A polytetrafluoroethylene and basalt composite fiber hollow ultrafiltration membrane

Abstract

A hollow ultrafiltration membrane of polytetrafluoroethylene and basalt composite fibers, belonging to a hollow ultrafiltration membrane for sewage treatment. The basalt fiber layer of the hollow ultrafiltration membrane is cylindrical, and a polytetrafluoroethylene layer is coated on the outside of the basalt fiber layer; micropores are densely distributed on the cylinder wall of the basalt fiber woven layer, and the bonding surface of the polytetrafluoroethylene layer and the basalt fiber layer is composited at high temperature to form a hollow ultrafiltration membrane with a composite fiber with a membrane center hole; the basalt fiber layer is made of basalt fibers interwoven and laminated by a braiding machine to form a cylindrical shape, and the center hole of the cylinder is the center hole of the membrane; it can isolate microorganisms, colloids and other turbid substances in the water; the polytetrafluoroethylene layer is made of polytetrafluoroethylene fibers interwoven and laminated by a braiding machine, and woven and coated on the outside of the basalt fiber layer. Advantages: The present invention has high cost performance, low price, non-toxic and environmentally friendly; basalt and polytetrafluoroethylene have similar melting points, high temperature composite, high breaking strength, good flame retardancy, high modulus, and can efficiently filter high-temperature toxic gases and dust.

Description

Technical Field

[0001] The invention relates to a hollow ultrafiltration membrane for sewage treatment, which is used in the technical field of sewage treatment, in particular to a hollow ultrafiltration membrane of polytetrafluoroethylene and basalt composite fibers. Background Art

[0002] At present, in the sewage treatment industry, ultrafiltration technology has been put into large-scale practical application. Ultrafiltration membrane is the core component of ultrafiltration equipment. It is a high-tech technology widely used in the purification of wastewater, solution separation, and extraction of useful substances from wastewater, and wastewater purification and reuse. The commonly used ultrafiltration membrane is an outer layer of a coating layer 1-1, whose material is polyvinylidene fluoride PVDF. PVDF is a fluoroplastic that can withstand a high temperature of 175°C and has a certain chemical resistance. The inner layer is a fiber braided layer 1-2, whose material is PP yarn or glass fiber woven into a cylindrical shape. The hole in the middle of the cylinder is a hollow hole 1-3, and micropores 1-4 are densely distributed on the fiber cylinder wall. The outer coating layer 1-1 is coated on the outside of the fiber braided layer 1-2, and then hot-melted to fuse the bonding surface of the coating layer 1-1 and the fiber braided layer 1-2 together.

[0003] like Figure 6 and Figure 7 , is a schematic diagram of the structure of a hollow fiber ultrafiltration membrane, including: a coating layer 1-1, a fiber braided layer 1-2, hollow holes 1-3 and micropores 1-4.

[0004] Raw water flows under pressure outside or inside the hollow fiber ultrafiltration membrane, and the coating layer 1-1 and the fiber braided layer 1-2 form micropores on the wall of the tube to separate water from impurities in the water. The separation method is external pressure separation. Ultrafiltration is a dynamic filtration process. The substances trapped by the micropores on the fiber tube wall can be discharged with the concentrated water without clogging the membrane surface, forming purification and recycling.

[0005] The hollow fiber ultrafiltration membrane in the prior art has the following disadvantages: low filtration accuracy, not resistant to high temperature and combustion, not resistant to strong acid and alkali, not resistant to corrosion, poor oxidation resistance, low electrical insulation in harsh environments, weak radiation resistance, poor hydrophilicity after long-term use, easy contamination and short life, high membrane cost and high energy consumption; the prior art is unable to handle high-difficulty wastewater (highly corrosive and highly polluting) such as landfill leachate concentrate, desulfurization wastewater, printing and dyeing wastewater, coal chemical wastewater, electroplating wastewater, leather making wastewater, medical wastewater, and storage chemical wastewater, as well as high-temperature toxic gases and dust. The current situation has always been a weak link in my country's environmental pollution prevention and control work.

