Interface evaporation material loaded with PDA / rGO photo-thermal hydrogel and preparation method of interface evaporation material

Abstract

The invention belongs to the field of interface evaporation materials, and provides an interface evaporation material loaded with PDA / rGO photo-thermal hydrogel and a preparation method of the interface evaporation material. The PDA / rGO photo-thermal hydrogel loaded interface evaporation material is composed of a sponge material and PDA / rGO photo-thermal hydrogel loaded on the sponge material, and the PDA / rGO photo-thermal hydrogel is composed of calcium alginate hydrogel and a polydopamine / reduced graphene oxide composite material loaded in a polymer network of the calcium alginate hydrogel. The polydopamine / reduced graphene oxide composite material is prepared from reduced graphene oxide and polydopamine combined on the surface of the reduced graphene oxide; the interface evaporation material takes a sponge material as a porous skeleton, the PDA / rGO photo-thermal hydrogel is attached to the porous skeleton, and the interface evaporation material has a porous structure. According to the invention, the long-term use stability and evaporation flux of the existing hydrogel-based interface evaporation material can be improved.

Description

Technical Field

[0001] The invention belongs to the field of interface evaporation materials and relates to an interface evaporation material loaded with PDA / rGO photothermal water gel and a preparation method thereof. Technical Background

[0002] Freshwater shortage is becoming a global problem, and extracting freshwater from seawater is an important way to obtain freshwater. At present, the methods for extracting freshwater from seawater mainly include reverse osmosis, multi-effect distillation and electrodialysis. However, these methods usually rely on large-scale infrastructure and consume a lot of energy, and there is a risk of secondary environmental pollution. In order to solve the shortage of freshwater and the current problems faced by seawater desalination, more effective seawater desalination and purification technologies need to be developed. Solar-driven interfacial evaporation is a sustainable method of using solar energy to produce clean water, which can reduce dependence on traditional fossil energy and reduce energy costs. It is also characterized by high efficiency, pollution-free and simple equipment structure.

[0003] A solar evaporator is a device that uses solar energy to evaporate water to purify and desalinate water. Solar evaporators usually have efficient photothermal materials. The photothermal materials absorb light energy in solar radiation and convert it into heat energy, which increases the temperature on the surface or inside of the evaporator, and then evaporates water to form water vapor, which is then condensed into liquid water, thereby achieving the production of clean water. The development of solar evaporators is driven by the development of photothermal materials with high photothermal efficiency. Common photothermal materials include metal nanoparticles, carbon-based materials, semiconductors, and polymers. These materials undergo energy level transitions by absorbing photons through electrons, followed by relaxation and energy release, which is manifested macroscopically as an increase in material temperature. The increase in material temperature intensifies the movement of water molecule clusters and is conducive to the escape of water molecules.

[0004] In order to prepare efficient interfacial evaporators, combining hydrogels with photothermal materials is a promising method, because the unique polymer network of hydrogels can reduce the evaporation enthalpy of water, the porous structure of hydrogels can match the light capture, water transmission and steam escape of the evaporator, and the hydrophilicity of hydrogels can ensure the continuous transmission of water. In order to increase the rate of interfacial evaporation and solve the problem of salt accumulation in the interfacial evaporator affecting the escape of water clusters, researchers have made a lot of efforts to improve the light absorption and thermal stability of photothermal materials and improve the pore structure inside the evaporator. However, the evaporation efficiency of existing interfacial evaporators and their long-term utilization stability in water environments need to be improved, especially in extreme seawater environments. The internal structure of the interfacial evaporator is easily destroyed, which in turn affects the evaporation rate and evaporation efficiency. This is a major problem faced by this field. In addition, the evaporation flux of existing hydrogel-based interfacial evaporation materials also needs to be improved. Summary of the invention

[0005] In view of the problems that the existing interface evaporation materials are poor in long-term use stability in water environments, especially seawater environments, and the evaporation flux needs to be improved, the present invention provides an interface evaporation material loaded with PDA / rGO photothermal water gel and a preparation method thereof, so as to improve the long-term use stability and evaporation flux of the existing hydrogel-based interface evaporation materials.

[0006] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is as follows:

[0007] The invention discloses an interface evaporation material loaded with PDA / rGO photothermal water gel, which is composed of a sponge material and the PDA / rGO photothermal water gel loaded on the sponge material, wherein the PDA / rGO photothermal water gel is composed of a calcium alginate hydrogel and a polydopamine / reduced graphene oxide composite material loaded in a polymer network of the calcium alginate hydrogel, and the polydopamine / reduced graphene oxide composite material is composed of reduced graphene oxide and polydopamine bonded to the surface of reduced graphene oxide; the interface evaporation material uses the sponge material as a porous skeleton, the PDA / rGO photothermal water gel is attached to the porous skeleton, and the interface evaporation material has a porous structure.

[0008] In the technical solution of the interface evaporation material loaded with PDA / rGO photothermal water gel, the content of the polydopamine / reduced graphene oxide composite material in the PDA / rGO photothermal water gel is preferably 0.5 to 2 g / L.

[0009] In the technical scheme of the interfacial evaporation material loaded with PDA / rGO photothermal water gel, a feasible method for preparing a polydopamine / reduced graphene oxide composite material is: fully dispersing graphene oxide in water to obtain a graphene oxide dispersion, adding Tris-HCl buffer with a concentration of 30 to 50 mmol / L and a pH value of 8 to 8.5 to the graphene oxide dispersion until the pH value of the obtained mixed solution is 7 to 8, and then adding dopamine hydrochloride to the obtained mixed solution, controlling the mass ratio of dopamine hydrochloride to graphene oxide to be (1.5 to 2): (1 to 2), fully reacting at 50 to 70°C, filtering the obtained reaction solution, and washing the obtained solid phase with water to obtain the obtained product.

[0010] Furthermore, in the technical scheme of the interfacial evaporation material loaded with PDA / rGO photothermal water gel, when preparing the polydopamine / reduced graphene oxide composite material, the concentration of the graphene oxide dispersion is preferably controlled to be 0.5-2 g / L; and the reaction time at 50-70° C. is controlled to be 24-30 h.

[0011] In the technical solution of the interface evaporation material loaded with PDA / rGO photothermal water gel, after the liquid medium in the interface evaporation material is dried and removed, the interface evaporation material after the liquid medium is removed has a micron-scale porous structure, for example, a porous structure with a pore size of 50 to 500 μm.

[0012] In the above-mentioned technical solution of the interfacial evaporation material loaded with PDA / rGO photothermal water gel, the sponge material is a polymer sponge material, and feasible sponge materials include any one of melamine sponge, polystyrene sponge, polyurethane sponge and polyvinyl alcohol sponge, but feasible sponge materials are not limited to the sponge materials listed above.

