Preparation method of super-hydrophobic polyurethane sponge for oil-water separation

Abstract

The present invention belongs to the field of oil-water separation technology, and in particular to a method for preparing a super-hydrophobic polyurethane sponge for oil-water separation. The present invention uses readily available commercial polyurethane sponges as substrates, which are modified by two-step continuous coating with polydopamine and graphene oxide, and then a reducing agent is used to reduce the graphene oxide on the sponge surface to obtain a super-hydrophobic polyurethane sponge. The sponge prepared by the above method has super-hydrophobicity and excellent adsorption capacity for oil products, and can achieve adsorption of diesel and crude oil. This sponge can be used in conjunction with an oil-water separator to achieve oil-water separation. The sponge prepared by this method has super-hydrophobicity and good mechanical properties, and can achieve cyclic oil-water separation.

Description

Technical Field

[0001] The invention belongs to the technical field of oil-water separation, and in particular relates to a method for preparing a super-hydrophobic polyurethane sponge for oil-water separation. Background Art

[0002] With the rapid development of the global economy and the continuous development of industrialization, offshore oil transportation and petrochemical industries have also developed rapidly. However, many accidents have occurred in the process, resulting in large amounts of oil spills. This has caused great damage to the environment and poses a great threat to aquatic life. On October 2, 2021, a serious offshore drilling platform leak occurred on the coast of California, USA. Approximately 3,000 barrels of crude oil leaked into the sea, causing great harm to nearby residents and the ecological environment. Therefore, it is increasingly important to be able to effectively separate oil and water and recover floating oil on the water surface. Therefore, there is an urgent need to develop a durable super-hydrophobic oil-water separation material.

[0003] Traditional oil-water separation methods are plagued by high production costs, low separation efficiency, and some methods can cause secondary environmental pollution. Therefore, there is an urgent need to develop methods for oil-water separation. Current adsorbent materials are widely used, but these adsorbents suffer from poor selectivity and limited recyclability, making them ineffective for oil-water separation in certain scenarios and potentially causing additional water pollution. In recent years, porous materials have become increasingly popular due to their low cost, excellent oil-water separation performance, and ease of use. This has made it possible to use commercial polyurethane sponges for effective oil-water separation. Compared to other adsorbents, polyurethane sponges possess superior three-dimensional porous structures, superior surface area, porosity, and superior mechanical properties. These sponges can achieve multiple cycles of oil absorption and desorption, allowing oil recovery through physical extrusion. Superhydrophobic sponges have been fabricated by modifying the surface roughness of polyurethane sponges and introducing nanoparticles.

[0004] In recent years, inspired by the adhesive properties of dopamine secreted by marine mussels, researchers have begun to construct micro- and nanostructures through dopamine surface modification. Dopamine self-polymerizes on the surface of these structures to form polydopamine, which is then combined with other substances to reduce the surface energy, thereby creating superhydrophobic porous structures or membrane structures. This provides a new approach and method for the simple preparation of superhydrophobic sponges. Summary of the Invention

[0005] To solve the technical problems involved above, the present invention uses cheap and readily available commercial polyurethane as a substrate, immerses a polydopamine-modified polyurethane sponge in a graphene oxide solution, and reduces the graphene oxide on the surface of the structure through an oxidation-reduction reaction, ultimately obtaining a superhydrophobic polyurethane sponge with excellent mechanical properties.

[0006] In order to achieve the above object, the present invention provides a method for preparing a reduced graphene oxide modified super-hydrophobic polyurethane sponge for oil-water separation, comprising the following steps:

[0007] Step 1: Dissolve dopamine hydrochloride powder in a beaker at a constant temperature, then adjust the pH of the solution to alkaline by adding Tris buffer (trishydroxymethylaminomethane). Place the pretreated polyurethane sponge in the beaker and place it in a magnetic stirrer for 12 to 15 hours. Then remove it and wash it with anhydrous ethanol and deionized water respectively. Then remove it and dry it in a 60-65°C forced air drying oven for 1 to 2 hours to obtain a polydopamine-coated polyurethane sponge.

[0008] The sponge is a commercial polyurethane sponge with a pore size of 40PPI to 60PPI. The pretreatment method is:

[0009] Cut the polyurethane sponge into 1cm pieces 3 The sponge block is placed in an ethanol solution for ultrasonic cleaning for 1 hour to 2 hours, then placed in deionized water for ultrasonic cleaning for 0.5 hour to 1 hour, and then taken out and dried in a 60-65° C. forced air drying oven for 1 hour to 2 hours to obtain a pretreated polyurethane sponge.

