Janus structure MXene-PA / MS interface evaporator with middle layer and preparation method and application of Janus structure MXene-PA / MS interface evaporator

Abstract

The invention discloses a Janus structure MXene-PA / MS interface evaporator with a middle layer and a preparation method and application of the Janus structure MXene-PA / MS interface evaporator, and belongs to the technical field of solar-driven interface evaporation seawater desalination and wastewater treatment. The interface evaporator has double-area configuration, the upper portion is a hydrophobic light absorption layer, and the hydrophobic light absorption layer is composed of a hydrophobic modified MXene material and a PA film; the upper part is a hydrophilic layer, the lower part is a hydrophobic modified MXene material, the PA film is positioned between the hydrophilic layer and the hydrophobic modified MXene material, the hydrophilic layer is arranged at the lower part and consists of hydrophilic MS sponge, and the innovative structure is combined with the ultrathin polyamide interlayer, so that the interface stability is remarkably improved, and the interface falling phenomenon of the traditional Janus material in the long-term use process is reduced. In addition, the optimal heat insulation performance of the material is ensured through fine control over the thickness of the hydrophobic layer, and due to the design, the interface evaporator has efficient light absorption, excellent heat management performance and excellent salt tolerance.

Description

Technical Field

[0001] The present invention belongs to the technical field of solar-driven interfacial evaporation for seawater desalination and wastewater treatment, and particularly relates to a Janus structure MXene-PA / MS interfacial evaporator with an intermediate layer, its preparation method and application. Background Art

[0002] Solar seawater desalination technology is an innovative solution to address the shortage of fresh water resources and has received extensive attention due to its environmental friendliness and sustainability. The core of this technology is to develop efficient photothermal conversion materials that can convert solar energy into heat energy for seawater evaporation. However, the high-salt environment poses a severe challenge to the salt tolerance of materials. The salts and ions in seawater may cause corrosion and pollution to the photothermal materials, thereby affecting their performance and service life. Therefore, improving the salt tolerance of materials is the key to the widespread application of solar seawater desalination technology. Among them, Janus structure materials exhibit significant potential due to their unique dual-sided characteristics and interfacial functions. Janus structure materials combine materials with different chemical and physical properties. One side is responsible for efficient photothermal conversion, and the other side has the ability to resist salting out and corrosion, which can effectively address the problem of salt accumulation during the seawater desalination process. Nevertheless, the existing Janus structure materials still face many challenges in practical applications. For example, the interface may fall off during long-term use, and heat dissipation will also lead to a decrease in evaporation efficiency. Therefore, how to precisely control the thickness of the hydrophobic layer is also a difficult problem. Traditional impregnation and pasting process methods are difficult to achieve a balance between material loading and mechanical properties, which directly affects the overall durability and functional performance of the materials.

[0003] Therefore, further improving the comprehensive performance of Janus structure materials, especially in terms of salt tolerance, mechanical stability, thermal management, and photothermal conversion efficiency, is still the key to the practical application of solar seawater desalination technology. Summary of the Invention

[0004] To solve the above technical problems, the present invention proposes a Janus structure MXene-PA / MS interfacial evaporator with an intermediate layer, its preparation method and application. The addition of the intermediate layer effectively separates the different functions of the upper and lower layers, avoids the problem of interface detachment that is extremely likely to occur in traditional single-layer structures, and at the same time greatly reduces heat dissipation, making the evaporator operate efficiently while significantly improving its stability.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] One of the technical solutions of the present invention:

[0007] The present invention provides a Janus-structured MXene-PA / MS interfacial evaporator with an intermediate layer, which has a sandwich structure. The lower layer is a hydrophilic layer, and the upper layer is a hydrophobic modified MXene material (C 18 H 37 -MXene), and the intermediate layer is a polyamide (PA) membrane;

[0008] The hydrophilic layer is composed of a melamine sponge (MS sponge), and the hydrophobic modified MXene material and the polyamide membrane form a hydrophobic light absorption layer.

[0009] In the Janus-structured MXene-PA / MS interfacial evaporator with an intermediate layer of the present invention, the intermediate polyamide membrane is an ultra-thin intermediate layer with a thickness of 3 μm.

[0010] The interfacial evaporator of the present invention has a dual-region configuration. The upper part is a hydrophobic light absorption layer (composed of a hydrophobic modified MXene material and a PA membrane, and the PA membrane is located between the hydrophilic layer and the hydrophobic modified MXene material), and the lower part is a hydrophilic layer composed of a hydrophilic MS sponge. This innovative structure, combined with the ultra-thin polyamide interlayer, significantly improves the interfacial stability, thus alleviating the interfacial peeling phenomenon that occurs in traditional Janus materials during long-term use. In addition, the fine control of the thickness of the hydrophobic light absorption layer (5.54 μm) ensures the best heat insulation performance of the material. This design enables the interfacial evaporator of the present invention to have efficient light absorption, excellent thermal management performance, and excellent salt tolerance.

[0011] The second technical solution of the present invention:

[0012] The present invention also provides a preparation method of the above-mentioned Janus-structured MXene-PA / MS interfacial evaporator with an intermediate layer, which includes the following steps:

[0013] Coat an aqueous solution on the surface of the MS sponge, and then coat an oil-phase solution to form a PA membrane through interfacial polymerization;

[0014] Coat a hydrophobic modified MXene material on the surface of the PA membrane to construct a hydrophobic light absorption layer;

[0015] After completing the construction of the hydrophobic light absorption layer, dry it to obtain the Janus-structured MXene-PA / MS interfacial evaporator with an intermediate layer.

