Preparation method of in-situ oxidized plant polyphenol modified stainless steel mesh

Abstract

The invention discloses a preparation method of an in-situ oxidized plant polyphenol modified stainless steel mesh, which comprises the following steps: step 1, taking a stainless steel mesh as a base material, sequentially carrying out ultrasonic cleaning in acetone, absolute ethyl alcohol and deionized water, and then drying; secondly, the cleaned and dried stainless steel mesh is soaked in a mixed solution of the solution A and the solution B to be coated; 3, adding an oxidizing agent into the mixed solution, and carrying out an in-situ oxidation reaction under an acidic condition; and 4, the modified stainless steel mesh is cleaned and dried, and the hydrophilic / underwater super-oleophobic stainless steel mesh is obtained. The stainless steel mesh prepared by the method shows a hydrophilic / underwater super-oleophobic wetting form, has good stability and durability in a harsh environment, and can separate an oil-water mixture and a high-concentration oil-in-water emulsion at ultrahigh permeation flux and good oil removal rate. The preparation method is simple and low in cost, and can be used for industrial production on a large scale.

Description

Technical Field

[0001] The invention belongs to the technical field of oily wastewater treatment, relates to a method for preparing a stainless steel mesh modified by in-situ oxidation of plant polyphenols, and specifically relates to a method for preparing a hydrophilic / underwater superoleophobic coating. Background Art

[0002] With the rapid development of all walks of life, the discharge of oily wastewater is also increasing year by year. The generation and discharge of a large amount of oily wastewater poses a major threat to the ecological environment, and with the enrichment of the food chain, it also poses a threat to human life and safety. Therefore, it is urgent to treat and dispose of oily wastewater reasonably. Filtration separation technology is recognized as an effective technology for on-demand separation based on droplet particle size, not only because of its simple operation, low cost, and no secondary pollution, but also because of the efficient filtration achieved by the screening mechanism during the separation process. However, in the long-term oil-water separation process, oil pollution is inevitable, which leads to blockage of the water passage of the filter medium, resulting in reduced flux and shortened service life.

[0003] Hydrophilic-underwater superoleophobic wetting materials can allow water phase to pass through at appropriate pore size, repel oil phase, effectively control dirt adhesion, and have obvious advantages in oil-water separation. Compared with other polymer membranes and fabrics, metal mesh has good mechanical strength and large pore size, which makes it wear-resistant and has ultra-high permeation flux. In addition, metal mesh is low-priced, easy to process, and can be used in large quantities for practical industrial applications.

[0004] CN118949713 A discloses a method for preparing a stainless steel mesh capable of separating an oil-water mixture and an oil-in-water emulsion. The two steps of hydrophilic modification involved in the preparation process of the method are complicated, and the hydrothermal reaction increases the difficulty and cost of industrial application. CN 113082853 B discloses a three-dimensional Janus stainless steel mesh capable of separating emulsified oil and water and a method for preparing the same. The dopamine and polyethyleneimine used in the method are expensive and cannot be mass-produced in practical applications, which increases the difficulty and cost of industrial application. Summary of the invention

[0005] In order to solve the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a method for preparing an in-situ oxidized plant polyphenol modified stainless steel mesh. The stainless steel mesh prepared by the method exhibits a hydrophilic / underwater superoleophobic wetting morphology, has good stability and durability in harsh environments, and can separate oil-water mixtures and high-concentration oil-in-water emulsions with ultra-high permeation flux and good oil removal rate in the application of oil-water separation. The preparation method of the present invention is simple, low-cost, and can be used in large quantities for industrial production.

[0006] The objective of the present invention is achieved through the following technical solutions:

[0007] A method for preparing a stainless steel mesh modified by in-situ oxidation of plant polyphenols comprises the following steps:

[0008] Step 1: Using a stainless steel mesh as a substrate, ultrasonically cleaning it in acetone, anhydrous ethanol and deionized water in sequence, and then drying it;

[0009] The cleaning time is 20 to 60 minutes;

[0010] The copper mesh has a size of 2-5 cm x 2-5 cm and a mesh size of 200-500.

