A method for preparing a membrane material for separating oil-water mixtures and oil-water emulsions

Abstract

The application relates to a preparation method of a membrane material for separating oil-water mixture and oil-water emulsion, and belongs to the field of water treatment membrane materials. In order to solve the problems of poor separation effect of conventional treatment process of a water supply plant on oil-water mixture and emulsion, secondary pollution and easy blocking of separation materials and separation process, the material preparation method steps are as follows: after microcrystalline cellulose is dissolved in an alkaline environment, sepiolite particles are blended, and then regeneration is carried out on a silicon dioxide nanofiber membrane, so that the membrane material can be used for effective separation of oil-water mixture and emulsion. The application can be used after conventional water treatment process, the separation efficiency of the oil-water mixture and emulsion can reach 99.99% at most, oil pollutants in raw water can be effectively separated, and the water requirement can be met. Compared with the conventional water treatment alone, the removal rate of the material on the oil emulsion pollutants in water is 61.73% higher, the removal effect is good, and the material is green and environment-friendly, and no secondary pollution is caused.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of water treatment materials, and is mainly used for the separation of oil-water mixtures and oil-water emulsions, and particularly relates to a membrane treatment method for dealing with oil pollution, which can be combined with conventional water treatment processes. BACKGROUND

[0002] Oil-water separation is an important environmental problem, which widely exists in the fields of industrial production, oil exploitation, ship transportation, etc. Membrane separation technology is widely used due to its low energy consumption, easy operation and no secondary pollutants. Among them, high polymer materials are widely used as raw materials for membranes due to their strong mechanical properties, low cost and easy modification. However, high polymer materials usually have long molecular lifetime and are difficult to degrade, which can easily cause secondary pollution, and there is also a problem of microplastic residue. In addition, part of the materials is ineffective in treating emulsified oil / water mixtures, especially emulsions with oil droplets smaller than 20 times. Although studies have shown that the performance of nanofiber membranes modified by inorganic particle coating, in-situ oxidation, hydrophilic polymer, etc. is greatly improved in oil-water separation, these methods will inevitably require complex instruments and harmful chemical reagents, resulting in increased water treatment cost and more serious environmental problems. Compared with organic polymer membranes, traditional inorganic nanofiber membranes have stable mechanical properties, good thermal stability, high temperature resistance and corrosion resistance, but also have disadvantages such as easy membrane pollution, poor flexibility and high-temperature calcination in the manufacturing process. Therefore, it is urgent to develop a new type of oil-water emulsion separation membrane with environmental friendliness, good antifouling property and good separation effect. SUMMARY

[0003] The purpose of the present application is to solve the problems of poor separation effect of conventional treatment processes in waterworks on oil-water mixtures and emulsions, secondary pollution and easy clogging of separation materials and separation process, and to provide a preparation method of a membrane material for oil-water mixture and oil-water emulsion separation, which provides an effective treatment material for the removal or enrichment of oil pollutants in drinking water.

[0004] The purpose of the present application is achieved by the following technical scheme:

[0005] A preparation method of a membrane material for oil-water mixture and oil-water emulsion separation, the method is that: microcrystalline cellulose is dissolved in an alkaline environment, then uniformly mixed with sepiolite particles, and then regenerated on a silicon dioxide nanofiber membrane to obtain the membrane material.

[0006] Further, the mass percentage of the microcrystalline cellulose is 3% to 8%, preferably 5%, the mass percentage of the sepiolite particles is 4% to 10%, preferably 8%, and the balance is an alkaline solution.

[0007] Further, the particle size of the sepiolite particles is 1500-2500 mesh, preferably 2000 mesh.

[0008] Further, the alkali solution used to dissolve the microcrystalline cellulose is composed of sodium hydroxide, urea and pure water in a ratio of 7:12:81.

[0009] Further, after the microcrystalline cellulose is put into the alkali solution, it is stirred in an ice bath until no obvious undissolved cellulose particles are observed (stirring at 1500 r / min for 2 hours), and then centrifuged at a speed of 6000-10000 r / min for 6-15 minutes, preferably at a speed of 8000 r / min for 10 minutes.

[0010] Further, the cellulose solution after centrifugation is blended with the sepiolite particles and stirred until well mixed (stirring at 1500 r / min for 15 minutes).

[0011] Further, the silica nanofiber membrane is soaked in the cellulose solution blended with the sepiolite particles for more than or equal to 0.5 hours (including 0.5 hours), preferably 1 hour, and then transferred to the anti-solvent for more than or equal to 1 hour (including 1 hour), preferably 2 hours.

[0012] Further, the silica nanofiber membrane needs to be washed with ethanol and water at least 3 times before soaking.

[0013] Further, the anti-solvent is composed of anhydrous ethanol and pure water in a volume ratio of 2-4.5:3, preferably 1:1.

[0014] The beneficial effects of the present application over the prior art are: the present application can be used after conventional water treatment processes, and the separation efficiency of oil-water mixtures and emulsions can reach 99.99%, which can effectively separate oil pollutants in raw water and meet the water discharge requirements. Compared with conventional water treatment alone, the removal rate of oil emulsion pollutants in water by the membrane material of the present application is 61.73% higher, the removal effect is good, and it is green and environmentally friendly without secondary pollution. The material has the advantages of simple operation, high work efficiency, reliable work, and wide popularization prospect. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 Figure for the removal of 5 types of oil emulsion sewage by the base film of Example 1 of the present application and the modified film. DETAILED DESCRIPTION

[0016] The technical solutions of the present application are further described below, but are not limited thereto. Any modification or equivalent replacement of the technical solutions of the present application without departing from the spirit and scope of the technical solutions of the present application shall be covered in the protection scope of the present application.

