Preparation method of salt-resistant 3D printing composite gel for treating sewage through photo-thermal photocatalysis

Abstract

The invention relates to the technical field of composite gel, in particular to a preparation method of salt-tolerant 3D printing composite gel for treating sewage through photo-thermal photocatalysis, which comprises the following steps: S1, respectively putting a thickening agent, a photo-thermal material and a photocatalytic material into a high-speed homogenizer, uniformly mixing, and then adding a matrix material to form uniform composite gel slurry; s2, defoaming the composite gel slurry, transferring the defoamed composite gel slurry into a 3D printer needle cylinder, and continuously printing a three-dimensional sample with a grating structure layer by layer by using a direct-writing 3D printing technology; and S3, immersing the printed grid structure into a cross-linking agent to form the 3D printing composite gel with a stable structure. Due to the hydrophilicity of the gel, it is guaranteed that water is continuously transported to an evaporation interface, and the evaporation rate of light-hot water is increased; the criss-cross grid structure of the composite gel promotes the generation of the Malangori effect, and prevents the evaporation rate from being reduced due to the blockage of salt crystals when the salt-containing sewage and wastewater are evaporated.

Description

Technical Field

[0001] The present invention relates to the technical field of composite gels, and in particular to a method for preparing a salt-resistant 3D printed composite gel for photothermal and photocatalytic treatment of sewage. Background Art

[0002] With the continuous growth of the global population, the continuous expansion of industrialization, and the increasingly severe environmental pollution problem, mankind is facing an unprecedented freshwater shortage crisis. The lack of freshwater resources has become one of the important bottlenecks restricting global sustainable development. In order to meet this challenge, people have begun to explore ways to extract clean water from seawater and wastewater, including water treatment technologies such as distillation, reverse osmosis and nanofiltration. However, these technologies are limited in their widespread application due to the complexity of equipment, high cost, and high energy consumption. Therefore, solar water evaporation technology, as a green and renewable water resource treatment technology, shows great application potential because it uses solar energy to heat and evaporate water and obtain clean water by condensing water vapor.

[0003] However, solar evaporation technology is currently mainly used to treat pure water. When faced with polluted water bodies with complex components, such as printing and dyeing wastewater, the use of solar water evaporation materials is also limited: first, during the desalination process of sewage and wastewater, a large amount of salt often accumulates on the surface of the evaporator, which not only reduces the evaporation efficiency, but also may cause corrosion and damage to the evaporator; second, as the evaporation process proceeds, pollutants in the water source will gradually accumulate, causing water quality to deteriorate, increasing the difficulty of subsequent treatment. Therefore, it is particularly important to study materials that can adapt to the purification of pollutants in high-salinity wastewater to produce clean water.

[0004] The rapid development of 3D printing technology has provided a new idea for the design of solar evaporators. As an effective, low-cost and multifunctional additive manufacturing technology, ink direct writing technology can be used to construct more complex and high-precision multi-level ordered porous structures, which not only helps to improve the water transfer efficiency of the evaporator and reduce heat loss, but also can achieve salt reflux through a carefully designed structure, effectively inhibiting the deposition of salt at the photothermal interface. However, traditional technologies can only use solar energy for photothermal evaporation or photocatalytic degradation. This single utilization method leads to low comprehensive utilization efficiency of solar energy. Photothermal evaporation mainly relies on solar energy to heat water to evaporate, while photocatalytic degradation focuses on using solar energy to excite catalysts to degrade organic pollutants in water. These two technologies are often carried out separately in practical applications, without achieving the synergistic effect of the two, thus failing to fully utilize the potential of solar energy. In addition, when treating actual sewage and wastewater, the photothermal water evaporation material with a simple structure is blocked by salt and contaminated by pollutants, which, on the one hand, reduces the efficiency of photothermal conversion to produce distilled water, and reduces the efficiency of sewage and wastewater treatment; on the other hand, the photothermal evaporation material needs to be replaced frequently, which brings about the problem of increased cost. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a method for preparing a salt-resistant 3D printed composite gel for photothermal and photocatalytic treatment of sewage, which solves the problem that traditional evaporation materials are easily blocked by salt crystals and easily contaminated by pollutants when treating polluted water.

