A 3D-printed biomimetic solar evaporator and its preparation method and its application in nanoplastic wastewater purification

Abstract

This invention relates to the field of photothermal materials technology, specifically to a 3D-printed biomimetic solar evaporator, its preparation method, and its application in wastewater purification using nanoplastics. The invention involves 3D printing a biomimetic solar evaporator base with a sorghum stalk morphology and modifying it with carbon powder prepared from carbonized sorghum stalks, thus constructing a 3D-printed biomimetic solar evaporator with carbon powder surface modification. This 3D-printed biomimetic solar evaporator exhibits excellent photothermal performance, good hydrophilicity, and abundant porosity. During the evaporation and purification process, wastewater containing nanoplastics is continuously transported to the evaporation interface. The carbon powder absorbs solar energy at the evaporation interface and converts it into heat energy, generating convection lifting, which causes water vapor to move upwards. Because the density of nanoplastics is much greater than that of air, the convection lifting cannot lift them upwards, and the nanoplastics remain in the wastewater, achieving the separation of nanoplastics from clean water vapor.

Description

Technical Field

[0001] This invention relates to the field of photothermal materials technology, specifically to a 3D-printed biomimetic solar evaporator and its preparation method, as well as its application in nanoplastic wastewater purification. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Plastics are widely used in industrial production and daily life. Statistics show that between 9 million and 23 million tons of plastic waste are discharged into oceans, rivers, and lakes globally each year. Plastic waste in water bodies decomposes into nanoplastics with smaller particle sizes (1–100 nm) through weathering, biodegradation, photodegradation, and thermal degradation. Due to their large specific surface area, complex surface properties, and good resistance to degradation, nanoplastic pollution in water bodies is becoming increasingly serious.

[0004] Currently, the main methods for treating nanoplastics in water include adsorption and coagulation sedimentation. Among these, adsorption is considered one of the most promising methods due to its simplicity and low cost. However, the adsorbent in adsorption methods gradually becomes clogged as adsorption proceeds, reducing the purification rate.

[0005] Solar interface evaporation is an emerging water treatment technology that purifies water by causing it to evaporate on the surface of a porous material through a photothermal effect. 3D printing is a typical additive manufacturing technology that allows the creation of products with arbitrary structures by controlling 3D printing models and programs. Currently, there are no reports of combining 3D printing technology with solar interface evaporation technology for removing nanoplastics from water. Summary of the Invention

[0006] To overcome the aforementioned problems, this invention provides a 3D-printed biomimetic solar evaporator, its fabrication method, and its application. This invention uses 3D printing to create a 3D-printed biomimetic solar evaporator base with the morphology of sorghum stalks. Carbon powder, prepared from carbonized sorghum stalks, is used for surface modification, constructing a 3D-printed biomimetic solar evaporator with carbon powder surface modification. It exhibits good light absorption performance across the entire solar spectrum and possesses a high evaporation rate and solar steam conversion efficiency, thus making it suitable as a solar evaporator. The 3D-printed biomimetic solar evaporator provided by this invention can effectively remove nanoplastics from water, achieving water purification.

[0007] To achieve the above technical objectives, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing a 3D-printed biomimetic solar evaporator, comprising: dissolving acrylamide, polyethylene glycol diacrylate, and polyethylene glycol in an aqueous solution of N-isopropylacrylamide and stirring to obtain solution a; stirring a photoinitiator and an organic solvent to obtain solution b; and adding solution a to solution b and mixing to obtain 3D printing ink.

[0009] A base with a sorghum-like vascular bundle structure was obtained by 3D printing using 3D printing ink.

[0010] The base of the sorghum-inspired vascular bundle structure was immersed in a carbon powder suspension, removed, and dried to obtain a 3D-printed biomimetic solar evaporator.

