A corrosion-resistant polyionic liquid coating and its preparation method

Abstract

The present invention discloses a corrosion-resistant polyionic liquid coating and a preparation method thereof. In the present invention, the ionic liquid monomer 3-ethyl-1-vinylimidazolium bromide is used to prepare polyionic liquid (PIL) by free radical polymerization, and then it is coated on the Cu@Cu(OH)2 filter material with superhydrophilic Cu(OH)2 nanoneedles coated copper mesh. Using the polyionic liquid as a protective coating for Cu(OH)2, the prepared Cu@Cu(OH)2-PIL filter material not only has the ability of oil-water separation in wastewater environment, but also has the ability to separate organic solvents with different polarities to a certain extent. XRD, SEM, XPS and other methods are used to analyze Cu@Cu(OH)2 and Cu@Cu(OH)2-PIL, as well as Cu@Cu(OH)2 and Cu@Cu(OH)2-PIL after being soaked in acid, alkali and salt solutions. It is found that the structure of the copper hydroxide layer on the surface of Cu@Cu(OH)2 collapses seriously after being soaked in NaOH and NaCl; after being soaked in HCl, the surface Cu(OH)2 completely reacts with HCl and loses the separation ability. However, the Cu@Cu(OH)2-PIL coated with PIL still retains a complete nano-copper hydroxide layer after being soaked in NaOH and NaCl, and still retains part of Cu(OH)2 after being soaked in HCl.

Description

Technical Field

[0001] The present invention relates to the technical field of liquid coating, and specifically relates to a polyionic liquid coating with corrosion resistance and a preparation method thereof. Background Art

[0002] With the rapid development of industry, oil spill accidents occur frequently, and the random discharge of wastewater and oils / organic solvents has an adverse impact on the global environment and ecosystem. On the other hand, the presence of water in engine oil can also cause problems such as reduced lubrication performance, increased oxidation and corrosion, and emulsification, thereby reducing the service efficiency and life of the engine. Therefore, efficient oil-water separation technology has attracted much attention. Traditional methods (such as combustion, mechanical collection, and chemical dispersion) have been used to remove oils and organic solvents from water, but they are less efficient and prone to secondary pollution. Materials with special wettability are considered important candidate materials for efficient oil-water separation due to their different affinities for water and oil.

[0003] Metal meshes, such as copper, stainless steel, etc., have been widely studied as the substrates of oil-water separation membranes because of their porous structure, excellent mechanical properties, low cost, feasibility of large-scale production, and easy adjustment of their microstructure and chemical composition. Among them, copper mesh, as a common metal filter, has excellent stability, flexibility, and anti-corrosion properties. In addition, rough microstructures such as nanorods, nanoneedles, and nanowires can be easily prepared on copper mesh by simple methods. Among these rough microstructures, constructing copper hydroxide nanostructures on the surface of copper mesh shows excellent performance in special wettability due to the hydrophilic functional groups on its surface. For example, Huaiyuan Wang et al. prepared a copper mesh coated with superhydrophilic and underwater superoleophobic Cu(OH)2 nanoneedles by anodic oxidation, and the filter achieved an oil / water separation efficiency of over 99.5%. Hao Li et al. formed four different surface morphologies of Cu(OH)2 or CuO, namely needle-like, bamboo-leaf-like, pine-needle-like, and peony-like, on the surface of Cu mesh by controlling the oxidation time and oxidation temperature of the chemical reaction. The superhydrophilicity and superoleophilicity of these materials endow them with excellent oil / water separation efficiency. However, the poor chemical stability of Cu(OH)2 affects its structural stability and separation effect when performing oil-water separation in harsh environments such as industrial wastewater. Adding a protective coating on the surface of Cu(OH)2 to prevent direct contact between the external environment and Cu(OH)2 and thus avoid chemical reactions is an effective method to improve the structural stability of Cu(OH)2.

[0004] Poly(ionic liquid) (PIL) is a polymer composed of repeating units of ionic liquid (IL) and a polymer backbone. They have strong chemical inertness, are not easily eroded and decomposed by chemicals, and can exist stably with many chemicals. Poly(ionic liquid) as a protective coating has shown great potential in many fields. For example, Shimou Chen et al. proposed a multifunctional water-blocking polyzwitterionic liquid coating, poly([2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)-tert-butyl acrylate), as a protective layer for zinc metal anodes to prevent water molecules from contacting the zinc metal anode, thereby inhibiting the hydrogen evolution reaction and electrode corrosion. Douglas L. Gin et al. studied a curable imidazole poly(ionic liquid) / ionic liquid coating, which can adsorb and remove up to >99% of the ortho-dichlorobenzene liquid coated on the substrate and can be used for sealing and decontamination of surfaces in contact with toxic industrial chemicals. When poly(ionic liquid) is used as a protective coating for Cu(OH)2 in oil-water separation, the easily damaged Cu(OH)2 can be wrapped by a poly(ionic liquid) film to prevent the Cu(OH)2 layer from being structurally damaged or undergoing chemical reactions under the influence of external environmental factors, and improve the structural and chemical stability of the copper hydroxide network during the oil-water separation process. In addition, the hydrophilic / hydrophobic properties of poly(ionic liquid) are flexible and variable and easy to regulate. By selecting appropriate ionic liquid monomers for polymerization, the coating can show specific affinities for oil and water, enhancing the separation ability of the copper hydroxide network for oil-water mixtures.

[0005] However, under the existing technology, the chemical stability of copper hydroxide is poor, which limits its wide use in the field of oil-water separation.