[0006] To achieve the above objectives, the present invention is implemented by the following technical scheme: a method for preparing a salt-resistant 3D printed composite gel for photothermal and photocatalytic treatment of sewage, wherein the raw materials of the 3D printed composite gel include four components: a base material, a thickener, a photothermal material, and a photocatalytic material; the method for preparing the 3D printed composite gel comprises the following steps: S1. A thickener with a solid content of 0.8 wt%-3.0 wt%, a photothermal material with a solid content of 0.5-3.0 mg / g, and a photocatalyst with a solid content of 0.5-3.0 mg / g are respectively put into a high-speed homogenizer and mixed evenly, and then 2 wt%-6 wt% of the base material is added and heated and stirred until completely dissolved to form a uniform composite gel slurry; S2. The composite gel slurry is transferred to a centrifuge for degassing, and then transferred to a syringe of a 3D printer, and a three-dimensional sample with a grid structure is continuously printed layer by layer using a direct writing 3D printing technology at room temperature; S3. Immerse the printed grid structure in a cross-linking agent of a specific concentration and cross-link it for a period of time to form a structurally stable 3D printed composite gel.

[0007] Preferably, in the step S1, the thickener is any one of cellulose nanofibers, cellulose nanocrystals and bacterial cellulose.

[0008] Preferably, in step S1, the photothermal material is any one of carbon black, carbon nanotubes, graphene oxide, reduced graphene oxide, polypyrrole, polyaniline, polydopamine, titanium carbide, silicon carbide, zirconium carbide and Mxene.

[0009] Preferably, in step S1, the photocatalyst is any one of TiO2, Cds, Fe2O3, ZnO, ZrO2, g-C3N4, ZIF-8, PCN-224, and Fe-UiO-66.

[0010] Preferably, in step S1, the matrix material is any one of sodium alginate, chitosan, gelatin, chitin, methyl cellulose, hydroxypropyl methyl cellulose, carboxymethyl cellulose, cellulose acetate, polyethylene glycol, and polyvinyl alcohol, and the solvent is one or more of water, ethanol, acetone, and dilute acid.

[0011] Preferably, in step S1, the heating temperature for heating and stirring is 35-95°C, and the homogenizing speed of the high-speed homogenizer is 5000-20000 r / min.

[0012] Preferably, in the step S2, the degassing rate of the centrifuge is 4000 r / min, the degassing time is 5 min, the inner diameter of the printing needle of the direct writing 3D printer is 0.41-0.61 mm, the printing pressure is 20-40 psi, and the printing speed is 8-12 mm / s.

[0013] Preferably, in step S2, the length and width of the grid structure are 1 cm-10 cm, the height is 1-10 cm, and the length of each small grid is 0.1 cm-5 cm.

[0014] Preferably, in step S3, the cross-linking agent is any one of calcium chloride, calcium lactate, and glutaraldehyde, 0.05%-5%, and the cross-linking time is 10 min-600 min.

[0015] The present invention provides a method for preparing a salt-resistant 3D printed composite gel for photothermal and photocatalytic treatment of sewage. It has the following beneficial effects: The present invention prepares a printable slurry by mixing photothermal material, photocatalytic material, thickener and matrix material. Due to the hydrophilicity of the gel, the water is continuously transported to the evaporation interface, which increases the evaporation rate of the photothermal water. The evaporation rate of water reaches 2.01 kg / (m 2 .h); In addition, the heat energy generated by photothermal conversion and evaporation drive the enrichment of pollutants in the gel, improving the catalytic efficiency.

[0016] The present invention uses direct writing 3D printing technology to print a crisscross grid structure of composite gel, which, on the one hand, realizes multiple absorption and reflection of light, has a wide spectral absorption range (250 nm-2500 nm), and a light absorption rate of 95%; on the other hand, it promotes the generation of the Marangoni effect, and avoids the blockage of salt crystals that reduces the evaporation rate when evaporating saline wastewater. In addition, the present invention explores the effect of salt on photodegradable dyes and explores the complex mechanism problems faced by evaporators in treating actual complex wastewater.

