Preparation method of oil-water separation membrane with super-philic property in medium and application thereof

Abstract

The application belongs to the field of materials, and provides a preparation method of an oil-water separation membrane with super-philic characteristics in medium, and the main steps are as follows: (1) pretreating wood naturally having a multi-stage pore structure, and enriching and penetrating the pore structure of the wood; (2) treating the wood with a modifier by using an ultrasonic immersion method, and respectively preparing underwater super-oleophilic wood membranes and oil-under super-hydrophilic wood membranes, which are all oil-water separation membranes and are oil-water separation membranes with super-philic characteristics in medium. The oil-water separation membrane with super-philic characteristics in medium provided by the application adopts a filtration-driven adsorption mode, can realize efficient separation of various oil-in-water or water-in-oil stable emulsions, and the efficiency is higher than 99.95%; and can also realize separation of high-viscosity oil product stable emulsions, and the viscosity of the oil product can be as high as 50 mPa s.

Description

Technical Field

[0001] The present invention belongs to the field of materials, relates to an oil-water emulsion separation membrane and a preparation method thereof, and specifically relates to a preparation method and application of an oil-water separation membrane with super affinity for a medium. Background Art

[0002] With the massive discharge of oily wastewater in production and daily life, and the frequent occurrence of offshore crude oil spills, the problem of oil pollution in water bodies is becoming increasingly serious, posing a serious threat to the ecological environment and human health. Therefore, finding an effective solution to this problem is urgent. Furthermore, industrial production processes (such as mining, textiles, and petrochemicals) also generate large amounts of water-containing waste oil, leading to direct waste and pollution of oil products. Water contamination in oil can severely impact the quality and performance of the oil, as well as the equipment it serves, and can even cause significant economic losses. Traditional oil-water separation methods include gravity, centrifugation, and flotation, but these methods are only capable of separating simple oil-water mixtures. They struggle to separate surfactant-stabilized emulsions with diameters of tens of microns and suffer from low separation efficiency, high costs, and low recycling rates. While conventional membrane materials are widely used for oil-water separation, their long processing time, susceptibility to contamination, lack of selectivity, and the need for pretreatment limit their application. Therefore, there is a need to develop new materials with high separation efficiency, excellent selectivity, and high stability for oil-water separation.

[0003] In recent years, inspired by biological phenomena such as the "self-cleaning" of lotus leaves and fish scales, materials with special wettability have been widely used in oil-water separation due to their completely opposite affinities for oil and water. The application of special wettability materials in oil-water separation includes filtration and adsorption. For example, patent CN115738740A uses a spray self-assembly method to spray tannic acid and metal ions onto the membrane surface to assemble a tannic acid-metal complex, which transforms the membrane surface from hydrophobic to hydrophilic. The prepared membrane has superhydrophilic / underwater superoleophobic properties for separating oil-in-water emulsions. Patent CN115591412A uses a modified titanium dioxide sol formed by the hydrolysis of tetrabutyl titanate and silane substances to prepare a superhydrophobic and superoleophilic oil-in-water emulsion separation membrane by single dip coating on a glass fiber membrane. These membranes can effectively block one phase and selectively pass the other phase, thereby achieving the separation of oil-water emulsions. However, since the pore size of the membrane used in the filtration method must be smaller than the droplet size, it will be limited by the size screening mechanism in actual separation, including the accumulation of blocked micro / nano droplets, resulting in a sharp drop in flux, and the blockage of high-viscosity oil in small channels, resulting in the inability to separate.

[0004] Currently, most reported adsorbents using adsorption methods are hydrophobic or superhydrophobic, limited to separating laminar oil-water mixtures or oil-in-water emulsions. The use of superhydrophilic adsorbents to separate water-in-oil emulsions is rarely achieved. Patent CN106698583A uses in-situ reduction of silver nanoparticles on a polypyrrole surface and fluorination to impart superhydrophobic / superoleophilic properties to a melamine sponge. This material exhibits good treatment efficiency and adsorption properties for oily wastewater. However, due to kinetic limitations, adsorption methods cannot fully and effectively separate oil-in-water emulsions and are ineffective at removing highly viscous oils. Summary of the Invention

[0005] In view of the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a method for preparing an oil-water separation membrane with super-affinity in the medium, which can achieve efficient separation of various oil-in-water or oil-in-water stable emulsions with an efficiency of not less than 99.95%.

