed, centrifugation, washing, and drying are performed to obtain crystalline two-dimensional bismuth oxy-sulfide nanosheets; the bismuth oxy-sulfide nanosheets are first added to a polyvinyl alcohol aqueous solution and glutaraldehyde, and then stirred until uniform; hydrochloric acid solution is then added and stirred until uniform to obtain a mixed liquid; the mixed liquid is poured onto a melamine foam skeleton; after gelation, freeze-drying and washing are performed; and finally, freeze-drying is performed to obtain a 3D bismuth oxy-sulfide-hydrogel-melamine evaporator. The method has the advantages of simple process and low cost; the light-heat conversion performance of bismuth oxy-sulfide and the unique solarization cloth structure design improve the capture and conversion efficiency of sunlight, and high-efficiency and stable solar light-heat seawater evaporation can be achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of solar photothermal material conversion, and particularly relates to a preparation method of a bismuth oxide-sulfide-hydrogel-melamine photothermal evaporator with a "sun-dried cloth structure" and application thereof. BACKGROUND

[0002] With the increasing scarcity of global freshwater resources and the intensifying impact of climate change on water resources, solar photothermal seawater evaporation technology, as a green and sustainable method of freshwater production, is gradually becoming an important way to solve the freshwater crisis. This technology uses solar energy as a heat source, converts light energy into heat energy through photothermal conversion materials, and then drives seawater evaporation to produce freshwater. In this process, the key step to trigger efficient solar water evaporation is through the core component vapor generator, i.e., solar photothermal conversion materials.

[0003] However, the existing photothermal conversion materials still have many challenges in the application of solar photothermal seawater evaporation. On the one hand, traditional photothermal materials such as metal nanoparticles (such as Au, Ag, Cu, etc.) have high photothermal conversion efficiency, but the high cost and easy agglomeration characteristics limit their widespread application. On the other hand, carbon-based photothermal materials (such as carbon nanotubes, graphene, etc.) have a wide spectral absorption range, but their poor hydrophilicity and low designability result in low water evaporation efficiency. In addition, traditional polymer materials (such as porphyrin, polyaniline, polypyrrole, etc.) have good designability and certain photothermal conversion performance, but their poor light bleaching resistance and easy decomposition also limit their performance in practical applications.

[0004] In recent years, semiconductor materials have attracted widespread attention due to their stable photothermal conversion performance and controllable optical properties. They generate photoelectrons and holes when excited by light. When photoelectrons and holes undergo non-radiative relaxation at their defect or impurity energy levels, the absorbed solar energy is converted into heat energy, thus exhibiting photothermal conversion performance. Although people have tried to expand the infrared absorption of traditional semiconductors through element doping and defect engineering, a series of defect-type plasmonic photothermal conversion materials (such as WO 3-x , TiO 2-x , Cu 2-x S, CuCr2O4, MoS2, WS2, Bi2Se3, MoO2, and MXene) have been developed. However, their infrared absorption is still weak, and the photothermal materials are toxic, which seriously restricts the improvement of photothermal conversion efficiency and practical application. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a preparation method of a high-efficiency, stable and low-cost bismuth oxysulfide-hydrogel-melamine photothermal evaporator with a simulated "bleached cloth structure" and application thereof, which has a simple process, low cost, and can realize efficient and stable solar photothermal seawater evaporation.

[0006] The technical solution of the present application is:

[0007] A preparation method of a bismuth oxysulfide-hydrogel-melamine photothermal evaporator (3DBi2OS2-Gel-MF) with a simulated "bleached cloth structure", comprising the following steps:

[0008] Step one: Dissolve dithiothreitol as a sulfur source and bismuth nitrate in an organic solvent according to a molar ratio of (1-2):1, stir and react at 80℃ for 0.5-4h, add a surfactant ligand for continuous reaction for 0.5-4h, the surfactant ligand is polyvinylpyrrolidone (PVP) with a molecular weight of 30000, then add sodium hydroxide aqueous solution, the molar ratio of sodium hydroxide to bismuth nitrate in the sodium hydroxide aqueous solution is 6.4:1, react at 180℃ for 1-8h, after the reaction is completed, centrifuge, wash, and dry to obtain crystalline two-dimensional (2D) bismuth oxysulfide nanosheets (Bi2OS2);