[0017] The wastewater treated by the present invention can be divided into two parts, one part is the condensed water collected by photothermal evaporation; the other part is the wastewater with pollutants removed after evaporation, thereby improving the treatment efficiency of complex wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a preparation flow chart of the present invention; Figure 2A schematic diagram of a porous structure model of a 3D printed composite gel of the present invention; Figure 3 The top view and side view of the three-dimensional grid structure of the present invention, wherein a is the top view and b is the side view; Figure 4 This is a scanning electron microscope image of the three-dimensional grid structure of the present invention, wherein a is the grid structure on the surface of the composite gel, and b is the rich porous network inside; Figure 5 This is a schematic diagram of the contact angle test of the 3D printed composite gel of the present invention; Figure 6 It is a schematic diagram of the UV-visible-infrared spectroscopy analysis of the 3D printed composite gel of the present invention; Figure 7 This is a graph showing the change in water evaporation mass over time of the 3D printed composite gel of the present invention; Figure 8 Schematic diagram of the photocatalytic performance of the 3D printed composite gel of the present invention. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Embodiment 1

[0020] like Figure 1-8 As shown, an embodiment of the present invention provides a method for preparing a salt-resistant 3D printed composite gel for photothermal and photocatalytic treatment of sewage, comprising the following steps: S1. First, 2.5 mg / g carbon black and 2.5 mg / g PCN-224 were added to 20 g of 1 wt% cellulose nanofiber aqueous solution, and the solution was homogenized at 10000 r / min for 10 min using a high-speed homogenizer to obtain a cellulose nanofiber composite aqueous solution. Then, 3 wt% sodium alginate powder was added to the solution, and the solution was heated to 60 °C and mechanically stirred for 30 min to obtain a composite gel slurry. S2. The composite gel slurry was transferred to a centrifuge for degassing at a speed of 4000 r / min for 5 min, and then transferred to the syringe of a slurry direct writing 3D printer. The inner diameter of the printing needle was 0.61 mm, the printing pressure was 30 psi, and continuous layer-by-layer printing was performed at room temperature to form a three-dimensional grid structure with a length of 2 cm, a width of 2 cm, and a height of 1 cm. S3. Immerse the printed three-dimensional grid structure in a 2 wt% calcium chloride solution for cross-linking for 30 min to obtain a structurally stable 3D printed porous gel.

[0021] Figure 2 is a porous structure model of the 3D printed composite gel; the top view and side view of the actual 3D printed composite gel grid are shown in Figure 3 a and Figure 3 In order to comprehensively evaluate the performance of the 3D printed composite gel grid with synergistic photothermal evaporation and photocatalysis, we conducted a number of characterization tests, including micromorphology, contact angle, absorbance, chemical structure, evaporation performance and photocatalytic performance. Figure 4 This is a scanning electron microscope image of the 3D printed three-dimensional grid structure. Figure 4 a intuitively shows the grid structure of the 3D printed composite gel surface, and Figure 4 b reveals its rich internal porous network. This structural design greatly promotes the rapid transport and efficient evaporation of water; Figure 5 Schematic diagram of contact angle test of the prepared porous gel. Figure 5 As shown, this gel material has excellent hydrophilicity. Combined with its unique grid structure, it effectively promotes the reflux of salt during evaporation and reduces the negative impact of salt crystallization on evaporation efficiency. Figure 6 UV-Vis-IR spectroscopic analysis of porous gels, such as Figure 6 As shown, the 3D printed composite gel exhibited a light absorption of up to 95%, fully demonstrating its potential in photothermal conversion; Figure 7 The water evaporation mass of the 3D printed composite gel changes over time. The 3D printed composite gel is combined with polystyrene foam to construct a photothermal evaporator, which is placed on an electronic balance to perform an evaporation test on the 3D printed composite gel. Figure 7 As shown, under one sun, the evaporation rate is 2.01 kg / (m 2 .h), much higher than the evaporation of pure water; Figure 8 Schematic diagram of the photocatalytic performance of 3D printed composite gel. Figure 8 As shown, both in the absence of salt (0 wt% NaCl, Figure 8 a) or high salt (10 wt% NaCl, Figure 8 b) Under the conditions of 3D printed composite gel, 10 ppm of methylene blue can be effectively degraded under one sun illumination. Embodiment 2