[0006] Therefore, a new solution needs to be proposed for the above problems. Summary of the Invention

[0007] The purpose of the present invention is to provide a poly(ionic liquid) coating with corrosion resistance and its preparation method to solve the technical problems proposed in the background art.

[0008] To achieve the above purpose, the present invention provides the following technical solution, a preparation method of a poly(ionic liquid) coating with corrosion resistance, at least including the following steps:

[0009] S1: After cleaning the copper mesh, it is treated with an HCl solution and then soaked in the HCl solution, and further soaked in a mixed alkaline solution to complete the preparation of Cu@Cu(OH)2;

[0010] S2: Prepare the poly(ionic liquid), and the preparation of the poly(ionic liquid) includes the synthesis of 3-ethyl-1-vinylimidazolium bromide and the preparation of PIL;

[0011] S3: Based on S1 and S2, prepare Cu@Cu(OH)2-PIL.

[0012] Further, the S1 at least includes the following steps:

[0013] Cut a copper mesh with a mesh size of 180 - 220 meshes into a square with a size of 1 - 3 cm * 1 - 3 cm, and ultrasonically clean it in absolute ethanol and water for 8 - 16 minutes respectively;

[0014] Soak the cleaned copper mesh in 6 - 18 mL of HCl for 8 - 16 minutes to remove organic pollutants and oxide layers;

[0015] Subsequently, wash the copper mesh soaked in hydrochloric acid with a large amount of water 3 - 5 times, soak the washed copper mesh in a 40 - 80 mL mixed alkaline solution containing NaOH (2 - 3 mol / L) and (NH4)2S2O8 (0.1 - 0.2 mol / L) for 5 - 15 minutes, and then wash it with distilled water;

[0016] Then place it on a watch glass and bake it under vacuum conditions at 45 - 65 °C for 1.5 - 3 hours to obtain Cu@Cu(OH)2.

[0017] Further, the synthesis of 3 - ethyl - 1 - vinylimidazolium bromide in the S2 at least includes the following steps:

[0018] The synthesis of 3 - ethyl - 1 - vinylimidazolium bromide in the S2 at least includes the following steps:

[0019] Weigh 4.5 - 5.0 g of 1 - vinylimidazole and 5.0 - 6.0 g of bromoethane, mix them in a flask, and stir at a certain temperature for 48 - 96 hours, and the temperature includes 15 - 25 °C;

[0020] The synthesized 3 - ethyl - 1 - vinylimidazolium bromide is washed several times with ethyl acetate and diethyl ether successively, and then vacuum - dried at room temperature for 8 - 14 hours to obtain 3 - ethyl - 1 - vinylimidazolium bromide, and the 3 - ethyl - 1 - vinylimidazolium bromide is IL - Br.

[0021] Further, the preparation of PIL in the S2 at least includes the following steps:

[0022] Dissolve the 3 - ethyl - 1 - vinylimidazolium bromide monomer and azobisisobutyronitrile as a radical initiator in methanol with twice the equal weight at a ratio of 49 - 52:1, store it under a nitrogen atmosphere, and react at 55 - 70 °C for 4 - 8 hours;

[0023] The prepared PIL was washed with methanol to remove unreacted monomers, then extracted with cold acetone and centrifuged, and finally dried in a vacuum drying oven at 50 °C to 60 °C for 7 h to 8 h to obtain the completed PIL, which is polyionic liquid.

[0024] Furthermore, the step S3 at least includes the following steps:

[0025] Weigh PIL and methanol with a mass ratio of 1:2. After dissolving the PIL, soak the prepared Cu@Cu(OH)2 in the PIL methanol solution for 20 min to 30 min;

[0026] Then soak it in methanol for 0.5 h to 1 h to wash away the excess polyionic liquid on the surface, and finally dry it in a vacuum at 50 °C to 70 °C for 2 h to 3 h to obtain Cu@Cu(OH)2-PIL.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] The present invention uses the ionic liquid monomer 3-ethyl-1-vinylimidazolium bromide to prepare polyionic liquid (PIL) by radical polymerization method, and then coats it on the Cu@Cu(OH)2 filter material with superhydrophilic Cu(OH)2 nanoneedles coated copper mesh. Using polyionic liquid as the protective coating of Cu(OH)2, the prepared Cu@Cu(OH)2-PIL filter material not only has the ability of oil-water separation in wastewater environment, but also has the ability to separate organic solvents with different polarities to a certain extent. By using methods such as XRD, SEM, and XPS to analyze Cu@Cu(OH)2 and Cu@Cu(OH)2-PIL, as well as Cu@Cu(OH)2 and Cu@Cu(OH)2-PIL after being soaked in acid, alkali, and salt solutions, it is found that the copper hydroxide layer structure on the surface of Cu@Cu(OH)2 collapses seriously after being soaked in NaOH and NaCl; after being soaked in HCl, the surface Cu(OH)2 completely reacts with HCl and loses the separation ability. However, the Cu@Cu(OH)2-PIL coated with PIL still retains the complete nano copper hydroxide layer after being soaked in NaOH and NaCl, and still retains part of Cu(OH)2 after being soaked in HCl. Therefore, this filter material still maintains good oil-water separation performance in harsh environments such as acid, alkali, and salt, showing good chemical stability. Description of the Drawings

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0030] Figure 1 This is the NMR spectrum of 3-ethyl-1-vinylimidazolium bromide of the present invention;

[0031] Figure 2 This is the infrared spectra of the monomer of 3-ethyl-1-vinylimidazolium bromide (IL-Br) and PIL of the present invention;

[0032] Figure 3 This is the XRD pattern of the filter material of the present invention;

[0033] Figure 4 This is the SEM image of the filter material of the present invention, where Figure 4 (a) is the original copper mesh; Figure 4 (b) is Cu@Cu(OH)2; Figure 4 (c) is Cu@Cu(OH)2-PIL; Figure 4 (d) is Cu@Cu(OH)2[HCl]; Figure 4 (e) is Cu@Cu(OH)2[NaOH]; Figure 4 (f) is Cu@Cu(OH)2[NaCl]; Figure 4 (g) is Cu@Cu(OH)2-PIL[HCl]; Figure 4 (h) is Cu@Cu(OH)2-PIL[NaOH]; Figure 4 (i) is Cu@Cu(OH)2-PIL[NaCl].

