Physical methods
Filtration: Filtration is a mechanical method used to separate solids from liquids or gases by passing the feed stream through a porous cloth, sheet or membrane, which retains the solids and allows the liquid to pass through.
Crystallization: Crystallization is a novel purification process. Generally, crystallization for purification process operates at lower pressure and temperature. In this process the energy consumption is low. In analytical and synthetic chemistry work, purchased reagents of doubtful purity may be recrystallized e.g. dissolved in a very pure solvent, and then crystallized, and the crystals recovered, in order to improve and/or verify their purity.
Centrifugation: Centrifugation 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.
Evaporation: Evaporation is used to remove volatile liquids from non-volatile solutes which cannot be done through filtration due to the small size of the substances.
Solvent extraction: Solvent extraction removes an impurity or recovers a desired product, by dissolving it in a solvent in which other components of the feed material are soluble.
Adsorption: This technique is used to remove impurities from chemicals by trapping it on the surface of solid adsorbents such as activated carbon which forms strong physical bonds with the impurity. It is not easy to remove very minute particles by filtration because such particles tend to clog the mesh. In such cases use of a filter aid that can selectively adsorb minute impurities is recommended. Any filter aid will do if it is porous, hydrophilic or solvophilic and has a rigid lattice. Celite, diatom earth and activated clay are frequently used. Activated charcoal has a wide surface area and can adsorb many organic compounds and is frequently used to remove smelly substances (in most cases organic compounds) from the air or water. Silica gel can adsorb water and is widely used as a desiccant.
Chromatography: This technique employs adsorption and desorption on a packed bed of a solid to purify multiple components of a single chemical.
Distillation: Distillation is the most commonly applied separation technology. This technique is based on the difference of boiling point of a chemical and the impurities present in it. Separation of liquid mixtures into components is accomplished by fractional distillation. The principle of fractional distillation can be explicable by use of the boiling point-composition diagram.
Filtration: Filtration is a mechanical method used to separate solids from liquids or gases by passing the feed stream through a porous cloth, sheet or membrane, which retains the solids and allows the liquid to pass through.
Crystallization: Crystallization is a novel purification process. Generally, crystallization for purification process operates at lower pressure and temperature. In this process the energy consumption is low. In analytical and synthetic chemistry work, purchased reagents of doubtful purity may be recrystallized e.g. dissolved in a very pure solvent, and then crystallized, and the crystals recovered, in order to improve and/or verify their purity.
Centrifugation: Centrifugation 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.
Evaporation: Evaporation is used to remove volatile liquids from non-volatile solutes which cannot be done through filtration due to the small size of the substances.
Solvent extraction: Solvent extraction removes an impurity or recovers a desired product, by dissolving it in a solvent in which other components of the feed material are soluble.
Adsorption: This technique is used to remove impurities from chemicals by trapping it on the surface of solid adsorbents such as activated carbon which forms strong physical bonds with the impurity. It is not easy to remove very minute particles by filtration because such particles tend to clog the mesh. In such cases use of a filter aid that can selectively adsorb minute impurities is recommended. Any filter aid will do if it is porous, hydrophilic or solvophilic and has a rigid lattice. Celite, diatom earth and activated clay are frequently used. Activated charcoal has a wide surface area and can adsorb many organic compounds and is frequently used to remove smelly substances (in most cases organic compounds) from the air or water. Silica gel can adsorb water and is widely used as a desiccant.
Chromatography: This technique employs adsorption and desorption on a packed bed of a solid to purify multiple components of a single chemical.
Distillation: Distillation is the most commonly applied separation technology. This technique is based on the difference of boiling point of a chemical and the impurities present in it. Separation of liquid mixtures into components is accomplished by fractional distillation. The principle of fractional distillation can be explicable by use of the boiling point-composition diagram.
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