[0022] The embodiment of the present invention provides a method for preparing a salt-resistant 3D printed composite gel for photothermal and photocatalytic treatment of sewage, comprising the following steps: S1. First, 0.5 mg / g, 1.0 mg / g, 1.5 mg / g, 2.0 mg / g, and 2.5 mg / g of carbon black were added together with 2.5 mg / g of PCN-224 into 20 g of 1 wt% cellulose nanofiber aqueous solution, and a high-speed homogenizer was used to homogenize at a speed of 10000 r / min for 10 min to obtain a cellulose nanofiber composite aqueous solution. Then, 3 wt% of sodium alginate powder was added to the solution, and the solution was heated to 60 °C and mechanically stirred for 30 min to obtain a composite gel slurry. S2. The composite gel slurry was transferred to a centrifuge for degassing at a speed of 4000 r / min for 5 min, and then transferred to the syringe of a slurry direct writing 3D printer. The inner diameter of the printing needle was 0.61 mm, the printing pressure was 30 psi, and continuous layer-by-layer printing was performed at room temperature to form a three-dimensional grid structure with a length of 2 cm, a width of 2 cm, and a height of 1 cm. S3. Immerse the printed three-dimensional grid structure in a 2 wt% calcium chloride solution for cross-linking for 30 min to obtain a structurally stable 3D printed porous gel.

[0023] This example investigates the effect of the amount of carbon black added on the light absorbance of the 3D printed composite gel. The absorbances of the 3D printed composite gels to which 0.5 mg / g, 1.0 mg / g, 1.5 mg / g, 2.0 mg / g, and 2.5 mg / g of carbon black were added were 90.74%, 92%, 92.666%, 94.31%, and 95.50%, respectively, indicating that the addition of carbon black significantly increased the light absorbance of the 3D printed composite gel. Embodiment 3

[0024] The embodiment of the present invention provides a method for preparing a salt-resistant 3D printed composite gel for photothermal and photocatalytic treatment of sewage, comprising the following steps: S1. First, 2.5 mg / g carbon black and 2.5 mg / g PCN-224 were added to 20 g of 1 wt% cellulose nanofiber aqueous solution, and the solution was homogenized at 10000 r / min for 10 min using a high-speed homogenizer to obtain a cellulose nanofiber composite aqueous solution. Then, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, and 6 wt% of sodium alginate powder were added to the solution, respectively, and the solution was heated to 60 °C and mechanically stirred for 30 min to obtain a composite gel slurry. S2. The composite gel slurry was transferred to a centrifuge for degassing at a speed of 4000 r / min for 5 min, and then transferred to the syringe of a slurry direct writing 3D printer. The inner diameter of the printing needle was 0.61 mm, the printing pressure was 30 psi, and continuous layer-by-layer printing was performed at room temperature to form a three-dimensional grid structure with a length of 2 cm, a width of 2 cm, and a height of 1 cm. S3. Immerse the printed three-dimensional grid structure in a 2 wt% calcium chloride solution for cross-linking for 30 min to obtain a structurally stable 3D printed porous gel.

[0025] This embodiment examines the effect of the amount of sodium alginate added on the molding properties of the 3D printing composite gel slurry. When the sodium alginate concentration is less than 3 wt%, the sodium alginate composite slurry configured in this embodiment does not have good shape retention. When the sodium alginate concentration is greater than 4 wt%, the sodium alginate composite slurry configured in this embodiment is not conducive to being extruded from the printing needle of the 3D printer due to its excessive viscosity. Therefore, the sodium alginate composite slurry needs to have good printability, and the amount of sodium alginate added needs to be controlled between 3 wt% and 4 wt%. Embodiment 4