[0006] The so-called high-difficulty wastewater generally refers to wastewater containing high ammonia nitrogen, high COD, high salt, high toxicity, and difficult microbial degradation components. If the high-difficulty wastewater is discharged directly into the water body without treatment, it will cause great pollution to the water body; if the high-difficulty wastewater is treated, the cost of treatment is high and the technical difficulty is great; high-difficulty wastewater is a technical problem that cannot be solved by conventional sewage treatment processes. High-difficulty wastewater includes: garbage leachate concentrate, printing and dyeing wastewater, electroplating wastewater, leather wastewater and medical wastewater. The difficulties in treatment are as follows:

[0007] The difficulties of the landfill leachate concentrate are desulfurization, energy consumption reduction, secondary pollution, etc., which cannot be handled by existing technologies and have been troubling domestic sewage experts.

[0008] The difficulties in treating the printing and dyeing wastewater are its complex composition, high organic content, deep chroma, low chemical oxygen demand and relatively low biochemical oxygen demand, poor biodegradability, and large discharge volume, which are difficult to meet with existing technologies.

[0009] The difficulty in treating the coal chemical wastewater is that the wastewater discharge is large and the water quality composition is complex. In addition to inorganic pollution such as ammonia, nitrogen, cyanide, and thiocyanate, it also contains phenols, oils, naphthalene, pyridine, quinoline, anthracene and other heterocyclic and polycyclic aromatic compounds.

[0010] The difficulty of electroplating wastewater is that the water quality of electroplating wastewater is complex and the composition is difficult to control. Chemical wastewater treatment equipment needs to treat heavy metal ions and cyanide such as chromium, copper, nickel, cadmium, zinc, gold, silver, etc. The treatment technology of the present invention will occupy an important position in the treatment of electroplating wastewater in the future because of its high separation efficiency, high precision, and ability to isolate and recover heavy metals.

[0011] The difficulty of the leather wastewater mentioned above is the increase in concentration of the three major indicators (COD, S2-, NH3-N) and the increase in salt content.

[0012] The difficulty of medical wastewater is that the production characteristics of chemical raw material pharmaceutical products are long processes, complex reactions, and many by-products. The reaction raw materials are often solvent substances or ring-structured compounds, which makes the pollutant components in the wastewater complex, with high content, high COD value, many toxic and harmful substances, and many biodegradable substances. This type of wastewater is often difficult to treat and has high treatment costs.

[0013] Among the highly difficult wastewaters mentioned above, strong acid and strong alkali wastewater is difficult to treat. Acidic wastewater mainly comes from chemical plants, fuel plants, electroplating plants, etc. Wastewater treatment mainly treats wastewater containing various harmful substances or heavy metal salts. The mass fraction of acid in wastewater treatment varies greatly, with the lowest being less than 1% and the highest being greater than 10%. Alkaline wastewater mainly comes from printing plants, leather factories, paper mills, refineries, etc. When treating wastewater, organic or inorganic alkalis will be encountered, and the mass fraction of alkalis may be higher than 5% and lower than 1%. In addition to acids and alkalis, acidic and alkaline wastewaters often contain acid salts, basic salts, and other inorganic and organic substances. Summary of the invention

[0014] The purpose of the present invention is to provide a polytetrafluoroethylene and basalt composite fiber hollow ultrafiltration membrane to solve the problems of low filtration accuracy, high temperature resistance, strong acid and alkali corrosion resistance, easy pollution and short life, high membrane cost and inability to treat high-difficulty wastewater in the prior art.

[0015] The object of the present invention is achieved as follows: the hollow ultrafiltration membrane comprises: a basalt fiber layer, a polytetrafluoroethylene layer, micropores and a membrane center hole; the basalt fiber layer is cylindrical, and a polytetrafluoroethylene layer is coated on the outside of the basalt fiber layer; micropores are densely distributed on the cylinder wall of the basalt fiber woven layer, and the bonding surface of the polytetrafluoroethylene layer and the basalt fiber layer is composited at high temperature to form a hollow ultrafiltration membrane with composite fibers having a membrane center hole.

