Preparation method and application of waste carbon-based material composite hydrogel

Abstract

The invention discloses a preparation method and application of a waste carbon-based material composite hydrogel, and the preparation method comprises the following steps: mixing a waste carbon-based material, a sodium alginate solid and a microcrystalline cellulose solid, adding water, grinding, freezing, freeze-drying and soaking to obtain the waste carbon-based material composite hydrogel. The preparation cost is low, the waste carbon-based raw material is fully utilized, and the high value of the waste is realized; the hydrogel with microcrystalline cellulose introduced is high in mechanical strength, and the problem that existing hydrogel is poor in mechanical property is solved; the method is simple in experimental operation, low in equipment requirement and free of an initiator, and hydrogel with different sizes and shapes can be prepared as required. The invention provides a method for high-valued and low-cost application of the waste carbon-based material, and also provides a thought for preparing hydrogel which is simple in preparation process and high in mechanical property for efficient photo-thermal water evaporation.

Description

Technical Field

[0001] This invention relates to a method for preparing a composite hydrogel made from waste carbon-based materials and its application, belonging to the fields of seawater desalination and water resource purification. Background Technology

[0002] Hydrogels, with their unique three-dimensional network structure, high hydrophilicity, and tunable physicochemical properties, have become a core material in solar-driven interfacial evaporation technology, primarily focusing on seawater desalination and water purification. Hydrogels can reduce the enthalpy of evaporation by regulating the state of their internal water (free water, bound water, and intermediate water), breaking through the theoretical evaporation rate limits of traditional materials. Moreover, hydrogels can uniformly load carbon-based materials (such as carbon black, graphene, biomass carbon materials, inorganic / organic semiconductors (such as λ-Ti3O5)) and nanoparticles (such as Ag and Cu), achieving efficient photothermal conversion while reducing heat loss through low thermal conductivity. Among carbon-based materials, graphene and carbon nanotubes, while exhibiting excellent performance, are expensive, limiting large-scale application. In contrast, carbon-based materials such as rice husk charcoal, printer toner, and activated carbon are widely available and inexpensive, yet their high added value potential remains untapped. Globally, approximately 150 million tons of rice husks are produced annually, most of which are directly incinerated or piled up to rot (Rice Science, 2024, 31, 14−32); approximately 6,000 tons of waste ink cartridge residue are generated annually (Separation and Purification Technology, 2025, 354, 128724); and approximately 1.8 million tons of activated carbon are produced annually, with 95% of powdered activated carbon being discarded due to high regeneration costs. Such "waste" Inefficient use not only wastes resources but also exacerbates the environmental burden.

[0003] While existing research (e.g., J. Mater. Chem. A, 2020, 8, 22645) has reported the preparation of rice husk carbon-based hydrogels, these methods rely on ball milling equipment, requiring precise control of the production process. Furthermore, their performance stability and durability under complex environments still need further improvement. In addition, most hydrogels utilize sodium alginate and calcium chloride crosslinking, which generally suffers from weak mechanical properties and poor crosslinking stability, severely limiting their practical application in solar-driven interfacial evaporation technology. Therefore, developing a hydrogel based on low-cost waste carbon-based materials, with a simple preparation process, scalable production capabilities, and both high strength and high water evaporation performance, is of great significance for promoting the industrialization of solar-driven interfacial evaporation technology. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a method for preparing composite hydrogels from waste carbon-based materials and their applications. The hydrogels prepared by this method have excellent mechanical properties and a high water evaporation rate.

[0005] Technical solution: This invention provides a method for preparing a composite hydrogel made from waste carbon-based materials, comprising the following steps: (1) Mix waste carbon-based material, sodium alginate solid and microcrystalline cellulose solid, add water and grind to obtain composite slurry; the waste carbon-based material is a substance that can be ground or mechanically processed into black (mainly because it can absorb visible light); (2) Freeze, freeze-dry and soak the composite slurry in step (1) to obtain the waste carbon-based composite hydrogel.

