Preparation method and application of a selectively adsorbed hydrophobic polyurethane sponge

Abstract

The application discloses a preparation method and application of a selectively adsorbed hydrophobic polyurethane sponge and belongs to the technical field of oil-water separation materials. Modified or unmodified silicon dioxide nanoparticles are doped in the inside of a polyurethane sponge framework, so that the hydrophobicity of the polyurethane sponge can be remarkably improved. The prepared hydrophobic polyurethane sponge selectively presents high adsorption to oil or a solvent, and can be used for adsorbing and separating oil / solvent type oily wastewater.

Description

Technical Field

[0001] This invention belongs to the field of oil-water separation materials technology, and particularly relates to a method for preparing and applying a selectively adsorbed hydrophobic polyurethane sponge. Background Technology

[0002] The recycling and treatment of oily wastewater has long been a major concern. Oily wastewater largely originates from the increase in oily domestic sewage and the discharge of industrial wastewater, posing a significant threat not only to the environment and human health but also to ecosystems. Therefore, achieving efficient separation and recycling of oily wastewater has become a major challenge. Wetting adsorbents with opposite affinities for water and oil have gained attention in oily wastewater treatment due to their simplicity, ease of recycling, and reusability. However, unprocessed adsorbents also suffer from strong hydrophilicity, poor mechanical properties, and low adsorption capacity, which limits their adsorption capacity in oil pollution treatment. Polyurethane materials, due to their inherent hydrophobic, oleophilic, and porous structures, are widely used in the preparation of oil-water separation adsorbents. Modified nanoparticles are also frequently introduced to improve the mechanical properties and adsorption performance of adsorbents. However, most current adsorbents possess universality in adsorbing various types of oil / solvents, resulting in low oil-water separation efficiency and speed for single types of oily wastewater. This fails to meet the needs of different application scenarios and cannot achieve targeted and efficient oil-water separation. Summary of the Invention

[0003] To address the problems existing in the prior art, this invention proposes a method for preparing and applying a selectively adsorbed hydrophobic polyurethane sponge. The polyurethane sponge prepared by doping with modified silica nanoparticles is an innovative method for selectively separating oil and water. This sponge material possesses a unique microporous structure and surface properties, enabling it to effectively selectively adsorb organic solvents or bio-oils while repelling water molecules. This invention improves the oil adsorption capacity by doping the polyurethane sponge with hydrophobic silica nanoparticles, giving it a porous microstructure and high specific surface area; it also increases the material's hydrophobicity, resulting in lower water adsorption, thus achieving oil-water separation. After modification with the modified silica nanoparticles, the hydrophobic polyurethane sponge, due to the special surface wetting properties of the modified silica nanoparticles, induces a phase separation process in the thermoplastic polyurethane, expanding the microporous structure of the polyurethane sponge and giving it a unique microporous structure and specific surface area. Furthermore, since the modified silica nanoparticles are embedded in the polyurethane sponge skeleton, the modified silica nanoparticles further optimize the polyurethane structure, forming a nanoscale rough structure. This enables the prepared hydrophobic polyurethane sponge to selectively adsorb different types of oils, avoiding the problem of low oil-water separation efficiency caused by the universal adsorption of multiple types of oils / solvents by polyurethane sponges.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] A selectively adsorbed hydrophobic polyurethane sponge, wherein the polyurethane sponge skeleton is doped with modified silica nanoparticles or unmodified silica nanoparticles.

[0006] Furthermore, the modified silica nanoparticles are silica nanoparticles modified with silane coupling agents.

[0007] Furthermore, the silane coupling agent is vinyltrimethoxysilane, phenyltrimethoxysilane, or γ-methacryloyloxypropyltrimethoxysilane (KH-570).

[0008] Furthermore, the method for preparing the modified silica nanoparticles is as follows:

[0009] 6.4 g of silica nanoparticles (particle size 15 nm) were added to a water / ammonia solution with a volume ratio of 3:17 and stirred and heated for 30 min to prepare mixture B. 14-16 mL of silane coupling agent and 160 mL of ethanol were added to mixture B and stirred at 60 °C for 6 h. After centrifugation, washing and drying, modified silica nanoparticles were obtained.

[0010] The selectively adsorbing hydrophobic polyurethane sponge proposed in this invention incorporates modified silica nanoparticles into the polyurethane sponge framework, effectively solving the problem of reduced hydrophobicity during use of polyurethane sponges prepared by traditional surface modification methods. The hydrophobic polyurethane sponge prepared by this invention can selectively and efficiently adsorb and separate oil / solvent-based wastewater.