[0016] Furthermore, the temperature of the interfacial polymerization is 70-90 °C, and the time is 50-70 s. Preferably, heat treatment is carried out at 80 °C for 60 s to complete the interfacial polymerization.

[0017] Further, the aqueous solution is an aqueous solution of m-phenylenediamine (MPD) with a concentration of 2 wt%. That is, the solvent of the aqueous solution in the present invention is water, and the solute is m-phenylenediamine. Exemplarily, the preparation method of the MPD aqueous solution with a concentration of 2 wt% is as follows: accurately weigh 2 g of MPD, add it to 98 g of deionized water, stir evenly, transfer the solution to a 100 mL volumetric flask, and make up the volume to the scale line with deionized water to obtain an MPD aqueous solution with a concentration of 2 wt%. MPD is easily oxidized, and the MPD aqueous solution is usually prepared and used immediately.

[0018] Further, the oil-phase solution is a n-hexane solution of trimesoyl chloride (TMC) with a concentration of 0.1 wt%. That is, the solvent in the oil-phase solution of the present invention is n-hexane, and the solute is trimesoyl chloride. Exemplarily, the preparation method of the TMC n-hexane solution with a concentration of 0.1 wt% is as follows: accurately weigh 0.1 g of TMC, add it to 99.9 g of n-hexane, stir until the TMC is completely dissolved, place the solution in an ultrasonic processor, and ultrasonically treat it for 10 - 20 min to obtain a TMC n-hexane solution with a concentration of 0.1 wt%.

[0019] Further, the hydrophobic modified MXene material is obtained by modifying the MXene material with octadecyltrimethoxysilane (OTMS).

[0020] Furthermore, the preparation method of the hydrophobic modified MXene material is as follows: mix the OTMS aqueous solution with the solution containing the MXene material. The volume ratio of the OTMS solution (composed of 0.5 vol% OTMS, 16.58 vol% deionized water, and 82.92 vol% ethanol) to the solution containing the MXene material is 1:20, and treat it at 80 °C for 1 h to obtain the hydrophobic modified MXene material.

[0021] Further, the preparation method of the MXene material is as follows: mix LiF and hydrochloric acid, and magnetically stir to make them react; add Ti3AlC2 powder, and magnetically stir and react under a water bath condition; wash and centrifuge the reaction solution until the pH of the solution is 6 to obtain a multi-layer MXene dispersion; ultrasonically crush the multi-layer MXene dispersion in a nitrogen atmosphere and an ice-water bath to obtain a solution containing exfoliated MXene nanosheets, and after centrifugation, obtain a solution containing the MXene material.

[0022] Furthermore, the preparation method of the MXene material is as follows: dissolve 1 g of LiF in 20 mL of 9 mol L -1In an HCl solution, magnetic stirring was carried out in a Teflon container for 15 min to fully mix and react the two, and then 1 g of Ti3AlC2 powder was slowly added. Magnetic stirring was carried out in a 35 °C water bath for 24 h to obtain a reaction solution, which at this time contained MXene and unetched MAX phase; then the above reaction solution was washed repeatedly with water and centrifuged at a high speed (10,000 r·min -1 ) until the pH = 6 to obtain a multi-layer MXene dispersion (both washing with water and high-speed centrifugation were repeated steps until the pH of the supernatant after centrifugation was 6); the obtained multi-layer MXene dispersion was placed in a nitrogen atmosphere, and then ultrasonic fragmentation treatment was carried out in an ice-water bath for 1 h to obtain a solution containing exfoliated MXene nanosheets; finally, the above solution was centrifuged at 10,000 r·min -1 for 1 h, and the obtained black supernatant was the solution containing the MXene material.

[0023] Furthermore, after coating with the hydrophobic modified MXene material, heat treatment was carried out to obtain the hydrophobic light absorption layer.

[0024] Furthermore, when coating with the hydrophobic modified MXene material, PVA (polyvinyl alcohol) was added to make the PA membrane and the hydrophobic modified MXene material adhere better. Exemplarily, an aqueous PVA solution with a concentration of 5 wt% was prepared, and 0.05 g of the above aqueous PVA solution was used for a cone with a diameter of 2.5 cm to adhere the PA membrane and the hydrophobic modified MXene material. Within this range, the PA membrane and the hydrophobic modified MXene material can adhere better without affecting the effect of the interfacial evaporator.

[0025] Furthermore, the temperature of the heat treatment was 50 - 70 °C, and the time was 25 - 35 min. Preferably, the temperature of the heat treatment was 60 °C and the time was 30 min.

[0026] Technical solution three of the present invention:

[0027] The present invention also provides an application of the above-mentioned Janus structure MXene-PA / MS interfacial evaporator with an intermediate layer in seawater desalination and / or wastewater treatment.

