Factors affecting filter membrane fouling and methods of prevention

The pollution of the filter membrane refers to the accumulation of substances on the surface of the filter membrane or inside the pores, which leads to a reduction in filtration efficiency and affects the performance and service life of the membrane filtration. So, what are the factors that affect the pollution of the filter membrane and how to prevent it in application?

The influence of particle size and shape in the filtration liquid. During the filtration process, smaller particles can easily penetrate the membrane pores. If the particle size is larger than the membrane pores, the particles will accumulate on the membrane surface or inside the membrane pores, causing physical damage to the membrane surface. Clogging, including some irregular-shaped particles, may be more likely to be trapped in the membrane pores, with more and more attached accumulation, which will later cause small particles to be unable to pass through the membrane pores; therefore, it is necessary to be targeted at the early stage of selection. The filtered particles are analyzed comprehensively. The size of the particles and the size of the membrane pores are selectively and targetedly used. Pre-filtration can be used for some large particles to minimize the contact between the predicted large particles and the membrane surface , reduce the interception pressure of the membrane.

The influence of particle interactions, particle-particle, particle-membrane interactions, electrostatic or van der Waals forces between particles can promote particle aggregation and subsequent fouling. For example, particles with hydrophobic surfaces have stronger interactions with the hydrophobic regions of the membrane. The interaction between charged particles and oppositely charged areas on the membrane surface causes fouling due to electrostatic attraction. When large particle aggregation groups or clusters are formed, pore clogging or surface fouling occurs; in the early stages of membrane selection Some membrane materials can be selected that can minimize the interaction between molecules and pollutants. For example, membranes with hydrated surfaces can prevent fouling by reducing interactions with water-soluble pollutants. The membrane surface can be treated to reduce the Measures such as roughness and energy, adjusting surface charge, or adding antibacterial agents to the surface can reduce the interaction between molecules, pollutants, and membrane surfaces.

The influence of the chemical properties of the solution, the pH value, ionic strength, chemical composition, etc. of the solution are also important factors affecting membrane fouling. They determine the chemical interaction between the membrane surface and the solution. For example, the pH value of the solution will change the particle and membrane surface. charge, the interaction between the particles and the membrane will change, thereby increasing or reducing the formation of fouling; the pH value of the solution exists by itself. If it is the main factor in membrane fouling during filtration, under certain conditions Under this condition, the pH value of the solution can be adjusted in the early stage, and some coagulation or flocculation methods can be added to make the pH neutral before filtration. Large particles can aggregate and precipitate, remove colloidal particles, etc., which will greatly dissolve the chemical. Possibility of contamination.

Due to the influence of bioburden in the solution, microorganisms multiply rapidly on the membrane surface and interact between molecules to form a sticky biofilm, which will lead to membrane fouling. In addition, operating conditions such as filtration speed, pressure and temperature will also affect membrane fouling. For example, too high operating pressure will cause particles to adhere to the membrane surface, and high temperature will promote the accelerated formation of biofouling. Optimize filtration conditions (such as operating pressure, temperature, etc.) , pH value), etc. Regular cleaning and maintenance of the membrane to remove pollutants can reduce the molecular interaction between pollutants and the membrane surface, prevent pollutants from being deposited on the membrane surface, and is also a more effective measure to prevent membrane fouling.

In summary, understanding the above factors and their interactions at the molecular level, various fouling mitigation strategies can be used to minimize membrane fouling, such as pretreatment, coagulation or flocculation, membrane surface modification, etc., which may not be possible. It completely prevents membrane fouling, but can help us reduce fouling, maintain the performance of the filter membrane, and extend the service life of the filter membrane. I hope the above can be a reference for membrane users.