Preparation method of membrane material for separating oil-water mixture and oil-water emulsion

Abstract

The invention discloses a preparation method of a membrane material for separating an oil-water mixture and an oil-water emulsion, and belongs to the field of water treatment membrane materials. In order to solve the problems that the conventional treatment process of a water supply plant has a poor separation effect on an oil-water mixture and an emulsion, and a separation material and a separation process are easy to generate secondary pollution, easy to block and the like, the preparation method of the material comprises the following steps: dissolving microcrystalline cellulose in an alkaline environment, blending with sepiolite particles, and regenerating on a silicon dioxide nanofiber membrane, the membrane can be used as a membrane material for effective separation of oil-water mixtures and emulsions. The device can be applied after a conventional water treatment process, the highest separation efficiency of an oil-water mixture and an emulsion can reach 99.99%, oil pollutants in raw water can be effectively separated, and the effluent requirement is met. Compared with single conventional water treatment, the material has the advantages that the removal rate of oil emulsion pollutants in water is 61.73% higher, the removal effect is good, the material is green and environment-friendly, and secondary pollution is avoided.

Description

Technical Field

[0001] The invention belongs to the field of water treatment materials, is mainly used for separation of oil-water mixtures and oil-water emulsions, and particularly relates to a membrane treatment method for coping with oil pollution that can be used in conjunction with conventional water treatment processes. Background Art

[0002] Oil-water separation is an important environmental issue, which is widely used in industrial production, oil extraction, shipping and other fields. Membrane separation technology is widely used because of its advantages of low energy consumption, easy operation and no secondary pollutants. Among them, polymer materials are widely used as raw materials for membranes because of their strong mechanical properties, low cost and easy modification. However, polymer materials usually have long molecular life and are difficult to degrade, which can easily cause secondary pollution and microplastic residues. In addition, some materials are ineffective in treating emulsified oil / water mixtures, especially emulsions with oil droplet sizes less than 20 times. Although studies have shown that the performance of nanofiber membranes modified by inorganic particle coating, in-situ oxidation, hydrophilic polymers and other methods in oil-water separation is greatly improved, these methods will inevitably require complex instruments and harmful chemical reagents, which will lead to higher water treatment costs and more far-reaching environmental problems. Compared with organic polymer membranes, traditional inorganic nanofiber membranes have the advantages of stable mechanical properties, good thermal stability, high temperature resistance and corrosion resistance, but they also have the disadvantages of easy membrane pollution, poor flexibility and high temperature calcination during the manufacturing process. Therefore, it is urgent to develop a new type of oil-water emulsion separation membrane that is environmentally friendly, has good antifouling properties, and has good separation effect. Summary of the invention

[0003] The purpose of the present invention is to solve the problems that the conventional treatment process of the water supply plant has poor separation effect on oil-water mixtures and emulsions, and the separation materials and separation processes are prone to secondary pollution and blockage. A method for preparing a membrane material for separating oil-water mixtures and oil-water emulsions is provided, and an effective treatment material is provided for the removal or enrichment of oil pollutants in drinking water.

[0004] The objective of the present invention is achieved through the following technical solutions:

[0005] A method for preparing a membrane material for separating oil-water mixtures and oil-water emulsions comprises the following steps: dissolving microcrystalline cellulose in an alkaline environment and then uniformly blending it with sepiolite particles, and then regenerating it on a silicon dioxide nanofiber membrane to obtain the membrane material.

[0006] Furthermore, 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 alkaline solution.

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

[0008] Furthermore, the formula of the alkaline solution used to dissolve microcrystalline cellulose is sodium hydroxide: urea: pure water = 7:12:81.

[0009] Furthermore, after microcrystalline cellulose is placed in an alkaline solution, it is stirred in an ice bath until no obvious undissolved cellulose particles are visible (stirring at a speed of 1500 r / min for two hours), and then centrifuged at a speed of 6000 r / min to 10000 r / min for 6 to 15 minutes, preferably at a speed of 8000 r / min for 10 minutes.

[0010] Furthermore, the centrifuged cellulose solution and the sepiolite particles are mixed and stirred until the mixture is uniform (stirring at a speed of 1500 r / min for 15 minutes).

[0011] Furthermore, the silica nanofiber membrane is immersed in the cellulose solution blended with sepiolite particles for more than 0.5 h (including 0.5 h), preferably 1 h, and then transferred to an anti-solvent and immersed for more than 1 h (including 1 h), preferably 2 h.

[0012] Furthermore, the silica nanofiber membrane needs to be washed at least three times with ethanol and water before immersion.

[0013] Furthermore, the antisolvent is composed of anhydrous ethanol and pure water in a volume ratio of 2 to 4.5:3, preferably 1:1.