[0016] The basalt fiber layer is made of basalt fibers interwoven and laminated by a braiding machine to form a cylinder, which is the supporting cylinder of the composite fiber hollow ultrafiltration membrane; the center hole of the cylinder is the center hole of the membrane, and the aperture of the center hole of the membrane is woven according to requirements; it can isolate microorganisms, colloids and other turbid substances in water.

[0017] The polytetrafluoroethylene layer is made of polytetrafluoroethylene film which is interwoven and laminated by a braiding machine and is braided and coated on the outside of the basalt fiber layer.

[0018] The polytetrafluoroethylene layer is formed by winding and coating the basalt fiber layer with a polytetrafluoroethylene film.

[0019] Beneficial effect: due to the adoption of the above scheme, the inner layer of the structural layer of the present invention is a basalt fiber layer, the basalt fiber layer is interwoven and laminated by a braiding machine to form a cylinder, which serves as a supporting cylinder for the composite fiber hollow ultrafiltration membrane, and the polytetrafluoroethylene layer coated outside the supporting cylinder is a polytetrafluoroethylene film, which is braided or wound around the supporting cylinder. Since the hot melting temperatures of the basalt fiber and the polytetrafluoroethylene film are close, at 330°C to 340°C, after high-temperature compounding, the basalt fiber and the polytetrafluoroethylene film are easily fused together, and the fused basalt fiber and the polytetrafluoroethylene film are then subjected to hydrophilic treatment to form a composite fiber hollow ultrafiltration membrane.

[0020] Since the inner and outer membranes of the present invention adopt a double-layer woven coating process and then high-temperature composite, the micropores are 0.1-0.3 microns, which can effectively remove bacteria, viruses, suspended matter, etc. in the water, so the filtration accuracy of the present invention is ultra-precise; the outer layer of the present invention is a polytetrafluoroethylene layer, so it has good low friction, smooth surface, easy to clean, low resistance, good flame retardancy, insulation, and long service life; since the continuous use temperature range of basalt fiber is -269-650℃, and polytetrafluoroethylene can be -18 0-260℃ long-term use, so the invention is resistant to high temperature, low temperature, strong acid, strong alkali, corrosion, oxidation, radiation, heat insulation and sound insulation, good filtration, super hydrophilicity, high throughput, compression strength and shear strength, suitable for use in various harsh environments, so for landfill leachate concentrate, desulfurization wastewater, printing and dyeing wastewater, coal chemical wastewater, electroplating wastewater, leather making wastewater, medical wastewater, storage chemical wastewater and other difficult wastewaters, the present invention can still realize physical filtration and purification treatment, solving a major problem of sewage treatment.

[0021] The prior art membrane will fail and be damaged early in strong acid and strong alkali wastewater; while the membrane of the present invention is resistant to strong acid and strong alkali, does not pollute in strong acid and strong alkali wastewater, and has a long service life.

[0022] The basalt fiber is a green, environmentally friendly, high-performance inorganic silicate fiber. It is one of the four major fibers that my country focuses on developing. It is composed of multiple oxides of silicon dioxide, aluminum oxide, calcium oxide and titanium dioxide. Basalt fiber is made by melting basalt stone at a high temperature of 1450℃-1500℃ and then quickly drawing it through a leaky plate. The continuous use temperature range of basalt fiber is -269~650℃. Compared with high-tech fibers such as carbon fiber and aramid ultra-high molecular weight polyethylene fiber (there are many types of high-tech fibers, including high-performance fibers, functional fibers, functional fibers, differential fibers, green fibers, and new chemical fiber varieties), basalt fiber has the characteristics of high strength and high modulus of high-tech fibers. In addition, basalt fiber also has unique high temperature resistance, strong acid and alkali resistance, oxidation resistance, radiation resistance, heat insulation and sound insulation, good filtration, compression strength and shear strength, suitable for use in various harsh environments, and high cost performance, low price, and is a natural inorganic non-metallic material.