[0011] Step 2: Immerse the stainless steel mesh cleaned and dried in step 1 into a mixed solution of solution A and solution B for coating, wherein:

[0012] The solution A is a mixed solution of tannic acid (TA) and Tris-HCl, wherein the concentrations of TA and Tris-HCl are 1.5-2.5 wt % and 1.15-1.25 wt % respectively;

[0013] The solution B is a homogeneous solution of tetraethyl orthosilicate (TEOS) and ethanol, and the concentration of tetraethyl orthosilicate is 3.5-4.0wt%;

[0014] The volume ratio of solution A to solution B is 10:2 to 10:5;

[0015] The pH of the mixed solution is 8 to 9;

[0016] The coating time is 20 to 60 minutes;

[0017] Step 3: adding an oxidant to the mixed solution of step 2, and performing an in-situ oxidation reaction under acidic conditions, wherein:

[0018] Under the acidic conditions, the pH value is 4 to 6;

[0019] The in-situ oxidation reaction is carried out on an air shaker at room temperature for 5 to 8 hours at a shaking speed of 120 to 150 rpm;

[0020] The oxidant is one of NaClO solution, NaClO3 and NaIO4, and the added amount is 3-5wt% of solution A;

[0021] Step 4: Clean and dry the stainless steel mesh modified in step 3 to obtain a hydrophilic / underwater super oleophobic stainless steel mesh, wherein:

[0022] The cleaning method comprises: using ethanol and deionized water to wash away the unreacted solution on the surface of the modified stainless steel mesh;

[0023] The drying temperature is 60-80°C and the drying time is 1-3h;

[0024] The hydrophilic / underwater superoleophobic stainless steel mesh exhibits underwater superoleophobic effects on dodecane, gasoline, diesel, etc.

[0025] The present invention uses a one-step coating method to deposit TA and SiO2 particles on the surface of a stainless steel mesh to construct a hydrophilic surface. The in-situ oxidation of TA is combined with the hydrolysis and condensation of TEOS to enhance the adhesion and hydrophilicity of the TA-SiO2 coating. The TA used in the present invention is a naturally occurring plant polyphenol, which is abundant in reserves, low in price, and has good biodegradability; it contains abundant catechol or gallic acid groups and can form a smooth light-colored coating on the surfaces of various substrates. The introduction of an oxidant can enhance the stability of the TA coating. Compared with the use of more NaIO4, the NaClO3 finally determined by the present invention is low in price and also has good oxidation ability for the TA coating. TEOS is cheap and easy to obtain. It can form nano-silicon dioxide with abundant hydroxyl groups by hydrolysis and condensation under alkaline conditions. It also has good hydrophilicity and can combine with TA under the action of hydrogen bonds to form a hydrophilic hybrid coating. Stainless steel mesh has good mechanical properties, low price, easy processing, and its micron-level pore size has ultra-high permeability flux. The special wetting material prepared with stainless steel mesh as the base has good corrosion resistance and good impact resistance in the continuous oil-water separation process, and can be used in large quantities in actual industrial applications.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] (1) The present invention uses a one-step coating method to deposit TA and SiO2 particles on the surface of a stainless steel mesh to construct a hydrophilic surface. The in-situ oxidation of TA is combined with the hydrolysis and condensation of TEOS to enhance the adhesion and hydrophilicity of the TA-SiO2 coating.

[0028] (2) The hydrophilic / underwater superoleophobic stainless steel mesh prepared by the present invention has an ultra-high permeation flux, and has excellent separation performance for oil-water mixtures and high-concentration oil-in-water emulsions through multi-layer stacking. It has good stability and durability in harsh environments, and exhibits good impact resistance and recyclability in the continuous oil-water separation process.

[0029] (3) The hydrophilic stainless steel mesh obtained by the present invention has a simple preparation process, mild reaction conditions, and low-cost materials, and is suitable for industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The water contact angle diagram of the stainless steel mesh in air before and after modification changes with time;

[0031] Figure 2 The contact angle diagram of stainless steel mesh under different oils in water before and after modification;

[0032] Figure 3 The water contact angle and underwater diesel contact angle of T2T-stainless steel mesh in solutions with different pH values;

[0033] Figure 4 The water contact angle and underwater diesel contact angle of T2T-stainless steel mesh immersed in salt solution for 7 days;

[0034] Figure 5 The water contact angle and underwater diesel contact angle of T2T-stainless steel mesh after 7 consecutive days of hydraulic flushing;

[0035] Figure 6 This is a diagram of the oil-water separation device;

[0036] Figure 7 The flux diagrams of T2T-stainless steel mesh with different stacking numbers for separation of pure water, oil-water mixture and high-concentration oil-in-water solution;

[0037] Figure 8 The oil removal rate diagram of T2T-stainless steel mesh with different stacking layers for separating oil-water mixture and high-concentration oil-in-water emulsion;

[0038] Fig. 9 Parameter diagram (pure water flux, oil-water mixture flux and oil removal rate) of 3-layer T2T-stainless steel mesh for oil-water mixture separation in cyclic test;

[0039] Fig.10 Graph showing separation parameters (pure color flux, oil-in-water emulsion flux, and oil removal) of a 3-layer T2T-stainless steel mesh for separation of a high concentration oil-in-water emulsion in a cyclic test. DETAILED DESCRIPTION

[0040] The technical solution of the present invention is further described below in conjunction with the embodiments, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention should be included in the protection scope of the present invention.

