The principle of ultrafiltration is also a principle of membrane separation process. Ultrafiltration uses a pressure active membrane to trap colloids, particles and substances with relatively high molecular weight in water under the action of external driving force (pressure), while water and small solute particles are permeable The separation process through the membrane. Through the micropore screening on the membrane surface, substances with a molecular weight of 3×10000-1×10000 can be retained. When the treated water passes through the membrane surface at a certain flow rate with the help of external pressure, water molecules and solutes with a molecular weight of less than 300-500 permeate the membrane, while particles and macromolecules larger than the membrane pores are intercepted due to sieving. So that the water is purified. In other words, when the water passes through the ultrafiltration membrane, most of the colloidal silicon contained in the water can be removed, and a large amount of organic matter can be removed at the same time.
The principle of ultrafiltration is not complicated. In the ultrafiltration process, because the trapped impurities continuously accumulate on the surface of the membrane, concentration polarization will occur. When the solute concentration on the membrane surface reaches a certain limit, a gel layer is formed, causing the membrane’s water permeability to drop sharply. This limits the application of ultrafiltration to a certain extent. For this reason, it is necessary to conduct research through experiments to determine the best process and operating conditions, minimize the impact of concentration polarization, and make ultrafiltration a reliable reverse osmosis pretreatment method.
In the ultrafiltration process, the deep water is driven by pressure and flows through the membrane surface. The deep agent (water) and small molecular solutes smaller than the membrane pores permeate the membrane to become the purification fluid (filtrate), the solutes larger than the membrane pores and The solute group is intercepted and discharged with the water flow to become a deep shrinkage liquid. The ultrafiltration process is dynamic filtration, and the separation is completed in a flowing state. The solute is only deposited on the membrane surface in a limited way, the ultrafiltration rate decays to a certain extent and tends to balance, and can be restored by cleaning.
Ultrafiltration is one of the membrane separation technologies driven by pressure. For the purpose of separating large molecules from small molecules, the membrane pore size is between 20-1000A°. The hollow fiber ultrafilter (membrane) has the advantages of high filling density in the unit solvent and small floor space.