Preparation of self-cleaning degradable cellulose acetate-based nanofiber membrane for oil-water separation

Abstract

The invention relates to a preparation method of a self-cleaning degradable cellulose acetate-based nanofiber membrane. According to the method, a degradable cellulose acetate nanofiber membrane is used as a substrate, and nano zinc oxide particles with photocatalytic performance are doped inwards, so that the cellulose acetate nanofiber membrane has the photocatalytic performance. The acetic acid nanofiber basement membrane has a large number of microbead structures, and fibers are uniform in thickness. After the nano zinc oxide particles are added, the fiber has more spindles, and the hydrophilicity of the nanofiber membrane is improved. After oil-water separation, pollutants such as oil drops blocking the fiber membrane can be effectively removed by utilizing photocatalysis. Different from common oil-water separation membranes with stable properties, the cellulose acetate-based nanofiber membrane can be degraded in the natural environment, so that environmental pollution is reduced. The self-cleaning degradable cellulose acetate-based nanofiber membrane is prepared through an electrostatic spinning method and has a good separation effect on various oil-in-water emulsions, and the separation efficiency can reach 97% or above.

Description

Technical Field

[0001] The present invention specifically relates to the field of oil-water separation, provides a method for preparing a self-cleaning and degradable cellulose acetate-based nanofiber membrane, and belongs to the field of environmentally friendly materials. Background Art

[0002] As a fossil energy, oil is the world's largest energy source. With the development of industry and the improvement of people's living standards, the demand for oil energy in countries around the world is increasing day by day. However, the discharge of oily wastewater not only threatens human health but also harms the ecological environment and causes soil pollution. For oil-water separation technology, traditional separation methods mainly include physical separation, chemical separation and biological separation. However, these traditional oil-water separation methods are inefficient, poorly selective, complex to operate and costly. Membrane separation technology has attracted widespread attention due to its energy saving, low cost and high permeability.

[0003] Traditional oil-water separation membranes are prone to clogging problems in the process of treating oil-water emulsions. When flushing with clean water, the oil droplets inside the membrane are difficult to discharge, resulting in a decrease in flux. The water after flushing contains oil, which may cause secondary pollution. This fatal disadvantage not only makes the membrane separation efficiency low and the energy consumption high, but also limits the application and development of this technology in the treatment of oily wastewater. Therefore, for cost-effectiveness and recyclability, the self-cleaning properties of the membrane should also be considered in practical applications. Dual-functional membranes with oil-water separation and self-cleaning functions are feasible solutions to pollution and harsh environments. In addition, most traditional oil-water separation membranes are high molecular polymers with stable chemical properties. These materials are difficult to dispose of after being discarded and are prone to secondary pollution. Therefore, the invention of a self-cleaning and degradable oil-water separation membrane is the key to solving the membrane clogging and environmental pollution in the oil-water separation process.

[0004] In this work, the degradable green material cellulose acetate was selected as the base material, and photocatalytic oxide nano zinc oxide particles were doped into it to prepare a precursor solution, and a self-cleaning degradable cellulose acetate-based nanofiber membrane was prepared by electrospinning. Summary of the invention

[0005] The purpose of the present invention is to provide a self-cleaning and degradable cellulose acetate-based nanofiber membrane for oil-water separation and a preparation method thereof, so as to overcome the shortcomings of the current traditional oil-water separation membranes, such as low membrane utilization due to clogging and microplastic pollution caused by non-degradable membranes.

[0006] To achieve the above purpose, the present specification provides a method for preparing a degradable oil-water separation nanofiber membrane with photocatalytic performance, wherein the acetate nanofiber substrate membrane has a large number of microbead structures and the fiber thickness is relatively uniform. After adding nano zinc oxide particles, the fiber has more spindles and the hydrophilicity of the nanofiber membrane is improved.

[0007] The invention relates to a method for preparing a degradable oil-water separation nanofiber membrane with photocatalytic performance, self-cleaning ability and high separation efficiency.

