A method for preparing a hydrophilic modified coating for an oil-water separation process and applications thereof

Abstract

The application relates to a preparation method of a hydrophilic modified coating for an oil-water separation process and application of the hydrophilic modified coating, and belongs to the oil-water separation field. The application aims to solve the problems that existing hydrophobic membranes are seriously polluted, and it is difficult to continuously and efficiently separate stable oil-water emulsions. The method comprises the following steps: I, preparing a modified solution; II, loading the coating. Application: the application is used for oil-water separation.

Description

Technical Field

[0001] This invention belongs to the field of oil-water separation. Background Technology

[0002] Due to the irreversible trend of global warming, large-scale melting of freshwater glaciers in polar regions and environmental pollution leading to the continuous depletion of freshwater lakes, rivers, glaciers, and groundwater resources have significantly reduced the freshwater resources available to humans. Furthermore, oily wastewater poses hazards such as difficulty in natural degradation, biotoxicity, and extremely high pollution levels. Therefore, developing efficient oil-water separation technologies is of paramount importance for environmental protection and resource recovery.

[0003] In the field of oil-water separation, traditional methods such as gravity separation, centrifugation, flotation, electrocoagulation, chemical and microbial oxidation generally suffer from significant drawbacks, including low efficiency, long service life, complex operation processes, and secondary environmental hazards caused by the use of toxic substances. In contrast, membrane separation technology is widely used due to its advantages such as high efficiency, ease of operation, and adjustable pore structure.

[0004] However, severe membrane fouling greatly limits the application of microfiltration membranes in oil-water separation, especially hydrophobic membranes. Specifically, oil droplets adhere to the membrane surface through interaction forces, causing membrane clogging and making it difficult to continuously and efficiently separate stable oil-water emulsions. Summary of the Invention

[0005] This invention aims to address the problem of severe fouling of existing hydrophobic membranes, which makes it difficult to continuously and efficiently separate stable oil-water emulsions. It provides a method for preparing a hydrophilic modified coating for oil-water separation processes and its application.

[0006] A method for preparing a hydrophilic modified coating for oil-water separation processes, comprising the following steps:

[0007] 1. Preparation of the modified solution;

[0008] Bovine serum albumin, a disulfide bond reducing agent, and a polyethylene glycol derivative were dispersed in a buffer solution to obtain a modified solution.

[0009] II. Load-bearing coating:

[0010] The hydrophobic microfiltration membrane was immersed in a modified solution, irradiated under ultraviolet light, and then incubated in a shaker. After incubation, it was taken out, washed, and finally dried to obtain a hydrophilic modified hydrophobic microfiltration membrane.

[0011] Application of a hydrophilic modified coating for oil-water separation processes.

[0012] The beneficial effects of this invention are:

[0013] This invention utilizes green and controllable protein self-assembly and click chemistry techniques to construct a robust and dense hydrophilic brush on the membrane surface, thereby efficiently and stably solving the problem of severe membrane fouling in microfiltration membranes during oil-water separation. It achieves selective permeation of different stable oil-water emulsions, maintaining a high emulsion rejection rate while still possessing a high emulsion separation flux, and exhibits high recovery flux, demonstrating its potential for long-term use in oil-water separation. Details are as follows:

[0014] By functionalizing the membrane with a protein coating, the hydrophilicity of the hydrophobic PVDF membrane was significantly improved, resulting in excellent retention capacity (up to 99.7%) for various oil-in-water emulsions in oil-water separation, demonstrating outstanding separation performance. The modified microfiltration membrane exhibited extremely high flux recovery (up to 97.8%) during cyclic separation, ensuring long-term operational stability and extending membrane lifespan. Simultaneously, separation efficiencies for various oils, including n-octane, diesel, and soybean oil, all reached over 97.8%, with a maximum of 99.7%. The functionalized hydrophilic protein coating is firmly adhered to the membrane surface through van der Waals forces, enhancing coating durability and anti-peeling ability, ensuring consistent separation performance, and overcoming bottlenecks such as poor substrate compatibility and weak interfacial bonding in traditional chemical modification. This technology is based on mercapto-olefin click chemistry, with simple and mild reaction conditions, requiring no harsh experimental environment, which helps reduce operational complexity and energy consumption, making its large-scale production application possible. Attached Figure Description

[0015] Figure 1 This is a scanning electron microscope image of the PVDF base film described in step two of Example 1;

[0016] Figure 2 The image shows a scanning electron microscope (SEM) image of the single-protein modified hydrophilic membrane without the addition of polyethylene glycol derivatives prepared in step two of Comparative Example 1.

