An oil-water separation membrane and a preparation method thereof

Abstract

The application discloses a preparation method of a high-flux oil-water separation membrane and relates to the technical field of oil-water separation. The preparation method of the high-flux oil-water separation membrane comprises the following steps: placing an organic separation base film on the surface of hot water, so that the lower surface of the base film is slowly infiltrated by water; slowly adding molten paraffin on the upper surface of the base film, so that the base film is stably placed in the oil-water interface, and the base film with holes filled with paraffin is obtained after cooling; submerging the base film filled with paraffin in a dopamine aqueous solution to react, so that a PDA-coated film is obtained; and immersing the coated film in n-hexane to remove the filled paraffin, so that the high-flux oil-water separation membrane is obtained. The preparation process is simple, the preparation cost is low, energy saving and environmental protection are achieved, the prepared oil-water separation membrane has high flux, and the separation effect is good.

Description

Technical Field

[0001] The present invention relates to the technical field of oil-water separation, and in particular to a method for preparing a high-throughput oil-water separation membrane. Background Art

[0002] With the increasing discharge of industrial and domestic oily wastewater, oily wastewater has become a global concern, presenting a significant threat to human health and well-being. Therefore, effectively separating this oily wastewater is crucial for both environmental protection and water conservation. Compared to traditional oil-water separation technologies, membrane separation operates at room temperature, exhibits no phase transition, offers a simple operation process, and boasts high single-stage separation efficiency. This has led to it becoming a hot topic and research area in oil-water separation, both domestically and internationally.

[0003] During the oil-water separation process, polymer membranes are easily fouled due to their inherent hydrophobicity. This fouling cannot be removed through simple physical cleaning, resulting in reduced water permeability and severe scaling. Contamination also reduces membrane flux, shortening its service life and increasing operating costs. Research has shown that enhancing the hydrophilicity of the membrane surface can not only improve membrane permeability but also effectively reduce membrane fouling during the separation process. To date, a variety of methods have been used to develop separation membranes with enhanced hydrophilicity, including blending modification, surface chemical modification, surface physical modification, and copolymerization modification.

[0004] Among the various modification technologies currently available, polydopamine (PDA) surface coatings have received widespread attention in recent years. Under weakly alkaline conditions, dopamine (DA) can oxidize and self-polymerize to form polydopamine (PDA). It can non-selectively and permanently adhere to almost any surface, making it hydrophilic. However, as research deepens, PDA coatings also have some difficult-to-solve problems. For example: PDA is deposited on the membrane surface and pore walls for too long, which easily produces aggregated particles, thereby clogging the membrane pores and causing a decrease in pore size and flux. Therefore, it is extremely necessary to develop an oil-water separation membrane with a hydrophilic and oleophobic surface and high flux. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a high-throughput oil-water separation membrane and a method thereof. The preparation method has a simple process, low material price, and no toxic reagents are involved in the experiment / production process. The obtained membrane has the characteristics of high flux and excellent separation performance in the oil-water separation process.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] An oil-water separation membrane is prepared by the following method:

[0008] (1) placing an organic separation membrane on a hot water surface so that its lower surface is slowly wetted by water; slowly pouring molten paraffin wax into the membrane so that the organic separation membrane is at a stable oil-water interface, and after cooling, a base membrane with pores filled with paraffin wax is obtained; (2) immersing the paraffin-filled base membrane in a dopamine aqueous solution to react and obtain a dopamine-coated membrane; (3) immersing the coated membrane in a n-hexane solution to remove the filled paraffin wax and obtain an oil-water separation membrane.

[0009] Preferably, the water temperature in step (1) is 55-80°C.

[0010] Preferably, the organic separation membrane in step (1) includes an organic hydrophobic separation membrane such as a nylon membrane, a polyvinylidene fluoride membrane, a polysulfone membrane, a polyamide membrane, or a polytetrafluoroethylene membrane.

[0011] Preferably, the melting temperature of the paraffin wax in step (1) is 48-50°C.