[0034] Figure 5 This is the XPS diagram of the filter material of the present invention;

[0035] Figure 6 This is the surface water contact angle picture of the filter material of the present invention, Figure 6 (a) is the original copper mesh; Figure 6 (b) is Cu@Cu(OH)2; Figure (c) is Cu@Cu(OH)2-PIL);

[0036] Figure 7 This is the separation efficiency and separation flux diagram of the filter material of the present invention;

[0037] Figure 8 This is the separation efficiency and separation flux diagram of the filter material under harsh conditions of the present invention. Detailed implementation manners

[0038] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0039] Example 1:

[0040] A preparation method of a polyionic liquid coating with corrosion resistance, comprising at least the following steps:

[0041] S1: After cleaning with a copper mesh, it is treated with an HCl solution and then soaked in the HCl solution, and further soaked in a mixed alkaline solution to complete the preparation of Cu@Cu(OH)2;

[0042] S2: Prepare a polyionic liquid, and the preparation of the polyionic liquid includes the synthesis of 3-ethyl-1-vinylimidazolium bromide and the preparation of PIL;

[0043] S3: Based on S1 and S2, prepare Cu@Cu(OH)2-PIL.

[0044] Furthermore, the S1 at least includes the following steps:

[0045] Cut a copper mesh of 180-220 mesh into a square with a size of 1-3 cm * 1-3 cm, and ultrasonically clean it in absolute ethanol and water for 8-16 minutes respectively;

[0046] Soak the cleaned copper mesh in 6-18 mL of HCl for 8-16 minutes to remove organic pollutants and oxide layers;

[0047] Subsequently, wash the copper mesh soaked in hydrochloric acid 3-5 times with a large amount of water, soak the washed copper mesh in 40-80 mL of a mixed alkaline solution containing NaOH (2-3 mol / L) and (NH4)2S2O8 (0.1-0.2 mol / L) and react for 5-15 minutes, and then wash it with distilled water;

[0048] Then place it on a watch glass and bake it for 1.5-3 hours under vacuum conditions at 45-65 °C to obtain Cu@Cu(OH)2.

[0049] Furthermore, the synthesis of 3-ethyl-1-vinylimidazolium bromide in S2 at least includes the following steps:

[0050] The synthesis of 3-ethyl-1-vinylimidazolium bromide in S2 at least includes the following steps:

[0051] Weigh 4.5-5.0 g of 1-vinylimidazole and 5.0-6.0 g of bromoethane, mix them in a flask, and stir at a certain temperature for 48-96 hours, and the temperature includes 15-25 °C;

[0052] The synthesized 3-ethyl-1-vinylimidazolium bromide was washed several times with ethyl acetate and then with diethyl ether, and then dried under vacuum at room temperature for 8 h to 14 h to obtain 3-ethyl-1-vinylimidazolium bromide, which is IL-Br.

[0053] Further, the preparation of PIL in S2 includes at least the following steps:

[0054] The 3-ethyl-1-vinylimidazolium bromide monomer and azobisisobutyronitrile as a radical initiator were dissolved in methanol with twice the equal weight at a ratio of 49-52:1, stored under a nitrogen atmosphere, and reacted at 55 °C to 70 °C for 4 h to 8 h;

[0055] The prepared PIL was washed with methanol to remove unreacted monomers, then extracted with cold acetone and centrifuged, and finally dried in a vacuum drying oven at 50 °C to 60 °C for 7 h to 8 h to obtain the prepared PIL, which is polyionic liquid.

[0056] Further, S3 includes at least the following steps:

[0057] Weigh PIL and methanol at a mass ratio of 1:2. After dissolving PIL, the prepared Cu@Cu(OH)2 was soaked in the PIL methanol solution for 20 min to 30 min;

[0058] Then it was soaked in methanol for 0.5 h to 1 h to wash away the excess polyionic liquid on the surface, and finally dried in a vacuum at 50 °C to 70 °C for 2 h to 3 h to obtain Cu@Cu(OH)2-PIL.

[0059] Example 2:

[0060] Based on the above Example 1, a preferred preparation method of a polyionic liquid coating with corrosion resistance is further proposed

[0061] S1: Preparation of Cu@Cu(OH)2;

[0062] S2: Preparation of polyionic liquid (PIL). The preparation of polyionic liquid (PIL) includes the synthesis of 3-ethyl-1-vinylimidazolium bromide and the preparation of PIL;

[0063] S3: Preparation of Cu@Cu(OH)2-PIL based on S1 and S2.