[0023] The English abbreviation of polytetrafluoroethylene is PTFE, commonly known as the "king of plastics". It is a high molecular polymer made by polymerization of tetrafluoroethylene as a monomer. After the polytetrafluoroethylene material is subjected to the expansion and biaxial stretching process, the wide band-shaped film made is evenly and densely covered with micropores. The micropores on the film are naturally formed after the polytetrafluoroethylene material is subjected to the expansion and biaxial stretching process. It has a good filtering effect. The micropore diameter of the film is between 0.1 and 0.3 microns, and it is evenly distributed and has a large porosity. It can filter dust particles while maintaining air circulation. Polytetrafluoroethylene has excellent heat and cold resistance and can be used for a long time at -180 to 260°C. This fiber material is resistant to strong acid, strong alkali, oxidation, and various organic substances, and is almost insoluble in all solvents; it is highly lubricating and has the lowest friction coefficient among fiber materials; it is non-adhesive, and the porous membrane has extremely fine and smooth surface fibers, a low friction coefficient, no dust, hydrophobicity, and stable chemical properties. The dust deposited on the surface is easy to clean up, and even wet dust is difficult to adhere. It is the fiber material with the lowest surface tension; it does not adhere to any substance and is non-toxic. In terms of filter material application, it can be used for filtering high-temperature and high-humidity dust and corrosion-resistant gases. It has good low friction, a smooth surface that is easy to clean, low resistance to use, good flame retardancy, insulation and heat insulation, and a long service life.

[0024] The present invention is a hollow ultrafiltration membrane of organic and inorganic high temperature composite, with inner and outer layers full of micropores. It is placed in a polluted water pool to be treated and subjected to negative pressure core extraction. Microorganisms, colloids, and other turbid substances in the water are intercepted and separated by the membrane, and the purified water is extracted from the membrane pores. Similarly, when filtering high-temperature industrial exhaust gas and dust, the polluted toxic particles and dust are isolated, and the purified gas is extracted from the membrane pores.

[0025] The invention solves the problems of low filtration accuracy, high temperature resistance, strong acid and alkali corrosion resistance, easy pollution and short life, high membrane cost and inability to treat high-difficulty wastewater in the prior art, thereby achieving the purpose of the invention.

[0026] Advantages: The invention has high cost performance, low price, non-toxic and environmentally friendly; since basalt is flame retardant, has high breaking strength, is resistant to strong acid and alkali corrosion, is anti-oxidant, anti-radiation, heat-insulating and sound-insulating, super-hydrophilic, pollution-free and has a long service life, and polytetrafluoroethylene has a melting point of 327°C and high fiber strength, the two are compounded at high temperature, so the invention has high breaking strength, good flame retardancy, high modulus, no adhesion, low friction, and can efficiently filter high-temperature toxic gases and dust, thus overcoming the problem of difficult waste water treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a front view of the structural schematic diagram of the present invention.

[0028] Figure 2 It is a top view of the structural schematic diagram of the present invention.

[0029] Figure 3 It is a left view of the structural schematic diagram of the present invention.

[0030] Figure 4 It is a working principle diagram of the external pressure ultrafiltration membrane of the present invention.

[0031] Figure 5 It is a structural diagram of embodiment 2 of the present invention.

[0032] Figure 6 It is a main view of the prior art structural schematic diagram.

[0033] Figure 7 It is a left view of the prior art structural schematic diagram.

[0034] In the figure, 1. basalt fiber layer; 2. polytetrafluoroethylene layer; 3. micropores; 4. central hole of the membrane tube; 5. micropores; 6. purified water; 7. water to be treated; 8. turbid matter.

