CN118543260A - A modified polyacrylonitrile microfiber oil-water separation material and preparation method thereof - Google Patents

Abstract

The invention provides a modified polyacrylonitrile microfiber oil-water separation material and a preparation method thereof, wherein the preparation method comprises the following steps: the method comprises the steps of obtaining polyacrylonitrile fiber after wet spinning and hot drawing, wherein the inside of the polyacrylonitrile fiber is provided with a fibrillating structure and is orderly arranged along the axial direction of the fiber, chopping the polyacrylonitrile fiber, putting the chopped polyacrylonitrile fiber and water into a mechanical crusher for shearing, disassembling and crushing to obtain polyacrylonitrile microfiber aqueous dispersion, and carrying out suction filtration by using a suction filtration bottle, washing by using deionized water, and drying by using an oven to obtain the polyacrylonitrile microfiber. And then carrying out amidoxime modification on the surface of the polyacrylonitrile microfiber by using hydroxylamine hydrochloride solution to increase the hydrophilicity of the polyacrylonitrile microfiber, thus obtaining the modified polyacrylonitrile microfiber. The preparation method is simple and convenient, and has industrialization potential; the polyacrylonitrile has certain chemical stability, the modified polyacrylonitrile microfiber has plasticity and certain self-supporting property, has affinity to water and has resistance to various oils and organic solvents in the presence of an oil-water mixture, can meet various oil-water separation environments and conditions, and provides an effective solution for purifying the oil-water mixture.

Description

A modified polyacrylonitrile microfiber oil-water separation material and preparation method thereof

Technical field:

The invention belongs to the field of new material processing and preparation, and relates to a method for preparing an oil-water separation material, and in particular to a method for preparing a modified polyacrylonitrile microfiber oil-water separation material.

Background technology:

In recent years, oily wastewater, as a by-product of human production and life, has hindered the process of sustainable development, destroyed the natural environment on which people depend for survival, and posed a huge threat to human life and safety. First, if oily wastewater is not treated or treated incompletely, the harmful substances in it will seep into the ground and converge with rivers, lakes and reservoirs, thereby polluting human freshwater resources; secondly, the density of oily wastewater is smaller than that of water, and it will cover the water surface and isolate oxygen, causing the death of aquatic plants and animals, thereby polluting the natural environment; finally, after oily wastewater is mixed with irrigation water sources, the harmful substances in it may be absorbed by crops and cause great harm to the human body. Therefore, it is particularly urgent to invent an efficient treatment method for oily wastewater.

In order to solve the above-mentioned effects of oily wastewater, many oil-water separation methods have been developed, including gravity separation, adsorption, membrane separation, etc. Gravity separation refers to the use of the immiscibility of oil and water phases and the difference in density to make the oil phase aggregate on the surface of the water phase, thereby achieving the effect of separation; adsorption refers to the use of adsorbents to adsorb one of the phases to achieve the purpose of separation; membrane separation refers to the use of various thin film materials with special structures to selectively allow one of the phases to pass through, which has the advantages of low energy consumption, convenient operation, and high separation efficiency. Therefore, in the process of studying oil-water separation methods, the preparation of oil-water separation membranes with different functions has become the focus of research by scholars and experts. Professor Xue Ming's research group at Jilin University coated a UiO-66 micro-nanostructure coating on a metal mesh and prepared a membrane, making the membrane hydrophilic and underwater superoleophobic, with an oil-water separation efficiency of up to 99.99%, and a maximum water flux of 12.7×10 ⁴ L/(m ² h). It can easily capture high-purity water with an oil content of less than 4ppm from various oil-water mixtures, and exhibits high stability and durability. However, the membrane's antifouling, reuse and corrosion resistance are weak, it does not have an efficient decontamination method, and has certain limitations in some complex corrosive oil-water separation environments. Mohamed Obaid et al. prepared polyvinylidene fluoride (PVDF) nanofiber felt by electrospinning, and then used triethanolamine (TEA) to modify the felt surface to form hydrophilic microspheres to obtain a modified PVDF oil-water separation membrane. The membrane also has an ultra-high water flux of 20664L/(m ² h) for oil-water separation and 2727L/(m ² h) for emulsion separation, with a separation efficiency of up to 99%. However, the electrospinning method for preparing PVDF nanofibers requires the addition of an organic solvent, N,N-dimethylformamide (DMF), which indirectly harms the environment and human health, and the preparation cycle is long, which is not conducive to large-scale production and application.

