Preparation method and application of bismuth oxysulfide-hydrogel-melamine photo-thermal evaporator imitating'sun cloth structure '

Abstract

The invention relates to a preparation method and application of a bismuth oxysulfide-hydrogel-melamine photo-thermal evaporator imitating a'sun cloth structure ', dithiothreitol and bismuth nitrate are dissolved in an organic solvent, a surfactant ligand is added, then a sodium hydroxide aqueous solution is added, after the reaction is finished, centrifugation, washing and drying are performed, and crystalline two-dimensional bismuth oxysulfide nanosheets are obtained; the preparation method comprises the following steps: adding bismuth oxysulfide nanosheets into a polyvinyl alcohol aqueous solution and glutaraldehyde, uniformly stirring, continuously adding a hydrochloric acid solution, continuously uniformly stirring to obtain a mixed liquid, pouring the mixed liquid onto a melamine foam skeleton, gelatinizing, freezing, drying, washing, and finally freeze-drying to obtain the 3D bismuth oxysulfide-hydrogel-melamine evaporator. The method has the advantages that the process is simple, the cost is low, by combining the photo-thermal conversion performance of bismuth oxysulfide and the unique sun-imitating cloth structural design, the sunlight capturing and conversion efficiency is improved, and efficient and stable solar photo-thermal seawater evaporation can be achieved.

Description

Technical Field

[0001] The invention belongs to the field of solar thermal material conversion, and specifically relates to a preparation method and application of a bismuth oxysulfide-hydrogel-melamine photothermal evaporator imitating a "cloth drying structure". Background Art

[0002] As global freshwater resources become increasingly scarce and the impact of climate change on water resources intensifies, solar thermal 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 fresh water. In this process, the key step to trigger efficient solar water evaporation is through the core component steam generator, that is, the solar thermal conversion material.

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

[0004] In recent years, semiconductor materials have attracted extensive attention due to their stable photothermal conversion performance and tunable optical properties. They generate photogenerated electrons and holes after being excited by light. When the photogenerated electrons and holes undergo non-radiative relaxation at their defect or impurity energy levels, they convert the absorbed solar energy into thermal energy, thus exhibiting photothermal conversion performance. Although people have tried hard to expand the light absorption of traditional semiconductors in the infrared region through element doping and defect engineering, a series of defect-type plasma photothermal conversion materials (such as WO) have been developed. 3-x 、TiO 2-x , Cu 2-x S, CuCr2O4, MoS2, WS2, Bi2Se3, MoO2 and MXene, etc.). However, its absorption in the infrared region is still weak, and the photothermal material is toxic, which seriously restricts the improvement of photothermal conversion efficiency and its practical application. Summary of the invention

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

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

[0007] A method for preparing a bismuth oxysulfide-hydrogel-melamine photothermal evaporator (3DBi2OS2-Gel-MF) imitating a "drying cloth structure" comprises the following steps:

[0008] Step 1, dissolving dithiothreitol as a sulfur source and bismuth nitrate in an organic solvent in a molar ratio of (1-2): 1, stirring and reacting at 80°C for 0.5-4h, adding a surfactant ligand and continuing the reaction for 0.5-4h, wherein the surfactant ligand is polyvinyl pyrrolidone (PVP) with a molecular weight of 30,000, and then adding a sodium hydroxide aqueous solution, wherein the molar ratio of sodium hydroxide to bismuth nitrate in the sodium hydroxide aqueous solution is 6.4:1, reacting at 180°C for 1-8h, and after the reaction is completed, centrifuging, washing, and drying to obtain crystalline two-dimensional (2D) bismuth oxysulfide nanosheets (Bi2OS2);

[0009] Step 2: First, add bismuth oxysulfide nanosheets to a 5% polyvinyl alcohol aqueous solution and glutaraldehyde, and stir and mix evenly for 1 hour. The mass volume ratio of the bismuth oxysulfide nanosheets to the polyvinyl alcohol aqueous solution is 0.025 g / mL, and the volume ratio of the polyvinyl alcohol aqueous solution to 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 1:1.5 g / mL, and continue to stir and mix evenly for 1 hour to obtain a mixed liquid; then evenly pour the mixed liquid onto a melamine foam skeleton, gel for 2 hours, and 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] Furthermore, the molar ratio of dithiothreitol to surfactant is 15:1.

[0011] Further, in step 2, the mixed liquid prepared by 0.1 g of bismuth oxysulfide nanosheets is poured onto an area of ​​4 cm 2 The melamine has a height of 1 cm.

