A magnetic-responsive superhydrophobic polyurethane sponge and its preparation method and application

Abstract

The present invention relates to a superhydrophobic polyurethane sponge with magnetic response for oil-water separation and a preparation method thereof. The superhydrophobic polyurethane sponge provided by the present invention is a bio-based durable material, which can be prepared by placing a polyurethane sponge in an aqueous solution of hydrochloric acid dopamine containing lignin and magnetic nanoparticles and then modifying it with a silane compound. Under the control of an external magnetic field, the superhydrophobic polyurethane sponge prepared by the present invention can selectively adsorb oil substances in the oil-water mixture directionally, improving its oil-water separation performance in oily wastewater, and the oil-water separation efficiency is as high as over 99.5%.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional materials, and particularly relates to a superhydrophobic polyurethane sponge with magnetic response for oil-water separation, its preparation method and application. Background Art

[0002] With the acceleration of the modernization process, during oil exploration, transportation and refining, oil spills and the discharge of industrial oily wastewater have caused serious damage to water resources and the ecological environment. Traditional oil-water separation methods mainly include gravity separation, centrifugation, adsorption, chemical methods, etc. The choice of oil-water separation method needs to consider the oil-water treatment environment at that time. Adsorption is a simple and convenient way for oil-water treatment. Traditional oil-water separation materials have poor oil absorption and water resistance, and absorb a large amount of water while absorbing oil, and the separation efficiency is only about 50%. Therefore, there is an urgent need to develop a superhydrophobic, oleophilic and environmentally friendly interfacial wettability oil-water separation material.

[0003] Sponges have a three-dimensional macroporous structure, a large specific surface area, good elasticity, wide raw materials and low prices. Therefore, using polyurethane sponges as oil-water separation materials has great advantages and good application prospects in practical applications. Many studies have modified sponges to be superhydrophobic and oleophilic through various physical or chemical means, and some have prepared superhydrophobic sponges with magnetic response. Magnetic sponges not only have superhydrophobicity and oleophilicity, but also can selectively adsorb oil substances in the oil-water mixture under the action of an external magnetic field, greatly improving the oil-water separation performance. However, most of the preparation steps are complex, or the magnetism is easily lost, which limits their application in the field of oil-water separation (Liu Hui, Research on the Preparation of Magnetic Composite Sponges and Their Oil-Water Separation Performance, Master's Thesis of Lanzhou Jiaotong University, April 2020). Summary of the Invention

[0004] To solve the above technical problems, the present invention provides a bio-based durable magnetic response superhydrophobic and oleophilic polyurethane sponge and its preparation method. The present invention places a polyurethane sponge in an aqueous solution of hydrochloric acid dopamine containing lignin and iron oxide nanoparticles, and then obtains the magnetic response superhydrophobic and oleophilic polyurethane sponge after being modified by a silane compound. Under the control of an external magnetic field, the superhydrophobic polyurethane sponge prepared by the present invention can selectively adsorb oil substances in the oil-water mixture, improving its oil-water separation performance in oily wastewater.

[0005] One of the purposes of the present invention is to provide a magnetic response superhydrophobic polyurethane sponge, which includes a polyurethane sponge, magnetic nanoparticles, lignin and a superhydrophobic component loaded on the polyurethane sponge, and the superhydrophobic component is obtained by reacting a silane compound with polydopamine.

[0006] Specifically,

[0007] The magnetic nanoparticles are selected from at least one of iron oxide (Fe₃O₄) and iron oxide (Fe₂O₃);

[0008] The particle size of the magnetic nanoparticles is 50 - 300 nm, preferably 100 - 200 nm;

[0009] The structural formula of the silane compound is C n H 2n+1 -Si(R)₃, where 6 ≤ n ≤ 20, and R is selected from at least one of alkoxy groups and halogens; preferably, 10 ≤ n ≤ 18, and R is selected from at least one of methoxy group, ethoxy group, and chlorine;

[0010] Based on the total mass percentage of the magnetic nanoparticles, lignin, and superhydrophobic component being 100%, the content of the magnetic nanoparticles is 0.1 - 20%, preferably 0.8 - 15%; the content of the lignin is 0.1 - 20%, preferably 0.8 - 15%; the content of the superhydrophobic component is 80 - 100%, preferably 70 - 98.4%.

[0011] The second object of the present invention is to provide a method for preparing the above-mentioned magnetoresponsive superhydrophobic polyurethane sponge, which includes placing the polyurethane sponge in an aqueous dopamine hydrochloride solution containing lignin and magnetic nanoparticles, heating and reacting, and then adding a silane compound for reaction to obtain the magnetoresponsive superhydrophobic polyurethane sponge; preferably, the preparation method specifically includes the following steps:

[0012] Step 1) Place the polyurethane sponge in an aqueous dopamine hydrochloride solution;

[0013] Step 2) Continuously add lignin and magnetic nanoparticles, mix evenly to obtain a mixed solution, and heat and react;

[0014] Step 3) Add the silane compound to a solvent, mix evenly to obtain a silane compound solution;

[0015] Step 4) Add the polyurethane sponge after the reaction in Step 2) to the silane compound solution in Step 3), heat and react to obtain the superhydrophobic polyurethane sponge.