When membrane separation is performed for oil-water separation, due to its abundant pore structure to absorb liquid phase, separation efficiency is high and separation flux is large. Polyacrylonitrile is a widely used general plastic, cheap and easy to obtain, and polyacrylonitrile microfiber is easy to prepare, and its physicochemical properties are stable, and it has hydrophilic characteristics. After shearing and disassembling, the fiber is prepared to obtain polyacrylonitrile microfibers, and then modified by amidoximation, the modified polyacrylonitrile microfibers with hydrophilic-underwater super-oleophobic characteristics that can be obtained. The modified polyacrylonitrile microfibers belong to hydrophilic oleophobic materials, with abundant microscopic pore structures to absorb and store water, and the preparation and processing are simple and easy to operate, the preparation cost is low, and it can be repeatedly reused, and there are obvious advantages in large-scale use and continuous production processes, and there is a certain guiding significance for the preparation of microfiber materials for oil-water separation.

Summary of the invention:

The purpose of the present invention is to prepare a microfiber oil-water separation material which has simple preparation and processing operation, significant oil-water separation effect, stable physical and chemical properties, can be repeatedly recycled, and can be produced on a large scale and continuously.

In order to achieve the above object, the present invention provides a preparation method of modified polyacrylonitrile microfiber oil-water separation material:

(1) chopping the polyacrylonitrile fibers obtained by wet spinning and hot drawing with a cutter to obtain polyacrylonitrile chopped fibers, and then placing the chopped fibers in a mechanical pulverizer, adding water, and mechanically shearing, disassembling, and pulverizing to obtain a polyacrylonitrile microfiber aqueous dispersion;

(2) filtering the polyacrylonitrile microfiber aqueous dispersion obtained in step (1), washing with deionized water, and drying in an oven to obtain polyacrylonitrile microfibers;

(3) The polyacrylonitrile microfibers obtained in step (2) are modified with a hydroxylamine hydrochloride solution to increase their surface hydrophilicity, and then filtered and washed with deionized water, and then placed in an oven for drying to obtain a modified polyacrylonitrile microfiber oil-water separation material.

Preferably, the chopped fibers in step (1) are 1-2 cm in length, and the ratio of added fibers to water is 2 L of water per 10 g of fibers. During mechanical shearing, disassembly and pulverization, the shear rate is 10 ⁵ s ^-1 , and the time is 10-90 minutes, more preferably 40-60 minutes, and most preferably 50 minutes.

Preferably, the concentration of the hydroxylamine hydrochloride solution in step (3) is 2-6%, most preferably 4%; the mass of the polyacrylonitrile microfibers is 5-15 g, most preferably 10 g; and the reaction time is 1-3 h, most preferably 2 h.

Compared with the prior art, the present invention has the following positive and beneficial effects:

(1) The present invention utilizes the fibrillated structure generated along the fiber axis inside the polyacrylonitrile fiber during the wet spinning and hot stretching process, and shears and disassembles it to break it, thereby destroying the weak radial intermolecular bonding force between the fibrillated structures and retaining the strong axial chemical bond bonding force, so that the fibrillated structure is exposed and polyacrylonitrile microfibers are obtained. The microfibers are hydrophilically modified by amidoximation with a hydroxylamine hydrochloride solution, and then the microfibers are interlaced and overlapped by suction filtration to support the obtained modified polyacrylonitrile microfiber oil-water separation membrane. This relatively novel method of mechanically disassembling the fibrillated structure to prepare microfibers, then improving their hydrophilicity by modification, and finally preparing the microfiber oil-water separation membrane by suction filtration solves the problems of complex processing operations, difficulty in reuse, and difficulty in large-scale continuous production in the preparation of existing oil-water separation materials, and can greatly reduce the cost of preparation.