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

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

[0014] Furthermore, in step 1, during washing, a mixed solution of isopropanol and anhydrous ethanol in a volume ratio of 1:1 or a mixed solution of isopropanol and water in a volume ratio of 1:1 is used for washing.

[0015] Furthermore, in step 2, liquid nitrogen is used for freezing.

[0016] Furthermore, in step 2, during washing, the mixture is soaked and washed with water for 3 times.

[0017] An application of a bismuth oxysulfide-hydrogel-melamine photothermal evaporator imitating a "drying cloth structure" prepared by the preparation method as described in claim 1 in a solar seawater evaporator.

[0018] The principle of the present invention is:

[0019] The present invention perfectly integrates bismuth oxysulfide nanosheets, melamine foam and hydrogel to form a complementary 3D structure; bismuth oxysulfide serves as a photothermal site, with good light absorption and photothermal conversion performance; hydrogel plays a role in absorbing water and retaining moisture, forming an evaporation surface similar to a "cloth surface"; melamine foam provides skeleton support, forming a structure similar to a "clothes rack". Among them, the synthesized bismuth oxysulfide is a crystalline, nano-sized 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 the capture of light and the subsequent escape of water vapor, and its powder state is not conducive to direct application in practice. The present invention adopts a 3D Bi2OS2-Gel-MF structure, which can make full use of the excellent dispersibility of bismuth oxysulfide, and can be better compounded with a melamine skeleton to imitate a "drying cloth structure". The unique "drying cloth" structural advantage of this 3DBi2OS2-Gel-MF improves the capture of sunlight, the overall photothermal conversion performance and the actual evaporation area, and promotes a small amount of volume water to quickly spread through the hydrophilic "clothes rack-melamine foam skeleton" to the "cloth surface-hydrogel" with light and hot water evaporation sites, while also avoiding the heat loss caused by the presence of a large amount of volume water, further improving the evaporation rate and energy efficiency.

[0021] Beneficial effects of the present invention:

[0022] (1) By combining the photothermal conversion performance of bismuth oxysulfide and the unique structural design of the tanning cloth, the efficiency of capturing and converting sunlight is significantly improved, allowing the evaporator to more efficiently convert solar energy into thermal energy to drive the evaporation of seawater.

[0023] (2) The structural design of the tanning cloth not only improves the photothermal conversion efficiency, but also optimizes the evaporation process through the water absorption and moisturizing properties of the hydrogel and the skeleton support of the melamine foam, allowing the evaporator to evaporate seawater at a higher rate, thereby improving the evaporation efficiency.

[0024] (3) The 3D Bi2OS2-Gel-MF evaporator with the "self-tanning cloth" structure of the present invention has excellent photothermal performance and seawater evaporation performance. According to experimental tests, the solar water evaporation rate of the 3D Bi2OS2-Gel-MF of the present invention is as high as 3.3 kg m -2 h -1 As well as an energy efficiency of 93.5%, which means that in the evaporation process, most of the input solar energy is effectively utilized, reducing energy waste. At the same time, the evaporator also has good universality of seawater salinity, can adapt to seawater of different salinities, and improves resource utilization.

[0025] (4) Compared with the traditional seawater evaporation method, the present invention uses solar energy as energy and does not consume fossil fuels. Therefore, no pollutants and greenhouse gas emissions are generated during use, which helps to reduce carbon emissions and achieve the goal of environmental protection and energy saving.

[0026] In summary, the process of the patented "bismuth oxysulfide-hydrogel-melamine photothermal evaporator with a tanning cloth structure" is simple, and it shows remarkable effects in improving photothermal conversion efficiency, optimizing the evaporation process, improving energy efficiency and resource utilization, environmental protection and energy saving, etc. It can be used for industrial wastewater evaporation treatment and indoor humidification, and is particularly suitable for solar seawater evaporation, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is an X-ray powder diffraction (XRD) characterization diagram of the Bi2OS2 nanosheets prepared in Example 2 of the present invention;

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

[0029] Figure 3The high-resolution transmission electron microscopy (HR-TEM), selected area electron diffraction and element mapping characterization images of the Bi2OS2 nanosheets prepared in Example 2 of the present invention, in which a. the transmission electron microscopy of Bi2OS2 at 20nm, b. the high-resolution transmission electron microscopy of Bi2OS2 at 2nm, c. the high-resolution selected area electron diffraction electron microscopy image of Bi2OS2, and def is the element mapping electron microscopy image of Bi2OS2 at 50nm;

