Melamine sponge with photo-thermal response and magnetic drive for oil absorption and fire extinguishment and preparation method of melamine sponge

Abstract

The invention discloses a photothermal response magnetic drive oil absorption fire extinguishing melamine sponge and a preparation method thereof, and belongs to the technical field of oil-water separation. According to the preparation method, common commercial melamine sponge is taken as a substrate, and the super-hydrophobic oil-absorbing and fire-extinguishing melamine sponge with photo-thermal response, magnetic driving characteristics and flame retardance is obtained through simple steps of self-polymerization of dopamine, coating of montmorillonite and sodium alginate, soaking of a mixed solution of polydimethylsiloxane and ferroferric oxide and the like. The adsorption efficiency of high-viscosity spilled oil such as crude oil under the illumination condition is obviously improved, efficient adsorption of oil fire on the water surface can be achieved under magnetic driving, the spilled oil is intensively contained in the sponge, meanwhile, rapid fire extinguishing is achieved by means of the flame retardant property of the sponge, and the sponge is an excellent material for achieving oil-water separation. Meanwhile, the method is simple in manufacturing process, and the prepared sponge is good in hydrophobicity, flame retardance and photo-thermal performance and can be applied to oil-water separation in a complex environment.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of oil-water separation, and particularly relates to a photo-thermal response magnetic driving flame-retardant melamine sponge for oil-water separation and a preparation method thereof. BACKGROUND

[0002] Oil spill accidents occurring in crude oil exploitation and offshore oil transportation can seriously affect the marine ecological environment and further threaten the survival and development of human beings. Moreover, the spilled oil is usually flammable and can easily cause sea surface flowing fire when encountering open fire. Therefore, it is particularly important to develop a method and material capable of effectively removing the spilled oil. Traditional oil spill treatment methods, such as in-situ combustion method, biodegradation method, and floatation method, have been gradually eliminated due to their high cost, long treatment period, and easy secondary pollution.

[0003] The adsorption method is a physical method for treating oil-containing wastewater by using porous adsorption materials to realize oil-water separation. The adsorption materials can treat the oil-containing wastewater quickly and efficiently without pollution. Moreover, the adsorbed oil can be recovered by extrusion, distillation, etc., and the used adsorption materials can be reused after simple treatment, thereby saving costs and realizing green and efficient oil removal. However, two-dimensional adsorption materials are not suitable for large-area spilled oil and waste oil treatment due to their limited adsorption capacity. In recent years, three-dimensional porous adsorption materials have gradually been applied in the field of oil-water separation due to their excellent oil-water separation performance and considerable adsorption capacity. Among them, melamine sponge and polyurethane sponge are relatively common. Melamine sponge is made of a wide range of materials, has low cost, high porosity, and excellent elasticity. However, it has amphiphilic properties (hydrophilic / lipophilic), which makes it unable to be directly applied to oil-water separation. However, it can be made hydrophobic while retaining its original lipophilicity by methods such as reducing its surface free energy and increasing its surface roughness, so as to be applied to oil-water separation. Meanwhile, considering the flammability of oil, improving the flame-retardant performance and fire extinguishing performance of melamine sponge is also one of the main technical problems to be solved by the present application. SUMMARY

[0004] The present application aims to provide a photo-thermal response magnetic driving flame-retardant oil-absorbing and fire-extinguishing melamine sponge and a preparation method thereof. The inexpensive and readily available melamine sponge is used as a base material, and an oil-absorbing and fire-extinguishing super-hydrophobic sponge with certain photo-thermal, flame-retardant, stable physical and chemical properties, and magnetic driving performance is prepared by polymerization, soaking, and other methods.

[0005] The technical scheme adopted by the present application is as follows: A preparation method of a photo-thermal response magnetic driving oil-absorbing and fire-extinguishing melamine sponge. The method comprises the following steps: Step one, preparing a polydopamine (PDA) layer on the surface of melamine sponge (MS) to obtain a dopamine-coated polyurethane sponge, denoted as PDA-MS.

