Extraction, also known as solvent extraction or liquid-liquid extraction, also known as extraction, is a unit operation in which the components of the system are separated by different solubility in the solvent. In other words, it is a method to transfer solute substances from one solvent to another by using the difference of solubility or distribution coefficient of substances in two mutually insoluble (or slightly soluble) solvents. Widely used in chemical, metallurgical, food, and other industries, general in the petroleum refining industry. In addition, the operation of separating two insoluble liquids after extraction is called separation. We commonly use the QuEChERS extraction tube to extract.
Solid-liquid extraction, also known as a leach, USES a solvent to separate the components of a solid mixture, such as the sugars in beets, from water. Extracting soybean oil from soybean with alcohol to increase oil yield; The liquid extract is made by extracting the active ingredients from the traditional Chinese medicine with water.
Although extraction is often used in chemical experiments, its operation does not cause changes in the chemical composition (or chemical reactions) of the extracted material, so extraction is a physical process.
Extraction is one of the methods used to purify and purify compounds in the organic chemistry laboratory. The desired substance can be extracted from a solid or liquid mixture by extraction.
Theory
The transfer of a substance from one solvent to another by taking advantage of the difference in the solubility or the distribution coefficient of a substance in two insoluble (or slightly soluble) solvents. After repeated extraction, most of the compounds were extracted.
The transfer of a substance from one solvent to another by taking advantage of the difference in the solubility or the distribution coefficient of a substance in two insoluble (or slightly soluble) solvents. After repeated extraction, most of the compounds were extracted.
The solvent extraction process generally consists of extraction, washing, and reverse extraction. Generally, the process of extracting the solute from the organic phase is called extraction, the process of removing other solutes or contents from the loaded organic phase is called scrubbing, and the process of water phase parsing the solute from the organic phase is called stripping.
The distribution law is the main basis of the extraction method theory. At the same time, when a certain soluble substance is added to two kinds of insoluble solvents, it can be dissolved in two kinds of solvents respectively. The experiment proves that, at a certain temperature, when the compound and the two kinds of solvents do not have decomposition, electrolysis, association, and solvation, the ratio of the compound in the two liquid layers is a constant value. This is true regardless of the amount of material added. It’s a physical change.
Organic compounds are generally more soluble in organic solvents than in water. Extracting compounds dissolved in water with organic solvents is a typical example of extraction. By adding a certain amount of electrolyte (such as sodium chloride) into the aqueous solution and using the “salting-out effect” to reduce the solubility of organic matter and extraction solvent in the aqueous solution, the extraction effect is often improved.
To extract the required solute completely from the solution, one extraction is usually not enough and must be repeated several times.
To extract the required solute completely from the solution, one extraction is usually not enough and must be repeated several times.
When you use a certain amount of solvent, you want to have as little left in the water as possible. And KV over KV plus S is always less than 1, so the bigger n is, the smaller wn is. In other words, it is better to divide the solvent several times and do multiple extractions than to do one extraction with the whole amount of solvent. But it should be noted that the above formula applies to solvents that are almost insoluble with water, such as benzene, carbon tetrachloride, etc. And water with a small amount of mutual solvent ether, the above formula is only approximate. But you can still qualitatively point to the expected outcome. Instrument: dispensing funnel.
Common extractants: toluene, dichloromethane, trichloromethane, gasoline, ether, straight-run gasoline, n-butanol, carbon tetrachloride.
Requirements: the extraction agent and the original solvent are immiscible.
The extractant and the solute do not react with each other.
The solubility of the solute in the extractant is much higher than that in the original solvent.
Correlation law: organic solvent is soluble in the organic solvent, the polar solvent is soluble in a polar solvent, and vice versa.
Requirements: the extraction agent and the original solvent are immiscible.
The extractant and the solute do not react with each other.
The solubility of the solute in the extractant is much higher than that in the original solvent.
Correlation law: organic solvent is soluble in the organic solvent, the polar solvent is soluble in a polar solvent, and vice versa.
Evolution
In 1842 e. – m. pelillo studied the extraction of uranyl nitrate from nitric acid solution by ethyl ether. In 1903 l. edilanu used liquid sulfur dioxide to extract aromatic hydrocarbons from kerosene, the first industrial use of extraction.
In the late 1940s, the need to produce nuclear fuel spurred extraction research and development.
In 1842 e. – m. pelillo studied the extraction of uranyl nitrate from nitric acid solution by ethyl ether. In 1903 l. edilanu used liquid sulfur dioxide to extract aromatic hydrocarbons from kerosene, the first industrial use of extraction.
In the late 1940s, the need to produce nuclear fuel spurred extraction research and development.
Today extraction is used in the petroleum refining industry and is widely used in the chemical, metallurgical, food, and atomic industries. For example, extraction has been used in the separation and refining of petroleum fractions, the extraction and purification of uranium, thorium, plutonium, the extraction and separation of non-ferrous metals, rare metals, precious metals, antibiotics, organic acids, alkaloids, and wastewater treatment.
Application
Compared with other methods for separating solution components, extraction has the advantages of operating at room temperature, saving energy, not involving solids and gases, and convenient operation. Extraction in the following several cases is usually beneficial: the boiling point of each component of the material liquid is similar, or even the formation of an azeotrope, for distillation is not easy to be effective occasions, such as the separation of alkane and aromatic hydrocarbons in the petroleum fraction, coal tar dephenolization; The separation of low-concentration high-boiling components, with rectification energy consumption, is large, such as dilute acetic acid dehydration; The separation of a variety of ions, such as the separation of mineral extract and net system, if the addition of chemicals for partial precipitation, not only poor separation quality, and filtration operations, the loss is also large; Separation of unstable substances (such as heat-sensitive substances), such as penicillin from fermentation broth.
Compared with other methods for separating solution components, extraction has the advantages of operating at room temperature, saving energy, not involving solids and gases, and convenient operation. Extraction in the following several cases is usually beneficial: the boiling point of each component of the material liquid is similar, or even the formation of an azeotrope, for distillation is not easy to be effective occasions, such as the separation of alkane and aromatic hydrocarbons in the petroleum fraction, coal tar dephenolization; The separation of low-concentration high-boiling components, with rectification energy consumption, is large, such as dilute acetic acid dehydration; The separation of a variety of ions, such as the separation of mineral extract and net system, if the addition of chemicals for partial precipitation, not only poor separation quality, and filtration operations, the loss is also large; Separation of unstable substances (such as heat-sensitive substances), such as penicillin from fermentation broth.
The application of extraction is still under development. Most elements in the periodic table can be extracted and separated by extraction. The selection and development of extraction agents, the determination of process and operating conditions, as well as the design and calculation of flow and equipment are all subjects of the extraction operation.
For example, in an extraction experiment, iodine water is mixed with carbon tetrachloride or benzene, shaken, and distilled to produce iodine crystals.
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