A method for preparing a PTFE oil-water separation composite membrane

Abstract

This invention aims to provide a method for preparing a PTFE oil-water separation composite membrane, mainly comprising: soaking a PTFE membrane in anhydrous ethanol and deionized water for a certain period of time to remove surface impurities and unclog pores; modifying the PTFE membrane by plasma treatment with air as the active gas, causing partial C-F bond breakage on the surface of the PTFE membrane to form a modified PTFE membrane with -OH and -COOH on the surface; completely immersing the modified PTFE membrane in Tris-NaH2PO4 buffer solution; subsequently adding dopamine (DA), hydroxyethyl methacrylate (HEMA) monomer, and zirconium butoxide, respectively; the in-situ polymerization reaction of HEMA initiated by dopamine proceeds rapidly on the membrane surface, forming highly hydrophilic DA-HEMA polymeric segments on the surface of the modified PTFE membrane; simultaneously, zirconium butoxide undergoes hydrolysis and condensation, and reacts with dopamine-HEMA and modified PTFE to form a PTFE composite material; and finally forming a modified PTFE composite membrane by rinsing with deionized water and drying. When this modified PTFE composite membrane is applied to an oil-water separation system, an oil-water separation efficiency of over 95% can be achieved.

Description

Technical Field

[0001] This invention relates to a method for preparing a modified PTFE composite membrane, belonging to the field of membrane preparation technology, specifically a method for preparing a PTFE oil-water separation composite membrane. This PTFE oil-water separation composite membrane has advantages such as high pure water flux, high flux recovery rate, high mechanical strength, and simple preparation, making it suitable for oil-water separation systems. Background Technology

[0002] Oily wastewater treatment is a global challenge, particularly due to the large-scale discharge of oily wastewater from the machinery, textile, food processing, and petrochemical industries. Traditional separation technologies are inefficient or ineffective in treating oil-water emulsions containing surfactants. Oily wastewater not only damages the ecological environment and threatens the survival of aquatic organisms, but also poses serious risks to human health, such as causing skin diseases, respiratory problems, and cancer. Therefore, developing efficient oil-water separation technologies to meet stringent water discharge standards and promote the implementation of water resource reuse policies has become particularly urgent.

[0003] Limitations of Traditional Oil-Water Separation Technologies: Traditional oil-water separation technologies, such as skimming, flotation, centrifugation, and sedimentation, suffer from drawbacks such as high energy consumption, complex operation, and low efficiency in removing emulsified oil when treating oily wastewater. Although membrane separation technology has gained attention due to its low energy consumption, simple operation, and high efficiency in separating emulsified oil, commonly used hydrophobic filtration membranes tend to result in low flux and severe oil contamination, limiting their widespread application. Patent CN202411958916 provides a ceramic-based oil-water separation membrane, its preparation method, and its application. This invention utilizes Ti3C2T... x Particles are peeled into sheets of Ti3C2T x Next, ZIF-62 was synthesized in situ on Ti3C2T sheets. x The process involves calcination followed by modification to obtain a ceramic-based oil-water separation membrane. However, this method is overly cumbersome, and the inorganic nanomaterials are prone to detachment, resulting in insufficient long-term membrane stability. Patent CN202411606820 discloses a method for preparing a hydrophilic PLA oil-water separation membrane. This method involves dissolving polylactic acid in an organic solvent to obtain a spinning solution, followed by electrospinning to obtain a PLA nanofiber membrane. The PLA nanofiber membrane is then immersed in a dopamine hydrochloride solution, followed by removal, washing, and drying to obtain the hydrophilic PLA oil-water separation membrane. However, this method produces membranes with low mechanical strength, and the polylactic acid is easily embedded during the spinning process, reducing the exposed hydrophilic sites.

[0004] Therefore, developing a highly efficient, economical, and mechanically strong oil-water separation membrane is an urgent technical challenge that needs to be addressed. Summary of the Invention

[0005] A method for preparing a PTFE oil-water separation composite membrane, the specific steps of which are as follows:

[0006] The commercial PTFE membrane was first pretreated by soaking it in anhydrous ethanol and deionized water for 1 hour each to remove surface impurities and unclog pores. Then, plasma treatment with air as the active gas was used to further pretreat the PTFE membrane. Following this, a 100 ml pH 8 Tris-NaH2PO4 buffer solution containing dopamine (DA), hydroxyethyl methacrylate (HEMA), and a certain amount of zirconium butoxide was prepared, and the pretreated PTFE membrane was immersed in this mixed solution for a period of time. After the reaction, the modified membrane was removed, rinsed with deionized water, and dried to finally form a PTFE oil-water separation composite membrane.

[0007] The content of DA in the buffer solution is 1-3 wt%;

[0008] The mass ratio of DA to HEMA is one of 1:5, 1:10, 1:15, or 1:20.

[0009] The content of zirconium n-butoxide in the buffer solution is 0.5-2 wt%.

[0010] The pretreated PTFE membrane is immersed in the mixed solution for 10-30 minutes.

