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Aseparation process is a method that converts amixture or asolution of chemical substances into two or more distinct product mixtures,[1] a scientific process of separating two or more substances in order to obtain purity. At least one product mixture from the separation is enriched in one or more of the source mixture's constituents. In some cases, a separation may fully divide the mixture into pure constituents. Separations exploit differences in chemical properties or physical properties (such as size, shape, charge, mass, density, or chemical affinity) between the constituents of a mixture.
Processes are often classified according to the particular properties they exploit to achieve separation. If no single difference can be used to accomplish the desired separation, multipleoperations can often be combined to achieve the desired end. Different processes are also sometimes categorized by their separating agent, i.e.mass separating agents orenergy separating agents.[2] Mass separating agents operate by addition of material to induce separation like the addition of an anti-solvent to induce precipitation. In contrast, energy-based separations cause separation by heating or cooling as in distillation.
Elements andcompounds in nature are impure to some degree. Often these raw materials must go through a separation before they can be put to productive use, making separation techniques essential for the modern industrial economy.
The purpose of separation may be:
Separations may be performed on a small scale, as in alaboratory for analytical purposes, or on a large scale, as in achemical plant.
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Some types of separation require complete purification of a certain component. An example is the production ofaluminum metal frombauxite ore throughelectrolysis refining. In contrast, an incomplete separation process may specify an output to consist of a mixture instead of a single pure component. A good example of an incomplete separation technique isoil refining. Crude oil occurs naturally as a mixture of varioushydrocarbons and impurities. The refining process splits this mixture into other, more valuable mixtures such asnatural gas,gasoline andchemical feedstocks, none of which are pure substances, but each of which must be separated from the raw crude.[citation needed]
In both complete separation and incomplete separation, a series or cascade of separations may be necessary to obtain the desired end products. In the case of oil refining, crude is subjected to a long series of individualdistillation steps, each of which produces a different product orintermediate.[citation needed]
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