[0011] In some embodiments, the concentration of the N-isopropylacrylamide aqueous solution is 3–7 mol·L⁻¹. -1 In solution a, the molar ratio of N-isopropylacrylamide, acrylamide, polyethylene glycol diacrylate, and polyethylene glycol solution is (3-7):(0.5-1):(0.001-0.01):(0.0001-0.002); the average molecular weight of the polyethylene glycol diacrylate is 200-600 g·mol⁻¹. -1 Preferably 200 g·mol -1 The molecular weight of the polyethylene glycol is 200–20000 g·mol⁻¹. -1 10000 g·mol is preferred -1 .

[0012] In some embodiments, the photoinitiator is one or more selected from 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 1-hydroxycyclohexylphenyl ketone, or 2-hydroxy-2-methyl-1-phenylpropanone; the organic solvent is one or more selected from acetone, ethyl acetate, isopropanol, or methanol; and the concentration of the photoinitiator is 0.1–0.6 mol·L⁻¹. -1 .

[0013] In some embodiments, the volume ratio of solution b to solution a is 1:(5-10).

[0014] In some embodiments, the 3D printing involves first designing and creating a model of a sorghum vascular bundle structure using a computer, and then curing it under ultraviolet light.

[0015] In some embodiments, the carbon powder is obtained by carbonizing straw in N2 at 600-1200°C for 2-6 hours; the straw is one or more of sorghum straw, sugarcane straw, or corn straw.

[0016] In some embodiments, the concentration of the toner suspension is 12-18 wt%; the immersion time in the toner suspension is 0.5-1 h; the drying temperature is 5-80°C, and the drying time is 0.5-1 h.

[0017] This invention improves the hydrophilicity and water transport capacity of the 3D printing substrate by adding polyethylene glycol as a hydrophilic agent; and improves the uniformity of photoinitiator dispersion in 3D printing ink by dissolving the photoinitiator in an organic solvent and then adding solution a to solution b.

[0018] In a second aspect, the present invention provides a 3D-printed biomimetic solar evaporator prepared using the method of the first aspect, wherein the 3D-printed biomimetic solar evaporator has a sorghum-like vascular bundle structure, and the surface of the 3D-printed biomimetic solar evaporator is uniformly distributed with carbon powder, the content of which is 12-28 wt%.

[0019] The carbon powder provided by this invention, as a photothermal material, has good light absorption performance across the entire solar spectrum and can convert solar energy into heat energy for photothermal evaporation, thus it can be used as a solar evaporator.

[0020] A third aspect of the present invention provides the application of the 3D-printed biomimetic solar evaporator described in the second aspect in water treatment.

[0021] In one or more embodiments, the water treatment includes seawater evaporation and wastewater treatment.

[0022] Preferably, wastewater treatment includes the purification of acidic and alkaline wastewater, the purification of organic dye wastewater, and the purification of nanoplastic wastewater.

[0023] The beneficial effects of this invention are as follows:

[0024] (1) This invention constructs a biomimetic solar evaporator base through crosslinking polymerization of N-isopropylacrylamide, acrylamide, polyethylene glycol diacrylate, and polyethylene glycol under the action of a photoinitiator and ultraviolet light. An organic solvent is used as a transition solvent to dissolve the photoinitiator in the organic solvent, and then solution a is added to solution b, thereby improving the uniformity of the photoinitiator dispersion in the 3D printing ink. This biomimetic solar evaporator base has a sorghum-like vascular bundle structure with abundant pores, which is beneficial for moisture transport.

[0025] (2) This invention modifies the surface of the biomimetic solar evaporator base with carbon powder, which possesses excellent photothermal properties and good hydrophilicity. The 3D-printed biomimetic solar evaporator provided by this invention exhibits good light absorption performance across the entire solar spectrum, enabling it to convert solar energy into heat energy for photothermal evaporation. Therefore, it can be used as a solar evaporator. Simultaneously, its good hydrophilicity and abundant pores accelerate the adsorption and evaporation of water, resulting in a high evaporation rate and solar steam conversion efficiency; specifically, the 3D-printed biomimetic solar evaporator achieves an evaporation rate of 3.443 kg·m³ under one standard solar irradiance. -2 ·h -1 The solar steam conversion efficiency can reach 117.8%.