[0009] Step two: first, add bismuth oxysulfide nanosheets to a 5% polyvinyl alcohol aqueous solution and glutaraldehyde, stir and mix uniformly for 1h, the mass-volume ratio of the bismuth oxysulfide nanosheets to the polyvinyl alcohol aqueous solution is 0.025g / mL, and the volume ratio of the polyvinyl alcohol aqueous solution to the glutaraldehyde is 20:1, then continue to add a 3.5% hydrochloric acid aqueous solution, the mass-volume ratio of the bismuth oxysulfide nanosheets to the hydrochloric acid aqueous solution is 1:1.5g / mL, and continue to stir for 1h to mix uniformly to obtain a mixed liquid; then uniformly pour the mixed liquid onto a melamine foam skeleton, gel for 2h, then perform a freeze-drying-washing procedure twice, and finally freeze-dry to obtain a 3D bismuth oxysulfide-hydrogel-melamine (3D Bi2OS2-Gel-MF) evaporator.

[0010] Further, the molar ratio of the dithiothreitol to the surfactant is 15:1.

[0011] Further, in step two, pour the mixed liquid prepared from 0.1g of bismuth oxysulfide nanosheets onto melamine with an area of 4cm 2 and a height of 1cm.

[0012] Further, the organic solvent is ethylene glycol.

[0013] Further, the concentration of the sodium hydroxide aqueous solution is 0.1-5mol / L.

[0014] Further, in step one, during washing, a mixed solution of isopropyl alcohol and anhydrous ethanol with a volume ratio of 1:1 or a mixed solution of isopropyl alcohol and water with a volume ratio of 1:1 is used for washing.

[0015] Further, in step two, during freezing, liquid nitrogen is used for freezing.

[0016] Further, in step two, during washing, water is used for soaking and washing for 3 times.

[0017] The application of a "cloth structure" imitated bismuth oxysulfide-hydrogel-melamine foam photothermal evaporator prepared by the preparation method of claim 1 in a solar seawater evaporator.

[0018] The principle of the present application is:

[0019] The present application perfectly integrates bismuth oxysulfide nanosheets, melamine foam and hydrogel to form a complementary 3D structure; bismuth oxysulfide serves as a photothermal site and has good light absorption and photothermal conversion performance; hydrogel serves as a water absorption and moisture retention function to form a "cloth surface" evaporation surface; and melamine foam provides a skeleton support to form a "clothes hanger" structure. The synthesized bismuth oxysulfide is a crystalline, nanoscale 2D sheet structure, which has good light absorption and photothermal conversion performance in the solar spectrum range, and has excellent dispersibility in water or alcohol solution.

[0020] The 2D structure of bismuth oxysulfide is not conducive to light capture and subsequent water vapor escape, and its powder state is not conducive to direct application in practice. The 3D Bi2OS2-Gel-MF structure used in the present application can fully utilize the excellent dispersibility of bismuth oxysulfide and better composite with the melamine skeleton to imitate a "cloth structure". The unique "cloth" structure of the 3D Bi2OS2-Gel-MF improves the capture of sunlight, the overall photothermal conversion performance and the actual evaporation area, and promotes the rapid transmission of a small amount of volume water through the hydrophilic "clothes hanger-melamine foam skeleton" to the "cloth surface-hydrogel" with photothermal water evaporation sites, while avoiding the heat loss caused by the presence of a large amount of volume water, further improving the evaporation rate and energy efficiency.

[0021] The present application has the following beneficial effects:

[0022] (1) By combining the photothermal conversion performance of bismuth oxysulfide and the unique imitated cloth structure design, the capture and conversion efficiency of sunlight is significantly improved, so that the evaporator can more efficiently convert solar energy into heat energy to drive seawater evaporation.

[0023] (2) The structure design of the tanning cloth not only improves the light-heat conversion efficiency, but also optimizes the evaporation process through the water absorption and moisture retention performance of the hydrogel and the skeleton support of the melamine foam, so that the evaporator can evaporate seawater at a higher rate, thereby improving the evaporation efficiency.

