Photothermal interface evaporation material with ultra-low evaporation enthalpy and preparation method and application thereof

Abstract

The application provides a photothermal interfacial evaporation material with ultra-low evaporation enthalpy, comprising a porous material (MS), a photothermal material (TM), a polysaccharide compound (S) and a polyvalent metal cation (M n+ ); wherein the photothermal material (TM) is surface-modified by a polyphenol compound (P); the polyphenol compound, the polysaccharide compound and the polyvalent metal cation form a supramolecular network system on the porous material (MS) to form the photothermal interfacial evaporation material with MS@P-TM / S structure. n+ @By adopting the technical scheme of the application, the polyphenol compound-modified photothermal material surface is rich in a large number of phenolic hydroxyl groups, and a supramolecular network structure is formed between the hydroxyl groups of the polysaccharide molecules and the polyvalent metal cations, so that the evaporator has ultra-low evaporation enthalpy and excellent water transport performance, the evaporator can be stably operated in a real environment for a long time, and the service life of the evaporator is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solar photothermal evaporation, in particular to a photothermal interfacial evaporation material with ultra-low evaporation enthalpy and a preparation method and application thereof. BACKGROUND

[0002] Interfacial photothermal evaporation is the most widely studied and most promising solar evaporation system. Influencing factors usually include light absorption, heat management, water transport, and salt resistance. However, the most important factor is that the current interfacial photothermal evaporator is limited by the performance of the material, resulting in a low water evaporation rate (1.5 kg·m -2 ·h -1 ). From the principle of interfacial photothermal evaporation technology, the core is to reduce the heat loss in the evaporation heating process, thereby reducing the evaporation enthalpy and improving the evaporation efficiency. Therefore, the literature (ACS Nano, 2021, 15, 13007-13018) reports that the use of PAN / CuS nanosheets to regulate water evaporation enthalpy can improve the photothermal conversion efficiency; the literature (Adv. Funct. Mater. 2022, 32, 2108586) reports that the CC / PPy needle array system forms microdroplets to reduce the evaporation enthalpy, thereby improving the evaporation rate. However, these materials are limited by the particularity of the material and the complexity of the preparation method and special requirements for equipment, and there are many technical and operational difficulties in promoting their use, resulting in high cost, low efficiency, and difficulty in industrialization for large-scale promotion.

[0003] Chinese invention patent CN114392698A provides a high-stability photothermal hydrogel sponge and a preparation method and application thereof. The invention allows the high-concentration solution to adhere to the sponge surface in the form of a thin layer without blocking the sponge pores after the sponge matrix absorbs the high-concentration solution. Through the subsequent coordination reaction of tannic acid and trivalent iron ions, as well as the hydrogen bond interaction between tannic acid and high molecular compounds, a high-stability thin-layer hydrogel is generated in situ on the sponge surface. The prepared thin-layer hydrogel retains the high porosity of the sponge, which is beneficial to the diffusion and backflow of salt ions, achieving the purpose of continuous and stable treatment of high-concentration brine. The solar-driven interfacial evaporation material prepared by using the photothermal hydrogel sponge processes samples with salt concentrations of 0.8wt%, 3.5wt%, and 10wt%, and the salinity after desalination is significantly reduced. The invention uses hydrogel material as photothermal material, and the hydrogel material has a cross-linked polymer network. Obviously, the patent accelerates the evaporation rate of water by reducing the evaporation enthalpy of water, but the gel adheres to the surface of the photothermal material in the form of a thin layer through hydrogen bond interaction, which cannot achieve long-term operation. SUMMARY

[0004] In view of the above, the purpose of the present application is to provide a photothermal interfacial evaporation material with ultra-low evaporation enthalpy and its preparation method and application, which has the characteristics of ultra-low evaporation enthalpy and high evaporation efficiency, especially the high stability photothermal evaporation function in high salt environment, especially the long-term resistance, realizing the multifunctional integrated photothermal evaporator of seawater desalination, wastewater purification, oil-water emulsion separation, etc.

[0005] In order to achieve the above purpose, the present application provides the following technical scheme.

[0006] The present application provides a photothermal interfacial evaporation material with ultra-low evaporation enthalpy, which comprises a porous material (MS), a photothermal material (TM), a polysaccharide compound (S) and a multivalent metal cation (M n +);Wherein, the photothermal material (TM) is surface modified by a polyphenol compound (P);The polyphenol compound, the polysaccharide compound and the multivalent metal cation form a supramolecular network system coated on the porous material (MS), forming the photothermal interfacial evaporation material with M n+ @MS@P-TM / S structure.

[0007] Preferably, the M n+ @MS@P-TM / S structure comprises loading the polyphenol compound on the porous material, and the porous substrate of MS@P-TM / S structure is formed by compounding the polyphenol compound with the polysaccharide compound, and the porous substrate is crosslinked with the multivalent metal cation.

[0008] Preferably, the polyphenol compound forms a large number of hydrophilic phenolic hydroxyl groups on the surface of the porous material;The polyphenol compound is at least one of dopamine, tannic acid, gallic acid and catechol.