[0014] The beneficial effects of the present invention compared with the prior art are as follows: the present invention can be used after conventional water treatment process, and the separation efficiency of oil-water mixture and emulsion can reach up to 99.99%, which can effectively separate oil pollutants in raw water and meet the water outlet requirements. Compared with conventional water treatment alone, the removal rate of the membrane material of the present invention for oil emulsion pollutants in water is 61.73% higher, the removal effect is good, and it is green and environmentally friendly, and will not produce secondary pollution. The material has the advantages of simple operation, high operating efficiency, reliable work, and broad promotion prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a diagram showing the removal of five types of oil emulsion wastewater by Example 1 of the present invention and the base membrane before modification. DETAILED DESCRIPTION

[0016] The technical solution of the present invention is further described below, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention should be included in the protection scope of the present invention.

[0017] In the present invention, the silica nanofiber membrane presents a three-dimensional network structure, which can well adsorb and fix microcrystalline cellulose, and sepiolite has good water absorption and water holding capacity, which can strengthen the hydration layer on the membrane surface during the treatment process and prevent the invasion of oil droplets. After the microcrystalline cellulose is dissolved and regenerated, it can not only self-assemble and wrap the sepiolite and silica nanofiber membrane, but also spontaneously form a micro-nano underwater super oleophobic structure to improve the oil-water separation efficiency. Finally, the raw materials of these three are all green materials, which can prevent secondary pollution during the treatment process.

[0018] Embodiment 1:

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

[0020] 1. Stir 5% microcrystalline cellulose in an alkaline solution of sodium hydroxide: urea: pure water = 7:12:81 at 1500r / min for 2h, then centrifuge at 8000r / min for 10 minutes. The centrifuged cellulose solution is mixed with 8% sepiolite particles with a particle size of 2000 mesh and stirred at 1500r / min for 15 minutes.

[0021] 2. After washing with ethanol and pure water, the silica nanofiber membrane was soaked in a cellulose solution blended with sepiolite particles for 1 hour, and then transferred to an antisolvent with a ratio of pure water: ethanol = 1:1 and soaked for 2 hours. Then, the 20 mg / L oil emulsion was filtered at a pressure of 0.08 MPa. 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 below 15.2%. The role of the antisolvent is to perform phase transformation, thereby changing the crystal structure and facilitating membrane formation.

[0022] Embodiment 2:

[0023] The difference between this embodiment and embodiment 1 is that the first centrifugal speed (6000-7000 r / min) and stirring time (6-7 min) in step 1 are changed. Then, the 20 mg / L oil emulsion is filtered under a pressure of 0.08 MPa, 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] Embodiment 3:

[0025] The difference between this embodiment and embodiment 1 is that the amount of sepiolite particles added in step 1 is 4% to 5%. Then, the 20 mg / L oil emulsion is filtered under a pressure of 0.08 MPa, 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 below 20%.

[0026] Embodiment 4:

[0027] The difference between this embodiment and embodiment 1 is that the ratio of ethanol to water in the antisolvent described in step 2 is changed to 3:2. Then, the 20 mg / L oil emulsion is filtered under a pressure of 0.08 MPa, and the oil-water emulsion separation efficiency 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 below 25%.

Claims

1. A method for preparing a membrane material for separation of oil-water mixture and oil-water emulsion, characterized in that: The method comprises the following steps: the microcrystalline cellulose is dissolved in an alkaline environment and then evenly mixed with sepiolite particles, and then regenerated on a silicon dioxide nanofiber membrane to obtain a membrane material.

2. The method for preparing a membrane material for separation of oil-water mixture and oil-water emulsion according to claim 1, characterized in that: The mass percentage of the microcrystalline cellulose is 3% to 8%, the mass percentage of the sepiolite particles is 4% to 10%, and the balance is alkaline solution.

3. The method for preparing a membrane material for separation of oil-water mixture and oil-water emulsion according to claim 1 or 2, characterized in that: The particle size of the sepiolite particles is 1500 mesh to 2500 mesh.

4. The method for preparing a membrane material for separation of oil-water mixture and oil-water emulsion according to claim 1, characterized in that: The alkaline solution formula used to dissolve microcrystalline cellulose is sodium hydroxide: Urea:pure water=7:12:

81.

5. The method for preparing a membrane material for separation of oil-water mixture and oil-water emulsion according to claim 1, characterized in that: After microcrystalline cellulose is placed in an alkaline solution, it is stirred in an ice bath until no obvious undissolved cellulose particles are visible, and then centrifuged at a speed of 6000r / min to 10000r / min for 6 to 15 minutes.

6. The method for preparing a membrane material for separation of oil-water mixture and oil-water emulsion according to claim 5, characterized in that: The centrifuged cellulose solution is blended with the sepiolite particles and stirred until the mixture is uniform.

7. The method for preparing a membrane material for separation of oil-water mixture and oil-water emulsion according to claim 6, characterized in that: The silica nanofiber membrane is soaked in the cellulose solution blended with sepiolite particles for more than 0.5 h, and then transferred to an anti-solvent and soaked for more than 1 h.

8. The method for preparing a membrane material for separation of oil-water mixture and oil-water emulsion according to claim 7, characterized in that: The silica nanofiber membrane needs to be washed with ethanol and water at least three times before immersion.

9. The method for preparing a membrane material for separation of oil-water mixture and oil-water emulsion according to claim 7, characterized in that: The antisolvent is composed of anhydrous ethanol and pure water in a volume ratio of 2 to 4.5:3.

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