[0026] (3) During the evaporation purification process, wastewater containing nanoplastics is continuously transported to the evaporation interface. Due to the excellent photothermal effect of carbon powder, it can absorb solar energy and convert it into heat energy at the evaporation interface, generating convection lifting, which causes water vapor to move upward. However, since the density of nanoplastics is much greater than that of air, convection lifting cannot lift it upward, and the nanoplastics will remain in the wastewater, thus achieving the separation of nanoplastics from clean water vapor.

[0027] (4) This invention uses a 3D-printed biomimetic solar evaporator to directly separate nanoplastics and water in wastewater containing nanoplastics, requiring only solar energy and no additional energy. The purification method is simple, low-cost, clean, and efficient, making it easy to promote in industry.

[0028] (5) This invention combines the removal of nanoplastics with solar interface evaporation, which has great potential in alleviating nanoplastic pollution and water shortages. Furthermore, the nanoplastic removal method provided by this invention will open up new avenues for the development of nanoplastic removal technology and the application of solar interface evaporation technology. Attached Figure Description

[0029] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0030] Figure 1 This is a schematic diagram of the fabrication process of the 3D-printed biomimetic solar evaporator in Example 1.

[0031] Figure 2 SEM images of cross-sections and longitudinal sections of sorghum stalks.

[0032] Figure 3 The images are microscope images of the 3D-printed biomimetic base in Example 1 at different magnifications: (a) low magnification and (b) high magnification.

[0033] Figure 4 (a) Mass variation graph and (b) Evaporation rate and efficiency graph for evaporators made with carbon powder at different carbonization temperatures.

[0034] Figure 5 (a) Mass variation graph and (b) Evaporation rate and efficiency graph for evaporators prepared with different amounts of carbon powder.

[0035] Figure 6 Transmission electron microscopy (TEM) images of pure water, nanoplastic-contaminated water from the nanoplastic group, and purified water collected after evaporation purification using a porous polypyrrole system. From left to right, the images show nanoplastic-contaminated water from the nanoplastic group, pure water, and purified water in a beaker after purification. Detailed Implementation

[0036] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0037] I. Preparation of 3D Printing Ink

[0038] Figure 1 This is a schematic diagram of the fabrication process for a 3D-printed biomimetic solar evaporator. Acrylamide, polyethylene glycol diacrylate, and polyethylene glycol are dissolved in an aqueous solution of N-isopropylacrylamide and stirred to obtain solution a. A photoinitiator is stirred with an organic solvent to obtain solution b. Solution a is then added to solution b and mixed to obtain 3D printing ink.

[0039] Example 1

[0040] N-Isopropylacrylamide was prepared to a concentration of 3.0 mol·L⁻¹. -1 Aqueous solution: Acrylamide, polyethylene glycol diacrylate, and polyethylene glycol were dissolved in an aqueous solution of N-isopropylacrylamide and stirred until homogeneous to obtain solution a. 1-Hydroxycyclohexylphenyl ketone was stirred with acetone to obtain a solution with a concentration of 0.6 mol·L⁻¹. -1 Solution b; then add solution a to solution b and mix well to obtain 3D printing ink. The molar ratio of N-isopropylacrylamide, acrylamide, polyethylene glycol diacrylate, and polyethylene glycol diacrylate is 3:0.5:0.001:0.0001; the average molecular weight of polyethylene glycol diacrylate is 200 g·mol⁻¹. -1 The molecular weight of polyethylene glycol is 10000 g·mol⁻¹ -1 The volume ratio of solution b to solution a is 1:10 when they are mixed.