[0016] In Step 1) of the above preparation method:

[0017] The polyurethane sponge is first cleaned with a cleaning agent and then dried. The cleaning agent is selected from at least one of water and organic solvents, preferably selected from at least one of water, acetone, and ethanol. More preferably, the cleaning with the cleaning agent is sequentially carried out with water, acetone, and ethanol; the drying temperature is 60 - 90 °C, and the drying time is 50 - 100 min;

[0018] The concentration of the dopamine hydrochloride aqueous solution is 1.5 to 25 mg / mL, preferably 2 to 20 mg / mL; the amount of the dopamine hydrochloride aqueous solution used only needs to completely immerse the polyurethane sponge.

[0019] An alkaline regulator is further added in the step 1). The alkaline regulator adjusts the pH of the dopamine hydrochloride aqueous solution to 7.5 to 9. The alkaline regulator is selected from an alkaline buffer solution or an inorganic alkaline compound solution, preferably at least one selected from Tris-HCl buffer solution, sodium hydroxide solution, potassium hydroxide solution, sodium carbonate solution, and sodium bicarbonate solution. The concentration of the above alkaline buffer solution or inorganic alkaline compound solution can adopt the solution concentration commonly used in the art, as long as it can adjust the pH of the dopamine hydrochloride aqueous solution to 7.5 to 9.

[0020] In the step 2) of the above preparation method:

[0021] The magnetic nanoparticles are selected from at least one of iron oxide and iron sesquioxide;

[0022] The particle size of the magnetic nanoparticles is 50 to 300 nm, preferably 100 to 200 nm;

[0023] Based on 100 parts of the amount of water in the dopamine hydrochloride aqueous solution, the amount of the lignin is 0.01 to 1 part, preferably 0.01 to 0.5 part;

[0024] Based on 100 parts of the amount of water in the dopamine hydrochloride aqueous solution, the amount of the magnetic nanoparticles is 0.01 to 1 part, preferably 0.01 to 0.5 part;

[0025] The temperature of the heating reaction in the step 2) is 20 to 40 °C, and the time of the heating reaction is 30 to 50 h; preferably, the temperature of the heating reaction in the step 2) is 25 to 35 °C, and the time of the heating reaction is 20 to 40 h;

[0026] Lignin and magnetic nanoparticles are continuously added to the step 1). After ultrasonic homogenization, the reaction is carried out at a certain temperature. After the heating reaction is completed, the sponge is taken out. The polyurethane sponge after the heating reaction needs to be washed and dried. Specifically, it can be washed with deionized water, the drying temperature is 60 to 90 °C, and the drying time is 5 to 8 h to obtain a polyurethane sponge wrapped with polydopamine and loaded with lignin and magnetic nanoparticles.

[0027] In the step 3) of the above preparation method:

[0028] The silane compound can adopt a common silane compound with a long aliphatic chain. The structural formula of the silane compound is C n H 2n+1-Si(R)3, where 6 ≤ n ≤ 20 and R is selected from at least one of alkoxy groups and halogens; preferably, 10 ≤ n ≤ 18 and R is selected from at least one of methoxy group, ethoxy group and chlorine; specifically, the silane compound is selected from at least one of n - hexyltrimethoxysilane, octyltrimethoxysilane, n - decyltrimethoxysilane, dodecyltrimethoxysilane, hexadecyltrimethoxysilane, octadecyltrimethoxysilane, n - hexyltriethoxysilane, octyltriethoxysilane, n - decyltriethoxysilane, dodecyltriethoxysilane, hexadecyltriethoxysilane, octadecyltriethoxysilane, n - hexyltrichlorosilane, octyltrichlorosilane, n - decyltrichlorosilane, dodecyltrichlorosilane, hexadecyltrichlorosilane, octadecyltrichlorosilane, and is preferably selected from at least one of n - decyltrimethoxysilane, dodecyltrimethoxysilane, hexadecyltrimethoxysilane, hexadecyltriethoxysilane, hexadecyltrichlorosilane;

[0029] The solvent is selected from one of ethanol, acetone, toluene, tetrahydrofuran, and n - hexane, and is preferably selected from at least one of ethanol and tetrahydrofuran;

[0030] Water and acetic acid are further added to the silane compound solution. Among them, the mass ratio of the solvent to water in the silane compound solution is 12:1 to 7:1, preferably 10:1 to 9:1; the mass ratio of the silane compound to the total amount of the solvent and water is 1:80 to 1:120, preferably 1:85 to 1:110; the mass ratio of water to acetic acid is 80:1 to 120:1, preferably 85:1 to 100:1. The acetic acid added to the silane compound solution can promote the hydrolysis reaction of the silane compound. The hydrolyzed alcohol hydroxyl groups condense with the active groups (such as hydroxyl groups and alkoxy groups) in lignin, and the silane compound is firmly fixed on the polyurethane sponge through chemical bonds. At the same time, the hydrolyzed alcohol hydroxyl groups can also react with the hydroxyl groups in dopamine to generate superhydrophobic components, making the modified polyurethane sponge have superhydrophobic properties.