[0024] (3) The 3D Bi2OS2-Gel-MF evaporator with the structure of the tanning cloth has excellent photo-thermal performance and seawater evaporation performance. According to experimental detection, the solar water evaporation rate of the 3D Bi2OS2-Gel-MF is as high as 3.3 kg m -2 h -1 and the energy efficiency is 93.5%, which means that most of the input solar energy is effectively utilized during the evaporation process, reducing energy waste. At the same time, the evaporator also has good seawater salinity universality, which can adapt to seawater of different salinity, improving the utilization rate of resources.

[0025] (4) Compared with traditional seawater evaporation methods, the present application uses solar energy as the energy source, without consuming fossil fuels, so it will not produce pollutants and greenhouse gas emissions during use, which helps to reduce carbon emissions and achieve the goal of environmental protection and energy saving.

[0026] In summary, the present application "sulfur-oxide bismuth-hydrogel-melamine photo-thermal evaporator with tanning cloth structure" has simple process, and has significant effect in improving light-heat conversion efficiency, optimizing evaporation process, improving energy efficiency and resource utilization, environmental protection and energy saving, etc., which can be used for industrial wastewater evaporation treatment, also can be used for indoor humidification, especially suitable for solar seawater evaporation, has wide application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is the x-ray powder diffraction (XRD) characterization diagram of the Bi2OS2 nanosheet prepared in embodiment 2 of the present application;

[0028] Figure 2 is the transmission electron microscope (TEM) characterization diagram of the Bi2OS2 nanosheet prepared in embodiment 2 of the present application, in which, a. transmission electron microscope diagram of Bi2OS2 in 50mg PVP synthesis system, b. transmission electron microscope diagram of Bi2OS2 in 100mg PVP synthesis system, c. transmission electron microscope diagram of Bi2OS2 in 150mg PVP synthesis system, d. transmission electron microscope diagram of Bi2OS2 in 200mg PVP synthesis system;

[0029] Figure 3High resolution transmission electron microscopy (HR-TEM), selected area electron diffraction and element Mapping characterization diagrams of Bi2OS2 nanosheets prepared in Example 2 of the present application, wherein, a. Transmission electron microscopy of Bi2OS2 at 20 nm, b. High resolution transmission electron microscopy of Bi2OS2 at 2 nm, c. High resolution selected area electron diffraction electron microscopy diagram of Bi2OS2, d. e. f. are element Mapping electron microscopy diagrams of Bi2OS2 at 50 nm;

[0030] Figure 4 Energy dispersive X-ray spectroscopy (EDX) characterization diagram of Bi2OS2 prepared in Example 2 of the present application;

[0031] Figure 5 X-ray photoelectron spectroscopy (XPS) diagram of Bi2OS2 prepared in Example 2 of the present application; wherein, a. Element peak full spectrum of Bi2OS2, b. 2s peak of S in Bi2OS2, c. 1s peak of O in Bi2OS2, d. 4f peak of Bi in Bi2OS2;

[0032] Figure 6 Scanning electron microscopy (SEM) diagram of 3D Bi2OS2-Gel-MF in Example 2 of the present application; wherein, a. Scanning electron microscopy diagram of 3D Bi2OS2-Gel-MF at 500 μm, b. Scanning electron microscopy diagram of 3D Bi2OS2-Gel-MF at 100 μm, c. Scanning electron microscopy diagram of 3D Bi2OS2-Gel-MF at 200 μm, d. Element Mapping diagram of 3D Bi2OS2-Gel-MF at 200 μm, e. Mapping diagram of C element of 3D Bi2OS2-Gel-MF at 200 μm, f. Mapping diagram of N element of 3D Bi2OS2-Gel-MF at 200 μm, g. Mapping diagram of O element of 3D Bi2OS2-Gel-MF at 200 μm, h. Mapping diagram of Bi element of 3D Bi2OS2-Gel-MF at 200 μm, i. Mapping diagram of S element of 3D Bi2OS2-Gel-MF at 200 μm;