[0006] The technical solution adopted by the present invention to solve the above-mentioned problems is:

[0007] A method for preparing an oil-water separation membrane with super affinity for a medium, characterized by the following main steps:

[0008] (1) Wood pretreatment: chemical treatment is used to remove lignin from the wood and enrich and penetrate its pore structure;

[0009] (2) Preparation of underwater super-oleophilic wood film: The wood obtained in step (1) is placed in an underwater super-oleophilic modifier and modified by ultrasonic impregnation. After drying, an underwater super-oleophilic wood film is obtained. The underwater super-oleophilic modifier is prepared by uniformly mixing a super-oleophilic long-chain alkane surface modifier, tetraethyl orthosilicate, and ethanol in a volume ratio of (1-5):5:500.

[0010] (3) Preparation of super-hydrophilic wood film under oil: The wood obtained in step (1) is placed in a super-hydrophilic modifier under oil and modified by ultrasonic impregnation. After drying, a super-hydrophilic wood film under oil can be obtained; wherein, the preparation method of the super-hydrophilic modifier under oil is to uniformly mix a super-hydrophilic fluorocarbon surface modifier, tetraethyl orthosilicate, and ethanol in a volume ratio of (0.5-1):1:50;

[0011] The underwater super-oleophilic wood membrane and the underwater super-hydrophilic wood membrane prepared in step (2) and step (3) respectively are both oil-water separation membranes, and are oil-water separation membranes with super-hydrophilic properties in the medium.

[0012] According to the above scheme, the original wood used in step (1) can be softwood or hardwood, with a thickness of 5 to 15 mm.

[0013] According to the above scheme, the specific process of step (1) is as follows:

[0014] 1) Place the original wood in a mixed solution of sodium sulfite and sodium hydroxide in a constant temperature water bath at 80°C for 2 to 4 hours;

[0015] 2) The wood obtained in step 1) is placed in a hydrogen peroxide solution in a constant temperature water bath at 80°C for 3-5 hours. After the reaction is complete, the wood is cleaned, dried completely, and set aside for later use. In step 1), the concentration of sodium sulfite is 0.4-0.6 mol / L, and the concentration of sodium hydroxide is 2-4 mol / L; in step 2), the concentration of hydrogen peroxide is 0.5-2 mol / L.

[0016] According to the above scheme, the ultrasonic impregnation process in step (2) and step (3) is as follows: immersing the pretreated wood in the modifier, ultrasonically treating for 5 minutes, drying in an oven at a temperature of 40 to 60° C. for 5 minutes, and repeating the operation 2 to 4 times.

[0017] According to the above scheme, the preparation method of the underwater super oleophilic modifier described in step (2) is: mixing a super oleophilic long-chain alkane surface modifier, tetraethyl orthosilicate, and ethanol in a volume ratio of (1-5):5:500, and stirring in air for 2-6 hours to obtain the underwater super oleophilic modifier.

[0018] According to the above scheme, in step (2), the super oleophilic long-chain alkane surface modifier is an alkylsilane with a carbon chain length of not less than twelve, which can be long-chain alkane trimethoxysilane, long-chain alkane triethoxysilane, long-chain alkane trichlorosilane, etc.

[0019] According to the above scheme, in step (3), the super-hydrophilic fluorocarbon surface modifier is a perfluoroalkyl acid or a fluorocarbon surfactant, etc., which can be a fluorocarbon surfactant FS-50, perfluorooctanoic acid, Nafion, etc.

