An anti-salt evaporator using a double-scale structure to realize salt migration and bidirectional water replenishment and a preparation method thereof

Abstract

This invention provides a salt-resistant evaporator and its preparation method that utilize a dual-scale structure to achieve salt migration and bidirectional water replenishment, belonging to the field of saline wastewater treatment such as seawater desalination. The salt-resistant evaporator of this invention includes: an evaporation main frame, composed of an array of micron-sized unit cells connected together, with micron-sized pores between each pair of micron-sized unit cells; millimeter-sized channels passing through the evaporation main frame and located at its geometric center, communicating with the micron-sized pores between each pair of micron-sized unit cells; and a hydrophilic photothermal conversion coating disposed on the outer surface of the evaporation main frame. The salt-resistant evaporator of this invention forms a temperature gradient and a concentration gradient inside, thereby triggering Marangoni convection, pumping salt from a high-concentration region (micron-sized unit cells) to a low-concentration region (millimeter-sized channels), and finally returning it to the solution to be evaporated, ultimately achieving real-time salt migration.

Description

Technical Field

[0001] This invention belongs to the field of saline wastewater treatment such as seawater desalination, and specifically relates to a salt-resistant evaporator that utilizes a dual-scale structure to achieve salt migration and bidirectional water replenishment, and its preparation method. Background Technology

[0002] Saline wastewater constitutes a significant proportion of wastewater, exhibiting poor biodegradability and posing a high challenge for treatment. Meanwhile, increasingly stringent environmental regulations are making zero (near-zero) discharge a necessary strategy for managing high-salinity wastewater. In zero (near-zero) discharge treatment processes, the key is to reduce the volume of wastewater by increasing its salinity and decreasing its volume, thereby reducing process energy consumption and costs. However, the volume reduction process for high-salinity wastewater requires substantial energy to achieve salt / water separation, resulting in carbon emissions far exceeding those of other industrial wastewater. Therefore, developing green and low-carbon wastewater concentration and volume reduction technologies is crucial for achieving energy-efficient treatment of high-salinity wastewater and promoting sustainable economic development in my country.

[0003] Solar interfacial evaporation technology utilizes solar energy for localized photothermal evaporation on the evaporator surface to achieve efficient salt / water separation. It is widely recognized as a green, low-carbon, and sustainable concentration and separation technology, and has received extensive research and attention in recent years. However, most existing solar evaporators are made of a single-scale structure or a single material. This leads to scale buildup on the evaporator surface and inside during the treatment of high-salt water, causing evaporator blockage and resulting in a sharp decline in system performance, even to the point of loss of processing capacity. This is currently the main bottleneck restricting the development and application of this technology. Summary of the Invention

[0004] This invention is made to solve the above-mentioned problems, and aims to provide a salt-resistant evaporator and its preparation method that utilizes a dual-scale structure to achieve salt migration and bidirectional water replenishment.

[0005] This invention provides a salt-resistant evaporator that utilizes a dual-scale structure to achieve salt migration and bidirectional water replenishment. It features: an evaporation main frame composed of an array of micron-sized unit cells, with each pair of micron-sized unit cells containing micron-sized pores; millimeter-sized channels passing through the evaporation main frame and located at its geometric center, communicating with the micron-sized pores between the pairs of micron-sized unit cells; and a hydrophilic photothermal conversion coating disposed on the outer surface of the evaporation main frame.

[0006] The salt-resistant evaporator provided by the present invention, which utilizes a dual-scale structure to achieve salt migration and bidirectional water replenishment, may also have the following feature: wherein the structure of the main evaporation frame includes any one of a cylinder, prism, pyramid, or frustum.

[0007] The salt-resistant evaporator provided by the present invention, which utilizes a dual-scale structure to achieve salt migration and bidirectional water replenishment, may also have the following feature: when the structure of the evaporator body frame is cylindrical, the diameter of the evaporator body frame is 4 to 20 mm.