[0041] Example 1

[0042] (1) A 300-mesh stainless steel mesh was cut into a size of 4 cm × 4 cm, and ultrasonically cleaned in acetone, anhydrous ethanol, and deionized water for 30 min in sequence to remove impurities such as dust and oil on the surface of the metal mesh. The mesh was then placed in a 60°C constant temperature drying oven and dried for 2 h to obtain a clean stainless steel mesh after pretreatment.

[0043] (2) Prepare a solution A of 2 wt% tannic acid (TA) and 1.21 wt% Tris-HCl, with a pH value of 8.5. Prepare a homogeneous solution B of 3.8 wt% tetraethyl orthosilicate (TEOS) and ethanol. Mix solution A and solution B in a volume ratio of 10:3, then quickly immerse a clean stainless steel mesh in the solution and perform hydrophilic coating in an ultrasonic field for 30 minutes.

[0044] (3) The pH value of the mixed solution was adjusted to 5, and the mixture was reacted on an air shaker at room temperature for 6 h, with the shaking speed maintained between 120 and 150 rpm. The modified stainless steel mesh was washed with ethanol and deionized water to remove the unreacted solution on the surface. The modified stainless steel mesh was then dried in a constant temperature drying oven at 60°C for 2 h to obtain the modified TT-stainless steel mesh.

[0045] Example 2

[0046] (1) A 300-mesh stainless steel mesh was cut into a size of 4 cm × 4 cm, and ultrasonically cleaned in acetone, anhydrous ethanol, and deionized water for 30 min in sequence to remove impurities such as dust and oil on the surface of the metal mesh. The mesh was then placed in a 60°C constant temperature drying oven and dried for 2 h to obtain a clean stainless steel mesh after pretreatment.

[0047] (2) Prepare a solution A of 2 wt% tannic acid (TA) and 1.21 wt% Tris-HCl, with a pH value of 8.5. Prepare a homogeneous solution B of 3.8 wt% tetraethyl orthosilicate (TEOS) and ethanol. Mix solution A and solution B in a volume ratio of 10:3, then quickly immerse a clean stainless steel mesh in the solution and perform hydrophilic coating in an ultrasonic field for 30 minutes.

[0048] (3) Add a NaClO solution with a concentration of 4 wt% of solution A to the mixed solution, adjust the pH value of the mixed solution to 5, and carry out an in-situ oxidation reaction on an air shaker at room temperature for 6 h, with the shaking speed maintained between 120 and 150 rpm. Wash the unreacted solution on the surface of the modified stainless steel mesh with ethanol and deionized water. Then dry it in a constant temperature drying oven at 60°C for 2 h to obtain the modified T1T-stainless steel mesh.

[0049] Example 3

[0050] (1) A 300-mesh stainless steel mesh was cut into a size of 4 cm × 4 cm, and ultrasonically cleaned in acetone, anhydrous ethanol, and deionized water for 30 min in sequence to remove impurities such as dust and oil on the surface of the metal mesh. The mesh was then placed in a 60°C constant temperature drying oven and dried for 2 h to obtain a clean stainless steel mesh after pretreatment.

[0051] (2) Prepare a solution A of 2 wt% tannic acid (TA) and 1.21 wt% Tris-HCl, with a pH value of 8.5. Prepare a homogeneous solution B of 3.8 wt% tetraethyl orthosilicate (TEOS) and ethanol. Mix solution A and solution B in a volume ratio of 10:3, then quickly immerse a clean stainless steel mesh in the solution and perform hydrophilic coating in an ultrasonic field for 30 minutes.

[0052] (3) Add NaClO3 at a concentration of 4 wt% of solution A to the mixed solution, adjust the pH value of the mixed solution to 5, and carry out in-situ oxidation reaction on an air shaker at room temperature for 6 h, with the shaking speed maintained between 120 and 150 rpm. Wash the unreacted solution on the surface of the modified stainless steel mesh with ethanol and deionized water. Then dry it in a constant temperature drying oven at 60°C for 2 h to obtain the modified T2T-stainless steel mesh.