[0020] The oil-water separation membranes prepared above include two types: underwater super-oleophilic wood membranes and sub-oil super-hydrophilic wood membranes. Among them, the underwater super-oleophilic wood membrane is used to separate oil-in-water emulsions with a separation efficiency exceeding 99.95%; the sub-oil super-hydrophilic wood membrane is used to separate water-in-oil emulsions with a separation efficiency also exceeding 99.95%. It can also achieve the separation of stable emulsions prepared using high-viscosity oils, with the viscosity of the oils reaching up to 50mPa s.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] First, the oil-water separation membrane of the present invention adopts a filtration-driven adsorption method, utilizing the super-affinity of the filter medium combined with the multi-level pore structure of wood to selectively adsorb oil or water in oil-in-water or oil-in-water stable emulsions;

[0023] Second, the substrate material used in the present invention is wood, which contains a large number of hierarchical pores. When used as a separation membrane, its large pore channels allow the continuous phase in the emulsion to pass through, while its small pores increase the contact area and promote adsorption. Traditional separation membranes use small pores to block dispersed droplets to achieve oil-water emulsion separation, but the accumulation of blocked micro / nano droplets leads to a sharp decrease in flux, and the high-viscosity oil in the small channels is blocked, resulting in separation failure.

[0024] Third, the preparation method of the present invention is simple and easy to operate. The prepared oil-water separation material has super-oleophilic properties underwater and super-hydrophilic properties under oil, respectively. It can achieve efficient separation of various oil-in-water or oil-in-water stable emulsions with an efficiency exceeding 99.95%. In particular, it can achieve the separation of stable emulsions prepared with high-viscosity oils, and the viscosity of the oils can be as high as 50mPa s. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 a is the contact angle of water in oil of the super-hydrophilic wood film prepared in Example 2, Figure 1 b is the contact angle of oil in water of the underwater superoleophilic wood film prepared in Example 1.

[0026] Figure 2 a is an electron microscope image of the original wood (hard pine) in Example 2; Figure 2 b is an electron microscope image of the wood film with super affinity for the medium prepared in Example 2.

[0027] Figure 3 a is an optical comparison diagram of the emulsion and the filtrate before and after separation of the edible oil-in-water emulsion by the underwater superoleophilic wood membrane prepared in Example 1; Figure 3 b is an optical comparison diagram of the emulsion and the filtrate before and after separation of the edible oil-in-water emulsion by the oil-submerged super-hydrophilic wood membrane prepared in Example 2.

[0028] Figure 4 This is a graph showing the separation efficiency of the water-in-lubricating oil emulsion obtained by circulating the wood membrane with super-affinity in the medium prepared in Example 2 three times, separating 200 mL of the emulsion each time. DETAILED DESCRIPTION

[0029] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0030] In the following examples, the purity of ethanol is ≥99.7%.

[0031] In the following examples, the oil-in-water emulsions used were prepared by mixing distilled water and edible oil (or lubricating oil or diesel, where the viscosity of edible oil is approximately 50 mPa s and the viscosities of lubricating oil and diesel are generally between 40 and 50 mPa s) in a volume ratio of 100:1, adding Tween 20 (0.1 g / L), and shaking thoroughly to obtain an edible oil-in-water emulsion (or, when lubricating oil or diesel is used, a lubricating oil-in-water emulsion or a diesel-in-water emulsion, respectively). Separation efficiency was determined by comparing the oil content in the filtrate after separation with the COD of distilled water.

[0032] In the following examples, the water-in-oil emulsion was prepared by mixing edible oil (or lubricating oil or diesel) and distilled water in a volume ratio of 100:1, adding 10 g / L of Span 80, and shaking to obtain the water-in-oil emulsion. Separation efficiency was determined by measuring the water content of the filtrate using a Karl Fischer titrator.

[0033] In the following embodiments, the wood is cut into the size of 30 mm long × 30 mm wide × 10 mm thick.

[0034] Example 1

[0035] A method for preparing an oil-water separation membrane having super affinity for a medium comprises the following steps:

[0036] (1) The hard pine wood was placed in a mixed solution of 2.5 mol / L sodium hydroxide and 0.4 mol / L sodium sulfite in a constant temperature water bath at 80°C for 3 h, and then chemically treated with a 1 mol / L hydrogen peroxide solution in a constant temperature water bath at 80°C for 3 h. After the treatment was complete, the wood was cleaned and dried for later use.

[0037] (2) Octadecyltrichlorosilane, tetraethyl orthosilicate, and ethanol were mixed in a volume ratio of 1:5:500, and then the mixed solution was stirred in air for 6 h to obtain an underwater super oleophilic modifier.