[0006] Specifically, the melamine sponge is cut into a cuboid block of 2 cm x 2 cm x 1 cm, and then the sponge is sequentially ultrasonically cleaned in anhydrous ethanol and deionized water for 30 min. The sponge is taken out and dried in a drying oven at 70 °C for 6-8 h to obtain clean melamine sponge without impurities. Then dopamine hydrochloride is dissolved in a Tris HCl aqueous solution, and magnetically stirred for one hour. Then the cleaned MS sponge is immersed in the above solution for 24 hours, and waits for the self-polymerization of dopamine. After taking it out, it is dried at 80 °C to obtain a PDA-MS sponge.

[0007] The concentration of dopamine hydrochloride is 2.5 mg / mL, and the concentration of Tris HCl is 10 mM, and the pH is 8.5.

[0008] The melamine sponge is preferably a commercially available melamine sponge which is cheap and easy to obtain, has small mass, strong adsorption performance, and stable mechanical properties, and has a pore size of 200 μm.

[0009] Step two, sodium montmorillonite (MMT) and sodium alginate (SA) powders are dissolved in deionized water, the pH value is adjusted to neutral, and a stable MMT / SA mixed solution is obtained. Then the PDA-MS is soaked in the MMT / SA mixed solution, taken out after fully absorbing, and dried to obtain a MMT / SA modified sponge, denoted as MMT / SA@PDA-MS.

[0010] Specifically, sodium montmorillonite (MMT) and sodium alginate (SA) powders are dissolved in deionized water, the pH value of the solution is adjusted to 7, and the mixed solution is ultrasonically treated for 30 min, and then stirred at room temperature for 6 h to obtain a stable MMT / SA mixed solution. Then the PDA-MS is soaked in the MMT / SA solution with different concentrations, and the sponge is continuously squeezed with tweezers so that the sponge fully absorbs the solute. After 20 min, the sample is taken out and dried in a 70 °C oven, and finally a MMT / SA modified sponge is obtained.

[0011] In the MMT / SA mixed solution, the mass ratio of sodium montmorillonite to sodium alginate is 1:1, and the mass concentration of sodium montmorillonite is 0.1-0.3 wt%.

[0012] Preferably, in the MMT / SA mixed solution, the mass concentrations of sodium montmorillonite and sodium alginate are both 0.2 wt%.

[0013] Step three, mixing polydimethylsiloxane (PDMS), curing agent and nano four-iron oxide particles in ethyl acetate uniformly to obtain a PDMS / Fe3O4 dispersion liquid; immersing the MMT / SA@PDA-MS in the PDMS / Fe3O4 dispersion liquid, taking out and drying after sufficient soaking, to obtain a photo-thermal response magnetic driving oil-absorbing fire-extinguishing melamine sponge, denoted as PDMA / Fe3O4@MMT / SA@PDA-MS.

[0014] Specifically, polydimethylsiloxane (PDMS) is added to an ethyl acetate solution and magnetically stirred for 20 min, then a curing agent is added and stirred for 10 min, and then nano four-iron oxide particles are added to the above solution, which is ultrasonically oscillated at room temperature (25°C) for 1 h to obtain a PDMS / Fe3O4 dispersion liquid. Then the MMT / SA@PDA-MS is immersed in the PDMS / Fe3O4 dispersion liquid, ultrasonically soaked for 10 min, and dried at 70°C for 12 h to obtain a PDMA / Fe3O4@MMT / SA@PDA-MS multifunctional sponge.

[0015] The mass ratio of polydimethylsiloxane to curing agent is 10:1; the curing agent is DOWSIL 184 Silicone Elastomer Base; and the concentration of polydimethylsiloxane in ethyl acetate is 40 mg / mL.

[0016] The mass ratio of nano four-iron oxide particles to polydimethylsiloxane is 1:1; and the nano four-iron oxide particles are preferably 50-nanometer-level particles.