[0028] By adding the aqueous monomer MPD and the oil-phase monomer TMC, a dense intermediate layer (PA membrane) was formed through interfacial polymerization, improving the mechanical stability and durability of the interfacial evaporator. By using the hydrophobic modified MXene material as the photothermal material, the photothermal conversion efficiency and salt tolerance of the interfacial evaporator were enhanced, enabling it to always operate efficiently and stably in the treatment of different concentrations of brine and wastewater containing heavy metals and / or dyes, and producing high-purity fresh water.

[0029] Exemplarily, the wastewater is wastewater containing heavy metals and / or dyes.

[0030] Compared with the prior art, the present invention has the following advantages and technical effects:

[0031] The interfacial evaporator with a Janus structure prepared by the present invention can not only obtain excellent evaporation performance in pure water, but also exhibit good long-term stability in concentrated salt solutions. The interfacial evaporator of the present invention has an evaporation rate of 1.49 kg·m -2 under the illumination condition of 1 kW·m -2 ·h -1 , and the evaporation efficiency reaches 92.8%; even after 10 hours of continuous operation in a 20 wt% NaCl solution, the evaporation rate remains stable at a relatively high level (after running in a 20 wt% NaCl solution for 10 h, the evaporation rate is 1.45 kg·m -2 ·h -1 ).

[0032] The preparation process of the interfacial evaporator of the present invention is simple, the raw materials are cheap and easily available, the evaporation performance is excellent, and it exhibits good stability in high-salt-concentration salt water. This evaporator provides a better solution for applications in complex environments such as seawater desalination, heavy metal wastewater treatment, and organic dye wastewater purification. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings that form a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0034] Figure 1 is the principle of the Janus structure MXene-PA / MS interfacial evaporator with an intermediate layer of the present invention during seawater desalination and / or wastewater treatment;

[0035] Figure 2 is the mass change of C 18 H 37 -MXene / PA / MS in Example 1, MXene / PA / MS in Comparative Example 1, and C 18 H 37 -MXene / MS in Comparative Example 2 during the continuous evaporation of a NaCl solution for ten hours;

[0036] Figure 3 is the thermal conductivity diagram of MS, C 18 H 37 -MXene / PA / MS in Example 1, and C 18 H 37 -MXene / MS in Comparative Example 2;

[0037] Figure 4 is C in Example 1 18 H37 - Evaporation rate of the MXene / PA / MS after 10 cycles;

[0038] Figure 5 Schematic diagram of the structure of the evaporation system self-made for the present invention;

[0039] Figure 6 Absorption spectra of different interfacial evaporators. Detailed implementation manners

[0040] Now, various exemplary implementation manners of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0041] It should be understood that the terms used in the present invention are only for describing specific implementation manners and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0042] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0043] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific implementation manners of the present invention specification, which are obvious to those skilled in the art. Other implementation manners obtained from the present invention specification are obvious to those skilled in the art. The present invention specification and embodiments are only exemplary.

[0044] Regarding the terms "comprising", "including", "having", "containing", etc. used herein, they are all open-ended terms, meaning including but not limited to.

[0045] The embodiments of the present invention provide a Janus-structured MXene-PA / MS interfacial evaporator with an intermediate layer, which has a sandwich structure, with a hydrophilic layer at the lower layer, a hydrophobic modified MXene material at the upper layer, and a polyamide (PA) membrane at the intermediate layer;

[0046] The hydrophilic layer is composed of melamine sponge (MS sponge), and the hydrophobic modified MXene material and the polyamide membrane form a hydrophobic light absorption layer.

[0047] In the Janus structure MXene-PA / MS interfacial evaporator of the present invention with an intermediate layer, the intermediate layer polyamide membrane is an ultra-thin intermediate layer with a thickness of 3 μm.

[0048] The interfacial evaporator of the present invention has a dual-region configuration. The upper hydrophobic light absorption layer is composed of a hydrophobic modified MXene material and a PA membrane, and the lower hydrophilic layer is composed of a hydrophilic MS sponge. This innovative structure, combined with the ultra-thin polyamide interlayer, significantly improves the interfacial stability, thus alleviating the interfacial shedding phenomenon that occurs in traditional Janus materials during long-term use. In addition, the fine control of the thickness (5.54 μm) of the hydrophobic light absorption layer ensures the best heat insulation performance of the material. This design enables the interfacial evaporator of the present invention to have efficient light absorption, excellent thermal management performance, and excellent salt tolerance.

[0049] The embodiment of the present invention also provides a preparation method of the above-mentioned Janus structure MXene-PA / MS interfacial evaporator with an intermediate layer, including the following steps:

[0050] Coat an aqueous solution on the surface of the MS sponge, and then coat an oil phase solution, and form a PA membrane through interfacial polymerization;

[0051] Coat a hydrophobic modified MXene material on the surface of the PA membrane to construct a hydrophobic light absorption layer;

[0052] After completing the construction of the hydrophobic light absorption layer, dry it to obtain the Janus structure MXene-PA / MS interfacial evaporator with an intermediate layer.