[0038] (3) Immersing the wood pretreated in step (1) in the modifier obtained in step (2) and ultrasonically treating it for 5 minutes, then drying it in an oven at a temperature of 50° C. for 5 minutes, and repeating the operation 3 times; after the wood is completely dried, an underwater super-oleophilic wood membrane is obtained, that is, an oil-water separation membrane with super-oleophilic properties in the medium.

[0039] Distilled water and cooking oil were mixed in a volume ratio of 100:1, Tween 20 (0.1 g / L) was added, and the mixture was shaken thoroughly to obtain a water-in-oil emulsion. Using a filtration device, the water-in-oil emulsion was separated in a filter cup under a negative pressure of 40 kPa. The time required was recorded, and the filtrate was collected. Distilled water was used as a control sample, and the COD of the resulting filtrate was measured, resulting in a separation efficiency of 99.96%.

[0040] like Figure 1 FIG. 2 b shows the contact angle of oil in water of the underwater super oleophilic wood film prepared in this example, indicating that the film has super oleophilic properties in water.

[0041] like Figure 3 As shown in a, the optical comparison diagram of the edible oil-in-water emulsion separated by the underwater super-oleophilic wood membrane prepared in this example before and after separation shows that the filtrate becomes clear and transparent.

[0042] Example 2

[0043] A method for preparing an oil-water separation membrane having super affinity for a medium comprises the following steps:

[0044] (1) The hard pine wood was placed in a mixed solution of 2.5 mol / L sodium hydroxide and 0.4 mol / L sodium sulfite in a constant temperature water bath at 80°C for 3 h, and then chemically treated with a 1 mol / L hydrogen peroxide solution in a constant temperature water bath at 80°C for 3 h. After the treatment was complete, the wood was cleaned and dried for later use.

[0045] (2) Fluorocarbon surfactant FS-50, tetraethyl orthosilicate, and ethanol were mixed in a volume ratio of 1:1:20 by ultrasonication to obtain an oil-water superhydrophilic modifier, that is, an oil-water separation membrane with superhydrophilic properties in the medium.

[0046] (3) Immersing the wood pretreated in step (1) in the modifier obtained in step (2) and ultrasonically treating it for 5 minutes, then drying it in an oven at a temperature of 50° C. for 5 minutes, repeating the operation three times until the wood is completely dried, thereby obtaining an oil-submerged super-hydrophilic wood membrane, which has super-hydrophilic properties in the medium.

[0047] The oil-based super-hydrophilic wood membrane prepared in this example was used to separate edible oil-in-water emulsions, and the separation efficiency was 99.95%. Figure 1 As shown in a, the contact angle of the superhydrophilic wood film under oil and water in oil indicates that it has superhydrophilic properties in oil.

[0048] The scanning electron microscope photos of the super hydrophilic wood film under oil prepared in Example are as follows: Figure 2 b shows a scanning electron microscope photo of the original wood Figure 2 Compared with a, its surface becomes rough after being treated with the modifier, and the modifier is successfully coated on the wood.

[0049] like Figure 3 As shown in b, the optical comparison diagram of the edible oil-in-water emulsion separated by the oil-submerged super-hydrophilic wood membrane prepared in this example before and after separation shows that the filtrate becomes clear and transparent.

[0050] like Figure 4The prepared super-hydrophilic wood membrane was used to separate the lubricating oil-in-water emulsion three times, with 200 mL separated each time. After each separation cycle, it was rinsed with ethanol and dried before continued use. It can be seen that the separation efficiency of 600 mL of emulsion can still reach 99.9% when the wood membrane is used to separate the emulsion.

[0051] Example 3

[0052] A method for preparing an oil-water separation membrane having super affinity for a medium comprises the following steps:

[0053] (1) The soft pine wood was placed in a mixed solution of 2.5 mol / L sodium hydroxide and 0.4 mol / L sodium sulfite in a constant temperature water bath at 80°C for 3 h, and then chemically treated with a 0.5 mol / L hydrogen peroxide solution in a constant temperature water bath at 80°C for 3 h. After the treatment was complete, the wood was cleaned and dried for later use.