[0053] Example 4

[0054] (1) A 300-mesh stainless steel mesh was cut into a size of 4 cm × 4 cm, and ultrasonically cleaned in acetone, anhydrous ethanol, and deionized water for 30 min in sequence to remove impurities such as dust and oil on the surface of the metal mesh. The mesh was then placed in a 60°C constant temperature drying oven and dried for 2 h to obtain a clean stainless steel mesh after pretreatment.

[0055] (2) Prepare a solution A of 2 wt% tannic acid (TA) and 1.21 wt% Tris-HCl, with a pH value of 8.5. Prepare a homogeneous solution B of 3.8 wt% tetraethyl orthosilicate (TEOS) and ethanol. Mix solution A and solution B in a volume ratio of 10:3, then quickly immerse a clean stainless steel mesh in the solution and perform hydrophilic coating in an ultrasonic field for 30 minutes.

[0056] (3) Add NaIO4 at a concentration of 4 wt% of solution A to the mixed solution, adjust the pH value of the mixed solution to 5, and carry out in-situ oxidation reaction on an air shaker at room temperature for 6 h, with the shaking speed maintained between 120 and 150 rpm. Wash the unreacted solution on the surface of the modified stainless steel mesh with ethanol and deionized water. Then dry it in a constant temperature drying oven at 60°C for 2 h to obtain the modified T3T-stainless steel mesh.

[0057] Performance Test:

[0058] (1) Hydrophilic and oleophobic performance test

[0059] The changes of the water contact angle (WCA) of the stainless steel mesh prepared in Examples 1 to 4 and the original stainless steel mesh in air over time are shown in FIG. Figure 1As shown. The water contact angle of the original stainless steel mesh is 128.73°. After modification, the water contact angle is reduced, and the initial water contact angles of TT-stainless steel mesh, T1T-stainless steel mesh, T2T-stainless steel mesh, and T3T-stainless steel mesh are 104.2°, 92.62°, 66.56°, and 88°, respectively. The water contact angle of the original stainless steel mesh remains above 118° after 45 minutes, while the water droplets on the surface of TT-stainless steel mesh, T1T-stainless steel mesh, T2T-stainless steel mesh, and T3T-stainless steel mesh are completely spread on the surface of the material at 43.3 minutes, 27.3 minutes, 19.25 minutes, and 37.8 minutes, respectively. From the above analysis, it can be seen that after the modification of the TA-SiO2 hydrophilic coating, the surface of the stainless steel mesh changes from hydrophobic to hydrophilic. In addition, the hydrophilicity of the TA-SiO2 coating oxidized by three different oxidants and air is compared, and it is concluded that the hydrophilicity of the coating is better after in-situ oxidation with NaClO3. Therefore, in the subsequent implementation scheme, the T2T-stainless steel mesh obtained by the NaClO3 oxidation coating in Example 3 is selected.

[0060] The underwater oil contact angle (UWOCA) of the T2T-stainless steel mesh prepared in Example 3 and the original stainless steel mesh is as follows: Figure 2 As shown. The underwater oil-water contact angles of the original stainless steel mesh for dodecane, gasoline, and diesel were 26.37°, 34.55°, and 89.48°, respectively, showing underwater oleophilicity. However, the underwater contact angles of these oils on the surface of the modified T2T-stainless steel mesh were 153.54°, 153.1°, and 154.9°, respectively, showing underwater superoleophobicity.

[0061] (2) Chemical stability test

[0062] The chemical stability of the material was evaluated by treating it in a simulated harsh environment. The T2T-stainless steel mesh prepared in Example 3 was placed in solutions with pH values ​​of 1, 3, 5, 7, 9, 11, and 13 for 24 hours, and then taken out to measure its water contact angle in the air and the contact angle of diesel underwater. At the same time, the T2T-stainless steel mesh prepared in Example 3 was also placed in a 1 mol / L NaCl solution for 1 to 7 days to measure its hydrophilicity and underwater oleophobicity. The water contact angle and underwater oil contact angle of the T2T-stainless steel mesh immersed in solutions with different pH values ​​and salt solutions are shown as follows: Figure 3 and Figure 4 As shown. Figure 3 and Figure 4 It can be seen that the T2T-stainless steel mesh can still maintain hydrophilicity and underwater oleophobicity after being treated with acidic, alkaline and salt solutions, indicating that the T2T-stainless steel mesh has good chemical stability.