[0006] In step (1), the carbon content of the waste carbon-based material is usually greater than 50 wt% (this can be relaxed to greater than 30 wt% for special composite carbon-based materials, but carbon must be the main functional carrier), and the carbon skeleton must maintain its basic structure (such as graphite phase, amorphous carbon, carbon chain structure of carbon nanotubes / fibers), rather than completely carbonized inorganic carbon (such as carbonates). Morphology and aggregation state: The physical form at the time of disposal must be clearly defined (affecting the difficulty of subsequent treatment). Common forms include: powder (such as waste activated carbon, carbon black, graphene waste); block / sheet (such as waste graphite electrodes, carbon fiber composite components, carbon paper); fibrous (such as waste carbon fiber filaments, carbon felt); porous structure (such as waste molecular sieve carbon, foam carbon).

[0007] Among them, the substances that can be ground or mechanically processed into black in step (1) include activated carbon, toner, carbon shell carbon and other black powders.

[0008] In step (1), the mass ratio of the waste carbon-based material, sodium alginate solid, and microcrystalline cellulose solid is 2:2~6:0.5~3, and the water evaporation rate is 1.74~3.07 kg / m³. 2 / h.

[0009] Furthermore, in step (1), the mass ratio of the waste carbon-based material, sodium alginate solid, and microcrystalline cellulose solid is 2:2:0.5~3, at which point the water evaporation rate is 2.26~3.07 kg / m³. 2 / h.

[0010] Furthermore, in step (1), the mass ratio of the waste carbon-based material, sodium alginate solid, and microcrystalline cellulose solid is 2:2:0.5~2, at which point the water evaporation rate is 2.42~3.07 kg / m³. 2 / h.

[0011] Furthermore, in step (1), the mass ratio of the waste carbon-based material, sodium alginate solid, and microcrystalline cellulose solid is 2:2:0.5~1, at which point the water evaporation rate is 2.53~3.07 kg / m³. 2 / h.

[0012] Furthermore, in step (1), the mass ratio of the waste carbon-based material, sodium alginate solid, and microcrystalline cellulose solid is 2:2:0.5~0.67, at which point the water evaporation rate is 2.96~3.07 kg / m³. 2 / h.

[0013] The waste carbon-based material mentioned in step (1) includes one or more of rice husk charcoal, waste toner cartridge powder, or activated carbon.

[0014] Furthermore, the waste carbon-based material mentioned in step (1) includes rice husk charcoal.

[0015] The experimental results of this invention are not affected by the source of the waste toner cartridge, that is, they are not affected by changes in the composition and content of the toner due to the printer model or the number of times the toner cartridge has been used.

[0016] The volume of water in step (1) is 20 to 50 mL.

[0017] The total mass concentration of the composite slurry in step (1) is 25~50 mg / mL. -1 .

[0018] In step (2), the freezing temperature is -180℃ to -80℃ and the freezing time is 4 to 12 hours.

[0019] The freeze-drying time in step (2) is 4 to 12 hours.

[0020] In step (2), the soaking solution is a CaCl2 solution with a mass fraction of 5% to 10%; the soaking time is 4 hours.

[0021] In step (2), the freeze-dried product is very dry overall, with low density and very light weight.

[0022] The present invention also provides a composite hydrogel of waste carbon-based materials prepared by the method.

[0023] The present invention also provides the application of the aforementioned waste carbon-based composite hydrogel in the preparation of solar interfacial evaporation materials.

[0024] The present invention also provides a solar interface evaporation material containing the aforementioned waste carbon-based material composite hydrogel.

[0025] The thickness and size of the composite hydrogel made from waste carbon-based materials do not affect the rate of water evaporation.

[0026] The solar interface evaporation material also includes a floating layer and a water supply layer. Its structure is distributed vertically. The uppermost layer is a photothermal layer material, namely the waste carbon-based composite hydrogel in the invention; the middle layer is a water supply layer; and the lowermost layer is a floating layer, with the water supply layer passing through the lowermost layer.

[0027] The bulk density of the floating layer material must be <1 g / cm³. 3 Buoyancy can be achieved through porous or hollow structural designs; low thermal conductivity: solid-state thermal conductivity ≤0.1 W / (m·K), preventing heat conduction to deeper water bodies. It is resistant to acids and alkalis, and to light aging: it does not decompose or release harmful substances in water bodies with pH 3-11 or under long-term ultraviolet radiation; it possesses a certain mechanical strength, can withstand water flow impact and minor external force contact, and is not easily damaged.

[0028] The floating layer includes any one of polystyrene foam, sponge foam, or polyvinyl chloride foam.

