Nanofiltration is a liquid-liquid separation method in which salt and small molecular substances pass through the nanofiltration membrane and trap large molecules under the driving force of pressure difference. It is also called low pressure reverse osmosis. The molecular weight cut-off range of nanofiltration membrane is 200-1000MWCO, which is between ultrafiltration and reverse osmosis. It is mainly used for the concentration and purification of macromolecular substances in solution.
Overview of Nanofiltration Membrane
1. The nanofiltration system mostly adopts cross-flow filtration. The cross-flow method avoids the blocking phenomenon during the dead-end filtration process: the material liquid flows through the surface of the membrane, and the liquid and small molecular substances pass through the nanofiltration membrane under the effect of pressure, while insoluble substances and large molecular substances are trapped ;
2. The material liquid has a sufficient flow rate to peel off the material retained by the membrane from the membrane surface. Continuous stripping reduces the degree of membrane pollution, so it can maintain a high membrane permeation flux for a long time.
3. Cross-flow filtration is an effective, reliable and economical membrane separation method.
4. The cross-flow process also avoids the situation of relying on the filter cake layer for filtering during dead-end filtration (such as plate and frame filter presses and drum vacuum filters). The separation occurs on the surface of the membrane rather than in the filter cake layer. The quality of the filtrate is uniform and stable throughout the process. The quality of the filtrate depends on the membrane itself, so that the production process is completely under effective control.