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How Much Do You Know About Nanofiltration Membranes?

Nanofiltration membranes are increasingly being utilized in various applications. When applying nanofiltration membranes, there are several important considerations. Without a proper understanding of nanofiltration membrane technology, it can be challenging to use these membranes effectively.

Understanding Nanofiltration Membranes

Nanofiltration membranes are often composite films, with their surface separation layer composed of polyelectrolytes, providing a certain retention rate for inorganic salts. Most commercially available nanofiltration membranes are produced by the interfacial polymerization method, where a thin separation layer with nanoscale pores is formed on a microporous base membrane.

The filtration performance of nanofiltration membranes is also influenced by factors such as membrane charge and the manufacturing process. Different nanofiltration membranes exhibit varying permeability to solutes, with generally higher retention rates for divalent ions compared to monovalent ions. In complex mixtures, the retention rate of monovalent ions may be further reduced. The actual separation performance of nanofiltration membranes is also affected by operational factors such as operating pressure, solute concentration, and temperature. For instance, permeate flux tends to increase with higher operating pressures, while retention rates may decrease with increasing solute concentration.

Knowledge Regarding Nanofiltration Membrane Elements

Enhancing Desalination Rates: Nanofiltration membrane elements elevate desalination rates to a certain degree. The performance of nanofiltration equipment is assessed based on the pollution the membrane elements endure. Concerning pollution, if it does not impair the desalination layer, the system will not reach a critical state.

Recovery After Cleaning: The water production capacity of nanofiltration membrane elements cannot fully recover to one hundred percent after cleaning. Generally, nanofiltration membranes restore most of their initial performance after offline cleaning. It is crucial to certify the membrane element's performance through proper installation.

Professional Cleaning Personnel: Cleaning should be conducted by professionals on-site. Performing offline cleaning on-site aims to prevent insufficient membrane elements and ensures efficient cleaning.

Preventing Membrane Fouling: Preventing membrane fouling is crucial. In the case of surface water sources, during rainy days when water turbidity increases, membrane fouling is more likely to occur. Choosing anti-pollution membranes is advisable. For stable deep groundwater sources, membranes suitable for brackish water can be selected. Conducting backwashing for 10 to 20 minutes before and after daily water production helps prevent membrane fouling. Additionally, routine activities such as backwashing and semi-annual replacement of quartz sand and activated carbon, as well as timely replacement of yellowed PP cotton, help reduce the membrane's burden and minimize the risk of fouling.

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