[0011] A method for preparing the selectively adsorbed hydrophobic polyurethane sponge includes the following steps:

[0012] Thermoplastic polyurethane particles were dissolved in a mixed solvent of 1,4-dioxane and water, and heated and stirred until completely dissolved to form a homogeneous solution, thus obtaining mixture A;

[0013] Modified silica nanoparticles or unmodified silica nanoparticles are added to the mixture A, stirred until uniformly dispersed, and then subjected to phase separation, freezing, and freeze-drying to obtain selectively adsorbed hydrophobic polyurethane sponge.

[0014] Furthermore, the mass percentage of thermoplastic polyurethane particles in the mixture A is 8-10%.

[0015] Furthermore, the volume ratio of 1,4-dioxane to water is (8.5:1.5) to (9.5:0.5). Different volume ratios of 1,4-dioxane to water result in polyurethanes with varying pore sizes (different structures), affecting the phase separation process of the polyurethane. Furthermore, the heating temperature for heating and stirring until completely dissolved into a homogeneous solution is 60°C, and the stirring time is 90 min.

[0016] Further, 0.9–1.8 g of the modified silica nanoparticles or unmodified silica nanoparticles are added to every 15 mL of the mixture A.

[0017] Further, the specific steps of phase separation, freezing, and freeze-drying are as follows: the solution, after being stirred until uniformly dispersed, is placed at a low temperature of -10°C for 30 minutes to induce phase separation, then frozen in a refrigerator at -5°C for 24 hours, and then freeze-dried in a vacuum freeze dryer at -50°C and 5 Pa for 24 hours. Freezing is to stabilize the structure of polyurethane (the solubility of polyurethane in the solvent decreases at low temperatures, causing it to precipitate as a porous sponge), and freeze-drying is to remove 1,4-dioxane and water to obtain the polyurethane sponge.

[0018] The present invention also provides the application of the selectively adsorbed hydrophobic polyurethane sponge in oil-water separation.

[0019] The selectively adsorbed hydrophobic polyurethane sponge of the present invention is used for the selective adsorption of organic solvents or bio-oils. The selectively adsorbed hydrophobic polyurethane sponge of the present invention is used for the adsorption and separation of oil / solvent-based wastewater. For example, the selectively adsorbed hydrophobic polyurethane sponge of the present invention can be used for the selective separation of different types of oily wastewater such as edible oil / water and laboratory solvent / water.

[0020] Compared with the prior art, the present invention has the following advantages and technical effects:

[0021] (1) The hydrophobic polyurethane sponge obtained by the present invention has good hydrophobic / oleophilic properties, and the preparation process is simple, low cost, and does not contain toxic substances, making it suitable for widespread promotion and application.

[0022] (2) The hydrophobic polyurethane sponge obtained by the present invention adopts a novel preparation method of doping hydrophobic silica nanoparticles inside the skeleton, which effectively solves the problem of reduced hydrophobicity of polyurethane sponge prepared by traditional surface modification methods during use.

[0023] (3) The hydrophobic polyurethane sponge obtained by the present invention can achieve efficient oil-water separation. Furthermore, the present invention uses substances with different functional groups to modify silica particles to obtain different hydrophobic polyurethane sponges, which make their saturation adsorption capacity for different bio-oils and organic solvents show obvious differences, thereby achieving selective adsorption of different bio-oils and organic solvents. This avoids the problem of low oil-water separation efficiency caused by the universal adsorption of polyurethane sponges for multiple types of oils / solvents. The separated filtrate has high purity and exhibits strong selectivity and high efficiency. Attached Figure Description

[0024] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0025] Figure 1 The infrared absorption spectra of the modified silica nanoparticles in Examples 1-3 and the unmodified silica nanoparticles in Example 4 are shown.

[0026] Figure 2 Transmission electron microscope images of modified silica nanoparticles in Examples 1-3 and unmodified silica nanoparticles in Example 4, where (a) is Example 1, (b) is Example 2, (c) is Example 3, and (d) is Example 4.

[0027] Figure 3 The images shown are scanning electron microscope (SEM) images of the hydrophobic polyurethane sponges prepared in Examples 1-4. The lower right corner shows SEM images at different magnifications, where (a) is Example 1, (b) is Example 2, (c) is Example 3, and (d) is Example 4.

[0028] Figure 4 The saturated adsorption capacity of the hydrophobic polyurethane sponges prepared in Examples 1-4 for different oils.

[0029] Figure 5 The saturated adsorption capacity of the hydrophobic polyurethane sponges prepared in Examples 1-4 for different solvent-based oils is shown.