[0017] The application further provides the photo-thermal response magnetic driving oil-absorbing fire-extinguishing melamine sponge prepared by the above method.

[0018] The application further provides the application of the above photo-thermal response magnetic driving oil-absorbing fire-extinguishing melamine sponge in water treatment, sea surface crude oil leakage, crude oil fire, etc.

[0019] The melamine sponge prepared by the application has water contact angle of 153° and oil contact angle of 0°, has super-hydrophobic and super-oleophilic properties, and has excellent adsorption performance. The application is subjected to a simple open flame burning experiment, and it is found that when the concentration of sodium-based montmorillonite and sodium alginate is 0.2 wt%, the modified sponge has the best flame retardant performance; and further thermal gravimetric analysis of the sponge is performed by using a thermal gravimetric analyzer, and the results show that, compared with the unmodified sponge, the initial decomposition temperature of the modified sponge is increased by 54.7℃, and the residual mass is increased by 2.2 times. In addition, the modified sponge has strong photo-thermal conversion performance, and when combined with a peristaltic pump and a solar simulator, it can collect up to 18.6 g of high-viscosity crude oil in ten minutes under light conditions, and only 8 g of crude oil can be filtered in 20 minutes without light. The sponge oil absorption and fire extinguishing experiment shows that the magnetic driving can realize contactless oil absorption and fire extinguishing.

[0020] The technical principles and beneficial effects of the application are as follows: The application uses common commercial melamine sponge as a substrate, and through simple steps such as dopamine self-polymerization, coating of montmorillonite and sodium alginate, soaking in a mixed solution of polydimethylsiloxane and ferroferric oxide, etc., an ultra-hydrophobic melamine sponge with photo-thermal response, magnetic driving characteristics and flame retardancy is obtained. The modified melamine sponge prepared by the above method not only has super-hydrophobicity, but also has magnetism, flame retardancy and photo-thermal properties. The adsorption efficiency of the modified melamine sponge for high-viscosity spilled oil such as crude oil is significantly improved under light conditions, and the modified melamine sponge can realize efficient adsorption of oil fire on the water surface under the driving of magnetic force, and can concentrate the spilled oil in the sponge, and at the same time, the modified melamine sponge can realize rapid fire extinguishing by virtue of the flame retardant property of the sponge itself, and is an excellent material for oil-water separation. At the same time, the method has simple manufacturing process, and the prepared sponge has good hydrophobicity, flame retardancy and photo-thermal properties, and can be applied to oil-water separation in complex environments.

[0021] The preparation material required by the present application is convenient to obtain, low in cost, and simple in preparation process, and the technical requirement is not high. The self-polymerization behavior of dopamine on the sponge surface is particularly important in the entire modification process. The product polydopamine after polymerization has good biocompatibility, strong adhesion performance and certain photothermal performance, which can not only reinforce the loading of montmorillonite and sodium alginate on the sponge, but also endow the sponge with certain light-heat conversion performance. At the same time, polydopamine can also provide more active sites for the sponge, and provide convenience for the subsequent loading of other materials on the sponge. Montmorillonite and sodium alginate endow the sponge with excellent flame retardance, ensuring the safety and reliability of the adsorption process. The addition of polydimethylsiloxane makes the sponge change from super-hydrophilic state to super-hydrophobic state, making the modified sponge have the possibility of application in the field of oil-water separation. At the same time, the introduction of magnetic nanoparticles endows the material with magnetic properties and light-heat conversion performance. In summary, the modified sponge prepared by simple methods such as polymerization and soaking has light-heat conversion performance, flame retardance, magnetic driving performance and super-hydrophobic and oleophilic performance. The magnetic driving performance improves the recovery efficiency of the sponge, and at the same time, the sponge can be driven to some areas which are difficult for people to enter or dangerous for adsorption operation, and the light-heat conversion performance enables the sponge to have the ability to adsorb thick oil and oil spills. The combination of multi-layer flame retardant materials and excellent adsorption capacity also provides the possibility for the application of melamine sponge in the scene of oil spill fire on the sea. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The preparation flow chart of the modified montmorillonite sodium alginate-ferroferric oxide coated melamine sponge of the present application; Figure 2 The SEM test results of the original sponge (a) and example 1 (b) and the EDS test results of example 1 (c); Figure 3 The water contact angle test of example 1; Figure 4 The water contact angle test of example 1 under different PH conditions; Figure 5 The physical stability test of example 1; Figure 6 The adsorption performance of example 1 to different oils and organic solvents (a) and the reusable performance test of example 1 (b); Figure 7 The experimental graph of example 1 adsorbing light oil and heavy oil; Figure 8 The comparison of example 1 and the original sponge in adsorbing oil droplets with or without light (a) and the result graph of using peristaltic pump to pump high-viscosity crude oil (b); Figure 9Effect diagram of the original sponge, example 1, comparative example 1, comparative example 2, comparative example 3 under the open flame burning; Figure 10 Thermogravimetric curve of the original sponge, comparative example 1, example 1; Figure 11 Mechanism diagram (a) of example 1 for extinguishing oil fire on the sea surface and oil absorption and fire extinguishing experiment diagram (b) of simulated oil fire on the sea surface. DETAILED DESCRIPTION

