Separation

In chemistry and chemical engineering, a separation process, or a separation technique, or simply a separation, is a method to achieve any mass transfer phenomenon that converts a mixture of substances into two or more distinct product mixtures, at least one of which is enriched in one or more of the mixture's constituents. In some cases, a separation may fully divide the mixture into its pure constituents. Separations are carried out based on differences in chemical properties, or physical properties such as size, shape, mass, density, or chemical affinity, between the constituents of a mixture, and are often classified according to the particular differences they use to achieve separation.

List of separation techniques

• Adsorption, adhesion of atoms, ions or molecules of gas, liquid, or dissolved solids to a surface
• Centrifugation and cyclonic separation, separates based on density differences
• 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 vaporisation
• Electrophoresis, separates organic molecules based on their different interaction with a gel under an electric potential (i.e., different travel)
• Elutriation
• Evaporation
• Extraction
  • Leaching
  • Liquid-liquid extraction
  • Solid phase extraction
• 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 float, and are recovered
  • Deinking, separating hydrophobic ink particles from 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
• 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

Separations based on phase equilibria

gas-liquid	gas-solid	liquid-solid	liquid-liquid	supercritical fluid-solid	supercritical fluid-liquid
distillation	adsorption	precipitation	extraction	supercritical-fluid chromatography	supercritical-fluid extraction
gas-liquid chromatography	sublimation	zone melting	partition chromatography
foam fractionation		crystallization
		ion exchange
		adsorption
		exclusion
		clathration

Separations based on rate phenomena

barrier separations	field separations
membrane filtration	electrophoresis
dialysis	ultracentrifugation
ultrafiltration	electrolysis
electrodialysis	field-flow fractionation
reverse osmosis