[0053] In the present invention, through interfacial polymerization, an ultrathin dense intermediate layer (PA membrane) is constructed on the surface of a hydrophilic macroporous substrate MS sponge, and then a hydrophobic light absorption layer is further constructed on the surface of the intermediate layer, thereby realizing the controllable construction of a hydrophobic layer on the surface of the hydrophilic macroporous substrate. The lower part of the interfacial evaporator of the present invention is a hydrophilic macroporous substrate MS sponge rich in water channels, which can rapidly transfer water molecules while minimizing heat loss to the greatest extent; the upper part is a hydrophobic light absorption layer (composed of a hydrophobic modified MXene material and a PA membrane, with the PA membrane located between the hydrophilic layer and the hydrophobic modified MXene material), which can realize the photothermal conversion to vaporize water molecules. It is worth mentioning that the addition of the ultrathin intermediate layer plays a crucial role. It effectively isolates the different functions of the upper and lower layers, solves the problem of interfacial detachment that is extremely likely to occur in traditional single-layer structures, and at the same time greatly reduces heat dissipation, enabling the interfacial evaporator to have significantly improved stability while operating efficiently. By adopting the ultrathin intermediate layer, the interfacial evaporator of the present invention integrates excellent thermal management, efficient photothermal conversion, and high salt tolerance and other functions, and has the advantages of simple preparation process, low cost, and high controllability of operation, showing great application prospects.

[0054] In the embodiments of the present invention, the temperature of interfacial polymerization is 70 - 90 °C, and the time is 50 - 70 s. Preferably, heat treatment is carried out at 80 °C for 60 s to complete interfacial polymerization.

[0055] In the embodiments of the present invention, the aqueous solution is an aqueous solution of m-phenylenediamine (MPD) with a concentration of 2 wt%. That is, the solvent of the aqueous solution in the present invention is water, and the solute is m-phenylenediamine. Exemplarily, the preparation method of an MPD aqueous solution with a concentration of 2 wt% is as follows: accurately weigh 2 g of MPD, add it to 98 g of deionized water, stir evenly, transfer the solution to a 100 mL volumetric flask, and make up the volume to the scale line with deionized water to obtain an MPD aqueous solution with a concentration of 2 wt%. Since MPD is easily oxidized, the MPD aqueous solution is usually prepared and used immediately.

[0056] In the embodiments of the present invention, the oil phase solution is a n-hexane solution of trimesoyl chloride (TMC) with a concentration of 0.1 wt%. That is, the solvent in the oil phase solution of the present invention is n-hexane, and the solute is trimesoyl chloride. Exemplarily, in the following embodiments of the present invention, the preparation method of a TMC n-hexane solution with a concentration of 0.1 wt% is as follows: accurately weigh 0.1 g of TMC, add it to 99.9 g of n-hexane, stir until the TMC is completely dissolved, place the solution in an ultrasonic processor, and ultrasonically treat it for 15 min to obtain a TMC n-hexane solution with a concentration of 0.1 wt%.

[0057] In an embodiment of the present invention, the hydrophobic modified MXene material is obtained by modifying the MXene material with octadecyltrimethoxysilane (OTMS). In the following embodiments of the present invention, the preparation method of the hydrophobic modified MXene material is as follows: Mix the OTMS aqueous solution with the solution containing the MXene material. The volume ratio of the OTMS solution (composed of 0.5 vol% OTMS, 16.58 vol% deionized water, and 82.92 vol% ethanol) to the solution containing the MXene material is 1:20, and treat at 80 °C for 1 h to obtain the hydrophobic modified MXene material.

[0058] In the present invention, OTMS is used to hydrophobically modify the MXene material, and the hydrophobic angle increases from 50.26° to 111.79°.

[0059] In an embodiment of the present invention, the preparation method of the MXene material is as follows: Dissolve 1 g of LiF in 20 mL of 9 mol·L - 1 HCl solution, magnetically stir in a Teflon container for 15 min to fully mix and react the two, then slowly add 1 g of Ti3AlC2 powder, and magnetically stir in a 35 °C water bath for 24 h to obtain a reaction solution. At this time, the solution contains MXene and the unetched MAX phase; then wash the above reaction solution repeatedly and centrifuge at high speed (10000 r·min -1 ) until the pH = 6 to obtain a multi-layer MXene dispersion (both washing and high-speed centrifugation are repeated steps until the pH of the supernatant after centrifugation is 6); Place the obtained multi-layer MXene dispersion in a nitrogen atmosphere, and then ultrasonically crush it in an ice-water bath for 1 h to obtain a solution containing exfoliated MXene nanosheets; Finally, centrifuge the above solution at 10000 r·min -1 rotation speed for 1 h, and the obtained black supernatant is the solution containing the MXene material.

[0060] In an embodiment of the present invention, after coating the hydrophobic modified MXene material, heat treatment is carried out to obtain a hydrophobic light absorption layer. When coating the hydrophobic modified MXene material, PVA (polyvinyl alcohol) is added to make the PA film and the hydrophobic modified MXene material adhere better. Exemplarily, prepare a 5 wt% PVA aqueous solution, and use 0.05 g of the above PVA aqueous solution for a cone with a diameter of 2.5 cm to adhere the PA film and the hydrophobic modified MXene material. Within this range, the PA film and the hydrophobic modified MXene material can adhere better without affecting the effect of the interfacial evaporator.

[0061] In an embodiment of the present invention, the temperature of the heat treatment is 50 - 70 °C, and the time is 25 - 35 min. Preferably, the temperature of the heat treatment is 60 °C and the time is 30 min.

[0062] The Janus-structured MXene-PA / MS interfacial evaporator with an intermediate layer provided by the embodiments of the present invention can be used for seawater desalination and / or wastewater treatment.