[0009] Preferably, the porous material is at least one of sponge, porous foam, metal foam, fiber and fabric;The photothermal material is at least one of graphene oxide, carbon black, carbon nanotube and copper oxide.

[0010] Preferably, the multivalent metal ion solution is a divalent and multivalent metal cation, including at least one of calcium ion, magnesium ion, zinc ion, copper ion, aluminum ion, iron ion, lanthanum ion and chromium ion solution.

[0011] Preferably, the polysaccharide compound comprises at least one of sodium alginate, chitosan, agarose and cellulose.

[0012] In order to achieve the purpose of the present application, the present application also provides another technical scheme, i.e. the preparation method of the above-mentioned photothermal interfacial evaporation material with ultra-low evaporation enthalpy, comprising the following steps:

[0013] S1. The porous material is cleaned and dried for standby; the cleaning is performed by ultrasonic cleaning with ethanol and water;

[0014] S2. The polyphenol compound is added to the aqueous solution of the photothermal material, and mixed uniformly to obtain a polyphenol compound modified photothermal material mixture;

[0015] S3. The solution of the polysaccharide compound and the polyphenol compound modified photothermal material mixture obtained in S2 are mixed uniformly to form a sol mixture;

[0016] S4. The porous material obtained after S1 treatment is soaked in the sol mixture obtained in S3, the liquid is completely immersed in the porous material by using a defoaming dip coating method, and dried to obtain a sol coated porous substrate with MS@P-TM / S structure;

[0017] S5. The porous substrate obtained in S4 is soaked in a polyvalent metal ion solution for crosslinking to form a photothermal interface evaporation material with MS@P-TM / S structure. n+ @MS@P-TM / S structure.

[0018] The defoaming dip coating method is at least one of vacuum defoaming, ultrasonic defoaming and extrusion defoaming.

[0019] The photothermal interface evaporation material with ultra-low evaporation enthalpy prepared by the above method is used as a photothermal evaporator, the evaporation enthalpy of water in the interior is 600-1100 J / g; the evaporation rate of water in a 3.5wt% sodium chloride solution is ≥3kg·m -2 ·h -1 .

[0020] Invention principle:

[0021] The present application forms a hydrophilic supramolecular network by utilizing the synergistic effect of polyphenol compounds, polysaccharide compounds and polyvalent metal cations through crosslinking, to regulate the cluster morphology between water molecules, form intermediate water that is easy to evaporate, significantly reduce the evaporation enthalpy of water, and increase the evaporation efficiency of photothermal materials.

[0022] Specifically, the application discloses a polyphenol compound modified photothermal material, a large number of hydrophilic phenolic hydroxyl groups are brought to the surface of the photothermal material through the bonding effect of the hydroxyl groups on the surface of the photothermal material and the polyphenol compound, the polyphenol compound can be combined with the hydrophilic functional groups such as hydroxyl groups and carboxyl groups of polysaccharide compounds, a large number of active water is generated through the cross-linking effect between active groups, a hydrophilic supramolecular network is formed, the cluster morphology of water molecules can be effectively regulated, the water molecule cluster becomes smaller, the diffusion capacity is enhanced, the intermediate water which is easy to evaporate is formed, thereby the evaporation enthalpy of water is reduced, the evaporation rate of water is improved, and the purpose of increasing the evaporation efficiency of the photothermal material is achieved. Meanwhile, the polyvalent metal ions are combined with the active groups of the polyphenol compound and the polysaccharide compound through coordination, a polyphenol compound / polysaccharide compound / polyvalent metal cation system is formed, and the system is stably coated on the skeleton of the porous substrate, so that the hydrophilic supramolecular network is formed, the long-term resistance is achieved, and the performance is stable.

[0023] In addition, the polyphenol compound / polysaccharide compound / polyvalent metal cation system also has high adhesion, antibacterial and sterilization functions, and has the synergistic effect of complementary advantages and multifunctional coupling, and finally a photothermal evaporator with super-low evaporation enthalpy, high evaporation rate and excellent long-term environmental resistance is obtained, and the functions of seawater desalination, sewage purification and oil-water emulsion separation are realized.

[0024] 1. By adopting the technical scheme of the application, the polyphenol compound modified photothermal material surface is rich in a large number of phenolic hydroxyl groups and the supramolecular network structure formed between the hydroxyl groups of polysaccharide molecules and polyvalent metal cations, which can effectively regulate the cluster morphology of water molecules, form intermediate water which is easy to evaporate, thereby significantly reduce the evaporation enthalpy of water inside, improve the evaporation efficiency, make the evaporator have super-low evaporation enthalpy and excellent water transport performance, ensure that the evaporator can be stably operated in the real environment for a long time, and improve the service life of the evaporator.

[0025] 2. By adopting the technical scheme of the application, the polyphenol compound modified photothermal material has good dispersibility, excellent photothermal performance and the convenience of operation under liquid phase conditions; meanwhile, the polyphenol compound / polysaccharide compound / polyvalent metal cation has good antibacterial performance, and the complementary advantages and multifunctional coupling are realized, and finally a high-stability photothermal evaporator with super-low evaporation enthalpy, high evaporation rate and long-term salt crystallization resistance is obtained, and the functions of seawater desalination, wastewater purification and oil-water emulsion separation are realized.

