Membranes are materials that are capable of separating mixtures in solutions or gases. The type of membranes chosen depends upon its application. There are many kinds of membranes available in the market and they can be categorised based on sizes and type of materials. Membranes can be organic, inorganic, ceramic or polymeric.
Generally, membranes are categorised as microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), reverse osmosis (RO), pervaporization, electrodialysis and dialysis. These membranes are differentiated based on their sizes and in some cases mechanisms. One of the common membranes used for production of clean water is UF and NF. UF membranes are capable of removing particulates, colloids and bacteria. Proteins and polysaccharides are also removed. However, NF membranes not only rejects particulates, colloids, bacteria, proteins and polysaccharides, they also reject multivalent ions, amino acids and sugars. Pore sizes of NF are usually in the range of 0.1 to 10 nm and they offer selective solute rejection based on both size and charge. Unlike reverse osmosis (RO) membranes, NF operates at low pressures. That being said, imagine how water filters work!
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AuthorProf. Dr Ani Idris |