Function of filter membrane

As the original structure of the filter, the filter membrane is very thin, so its filtration mechanism is mainly the screen removal effect, and the adsorption effect is very small. Therefore, the filtration accuracy of the filter membrane is higher, the particle size control is more stable, and the backwashing is easier to restore the performance. However, if the water contains oil, it is easy to block and difficult to backwash. Many researchers at home and abroad have been based on the hydrophilicity of ceramic materials and hope to use ceramic membrane to treat water, but after research, it is generally believed that the membrane pollution problem is still difficult to solve. Membrane fouling is a very complex problem, but one thing is certain, that is, a large amount of organic matter in pollutants is determined, but it usually pays attention to the membrane itself rather than the supporting layer.

According to the adsorption mechanism and pore characteristics of membrane and support layer, it can explain why membrane filtration is not easy to block water and is easy to be blocked by oil and water. For general solid suspensions, particles larger than the membrane pores are captured (shielded) on the surface of the membrane, and particles smaller than the membrane pores pass through the membrane pores because the filter membrane is very thin and cannot be adsorbed on the membrane. Although the supporting layer of these particles is relatively thick, the pores are larger than the membrane pores, which is not enough to produce adsorption. This can only eliminate the influence of screening, so it is easy to backwash. For the oil in water, due to the instability of oil droplets, the oil droplets larger than the membrane pores are not necessarily screened, because they may split into droplets smaller than the membrane pores through the membrane pores. Although they can pass through the membrane itself, they can aggregate into large oil droplets in the support layer and adsorb in the pores of the support layer, which cannot be deleted. Therefore, oily water will block the membrane filter and is difficult to backwash. Therefore, the filter is suitable for water filtration in low permeability formation, but not for oily sewage filtration.

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