A solar interfacial evaporator based on a lotus seedpod structure and its preparation method

Abstract

A solar interface evaporator based on a lotus seedpod structure and its preparation method disclosed by the present invention belong to the technical field of solar energy utilization. By compounding a 3D spacer fabric, an aerogel matrix, and a reduced graphene oxide aerogel surface layer, a three-phase composite structure solar interface evaporator with the characteristics of a lotus seedpod-like bionic structure is obtained. This solar interface evaporator can achieve excellent evaporation rates and evaporation efficiencies. At the same time, a large number of directional water transport channels ensure sufficient water supply, ensuring that the salt concentration on the evaporator surface never reaches saturation, showing excellent salt tolerance, breaking through the limitations of traditional solar interface evaporators being unstable and prone to salt crystallization in high-concentration brine and wastewater environments for a long time, and greatly enhancing the practical applicability of solar interface evaporators in the fields of seawater desalination and wastewater treatment.

Description

Technical Field

[0001] The present invention belongs to the technical field of solar energy utilization, and particularly relates to a solar interfacial evaporator based on a lotus seedpod structure and a preparation method thereof. Background Art

[0002] With the increasing deterioration of the environment and the continuous aggravation of water pollution, the scarcity of fresh water resources has become an urgent problem. The oceans of the world contain more than 1.35 billion cubic kilometers of water, accounting for about 97% of the total water volume on the earth. Therefore, seawater desalination will surely be one of the important means to solve the problem of fresh water shortage.

[0003] Seawater desalination technology refers to the technology of removing salts from seawater or waste water to obtain fresh water. Traditional seawater desalination technologies such as distillation, electrodialysis, multi-stage flash evaporation, reverse osmosis, etc. often require a large amount of thermal energy or electrical energy to drive the system to produce fresh water, and have problems such as high energy consumption, complex operation, high operating cost and environmental pollution. Therefore, it is difficult to become a long-term solution. For this reason, some new seawater desalination technologies that combine renewable energy with seawater desalination have been proposed, such as solar-driven interfacial evaporation technology.

[0004] Solar-driven interfacial evaporation technology uses an interfacial solar steam generator floating on the air / water interface to absorb solar radiant energy and convert it into heat energy, thereby evaporating water, and the generated heat energy is concentrated in the interfacial area. Therefore, compared with traditional seawater desalination technologies, solar-driven interfacial evaporation technology has higher photothermal conversion efficiency and fresh water production efficiency.

[0005] However, the current solar interfacial evaporator still has the following problems:

[0006] 1) Most solar interfacial evaporators have weak mechanical strength and easy-to-collapse structures;

[0007] 2) The surfaces of commonly used solar interfacial evaporators are usually flat, which results in low light absorption rate;

[0008] 3) Most solar interfacial evaporators lack the function of directional water transportation, resulting in insufficient water supply at the gas-liquid interface of the solar interfacial evaporator, which affects the continuous evaporation ability of the solar interfacial evaporator;

[0009] 4) Most solar interfacial evaporators have poor salt tolerance during the evaporation process. Since the surface salt of the photothermal material reaches supersaturated concentration during the evaporation process, salt crystallization occurs and blocks the water transportation channels, hindering water transportation, and even affecting light absorption and the escape of water vapor; ultimately greatly reducing its seawater desalination performance, and even causing the device to fail. Summary of the Invention

[0010] To solve the problems existing in the above-mentioned prior art, the present invention discloses a solar interface evaporator based on a lotus seedpod structure, with reasonable structural design and simple manufacturing process, comprehensively improving the water transportation, light absorption, mechanical properties and salt tolerance of the solar interface evaporator, and greatly enhancing the practical applicability of the solar interface evaporator in the fields of seawater desalination and wastewater treatment.

[0011] The present invention is realized through the following technical solutions:

[0012] The present invention discloses a solar interface evaporator based on a lotus seedpod structure, which includes a 3D spacer fabric, an aerogel matrix and a reduced graphene oxide aerogel surface layer; the upper layer of the 3D spacer fabric has a hexagonal mesh structure, the middle layer is spacer filaments treated by low-temperature plasma, and the lower layer has a chain stitch and weft insertion structure; the reduced graphene oxide aerogel surface layer and the aerogel matrix are filled in the 3D spacer fabric in a layered composite manner, and the reduced graphene oxide aerogel surface layer forms concave holes at the hexagonal mesh structure; the filling coefficient of the reduced graphene oxide aerogel surface layer is 10% - 15%, and the filling coefficient of the aerogel matrix is 85% - 90%.

[0013] Preferably, the knitting yarns of the upper layer, the middle layer and the lower layer of the 3D spacer fabric are all polyester.

[0014] Preferably, the aerogel matrix is sodium alginate aerogel, and the reduced graphene oxide aerogel surface layer is reduced graphene oxide sodium alginate aerogel.

[0015] Preferably, the density is 0.09422 - 0.12114 g·cm -3 ; under 1 kW·m -2 illumination, the evaporation rate is 1.85 kg·m -2 ·h -1 , and the corresponding evaporation efficiency is 96.4%.

