All-weather evaporation device and its preparation method and application

Abstract

The present invention discloses an all-weather evaporation device, its preparation method, and application. This invention relates to the technical field of evaporation devices. The present invention comprises a water-evaporation aerogel and a heat-storage aerogel. The water-evaporation aerogel is nested within a ring-shaped heat-storage aerogel. The water-evaporation aerogel is produced by freeze-drying a mixed solution of a montmorillonite-based photocatalyst, graphene oxide, polyvinyl alcohol, and cellulose nanocrystals. The heat-storage aerogel is produced by freeze-drying a mixed solution of multi-walled carbon nanotubes, polyvinyl alcohol, and cellulose nanocrystals, followed by impregnation with a phase change material. The all-weather evaporation device of the present invention has both strong water evaporation and pollutant degradation capabilities.

Description

Technical Field

[0001] The present invention relates to the technical field of evaporation devices, and in particular to an all-weather evaporation device and a preparation method and application thereof. Background Art

[0002] Due to the discontinuity of sunlight and the heat loss caused by the weak light absorption of water, the evaporation efficiency of seawater is very low and the fresh water production is small; the pollutant treatment efficiency is low, the clean water production is small, and the pressure on fresh water use cannot be alleviated.

[0003] Storing solar energy through thermal energy storage technology can effectively alleviate the continuity of solar energy and effectively improve the utilization rate of sunlight. Phase change materials, as a thermal energy storage material, are often introduced into solar interface evaporation devices due to their high heat storage capacity and stable phase change temperature.

[0004] Research on the application of interfacial evaporation devices incorporating phase change materials in seawater desalination has yielded some success. However, research and development efforts that effectively balance the amount of phase change material used and the water evaporation pathways are limited. This is primarily due to limitations in the device's application environment. Excessive amounts of phase change material clog the evaporation pores, hindering water transfer from the water column to the evaporation interface and inhibiting evaporation. Meanwhile, insufficient amounts of phase change material reduce the latent heat released in darkness, resulting in insignificant improvements in evaporator continuity. Therefore, developing a solar interfacial evaporation device with a rational structure, strong water evaporation capacity, and robust pollutant degradation capabilities is crucial for alleviating freshwater shortages using seawater / wastewater. Summary of the Invention

[0005] The purpose of the present invention is to address the above-mentioned deficiencies in the prior art and to provide an all-weather evaporation device with strong water evaporation and pollutant degradation capabilities, as well as a preparation method and application thereof.

[0006] The present invention provides an all-weather evaporation device, comprising a water evaporation aerogel and a heat storage aerogel, wherein the water evaporation aerogel is nested in a ring-shaped heat storage aerogel; the water evaporation aerogel is produced by freeze-drying a mixed solution of montmorillonite-based photocatalyst, graphene oxide, polyvinyl alcohol and cellulose nanocrystals; and the heat storage aerogel is produced by freeze-drying a mixed solution of multi-walled carbon nanotubes, polyvinyl alcohol and cellulose nanocrystals and then impregnating the solution with a phase change material.

[0007] Furthermore, the montmorillonite-based photocatalyst is prepared by grinding and calcining montmorillonite and urea powder.

[0008] Furthermore, the mass ratio of montmorillonite to urea is 1:10; the grinding time is 30 minutes, the calcination temperature is 550°C, and the heating rate is 10°C / min.

[0009] Furthermore, the mass ratio of the montmorillonite-based photocatalyst and graphene oxide is 1:1-3; the mass ratio of the polyvinyl alcohol solution and the cellulose nanocrystal solution is 1:1-2; the mass ratio of the montmorillonite-based photocatalyst to the polyvinyl alcohol solution is 1:10-100; the concentration of the polyvinyl alcohol solution is not more than 5wt%; and the concentration of the cellulose nanocrystal solution is not more than 2wt%.

[0010] Furthermore, the mass ratio of the multi-walled carbon nanotubes, polyvinyl alcohol solution and cellulose nanocrystal solution is 1:10-50:10-50; the concentration of the polyvinyl alcohol solution is not greater than 5wt%; and the concentration of the cellulose nanocrystal solution is not greater than 2wt%.