[0013] The present invention also provides a method for preparing the above-mentioned interface evaporation material loaded with PDA / rGO photothermal water gel, comprising the following steps:

[0014] (1) fully dispersing the polydopamine / reduced graphene oxide composite material in water, then adding sodium alginate to the obtained polydopamine / reduced graphene oxide composite material dispersion and fully dissolving and dispersing it to obtain a gel precursor solution;

[0015] (2) completely immersing the cleaned and dried sponge material in a gel precursor solution to allow the sponge material to fully absorb the gel precursor solution, and placing the sponge material that has absorbed the gel precursor solution in a vacuum environment at a temperature of 60 to 80° C. for degassing and drying to obtain a sponge material loaded with a gel precursor;

[0016] (3) The sponge material loaded with the gel precursor is completely immersed in an aqueous solution of calcium ions and allowed to stand until the gel precursor in the sponge material is converted into a gel state, thereby obtaining an interfacial evaporation material loaded with PDA / rGO photothermal water gel.

[0017] In step (1) of the technical solution of the preparation method of the interfacial evaporation material loaded with PDA / rGO photothermal water gel, the concentration of the polydopamine / reduced graphene oxide composite material in the gel precursor solution is preferably 0.5-2 g / L, and the concentration of sodium alginate is preferably 10-40 g / L.

[0018] In step (2) of the technical solution of the preparation method of the interfacial evaporation material loaded with PDA / rGO photothermal water gel, the purpose of completely immersing the cleaned and dried sponge material in the gel precursor solution is to allow the sponge material to fully absorb the gel precursor solution. The time for which the sponge material is immersed in the gel precursor solution is determined according to the size of the sponge material, with the principle that the gel precursor solution completely permeates the sponge material. Usually, the sponge material is completely immersed in the gel precursor solution and maintained for at least 2 hours before degassing and drying operations are performed.

[0019] In step (2) of the technical solution of the preparation method of the interface evaporation material loaded with PDA / rGO photothermal water gel, the role of the degassing operation is to remove the air between the gel precursor and the sponge material as the porous skeleton, so that the gel precursor is more firmly attached to the porous skeleton; the degassing time is related to the size of the sponge material and the vacuum degree of the vacuum environment. Under the same vacuum degree conditions, the larger the size of the sponge material, the longer the required degassing time. When the size of the sponge material is constant, the greater the vacuum degree of the vacuum environment, the shorter the required degassing time. In the process of degassing, it is also necessary to dry and remove the moisture in the sponge material that has absorbed the gel precursor. In order to meet the above-mentioned degassing and drying requirements, usually, when the vacuum degree of the vacuum environment is -0.08 to -0.01MPa and the temperature is 60 to 80°C, the required degassing and drying time is generally 2 to 10h.

[0020] In step (3) of the technical solution of the preparation method of the interfacial evaporation material loaded with PDA / rGO photothermal water gel, the aqueous solution of calcium ions is prepared from water-soluble calcium salt and water, and the concentration of the water-soluble calcium salt in the aqueous solution of calcium ions is 5wt% to 10wt%.

[0021] In step (3) of the technical solution of the above-mentioned method for preparing the interfacial evaporation material loaded with PDA / rGO photothermal water gel, the sponge material loaded with the gel precursor is completely immersed in an aqueous solution of calcium ions and then generally left to stand for 10 to 30 hours to obtain the interfacial evaporation material loaded with PDA / rGO photothermal water gel.

[0022] The technical concept of the present invention mainly lies in:

[0023] Reduced graphene oxide has excellent light-to-heat conversion ability, but reduced graphene oxide has a tendency to irreversibly agglomerate, and even re-deposit into graphite through van der Waals interactions. Polydopamine can maintain the relative stability of the structure under illumination, and the energy loss of light-to-heat conversion is also very small, but long-term exposure of polydopamine to high-intensity illumination will have an adverse effect on its performance. In order to solve the agglomeration problem of reduced graphene oxide and the problem that the durability of polydopamine under strong illumination is not good. The present invention utilizes dopamine hydrochloride to self-polymerize on the surface of graphene oxide to form a polydopamine layer, and the functional groups such as phenolic hydroxyl groups in polydopamine react with the oxidized functional groups (such as -O-, -COOH, etc.) on the surface of graphene oxide, thereby reducing graphene oxide, and the reduction process not only removes a part of the oxidized functional groups on the surface of graphene oxide, but also restores its conjugated structure, so that the reduced graphene oxide has fewer residual oxygen-containing groups and vacancy defects, thereby improving its light-to-heat conversion performance. The coating of polydopamine can also alleviate the agglomeration problem of reduced graphene oxide. At the same time, the combination of polydopamine and reduced graphene oxide not only enhances the stability of polydopamine, but also provides it with more active sites. Thus, the above limitations of both are overcome at the same time, achieving efficient and continuous photothermal conversion.

[0024] The present invention combines a polydopamine / reduced graphene oxide composite material with a calcium alginate hydrogel, and loads it on a sponge material as a porous skeleton. The hydrophilicity of the hydrogel and the porous structure of the sponge material provide a basis for the continuous transport of water. Combined with the excellent photothermal conversion performance and stability of the polydopamine / reduced graphene oxide composite material, the present invention gives the interface evaporation material the ability to evaporate water efficiently, continuously and stably for a long time under illumination conditions. On the one hand, the improvement of the photothermal conversion performance of the polydopamine / reduced graphene oxide composite material can improve the evaporation flux of the existing hydrogel-based interface evaporation material. On the other hand, the improvement of the stability of the polydopamine / reduced graphene oxide composite material can improve the long-term use stability and salt resistance of the existing hydrogel-based interface evaporation material.

[0025] The interfacial evaporation material of the PDA / rGO photothermal water gel provided by the present invention can be used for seawater desalination and water purification, especially for purification of industrial wastewater, organic wastewater, oily wastewater and the like.