[0023] The application will be described in detail below with examples, but they should not be understood as limiting the scope of protection of the application.

[0024] The photothermal magnetic melamine oil absorption sponge for oil-water separation provided by the application can effectively absorb various oils and organic solvents, and has excellent flame retardant performance. The raw materials and reagents used in the following specific examples of the application are as follows: Melamine sponge (MS), soybean oil, diesel oil were purchased from local supermarket, glycerol was purchased from Shandong Zhenxin Kang Medical Technology Co., Ltd., dopamine hydrochloride (98%), tris (hydroxymethyl) aminomethane (superior pure, Tris HCl), sodium alginate (chemical pure, SA), anhydrous ethanol (AE), deionized water (DW), ethyl acetate were purchased from National Pharmaceutical Group Chemical Reagent Co., Ltd., polydimethylsiloxane (PDMS) and curing agent were purchased from Dow Corning Corporation, nano-Fe3O4 NPs (50 nm) were purchased from Bisley New Material (Suzhou) Co., Ltd., sodium-based montmorillonite (MMT) was purchased from Fengfeng Mineral Powder Factory, n-hexane (analytical pure) was purchased from Fuyu Reagent Co., Ltd., dichloromethane (analytical pure) was purchased from Xilong Chemical Co., Ltd.

[0025] The performance test method is as follows: (1) Oil and organic solvent absorption capacity test: the oil absorption capacity and recycling performance of the prepared modified hydrophobic and lipophilic sponge were tested, and the saturated absorption capacity of the sponge was calculated using the following formula:

[0026] In the formula, M0 is the mass of the sponge before oil absorption, M1 is the mass of the sponge after oil absorption, and Q is the saturated absorption capacity of the sponge.

[0027] Cyclic oil absorption capacity test: in each cycle, the weight of the saturated sponge and the sponge after complete extrusion was recorded respectively, so as to explore the recycling performance.

[0028] (2) Flame retardant performance test: the sponges modified by three different concentrations of montmorillonite and sodium alginate were respectively subjected to open flame combustion test, the volume change of the sponge after combustion was observed, and then the flame retardant effect was further analyzed by a thermogravimetric tester.

[0029] (3) Photo-thermal oil removal performance test: Control the light conditions, and reflect the photo-thermal performance of the modified sponge through the experiments of adsorbing crude oil droplets and simulating water surface crude oil cleaning.

[0030] (4) Water surface oil fire extinguishing test: The ethyl acetate ignited on the water surface is regarded as the burning oil spill on the sea, and the modified sponge is used to adsorb and extinguish the burning oil spill.