[0011] Furthermore, the phase change material includes one or more of lauric acid, stearic acid, and phase change paraffin.

[0012] Furthermore, the phase change material is lauric acid, and in the heat storage aerogel, the mass ratio of aerogel to lauric acid is 1:5 to 1:10.

[0013] Furthermore, the phase change material is impregnated in a vacuum impregnation process at a temperature of 40 to 60° C. and for a time of 2 to 5 hours.

[0014] A method for preparing the all-weather evaporation device as described above comprises mixing a montmorillonite-based photocatalyst, graphene oxide, a polyvinyl alcohol solution, and a cellulose solution, and then pouring the mixture into a mold, followed by directional solidification and freeze drying to obtain a water evaporation aerogel;

[0015] The multi-walled carbon nanotubes, polyvinyl alcohol solution and cellulose solution are mixed and poured into a ring mold, and then freeze-dried by directional solidification to obtain an aerogel, and then the aerogel is vacuum impregnated with a phase change material to obtain a water evaporation aerogel;

[0016] The evaporation aerogel is nested in the annular heat storage aerogel to obtain the all-weather evaporation device.

[0017] An application of the all-weather evaporation device as described above in seawater desalination and sewage purification can be to nest the all-weather evaporation device on absorbent cotton in an insulating foam ring, and float the all-weather evaporation device on the liquid with the help of the insulating foam ring.

[0018] Beneficial effects:

[0019] The present invention utilizes graphene oxide to regulate montmorillonite-based photocatalysts and prepares them into porous network water evaporation aerogels containing vertical channels. The montmorillonite-based photocatalysts themselves have photocatalytic degradation capabilities. The introduction of graphene oxide enhances the photocatalytic degradation capabilities of the water evaporation aerogels. The water evaporation aerogels of the present invention have both the capabilities of seawater desalination and photocatalytic degradation of dye pollutants. The heat storage aerogel comprises multi-walled carbon nanotubes impregnated with a phase change material. The water evaporation aerogels are then nested within the annular heat storage aerogels to separate the water evaporation channels and the phase change material, thereby preventing the phase change material from obstructing steam escape and preventing the introduction of the phase change material from increasing thermal conductivity and thereby increasing heat loss.

[0020] The heat storage aerogel of the present invention has the ability to release latent heat and convert light into heat. The absorbance is over 90% in the entire spectrum. Under continuous sunlight irradiation, it can provide heat to the water evaporating aerogel. Under lightless conditions, the latent heat released can keep the water evaporating aerogel warm, so that even in lightless conditions, a good water evaporation rate can be maintained.

[0021] The water evaporation aerogel and thermal storage aerogel of the present invention feature a rational ratio of polyvinyl alcohol and cellulose nanocrystals, resulting in a stable aerogel with a rich pore structure, which accelerates the transport of water molecules. The rich pore structure of the thermal storage aerogel also provides more space for the impregnation of phase change materials.

[0022] The all-weather evaporation device of the present invention has strong water evaporation capacity and pollutant degradation capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a photo of the water evaporation aerogel prepared in Example 1.

[0024] Figure 2 This is a photo of the water evaporation aerogel prepared in Example 2.

[0025] Figure 3 This is a photo of the water evaporation aerogel prepared in Example 3.

[0026] Figure 4 This is a photo of the water evaporation aerogel prepared in Example 4.

[0027] Figure 5 This is a photo of the water evaporation aerogel prepared in Example 5.

[0028] Figure 6 This is a photo of the heat storage aerogel prepared in Example 1.

[0029] Figure 7 Photo of an all-weather evaporation unit on cotton wool nested in insulating foam.

[0030] Figure 8 This is a scanning electron microscope photograph of the morphology of the water evaporation aerogel in Example 2.

[0031] Figure 9 This is the seawater desalination test result of Example 2. DETAILED DESCRIPTION

[0032] The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments.