(2) In the method for preparing modified polyacrylonitrile microfiber oil-water separation material of the present invention, the required raw material is polyacrylonitrile fiber, which is cheap and easy to obtain, and has excellent hydrophilicity and oleophobicity and physical and chemical stability. The preparation process is simple to operate, requires fewer chemical reagents, causes less damage to the human body and the environment, and the preparation process is simple and safe. In the process of disassembling and preparing microfibers, only the physical form changes, and the chemical structure and functional groups of polyacrylonitrile are not destroyed, so the chemical stability and hydrophilicity of the fiber itself are not lost.

(3) The modified polyacrylonitrile microfibers prepared by the present invention have micro-nano-scale pores at the microscopic level, which are formed by the interpenetration, overlap and support between the modified polyacrylonitrile microfibers, but at the macroscopic level, the microfibers are loose and plastic. Therefore, the microfibers can be prepared into various shapes by suction filtration to meet the requirements of oil-water separation in a complex environment or specific equipment in a set form (Figure 2).

(4) The modified polyacrylonitrile microfiber oil-water separation material prepared by the present invention has micro-nano-scale pores, which can efficiently adsorb and retain the water phase. At the same time, after being modified by amidoximation with hydroxylamine hydrochloride solution, the hydrophilicity of the microfiber is further enhanced, and it has superoleophobicity underwater (Figures 5 and 6).

(5) The physical and chemical stability of modified polyacrylonitrile microfiber oil-water separation materials also provides a guarantee for their recycling. After use, the contaminated modified polyacrylonitrile microfiber oil-water separation membrane can be fully dispersed in water to return to a loose microfiber form. Then, the oil stains can be removed by certain means, and the microfibers can be recycled and prepared into microfiber membranes for continued oil-water separation, and the ultra-high separation efficiency can still be maintained (Figure 8).

Description of the drawings:

FIG. 1 is an equation for the amidoximation reaction of preparing modified polyacrylonitrile microfibers (AOPNF) from polyacrylonitrile microfibers (PNF).

FIG. 2 is a physical picture, a loose physical picture and a field emission scanning electron microscope (FE-SEM) morphology picture of the polyacrylonitrile and modified polyacrylonitrile microfiber membranes in Example 1, and a display of the plasticity of the modified polyacrylonitrile microfibers.

FIG. 3 is an X-ray photoelectron spectroscopy (XPS) analysis chart of the polyacrylonitrile microfibers and modified polyacrylonitrile microfibers in Example 1.

FIG. 4 is an infrared (FTIR-ATR) analysis of polyacrylonitrile microfibers and modified polyacrylonitrile microfibers in Example 1

FIG. 5 is a comparison of the water contact angle in air, the underwater chloroform contact angle, and the underwater cyclohexane contact angle of the polyacrylonitrile and modified polyacrylonitrile microfibers in Example 1.

FIG. 6 shows the time required for the same volume (10 μL) of water to be completely adsorbed by the polyacrylonitrile and modified polyacrylonitrile microfiber membranes in Example 1.

FIG. 7 is a photograph of the modified polyacrylonitrile microfiber membrane in Example 1 blocking oil (chloroform) and the process of separating the cyclohexane (red)-water (blue) oil-water mixture.

FIG8 shows the separation efficiency and average separation efficiency of the polyacrylonitrile microfiber membrane, the modified polyacrylonitrile microfiber membrane and the modified polyacrylonitrile microfiber membrane that was broken up, recovered and re-prepared for cyclohexane-water-oil-water mixture in 10 cycles in Example 1.