[0030] Figure 4 This is an energy dispersive X-ray spectroscopy (EDX) characterization diagram of Bi2OS2 prepared in Example 2 of the present invention;

[0031] Figure 5 This is an X-ray photoelectron spectrum (XPS) diagram of Bi2OS2 prepared in Example 2 of the present invention; in the figure, a. full spectrum of element peaks 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 3D Bi2OS2-Gel-MF in Example 2 of the present invention is a scanning electron microscope (SEM) image; in the figure, a. SEM image of 3D Bi2OS2-Gel-MF at 500μm, b. SEM image of 3D Bi2OS2-Gel-MF at 100μm, c. SEM image of 3D Bi2OS2-Gel-MF at 200μm, d. Element Mapping image of 3D Bi2OS2-Gel-MF at 200μm, e. Mapping image of C element of 3D Bi2OS2-Gel-MF at 200μm, f. Mapping image of N element of 3D Bi2OS2-Gel-MF at 200μm, g. Mapping image of O element of 3D Bi2OS2-Gel-MF at 200μm, h. Mapping image of Bi element of 3D Bi2OS2-Gel-MF at 200μm, i. 3D Mapping of S element in Bi2OS2-Gel-MF at 200μm;

[0033] Figure 73D Bi2OS2-Gel-MF in Example 2 of the present invention is a solar thermal water evaporation performance diagram; in the figure, a. ultraviolet visible near infrared absorption spectrum (UV-VIS-NIR) diagram of 3D Bi2OS2-Gel-MF in the range of 200-2500nm of the sunlight spectrum, b. photothermal conversion performance diagram of 3D Bi2OS2-Gel-MF in a dry state under 1Sun irradiation, c. photothermal conversion performance diagram of 3D Bi2OS2-Gel-MF when it starts to evaporate under 1Sun irradiation, d. rate comparison diagram of 3D Bi2OS2-Gel-MF under 1Sun irradiation, e. evaporation rate and energy efficiency diagram of 3DBi2OS2-Gel-MF in different evaporation environments under 1Sun irradiation, f. evaporation rate diagram of 3DBi2OS2-Gel-MF under 0-2Sun irradiation;

[0034] Figure 8 This is a performance diagram of solar thermal seawater desalination and wastewater purification of 3D Bi2OS2-Gel-MF in Example 2 of the present invention, in which a. salinity value of purified water collected after desalination and evaporation of 3D Bi2OS2-Gel-MF at 3.5wt% and 100wt% salinity samples, b. main element content of purified water collected after desalination and evaporation of 3D Bi2OS2-Gel-MF at 3.5wt% salinity sample, c. performance diagram of purified water collected by evaporation of dye wastewater sample by 3D Bi2OS2-Gel-MF, d. performance diagram of purified water collected by evaporation of heavy metal wastewater sample by 3D Bi2OS2-Gel-MF, e. resistance value of 3.5wt% salinity sample water, f. resistance value of purified water collected after desalination and evaporation of 3.5wt% salinity sample, g. resistance value of residential water sample, h. resistance value of ultrapure water sample. DETAILED DESCRIPTION

[0035] In order to further understand the present invention, preferred embodiments of the present invention are described below. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0036] The terms used in the present invention generally have the meanings commonly understood by those of ordinary skill in the art, unless otherwise specified. In order to enable those of ordinary skill in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below in conjunction with embodiments.

[0037] In the following examples, various processes and methods not described in detail are conventional methods known in the art. Unless otherwise specified, the materials, reagents, devices, instruments, equipment, etc. used in the following examples can be obtained from commercial sources.

[0038] The present invention is further described below with reference to the examples.

[0039] Example 1

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

[0041] Step 2: First, add 0.1 g of bismuth oxysulfide nanosheets to 4 mL of polyvinyl alcohol aqueous solution (5 wt%) and 0.02 mL of glutaraldehyde and stir to mix evenly for 1 h, then continue to add 0.15 mL of hydrochloric acid aqueous solution (3.5 wt%) and continue to stir for 1 h to mix evenly; then evenly pour it onto a 2×2×1 cm (length×width×height) melamine foam skeleton, gel for 2 h, and then perform liquid nitrogen freeze-drying-water immersion washing 3 times twice, and finally freeze-dry to obtain a 3D bismuth oxysulfide-hydrogel-melamine (3D Bi2OS2-Gel-MF) evaporator.

