Flexible ceramic membrane and its preparation method and application

Abstract

The present invention relates to a flexible ceramic membrane, its preparation method, and its application, belonging to the field of environmentally friendly water treatment technology. The flexible ceramic membrane is made from the following raw materials in the following weight percentages: 5%-10% ceramic membrane particles and 90%-95% polytetrafluoroethylene particles. This flexible ceramic membrane improves the membrane material's pressure bearing capacity and chemical stability. Furthermore, due to the ceramic material's good hydrophilicity, it also enhances the membrane material's anti-pollution ability. The resulting flexible ceramic membrane combines the flexibility of organic membrane materials with the rigidity and compressive resistance of inorganic ceramic membranes.

Description

Technical Field

[0001] The present invention relates to the technical field of environmentally friendly water treatment, and in particular to a flexible ceramic membrane and a preparation method and application thereof. Background Art

[0002] In the environmental protection industry, water treatment usually uses organic membrane materials for filtration. However, during the application process, due to the poor pressure-bearing capacity of traditional organic membranes, they are often easily flattened and deformed under high pressure and difficult to recover. In addition, traditional organic membranes have weak anti-fouling ability and are easily clogged. They have a short service life and are not resistant to high temperatures.

[0003] Therefore, there is also a solution to use inorganic ceramic membranes for water filtration, but inorganic ceramic membranes have the problem of being brittle and easy to break, and the chemical properties of ceramic membranes are unstable and easily react with silicon, causing the membrane pores to be blocked; the cost is high. Summary of the Invention

[0004] Based on this, it is necessary to provide a flexible ceramic membrane and its preparation method and application to address the above problems. The flexible ceramic membrane can maintain good flexibility while having high strength and toughness. The membrane filaments will not be flattened or deformed under high pressure. It has good hydrophilicity, can delay membrane fouling and prolong its service life. It has stable chemical properties such as acid resistance, alkali resistance and high temperature resistance, and does not react with any substance at room temperature. It has the advantages of low cost, high flux and low energy consumption.

[0005] A flexible ceramic membrane is prepared from the following raw materials in the following weight percentages:

[0006] Ceramic membrane particles 5%-10%

[0007] Polytetrafluoroethylene particles 90%-95%.

[0008] The above-mentioned flexible ceramic membrane forms a certain nano-scale spherical composite material by including polytetrafluoroethylene particles around the ceramic membrane particles, and combines the good rigidity of the ceramic membrane particles with the good chemical stability of polytetrafluoroethylene (PTFE), thereby improving the pressure bearing capacity and chemical stability of the final membrane material. Since the ceramic membrane particles change the hydrophilic angle of the polytetrafluoroethylene material, the hydrophilicity of the membrane material is improved, and the anti-pollution ability of the membrane material is improved, the obtained flexible ceramic membrane has both the flexibility of the organic membrane material and the rigidity and pressure resistance of the inorganic ceramic membrane.

[0009] In one embodiment, the particle size of the polytetrafluoroethylene particles is 0.2-0.5 μm, and the particle size of the ceramic membrane particles is 5-100 times the particle size of the polytetrafluoroethylene particles. By combining the particle sizes of these materials, the polytetrafluoroethylene particles can be well and evenly wrapped around the ceramic membrane particles, forming a composite material with high uniformity and excellent wrapping effect.

[0010] In one embodiment, the ceramic membrane particles are selected from at least one of titanium dioxide, corundum, aluminum oxide, and silicon carbide. The ceramic membrane particles can be well integrated with polytetrafluoroethylene to form a composite material with stable and uniform performance.

[0011] The present invention also discloses a method for preparing the above-mentioned flexible ceramic membrane, comprising the following steps:

[0012] Mixing: Take ceramic membrane particles and polytetrafluoroethylene particles, add co-solvent, heat and stir to wrap polytetrafluoroethylene around the ceramic membrane particles to form a composite membrane material;

[0013] Material preparation: Place the above composite membrane material in a rod tank and stir it thoroughly to make a hollow tubular rod;

[0014] Molding: Extruding the tubular rod into a hollow thin tubular material using an extruder;

[0015] Removal: Heat in an oven to remove the cosolvent;

[0016] Stretching and shaping: the above-mentioned hollow thin tubular material is heated and stretched 2 to 6 times in an oven to shape it.