[0041] Example 2

[0042] N-Isopropylacrylamide was prepared to a concentration of 5.0 mol·L⁻¹. -1Aqueous solution: Acrylamide, polyethylene glycol diacrylate, and polyethylene glycol are dissolved in an aqueous solution of N-isopropylacrylamide and stirred until homogeneous to obtain solution a. 2-Hydroxy-2-methyl-1-phenylpropanone is then mixed with methanol to obtain a solution with a concentration of 0.1 mol·L⁻¹. -1 Solution b; then add solution a to solution b and mix well to obtain 3D printing ink. The molar ratio of N-isopropylacrylamide, acrylamide, polyethylene glycol diacrylate, and polyethylene glycol diacrylate is 7:1:0.01:0.002; the average molecular weight of polyethylene glycol diacrylate is 400 g·mol⁻¹. -1 The molecular weight of polyethylene glycol is 5000 g·mol⁻¹. -1 The volume ratio of solution b to solution a is 1:8 when they are mixed.

[0043] Example 3

[0044] N-Isopropylacrylamide was prepared to a concentration of 7.0 mol·L⁻¹. -1 Aqueous solution: Acrylamide, polyethylene glycol diacrylate, and polyethylene glycol are dissolved in an aqueous solution of N-isopropylacrylamide and stirred until homogeneous to obtain solution a. 1-Hydroxycyclohexylphenyl ketone is stirred with ethyl acetate to obtain a solution with a concentration of 0.2 mol·L⁻¹. -1 Solution b; then add solution a to solution b and mix well to obtain 3D printing ink. The molar ratio of N-isopropylacrylamide, acrylamide, polyethylene glycol diacrylate, and polyethylene glycol diacrylate is 3:0.5:0.005:0.0005, and the average molecular weight of polyethylene glycol diacrylate is 600 g·mol⁻¹. -1 The molecular weight of polyethylene glycol is 20000 g·mol⁻¹ -1 The volume ratio of solution b to solution a is 1:5 when they are mixed.

[0045] Comparative Example 1

[0046] N-Isopropylacrylamide was prepared to a concentration of 3.0 mol·L⁻¹. -1 Aqueous solution: Acrylamide and polyethylene glycol diacrylate were dissolved in an aqueous solution of N-isopropylacrylamide and stirred until homogeneous to obtain solution a. Solution a was obtained by stirring 1-hydroxycyclohexylphenyl ketone with deionized water to obtain a solution with a concentration of 0.2 mol·L⁻¹. -1 Solution b; then add solution a to solution b and mix well to obtain 3D printing ink. The molar ratio of N-isopropylacrylamide, acrylamide, and polyethylene glycol diacrylate is 3:0.5:0.005, and the average molecular weight of polyethylene glycol diacrylate is 600 g·mol⁻¹. -1 The volume ratio of solution b to solution a is 1:10 when they are mixed.

[0047] II. 3D Printing Models and Programs

[0048] The 3D printing inks prepared in Examples 1-3 and Comparative Example 1 were added to a 3D printer, and a 3D printed biomimetic solar evaporator base was fabricated according to the following printing model and procedure.

[0049] 3D Printed Model: A sorghum stalk-like printing model was constructed using SketchUp software, consisting of one 400μm diameter circle and two 200μm diameter circles, stacked to form an area of ​​1000×1000μm. 2 The units are stacked to form a 1×1×1cm unit. 3 The cube is generated and exported as an STL file.

[0050] 3D printing process: First, a sorghum stalk-like printing model is created using computer-aided design software. Then, a 3D printing system (Bio-Architect PR-PRO) emits 405nm ultraviolet light to solidify the 3D printing ink, thereby preparing a 3D printed biomimetic solar evaporator base.

[0051] III. 3D Printed Biomimetic Solar Evaporator Base with Toner Surface Modification

[0052] The 3D-printed biomimetic solar evaporator base was immersed in a suspension of toner and then dried to obtain the 3D-printed biomimetic solar evaporator.

[0053] Scanning electron microscopy was used to examine cross-sections and longitudinal sections of sorghum stalks. The results are as follows: Figure 2 As shown, from Figure 2 As can be seen, sorghum stalks contain vascular bundles, which form water transport units, providing high-speed water transport support for efficient solar evaporation. The thin-walled cells of the sorghum stalks surround the vascular bundles, effectively reducing light reflection at the evaporation interface and enhancing light scattering, thereby improving the sorghum stalks' ability to absorb sunlight.