[0017] Figure 3 This is a scanning electron microscope image of the hydrophilic PVDF membrane with the interface protein coating prepared in step two of Example 1;

[0018] Figure 4 The hydrophilic PVDF membrane with the interfacial protein coating prepared in step two of Example 1 is used to measure the emulsion separation flux and emulsion retention rate in different oil-in-water emulsions.

[0019] Figure 5 The flux recovery rate of the hydrophilic PVDF membrane with interfacial protein coating prepared in step two of Example 1 after retaining water-encapsulated n-octane, soybean oil, and n-heptane emulsions;

[0020] Figure 6The pure water flux of the PVDF base membrane described in step two of Example 1, the single-protein modified hydrophilic membrane without the addition of polyethylene glycol derivatives prepared in step two of Comparative Example 1, and the hydrophilic PVDF membrane with interfacial protein coating prepared in step two of Example 1 are compared.

[0021] Figure 7 Chemical stability test of the hydrophilic PVDF membrane with interfacial protein coating prepared in step two of Example 1;

[0022] Figure 8 Infrared data of the PVDF base membrane described in step two of Example 1, the single-protein modified hydrophilic membrane without polyethylene glycol derivative prepared in step two of Comparative Example 1, and the hydrophilic PVDF membrane with interfacial protein coating prepared in step two of Example 1. Detailed Implementation

[0023] The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any combination of the specific embodiments.

[0024] Specific Implementation Method 1: This implementation method provides a method for preparing a hydrophilic modified coating for oil-water separation processes, which is carried out according to the following steps:

[0025] 1. Preparation of the modified solution;

[0026] Bovine serum albumin, a disulfide bond reducing agent, and a polyethylene glycol derivative were dispersed in a buffer solution to obtain a modified solution.

[0027] II. Load-bearing coating:

[0028] The hydrophobic microfiltration membrane was immersed in a modified solution, irradiated under ultraviolet light, and then incubated in a shaker. After incubation, it was taken out, washed, and finally dried to obtain a hydrophilic modified hydrophobic microfiltration membrane.

[0029] In this embodiment, bovine serum albumin (BSA) is used as a raw material for interface modification. Under the action of a reducing agent, it undergoes conformational unfolding, forming a β-amyloid deposited protein layer on the surface of a hydrophobic substrate through self-assembly. Simultaneously, the conformational unfolding exposes abundant active groups such as amino, carboxyl, and thiol groups for subsequent grafting. A hydrophilic functionalized protein coating is obtained through a thiol-ene click chemical reaction between the free thiol groups and a polyethylene glycol derivative. This hydrophilic protein coating can be firmly coated onto the surface of a hydrophobic microfiltration membrane via van der Waals interactions.

[0030] The beneficial effects of this embodiment are:

[0031] This embodiment utilizes green and controllable protein self-assembly and click chemistry techniques to construct a robust and dense hydrophilic brush on the membrane surface, thereby efficiently and stably solving the problem of severe membrane fouling in the oil-water separation process of microfiltration membranes. It achieves selective permeation of different stable oil-water emulsions, maintaining a high emulsion rejection rate while still possessing a high emulsion separation flux, and exhibits high recovery flux, demonstrating its potential for long-term use in oil-water separation. Details are as follows:

[0032] By functionalizing the membrane with a protein coating, the hydrophilicity of the hydrophobic PVDF membrane was significantly improved, resulting in excellent retention capacity (up to 99.7%) for various oil-in-water emulsions in oil-water separation, demonstrating outstanding separation performance. The modified microfiltration membrane exhibited extremely high flux recovery (up to 97.8%) during cyclic separation, ensuring long-term operational stability and extending membrane lifespan. Simultaneously, separation efficiencies for various oils, including n-octane, diesel, and soybean oil, all reached over 97.8%, with a maximum of 99.7%. The functionalized hydrophilic protein coating is firmly adhered to the membrane surface through van der Waals forces, enhancing coating durability and anti-peeling ability, ensuring consistent separation performance, and overcoming bottlenecks such as poor substrate compatibility and weak interfacial bonding in traditional chemical modification. This technology is based on mercapto-olefin click chemistry, with simple and mild reaction conditions, requiring no harsh experimental environment, which helps reduce operational complexity and energy consumption, making its large-scale production application possible.