[0030] Figure 6 Electron micrographs of peanut oil / water mixture before (left) and after (right) adsorption using the hydrophobic polyurethane sponge of Example 1. Detailed Implementation

[0031] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0032] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0033] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0034] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0035] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0036] All raw materials used in the following embodiments of the present invention are commercially available. As examples, 1,4-dioxane, silica nanoparticles (15 nm in diameter), ammonia, vinyltrimethoxysilane, phenyltrimethoxysilane, cyclohexane, carbon tetrachloride, and dichloromethane were purchased from Shanghai Maclean Biochemical Technology Co., Ltd. KH-570 silane coupling agent was purchased from Wuhan Lanabai Pharmaceutical Chemical Co., Ltd. Ethanol and petroleum ether were purchased from Hangzhou Gaojing Chemical Co., Ltd. Peanut oil was purchased from Shandong Luhua Group Co., Ltd., blended oil was purchased from Jinlongyu Food Co., Ltd., and soybean oil was purchased from Yushan County Dachengcang Food Co., Ltd.

[0037] This invention modifies silica nanoparticles by selecting substances with similar functional groups based on the functional groups of different oils in oily wastewater. The modified silica nanoparticles are then incorporated into a polyurethane framework to obtain a hydrophobic polyurethane sponge with selective adsorption for different oils. This invention prepares a hydrophobic polyurethane sponge by doping modified silica nanoparticles into a polyurethane sponge framework for targeted and efficient oil-water separation. The porous structure of the polyurethane sponge provides high porosity, large specific surface area, and interconnected pores, which helps to store adsorbed oil / solvent, thereby increasing the saturated adsorption capacity. Polyurethane adsorbent materials are widely used in oil-water separation due to their hydrophobic properties; however, their universal adsorption of various types of oil leads to problems such as low oil-water separation efficiency, limiting their development in single-oil adsorption scenarios. The present invention discloses a selectively adsorbing hydrophobic polyurethane sponge, which improves the adsorption performance of oils with similar functional groups in oily wastewater by modifying silica with substances having different functional groups and incorporating them into the framework of the polyurethane sponge. This effectively achieves selective adsorption of different types of oils / solvents by the polyurethane sponge, solving the problem of low efficiency due to the general adsorption of current polyurethane adsorption materials.

[0038] In some embodiments of the present invention, a method for preparing selectively adsorbed hydrophobic polyurethane sponge is provided, comprising the following steps:

[0039] a) Add 6.4 g of silica nanoparticles (particle size 15 nm) to a water / ammonia solution with a volume ratio of ammonia and water of 3:17, and stir and heat at 60 °C for 30 min to prepare mixture A;

[0040] b) Add 14-16 mL of silane coupling agent and 160 mL of ethanol to mixture A, heat and stir at 60 °C for 6 h, centrifuge, wash three times with ethanol and deionized water, and dry at 60 °C for 12 h to obtain modified silica nanoparticles for later use.

[0041] c) Dissolve thermoplastic polyurethane particles of different mass ratios in mixed solvents of 1,4-dioxane / water of different volume ratios, and heat and stir at 60°C for 90 min until completely dissolved to form a homogeneous solution, to obtain mixture B;

[0042] d) Modified silica nanoparticles were added to 15 mL of mixed solution B at different masses and stirred until uniformly dispersed to obtain a mixed solution. The solution was placed at -10℃ for 30 min to induce phase separation. Then it was transferred to a freezer at -5℃ for 24 h to separate the phase and freeze-dry the sample completely. The sample was then transferred to a vacuum freeze dryer and freeze-dried at -50℃ for 24 h at 5 Pa atmospheric pressure to finally obtain selectively adsorbed hydrophobic polyurethane sponge.

[0043] In some embodiments of the present invention, in step b), the volume of vinyltrimethoxysilane added to 160 mL of ethanol is 14.4 mL; in step c), the mass percentage of thermoplastic polyurethane particles in mixture B is 8%, the volume ratio of water to 1,4-dioxane is 9.5:0.5, and the total volume of water / 1,4-dioxane is 10 mL; in step d), the mass of modified silica nanoparticles added is 1 g.

[0044] In some embodiments of the present invention, in step b), the volume of KH-570 silane coupling agent (γ-methacryloxypropyltrimethoxysilane coupling agent) added to 160 mL of ethanol is 14.4 mL; in step c), the mass percentage of thermoplastic polyurethane particles in mixture B is 8%, the volume ratio of water to 1,4-dioxane is 9.5:0.5, and the total volume of water / 1,4-dioxane is 10 mL; in step d), the mass of modified silica nanoparticles added is 1 g.

[0045] In some embodiments of the present invention, in step b), the volume of phenyltrimethoxysilane added to 160 mL of ethanol is 16 mL; in step c), the mass percentage of thermoplastic polyurethane particles in mixture B is 10%, the volume ratio of water to 1,4-dioxane is 9:1, and the total volume of water to 1,4-dioxane is 10 mL; in step d), the mass of modified silica nanoparticles added is 0.9 g.

[0046] The following embodiments are further illustrations of the technical solution of the present invention.