[0042] Example 2

[0043] Step 1: Dissolve dithiothreitol (0.2 mmol) and bismuth nitrate (0.1 mmol) in ethylene glycol reagent, stir and react at 80 ° C for 2 h, then add 200 mg of polyvinyl pyrrolidone (PVP: 30000) ligand to continue the reaction for 2 h, and then add 320 μL of sodium hydroxide aqueous solution (2M), react at 180 ° C for 6 h. After the reaction is completed, centrifuge, wash with a mixed solution of isopropanol and anhydrous ethanol in a volume ratio of 1:1, and dry to obtain crystalline two-dimensional (2D) bismuth oxysulfide nanosheets (Bi2OS2);

[0044] Step 2: First, add 0.1 g of bismuth oxysulfide nanosheets to 4 mL of polyvinyl alcohol aqueous solution (5 wt%) and 0.02 mL of glutaraldehyde and stir to mix evenly for 1 h, then continue to add 0.15 mL of hydrochloric acid aqueous solution (3.5 wt%) and continue to stir for 1 h to mix evenly; then evenly pour it onto a 2×2×1 cm (length×width×height) melamine foam skeleton, gel for 2 h, and then perform liquid nitrogen freeze-drying-water immersion washing 3 times twice, and finally freeze-dry to obtain a 3D bismuth oxysulfide-hydrogel-melamine (3D Bi2OS2-Gel-MF) evaporator.

[0045] Example 3

[0046] Step 1: Dissolve dithiothreitol (0.2 mmol) and bismuth nitrate (0.1 mmol) in ethylene glycol reagent, stir and react at 80°C for 4 hours, then add 300 mg of polyvinyl pyrrolidone (PVP: 30000) ligand and continue to react for 4 hours, then add 320 μL of sodium hydroxide aqueous solution (2M), react at 180°C for 8 hours, after the reaction is completed, centrifuge, wash with a mixed solution of isopropanol and anhydrous ethanol in a volume ratio of 1:1, and dry to obtain crystalline two-dimensional (2D) bismuth oxysulfide nanosheets (Bi2OS2);

[0047] Step 2: First, add 0.1 g of bismuth oxysulfide nanosheets to 4 mL of polyvinyl alcohol aqueous solution (5 wt%) and 0.02 mL of glutaraldehyde and stir to mix evenly for 1 h, then continue to add 0.15 mL of hydrochloric acid aqueous solution (3.5 wt%) and continue to stir for 1 h to mix evenly; then evenly pour it onto a 2×2×1 cm (length×width×height) melamine foam skeleton, gel for 2 h, and then perform liquid nitrogen freeze-drying-water immersion washing 3 times twice, and finally freeze-dry to obtain a 3D bismuth oxysulfide-hydrogel-melamine (3D Bi2OS2-Gel-MF) evaporator.

[0048] Comparative Example 1

[0049] The sulfur source dithiothreitol in Example 2 was replaced by thioacetamide, and the other procedures were the same as in Example 2. However, crystalline two-dimensional (2D) bismuth oxysulfide nanosheets could not be synthesized.

[0050] Comparative Example 2

[0051] The sulfur source dithiothreitol in Example 2 was replaced by thiourea, and the other steps were the same as in Example 2. However, crystalline two-dimensional (2D) bismuth oxysulfide nanosheets could not be synthesized.

[0052] Comparative Example 3

[0053] The polyvinyl pyrrolidone (PVP: 30000) in Example 2 was replaced by polyvinyl pyrrolidone (PVP: 100000), and the other conditions were the same as in Example 2. However, it was not possible to synthesize crystalline two-dimensional (2D) bismuth oxysulfide nanosheets.

[0054] Characterization and performance testing of Bi2OS2-Gel-MF prepared in Example 2

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

[0056] 2. The surface morphology of Bi2OS2 was observed by transmission electron microscopy (TEM). Figure 2As can be seen from a, b and c in the figure, Bi2OS2 presents a 2D nanosheet structure. With the different PVP dosages, Bi2OS2 finally presents a uniform 2D square nanosheet structure, which effectively improves the specific surface area and crystalline structure of the material. Figure 3 As can be seen from a and b in Figure 1, Bi2OS2 has obvious lattice fringes. Figure 3 It can also be seen from the c-area selected electron diffraction in Figure 1 that Bi2OS2 has an obvious electron diffraction lattice, and its electron diffraction structure analysis is consistent with the HRTEM and XRD results, indicating its good crystallinity and crystalline structure. Figure 3 As can be seen from images d, e, and f, the Bi, S, and O elements in the Bi2OS2 element mapping are distributed very evenly.