[0026] Compared with the prior art, the technical solution provided by the present invention produces the following beneficial effects:

[0027] 1. The present invention provides an interface evaporation material loaded with PDA / rGO photothermal water gel, the interface evaporation material is composed of a sponge material and a PDA / rGO photothermal water gel loaded on the sponge material, the PDA / rGO photothermal water gel is composed of a calcium alginate hydrogel and a polydopamine / reduced graphene oxide composite material loaded in a polymer network of the calcium alginate hydrogel, the polydopamine / reduced graphene oxide composite material is composed of reduced graphene oxide and polydopamine bound to the surface of reduced graphene oxide; the interface evaporation material uses the sponge material as a porous skeleton, the PDA / rGO photothermal water gel is attached to the porous skeleton, and the interface evaporation material has a porous structure. The interface evaporation material of the present invention combines reduced graphene oxide with polydopamine, solves the problem that reduced graphene oxide is easy to agglomerate and the durability of polydopamine under strong light is poor, and the obtained polydopamine / reduced graphene oxide composite material has efficient and long-lasting light-to-heat conversion ability. The present invention combines a polydopamine / reduced graphene oxide composite material with a calcium alginate hydrogel, and loads it on a sponge material as a porous skeleton. The hydrophilicity of the hydrogel and the porous structure of the sponge material provide a basis for the continuous transport of water. On this basis, combined with the light-to-heat conversion performance and stability of the polydopamine / reduced graphene oxide composite material, the obtained interface evaporation material is endowed with the ability to evaporate water efficiently, continuously and stably for a long time under illumination conditions. Compared with the existing hydrogel-based interface evaporation materials, the present invention effectively improves the long-term use stability and salt resistance of such interface evaporation materials, and at the same time effectively improves the evaporation flux of such interface evaporation materials.

[0028] 2. The present invention has been experimentally verified that the interface evaporation material loaded with PDA / rGO photothermal water gel of the present invention can be applied to the desalination of simulated seawater with different salinities and different pH values, and can also be used to purify dye wastewater and oily wastewater, and has excellent seawater desalination and wastewater purification capabilities. The purified water obtained by desalinating seawater meets the standards for drinking water, and the removal rate of organic dyes in dye wastewater can reach more than 99.9%. The purified water obtained by purifying oily wastewater does not contain oil droplets. This shows that the interface evaporation material loaded with PDA / rGO photothermal water gel of the present invention can be applied in multiple scenarios, not only for seawater desalination, but also for the purification of water bodies including industrial wastewater, organic wastewater, oily wastewater, etc.

[0029] 3. The present invention experimentally confirms that the interfacial evaporator constructed by the interfacial evaporation material loaded with PDA / rGO photothermal water gel of the present invention desalinates simulated seawater under different conditions. After the same interfacial evaporation material of the present invention is recycled for 75 days, the interfacial evaporation rate does not show a significant decrease. After 75 days of recycling, the internal network structure of the interfacial evaporation material remains stable, and has excellent recycling performance and long-term stability.

[0030] 4. The present invention has experimentally confirmed that the interface evaporation material loaded with PDA / rGO photothermal water gel of the present invention has excellent evaporation flux. 2 ) simulated sunlight, room temperature (26±2°C) and a humidity of about 60% were used to evaporate the simulated seawater, and the evaporation flux (evaporation rate) reached 5-6 kg m -2 h -1 Moreover, after 75 days of seawater evaporation cycle experiment, the evaporation flux of simulated seawater was still at 5kgm -2 h -1 The present invention effectively improves the evaporation flux of existing hydrogel-based interface evaporation materials, especially the evaporation flux during long-term cyclic use.

[0031] 5. The present invention also provides a method for preparing the above-mentioned interfacial evaporation material loaded with PDA / rGO photothermal water gel. The method is simple to operate, the preparation conditions are easy to achieve, the preparation process is green, environmentally friendly and pollution-free, and is conducive to promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Figures (a) and (b) are TEM images of GO and PDA / rGO in Example 1.

[0033] Figure 2 Figures (a) and (b) are photos and SEM images of the MS sponge used in Example 1. Figure 2 Figures (c) and (d) are photos and SEM images of freeze-dried PRSH.

[0034] Figure 3 are the IR-Vis-UV absorption spectra of GO, PDA / rGO, MS and freeze-dried PRSH, and PDA.

[0035] Figure 4 It is the absorbance curve of PDA / rGO dispersion and GO dispersion under UV-visible light.

[0036] Figure 5 Figures (a), (b), and (c) are the C1s XPS spectra of GO, PDA / rGO, and PDA, respectively. Figure 5 Figure (d) is the N1s XPS spectrum of PDA / rGO.

[0037] Figure 6 When PRSH is used as the interface evaporation material, the infrared imaging and temperature of the PRSH surface and the simulated seawater in the beaker after irradiation under the solar simulator for 0, 20 and 180 minutes.

[0038] Figure 7 This is a comparison chart of the evaporation flux of the interface evaporator when MS, MSAP and PRSH are used as the interface evaporation materials.

[0039] Figure 8 It is the relationship between the temperature and vapor pressure of the MS, MSAP and PRSH surfaces after the evaporation process stabilizes.

[0040] Fig. 9 These are photos of MSAG after being recycled for different periods of time.

[0041] Fig.10 It is the test result of the evaporation rate of MSAG during the recycling process.

[0042] Fig.11 It is the evaporation rate test result after PRSH is circulated for different time periods under different conditions.

[0043] Fig.12 These are SEM images of the interior of PRSH after PRSH was recycled for different time periods.

[0044] Fig.13 It is the evaporation rate of simulated seawater with different pH values ​​using PRSH as the interface evaporation material, and the pH value comparison chart of the simulated seawater before evaporation and the purified water obtained after evaporation. DETAILED DESCRIPTION

[0045] The following examples further illustrate the interface evaporation material loaded with PDA / rGO photothermal water gel and the preparation method thereof provided by the present invention. It is necessary to point out that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. The technical personnel in the relevant field make some non-essential improvements and adjustments to the present invention according to the above invention content for specific implementation, which still falls within the scope of protection of the present invention.

[0046] Example 1

[0047] In this embodiment, the steps for preparing the interfacial evaporation material (PRSH) loaded with PDA / rGO photothermal water gel are as follows:

[0048] (1) Graphene oxide (GO) was ultrasonically dispersed in deionized water to obtain a GO dispersion with a concentration of 2 g / L, and a tris-hydrochloric acid (Tris-HCl) buffer with a concentration of 50 mmol / L and a pH of 8.5 was added dropwise to the GO dispersion, and the volume ratio of the total amount of Tris-HCl buffer added to the GO dispersion was controlled to be 1:4. The resulting mixed solution was transferred to a 60°C constant temperature water bath, and dopamine hydrochloride was added to the mixed solution to control the ratio of dopamine hydrochloride to GO. The mass ratio was 1:1, and the reaction was stirred for 24 hours. Dopamine hydrochloride reduced GO to reduced graphene oxide (rGO). At the same time, dopamine hydrochloride polymerized to form polydopamine (PDA) and combined with the rGO surface to obtain a polydopamine / reduced graphene oxide composite material (PDA / rGO). The obtained reaction solution was filtered, and the obtained solid phase was washed with deionized water to obtain PDA / rGO. PDA / rGO was re-dispersed in deionized water to obtain a PDA / rGO dispersion with a concentration of 2 g / L.