[0031] In the above - mentioned preparation method:

[0032] In step 4), the temperature of the heating reaction is 50 - 80 °C, and the time of the heating reaction is 1 - 4 h; preferably, the temperature of the heating reaction is 55 - 75 °C, and the time of the heating reaction is 2.5 - 3.5 h;

[0033] The superhydrophobic polyurethane sponge obtained after the heating reaction in step 4) also needs to be washed and dried. Preferably, the drying temperature is 60 - 90 °C, and the drying time is 1 - 3 h; the washing can be carried out with common washing solvents, such as water or common organic solvents.

[0034] A third object of the present invention is to provide a magnetic-responsive superhydrophobic polyurethane sponge as described above or a magnetic-responsive superhydrophobic polyurethane sponge obtained by the above preparation method, which is applied to oil-water separation.

[0035] A method for preparing magnetic hydrophobic sponge using mussel biomimetic chemistry and dopamine hydrochloride has been reported, but the prepared magnetic sponge has unstable shape, poor durability, poor oil-water selectivity, and poor wetting effect. In the present invention, bio-based lignin is added. Lignin itself is a macromolecule with a three-dimensional network structure of biomass, containing active groups phenolic hydroxyl and alcoholic hydroxyl. While increasing the surface roughness of the sponge, it reduces the surface energy of the sponge.

[0036] The present invention utilizes the principle of mussel adhesive protein, and dopamine hydrochloride self-polymerizes to firmly fix lignin and magnetic iron oxide nanoparticles on the polyurethane sponge framework; in addition, the active groups in lignin condense with the alcoholic hydroxyl groups after hydrolysis of long-chain silane compounds, and the long-chain silane is firmly fixed on the polyurethane sponge through chemical bonds, thereby preparing a bio-based durable magnetic-responsive superhydrophobic and oleophilic modified polyurethane sponge.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] 1. The superhydrophobic polyurethane sponge in the present invention greatly changes the surface wettability of the sponge, and the contact angle with water reaches 165°, enabling it to have the properties of superhydrophobic and oleophilic. Under the control of an external magnetic field, it can selectively adsorb oil substances in the oil-water mixture, improving its oil-water separation performance in oily wastewater, and the oil-water separation efficiency is as high as over 99.5%;

[0039] 2. The lignin used in the present invention is a natural biological macromolecule with a three-dimensional network structure, which is the second most abundant natural renewable material, green and environmentally friendly. The introduction of lignin greatly improves the utilization value of lignin. In the present invention, the active groups of lignin are connected to the sponge surface through chemical bonds with long-chain silane, which is more firm and not easy to fall off, improving the wear-resistant and durable performance of the sponge and increasing the service life of the sponge. After repeatedly rubbing the surface of the sponge with sandpaper for 100 cycles, the contact angle still remains above 150°;

[0040] 3. The lignin molecule in the present invention contains a large number of oxygen-containing groups, which can react with other functional molecules to achieve biomass recycling; utilizing the principle of mussel adhesive protein, dopamine hydrochloride self-polymerizes to firmly fix lignin and magnetic nanoparticles on the sponge framework, and then combining with low surface energy silane substances, a bio-based durable magnetic-responsive superhydrophobic and oleophilic polyurethane sponge can be prepared. Description of the Drawings

[0041] Figure 1Scanning electron micrograph of the polyurethane sponge before the reaction in Example 1.

[0042] Figure 2 Scanning electron micrograph of the superhydrophobic polyurethane sponge prepared in Example 1. It can be seen that lignin and Fe₃O₄ particles are loaded on the polyurethane sponge.

[0043] Figure 3 For the superhydrophobic polyurethane sponge prepared in Example 3, and after repeatedly rubbing the surface of the sponge material with sandpaper, the contact angle with water was measured every 10 cycles of rubbing. Figure 3 In it, the abscissa is the number of rubbing times, and the ordinate is the contact angle.

[0044] Figure 4 For the polyurethane sponge prepared in Comparative Example 1, and after repeatedly rubbing the surface of the sponge material with sandpaper, the contact angle with water was measured every 10 cycles of rubbing. Figure 4 In it, the abscissa is the number of rubbing times, and the ordinate is the contact angle.