[0033] Figure 7Figure of solar photothermal water evaporation performance of 3D Bi2OS2-Gel-MF in Example 2 of the present application; in the figure, a. UV-Vis-NIR absorption spectrum (UV-VIS-NIR) of 3D Bi2OS2-Gel-MF in the solar spectrum range of 200-2500 nm, b. photothermal conversion performance of 3D Bi2OS2-Gel-MF under 1 Sun irradiation in dry state, c. photothermal conversion performance of 3D Bi2OS2-Gel-MF under 1 Sun irradiation at the beginning of evaporation state, d. rate comparison of 3D Bi2OS2-Gel-MF under 1 Sun irradiation, e. evaporation rate and energy efficiency of 3D Bi2OS2-Gel-MF under 1 Sun irradiation in different evaporation environments, f. evaporation rate of 3D Bi2OS2-Gel-MF under 0-2 Sun irradiation;

[0034] Figure 8 Figure of solar photothermal seawater desalination and wastewater purification performance of 3D Bi2OS2-Gel-MF in Example 2 of the present application; in the figure, a. salinity value of purified water collected after desalination evaporation of 3D Bi2OS2-Gel-MF under 3.5wt% and 100wt% salinity samples, b. main element content in purified water collected after desalination evaporation of 3D Bi2OS2-Gel-MF under 3.5wt% salinity sample, c. performance of purified water collected after evaporation of dye wastewater sample of 3D Bi2OS2-Gel-MF, d. performance of purified water collected after evaporation of heavy metal wastewater sample of 3D Bi2OS2-Gel-MF, e. resistance value of 3.5wt% salinity sample water, f. resistance value of purified water collected after desalination evaporation under 3.5wt% salinity sample, g. resistance value of resident life water sample, h. resistance value of ultrapure water sample. DETAILED DESCRIPTION

[0035] In order to further understand the present application, the preferred embodiments of the present application are described below, but it should be understood that these descriptions are only for further illustrating the features and advantages of the present application, but not for limiting the claims of the present application.

[0036] The terms used in the present application generally have the meanings commonly understood by those of ordinary skill in the art, unless otherwise defined. In order for those skilled in the art to better understand the technical solutions of the present application, the present application will be further described in detail below with reference to the examples.

[0037] In the following examples, various processes and methods not described in detail are conventional methods known in the art. The materials, reagents, devices, instruments, equipment, etc. used in the following examples, if not specifically stated, can be obtained from commercial channels.

[0038] The application is further illustrated by the following examples.

[0039] Example 1

[0040] Step one, dissolve dithiothreitol (0.1 mmol) and bismuth nitrate (0.1 mmol) in ethylene glycol reagent, stir at 80°C for 0.5h, then add 200mg polyvinylpyrrolidone (PVP: 30000) ligand and continue to react for 0.5h, then add 320μL sodium hydroxide aqueous solution (2M), react at 180°C for 1h, after the reaction is completed, centrifugal, wash with a mixture of isopropanol and anhydrous ethanol with a volume ratio of 1:1, dry, and obtain a small amount of bismuth oxy sulfide nanosheet (Bi2OS2);

[0041] Step two, first, 0.1g bismuth oxy sulfide nanosheet is added to 4mL polyvinyl alcohol aqueous solution (5wt%) and 0.02mL glutaraldehyde, stir and mix uniformly for 1h, then continue to add 0.15mL hydrochloric acid aqueous solution (3.5wt%) and continue to stir for 1h; then uniformly pour onto a melamine foam skeleton with a size of 2×2×1cm (length×width×height), gel for 2h, then perform liquid nitrogen freezing-drying-water soaking and washing 3 times twice, finally freeze-dry to obtain a 3D bismuth oxy sulfide-hydrogel-melamine (3D Bi2OS2-Gel-MF) evaporator.

[0042] Example 2

[0043] Step one, dissolve dithiothreitol (0.2 mmol) and bismuth nitrate (0.1 mmol) in ethylene glycol reagent, stir at 80°C for 2h, then add 200mg polyvinylpyrrolidone (PVP: 30000) ligand and continue to react for 2h, then add 320μL sodium hydroxide aqueous solution (2M), react at 180°C for 6h, after the reaction is completed, centrifugal, wash with a mixture of isopropanol and anhydrous ethanol with a volume ratio of 1:1, dry, and obtain crystalline two-dimensional (2D) bismuth oxy sulfide nanosheet (Bi2OS2);

[0044] Step two, first, 0.1g bismuth oxy sulfide nanosheet is added to 4mL polyvinyl alcohol aqueous solution (5wt%) and 0.02mL glutaraldehyde, stir and mix uniformly for 1h, then continue to add 0.15mL hydrochloric acid aqueous solution (3.5wt%) and continue to stir for 1h; then uniformly pour onto a melamine foam skeleton with a size of 2×2×1cm (length×width×height), gel for 2h, then perform liquid nitrogen freezing-drying-water soaking and washing 3 times twice, finally freeze-dry to obtain a 3D bismuth oxy sulfide-hydrogel-melamine (3D Bi2OS2-Gel-MF) evaporator.