[0029] The density, resilience, flammability, and raw materials of the sponge foam did not affect the experimental results.

[0030] The present invention also provides the application of the waste carbon-based composite hydrogel or the solar interface evaporation material in seawater desalination or water purification.

[0031] According to the method of this invention, without adding sodium alginate and keeping other raw materials and conditions unchanged, it is impossible to prepare a composite hydrogel of waste carbon-based materials. However, without adding microcrystalline cellulose and keeping other raw materials and conditions unchanged, the maximum compressive stress at 50% deformation is 103 kPa, with a corresponding storage modulus of 630 Pa and a water evaporation rate of 1.97 kg / m³. 2 / h. With the addition of 25 wt% microcrystalline cellulose, and other raw materials and conditions remaining unchanged, the maximum compressive stress at 50% deformation is 572 kPa, corresponding to a storage modulus of 1260 Pa, and a moisture evaporation rate of 3.07 kg / m³. 2 / h. With the addition of 50 wt% microcrystalline cellulose, and other raw materials and conditions remaining unchanged, the maximum compressive stress at 50% deformation is 171 kPa, corresponding to a storage modulus of 790 Pa, and a moisture evaporation rate of 2.42 kg / m³. 2 / h.

[0032] Mechanism of the invention: In the method of this invention, the mass fraction of microcrystalline cellulose is a key indicator affecting strength and water evaporation rate. The network cross-linked with sodium alginate and calcium ions is a flexible network structure, relatively prone to collapse. Microcrystalline cellulose, as a natural, rigid, highly crystalline biomass polysaccharide, forms a support structure with a mass fraction of 25% when combined with the flexible network of sodium alginate and calcium ions, exhibiting a permeable porous structure that ensures water transport and overflow. However, microcrystalline cellulose with a mass fraction of 50% associates due to its own hydrogen bond interactions, leading to localized collapse. Therefore, the mass fraction of microcrystalline cellulose affects the permeable porous structure and effective water transport, and is also a key indicator affecting strength and water evaporation rate.

[0033] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: 1. The preparation cost of the present invention is low, making full use of "waste carbon-based raw materials" to achieve high value of waste; 2. The hydrogel with the introduction of microcrystalline cellulose has high mechanical strength, solving the problem of weak mechanical properties of current hydrogels; 3. The experimental operation is simple, the equipment requirements are low, no initiator is required, and hydrogels of different sizes and shapes can be prepared as needed; 4. This method provides a way for the high value and low cost application of waste carbon-based materials, and also provides a way for preparing hydrogels with simple process and strong mechanical properties for efficient photothermal evaporation. Attached Figure Description

[0034] Figure 1 Photographs and scanning electron microscope images of the rice husk carbon composite hydrogel (A) prepared in Example 1, the waste selenium drum toner composite hydrogel (B) prepared in Example 2, and the activated carbon material composite hydrogel (C) prepared in Example 8; Figure 2 This is a schematic diagram of a solar-powered interfacial evaporation device. Figure 3 Stress-strain curves (A) and storage modulus (B) of rice husk carbon composite hydrogels with different microcrystalline cellulose contents. Figure 4 Rice husk charcoal composite hydrogel (Example 1), waste selenium toner composite hydrogel (Example 2), and activated carbon material composite hydrogel (Example 7) were tested under a light intensity of 1 kW m. -2 The graph shows the change in seawater evaporation mass after 1 hour of testing. Detailed Implementation

[0035] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0036] Example 1 Fresh rice husks were dried at 120°C for 6 hours to obtain dried rice husks. Next, 1000 g of dried rice husks were evenly packed into a tube furnace and heated at 12 L / min. -1Air was introduced at a rate of 100°C to gradually increase the temperature. The temperature was increased to 200°C within 20 min and held for 1 h. The temperature was then increased to 500°C and held for 3 h. After cooling, 218 g of rice husk charcoal was obtained.