[0016] The preparation method of the above-mentioned solar interface evaporator based on a lotus seedpod structure disclosed by the present invention includes the following steps:

[0017] S1: Weave a 3D spacer fabric and place it in a mold. The upper layer of the 3D spacer fabric has a hexagonal mesh structure, the middle layer is spacer filaments treated by low-temperature plasma, and the lower layer has a chain stitch and weft insertion structure;

[0018] S2: Pour the fluid aerogel into the mold to fill and freeze the lower layer of the 3D spacer fabric;

[0019] S3: Pour the fluid reduced graphene oxide aerogel into the mold to fill and freeze the remaining part of the 3D spacer fabric;

[0020] S4: Freeze-dry the obtained product, perform cross-linking reaction and rinse it several times repeatedly;

[0021] S5: Perform hydrothermal reduction reaction on the washed product and rinse it several times repeatedly; Obtain a solar interface evaporator based on the lotus seedpod structure after freeze-drying.

[0022] Preferably, in S1, the discharge power of the low-temperature plasma treatment is 50%, the discharge time is 480 s, and the temperature is 20°C to 30°C.

[0023] Preferably, in S2 and S3, the freezing temperature is lower than -40°C and the time is 2 h.

[0024] Preferably, in S4 and S5, the freeze-drying temperature is lower than -40°C, the time is 2 to 3 days, and the pressure is less than 100 Pa.

[0025] Preferably, in S5, the hydrothermal reduction reaction is carried out in an L-AA solution, and the concentration of the L-AA solution is 10 mg·mL -1 , the temperature of the hydrothermal reduction reaction is 95°C and the time is 2 h.

[0026] Preferably, in S4 and S5, deionized water is used for rinsing.

[0027] Compared with the prior art, the present invention has the following beneficial technical effects:

[0028] A solar interface evaporator based on the lotus seedpod structure disclosed by the present invention composites a 3D spacer fabric, an aerogel matrix, and a reduced graphene oxide aerogel surface layer to obtain a three-phase composite structure solar interface evaporator with the characteristics of a lotus seedpod-like bionic structure. Inside the evaporator, the chain stitch and weft insertion structure on the lower layer of the 3D spacer fabric can achieve rapid water absorption due to the lotus root-like capillary effect generated by the tight interweaving of warp and weft yarns. By coating the spacer filaments treated by low-temperature plasma with the aerogel matrix, a plurality of directional water channels are constructed. After the spacer filaments are treated by low-temperature plasma, the surface becomes rough, and some chemical bonds are broken after ion bombardment, thus exposing a large number of hydrophilic groups, enabling the aerogel matrix to better coat the spacer filaments. The directional water channels constructed thereby can achieve efficient water transportation. At the same time, the rich directional water channels generate salt concentration and temperature gradients in the vertical direction, which can induce the Marangoni effect, promoting the dissolution of salt and the evaporation of water. In addition, the lotus seedpod-shaped concave holes formed at the hexagonal mesh structure of the reduced graphene oxide aerogel surface layer can effectively absorb sunlight. Thanks to this unique bionic structure, the solar interface evaporator designed based on the lotus seedpod-shaped bionic structure can achieve excellent evaporation rate and evaporation efficiency. At the same time, the 3D spacer fabric has good structural mechanical properties, which is beneficial to enhancing the mechanical properties of the overall structure. In addition, thanks to the hydrophilic aerogel matrix and a large number of directional water channels, the solar interface evaporator of the present invention also has excellent salt tolerance. Specifically, as the evaporation process proceeds, salt tends to precipitate on the surface of the evaporator, resulting in a higher salt concentration than that of the water source. In the solar interface evaporator of the present invention, the spacer filaments connect the upper and lower surface layers of the 3D spacer fabric. Therefore, the water channels constructed by coating the spacer filaments treated by low-temperature plasma with the aerogel matrix also connect the evaporation surface and the water source. This ensures that the salt can be quickly transferred from the high-salt-concentration evaporation surface to the low-salt-concentration water source along the shortest path through diffusion and convection, thus eliminating the influence of salt accumulation on the seawater desalination performance of the evaporator and showing excellent salt tolerance.

[0029] Furthermore, the aerogel used is sodium alginate aerogel. Sodium alginate is a by-product after extracting iodine and mannitol from brown algae such as kelp or Sargassum. It is a natural polysaccharide with good hydrophilicity, stability, solubility, viscosity, and safety, and is harmless to the human body.

[0030] The preparation method of the above-mentioned solar interface evaporator based on the lotus seedpod structure disclosed by the present invention has simple process, mild reaction conditions, and is suitable for industrial production. As a solar-driven interface evaporation material, seawater desalination material, wastewater treatment material, etc., it has a wide range of applications and good market prospects. Description of the Drawings

[0031] Figure 1 It is a schematic structural diagram of the solar interface evaporator based on the lotus seedpod structure of the present invention;

[0032] Figure 2 is the surface topography of Example 1 of the present invention;

[0033] Figure 3 is the surface topography of the spacer filaments between Comparative Example 2 and Example 1. (a) and (b) are respectively the surface of the spacer filaments in Comparative Example 2 and the case of the aerogel coating the spacer filaments; (c) and (d) are respectively the surface of the spacer filaments in Example 1 and the case of the aerogel coating the spacer filaments;

[0034] Figure 4 is the chart of water repellency comparison of Comparative Example 1, Comparative Example 2 and Example 1 of the present invention;

[0035] Figure 5 is the chart of light absorption comparison data of Comparative Example 1, Comparative Example 2 and Example 1 of the present invention;

[0036] Figure 6 is the chart of mechanical property comparison of Comparative Example 1, Comparative Example 2 and Example 1 of the present invention;

[0037] Figure 7 is the chart of temperature rise comparison of Comparative Example 1, Comparative Example 2 and Example 1 of the present invention;

[0038] Figure 8 is the chart of evaporation rate and evaporation efficiency comparison of Comparative Example 1, Comparative Example 2 and Example 1 of the present invention;

[0039] Figure 9 is the chart of anti-salt performance test data of Example 1 of the present invention;

[0040] Figure 10 is the chart of seawater desalination and wastewater application test data of Example 1 of the present invention;

[0041] Figure 11 is the chart of desalination and purification ability data of Example 1 of the present invention.