[0008] The object of the present invention is achieved in that:

[0009] (1) 0.49 g of cellulose acetate (CA) and 0.49 g of polyvinyl pyrrolidone (PVP) (mass ratio of 1:1) were dissolved in an acetone / N,N-dimethylformamide (DMF) mixture (volume ratio of 3:2) to obtain a 10 wt% CA / PVP spinning solution;

[0010] (2) adding 0.37 g of nano zinc oxide particles to (1), and dispersing the zinc oxide particles more evenly by ultrasonic vibration to obtain a 3.5 wt % ZnO / CA / PVP spinning solution;

[0011] (3) The spinning solution obtained in step (2) is filled into a syringe with a metal needle for electrospinning. The generated nanofibers are collected on a metal roller. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Attached Figure 1 This is a scanning electron microscope picture of the cellulose acetate-based nanofiber substrate membrane of the present invention. It can be seen from the figure that different experimental parameters can be used to prepare fiber membranes, but the fiber membrane prepared under the optimal parameter conditions has a microbead structure, a more uniform size, and higher spinnability.

[0013] Attached Figure 2 This is a scanning electron microscope image of the self-cleaning and degradable cellulose acetate-based nanofiber membrane prepared after adding photocatalyst zinc oxide particles in the present invention.

[0014] Attached Figure 3 is the water contact angle of the nanofiber membrane in air and the oil contact angle under water.

[0015] Attached Figure 4 Diagram of the oil-water separation device based on self-cleaning and degradable cellulose acetate-based nanofiber membrane.

[0016] Attached Figure 5 This is a diagram showing the degradation effect of organic matter such as oil droplets clogging the membrane under ultraviolet light after oil-water separation by a self-cleaning and degradable cellulose acetate-based nanofiber membrane. DETAILED DESCRIPTION

[0017] (1) Prepare self-cleaning and degradable cellulose acetate-based nanofiber membrane substrate membrane and select the optimal solution. Select solution 1: Dissolve 0.69g CA and 0.29g PVP (mass ratio of 7:3) into an acetone / DMF mixture (volume ratio of 3:2); obtain a 10wt% CA / PVP spinning solution. Select solution 2: Dissolve 0.49g CA and 0.49g PVP (mass ratio of 1:1) into an acetone / DMF mixture (volume ratio of 3:2); obtain a 10wt% CA / PVP spinning solution. Select solution 3: Dissolve 0.97g CA and 0.42g PVP (mass ratio of 7:3) into an acetone / DMF mixture (volume ratio of 3:2); obtain a 14wt% CA / PVP spinning solution. Scheme 4 was selected: 0.62 g CA and 0.62 g PVP (mass ratio of 1:1) were dissolved in an acetone / DMF mixture (volume ratio of 3:2); a 14 wt% CA / PVP spinning solution was obtained. The results showed that nanofiber membranes could be prepared under different schemes, but the nanofiber membrane prepared in scheme 2 had a microbead structure, uniform fiber size, and the highest spinnability;

[0018] (2) Add nano ZnO particles to the best solution in step (1) to give the nanofiber membrane photocatalytic properties. There are four specific solutions. Select Solution 1: Dissolve 0.49g CA, 0.49g PVP (mass ratio of 1:1) and 0.05g ZnO in an acetone / DMF mixture (volume ratio of 3:2); obtain a 0.5wt% ZnO / CA / PVP spinning solution. Select Solution 2: Dissolve 0.49g CA, 0.49g PVP (mass ratio of 1:1) and 0.1g ZnO in an acetone / DMF mixture (volume ratio of 3:2); obtain a 1wt% CA / PVP spinning solution. Select Solution 3: Dissolve 0.49g CA, 0.49g PVP (mass ratio of 1:1) and 0.37g ZnO in an acetone / DMF mixture (volume ratio of 3:2); obtain a 3.5wt% ZnO / CA / PVP spinning solution. Scheme 4 was selected: 0.49g CA, 0.49g PVP (mass ratio of 1:1) and 0.74g ZnO were dissolved in an acetone / DMF mixture (volume ratio of 3:2); a 7wt% ZnO / CA / PVP spinning solution was obtained. After sufficient magnetic stirring, electrospinning was performed to prepare the nanofiber membrane. After testing the photocatalytic properties, mechanical properties and wettability of the nanofiber membrane, Scheme 3 was found to be the best scheme;