[0054] (2) Octadecyltrichlorosilane, tetraethyl orthosilicate, and ethanol were mixed in a volume ratio of 1:5:500, and the mixed solution was stirred in air for 6 h to obtain an underwater super oleophilic modifier.

[0055] (3) The wood pretreated in step (1) was immersed in the modifier obtained in step (2) and ultrasonically treated for 5 minutes. The wood was then dried in an oven at 50°C for 5 minutes. This process was repeated three times until the wood was completely dried, thereby obtaining an underwater superoleophilic wood membrane. The membrane was used to separate a lubricating oil-in-water emulsion with a separation efficiency of 99.98%.

[0056] Example 4

[0057] A method for preparing an oil-water separation membrane with super affinity for a medium comprises the following steps:

[0058] (1) The soft pine wood was placed in a mixed solution of 2.5 mol / L sodium hydroxide and 0.4 mol / L sodium sulfite in a constant temperature water bath at 80°C for 3 h, and then chemically treated with a 0.5 mol / L hydrogen peroxide solution in a constant temperature water bath at 80°C for 3 h. After the treatment was complete, the wood was cleaned and dried for later use.

[0059] (2) Fluorocarbon surfactant FS-50, tetraethyl orthosilicate, and ethanol were mixed in a volume ratio of 1:1:20 and ultrasonically prepared to obtain an oil-based superhydrophilic modifier.

[0060] (3) The wood pretreated in step (1) was immersed in the modifier obtained in step (2) and ultrasonically treated for 5 minutes, and then dried in an oven at a temperature of 50°C for 5 minutes. The operation was repeated 3 times. After the wood was completely dried, an oleophobic / oil-submerged super-hydrophilic wood film was obtained, which was used to separate lubricating oil-in-water emulsion with a separation efficiency of 99.95%.

[0061] Example 5

[0062] A method for preparing an oil-water separation membrane with super affinity for a medium comprises the following steps:

[0063] (1) The paulownia wood was placed in a mixed solution of 2.5 mol / L sodium hydroxide and 0.4 mol / L sodium sulfite in a constant temperature water bath at 80°C for 3 h, and then chemically treated with a 1 mol / L hydrogen peroxide solution in a constant temperature water bath at 80°C for 3 h. After the treatment was complete, the wood was cleaned and dried for later use.

[0064] (2) Octadecyltrichlorosilane, tetraethyl orthosilicate, and ethanol were mixed in a volume ratio of 1:5:500, and the mixed solution was stirred in air for 6 h to obtain an underwater super oleophilic modifier.

[0065] (3) The wood pretreated in step (1) was immersed in the modifier obtained in step (2) and ultrasonically treated for 5 minutes. The wood was then dried in an oven at 50°C for 5 minutes. This process was repeated three times until the wood was completely dried, resulting in an underwater super-oleophilic wood membrane. The membrane was used to separate edible oil-in-water emulsions with a separation efficiency of 99.95%.

[0066] Example 6

[0067] A method for preparing an oil-water separation membrane with super affinity for a medium comprises the following steps:

[0068] (1) The paulownia wood was placed in a mixed solution of 2.5 mol / L sodium hydroxide and 0.4 mol / L sodium sulfite in a constant temperature water bath at 80°C for 3 h, and then chemically treated with a 1 mol / L hydrogen peroxide solution in a constant temperature water bath at 80°C for 3 h. After the treatment was complete, the wood was cleaned and dried for later use.

[0069] (2) Fluorocarbon surfactant FS-50, tetraethyl orthosilicate, and ethanol were mixed in a volume ratio of 1:1:20 and ultrasonically prepared to obtain an oil-based superhydrophilic modifier.

[0070] (3) The wood pretreated in step (1) was immersed in the modifier obtained in step (2) and ultrasonically treated for 5 minutes, and then dried in an oven at a temperature of 50°C for 5 minutes. The operation was repeated three times. After the wood was completely dried, an oil-submerged super-hydrophilic wood membrane was obtained, which was used to separate edible oil-in-water emulsion with a separation efficiency of 99.96%.