[0063] (3) Mechanical stability test

[0064] The mechanical stability of the metal mesh was tested by a hydraulic flushing test. The T2T-stainless steel mesh prepared in Example 3 was placed in an aqueous solution on an air shaker at room temperature, and the shaking speed was set to 200 rpm. The hydrophilicity and underwater oleophobicity of the T2T-stainless steel mesh were measured after hydraulic flushing for 1 to 7 days. Figure 5 As shown in the figure, after 7 days of strong hydraulic scouring, the water contact angle of the T2T-stainless steel mesh floats around 60°, and the oil contact angle remains above 150°, still maintaining good hydrophilicity and underwater superoleophobicity, indicating that the modified metal mesh has excellent mechanical stability.

[0065] (4) Oil-water separation efficiency test

[0066] The oil-water separation efficiency and flux of the metal mesh were tested by dead-end filtration. The T2T-stainless steel mesh prepared in Example 3 was fixed on the dead-end filtration device ( Figure 6 ), and the metal mesh was wetted with deionized water before separation. Diesel and water were mixed in a volume ratio of 1:9 to form a mixed solution, which was stirred with an electric stirrer at 1500 rpm for 30 minutes to form an oil-water mixture. The oil-water mixture was used for separation after being stable for 1 hour. A high-concentration water-in-oil emulsion was formed by stirring 10 g / L diesel and 200 mg / L sodium dodecyl sulfate with an electric stirrer at 1500 rpm for 1 hour. The emulsion was used for separation after being stable for 12 hours. 200 mL of oil-water solution and water-in-oil emulsion were separated under gravity. The oil concentration in the filtrate was determined by ultraviolet spectrophotometry. The specific experimental method was based on the Chinese national standard "Ultraviolet spectrophotometry for the determination of petroleum in water quality" (HJ 970-2018). The oil removal rate (R) was calculated according to formula (1). The flux (J) was calculated by the time required to take 100 mL of filtrate during the solution separation process, as shown in formula (2).

[0067]

[0068] Where R is the oil removal rate (%), c0 is the initial concentration of the emulsion (mg / L), and c1 is the concentration of the filtrate (mg / L).

[0069]

[0070] Where J is the membrane flux (L·m -2 ·h -1 ), T is the sampling time (h), A is the effective area of ​​the membrane (4.15×10 -4 m 2 ).

[0071] The separation efficiency and flux of the stainless steel mesh with different numbers of layers prepared in Example 3 for oil-water mixture and high-concentration oil-in-water emulsion are as follows: Figure 7 , Table 1 and Figure 8, as shown in Table 2. Figure 7-8 As can be seen from Table 1-2, with the increase of the number of metal mesh layers, the flux of pure water, the flux of oil-water mixture and the flux of water-in-oil emulsion gradually decreases, while the oil removal rate gradually increases. This is because the randomly superimposed metal mesh forms some irregular capillary channels with special wettability. When the oil droplets enter these channels, they are subjected to the capillary force and adhesion generated by the capillary channels and wettability. Some oil droplets with a particle size smaller than the average pore size of the mesh are intercepted, causing them to break the emulsion and eventually aggregate into large oil droplets that are intercepted by the metal mesh, successfully separating the high-concentration emulsion; the large-size oil droplets in the oil-water mixture are successfully screened by the mesh under the effect of the size interception effect. However, the multi-layer superimposed mesh also reduces the original pores of the metal mesh, making the water passage narrower, showing a phenomenon of reduced flux. It can be seen from the separation parameters that when the metal mesh is superimposed to 2 layers or more, the separation efficiency of the oil-water mixture has reached 99%, but the separation parameter of the emulsion is lower when 2 layers are superimposed, which is 80.01%. When the number of metal mesh stacking layers is 3, the oil removal rate of the emulsion increases rapidly to 95.63%, which is not much different from the oil removal rate when the number of stacking layers is 4, and the flux parameters are basically the same. Therefore, the 3-layer stacked metal mesh is finally used to separate the oil-water mixture and the high-concentration oil-in-water emulsion.