[0033] Example 1:

[0034] (1) Preparation of montmorillonite-based photocatalyst: 1.00 g of montmorillonite ore and 10.00 g of urea were thoroughly ground and placed in a 50 ml corundum crucible tightly sealed with double-layer tin foil. The crucible was calcined in a muffle furnace at 550 °C at a heating rate of 10 °C / min for 3 h.

[0035] (2) Preparation of water evaporation aerogel: 20.00 g of 5 wt% polyvinyl alcohol aqueous solution and 20.00 g of 2 wt% cellulose nanocrystal aqueous solution were placed in a beaker, 0.60 g of montmorillonite-based photocatalyst and 0.20 g of graphene oxide were added, and magnetic stirring was continued for 30 minutes, followed by constant temperature ultrasonication at 25°C, and repeated three times to obtain a mixed solution. The solution was poured into a mold with a diameter of 3 cm and a height of 2 cm placed on a copper plate pre-cooled with liquid nitrogen, directionally solidified, and freeze-dried for 72 hours. The water evaporation aerogel obtained was as follows: Figure 1 shown.

[0036] (3) Preparation of heat storage aerogel: 20.00g of 5wt% polyvinyl alcohol aqueous solution and 20.00g of 2wt% cellulose nanocrystal aqueous solution were placed in a beaker, 0.40g of multi-walled carbon nanotubes were added, and magnetic stirring was continued for 30 minutes, followed by constant temperature ultrasonication at 25°C, and repeated three times to obtain a mixed solution. The solution was poured into a ring mold with an inner diameter of 2cm, an outer diameter of 3cm, and a height of 2cm placed on a copper plate pre-cooled with liquid nitrogen, directionally solidified, and freeze-dried for 72 hours. After freeze-drying, the mass was measured, and lauric acid 10 times the mass of the aerogel was taken and vacuum impregnated in a vacuum drying oven at 60°C for 2 hours. The heat storage aerogel obtained was as follows: Figure 6 shown.

[0037] (4) Preparation of evaporation device: The water evaporation aerogel in step 2 is nested in the heat storage aerogel in step 3, and then placed on about 0.4g of absorbent cotton nested in the insulation foam to obtain an evaporation device as shown in FIG. Figure 7 shown.

[0038] Water evaporation capacity test: The evaporation device was placed in a beaker containing deionized water. A xenon lamp was used as the solar light source. An optical power meter was used to measure the solar energy density. An electronic balance was used to monitor the change in water mass during the solar-driven evaporation process. The ambient temperature and humidity were 26°C and 50%, respectively. Under continuous one-sun illumination, the water evaporation rate was 4.55 kg m -2 h -1 The water evaporation rate in 30 min without light was determined to be 2.06 kg m -2 h -1 .

[0039] Degradation test of dye wastewater: Methyl orange (AOⅡ, 30ml, 20mg / mL) was used as a model pollutant. Before photocatalysis, the water evaporation aerogel was placed in a completely dark environment and immersed in the dye. After reaching the adsorption-desorption equilibrium (30 minutes), 1.5mL PMS (10g / L) was added and the xenon lamp was turned on to initiate the degradation reaction under the irradiation of one sun. Every 10 minutes, 1mL of the solution was extracted and placed in a centrifuge tube together with 1mL of sodium nitrite (1mol / L) prepared in advance and mixed evenly to terminate the reaction. The concentration of AOⅡ was measured by spectrophotometer at λ=486nm. The dye degradation rate was 71%.

[0040] Example 2:

[0041] Step (1) is the same as in Example 1.

[0042] (2) Preparation of water evaporation aerogel: 20.00 g of 5 wt% polyvinyl alcohol aqueous solution and 20.00 g of 2 wt% cellulose nanocrystal aqueous solution were placed in a beaker, 0.40 g of montmorillonite-based photocatalyst and 0.40 g of graphene oxide were added, and magnetic stirring was continued for 30 minutes, followed by constant temperature ultrasonication at 25°C, and repeated three times to obtain a mixed solution. The solution was poured into a mold with a diameter of 3 cm and a height of 2 cm placed on a copper plate pre-cooled with liquid nitrogen, directionally solidified, and freeze-dried for 72 hours. The water evaporation aerogel obtained was as follows: Figure 2 shown.

