A novel biomass-based solar water evaporator and its preparation method and application

Abstract

The present invention discloses a novel biomass-based solar water evaporator and its preparation method and application, which relates to the field of energy conversion technology. The solar water evaporator comprises a water transmission layer, a heat insulation layer and a photothermal conversion layer, wherein the water transmission layer is a porous network skeleton in the shape of a super-hydrophilic vertical array pipe, the heat insulation layer is a super-hydrophilic and high-thermal-resistance silica aerogel coating forming a stable interface on the water transmission layer, and the photothermal conversion material has good photothermal conversion ability and is coated on the heat insulation layer to form a photothermal interface. The raw materials of the present invention are widely available and low in cost. The preparation method is simple, convenient and easy to implement, and can be assembled into a water evaporator with a fast water evaporation rate and high energy efficiency, so it is conducive to large-scale production. The present invention can be used for interfacial solar evaporation, has the advantages of efficient production of clean water, long-term stability, good anti-fouling and salt resistance, and has broad application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of energy conversion water evaporator preparation, in particular to a novel biomass-based solar water evaporator and a preparation method and application thereof. Background Art

[0002] Freshwater shortages are increasingly becoming a significant challenge to society's sustainable and stable development. It's reported that approximately one-third of the world's population lacks access to clean drinking water. With population growth and increasingly severe environmental challenges, the demand for clean freshwater resources is increasing. Exploring advanced, low-energy water purification technologies is key to alleviating freshwater shortages. The emergence of photothermal conversion technology has greatly expanded the application of solar energy in power generation, domestic water heating, and seawater desalination and purification.

[0003] Solar-driven water evaporation is considered a promising, low-energy, and environmentally friendly technology for alleviating freshwater shortages. However, currently common industrial methods such as reverse osmosis, electrodialysis, and multi-stage flash evaporation consume excessive amounts of electricity, require complex infrastructure, and release waste gases into the environment, which is inconsistent with long-term human development. However, conventional solar distillation systems, which place the solar absorber at the bottom or disperse it evenly throughout the bulk water, result in photothermal losses and limited solar evaporation performance. To overcome this shortcoming, researchers have proposed interfacial solar steam generation (SVG), which relocates the light-absorbing and photothermal conversion materials closer to the evaporation surface. This improves steam generation efficiency by reducing heat loss to the bulk water and the environment. However, in this design, photothermal conversion efficiency and evaporation rate often cannot be improved simultaneously, hindering real-world application. Furthermore, the design and process complexity of conventional water evaporators and their use of secondary raw materials significantly limit the available material options. This results in suboptimal evaporation performance and prevents large-scale application. Summary of the Invention

[0004] The purpose of the present invention is to solve at least one of the technical problems existing in the prior art and to provide a novel biomass-based solar water evaporator and a preparation method and application thereof.

[0005] The technical solutions of the present invention are as follows:

[0006] A novel biomass-based solar water evaporator comprises, from bottom to top, a water transmission layer, a heat insulation layer, and a light-to-heat conversion layer;

[0007] Among them, the water transport layer is a porous network skeleton structure in the shape of a super-hydrophilic vertical array pipeline;

[0008] The thermal insulation layer is a super-hydrophilic silica aerogel with high thermal resistance, and its coating forms a stable interface on the water transmission layer;

[0009] The light-to-heat conversion layer has good light-to-heat conversion capability, and is coated on the heat-insulating layer to form a light-to-heat interface.

[0010] The present invention also discloses a method for preparing a novel biomass-based solar water evaporator, comprising the following steps:

[0011] S1: heating the biomass waste material I to 600-1000°C under protective gas, and cooling the biomass waste material to obtain a silicon dioxide-carbon mixed material;

[0012] S2: The silicon dioxide-carbon mixed material is further heated to 1100-1700° C. under a protective gas, and then cooled to obtain a material for a light-to-heat conversion layer;

[0013] S3: using the biomass waste II according to the methods of steps S1 and S2 to synthesize a water transport layer material having a vertical array of pipes;

[0014] S4: Using two silicon-containing precursors, first hydrolyze, then undergo two-step acid-base catalysis, and finally freeze-dry in vacuum to obtain silica aerogel for thermal insulation layer;

[0015] S5: Then, the heat insulation layer is coated with silica aerogel on the water transmission layer, and the light-to-heat conversion layer is coated on the heat insulation layer.