[0045] Figure 5 Separation process diagram of the superhydrophobic polyurethane sponge, n-hexane and water prepared in Example 3 under the control of an external magnetic field. Among them, a is the state of water and n-hexane without an external magnetic field (magnet); b and c are under an external magnetic field, and the prepared sponge moves with the movement of the magnet (moves to the left side of the beaker) and gradually absorbs n-hexane above the water; d is the remaining water in the beaker after separation, and the water is stained with methylene blue; e is the collected n-hexane, and the n-hexane is stained with oil red.

[0046] Figure 6 Schematic diagram of the in-situ continuous oil-water separation system device. Detailed implementation manners

[0047] The present invention will be specifically described below in conjunction with specific embodiments. It is necessary to point out here that the following embodiments are only for further illustration of the present invention and cannot be understood as limiting the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention still fall within the protection scope of the present invention.

[0048] The test methods and test conditions adopted in the embodiments are as follows:

[0049] In the present invention, Figure 6 The continuous oil-water separation system shown is used for oil-water separation testing. By combining a suction flask and a vacuum device with the prepared sponge, oil can be continuously collected at the oil-water interface, realizing in-situ purification of oil-polluted water. The superhydrophobic sponge is plugged at one end of the tube, and the other end of the tube is connected to a vacuum pump. After starting the vacuum system, the tube blocked by the superhydrophobic sponge is immersed in the oil-water interface, and the superhydrophobic sponge can continuously collect the oil phase. The oil-water separation efficiency is:

[0050] R(%) = (M1 / M0) * 100%

[0051] Wherein, R% - oil removal rate, measuring the efficiency of oil-water separation;

[0052] M0 - mass of the oil phase before separation;

[0053] M1 - mass of the oil phase after separation.

[0054] The sources of the raw materials used in the examples are as follows:

[0055] Enzymatic lignin was provided by Shandong Longli Biotechnology Co., Ltd., with a lignin content of ≥90%, residual sugar content of ≤5%, ash content of ≤5%, and phenolic hydroxyl content of ≥10%.

[0056] The Fe3O4 nanoparticles were self-made and prepared by the chemical co-precipitation method. The preparation method is as follows:

[0057] Fe2(SO4)3 and FeSO4·7H2O were configured into a 0.28 mol / L solution, where the ratio of Fe 3+ :Fe 2+ was 1.5:1. A 0.23 mol / L NaOH solution was slowly added dropwise at 60°C until all the black substances precipitated under the adsorption of a magnet and the solution almost became transparent, and the pH value of the solution did not change within 1 min. Stirring was continued for 20 min under N2 protection, and the precipitate was washed, filtered by suction, and dried in vacuo to obtain Fe3O4 nanoparticles with a particle size of 100 - 200 nm.

[0058] Other raw materials used in the examples were all commercially available products.

[0059] Example 1

[0060] Step 1) A 2×2×2 cm polyurethane sponge was successively washed with deionized water, acetone, and ethanol, and then placed in an oven at 60°C for 100 min, and dried for later use;

[0061] Step 2) The sponge in Step 1) was placed in 50 ml of a 2 mg / mL hydrochloric acid dopamine aqueous solution, and the pH value of the hydrochloric acid dopamine aqueous solution was adjusted to 7.5 with a 1 mol / L sodium hydroxide solution;

[0062] Step 3) 5 mg of lignin and 5 mg of Fe3O4 nanoparticles were added to Step 2), and ultrasonicated for 15 min, and reacted at 25°C for 40 h. After the reaction, the sponge was taken out, washed with deionized water, and placed in an oven at 60°C for 8 h to obtain a polyurethane sponge wrapped with polydopamine, lignin, and Fe3O4;

[0063] Step 4) Add 0.50 g of n-decyltrimethoxysilane, 5 g of water, and 55 mg of acetic acid to 50 g of ethanol, and ultrasonicate for 15 min;

[0064] Step 5) Add the sponge after the reaction in Step 3) to Step 4), take it out after magnetic stirring at 55 °C for 3.5 h, wash it with deionized water, and place it in an oven at 60 °C for 3 h to obtain a bio-based durable magneto-responsive superhydrophobic polyurethane sponge.

[0065] Example 2

[0066] Step 1) Wash a 2×2×2 cm polyurethane sponge successively with deionized water, acetone, and ethanol, place it in an oven at 70 °C for 90 min, and dry it for later use;

[0067] Step 2) Place the sponge in Step 1) into 50 ml of a 6 mg / mL hydrochloric acid dopamine aqueous solution, and adjust the pH value of the hydrochloric acid dopamine aqueous solution to 8 with 1 mol / L potassium hydroxide solution;

[0068] Step 3) Add 60 mg of lignin and 50 mg of iron oxide nanoparticles to Step 2), ultrasonicate for 18 min, react at 28 °C for 35 h, take out the sponge after the reaction, wash it with deionized water, and place it in an oven at 65 °C for 7.5 h to obtain a polyurethane sponge wrapped with polydopamine, lignin, and iron oxide;

[0069] Step 4) Add 0.55 g of dodecyltrimethoxysilane, 5.1 g of water, and 57 mg of acetic acid to 50 g of ethanol, and ultrasonicate for 17 min;

[0070] Step 5) Add the sponge after the reaction in Step 3) to Step 4), take it out after magnetic stirring at 60 °C for 3.2 h, wash it with deionized water, and place it in an oven at 70 °C for 2.5 h to obtain a bio-based durable magneto-responsive superhydrophobic polyurethane sponge.