[0054] To this end, this invention designs a 3D-printed biomimetic base based on the vascular bundle structure of sorghum and modifies its surface with carbon powder, wherein the carbon powder is prepared by carbonization of sorghum straw. Microscopic images of the biomimetic solar evaporator base, obtained using a microscope at high magnification, are shown below. Figure 3 As shown, the 3D-printed biomimetic solar evaporator base is composed of sorghum-inspired vascular bundles with a diameter of 200–400 μm.

[0055] To further investigate the effects of carbonization temperature and carbon powder addition amount on evaporation rate and solar steam conversion efficiency.

[0056] 3.1 Carbonization temperature

[0057] This invention places sorghum stalks, sugarcane stalks, or corn stalks in a tube furnace under N2, and carbonizes them at temperatures of 600℃, 800℃, 1000℃, and 1200℃ for 2 hours to obtain carbon powder at different carbonization temperatures. The carbon powder prepared at the above four temperatures is then mixed with deionized water to prepare a suspension with a mass fraction of 18wt%. The 3D-printed biomimetic solar evaporator base prepared in Example 1 is immersed in the 18wt% carbon powder suspension for 1 hour, and then dried in a 60℃ oven for 1 hour to obtain a carbon powder-modified 3D-printed biomimetic solar evaporator.

[0058] 3D-printed biomimetic solar evaporators made from toner powders with different carbonization temperatures were placed in beakers containing deionized water, and the test results are as follows. Figure 4 As shown, the 3D-printed biomimetic solar evaporator modified with carbon powder obtained by carbonizing sorghum straw at 800℃ for 2 hours has the best water absorption effect and the highest evaporation rate and efficiency.

[0059] 3.2 Amount of toner added

[0060] This invention involves placing sorghum straw in a tube furnace filled with N2 and treating it at 800℃ for 2 hours to obtain carbon powder. The carbon powder is then mixed with deionized water to prepare suspensions with a mass fraction of 12-18 wt%. The 3D-printed biomimetic solar evaporator base prepared in Example 1 is immersed in the suspensions with different carbon powder contents for 1 hour, and then dried in a 60℃ oven for 1 hour to obtain a carbon powder-modified 3D-printed biomimetic solar evaporator.

[0061] 3D-printed biomimetic solar evaporators with different toner contents were placed in beakers containing deionized water, and the test results are as follows. Figure 5 As shown, the 3D-printed bionic solar evaporator prepared by soaking in an 18wt% toner suspension has the highest toner content of 21.7wt%. The 3D-printed bionic solar evaporator modified with 21.7wt% toner has the best water absorption effect and the highest evaporation rate and efficiency.

[0062] IV. Purification of Water Polluted by Nanoplastics

[0063] This invention employs a simple condensate collection device to conduct experiments on seawater desalination, acid and alkaline wastewater purification, organic wastewater purification, and nanoplastic wastewater purification using the solar evaporator provided in Example 1. The condensate collection device includes a large petri dish at the bottom, a small beaker placed inside the large petri dish, and a large beaker placed outside the small beaker.

[0064] The specific testing process is as follows: Pour an appropriate amount of nano-plastic wastewater into a small beaker; make a square through hole in the center of a foam with a diameter smaller than that of the small beaker. The side length of the through hole is slightly smaller than that of the 3D-printed bionic solar evaporator. The 3D-printed bionic solar evaporator is perfectly embedded in the through hole and will not fall off. Place the foam with the 3D-printed bionic solar evaporator fixed on it on the water surface, and then place a large beaker over the small beaker and under an artificial sun lamp. The condensate will collect on the large beaker and run down the inner wall of the large beaker. Finally, the condensate can be collected on the large petri dish at the bottom.