[0049] (2) Sodium alginate (SA) was added to the PDA / rGO dispersion, and the mixture was fully stirred to dissolve and disperse to obtain a gel precursor solution. In the gel precursor solution, the concentration of SA was 20 g / L and the concentration of PDA / rGO was 2 g / L. A melamine (MS) sponge with a length × width × height of 2 × 2 × 1 cm was ultrasonically cleaned with ethanol and water in turn, and then vacuum dried.

[0050] (3) The cleaned and dried MS sponge is completely immersed in the gel precursor solution and maintained for 2 hours to allow the sponge material to fully absorb the gel precursor solution. The sponge material that has absorbed the gel precursor solution is placed in a vacuum drying oven at a vacuum degree of -0.08 to -0.01 MPa and a temperature of 80°C for 3 hours for degassing and drying to obtain an MS sponge loaded with a gel precursor.

[0051] (4) The MS sponge loaded with gel precursor was completely immersed in a 5 wt% calcium chloride solution for 12 h. During the immersion process, SA and Ca 2+ The PDA / rGO photothermal water gel was obtained by cross-linking calcium alginate and loaded on the MS sponge. The obtained product was taken out and washed with deionized water to obtain the interfacial evaporation material loaded with PDA / rGO photothermal water gel, which was recorded as PRSH.

[0052] The raw materials used in this example, the intermediate products in the preparation process and the final product prepared are characterized below.

[0053] Transmission electron microscopy (TEM) was used to observe the microstructure of GO and PDA / rGO. Figure 1 Figures (a) and (b) are TEM images of GO and PDA / rGO, respectively. Figure 1As can be seen from Figure (b), in PDA / rGO, a PDA coating layer is formed on the surface of rGO.

[0054] The PRSH was freeze-dried, and the microstructure of the MS sponge and freeze-dried PRSH was observed using a scanning electron microscope (SEM). Figure 2 As shown, Figure 2 Figures (a) and (b) are photos and SEM images of MS sponge. Figure 2 Figures (c) and (d) are photos and SEM images of freeze-dried PRSH. Figure 2 It can be seen that the color of the MS sponge changed from white to black after loading the PDA / rGO photothermal gel. This is because PDA / rGO is black, and both the MS sponge and freeze-dried PRSH have rich porous structures.

[0055] Infrared-visible-ultraviolet absorption spectra of GO, PDA / rGO, PDA, MS sponge, and freeze-dried PRSH were performed. The results are shown in Figure 3 As shown in the figure, AM1.5G is the international standard for the full spectrum of sunlight. Figure 3 It can be seen that PDA / rGO exhibits better full-spectrum absorption capacity, which can reach 100%, while PDA and GO alone exhibit absorption capacity of UV-visible light-infrared light of nearly 30% and 80%, respectively, which is more obvious in the near-ultraviolet region. Similarly, compared with MS sponge, PRSH has basically the same full-spectrum absorption capacity as PDA / rGO, that is, the absorption capacity of PDA / rGO for the full spectrum is basically not affected by calcium alginate and MS sponge.

[0056] PDA / rGO and GO were dispersed in deionized water to form a dispersion with a concentration of 2 g / L. The absorbance curves of the two dispersions under UV-visible light were tested. The results are as follows: Figure 4 As shown by Figure 4It can be seen that since the loose electrons held in GO can be easily excited from π orbitals to π* orbitals under solar radiation, when the frequency of the incident light matches the possible electronic transitions within the molecule, the excited electrons will be promoted from the ground state (highest occupied molecular orbital, HOMO) to the lowest unoccupied molecular orbital (LUMO). When the excited electrons relax to the ground state through electron-phonon coupling, heat is released from the excited electrons to the vibration mode of the entire atomic lattice, resulting in an increase in the temperature of the macroscopic carbon material. Similarly, the organic polymer PDA follows the photothermal mechanism of the electronic conjugation effect. The conjugation effect occurs when adjacent π electrons overlap, or the interaction between π bonds and p-orbital electrons causes electron density redistribution. The hyperconjugation effect occurs when a partially filled p-orbital electron cloud interacts with adjacent σ-bond electrons. Electrons in the π orbital transition to the π* orbital after being excited by light, and heat is released when the electrons return to the ground state, allowing the material to complete the photothermal conversion process. For this reason, the photothermal conversion of both carbon-based materials GO and high molecular polymer PDA comes from the thermal vibration of molecules. As the number of π bonds increases, the energy level difference between HOMO and LUMO decreases. A large number of conjugated π bonds promote the electrons to be excited and transition under almost all wavelengths of sunlight. When GO is reduced to form rGO, the absorption peak in the UV-visible spectrum changes significantly. The maximum absorption peak of rGO will be red-shifted, which reflects the change in GO structure during the reduction process. By analyzing these red-shift phenomena, the degree of reduction of GO and the recovery of its structure can be preliminarily judged.

[0057] X-ray photoelectron spectroscopy (XPS) was used to test the C1s XPS data of dry GO, PDA and PDA / rGO and the N1s XPS data of PDA / rGO. The results are as follows: Figure 5 As shown, Figure 5 Figures (a), (b), and (c) are the C1s XPS spectra of GO, PDA / rGO, and PDA, respectively. Figure 5 Figure (d) is the N1s XPS spectrum of PDA / rGO. Figure 5 As shown in Figure (a), the C1s core level spectrum of GO can be bent into five peak components with binding energies of approximately 282.80, 284.80, 286.65, 287.59, and 288.90 eV, respectively, which are attributed to the sp 2 , sp 3 Hybridization, bond energy of CO, C=O and OC=O functional groups; Figure 5As shown in Figure (b), the XPSC 1s core-level spectrum of PDA / rGO can also be fitted into five peak components, which are 284.80, 285.85.58, 286.44, 288.87 and 289.933 eV, respectively, which are composed of CC, CN, CO, C=O and OC=O, respectively. Among them, the CN peak component at the binding energy of 285.58 eV and the N1s peak component at ~400 eV are consistent with the existence of the PDA layer covering the surface, see Figure 5 (c) shows that the C1s core-level spectral line shape of PDA / rGO is similar to that of PDA.

[0058] Comparative Example 1

[0059] In this comparative example, the interfacial evaporation material (MSAP) loaded with PDA photothermal water gel was prepared, and the steps were as follows:

[0060] (1) SA was dissolved in deionized water to obtain a SA solution, and dopamine hydrochloride was added to the SA solution to obtain a gel precursor solution. In the gel precursor solution, the concentration of SA was 20 g / L and the concentration of dopamine hydrochloride was 2 g / L. A MS sponge with a length × width × height of 2 × 2 × 1 cm was ultrasonically cleaned with ethanol and water in turn, and vacuum dried.