[0071] Example 3

[0072] Step 1) Wash a 2×2×2 cm polyurethane sponge successively with deionized water, acetone, and ethanol, place it in an oven at 80 °C for 70 min, and dry it for later use;

[0073] Step 2) Place the sponge in Step 1) into 50 ml of a 10 mg / mL hydrochloric acid dopamine aqueous solution, and adjust the pH value of the hydrochloric acid dopamine aqueous solution to 8 with Tris-HCl buffer solution (pH value of 9).

[0074] Step 3) Add 160 mg of lignin and 150 mg of iron oxide nanoparticles into the product of Step 2), sonicate for 20 min, react at 30 °C for 30 h. After the reaction, take out the sponge, wash it with deionized water and then place it in an oven at 70 °C for 7 h to obtain a polyurethane sponge wrapped with polydopamine, lignin and iron oxide.

[0075] Step 4) Add 0.58 g of cetyltrimethoxysilane, 5.2 g of water and 58 mg of acetic acid into 50 g of ethanol, and sonicate for 18 min.

[0076] Step 5) Add the sponge after the reaction in Step 3) into the product of Step 4), stir magnetically at 65 °C for 3 h, then take it out, wash it with deionized water and place it in an oven at 75 °C for 2 h to obtain a bio-based durable magnetoresponsive superhydrophobic polyurethane sponge.

[0077] Example 4

[0078] Step 1) Wash a 2×2×2 cm polyurethane sponge successively with deionized water, acetone and ethanol, then place it in an oven at 80 °C for 60 min, and dry it for later use.

[0079] Step 2) Place the sponge in Step 1) into 50 ml of 15 mg / mL hydrochloric acid dopamine aqueous solution, and adjust the pH value of the hydrochloric acid dopamine aqueous solution to 8.5 with Tris-HCl buffer solution (pH value is 9).

[0080] Step 3) Add 210 mg of lignin and 200 mg of iron oxide nanoparticles into the product of Step 2), sonicate for 25 min, react at 32 °C for 25 h. After the reaction, take out the sponge, wash it with deionized water and then place it in an oven at 80 °C for 6 h to obtain a polyurethane sponge wrapped with polydopamine, lignin and iron oxide.

[0081] Step 4) Add 0.60 g of cetyltrimethoxysilane, 5.3 g of water and 59 mg of acetic acid into 50 g of ethanol, and sonicate for 19 min.

[0082] Step 5) Add the sponge after the reaction in Step 3) into the product of Step 4), stir magnetically at 70 °C for 2.8 h, then take it out, wash it with deionized water and place it in an oven at 80 °C for 1.5 h to obtain a bio-based durable magnetoresponsive superhydrophobic polyurethane sponge.

[0083] Example 5

[0084] Step 1) Wash a 2×2×2 cm polyurethane sponge successively with deionized water, acetone and ethanol, then place it in an oven at 90 °C for 50 min, and dry it for later use.

[0085] Step 2) Place the sponge in Step 1) into 50 ml of 20 mg / mL hydrochloric acid dopamine aqueous solution, and adjust the pH value of the hydrochloric acid dopamine aqueous solution to 9 with Tris-HCl buffer solution (pH value is 9);

[0086] Step 3) Add 250 mg of lignin and 250 mg of iron tetroxide nanoparticles into Step 2), ultrasonicate for 30 min, react at 35 °C for 20 h, take out the sponge after the reaction, wash it with deionized water and then place it in an oven at 90 °C for 5 h to obtain a polyurethane sponge wrapped with polydopamine, lignin and iron tetroxide;

[0087] Step 4) Add 0.62 g of cetyltriethoxysilane, 5.5 g of water, and 60 mg of acetic acid into 50 g of ethanol, and ultrasonicate for 20 min;

[0088] Step 5) Add the sponge after the reaction in Step 3) into Step 4), take it out after magnetic stirring at 75 °C for 2.5 h, wash it with deionized water and then place it in an oven at 90 °C for 1 h to obtain a bio-based durable magnetic-responsive superhydrophobic polyurethane sponge.