[0047] Example 1

[0048] A method for preparing selectively adsorbed hydrophobic polyurethane sponge:

[0049] a) Add 6.4 g of silica nanoparticles (particle size of 15 nm) to a water / ammonia solution with a volume ratio of ammonia and water of 3:17, and stir and heat at 60 °C for 30 min to prepare mixture A;

[0050] b) Add 14.4 mL of vinyltrimethoxysilane and 160 mL of ethanol to mixture A, heat and stir at 60 °C for 6 h, centrifuge, wash three times with ethanol and deionized water, and dry at 60 °C for 12 h to obtain modified silica nanoparticles for later use.

[0051] c) Dissolve thermoplastic polyurethane particles in a mixed solvent of 1,4-dioxane / water with a volume ratio of 9.5:0.5. The mass percentage of thermoplastic polyurethane particles in mixture B is 8%, and the total volume of water / 1,4-dioxane is 10 mL. Heat and stir at 60 °C for 90 min until completely dissolved to form a homogeneous solution to obtain mixture B.

[0052] d) Add 1g of modified silica nanoparticles to 15mL of mixed solution B and stir until evenly dispersed to obtain a mixed solution. Place it at -10℃ for 30min to induce phase separation, then transfer it to a -5℃ freezer for 24h to separate the phases and freeze-dry the sample completely. Then transfer it to a vacuum freeze dryer and freeze-dry it at 5Pa atmospheric pressure and -50℃ for 24h to finally obtain selectively adsorbed hydrophobic polyurethane sponge.

[0053] The infrared absorption spectrum of the vinyltrimethoxysilane-modified silica nanoparticles obtained in this embodiment is as follows: Figure 1 As shown (see details) Figure 1 Vinyltrimethoxysilane), from Figure 1 It can be seen that: 1630cm -1 The peak at this point is a characteristic absorption peak of C=C, indicating that vinyltrimethoxysilane has successfully modified silica nanoparticles, and the resulting modified silica nanoparticles have superhydrophobic properties.

[0054] The transmission electron microscope image of the vinyltrimethoxysilane-modified silica nanoparticles obtained in this embodiment is shown below. Figure 2 As shown in (a), by Figure 2 It can be seen that the silica nanoparticles modified with vinyltrimethoxysilane are uniformly dispersed and the particle size does not change significantly. That is, the morphology of silica nanoparticles does not change before and after vinyltrimethoxysilane modification.

[0055] The scanning electron microscope image of the vinyltrimethoxysilane-modified silica nanoparticles obtained in this embodiment is shown below. Figure 3 As shown in (a), by Figure 3 It is known that the polyurethane sponge prepared by vinyltrimethoxysilane-modified silica nanoparticles exhibits a porous and interconnected pore structure inside and on the skeleton, which helps to improve the saturated adsorption capacity for oil.

[0056] The selectively adsorbed hydrophobic polyurethane sponge obtained in this embodiment has hydrophobic / oleophilic properties. The polyurethane sponge prepared by vinyltrimethoxysilane-modified silica nanoparticles has a static water contact angle of 142° and an underwater oil contact angle of 0°. The polyurethane sponge prepared by vinyltrimethoxysilane-modified silica nanoparticles exhibits average saturated adsorption capacities of 2.85 g / g, 2.8 g / g, and 3.4 g / g for peanut oil, blended oil, and soybean oil, respectively, and average saturated adsorption capacities of 12.1 g / g, 2.6 g / g, 7 g / g, 2.4 g / g, and 2.5 g / g for dichloromethane, cyclohexane, carbon tetrachloride, petroleum ether, and ethanol, respectively.

[0057] Example 2

[0058] A method for preparing selectively adsorbed hydrophobic polyurethane sponge:

[0059] a) Add 6.4 g of silica nanoparticles (particle size of 15 nm) to a water / ammonia solution with a volume ratio of ammonia and water of 3:17, and stir and heat at 60 °C for 30 min to prepare mixture A;

[0060] b) Add 14.4 mL of KH-570 silane coupling agent and 160 mL of ethanol to mixture A, heat and stir at 60 °C for 6 h, centrifuge, wash three times with ethanol and deionized water, and dry at 60 °C for 12 h to obtain modified silica nanoparticles for later use.

[0061] c) Dissolve thermoplastic polyurethane particles in a mixed solvent of 1,4-dioxane / water with a volume ratio of 9.5:0.5. The mass percentage of thermoplastic polyurethane particles in mixture B is 8%, and the total volume of water / 1,4-dioxane is 10 mL. Heat and stir at 60 °C for 90 min until completely dissolved to form a homogeneous solution to obtain mixture B.

[0062] d) Add 1g of modified silica nanoparticles to 15mL of mixed solution B and stir until evenly dispersed to obtain a mixed solution. Place it at -10℃ for 30min to induce phase separation, then transfer it to a -5℃ freezer for 24h to separate the phases and freeze-dry the sample completely. Then transfer it to a vacuum freeze dryer and freeze-dry it at 5Pa atmospheric pressure and -50℃ for 24h to finally obtain selectively adsorbed hydrophobic polyurethane sponge.