[0065] The 3D-printed biomimetic solar evaporator base prepared in Example 1 was formulated with carbon powder prepared at 800℃ to create a 21.7 wt% carbon powder-modified 3D-printed biomimetic solar evaporator. The 3D-printed biomimetic solar evaporator modified with 21.7 wt% carbon powder was immersed in polluted water containing PP nanoplastics for 1 hour. Transmission electron micrographs of pure water, polluted water containing PP nanoplastics, purified water collected after purification, and residual purified water in a beaker are shown below. Figure 6 As shown. From Figure 6 The results show that the purified water does not contain nanoplastics. This indicates that the porous polypyrrole solar evaporator has a good purification capacity for nanoplastics in water, with an evaporation rate of 3.443 kg·m³ under one standard solar irradiance. -2 ·h -1 The solar steam conversion efficiency can reach 117.8%.

[0066] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for fabricating a 3D-printed biomimetic solar evaporator, characterized in that, Acrylamide, polyethylene glycol diacrylate, and polyethylene glycol are dissolved in an aqueous solution of N-isopropylacrylamide and stirred to obtain solution a; a photoinitiator is stirred with an organic solvent to obtain solution b; solution a is added to solution b and mixed to obtain 3D printing ink; Using 3D printing ink, a base with a sorghum-like vascular bundle structure was obtained through 3D printing. The base of the sorghum-inspired vascular bundle structure was immersed in a carbon powder suspension, then removed and dried to obtain a 3D-printed biomimetic solar evaporator. The concentration of the aqueous solution of N-isopropylacrylamide is 3.0~7.0 mol·L⁻¹. -1 ; In solution a, the molar ratio of N-isopropylacrylamide, acrylamide, polyethylene glycol diacrylate, and polyethylene glycol is (3~7): (0.5~1): (0.001~0.01): (0.0001~0.002). The average molecular weight of the polyethylene glycol diacrylate is 200-600 g·mol⁻¹ -1 The polyethylene glycol has a molecular weight of 200~20000 g·mol⁻¹. -1 ; The carbon powder is obtained by carbonizing straw in N2 at 600~1200℃ for 2~6 hours; the straw is one or more of sorghum straw, sugarcane straw or corn straw. The concentration of the toner suspension is 12-18 wt%; the immersion time in the toner suspension is 0.5-1 h; the drying temperature is 50-80℃, and the drying time is 0.5-1 h.

2. The preparation method according to claim 1, characterized in that, The average molecular weight of the polyethylene glycol diacrylate is 200 g·mol⁻¹ -1 The molecular weight of the polyethylene glycol is 10000 g·mol⁻¹. -1 .

3. The preparation method according to claim 1, characterized in that, The photoinitiator is one or more selected from 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 1-hydroxycyclohexylphenyl ketone, or 2-hydroxy-2-methyl-1-phenylpropanone; the organic solvent is one or more selected from acetone, ethyl acetate, isopropanol, or methanol; and the concentration of the photoinitiator is 0.1~0.6 mol·L⁻¹. -1 .

4. The preparation method according to claim 1, characterized in that, The volume ratio of solution b to solution a is 1:(5-10).

5. The preparation method according to claim 1, characterized in that, The 3D printing process involves first designing and creating a model of a sorghum vascular bundle structure using a computer, and then curing it under ultraviolet light.

6. A 3D-printed biomimetic solar evaporator obtained by the preparation method according to any one of claims 1 to 5, characterized in that, The 3D-printed biomimetic solar evaporator has a sorghum-like vascular bundle structure, and the surface of the 3D-printed biomimetic solar evaporator is uniformly distributed with carbon powder, the content of which is 12~28wt%.

7. The application of the 3D-printed biomimetic solar evaporator as described in claim 6 in water treatment.

8. The application as described in claim 7, characterized in that, The water treatment includes seawater evaporation and wastewater treatment.

9. The application as described in claim 8, characterized in that, Wastewater treatment includes the purification of acidic and alkaline wastewater, the purification of organic dye wastewater, and the purification of nanoplastic wastewater.

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