[0064] S1 includes at least the following steps:

[0065] The 200-mesh copper mesh was cut into 2 cm * 2 cm and ultrasonically cleaned in absolute ethanol and water for 10 minutes respectively;

[0066] Immerse the cleaned copper mesh in 10 mL of HCl solution (0.1 mol / L) for 10 minutes to remove organic pollutants and oxide layers;

[0067] Subsequently, wash the copper mesh immersed in hydrochloric acid three times with a large amount of water. Then immerse the washed copper mesh in 50 mL of a mixed alkaline solution containing NaOH (2.5 mol / L) and (NH4)2S2O8 (0.1 mol / L) and react for 10 min, followed by washing with distilled water;

[0068] Then place it on a watch glass and dry it under vacuum at 50 °C for 2 hours to obtain Cu@Cu(OH)2.

[0069] The synthesis of 3-ethyl-1-vinylimidazolium bromide in S2 includes at least the following steps:

[0070] Weigh 4.70 g (0.05 mol) of 1-vinylimidazole and 5.99 g (0.055 mol) of bromoethane, mix them in a flask, and stir at room temperature for 3 days;

[0071] The synthesized 3-ethyl-1-vinylimidazolium bromide (IL-Br) is washed several times with ethyl acetate and diethyl ether successively, and then dried under vacuum at room temperature for 12 h to obtain 3-ethyl-1-vinylimidazolium bromide.

[0072] The NMR spectrum of 3-ethyl-1-vinylimidazolium bromide is as Figure 1 .

[0073] In the figure: 1 HNMR(400 MHz, DMSO-d6) δ (ppm): 9.73 (s, 1H, N-CH=N + ), 8.28 (t, 1H, one proton of CH=CH in ring), 8.02 (t, 1H, one proton of CH=CH in ring), 7.36 (dd, J = 15.6, 8.8 Hz, 1H, one proton of CH2=), 6.03 (dd, J = 15.6, 2.4 Hz, 1H, one proton of CH2=), 5.43 (dd, J = 8.8, 2.4 Hz, 1H, =CH-), 4.27 (q, J = 3.33 Hz, 2H, N + -CH2-), 1.47 (t, J = 7.2 Hz, 3H, -CH3).

[0074] 9.73 (s, 1H, N-CH=N+): A single peak signal, attributed to one proton in the imine structure.

[0075] 8.28 (t, 1H of CH=CH in the ring): triplet, attributed to one proton in the cyclic conjugated system.

[0076] 8.02 (t, 1H of CH=CH in the ring): triplet, attributed to one proton in the cyclic conjugated system.

[0077] 7.36 (dd, J = 15.6, 8.8 Hz, 1H, CH2=): doublet of doublets signal, attributed to one proton on the terminal double bond.

[0078] 6.03 (dd, J = 15.6, 2.4 Hz, 1H, CH2=): attributed to the other proton on the terminal double bond.

[0079] 5.43 (dd, J = 8.8, 2.4 Hz, 1H, =CH-): attributed to one proton on a double bond carbon.

[0080] 4.27 (q, J = 3.33 Hz, 2H, N+-CH2-): quartet signal, attributed to two protons on the methylene directly connected to a nitrogen atom and a methyl group.

[0081] 1.47 (t, J = 7.2 Hz, 3H, -CH3): triplet signal, attributed to three protons on the methyl directly connected to a methylene.

[0082] These NMR data indicate that the compound has functional groups such as a conjugated system, alkenyl double bond, and ethyl group.

[0083] The preparation of PIL in S2 includes at least the following steps:

[0084] Dissolve 3-ethyl-1-vinylimidazolium bromide monomer and azobisisobutyronitrile (AIBN) as a radical initiator in methanol with twice the equal weight at a ratio of 50:1 (molar ratio), store under a nitrogen atmosphere, and react at 65 °C for 6 h;

[0085] The prepared PIL is washed with methanol to remove unreacted monomers, then extracted with cold acetone and centrifuged, and finally dried in a vacuum drying oven at 40 °C for 8 h to obtain the completed PIL, and PIL is poly(ionic liquid).

[0086] The FTIR of the prepared IL-Br monomer and PIL is as Figure 2 shown, and the broad band in the range of 3180 - 2850 cm -1 is attributed to the stretching vibration of the C-H group, and at 1632 cm -1 、1547 cm -1 and 1160 cm -1The peak belongs to the characteristic band of the imidazole ring, indicating the presence of imidazole groups in the polycation framework. It is worth noting that the peak at 1663 cm -1 on IL-Br is caused by the stretching vibration of the unsaturated C═C of the vinyl group, but it is not observed on PIL. This indicates that the vinyl group in IL-Br is consumed during the polymerization process, and the obtained PIL has a high degree of polymerization.

[0087] S3 includes at least the following steps:

[0088] Weigh PIL and methanol with a mass ratio of 1:2. After dissolving PIL, immerse the prepared Cu@Cu(OH)2 in the PIL methanol solution for 30 min;

[0089] Then immerse it in methanol for 1 h, wash off the excess polyionic liquid on the surface, and finally dry it in vacuum at 60 °C for 2 h to obtain Cu@Cu(OH)2-PIL.

[0090] Example 3:

[0091] A corrosion-resistant polyionic liquid coating is obtained by using the preparation method of a corrosion-resistant polyionic liquid coating based on the above Example 1, that is, Cu@Cu(OH)2-PIL.

[0092] Based on the above Example 1 and Example 2, the following detection method is further proposed:

[0093] Oil-water separation experiment

[0094] Fix the prepared Cu@Cu(OH)2 and Cu@Cu(OH)2-PIL between two glass tubes. Slowly pour 20 mL of the stratified oil-water mixture or hexadecane / methanol mixture (w / w = 1:1) into the upper tube, and complete the separation quickly under the action of gravity, and collect the permeate. When performing oil / water or hexadecane / methanol separation, fully wet the copper mesh with water or methanol, and then let the mixture flow into the upper tube through a separatory funnel for oil / water or hexadecane / methanol separation. In addition, for visualizing the separation in the experiment, water and methanol are colored with methylene blue. The separation efficiency (η) is calculated by the following formula: η = M / M0 * 100%, where M0 and M represent the mass of water or methanol before and after separation, respectively. The separation flux (F) is calculated by the following formula: F = V / At, where V is the separation volume, A is the area of the effective filtration copper mesh (m 2 ), and t is the separation time (h).