[0033] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the concentration of bovine serum albumin in the modified solution described in step one is 1 mg / mL to 3 mg / mL. Everything else is the same as in Specific Implementation Method One.

[0034] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that: the disulfide bond reducing agent mentioned in step one is tris(2-carboxyethyl)phosphine; and the concentration of the disulfide bond reducing agent in the modified solution mentioned in step one is 5 mg / mL to 10 mg / mL. Everything else is the same as in Specific Implementation Method One or Two.

[0035] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that: the polyethylene glycol derivative mentioned in step one is one or a combination of several of polyethylene glycol methacrylate, polyethylene glycol diacrylate, and allyloxy polyoxyethylene ether; the concentration of the polyethylene glycol derivative in the modified solution mentioned in step one is 20 mg / mL to 80 mg / mL. Everything else is the same as in Specific Implementation Methods One to Three.

[0036] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that the buffer solution mentioned in step one is a phosphate buffer solution, and the concentration of the phosphate buffer solution is 0.1M~0.2M, with a pH of 6~8. Everything else is the same as in Specific Implementation Methods One to Four.

[0037] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the hydrophobic microfiltration membrane mentioned in step two is a polytetrafluoroethylene (PTFE) microfiltration membrane or a polyvinylidene fluoride (PVDF) microfiltration membrane. Everything else is the same as in Specific Implementation Methods One to Five.

[0038] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One through Six in that: in step two, the ultraviolet light wavelength is 240nm~270nm and the ultraviolet radiation intensity is 15mW / cm². 2 ~30mW / cm 2 Under the specified conditions, ultraviolet irradiation is carried out for 0.5 to 6 hours. Other procedures are the same as in any of the specific implementation methods one through six.

[0039] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that: in step two, the incubation period is 3 to 24 hours at room temperature and a shaking speed of 60 to 120 r / min. Everything else is the same as in Specific Implementation Methods One to Seven.

[0040] Specific Implementation Method Nine: This implementation method describes the application of a hydrophilic modified coating in an oil-water separation process.

[0041] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Method Nine in that the separation efficiency of the oil-in-water emulsion during the oil-water separation process is above 97.8%. Everything else is the same as in Specific Implementation Method Nine.

[0042] The beneficial effects of the present invention are verified using the following embodiments:

[0043] Example 1:

[0044] A method for preparing a hydrophilic modified coating for oil-water separation processes, comprising the following steps:

[0045] 1. Preparation of the modified solution;

[0046] Bovine serum albumin, a disulfide bond reducing agent, and a polyethylene glycol derivative were dispersed in phosphate buffer to obtain a modified solution.

[0047] The modified solution contains bovine serum albumin at a concentration of 1 mg / mL, and the purity of the bovine serum albumin is greater than 96%.

[0048] The disulfide bond reducing agent is tris(2-carboxyethyl)phosphine; the concentration of the disulfide bond reducing agent in the modified solution is 6 mg / mL;

[0049] The polyethylene glycol derivative is polyethylene glycol methacrylate (PEGMA); the concentration of the polyethylene glycol derivative in the modified solution is 40 mg / mL;

[0050] The phosphate buffer solution has a concentration of 0.1 M and a pH of 7.4.

[0051] II. Load-bearing coating:

[0052] The hydrophobic microfiltration membrane was immersed in the modified solution, first under ultraviolet light at a wavelength of 254 nm and an ultraviolet radiation intensity of 15 mW / cm². 2 Under the conditions of UV irradiation for 2 hours, the membrane was then incubated in a shaker for 16 hours at room temperature and a shaker speed of 80 r / min. After incubation, the membrane was removed, washed, and finally dried to obtain a hydrophilic PVDF membrane with an interfacial protein coating.

[0053] The hydrophobic microfiltration membrane is a polyvinylidene fluoride microfiltration membrane (PVDF microfiltration membrane, diameter 47mm, average pore size 0.22μm, purchased from Nantong Longjin Membrane Technology Co., Ltd.), i.e. PVDF base membrane.

[0054] Example 2: This example differs from Example 1 in that the polyethylene glycol derivative mentioned in step one is allyloxy polyoxyethylene ether (APEG). Everything else is the same as in Example 1.

[0055] Example 3: This example differs from Example 1 in that: in step two, the ultraviolet irradiation is 0.5 hours; and incubation in a shaker is 12 hours. Everything else is the same as in Example 1.

[0056] Example 4: This example differs from Example 1 in that the concentration of bovine serum albumin in the modified solution described in step one is 2 mg / mL. Everything else is the same as in Example 1.