[0072] Table 1

[0073] 1st floor 2nd floor 3 layers 4 layers <![CDATA[Pure water flux (L·m -2 ·h -1 )]]> 480589.52 462510.92 453972.26 425190.156 <![CDATA[Oil-water mixture throughput (L·m -2 ·h -1 )]]> 173987.00 140515.22 117189.03 115086.576 <![CDATA[Oil-in-water emulsion through (L·m -2 ·h -1 )]]> 556758.43 491803.28 257938.78 208981.56

[0074] Table 2

[0075] 1st floor 2nd floor 3 layers 4 layers Oil removal rate of oil-water mixture (%) 2.38 99.57 99.98 99.98 Oil removal rate of water-in-oil emulsion (%) 68.7 80.01 95.63 97.32

[0076] (5) Cyclic performance test

[0077] use Figure 6 The separation device was used to carry out cyclic testing on three superimposed metal meshes. Fig. 9 and Fig.10 The pure water flux, oil-water flux and oil removal rate of the T2T-stainless steel mesh prepared in Example 3 for 25 cycles of separation of diesel / water mixture and high-concentration diesel-in-water emulsion. During the cycle separation, the pure water flux was always maintained at 6.5×10 5 L·m -2 ·h -1 Above, the flux of oil-water mixture and oil-in-water emulsion is kept at 1.1×10 5 L·m -2 ·h -1 As shown above, the oil removal rate of the oil-water mixture is maintained at more than 99.4%, and the oil removal rate of the water-in-oil emulsion is maintained at more than 81%. Through the above analysis, it can be seen that the hydrophilic / underwater superoleophobic metal mesh of the present invention has good recyclability and can be used for the separation of oil-water mixture and high-concentration water-in-oil emulsion for a long time. In short, the hydrophilic / underwater superoleophobic metal mesh of the present invention has excellent comprehensive performance.

Claims

1. A method for preparing a stainless steel mesh modified by in-situ oxidation of plant polyphenols, characterized in that The method comprises the following steps: Step 1: Using a stainless steel mesh as a substrate, ultrasonically cleaning it in acetone, anhydrous ethanol and deionized water in sequence, and then drying it; Step 2: Immerse the stainless steel mesh cleaned and dried in step 1 in a mixed solution of solution A and solution B for coating, wherein: solution A is a mixed solution of tannic acid and Tris-HCl, and the concentrations of TA and Tris-HCl are 1.5-2.5wt% and 1.15-1.25wt% respectively; solution B is a homogeneous solution of tetraethyl orthosilicate and ethanol, and the concentration of tetraethyl orthosilicate is 3.5-4.0wt%; the volume ratio of solution A to solution B is 10:2-10:5; Step 3, adding an oxidant to the mixed solution of step 2, and performing an in-situ oxidation reaction under acidic conditions, wherein: the oxidant is one of NaClO solution, NaClO3 and NaIO4, and the added amount is 3-5wt% of solution A; Step 4: Clean and dry the stainless steel mesh modified in step 3 to obtain a hydrophilic / underwater superoleophobic stainless steel mesh.

2. The method for preparing the in-situ oxidized plant polyphenol modified stainless steel mesh according to claim 1, characterized in that In the step 1, the cleaning time is 20 to 60 minutes.

3. The method for preparing the in-situ oxidized plant polyphenol modified stainless steel mesh according to claim 1, characterized in that In the step 1, the copper mesh has a size of 2-5 cm×2-5 cm and a mesh size of 200-500.

4. The method for preparing the in-situ oxidized plant polyphenol modified stainless steel mesh according to claim 1, characterized in that In the step 2, the pH of the mixed solution is 8-9.

5. The method for preparing the in-situ oxidized plant polyphenol modified stainless steel mesh according to claim 1, characterized in that In the step 2, the coating time is 20 to 60 minutes.

6. The method for preparing the in-situ oxidized plant polyphenol modified stainless steel mesh according to claim 1, characterized in that In the step 3, under acidic conditions, the pH value is 4 to 6.

7. The method for preparing the in-situ oxidized plant polyphenol modified stainless steel mesh according to claim 1, characterized in that In the step 3, the in-situ oxidation reaction is carried out on an air shaker at room temperature for 5 to 8 hours at a shaking speed of 120 to 150 rpm.

8. The method for preparing the in-situ oxidized plant polyphenol modified stainless steel mesh according to claim 1, characterized in that In the step 4, the cleaning method is: using ethanol and deionized water to wash away the unreacted solution on the surface of the modified stainless steel mesh.

9. The method for preparing the in-situ oxidized plant polyphenol modified stainless steel mesh according to claim 1, characterized in that In the step 4, the drying temperature is 60 to 80° C. and the drying time is 1 to 3 hours.

10. Use of the stainless steel mesh prepared by the method according to any one of claims 1 to 9 in oil-water separation.

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