[0089] Comparative Example 1

[0090] Step 1) Wash a 2×2×2 cm polyurethane sponge with deionized water, acetone, and ethanol, place it in an oven at 70 °C for 90 min, and dry it for later use;

[0091] Step 2) Place the sponge in Step 1) into 50 ml of 6 mg / mL hydrochloric acid dopamine aqueous solution, and adjust the pH value of the hydrochloric acid dopamine aqueous solution to 8 with 1 mol / L potassium hydroxide solution;

[0092] Step 3) Add 200 mg of iron tetroxide nanoparticles into Step 2), ultrasonicate for 18 min, react at 28 °C for 35 h, take out the sponge after the reaction, wash it with deionized water and then place it in an oven at 65 °C for 7.5 h to obtain a polyurethane sponge wrapped with polydopamine and iron tetroxide;

[0093] Step 4) Add 0.55 g of dodecyltrimethoxysilane, 5.1 g of water, and 57 mg of acetic acid into 50 g of ethanol, and ultrasonicate for 17 min;

[0094] Step 5) Add the sponge after the reaction in Step 3) into Step 4), take it out after magnetic stirring at 60 °C for 3.2 h, wash it with deionized water and then place it in an oven at 70 °C for 2.5 h to obtain the corresponding polyurethane sponge.

[0095] Comparative Example 2

[0096] Step 1) Wash a 2×2×2 cm polyurethane sponge with deionized water, acetone, and ethanol, place it in an oven at 70 °C for 90 min, and dry it for later use;

[0097] Step 2) Place the sponge in Step 1 into 50 ml of 6 mg / mL dopamine hydrochloride aqueous solution, and adjust the pH value of the dopamine hydrochloride aqueous solution to 8 with 1 mol / L potassium hydroxide solution.

[0098] Step 3) Add 210 mg of lignin to Step 2, ultrasonicate for 18 min, react at 28 °C for 35 h. After the reaction is completed, take out the sponge, wash it with deionized water and place it in an oven at 65 °C for 7.5 h to obtain a polyurethane sponge wrapped with polydopamine and lignin.

[0099] Step 4) Add 0.55 g of dodecyltrimethoxysilane, 5.1 g of water, and 57 mg of acetic acid to 50 g of ethanol, and ultrasonicate for 17 min.

[0100] Step 5) Add the sponge after the reaction in Step 3) to Step 4), take it out after magnetic stirring at 60 °C for 3.2 h, wash it with deionized water and place it in an oven at 70 °C for 2.5 h to obtain the corresponding polyurethane sponge.

[0101] Comparative Example 3

[0102] Step 1) Wash a 2×2×2 cm polyurethane sponge with deionized water, acetone, and ethanol, place it in an oven at 70 °C for 90 min, and dry it for later use.

[0103] Step 2) Place the sponge in Step 1 into 50 ml of 6 mg / mL dopamine hydrochloride aqueous solution, and adjust the pH value of the dopamine hydrochloride aqueous solution to 8 with 1 mol / L potassium hydroxide solution.

[0104] Step 3) Add 210 mg of lignin and 210 mg of iron oxide nanoparticles to Step 2, ultrasonicate for 18 min, react at 28 °C for 35 h. After the reaction is completed, take out the sponge, wash it with deionized water and place it in an oven at 65 °C for 7.5 h to obtain a polyurethane sponge wrapped with polydopamine and lignin.

[0105] Step 4) Wash the sponge after the reaction in Step 3) with deionized water and place it in an oven at 90 °C for 1 h to obtain the corresponding polyurethane sponge.

[0106] The test results of the polyurethane sponges prepared in Examples 1 to 5 and Comparative Examples 1 to 3 are as follows:

[0107] Table 1. Separation efficiency of n-hexane / water

[0108] Separation efficiency (R%) Example 1 99.52 Example 2 99.60 Example 3 99.73 Example 4 99.79 Example 5 99.81 Comparative Example 1 85 Comparative Example 2 20 Comparative Example 3 0

[0109] Table 1 lists the separation efficiency of the modified polyurethane sponges obtained in Examples 1-5 and Comparative Examples 1-3 for the n-hexane / water mixture. From the results in Table 1, it can be seen that in Comparative Example 1, without adding lignin, the separation efficiency decreased to 85%. In Comparative Example 2, without adding Fe₃O₄ nanoparticles, the separation efficiency decreased to 20%. In Comparative Example 3, without adding silane, the separation efficiency was only 0. Comparative Examples 2 and 3 were much lower than Examples 1-5.

[0110] Combined with Table 1 and Figure 4 it can be seen that in Comparative Example 1, without adding lignin, the prepared sponge had extremely poor wear resistance and durability. After 10 times of friction, the contact angle decreased below 100 degrees, and the oil-water separation efficiency was also low, indicating that lignin played an extremely important role in the wear resistance and durability of the sponge. In Comparative Example 2, without adding Fe₃O₄ nanoparticles, the sponge could not effectively adsorb oil substances directionally, and the separation efficiency was extremely low. In Comparative Example 3, without adding silane, the prepared sponge lost its hydrophobic and oleophilic properties, and oil and water could not be effectively separated, indicating that the wear resistance, hydrophobic and oleophilic properties of the sponge prepared in the present invention were the result of the combined action of lignin and the hydrophobic layer formed by the reaction of polydopamine and silane. The addition of Fe₃O₄ could effectively adsorb oil substances directionally and improve the oil-water separation efficiency.