[0037] 200 mg of rice husk charcoal was mixed with 200 mg of sodium alginate solid at a 1:1 mass ratio, and 25 mL of deionized water was added. Then, 67 mg of microcrystalline cellulose solid (Shanghai Titan Technology Co., Ltd. Exploration Platform, CAS: 9004-34-6, Product No.: 013631678) was added. The mixture was thoroughly ground in a mortar and pestle while allowing continuous evaporation of moisture, resulting in a total mass concentration of 25 mg / mL. -1 The composite slurry was poured into a mold and frozen at -80 °C for 12 h to completely solidify it from a fluid state. After freezing, it was freeze-dried in a freeze dryer for 12 h to obtain a preform of hydrogel. The obtained hydrogel preform was then immersed in 200 mL of a 10% CaCl2 solution for 4 h to prepare a waste carbon-based composite hydrogel, which was then characterized by scanning electron microscopy. Figure 1 As shown in A. (As indicated by...) Figure 2 As shown, a photothermal layer (the aforementioned waste carbon-based composite hydrogel) and a water supply layer (a 1 cm wide nonwoven fabric) are placed on a floating layer of polystyrene foam (Wuxi Xingda Foam Plastic New Material Co., Ltd., item number: XC-401, specification: PKF-303XS). The water supply layer is positioned below the photothermal layer, between the photothermal layer and the floating layer, and is introduced into the water body through the floating layer, thus obtaining the solar interface evaporation material. Finally, the solar interface evaporation material is placed under a light intensity of 1 kW m². -2 A full-spectrum optical power meter was used to simulate vertical irradiation under sunlight using a xenon lamp. The water evaporation rate was calculated using the formula: change in water mass in the evaporator / evaporation area / time. The results show ( Figure 4 The water evaporation rate on the surface of the solar interface evaporation material is 3.07 kg m³. -1 h -1 .like Figure 3 As shown, when 25% microcrystalline cellulose is added, the maximum compressive stress at 50% deformation is 572 kPa, and the corresponding storage modulus is 1260 Pa.

[0038] Example 2

[0039] The waste toner cartridges were sourced from Suzhou Lejia Sanitary Ware (Suzhou) Co., Ltd., and their chemical composition is as follows: SiO2 3.53%, Al2O3 16.90%, Fe2O3 1.19%, MgO 0.18%, CaO 1.86%, Na2O 2.91%, TiO2 0.61%, ZnO 3.38%, CuO 6.08%, SO3 17.9%, NiO 2.46%, Cr2O3 42.9%, PbO 0.01%, P2O5 0.04%, Cl 0.05%.

[0040] 200 mg of waste toner was mixed with 200 mg of sodium alginate solid at a 1:1 mass ratio, followed by 25 mL of deionized water, and then 67 mg of microcrystalline cellulose solid. The mixture was thoroughly ground in a mortar and pestle while allowing moisture to evaporate continuously, resulting in a total mass concentration of 25 mg / mL. -1 The composite slurry was poured into a mold and frozen at -80 °C for 12 h to completely solidify it from a fluid state. After freezing, it was freeze-dried in a freeze dryer for 12 h to obtain a preform of hydrogel. The obtained hydrogel preform was then immersed in 200 mL of a 10% CaCl2 solution for 4 h to prepare a waste carbon-based composite hydrogel, which was then characterized by scanning electron microscopy. Figure 1 As shown in Figure B, a solar interface evaporation material was prepared according to the method of Example 1. A photothermal layer (the aforementioned waste carbon-based composite hydrogel) and a water supply layer (a 1 cm wide nonwoven fabric) were placed on a floating layer of polystyrene foam. The water supply layer was positioned below the photothermal layer, between the photothermal layer and the floating layer, and was introduced into the water body through the floating layer. Finally, the solar interface evaporation material was placed under a light intensity of 1 kW m². -2 The water evaporation rate was calculated by vertically irradiating the sample under a full-spectrum optical power meter simulating sunlight with a xenon lamp. The results show ( Figure 4 The water evaporation rate on the surface of the solar interface evaporation material is 2.53 kg m³. -1 h -1 .

