Preparation method of PTFE oil-water separation composite membrane

Abstract

The invention aims to provide a preparation method of a PTFE (polytetrafluoroethylene) oil-water separation composite membrane, which mainly comprises the following steps: soaking a PTFE membrane in absolute ethyl alcohol and deionized water for a certain time, removing surface impurities, dredging holes, modifying the PTFE membrane by using plasma treatment with air as active gas, and breaking part of C-F bonds on the surface of the PTFE membrane, so as to obtain the PTFE oil-water separation composite membrane. The preparation method comprises the following steps: carrying out in-situ polymerization on a PTFE membrane to form a modified PTFE membrane with-OH and-COOH on the surface, completely soaking the modified PTFE membrane in a Tris-NaH2PO4 buffer solution, then respectively adding dopamine (DA), a hydroxyethyl methylacrylate (HEMA) monomer and zirconium n-butoxide, rapidly carrying out HEMA in-situ polymerization reaction initiated by dopamine on the surface of the membrane, forming a high-hydrophilicity DA-HEMA polymerization chain segment on the surface of the modified PTFE membrane, and carrying out hydrolysis and polycondensation on the zirconium n-butoxide at the same time, thereby obtaining the high-hydrophilicity PTFE membrane. The preparation method comprises the following steps: adding modified PTFE into a reaction kettle, reacting with dopamine-HEMA and modified PTFE to form a PTFE composite material, leaching with deionized water, and drying to finally form the modified PTFE composite membrane. The modified PTFE composite membrane is applied to an oil-water separation system, and the oil-water separation efficiency can reach 95% or above.

Description

Technical Field

[0001] The present invention relates to a preparation method of a modified PTFE composite membrane, belonging to the technical field of membrane preparation, and specifically designing a preparation method of a PTFE oil-water separation composite membrane. The PTFE oil-water separation composite membrane has the advantages of high pure water flux, high flux recovery rate, high mechanical strength of the membrane, and simple preparation, and is applicable to the oil-water separation system. Background Art

[0002] The treatment of oily wastewater is a global challenge, especially due to the large discharge of oily wastewater from the mechanical industry, textile industry, food processing industry, and petrochemical industry. Traditional separation technologies have low treatment efficiency or are unable to treat oil-water emulsions stabilized by surfactants. Oily wastewater not only damages the ecological environment and threatens the survival of aquatic organisms, but also poses a serious risk to human health, such as causing skin diseases, respiratory problems, and cancer. Therefore, it has become particularly urgent to develop efficient oil-water separation technologies to meet strict water discharge standards and promote the implementation of water resource reuse policies.

[0003] Limitations of traditional oil-water separation technologies Traditional oil-water separation technologies such as skimming, flotation, centrifugation, and sedimentation have disadvantages such as high energy consumption, complex operation, and low removal efficiency of emulsified oil when treating oily wastewater. Although membrane separation technology has received attention due to its low energy consumption, simple operation, and high efficiency in separating emulsified oil, commonly used hydrophobic filtration membranes are prone to low flux and serious oil pollution, limiting their wide application. Patent CN202411958916 provides a ceramic-based oil-water separation membrane and its preparation method and application. In this invention, Ti3C2T x particles are exfoliated into lamellar Ti3C2T x , and then ZIF-62 is in-situ synthesized in the lamellar Ti3C2T x and calcined, and finally modified to obtain a ceramic-based oil-water separation membrane. The method for preparing the membrane by this method is too cumbersome, and at the same time, inorganic nanomaterials are also prone to shedding, and the long-term stability of the membrane is somewhat lacking; Patent CN202411606820 relates to a preparation method of a hydrophilic PLA oil-water separation membrane. Poly(lactic acid) is dissolved in an organic solvent to obtain a spinning solution for electrospinning to prepare a PLA nanofiber membrane; the PLA nanofiber membrane is impregnated in a hydrochloric acid dopamine solution, and then the membrane cloth is taken out, washed, and dried to obtain the hydrophilic PLA oil-water separation membrane. The membrane prepared by this method has low mechanical strength, and at the same time, poly(lactic acid) is easily entrapped during the electrospinning process, resulting in a reduction in exposed hydrophilic sites.