[0017] In the present application, the silica nanofiber membrane presents a three-dimensional network structure, which can well adsorb and fix microcrystalline cellulose, and the sepiolite has good water absorption and water holding capacity, which can strengthen the hydration layer on the membrane surface during the treatment process to prevent the invasion of oil droplets. After the dissolution and regeneration of microcrystalline cellulose, not only can the sepiolite and silica nanofiber membrane be self-assembled and wrapped and fixed, but also a micro-nano underwater super-oil-repellent structure can be spontaneously formed to improve the oil-water separation efficiency. Finally, all the three raw materials are green materials, which can prevent secondary pollution during the treatment process.

[0018] Example 1

[0019] A preparation method of a membrane material for separating oil-water mixture and oil-water emulsion, which is carried out according to the following steps:

[0020] I. 5% of microcrystalline cellulose is stirred in an alkaline solution of sodium hydroxide: urea: pure water = 7:12:81 at a speed of 1500 r / min for 2h, and then centrifuged at a speed of 8000 r / min for 10 minutes. After centrifugation, the cellulose solution is blended with 8% of sepiolite particles with a particle size of 2000 mesh, and then stirred at a speed of 1500 r / min for 15 minutes.

[0021] II. The silica nanofiber membrane washed with ethanol and pure water is soaked in the cellulose solution blended with sepiolite particles for 1 hour, and then transferred to an anti-solvent of pure water: ethanol = 1:1 for 2 hours. Then, 20mg / L of oil emulsion is subjected to suction filtration under a pressure of 0.08Mpa, and the oil-water emulsion separation efficiency can reach more than 99.5%, the flux recovery rate can be maintained at more than 96%, and the flux attenuation rate can be maintained at less than 15.2%. The role of the anti-solvent is to perform phase inversion, thereby changing the crystal structure and assisting film formation.

[0022] Example 2

[0023] The difference between this embodiment and example 1 is that the first centrifugal speed (6000-7000 r / min) and stirring time (6-7 min) in step I are changed. Then, 20mg / L of oil emulsion is subjected to suction filtration under a pressure of 0.08Mpa, and the oil-water emulsion separation efficiency can reach more than 99.2%, the flux recovery rate can be maintained at more than 95%, and the flux attenuation rate can be maintained at less than 15.6%.

[0024] Example 3

[0025] The difference between this embodiment and example 1 is that the amount of sepiolite particles added in step I is 4% to 5%. Then, 20mg / L of oil emulsion is subjected to suction filtration under a pressure of 0.08Mpa, and the oil-water emulsion separation efficiency can reach more than 99.0%, the flux recovery rate can be maintained at more than 85%, and the flux attenuation rate can be maintained at less than 20%.

[0026] Example 4:

[0027] The difference between this example and example 1 is that the ratio of ethanol and water in the anti-solvent described in step two is changed, ethanol: water = 3:2. Then the oil emulsion of 20 mg / L is extracted under the pressure of 0.08 MPa, the separation efficiency of oil-water emulsion can reach more than 99.5%, the flux recovery rate can be maintained at more than 85%, and the flux attenuation rate can be maintained at less than 25%.

Claims

1. A method for the preparation of a membrane material for the separation of oil-water mixtures and oil-water emulsions, characterized in that: The method is: microcrystalline cellulose is dissolved in an alkaline environment, then is uniformly mixed with sepiolite particles, and then is regenerated on a silica nanofiber membrane to obtain a membrane material; the mass percentage of the microcrystalline cellulose is 3-8%, the mass percentage of the sepiolite particles is 4-10%, and the rest is an alkaline solution; the particle size of the sepiolite particles is 1500-2500 mesh.

2. The method of claim 1, wherein: The alkaline solution used to dissolve the microcrystalline cellulose has the following formula: Urea: pure water = 7:12:

81.

3. The method for preparing the membrane material for separating oil-water mixtures and oil-water emulsions according to claim 1, characterized in that: After the microcrystalline cellulose is placed in the alkaline solution, it is stirred in an ice bath until no obvious undissolved cellulose particles can be seen, and then is centrifuged at a speed of 6000-10000 r / min for 6-15 minutes.

4. The method of claim 3, wherein the membrane material is prepared by the steps of: After centrifugation, the cellulose solution is mixed with sepiolite particles and then is stirred until the mixture is uniform.

5. The method for preparing the membrane material for separating oil-water mixtures and oil-water emulsions according to claim 4, characterized in that: The silica nanofiber membrane is soaked in the cellulose solution mixed with sepiolite particles for more than 0.5 h, and then is transferred to an anti-solvent for more than 1 h to obtain the membrane material.

6. The method of claim 5, wherein the membrane material is prepared by the steps of: The silica nanofiber membrane needs to be cleaned with ethanol and water at least 3 times before soaking.

7. The method of claim 5, wherein the membrane material is prepared by the steps of: a) providing a porous membrane; b) coating the porous membrane with a hydrophilic polymer; c) coating the porous membrane with a hydrophobic polymer; and d) coating the porous membrane with a hydrophilic polymer. The anti-solvent is composed of anhydrous ethanol and pure water in a volume ratio of 2-4.5:3.

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