[0017] The above-mentioned method for preparing flexible ceramic membranes fully considers the physical and chemical properties of polytetrafluoroethylene and ceramic materials, so that they can be well combined in the above-mentioned reaction process to form a composite material, achieving the characteristics of both good organic membrane stability and inorganic membrane rigidity. Specifically, in the mixing step, with the help of a cosolvent, polytetrafluoroethylene particles are first formed into a nano-scale spherical composite material with ceramic membrane particles as the core; then, in the material preparation step, the spherical composite material is further reacted and homogenized to form a tubular rod that can be subsequently formed; in the forming step, the above-mentioned tubular rod is first preliminarily formed, and then the cosolvent is removed in the removal step; finally, it is stretched and shaped to obtain a stable product. The stretching ratio determines the filtration pore size of the final flexible ceramic membrane product. The higher the stretching ratio, the larger the pore size.

[0018] In one embodiment, in the mixing step, the temperature is heated to 200-260° C. to form a composite membrane material with the ceramic membrane particles and polytetrafluoroethylene;

[0019] In the molding step, extrusion molding is performed at 260±20°C;

[0020] In the removal step, the cosolvent is removed at 175±20°C;

[0021] In the stretching and shaping step, the material is heated and stretched at 260±20°C for shaping.

[0022] The flexible ceramic membrane prepared with the above temperature parameters can have better physical and chemical properties.

[0023] In one embodiment, in the mixing step, the cosolvent is selected from kerosene; and in the preparation step, the material is stirred thoroughly for 30±10 minutes.

[0024] In one embodiment, in the forming step, the inner diameter of the hollow thin tubular material is 0.5 mm-10 mm, and the outer diameter is 1 mm-12 mm.

[0025] In one embodiment, in the stretching and shaping step, the hollow thin tubular material is stretched 2-6 times.

[0026] In one embodiment, in the stretching and shaping step, the stretching is performed within 1-3 hours.

[0027] The invention also discloses the application of the flexible ceramic membrane in water filtering equipment.

[0028] The above-mentioned flexible ceramic membrane is applied to water filtration equipment. It can withstand high pressure, has good hydrophilicity, can delay membrane fouling and clogging, and extend its service life. It also has stable chemical properties such as acid resistance, alkali resistance, high temperature resistance, and organic solvent resistance, and does not react with any substance at room temperature. It has the advantages of low cost, large flux, and low energy consumption.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The flexible ceramic membrane of the present invention forms a certain nano-scale spherical composite material by including polytetrafluoroethylene particles around the ceramic membrane particles, and utilizes the good rigidity of the ceramic membrane particles combined with the good chemical stability of polytetrafluoroethylene (PTFE) to improve the pressure bearing capacity and chemical stability of the final membrane material. In addition, since the ceramic membrane particles change the hydrophilic angle of the polytetrafluoroethylene material, the hydrophilic angle is increased from 110° of the conventional organic membrane to 50-60° of the present invention, the anti-pollution ability of the membrane material is improved, so that the obtained flexible ceramic membrane has both the flexibility of the organic membrane material and the rigidity and pressure resistance of the inorganic ceramic membrane. The flexible ceramic membrane can withstand a pressure of up to 3-5kg, so that the flexible ceramic membrane can be cleaned by a relatively intense cleaning method, with a very good cleaning effect.

[0031] It has the following advantages: ① The flexible ceramic membrane can maintain good flexibility while possessing high strength and toughness. Under high pressure, the membrane filaments will not be flattened or deformed, and their tensile strength is greater than 50kg; ② The membrane filaments have stable chemical properties and do not react with any substances at room temperature, solving the scaling problem of traditional membranes; ③ It is acid-resistant (such as 30% hydrochloric acid), alkali-resistant (pH up to 13), high-temperature-resistant, and resistant to organic solvents; ④ It has good hydrophilicity, can delay membrane fouling and extend its service life; ⑤ Low cost, large flux, and low energy consumption.

[0032] Especially when titanium dioxide and polytetrafluoroethylene are selected to work together, it not only has the advantages of easy availability of raw materials, low cost, and strong practical applicability, but also has a certain antibacterial effect, avoiding the problem of membrane material being blocked due to bacterial growth.