[0008] The salt-resistant evaporator provided by this invention, which utilizes a dual-scale structure to achieve salt migration and bidirectional water replenishment, may also have the following feature: wherein the shape of the micron-scale unit cell is... Figure 4 For any of the shapes shown, the size of a micron-sized unit cell is 50–900 μm.

[0009] The salt-resistant evaporator provided by the present invention, which utilizes a dual-scale structure to achieve salt migration and bidirectional water replenishment, may also have the following features: the cross-sectional shape of the millimeter-level channel includes any one of a circle, a rectangle, or a triangle, and the hydraulic diameter of the millimeter-level channel is 1 to 3 mm.

[0010] The salt-resistant evaporator provided by this invention, which utilizes a dual-scale structure to achieve salt migration and bidirectional water replenishment, may also have the following feature: wherein the hydrophilic photothermal conversion coating is an organic coating or an inorganic coating, and the material of the hydrophilic photothermal conversion coating includes any one or more of gold, silver, copper, platinum, carbon nanotubes, acrylic resin, graphene, or dopamine.

[0011] The salt-resistant evaporator that utilizes a dual-scale structure to achieve salt migration and bidirectional water replenishment provided by the present invention may also have the following features: wherein, the salt-resistant evaporator that utilizes a dual-scale structure to achieve salt migration and bidirectional water replenishment achieves real-time salt migration through Marangoni convection inside, and the salt-resistant evaporator that utilizes a dual-scale structure to achieve salt migration and bidirectional water replenishment can achieve water replenishment along its length direction and water replenishment from millimeter-level channels to micrometer-level unit cells.

[0012] This invention also provides a method for preparing a salt-resistant evaporator that utilizes a dual-scale structure to achieve salt migration and bidirectional water replenishment. The method, used to prepare any of the aforementioned salt-resistant evaporators that utilize a dual-scale structure to achieve salt migration and bidirectional water replenishment, includes the following steps: S10, establishing a three-dimensional structural model of the evaporator's main frame and millimeter-level channels using three-dimensional modeling software and performing 3D printing; S20, setting a hydrophilic photothermal conversion coating on the surface of the evaporator's main frame to obtain the salt-resistant evaporator that utilizes a dual-scale structure to achieve salt migration and bidirectional water replenishment.

[0013] The method for preparing a salt-resistant evaporator that utilizes a dual-scale structure to achieve salt migration and bidirectional water replenishment provided by the present invention may also have the following features: between step S10 and step S20, step S11 is further included: using a plasma cleaner to remove impurities from the surface of the printed evaporation body frame; in step S20, after setting the hydrophilic photothermal conversion coating, the surface of the hydrophilic photothermal conversion coating is also cleaned using a plasma cleaner.

[0014] The method for preparing a salt-resistant evaporator that utilizes a dual-scale structure to achieve salt migration and bidirectional water replenishment provided by the present invention may also have the following features: in step S10, the 3D printing method includes any one of resin-based 3D printing, ceramic-based 3D printing, metal 3D printing, or 3D printing based on surface projection lithography technology; in step S20, the method for setting the hydrophilic photothermal conversion coating includes any one or more of chemical deposition, magnetron sputtering, or chemical plating.

[0015] The role and effect of invention

[0016] According to the present invention, a salt-resistant evaporator utilizing a dual-scale structure to achieve salt migration and bidirectional water replenishment, and its preparation method, the salt-resistant evaporator comprises: an evaporation main frame, composed of an array of micron-sized unit cells connected together, with micron-sized pores between each pair of micron-sized unit cells; millimeter-sized channels passing through the evaporation main frame and located at the geometric center of the evaporation main frame, the millimeter-sized channels communicating with the micron-sized pores between each pair of micron-sized unit cells; and a hydrophilic photothermal conversion coating disposed on the outer surface of the evaporation main frame. The salt-resistant evaporator is prepared by the following method: S10, establishing a three-dimensional structural model of the evaporation main frame and the millimeter-sized channels using three-dimensional modeling software and performing 3D printing; S20, disposing of the hydrophilic photothermal conversion coating on the surface of the evaporation main frame, thereby obtaining the salt-resistant evaporator utilizing a dual-scale structure to achieve salt migration and bidirectional water replenishment.