[0111] The present invention Figure 5 places the superhydrophobic polyurethane sponge obtained in Example 3 in a mixed solvent of n-hexane and water (where methyl blue is added to the water and oil red is added to the n-hexane), and observes the separation process of the superhydrophobic polyurethane sponge and the solvent under the action of an external magnetic field. Figure 5 In it, a shows the state of the superhydrophobic polyurethane sponge in water and n-hexane without applying a magnetic field. The superhydrophobic polyurethane sponge is stationary in the middle of the solvent, and water and n-hexane are layered. When an external magnetic field is applied, the superhydrophobic polyurethane sponge moves with the movement of the magnetic field (see the sponge moving to the left side of the beaker in b and c), and gradually absorbs the n-hexane above the water; d shows the water stained with methyl blue remaining in the beaker after separation; e shows the n-hexane stained with oil red collected, indicating that the magnetic-responsive superhydrophobic polyurethane sponge provided by the present invention exhibits excellent oil-water separation performance under the action of a magnetic field.

Claims

1. A magnetoresponsive superhydrophobic polyurethane sponge, comprising a polyurethane sponge, and magnetic nanoparticles, lignin and a superhydrophobic component loaded on the polyurethane sponge, wherein the superhydrophobic component is obtained by reacting a silane compound with polydopamine; the polyurethane sponge is placed in an aqueous dopamine hydrochloride solution containing lignin and magnetic nanoparticles, after heating and reacting, a silane compound is added for reaction to obtain the magnetoresponsive superhydrophobic polyurethane sponge.

2. The superhydrophobic polyurethane sponge according to claim 1, wherein the magnetic nanoparticles are selected from at least one of iron tetroxide and iron oxide; and / or, the particle size of the magnetic nanoparticles is 50 - 300 nm; and / or, The structural formula of the silane compound is C n H 2n+1 -Si(R)3, where 6 ≤ n ≤ 20 and R is selected from at least one of alkoxy groups and halogens.

3. The superhydrophobic polyurethane sponge according to claim 2, wherein the particle size of the magnetic nanoparticles is 100 - 200 nm; and / or, The structural formula of the silane compound is C n H 2n+1 -Si(R)3, where 10 ≤ n ≤ 18 and R is selected from at least one of methoxy, ethoxy, and chlorine.

4. The superhydrophobic polyurethane sponge according to claim 1, wherein taking the total mass percentage of the magnetic nanoparticles, lignin and the superhydrophobic component as 100%, the content of the magnetic nanoparticles is 0.1 - 20%, the content of the lignin is 0.1 - 20%, and the content of the superhydrophobic component is 80 - 100%.

5. The superhydrophobic polyurethane sponge according to claim 4, wherein taking the total mass percentage of the magnetic nanoparticles, lignin and the superhydrophobic component as 100%, the content of the magnetic nanoparticles is 0.8 - 15%, the content of the lignin is 0.8 - 15%, and the content of the superhydrophobic component is 70 - 98.4%.

6. A preparation method of the magnetoresponsive superhydrophobic polyurethane sponge according to any one of claims 1 - 5, comprising placing the polyurethane sponge in an aqueous dopamine hydrochloride solution containing lignin and magnetic nanoparticles, after heating and reacting, adding a silane compound for reaction to obtain the magnetoresponsive superhydrophobic polyurethane sponge.

7. The preparation method according to claim 6, characterized in that, The preparation method specifically comprises the following steps: Step 1) Place the polyurethane sponge in an aqueous dopamine hydrochloride solution; Step 2) Continuously add lignin and magnetic nanoparticles, mix evenly to obtain a mixed solution, and heat and react; Step 3) Add the silane compound into a solvent, mix evenly to obtain a silane compound solution; Step 4) Add the polyurethane sponge after heating and reacting in Step 2) into the silane compound solution obtained in Step 3), heat and react to obtain the superhydrophobic polyurethane sponge.

8. The preparation method according to claim 7, wherein In the said Step 1): the polyurethane sponge is first cleaned with a cleaning agent and then dried; and / or, the concentration of the aqueous dopamine hydrochloride solution is 1.5 - 25 mg / mL; and / or, an alkaline regulator is further added in Step 1).

9. The preparation method according to claim 8, wherein the cleaning agent is selected from at least one of water and an organic solvent; and / or, the drying temperature is 60 - 90 °C, and the drying time is 50 - 100 min; and / or, the concentration of the aqueous dopamine hydrochloride solution is 2 - 20 mg / mL; and / or, the alkaline regulator is selected from an alkaline buffer solution or an inorganic alkaline compound solution.

10. The preparation method according to claim 9, characterized in that the cleaning agent is selected from at least one of water, acetone, and ethanol; and / or, the alkaline regulator is selected from at least one of Tris-HCl buffer solution, sodium hydroxide solution, potassium hydroxide solution, sodium carbonate solution, and sodium bicarbonate solution.