Example 1

The polyacrylonitrile fibers obtained by wet spinning and hot drawing were cut into 1-2 cm with a cutter to obtain short-cut fibers, which were placed in a mechanical pulverizer, and 2L of water was added for mechanical shearing, disassembly, and crushing for 50 minutes at a shear rate of 10 ⁵ s ^-1 . After the shearing, disassembly, and crushing were completed, the obtained polyacrylonitrile microfiber aqueous dispersion was filtered to remove water, washed with deionized water 3 times, and then placed in an oven at 70°C for 2 hours to obtain polyacrylonitrile microfibers. Subsequently, 1L of 4% hydroxylamine hydrochloride solution was adjusted to pH 8 with sodium carbonate, and then 10g of polyacrylonitrile microfibers were added and reacted at 60°C for 2 hours to obtain a modified polyacrylonitrile microfiber oil-water separation material.

The modified polyacrylonitrile microfiber oil-water separation material obtained in this example has a diameter of about 2-10 μm and a length of about 10-100 μm. It is filtered to form a membrane, and the test results show that the water contact angle in the air, the underwater chloroform contact angle and the underwater cyclohexane contact angle are 82°, 160° and 174° respectively. The modified polyacrylonitrile microfiber membrane is hydrophilic and oleophobic, can block chloroform, and has a separation efficiency of 99.16% for cyclohexane-water mixture.

This modified polyacrylonitrile microfiber preparation method is efficient and convenient, with a short preparation cycle, is friendly to human health and the environment, and is conducive to large-scale industrial preparation. At the same time, the polyacrylonitrile microfiber material has plasticity due to its macroscopic "loose" characteristics and can be filtered into various shapes (as shown in Figure 2). Combined with the excellent solvent resistance of polyacrylonitrile itself, it shows that it can adapt to different environments and can achieve efficient oil-water separation under various practical conditions. The used modified polyacrylonitrile microfiber membrane is broken up and dispersed in water to form an aqueous dispersion. After removing the stains on the surface, it is recovered and filtered to form a membrane, and then used again in the cyclohexane-water mixture separation experiment. The separation efficiency is still as high as 98.84% (as shown in Figure 8).

Example 2

The polyacrylonitrile fibers obtained by wet spinning and hot drawing were cut into 1-2 cm with a cutter to obtain short-cut fibers, which were placed in a mechanical pulverizer, and 2L of water was added for mechanical shearing, disassembly, and crushing for 10 minutes at a shear rate of 10 ⁵ s ^-1 . After the shearing, disassembly, and crushing were completed, the obtained polyacrylonitrile microfiber aqueous dispersion was filtered to remove water, washed with deionized water 3 times, and then placed in an oven at 70°C for 2 hours to obtain polyacrylonitrile microfibers. Subsequently, 1L of 4% hydroxylamine hydrochloride solution was adjusted to pH 8 with sodium carbonate, and then 10g of polyacrylonitrile microfibers were added and reacted at 60°C for 2 hours to obtain a modified polyacrylonitrile microfiber oil-water separation material.

The modified polyacrylonitrile microfiber oil-water separation material obtained in this example has a diameter of about 10-30 μm and a length of about 10-500 μm. It is filtered to form a membrane, and the test results show that the water contact angle in the air, the underwater chloroform contact angle and the underwater cyclohexane contact angle are 90°, 146° and 147° respectively. The modified polyacrylonitrile microfiber membrane is hydrophilic and oleophobic, can block chloroform, and has a separation efficiency of 98.42% for cyclohexane-water mixture.

Example 3

The polyacrylonitrile fibers obtained by wet spinning and hot drawing were cut into 1-2 cm with a cutter to obtain short-cut fibers, which were placed in a mechanical pulverizer, and 2L of water was added for mechanical shearing, disassembly, and crushing for 90 minutes at a shear rate of 10 ⁵ s ^-1 . After the shearing, disassembly, and crushing were completed, the obtained polyacrylonitrile microfiber aqueous dispersion was filtered to remove water, washed with deionized water 3 times, and then placed in an oven at 70°C for 2 hours to obtain polyacrylonitrile microfibers. Subsequently, 1L of 4% hydroxylamine hydrochloride solution was adjusted to pH 8 with sodium carbonate, and then 10g of polyacrylonitrile microfibers were added and reacted at 60°C for 2 hours to obtain a modified polyacrylonitrile microfiber oil-water separation material.