[0017] Therefore, the salt-resistant evaporator prepared using the method of the present invention for realizing salt migration and bidirectional water replenishment through a dual-scale structure has the following advantages:

[0018] (1) The salt-resistant evaporator relies on its own two-scale structure (micron-level single cell and millimeter-level channel) and photothermal conversion coating to form a temperature gradient and density gradient inside the evaporator, thereby realizing regional temperature management and concentration management.

[0019] (2) The salt-resistant evaporator triggers Marangoni convection by relying on its own temperature and concentration management. Marangoni convection spontaneously sends salt ions from inside the evaporator back to the solution to be evaporated, which can effectively avoid the problem of salt scale clogging the evaporator.

[0020] (3) The photothermal conversion coating of the salt-resistant evaporator is a hydrophilic coating. Combined with the dual-scale structure of the salt-resistant evaporator itself, water can be replenished in two directions inside the salt-resistant evaporator, namely water replenishment along the length of the salt-resistant evaporator and water replenishment in the horizontal direction from the millimeter-level channel to the micron-level unit cell. This can efficiently and quickly replenish water inside the evaporator and keep the evaporation interface moist. Once the evaporator has a salt content, it can be quickly dissolved, which further avoids the problem of salt scale clogging the evaporator. Attached Figure Description

[0021] Figure 1 This is a three-dimensional structural diagram of the salt-resistant evaporator in Embodiment 1 of the present invention;

[0022] Figure 2 This is a cross-sectional view of the salt-resistant evaporator in Embodiment 1 of the present invention;

[0023] Figure 3 This is a structural diagram of a micron-sized single cell of the salt-resistant evaporator in Embodiment 1 of the present invention;

[0024] Figure 4 This is a schematic diagram of several different structures of the micron-scale unit cell of the salt-resistant evaporator of the present invention;

[0025] Figure 5 This is a histogram showing the evaporation performance of sample 5 in salt water of different concentrations in the test examples of this invention.

[0026] Figure 6 This is a histogram of the long-term salt resistance performance of sample 5 in the test example of this invention in 20wt% salt water and under 1 solar intensity (1kW). Detailed Implementation

[0027] To make the technical means, creative features, objectives and effects of the present invention easy to understand, the following embodiments, in conjunction with the accompanying drawings, specifically illustrate a salt-resistant evaporator and its preparation method that utilizes a dual-scale structure to achieve salt migration and bidirectional water replenishment.

[0028] <Example 1>

[0029] This embodiment provides a salt-resistant evaporator and its preparation method that utilizes a dual-scale structure to achieve salt migration and bidirectional water replenishment.

[0030] Figure 1 This is a three-dimensional structural diagram of the salt-resistant evaporator in Embodiment 1 of the present invention; Figure 2 This is a cross-sectional view of the salt-resistant evaporator in Embodiment 1 of the present invention.

[0031] like Figures 1-2As shown, this embodiment provides a salt-resistant evaporator 100 that utilizes a dual-scale structure to achieve salt migration and bidirectional water replenishment, including an evaporation main frame 10, millimeter-level channels 20, and a hydrophilic photothermal conversion coating (not shown in the figure).

[0032] The evaporation main frame 10 has a cylindrical structure with a diameter of 4 mm. The evaporation main frame 10 is composed of micron-sized unit cells 11 connected in an array.

[0033] Figure 3 This is a structural diagram of a micron-sized single cell of the salt-resistant evaporator in Embodiment 1 of the present invention.