11. The preparation method according to claim 8, characterized in that the cleaning with the cleaning agent is carried out by sequentially cleaning with water, acetone, and ethanol; and / or, the alkaline regulator adjusts the pH of the dopamine hydrochloride aqueous solution to 7.5 - 9.

12. The preparation method according to claim 7, characterized in that, In step 2): the magnetic nanoparticles are selected from at least one of magnetite and iron oxide; and / or, the particle size of the magnetic nanoparticles is 50 - 300 nm; and / or, calculated based on 100 parts of the amount of water in the dopamine hydrochloride aqueous solution, the amount of lignin is 0.01 - 1 part; and / or, calculated based on 100 parts of the amount of water in the dopamine hydrochloride aqueous solution, the amount of the magnetic nanoparticles is 0.01 - 1 part; and / or, the temperature of the heating reaction in step 2) is 20 - 40 °C, and the heating reaction time is 30 - 50 h; and / or, the polyurethane sponge after the heating reaction in step 2) needs to be cleaned and dried.

13. The preparation method according to claim 12, characterized in that the particle size of the magnetic nanoparticles is 100 - 200 nm; and / or, calculated based on 100 parts of the amount of water in the dopamine hydrochloride aqueous solution, the amount of lignin is 0.01 - 0.5 part; and / or, calculated based on 100 parts of the amount of water in the dopamine hydrochloride aqueous solution, the amount of the magnetic nanoparticles is 0.01 - 0.5 part; and / or, the temperature of the heating reaction in step 2) is 25 - 35 °C, and the heating reaction time is 20 - 40 h; and / or, after the heating reaction in step 2), the drying temperature is 60 - 90 °C, and the drying time is 5 - 8 h.

14. The preparation method according to claim 7, wherein In step 3): The structural formula of the silane compound is C n H 2n+1 -Si(R)3, where 6 ≤ n ≤ 20, and R is selected from at least one of an alkoxy group and a halogen; and / or, the solvent is selected from one of ethanol, acetone, toluene, tetrahydrofuran, and n-hexane; and / or, water and acetic acid are further added to the silane compound solution.

15. The preparation method according to claim 14, characterized in that The structural formula of the silane compound is C n H 2n+1 -Si(R)3, where 10 ≤ n ≤ 18, and R is selected from at least one of methoxy, ethoxy, and chlorine; and / or, the solvent is selected from at least one of ethanol and tetrahydrofuran.

16. The preparation method according to claim 15, characterized in that the silane compound is selected from at least one of n-hexyltrimethoxysilane, octyltrimethoxysilane, n-decyltrimethoxysilane, dodecyltrimethoxysilane, hexadecyltrimethoxysilane, octadecyltrimethoxysilane, n-hexyltriethoxysilane, octyltriethoxysilane, n-decyltriethoxysilane, dodecyltriethoxysilane, hexadecyltriethoxysilane, octadecyltriethoxysilane, n-hexyltrichlorosilane, octyltrichlorosilane, n-decyltrichlorosilane, dodecyltrichlorosilane, hexadecyltrichlorosilane, and octadecyltrichlorosilane; and / or, in the silane compound solution, the mass ratio of the solvent to water is 12:1 - 7:1; and / or, In the silane compound solution, the mass ratio of the silane compound to the total amount of the solvent and water is 1:80 to 1:120; and / or, In the silane compound solution, the mass ratio of water to acetic acid is 80:1 to 120:

1.

17. The preparation method according to claim 16, wherein The silane compound is selected from at least one of n-decyltrimethoxysilane, dodecyltrimethoxysilane, hexadecyltrimethoxysilane, hexadecyltriethoxysilane, and hexadecyltrichlorosilane; and / or, In the silane compound solution, the mass ratio of the solvent to water is 10:1 to 9:1; and / or, In the silane compound solution, the mass ratio of the silane compound to the total amount of the solvent and water is 1:85 to 1:110; and / or, In the silane compound solution, the mass ratio of water to acetic acid is 85:1 to 100:

1.

18. The preparation method according to claim 7, wherein The temperature of the heating reaction in step 4) is 50 to 80 °C, and the heating reaction time is 1 to 4 h; and / or, The superhydrophobic polyurethane sponge obtained after the heating reaction in step 4) also needs to be washed and dried.

19. The preparation method according to claim 18, wherein The temperature of the heating reaction in step 4) is 55 to 75 °C, and the heating reaction time is 2.5 to 3.5 h; and / or, After the heating reaction in step 4), the drying temperature is 60 to 90 °C, and the drying time is 1 to 3 h.

20. A magnetoresponsive superhydrophobic polyurethane sponge according to any one of claims 1 to 5 or a magnetoresponsive superhydrophobic polyurethane sponge obtained by the preparation method according to any one of claims 6 to 19 is applied to oil-water separation.

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