[0057] Example 5: This example differs from Example 1 in that the concentration of the disulfide bond reducing agent in the modified solution described in step one is 8 mg / mL. Everything else is the same as in Example 1.

[0058] Example 6: This example differs from Example 1 in that the polyethylene glycol derivative mentioned in step one is polyethylene glycol diacrylate (PEGA). Everything else is the same as in Example 1.

[0059] Comparative Example 1: This example differs from Example 1 in that the addition of the polyethylene glycol derivative is omitted in step one; and a single-protein modified hydrophilic membrane without the addition of the polyethylene glycol derivative is prepared in step two. Everything else is the same as in Example 1.

[0060] Comparative Example 2: This example differs from Example 1 in that the purchased commercial oil-water separator was not treated in any way; the hydrophobic microfiltration membrane (PVDF-based membrane) from Example 1 was used directly. Everything else is the same as in Example 1.

[0061] The hydrophilicity of the hydrophilic PVDF membrane with the interfacial protein coating prepared in Example 1 was tested, and it achieved complete wetting of ultrapure water within 19 seconds.

[0062] The PVDF membranes of the examples and comparative examples were tested using a vacuum filtration device with a filtration area of ​​12.566 mm². 2 The separation flux and emulsion retention performance of water-in-octane emulsion and water-in-soybean oil emulsion were tested by applying a filtration pressure of 0.5 bar.

[0063] Table 1

[0064]

[0065] Figure 1 The image shows a scanning electron microscope (SEM) image of the PVDF base membrane described in step two of Example 1. As can be seen from the image, its surface is smooth and its pore structure is clear, exhibiting typical microfiltration membrane morphology characteristics.

[0066] Figure 2 The image shows a scanning electron microscope (SEM) image of the single-protein modified hydrophilic membrane prepared in step two of Comparative Example 1 without the addition of polyethylene glycol derivatives. As can be seen from the image, due to the thinness of the BSA coating, the surface morphology of the membrane did not change significantly compared to the base membrane, and the original porous structure was still retained, but the pore walls were slightly rough, indicating that the protein coating was successfully deposited.

[0067] Figure 3 The image shows a scanning electron microscope (SEM) image of the hydrophilic PVDF membrane with an interfacial protein coating prepared in step two of Example 1. As can be seen from the image, the membrane surface exhibits a slight network or wrinkled morphology, which is attributed to the successful grafting of PEGMA segments onto the membrane surface to form a polymer coating layer.

[0068] Figure 4 The figure shows the emulsion separation flux and retention rate of the hydrophilic PVDF membrane with interfacial protein coating prepared in step two of Example 1 for different oil-in-water emulsions; as can be seen from the figure, the separation flux for the water-in-heptane emulsion can reach 2827 L·m -2 ·h -1 ·bar -1 The separation efficiency for different oil products such as n-octane, diesel, and soybean oil all reached over 97.8%, with the highest reaching 99.7%.

[0069] Flux recovery rate (FRR) tests were conducted on a vacuum filtration unit at an operating pressure of 0.1 MPa. The initial pure water flux (J) was recorded at 0.1 MPa. w1Then, the process was switched to an oil-water emulsion. After filtration, the membrane was backwashed with deionized water at 0.1 MPa for 5 minutes, and the pure water flux (J) was tested again. w2 FRR is calculated using the following formula: ; Figure 5 The figure shows the flux recovery rate of the hydrophilic PVDF membrane with interfacial protein coating prepared in step two of Example 1 after retaining water-encapsulated n-octane, soybean oil, and n-heptane emulsions. As can be seen from the figure, the flux recovery rate of the hydrophilic PVDF membrane with interfacial protein coating after the first cycle of water-encapsulated n-octane emulsion can reach 97.8%, while the flux recovery rate after the first cycle of water-encapsulated soybean oil emulsion and water-encapsulated n-heptane emulsion is 96.8%.

[0070] Figure 6 The figure compares the pure water flux of the PVDF base membrane described in step two of Example 1, the single-protein modified hydrophilic membrane without polyethylene glycol derivatives prepared in step two of Comparative Example 1, and the hydrophilic PVDF membrane with interfacial protein coating prepared in step two of Example 1. As shown in the figure, the water flux of the PVDF membrane is 6298 L·m⁻¹. -2 ·h -1 ·bar -1 The flux of the single-protein modified hydrophilic membrane without the addition of polyethylene glycol derivatives was 8534 L·m. -2 ·h -1 ·bar -1 The flux of the hydrophilic PVDF membrane with the interface protein coating is 10632 L·m. -2 ·h -1 ·bar -1 Compared to PVDF membranes, the improvement is significant, demonstrating its excellent hydrophilic modification ability.