[0004] Therefore, it is an urgent technical problem to be solved to prepare an efficient, economical, and high-mechanical-strength oil-water separation membrane. Summary of the Invention

[0005] A preparation method of a PTFE oil-water separation composite membrane is as follows: The PTFE commercial membrane is first pretreated by soaking it in absolute ethanol and deionized water for 1 h respectively, aiming to remove surface impurities and hydrophobic pores. The PTFE membrane is pretreated by using air as the plasma treatment of the active gas. Subsequently, 100 ml of Tris-NaH2PO4 buffer solution with pH = 8 is prepared. The buffer solution contains dopamine (DA), 2-hydroxyethyl methacrylate (HEMA) and a certain amount of zirconium n-butoxide. The pretreated PTFE membrane is soaked in this mixed solution for a period of time. After the reaction, the modified membrane is taken out, rinsed with deionized water and dried to finally form a PTFE oil-water separation composite membrane.

[0006] Among them, the content of DA in the buffer solution is 1-3 wt%; Among them, the mass ratio of DA to HEMA is one of 1:5, 1:10, 1:15, 1:20; Among them, the content of zirconium n-butoxide in the buffer solution is 0.5-2 wt%; Among them, the pretreated PTFE membrane is soaked in this mixed solution for 10-30 min; In the present invention, the PTFE membrane is modified by using air as the plasma treatment of the active gas, so that some C-F bonds of the PTFE membrane are broken to form a modified PTFE membrane with -OH and -COOH on the surface. In an environment with pH = 8, DA, HEMA monomers and zirconium n-butoxide are introduced. Since DA is a good binder and initiator, the in-situ polymerization reaction of HEMA initiated by DA proceeds rapidly on the membrane surface, and a highly hydrophilic DA-HEMA polymer chain segment is formed on the surface of the modified PTFE membrane. At the same time, zirconium n-butoxide undergoes hydrolysis and polycondensation and reacts with DA-HEMA and the modified PTFE to form a PTFE oil-water separation composite membrane. The prepared oil-water separation membrane has the advantages of hydrophilic and oleophobic properties and high mechanical strength. At the same time, the preparation method of this PTFE oil-water separation composite membrane is simple and has broad application prospects. Specific embodiments

[0007] The PTFE commercial membrane is first pretreated by soaking it in absolute ethanol and deionized water for 1 h respectively, aiming to remove surface impurities and hydrophobic pores. The performance is tested with a 5 g / L soybean oil solution at 0.1 bar. Through the analysis of the TOC results, the oil-water separation efficiency of the PTFE membrane can reach 10.27%, and the flux is 1500.48 L·m -2 ·h -1 , and after long-term operation, the flux recovery rate can reach 76.32%. Examples

[0008] The PTFE commercial membrane was first pretreated by soaking it in absolute ethanol and deionized water for 1 h respectively, aiming to remove surface impurities and open pores. The PTFE membrane was modified by using air as the plasma treatment of the reactive gas. Subsequently, 100 ml of Tris-NaH2PO4 buffer solution with pH = 8 was prepared. The buffer solution contained 1 wt% DA, a certain amount of HEMA (the mass ratio of DA to HEMA was 1:5 respectively), and 0.5 wt% zirconium butoxide. The pretreated PTFE membrane was immersed in this mixed solution. After 10 min of reaction, the modified membrane was taken out, rinsed with deionized water and dried, and finally a modified PTFE oil-water separation composite membrane was formed. The performance was tested with a 5 g / L soybean oil solution at 0.1 bar. Through the analysis of the TOC results, the oil-water separation efficiency of the modified PTFE oil-water separation composite membrane could reach 97.39%, and the flux was 790.32 L·m -2 ·h -1 After long-term operation, the flux recovery rate could reach 96.56%. Example