[0041] Example 3

[0042] 200 mg of rice husk charcoal (prepared as in Example 1) was mixed with 200 mg of sodium alginate solid at a 1:1 mass ratio. 25 mL of deionized water was added, followed by 50 mg of microcrystalline cellulose solid. The mixture was thoroughly ground in a mortar while allowing moisture to evaporate continuously, resulting in a total mass concentration of 25 mg / mL. -1The composite slurry was poured into a mold according to the preparation requirements and frozen at -80 ℃ for 8 h to completely change it from a fluid state to a solid state. After freezing, it was placed in a freeze dryer and freeze-dried for 12 h to obtain a preform of hydrogel. The obtained hydrogel preform was immersed in 200 mL of 10% CaCl2 solution for 4 h to prepare the waste carbon-based material composite hydrogel. Solar interface evaporation material was prepared according to the method of Example 1. A photothermal layer (the waste carbon-based material composite hydrogel prepared above) and a water supply layer (a non-woven fabric with a width of 1 cm) were set on a floating polystyrene foam layer. The water supply layer was pressed below the photothermal layer, located between the photothermal layer and the floating layer, and introduced into the water body through the floating layer. Finally, the solar interface evaporation material was subjected to a light intensity of 1 kW m². -2 The water evaporation rate was calculated by vertically irradiating the surface of the solar interface evaporation material using a full-spectrum optical power meter under simulated solar xenon lamp illumination. The results showed that the water evaporation rate on the surface of the solar interface evaporation material was 2.96 kg m³. -1 h -1 .

[0043] Example 4

[0044] 200 mg of rice husk charcoal (prepared as in Example 1) was mixed with 200 mg of sodium alginate solid at a 1:1 mass ratio. 20 mL of deionized water was added, followed by 100 mg of microcrystalline cellulose solid. The mixture was thoroughly ground in a mortar while allowing moisture to evaporate continuously, resulting in a total mass concentration of 25 mg / mL. -1 The composite slurry was poured into a mold according to the preparation requirements and frozen at -180 ℃ for 4 h to completely change it from a flowing state to a solid state. After freezing, it was placed in a freeze dryer and freeze-dried for 4 h to obtain a preform of hydrogel. The obtained hydrogel preform was immersed in 200 mL of 5% CaCl2 solution for 4 h to prepare the waste carbon-based material composite hydrogel. Solar interface evaporation material was prepared according to the method of Example 1. A photothermal layer (the waste carbon-based material composite hydrogel prepared above) and a water supply layer (a non-woven fabric with a width of 1 cm) were set on a floating polystyrene foam layer. The water supply layer was pressed below the photothermal layer, located between the photothermal layer and the floating layer, and introduced into the water body through the floating layer. Finally, the solar interface evaporation material was subjected to a light intensity of 1 kW m². -2 The water evaporation rate was calculated by vertically irradiating the surface of the solar interface evaporation material using a full-spectrum optical power meter under simulated solar xenon lamp illumination. The results showed that the water evaporation rate on the surface of the solar interface evaporation material was 2.84 kg m³. -1 h -1 .

[0045] Example 5

[0046] 200 mg of rice husk charcoal (prepared as in Example 1) was mixed with 400 mg of sodium alginate solid at a mass ratio of 1:2. 50 mL of deionized water was added, followed by 300 mg of microcrystalline cellulose solid. The mixture was thoroughly ground in a mortar while allowing moisture to evaporate continuously, resulting in a total mass concentration of 25 mg / mL. -1 The composite slurry was poured into a mold according to the preparation requirements and frozen at -80 ℃ for 6 h to completely solidify it from a fluid state. After freezing, it was placed in a freeze dryer and freeze-dried for 12 h to obtain a preform of hydrogel. The obtained hydrogel preform was then immersed in 200 mL of 10% CaCl2 solution for 4 h to prepare the waste carbon-based material composite hydrogel. Solar interface evaporation material was prepared according to the method of Example 1. A photothermal layer (the waste carbon-based material composite hydrogel prepared above) and a water supply layer (a 1 cm wide nonwoven fabric) were set on a floating polystyrene foam layer. The water supply layer was placed below the photothermal layer, between the photothermal layer and the floating layer, and was introduced into the water body through the floating layer. Finally, the solar interface evaporation material was subjected to a light intensity of 1 kW m². -2 The water evaporation rate was calculated by vertically irradiating the surface of the solar interface evaporation material using a full-spectrum optical power meter under simulated solar xenon lamp illumination. The results showed that the water evaporation rate on the surface of the solar interface evaporation material was 1.97 kg m³. -1 h -1 .