[0016] As a preferred embodiment of the present invention, the specific process of step S5 is as follows:

[0017] a. First, dissolving chitosan in acetic acid to obtain a chitosan solution;

[0018] b. Then, the silica aerogel and the silica - carbon mixed material were added to the chitosan solution, and then the binder solution was added and mixed uniformly to obtain SA colloid and SCC colloid, respectively;

[0019] c. SA colloid is applied to the surface of the water transport layer material with a certain thickness, and then a layer of SCC colloid is applied after a period of time. Finally, a new biomass-based solar water evaporator is obtained through freeze vacuum drying.

[0020] As a preferred embodiment of the present invention, in step b: the binder is one or more of polyacrylamide, naphthol, polyurethane adhesive, epoxy resin adhesive; and / or;

[0021] In step c, the coating thickness is 1-5 mm.

[0022] As a preferred embodiment of the present invention, the biomass waste I includes one or more of rice husks, straw, wheat bran, corn cobs, sawdust, and bagasse;

[0023] Biomass waste II includes one or more of wood, bamboo, reed, mushroom, and sugarcane.

[0024] As a preferred embodiment of the present invention, in step S1, the heating rate is 5-25°C / min, and after heating to the specified temperature, the temperature is kept at this temperature for 0.5-2h.

[0025] As a preferred embodiment of the present invention, in step S2, the heating rate is 1-10°C / min, and after heating to the specified temperature, the temperature is kept at this temperature for 0.5-2h.

[0026] As a preferred embodiment of the present invention, in steps S1 to S3: the protective gas is at least one of nitrogen, argon, and helium, and the flow rate is 40-150 sccm.

[0027] As a preferred embodiment of the present invention, in step S4: the silicon source is one or more of water glass, methyltrimethoxysilane (MTMS), methyltriethoxysilane (MTES), dimethyldimethoxysilane (DMDMS), trimethylmethoxysilane (TMMS), and / or the acid is one of hydrochloric acid, sulfuric acid, and nitric acid, and the base is one of sodium hydroxide, ammonia water, and potassium hydroxide.

[0028] The present invention also discloses an application of the novel biomass-based solar water evaporator as described above or the novel biomass-based solar water evaporator prepared by any of the preparation methods described above in solar-driven water evaporation and seawater desalination.

[0029] The present invention can achieve at least one of the following beneficial effects:

[0030] 1) The raw materials used in the method of the present invention are widely available and low in cost, and biomass waste can be recycled, which is conducive to sustainable development;

[0031] 2) The preparation process of the present invention is simple, does not require subsequent treatment, and can be used for large-scale production;

[0032] 3) The present invention fully utilizes the vertical array porous structure of natural biomass as a water transport layer to greatly improve the water flux, thereby accelerating the evaporation rate and efficiency;

[0033] 4) The present invention utilizes the light absorption capacity and light-to-heat conversion characteristics of carbon materials and semiconductors as the evaporator light-to-heat conversion layer to fully absorb sunlight and provide continuous energy transmission.

[0034] 5) The present invention uses aerogel as the insulation layer material, which has a very excellent thermal insulation effect and greatly reduces heat loss.

[0035] 6) This invention utilizes the properties of different materials in the form of a coating to assemble a new sandwich-type water evaporator (CAS). This evaporator exhibits long-term stability and salt tolerance, providing a new strategy for the development of large-scale solar desalination of seawater using sandwich-type evaporators to obtain clean water. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is a schematic diagram of a water evaporator CAS;

[0037] 1-light-to-heat conversion layer, 2-thermal insulation layer, 3-water transport layer;

[0038] Figure 2 This is a field emission scanning electron microscope image of the carbonized native wood CNW obtained in Example 2;

[0039] Figure 3 This is a field emission scanning electron microscope image of the silica aerogel SA obtained in Example 4;

[0040] Figure 4 This is a field emission scanning electron microscope image of the silicon carbide fiber wire and carbon mixed material SCC in Example 3;

[0041] Figure 5 The full spectrum light absorptivity curves of CNW, SCC and SA obtained in Examples 2-4;

[0042] Figure 6 Static graphs of contact angles of NW, CNW, CS, and CAS evaporators obtained in Examples 1-4;

[0043] Figure 7 The curves of the mass change of NW, CNW, CS and CAS evaporators obtained in Examples 1-4 over time;

[0044] Figure 8 The evaporation rates and corresponding equivalent enthalpies of NW, CNW, CS and CAS evaporators obtained in Examples 1-4 are shown. DETAILED DESCRIPTION

[0045] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0046] like Figure 1As shown, in a preferred embodiment of the present invention, carbonized native wood (CNW) is used as a supporting water transmission layer 3, and then silica aerogel (SA) is first coated on the CNW surface as a thermal insulation layer 2, and then silicon carbide and carbon hybrid material (SCC) is coated on the surface of the SA coating as a photothermal conversion material 1, and a water evaporator CAS is formed after freeze-drying.

