Preparation method of patterned liquid injection porous fiber membrane

Abstract

The invention relates to a preparation method of a patterned liquid injection porous fiber membrane, and belongs to the technical field of new materials. Firstly, a polyacrylonitrile / polyvinyl alcohol fiber membrane is prepared through an electrostatic spinning technology, the surface of the polyacrylonitrile / polyvinyl alcohol fiber membrane is modified with hydrophobic patterns, then a hydrophilic area is immersed into a water phase and a hydrophobic area is immersed into an oil phase in sequence, and finally the patterned oil-water two-phase injection porous fiber membrane is obtained. According to the fiber membrane prepared by the method, an injected water phase can allow water flow to pass through, oil drops are intercepted, and the oil drops are enriched on the surface; the injected oil phase can be limited in a hydrophobic area on the surface of the membrane by the water phase, the'capture-coalescence-separation 'behaviors of oil drops are manipulated, and demulsification of the emulsion is achieved. The separation flux (3520 liters per square meter per hour) of the fiber membrane reaches ten times that of a commercial separation membrane, the separation efficiency is greater than 99%, efficient and lasting separation of oily sewage can be realized, and the fiber membrane has a good application prospect in actual industrial production.

Description

Technical Field

[0001] The invention relates to an oil-water separation material, in particular to a preparation method of a patterned liquid-injected porous fiber membrane material, belonging to the technical field of new materials. Background Art

[0002] A large amount of oily wastewater is generated in industries such as oil extraction, mechanical processing, coking and refining, and food processing. These oily wastewaters enter water bodies through various channels, causing serious water resource pollution, energy waste, and even endangering human health. Oil products in water often exist in the form of floating oil and emulsified oil. Floating oil can be separated by gravity, while emulsified oil is stably dispersed in water in the form of tiny droplets, which is difficult to handle. At present, traditional oil-water emulsion treatment technologies mainly include strong centrifugation, air flotation, and flocculation. These methods have obvious limitations, such as low separation accuracy and high energy consumption of air flotation and centrifugation; chemical flocculation will cause secondary pollution to water bodies. Obviously, these traditional methods have gradually failed to meet the current emission standards for oil-water emulsion treatment. Therefore, new oil-water emulsion treatment technologies are urgently needed.

[0003] In recent years, membrane separation technology has been considered to be the most promising technology in the field of oil-water emulsion treatment due to its advantages of high separation accuracy, low energy consumption, recyclable concentrate and easy modular assembly. At present, the commonly used super-wetting membrane materials mainly include super-hydrophilic / underwater super-oleophobic membrane materials, super-hydrophobic / super-oleophilic membrane materials and liquid-injected membrane materials. The surface of super-hydrophilic / underwater super-oleophobic membrane materials has hydrophilic groups and micro-nano structures, which can achieve rapid separation of oil-water emulsions by repelling oil droplets in water. However, during long-term use, the merging of oil droplets is uncontrolled, and oil droplets are easily adhered to the membrane surface or in the pores to cause membrane pollution, resulting in membrane blockage and thus a decrease in separation flux. The surface of super-hydrophobic / super-oleophilic membrane materials has hydrophobic groups and micro-nano structures, which can achieve rapid separation of oil-water emulsions by repelling water droplets in the oil phase. However, the free dispersion of oil droplets in water is uncontrolled, resulting in a slow coalescence rate of oil droplets and a low separation efficiency of membrane materials. Liquid-injected membrane materials are a solid-liquid composite material prepared by injecting liquid into a porous substrate, and their surface wetting properties are closely related to the liquid injected into their pores. However, the presence of surfactants makes the small oil droplets more stable, so the efficiency of oil droplet coalescence is limited. Therefore, how to control the coalescence of tiny oil droplets in oily wastewater and achieve emulsion demulsification has become a key issue in improving material separation efficiency and separation stability.