[0095] Stability test under harsh environments (acids, alkalis, salts)

[0096] The prepared Cu@Cu(OH)2 and Cu@Cu(OH)2-PIL were respectively immersed in 50 mL of aqueous solutions of 1 mol / L HCl, 1 mol / L NaOH, and 1 mol / L NaCl for 12 h, and then washed with distilled water. Then they were dried in a vacuum drying oven at 60 °C for 2 h and used for the oil-water separation experiment to investigate their stability under harsh environments.

[0097] Furthermore, the results and discussions are presented as follows:

[0098] X-ray diffraction (XRD) analysis

[0099] The XRD patterns of the samples are as Figure 3 shown. As can be seen from Figure 3 (A), obvious diffraction peaks of pure copper mesh exist at 2θ = 43.7°, 50.8°, and 74.5°, corresponding to the (111), (200), and (220) crystal planes of copper, respectively. In Cu@Cu(OH)2 and Cu@Cu(OH)2-PIL, in addition to the obvious Cu diffraction peaks, diffraction peaks also exist at 2θ = 17.2°, 24.2°, 34.5°, 40.2°, and 53.8°, corresponding to the (020), (021), (002), (130), and (150) crystal planes of Cu(OH)2, respectively, indicating that Cu(OH)2 was successfully constructed on the copper mesh. Figure 3 (B) shows the XRD patterns of Cu@Cu(OH)2 after being treated with HCl, NaOH, and NaCl. It can be seen that the XRD patterns of Cu@Cu(OH)2[NaOH] and Cu@Cu(OH)2[NaCl] after being treated with NaOH and NaCl have no obvious changes, but new diffraction peaks appear at 2θ = 28.7°, 47.7°, and 56.5° for Cu@Cu(OH)2[HCl] after being treated with HCl, corresponding to the (111), (220), and (311) crystal planes of CuCl, respectively. According to the XRD results, the proposed chemical reaction is as follows:

[0100] Cu(OH)2 + Cu + 2HCl → 2CuCl + 2H2O

[0101] Obviously, Cu@Cu(OH)2 is easily corroded in an acidic environment. And Figure 3In (C), the XRD patterns of Cu@Cu(OH)2-PIL[NaOH] and Cu@Cu(OH)2-PIL[NaCl] after being treated with NaOH and NaCl show no obvious changes compared with Cu@Cu(OH)2-PIL. However, the diffraction peak of Cu(OH)2 in Cu@Cu(OH)2-PIL[HCl] after being treated with HCl significantly weakens or even disappears, and no CuCl diffraction peak appears, indicating that the presence of PIL can play a certain protective role on the surface of the filter material under strong acid conditions.

[0102] Scanning electron microscopy (SEM) analysis

[0103] Figure 4 The SEM images show that the surface of the original copper mesh is smooth, while the surface of Cu@Cu(OH)2 corroded by ammonia is completely covered by a dense nanoneedle array ( Figure 4 b). Comparing with the XRD results, it shows that needle-like copper hydroxide is formed on the surface after copper is corroded by ammonia. This kind of nanoneedle array can increase the surface roughness of the filter material, enhance the wettability of the filter material, and improve the separation efficiency. Figure 4 c It can be found that there are irregular flaky substances on the surface of Cu@Cu(OH)2-PIL, which may be caused by the uneven coating of PIL on the surface of the filter material, indicating that the surface of the Cu@Cu(OH)2-PIL filter material is covered by PIL. Figure 4 d - e are the SEM images of Cu@Cu(OH)2 after being soaked in HCl, NaOH, and NaCl. Figure 4 From d, it can be seen that the needle-like copper hydroxide on the surface of Cu@Cu(OH)2 completely disappears, and a smooth surface appears again. Combining with the XRD results, it can be known that after being treated with HCl, HCl reacts with Cu(OH)2 and metallic Cu to form CuCl. Figure 4 e and 4f show that the needle-like copper hydroxide layer in Cu@Cu(OH)2 after being treated with NaOH and NaCl shows serious structural collapse. Thus, it can be seen that Cu@Cu(OH)2 is structurally unstable in harsh environments such as strong acids, strong alkalis, and strong salts. Figure 4 g - i are the SEM images of Cu@Cu(OH)2-PIL after being treated with HCl, NaOH, and NaCl. Figure 4 g shows that after being treated with HCl, many nano-flaky structures are piled up on the surface of the copper mesh, which is different from the smooth surface in 4d, indicating that the surface-coated PIL can effectively protect the surface structure of the filter material under strong acid. In addition, Figure 4 h and 4i results show that the needle-like copper hydroxide layer still remains intact on the surface of Cu@Cu(OH)2-PIL after being soaked in NaOH and NaCl, further indicating that the coating of PIL makes the filter material have strong stability in harsh environments such as strong acids, strong alkalis, and strong salts.