[0047] Example 6

[0048] 200 mg of rice husk charcoal (prepared as in Example 1) was mixed with 200 mg of sodium alginate solid at a 1:1 mass ratio. 25 mL of deionized water was added, followed by 300 mg of microcrystalline cellulose solid. The mixture was thoroughly ground in a mortar while allowing moisture to evaporate continuously, resulting in a total mass concentration of 25 mg / mL. -1The composite slurry was poured into a mold according to the preparation requirements and frozen at -80 ℃ for 12 h to completely change it from a fluid state to a solid state. After freezing, it was placed in a freeze dryer and freeze-dried for 12 h to obtain a preform of hydrogel. The obtained hydrogel preform was immersed in 200 mL of 10% CaCl2 solution for 4 h to prepare the waste carbon-based material composite hydrogel. Solar interface evaporation material was prepared according to the method of Example 1. A photothermal layer (the waste carbon-based material composite hydrogel prepared above) and a water supply layer (a non-woven fabric with a width of 1 cm) were set on a floating layer of polystyrene foam. The water supply layer was pressed below the photothermal layer, located between the photothermal layer and the floating layer, and introduced into the water body through the floating layer. Finally, the solar interface evaporation material was subjected to a light intensity of 1 kW m². -2 The water evaporation rate was calculated by vertically irradiating the surface of the solar interface evaporation material using a full-spectrum optical power meter under simulated solar xenon lamp illumination. The results showed that the water evaporation rate on the surface of the solar interface evaporation material was 2.33 kg m³. -1 h -1 .

[0049] Example 7

[0050] 200 mg of activated carbon was mixed with 200 mg of sodium alginate solid at a 1:1 mass ratio, followed by 25 mL of deionized water, and then 67 mg of microcrystalline cellulose solid. The mixture was thoroughly ground in a mortar and pestle while allowing water to evaporate continuously, resulting in a total mass concentration of 25 mg / mL. -1 The composite slurry was poured into a mold according to the preparation requirements and frozen at -80 ℃ for 12 h to completely change it from a fluid state to a solid state. After freezing, it was placed in a freeze dryer and freeze-dried for 12 h to obtain a preform of hydrogel. The obtained hydrogel preform was immersed in 200 mL of 10% CaCl2 solution for 4 h to prepare the waste carbon-based material composite hydrogel. Solar interface evaporation material was prepared according to the method of Example 1. A photothermal layer (the waste carbon-based material composite hydrogel prepared above) and a water supply layer (a non-woven fabric with a width of 1 cm) were set on a floating layer of polystyrene foam. The water supply layer was pressed below the photothermal layer, located between the photothermal layer and the floating layer, and introduced into the water body through the floating layer. Finally, the solar interface evaporation material was subjected to a light intensity of 1 kW m². -2 The water evaporation rate was calculated by vertically irradiating the sample under a full-spectrum optical power meter simulating sunlight with a xenon lamp. The results show ( Figure 4 The water evaporation rate on the surface of the solar interface evaporation material is 2.26 kg m³. -1 h -1 .

[0051] Example 8

[0052] 200 mg of activated carbon granules were mixed with 200 mg of sodium alginate solid at a 1:1 mass ratio, and 40 mL of deionized water was added. Then, 200 mg of microcrystalline cellulose solid was added, and the mixture was thoroughly ground in a mortar and pestle while allowing water to evaporate continuously, resulting in a total mass concentration of 25 mg / mL. -1 The composite slurry was prepared by pouring it into a mold according to the preparation requirements and freezing it at -80 ℃ for 12 h to completely solidify it from a fluid state. After freezing, it was placed in a freeze dryer and freeze-dried for 12 h to obtain a preform of hydrogel. The preform of hydrogel was then immersed in 200 mL of 10% CaCl2 solution for 4 h to prepare the waste carbon-based material composite hydrogel, which was then characterized by scanning electron microscopy. Figure 1 As shown in Figure C, a solar interface evaporation material was prepared according to the method of Example 1. A photothermal layer (the aforementioned waste carbon-based composite hydrogel) and a water supply layer (a 1 cm wide nonwoven fabric) were placed on a floating layer of polystyrene foam. The water supply layer was positioned below the photothermal layer, between the photothermal layer and the floating layer, and was introduced into the water body through the floating layer. Finally, the solar interface evaporation material was subjected to a light intensity of 1 kW m². -2 The water evaporation rate was calculated by vertically irradiating the surface of the solar interface evaporation material using a full-spectrum optical power meter under simulated solar xenon lamp illumination. The results showed that the water evaporation rate on the surface of the solar interface evaporation material was 1.74 kg m³. -1 h -1 .