[0042] In the figure: 1 is a 3D spacer fabric, 2 is an aerogel matrix, and 3 is a reduced graphene oxide aerogel surface layer. Detailed implementation manners

[0043] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0044] As Figure 1, which is a structural schematic diagram of a solar interface evaporator based on a lotus pod structure of the present invention, comprising a 3D spacer fabric 1, an aerogel matrix 2 and a reduced graphene oxide aerogel surface layer 3; the upper layer of the 3D spacer fabric 1 is a hexagonal mesh structure, the middle layer is a spacer yarn treated by low-temperature plasma, and the lower layer is a chain weft structure; the reduced graphene oxide aerogel surface layer 3 and the aerogel matrix 2 are layered and compositely filled in the 3D spacer fabric 1, and the reduced graphene oxide aerogel surface layer 3 forms concave holes at the hexagonal mesh structure; the filling factor of the reduced graphene oxide aerogel surface layer 3 is 10% to 15%, and the filling factor of the aerogel matrix 2 is 85% to 90%.

[0045] In a preferred embodiment of the present invention, the knitting yarns of the upper layer, the middle layer and the lower layer of the 3D spacer fabric 1 are all made of polyester.

[0046] In a preferred embodiment of the present invention, the aerogel matrix 2 is sodium alginate aerogel, and the reduced graphene oxide aerogel surface layer 3 is reduced graphene oxide sodium alginate aerogel.

[0047] The prepared solar interface evaporator based on the lotus pod structure generally has a density of 0.09422 to 0.12114 g cm -3 .

[0048] The solar interface evaporator based on the lotus pod structure can be prepared by the following method, and the detailed steps are as follows:

[0049] Step 1: The 3D spacer fabric 1 is woven by a double needle bar Raschel warp knitting machine with 6 comb bars GB1 to GB6, wherein the yarns carried by GB1, GB2, GB4, GB5 and GB6 are polyester multifilaments, and the yarns carried by GB3 are polyester monofilaments; the comb bars GB1 and GB2 knit the lower surface of the 3D spacer fabric 1 on the front needle bar, and the comb bars GB4, GB5 and GB6 knit the upper surface of the fabric on the rear needle bar, and the comb bar GB3 carries the spacer yarns, which are alternately knitted on the front and rear needle beds to connect the upper and lower surfaces of the spacer fabric with the spacer yarns, thereby forming the 3D spacer fabric 1;

[0050] Step 2: The cut 3D spacer fabric 1 is ultrasonically treated in acetone, water and ethanol solutions for 10 min respectively, and then dried in an oven at 90-100° C. for 1-2 h;

[0051] Step 3: The dried 3D spacer fabric 1 is subjected to plasma treatment using a low-temperature plasma surface treatment machine, with a discharge power of 50%, a discharge time of 480 seconds, and a temperature of 20° C. to 30° C.;

[0052] Step 4: Dissolve 50 mg of SA in 10 ml of deionized water and stir thoroughly with a magnetic stirrer for 1 to 2 h to form a uniform solution;

[0053] Step 5: Place the plasma-treated 3D spacer fabric 1 into a mold with a diameter of 3.4 cm and a height of 1 cm, and pour the uniform solution prepared in step 4 into the mold covered with the plasma-treated 3D spacer fabric 1 for filling, with a filling factor of 85% to 90%;

[0054] Step 6: Place the mold in a refrigerator and pre-freeze it at -40°C for 1 hour;

[0055] Step 7: Dissolve 15 mg of graphene oxide and 9 mg of sodium alginate in 3 mL of deionized water and stir thoroughly with a magnetic stirrer for 30 min to form a uniform solution;

[0056] Step 8: Add 15 mg GOPS and 150 μL glacial acetic acid to the homogeneous solution prepared in step 7, and stir thoroughly with a magnetic stirrer for 1 to 2 h to form a homogeneous solution;

[0057] Step 9: pouring the uniform solution prepared in step 8 into the pre-frozen mold prepared in step 6, so that the uniform solution fills the remaining portion of the plasma-treated 3D spacer fabric 1 in the mold, with a filling factor of 10% to 15%;

[0058] Step 10: At this point, the plasma-treated 3D spacer fabric 1 has been completely filled;

[0059] Step 11: Place the sample in a refrigerator and freeze it at -40°C for 24 hours, then transfer it to a freeze dryer and freeze dry it at a pressure of 100 Pa and a temperature of -100°C for 36 to 48 hours;

[0060] Step 12: Place the freeze-dried sample in a 5% mass fraction CaCl2 solution overnight to allow it to undergo Ca 2+ cross-linked and washed repeatedly with deionized water;

[0061] Step 13: Place the cleaned sample into a 10 mg mL -1 The samples were hydrothermally reduced in L-AA solution at 95 °C for 2 h and repeatedly washed with deionized water.

[0062] Step 13: Place the cleaned sample in a refrigerator and freeze it at below -40°C for 24 hours, then transfer it to a freeze dryer and freeze-dry it for 36 to 48 hours at a pressure of 100 Pa and a temperature of -100°C to obtain a solar interface evaporator based on a lotus pod structure.