[0057] 3. Characterization of Bi2OS2 by X-ray photoelectron spectroscopy (XPS) Figure 5 It can be seen that Bi, O, and S elements are all present, and the Bi element is in a +3 valence state, the O element is in a +2 valence state, and the S element is in a +2 valence state, which indicates the successful synthesis of Bi2OS2.

[0058] 4. The morphology and structure of Bi2OS2-Gel-MF were observed by scanning electron microscopy (TEM). Figure 6 As can be seen from a, b and c in the figure, Bi2OS2-Gel-MF presents a porous three-dimensional structure. The coexistence of MF skeleton and Bi2OS2-Gel can be observed in the magnified area, and Bi2OS2-Gel is spread on the MF skeleton to form a "drying cloth structure", which shows that the present invention has successfully synthesized Bi2OS2-Gel-MF.

[0059] 5. The sunlight absorption capacity of Bi2OS2-Gel-MF was observed by ultraviolet-visible near-infrared absorption spectroscopy (UV-VIS-NIR). Figure 7 As can be seen from a in the figure, the light absorption performance of Bi2OS2-Gel-MF in the wavelength range of 200-2500nm is much better than that of Bi2OS2-Gel and pure melamine foam (MF), which illustrates the advantage of Bi2OS2-Gel-MF's imitation "drying cloth structure".

[0060] 6. Solar hot water, seawater evaporation and wastewater purification testing

[0061] The 3D Bi2OS2-Gel-MF evaporator was placed on the top center of the insulation layer foam. The center of the insulation layer foam had a hydrophilic cotton core for transferring sample water to the evaporator. The evaporator was then moved as a whole to the top of a beaker containing sample water. The beaker was then moved onto a balance. Finally, the solar simulator was placed directly above the evaporator to obtain a solar seawater evaporation system.

[0062] The 3D Bi2OS2-Gel-MF evaporator was tested for solar seawater evaporation. When the solar thermal conversion performance was tested, the dry 3D Bi2OS2-Gel-MF evaporator was placed directly under the light source of the solar simulator, and the light intensity was set at 0.1 W cm -2 The temperature changes of the Bi2OS2-Gel-MF evaporator surface before and after irradiation for 5 min were monitored in real time by a thermal infrared imager (Testo 865). Figure 7 In a, when irradiated with light, the surface temperature of the 3D Bi2OS2-Gel-MF evaporator rose rapidly, from 25°C at room temperature to 84.6°C in just 2 minutes. After 3 minutes, the temperature was basically stabilized at 86.0°C. The photothermal conversion performance was much better than that of the uncompounded MF, indicating the rapid and excellent photothermal conversion performance of Bi2OS2-Gel-MF. Figure 7 In b, the temperature change during the solar water evaporation test is shown. At this time, the 3D Bi2OS2-Gel-MF evaporator is in a state of connection with the sample water, that is, in a wet state, and the irradiated light intensity is set to 0.1 W cm -2 The temperature change of the Bi2OS2-Gel-MF evaporator surface before and after irradiation for 2 hours was monitored in real time by a thermal infrared imager (Testo865). The mass change of the process was recorded by a balance. The process was repeated three times and the average value was taken. Figure 7 In c, when illuminated, the surface temperature of the 3D Bi2OS2-Gel-MF evaporator rises slowly compared to the dry state, rising from 25°C at room temperature to 41.8°C in 10 minutes and stabilizing at around 42°C. The huge temperature difference between the dry and wet states indicates that a large amount of heat energy is used for water evaporation. Figure 7 The change in the water mass of the sample was recorded in d. The water evaporation rate of 3D Bi2OS2-Gel-MF was calculated to be 3.3 kg m -2 h -1 , which is much better than the evaporation performance of bulk water and Bi2OS2-Gel, indicating that 3D Bi2OS2-Gel-MF has efficient water evaporation capability. Figure 7 In Figure 5, in the water evaporation of samples under three different salinities (0, 3.5wt%, 100wt%), the water evaporation rate of 3D Bi2OS2-Gel-MF was almost unaffected by the increase in salinity, showing good stability and continuous seawater desalination potential.