[0026] 3. The porous material selected in the application includes a fabric or a sponge and other materials with high porosity, strong capillary action, fast water transport performance, which is beneficial to the diffusion of salt ions, ensures that the salt concentration inside the evaporator is always lower than the saturation value to prevent the precipitation of salt to hinder the operation of the evaporator, the water vapor overflow rate is fast, which is beneficial to the flow of high-concentration salt solution to speed up the evaporation rate, and the purpose of high-speed, continuous and stable high-concentration salt water treatment is realized. Attached Figure Description

[0027] Figure 1 Schematic diagram showing the relationship between different sodium alginate contents, evaporation efficiency, and enthalpy of evaporation in Examples 1 and 7-9 of this invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0029] This invention provides a method for preparing a photothermal interface evaporation material with ultra-low enthalpy of evaporation, comprising the following steps:

[0030] (1) Clean the porous material with ethanol and water using ultrasonic cleaning, and dry it for later use; the porous material is at least one of sponge, porous foam, metal foam, fiber, and fabric;

[0031] (2) Add the polyphenol compound to a 0.5-4.0 mg / mL aqueous solution of the photothermal material and mix thoroughly to obtain a polyphenol compound-modified photothermal material mixture; wherein the amount of polyphenol compound added is 50-400 wt% of the photothermal material;

[0032] Furthermore, the photothermal material is at least one of graphene oxide, carbon black, carbon nanotubes, copper oxide, etc.; the surface of the photothermal material is rich in a large number of hydroxyl active groups, which can undergo bonding reactions with other hydroxyl, carboxyl and other groups, thereby adhering to the surface of the photothermal material and forming a photothermal material with a modifying effect.

[0033] Furthermore, the polyphenolic compound is at least one of dopamine, tannic acid, gallic acid, and catechol.

[0034] (3) Mix the 0.5-4.0 wt% polysaccharide compound solution and the polyphenol compound modified photothermal material mixture from step (2) evenly to form a sol.

[0035] The polysaccharide compound is at least one of sodium alginate, chitosan, agarose, cellulose, etc.

[0036] (4) Immerse the porous substrate in step (1) in the sol mixture in step (3), and use a degassing dip coating method to completely immerse the liquid in the porous substrate, and dry to obtain a sol-coated porous substrate with MS@P-TM / S structure.

[0037] Specifically, the defoaming dip coating method is at least one of vacuum defoaming, ultrasonic defoaming, and extrusion defoaming.

[0038] (5) The porous substrate coated with the sol in step (4) is immersed in a solution of polyvalent metal ions to crosslink, forming a photothermal interfacial evaporation material with ultra-low evaporation enthalpy.

[0039] Specifically, the solution of polyvalent metal ions is at least one of divalent and divalent or higher metal cations, such as calcium ions, magnesium ions, zinc ions, copper ions, aluminum ions, iron ions, lanthanum ions, and chromium ions.

[0040] The polyvalent metal ions interact with active groups such as hydroxyl groups, carboxyl groups, and the like in the polyphenol compounds and polysaccharide compounds in the porous substrate through coordination, forming a supramolecular network system between the polyphenol compounds, polysaccharide compounds, and polyvalent metal cations, which is coated on the porous material to form a M n+ @MS@P-TM / S structure, a photothermal interfacial evaporation material with ultra-low evaporation enthalpy.

[0041] The technical solutions of the present application are further analyzed through specific examples below.

[0042] Example 1

[0043] The present embodiment provides a preparation method of a photothermal interfacial evaporation material with ultra-low evaporation enthalpy, wherein graphene oxide (GO) is used as a photothermal material, and the method specifically comprises the following steps:

[0044] (1) 400 mg of tannic acid (TA) is added to 50 mL of 2 mg / mL graphene oxide (GO) suspension, the pH is adjusted to 8.5 by adding trimethylol aminomethane (Tris), and the mixture is uniformly dispersed by ultrasonic dispersion and stirred for 24 h to form a mixed solution A; the graphene oxide surface in the mixed solution is attached with a large number of active groups;

[0045] (2) Sodium alginate (SA) is dissolved in deionized water at 80°C to form a 4 wt% (m / v) sodium alginate (SA) solution, denoted as solution B;

[0046] (3) Equal volumes of A and B are mixed uniformly by vigorous stirring for 12 h to form a mixed solution C; the sodium alginate reacts with the active groups on the surface of the graphene oxide;

[0047] (4) The cleaned and dried melamine sponge (MS) is immersed in the mixed solution C and defoamed by vacuum defoaming to obtain a porous substrate with an MS@TA-GO / SA structure;

[0048] (4) The cleaned and dried melamine sponge (MS) is immersed in the mixed solution C and defoamed by vacuum defoaming to obtain a porous substrate with an MS@TA-GO / SA structure;

[0049] (5) The completely infiltrated sponge was taken out, dried at 80℃, and then placed in a 5wt% CaCl2 solution for cross-linking reaction. After 6h, it was taken out and purified with deionized water to remove free tannic acid (TA) and CaCl2, obtaining Ca 2+ @MS@TA-GO / SA photothermal evaporation material.