[0071] Example 7

[0072] A method for preparing an oil-water separation membrane with super affinity for a medium comprises the following steps:

[0073] (1) The hard pine wood was placed in a mixed solution of 2.5 mol / L sodium hydroxide and 0.4 mol / L sodium sulfite in a constant temperature water bath at 80°C for 3 h, and then chemically treated with a 1 mol / L hydrogen peroxide solution in a constant temperature water bath at 80°C for 3 h. After the treatment was complete, the wood was cleaned and dried for later use.

[0074] (2) Hexadecyltriethoxysilane, tetraethyl orthosilicate, and ethanol were mixed in a volume ratio of 2:5:500, and the mixed solution was stirred in air for 4 h to obtain an underwater super oleophilic modifier.

[0075] (3) The wood pretreated in step (1) was immersed in the modifier obtained in step (2) and ultrasonically treated for 5 minutes, and then dried in an oven at a temperature of 50°C for 5 minutes. The operation was repeated 3 times. After the wood was completely dried, an underwater super-oleophilic wood membrane was obtained, which was used to separate water-in-lubricating oil emulsion with a separation efficiency of 99.95%.

[0076] Example 8

[0077] A method for preparing an oil-water separation membrane with super affinity for a medium comprises the following steps:

[0078] (1) The hard pine wood was placed in a mixed solution of 2.5 mol / L sodium hydroxide and 0.4 mol / L sodium sulfite in a constant temperature water bath at 80°C for 3 h, and then chemically treated with a 1 mol / L hydrogen peroxide solution in a constant temperature water bath at 80°C for 3 h. After the treatment was complete, the wood was cleaned and dried for later use.

[0079] (2) Perfluorooctanoic acid and tetraethyl orthosilicate were mixed in a volume ratio of 1:2:40 and ultrasonically prepared to obtain an oil-based superhydrophilic modifier.

[0080] (3) The wood pretreated in step (1) was immersed in the modifier obtained in step (2) and ultrasonically treated for 5 minutes, and then dried in an oven at a temperature of 50°C for 5 minutes. The operation was repeated 3 times. After the wood was completely dried, an oil-submerged super-hydrophilic wood membrane was obtained, which was used to separate lubricating oil-in-water emulsion with a separation efficiency of 99.97%.

[0081] Example 9

[0082] A method for preparing an oil-water separation membrane with super affinity for a medium comprises the following steps:

[0083] (1) The hard pine wood was placed in a mixed solution of 2.5 mol / L sodium hydroxide and 0.4 mol / L sodium sulfite in a constant temperature water bath at 80°C for 3 h, and then chemically treated with a 1 mol / L hydrogen peroxide solution in a constant temperature water bath at 80°C for 3 h. After the treatment was complete, the wood was cleaned and dried for later use.

[0084] (2) Dodecyltrimethoxysilane, tetraethyl orthosilicate, and 99.7% ethanol were mixed in a volume ratio of 2:5:500, and the mixed solution was stirred in air for 4 h to obtain an underwater super oleophilic modifier.

[0085] (3) The wood pretreated in step (1) was immersed in the modifier obtained in step (2) and ultrasonically treated for 5 minutes, and then dried in an oven at a temperature of 50°C for 5 minutes. The operation was repeated 3 times. After the wood was completely dried, an underwater super-oleophilic wood membrane was obtained, which was used to separate water-in-diesel emulsion with a separation efficiency of 99.96%.

[0086] Example 10

[0087] A method for preparing an oil-water separation membrane with super affinity for a medium comprises the following steps:

[0088] (1) The hard pine wood was placed in a mixed solution of 2.5 mol / L sodium hydroxide and 0.4 mol / L sodium sulfite in a constant temperature water bath at 80°C for 3 h, and then chemically treated with a 1 mol / L hydrogen peroxide solution in a constant temperature water bath at 80°C for 3 h. After the treatment was complete, the wood was cleaned and dried for later use.

[0089] (2) Nafion, tetraethyl orthosilicate, and 99.7% ethanol were mixed in a volume ratio of 1:1:20 and ultrasonically prepared to obtain an oil-based superhydrophilic modifier.