[0047] A preferred embodiment of the present invention provides a method for preparing a novel biomass-based solar water evaporator, comprising the following steps:

[0048] S1. Place the porcelain boat filled with biomass waste I into the tubular furnace equipment, and introduce protective gas to exhaust the air in the tubular furnace equipment;

[0049] S2. Maintaining the protective gas flow, the porcelain boat filled with biomass waste I is heated to 600-1000° C. to synthesize the silica-carbon composite material; then, heating is stopped, the gas flow is continued, and the boat is slowly cooled to room temperature to uniformly synthesize the silica-carbon composite material;

[0050] S3, continuing to pass the protective gas and heating to 1100-1700° C. to grow the silicon carbide-carbon composite material, a precursor of the photocatalyst;

[0051] S4. Turn off the heating power supply, continue to introduce protective gas, slowly cool to room temperature, and evenly synthesize the silicon carbide-carbon composite material in the porcelain boat;

[0052] S5, replacing biomass waste I with biomass waste II, repeating steps S1 and S2, and uniformly synthesizing a water transport layer material (CNW) having vertical array channels;

[0053] S6. Using two silicon source-containing precursors, first hydrolyzing them, then subjecting them to two-step acid-base catalysis, and finally freeze-drying them in vacuum to obtain a thermal insulation layer silica aerogel material (SA);

[0054] In step S1: the biomass waste I includes one or more of rice husks, straw, wheat bran, corn cobs, sawdust, and bagasse; the biomass waste II includes one or more of wood, bamboo, reeds, mushrooms, and sugarcane; and / or the material of the porcelain boat is alumina.

[0055] In step S2: the heating rate is 5-25°C / min, and after heating to the specified temperature, the temperature is kept for 0.5-2h.

[0056] In step S3: the heating rate is 1-10°C / min, and after heating to the specified temperature, the temperature is kept for 0.5-2h.

[0057] In steps S1 to S4: the gas introduced is at least one of nitrogen, argon, and helium, and the flow rate is 40-150 sccm.

[0058] In step S6: the silicon source is one or more of water glass, methyltrimethoxysilane (MTMS), methyltriethoxysilane (MTES), dimethyldimethoxysilane (DMDMS), and trimethylmethoxysilane (TMMS); the acid is one of hydrochloric acid, sulfuric acid, and nitric acid; and the base is one of sodium hydroxide, ammonia water, and potassium hydroxide.

[0059] In step S7b: the adhesive is one or more of polyacrylamide (PAM), naphthol, polyurethane adhesive, and epoxy resin adhesive.

[0060] In step S7c: the coating thickness is 1-5 mm.

[0061] The following are specific examples, where the biomass wastes I and II are raw wood and rice husks, respectively, the dual silicon sources are water glass and methyltrimethylsilane, and the binder is naphthol.

[0062] Example 1

[0063] 1) The biomass waste II - original wood is placed in an oven and dried at a temperature of 60°C to obtain a water evaporator NW.

[0064] The full spectrum light absorption rate curve of the solar water evaporator NW is shown in the attached figure. Figure 5 As shown in Figure 3, it shows that NW has a weak ability to absorb sunlight, with an absorbance of only about 2%.

[0065] Example 2

[0066] 1) The biomass waste II - original wood was placed in an oven and dried at a temperature of 60°C.

[0067] 2) The dried raw wood was spread on a porcelain boat filled with high-purity alumina, and then placed in the middle of the high-temperature zone of a tube furnace. Argon gas was then continuously passed through the boat for 30 minutes at a flow rate of 80 sccm to expel all the air inside and allow the boat to react in an argon atmosphere.

[0068] 3) After step 2), the tubular furnace was heated to 900°C at a heating rate of 10°C / min, maintained at this temperature for 1 hour, the heating was turned off, and then the temperature was cooled to room temperature with the furnace. During this process, argon gas was maintained at a gas flow rate of 80 sccm to obtain a water evaporator CNW.

[0069] The full spectrum light absorption rate curve of the solar water evaporator NW is shown in the attached figure. Figure 5 As shown, CNW has a strong ability to absorb sunlight, nearly 100%. Figure 2 A scanning electron microscope image of a solar water evaporator CNW is shown, clearly showing that the CNW is composed of many vertically arranged tubes.