[0026] The embodiment of the present invention provides a method for preparing a salt-resistant 3D printed composite gel for photothermal and photocatalytic treatment of sewage, comprising the following steps: S1. First, 2.5 mg / g carbon black and 2.5 mg / g PCN-224 were added to 20 g of 1 wt% cellulose nanofiber aqueous solution, and the solution was homogenized at 10000 r / min for 10 min using a high-speed homogenizer to obtain a cellulose nanofiber composite aqueous solution. Then, 3 wt% sodium alginate powder was added to the solution, and the solution was heated to 60 °C and mechanically stirred for 30 min to obtain a composite gel slurry. S2. The composite gel slurry was transferred to a centrifuge for degassing at a speed of 4000 r / min for 5 min, and then transferred to the syringe of a slurry direct writing 3D printer. The inner diameter of the printing needle was 0.61 mm, the printing pressure was 30 psi, and continuous layer-by-layer printing was performed at room temperature to form a three-dimensional grid structure with a length of 2 cm, a width of 2 cm, and a height of 1 cm. S3. The printed three-dimensional grid structure was immersed in 1 wt%, 1.5 wt%, and 2 wt% calcium chloride solutions for cross-linking for 30 min to obtain a structurally stable 3D printed porous gel.

[0027] This example investigates the effect of CaCl2 concentration on the degree of cross-linking of 3D printed sodium alginate grids. Within a fixed period of 30 min, the stability of the 3D printed composite gel cross-linked at 1 wt% and 1.5 wt% CaCl2 concentrations is poorer than that at 2 wt%. This is because the lower the CaCl2 concentration, the slower the penetration into sodium alginate.

[0028] Comparative Example 1: The comparative example of the present invention provides a method for preparing a 3D printed composite gel, comprising the following steps: S1. First, 2.5 mg / g of carbon black, carbon nanotubes, graphene oxide, reduced graphene oxide, polypyrrole, polyaniline, polydopamine, titanium carbide, silicon carbide, zirconium carbide and Mxene and 2.5 mg / g of PCN-224 were added to 20 g of 1 wt% cellulose nanofiber aqueous solution, and a high-speed homogenizer was used to homogenize at a speed of 10000 r / min for 10 min to obtain a cellulose nanofiber composite aqueous solution. Then, 3 wt% of sodium alginate powder was added to the solution, and the solution was heated to 60 °C and mechanically stirred for 30 min to obtain a composite gel slurry. S2. The composite gel slurry was transferred to a centrifuge for degassing at a speed of 4000 r / min for 5 min, and then transferred to the syringe of a slurry direct writing 3D printer. The inner diameter of the printing needle was 0.61 mm, the printing pressure was 30 psi, and continuous layer-by-layer printing was performed at room temperature to form a three-dimensional grid structure with a length of 2 cm, a width of 2 cm, and a height of 1 cm. S3. Immerse the printed three-dimensional grid structure in a 2 wt% calcium chloride solution for cross-linking for 30 min to obtain a structurally stable 3D printed porous gel.

[0029] This comparative example examines the effect of adding different photothermal materials on the photothermal evaporation performance and photocatalytic performance of 3D printed composite gel.

[0030] Comparative Example 2: The comparative example of the present invention provides a method for preparing a 3D printed composite gel, comprising the following steps: S1. First, 2.5 mg / g carbon black and 2.5 mg / g TiO2, Cds, Fe2O3, ZnO, ZrO2, g-C3N4, ZIF-8, PCN-224, and Fe-UiO-66 were added to 20 g of 1 wt% cellulose nanofiber aqueous solution, and a high-speed homogenizer was used to homogenize the solution at a speed of 10000 r / min for 10 min to obtain a cellulose nanofiber composite aqueous solution. Then, 3 wt% sodium alginate powder was added to the solution, and the solution was heated to 60 °C and mechanically stirred for 30 min to obtain a composite gel slurry. S2. The composite gel slurry was transferred to a centrifuge for degassing at a speed of 4000 r / min for 5 min, and then transferred to the syringe of a slurry direct writing 3D printer. The inner diameter of the printing needle was 0.61 mm, the printing pressure was 30 psi, and continuous layer-by-layer printing was performed at room temperature to form a three-dimensional grid structure with a length of 2 cm, a width of 2 cm, and a height of 1 cm. S3. Immerse the printed three-dimensional grid structure in a 2 wt% calcium chloride solution for cross-linking for 30 min to obtain a structurally stable 3D printed porous gel.

[0031] This comparative example examines the effect of adding different photocatalytic materials on the photothermal evaporation performance and photocatalytic performance of 3D printed composite gel.

