3.4.5 Short application description
Nanofiltration is a pressure related membrane based filtration technology and is much the same as reverse osmosis. The main difference is the degree of removal of monovalent ions.
Membrane filtration operates on the principle that particle separation depends on a pore size and pore size distribution. Membranes require a pressure to drive the clean fluid through the membrane, leaving behind the concentrate containing the separated particles. As the concentration of the fluid being rejected increases, the driving force required to continue concentrating the fluid also increases. The pressure required to work can be induced by pressure or by vacuum.
Nanofiltration is most commonly used to separate a solution that has a mixture of some desirable components and some that are not desirable.
In much of the developing world, clean drinking water is hard to come by, and nanotechnology provides one solution. While nanofiltration is used for the removal of other substances from a water source, it is also commonly used for the desalination of water. As seen in a recent study in South Africa, tests were run using polymeric nanofiltration in conjunction with reverse osmosis to treat brackish groundwater. These tests produced potable water, but as the researchers expected, the reverse osmosis removed a large majority of solutes. This left the water void of any essential nutrients (calcium, magnesium ions, etc.), placing the nutrient levels below that of the required World Health Organization standards.
Unique filtration effectiveness in combination with low pressure drop make nanomaterials a superb filtration media, with application in clean-rooms, surgery rooms and other facilities where high filtration, effectiveness in prohibiting bacteria and other micro-organisms and micro particles is essential.
Dynamic industrial expansion and increasing requirements and standards of air treatment, are factors that lead to the search for new and more effective filtration materials.
Air filters are used in the cleaning of inlet and exhaust air in households, as well as industrial, ventilation and air-conditioning systems. It is also necessary to convey clean air to surgical rooms, to clean rooms, to laboratories and to many industrial processes such as combustion engines, turbo generators, and for the cleaning of waste air, for example from nuclear power stations.
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