[0034] The structure of a micron-sized unit cell 11 is as follows Figure 3 As shown, its size is 600μm, and different micron-sized unit cells 11 are surrounded by micron-sized pores.

[0035] The millimeter-scale channel 20 passes through the evaporation main frame 10 and is coaxial with the cylindrical evaporation main frame 10. Its hydraulic diameter is 1 mm. The millimeter-scale channel 20 is connected to the micron-scale pores wrapped between each pair of micron-scale unit cells 11.

[0036] A hydrophilic photothermal conversion coating is applied to the outer surface of the evaporation body frame 10, and its material is carbon nanotubes and acrylic resin.

[0037] This embodiment also provides a method for preparing a salt-resistant evaporator that utilizes a dual-scale structure to achieve salt migration and bidirectional water replenishment, used to prepare the salt-resistant evaporator 100 in this embodiment that utilizes a dual-scale structure to achieve salt migration and bidirectional water replenishment, including the following steps:

[0038] S10. A three-dimensional structural model of the evaporation main frame 10 and the millimeter-level channel 20 is established using three-dimensional modeling software and then 3D printed.

[0039] The 3D printing method includes any one of resin-based 3D printing, ceramic-based 3D printing, metal 3D printing, or 3D printing based on surface projection lithography. (In this embodiment, 3D printing based on surface projection lithography is selected.)

[0040] S11, use a plasma cleaner to remove impurities from the surface of the printed evaporation body frame 10.

[0041] S20, a hydrophilic photothermal conversion coating is applied to the surface of the evaporator frame 10, and the surface of the hydrophilic photothermal conversion coating is cleaned using a plasma cleaner to obtain a salt-resistant evaporator 100.

[0042] The method for setting the hydrophilic photothermal conversion coating includes any one or more of chemical deposition, magnetron sputtering, or electroless plating. (In this embodiment, chemical deposition is selected.)

[0043] <Example 2>

[0044] In this embodiment, several different salt-resistant evaporators were prepared using the salt-resistant evaporator preparation method of Example 1, which utilizes a dual-scale structure to achieve salt migration and bidirectional water replenishment. These evaporators are referred to as Sample 1, Sample 2, Sample 3, Sample 4, Sample 6, and Sample 7, respectively.

[0045] The salt-resistant evaporator 100 prepared in Example 1 is designated as Sample 5.

[0046] The specific parameters of the preparation process and the results of samples 1-7 are shown in Table 1. The other conditions are the same as those in Example 1 and will not be repeated.

[0047] Figure 4 This is a schematic diagram of several different structures of the micron-scale unit cell of the salt-resistant evaporator of the present invention. For example... Figure 4 As shown, different choices of the shape of a micrometer-scale unit cell are as follows: Figure 4 As shown in (a)(b)(c)(d)(e).

[0048] Table 1 (Comparison of parameters of preparation process and final product for samples 1-7)

[0049]

[0050] In Table 1, the hydrophilic photothermal conversion coating materials of samples 1 and 2 were prepared by magnetron sputtering.

[0051] The method for setting the hydrophilic photothermal conversion coating material of sample 3 is to apply a pure gold coating to the surface of the evaporation host frame by magnetron sputtering, and then to plate a layer of metallic copper with a thickness of 1-5 μm on the gold surface by electrochemical method. Then, it is placed in a muffle furnace and heated at 500℃ for 5 hours.

[0052] The hydrophilic photothermal conversion coating material of sample 4 was applied by chemical plating.

[0053] The method for preparing the hydrophilic photothermal conversion coating material of sample 5 is to prepare a hydrophilic coating solution by mixing hydrophilic multi-walled carbon nanotubes, propionic acid resin, deionized water and surfactant together and stirring evenly. Then, the evaporation main frame, which has been cleaned by a plasma cleaner, is placed in the aforementioned hydrophilic coating solution for 6 hours, and then it is taken out and dried in an oven.