[0032] Comparative Example 3: The comparative example of the present invention provides a method for preparing a 3D printed composite gel, comprising the following steps: S1. First, 2.5 mg / g carbon black and 2.5 mg / g PCN-224 were added to 20 g of 1 wt% aqueous solution of cellulose nanofibers, cellulose nanocrystals and bacterial cellulose, and homogenized at 10000 r / min for 10 min using a high-speed homogenizer to obtain a cellulose composite aqueous solution. Then, 3 wt% sodium alginate powder was added to the solution, and the solution was heated to 60 °C and mechanically stirred for 30 min to obtain a composite gel slurry. S2. The composite gel slurry was transferred to a centrifuge for degassing at a speed of 4000 r / min for 5 min, and then transferred to the syringe of a slurry direct writing 3D printer. The inner diameter of the printing needle was 0.61 mm, the printing pressure was 30 psi, and continuous layer-by-layer printing was performed at room temperature to form a three-dimensional grid structure with a length of 2 cm, a width of 2 cm, and a height of 1 cm. S3. Immerse the printed three-dimensional grid structure in a 2 wt% calcium chloride solution for cross-linking for 30 min to obtain a structurally stable 3D printed porous gel.

[0033] This comparative example examines the effect of adding different thickeners on the formability of 3D printed composite gels and the effect of water evaporation rate.

[0034] Comparative Example 4: The comparative example of the present invention provides a method for preparing a 3D printed composite gel, comprising the following steps: S1. First, 2.5 mg / g of carbon black and 2.5 mg / g of PCN-224 were added to 20 g of 1 wt% cellulose nanofiber aqueous solution, and homogenized at 10000 r / min for 10 min using a high-speed homogenizer to obtain a cellulose nanofiber composite aqueous solution. Then, 3 wt% of sodium alginate, chitosan, gelatin, chitin, methyl cellulose, hydroxypropyl methyl cellulose, carboxymethyl cellulose, cellulose acetate, polyethylene glycol, and polyvinyl alcohol were added to the solution, and the solvent was one or more of water, ethanol, acetone, and dilute acid. The mixture was heated and mechanically stirred for 30 min to obtain a composite gel slurry. S2. The composite gel slurry was transferred to a centrifuge for degassing at a speed of 4000 r / min for 5 min, and then transferred to the syringe of a slurry direct writing 3D printer. The inner diameter of the printing needle was 0.61 mm, the printing pressure was 30 psi, and continuous layer-by-layer printing was performed at room temperature to form a three-dimensional grid structure with a length of 2 cm, a width of 2 cm, and a height of 1 cm. S3. Immerse the printed three-dimensional grid structure in a 2 wt% calcium chloride solution for cross-linking for 30 min to obtain a structurally stable 3D printed porous gel.

[0035] This comparative example examines the effects of different matrix materials on the water transportability and water evaporation rate of 3D printed composite gels.

[0036] Comparative Example 5: The comparative example of the present invention provides a method for preparing a 3D printed composite gel, comprising the following steps: S1. First, 2.5 mg / g carbon black and 2.5 mg / g PCN-224 were added to 20 g of 1 wt% cellulose nanofiber aqueous solution, and the solution was homogenized at 10000 r / min for 10 min using a high-speed homogenizer to obtain a cellulose nanofiber composite aqueous solution. Then, 3 wt% sodium alginate powder was added to the solution, and the solution was heated to 60 °C and mechanically stirred for 30 min to obtain a composite gel slurry. S2. The composite gel slurry was transferred to a centrifuge for degassing at a speed of 4000 r / min for 5 min, and then transferred to the syringe of a slurry direct writing 3D printer. The inner diameter of the printing needle was 0.61 mm, the printing pressure was 30 psi, and continuous layer-by-layer printing was performed at room temperature to form a three-dimensional grid structure with a length of 2 cm, a width of 2 cm, and a height of 1 cm. S3. The printed three-dimensional grid structure was immersed in 2 wt% calcium chloride, calcium lactate, and glutaraldehyde solutions for cross-linking for 30 min to obtain a structurally stable 3D printed porous gel.