[0063] Example 1

[0064] A 3D spacer fabric 1 with a hexagonal mesh structure on the upper surface and a chain weft structure on the lower surface is knitted on a double needle bar Raschel warp knitting machine with a machine number of E18. The double needle bar Raschel warp knitting machine has 6 combs (GB1 to GB6), of which GB1 and GB2 are used to knit the lower surface of the 3D spacer fabric 1 on the front needle bar; GB4, GB5 and GB6 are used to knit the upper surface of the fabric on the rear needle bar; GB3 combs carry spacer yarns, which are alternately knitted on the front and rear needle beds to connect the upper and lower surfaces of the 3D spacer fabric 1 with spacer yarns, thereby forming the final three-dimensional overall structure. The yarns carried by GB1, GB2, GB4, GB5 and GB6 are 300D / 96F polyester multifilaments; GB3 is carried by polyester monofilaments with a diameter of 0.16mm; the resulting fabric has a thickness of 7mm and a surface density of 680g·cm -2 . After leaving the machine, the cut 3D spacer fabric 1 was ultrasonically treated in acetone, water and ethanol solutions for 10 minutes to remove impurities, and then dried in a 90°C oven for 1 hour; the dried 3D spacer fabric 1 was plasma treated with a low-temperature plasma surface treatment machine, with a discharge power of 50%, a discharge time of 480 seconds, and a temperature of 20°C. Subsequently, 50 mg SA was dissolved in 10 ml deionized water and magnetically stirred for 1 hour to form an aerogel matrix 2, and then the aerogel matrix 2 was poured into the mold covered with the plasma-treated 3D spacer fabric 1 for filling, and the filling factor was 85% of the plasma-treated 3D spacer fabric 1, and the mold was placed in a refrigerator and pre-frozen below -40°C for 1 hour. Then, 15 mg of graphene oxide and 9 mg of sodium alginate were dispersed in 3 mL of deionized water and stirred for 30 min with a magnetic stirrer to form a uniform solution. Then, 15 mg of GOPS and 150 μL of glacial acetic acid were added. After magnetic stirring for 1 h, the obtained reduced graphene oxide aerogel was poured onto the surface of the pre-frozen sample to fill the remaining part of the plasma-treated 3D spacer fabric 1 in the mold, and the filling factor was 15% of the plasma-treated 3D spacer fabric 1. At this point, the plasma-treated 3D spacer fabric 1 has been completely filled. The sample was placed in a refrigerator and frozen at below -40°C for 24 h, and then transferred to a freeze dryer for freeze drying at a pressure of 100 Pa and a temperature of -100°C for 36 h. Subsequently, the freeze-dried sample was immersed in a 5% mass fraction CaCl2 solution overnight to allow it to undergo CaCl2 drying. 2+ Cross-linked and washed repeatedly with deionized water. Then 10 mg mL -1The L-AA solution hydrothermally reduces the sample for 2 h at a temperature of 95 °C and is repeatedly washed with deionized water. The washed sample is placed in a refrigerator and frozen at -40 °C or below for 24 h, and then transferred to a freeze dryer for freeze drying for 36 h under the conditions of a pressure of 100 Pa and a temperature of -100 °C to obtain a solar interface evaporator based on a lotus seedpod structure with a density of 0.09422 g·cm -3 .

[0065] Example 2

[0066] Weave a 3D spacer fabric 1 with a hexagonal mesh structure on the upper surface and a chain stitch weft insertion structure on the lower surface on a double needle bed Raschel warp knitting machine with machine number E18. The double needle bed Raschel warp knitting machine has 6 guide bars (GB1-GB6). Among them, guide bars GB1 and GB2 knit the lower surface of the 3D spacer fabric 1 on the front needle bed; guide bars GB4, GB5, and GB6 knit the upper surface of the fabric on the back needle bed; the guide bar GB3 carries spacer yarns and alternately knits on the front and back needle beds to connect the upper and lower surfaces of the 3D spacer fabric 1 with spacer yarns, thus forming the final three-dimensional integral structure. The yarns carried on GB1, GB2, GB4, GB5, and GB6 are 300D / 96F polyester multifilaments; the yarn carried on GB3 is a polyester monofilament with a diameter of 0.16 mm; the obtained fabric has a thickness of 7 mm and a surface density of 680 g·cm -2. After leaving the machine, the cut 3D spacer fabric 1 was ultrasonically treated in acetone, water and ethanol solutions for 10 minutes to remove impurities, and then dried in a 95°C oven for 1.5 hours; the dried 3D spacer fabric 1 was plasma treated with a low-temperature plasma surface treatment machine, with a discharge power of 50%, a discharge time of 480 seconds, and a temperature of 25°C. Subsequently, 50 mg SA was dissolved in 10 ml deionized water and magnetically stirred for 1.5 hours to form an aerogel matrix 2, and then the aerogel matrix 2 was poured into the mold covered with the plasma-treated 3D spacer fabric 1 for filling, and the filling factor was 87% of the plasma-treated 3D spacer fabric 1, and the mold was placed in a refrigerator and pre-frozen below -40°C for 1 hour. Then, 15 mg of graphene oxide and 9 mg of sodium alginate were dispersed in 3 mL of deionized water and stirred for 30 min with a magnetic stirrer to form a uniform solution. Then, 15 mg of GOPS and 150 μL of glacial acetic acid were added. After magnetic stirring for 1.5 h, the obtained reduced graphene oxide aerogel was poured onto the surface of the pre-frozen sample to fill the remaining part of the plasma-treated 3D spacer fabric 1 in the mold, and the filling factor was 13% of the plasma-treated 3D spacer fabric 1. At this point, the plasma-treated 3D spacer fabric 1 has been completely filled. The sample was placed in a refrigerator and frozen at below -40°C for 24 h, and then transferred to a freeze dryer and freeze-dried for 42 h at a pressure of 100 Pa and a temperature of -100°C. Subsequently, the freeze-dried sample was immersed in a 5% mass fraction CaCl2 solution overnight to allow it to undergo CaCl2 drying. 2+ Cross-linked and washed repeatedly with deionized water. Then 10 mg mL -1 The sample was hydrothermally reduced with L-AA solution at 95°C for 2 hours and washed repeatedly with deionized water. The washed sample was placed in a refrigerator and frozen at -40°C for 24 hours, then transferred to a freeze dryer and freeze-dried for 42 hours at a pressure of 100 Pa and a temperature of -100°C to obtain a solar interface evaporator based on a lotus pod structure with a density of 0.10768 g·cm -3 .