[0012] Preferably, the oil-water ratio (ratio of paraffin wax to water, volume ratio) of the oil-water interface in step (1) is 1:30-50.

[0013] Preferably, in step (1), the organic separation membrane is placed at the oil-water interface for a period of 0 to 90 minutes.

[0014] Preferably, the preparation method of the PDA coating film in step (2) is a conventional method in the art, for example, the paraffin-filled base film is placed in a DA aqueous solution, magnetically stirred, reacted for 0 to 48 hours, and then washed with a large amount of deionized water to remove the unreacted DA on the surface, and dried to obtain a PDA coating film.

[0015] Preferably, the pH value of the dopamine aqueous solution in step (2) is 8.3-8.7, and the concentration is 0-4 mg / mL; the pH value is preferably 8.5.

[0016] Preferably, the method for removing paraffin from the coating film in step (3) is a conventional method in the art, such as immersing the coating film in n-hexane for 3 to 5 minutes, then rinsing with n-hexane 3 to 4 times, and then drying.

[0017] Another object of the present invention is to provide a method for preparing the high-throughput oil-water separation membrane, comprising the following steps:

[0018] (1) placing an organic separation base membrane on a hot water surface so that its lower surface is slowly wetted by water; slowly adding molten paraffin wax to the upper surface of the membrane so that the base membrane is stably placed at the oil-water interface; after cooling, a base membrane with pores filled with paraffin wax is obtained;

[0019] (2) immersing the paraffin-filled basement membrane in a dopamine aqueous solution to react and obtain a dopamine-coated membrane;

[0020] (3) The coated membrane is immersed in a n-hexane solution to remove the filled paraffin wax to obtain an oil-water separation membrane.

[0021] In addition, the present invention also includes the application of a high-throughput oil-water separation membrane, which can be applied to the field of oil-water separation technology.

[0022] The beneficial effects of the present invention are: the preparation method is simple in process, the material price is low, no toxic reagents are involved in the experiment / production process, and the obtained membrane has the characteristics of high flux and excellent separation performance in the oil-water separation process. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 These are SEM images of the oil-water separation membrane of Example 5 before and after paraffin removal, where (a) is the SEM image of the paraffin surface after coating with PDA; (b) is the SEM image of the water surface after coating with PDA; (c) is the SEM image of the paraffin surface after paraffin removal with n-hexane; and (d) is the SEM image of the water surface after paraffin removal with n-hexane.

[0024] Figure 2 is the pure water flux of the oil-water separation membrane of Examples 1 to 6;

[0025] Figure 3 is the pure water flux of the oil-water separation membrane of Examples 7 to 11;

[0026] Figure 4 The permeation flux and separation efficiency of the oil-water separation membrane of Example 13 for different oil-water mixtures;

[0027] Figure 5 The separation efficiency and circulation performance of the oil-water separation membrane of Example 13 are shown. DETAILED DESCRIPTION

[0028] The following examples are used to further illustrate the present invention; however, they are not intended to limit or define the scope of the present invention.

[0029] Example 1

[0030] Embodiment 1 of the present invention is a method for preparing an oil-water separation membrane, comprising:

[0031] 1) Place the PVDF membrane on a 65°C hot water surface and allow the lower surface to be slowly soaked in water for 10 minutes;

[0032] 2) Slowly pour 65°C molten paraffin wax into the membrane, placing it at a stable oil-water interface with an oil-water ratio of 1:40. After cooling to room temperature, the PVDF membrane with pores filled with paraffin wax is obtained.

[0033] 3) Immerse the paraffin-filled PVDF base membrane in a 2 mg / mL DA solution at a pH of 8.5 and react under magnetic stirring for 0 h to obtain a PDA-coated membrane;

[0034] 4) Immerse the coated membrane in n-hexane for 3-5 minutes, then rinse with n-hexane 3-4 times and dry. Remove the paraffin wax filling inside to obtain a high-flux oil-water separation membrane.