[0010] Step 2: Weigh graphene oxide (GO) powder and dissolve it in deionized water via ultrasonic dispersion to obtain a GO aqueous solution. The polydopamine-coated polyurethane sponge obtained in Step 1 is then placed in the solution and ultrasonically dispersed to allow the polyurethane sponge to fully absorb the GO solution. The GO solution is then removed from the sponge by centrifugation. The GO-coated polydopamine sponge is then placed in a forced air drying oven and dried for 1–2 hours to obtain multiple graphene oxide-polydopamine-coated polyurethane sponges.

[0011] Step 3: Place a hydroiodic acid (HI) solution in a beaker and heat it to 70-75°C in a constant temperature water bath. Place the graphene oxide-coated polydopamine sponge from step 2 in the constant temperature heated HI solution for 10-15 seconds, then take out the reduced graphene oxide (rGO)-polydopamine-coated polyurethane sponge, and place the obtained sponge in a 60-65°C forced air drying oven for 1h-2h to obtain a superhydrophobic reduced graphene oxide-coated polydopamine sponge.

[0012] Furthermore, in step 1, the concentration of the dopamine solution is 1.2-2 mg / ml, and the pH is 8-9.

[0013] Furthermore, in step 1, the setting temperature of the magnetic stirrer is 25-35° C., and the rotation speed is 2000-3000 r / min.

[0014] Furthermore, the concentration of the GO aqueous solution in step 2 is 3-7 mg / ml.

[0015] Furthermore, in step 2, the polyurethane sponge coated with polydopamine is immersed in the GO solution and ultrasonically dispersed for 0.5 h to 1 h using an ultrasonic dispersion instrument.

[0016] Furthermore, the mass fraction of the HI solution in step 3 is 55% to 58%. The graphene oxide-coated polydopamine polyurethane sponge is squeezed in the HI solution to fully absorb the HI solution, and the treatment time is 10s to 15s.

[0017] The reduced graphene oxide modified super-hydrophobic polyurethane sponge prepared by the present invention is used for oil-water separation.

[0018] Furthermore, the reduced graphene oxide modified super-hydrophobic polyurethane sponge prepared by the present invention is used for the adsorption and separation of diesel or crude oil in water.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] In the prior art, there are many cases of using mussel biomimetic methods to modify the surface of material structures using dopamine hydrochloride for use in the field of oil-water separation. However, in most cases, the modified materials perform poorly in complex oil-water separation environments. The present invention prepares a reduced graphene oxide-modified super-hydrophobic polyurethane sponge for oil-water separation, which is prepared by co-modifying polydopamine and graphene oxide. In the present invention, polydopamine is first coated on the surface of the polyurethane sponge structure. The polyurethane sponge is immersed in a dopamine hydrochloride solution, and then a Tris buffer solution is added to the solution. This causes dopamine to undergo a self-polymerization reaction under alkaline conditions to produce polydopamine, which is evenly coated on the sponge structure surface, thereby increasing the roughness of the sponge structure. Not only can it be firmly bonded to the graphene oxide, but it can also be chemically bonded to the hydroxyl groups on the sponge. This provides conditions for the deposition of graphene oxide. The team then coated the surface of a polydopamine-coated polyurethane sponge with graphene oxide by simply impregnating it with a GO solution, thereby producing a durable graphene oxide-polydopamine-coated polyurethane sponge. The graphene oxide on the sponge surface was then reduced using the redox properties of a constant-temperature HI solution to produce a superhydrophobic sponge coated with reduced graphene oxide. This sponge exhibited superhydrophobicity, with a hydrophobicity angle of up to 162°.

[0021] The super-hydrophobic polyurethane sponge modified with reduced graphene oxide for oil-water separation, prepared by the present invention, has a water contact angle of 162° and an oil droplet contact angle of 0°. Its diesel adsorption capacity can reach 29.8 times its own weight, and even after 20 cycles of oil absorption and desorption, the super-hydrophobic sponge's contact angle remains above 150°. Its initial adsorption capacity for crude oil can reach 24.9 times its own weight. This allows for the absorption of underwater oil products and effective oil-water separation.