[0061] (2) The cleaned and dried MS sponge is completely immersed in the gel precursor solution and maintained for 2 hours to allow the sponge material to fully absorb the gel precursor solution. The sponge material that has absorbed the gel precursor solution is placed in a vacuum drying oven at a vacuum degree of -0.08 to -0.01 MPa and a temperature of 80°C for 3 hours for degassing and drying to obtain an MS sponge loaded with a gel precursor.

[0062] (3) The MS sponge loaded with gel precursor was completely immersed in a 5 wt% calcium chloride solution for 12 h. During the immersion process, SA and Ca 2+ The PDA photothermal water gel was obtained by cross-linking calcium alginate and loaded on the MS sponge. The obtained product was taken out and washed with deionized water to obtain the interfacial evaporation material loaded with the PDA photothermal water gel, which was recorded as MSAP.

[0063] Example 2

[0064] In this example, the evaporation performance of MS, PRSH prepared in Example 1, and MSAP prepared in Comparative Example 1 were tested.

[0065] Prepare simulated seawater with a salinity of 3.5wt%. Use MS, PRSH and MSAP as interface evaporation materials to construct interface evaporators, respectively. Support the interface evaporation materials with polyethylene foam (i.e., form an interface evaporator) and float them in a beaker containing 50mL simulated seawater. Place the beaker on an electronic balance and place it directly below a solar simulator equipped with an AM1.5G filter. The distance between the interface evaporation material and the solar simulator is measured and calibrated by a solar power meter so that the light intensity received on the surface of the interface evaporation material is 1 standard sunlight intensity (1kW / m 2 ), seawater was evaporated under the aforementioned conditions of simulated sunlight, room temperature (26±2°C) and a humidity of about 60%. During the evaporation process, the data of the electronic balance was recorded every 10 minutes to obtain the mass loss of the simulated seawater in the beaker under light, and the surface temperature of the interface evaporating material and the temperature of the simulated seawater in the beaker were recorded in real time using an infrared imaging instrument.

[0066] When the surface temperature remains balanced, that is, the evaporation process is stable, the evaporation rate (EvaporationRate) is calculated by formula (1):

[0067]

[0068] In formula (1), △m (kg) is the mass loss of simulated seawater, A (m 2 ) is the effective evaporation area of ​​the interface evaporator, and △t(h) is the exposure time under simulated sunlight.

[0069] When the evaporation process is stable, the saturated vapor pressure is calculated by formula (2):

[0070]

[0071] In formula (2), P 0 (mmHg) is the saturated vapor pressure, T (℃) is the temperature of the surface of the evaporating material at the interface after the evaporation process stabilizes, A, B, and C are three important parameters, A=8.07131, B=1730.63, and C=233.426.

[0072] Figure 6 When PRSH is used as the interface evaporation material, the infrared imaging and temperature of the PRSH surface and the simulated seawater in the beaker after irradiation under the solar simulator for 0, 20 and 180 minutes are shown. Figure 6 It can be seen that with the increase of simulated sunlight irradiation time, the temperature of the PRSH surface gradually increased and stabilized at around 72°C, and the temperature of the simulated seawater in the beaker also gradually increased. After 180 minutes of irradiation, the temperature of the simulated seawater in the beaker increased to 41.2°C.

[0073] Figure 7This is a comparison chart of the evaporation flux of the interface evaporator when MS, MSAP and PRSH are used as the interface evaporation materials. Figure 8 is the relationship between the temperature and vapor pressure of the MS, MSAP and PRSH surfaces after the evaporation process stabilizes. Figures 7-8 It can be seen that when PRSH is used as the interface evaporation material, the evaporation rate and saturated vapor pressure of the interface evaporator are significantly better than those when MS and MSAP are used as the interface evaporation materials.

[0074] Comparative Example 2

[0075] In this comparative example, the interfacial evaporation material (MSAG) loaded with GO photothermal water gel was prepared by the following steps:

[0076] (1) SA was dissolved in deionized water to obtain a SA solution, and GO was added to the SA solution to obtain a gel precursor solution. In the gel precursor solution, the concentration of SA was 20 g / L and the concentration of GO was 2 g / L. A MS sponge with a length × width × height of 2 × 2 × 1 cm was ultrasonically cleaned with ethanol and water in turn, and vacuum dried.

[0077] (2) The cleaned and dried MS sponge is completely immersed in the gel precursor solution and maintained for 2 hours to allow the sponge material to fully absorb the gel precursor solution. The sponge material that has absorbed the gel precursor solution is placed in a vacuum drying oven at a vacuum degree of -0.08 to -0.01 MPa and a temperature of 80°C for 3 hours for degassing and drying to obtain an MS sponge loaded with a gel precursor.

[0078] (3) The MS sponge loaded with gel precursor was completely immersed in a 5 wt% calcium chloride solution for 12 h. During the immersion process, SA and Ca 2+ GO photothermal water gel was obtained by cross-linking calcium alginate and loaded on MS sponge. The obtained product was taken out and washed with deionized water to obtain the interface evaporation material loaded with GO photothermal water gel, which was recorded as MSAG.

[0079] Comparative Example 3

[0080] In this comparative example, the change in evaporation rate of the MSAG prepared in comparative example 2 was tested after multiple cycles of use.

[0081] Prepare simulated seawater with a salinity of 3.5%. Use MSAG as the interface evaporation material to construct an interface evaporator. The interface evaporation material is supported by polyethylene foam (i.e., forming an interface evaporator) and floated in a beaker containing 50 mL of simulated seawater. The interface evaporation material is placed directly below a solar simulator equipped with an AM1.5G filter. The distance between the interface evaporation material and the solar simulator is measured and calibrated by a solar power meter so that the light intensity received on the surface of the interface evaporation material is 1 standard sunlight intensity (1 kW / m 2), evaporated seawater was used in multiple cycles under the aforementioned conditions of simulated sunlight, room temperature (26±2°C) and a humidity of about 60%, and the mass change of the simulated seawater was recorded every 1 hour. The first cycle took 3 hours, the second cycle took 11 hours, and the two cycles took a total of 14 hours. After each cycle, the interface evaporation material was fully washed with deionized water and soaked overnight, and then the next cycle of seawater evaporation was carried out, and the evaporation rate of each cycle in each hour was calculated.