[0035] Example 2

[0036] The difference between Example 2 of the present invention and Example 1 is that: the magnetic stirring reaction time in 3) is 6 hours.

[0037] Example 3

[0038] The difference between Example 3 of the present invention and Example 1 is that: the magnetic stirring reaction time in 3) is 12 hours.

[0039] Example 4

[0040] The difference between Example 4 of the present invention and Example 1 is that: the magnetic stirring reaction time in 3) is 18 hours.

[0041] Example 5

[0042] The difference between Example 5 of the present invention and Example 1 is that: the magnetic stirring reaction time in 3) is 24 hours.

[0043] Example 6

[0044] The difference between Example 6 of the present invention and Example 1 is that: the magnetic stirring reaction time in 3) is 48 hours.

[0045] Example 7

[0046] The seventh embodiment of the present invention is different from the above embodiments in that:

[0047] 1) Place the PVDF membrane on a 65°C hot water surface and allow the lower surface to be slowly soaked in water for 10 minutes;

[0048] 2) Slowly pour 65°C molten paraffin into the membrane to place it at a stable oil-water interface with an oil-water ratio of 1:40.

[0049] After cooling to room temperature, a PVDF-based membrane with pores filled with paraffin was obtained;

[0050] 3) Immerse the paraffin-filled PVDF base membrane in a DA solution with a pH of 8.5 and a concentration of 0 mg / mL and react under magnetic stirring for 24 hours to obtain a PDA-coated membrane;

[0051] 4) Immerse the coated membrane in n-hexane for 3-5 minutes, then rinse with n-hexane 3-4 times and dry. Remove the paraffin wax filling inside to obtain a high-flux oil-water separation membrane.

[0052] Example 8

[0053] The difference between Example 8 of the present invention and Example 7 is that: the pH of the dopamine aqueous solution in 3) is 8.5, and the concentration is 0.5 mg / mL.

[0054] Embodiment 9

[0055] The difference between Example 9 of the present invention and Example 7 is that: the pH of the dopamine aqueous solution in 3) is 8.5, and the concentration is 1 mg / mL.

[0056] Example 10

[0057] The difference between Example 10 of the present invention and Example 7 is that: the pH of the dopamine aqueous solution in 3) is 8.5, and the concentration is 2 mg / mL.

[0058] Example 11

[0059] The difference between Example 11 of the present invention and Example 7 is that: the pH of the dopamine aqueous solution in 3) is 8.5, and the concentration is 4 mg / mL.

[0060] Example 12

[0061] The twelfth embodiment of the present invention differs from the above embodiments in that:

[0062] 1) Place the PVDF membrane on a 65°C hot water surface and allow the lower surface to be slowly soaked in water for 0 min;

[0063] 2) Slowly pour 65°C molten paraffin wax into the membrane, placing it at a stable oil-water interface with an oil-water ratio of 1:40. After cooling to room temperature, the PVDF membrane with pores filled with paraffin wax is obtained.

[0064] 3) Immerse the paraffin-filled PVDF base membrane in a 2 mg / mL DA solution at a pH of 8.5 and react under magnetic stirring for 12 h to obtain a PDA-coated membrane;

[0065] 4) Immerse the coated membrane in n-hexane for 3-5 minutes, then rinse with n-hexane 3-4 times and dry. Remove the paraffin wax filling inside to obtain a high-flux oil-water separation membrane.

[0066] Example 13

[0067] The difference between Example 13 of the present invention and Example 12 is that: 1) the lower surface of the PVDF membrane is soaked in water for 20 minutes.

[0068] Example 14

[0069] The difference between Example 14 and Example 12 of the present invention is that: 1) the lower surface of the PVDF membrane is soaked in water for 30 minutes.

[0070] Example 15

[0071] The difference between Example 15 and Example 12 of the present invention is that: 1) the lower surface of the PVDF membrane is soaked in water for 60 minutes.

[0072] Example 16

[0073] The difference between Example 16 and Example 12 of the present invention is that: 1) the lower surface of the PVDF membrane is soaked in water for 90 minutes.