[0053] Example 9

[0054] 200 mg of rice husk charcoal (prepared as in Example 1) was mixed with 600 mg of sodium alginate solid at a mass ratio of 1:3. 50 mL of deionized water was added, followed by 300 mg of microcrystalline cellulose solid. The mixture was thoroughly ground in a mortar while allowing moisture to evaporate continuously, resulting in a total mass concentration of 25 mg / mL. -1The composite slurry was poured into a mold according to the preparation requirements and frozen at -180 ℃ for 4 h to completely change it from a fluid state to a solid state. After freezing, it was placed in a freeze dryer and freeze-dried for 4 h to obtain a preform of hydrogel. The obtained hydrogel preform was immersed in 200 mL of 10% CaCl2 solution for 4 h to prepare the waste carbon-based material composite hydrogel. Solar interface evaporation material was prepared according to the method of Example 1. A photothermal layer (the waste carbon-based material composite hydrogel prepared above) and a water supply layer (a non-woven fabric with a width of 1 cm) were set on a floating polystyrene foam layer. The water supply layer was pressed below the photothermal layer, located between the photothermal layer and the floating layer, and introduced into the water body through the floating layer. Finally, the solar interface evaporation material was subjected to a light intensity of 1 kW m². -2 The water evaporation rate was calculated by vertically irradiating the surface of the solar interface evaporation material using a full-spectrum optical power meter under simulated solar xenon lamp illumination. The results showed that the water evaporation rate on the surface of the solar interface evaporation material was 1.95 kg m³. -1 h -1 .

[0055] Example 10

[0056] 200 mg of rice husk charcoal (prepared as in Example 1) was mixed with 600 mg of sodium alginate solid at a mass ratio of 1:3. 50 mL of deionized water was added, followed by 200 mg of microcrystalline cellulose solid. The mixture was thoroughly ground in a mortar while maintaining continuous evaporation of moisture, resulting in a total mass concentration of 50 mg / mL. -1 The composite slurry was poured into a mold according to the preparation requirements and frozen at -80 ℃ for 12 h to completely change it from a fluid state to a solid state. After freezing, it was placed in a freeze dryer and freeze-dried for 12 h to obtain a preform of hydrogel. The obtained hydrogel preform was immersed in 200 mL of 10% CaCl2 solution for 4 h to prepare the waste carbon-based material composite hydrogel. Solar interface evaporation material was prepared according to the method of Example 1. A photothermal layer (the waste carbon-based material composite hydrogel prepared above) and a water supply layer (a non-woven fabric with a width of 1 cm) were set on a floating layer of polystyrene foam. The water supply layer was pressed below the photothermal layer, located between the photothermal layer and the floating layer, and introduced into the water body through the floating layer. Finally, the solar interface evaporation material was subjected to a light intensity of 1 kW m². -2 The water evaporation rate was calculated by vertically irradiating the surface of the solar interface evaporation material using a full-spectrum optical power meter under simulated solar xenon lamp illumination. The results showed that the water evaporation rate on the surface of the solar interface evaporation material was 2.03 kg / m³. -1 h -1 .

[0057] Example 11

[0058] 200 mg of rice husk charcoal was mixed with 200 mg of sodium alginate solid at a 1:1 mass ratio, followed by 25 mL of deionized water. Then, 200 mg of microcrystalline cellulose solid was added. The mixture was thoroughly ground in a mortar and pestle while allowing water to evaporate continuously, resulting in a total mass concentration of 25 mg / mL. -1 The composite slurry was poured into a mold according to the preparation requirements and frozen at -80 ℃ for 12 h to completely change it from a fluid state to a solid state. After freezing, it was placed in a freeze dryer and freeze-dried for 12 h to obtain a preform of hydrogel. The obtained hydrogel preform was immersed in 200 mL of 10% CaCl2 solution for 4 h to prepare the waste carbon-based material composite hydrogel. Solar interface evaporation material was prepared according to the method of Example 1. A photothermal layer (the waste carbon-based material composite hydrogel prepared above) and a water supply layer (a non-woven fabric with a width of 1 cm) were set on a floating layer of polystyrene foam. The water supply layer was pressed below the photothermal layer, located between the photothermal layer and the floating layer, and introduced into the water body through the floating layer. Finally, the solar interface evaporation material was subjected to a light intensity of 1 kW m². -2 The water evaporation rate was calculated by vertically irradiating the surface of the solar interface evaporation material using a full-spectrum optical power meter under simulated solar xenon lamp illumination. The results showed that the water evaporation rate at the solar interface evaporation material surface was 2.42 kg m³. -1 h -1 .like Figure 3 As shown, when 50% microcrystalline cellulose is added, the maximum compressive stress at 50% deformation is 171 kPa, and the corresponding storage modulus is 790 Pa.