[0063] The infrared absorption spectrum of the KH-570 silane coupling agent modified silica nanoparticles obtained in this embodiment is as follows: Figure 1 As shown (see details) Figure 1 KH-570 silane coupling agent), from Figure 1 It can be seen that: 1715cm -1 The peak at the position corresponds to the stretching vibration peak of C=O, indicating that KH-570 silane coupling agent has successfully modified silica nanoparticles, and the resulting modified silica nanoparticles have superhydrophobic properties.

[0064] The transmission electron microscope image of the KH-570 silane coupling agent modified silica nanoparticles obtained in this embodiment is shown below. Figure 2 As shown in (b), by Figure 2 It can be seen that the silica nanoparticles modified by KH-570 silane coupling agent are uniformly dispersed and the particle size does not change significantly. That is, the morphology of silica nanoparticles does not change before and after modification by KH-570 silane coupling agent.

[0065] The scanning electron microscope image of the KH-570 silane coupling agent modified silica nanoparticles obtained in this embodiment is shown below. Figure 3 As shown in (b), by Figure 3 It can be seen that the micropores of the polyurethane sponge modified by KH-570 silane coupling agent are uniformly distributed, with a pore size of about 5μm, and the nanoscale rough structure on the polyurethane sponge skeleton is obvious.

[0066] The polyurethane sponge obtained in this embodiment has hydrophobic / oleophilic properties. The water contact angle of the polyurethane sponge prepared by KH-570 silane coupling agent modified silica nanoparticles is 131°, and its underwater oil contact angle is 0°. The polyurethane sponge prepared by KH-570 silane coupling agent modified silica nanoparticles showed average saturated adsorption capacities of 3 g / g, 3 g / g, and 3.6 g / g for peanut oil, blended oil, and soybean oil, respectively, and average saturated adsorption capacities of 9 g / g, 2.5 g / g, 6.1 g / g, 2.4 g / g, and 2.5 g / g for dichloromethane, cyclohexane, carbon tetrachloride, petroleum ether, and ethanol, respectively.

[0067] Example 3

[0068] A method for preparing selectively adsorbed hydrophobic polyurethane sponge:

[0069] a) Add 6.4 g of silica nanoparticles (particle size of 15 nm) to a water / ammonia solution with a volume ratio of ammonia and water of 3:17, and stir and heat at 60 °C for 30 min to prepare mixture A;

[0070] b) Add 16 mL of phenyltrimethoxysilane and 160 mL of ethanol to mixture A, heat and stir at 60 °C for 6 h, centrifuge, wash three times with ethanol and deionized water, and dry at 60 °C for 12 h to obtain modified silica nanoparticles for later use.

[0071] c) Dissolve thermoplastic polyurethane particles in a mixed solvent with a volume ratio of 9:1 1,4-dioxane / water. The mass percentage of thermoplastic polyurethane particles in mixture B is 10%, and the total volume of water / 1,4-dioxane is 10 mL. Heat and stir at 60 °C for 90 min until completely dissolved into a homogeneous solution to obtain mixture B.

[0072] d) Add 0.9 g of modified silica nanoparticles to 15 mL of mixed solution B and stir until evenly dispersed to obtain a mixed solution. Place it at -10℃ for 30 min to induce phase separation. Then transfer it to a freezer at -5℃ for 24 h to separate the phases and freeze-dry the sample completely. Then transfer it to a vacuum freeze dryer and freeze-dry at 5 Pa at -50℃ for 24 h to finally obtain selectively adsorbed hydrophobic polyurethane sponge.

[0073] The infrared absorption spectrum of the phenyltrimethoxysilane-modified silica nanoparticles obtained in this embodiment is shown below. Figure 1 As shown (see details) Figure 1 (Phenylacetyltrimethoxysilane), 1650cm -1 and 1450cm -1 The peak at 2930 cm⁻¹ is a characteristic absorption peak of the benzene ring. -1 The peak at this point is a characteristic absorption peak of methyl, indicating that phenyltrimethoxysilane has successfully modified silica nanoparticles, and the resulting modified silica nanoparticles have superhydrophobic properties.

[0074] The transmission electron microscopy image of the phenyltrimethoxysilane-modified silica nanoparticles obtained in this embodiment is shown below. Figure 2 As shown in (c), by Figure 2 It can be seen that the particle size of the silica nanoparticles modified by phenyltrimethoxysilane did not change significantly, indicating that the modification of phenyltrimethoxysilane enhanced the hydrophobicity of silica without affecting its structure.