[0104] XPS analysis

[0105] The chemical compositions of Cu@Cu(OH)2, Cu@Cu(OH)2-PIL filter materials, and their samples treated with HCl, NaOH, and NaCl were characterized by XPS. Figure 5 A and 5B. Figure 5 Compared with Cu@Cu(OH)2, Cu@Cu(OH)2[HCl], Cu@Cu(OH)2[NaOH] and Cu@Cu(OH)2[NaCl] in A, Figure 5 The N element appeared in Cu@Cu(OH)2-PIL, Cu@Cu(OH)2-PIL[HCl], Cu@Cu(OH)2-PIL[NaOH] and Cu@Cu(OH)2-PIL[NaCl] in B, which was attributed to the N element contained in the introduced PIL. The results verified that the PIL was successfully introduced onto Cu@Cu(OH)2. In addition, the Br element can be detected in Cu@Cu(OH)2-PIL, which is also attributed to the Br in PIL. - However, no Br element was detected in Cu@Cu(OH)2-PIL[HCl], Cu@Cu(OH)2-PIL[NaOH] and Cu@Cu(OH)2-PIL[NaCl], which may be due to the exchange of anions of PIL during the immersion of the filter material in HCl, NaOH and NaCl solutions.

[0106] Figure 5 (C) is the Cu 2p spectrum of the filter material. 3 / 2 and Cu2p 1 / 2 Among them, the Cu 2p 3 / 2 There is only one sharp characteristic peak at 935.0±0.3 eV, corresponding to Cu 2+ , and Cu appeared at 938.2-946.7eV 2+ The satellite characteristic peaks are due to Cu(OH)2. It is worth noting that the Cu in Cu@Cu(OH)2[HCl] 2+ The characteristic peak and its satellite peaks disappeared, and Cu appeared at 933.2eV. 0 Cu + The characteristic peaks indicate that after Cu@Cu(OH)2 was treated with HCl, Cu(OH)2 reacted with HCl to generate Cu 0 Cu + , XRD results have confirmed the existence of CuCl. Figure 5(D), the peaks of Cu@Cu(OH)2, Cu@Cu(OH)2[NaOH], and Cu@Cu(OH)2[NaCl] at 531.0 ± 0.3 eV correspond to the crystal phase oxidation state peaks. Combining with Figure 5 (C) results, indicating the presence of Cu(OH)2. The peak at 532.3 eV in Cu@Cu(OH)2[HCl] is the peak of H2O, which may be the H2O generated by the reaction of Cu(OH)2 on the filter material surface with HCl.

[0107] Figure 5 In the Cu 2p energy spectrum of (E), Cu@Cu(OH)2-PIL, Cu@Cu(OH)2-PIL[HCl], Cu@Cu(OH)2-PIL[NaOH], and Cu@Cu(OH)2-PIL[NaCl] all detected the Cu 2+ characteristic peak at 934.7 ± 0.2 eV, and Cu 2+ satellite peaks appeared at 938 - 945 eV. Combining with Figure 5 (F) O1s energy spectrum, it can be seen that Cu(OH)2 exists on the surface of these filter materials. In addition, Cu@Cu(OH)2-PIL[HCl] also showed a Cu 0 / Cu + characteristic peak at 933.1 eV, which is still the result of the reaction of Cu(OH)2 with HCl. Different from Figure 5 (C) Cu@Cu(OH)2[HCl] which only has Cu 0 / Cu + , both Cu 0 / Cu + and Cu 2+ exist in Cu@Cu(OH)2-PIL[HCl], indicating that the PIL coated on the surface of Cu@Cu(OH)2 can protect the chemical composition on the filter material surface to a certain extent in a strong acid environment. At the same time, Figure 5 (C) - (D) results confirm that Cu(OH)2 still exists on the surface of Cu@Cu(OH)2 and Cu@Cu(OH)2-PIL after being treated with NaOH and NaCl, indicating that Cu@Cu(OH)2 and Cu@Cu(OH)2-PIL can exhibit excellent chemical stability in strong alkali and strong salt environments.

[0108] Surface wettability of the filter material

[0109] The surface wettability of the filter material was studied by measuring the contact angle of water droplets. As Figure 6As shown, the original copper mesh exhibits hydrophobicity with a water contact angle of 109.9° in air. When water droplets come into contact with Cu@Cu(OH)2 and Cu@Cu(OH)2-PIL, they are immediately diffused and absorbed, and the water angle is 0°, indicating that the surface of Cu@Cu(OH)2 has superhydrophilicity. When a water droplet contacts Cu@Cu(OH)2-PIL, its initial contact angle is 55.4°, but the water droplet can diffuse and penetrate into the filter medium within 5 seconds, resulting in a final water contact angle of 0°, indicating that the surface of Cu@Cu(OH)2-PIL also has hydrophilicity. Compared with Cu@Cu(OH)2, the initial contact angle of Cu@Cu(OH)2-PIL with water becomes larger. The reason may be that the alkyl groups of the imidazolium substituents in the polyionic liquid reduce the surface tension of the polyionic liquid, thus weakening the hydrophilicity when the surface of the filter medium contacts water.