[0022] The raw materials required for the preparation of the present invention are inexpensive and readily available, the preparation process is simple and easy to understand, and the reaction conditions are simple and uncomplicated. The resulting reduced graphene oxide-modified super-hydrophobic polyurethane sponge for oil-water separation has excellent adsorption effect on oil products. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a flow chart for preparing the polyurethane sponge coated with reduced graphene oxide-polydopamine of the present invention;

[0024] Figure 2 The water drop contact angle test of the superhydrophobic reduced graphene oxide-coated polydopamine polyurethane sponge in Example 2;

[0025] Figure 3 The scanning electron microscope images of the polyurethane sponge and the modified polyurethane sponge involved in Examples 1, 2, and 3 at different magnifications are shown;

[0026] Figure 4 Super hydrophobicity test of the pretreated polyurethane sponge and modified polyurethane sponge involved in Examples 1, 2, and 3;

[0027] Figure 5 The oil absorption capacity test of the polyurethane sponge coated with reduced graphene oxide-polydopamine at room temperature in Example 2;

[0028] Figure 6 The mechanical properties of the polyurethane sponge coated with reduced graphene oxide-polydopamine at room temperature in Example 2 were tested;

[0029] Figure 7 This is the CCl4 absorption process of underwater dyeing at room temperature in Example 2. DETAILED DESCRIPTION

[0030] The present invention proposes a super-hydrophobic polyurethane sponge modified with reduced graphene oxide for oil-water separation, which effectively adsorbs oil products. This makes a significant contribution to the field of oil-water separation. The preparation of the super-hydrophobic sponge is described in more detail using specific examples. The present invention is described in detail below with reference to specific examples.

[0031] The raw materials used in the examples are all commercially available chemicals.

[0032] Graphene oxide (GO) was purchased from Shenzhen Suiheng Technology Co., Ltd. (Shenzhen, China).

[0033] Deionized water (H2O) and dopamine hydrochloride (98%, Wokai) were purchased from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China).

[0034] Hydroiodic acid (HI, 55.0-58.0%) was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. (Shanghai, China).

[0035] Tris (hydroxymethylaminomethane, ≥99.9%) was purchased from Shanghai MacLean Biochemical Technology Co., Ltd. (Shanghai, China).

[0036] Sudan III was purchased from Shanghai Bid Pharmaceutical Technology Co., Ltd. (Shanghai, China).

[0037] Ethanol (AR, 95.0%) was purchased from Shanghai Boer Chemical Reagent Co., Ltd. (Shanghai, China).

[0038] Crude oil was provided by Sinopec Northwest Oilfield Company (Urumqi).

[0039] Diesel oil was purchased from Sinopec (China).

[0040] All chemical reagents were of analytical grade.

[0041] The preparation method of the reduced graphene oxide modified polyurethane sponge of the present invention is mainly divided into three processes. Process 1 is to coat the pretreated sponge with polydopamine, and dopamine undergoes a self-polymerization reaction in an alkaline environment and is coated on the surface of the sponge structure; Process 2 is to soak the cleaned polydopamine-coated sponge obtained in process 1 in graphene oxide solutions of different concentrations at room temperature, and use an ultrasonic dispersion instrument for ultrasonic dispersion; Process 3 is to place the sponge soaked with graphene oxide in a hydroiodic acid solution, and reduce the graphene oxide to obtain a reduced graphene oxide-polydopamine modified polyurethane sponge. The sponge is washed and dried to obtain a superhydrophobic modified sponge. The specific preparation process is shown in Figure 1 .

[0042] Example 1

[0043] Step 1: Pre-treat the polyurethane sponge. Cut the polyurethane sponge into 1cm 3 The polyurethane sponge block was placed in an ethanol solution for ultrasonic cleaning for 1.5 hours, and then placed in deionized water for ultrasonic cleaning for 0.5 hours; after being taken out, it was dried in a 65°C forced air drying oven for 2 hours.

[0044] Step 2: Dissolve 80 mg of dopamine hydrochloride powder in 60 ml of deionized water at a constant temperature (25°C). Then, add Tris buffer (tris(hydroxymethyl)aminomethane)) to adjust the pH of the solution to 8.5. Four to six pretreated polyurethane sponges from step 1 are placed in a beaker and placed in a magnetic stirrer for 15 hours. The sponges are then washed with anhydrous ethanol and deionized water, respectively. The sponges are then dried in a 60°C forced air drying oven for 2 hours to obtain polydopamine-coated polyurethane sponges.

[0045] Step 3, prepare a GO solution with a concentration of 3 mg / ml: Weigh 60 mg of graphene oxide (GO) powder and dissolve it in 20 ml of deionized water by ultrasonic dispersion to obtain a 3 mg / ml GO solution. Place 4 to 6 polydopamine-coated polyurethane sponges obtained in step 2 into the GO solution, and then ultrasonically disperse them to allow the polyurethane sponges to fully absorb the GO solution. Subsequently, the GO solution is removed from the sponges by centrifugation. The GO-coated polydopamine sponges are then placed in a forced air drying oven and dried for 2 hours to obtain multiple graphene oxide-coated polydopamine polyurethane sponges.

