Solvent extraction separates substances using a solvent based on their solubility. The substance to be extracted is dissolved in a liquid with a solvent, then shaken and separated. Polar solvents dissolve polar and ionic compounds, while non-polar solvents dissolve non-polar substances. It is used in petrochemical refining, uranium refining, essential oil production, and environmental remediation. It is also used in laboratory analysis.
Solvent extraction is a method of separating one substance from one or more others using a solvent. It is based on variations in the solubility of different compounds in different substances. In most cases, the substance to be extracted, which can be a solid, liquid or gas, is dissolved in a liquid, together with other substances, and a liquid solvent, sometimes called liquid-liquid, is used for the extraction extraction. The technique can also be applied to solid materials that contain compounds that need to be extracted. This method is used extensively in industry and in the laboratory to refine, isolate and purify a variety of useful compounds.
method
A solvent will be chosen which does not mix with the compound in which the substance of interest is currently dissolved, so that, if left undisturbed, they form two separate layers, as with oil and water. It is also important that the compound to be extracted has greater solubility in the solvent that has been added and that this does not dissolve any unwanted substances in the original mixture. Once added, the two liquids can be shaken together for some time and then allowed to sit for a while to separate. The choice of solvent to use will depend on the chemical and physical properties of all the substances present in the mixture. It may be necessary to carry out the process in stages, using different solvents.
Types of solvent
There are two main types. In polar solvents, molecules have a negative electric charge at one end and a positive charge at the other. This is because one of the atoms tends to pull negatively charged electrons towards itself, leaving the rest of the molecule with a positive charge. Oxygen tends to do this, especially when bonded to hydrogen, so many liquids with oxygen-hydrogen bonds, such as water, are polar solvents. Other examples are alcohols, such as methanol and ethanol, and acetone.
In a non-polar solvent, there is relatively little electrical polarity in the molecule. Examples are hydrocarbons, such as pentane, hexane, benzene and toluene, which have only carbon-hydrogen bonds, where none of the atoms tend to push electrons away from each other. Chloroform is another commonly used example. It is a general rule that polar solvents are good at dissolving polar and ionic compounds, but not non-polar substances, while the opposite is true for non-polar solvents. There is, however, a good deal of variation within these categories, and some solvents are more polar than others.
it is used
One of the most widespread industrial uses of this technique is in the petrochemical refining industry. While petroleum products are processed, impurities remain in the raw products. Using suitable solvents, the useful material can be separated from the unwanted substances, and then further extraction can be used to separate the different grades of hydrocarbons according to their uses, which can be as fuels, lubricants or as raw materials for the industry . Solvent extraction is also used in refining uranium for nuclear reactors.
This method is also employed in the production of essential oils, which are used in perfumes, aromatherapy and as flavorings, from plant material. The technique is often preferred where distillation is not suitable. Where the soil has been contaminated with pollutants, solvent extraction can be used to remove some as part of an environmental remediation project. This can be an effective method where the contaminants are themselves solvents. In the laboratory, the technique is widely used in the analysis of samples to determine which substances are present and in what quantities.
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