[0082] Photos of MSAG before the second cycle began Fig. 9 As shown in Figure (a), the photo of MSAG after the second cycle for 1 hour is as follows Fig. 9 As shown in Figure (b), the photo of MSAG after the second cycle for 4 hours is as follows Fig. 9 As shown in Figure (c), after the second cycle, the MSAG was washed with deionized water and soaked overnight. Fig. 9 As shown in Figure (d). Fig. 9 It can be seen that MSAG turned black after 1 hour of the second cycle, because the GO therein underwent carbonization reduction. After 4 hours of the second cycle, salt crystals appeared on the surface of MSAG, indicating that its internal channels were slowly blocked, and the driving force for water to evaporate upward was suppressed. The crystallization rate was greater than the evaporation rate of water. After agglomeration, the salt crystals were difficult to dissolve and return to the bulk water. After the second cycle, the MSAG was washed with deionized water and soaked overnight. It was visibly that the structure of MSAG collapsed, and the gel adhered to its surface fell off, making it difficult to achieve continuous evaporation.

[0083] During the two cycles, the evaporation rate per hour is Fig.10 As shown, Fig.10 In the figure, the cycle time of 1 to 3 hours is the first cycle (green bar graph), and the cycle time of 4 to 14 hours is the second cycle (yellow bar graph). Fig.10 It can be seen that the evaporation rate in the first cycle is higher than that in the second cycle. The average evaporation rate in the first cycle is 5.94 kg m -2 h -1 In the second cycle, the evaporation rate dropped to 5 kg m -2 h -1 Below this value, the evaporation is not stable enough, and the average evaporation rate in the second cycle is 5.21 kg m -2 h -1 .

[0084] Example 3

[0085] In this example, the change in evaporation rate of the PRSH prepared in Example 1 after multiple cycles of use was tested.

[0086] Prepare different solutions for cycle experiments, as follows: Fig.11 As shown, including: simulated seawater with a salinity of 3.5% ( Fig.11 3.5wt% NaCl in ), simulated seawater with a salinity of 5% ( Fig.11 5wt% NaCl in ), simulated seawater with a salinity of 10% ( Fig.11 10wt% NaCl in ), pH=9 and 3.5% salinity simulated seawater ( Fig.11 3.5wt% NaCl pH = 9), and also pure water ( Fig.11 of pure water).

[0087] The interface evaporator was constructed using PRSH as the interface evaporation material. The interface evaporation material was supported by polyethylene foam (i.e., forming an interface evaporator) and floated in a beaker containing 50 mL of simulated seawater. The interface evaporation material was placed directly below a solar simulator equipped with an AM1.5G filter. The distance between the interface evaporation material and the solar simulator was measured and calibrated using a solar power meter so that the light intensity received on the surface of the interface evaporation material was 1, 1.5, and 2 standard solar intensities ( Fig.11 In the figure, 1.5sun3.5wt%NaCl and 1.5sun3.5wt%NaCl represent experiments conducted at 1.5 and 2 standard sunlight intensities, and the other bar graphs represent experiments conducted at 1 standard sunlight intensity). Under the aforementioned simulated sunlight, room temperature (26±2°C) and humidity of about 60%, the evaporated seawater was used in multiple cycles, and the mass change of the simulated seawater was recorded every 1 hour. Each cycle took from several hours to several days, for a total of seven cycles, which took a total of 75 days. After each cycle, the interface evaporation material was fully washed with deionized water and soaked overnight, and then the next cycle of seawater evaporation was carried out. The evaporation rate was calculated 2 to 10 times for each cycle. The specific cycle experimental conditions and evaporation rate test results are shown in Figure 2. Fig.11 As shown, Fig.11 The bars of different colors represent different cycles, and the bars of the same color belong to the same cycle.

[0088] Depend on Fig.11 It can be seen that during the 75-day cycle experiment under different conditions, the evaporation rate of the same PRSH was slightly lower than 5 kg m -2 h -1 Except for this, the other evaporation rate values ​​were kept at 5 kg m -2 h -1 The PRSH after 4, 7, 23 and 75 days of recycling in this example was washed with deionized water and soaked overnight, and then subjected to SEM testing. The results are as follows: Fig.12 As shown. Fig.12It can be seen that after 75 days of cyclic use, the internal network structure of PRSH remains stable without serious shrinkage. Combining Comparative Example 3 with this embodiment, it can be seen that PRSH has excellent cyclic use performance and long-term use stability.

[0089] Example 4

[0090] In this example, the evaporation (purification) performance of the PRSH prepared in Example 1 on simulated seawater of different pH values ​​was tested.

[0091] Simulated seawater with a salinity of 3.5% was prepared, and the pH value of the simulated seawater was adjusted with NaOH or / and HCl solution to obtain simulated seawater with pH values ​​of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, and 14. The PRSH was supported by polyethylene foam (i.e., an interface evaporator was formed) and floated in beakers containing 50 mL of the simulated seawater with different pH values. Each beaker was placed on an electronic balance and directly under a solar simulator equipped with an AM1.5G filter. The distance between the PRSH and the solar simulator was measured and calibrated by a solar power meter so that the light intensity received on the surface of the PRSH was 1 standard sunlight intensity (1 kW / m 2 ), evaporate seawater under the aforementioned conditions of simulated sunlight, room temperature (26±2°C) and a humidity of about 60%. During the evaporation of seawater, record the data of the electronic balance every 1 hour to obtain the mass loss of the simulated seawater in the beaker under light, calculate the evaporation rate, and use pH test paper to test the pH values ​​of the simulated seawater before evaporation and the purified water obtained by evaporation, and compare with the standard colorimetric card and record them.

[0092] The test results of this embodiment are as follows Fig.13 As shown in the figure, Before purification represents the test result of simulated seawater with pH test paper before evaporation, and After purification represents the test result of purified water obtained by evaporation with pH test paper after evaporation. Fig.13 It can be seen that the pH values ​​of the purified water obtained after evaporation of simulated seawater with different pH values ​​are basically the same, all at a level of about pH = 7, which shows that the PRSH provided by the present invention can purify seawater with different pH values. The ICP ion test was performed on the purified water collected in this embodiment, and the results showed that the water quality of the collected purified water met the drinking water standards of the World Health Organization.

[0093] Example 5

[0094] In this example, the ability of the PRSH prepared in Example 1 to purify dye wastewater was tested.