[0067] Example 3

[0068] The 3D spacer fabric 1 with a hexagonal mesh structure on the upper surface and a chain stitch weft insertion structure on the lower surface is knitted on a double needle bed Raschel warp knitting machine with machine number E18. The double needle bed Raschel warp knitting machine has 6 guide bars (GB1 - GB6). Among them, two guide bars, GB1 and GB2, knit the lower surface of the 3D spacer fabric 1 on the front needle bed; three guide bars, GB4, GB5, and GB6, knit the upper surface of the fabric on the back needle bed; the guide bar GB3 carries spacer yarns and alternately knits on the front and back needle beds to connect the upper and lower surfaces of the 3D spacer fabric 1 with spacer yarns, thus forming the final three - dimensional integral structure. The yarns carried on GB1, GB2, GB4, GB5, and GB6 are 300D / 96F polyester multifilaments; the yarn carried on GB3 is a polyester monofilament with a diameter of 0.16 mm; the thickness of the obtained fabric is 7 mm, and the areal density is 680 g·cm -2 . After taking off the machine, the cut 3D spacer fabric 1 is ultrasonically treated in acetone, water, and ethanol solutions for 10 min to remove impurities, and dried in an oven at 100 °C for 2 h; the dried 3D spacer fabric 1 is treated with a low - temperature plasma surface treatment machine. The discharge power is 50%, the discharge time is 480 s, and the temperature is 30 °C. Subsequently, 50 mg of SA is dissolved in 10 ml of deionized water and magnetically stirred for 2 h to form the aerogel matrix 2. Then, the aerogel matrix 2 is poured into a mold lined with the plasma - treated 3D spacer fabric 1 for filling. The filling height is 90% of the plasma - treated 3D spacer fabric 1, and the mold is placed in a refrigerator and pre - frozen at - 40 °C or below for 1 h. Then, 15 mg of graphene oxide and 9 mg of sodium alginate are dispersed in 3 mL of deionized water and stirred thoroughly with a magnetic stirrer for 30 min to form a homogeneous solution. Subsequently, 15 mg of GOPS and 150 μL of glacial acetic acid are added, and after magnetic stirring for 2 h, the prepared reduced graphene oxide aerogel is poured onto the surface of the pre - frozen sample to fill the remaining part of the plasma - treated 3D spacer fabric 1 in the mold. The filling height is 10% of the plasma - treated 3D spacer fabric 1. At this point, the plasma - treated 3D spacer fabric 1 has been completely filled. The sample is placed in a refrigerator and frozen at - 40 °C or below for 24 h, and then transferred to a freeze - dryer and freeze - dried for 48 h under the conditions of a pressure of 100 Pa and a temperature of - 100 °C. Subsequently, the freeze - dried sample is soaked in a 5% mass fraction of CaCl2 solution overnight to carry out Ca 2+ cross - linking and washed repeatedly with deionized water. Then, with 10 mg·mL -1The L-AA solution hydrothermally reduces the sample at 95 °C for 2 h and repeatedly washes it with deionized water. The washed sample is placed in a refrigerator and frozen at -40 °C or below for 24 h, and then transferred to a freeze dryer for freeze drying at a pressure of 100 Pa and a temperature of -100 °C for 48 h to obtain a solar interface evaporator based on a lotus seedpod structure with a density of 0.12114 g·cm -3 .

[0069] Comparative Example 1:

[0070] Compared with Example 1, the difference is only that the 3D spacer fabric 1 is not added, and the reduced graphene oxide aerogel completely fills the mold. The thickness of Comparative Example 1 is 7 mm and the diameter is 32 mm.

[0071] Comparative Example 2:

[0072] Compared with Example 1, the difference is only that the 3D spacer fabric 1 is not subjected to low-temperature plasma treatment. The thickness of Comparative Example 2 is 7 mm and the diameter is 32 mm.

[0073] The following analyzes the effects of the present invention through experiments on Example 1, Comparative Example 1, and Comparative Example 2:

[0074] 1. Microscopic morphology of spacer filaments between Comparative Example 2 and Example 1

[0075] Experimental method: A laser scanning confocal microscope was used to observe and evaluate the surface flatness of Example 1. A field emission scanning electron microscope was used to observe the microscopic morphology of different materials and take pictures for recording.