[0046] Step 4: Place a hydroiodic acid (HI) solution in a beaker and heat it to 70°C in a constant temperature water bath. Place the graphene oxide-coated polydopamine polyurethane sponge in step 3 in a constant temperature heated HI solution for 10s (squeeze the sponge fully to make it fully contact with the HI solution), then take out the reduced graphene oxide (rGO) and polydopamine-coated polyurethane sponge, and wash the obtained sponge with anhydrous ethanol and deionized water three times. The cleaned sponge is then placed in a 60°C forced air drying oven for 2h to obtain a superhydrophobic reduced graphene oxide-coated polydopamine polyurethane sponge.

[0047] The water contact angle test of the reduced graphene oxide modified super-hydrophobic polyurethane sponge for oil-water separation prepared in the above steps was performed, and the WCA was 136°.

[0048] Example 2

[0049] The 3 mg / ml GO solution in Example 1 was replaced by a 5 mg / ml GO solution, and the remaining steps were the same as those in Example 1.

[0050] The water contact angle test of the reduced graphene oxide modified super-hydrophobic polyurethane sponge for oil-water separation prepared in this example was performed, and the WCA was 162°.

[0051] Example 3

[0052] The 3 mg / ml GO solution in Example 1 was replaced by a 7 mg / ml GO solution, and the remaining steps were the same as those in Example 1.

[0053] The water contact angle test of the reduced graphene oxide modified super-hydrophobic polyurethane sponge for oil-water separation prepared in this example was performed, and the WCA was 144°.

[0054] Figure 2 This is the water drop contact angle of the superhydrophobic reduced graphene oxide-coated polydopamine polyurethane sponge in Example 2. It can be seen that the water contact angle reaches 162°, so the prepared sponge has superhydrophobicity.

[0055] Figure 3 The following are scanning electron microscope images of the polyurethane sponge and modified polyurethane sponge involved in Examples 1, 2, and 3 at different magnifications. Figure 3 (a, a1) are the sponge structures of pretreated polyurethane sponge at different magnifications; Figure 3 (b, b1) are the sponge structures of polydopamine-coated polyurethane sponge at different magnifications; Figure 3 (c, c1) are the sponge structures of polydopamine-coated polyurethane sponge soaked in graphene oxide at different magnifications; Figure 3 (d, d1) are the sponge structures of reduced graphene oxide-polydopamine coated polyurethane sponge treated with HI solution at different magnifications. Figure 3 It can be seen that the surface of the blank sponge structure has a smooth structure, while the surfaces of the sponge structures in different steps have different degrees of roughness.

[0056] Figure 4 The super-hydrophobicity tests of the pretreated polyurethane sponge and the modified polyurethane sponge involved in Examples 1, 2, and 3 also include the hydrophobicity tests of the graphene oxide-polydopamine coated polyurethane sponge and the reduced graphene oxide-polydopamine coated polyurethane sponge under different GO solution concentrations (three contact angle tests were performed on the modified sponge under each GO concentration, and the average value was taken. Figure 4 (a) shows the water contact angles of sponges obtained under different treatment steps, namely, pretreated sponge, polydopamine-coated polyurethane sponge, polydopamine-coated polyurethane sponge soaked in graphene oxide solution, and reduced graphene oxide-polydopamine-coated polyurethane sponge. Figure 4 (b) Water contact angle test of polydopamine-coated polyurethane sponge soaked in graphene oxide solution obtained by soaking in GO solution with different concentrations. Figure 4 (c) Water contact angle test of polyurethane sponge coated with reduced graphene oxide-polydopamine at different concentrations.

[0057] Figure 5The oil absorption capacity of the reduced graphene oxide-polydopamine-coated polyurethane sponge in Example 2 was tested at room temperature. 20 oil absorption and decomposition tests were performed on diesel and crude oil, respectively. The adsorption capacity for diesel reached a maximum of 29.8 times its own weight, with no significant change after 20 cycles. The initial adsorption capacity for crude oil reached 24.9 times its own weight, then decreased to 11.4 times its own weight after five cycles. It remained stable within 20 cycles, remaining at around 11.4 times. Therefore, the sponge exhibits adsorption properties for crude oil.