[0074] Embodiment 17

[0075] The twelfth embodiment of the present invention differs from the above embodiments in that:

[0076] 1) Place the PVDF membrane on a 65°C hot water surface and allow the lower surface to be slowly soaked in water for 0 min;

[0077] 2) Slowly pour 65°C molten paraffin wax into the membrane, placing it at a stable oil-water interface with an oil-water ratio of 1:30. After cooling to room temperature, the PVDF membrane with pores filled with paraffin wax is obtained.

[0078] 3) Immerse the paraffin-filled PVDF base membrane in a 2 mg / mL DA solution at a pH of 8.5 and react under magnetic stirring for 12 h to obtain a PDA-coated membrane;

[0079] 4) Immerse the coated membrane in n-hexane for 3-5 minutes, then rinse with n-hexane 3-4 times and dry. Remove the paraffin wax filling inside to obtain a high-flux oil-water separation membrane.

[0080] The twelfth embodiment of the present invention differs from the above embodiments in that:

[0081] 1) Place the PVDF membrane on a 65°C hot water surface and allow the lower surface to be slowly soaked in water for 0 min;

[0082] 2) Slowly pour 65°C molten paraffin wax into the membrane, placing it at a stable oil-water interface with an oil-water ratio of 1:50. After cooling to room temperature, the PVDF membrane with pores filled with paraffin wax is obtained.

[0083] 3) Immerse the paraffin-filled PVDF base membrane in a 2 mg / mL DA solution at a pH of 8.5 and react under magnetic stirring for 12 h to obtain a PDA-coated membrane;

[0084] 4) Immerse the coated membrane in n-hexane for 3-5 minutes, then rinse with n-hexane 3-4 times and dry. Remove the paraffin wax filling inside to obtain a high-flux oil-water separation membrane.

[0085] Example 18

[0086] The seventeenth embodiment of the present invention is different from the above embodiments in that the organic separation membrane used is a nylon membrane.

[0087] Example 19

[0088] The eighteenth embodiment of the present invention is different from the above embodiments in that the organic separation membrane used is a polysulfone membrane.

[0089] Example 20

[0090] The nineteenth embodiment of the present invention is different from the above embodiments in that the organic separation membrane used is a polyamide membrane.

[0091] Example 21

[0092] The difference between the twentieth embodiment of the present invention and the above embodiments is that the organic separation membrane used is a polytetrafluoroethylene membrane.

[0093] The oil-water separation membrane prepared in Example 5 was observed using a scanning electron microscope, and its SEM image is as follows: Figure 1 As shown. Figure 1 The results show that the filling and removal of paraffin wax have no effect on the loaded PDA, and due to the filling of paraffin wax, PDA is only loaded on the membrane surface.

[0094] The oil-water separation membranes obtained in the above examples were subjected to flux tests and oil-water separation tests.

[0095] The flux test procedure is as follows: 200 mL of deionized water is taken and the membrane is placed in the separation device for water flux testing. The water flow time is recorded. The average value is calculated after multiple measurements (at least 3).

[0096] The experimental results show that the flux of the high-throughput oil-water separation membrane prepared by this method reaches 12000 L m 2 h -1 bar- 1 above,

[0097] The oil-water separation test procedure involves taking 50 mL of each of petroleum ether, n-hexane, toluene, chloroform, 1,2-dichloroethane, and carbon tetrachloride and 50 mL of water to form an oil-water mixture. The separation device then performs the oil-water separation test on both sides of the membrane, recording the mass of oil or water before and after separation. The oil-water separation efficiency is calculated using the following formula:

[0098] Separation efficiency η = M t / M0×100%.

[0099] Where MO is the initial weight of oil or water before separation, and Mt is the weight of oil or water after separation.

[0100] At the same time, 50 mL of petroleum ether and 50 mL of water were taken to form an oil-water mixture and the oil-water separation membrane was subjected to a cyclic performance test. It can be seen that even after 20 cycles, the flux still remained at 10500 L m 2 h -1 bar -1 At the same time, its separation efficiency can be maintained above 98%, indicating that it has good recyclability.