[0063] exist Figure 8In a and b, 3D Bi2OS2-Gel-MF also showed good purification ability. For 3.5wt% and 100wt% seawater samples, the salinity of the purified water was significantly reduced by about 3-4 orders of magnitude, among which K + , Na + , Ca 2+ ,Mg 2+ , the concentrations of the four main ions decreased by 3-4 orders of magnitude. Figure 8 In Figures c and d, 3DBi2OS2-Gel-MF also showed good purification ability in the solar purification test of dye wastewater and industrial wastewater. Figure 8 In the experiment, the resistance values ​​of seawater, purified water collected by evaporation, domestic water and ultrapure water samples were tested respectively, which showed that the ion content of purified water reached the standard of domestic drinking water for residents.

[0064] Obviously, the above embodiments are merely examples for clear explanation, and are not intended to limit the embodiments. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. The obvious changes or modifications derived from them are still within the protection scope of the invention.

Claims

1. A method for preparing a bismuth oxysulfide-hydrogel-melamine photothermal evaporator imitating a "drying cloth structure", comprising the following steps: Step 1, dissolving dithiothreitol as a sulfur source and bismuth nitrate in an organic solvent in a molar ratio of (1-2): 1, stirring and reacting at 80°C for 0.5-4h, adding a surfactant ligand and continuing the reaction for 0.5-4h, wherein the surfactant ligand is polyvinyl pyrrolidone with a molecular weight of 30,000, and then adding a sodium hydroxide aqueous solution, wherein the molar ratio of sodium hydroxide to bismuth nitrate in the sodium hydroxide aqueous solution is 6.4:1, reacting at 180°C for 1-8h, and after the reaction is completed, centrifuging, washing, and drying to obtain crystalline two-dimensional bismuth oxysulfide nanosheets; Step 2: first add bismuth oxysulfide nanosheets to a 5% polyvinyl alcohol aqueous solution and glutaraldehyde, and stir and mix evenly for 1 hour, wherein the mass volume ratio of the bismuth oxysulfide nanosheets to the polyvinyl alcohol aqueous solution is 0.025 g / mL, and the volume ratio of the polyvinyl alcohol aqueous solution to glutaraldehyde is 20:1, and then continue to add a 3.5% hydrochloric acid aqueous solution, wherein the mass volume ratio of the bismuth oxysulfide nanosheets to the hydrochloric acid aqueous solution is 1:1.5 g / mL, and continue to stir and mix evenly for 1 hour to obtain a mixed liquid; then evenly pour the mixed liquid onto the melamine foam skeleton, gel for 2 hours, and then perform a freeze-drying-washing procedure twice, and finally freeze-dry to obtain a 3D bismuth oxysulfide-hydrogel-melamine evaporator.

2. The method for preparing the bismuth oxysulfide-hydrogel-melamine photothermal evaporator imitating the "drying cloth structure" according to claim 1 is characterized in that: The molar ratio of dithiothreitol to surfactant is 15:

1.

3. The method for preparing the bismuth oxysulfide-hydrogel-melamine photothermal evaporator imitating the "drying cloth structure" according to claim 1 is characterized in that: Step 2: pour the mixed liquid made of 0.1g bismuth oxysulfide nanosheets into an area of ​​4cm 2 The melamine has a height of 1 cm.

4. The method for preparing the bismuth oxysulfide-hydrogel-melamine photothermal evaporator imitating the "drying cloth structure" according to claim 1 is characterized in that: The organic solvent is ethylene glycol.

5. The method for preparing the bismuth oxysulfide-hydrogel-melamine photothermal evaporator imitating the "drying cloth structure" according to claim 1 is characterized in that: The concentration of the sodium hydroxide aqueous solution is 0.1 to 5 mol / L.

6. The method for preparing the bismuth oxysulfide-hydrogel-melamine photothermal evaporator imitating the "drying cloth structure" according to claim 1 is characterized in that: In step 1, during washing, a mixed solution of isopropanol and anhydrous ethanol in a volume ratio of 1:1 or a mixed solution of isopropanol and water in a volume ratio of 1:1 is used for washing.

7. The method for preparing the bismuth oxysulfide-hydrogel-melamine photothermal evaporator imitating the "drying cloth structure" according to claim 1 is characterized in that: In step 2, during freezing, liquid nitrogen is used for freezing.

8. The method for preparing the bismuth oxysulfide-hydrogel-melamine photothermal evaporator imitating the "drying cloth structure" according to claim 1 is characterized in that: In step 2, when washing, soak and wash with water for 3 times.

9. Application of a bismuth oxysulfide-hydrogel-melamine photothermal evaporator imitating a "drying cloth structure" prepared by the preparation method as claimed in claim 1 in a solar seawater evaporator.

Images