[0071] In Example 1, the hydrophilic PVDF membrane with the interface protein coating prepared in step 2 was immersed in 1M HCl solution, 1M NaOH solution, 1M NaCl solution and the organic solvent n-hexane for 24 hours, and the pure water flux of the membrane was tested. Figure 7 Chemical stability testing of the hydrophilic PVDF membrane with interfacial protein coating prepared in step two of Example 1; after soaking in 1M HCl, NaOH, NaCl and the organic solvent n-hexane for 24 hours, the pure water flux was 10628 L·m⁻¹. -2 ·h -1 ·bar -1 10622 L·m -2 ·h -1 ·bar -1 10280L·m -2 ·h -1 ·bar -1 and 10532 L·m -2 ·h -1 ·bar-1 Therefore, it can be seen that the coating has excellent durability and peel resistance.

[0072] Figure 8 The infrared data are for the PVDF base film described in step two of Example 1, the single-protein modified hydrophilic film without the addition of polyethylene glycol derivative prepared in step two of Comparative Example 1, and the hydrophilic PVDF film with interfacial protein coating prepared in step two of Example 1. As can be seen from the figure, the appearance of the hydroxyl vibration peak in the hydrophilic PVDF film with interfacial protein coating prepared in step two of Example 1 proves the rationality of the improved hydrophilicity.

Claims

1. A method for preparing a hydrophilic modified coating for oil-water separation processes, characterized in that... It is done in the following steps:

1. Preparation of the modified solution; Bovine serum albumin, a disulfide bond reducing agent, and a polyethylene glycol derivative were dispersed in a buffer solution to obtain a modified solution. II. Load-bearing coating: The hydrophobic microfiltration membrane was immersed in a modified solution, irradiated under ultraviolet light, and then incubated in a shaker. After incubation, it was removed, washed, and finally dried to obtain a hydrophilic modified hydrophobic microfiltration membrane.

2. The method for preparing a hydrophilic modified coating for oil-water separation process according to claim 1, characterized in that... The concentration of bovine serum albumin in the modified solution described in step one is 1 mg / mL to 3 mg / mL.

3. The method for preparing a hydrophilic modified coating for oil-water separation process according to claim 1, characterized in that... The disulfide bond reducing agent mentioned in step one is tris(2-carboxyethyl)phosphine; the concentration of the disulfide bond reducing agent in the modified solution mentioned in step one is 5 mg / mL to 10 mg / mL.

4. The method for preparing a hydrophilic modified coating for oil-water separation process according to claim 1, characterized in that... The polyethylene glycol derivative mentioned in step one is one or a combination of several of polyethylene glycol methacrylate, polyethylene glycol diacrylate and allyloxy polyoxyethylene ether; the concentration of the polyethylene glycol derivative in the modified solution mentioned in step one is 20 mg / mL to 80 mg / mL.

5. The method for preparing a hydrophilic modified coating for oil-water separation process according to claim 1, characterized in that... The buffer solution mentioned in step one is a phosphate buffer solution, and the concentration of the phosphate buffer solution is 0.1M~0.2M, pH=6~8.

6. The method for preparing a hydrophilic modified coating for oil-water separation process according to claim 1, characterized in that... The hydrophobic microfiltration membrane mentioned in step two is a polytetrafluoroethylene microfiltration membrane or a polyvinylidene fluoride microfiltration membrane.

7. The method for preparing a hydrophilic modified coating for oil-water separation process according to claim 1, characterized in that... In step two, the ultraviolet light wavelength is 240nm~270nm and the ultraviolet radiation intensity is 15mW / cm². 2 ~30mW / cm 2 Under these conditions, ultraviolet irradiation lasts for 0.5 to 6 hours.

8. The method for preparing a hydrophilic modified coating for oil-water separation process according to claim 1, characterized in that... In step two, incubate for 3 to 24 hours at room temperature and a shaking speed of 60 to 120 r / min.

9. The application of a hydrophilic modified coating prepared according to claim 1 for use in an oil-water separation process, characterized in that... It is used for oil-water separation.

10. The application of a hydrophilic modified coating for an oil-water separation process according to claim 9, characterized in that... The separation efficiency of oil-in-water emulsions during the oil-water separation process is over 97.8%.

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