[0031] Example 1

[0032] The preparation flow chart of the modified montmorillonite sodium alginate-ferroferric oxide coated melamine sponge is as Figure 1 .

[0033] Step 1, cut the melamine sponge into 2 cm x 2 cm x 1 cm cuboid blocks, then put the sponge into anhydrous ethanol and deionized water for ultrasonic cleaning for 30 min, take out the sponge and dry it in a 70°C drying oven for 6-8 h to obtain clean and impurity-free melamine sponge. Then dissolve 250 mg of dopamine hydrochloride in 100 mL of Tris HCl aqueous solution, magnetically stir for one hour, then immerse the cleaned MF sponge in the above solution for 24 hours, wait for the self-polymerization of dopamine, take it out and dry it in an 80°C environment to obtain PDA-MS sponge.

[0034] Step 2, dissolve 0.2 g of MMT and 0.2 g of SA in 100 mL of deionized water, adjust the pH value of the solution to 7, ultrasonically mix for 30 min, and then stir at room temperature for 6 h to obtain a 0.2wt% MMT / SA mixture. Then immerse the PDA-MS in the 0.2wt% MMT / SA solution, and continuously squeeze the sponge with tweezers to allow the sponge to fully absorb the solute. After 20 min, take it out, and then dry the sample in a 70°C oven to obtain 2-MMT / SA@PDA-MS (0.2wt% MMT, 0.2wt% SA)

[0035] Step three, add 2.5 g of PDMS to 60 mL of ethyl acetate solution and magnetically stir for 20 min, then add 0.25 g of curing agent (DOW SlL 184 Silicone Elastomer Base) and stir for 10 min, then add 2.0 g of nano-ferroferric oxide particles to the above solution, ultrasonically shake for 1 h at room temperature (25°C) to obtain a PDMS / Fe3O4 dispersion. Then immerse the MMT / SA@PDA-MS in the PDMS / Fe3O4 dispersion, ultrasonically soak for 10 min, and dry at 70°C for 12 h to obtain a PDMA / Fe3O4@MMT / SA@PDA-MS multifunctional sponge.

[0036] Comparative Example 1

[0037] The difference between Comparative Example 1 and Example 1 is that Comparative Example 1 does not include Step Three, i.e., PDMS and Fe3O4 are not added.

[0038] Comparative Example 2

[0039] The difference between Comparative Example 2 and Comparative Example 1 is that in Step Two, 0.1 g of MMT and 0.1 g of SA are dissolved in 100 mL of deionized water, the pH of the solution is adjusted to 7, the mixture is ultrasonically treated for 30 min, and then stirred at room temperature for 6 h to obtain a 0.1wt% MMT / SA mixture. Subsequently, the PDA-MS is immersed in the 0.1wt% MMT / SA solution, and the sponge is continuously squeezed with tweezers so that the sponge fully absorbs the solute. After 20 min, it is taken out and then placed in a 70°C oven to dry, obtaining 1-MMT / SA@PDA-MS (0.1wt% MMT, 0.1wt% SA).

[0040] Comparative Example 3

[0041] The difference between Comparative Example 3 and Comparative Example 1 is that in Step Two, 0.3 g of MMT and 0.3 g of SA are dissolved in 100 mL of deionized water, the pH of the solution is adjusted to 7, the mixture is ultrasonically treated for 30 min, and then stirred at room temperature for 6 h to obtain a 0.1wt% MMT / SA mixture. Subsequently, the PDA-MS is immersed in the 0.3wt% MMT / SA solution, and the sponge is continuously squeezed with tweezers so that the sponge fully absorbs the solute. After 20 min, it is taken out and then placed in a 70°C oven to dry, obtaining 3-MMT / SA@PDA-MS (0.3wt% MMT, 0.3wt% SA).