[0054] The method for preparing the hydrophilic photothermal conversion coating material of sample 6 is to prepare a hydrophilic coating solution by mixing hydrophilic graphene, propionic acid resin, deionized water and surfactant together and stirring evenly. Then, the evaporation main frame, which has been cleaned by a plasma cleaner, is placed in the aforementioned hydrophilic coating solution for 6 hours, and then taken out and dried in an oven.

[0055] The method for preparing the hydrophilic photothermal conversion coating material of sample 7 is as follows: prepare a hydrophilic coating solution by mixing hydrophilic carbon powder, propionic acid resin, anhydrous ethanol and surfactant together and stirring evenly; then place the evaporation main frame cleaned by plasma cleaner in the aforementioned hydrophilic coating solution for 6 hours, and then take it out and dry it in an oven.

[0056] <Test Example>

[0057] This test case performs performance tests on sample 5 from Examples 1 and 2.

[0058] The testing method is as follows:

[0059] Sample 5 was placed in saline solutions of different concentrations (the containers were placed on an electronic balance), and the changes in the saline solution were tested every 12 hours under a sunlight intensity of 1 kW.

[0060] Figure 5 This is a histogram showing the evaporation performance of sample 5 in saline solutions of different concentrations in the test examples of this invention. (Example:) Figure 5 As shown, the evaporation flux of sample 5 is approximately 3.417 kg / (m²). 2 ·h).

[0061] Figure 6 This is a histogram of the long-term salt resistance performance of sample 5 in the test examples of this invention in 20wt% salt water and under 1 kW of sunlight. Figure 6 As shown, the evaporation performance of sample 5 remained stable during the 120-hour test period.

[0062] The role and effect of the embodiments

[0063] In this embodiment, the salt-resistant evaporator, which utilizes a dual-scale structure to achieve salt migration and bidirectional water replenishment, maintains communication between micron-level unit cells and millimeter-level channels, effectively ensuring salt migration and water replenishment between the micron-level unit cells and millimeter-level channels.

[0064] The combined effect of the dual-scale frame structure and the hydrophilic photothermal conversion coating of the salt-resistant evaporator creates a concentration gradient and a temperature gradient inside the evaporator, enabling regional concentration and heat management. This triggers Marangoni convection, which spontaneously pumps the salt inside the evaporator into the solution to be evaporated, achieving real-time salt migration.

[0065] The salt-resistant evaporator, which utilizes a dual-scale structure to achieve salt migration and bidirectional water replenishment, enables real-time salt migration through Marangoni convection. This dual-scale structure allows for water replenishment along its length and from millimeter-level channels to micrometer-level single cells.

[0066] In step S11, using a plasma cleaner to remove impurities from the surface of the printed evaporation main frame can enhance the adhesion of the photothermal conversion coating; in step S20, using a plasma cleaner to clean the surface of the hydrophilic photothermal conversion coating can further enhance its hydrophilicity.

[0067] In this embodiment, the hydrophilic photothermal conversion coating maintains strong hydrophilicity, ensuring efficient and rapid water replenishment of the salt-resistant evaporator during operation.

[0068] During operation, the micron-sized unit cells of the salt-resistant evaporator convert light energy into heat energy through a photothermal conversion process, heating the water on the evaporation surface to generate steam, thereby significantly increasing the local salt concentration. Meanwhile, the water in the millimeter-sized channels, being farther from the heat source, is difficult to heat, and therefore its salt concentration remains unchanged. Thus, a temperature and concentration gradient are formed within the salt-resistant evaporator, triggering Marangoni convection. Marangoni convection pumps salt from the high-concentration region (micron-sized unit cells) to the low-concentration region (millimeter-sized channels), ultimately returning it to the solution to be evaporated (achieved through real-time salt migration).