[0043] Steps (3), (4), (5) and (6) are the same as in Example 1.

[0044] Under continuous sunlight, the evaporation rate of water is 4.80 kg m -2 h -1 The water evaporation rate in 30 min without light was determined to be 2.01 kg m -2 h -1 ; The dye degradation rate is 92%.

[0045] Desalinated seawater ion concentration test: Place the evaporation device between a transparent glass cover and a transparent glass plate, collect 1 mL of distilled water desalinated in step (5) and 1 mL of undesalinated seawater for inductively coupled plasma atomic emission spectrometry test. The measured ions are Na + , K + , Ca 2+ Mg 2+ .

[0046] Figure 9 The desalination test results of Example 2 are as follows: Figure 9 It can be seen that the evaporation device prepared in this embodiment has a strong seawater desalination capacity.

[0047] Example 3:

[0048] Step (1) is the same as in Example 1.

[0049] (2) Preparation of water evaporation aerogel: 20.00 g of 5 wt% polyvinyl alcohol aqueous solution and 20.00 g of 2 wt% cellulose nanocrystal aqueous solution were placed in a beaker, 0.20 g of montmorillonite-based photocatalyst and 0.60 g of graphene oxide were added, and magnetic stirring was continued for 30 minutes, followed by constant temperature ultrasonication at 25°C, and repeated three times to obtain a mixed solution. The solution was poured into a mold with a diameter of 3 cm and a height of 2 cm placed on a copper plate pre-cooled with liquid nitrogen, directionally solidified, and freeze-dried for 72 hours. The water evaporation aerogel obtained was as follows: Figure 3 As shown.

[0050] Steps (3), (4), (5) and (6) are the same as in Example 1.

[0051] Under continuous sunlight, the evaporation rate of water is 4.56 kg m -2 h -1 The water evaporation rate in 30 min without light was determined to be 2.08 kg m -2 h -1 ; The dye degradation rate is 37%.

[0052] Example 4:

[0053] Step (1) is the same as in Example 1.

[0054] (2) Preparation of water evaporation aerogel: 20.00 g of 5 wt% polyvinyl alcohol aqueous solution and 20.00 g of 2 wt% cellulose nanocrystal aqueous solution were placed in a beaker, 0.80 g of montmorillonite-based photocatalyst was added, magnetic stirring was continued for 30 minutes, and ultrasonication was performed at a constant temperature of 25°C, and repeated three times to obtain a mixed solution. The solution was poured into a mold with a diameter of 3 cm and a height of 2 cm placed on a copper plate pre-cooled with liquid nitrogen, directionally solidified, and freeze-dried for 72 hours. The water evaporation aerogel obtained was as follows: Figure 4 shown.

[0055] Steps (3), (4), (5) and (6) are the same as in Example 1.

[0056] Under continuous sunlight, the evaporation rate of water is 3.42 kg m -2 h -1 The water evaporation rate in 30 min without light was determined to be 2.06 kg m -2 h -1 ; The dye degradation rate is 84%.

[0057] Comparative Example 1:

[0058] (1) Preparation of water evaporation aerogel: 20.00 g of 5 wt% polyvinyl alcohol aqueous solution and 20.00 g of 2 wt% cellulose nanocrystal aqueous solution were placed in a beaker, 0.80 g of graphene oxide was added, and magnetic stirring was continued for 30 minutes, followed by constant temperature ultrasonication at 25°C, and repeated three times to obtain a mixed solution. The solution was poured into a mold with a diameter of 3 cm and a height of 2 cm placed on a copper plate pre-cooled with liquid nitrogen, directionally solidified, and freeze-dried for 72 hours. The water evaporation aerogel obtained was as follows: Figure 5 shown.

[0059] Steps (2), (3), (4), and (5) are the same as steps (3), (4), (5), and (6) in Example 1.