[0004] In order to address the key issues that oil droplets on the surface of super-wetting membrane materials are slow to coalesce and easy to clog, resulting in low separation efficiency and difficulty in achieving long-term separation, the present invention prepares a patterned liquid-injected porous fiber membrane that integrates self-driven oil droplet coalescence and efficient oil-water separation. The water-injected area can allow the water phase to pass through, intercepting oil droplets and enriching them on the surface; the oil-injected area can capture and coalesce oil droplets to achieve emulsion breaking, ultimately achieving efficient and long-lasting oil-water emulsion processing. Summary of the invention

[0005] The present invention specifically relates to a method for preparing a patterned liquid-infused porous fiber membrane. The fiber membrane prepared by the method significantly improves the service life in the oil-water separation process, realizes long-term separation, and effectively solves the current problems of easy clogging of the separation membrane and reduced separation flux.

[0006] The implementation process of the present invention is briefly explained below. First, a hydrophilic polyacrylonitrile / polyvinyl alcohol fiber membrane is prepared by electrospinning technology, and then the fiber membrane is hydrolyzed, and then a hydrophobic pattern is modified on its surface by a spraying process, and then the fiber membrane is injected with water and oil in sequence, and finally a patterned oil-water two-phase injected polyacrylonitrile / polyvinyl alcohol fiber membrane is obtained.

[0007] The present invention specifically relates to a method for preparing a patterned liquid-infused porous fiber membrane, which is achieved by the following specific steps:

[0008] (1) Polyacrylonitrile and polyvinyl alcohol are dissolved in dimethyl sulfoxide, the mass fraction of polyacrylonitrile is 6% to 12%, and the mass fraction of polyvinyl alcohol is 1% to 4%, and magnetic stirring is performed in a water bath at 90 degrees Celsius for 6 hours to obtain a polyacrylonitrile / polyvinyl alcohol precursor.

[0009] (2) Turn on the spinning machine and set the temperature to 30 degrees Celsius and the humidity to 50%, and preheat for 30 minutes; draw the polyacrylonitrile / polyvinyl alcohol precursor solution into the syringe and install a 20-24 gauge needle; install the syringe with the needle into the injection pump of the electrospinning equipment; adjust the propulsion speed of the injection pump to 0.5-2 mg per hour; adjust the distance from the needle to the roller receiver to 10-20 cm; the translation distance is 50-100 cm; wrap a layer of tin foil on the roller receiver and adjust the rotation speed of the roller receiver to 40-80 revolutions per minute; connect the positive voltage of the high-voltage power supply to the syringe needle and adjust the voltage to 5-10 kV; connect the negative voltage of the high-voltage power supply to the roller receiver and adjust the voltage to -1-3 kV; the spinning time is 1-2 hours to obtain the polyacrylonitrile / polyvinyl alcohol fiber membrane; put the polyacrylonitrile / polyvinyl alcohol fiber membrane into a 30 degree Celsius oven and dry it for 12 hours.

[0010] (3) Prepare 1 to 3 mol sodium hydroxide solution and 1 to 3 mol hydrochloric acid solution respectively; immerse the polyacrylonitrile / polyvinyl alcohol fiber membrane in the sodium hydroxide solution and hydrolyze it in a 50 degree Celsius water bath for 1 to 3 hours, take out the fiber membrane and wash it with deionized water until it is neutral; then immerse the alkali-treated polyacrylonitrile / polyvinyl alcohol fiber membrane in the hydrochloric acid solution and hydrolyze it at room temperature for 0.5 to 2 hours, take it out and wash it with deionized water until it is neutral, and put it in a 60 degree Celsius oven to dry for 6 hours for use.

[0011] (4) preparing a mixed solution of silica, polydimethylsiloxane, curing agent and ethyl acetate in a mass ratio of (1-3): (1-10): (0.1-1): (85-95), and loading the mixed solution into an electric spray gun; placing a mask with a hollow pattern on the upper side of the fiber membrane, spraying the mixed solution, and obtaining a patterned fiber membrane.

[0012] (5) The prepared patterned fiber membrane is immersed in a water bath and an oil bath in turn at room temperature, and water and oil are injected using capillary force to finally obtain a patterned liquid-infused porous fiber membrane.