[0076] Experimental results: As shown in Figure 2 and Figure 3 , it can be seen from Figure 2 that there are many uniform honeycomb-shaped concave holes on the surface of Example 1, which proves the formation of lotus head-shaped concave holes at the hexagonal mesh structure of the reduced graphene oxide aerogel surface layer. This is because the hexagonal mesh structure has a larger mesh area compared with other structures, and the solution is slightly sunken during the filling process and the freeze-drying process. It can be seen from Figure 3 that in Comparative Example 2, the surface of the spacer filaments without plasma treatment is smooth, as shown in Figure 3 a; the coating effect of the aerogel matrix 2 on the spacer filaments is poor, as shown in Figure 3 b; while in Example 1, a large number of particles and pits can be observed on the surface of the spacer filaments after plasma treatment, as shown in Figure 3 c; this provides more active sites for the coating of the aerogel matrix 2, so the spacer filaments are almost completely coated, as shown in Figure 3As shown in d. The spacer filaments coated with the aerogel matrix 2 can be constructed into multiple directional water transport channels, which is beneficial to the transport of moisture.

[0077] 2. Water repellency of Comparative Example 1, Comparative Example 2 and Example 1

[0078] Experimental method: Place a paper towel of the same area on the surfaces of dry Comparative Example 1, Comparative Example 2 and Example 1, and then put them into a petri dish containing 10 ml of methylene blue. At the same time, take pictures to record the time it takes for the methylene blue to be absorbed to the top surfaces of Comparative Example 1, Comparative Example 2 and Example 1; and use the following formula to calculate the weight water content (Wg) of Comparative Example 1, Comparative Example 2 and Example 1 at the same moment to further evaluate the water repellency:

[0079] Wg = (m1 - m0) / m0

[0080] In the formula, m0 is the weight of dry Comparative Example 1, Comparative Example 2 and Example 1 at the same moment, and m1 is the weight of wet Comparative Example 1, Comparative Example 2 and Example 1 at the same moment.

[0081] Experimental results: As Figure 4 shown, from Figure 4 a, it can be seen that: in Comparative Example 1 and Comparative Example 2, it can be observed that the time it takes for the methylene blue to be absorbed to their top surfaces is 7 s and 6 s respectively; while in Example 1, it can be observed that it only takes 4 s for the methylene blue to completely cover its surface. This is because in Example 1, the synergistic effect of the capillary action inside the 3D spacer fabric 1 and multiple directional water transport channels accelerates the transport of water to its top. Figure 4 b further analyzes the water repellency of different samples. From Figure 4 b, it can be seen that: Example 1 quickly reaches saturation (36.5 g·g -1 ) within only 4 s, and Comparative Example 1 and Comparative Example 2 reach saturation in 7 s (60 g·g -1 ) and 6 s (35.9 g·g -1 ) respectively. Therefore, Example 1 can not only achieve rapid water transport, maintain continuous water supply on the top surface, but also the lower water content can prevent further heat dissipation.

[0082] 3. Light absorption properties of Comparative Example 1, Comparative Example 2 and Example 1

[0083] Experimental method: Use an ultraviolet-visible-near-infrared spectrometer to measure the optical reflection and transmission spectra of the surfaces of Comparative Example 1, Comparative Example 2 and Example 1 in the range of 200 - 2500 nm. Use an integrating sphere to collect the reflected light, and use the following formula to calculate the light absorption efficiency (A):

[0084] A = 1 - R - T

[0085] Where R is the reflection efficiency and T is the transmission efficiency.

[0086] Experimental results: As Figure 5 shown, the light absorption rate of Comparative Example 1 is about 90%; while the light absorption rate of Example 1 is increased to about 95.6%. This is because compared with the planar structure of the top surface of Comparative Example 1, in Example 1, the showerhead-shaped concave holes formed by the hexagonal mesh structure on the surface layer of the 3D spacer fabric 1 can increase the capture area of sunlight, promote light refraction, and thus effectively absorb sunlight. At the same time, it is observed that Comparative Example 2 shows a light absorption rate similar to that of Example 1 (about 95%), indicating that whether the 3D spacer fabric 1 is treated by plasma has little effect on the light absorption performance of the material.

[0087] 4. Mechanical properties of Comparative Example 1, Comparative Example 2 and Example 1

[0088] Experimental method: Using a universal material testing machine, under the conditions of a compression rate of 2 mm·min -1 , and a strain of 50%, a 10-cycle compression test was carried out on Comparative Example 1, Comparative Example 2 and Example 1. And the following formula was used to calculate the compression modulus (E) of different materials:

[0089] E = σ / ε

[0090] Where σ is the compression stress and ε is the corresponding compression strain.

[0091] Experimental results: As Figure 6 shown, from Figure 6 it can be seen that at a strain of 50%, the maximum stress of Example 1 is 36.4 kPa ( Figure 6 a), while the maximum stresses of Comparative Example 1 and Comparative Example 2 are about 0.9 kPa ( Figure 6 b) and 31.6 kPa ( Figure 6 c), respectively. The calculated compression modulus of Example 1 is 90.8 kPa, which is more than 36 times that of Comparative Example 1 (2.5 kPa), indicating that Example 1 has excellent mechanical properties. And even under a weight of 500 g, no mechanical deformation or damage of Example 1 was observed, as Figure 6 shown in d. Example 1 has excellent mechanical properties and superelasticity. This is because the unique three-dimensional structure of the 3D spacer fabric 1 promotes stress transfer, the spacer yarns are compressed and bent accordingly, dispersing the pressure and avoiding stress concentration. In addition, when the external force disappears, the spacer yarns behave like upright micro springs, which is beneficial to elastic recovery.