[0090] (3) The wood pretreated in step (1) was immersed in the modifier obtained in step (2) and ultrasonically treated for 5 minutes, and then dried in an oven at a temperature of 50°C for 5 minutes. The operation was repeated 3 times. After the wood was completely dried, an oil-submerged super-hydrophilic wood membrane was obtained, which was used to separate diesel-water emulsion with a separation efficiency of 99.97%.

[0091] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing an oil-water separation membrane having super affinity for a medium, characterized in that: The main steps are: (1) Wood pretreatment: chemical treatment is used to remove lignin from the wood and enrich and penetrate its pore structure; (2) Preparation of underwater super-oleophilic wood film: The wood obtained in step (1) is placed in an underwater super-oleophilic modifier and modified by ultrasonic impregnation. After drying, an underwater super-oleophilic wood film can be obtained. The preparation method of the underwater super-oleophilic modifier is as follows: a super-oleophilic long-chain alkane surface modifier, tetraethyl orthosilicate, and ethanol are mixed in a volume ratio of (1-5): 5:500, and the mixture is stirred in air for 2-6 hours. (3) Preparation of super-hydrophilic wood film under oil: The wood obtained in step (1) is placed in a super-hydrophilic modifier under oil and modified by ultrasonic impregnation. After drying, a super-hydrophilic wood film under oil can be obtained. The super-hydrophilic modifier under oil is prepared by uniformly mixing a super-hydrophilic fluorocarbon surface modifier, tetraethyl orthosilicate, and ethanol in a volume ratio of (0.5-1):1:

50. The underwater super-oleophilic wood membrane and the underwater super-hydrophilic wood membrane prepared in step (2) and step (3) respectively are both oil-water separation membranes with super-hydrophilic properties in the medium.

2. The method for preparing an oil-water separation membrane having super affinity for a medium according to claim 1, characterized in that: In step (2), the super oleophilic long-chain alkane surface modifier is an alkylsilane with a carbon chain length of not less than twelve.

3. The method for preparing an oil-water separation membrane having super affinity for a medium according to claim 2, characterized in that: The super oleophilic long-chain alkane surface modifier includes one or more of long-chain alkane trimethoxysilane, long-chain alkane triethoxysilane, and long-chain alkane trichlorosilane.

4. The method for preparing an oil-water separation membrane having super affinity for a medium according to claim 1, characterized in that: In step (3), the super-hydrophilic fluorocarbon surface modifier is a perfluoroalkyl acid or a fluorocarbon surfactant.

5. The method for preparing an oil-water separation membrane having super affinity for a medium according to claim 4, characterized in that: The super-hydrophilic fluorocarbon surface modifier is one or more of the fluorocarbon surfactant FS-50, perfluorooctanoic acid, and Nafion.

6. The method for preparing an oil-water separation membrane having super affinity for a medium according to claim 1, characterized in that: The wood used in step (1) is raw wood, softwood or hardwood, cut to a thickness of 5 to 15 mm.

7. The method for preparing an oil-water separation membrane having super affinity for a medium according to claim 1, characterized in that: The specific process of step (1) is as follows: 1) Place the original wood in a mixed solution of sodium sulfite and sodium hydroxide in a constant temperature water bath at 80°C for 2-4 hours; 2) Place the wood obtained in step 1) in a hydrogen peroxide solution in a constant temperature water bath at 80°C for 3-5 hours. After the reaction is complete, clean the wood, dry it completely, and set aside for later use. Among them, the concentration of sodium sulfite is 0.4~0.6 mol / L, the concentration of sodium hydroxide is 2~4 mol / L; and the concentration of hydrogen peroxide is 0.5~2 mol / L.

8. The method for preparing an oil-water separation membrane having super affinity for a medium according to claim 1, characterized in that: The ultrasonic impregnation process in step (2) and step (3) is as follows: immersing the pretreated wood in the modifier, ultrasonically treating for 3 to 8 minutes, drying in an oven at a temperature of 40 to 60°C for 3 to 8 minutes, and repeating the operation 2 to 4 times.

9. Application of the oil-water separation membrane with super affinity in the medium prepared by the method of claim 1, characterized in that: Underwater superoleophilic wood membrane is used for separation of oil-in-water emulsion; underwater superhydrophilic wood membrane is used for separation of oil-in-water emulsion.

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