List of purification methods in chemistry
Encyclopedia
Purification in a chemical context is the physical separation of a chemical substance of interest from foreign or contaminating
substances. The following list of chemical purification methods should not be considered exhaustive.
Contamination
Contamination is the presence of a minor and unwanted constituent in material, physical body, natural environment, at a workplace, etc.-Specifics:"Contamination" also has more specific meanings in science:...
substances. The following list of chemical purification methods should not be considered exhaustive.
- Affinity purification is used to purify proteins by retaining them on a column through their affinity to antibodies, enzymes or receptors which have been immobilised on the column.
- FiltrationFiltrationFiltration is commonly the mechanical or physical operation which is used for the separation of solids from fluids by interposing a medium through which only the fluid can pass...
is a mechanical method to separate solidSolidSolid is one of the three classical states of matter . It is characterized by structural rigidity and resistance to changes of shape or volume. Unlike a liquid, a solid object does not flow to take on the shape of its container, nor does it expand to fill the entire volume available to it like a...
s from liquidLiquidLiquid is one of the three classical states of matter . Like a gas, a liquid is able to flow and take the shape of a container. Some liquids resist compression, while others can be compressed. Unlike a gas, a liquid does not disperse to fill every space of a container, and maintains a fairly...
s or gasGasGas is one of the three classical states of matter . Near absolute zero, a substance exists as a solid. As heat is added to this substance it melts into a liquid at its melting point , boils into a gas at its boiling point, and if heated high enough would enter a plasma state in which the electrons...
es by passing the feed stream through a porous sheet such as a cloth or membrane, which retains the solids and allows the liquid to pass through. - CentrifugationCentrifugationCentrifugation is a process that involves the use of the centrifugal force for the sedimentation of mixtures with a centrifuge, used in industry and in laboratory settings. More-dense components of the mixture migrate away from the axis of the centrifuge, while less-dense components of the mixture...
is a process in which light particles are revolved over high speed with the help of electric motor so that the fine particles which do not settle at bottom would settle down. - EvaporationEvaporationEvaporation is a type of vaporization of a liquid that occurs only on the surface of a liquid. The other type of vaporization is boiling, which, instead, occurs on the entire mass of the liquid....
is used to remove volatile liquids from non-volatile solutes which cannot be done through filtration due to the small size of the substances. - Extraction removes an impurity, or recovers a desired product, by dissolving it in a solventSolventA solvent is a liquid, solid, or gas that dissolves another solid, liquid, or gaseous solute, resulting in a solution that is soluble in a certain volume of solvent at a specified temperature...
in which other components of the feed material are insolubleSolubilitySolubility is the property of a solid, liquid, or gaseous chemical substance called solute to dissolve in a solid, liquid, or gaseous solvent to form a homogeneous solution of the solute in the solvent. The solubility of a substance fundamentally depends on the used solvent as well as on...
. - CrystallizationCrystallizationCrystallization is the process of formation of solid crystals precipitating from a solution, melt or more rarely deposited directly from a gas. Crystallization is also a chemical solid–liquid separation technique, in which mass transfer of a solute from the liquid solution to a pure solid...
separates a product from a liquid feedstream, often in extremely pure form, by cooling the feedstream or adding precipitants which lower the solubilitySolubilitySolubility is the property of a solid, liquid, or gaseous chemical substance called solute to dissolve in a solid, liquid, or gaseous solvent to form a homogeneous solution of the solute in the solvent. The solubility of a substance fundamentally depends on the used solvent as well as on...
of the desired product so that it forms crystals. The pure solid crystals are then separated from the remaining liquor by filtration or centrifugation. In analytical and synthetic chemistry work, purchased reagents of doubtful purity may be recrystallized, e.g. dissolved in a very pure solvent, then crystallized and the crystals recovered, in order to improve and/or verify their purity. - AdsorptionAdsorptionAdsorption is the adhesion of atoms, ions, biomolecules or molecules of gas, liquid, or dissolved solids to a surface. This process creates a film of the adsorbate on the surface of the adsorbent. It differs from absorption, in which a fluid permeates or is dissolved by a liquid or solid...
