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Filters
Filters: A device to seperate mixtures
Filtration is a mechanical or physical operation which is used for the seperation of solids from fluids (liquids or gases) by interposing a medium to fluid flow through which the fluid can pass, but the solids (or at least part of the solids) in the fluids are reatined. It has to be emphasised that the separation is NOT complete, and it will depend on the pore size and the thickness of the medium as well as the mechanisms that occur during filtration.
Filtration is used for the purification of fluids: for instance seperating dust from the atmosphere to clean ambient air.
Filtration, as a physical operation is very important in chemistry for the seperation of materials of different chemical composition in solution (or solids which can be disccolved ) by first using a reagent to precipitate one of the materials and then use a filter to separate the solid from the other material(s)
Filtration is also important and widely used as one of the unit operations of chemical engineering.
In chemistry and common usage, a filter is a device (usually a membrane or layer) that is designed to block certain objects or substances while letting others through. Filters are often used to remove harmful substances from air or water, for example to remove air pollution, to make water drinkable, to prepare coffee. In domestic food and drink preparation where bulk solids are removed from liquids, this is often called a strainer.
Filtrate is the liquid produced after filtering a suspension of a solid in a liquid. Filtrand or residue is the solid residue remaining in the filter following filtration.
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