[0063] The principle of the Janus-structured MXene-PA / MS interfacial evaporator with an intermediate layer of the present invention during seawater desalination and / or wastewater treatment is shown in Figure 1 。

[0064] In the present invention, by adding the aqueous monomer MPD and the oil-phase monomer TMC, a dense intermediate layer (PA membrane) is formed through interfacial polymerization, which improves the mechanical stability and durability of the interfacial evaporator. By using a hydrophobic modified MXene material as the photothermal material, the photothermal conversion efficiency and salt tolerance of the interfacial evaporator are enhanced, enabling it to operate efficiently and stably in different concentrations of brine and the treatment of wastewater containing heavy metals and / or dyes, and producing high-purity fresh water.

[0065] Exemplarily, the wastewater is wastewater containing heavy metals and / or dyes.

[0066] The present invention measures the performance of the interfacial evaporator with a self-made evaporation system. The measurement system consists of a xenon light source with a solar filter (AM 1.5), a light power density meter, an infrared camera, a computer, and an analytical balance. The xenon light source is used to simulate solar radiation, the light power density meter measures the illumination intensity of the simulated sunlight, the surface temperature of the evaporator is monitored in real time by the infrared camera, the mass change of water is recorded by the analytical balance and the computer connected thereto, and the illumination intensity is changed by adjusting the distance between the evaporator sample and the xenon lamp to study the photothermal conversion performance of the sample under different illumination intensities. Exemplarily, when the Janus-structured MXene-PA / MS interfacial evaporator with an intermediate layer of the present invention is used for seawater desalination, the application method is: placing the Janus-structured MXene-PA / MS interfacial evaporator with an intermediate layer in seawater and performing seawater desalination under sunlight irradiation. The sunlight irradiation intensity can be 1 - 3 kW·m -2 。

[0067] Exemplarily, when the Janus-structured MXene-PA / MS interfacial evaporator with an intermediate layer of the present invention is used for wastewater treatment, the application method is: placing the Janus-structured MXene-PA / MS interfacial evaporator with an intermediate layer in the wastewater to be treated and performing wastewater treatment under sunlight irradiation. The sunlight irradiation intensity can be 1 - 3 kW·m -2 。

[0068] Exemplarily, the Janus-structured MXene-PA / MS interfacial evaporator with an intermediate layer of the present invention can treat wastewater with a water body salt concentration of 3.5 - 20 wt%.

[0069] In the following examples and comparative examples of the present invention, the calculation method of the evaporation rate is: m = m light -m dark , where m is the evaporation rate (kg·m -2 ·h -1 ), m light is the evaporation rate of the evaporator under light conditions (kg·m -2 ·h -1 ), m dark is the evaporation rate of the evaporator in the dark field after removing the light (kg·m -2 ·h -1 ); the calculation method of the evaporation efficiency (%) is: η = m·H LV / qiC opt ×100%, m is the evaporation rate (kg·m -2 ·h -1 ), q i C opt is the total solar input energy, where qi is the standard solar irradiance (1kW·m -2 ), Copt is the simulated light power density (W·m -2 ), and H LV represents the total enthalpy (J) required to convert liquid water into steam.

[0070] When testing the performance data of the interfacial evaporator of the present invention, an MS sponge without any modification was used as a comparison.

[0071] As an innovative solution to address the shortage of fresh water resources, solar desalination technology has received extensive attention due to its environmental friendliness and sustainability. To improve the evaporation performance, researchers are exploring various photothermal materials to enhance the light absorption capacity and local thermal effect of the evaporator. Such as transition metal sulfides, carbon nanotubes, graphene and its derivatives. However, the high-salt environment poses a severe challenge to the salt tolerance of materials. The salts and ions in seawater may cause corrosion and pollution to the photothermal materials, thereby affecting their performance and service life. Therefore, improving the salt tolerance of materials is the key to the widespread application of solar desalination technology. For a long time, researchers have proposed various solutions to improve the salt tolerance of materials. Among them, Janus structure materials show significant potential due to their unique dual-sided characteristics and interfacial functions. Janus structure materials combine materials with different chemical and physical properties. One side is responsible for efficient photothermal conversion, and the other side has the ability to resist salting out and corrosion, which can effectively address the problem of salt accumulation during the seawater desalination process. Nevertheless, the existing Janus structure materials still face many challenges in practical applications. First of all, the mechanical properties and heat insulation properties of the materials are often insufficient. During long-term use, the interface may fall off, and at the same time, the heat dissipation will also lead to a decrease in evaporation efficiency. Therefore, the lack of mechanical stability and heat insulation has become one of the main problems hindering the widespread application of Janus materials (such as the thermal conductivity of the Janus material disclosed in Maosong Tian et al., Biomass-based solar evaporation: Sustainable solutions for efficient and eco-friendly water supply, 2024 is 0.113W·m -1 ·K -1 ). Secondly, how to precisely control the thickness of the hydrophobic layer is also a difficult problem. Traditional impregnation and pasting process methods are difficult to achieve a balance between the material loading and mechanical properties, which directly affects the overall durability and functional performance of the material. Compared with the general Janus structure, in the present invention, through the introduction of a polyamide (PA) intermediate layer, the loading amount of the photothermal material on the evaporation surface is precisely controlled, the heat management is optimized compared with full impregnation, and at the same time, the problems of easy interface shedding and heat dissipation in the traditional single-layer structure are solved. Therefore, the interfacial evaporator with a Janus structure having an ultra-thin intermediate layer in the present invention not only improves the evaporation performance, but also effectively reduces the accumulation of salt crystallization, thereby ensuring its long-term stable operation in a high-salt concentration environment.