[0035] 1-1, covering layer; 1-2, fiber yarn braiding layer; 1-3, hollow hole; 1-4, micropore. DETAILED DESCRIPTION

[0036] Embodiment 1: The hollow ultrafiltration membrane comprises: a basalt fiber layer 1, a polytetrafluoroethylene layer 2, micropores 3, and a membrane center hole 4; the basalt fiber layer 1 is cylindrical, and the polytetrafluoroethylene layer 2 is coated on the outside of the basalt fiber layer 1; the micropores 3 are densely distributed on the cylinder wall of the basalt fiber woven layer, and the bonding surface of the polytetrafluoroethylene layer 2 and the basalt fiber layer 1 is high-temperature composited to form a hollow ultrafiltration membrane with composite fibers having a membrane center hole 4.

[0037] The basalt fiber layer 1 is made of basalt fibers woven by a braiding machine into an interwoven and laminated cylinder, which is the supporting cylinder of the composite fiber hollow ultrafiltration membrane; the center hole of the cylinder is the membrane center hole 5, and the aperture of the membrane center hole 5 is woven according to requirements; the micropores 3 on the wall of the basalt fiber layer can isolate microorganisms, colloids and other turbid substances in the water.

[0038] The polytetrafluoroethylene film is a wide band film formed by a biaxial stretching process. The wide band film is woven on the supporting cylinder of the basalt fiber 1 by a weaving machine. During the weaving process, the wide band films are interwoven and laminated with each other, and then the gaps at the weaving intersections are sealed and integrated by hot melting. The micropores on the polytetrafluoroethylene film still exist, and it has a good filtering effect.

[0039] The film made of polytetrafluoroethylene material after the expansion and biaxial stretching process is a microporous film with a pore size between 0.1 and 0.3 microns, uniform distribution, and high porosity. It can filter dust particles while maintaining air circulation. Due to the extremely fine, smooth, low friction coefficient, dust-free, hydrophobic, and stable chemical properties of the polytetrafluoroethylene film surface, the dust deposited on the surface is easy to clean up, and even wet dust is difficult to adhere. The polytetrafluoroethylene layer 2 and the basalt fiber layer 1 are compounded at high temperature to form a hollow fiber ultra-fine filtration membrane.

[0040] Embodiment 2: Figure 5 In the invention, the polytetrafluoroethylene layer 2 adopts a polytetrafluoroethylene film as a wide band film, which is wound and coated on the supporting cylinder of the basalt fiber layer 1, and then the winding and coating gaps are sealed and integrated by hot melting, and the micropores on the polytetrafluoroethylene film still exist, which has a good filtering effect.

[0041] The rest is the same as Example 1.

Claims

1. A polytetrafluoroethylene and basalt composite fiber hollow ultrafiltration membrane, characterized in that: The hollow ultrafiltration membrane includes: a basalt fiber layer, a polytetrafluoroethylene layer, micropores and a membrane center hole; the basalt fiber layer is cylindrical, and a polytetrafluoroethylene layer is coated on the outside of the basalt fiber layer; micropores are densely distributed on the cylinder wall of the basalt fiber woven layer, and the bonding surface of the polytetrafluoroethylene layer and the basalt fiber layer is composited at high temperature to form a hollow ultrafiltration membrane with composite fibers having a membrane center hole; The basalt fiber layer is made of basalt fibers interwoven and laminated by a braiding machine to form a cylinder, which is the supporting cylinder of the composite fiber hollow ultrafiltration membrane; the center hole of the cylinder is the center hole of the membrane, and the aperture of the center hole of the membrane is woven according to requirements; it can isolate microorganisms, colloids and other turbid substances in water; The polytetrafluoroethylene layer is made of polytetrafluoroethylene film which is interwoven and laminated by a braiding machine and braided and coated on the outside of the basalt fiber layer; Or the polytetrafluoroethylene layer is formed by winding a polytetrafluoroethylene film and coating the basalt fiber layer; The thermal melting temperatures of basalt fiber and polytetrafluoroethylene film are close, at 330℃~340℃. After high-temperature compounding, basalt fiber and polytetrafluoroethylene film are easily fused together. The fused basalt fiber and polytetrafluoroethylene film are then hydrophilized to form a composite fiber hollow ultrafiltration membrane.

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