[0045] Example 3

[0046] Step one, dissolve dithiothreitol (0.2 mmol) and bismuth nitrate (0.1 mmol) in ethylene glycol reagent, stir at 80°C for 4h, then add 300mg polyvinylpyrrolidone (PVP: 30000) ligand and continue to react for 4h, then add 320μL sodium hydroxide aqueous solution (2M), react at 180°C for 8h, after the reaction is completed, centrifugal, wash with a mixture of isopropyl alcohol and anhydrous ethanol with a volume ratio of 1:1, dry to obtain crystalline two-dimensional (2D) bismuth oxychalcogenide nanosheet (Bi2OS2);

[0047] Step two, first, 0.1g bismuth oxychalcogenide nanosheet is added to 4mL polyvinyl alcohol aqueous solution (5wt%) and 0.02mL glutaraldehyde, stirred and mixed uniformly for 1h, then 0.15mL hydrochloric acid aqueous solution (3.5wt%) is continuously added and stirred for 1h; then uniformly cast on a melamine foam skeleton with a size of 2×2×1cm (length×width×height), after gelation for 2h, then liquid nitrogen freezing-drying-water immersion washing procedure twice, finally freeze-dried to obtain 3D bismuth oxychalcogenide-hydrogel-melamine (3D Bi2OS2-Gel-MF) evaporator.

[0048] Comparative example 1

[0049] The sulfur source dithiothreitol of example 2 is replaced with thioacetamide, and the others are the same as example 2. Crystalline two-dimensional (2D) bismuth oxychalcogenide nanosheet cannot be synthesized.

[0050] Comparative example 2

[0051] The sulfur source dithiothreitol of example 2 is replaced with thiourea, and the others are the same as example 2. Crystalline two-dimensional (2D) bismuth oxychalcogenide nanosheet cannot be synthesized.

[0052] Comparative example 3

[0053] The polyvinylpyrrolidone (PVP: 30000) of example 2 is replaced with polyvinylpyrrolidone (PVP: 100000), and the others are the same as example 2. Crystalline two-dimensional (2D) bismuth oxychalcogenide nanosheet cannot be synthesized.

[0054] Bi2OS2-Gel-MF prepared in example 2 is characterized and performance tested

[0055] 1. The obvious sharp peaks are observed by x-ray powder diffraction (XRD), from Figure 1 It can be seen that these sharp and obvious characteristic peaks match the characteristic peaks of standard Bi2OS2 species. It shows the successful synthesis of Bi2OS2 and the purity of the phase.

[0056] 2. The surface morphology of Bi2OS2 is observed by transmission electron microscopy (TEM), from Figure 2As can be seen from a, b and c in FIG. 6, Bi2OS2 presents a 2D nanosheet structure, and with different PVP dosages, Bi2OS2 finally presents a uniform 2D square nanosheet structure, effectively improving the specific surface area and crystalline structure of the material. Figure 3 As can be seen from a and b in FIG. 7, Bi2OS2 has obvious lattice fringes, and as can be seen from c in FIG. 7, Bi2OS2 has obvious electron diffraction points. Figure 3 As can be seen from c in FIG. 7, Bi2OS2 also has obvious electron diffraction points in selected area electron diffraction, and the electron diffraction structure analysis is consistent with the results of HRTEM and XRD, indicating good crystallinity and crystalline structure. Figure 3 As can be seen from d, e and f in FIG. 8, the Bi, S and O elements in the element Mapping of Bi2OS2 are very uniform.