[0075] The scanning electron microscope image of the phenyltrimethoxysilane-modified silica nanoparticles obtained in this embodiment is shown below. Figure 3 As shown in (c), by Figure 3 It is known that the pore size of the phenyltrimethoxysilane-modified silica nanoparticle composite polyurethane sponge is about 5-10 μm. The surface of the polyurethane sponge skeleton is rough and stacked in layers, which further increases the surface area of ​​the polyurethane sponge.

[0076] The polyurethane sponge obtained in this embodiment exhibits hydrophobic / oleophilic properties. The water contact angle of the phenyltrimethoxysilane-modified polyurethane sponge is 145°, and its underwater oil contact angle is 0°. The polyurethane sponge prepared from phenyltrimethoxysilane-modified silica nanoparticles showed average saturated adsorption capacities of 3.4 g / g, 3.1 g / g, and 2.8 g / g for peanut oil, blended oil, and soybean oil, respectively, and average saturated adsorption capacities of 14.9 g / g, 2.5 g / g, 2.5 g / g, 2.3 g / g, and 2.5 g / g for dichloromethane, cyclohexane, carbon tetrachloride, petroleum ether, and ethanol, respectively.

[0077] Example 4

[0078] A method for preparing selectively adsorbed hydrophobic polyurethane sponge:

[0079] a) Dissolve thermoplastic polyurethane particles in a mixed solvent of 1,4-dioxane / water with a volume ratio of 9.5:0.5, the total volume of water / 1,4-dioxane is 10 mL, and heat and stir at 60 °C for 90 min until completely dissolved to form a homogeneous solution, to obtain mixture B, in which the mass percentage of thermoplastic polyurethane particles is 9%;

[0080] b) Add 1.6g of silica nanoparticles (particle size of 15nm) to 15mL of mixture B, stir until evenly dispersed to obtain a mixed solution, place it at -10℃ for 30min to induce phase separation, then transfer it to a freezer at -5℃ for 24h to separate the phase and completely freeze-dry the sample, then transfer it to a vacuum freeze dryer and freeze-dry at 5Pa atmospheric pressure and -50℃ for 24h to finally obtain selectively adsorbed hydrophobic polyurethane sponge.

[0081] This embodiment uses purchased silica nanoparticles to directly prepare selectively adsorbed hydrophobic polyurethane sponges. Hereafter, the purchased silica nanoparticles will be referred to as unmodified silica nanoparticles. The infrared absorption spectrum of the unmodified silica nanoparticles in this embodiment is shown below. Figure 1 As shown (see details) Figure 1 Unmodified silica (in this embodiment), transmission electron microscopy image of unmodified silica nanoparticles is shown below. Figure 2 As shown in (d), the scanning electron microscope image of the unmodified silica nanoparticles in this embodiment is as follows. Figure 3 As shown in (d).

[0082] In this embodiment, the polyurethane sponge skeleton prepared from unmodified silica nanoparticles exhibits a porous structure and possesses hydrophobic / oleophilic properties. Compared to the polyurethane sponge prepared by directly adding silica nanoparticles in Example 4, the polyurethane sponge phase of Example 1, which added vinyltrimethoxysilane-modified silica nanoparticles, exhibits a more ordered porous structure.

[0083] The polyurethane sponge prepared from unmodified silica nanoparticles exhibited a lower water contact angle (105°) compared to polyurethane sponges prepared from other modified silica nanoparticles, with an underwater oil contact angle of 22°. The polyurethane sponge prepared from unmodified silica nanoparticles showed average saturated adsorption capacities of 2.6 g / g for peanut oil, 2.2 g / g for blended oil, and 2.8 g / g for soybean oil, and average saturated adsorption capacities of 39 g / g for dichloromethane, 2.4 g / g for cyclohexane, 9.5 g / g for carbon tetrachloride, 2.3 g / g for petroleum ether, and 2.5 g / g for ethanol.

[0084] Comparative Example 1

[0085] a) Add 6.4 g of silica nanoparticles (particle size of 15 nm) to a water / ammonia solution with a volume ratio of ammonia and water of 3:17, and stir and heat at 60 °C for 30 min to prepare mixture A;

[0086] b) Add 10 mL of vinyltrimethoxysilane and 160 mL of ethanol to mixture A, heat and stir at 60 °C for 6 h, centrifuge, wash three times with ethanol and deionized water, and dry at 60 °C for 12 h to obtain modified silica nanoparticles for later use.

[0087] c) Dissolve thermoplastic polyurethane particles in a mixed solvent of 1,4-dioxane / water with a volume ratio of 8.5:1.5. The mass percentage of thermoplastic polyurethane particles in mixture B is 8%, and the total volume of water / 1,4-dioxane is 10 mL. Heat and stir at 60 °C for 90 min until completely dissolved into a homogeneous solution to obtain mixture B.