[0101] Comparative Example 1

[0102] The effect data of Example 1 in CN109499393A (A super-hydrophilic PVDF oil-water separation membrane for separating oily wastewater and its preparation method and application) shows that the membrane flux during the oil-water separation process is 4000 L / (m 2 .h.bar).

[0103] Comparative Example 2

[0104] According to the experimental data of the literature "Preparation and Oil-Water Separation Performance of Super Hydrophilic-Underwater Super Oleophobic PVDF-g-PAA Porous Membrane", the separation efficiency of PVDF-g-PAA asymmetric membrane is 98%, and the flux is 444L / (m 2 h) or above.

[0105] Comparative Example 3

[0106] The experimental data in the literature "Preparation of super-hydrophilic / underwater super-oleophobic PVDF composite membrane and study on oil / water emulsion separation performance" show that the composite membrane has a high flux (1000±44Lm -2 h -1 bar -1 ) and good separation efficiency (98%).

[0107] Comparative Example 4

[0108] According to experimental data in the literature "Superhydrophilic and underwater superoleophobic PVDF membranes via plasma-induced surface PEGDA for effective separation of oil-in-water emulsions", the oil-water flux of the modified membrane can reach 2400Lm at a pressure of 5KPa. -2 h-1 , in addition, the oil retention rate is above 90%.

[0109] Comparative Example 5

[0110] According to experimental data from the literature "Superhydrophilic and underwater superoleophobic poly(acrylonitrile-co-methyl acrylate) membrane for highly efficient separation of oil-in-water emulsions", the flux of (acrylonitrile-methyl acrylate) (P(AN-MA)) microfiltration membrane can reach 4341Lm at a working pressure of 0.02MPa. -2 h -1 .

[0111] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. An oil-water separation membrane, the separation membrane being prepared by the following method: (1) Place the organic separation membrane on the surface of hot water so that its lower surface is slowly wetted by water; slowly pour molten paraffin wax into it so that the organic separation membrane is at a stable oil-water interface, and after cooling, a base membrane with pores filled with paraffin wax is obtained; (2) immersing the paraffin-filled basement membrane in a dopamine aqueous solution to react and obtain a dopamine-coated membrane; (3) Immersing the coated membrane in n-hexane solution to remove the filled paraffin wax to obtain an oil-water separation membrane; The water temperature in step (1) is 55-80°C; The filter membrane is placed at the oil-water interface for 20 to 90 minutes.

2. The oil-water separation membrane according to claim 1, characterized in that The organic separation membrane in step (1) includes organic hydrophobic separation membranes such as nylon membrane, polyvinylidene fluoride membrane, polysulfone membrane, polyamide membrane, and polytetrafluoroethylene membrane.

3. The oil-water separation membrane according to claim 1, characterized in that The melting temperature of the paraffin wax is 48-50°C.

4. The oil-water separation membrane according to claim 1, characterized in that The oil-water ratio of the oil-water interface is 1:30~50.

5. The oil-water separation membrane according to claim 1, characterized in that The pH value of the dopamine aqueous solution is 8.3-8.5, and the concentration is 0-4 mg / mL.

6. The method for preparing an oil-water separation membrane according to claim 1, wherein: The method comprises the following steps: (1) Place the organic separation membrane on the surface of hot water so that its lower surface is slowly wetted by water; slowly pour molten paraffin wax into it so that the organic separation membrane is at a stable oil-water interface, and after cooling, a base membrane with pores filled with paraffin wax is obtained; (2) The base membrane filled with paraffin wax is immersed in a dopamine aqueous solution to react and obtain a dopamine coating membrane; (3) The coating membrane is immersed in a n-hexane solution to remove the filled paraffin wax and obtain an oil-water separation membrane.

7. Use of the oil-water separation membrane according to any one of claims 1 to 5, characterized in that: The oil-water separation membrane can be applied to the technical field of oil-water separation.

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