[0013] The method for preparing a patterned liquid-infused porous fiber membrane provided by the present invention can achieve efficient and lasting separation of oil-in-water emulsions, so as to achieve large-scale promotion and application in the field of oily wastewater treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Attached Figure 1 This is a scanning electron microscope image of the fiber membrane prepared in the present invention.

[0015] Attached Figure 2 These are optical pictures of the fiber membrane prepared by the present invention after water injection and oil injection.

[0016] Attached Figure 3 Schematic diagram of the coalescence-floating process of oil droplets in the oil injection area of ​​the fiber membrane prepared by the present invention.

[0017] Attached Figure 4 A diagram showing the separation performance of the fiber membrane prepared in the present invention for oil-in-water emulsion. DETAILED DESCRIPTION

[0018] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0019] Example 1: 0.5 g of polyacrylonitrile and 0.1 g of polyvinyl alcohol were weighed and added into 4.5 ml of dimethyl sulfoxide solution, and magnetically stirred in a water bath at 90 degrees Celsius for 6 hours to obtain a polyacrylonitrile / polyvinyl alcohol precursor. Turn on the spinning machine, set the temperature to 30 degrees Celsius, the humidity to 50%, and preheat for 30 minutes; use a 5 ml syringe to absorb the precursor solution and install a 21-gauge needle; install the syringe into the injection pump of the electrospinning equipment; adjust the propulsion speed of the injection pump to 1 mg per hour; adjust the distance from the needle to the roller receiver to 10 cm; the translation distance is 60 cm; wrap a layer of tin foil on the roller receiver, and adjust the rotation speed of the roller receiver to 60 revolutions per minute; connect the positive voltage of the high-voltage power supply to the syringe needle, and adjust the voltage to 8 kV; connect the negative voltage of the high-voltage power supply to the roller receiver, and adjust the voltage to -0.5 kV; the spinning time is 1.5 hours to obtain polyacrylonitrile / polyvinyl alcohol fiber membrane; put the polyacrylonitrile / polyvinyl alcohol fiber membrane into a 30-degree Celsius oven and dry it for 12 hours for use. 5 grams of sodium hydroxide was dissolved in 50 milliliters of deionized water to prepare a sodium hydroxide solution, 0.01 square meters of fiber membrane was cut and immersed in the sodium hydroxide solution and hydrolyzed in a 50-degree Celsius water bath for 1.5 hours, and then washed with deionized water until neutral; 8 milliliters of 38% concentrated hydrochloric acid was slowly poured into 50 milliliters of deionized water to prepare a hydrochloric acid solution, and the above fiber membrane was immersed in the hydrochloric acid solution and hydrolyzed at room temperature for 1 hour, and then washed with deionized water until neutral, and placed in a 60-degree Celsius oven for 6 hours for use. 0.15 grams of silicon dioxide, 0.5 grams of polydimethylsiloxane and 0.05 grams of curing agent were respectively measured and dissolved in 10 milliliters of ethyl acetate, and magnetically stirred at room temperature for 2 hours to obtain a mixed solution. The mixed solution was loaded into an electric spray gun; a mask with a circular hollow pattern was placed on the upper side of the fiber membrane, and the mixed solution was sprayed to obtain a patterned fiber membrane. The prepared patterned fiber membrane is immersed in a water bath and an oil bath in turn at room temperature, and water and oil are injected using capillary force to finally obtain a patterned liquid-infused porous fiber membrane.

[0020] Attached Figure 1 Scanning electron microscope images of polyacrylonitrile / polyvinyl alcohol fiber membrane and patterned modified fiber membrane. As can be seen from the figure, the polyacrylonitrile / polyvinyl alcohol fiber membrane has high porosity and small pore size; after patterning, circular hydrophobic areas can be seen on the surface, in which silica and polydimethylsiloxane are randomly and evenly modified on the fiber.