[0088] d) Add 1.8g of modified silica nanoparticles to 15mL of mixed solution B and stir until evenly dispersed to obtain a mixed solution. Place it at -10℃ for 30min to induce phase separation, then transfer it to a -5℃ freezer for 24h to separate the phases and freeze-dry the sample completely. Then transfer it to a vacuum freeze dryer and freeze-dry at 5Pa atmospheric pressure and -50℃ for 24h to finally obtain polyurethane sponge.

[0089] The silica nanoparticles obtained in this comparative example lack hydrophobic properties, primarily because the amount of vinyltrimethoxysilane used is relatively small, resulting in only partial modification of the silica; the silica nanoparticles as a whole are not hydrophobic. The incorporation of nano-silica particles into polyurethane not only alters the surface composition of the polyurethane sponge but also influences the microstructure during phase separation. Surface composition and microstructure are the most significant factors affecting the contact angle of the polyurethane sponge. Under the dual influence of surface composition and microstructure, the polyurethane sponge prepared in this comparative example lacks both hydrophobic and oleophilic properties, and cannot completely adsorb oil from oil / water mixtures.

[0090] Comparative Example 2

[0091] Same as Example 2, except that the amount of modified silica nanoparticles added in step d) is 0.5g.

[0092] The polyurethane sponge prepared in this comparative example showed average saturated adsorption capacities of 1.8 g / g for peanut oil, 2.1 g / g for blended oil, and 3.3 g / g for soybean oil, and average saturated adsorption capacities of 6.3 g / g for dichloromethane, 2 g / g for cyclohexane, 4.2 g / g for carbon tetrachloride, 1.7 g / g for petroleum ether, and 2.9 g / g for ethanol. Due to the low mass of modified silica nanoparticles added in this comparative example, the polyurethane sponge prepared in this comparative example only exhibited hydrophobic properties in certain regions, and could not efficiently separate oil-water mixtures; furthermore, the purity of the separated water and oil was low.

[0093] Comparative Example 3

[0094] Same as Example 1, except that the volume ratio of 1,4-dioxane / water is 7:3.

[0095] Since thermoplastic polyurethane is mainly soluble in hot 1,4-dioxane but insoluble in water, during phase separation, as the temperature of the mixed solution decreases, the dissolved polyurethane precipitates from the solvent and is separated by a suitable amount of immiscible water, thus forming pores. Compared to Example 1, the proportion of water in the mixed solvent used in this example is significantly increased. Excessive water leads to excessively large pores, causing the polyurethane skeleton to collapse and reducing the surface area of ​​the polyurethane sponge. The average saturated adsorption capacities of the polyurethane sponge prepared in this comparative example for peanut oil, blended oil, and soybean oil are 1.2 g / g, 1.1 g / g, and 1.6 g / g, respectively, and the average saturated adsorption capacities for dichloromethane, cyclohexane, carbon tetrachloride, petroleum ether, and ethanol are 3.4 g / g, 0.9 g / g, 2.8 g / g, 1.3 g / g, and 1.5 g / g, respectively. Compared to Example 1, the overall adsorption capacity of the polyurethane sponge prepared in this comparative example is greatly reduced, making selective adsorption difficult to achieve.

[0096] Comparative Example 4

[0097] Same as Example 1, except that step d) is as follows: 1g of modified silica nanoparticles are added to 15mL of mixed solution B and stirred until evenly dispersed to obtain a mixed solution. The solution is placed at -10℃ for 30min to induce phase separation. Then it is transferred to a vacuum freeze dryer and freeze-dried at 5Pa atmospheric pressure and -50℃ for 24h to finally obtain polyurethane sponge.

[0098] The polyurethane sponge obtained in this comparative example has a relatively dense surface with few micropores, the pore size of which is approximately 200–500 nm. The static contact angle with water and the underwater oil contact angle are 92° and 47°, respectively. The average saturated adsorption capacities for peanut oil, blended oil, and soybean oil are 0.9 g / g, 0.7 g / g, and 1.3 g / g, respectively; and the average saturated adsorption capacities for dichloromethane, cyclohexane, carbon tetrachloride, petroleum ether, and ethanol are 2.2 g / g, 0.6 g / g, 0.8 g / g, 0.5 g / g, and 0.4 g / g, respectively. Because this comparative example did not undergo a freezing process and was directly freeze-dried after induced phase separation, the polyurethane did not undergo complete phase separation in the 1,4-dioxane / water mixed solvent. Compared to Example 1, the polyurethane sponge obtained in this comparative example has a significantly smaller volume, smaller internal pores, and lower adsorption capacity.

[0099] As can be seen from the above, the polyurethane foams obtained in Examples 1 to 4 all exhibit hydrophobic / oleophilic properties.