[0042] Performance Test 1: (Hydrophobicity, Physical and Chemical Stability Test)

[0043] Figure 1 Figure 2 The scanning electron microscope images of the original sponge and the sponge prepared in Example 1 at different magnifications (100 μm, 10 μm, 3 μm) show that the surface of the original sponge is relatively smooth, while the surface of the modified sponge is obviously rougher, which can explain from the microscopic level that the hydrophobic performance of the sponge has been significantly improved.

[0044] Figure 2 Figure 3 a is the direct manifestation of the hydrophobicity of the sponge prepared in Example 1, and the obvious silver mirror phenomenon can be seen. Further water contact angle test shows that the external water contact angle is 153.5° (Figure 2 Figure 3 b), and the internal section water contact angle is 150.2° (Figure 2 Figure 3 c).

[0045] Figure 1 shows the water contact angle of the sponge prepared in Example 1 in solutions with different pH values. The test results show that the minimum water contact angle of the sponge is 150° (pH = 1), and the maximum water contact angle of the sponge is 155.5° (pH = 7), indicating that the modified sponge has good chemical stability and can adapt to oil adsorption in various environments. Figure 4 Figure 5 Figure 2 shows that the sponge prepared in Example 1 maintains a good shape after being folded, stretched and compressed, indicating that the modified sponge has good physical stability.

[0046] Performance Test 2: (adsorption capacity and adsorption stability test)

[0047] Figure 3 shows the saturated adsorption of the sponge prepared in Example 1 for various oils and organic solvents. For dichloromethane, diesel and n-hexane, which have low viscosity and are easily volatile, the adsorption capacity is 18.38 g / g, 12.09 g / g and 9.77 g / g, respectively. For soybean oil and glycerol, which have slightly higher viscosity, the saturated adsorption capacity is 11.45 g / g and 19.04 g / g, respectively. Figure 6 Figure 6 Figure 4 shows the repeated adsorption test of the sponge prepared in Example 1 for diesel. The saturated adsorption capacity is 13 g / g in the first adsorption, and the oil absorption is about 14.5 times the weight of the sponge. With the increase of adsorption-extrusion times, the saturated adsorption capacity gradually decreases, and finally stabilizes at about 4.2 g / g, which is due to the fact that the oil inside the sponge cannot be completely removed during extrusion.

[0048] In order to intuitively show the adsorption capacity of the sponge prepared in Example 1 for light oil and heavy oil, water and underwater oil adsorption experiments were designed (Figure 5). Figure 7 From the figure, it can be seen that the modified sponge can effectively adsorb light oil-diesel and heavy oil-dichloromethane.

[0049] Performance Test 3: (light-heat oil removal performance and flame retardant performance test)

[0050] Because the viscosity of crude oil is large and the flowability is low, conventional adsorption materials cannot effectively adsorb crude oil. However, a large number of scholars have shown that the viscosity of crude oil is negatively correlated with temperature, so the scheme of adsorbing crude oil by increasing the temperature to reduce the viscosity of crude oil is feasible. The modified sponge prepared in the present application contains polydopamine and nano-ferroferric oxide with light-heat conversion performance, which can effectively convert light energy into heat energy when illuminated, thereby indirectly increasing the temperature of the crude oil and increasing its flowability.

[0051] Figure 6 shows the saturated adsorption of the sponge prepared in Example 1 for various oils and organic solvents. For dichloromethane, diesel and n-hexane, which have low viscosity and are easily volatile, the adsorption capacity is 18.38 g / g, 12.09 g / g and 9.77 g / g, respectively. For soybean oil and glycerol, which have slightly higher viscosity, the saturated adsorption capacity is 11.45 g / g and 19.04 g / g, respectively. Figure 8 ​​a The absorption of crude oil droplet by the sponge of Example 1 and the original sponge under light and without light. It can be seen that the modified sponge and the original sponge need 6 minutes and 16 seconds to absorb a drop of crude oil without light, while the modified sponge can absorb the crude oil droplet completely in 57 seconds under light. In order to simulate the absorption of crude oil on the sea, a set of oil spill cleaning device (attached Figure 8 b) is composed of the modified sponge of Example 1, a peristaltic pump and a sunlight simulator. Without light, due to the characteristics of high viscosity and low flowability of crude oil, only 8 g of crude oil is collected within 20 minutes; while under light, the surface of the sponge is rapidly heated, the heat is transferred to the bottom, thereby heating the crude oil and increasing its flowability, and up to 16.8 g of high-viscosity crude oil is collected within 10 minutes.