[0050] In this embodiment, Ca 2+ The evaporation enthalpy of water in the @MS@TA-GO / SA photothermal evaporator is 610J / g, which is much lower than the evaporation enthalpy of pure water, which is 2400J / g.

[0051] When a 3.5wt% sodium chloride solution is used as simulated seawater, its evaporation rate can reach 3.19kg·m -2 ·h -1 After evaporation, the sodium chloride content in the collected condensed water is <1mg·mL -1 , and under the irradiation of a xenon lamp simulating sunlight for 36h, the radiation power is 1kw·m -2 , and no salt crystals appear, which represents excellent anti-salt crystallization performance.

[0052] After evaporation of simulated wastewater represented by 10mg / L methyl orange and methylene blue, the removal rate of the two dyes in the collected condensed water is more than 98%.

[0053] After evaporation of a silicon oil water emulsion with an oil content of 10000ppm, the removal rate of silicon oil in the collected condensed water is more than 98%.

[0054] Embodiment 2

[0055] The embodiment provides a preparation method of a photothermal interface evaporation material with ultra-low evaporation enthalpy, comprising the following steps:

[0056] (1) 400mg of dopamine hydrochloride (DA) was added to 50mL of 2mg / mL graphene oxide (GO) suspension, the pH was adjusted to 8.5 by adding tris, and the mixture was uniformly dispersed by ultrasonic dispersion and stirred for 24h to form a mixed solution A;

[0057] (2) Sodium alginate (SA) was dissolved in deionized water at 80℃ to form a 2wt% (m / v) SA solution, denoted as solution B.

[0058] (3) Equal volumes of A and B were mixed uniformly by vigorous stirring for 12h to form a mixed solution C.

[0059] (4) The melamine sponge (MS) cleaned by ultrasonic washing with ethanol and water and dried was soaked in the mixed solution C and deaerated by vacuum deaeration to obtain a porous substrate with the structure of MS@PDA-GO / SA;

[0060] (5) The completely infiltrated sponge was taken out, dried at 80℃, and then crosslinked in a 5wt% CaCl2 solution for 6h. The free PDA and CaCl2 were removed by deionized water purification to obtain Ca 2+ The PDA-GO / SA material was used as a photothermal evaporation material.

[0061] In this embodiment, the prepared Ca 2+ The PDA-GO / SA material was used as a photothermal evaporation material, and the water evaporation enthalpy was 1080J / g, which was much lower than the water evaporation enthalpy of 2400J / g.

[0062] When the evaporation rate of the PDA-GO / SA material was measured in a 3.5wt% NaCl solution as simulated seawater, the evaporation rate reached 3.23kg·m -2 ·h -1 The NaCl content in the collected condensed water after evaporation was <1mg·mL -1 , and no salt crystals appeared under xenon lamp simulated sunlight for 36h, which showed excellent anti-salt crystallization performance.

[0063] The removal rate of the two dyes in the collected condensed water after evaporation of the simulated wastewater represented by 10mg / L methyl orange and methylene blue was more than 98%.

[0064] The removal rate of the two dyes in the collected condensed water after evaporation of the simulated wastewater represented by 10mg / L methyl orange and methylene blue was more than 98%.

[0065] Example 3

[0066] The present embodiment provides a preparation method of a photothermal interfacial evaporation material with ultra-low evaporation enthalpy, comprising the following steps:

[0067] (1) 200mg of dopamine hydrochloride (DA) was added to 50mL of 2mg / mL carbon black (CB) suspension, and the pH was adjusted to 8.5 by adding Tris. The mixture was uniformly dispersed by ultrasonic treatment and stirred for 24h to form a mixed solution A;

[0068] (2) Sodium alginate (SA) was dissolved in deionized water at 80℃ to form a 4wt% (m / v) SA solution, denoted as solution B;

[0069] (3) Equal volumes of A and B were mixed uniformly by vigorous stirring for 12h to form a mixed solution C.

[0070] (4) The melamine sponge (MS) cleaned by ultrasonic treatment with ethanol and water and dried was soaked in the mixed solution C and degassed by vacuum.

[0071] (5) The completely infiltrated sponge was taken out, dried at 80°C, and then placed in a 5wt% CuCl2 solution for crosslinking for 6h. After taking out, the free PDA and CuCl2 were removed by deionized water purification to obtain Cu 2+ @MS@PDA-CB / SA photothermal evaporative material.

[0072] In this embodiment, the Cu 2+ @MS@PDA-CB / SA photothermal evaporator. The evaporation enthalpy of water in the photothermal evaporator is 805J / g, which is much lower than the evaporation enthalpy of pure water, which is 2400J / g. When a 3.5wt% sodium chloride solution is used as a simulated seawater, the evaporation rate can reach 3.13kg·m -2 ·h -1 After evaporation, the sodium chloride content in the collected condensed water is <1mg·mL -1 , and under simulated sunlight irradiation for 36h, no salt crystallization occurs, which represents excellent anti-salt crystallization performance.

[0073] After evaporation of the simulated wastewater represented by 10mg / L methyl orange and methylene blue, the removal rate of the two dyes in the collected condensed water is more than 98%.