[0057] 3. Bi2OS2 is characterized by X-ray photoelectron spectroscopy (XPS) spectrum, and as can be seen from FIG. 9, Bi, O and S elements exist, and the Bi element is in +3 valence state, the O element is in +2 valence state, and the S element is in +2 valence state, indicating the successful synthesis of Bi2OS2. Figure 5

[0058] 4. The morphology structure of Bi2OS2-Gel-MF is observed by scanning electron microscopy (SEM), and as can be seen from a, b and c in FIG. 10, Bi2OS2-Gel-MF presents a porous three-dimensional structure, and in the enlarged area, the coexistence of MF skeleton and Bi2OS2-Gel can be observed, and Bi2OS2-Gel spreads on the MF skeleton to form a kind of "sun-dried cloth structure", indicating that Bi2OS2-Gel-MF is successfully synthesized. Figure 6

[0059] 5. The sunlight absorption capacity of Bi2OS2-Gel-MF is observed by ultraviolet-visible near-infrared absorption spectrum (UV-VIS-NIR), and as can be seen from a in FIG. 11, the light absorption performance of Bi2OS2-Gel-MF in the wavelength range of 200-2500 nm is far superior to that of Bi2OS2-Gel and pure melamine foam (MF), indicating the advantage of the "sun-dried cloth structure" of Bi2OS2-Gel-MF. Figure 7

[0060] 6. Solar photothermal water and seawater evaporation and wastewater purification test

[0061] The 3D Bi2OS2-Gel-MF evaporator is placed on the top center of the heat insulation layer foam, the center of the heat insulation layer foam is provided with a hydrophilic cotton core for conveying sample water to the evaporator, then the whole is moved to the top of a beaker containing sample water, the beaker is moved to a balance, and finally a solar simulator is placed directly above the evaporator, to obtain a solar seawater evaporation system. ​​​

[0062] Solar seawater evaporation test was performed on 3D Bi2OS2-Gel-MF evaporator. When solar light-heat conversion performance was performed, 3D Bi2OS2-Gel-MF evaporator in dry state was placed directly under the light source of solar simulator, and the light intensity was set to 0.1 W cm -2 The temperature change of Bi2OS2-Gel-MF evaporator surface before and after irradiation for 5 min was monitored in real time by thermal infrared imager (Testo 865). In Figure 7 In a of, when irradiation was performed, the surface temperature of 3D Bi2OS2-Gel-MF evaporator rapidly rose, from room temperature of 25 °C to 84.6 °C in only 2 min, and the temperature was basically stable at 86.0 °C in 3 min, and the light-heat conversion performance was far superior to that of un-composite MF, indicating that Bi2OS2-Gel-MF had rapid and excellent light-heat conversion performance. In Figure 7 In b of, the temperature change during solar water evaporation test was shown, at this time, 3D Bi2OS2-Gel-MF evaporator was in the state of connecting with sample water, i.e. wet state, and the light intensity of irradiation was set to 0.1 W cm -2 The temperature change of Bi2OS2-Gel-MF evaporator surface before and after irradiation for 2 h was monitored in real time by thermal infrared imager (Testo 865), and the mass change during the process was recorded by balance, which was repeated three times and averaged. In Figure 7 In c of, when irradiation was performed, the surface temperature of 3D Bi2OS2-Gel-MF evaporator rose slowly compared with that in dry state, from room temperature of 25 °C to 41.8 °C in 10 min, and was stable at about 42 °C, and the huge temperature difference between dry and wet states indicated that a large amount of heat energy was used for water evaporation. In Figure 7 In d of, the mass change of sample water was recorded, and the water evaporation rate of 3D Bi2OS2-Gel-MF was calculated to be 3.3 kg m -2 h -1 , which was far superior to the evaporation performance of bulk water and Bi2OS2-Gel, indicating that 3D Bi2OS2-Gel-MF had high efficient water evaporation capacity. In Figure 7 In e of, in sample water evaporation under three different salinities (0, 3.5 wt%, 100 wt%), the water evaporation rate of 3D Bi2OS2-Gel-MF was almost not affected by the increase of salinity, which showed good stability and continuous seawater desalination potential.

[0063] In Figure 8Among a and b, 3D Bi2OS2-Gel-MF also showed good purification ability. For 3.5wt%, 100wt% seawater samples, the salinity of the purified water was significantly reduced by about 3-4 orders of magnitude, in which the concentration of K + , Na + , Ca 2+ , Mg 2+ , the four main ions were reduced by 3-4 orders of magnitude. In Figure 8 c and d, 3D Bi2OS2-Gel-MF also showed good purification ability in solar purification tests of dye wastewater and industrial wastewater. In Figure 8 e, the resistance value test of seawater, evaporated and purified water, domestic water and ultrapure water samples was tested respectively, which showed that the ion content of the purified water reached the standard of domestic drinking water.