The modified polyacrylonitrile microfiber oil-water separation material obtained in this example has a diameter of about 1-10 μm and a length of about 5-100 μm. It is filtered to form a membrane, and the test results show that the water contact angle in the air, the underwater chloroform contact angle and the underwater cyclohexane contact angle are 98°, 159° and 153° respectively. The modified polyacrylonitrile microfiber membrane is hydrophilic and oleophobic, can block chloroform, and has a separation efficiency of 98.51% for cyclohexane-water mixture.

Example 4

The polyacrylonitrile fibers obtained by wet spinning and hot drawing were cut into 1-2 cm with a cutter to obtain short-cut fibers, which were placed in a mechanical pulverizer, and 2L of water was added for mechanical shearing, disassembly, and crushing for 50 minutes at a shear rate of 10 ⁵ s ^-1 . After the shearing, disassembly, and crushing were completed, the obtained polyacrylonitrile microfiber aqueous dispersion was filtered to remove water, washed with deionized water 3 times, and then placed in an oven at 70°C for 2 hours to obtain polyacrylonitrile microfibers. Subsequently, 1L of 2% hydroxylamine hydrochloride solution was adjusted to pH 8 with sodium carbonate, and then 10g of polyacrylonitrile microfibers were added and reacted at 60°C for 2 hours to obtain a modified polyacrylonitrile microfiber oil-water separation material.

The modified polyacrylonitrile microfiber oil-water separation material obtained in this example has a diameter of about 2-10 μm and a length of about 10-100 μm. It is filtered to form a membrane, and the test results show that the water contact angle in the air, the underwater chloroform contact angle and the underwater cyclohexane contact angle are 110°, 148° and 155° respectively. The modified polyacrylonitrile microfiber membrane is hydrophilic and oleophobic, can block chloroform, and has a separation efficiency of 98.78% for cyclohexane-water mixture.

Example 5

The polyacrylonitrile fibers obtained by wet spinning and hot drawing were cut into 1-2 cm with a cutter to obtain short-cut fibers, which were placed in a mechanical pulverizer, and 2L of water was added for mechanical shearing, disassembly, and crushing for 50 minutes at a shear rate of 10 ⁵ s ^-1 . After the shearing, disassembly, and crushing were completed, the obtained polyacrylonitrile microfiber aqueous dispersion was filtered to remove water, washed with deionized water 3 times, and then placed in an oven at 70°C for 2 hours to obtain polyacrylonitrile microfibers. Subsequently, 1L of 6% hydroxylamine hydrochloride solution was adjusted to pH 8 with sodium carbonate, and then 10g of polyacrylonitrile microfibers were added and reacted at 60°C for 2 hours to obtain a modified polyacrylonitrile microfiber oil-water separation material.

The modified polyacrylonitrile microfiber oil-water separation material obtained in this example has a diameter of about 2-10 μm and a length of about 10-100 μm. It is filtered to form a membrane, and the test results show that the water contact angle in the air, the underwater chloroform contact angle and the underwater cyclohexane contact angle are 108°, 133° and 148° respectively. The modified polyacrylonitrile microfiber membrane is hydrophilic and oleophobic, can block chloroform, and has a separation efficiency of 98.11% for cyclohexane-water mixture.