[0060] Under continuous sunlight, the evaporation rate of water is 4.50 kg m -2 h -1 The water evaporation rate in 30 min without light was determined to be 1.90 kg m -2 h -1 ; The dye degradation rate is 12%.

[0061] Any matters not mentioned above shall be subject to the existing technology.

[0062] Although some specific embodiments of the present invention have been described in detail through examples, those skilled in the art should understand that the above examples are for illustration only and are not intended to limit the scope of the present invention. Those skilled in the art of the present invention may make various modifications or additions to the described specific embodiments or replace them in similar ways, but they will not deviate from the direction of the present invention or exceed the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent replacements, improvements, etc. made to the above embodiments based on the technical essence of the present invention should be included in the scope of protection of the present invention.

Claims

1. An all-weather evaporation device, characterized in that: The invention comprises a water evaporation aerogel and a heat storage aerogel, wherein the water evaporation aerogel is nested in a ring-shaped heat storage aerogel; the water evaporation aerogel is prepared by freeze-drying a mixed solution of a montmorillonite-based photocatalyst, graphene oxide, a polyvinyl alcohol solution and a cellulose nanocrystal solution; The heat storage aerogel is prepared by freeze-drying a mixed solution of multi-walled carbon nanotubes, polyvinyl alcohol solution and cellulose nanocrystal solution and then impregnating the solution with a phase change material; The montmorillonite-based photocatalyst is prepared by grinding and calcining montmorillonite and urea powder.

2. The all-weather evaporation device according to claim 1, characterized in that: The mass ratio of montmorillonite to urea is 1:1-10; the grinding time is 5-30 minutes; the calcination temperature is 400-550°C; and the heating rate is 5-10°C / min.

3. The all-weather evaporation device according to claim 1, characterized in that: In the water evaporation aerogel, the mass ratio of the montmorillonite-based photocatalyst to the graphene oxide is 1:1-3; the mass ratio of the polyvinyl alcohol solution to the cellulose nanocrystal solution is 1:1-2; the mass ratio of the montmorillonite-based photocatalyst to the polyvinyl alcohol solution is 1:10-100; and the concentration of the polyvinyl alcohol solution is not greater than 5 wt%; The concentration of the cellulose nanocrystal solution is no more than 2 wt %.

4. The all-weather evaporation device according to claim 1, characterized in that: In the thermal storage aerogel, the mass ratio of the multi-walled carbon nanotubes, the polyvinyl alcohol solution, and the cellulose nanocrystal solution is 1:10-50:10-50; the concentration of the polyvinyl alcohol solution is not greater than 5 wt%; The concentration of the cellulose nanocrystal solution is no more than 2 wt%.

5. The all-weather evaporation device according to claim 1, characterized in that: The phase change material includes one or more of lauric acid, stearic acid, and phase change paraffin.

6. The all-weather evaporation device according to claim 1, characterized in that: The phase change material is lauric acid. In the heat storage aerogel, the mass ratio of aerogel to lauric acid is 1:5-10.

7. The all-weather evaporation device according to claim 1, characterized in that: The phase change material is impregnated by vacuum impregnation at a temperature of 40 to 60°C and a time of 2 to 5 hours.

8. A method for preparing the all-weather evaporation device according to any one of claims 1 to 7, characterized in that: The montmorillonite-based photocatalyst, graphene oxide, polyvinyl alcohol solution, and cellulose solution were stirred and mixed, then poured into a mold, and freeze-dried by directional solidification to obtain water evaporation aerogel; The multi-walled carbon nanotubes, polyvinyl alcohol solution and cellulose solution are mixed and poured into a ring mold, and then freeze-dried by directional solidification to obtain aerogel, and then the aerogel is vacuum impregnated with phase change material to obtain heat storage aerogel; The water evaporation aerogel is nested in the annular heat storage aerogel to obtain the all-weather evaporation device.

9. Use of the all-weather evaporation device according to any one of claims 1 to 7 in seawater desalination or sewage purification.

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