[0074] After evaporation of the silicon oil water emulsion with an oil content of 10000ppm, the removal rate of silicon oil in the collected condensed water is more than 98%.

[0075] Example 4

[0076] The embodiment provides a preparation method of a photothermal interfacial evaporation material with ultra-low evaporation enthalpy, which comprises the following steps:

[0077] (1) 200mg of dopamine hydrochloride (DA) was added to 50mL of 2mg / mL carbon nanotube (CNTs) suspension, and the pH was adjusted to 8.5 by adding Tris. After ultrasonic dispersion, the mixture was stirred for 24h to form a mixed solution A.

[0078] (2) Chitosan (CS) was dissolved in deionized water at 80°C to form a 4wt%(m / v) CS solution, which was denoted as solution B.

[0079] (3) Equal volumes of A and B were mixed uniformly by vigorous stirring for 12h to form a mixed solution C.

[0080] (4) Melamine sponge (MS) cleaned by ultrasonic washing with ethanol and water and dried was soaked in the mixed solution C and then deaerated by ultrasonic. The completely infiltrated sponge was taken out, dried at 80°C, and then placed in a 5wt% FeCl3 solution for crosslinking for 6h. After taking out, the free PDA and FeCl3 were removed by deionized water purification to obtain Fe 3+ @MS@PDA-CNTs / CS photothermal evaporator.

[0081] In this embodiment, Fe 3+ The evaporation enthalpy of water in the MS@PDA-CNTs / CS photothermal evaporator is 1081 J / g, which is much lower than the evaporation enthalpy of pure water, which is 2400 J / g.

[0082] When the evaporation rate of the MS@PDA-CNTs / CS photothermal evaporator can reach 3.09 kg·m -2 ·h -1 , the sodium chloride content in the collected condensed water after evaporation is <1 mg·mL -1 , and no salt crystals appear under simulated sunlight for 36 h, which represents excellent anti-salt crystallization performance.

[0083] After evaporation of the simulated wastewater represented by 10 mg / L of methyl orange and methylene blue, the removal rate of the two dyes in the collected condensed water is more than 98%.

[0084] After evaporation of the silicon oil water emulsion containing 10000 ppm of silicon oil, the removal rate of silicon oil in the collected condensed water is more than 98%.

[0085] Example 5

[0086] The embodiment provides a preparation method of a photothermal interface evaporation material with ultra-low evaporation enthalpy, comprising the following steps:

[0087] (1) 200 mg gallic acid (GA) is added to 50 mL of 2 mg / mL carbon nanotube (CNTs) suspension, the pH is adjusted to 8.5 by adding trimethylol aminomethane (Tris), and the mixture is uniformly dispersed by ultrasonic dispersion and stirred for 24 h to form a mixed solution A;

[0088] (2) 7 g of NaOH and 12 g of urea are dissolved in 81 g of the mixed solution A to form a mixed solution B.

[0089] (3) Cellulose powder is dissolved in the mixed solution B at -15°C to form a 4 wt% (m / v) cellulose solution, which is denoted as a mixed solution C.

[0090] (4) Melamine sponge (MS) cleaned by ultrasonic washing with ethanol and water and dried is soaked in the mixed solution C and defoamed by extrusion.

[0091] (5) The completely soaked sponge is taken out, dried at 80°C, and then crosslinked in a 5 wt% FeCl3 solution for 6 h. After that, the sponge is taken out and purified with deionized water to remove free PDA and FeCl3, and a Fe 3+ @MS@GA-CNTs / cellulose photothermal evaporator is obtained.

[0092] Fe 3+ @MS@GA-CNTs / cellulose light-thermal evaporator, the evaporation enthalpy of water is 1103J / g, which is much lower than the evaporation enthalpy of pure water, which is 2400J / g.

[0093] When the evaporation rate of 3.5wt% sodium chloride solution as simulated seawater can reach 3.26kg·m -2 ·h -1 , and after evaporation, the sodium chloride content in the collected condensed water is <1mg·mL -1 , and under simulated sunlight for 36h, no salt crystallization occurs, which represents excellent anti-salt crystallization performance.

[0094] After evaporation of the simulated wastewater represented by 10mg / L of methyl orange and methylene blue, the removal rate of the two dyes in the collected condensed water is more than 98%.

[0095] After evaporation of the silicon oil water emulsion containing 10000ppm of silicon oil, the removal rate of silicon oil in the collected condensed water is more than 98%.

[0096] Example 6

[0097] The present embodiment provides a preparation method of a light-thermal interface evaporation material with ultra-low evaporation enthalpy, comprising the following steps:

[0098] (1) 200mg gallic acid (GA) was added to 50mL of 2mg / mL carbon black (CB) suspension, the pH was adjusted to 8.5 by tris, and the mixture was uniformly dispersed by ultrasonic, and stirred for 24h to form a mixed solution A;

[0099] (2) Chitosan (CS) was dissolved in deionized water at 80℃ to form a 4wt% (m / v) CS solution, denoted as solution B.

[0100] (3) Equal volume of A and B was mixed uniformly by vigorous stirring for 12h to form a mixed solution C.