[0037] This comparative example examines the effects of different cross-linking agents on the cross-linking molding of 3D printed composite gels.

[0038] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a salt-tolerant 3D printed composite gel for photothermal and photocatalytic treatment of sewage, characterized in that: The raw materials of the 3D printing composite gel include four components: a base material, a thickener, a photothermal material, and a photocatalytic material; the preparation method of the 3D printing composite gel includes the following steps: S1. A thickener with a solid content of 0.8 wt%-3.0 wt%, a photothermal material with a solid content of 0.5-3.0 mg / g, and a photocatalyst with a solid content of 0.5-3.0 mg / g are respectively put into a high-speed homogenizer and mixed evenly, and then 2 wt%-6 wt% of the base material is added and heated and stirred until completely dissolved to form a uniform composite gel slurry; S2. The composite gel slurry is transferred to a centrifuge for degassing, and then transferred to a syringe of a 3D printer, and a three-dimensional sample with a grid structure is continuously printed layer by layer using a direct writing 3D printing technology at room temperature; S3. Immerse the printed grid structure in a cross-linking agent of a specific concentration and cross-link for a period of time to form a structurally stable 3D printed composite gel.

2. The method for preparing the salt-resistant 3D printed composite gel for photothermal and photocatalytic treatment of sewage according to claim 1, characterized in that: In the step S1, the thickener is any one of cellulose nanofibers, cellulose nanocrystals, and bacterial cellulose.

3. The method for preparing the salt-resistant 3D printed composite gel for photothermal and photocatalytic treatment of sewage according to claim 1, characterized in that: In the step S1, the photothermal material is any one of carbon black, carbon nanotubes, graphene oxide, reduced graphene oxide, polypyrrole, polyaniline, polydopamine, titanium carbide, silicon carbide, zirconium carbide and Mxene.

4. The method for preparing the salt-resistant 3D printed composite gel for photothermal and photocatalytic treatment of sewage according to claim 1, characterized in that: In the step S1, the photocatalyst is any one of TiO2, Cds, Fe2O3, ZnO, ZrO2, g-C3N4, ZIF-8, PCN-224, and Fe-UiO-66.

5. The method for preparing the salt-resistant 3D printed composite gel for photothermal and photocatalytic treatment of sewage according to claim 1, characterized in that: In the step S1, the matrix material is any one of sodium alginate, chitosan, gelatin, chitin, methyl cellulose, hydroxypropyl methyl cellulose, carboxymethyl cellulose, cellulose acetate, polyethylene glycol, and polyvinyl alcohol, and the solvent is one or more of water, ethanol, acetone, and dilute acid.

6. The method for preparing the salt-resistant 3D printed composite gel for photothermal and photocatalytic sewage treatment according to claim 1, characterized in that: In the step S1, the heating temperature for heating and stirring is 35-95° C., and the homogenizing speed of the high-speed homogenizer is 5000-20000 r / min.

7. The method for preparing the salt-resistant 3D printed composite gel for photothermal and photocatalytic treatment of sewage according to claim 1, characterized in that: In the step S2, the degassing rate of the centrifuge is 4000 r / min, the degassing time is 5 min, the inner diameter of the printing needle of the direct writing 3D printer is 0.41-0.61 mm, the printing pressure is 20-40 psi, and the printing speed is 8-12 mm / s.

8. The method for preparing the salt-resistant 3D printed composite gel for photothermal and photocatalytic sewage treatment according to claim 1, characterized in that: In the step S2, the length and width of the grid structure are 1 cm-10 cm, the height is 1-10 cm, and the length of each small grid is 0.1 cm-5 cm.

9. The method for preparing the salt-resistant 3D printed composite gel for photothermal and photocatalytic treatment of sewage according to claim 1, characterized in that: In the step S3, the cross-linking agent is any one of calcium chloride, calcium lactate, and glutaraldehyde, the concentration of the cross-linking agent is 0.05%-5%, and the cross-linking time is 10 min-600 min.

10. Application of the salt-resistant 3D printing composite gel prepared by the preparation method according to any one of claims 1 to 9 in the fields of solar thermal water production and degradation of saline sewage and wastewater.

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