[0100] Examples 1-4 are preferred embodiments. The polyurethane sponges prepared exhibit a porous structure in their internal framework. The water static contact angles of the polyurethane sponges prepared by vinyltrimethoxysilane modified silica nanoparticles, KH-570 silane coupling agent modified silica nanoparticles, phenyltrimethoxysilane modified silica nanoparticles, and unmodified silica nanoparticles reach 142°, 131°, 145°, and 105°, respectively, achieving a hydrophobic effect. The underwater oil contact angles reach 0°, 0°, 0°, and 22°, respectively, achieving an oleophilic effect.

[0101] The saturated adsorption capacity of the hydrophobic polyurethane sponges prepared in Examples 1-4 for different oils is shown in the figure. Figure 4 .from Figure 4 It can be seen that, compared with the unmodified silica polyurethane obtained in Example 4, the vinyltrimethoxysilane modified polyurethane, KH-570 silane coupling agent modified polyurethane, and phenyltrimethoxysilane modified polyurethane obtained in Examples 1 to 3 respectively have higher saturation adsorption capacity for peanut oil, blended oil and soybean oil.

[0102] The saturated adsorption capacity of the hydrophobic polyurethane sponges prepared in Examples 1-4 for different solvent-based oils is shown in the figures. Figure 5 .from Figure 5 As can be seen, the unmodified silica polyurethane obtained in Example 4 showed significantly higher saturated adsorption capacities for dichloromethane and carbon tetrachloride than the modified silica polyurethane obtained in Examples 1-3, while the saturated adsorption capacities for cyclohexane, petroleum ether, and ethanol were very similar to those of the modified silica polyurethane. This indicates that the modified silica polyurethane can significantly increase the adsorption capacity of polyurethane for commonly used edible oils, but cannot increase or even decrease the adsorption capacity for commonly used organic solvents in laboratories, thus achieving selective oil-water separation using polyurethane sponges. Therefore, different modified polyurethanes can be selected for different types of oil-water mixed wastewater to separate oil and water as needed, achieving more efficient oil-water separation.

[0103] The polyurethane sponges obtained in Examples 1-4 not only effectively adsorbed oil from oil-water mixtures but also exhibited excellent oil-water separation efficiency. The separated water showed high purity (the separated water was clear and transparent under an electron microscope, with no obvious oil droplets). Electron microscope images of peanut oil / water mixtures before (left) and after (right) adsorption using the hydrophobic polyurethane sponge of Example 1 are shown below. Figure 6 As shown.

[0104] The polyurethane sponges obtained in Comparative Examples 1 and 2 had poor hydrophobicity due to the failure to successfully modify silica and the low content of doped silica, making it difficult to achieve selective adsorption of solvents / oils.

[0105] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. The application of a selectively adsorbing hydrophobic polyurethane sponge in the selective adsorption and separation of oil / solvent-based wastewater, characterized in that, The oil / solvent type wastewater is selected from edible oil / water and laboratory solvent / water; The skeleton of the selectively adsorbed hydrophobic polyurethane sponge is doped with modified silica nanoparticles or unmodified silica nanoparticles. The modified silica nanoparticles are silica nanoparticles modified with silane coupling agent. The preparation method of the modified silica nanoparticles is as follows: 6.4 g of silica nanoparticles with a particle size of 15 nm are added to a water / ammonia solution with a volume ratio of 3:17 and stirred and heated for 30 min to prepare a mixture B; 14-16 mL of silane coupling agent and 160 mL of ethanol are added to the mixture B, and the mixture is stirred at 60 °C for 6 h. After centrifugation, washing, and drying, the modified silica nanoparticles are obtained. The silane coupling agent is vinyltrimethoxysilane, phenyltrimethoxysilane, or γ-methacryloxypropyltrimethoxysilane; The method for preparing the selectively adsorbed hydrophobic polyurethane sponge includes the following steps: Thermoplastic polyurethane particles were dissolved in a mixed solvent of 1,4-dioxane and water, and heated and stirred until completely dissolved to form a homogeneous solution, thus obtaining mixture A; Modified silica nanoparticles or unmodified silica nanoparticles are added to the mixture A, stirred until uniformly dispersed, and then subjected to phase separation, freezing and freeze-drying to obtain selectively adsorbed hydrophobic polyurethane sponge. The specific steps of phase separation, freezing and freeze-drying are as follows: the solution after being stirred until it is evenly dispersed is placed at a low temperature of -10℃ for 30 min to induce phase separation, then placed in a refrigerator at -5℃ for 24 h, and then placed in a vacuum freeze dryer for freeze-drying at 5 Pa atmospheric pressure and -50℃ for 24 h. The volume ratio of 1,4-dioxane to water is (8.5:1.5) to (9.5:0.5). Add 0.9~1.8 g of the modified silica nanoparticles or unmodified silica nanoparticles to every 15 mL of the mixture A.

2. The application according to claim 1, characterized in that, The mass percentage of thermoplastic polyurethane particles in the mixture A is 8-10%.

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