[0092] 5. Heat-up properties of Comparative Example 1, Comparative Example 2 and Example 1

[0093] Experimental method: Place Comparative Example 1, Comparative Example 2, and Example 1 in water and let them float on the water surface. Align an infrared imager at the top of the materials; under sunlight irradiation, take pictures once every 5 minutes and record the surface temperature of the carbonized banana stalks at the top.

[0094] Experimental results: As Figure 7 shown, at any moment, Example 1 has a higher surface temperature than Comparative Example 1. At 10 minutes, the surface temperature of Example 1 rises rapidly to 36.7 °C, and then stabilizes at 40.5 °C at 30 minutes, while the corresponding surface temperatures of Comparative Example 1 at the same moments are only 33.4 °C and 37.5 °C respectively. This is because Example 1 can convert the absorbed light energy into heat more efficiently and quickly, showing excellent photothermal performance. In addition, it is observed that Comparative Example 2 has a surface temperature similar to that of Example 1, but overall the surface temperature of Example 1 is relatively higher. This is because the aerogel matrix has a better coating effect on the plasma-treated spacer filaments. Since the aerogel has a low thermal conductivity, this makes Example 1 have better heat insulation and lower heat loss.

[0095] 6. Evaporation rate and evaporation efficiency of Comparative Example 1, Comparative Example 2, and Example 1

[0096] Experimental method: Under sunlight irradiation (1 kW·m -2 ), collect the weight change (m) of water within 60 minutes through a computer, and calculate the evaporation rate (v) and evaporation efficiency (η) of different materials using the following formulas:

[0097] v = m / (s × t)

[0098] where s is the evaporation area of different materials and t is the evaporation duration (60 minutes).

[0099] η = (v × h LV ) / q i

[0100] where h LV is the latent heat of liquid-gas phase change of water, and q i is the energy density of sunlight irradiation (1 kW·m -2 ).

[0101] Experimental results: As Figure 8 shown in a, it can be seen from the figure that the mass change of water in Example 1 reaches 1.853 kg·m -2 within 60 minutes, which is about 4 times the mass change of pure water under the same conditions (0.451 kg·m -2 ), and is higher than the evaporation amounts of Comparative Example 1 and Comparative Example 2 (1.480 and 1.713 kg·m -2)。The evaporation rates and evaporation efficiencies of different materials were calculated and compared according to the formula, as Figure 8 shown in -2 Figure -1 2b. Under the irradiation of one sun, the evaporation rate of Example 1 reached 1.853 kg·m -2 − -1 2·h -2 − -1 1, and the evaporation efficiency was 96.52%, higher than the evaporation rate (1.480 kg·m

[0102] 7. Salt resistance test of Example 1

[0103] Experimental method: To prove the excellent salt resistance of Example 1, the evaporation rates of Example 1 in different salt concentration solutions (3.5 wt% NaCl, 10 wt% NaCl, 15 wt% NaCl, and 20 wt% NaCl) were tested (1 kW·m -2 − -2 2). The evaporation rate of Example 1 in a high-salinity solution (20 wt% NaCl) for 10 h was tested (1 kW·m

[0104] − Figure 9 2). And 0.5 g and 1.0 g of NaCl solids were placed on the surface of Example 1 respectively, and the salt resistance of Example 1 was further investigated by recording the dissolution time of salt crystals. -2 − -1 1, and the corresponding evaporation efficiency also decreased slightly, being 95.42%, 94.48%, 93.39%, and 90.37% respectively. This is because the higher the concentration of the brine, the greater the surface tension, resulting in a slight decrease in the evaporation rate. In addition, as Figure 9 shown in -2 Figure -1and 81.41%), and no salt deposition was found on the surface of Example 1 during the long-term evaporation process, as Figure 9 shown in c. 0.5 g and 1.0 g of NaCl were respectively placed on the surface of Example 1, and it was also observed that the salt crystals rapidly dissolved within 450 s and 30 min respectively, as Figure 9 shown in d. This is attributed to the synergistic effect of the directional and efficient water transport channels and the high surface temperature in Example 1, which enables it to exhibit excellent salt resistance during the evaporation process of long-term high-salinity solutions.

[0105] 8. Desalination and wastewater application tests of Example 1

[0106] Experimental method: To prove that Example 1 can be applied to different water environments, its evaporation performance (1 kW·m -2 ) was tested in seawater (real Bohai Sea seawater), wastewater (wastewater containing heavy metal ions), acid solution (HNO3 solution), alkali solution (NaOH solution), and different dye solutions (methyl orange (MO), methylene blue (MB), and rhodamine B (RB)).

[0107] Experimental results: As Figure 10 shown in a, the evaporation rates of Example 1 in seawater (real Bohai Sea seawater), wastewater (wastewater containing heavy metal ions), acid, and alkali solutions were 1.814, 1.827, 1.843, and 1.835 kg·m -2 ·h -1 respectively, and its evaporation efficiencies were 94.49%, 95.16%, 95.99%, and 95.58% respectively. The pH values of the solutions before and after evaporation under acidic / alkaline conditions were tested, and it was found that the pH values of the collected solutions after evaporation were all neutral, as Figure 10 shown in b. To study the purification ability of Example 1 for dye solutions, the absorbance of the solutions before and after evaporation was characterized by UV-Vis spectroscopy. The characteristic absorption peaks of MO, MB, and RB solutions almost completely disappeared after purification by Example 1, as Figure 10 shown in c, 10d, and 10e. The results show that Example 1 can be applied to different water environments, has the potential to balance the pH value under acidic or alkaline conditions, and also exhibits excellent purification effects on dye wastewater.