[0052] Since most oils are flammable, and most of the current adsorbent materials are flammable materials, therefore, improving the flame retardant performance of the adsorbent material is also an important indicator for evaluating the practicality of the adsorbent material. The montmorillonite and sodium alginate which are cheap and easy to obtain are used as flame retardants and loaded on the sponge, which significantly improves the flame retardant performance of the sponge. As shown in the attached Figure 9 figure, the original MS, the sponge prepared by Comparative Examples 1-3 and the sponge prepared by Example 1 are burned with an open flame, and the volume change of the sponge before and after burning is compared. It is not difficult to see that the volume of the original sponge is sharply reduced after being exposed to fire, and the volume is about 1 / 2 of the volume before burning after being burned by the open flame for 14 seconds, while the volume of the sponge with the added flame retardant is only slightly reduced after being burned. By comparing the volumes of the sponges modified by three different concentrations of flame retardants (Comparative Example 1, Comparative Example 2, Comparative Example 3) after burning, it is found that the volume of the sponge prepared by Comparative Example 1 is reduced the least, which indicates that the flame retardant effect is the best.

[0053] As shown in the attached Figure 10As shown, thermogravimetric analysis (TGA) tests were further conducted on the original MS, Comparative Example 1, and Example 1 to evaluate the thermal stability of the modified sponge. Analysis revealed that the initial decomposition temperatures of the original MS, Comparative Example 1, and the sponges prepared in Example 1 were approximately 220℃, 250℃, and 280℃, respectively; the maximum decomposition rate temperatures were approximately 396.5℃, 404.2℃, and 451.2℃, respectively; and the residual masses at 800℃ were 16.65%, 32.86%, and 37.28%, respectively. Compared to the unmodified MS sponge, Comparative Example 1 showed an initial decomposition temperature increase of 30℃, a maximum decomposition rate temperature increase of 8℃, and a nearly doubled residual mass. This is because layered silicate MMT can form a carbon layer at high temperatures, acting as a physical barrier, delaying thermal decomposition and the generation of flammable gases. Meanwhile, the carboxylic acid groups contained in SA may release non-flammable gases such as CO2 during combustion, diluting oxygen and flammable gases. These components work synergistically with MMT to form a denser carbon layer. The flame retardant effect of Example 1 is better than that of Comparative Example 1. This is because PDMS can not only act as a hydrophobic component, but also has high thermal stability. Its decomposition temperature is usually 400℃-500℃. In addition, the SiO2 produced by the decomposition of PDMS can further enhance the stability of the carbon layer.

[0054] Performance Test 4: (Water Surface Oil Fire Extinguishing Test)

[0055] Appendix Figure 11 Diagram a illustrates the mechanism of extinguishing oil fires on the sea surface using flame-retardant sponges. In the initial stage of an oil spill, a modified sponge is placed in the spill. Utilizing the sponge's magnetic drive and oil absorption properties, it rapidly absorbs the burning and igniting oil, concentrating the fire within the sponge. Then, relying on the sponge's inherent flame-retardant properties to isolate oxygen, the fire is gradually extinguished, achieving the purpose of oil absorption and fire suppression. The structure of the oil-absorbing sponge can be divided into three layers: the surface layer is amorphous SiO2 generated after the pyrolysis of PDMS; the middle layer is a carbon layer and Fe3O4; and the bottom layer is the intact oil-containing sponge. (See attached diagram.) Figure 11 Example b shows the oil absorption and fire extinguishing experiment using the sponge prepared in Example 1. Magnetic force was used to achieve non-contact oil absorption and extinguishing. It can be seen that in the initial stage of the oil spill (ethyl acetate stained with Sudan III), when the modified sponge was placed in the oil spill, the fire was gradually drawn to the sponge within 4 to 33 seconds, and the fire gradually decreased. From 33 to 64 seconds, the fire continued to decrease until it was extinguished. This is because the modified sponge has considerable oil absorption capacity and flame-retardant properties, which ensures its ability to perform adsorption operations in complex environments. Cutting the sponge after oil absorption and extinguishing reveals a distinct three-layer structure—a SiO2 layer, a carbon layer, and a sponge layer.