[0072] All raw materials used in the examples and comparative examples of the present invention were obtained through commercial purchases. As an example, the melamine sponge (MS sponge) was purchased from Shenzhen Zhenhua Foam Technology Co., Ltd., and it is a cylindrical sponge with a diameter of 25 mm and a thickness of 10 mm.

[0073] It should be noted that the parts not described in detail in the present invention are all conventional operation means in the art and are not the focus of the present invention. For example, the specific preparation method of the PVA aqueous solution is obtained by a conventional method.

[0074] The technical solution of the present invention will be further described below through examples.

[0075] Example 1

[0076] This example provides a preparation method of a Janus structure MXene-PA / MS interfacial evaporator with an intermediate layer, and the specific steps are as follows:

[0077] S1. Use a cylindrical MS sponge with a diameter of 25 mm and a thickness of 10 mm as the support layer;

[0078] S2. First, coat 10 mL of an aqueous solution of m-phenylenediamine (MPD) with a concentration of 2 wt% on the surface of the MS sponge, and then coat 10 mL of a hexane solution of trimesoyl chloride (TMC) with a concentration of 0.1 wt%. After interfacial polymerization for 2 min, remove the oil-phase solution on the surface, and then place it in an oven for heat treatment at 80 °C for 60 s to form a polyamide (PA) film on the MS surface, with a thickness of 3 μm;

[0079] S3. Modify the MXene material with octadecyltrimethoxysilane (OTMS) to obtain a hydrophobic modified MXene material. Then, bond the hydrophobic modified MXene material to the surface of the formed intermediate layer PA film with PVA and perform heat treatment at 60 °C for 30 min. The preparation method of the MXene material is as follows: Dissolve 1 g of LiF in 20 mL of 9 mol·L -1 HCl solution, magnetically stir in a Teflon container for 15 min to fully mix and react the two, then slowly add 1 g of Ti3AlC2 powder, and magnetically stir in a 35 °C water bath for 24 h to obtain a reaction solution. At this time, the solution contains MXene and the unetched MAX phase; then, wash the above reaction solution repeatedly with water and centrifuge at high speed (10000 r·min -1 ) until the pH = 6 (both washing with water and high-speed centrifugation are repeated steps until the pH of the supernatant after centrifugation is 6) to obtain a multi-layer MXene dispersion; place the obtained multi-layer MXene dispersion in a nitrogen atmosphere, and then perform ultrasonic fragmentation treatment in an ice-water bath for 1 h to obtain a solution containing exfoliated MXene nanosheets; finally, centrifuge the above solution at 10000 r·min -1Centrifuge at a rotational speed for 1 h, and the obtained black supernatant is the solution containing the MXene material; the preparation method of the hydrophobic modified MXene is as follows: mix the OTMS aqueous solution with the solution containing the MXene material, and the volume ratio of the OTMS solution (composed of 0.5 vol% OTMS, 16.58 vol% deionized water and 82.92 vol% ethanol) to the solution containing the MXene material is 1:20, and treat at 80 °C for 1 h to obtain the hydrophobic modified MXene material;

[0080] S4. After the heat treatment, put it into deionized water, and after drying, obtain the Janus structure MXene-PA / MS interfacial evaporator with an intermediate layer, denoted as C 18 H 37 -MXene / PA / MS.

[0081] Perform performance tests on the prepared interfacial evaporator: the solar interfacial evaporation experiment is measured in a self-made evaporation system in the laboratory. The measurement system consists of a xenon light source with a solar filter (AM 1.5), a light power density meter, an infrared camera, a computer, and an analytical balance. Simulate sunlight radiation through the xenon light source, measure the illumination intensity of the simulated sunlight with the light power density meter, monitor the surface temperature of the evaporator in real time through the infrared camera, record the mass change of water by the analytical balance and the computer connected to it, and change the illumination intensity by adjusting the distance between the evaporator sample and the xenon lamp to study the photothermal conversion performance of the sample under different illumination intensities (the structural schematic diagram is as Figure 5 shown). Under the light irradiation intensity of 1 kW·m -2 , the evaporation rate in pure water is 1.49 kg·m -2 ·h -1 , and the evaporation efficiency is 92.8%; when the light irradiation intensities are 1.5, 2, and 3 kW·m -2 respectively, the evaporation rates in pure water are 1.89, 2.35, and 3.32 kg·m -2 ·h -1 respectively, and the evaporation efficiencies are 92.5%, 91.2%, and 90.3%; when the water body salt concentration is 3.5 - 20 wt%, the evaporation rate remains at 1.47 - 1.49 kg·m -2 ·h -1 . The interfacial evaporator of this example also shows excellent effects on the removal of heavy metal ions. The concentrations of heavy metal ions Ni 2+ , Cu 2+ , Zn 2+ , Cd 2+ and Pb 2+ in the original industrial wastewater are as high as about 1601.51 mg·L -1 , 1592 mg·L -1, 1648.18 mg·L -1 , 1836.9 mg·L -1 and 1372.59 mg·L -1 ; under the light irradiation intensity of 1 kW·m -2 , after 3 h of purification by the interfacial evaporator, the ion concentrations in the condensate water are reduced to approximately 0.07 mg·L -1 , 0.15 mg·L -1 , 0.06 mg·L -1 , 0.07 mg·L -1 , 0.13 mg·L -1 , and the condensate water obtained after purification meets the WHO drinking water standard; after operating in a sodium chloride solution with a mass concentration of 20% (20 wt% NaCl solution) for 10 h, the evaporation rate is 1.45 kg·m -2 ·h -1 , and after operating under outdoor natural light conditions for 10 h, the net water production can reach 9 kg·m -2 .