[0011] This invention modifies PTFE membranes using plasma treatment with air as the active gas, causing partial CF bond breakage and forming a modified PTFE membrane with -OH and -COOH groups on its surface. In an environment of pH 8, DA, HEMA monomers, and zirconium butoxide are introduced. Since DA is a good binder and initiator, the in-situ polymerization of HEMA initiated by DA proceeds rapidly on the membrane surface, forming highly hydrophilic DA-HEMA polymeric segments on the modified PTFE membrane surface. Simultaneously, zirconium butoxide undergoes hydrolysis and condensation, reacting 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 being hydrophilic and oleophobic, and possessing high mechanical strength. Furthermore, the preparation method of this PTFE oil-water separation composite membrane is simple and has broad application prospects. Detailed Implementation

[0012] Compare with Example 1:

[0013] The commercial PTFE membrane was pretreated by soaking it in anhydrous ethanol and deionized water for 1 hour each to remove surface impurities and unclog pores. Performance testing was then conducted using a 5 g / L soybean oil solution at 0.1 bar. TOC analysis showed that the PTFE membrane achieved an oil-water separation efficiency of 10.27% and a flux of 1500.48 L·m⁻¹. -2 ·h -1 After long-term operation, the throughput recovery rate can reach 76.32%.

[0014] Example 1:

[0015] The commercial PTFE membrane was pretreated by soaking it in anhydrous ethanol and deionized water for 1 h each to remove surface impurities and unclog pores. The PTFE membrane was then modified using plasma treatment with air as the active gas. Subsequently, a 100 ml pH 8 Tris-NaH2PO4 buffer solution was prepared, containing 1 wt% DA, a certain amount of HEMA (DA to HEMA mass ratio 1:5), and 0.5 wt% zirconium butoxide. The pretreated PTFE membrane was immersed in this mixed solution for 10 min. After the reaction, the modified membrane was removed, rinsed with deionized water, and dried to form the modified PTFE oil-water separation composite membrane. Performance tests were conducted using a 5 g / L soybean oil solution at 0.1 bar. TOC analysis showed that the modified PTFE oil-water separation composite membrane achieved an oil-water separation efficiency of 97.39% and a flux of 790.32 L·m⁻¹. -2 ·h -1 After long-term operation, the throughput recovery rate can reach 96.56%.

[0016] Example 2:

[0017] The commercial PTFE membrane was pretreated by soaking in anhydrous ethanol and deionized water for 1 h each to remove surface impurities and unclog pores. The PTFE membrane was then modified using plasma treatment with air as the active gas. Subsequently, a 100 ml pH 8 Tris-NaH2PO4 buffer solution was prepared, containing 2 wt% DA, a certain amount of HEMA (DA to HEMA mass ratio 1:10), and 1 wt% zirconium butoxide. The pretreated PTFE membrane was immersed in this mixed solution for 20 min. After the reaction, the modified membrane was removed, rinsed with deionized water, and dried to form the modified PTFE oil-water separation composite membrane. Performance tests were conducted using a 5 g / L soybean oil solution at 0.1 bar. TOC analysis showed that the modified PTFE oil-water separation composite membrane achieved an oil-water separation efficiency of 98.47% and a flux of 860.68 L·m⁻¹. -2 ·h-1 After long-term operation, the throughput recovery rate can reach 97.43%.

[0018] Example 3:

[0019] The commercial PTFE membrane was pretreated by soaking in anhydrous ethanol and deionized water for 1 h each to remove surface impurities and unclog pores. The PTFE membrane was then modified using plasma treatment with air as the active gas. Subsequently, a 100 ml pH 8 Tris-NaH2PO4 buffer solution was prepared, containing 3 wt% DA, a certain amount of HEMA (DA to HEMA mass ratio 1:15), and 2 wt% zirconium butoxide. The pretreated PTFE membrane was immersed in this mixed solution for 30 min. After the reaction, the modified membrane was removed, rinsed with deionized water, and dried to form the modified PTFE oil-water separation composite membrane. Performance tests were conducted using a 5 g / L soybean oil solution at 0.1 bar. TOC analysis showed that the modified PTFE oil-water separation composite membrane achieved an oil-water separation efficiency of 99.43% and a flux of 890.74 L·m⁻¹. -2 ·h -1 After long-term operation, the throughput recovery rate can reach 98.28%.

[0020] Table 1. Oil-water separation effect of a PTFE oil-water separation composite membrane.

[0021] project <![CDATA[Flux (L·m -2 ·h -1 )]]> Oil-water separation efficiency (%) Flux recovery rate (%) Compare with 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%

[0022] As shown in Table 1, compared to the conventional PTFE commercial membrane (Control Example 1), the modified PTFE oil-water separation composite membrane showed an increase in oil-water separation efficiency from 10.27% to 99.43% after performance testing with a 5 g / L soybean oil solution at 0.1 bar. After long-term operation, the flux recovery rate increased from 76.32% to 98.28%. The slight decrease in flux is attributed to the influence of the highly hydrophilic DA-HEMA polymer segments grafted onto the surface of the modified PTFE oil-water separation composite membrane on the membrane pore size, making the modified membrane's pore size 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 first pretreated by soaking it in anhydrous ethanol and deionized water for 1 hour each to remove surface impurities and clear pores. Then, the PTFE membrane was treated with plasma using air as the active gas to obtain a modified PTFE membrane. Subsequently, 100 ml of Tris-NaH2PO4 buffer solution with pH=8 was prepared. The buffer solution contained dopamine (DA), a certain amount of HEMA and a certain amount of zirconium butoxide. The pretreated PTFE membrane was immersed in the buffer solution for a period of time. After the reaction was completed, the modified membrane was removed, rinsed with deionized water and dried to finally obtain the modified PTFE oil-water separation composite membrane.

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

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

15.

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

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