[0110] Oil-water separation experiment

[0111] Low-viscosity oils (n-hexane and petroleum ether) and high-viscosity oil (n-hexadecane) were selected as the oil phases, and the "water removal" performance of Cu@Cu(OH)2 and Cu@Cu(OH)2-PIL was studied by separating layered oil / water mixtures. n-Hexadecane was selected as the oil phase, and the "methanol removal" performance of Cu@Cu(OH)2 and Cu@Cu(OH)2-PIL was studied by separating layered oil / methanol mixtures. All experiments were carried out under the condition that only gravity was the sole driving force. Water or methanol completely penetrated through the filter medium, and the oil phase was sealed and remained at the top of the filter medium. For different oil-water mixtures, the oil could be closed at the upper end of the filter medium for at least 2 hours. As Figure 7 (A) shows, the separation efficiency of Cu@Cu(OH)2 and Cu@Cu(OH)2-PIL is between 93% - 97%, and the separation efficiency for the oil-water mixture of high-viscosity oil is higher than that for the oil-water mixture of low-viscosity oil. Due to the relatively large pores of the copper mesh, the separation process is relatively fast. The entire oil / water separation after stacking three filter media is completed only within 3 - 5 seconds. Therefore, the permeation amount of the filter medium is relatively high. In the water mixture of low-viscosity oils (n-hexane and petroleum ether), the water flux value of Cu@Cu(OH)2 under the action of gravity is about 40,000 L / (m 2 ·h) (as shown in 7(B)), and for the water mixture of high-viscosity oil (n-hexadecane), the water flux value under the action of gravity is about 30,000 L / (m 2 ·h). While for Cu@Cu(OH)2-PIL in petroleum ether / water (higher than 50,000 L / (m 2 ·h)) and n-hexadecane / water (higher than 40,000 L / (m 2·h)), the water flux in the mixture is significantly higher than that of Cu@Cu(OH)2. Meanwhile, using n-hexadecane and methanol as two solvents with different polarities, the separation performance of Cu@Cu(OH)2 and Cu@Cu(OH)2-PIL for organic solvents with different polarities was tested. First, methanol quickly passes through the oil-wetted Cu@Cu(OH)2. After the methanol flows out, Cu@Cu(OH)2 cannot retain n-hexadecane and then it will slowly flow down through Cu@Cu(OH)2. In contrast, when Cu@Cu(OH)2-PIL is used to separate methanol / n-hexadecane, after the methanol flows out, n-hexadecane will be briefly blocked and then flow down slowly. Its methanol separation efficiency is 90.3 ± 1.8%, and the methanol flux value under gravity is about 19,000 L / (m 2 ·h), and the results show that Cu@Cu(OH)2-PIL has a certain separation ability for methanol and n-hexadecane.

[0112] Considering that industrial wastewater is mostly in acidic, alkaline or saline environments, the corrosion resistance of Cu@Cu(OH)2 and Cu@Cu(OH)2-PIL in harsh environments was investigated. Using n-hexane as the oil phase, the oil / water separation performance of the filter materials of Cu@Cu(OH)2 and Cu@Cu(OH)2-PIL after being immersed in 1 mol / L HCl, 1 mol / L NaOH and 1 mol / L NaCl aqueous solutions for 12 h was tested. After stacking three pieces of the immersed filter materials for oil / water separation, the whole separation process was completed within 3 - 5 seconds, and its separation efficiency is as Figure 8 (A) shown. When Cu@Cu(OH)2 is immersed in HCl and then used for n-hexane / water separation, after the water flows out, the filter material cannot retain n-hexane, resulting in separation failure. For the n-hexane / water mixture after Cu@Cu(OH)2 is immersed in NaOH and NaCl, the separation efficiency is greater than 93%, and the water flux value is greater than 40,000 L / (m 2 ·h). Therefore, Cu@Cu(OH)2 after being immersed in NaOH and NaCl still has good oil / water separation performance. Different from Cu@Cu(OH)2, Cu@Cu(OH)2-PIL can be used for n-hexane / water mixture separation after being immersed in HCl, NaOH and NaCl, and its separation efficiencies are 90.0%, 94.7% and 92.8% respectively. And the water flux value of Cu@Cu(OH)2-PIL after being immersed in HCl is lower than 40,000 L / m 2 h, while the water flux values of Cu@Cu(OH)2-PIL after being immersed in NaOH and NaCl are still higher than 40,000 L / (m 2· h). It shows that HCl immersion will lead to a decrease in the oil separation efficiency of Cu@Cu(OH)2-PIL, while NaOH and NaCl immersions can still endow Cu@Cu(OH)2-PIL with good oil / water separation performance.

[0113] The above results indicate that both Cu@Cu(OH)2 and Cu@Cu(OH)2-PIL have good alkali and salt resistance, but Cu@Cu(OH)2 does not have acid resistance, while Cu@Cu(OH)2-PIL has certain acid resistance. This is related to the surface structure and chemical properties of Cu@Cu(OH)2 and Cu@Cu(OH)2-PIL after being immersed in HCl, NaOH, and NaCl. The XRD, SEM, and XPS results of the filter materials show that the needle-like copper hydroxide layer still remains intact on the surface of Cu@Cu(OH)2-PIL after being immersed in NaOH and NaCl. In Cu@Cu(OH)2 after being immersed in NaOH and NaCl, although the needle-like copper hydroxide layer shows serious structural collapse, its surface chemical composition has not changed. This may be an important reason why Cu@Cu(OH)2 and Cu@Cu(OH)2-PIL still have good oil / water separation performance after being immersed in NaOH and NaCl. In addition, the SEM results show that after HCl immersion, Cu@Cu(OH)2 is severely eroded by acid, and the needle-like copper hydroxide on the surface completely disappears, while a nano-sheet structure accumulates on the surface of Cu@Cu(OH)2-PIL. XRD and XPS further confirm that after being treated with HCl, Cu(OH)2 on the surface of Cu@Cu(OH)2 completely reacts with HCl to form metallic Cu or CuCl, while in Cu@Cu(OH)2-PIL, in addition to Cu 0 / Cu + , Cu(OH)2 also exists simultaneously. Therefore, in a strong acid environment, the PIL coated on the surface of Cu@Cu(OH)2 protects the stability of the surface structure and chemical composition of the filter material to a certain extent, enabling Cu@Cu(OH)2-PIL to have certain oil-water separation performance. The above results show that Cu@Cu(OH)2-PIL has the ability to be used in wastewater environments.

