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Membrane Material Selection
- Jul 26, 2018 -

Membrane material selection

Membrane materials are at the heart of membrane technology. The adsorption of contaminants on the membrane is the result of interactions between membranes, solvents, and contaminants, and is of course related to membrane surface properties and membrane pore size. According to the nature of the pollutants, the selection of suitable pollution-resistant membrane materials can effectively reduce the adsorption of pollutants by the membrane.

The choice of membrane materials is mainly based on the hydrophobicity, mechanical strength, chargeability, chemical cleaning performance and surface roughness of the membrane materials.

Many pollutants in the sewage system are charged. The metal hydroxide colloid is generally positively charged, and many polymer flocs are negatively charged. Correctly judging the chargeability of the main pollutants in the sewage is of great significance for film selection. If the charge of the ultrafiltration membrane is the same as that of the main pollutant in the sewage, membrane fouling will be reduced due to repulsion. In addition, changing the pH of the sewage can change the zeta potential of the membrane surface. Therefore, it is also possible to reduce membrane fouling by adjusting the pH of the sewage.

For the choice of the hydrophobicity of the membrane material, in general, the hydrophilic membrane has better anti-pollution ability in water treatment, because most of the pollutants in the water are hydrophobic substances. However, the hydrophilic membrane made of a hydrophilic material has a slightly poor chemical stability and a narrow pH range, and a hydrophobic membrane made of a hydrophobic polymer material such as PVDF is more stable in chemical properties and mechanical strength. High and widely used. In order to improve the anti-pollution ability of the hydrophobic membrane, the membrane manufacturer generally adopts different chemical modification methods to modify the original hydrophobic membrane to a hydrophilic membrane. At present, most of the ultrafiltration is a modified hydrophilic membrane, and the degree of hydrophilicity varies depending on the modification method of each manufacturer.