Example 6

The polyacrylonitrile fibers obtained by wet spinning and hot drawing were cut into 1-2 cm with a cutter to obtain short-cut fibers, which were placed in a mechanical pulverizer, and 2L of water was added for mechanical shearing, disassembly, and crushing for 50 minutes at a shear rate of 10 ⁵ s ^-1 . After the shearing, disassembly, and crushing were completed, the obtained polyacrylonitrile microfiber aqueous dispersion was filtered to remove water, washed with deionized water 3 times, and then placed in an oven at 70°C for 2 hours to obtain polyacrylonitrile microfibers. Subsequently, 1L of 4% hydroxylamine hydrochloride solution was adjusted to pH 8 with sodium carbonate, and then 5g of polyacrylonitrile microfibers were added and reacted at 60°C for 2 hours to obtain a modified polyacrylonitrile microfiber oil-water separation material.

The modified polyacrylonitrile microfiber oil-water separation material obtained in this example has a diameter of about 2-10 μm and a length of about 10-100 μm. It is filtered to form a membrane, and the test results show that the water contact angle in the air, the underwater chloroform contact angle and the underwater cyclohexane contact angle are 88°, 153° and 160° respectively. The modified polyacrylonitrile microfiber membrane is hydrophilic and oleophobic, can block chloroform, and has a separation efficiency of 98.28% for cyclohexane-water mixture.

Example 7

The polyacrylonitrile fibers obtained by wet spinning and hot drawing were cut into 1-2 cm with a cutter to obtain short-cut fibers, which were placed in a mechanical pulverizer, and 2L of water was added for mechanical shearing, disassembly, and crushing for 50 minutes at a shear rate of 10 ⁵ s ^-1 . After the shearing, disassembly, and crushing were completed, the obtained polyacrylonitrile microfiber aqueous dispersion was filtered to remove water, washed with deionized water 3 times, and then placed in an oven at 70°C for 2 hours to obtain polyacrylonitrile microfibers. Subsequently, 1L of 4% hydroxylamine hydrochloride solution was adjusted to pH 8 with sodium carbonate, and then 15g of polyacrylonitrile microfibers were added and reacted at 60°C for 2 hours to obtain a modified polyacrylonitrile microfiber oil-water separation material.

The modified polyacrylonitrile microfiber oil-water separation material obtained in this example has a diameter of about 2-10 μm and a length of about 10-100 μm. It is filtered to form a membrane, and the test results show that the water contact angle in the air, the underwater chloroform contact angle and the underwater cyclohexane contact angle are 80°, 160° and 166° respectively. The modified polyacrylonitrile microfiber membrane is hydrophilic and oleophobic, can block chloroform, and has a separation efficiency of 98.56% for cyclohexane-water mixture.

Example 8

The polyacrylonitrile fibers obtained by wet spinning and hot drawing were cut into 1-2 cm with a cutter to obtain short-cut fibers, which were placed in a mechanical pulverizer, and 2L of water was added for mechanical shearing, disassembly, and crushing for 50 minutes at a shear rate of 10 ⁵ s ^-1 . After the shearing, disassembly, and crushing were completed, the obtained polyacrylonitrile microfiber aqueous dispersion was filtered to remove water, washed with deionized water 3 times, and then placed in an oven at 70°C for 2 hours to obtain polyacrylonitrile microfibers. Subsequently, 1L of 4% hydroxylamine hydrochloride solution was adjusted to pH 8 with sodium carbonate, and then 10g of polyacrylonitrile microfibers were added and reacted at 60°C for 1 hour to obtain a modified polyacrylonitrile microfiber oil-water separation material.

The modified polyacrylonitrile microfiber oil-water separation material obtained in this example has a diameter of about 2-10 μm and a length of about 10-100 μm. It is filtered to form a membrane, and the test results show that the water contact angle in the air, the underwater chloroform contact angle and the underwater cyclohexane contact angle are 82°, 160° and 174° respectively. The modified polyacrylonitrile microfiber membrane is hydrophilic and oleophobic, can block chloroform, and has a separation efficiency of 99.16% for cyclohexane-water mixture.