[0101] (4) Melamine sponge (MS) cleaned by ultrasonic with ethanol and water and dried was soaked in mixed solution C and defoamed by ultrasonic, then the completely soaked sponge was taken out and dried at 80℃, then crosslinked in 5wt% FeCl3 solution for 6h, then purified with deionized water to remove free GA and FeCl3, to obtain Fe 3+ @MS@GA-CB / CS light-thermal evaporator.

[0102] The present embodiment, Fe 3+ @MS@GA-CB / CS light-thermal evaporator, the evaporation enthalpy of water is 1006J / g, which is much lower than the evaporation enthalpy of pure water, which is 2400J / g.

[0103] When a 3.5 wt% sodium chloride solution is used as a simulated seawater, its evaporation rate can reach 3.13 kg·m³. -2 ·h -1 The sodium chloride content in the condensate collected after evaporation is <1 mg / mL. -1 Furthermore, after being exposed to simulated sunlight for 36 hours, no salt crystals appeared, demonstrating excellent resistance to salt crystallization.

[0104] The removal rate of the two dyes in the condensate collected after evaporation of simulated wastewater, represented by methyl orange and methylene blue at a concentration of 10 mg / L, exceeded 98%.

[0105] The removal rate of silicone oil in the condensate collected after evaporation of a silicone oil water emulsion with an oil content of 10,000 ppm exceeded 98%.

[0106] Example 7

[0107] The only difference between this embodiment and embodiment 1 is that in step (2), sodium alginate (SA) is dissolved in deionized water at 80°C to form a 2wt% (m / v) sodium alginate (SA) solution, denoted as solution B. All other steps are the same.

[0108] In this embodiment, the prepared Ca 2+ The enthalpy of evaporation of water in the @MS@TA-GO / SA photothermal evaporator is 1080 J / g, which is much lower than the enthalpy of evaporation of pure water, which is 2400 J / g.

[0109] When a 3.5 wt% sodium chloride solution is used as a simulated seawater, its evaporation rate can reach 3.20 kg·m³. -2 ·h -1 The sodium chloride content in the condensate collected after evaporation is <1 mg / mL. -1 Furthermore, xenon lamps were used to simulate sunlight exposure for 36 hours, with a radiation power of 1 kW·m². -2 No salt crystals were observed, demonstrating excellent resistance to salt crystallization.

[0110] Example 8

[0111] The only difference between this embodiment and embodiment 1 is that in step (2), sodium alginate (SA) is dissolved in deionized water at 80°C to form a 1wt% (m / v) sodium alginate (SA) solution, denoted as solution B. All other steps are the same.

[0112] In this embodiment, the prepared Ca 2+ The enthalpy of evaporation of water in the @MS@TA-GO / SA photothermal evaporator is 1910 J / g, which is much lower than the enthalpy of evaporation of pure water, which is 2400 J / g.

[0113] When a 3.5 wt% sodium chloride solution is used as a simulated seawater, its evaporation rate can reach 2.67 kg·m³. -2 ·h -1 The sodium chloride content in the condensate collected after evaporation is <1 mg / mL. -1 Furthermore, xenon lamps were used to simulate sunlight exposure for 36 hours, with a radiation power of 1 kW·m². -2 No salt crystals were observed, demonstrating excellent resistance to salt crystallization.

[0114] Example 9

[0115] The only difference between this embodiment and embodiment 1 is that in step (2), sodium alginate (SA) is dissolved in deionized water at 80°C to form a 0.5 wt% (m / v) sodium alginate (SA) solution, which is denoted as solution B. All other steps are the same.

[0116] In this embodiment, the prepared Ca 2+ The enthalpy of evaporation of water in the @MS@TA-GO / SA photothermal evaporator is 1370 J / g, which is much lower than the enthalpy of evaporation of pure water, which is 2400 J / g.

[0117] When a 3.5 wt% sodium chloride solution is used as a simulated seawater, its evaporation rate can reach 2.19 kg·m³. -2 ·h -1 The sodium chloride content in the condensate collected after evaporation is <1 mg / mL. -1 Furthermore, xenon lamps were used to simulate sunlight exposure for 36 hours, with a radiation power of 1 kW·m². -2 No salt crystals were observed, demonstrating excellent resistance to salt crystallization.

[0118] Compare with Example 1

[0119] The only difference between this comparative example and Example 3 is that PDA was not used to modify carbon black (CB) nanoparticles, and the resulting photothermal evaporation material has a Cu structure. 2+ @MS@CB / SA.

[0120] The mixture A prepared in step (1) is very unstable, and the CB nanoparticles agglomerate and settle.

[0121] Cu prepared using this comparative example 2+ The @MS@CB / SA is used as a photothermal evaporator, in which the enthalpy of water vaporization is 1800 J / g, indicating that the presence of PDA helps to reduce the enthalpy of water vaporization.

[0122] When a 3.5 wt% sodium chloride solution is used as a simulated seawater, its evaporation rate can reach 2.5 kg·m³. -2 ·h -1 The sodium chloride content in the condensate collected after evaporation is <1 mg / mL. -1, and no salt crystallization appeared after irradiation under simulated sunlight for 36 h, which represented excellent anti-salt crystallization performance.