[0033] The present invention provides a method for preparing a flexible ceramic membrane, which fully considers the physical and chemical properties of polytetrafluoroethylene and ceramic materials, so that they can be well combined in the above reaction process to form a composite material, thereby achieving the characteristics of good stability of organic membrane and rigidity of inorganic membrane. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a partial process flow chart for preparing the flexible ceramic membrane in Example 1;

[0035] Figure 2 This is an electron microscope photo of the flexible ceramic membrane in Example 1;

[0036] Figure 3 for Figure 2 Enlarged photo of;

[0037] Figure 4 This is a schematic structural diagram of the water purification and filtration equipment in Example 2;

[0038] Figure 5 This is a flow diagram of the water purification and filtration equipment in Example 2.

[0039] Among them: 100. Shell; 110. Water purification chamber; 111. Water production port; 112. Water production valve; 121. Water inlet; 122. Water inlet valve; 123. Cross-flow port; 124. Cross-flow valve; 125. Sewage outlet; 126. Sewage valve; 200. Tubular membrane filament; 300. Cavitation generating device; 410. Air return valve. DETAILED DESCRIPTION

[0040] To facilitate understanding of the present invention, the present invention will be described more fully below with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the accompanying drawings. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the present disclosure.

[0041] It should be noted that when an element is referred to as being “fixed to” another element, it may be directly on the other element or there may be an intermediate element. When an element is referred to as being “connected to” another element, it may be directly connected to the other element or there may be an intermediate element at the same time.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used herein in the specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0043] Example 1

[0044] A flexible ceramic membrane, such as Figure 1 As shown, it is prepared by the following method:

[0045] 1. Mixing:

[0046] Take the following raw materials, add about 125g of cosolvent and mix well:

[0047] Ceramic membrane particles (TiO2) 7.5g

[0048] 92.5g polytetrafluoroethylene granules

[0049] The particle size of the ceramic membrane particles is 1 to 5 μm, the particle size of the polytetrafluoroethylene particles is 0.2 to 0.5 μm, the co-solvent is kerosene, heated to 200-260°C, and stirred to wrap the polytetrafluoroethylene around the ceramic membrane particles to form a composite membrane material;

[0050] 2. Material preparation:

[0051] The composite membrane material is placed in a rod tank and fully stirred for 30 minutes to form a hollow tubular rod.

[0052] 3. Molding:

[0053] The tubular rod is extruded at 260° C. using an extruder to form a hollow thin tubular material. The inner diameter of the hollow thin tubular material is 0.5 mm to 10 mm, and the outer diameter is 1 mm to 12 mm.

[0054] 4. Removal:

[0055] The hollow thin tubular material is heated in an oven at 175° C. to remove the cosolvent;

[0056] 5. Stretch and shape:

[0057] The hollow thin tubular material is stretched 2 to 6 times at 260°C for 1 to 3 hours to obtain a tubular membrane. The filtration pore size of the tubular membrane is 0.5 μm. Figure 2-3 shown. Figure 2 This is a photo of tubular membrane filaments under an electron microscope. Figure 3 for Figure 1 Enlarged photo of .

[0058] Example 2

[0059] The invention discloses an application of a flexible ceramic membrane, wherein the flexible ceramic membrane is used as a tubular membrane thread in a water purification and filtration device.

[0060] The above water purification and filtration equipment Figure 4 As shown, it includes: a shell 100, tubular membrane filaments 200, an air return generating device and a cavitation generating device 300.

[0061] The housing 100 includes a water purification chamber 110, which divides the internal space of the housing 100 into a water purification chamber within the water purification chamber and a filtration chamber outside the water purification chamber. The water purification chamber is provided with a water production port 111, and the filtration chamber is provided with a water inlet 121, a cross-flow port 123, and a sewage outlet 125. The water production port is provided at the top of the housing, the sewage outlet is provided at the bottom of the housing, the water inlet is provided at the bottom of the housing, and the cross-flow port is provided at the top of the housing. In addition, the water production port 111 is provided with a water production valve 112, the water inlet 121 is provided with a water inlet valve 122, the cross-flow port 123 is provided with a cross-flow valve 124, and the sewage outlet 125 is provided with a sewage valve 126.

[0062] The tubular membrane thread 200 is a hollow long tubular structure, and its tube wall is provided with gaps for filtration. Several tubular membrane threads are installed in the filter cavity, and the openings at both ends of the tubular membrane thread are installed on the water purification chamber, and the middle part droops to form a U-shaped structure; the inner wall of the tubular membrane thread is connected to the water purification chamber through the interface of the water purification chamber, and the outer wall of the tubular membrane thread is connected to the filter cavity.

