Author: Site Editor Publish Time: 2022-09-27 Origin: Site
The principle of ultrafiltration water treatment is a membrane separation and filtration technique using a certain pressure difference as the driving force, UF ultrafiltration membrane modules are mostly made of polymeric materials. Most suitable for the separation and thickening of solutes in solution, but also commonly used in other separation techniques difficult to complete the separation of colloidal suspensions, its application areas are expanding.
Ultrafiltration membrane components in operation after a period of time to carry out regular cleaning, in order to ensure a certain membrane water flux, and extend the service life of the membrane. Cleaning technology is generally based on the nature of the membrane and the nature of the processing fluid to determine. Usually similar to reverse osmosis membranes, i.e. hydraulic cleaning followed by cleaning with different chemical detergents depending on the situation, ionic solvents for electroplating or electrophoresis materials, and bridge-bonding solvents for water-soluble organic coatings. For different membrane components, different cleaning methods can be used, such as tubular components can be mechanically cleaned with sponge balls, hollow fibre components can be backwashed, etc., for the food industry membrane also needs to be disinfected.
Before use, membrane components are generally immersed in a protective solution for sealed storage to prevent shrinkage of the wet state membrane after dehydration, and the membrane pore size becomes smaller, causing damage to the membrane structure and resulting in a decrease in water flux.
1, short-term preservation: ultrafiltration membrane such as the suspension of the use of ultrafiltration membrane sterilization backwash once, in the backwash water to add 15ppm (ml / L) of bactericidal agent before the ultrafiltration membrane water inlet valve, discharge valve and adjustment valve to close, to maintain the ultrafiltration membrane seal and sterilization role.
2, long-term preservation: ultrafiltration membrane such as long-term stop using, the first ultrafiltration membrane sterilization backwash once, and then in the ultrafiltration membrane in the injection of protective liquid and sealed preservation.
Ultrafiltration membrane structure can be divided into symmetrical and asymmetrical, symmetrical structure is isotropic, no skin, the pores in all directions are the same, belong to the deep filtration. Asymmetric has a denser surface layer and a finger-like structure with a bottom layer that is within 0.1 microns in thickness and has well-arranged micropores, while the bottom layer is 200 to 250 microns in thickness and is surface filtration.
UF ultrafiltration membrane components used in water treatment are generally asymmetric membranes. The membrane materials for ultrafiltration membranes are mainly cellulose, polycarbonate, polyvinyl chloride, polyvinylidene fluoride, polysulfone, polyacrylonitrile, polyamide, polysulfone amide, sulfonated polysulfone, cross-linked polyvinyl alcohol, modified acrylic polymer and other types.