[0069] The photothermal conversion coating of the salt-resistant evaporator in this embodiment is a hydrophilic photothermal conversion coating, which enables the salt-resistant evaporator in this embodiment to have the same vertical water replenishment capability as conventional salt-resistant evaporators. However, the salt-resistant evaporator in this embodiment adopts a two-scale structural design (micron-level unit cells and millimeter-level channels). During operation, both the micron-level unit cells and the millimeter-level channels are filled with water, which opens up a second water replenishment path within the evaporator—horizontal water replenishment from the millimeter-level channels to the micron-level unit cells. Under the combined effect of these two water replenishment paths, the salt-resistant evaporator always maintains efficient and rapid water replenishment, keeping the evaporation interface moist for a long time. Once the evaporator has a salt content, it can be quickly dissolved, which further avoids the problem of salt scale clogging the evaporator.

[0070] As can be seen from <Example 1>, <Example 2> and <Test Example>, the salt-resistant evaporator of this scheme, which utilizes a dual-scale structure to achieve salt migration and bidirectional water replenishment, has good salt migration and bidirectional water replenishment anti-salt evaporation effects.

[0071] Those skilled in the art should understand that this invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to this invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A salt-resistant evaporator utilizing a dual-scale structure to achieve salt migration and bidirectional water replenishment, characterized in that, The salt-resistant evaporator is used to provide 3.417 kg / (m³) of salt water continuously for 120 hours under 1 solar radiation intensity for a 20 wt% brine solution. 2 The steady-state evaporation flux (·h) The salt-resistant evaporator includes an evaporation body frame, millimeter-level channels, and a hydrophilic photothermal conversion coating. The evaporation main frame is a 4mm cylinder, which is composed of an array of 600μm micrometer-sized unit cells connected together. Each pair of micrometer-sized unit cells contains micrometer-sized pores. The millimeter-scale channel passes through the evaporation main frame and is located at the geometric center of the evaporation main frame. The millimeter-scale channel is connected to the micrometer-scale pores enclosing each pair of micrometer-scale unit cells. The cross-section of the millimeter-scale channel is circular and its hydraulic diameter is 1 mm. The hydrophilic photothermal conversion coating is disposed on the outer surface of the evaporation body frame, and the material of the hydrophilic photothermal conversion coating includes hydrophilic multi-walled carbon nanotubes and acrylic resin. The salt-resistant evaporator achieves water replenishment along its length and from the millimeter-level channel to the micrometer-level cell through a dual-scale structure formed by the micrometer-level cell and the millimeter-level channel, and actively triggers Marangoni convection. The interior of the salt-resistant evaporator spontaneously returns salt ions from its interior to the brine through Marangoni convection.

2. A method for preparing a salt-resistant evaporator that utilizes a dual-scale structure to achieve salt migration and bidirectional water replenishment, characterized in that, The method for preparing the salt-resistant evaporator of claim 1, which utilizes a dual-scale structure to achieve salt migration and bidirectional water replenishment, comprises the following steps: S10, Use 3D modeling software to establish a 3D structural model of the evaporation main frame and the millimeter-level channel and perform 3D printing; S20, the hydrophilic photothermal conversion coating is applied to the surface of the evaporator body frame to obtain the salt-resistant evaporator.

3. The method for preparing a salt-resistant evaporator utilizing a dual-scale structure to achieve salt migration and bidirectional water replenishment according to claim 2, characterized in that: in, Between steps S10 and S20, there is also a step S11: using a plasma cleaner to remove impurities from the surface of the printed evaporation body frame. In step S20, after the hydrophilic photothermal conversion coating is applied, the surface of the hydrophilic photothermal conversion coating is cleaned using a plasma cleaning machine.

4. The method for preparing a salt-resistant evaporator utilizing a dual-scale structure to achieve salt migration and bidirectional water replenishment according to claim 2 or 3, characterized in that: in, In step S10, the 3D printing method includes any one of resin-based 3D printing, ceramic-based 3D printing, metal 3D printing, or 3D printing based on surface projection lithography. In step S20, the method for setting the hydrophilic photothermal conversion coating is chemical deposition.

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