[0082] Comparative Example 1

[0083] This comparative example provides a preparation method of an interfacial evaporator containing an MXene material without hydrophobic modification, and the specific steps are as follows:

[0084] S1. Use a cylindrical MS sponge with a diameter of 25 mm and a thickness of 10 mm as the support layer;

[0085] S2. The same as in Example 1;

[0086] S3. Bond the MXene material on the surface of the formed intermediate layer PA membrane with PVA and heat-treat it at 60 °C for 30 min, where the preparation method of the MXene material is the same as in Example 1;

[0087] S4. The same as in Example 1, and the obtained interfacial evaporator is denoted as MXene / PA / MS.

[0088] Perform performance tests on the prepared interfacial evaporator, and the test method is the same as in Example 1. Under the light irradiation intensity of 1 kW·m -2 , the evaporation rate is 1.46 kg·m -2 ·h -1 , and the evaporation efficiency is 91.13%; after operating in a sodium chloride solution with a mass concentration of 20% for 10 h, the evaporation rate is 0.84 kg·m -2 ·h -1 .

[0089] Combining Example 1 and Comparative Example 1, it can be seen that in the present invention, the hydrophilicity-hydrophobicity of the photothermal conversion material can significantly improve the evaporation performance of the evaporator. This is because the hydrophobic modification of MXene by OTMS makes the C 18 H 37 -MXene surface covered with long-chain alkane groups. These long alkyl chains effectively reduce the light reflection on the surface of the evaporation material, increasing its light absorption rate to 95% in the range of 300 - 1500 nm. And the interlayer spacing of the modified C 18 H 37 -MXene is larger than that of the original MXene, which is beneficial to the capture and utilization of light (as Figure 6 shown). Secondly, in the design of the C 18 H 37 -MXene / PA / MS evaporator, the photothermal material only covers the upper surface of the PA / MS, and below it is a porous MS sponge with a low thermal conductivity, and the pores are filled with air. This structure can effectively block the heat transfer inside the evaporation system during the evaporation process, thereby reducing the heat loss to the underlying bulk water.

[0090] Comparative Example 2

[0091] This comparative example provides a preparation method of an interfacial evaporator without a PA intermediate layer. The specific steps are as follows:

[0092] S1. The same as in Example 1;

[0093] S2. Dropwise coat the hydrophobic MXene material modified with OTMS (the dosage and preparation method of the hydrophobic MXene material modified with OTMS are the same as those in Example 1) on the surface of the MS sponge, and heat-treat it at 60 °C for 30 min;

[0094] S3. The same as S4 in Example 1, and the obtained evaporator is denoted as C 18 H 37 -MXene / MS.

[0095] Perform performance tests on the prepared interfacial evaporator. The test method is the same as in Example 1. Under a light irradiation intensity of 1 kW·m -2 , the evaporation rate is 1.43 kg·m -2 ·h -1 , and the evaporation efficiency is 90.68%; after operating in a sodium chloride solution with a mass concentration of 20% for 10 h, the evaporation rate is 1.45 kg·m -2 ·h -1 .

[0096] Combining Example 1 and Comparative Example 2, it can be seen that in the present invention, the hydrophilicity-hydrophobicity of the intermediate layer and the photothermal conversion material determines the level of evaporation performance. The C 18 H37 - The MXene / MS evaporator, due to the overall loading of hydrophobic photothermal materials, will hinder the water transportation to a certain extent, and at the same time cause heat loss due to direct contact with the water at the lower part of the evaporator; and due to heat loss and heat dispersion in the water at the lower part of the evaporator, the photothermal materials in direct contact with the water cannot provide enough heat to quickly evaporate water molecules, thus limiting the evaporation rate.

[0097] Comparative Example 3

[0098] This comparative example provides a preparation method of an interfacial evaporator without a photothermal conversion material, and the specific steps are as follows:

[0099] S1. The same as in Example 1;

[0100] S2. The same as in Example 1;

[0101] S3. After heat treatment, the evaporator is placed in deionized water, and after drying, an interfacial evaporator with a Janus structure is obtained, denoted as PA / MS.

[0102] The performance of the prepared interfacial evaporator is tested, and the test method is the same as in Example 1. Under a light irradiation intensity of 1 kW·m -2 ², the evaporation rate is 0.73 kg·m -2 ⁻²·h -1 ⁻¹, and the evaporation efficiency is 41.84%; after operating in a sodium chloride solution with a mass concentration of 20% for 10 h, the evaporation rate is 0.51 kg·m -2 ⁻²·h -1 .