[0095] Methylene blue and Congo red were dissolved in deionized water to obtain methylene blue solution and Congo red solution with a concentration of 50 mg / L. An interface evaporator was constructed using PRSH as the interface evaporation material. The interface evaporation material was supported by polyethylene foam (i.e., an interface evaporator was formed) and floated in a beaker containing 50 mL of dye solution (methylene blue solution or Congo red solution). The beaker was placed on an electronic balance and placed directly below a solar simulator equipped with an AM1.5G filter. The distance between the interface evaporation material and the solar simulator was measured and calibrated by a solar power meter so that the light intensity received on the surface of the interface evaporation material was 1 standard sunlight intensity (1 kW / m 2 ), the dye solution was evaporated for 3 hours under the aforementioned conditions of simulated sunlight, room temperature (26±2℃) and a humidity of about 60%, the evaporated purified water was collected, the concentrations of methylene blue and Congo red in the purified water were tested, and the removal rates of methylene blue and Congo red were calculated. The results showed that the removal rate of methylene blue in the methylene blue solution by constructing an interfacial evaporator using PRSH as the interfacial evaporation material was above 99.9%, and the removal rate of Congo red in the Congo red solution was also above 99.9%.

[0096] Example 6

[0097] In this example, the ability of the PRSH prepared in Example 1 to purify an oil-water mixture was tested.

[0098] Soybean oil and deionized water were fully mixed to obtain an oil-water mixture solution with a soybean oil concentration of 5 wt%. An interface evaporator was constructed using PRSH as an interface evaporation material. The interface evaporation material was supported by polyethylene foam (i.e., an interface evaporator was formed) and floated in a beaker containing 50 mL of the oil-water mixture solution. The beaker was placed on an electronic balance and directly below a solar simulator equipped with an AM1.5G filter. The distance between the interface evaporation material and the solar simulator was measured and calibrated by a solar power meter so that the light intensity received on the surface of the interface evaporation material was 1 standard sunlight intensity (1 kW / m 2 ), the dye solution was evaporated for 3 hours under the aforementioned simulated sunlight, room temperature (26±2° C.) and about 60% humidity conditions, and the evaporated purified water was collected. The purified water collected in this embodiment does not contain oil droplets.

[0099] The above embodiments illustrate that the interfacial evaporation material loaded with PDA / rGO photothermal water gel provided by the present invention is used for seawater desalination and water purification, especially for the purification of industrial wastewater, organic wastewater, oily wastewater, etc.

[0100] Example 7

[0101] In this embodiment, the steps for preparing the interface evaporation material loaded with PDA / rGO photothermal water gel are as follows:

[0102] (1) GO was ultrasonically dispersed in deionized water to obtain a GO dispersion with a concentration of 0.5 g / L. Tris-HCl buffer with a concentration of 30 mmol / L and a pH of 8.0 was added dropwise to the GO dispersion. When the pH value of the GO dispersion was between 7 and 8, the addition was stopped. The resulting mixed solution was transferred to a 50° C. constant temperature water bath. Dopamine hydrochloride was added to the mixed solution. The mass ratio of dopamine hydrochloride to GO was controlled to be 1.5:2. The mixture was stirred for 30 hours. Dopamine hydrochloride reduced GO to rGO. At the same time, dopamine hydrochloride polymerized to form PDA and bound to the surface of rGO to obtain PDA / rGO. The resulting reaction solution was filtered. The resulting solid phase was washed with deionized water to obtain PDA / rGO. The PDA / rGO was re-dispersed in deionized water to obtain a PDA / rGO dispersion with a concentration of 0.5 g / L.

[0103] (2) SA was added to the PDA / rGO dispersion, and the mixture was fully stirred to dissolve and disperse to obtain a gel precursor solution. In the gel precursor solution, the concentration of SA was 10 g / L and the concentration of PDA / rGO was 0.5 g / L. A polyurethane sponge (PU) with a length × width × height of 4 × 4 × 1 cm was ultrasonically cleaned with ethanol and water in turn, and then vacuum dried.

[0104] (3) Completely immerse the cleaned and dried PU sponge in the gel precursor solution and keep it for 5 hours to allow the sponge material to fully absorb the gel precursor solution. Place the sponge material that has absorbed the gel precursor solution in a vacuum drying oven with a vacuum degree of -0.08 to -0.01 MPa and a temperature of 80°C for 5 hours for degassing and drying to obtain a PU sponge loaded with a gel precursor.

[0105] (4) The PU sponge loaded with gel precursor was completely immersed in a 5wt% calcium chloride solution for 12 h. During the immersion process, SA and Ca 2+ The PDA / rGO photothermal water gel was obtained by cross-linking calcium alginate and loaded on the MS sponge. The obtained product was taken out and washed with deionized water to obtain the interfacial evaporation material loaded with the PDA / rGO photothermal water gel.

[0106] Example 8

[0107] In this embodiment, the steps for preparing the interface evaporation material loaded with PDA / rGO photothermal water gel are as follows:

[0108] (1) GO was ultrasonically dispersed in deionized water to obtain a GO dispersion with a concentration of 1 g / L. Tris-HCl buffer with a concentration of 40 mmol / L and a pH of 8.5 was added dropwise to the GO dispersion. When the pH value of the GO dispersion was between 7 and 8, the addition was stopped. The resulting mixed solution was transferred to a 60° C. constant temperature water bath. Dopamine hydrochloride was added to the mixed solution. The mass ratio of dopamine hydrochloride to GO was controlled to be 2:1. The mixture was stirred for 24 hours. Dopamine hydrochloride reduced GO to rGO. At the same time, dopamine hydrochloride polymerized to form PDA and bound to the surface of rGO to obtain PDA / rGO. The resulting reaction solution was filtered, and the resulting solid phase was washed with deionized water to obtain PDA / rGO. The PDA / rGO was re-dispersed in deionized water to obtain a PDA / rGO dispersion with a concentration of 1 g / L.

[0109] (2) SA was added to the PDA / rGO dispersion, and the mixture was fully stirred to dissolve and disperse to obtain a gel precursor solution. In the gel precursor solution, the concentration of SA was 30 g / L and the concentration of PDA / rGO was 1 g / L. A MS sponge with a length × width × height of 4 × 4 × 1.2 cm was ultrasonically cleaned with ethanol and water in turn, and then dried in a vacuum.

[0110] (3) The cleaned and dried MS sponge is completely immersed in the gel precursor solution and maintained for 4 hours to allow the sponge material to fully absorb the gel precursor solution. The sponge material that has absorbed the gel precursor solution is placed in a vacuum drying oven at a vacuum degree of -0.08 to -0.01 MPa and a temperature of 80°C for 5 hours for degassing and drying to obtain an MS sponge loaded with a gel precursor.

[0111] (4) The MS sponge loaded with gel precursor was completely immersed in a 10 wt% calcium chloride solution for 12 h. During the immersion process, SA and Ca 2+ The PDA / rGO photothermal water gel was obtained by cross-linking calcium alginate and loaded on the MS sponge. The obtained product was taken out and washed with deionized water to obtain the interfacial evaporation material loaded with the PDA / rGO photothermal water gel.