removes a soluble impurity from a feedstream by trapping it on the surface of a solid material such as activated carbonActivated carbonActivated carbon, also called activated charcoal, activated coal or carbo activatus, is a form of carbon that has been processed to make it extremely porous and thus to have a very large surface area available for adsorption or chemical reactions.The word activated in the name is sometimes replaced...
which forms strong noncovalent chemical bonds with the impurity. ChromatographyChromatographyChromatography is the collective term for a set of laboratory techniques for the separation of mixtures....
employs adsorption and desorption on a packed bed of a solid to purify multiple components of a single feedstream. - SmeltingSmeltingSmelting is a form of extractive metallurgy; its main use is to produce a metal from its ore. This includes iron extraction from iron ore, and copper extraction and other base metals from their ores...
is used to produce metalMetalA metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...
s from raw oreOreAn ore is a type of rock that contains minerals with important elements including metals. The ores are extracted through mining; these are then refined to extract the valuable element....
, and involves adding chemicals to the ore and heating it up to the melting point of the metal. - RefiningRefiningRefining is the process of purification of a substance or a form. The term is usually used of a natural resource that is almost in a usable form, but which is more useful in its pure form. For instance, most types of natural petroleum will burn straight from the ground, but it will burn poorly...
is used primarily in the petroleumPetroleumPetroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...
industry, whereby crude oil is heated and separated into stages according to the condensation points of the various elements. - DistillationDistillationDistillation is a method of separating mixtures based on differences in volatilities of components in a boiling liquid mixture. Distillation is a unit operation, or a physical separation process, and not a chemical reaction....
, widely used in petroleum refining and in purification of ethanolEthanolEthanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...
separates volatile liquids on the basis of their boiling point. - Water purificationWater purificationWater purification is the process of removing undesirable chemicals, materials, and biological contaminants from contaminated water. The goal is to produce water fit for a specific purpose...
combines a number of methods to produce potable or drinking waterDrinking waterDrinking water or potable water is water pure enough to be consumed or used with low risk of immediate or long term harm. In most developed countries, the water supplied to households, commerce and industry is all of drinking water standard, even though only a very small proportion is actually...
. - Downstream processingDownstream processingDownstream processing refers to the recovery and purification of biosynthetic products, particularly pharmaceuticals, from natural sources such as animal or plant tissue or fermentation broth, including the recycling of salvageable components and the proper treatment and disposal of waste. It is an...
refers to purification of chemicals, pharmaceuticals and food ingredients produced by fermentationIndustrial fermentationIndustrial fermentation is the intentional use of fermentation by microorganisms such as bacteria and fungi to make products useful to humans. Fermented products have applications as food as well as in general industry.- Food fermentation :...
or synthesized by plant and animal tissues, for example antibiotics, citric acidCitric acidCitric acid is a weak organic acid. It is a natural preservative/conservative and is also used to add an acidic, or sour, taste to foods and soft drinks...
, vitamin EVitamin EVitamin E is used to refer to a group of fat-soluble compounds that include both tocopherols and tocotrienols. There are many different forms of vitamin E, of which γ-tocopherol is the most common in the North American diet. γ-Tocopherol can be found in corn oil, soybean oil, margarine and dressings...
, and insulinInsulinInsulin is a hormone central to regulating carbohydrate and fat metabolism in the body. Insulin causes cells in the liver, muscle, and fat tissue to take up glucose from the blood, storing it as glycogen in the liver and muscle....
. - FractionationFractionationSee also: Fractionated spacecraftFractionation is a separation process in which a certain quantity of a mixture is divided up in a number of smaller quantities in which the composition changes according to a gradient. Fractions are collected based on differences in a specific property of the...
refers to a purification strategy in which some relatively inefficient purification method is repeatedly applied to isolate the desired substance in progressively greater purity. - ElectrolysisElectrolysisIn chemistry and manufacturing, electrolysis is a method of using a direct electric current to drive an otherwise non-spontaneous chemical reaction...
refers to the breakdown of substances using an electric current. This removes impurities in a substance that an electric current is run through - Sublimation is the process of changing of any substance (usually on heating) from a solid to a gas (or from gas to a solid) without passing through liquid phase.