[0063] The cavitation outlet of the cavitation generating device 300 is arranged at the bottom of the shell; the gas outlet of the gas return generating device is connected to the water purification chamber through the gas return valve 410.

[0064] The above-mentioned water purification and filtration equipment is used to filter wastewater (sewage), including the following steps:

[0065] 1. Water filtration

[0066] Wastewater to be filtered is introduced into the filter chamber through the water inlet. The wastewater is intercepted by the tubular membrane filaments, while the clean water enters the water purification chamber through the gaps in the tubular membrane filaments, completing the filtration. Furthermore, by adjusting the sizes of the water production valve, cross-flow valve, and water inlet valve, the pressure in the filter chamber is greater than that in the water purification chamber. Under this "back pressure," the tubular membrane filaments not only do not become flattened and deformed, but instead achieve a higher filtration accuracy, thereby intercepting smaller pollutants, achieving better filtration results and being less susceptible to clogging.

[0067] 1.1. Groundwater filtration

[0068] Take groundwater for filtration, and the filtration effect is as follows: Figure 4 shown.

[0069] Table 1. Groundwater filtration effect

[0070] Before filtration After filtering COD content 137mg / L 118mg / L pH 7 7 Scattering turbidity 100mg / L <1NTU

[0071] Note: COD refers to Chemical Oxygen Demand.

[0072] The above results show that the water purification and filtration equipment and method of this embodiment can achieve a good filtration effect. Figure 4 As shown, the above-mentioned water purification filtration equipment and method can provide continuous filtration, have a large flow rate and good durability.

[0073] 1.2. Filtration of electroplating wastewater containing nickel hydroxide

[0074] The nickel hydroxide electroplating wastewater was filtered, and the filtering effect is shown in the following table.

[0075] Table 2. Comparison of nickel ion removal rates

[0076]

[0077] The above results show that the flexible ceramic membrane has a high removal rate for nickel ions. The "Electroplating Pollutant Emission Standard" (GB21900-2008) stipulates that the total nickel emission limit is 0.5 mg / L. Depending on the concentrated water content, when the concentrated water nickel ion content is lower than 7-8 mg / L, the water outlet of the flexible ceramic membrane can meet this standard.

[0078] 1.3. PCB circuit board comprehensive wastewater filtration

[0079] The comprehensive wastewater from PCB circuit boards was filtered and operated continuously for 3 months at a pH of 8. Sampling was carried out for 3 consecutive days at the end of the 3rd month. The filtration effect is shown in the following table.

[0080] Table 3. Sampling results on September 26

[0081]

[0082] Table 4. Sampling results on September 27

[0083]

[0084] Table 5. Sampling results on September 28

[0085]

[0086] The above results show that after continuous operation for 3 months under the condition of pH 8, the water purification filtration equipment and method of this embodiment can also achieve good filtration effect, and have the advantages of good alkali resistance and high durability.

[0087] 1.4. Waste acid filtration

[0088] A 30% waste hydrochloric acid solution was filtered, and the inlet SS (total suspended solids) was 150 mg / L. After filtration, the outlet SS was <1 NTU (scattering turbidity unit), indicating that the water purification filtration equipment and method of this embodiment have good filtration effect and the advantage of strong acid resistance.

[0089] 2. Online cleaning steps

[0090] 2.1 Positive aeration scrubbing:

[0091] First, cavitation is filled into the filter cavity through the cavitation generating device. The upward movement of the cavitation causes the tubular membrane wire with a U-shaped structure drooping in the middle to vibrate, so that the pollutants adhering to the outer wall of the tubular membrane wire fall into the wastewater in the filter cavity. The wastewater is then discharged through the cross-flow port and / or the sewage outlet, thus completing the front aeration scrubbing. The pressure that the tubular membrane wire can withstand during the above-mentioned front aeration scrubbing is 3-5kg.

[0092] 2.2 Gas backwash:

[0093] First, open the air backwash valve 410, and fill the water purification chamber with gas through the air backwash generating device, so that the gas flows from the inside of the tubular membrane to the outside in the opposite direction of the water flow, so that the pollutants adhering to the outer wall of the tubular membrane fall into the wastewater in the filter chamber, and then the wastewater is discharged through the cross-flow port and / or the sewage outlet, thus completing the air backwash. The pressure that the tubular membrane can withstand during the above-mentioned air backwash is 3-5kg.