[0108] 9. Desalination and purification capabilities of Example 1

[0109] Experimental method: Using a solar simulator as the light source, polystyrene foam was stuffed into the mouth of a beaker and extended into a beaker containing real Bohai Sea water or a solution containing heavy metal ions to serve as a drainage function. Then, the moistened Example 1 was placed above the polystyrene foam, and the entire device was placed on a balance and evaporated under light; a self-made collection device was used to collect the condensed water; the concentrations of Na + 、Mg 2+ 、K + and Ca 2+ in the sea water and the collected condensed water were tested by inductively coupled plasma mass spectrometry; then, the concentrations of heavy metal ions (Mn 2+ 、Co 2 + 、Cu 2+ and Cr 3+ ) in the original heavy metal ion solution and their respective collected condensed water were tested separately.

[0110] Experimental results: As shown in Figure 11 a, it can be seen that the concentrations of Na + 、Mg 2+ 、K + and Ca 2+ decreased from 10977.58, 1317.4, 368.75 and 417.6 mg·L -1 to 1.507, 0.222, 0.513 and 1.381 mg·L -1 respectively, which are far lower than the drinking water standards stipulated by the World Health Organization (WHO) and the United States Environmental Protection Agency (EPA). In addition, the concentrations of heavy metal ions Mn 2+ 、Co 2+ 、Cu 2 + and Cr 3+ in the collected condensed water decreased sharply from 500 mg·L -1 to 0, 0.014, 0.154 and 0.022 mg·L -1 respectively, which are far lower than the ion concentration levels required for wastewater discharge, as shown in Figure 11 b. This indicates that Example 1 not only has the ability of seawater desalination but also has the ability to treat and purify wastewater.

[0111] It should be noted that the above description is only a part of the embodiments of the present invention. Equivalent changes made according to the system described in the present invention are all included in the protection scope of the present invention. Those skilled in the technical field to which the present invention pertains can make similar alternative ways to the specific examples described as long as they do not deviate from the structure of the present invention or exceed the scope defined by the claims of this right, and all belong to the protection scope of the present invention.

Claims

1. A solar interface evaporator based on the lotus seedpod structure, characterized in that, It includes a 3D spacer fabric (1), an aerogel matrix (2), and a reduced graphene oxide aerogel surface layer (3); the upper layer of the 3D spacer fabric (1) has a hexagonal mesh structure, the middle layer has spacer filaments treated by low-temperature plasma, and the lower layer has a tricot stitch structure; the reduced graphene oxide aerogel surface layer (3) and the aerogel matrix (2) are laminated and filled in the 3D spacer fabric (1), and the reduced graphene oxide aerogel surface layer (3) forms concave holes at the hexagonal mesh structure; the filling coefficient of the reduced graphene oxide aerogel surface layer (3) is 10% - 15%, and the filling coefficient of the aerogel matrix (2) is 85% - 90%; The solar interface evaporator based on the lotus seedpod structure is prepared according to the following steps: S1: Weave the 3D spacer fabric (1) and place it in a mold. The upper layer of the 3D spacer fabric (1) has a hexagonal mesh structure, the middle layer has spacer filaments treated by low-temperature plasma, and the lower layer has a tricot stitch structure; S2: Pour the fluid aerogel into the mold to fill and freeze the lower layer of the 3D spacer fabric (1); S3: Pour the fluid reduced graphene oxide aerogel into the mold to fill and freeze the remaining part of the 3D spacer fabric (1); S4: Freeze-dry the obtained product, carry out a cross-linking reaction, and rinse it several times; S5: Carry out a hydrothermal reduction reaction on the washed product and rinse it several times; after freeze-drying, a solar interface evaporator based on the lotus seedpod structure is obtained.

2. The solar interfacial evaporator based on the lotus seedpod structure according to claim 1, wherein The weaving yarns of the upper layer, middle layer, and lower layer of the 3D spacer fabric (1) are all polyester.

3. The solar interfacial evaporator based on the lotus seedpod structure according to claim 1, wherein The aerogel matrix (2) is sodium alginate aerogel, and the reduced graphene oxide aerogel surface layer (3) is reduced graphene oxide sodium alginate aerogel.

4. The solar interfacial evaporator based on the lotus seedpod structure according to claim 1, wherein, The density is 0.09422 - 0.12114 g·cm -3 ; under the illumination of 1 kW·m -2 , the evaporation rate is 1.85 kg·m -2 ·h -1 , and the corresponding evaporation efficiency is 96.4%.

5. The solar interfacial evaporator based on the lotus seedpod structure according to claim 1, wherein, In S1, the discharge time is 480 s, and the temperature is 20 °C - 30 °C.

6. The solar interfacial evaporator based on the lotus seedpod structure according to claim 1, wherein In S2 and S3, the freezing temperature is lower than -40 °C, and the time is 2 h.

7. The solar interfacial evaporator based on the lotus seedpod structure according to claim 1, wherein, In S4 and S5, the freeze-drying temperature is lower than -40 °C, the time is 2 - 3 days, and the pressure is less than 100 Pa.

8. The solar interfacial evaporator based on the lotus seedpod structure according to claim 1, wherein, In S5, the hydrothermal reduction reaction was carried out in an L-AA solution with a concentration of 10 mg·mL -1 , the temperature of the hydrothermal reduction reaction was 95 °C, and the time was 2 h.

9. The solar interfacial evaporator based on the lotus seedpod structure according to claim 1, wherein, In S4 and S5, the rinsing is all carried out with deionized water.

Images