[0103] Combining Example 1 and Comparative Example 3, it can be seen that in the present invention, there is an important synergistic effect between the intermediate layer and the photothermal material. The photothermal material can efficiently absorb sunlight and convert it into heat energy. With special optical properties, it has high absorption and low reflection in the solar spectrum range, improving the photothermal conversion efficiency. After absorbing light energy, it quickly heats up, promoting the seawater to quickly reach a relatively high temperature and accelerating evaporation. The existence of the intermediate layer effectively isolates the different functions of the upper and lower layers, avoiding the interfacial peeling problem that is extremely likely to occur in the traditional single-layer structure. At the same time, compared with the fully submerged evaporator, the heat loss is greatly reduced, so that the stability of the evaporator is significantly improved while operating efficiently.

[0104] Taking the interfacial evaporators of Example 1 and Comparative Examples 1-2 as examples, their stability in high-salt-concentration salt water is tested. The specific method is as follows: Under a light intensity of 1 kW·m -2 ², the evaporator operates in a sodium chloride solution with a mass concentration of 20% for 10 h; the results are as Figure 2 shown, and it can be seen that the C 18 H 37-MXene / PA / MS interfacial evaporator exhibits good stability in high-salt-concentration brine.

[0105] C in Example 1 18 H 37 -MXene / PA / MS, MS in Comparative Example 3, and C in Comparative Example 2 18 H 37 The thermal conductivity diagrams of -MXene / MS are as Figure 3 shown, MS, C 18 H 37 -MXene / PA / MS, C 18 H 37 The thermal conductivities of -MXene / MS are approximately 3.52×10 -2 W·m -1 ·K -1 、3.64×10 -2 W·m -1 ·K -1 and 3.89×10 -2 W·m -1 ·K -1 . It is worth noting that although the thermal conductivities of the above evaporators have all reached the standard of efficient heat insulation, the thermal conductivity of C 18 H 37 -MXene / PA / MS is lower than that of C 18 H 37 -MXene / MS, and the actual use effect is better. In the design of the C 18 H 37 -MXene / PA / MS evaporator, the photothermal material only covers the upper surface of PA / MS, and below it is a porous MS sponge with a lower thermal conductivity, and the pores are filled with air. This structure can effectively block the heat transfer inside the evaporation system during the evaporation process, thereby reducing the heat loss to the underlying bulk water and significantly improving the evaporation efficiency. Taking the interfacial evaporator prepared in Example 1 as an example, its cycling performance was tested. The specific method was as follows: under a constant solar irradiance of 1 Kw·m -2 , after 10 consecutive evaporation cycles of 60 minutes each; the results are as Figure 4 shown. It can be seen that after 10 evaporation cycles, the sample did not break or collapse, and the evaporation rate remained basically unchanged.

[0106] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A Janus structure MXene-PA / MS interface evaporator with an intermediate layer, characterized in that: The lower layer is a hydrophilic layer, the upper layer is a hydrophobic modified MXene material, and the middle layer is a polyamide membrane; The hydrophilic layer is composed of melamine sponge, and the hydrophobic modified MXene material and the polyamide film constitute a hydrophobic light absorption layer.

2. A method for preparing a Janus structure MXene-PA / MS interface evaporator with an intermediate layer as claimed in claim 1, characterized in that: The following steps are involved: A water phase solution is coated on the surface of a melamine sponge, and then an oil phase solution is coated to form a polyamide film through interfacial polymerization; Coating a hydrophobic modified MXene material on the surface of the polyamide film to construct a hydrophobic light absorption layer; After the hydrophobic light absorption layer is constructed, it is dried to obtain the Janus structure MXene-PA / MS interface evaporator with an intermediate layer.

3. The preparation method according to claim 2, characterized in that: The aqueous phase solution is a 2 wt % m-phenylenediamine aqueous solution.

4. The preparation method according to claim 2, characterized in that: The oil phase solution is a 0.1 wt % trimesoyl chloride n-hexane solution.

5. The preparation method according to claim 2, characterized in that: The hydrophobically modified MXene material is obtained by modifying the MXene material with octadecyltrimethoxysilane.

6. The preparation method according to claim 5, characterized in that: The preparation method of the MXene material is as follows: LiF and hydrochloric acid are mixed and magnetically stirred to react the two; Ti3AlC2 powder is added and magnetically stirred to react in a water bath; the solution after the reaction is washed with water and centrifuged until the pH of the solution is 6 to obtain a multilayer MXene dispersion; the multilayer MXene dispersion is ultrasonically crushed in a nitrogen atmosphere and an ice-water bath to obtain a solution containing exfoliated MXene nanosheets, and after centrifugation, a solution containing the MXene material is obtained.

7. The preparation method according to claim 2, characterized in that: After coating the hydrophobically modified MXene material, heat treatment is performed to obtain the hydrophobic light absorbing layer.

8. The preparation method according to claim 7, characterized in that: The heat treatment temperature is 50-70°C and the time is 25-35 minutes.

9. The preparation method according to claim 8, characterized in that: The heat treatment temperature is 60° C. and the time is 30 min.

10. Use of the Janus structure MXene-PA / MS interface evaporator with an intermediate layer as claimed in claim 1 in seawater desalination and / or wastewater treatment.

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