[0056] The above merely describes the preferred embodiments of the present application, and it should be pointed out that, for those skilled in the art, several improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered as falling within the protection scope of the present application.

Claims

1. A method for preparing a photothermal responsive magnetically driven oil-absorbing and fire-extinguishing melamine sponge, characterized in that, Includes the following steps: Step 1: Immerse the pre-cleaned melamine sponge in a hydrochloric acid dopamine solution to prepare a polydopamine layer on the surface of the melamine sponge, and obtain a polydopamine-coated polyurethane sponge, denoted as PDA-MS; Step 2: Dissolve sodium montmorillonite and sodium alginate in deionized water, adjust the pH to neutral, and obtain a stable MMT / SA mixture. Then, immerse the PDA-MS in the MMT / SA mixture, remove it after full absorption, and dry it to obtain the MMT / SA modified sponge, denoted as MMT / SA@PDA-MS. Step 3: Mix polydimethylsiloxane, curing agent and nano-iron oxide particles evenly in ethyl acetate to obtain PDMS / Fe3O4 dispersion; immerse MMT / SA@PDA-MS in PDMS / Fe3O4 dispersion, remove and dry after full soaking to obtain the photothermal responsive magnetically driven oil-absorbing and fire-extinguishing melamine sponge, denoted as PDMA / Fe3O4@MMT / SA@PDA-MS.

2. The preparation method of the photothermal responsive magnetically driven oil-absorbing and fire-extinguishing melamine sponge according to claim 1, characterized in that, The mass concentration of the dopamine hydrochloride solution mentioned in step one is 2.5 mg / mL, and the pH is 8.

5.

3. The preparation method of the photothermal responsive magnetically driven oil-absorbing and fire-extinguishing melamine sponge according to claim 1, characterized in that, In the MMT / SA mixture described in step two, the mass ratio of sodium montmorillonite to sodium alginate is 1:1, and the mass concentration of sodium montmorillonite is 0.1-0.3 wt%.

4. The preparation method of the photothermal responsive magnetically driven oil-absorbing and fire-extinguishing melamine sponge according to claim 1, characterized in that, In step three, the mass ratio of polydimethylsiloxane to curing agent is 10:

1.

5. The preparation method of the photothermal responsive magnetically driven oil-absorbing and fire-extinguishing melamine sponge according to claim 1, characterized in that, The concentration of polydimethylsiloxane in ethyl acetate is 40 mg / mL.

6. The preparation method of the photothermal responsive magnetically driven oil-absorbing and fire-extinguishing melamine sponge according to claim 1, characterized in that, The mass ratio of nano-iron oxide particles to polydimethylsiloxane is 1:

1.

7. The preparation method of the photothermal responsive magnetically driven oil-absorbing and fire-extinguishing melamine sponge according to claim 1, characterized in that, The melamine sponge mentioned in step one has a pore size of 200 μm.

8. The photothermal responsive magnetically driven oil-absorbing and fire-extinguishing melamine sponge prepared by the method according to any one of claims 1-7.

9. The application of the photothermal responsive magnetically driven oil-absorbing and fire-extinguishing melamine sponge as described in claim 8, characterized in that, Applications include oil-water separation and crude oil spills at sea.

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