[0059] Comparative Example 1 200 mg of rice husk charcoal was mixed with 200 mg of sodium alginate solid at a 1:1 mass ratio, and 25 mL of deionized water was added. Then, 0 mg of microcrystalline cellulose solid was added. The mixture was thoroughly ground in a mortar while allowing water to evaporate continuously, resulting in a total mass concentration of 25 mg / mL. -1The composite slurry was poured into a mold according to the preparation requirements and frozen at -80 ℃ for 12 h to completely change it from a fluid state to a solid state. After freezing, it was placed in a freeze dryer and freeze-dried for 12 h to obtain a preform of hydrogel. The obtained hydrogel preform was immersed in 200 mL of 10% CaCl2 solution for 4 h to prepare the waste carbon-based material composite hydrogel. Solar interface evaporation material was prepared according to the method of Example 1. A photothermal layer (the waste carbon-based material composite hydrogel prepared above) and a water supply layer (a non-woven fabric with a width of 1 cm) were set on a floating layer of polystyrene foam. The water supply layer was pressed below the photothermal layer, located between the photothermal layer and the floating layer, and introduced into the water body through the floating layer. Finally, the solar interface evaporation material was subjected to a light intensity of 1 kW m². -2 The water evaporation rate was calculated by vertically irradiating the surface of the solar interface evaporation material using a full-spectrum optical power meter under simulated solar xenon lamp illumination. The results showed that the water evaporation rate on the surface of the solar interface evaporation material was 1.82 kg / m³. -1 h -1 .like Figure 3 As shown, without the addition of cellulose, the maximum compressive stress at 50% deformation was 103 kPa, and the corresponding storage modulus was 630 Pa.

Claims

1. A method for preparing a composite hydrogel made from waste carbon-based materials, characterized in that, Includes the following steps: (1) Mix waste carbon-based material, sodium alginate solid and microcrystalline cellulose solid, add water and grind to obtain composite slurry; the waste carbon-based material is a black material used to absorb visible light; (2) Freeze, freeze-dry and soak the composite slurry in step (1) to obtain the waste carbon-based composite hydrogel.

2. The preparation method according to claim 1, characterized in that, The mass ratio of the waste carbon-based material, sodium alginate solid and microcrystalline cellulose solid mentioned in step (1) is 2:2~6:0.5~3.

3. The preparation method according to claim 1, characterized in that, The waste carbon-based materials mentioned in step (1) include one or more of rice husk charcoal, waste toner cartridge powder, or activated carbon.

4. The preparation method according to claim 1, characterized in that, The total mass concentration of the composite slurry mentioned in step (1) is 25~50 mg / mL. -1 .

5. The preparation method according to claim 1, characterized in that, The freezing temperature in step (2) is -180℃ to -80℃, and the freezing time is 4 to 12 hours.

6. The preparation method according to claim 1, characterized in that, The freeze-drying time in step (2) is 4 to 12 hours.

7. The preparation method according to claim 1, characterized in that, The soaking solution in step (2) is a CaCl2 solution with a mass fraction of 5% to 10%.

8. The application of the waste carbon-based composite hydrogel obtained by the preparation method according to any one of claims 1 to 7 in the preparation of solar interfacial evaporation materials.

9. A solar energy interface evaporation material, characterized in that, It contains the waste carbon-based material composite hydrogel obtained by the preparation method according to any one of claims 1 to 7.

10. The application of the waste carbon-based composite hydrogel obtained by the preparation method according to any one of claims 1 to 7 or the solar interface evaporation material according to claim 9 in seawater desalination or water purification.

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