[0070] Example 3

[0071] 1) Obtaining the water evaporator water transport layer material CNW is consistent with that in specific embodiment 2.

[0072] 2) The biomass waste - rice husk was washed with ultrapure water three times and then dried in an oven at 60°C.

[0073] 3) The dried rice husks were filled with high-purity alumina in a porcelain boat, which was then placed in the middle of the high-temperature zone of a tube furnace. Argon was then passed through the boat for 30 minutes at a flow rate of 80 sccm to expel all air and allow the boat to react in an argon atmosphere.

[0074] 4) After step 3), the tubular furnace was heated to 800°C at a heating rate of 10°C / min, kept constant at this temperature for 1 hour, the heating was turned off, and then the temperature was cooled to room temperature with the furnace. During this process, argon gas was maintained at a gas flow rate of 80 sccm to obtain a composite material of silicon dioxide and carbon.

[0075] 5) After step 4), the sample was not removed from the tube furnace, and argon gas was continued to flow for 30 minutes at a gas flow rate of 80 sccm to exhaust the air inside and maintain the argon atmosphere in the tube.

[0076] 6) The tube furnace is then heated to 1400°C at a heating rate of 5°C / min, maintained at this temperature for 1 hour, the heating is turned off, and the temperature is then cooled to room temperature with the furnace. Argon gas needs to be maintained during this process, and the gas flow rate is also maintained at 80 seem, to obtain a photothermal conversion material - a mixed material of silicon carbide and carbon (SCC).

[0077] 7) The SCC coating obtained after step 6) is on the surface of CNW. The specific preparation process is as follows:

[0078] a. First, dissolve 1 g of chitosan in 60 ° C acetic acid (60 mL, 11.6 mol L -1 ), chitosan solution can be obtained.

[0079] b. Then, the optimized dose of SCC powder was added to 0.5 mL of chitosan solution, and then a trace amount of naphthol solution was added and stirred for a period of time to obtain a uniform colloidal SCC.

[0080] 8) The obtained SCC colloid was coated on the surface of the obtained CNW with a thickness of 1 mm, and then dried by freeze vacuum double-layer water evaporator, named CS.

[0081] As attached Figure 3 and 4 The scanning electron microscope images of SA and SCC are shown respectively, which clearly show that SA is composed of many disordered and irregular particles, and SCC is composed of many chaotic fiber lines mixed with carbon blocks.

[0082] Example 4

[0083] 1) The preparation method of the water evaporator water transport layer CNW and the light-to-heat conversion material SCC is consistent with that in Specific Example 4;

[0084] 2) Using two silicon-containing precursors, water glass and methyltrimethylsilane (MTMS), they are first hydrolyzed to obtain a water glass solution and a MTMS solution, respectively. The water glass is then catalyzed by 0.5M HCl, and the MTMS solution is catalyzed by 2M ammonia. The two solutions are then mixed in a volume ratio of 4:1 to obtain a sol, which is then aged for two days to obtain a gel. Finally, a thermal insulation layer silica aerogel material (SA) is obtained by vacuum freeze drying;

[0085] 3) The SA coating obtained after step 2) is applied on the CNW surface. The specific preparation process is as follows:

[0086] a. First, dissolve 1 g of chitosan in 60 ° C acetic acid (60 mL, 11.6 mol L -1 ), chitosan solution can be obtained.

[0087] b. Then, the optimized dose of SA powder was added to 0.5 mL of chitosan solution, and then a trace amount of naphthol solution was added and stirred for a period of time to obtain a uniform colloidal SA.

[0088] 4) Use the obtained SA colloid to apply SA colloid with a thickness of 1 mm on the surface of CNW and let it stand for a while.

[0089] 5) After obtaining the CNW of SA coating in step 4), a 1 mm thick SCC layer was coated on the surface of the SA coating. The SCC coating preparation method was to replace the SA in step 3) with SCC, and the other steps were the same.

[0090] 6) After obtaining the SA and SCC double-coated CNW in step 5), it is frozen at -60°C and then dried in a vacuum freeze dryer with a vacuum degree of 10 Pa. After drying, a water evaporator CAS can be obtained.