Example 9

The polyacrylonitrile fibers obtained by wet spinning and hot drawing were cut into 1-2 cm with a cutter to obtain short-cut fibers, which were placed in a mechanical pulverizer, and 2L of water was added for mechanical shearing, disassembly, and crushing for 50 minutes at a shear rate of 10 ⁵ s ^-1 . After the shearing, disassembly, and crushing were completed, the obtained polyacrylonitrile microfiber aqueous dispersion was filtered to remove water, washed with deionized water 3 times, and then placed in an oven at 70°C for 2 hours to obtain polyacrylonitrile microfibers. Subsequently, 1L of 4% hydroxylamine hydrochloride solution was adjusted to pH 8 with sodium carbonate, and then 10g of polyacrylonitrile microfibers were added and reacted at 60°C for 3 hours to obtain a modified polyacrylonitrile microfiber oil-water separation material.

The modified polyacrylonitrile microfiber oil-water separation material obtained in this example has a diameter of about 2-10 μm and a length of about 10-100 μm. It is filtered to form a membrane, and the test results show that the water contact angle in the air, the underwater chloroform contact angle and the underwater cyclohexane contact angle are 96°, 161° and 153° respectively. The modified polyacrylonitrile microfiber membrane is hydrophilic and oleophobic, can block chloroform, and has a separation efficiency of 98.22% for cyclohexane-water mixture.

Table 1 Parameters and experimental results in each example

*Parameters or conditions marked in green are changed compared with Example 1.

Claims (6)

1. The modified polyacrylonitrile microfiber oil-water separation material and the preparation method thereof are characterized by comprising the following steps:

(1) Chopping polyacrylonitrile fibers obtained after wet spinning and hot drawing by using a cutter to obtain polyacrylonitrile chopped fibers, putting the chopped fibers into a mechanical crusher, adding water, and mechanically shearing, disassembling and crushing to obtain polyacrylonitrile microfiber aqueous dispersion;

(2) Carrying out suction filtration on the polyacrylonitrile microfiber aqueous dispersion liquid obtained in the step (1), washing with deionized water, and then putting into a drying oven for drying to obtain polyacrylonitrile microfiber;

(3) And (3) modifying the polyacrylonitrile microfiber obtained in the step (2) by using hydroxylamine hydrochloride solution to increase the surface hydrophilicity, filtering, washing by using deionized water, and drying in an oven to obtain the modified polyacrylonitrile microfiber oil-water separation material.

2. The method according to claim 1, wherein the length of the polyacrylonitrile chopped fiber in the step (1) is 1-2cm, the ratio of the mass of the polyacrylonitrile fiber added to the deionized water added in the mechanical shearing, disassembling and crushing processes is 10g of fiber to 2L of deionized water, the shearing rate is 10 ⁵s^-1, and the time is 10-90 minutes.

3. The method according to claim 1, wherein the polyacrylonitrile microfiber aqueous dispersion in step (2) is filtered in a filter flask under a vacuum pressure of 0.03MPa, washed 3 times with deionized water, and dried in an oven at 70 ℃ for 2 hours after removal.

4. The method according to claim 1, wherein the surface hydrophilic modification is carried out by using a hydroxylamine hydrochloride solution in the step (3), the concentration of the hydroxylamine hydrochloride solution is 2-6%, the amount is 1L, the amount of the polyacrylonitrile microfiber is 5-15g, the stirring rate is 200rpm, the reaction temperature is 60 ℃, the reaction time is 1-3 hours, the deionized water is 3 times, the oven temperature is 70 ℃, and the drying time is 2 hours.

5. The preparation method according to claim 1, wherein the obtained modified polyacrylonitrile microfiber has a diameter ranging from 1 to 30 μm and a length ranging from 5 to 100 μm, the modified polyacrylonitrile microfiber film prepared by suction filtration has an air water contact angle of 80 to 110 degrees, an underwater chloroform contact angle of 130 to 160 degrees, an underwater cyclohexane contact angle of 145 to 175 degrees, and a cyclohexane/water mixture separation efficiency of 98.1 to 99.2%.

6. A modified polyacrylonitrile microfiber oil-water separation material, characterized by being prepared from the experimental parameters according to any one of claims 1 to 5.