Ultrafiltration membrane, is a kind of pore size specifications consistent, the rated pore size range is 0.01 micron.Under proper pressure on one side of the membrane, solute molecules smaller than the pore diameter can be screened out to separate particles larger than 500 Dalton (atomic mass unit) and larger than 10 nanometers in size.Ultrafiltration membrane is one of the earliest polymer separation membranes developed.
Ultrafiltration membrane is widely used in industry and has become one of the new chemical unit operations.For the separation, concentration and purification of biological products, pharmaceutical products and food industry;Also used in blood treatment, wastewater treatment and ultrapure water preparation terminal treatment equipment.In our country, using ultrafiltration membrane has been successfully used by enrichment purification and water purification equipment research and development of Chinese herbal medicine, especially the domestic development of PVC alloy ultrafiltration membrane, to overcome the ordinary PVC material industrialization production of ultrafiltration membrane world difficult problem, reduces the production cost of ultrafiltration membrane and the running energy consumption, improve the ultrafiltration membrane filtration performance and service life, energy conservation and emissions reduction listed by the state intellectual property office of the recommended products.With the development of ultrafiltration membrane, its screening function will be improved and strengthened.
The structure of ultrafiltration membrane can be divided into symmetry and asymmetry.The former is isotropic, no cortex, pores in all directions are the same, belonging to deep filtering;The latter has a denser surface layer and a bottom layer dominated by finger-like structure. The thickness of the surface layer is 0.1 micron or less, and it has ordered micropores. The bottom layer thickness is 200~250 microns, which belongs to the surface filtration.The ultrafiltration membrane used in industry is generally asymmetric membrane.The membrane materials of ultrafiltration membrane mainly include cellulose and its derivatives, polycarbonate, polyvinyl chloride, polyvinylidene fluoride, polysulfone, polyacrylonitrile, polyamide, polysulfone amide, sulfonated polysulfone, cross-chain polyvinyl alcohol, modified acrylic polymer and so on.
Ultrafiltration membrane screening process, driven by the pressure difference on both sides of the membrane, ultrafiltration membrane as the filter medium, under certain pressure, when the original fluid flow through the membrane surface, ultrafiltration membrane surface with many tiny pores allow only water and small molecules through and become through the liquid, and concentrate in the volume is greater than the membrane surface micro aperture that substance is trapped in the liquid side of the membrane, liquid becomes, thus achieve the purpose of purification, separation and enrichment of concentrate.Per metre long silk ultrafiltration membrane on the wall there are about 6 billion 0.01 micron pores, the pore size is only allowed water molecules, the beneficial minerals and trace elements in the water, and are now known to the world's smallest bacteria volume in 0.2 micron, so bacteria as well as the volume is much bigger than bacteria colloid, rust, suspended solids, such as sand, macromolecular organic matter can be trapped and ultrafiltration membrane, the purification process was realized.