[0091] The hydrophilicity of different evaporators was analyzed by contact angle. Figure 6As shown in the graph, the time required for complete absorption of water droplets by the evaporators of native wood NW, carbonized native wood CNW, SCC-coated CNW, and double-coated CAS is 0.69 s, 0.35 s, 0.22 s, and 0.02 s, respectively. This indicates that the CAS evaporator has higher superhydrophilicity and the best water transport capacity.

[0092] Attachment Figure 7 The following is the trend of the decrease in the mass of seawater over time when water is evaporated and desalinated by different evaporators driven by solar energy. It clearly shows that the CAS changes the most, indicating the fastest evaporation rate. Figure 8 The evaporation rate and corresponding enthalpy change of pure seawater and different evaporators under the intensity of one sun are shown. It can be seen that the CAS evaporation efficiency is as high as 4.21 kg / m -2 h -1 , which are 2.03, 2.54, 3.73, and 12.76 times those of evaporators CS, CNW, NW, and pure seawater, respectively. The corresponding enthalpy change of evaporator CAS is 0.8118 MJ kg -1 Compared with pure seawater, it has dropped by about 3 times.

[0093] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A novel biomass-based solar water evaporator, characterized in that: From bottom to top, it includes a water transmission layer, a heat insulation layer, and a light-to-heat conversion layer; Among them, the water transport layer is a porous network skeleton structure in the shape of a super-hydrophilic vertical array pipeline; The thermal insulation layer is a super-hydrophilic silica aerogel with high thermal resistance, and its coating forms a stable interface on the water transmission layer; The light-to-heat conversion layer has good light-to-heat conversion capability, and the coating forms a light-to-heat interface on the thermal insulation layer; The preparation method of the novel biomass-based solar water evaporator comprises the following steps: S1: heating the biomass waste material I to 600-1000° C. under protective gas, and cooling the biomass waste material to obtain a silicon dioxide-carbon mixed material; S2: The silicon dioxide-carbon mixed material is further heated to 1100-1700° C. under a protective gas, and then cooled to obtain a material for a light-to-heat conversion layer; S3: using the biomass waste II according to the methods of steps S1 and S2 to synthesize a water transport layer material having a vertical array of pipes; S4: Using two silicon-containing precursors, first hydrolyze, then undergo two-step acid-base catalysis, and finally freeze-dry in vacuum to obtain silica aerogel for thermal insulation layer; S5: Then, sequentially coating the water transmission layer with a heat insulation layer of silica aerogel and coating the light-to-heat conversion layer with a material on the heat insulation layer; The biomass waste material I includes one or more of rice husk, straw, wheat bran, corn cob, sawdust, and bagasse; Biomass waste II includes one or more of wood, bamboo, reed, mushroom, and sugarcane.

2. A novel biomass-based solar water evaporator according to claim 1, characterized in that: The specific process of step S5 is as follows: a. First, dissolve chitosan in acetic acid to obtain a chitosan solution; b. Then, the silica aerogel and the silica-carbon hybrid material were added to the chitosan solution, followed by the binder solution, and mixed evenly to obtain SA colloid and SCC colloid, respectively. c. SA colloid is applied to the surface of the water transport layer material to a certain thickness. After a period of time, a layer of SCC colloid is applied. Finally, a new biomass-based solar water evaporator is obtained by freeze-vacuum drying.

3. A novel biomass-based solar water evaporator according to claim 2, characterized in that: In step b, the adhesive is one or more of polyacrylamide, naphthol, polyurethane adhesive, and epoxy resin adhesive; and / or; In step c, the coating thickness is 1-5 mm.

4. A novel biomass-based solar water evaporator according to claim 1, characterized in that: In step S1, the heating rate is 5-25°C / min, and after heating to the specified temperature, the temperature is kept for 0.5-2h.

5. A novel biomass-based solar water evaporator according to claim 1, characterized in that: In step S2, the heating rate is 1-10°C / min, and after heating to the specified temperature, the temperature is kept for 0.5-2h.

6. A novel biomass-based solar water evaporator according to claim 1, characterized in that: In steps S1-S3, the protective gas is at least one of nitrogen, argon, and helium, and the flow rate is 40-150 sccm.

7. A novel biomass-based solar water evaporator according to claim 1, characterized in that: In step S4, the silicon source is one or more of water glass, methyltrimethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane, trimethylmethoxysilane, and / or the acid is one of hydrochloric acid, sulfuric acid, and nitric acid, and the base is one of sodium hydroxide, ammonia water, and potassium hydroxide.

8. Use of the novel biomass-based solar water evaporator according to any one of claims 1 to 7 in solar-driven water evaporation and seawater desalination.

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