Separation process

A separation process is a method that converts a mixture or a solution of chemical substances into two or more distinct product mixtures, ^[1] a scientific process of distinguishing two or more substance 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, 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, multiple operations can often be combined to achieve the desired end.

With a few exceptions, elements or compounds exist in nature in an impure state. 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:

analytical: to identify the size of each fraction of a mixture is attributable to each component without attempting to harvest the fractions.
preparative: to "prepare" fractions for input into processes that benefit when components are separated.

Separations may be performed on a small scale, as in a laboratory for analytical purposes, or on a large scale, as .

Complete and incomplete separation

Some types of separation require complete purification of a certain component. An example is the production of aluminum metal from bauxite ore through electrolysis 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 is oil refining. Crude oil occurs naturally as a mixture of various hydrocarbons and impurities. The refining process splits this mixture into other, more valuable mixtures such as natural gas, gasoline and chemical feedstocks, none of which are pure substances, but each of which must be separated from the raw crude.

In both cases of complete and incomplete separation, a series 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 individual distillation steps, each of which produces a different product or intermediate.

List of separation techniques

Sponge, adhesion of atoms, ions or molecules of gas, liquid, or dissolved solids to a surface
Centrifugation and cyclonic separation, separates based on density differences
Chelation
Filtration
Centrifugation

Chromatography

Chromatography separates dissolved substances by different interaction with (i.e., travel through) a material.

Crystallization
Decantation
Demister (vapor), removes liquid droplets from gas streams
Distillation, used for mixtures of liquids with different boiling points
Drying, removes liquid from a solid by vaporization or evaporation

Electrophoresis

Electrophoresis, separates organic molecules based on their different interaction with a gel under an electric potential (i.e., different travel)

Capillary electrophoresis

Electrostatic separation, works on the principle of corona discharge, where two plates are placed close together and high voltage is applied. This high voltage is used to separate the ionized particles.
Elutriation
Evaporation

Extraction

Extraction

Field flow fractionation

Flotation

Flotation
- Dissolved air flotation, removes suspended solids non-selectively from slurry by bubbles that are generated by air coming out of solution
- Froth flotation, recovers valuable, hydrophobic solids by attachment to air bubbles generated by mechanical agitation of an air-slurry mixture, which floats, and are recovered
- Deinking, separating hydrophobic ink particles from the hydrophilic paper pulp in paper recycling

Flocculation, separates a solid from a liquid in a colloid, by use of a flocculant, which promotes the solid clumping into flocs
Filtration – Mesh, bag and paper filters are used to remove large particulates suspended in fluids (e.g., fly ash) while membrane processes including microfiltration, ultrafiltration, nanofiltration, reverse osmosis, dialysis (biochemistry) utilising synthetic membranes, separates micrometre-sized or smaller species
Fractional distillation
Fractional freezing
Oil-water separation, gravimetrically separates suspended oil droplets from waste water in oil refineries, petrochemical and chemical plants, natural gas processing plants and similar industries
Magnetic separation
Precipitation
Recrystallization
Scrubbing, separation of particulates (solids) or gases from a gas stream using liquid.
Sedimentation, separates using vocal density pressure differences
- Gravity separation
Sieving
Stripping
Sublimation
Vapor-liquid separation, separates by gravity, based on the Souders-Brown equation
Winnowing
Zone refining

References

^ Wilson, Ian D.; Adlard, Edward R.; Cooke, Michael; et al., eds. (2000). Encyclopedia of separation science. San Diego: Academic Press. ISBN 978-0-12-226770-3.

External links

Separation of Mixtures Using Different Techniques Archived 2013-06-05 at the Wayback Machine, instructions for performing classroom experiments
Separation of Components of a Mixture Archived 2013-06-05 at the Wayback Machine, instructions for performing classroom experiments

[1] Wilson, Ian D.; Adlard, Edward R.; Cooke, Michael; et al., eds. (2000). Encyclopedia of separation science. San Diego: Academic Press. ISBN 978-0-12-226770-3.

[1]

v t e Separation processes
Processes	Absorption Acid–base extraction Adsorption Chromatography Cross-flow filtration Crystallization Cyclonic separation Decantation Dialysis Dissolved air flotation Distillation Drying Electrochromatography Electrofiltration Extraction Filtration Flocculation Froth flotation Gravity separation Leaching Liquid–liquid extraction Electroextraction Microfiltration Osmosis Precipitation Recrystallization Reverse osmosis Sedimentation Solid-phase extraction Sublimation Ultrafiltration
Devices	API oil–water separator Belt filter Centrifuge Depth filter Electrostatic precipitator Evaporator Filter press Fractionating column Leachate Mixer-settler Protein skimmer Rapid sand filter Rotary vacuum-drum filter Scrubber Spinning cone Still Sublimation apparatus Vacuum ceramic filter
Multiphase systems	Aqueous two-phase system Azeotrope Eutectic
Concepts	Unit operation

v t e Analytical chemistry
Instrumentation	Atomic absorption spectrometer Flame emission spectrometer Gas chromatograph High-performance liquid chromatograph Infrared spectrometer Mass spectrometer Melting point apparatus Microscope Optical spectrometer Spectrophotometer
Techniques	Calorimetry Chromatography Electroanalytical methods Gravimetric analysis Ion mobility spectrometry Mass spectrometry Spectroscopy Titration
Sampling	Coning and quartering Dilution Dissolution Filtration Masking Pulverization Sample preparation Separation process Sub-sampling
Calibration	Chemometrics Calibration curve Matrix effect Internal standard Standard addition Isotope dilution
Prominent publications	Analyst Analytica Chimica Acta Analytical and Bioanalytical Chemistry Analytical Chemistry Analytical Biochemistry
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v t e Branches of chemistry
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See also	History of chemistry Nobel Prize in Chemistry Timeline of chemistry of element discoveries "The central science" Chemical reaction Catalysis Chemical element Chemical compound Atom Molecule Ion Chemical substance Chemical bond Alchemy Quantum mechanics
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Separation process

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