[0123] The removal rate of two dyes in the collected condensate water was 90% after evaporation of simulated wastewater represented by 10 mg / L of methyl orange and methylene blue.

[0124] The removal rate of silicone oil in the collected condensate water was 90% after evaporation of silicone oil water emulsion with an oil content of 10000 ppm.

[0125] Comparative Example 2

[0126] The difference between this comparative example and Example 3 is that sodium alginate (SA) and metal ions are not used, and a photothermal evaporation material with a MS@PDA-CB structure is prepared. Only a small amount of CB nanoparticles is coated on the sponge in the photothermal evaporation material, because PDA has certain adhesion to attach it to the sponge.

[0127] The MS@PDA-CB prepared in this comparative example is used as a photothermal evaporator, and the evaporation enthalpy of water is 2200 J / g.

[0128] When a 3.5 wt% sodium chloride solution is used as simulated seawater, the evaporation rate can reach 1.2 kg·m -2 ·h -1 , because the coated photothermal material is less, the absorbed light energy is less, and the evaporation rate is low. The sodium chloride content in the collected condensate water after evaporation is <1 mg·mL -1 , and NaCl is deposited on the surface of the evaporator after irradiation under simulated sunlight for 36 h, because the capillary action of melamine sponge (MS) is weak, and NaCl in the evaporator cannot be dissolved in time, resulting in salt precipitation.

[0129] The removal rate of two dyes in the collected condensate water was 90% after evaporation of simulated wastewater represented by 10 mg / L of methyl orange and methylene blue; the removal rate of silicone oil in the collected condensate water was more than 92% after evaporation of silicone oil water emulsion with an oil content of 10000 ppm.

[0130] Comparative Example 3

[0131] The difference between this comparative example and Example 3 is that sodium alginate (SA) is not added, and a photothermal evaporation material with a Cu 2+ @MS@PDA-CB structure is prepared. Only a small amount of CB nanoparticles is coated on the sponge in the photothermal evaporation material, because PDA has certain adhesion to attach it to the sponge.

[0132] The Cu 2+MS@PDA-CB as a photothermal evaporator, wherein the water evaporation enthalpy is 2185 J / g.

[0133] When the 3.5wt% sodium chloride solution is used as simulated seawater, the evaporation rate can reach 1.45kg·m -2 ·h -1 This is because the coated photothermal material is less, the absorbed light energy is less, the evaporation rate is low, and the sodium chloride content in the collected condensed water after evaporation is <1mg·mL -1 After 36h of simulated sunlight irradiation, NaCl is deposited on the surface of the evaporator, because the capillary action of melamine sponge (MS) is weak, which cannot dissolve NaCl in the evaporator in time, resulting in salt precipitation.

[0134] After evaporation of the simulated wastewater represented by 10mg / L of methyl orange and methylene blue, the removal rate of the two dyes in the collected condensed water is 92%; after evaporation of the silicon oil water emulsion containing 10000ppm of silicon oil, the removal rate of silicon oil in the collected condensed water is more than 94%.

[0135] Referring to Figure 1 The figure shows the relationship between the different contents of sodium alginate in examples 1 and 7-9 of the present application and the evaporation efficiency and evaporation enthalpy, wherein the column chart is the evaporation rate and the line chart is the evaporation enthalpy.

[0136] As can be seen from the figure, when the concentration of sodium alginate is from 0.5 to 4wt%, the evaporation rate increases significantly, and when the concentration changes from 2wt% to 4wt%, the evaporation rate does not change significantly; while the evaporation enthalpy decreases significantly. Obviously, in the above examples, the influence of 2-4wt% is more obvious.

[0137] Based on the above example results, the addition amount of sodium alginate has a significant influence on the performance of the photothermal evaporator.

[0138] Further, the results of examples 1-9 and control examples 1-3 are further analyzed as follows:

[0139] First, under the condition that the photothermal material is not surface modified, the photothermal material mixed solution prepared by the method of the present application has poor dispersibility and occurs agglomeration and sedimentation, which causes the photothermal material to not be able to fully bond with the active groups on the surface of the polysaccharide compound, so that the structural stability of the photothermal evaporator is slightly poor.

[0140] Second, after the photothermal material is only modified by the polyphenol compound and then used as a photothermal evaporator to treat a salt water solution, the water evaporation enthalpy is slightly reduced, which indicates that the presence of PDA helps to reduce the water evaporation enthalpy, and the reason is that the PDA contains a large amount of -OH and -NH2 to produce hydrogen bonding, but the effect of pure hydrogen bonding is relatively weak, and the promotion effect on the evaporation of water molecules is not large. Therefore, the decrease of the water evaporation enthalpy is not obvious.

[0141] Third, without using polysaccharide compounds, directly applying polyvalent metal cations to the surface of polyphenol compounds through coordination reaction can further increase the stability of the modified layer, and it also has a certain reducing effect on the evaporation enthalpy of water, but it is not obvious.

[0142] In summary, through the technical solutions of the embodiments, it can be speculated that there is a synergistic effect in the polyphenol compound / polysaccharide compound / multivalent metal cation system used in the application.