[0114] In summary:

[0115] In the present invention, a Cu@Cu(OH)2 filter material with superhydrophilicity was prepared using a copper mesh, and a PIL was coated on its surface, successfully preparing Cu@Cu(OH)2-PIL modified by PIL and capable of oil-water separation in a wastewater environment. The separation results of the layered oil-water mixture showed that Cu@Cu(OH)2 and Cu@Cu(OH)2-PIL could effectively separate the oil / water mixture, and Cu@Cu(OH)2-PIL also had the ability to separate some organic solvents with different polarities. The XRD, SEM, and XPS results showed that the structure of the copper hydroxide layer on the surface of Cu@Cu(OH)2 collapsed after being soaked in NaOH and NaCl, but the surface chemical composition did not change. The complete nano copper hydroxide layer was still retained on the surface of Cu@Cu(OH)2-PIL after being soaked in NaOH and NaCl. Therefore, Cu@Cu(OH)2 and Cu@Cu(OH)2-PIL in an alkaline or saline environment still had good oil / water separation performance. Different from this, Cu@Cu(OH)2 soaked in HCl was severely eroded by the acid and its surface became smooth, while the surface of Cu@Cu(OH)2-PIL after being soaked in HCl was stacked with nano-sheet structures. In addition to the Cu 0 / Cu + species, there was also some Cu(OH)2, making Cu@Cu(OH)2-PIL still have a certain oil-water separation performance in an acidic environment. The above results indicate that the polyionic liquid as a coating successfully protected the filter material from (or reduced) the corrosion and side reactions of acids, alkalis, and salts in the wastewater environment, and improved the separation performance and stability of the filter material in a harsh environment.

[0116] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be regarded as limiting the claimed rights.

Claims

1. A preparation method of a polyionic liquid coating with corrosion resistance, characterized in that: At least include the following steps: S1: After cleaning with a copper mesh, it is treated with an HCl solution and then soaked in the HCl solution, and further soaked in a mixed alkaline solution to complete the preparation of Cu@Cu(OH)2; S2: Prepare a polyionic liquid, and the preparation of the polyionic liquid includes the synthesis of 3-ethyl-1-vinylimidazolium bromide and the preparation of PIL; The synthesis of 3-ethyl-1-vinylimidazolium bromide in S2 at least includes the following steps: Weigh 4.5 g to 5.0 g of 1-vinylimidazole and 5.0 g to 6.0 g of bromoethane and mix them in a flask, and stir at a certain temperature for 48 h to 96 h, and the temperature includes 15 °C to 25 °C; The synthesized 3-ethyl-1-vinylimidazolium bromide is washed several times with ethyl acetate and ether, and then vacuum dried at room temperature for 8 h to 14 h to obtain 3-ethyl-1-vinylimidazolium bromide, and the 3-ethyl-1-vinylimidazolium bromide is IL-Br; The preparation of PIL in S2 at least includes the following steps: Dissolve 3-ethyl-1-vinylimidazolium bromide monomer and azobisisobutyronitrile as a radical initiator in methanol with twice the equal weight according to a ratio of 49 to 52:1, store it under a nitrogen atmosphere, and react at 55 °C to 70 °C for 4 h to 8 h; The prepared PIL is washed with methanol to remove unreacted monomers, then extracted with cold acetone and centrifuged, and finally dried in a vacuum drying oven at 40 °C to 60 °C for 7 h to 8 h to obtain the prepared PIL, and the PIL is the polyionic liquid S3: Based on S1 and S2, prepare Cu@Cu(OH)2-PIL.

2. The preparation method of a polyionic liquid coating with corrosion resistance according to claim 1, characterized in that: S1 at least includes the following steps: Cut a copper mesh of 180 to 220 meshes into a square, and the size of the square is 1 to 3 cm * 1 to 3 cm, and ultrasonically clean it in anhydrous ethanol and water for 8 min to 16 min respectively; Soak the cleaned copper mesh in 6 mL to 18 mL of HCl solution for 8 min to 16 min to remove organic pollutants and oxide layers; Subsequently, wash the copper mesh soaked in hydrochloric acid 3 to 5 times with a large amount of water, soak the washed copper mesh in 40 mL to 80 mL of a mixed alkaline solution containing NaOH and (NH4)2S2O8 for 5 min to 15 min, and then wash it with distilled water. The concentration of NaOH used is 2 to 3 mol / L, and the concentration of (NH4)2S2O8 used is 0.1 to 0.2 mol / L; Then place it on a watch glass and bake it for 1.5 h to 3 h under vacuum conditions at 45 °C to 65 °C to obtain Cu@Cu(OH)2.

3. The preparation method of a polyionic liquid coating with corrosion resistance according to claim 1, characterized in that: S3 at least includes the following steps: Weigh PIL and methanol at a mass ratio of 1:2, dissolve the PIL, and soak the prepared Cu@Cu(OH)2 in the PIL methanol solution for 20 min to 30 min; Then soak it in methanol for 0.5 h to 1 h, wash away the excess polyionic liquid on the surface, and finally dry it under vacuum at 50 °C to 70 °C for 2 h to 3 h to obtain Cu@Cu(OH)2-PIL.

4. A poly ionic liquid coating with corrosion resistance, characterized in that: A corrosion-resistant polyionic liquid coating is prepared by using the preparation method of a corrosion-resistant polyionic liquid coating according to any one of claims 1-3, which is Cu@Cu(OH)2-PIL.

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