[0058] Figure 6 The mechanical properties of the polyurethane sponge coated with reduced graphene oxide-polydopamine at room temperature in Example 2 were tested. The polyurethane sponge coated with reduced graphene oxide-polydopamine was subjected to 20 oil absorption-deoiling experiments. Figure 6 As shown in the figure, the shape of the superhydrophobic modified sponge did not change significantly. The WCA was 152° after 10 cycles, 141° after 20 cycles, and 156° after 30 cycles. The hydrophobicity did not change significantly. This proves that the mechanical properties of the sponge are excellent.

[0059] Figure 7 For Example 2, at room temperature, the CCl4 dyed underwater was absorbed. Figure 7 As shown, Figure 7 Process 1 shows that Sudan III stained CCl4 sinks to the bottom of the water. Figure 7 Step 2 is to press the sponge into the bottom of the water to contact Sudan III stained CCl4. Figure 7 Process 3 shows that the superhydrophobic sponge selectively adsorbs Sudan III-stained CCl4 on the bottom of the water, which shows that the prepared superhydrophobic sponge can perform stable oil-water separation.

[0060] In summary, the comparison of water contact angles confirms the successful modification of the superhydrophobic sponge. The formation of a roughened surface structure, as demonstrated by SEM, further confirms the successful preparation of the modified sponge. The contact angle of the superhydrophobic sponge can be tuned by varying the concentration of the GO solution. Notably, as the GO concentration increases, the sponge's hydrophobicity initially increases and then decreases.

Claims

1. A method for preparing a reduced graphene oxide modified super-hydrophobic polyurethane sponge for oil-water separation, characterized in that: The specific steps include: (1) Under constant temperature conditions, dopamine hydrochloride powder was dissolved in water, and Tris buffer was added to adjust the pH of the dopamine solution to alkaline. The pretreated polyurethane sponge was immersed in the dopamine solution and placed in a magnetic stirrer for 12 h to 15 h. After that, the sponge was taken out, washed, and dried to obtain a polydopamine-coated polyurethane sponge. The concentration of the dopamine solution was 1.2 to 2 mg / ml, and the pH was 8 to 9. The temperature of the magnetic stirrer was set at 25 to 35 °C, and the speed was 2000 to 3000 r / min. (2) Ultrasonic dispersion of graphene oxide powder in deionized water to obtain a GO aqueous solution; soaking a polyurethane sponge coated with polydopamine in the GO aqueous solution and ultrasonically dispersing the polyurethane sponge to allow the polydopamine-coated polyurethane sponge to fully absorb GO; centrifugation and drying to obtain a polydopamine-coated polyurethane sponge coated with graphene oxide; the concentration of the GO aqueous solution is 5 mg / ml; (3) Heat the hydroiodic acid solution to 70-75°C in a water bath, place the graphene oxide-coated polydopamine polyurethane sponge into the hydroiodic acid solution, the mass fraction of the hydroiodic acid solution is 55%-58%, squeeze the graphene oxide-coated polydopamine polyurethane sponge in the hydroiodic acid solution to fully absorb the hydroiodic acid solution, and the treatment time is 10s-15s to convert the GO on its surface into rGO; take it out and dry it to obtain the reduced graphene oxide modified superhydrophobic polyurethane sponge.

2. the preparation method of the reduced graphene oxide modified super-hydrophobic polyurethane sponge for oil-water separation according to claim 1, is characterized in that, Use an ultrasonic dispersion instrument to perform ultrasonic dispersion for 0.5 h to 1 h.

3. The preparation method of reduced graphene oxide modified super-hydrophobic polyurethane sponge for oil-water separation according to claim 1, wherein The drying is carried out in a forced air drying oven at 60-65° C. for 1-2 hours.

4. The preparation method of reduced graphene oxide modified super-hydrophobic polyurethane sponge for oil-water separation according to claim 1, wherein The preparation method of the pretreated polyurethane sponge comprises the following steps: cutting the polyurethane sponge into cubic blocks of 1 cm×1 cm×1 cm in size; placing the polyurethane sponge blocks in an ethanol solution for ultrasonic cleaning for 1 to 2 hours, and then placing the polyurethane sponge blocks in deionized water for ultrasonic cleaning for 0.5 to 1 hour; taking out the blocks and drying them in a 60 to 65° C. forced air drying oven for 1 to 2 hours to obtain the pretreated polyurethane sponge; the pore size of the polyurethane sponge is 40 PPI to 60 PPI.

5. the application of reduced graphene oxide modified super-hydrophobic polyurethane sponge prepared by the method described in claim 1, is characterized in that, The reduced graphene oxide modified super-hydrophobic polyurethane sponge is used for oil-water separation.

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