[0009] The PTFE commercial membrane was first pretreated by soaking it in absolute ethanol and deionized water for 1 h respectively, aiming to remove surface impurities and open pores. The PTFE membrane was modified by using air as the plasma treatment of the reactive gas. Subsequently, 100 ml of Tris-NaH2PO4 buffer solution with pH = 8 was prepared. The buffer solution contained 2 wt% DA, a certain amount of HEMA (the mass ratio of DA to HEMA was 1:10 respectively), and 1 wt% zirconium butoxide. The pretreated PTFE membrane was immersed in this mixed solution. After 20 min of reaction, the modified membrane was taken out, rinsed with deionized water and dried, and finally a modified PTFE oil-water separation composite membrane was formed. The performance was tested with a 5 g / L soybean oil solution at 0.1 bar. Through the analysis of the TOC results, the oil-water separation efficiency of the modified PTFE oil-water separation composite membrane could reach 98.47%, and the flux was 860.68 L·m -2 ·h -1 After long-term operation, the flux recovery rate could reach 97.43%. Example

[0010] The PTFE commercial membrane was first pretreated by soaking it in absolute ethanol and deionized water for 1 h respectively, aiming to remove surface impurities and unblock pores. The PTFE membrane was modified by using air as the plasma treatment of the reactive gas. Subsequently, 100 ml of Tris-NaH2PO4 buffer solution with pH = 8 was prepared, which contained 3 wt% DA, a certain amount of HEMA (the mass ratio of DA to HEMA was 1:15 respectively), and 2 wt% zirconium butoxide. The pretreated PTFE membrane was soaked in this mixed solution. After 30 min of reaction, the modified membrane was taken out, rinsed with deionized water and dried, and finally a modified PTFE oil-water separation composite membrane was formed. The performance was tested with a 5 g / L soybean oil solution at 0.1 bar. Through the analysis of the TOC results, the oil-water separation efficiency of the modified PTFE oil-water separation composite membrane could reach 99.43%, and the flux was 890.74 L·m -2 ·h -1 After long-term operation, the flux recovery rate could reach 98.28%.

[0011] Table 1 Oil-water separation effect of a PTFE oil-water separation composite membrane Project <![CDATA[Flux (L·m -2 ·h -1 )]]> Oil-water separation efficiency (%) Flux recovery rate (%) Comparative Example 1 1500.48 10.27％ 76.32% Example 1 790.32 97.39％ 96.56% Example 2 860.68 98.47％ 97.43% Example 3 890.74 99.43％ 98.28% As can be seen from Table 1: Compared with the conventional PTFE commercial membrane (Control Example 1), through the performance test with a 5 g / L soybean oil solution at 0.1 bar and the analysis of the TOC results, it can be obtained that the oil-water separation efficiency of the modified PTFE oil-water separation composite membrane increased from the original 10.27% to 99.43%. After long-term operation, the flux recovery rate increased from the original 76.32% to 98.28%. The reason for the slight decrease in flux is that the highly hydrophilic DA-HEMA polymer chain segments grafted on the surface of the modified PTFE oil-water separation composite membrane affect the membrane pores, and the pore size of the modified membrane is more suitable for oil-water separation.

Claims

1. A method for preparing a PTFE oil-water separation composite membrane, the specific steps of which are as follows: The commercial PTFE membrane was pretreated by soaking it in anhydrous ethanol and deionized water for 1 h respectively to remove surface impurities and dredge holes. The PTFE membrane was treated with plasma using air as the active gas to obtain a modified PTFE membrane. Then 100 ml of Tris-NaH2PO4 buffer with pH=8 was prepared. The buffer solution contained dopamine (DA), a certain amount of HEMA and a certain amount of zirconium n-butoxide. The pretreated PTFE membrane was soaked in the mixed solution for a period of time. After the reaction was completed, the modified membrane was taken out, rinsed with deionized water and dried to finally obtain a modified PTFE oil-water separation composite membrane.

2. A method for preparing a PTFE oil-water separation composite membrane as claimed in claim 1, characterized in that: The content of DA in the buffer solution is 1-3 wt %.

3. A method for preparing a PTFE oil-water separation composite membrane as claimed in claim 1, characterized in that: The mass ratio of DA to HEMA is preferably any one of 1:5, 1:10, 1:15, and 1:

20.

4. A method for preparing a PTFE oil-water separation composite membrane as claimed in claim 1, characterized in that: The content of zirconium n-butoxide in the buffer solution is 0.5-2 wt%.

5. A method for preparing a PTFE oil-water separation composite membrane as claimed in claim 1, characterized in that: The pretreated PTFE membrane is immersed in the mixed solution for 10-30 minutes.