[0064] Obviously, the above examples are only examples for the sake of clarity, and are not limited to the examples. Based on the above description, other different forms of changes or variations can also be made by those skilled in the art. Here, it is not necessary and impossible to exhaust all examples. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A method for preparing a "solar cloth structure" imitated bismuth oxysulfide-hydrogel-melamine photothermal evaporator, comprising the following steps: Step one, dissolving dithiothreitol as a sulfur source and bismuth nitrate in an organic solvent according to a molar ratio of (1-2) : 1, stirring and reacting at 80 ℃ for 0.5-4 h, adding a surfactant ligand with a molecular weight of 30000 for polyvinylpyrrolidone to continue reacting for 0.5-4 h, then adding an aqueous sodium hydroxide solution, the molar ratio of sodium hydroxide to bismuth nitrate in the aqueous sodium hydroxide solution being 6.4: 1, reacting at 180 ℃ for 1-8 h, after the reaction, centrifuging, washing, and drying to obtain crystalline two-dimensional bismuth oxysulfide nanosheets; Step two, first stirring and mixing the bismuth oxysulfide nanosheets in a 5% polyvinyl alcohol aqueous solution and glutaraldehyde for 1 h, the mass-volume ratio of the bismuth oxysulfide nanosheets to the polyvinyl alcohol aqueous solution being 0.025 g / mL, the volume ratio of the polyvinyl alcohol aqueous solution to the glutaraldehyde being 20: 1, then adding a 3.5% hydrochloric acid aqueous solution, the mass-volume ratio of the bismuth oxysulfide nanosheets to the hydrochloric acid aqueous solution being 1: 1.5 g / mL, and continuing to stir for 1 h to mix uniformly to obtain a mixed liquid; then uniformly pouring the mixed liquid onto a melamine foam skeleton, gelling for 2 h, then performing a freeze-drying-washing procedure twice, and finally freeze-drying to obtain a 3D bismuth oxysulfide-hydrogel-melamine evaporator.

2. The process for the preparation of Bi2Sx-hydrogel-melamine photothermal evaporator of "sun-bleached fabric structure" according to claim 1, characterized by: The molar ratio of the dithiothreitol to the surfactant is 15:

1.

3. The process for the preparation of Bi2Sx-hydrogel-melamine photothermal evaporator of "sun-bleached fabric structure" according to claim 1, characterized by: Step two, according to each 0.1 g bismuth oxide nanometer piece of sulfur mixed liquid pouring to the area is 4 cm 2 Melamine, the height of the melamine is 1 cm.

4. The process for the preparation of Bi2Sx-hydrogel-melamine photothermal evaporator of "sun-bleached fabric structure" according to claim 1, characterized by: The organic solvent is ethylene glycol.

5. The process for the preparation of Bi2Sx-hydrogel-melamine photothermal evaporator in the structure of "simulated sun bleached cloth" according to claim 1, characterized by: The concentration of the aqueous sodium hydroxide solution is 0.1-5 mol / L.

6. The process for the preparation of Bi2Sx-hydrogel-melamine photothermal evaporator in the structure of "simulated sun bleached cloth" according to claim 1, characterized by: In step one, when washing, a mixed solution of isopropyl alcohol and anhydrous ethanol with a volume ratio of 1: 1 or a mixed solution of isopropyl alcohol and water with a volume ratio of 1: 1 is used for washing.

7. The process for the preparation of Bi2Sx-hydrogel-melamine photothermal evaporator in the structure of "simulated sun bleached cloth" according to claim 1, characterized by: In step two, when freezing, liquid nitrogen is used for freezing.

8. The process for the preparation of Bi2Sx-hydrogel-melamine photothermal evaporator in the structure of "simulated sun bleached cloth" according to claim 1, characterized by: In step two, when washing, water is used for soaking and washing for 3 times.

9. Application of a "solar cloth structure" imitated bismuth oxysulfide-hydrogel-melamine photothermal evaporator prepared by the preparation method of claim 1 in a solar sea water evaporator.

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