[0143] The polyphenol compound modifies the photothermal material, and the hydroxyl groups on the surface of the photothermal material are attached to the surface of the photothermal material through the action of the polyphenol compound and the bonding effect. A large number of hydrophilic phenolic hydroxyl groups are present on the surface of the photothermal material, which can combine with the hydrophilic functional groups such as hydroxyl groups and carboxyl groups of polysaccharide compounds. The cross-linking action between active groups produces a large amount of active water, forms a hydrophilic supramolecular network, effectively regulates the cluster morphology of water molecules, and the water molecule cluster becomes smaller, the diffusion ability is enhanced, and the intermediate water that is easy to evaporate is formed, thereby achieving the purpose of reducing the evaporation enthalpy of water and increasing the evaporation rate of water.

[0144] At the same time, the polyphenol compound, the polysaccharide compound, and the multivalent cation are attached to the surface of the porous material through chemical bonding effect, which can improve the stability of the photothermal evaporation material, improve its long-term resistance in high-salt environment. At the same time, it can also be compatible with the advantages of polyphenol compound / polysaccharide compound / multivalent metal cation, provide the function of seawater desalination, sewage purification, and oil-water emulsion separation for the photothermal evaporation material, realize the multifunctional integration of the photothermal interface evaporation material with ultra-low evaporation enthalpy, and provide a more efficient path for seawater desalination technology.

[0145] The above is only a preferred embodiment of the present application, and does not limit the protection scope of the present application. For those skilled in the art, the present application can have various changes and variations. Any changes, modifications, replacements, integrations, and parameter changes to these embodiments within the spirit and principles of the present application, which can realize the same function without departing from the principles and spirit of the present application, fall within the protection scope of the present application.

Claims

1. A photothermal interface evaporation material having an ultra-low evaporation enthalpy, characterized in that, comprising a porous material MS, a photothermal material TM, a polysaccharide compound S and a polyvalent metal cation M n+ ; The photothermal material TM is surface-modified by a polyphenol compound P. The supramolecular network system formed between the polyphenol compound, the polysaccharide compound and the polyvalent metal cation is coated on the porous material MS to form a M n+ @MS@P-TM / S structure of the photo-thermal interface evaporation material; The M n+ The MS@P-TM / S structure comprises loading the polyphenol compound on the porous material, and the porous substrate compounded with the polysaccharide compound to form the MS@P-TM / S structure, and the porous substrate is crosslinked with the polyvalent metal cation. The polysaccharide compound includes at least one of sodium alginate, chitosan, agarose, and cellulose. The polyphenol compound forms a large number of hydrophilic phenolic hydroxyl groups on the surface of the porous material; the polyphenol compound is at least one of dopamine, tannic acid, gallic acid, and catechol. The photothermal material is at least one of graphene oxide, carbon black, carbon nanotube, and copper oxide. The polyvalent metal cation M n+ is a divalent and higher valent metal cation, including at least one of calcium ion, magnesium ion, zinc ion, copper ion, aluminum ion, iron ion, lanthanum ion, and chromium ion.

2. The photothermal interface evaporation material with ultra-low evaporation enthalpy of claim 1, wherein, The porous material is at least one of sponge, porous foam, metal foam, fiber, and fabric.

3. A method of preparing a photothermal interface evaporation material having an ultra-low evaporation enthalpy according to any one of claims 1-2, characterized in that, The method comprises the following steps: S1. The porous material is cleaned and dried for standby; S2. The polyphenol compound is added to an aqueous solution of the photothermal material and mixed uniformly to obtain a polyphenol compound-modified photothermal material mixture; S3. The polysaccharide compound solution and the polyphenol compound-modified photothermal material mixture obtained in S2 are mixed uniformly to form a sol mixture; S4. The porous material obtained in S1 is soaked in the sol mixture obtained in S3, the liquid is completely immersed in the porous material by a defoaming dip-coating method, and then dried to obtain a sol-coated porous substrate with an MS@P-TM / S structure; S5. The porous substrate obtained in S4 is soaked in a solution of polyvalent metal cations for crosslinking to form a photothermal interfacial evaporation material with ultra-low evaporation enthalpy.

4. The method of claim 3, wherein the photothermal interface evaporation material having an ultra-low evaporation enthalpy is prepared by, The defoaming dip-coating method is at least one of vacuum defoaming, ultrasonic defoaming, and extrusion defoaming.

5. A photothermal evaporator using the photothermal interfacial evaporative material with ultra-low evaporation enthalpy according to any one of claims 1-2 or the photothermal evaporative material prepared according to the preparation method of claims 3 or 4, wherein the evaporation enthalpy of water in the photothermal evaporator is 600-1100 J / g; the evaporation rate of water in a 3.5 wt% sodium chloride solution is ≥ 3 kg·m -2 ·h -1 .

6. Use of the photothermal interfacial evaporation material with ultra-low evaporation enthalpy according to any one of claims 1-2 as a solar photothermal evaporation material, a photothermal seawater desalination material, a high-concentration seawater desalination material, a sewage purification treatment material, and / or an oil-water emulsion separation material.

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