[0021] Attached Figure 2 The optical images of the circular and triangular pattern fiber membranes prepared in this experiment after water and oil injection. It can be seen from the figure that the circular patterns are evenly distributed on the membrane surface, and the color of the circular patterns after oil injection is darker, proving that the patterned liquid-injected polyacrylonitrile / polyvinyl alcohol fiber membrane was successfully prepared.

[0022] Attached Figure 3 Schematic diagram of the coalescence-floating process of oil droplets in the patterned oil injection area. As can be seen from the figure, when the oil droplets are small, they first spread in the oil injection area. As the oil droplets continue to coalesce and become larger, the underwater oleophobic angle gradually increases, and finally they break away from the oil injection surface to form large oil droplets, proving that the patterned liquid injection fiber membrane has a demulsification effect on oil droplets in water.

[0023] Attached Figure 4 This is a graph showing the separation performance of polyacrylonitrile / polyvinyl alcohol fiber membrane and patterned liquid-infused fiber membrane for water-in-oil emulsion. As can be seen from the figure, the patterned liquid-infused fiber membrane has a much higher oil retention rate than the original fiber membrane, showing excellent emulsion separation performance, with a retention rate of more than 99%, and the separated water can meet the national sewage discharge standards.

Claims

1. The present invention specifically relates to a method for preparing a patterned liquid-infused porous fiber membrane, which is specifically obtained by the following method: (1) Polyacrylonitrile and polyvinyl alcohol are dissolved in dimethyl sulfoxide, the mass fraction of polyacrylonitrile is 6% to 12%, and the mass fraction of polyvinyl alcohol is 1% to 4%, and magnetic stirring is performed in a water bath at 90 degrees Celsius for 6 hours to obtain a polyacrylonitrile / polyvinyl alcohol precursor. (2) Turn on the spinning machine and set the temperature to 30 degrees Celsius and the humidity to 50%, and preheat for 30 minutes; draw the polyacrylonitrile / polyvinyl alcohol precursor solution into the syringe and install a 20-24 gauge needle; install the syringe with the needle into the injection pump of the electrospinning equipment; adjust the propulsion speed of the injection pump to 0.5-2 mg per hour; adjust the distance from the needle to the roller receiver to 10-20 cm; the translation distance is 50-100 cm; wrap a layer of tin foil on the roller receiver and adjust the rotation speed of the roller receiver to 40-80 revolutions per minute; connect the positive voltage of the high-voltage power supply to the syringe needle and adjust the voltage to 5-10 kV; connect the negative voltage of the high-voltage power supply to the roller receiver and adjust the voltage to -1-3 kV; the spinning time is 1-2 hours to obtain the polyacrylonitrile / polyvinyl alcohol fiber membrane; put the polyacrylonitrile / polyvinyl alcohol fiber membrane into a 30 degree Celsius oven and dry it for 12 hours. (3) Prepare 1 to 3 mol sodium hydroxide solution and 1 to 3 mol hydrochloric acid solution respectively; immerse the polyacrylonitrile / polyvinyl alcohol fiber membrane in the sodium hydroxide solution and hydrolyze it in a 50 degree Celsius water bath for 1 to 3 hours, take out the fiber membrane and wash it with deionized water until it is neutral; then immerse the alkali-treated polyacrylonitrile / polyvinyl alcohol fiber membrane in the hydrochloric acid solution and hydrolyze it at room temperature for 0.5 to 2 hours, take it out and wash it with deionized water until it is neutral, and put it in a 60 degree Celsius oven to dry for 6 hours for use. (4) preparing a mixed solution of silica, polydimethylsiloxane, curing agent and ethyl acetate in a mass ratio of (1-3): (1-10): (0.1-1): (85-95), and loading the mixed solution into an electric spray gun; placing a mask with a hollow pattern on the upper side of the fiber membrane, spraying the mixed solution, and obtaining a patterned fiber membrane. (5) The prepared patterned fiber membrane is immersed in a water bath and an oil bath in turn at room temperature, and water and oil are injected using capillary force to finally obtain a patterned liquid-infused porous fiber membrane.

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