[0112] Example 9

[0113] In this embodiment, the steps for preparing the interface evaporation material loaded with PDA / rGO photothermal water gel are as follows:

[0114] (1) GO was ultrasonically dispersed in deionized water to obtain a GO dispersion with a concentration of 1.5 g / L. Tris-HCl buffer with a concentration of 50 mmol / L and a pH of 8.5 was added dropwise to the GO dispersion. When the pH value of the GO dispersion was between 7 and 8, the addition was stopped. The resulting mixed solution was transferred to a 65° C. constant temperature water bath. Dopamine hydrochloride was added to the mixed solution. The mass ratio of dopamine hydrochloride to GO was controlled to be 1:1. The mixture was stirred for 24 hours. Dopamine hydrochloride reduced GO to rGO. At the same time, dopamine hydrochloride polymerized to form PDA and bound to the surface of rGO to obtain PDA / rGO. The resulting reaction solution was filtered. The resulting solid phase was washed with deionized water to obtain PDA / rGO. The PDA / rGO was re-dispersed in deionized water to obtain a PDA / rGO dispersion with a concentration of 1.5 g / L.

[0115] (2) SA was added to the PDA / rGO dispersion, and the mixture was fully stirred to dissolve and disperse to obtain a gel precursor solution. In the gel precursor solution, the concentration of SA was 40 g / L and the concentration of PDA / rGO was 1.5 g / L. A MS sponge with a length × width × height of 4 × 4 × 1.5 cm was ultrasonically cleaned with ethanol and water in turn, and then dried in vacuum.

[0116] (3) The cleaned and dried MS sponge is completely immersed in the gel precursor solution and maintained for 5 hours to allow the sponge material to fully absorb the gel precursor solution. The sponge material that has absorbed the gel precursor solution is placed in a vacuum drying oven at a vacuum degree of -0.08 to -0.01 MPa and a temperature of 80°C for 5 hours for degassing and drying to obtain an MS sponge loaded with a gel precursor.

[0117] (4) The MS sponge loaded with gel precursor was completely immersed in a 10 wt% calcium chloride solution for 12 h. During the immersion process, SA and Ca 2+ The PDA / rGO photothermal water gel was obtained by cross-linking calcium alginate and loaded on the MS sponge. The obtained product was taken out and washed with deionized water to obtain the interfacial evaporation material loaded with the PDA / rGO photothermal water gel.

[0118] The above embodiments are only preferred implementations of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, improvements without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. The interface evaporation material loaded with PDA / rGO photothermal water gel is characterized in that: The interface evaporation material consists of a sponge material and a PDA / rGO photothermal water gel loaded on the sponge material; the PDA / rGO photothermal water gel consists of a calcium alginate hydrogel and a polydopamine / reduced graphene oxide composite material loaded in a polymer network of the calcium alginate hydrogel; the polydopamine / reduced graphene oxide composite material consists of reduced graphene oxide and polydopamine bound to the surface of reduced graphene oxide; the interface evaporation material uses the sponge material as a porous skeleton, the PDA / rGO photothermal water gel is attached to the porous skeleton, and the interface evaporation material has a porous structure.

2. The interface evaporation material loaded with PDA / rGO photothermal water gel according to claim 1, characterized in that: In the PDA / rGO photothermal water gel, the content of the polydopamine / reduced graphene oxide composite material is 0.5-2 g / L.

3. The interface evaporation material loaded with PDA / rGO photothermal water gel according to claim 2, characterized in that: The preparation method of the polydopamine / reduced graphene oxide composite material comprises: fully dispersing graphene oxide in water to obtain a graphene oxide dispersion liquid, dripping a Tris-HCl buffer solution with a concentration of 30 to 50 mmol / L and a pH value of 8 to 8.5 into the graphene oxide dispersion liquid until the pH value of the obtained mixed solution is 7 to 8, then adding dopamine hydrochloride to the obtained mixed solution, controlling the mass ratio of dopamine hydrochloride to graphene oxide to be (1.5 to 2): (1 to 2), fully reacting at 50 to 70° C., filtering the obtained reaction liquid, and washing the obtained solid phase with water to obtain the composite material.

4. The interface evaporation material loaded with PDA / rGO photothermal water gel according to claim 3, characterized in that: The concentration of the graphene oxide dispersion is 0.5-2 g / L.

5. The interface evaporation material loaded with PDA / rGO photothermal water gel according to claim 3, characterized in that: The reaction time is controlled at 50-70°C for 24-30 hours.

6. The interface evaporation material loaded with PDA / rGO photothermal water gel according to any one of claims 1 to 5, characterized in that: The sponge material is a polymer sponge material.

7. The method for preparing the interfacial evaporation material loaded with PDA / rGO photothermal water gel according to any one of claims 1 to 6, characterized in that: The following steps are involved: (1) fully dispersing the polydopamine / reduced graphene oxide composite material in water, then adding sodium alginate to the obtained polydopamine / reduced graphene oxide composite material dispersion and fully dissolving and dispersing it to obtain a gel precursor solution; (2) completely immersing the cleaned and dried sponge material in a gel precursor solution to allow the sponge material to fully absorb the gel precursor solution, and placing the sponge material that has absorbed the gel precursor solution in a vacuum environment at a temperature of 60 to 80° C. for degassing and drying to obtain a sponge material loaded with a gel precursor; (3) The sponge material loaded with the gel precursor is completely immersed in an aqueous solution of calcium ions and allowed to stand until the gel precursor in the sponge material is converted into a gel state, thereby obtaining an interfacial evaporation material loaded with PDA / rGO photothermal water gel.

8. The method for preparing the interfacial evaporation material loaded with PDA / rGO photothermal water gel according to claim 7, characterized in that: In the gel precursor solution of step (1), the concentration of the polydopamine / reduced graphene oxide composite material is 0.5-2 g / L, and the concentration of sodium alginate is 10-40 g / L.

9. The method for preparing the interfacial evaporation material loaded with PDA / rGO photothermal water gel according to claim 7, characterized in that: In step (2), the cleaned and dried sponge material is completely immersed in the gel precursor solution and maintained for at least 2 hours before degassing and drying operations are performed, and the degassing and drying time is controlled to be 2 to 10 hours.

10. The method for preparing the interfacial evaporation material loaded with PDA / rGO photothermal water gel according to any one of claims 7 to 9, characterized in that: The aqueous solution of calcium ions in step (3) is prepared from water-soluble calcium salt and water. In the aqueous solution of calcium ions, the concentration of the water-soluble calcium salt is 5wt% to 10wt%.

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