[0094] Example 3

[0095] A water purification and filtration device is basically the same as the device in Example 2, except that the ceramic membrane particles selected for the flexible ceramic membrane are silicon carbide. The above-mentioned water purification and filtration device is used to filter wastewater. It is found that after running for a period of time, the filtration flux is seriously affected due to bacterial growth.

[0096] Example 4

[0097] A water purification and filtration device is substantially the same as the device of Example 2, except that the removal step is omitted during the preparation of the flexible ceramic membrane. Ultimately, no formed flexible ceramic membrane can be obtained.

[0098] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0099] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. Application of a flexible ceramic membrane in water filtration equipment, characterized in that: The flexible ceramic membrane has a high nickel ion removal rate when filtering electroplating wastewater containing nickel hydroxide; the flexible ceramic membrane is used as a tubular membrane wire in a filtration device; The filtering device comprises: a housing (100), tubular membrane filaments (200), an air backflow generating device and a cavitation generating device (300); The shell (100) includes a water purification chamber (110), wherein the water purification chamber (110) divides the internal space of the shell (100) into a water purification chamber inside the water purification chamber and a filter chamber outside the water purification chamber. The water purification chamber is provided with a water production port (111), and the filter chamber is provided with a water inlet (121), a cross-flow port (123), and a sewage outlet (125). The water production port is provided at the top of the shell, the sewage outlet is provided at the bottom of the shell, the water inlet is provided at the lower part of the shell, and the cross-flow port is provided at the upper part of the shell. Furthermore, the water production port (111) is provided with a water production valve (112), the water inlet (121) is provided with a water inlet valve (122), the cross-flow port (123) is provided with a cross-flow valve (124), and the sewage outlet (125) is provided with a sewage outlet valve (126). The tubular membrane thread (200) is a hollow long tubular structure, and its tube wall is provided with a gap for filtering. A plurality of the tubular membrane threads are installed in the filter cavity, and the openings at both ends of the tubular membrane thread are installed on the water purification chamber, and the middle part droops to form a U-shaped structure; the inner wall of the tubular membrane thread is connected to the water purification chamber through the interface of the water purification chamber, and the outer wall of the tubular membrane thread is connected to the filter cavity; The cavitation outlet of the cavitation generating device (300) is provided at the bottom of the housing; the gas outlet of the gas return generating device is connected to the water purification chamber via a gas return valve (410); The flexible ceramic membrane is prepared from the following raw materials in the following weight percentages: Ceramic membrane particles 5%-10% Polytetrafluoroethylene particles 90%-95% The particle size of the polytetrafluoroethylene particles is 0.2-0.5 μm, and the particle size of the ceramic membrane particles is 5-100 times the particle size of the polytetrafluoroethylene particles; The ceramic membrane particles are selected from: titanium dioxide; The flexible ceramic membrane is prepared by the following method: Mixing: Take ceramic membrane particles and polytetrafluoroethylene particles, add co-solvent, heat to 200-260℃, and stir to wrap polytetrafluoroethylene around the ceramic membrane particles. The polytetrafluoroethylene particles form a nano-scale spherical composite material with the ceramic membrane particles as the core; Material preparation: Place the above composite membrane material in a rod tank and stir it thoroughly to make a hollow tubular rod; Molding: The tubular rod is extruded at 260±20°C into a hollow thin tubular material with an inner diameter of 0.5mm-10mm and an outer diameter of 1mm-12mm; Removal: heating in an oven at 175±20°C to remove the cosolvent; the cosolvent is selected from kerosene; Stretching and shaping: heating the above-mentioned hollow thin tubular material in an oven at 260±20℃ and stretching it 2-6 times to shape within 1-3 hours to obtain a tubular membrane yarn; The flexible ceramic membrane has a hydrophilic angle of 50-60°, can withstand a pressure of 3-5 kg, has a tensile strength greater than 50 kg, and is acid-resistant and alkali-resistant.

2. The use of the flexible ceramic membrane in water filtration equipment according to claim 1, characterized in that: In the material preparation step, the mixture was stirred thoroughly for 30±10 min.

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