[0019] (3) Attachment Figure 4The schematic diagram of the water-in-oil emulsion separation device of the nanofiber membrane is shown. The self-cleaning and degradable cellulose acetate-based nanofiber membrane is sandwiched in the middle of the separation device, and the water phase quickly passes through the nanofiber membrane under a negative pressure of -25kPa. The water-in-oil emulsion before separation is milky white and opaque, and the filtrate after separation is transparent. In addition, the results show that the separation efficiency of the nanofiber membrane for different water-in-oil emulsions is above 97%;

[0020] (4) Attachment Figure 5 The photocatalytic performance of the nanofiber membrane was demonstrated. The nanofiber membrane became clogged after oil-water separation. When it was placed under ultraviolet light, it was found that the oil and other pollutants that caused the membrane to clog disappeared significantly within three hours. When the nanofiber membrane was used for oil-water separation again, the flux was significantly restored, thus effectively solving the problem of membrane clogging;

[0021] (5) Cellulose acetate is a biodegradable material. The discarded nanofiber membrane was buried in the soil to simulate the natural environment, and its degradation was observed after a period of time.

Claims

1. A method for preparing a self-cleaning and degradable cellulose acetate-based nanofiber membrane for oil-water separation, characterized in that: The steps include: (I) Select green and degradable materials to prepare a self-cleaning and degradable nanofiber membrane substrate for oil-water separation. The specific preparation process is as follows: (1) Cellulose acetate (CA) and polyvinyl pyrrolidone (PVP) were added to an acetone / N,N-dimethylformamide (DMF) mixture and stirred at 40°C for 4 hours to obtain a transparent spinning solution. The solution was loaded into a syringe for electrospinning to obtain an acetate nanofiber membrane. (2) Place the nanofiber membrane in a 60°C oven for 5 h to remove excess solvent. (ii) Adding nano zinc oxide particles with photocatalytic properties to prepare a self-cleaning and degradable cellulose acetate-based nanofiber membrane, the specific preparation process is as follows: (1) Cellulose acetate (CA), polyvinyl pyrrolidone (PVP) and ZnO particles were added to an acetone / N,N-dimethylformamide (DMF) mixture, mixed evenly by ultrasonic vibration and stirred at 40°C for 4 h to obtain a transparent spinning solution. The solution was loaded into a syringe for electrospinning to obtain a self-cleaning and degradable nanofiber membrane. (2) Place the nanofiber membrane in a 60°C oven for 5 h to remove excess solvent.

2. The method for preparing the self-cleaning and degradable nanofiber membrane substrate according to claim 1, characterized in that: In step (i), the amount of cellulose acetate added in (1) is 0.49 g, the amount of polyvinyl pyrrolidone added is 0.49 g, the acetone solution is 6 ml, and the N,N-dimethylformamide solution is 4 ml.

3. The method for preparing the self-cleaning and degradable nanofiber membrane substrate according to claim 1, characterized in that: In step (ii), the amount of ZnO added in (1) is 0.37 g, the acetone solution is 6 ml, and the N,N-dimethylformamide solution is 4 ml.

4. The method for preparing the self-cleaning and degradable nanofiber membrane substrate according to claim 1, characterized in that: The voltage for electrospinning described in step (1) is 13KV, and the drum receiving speed is 60rpm.

5. The method for preparing a self-cleaning biodegradable cellulose acetate-based nanofiber membrane according to claim 1, characterized in that: In step (ii), the voltage of the electrospinning in (1) is 13 KV, the drum receiving speed is 60 rpm, and the injection speed is 0.1 mm / min.

Images