what are the best approaches to aolvent replacement water or super critical fluid??
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Answer:
A supercritical fluid (SCF) is any substance at a temperature and pressure above its critical point, where distinct liquid and gas phases do not exist, but below the pressure required to compress it into a solid.[1] It can effuse through porous solids like a gas, overcoming the mass transfer limitations that slow liquid transport through such materials. SCF are much superior to gases in their ability to dissolve materials like liquids or solids. In addition, close to the critical point, small changes in pressure or temperature result in large changes in density, allowing many properties of a supercritical fluid to be "fine-tuned".
Supercritical fluids occur in the atmospheres of the gas giants Jupiter and Saturn, the terrestrial planet Venus, and probably in those of the ice giants Uranus and Neptune. Supercritical water is found on Earth, such as the water issuing from black smokers, a type of underwater hydrothermal vent.[2] They are used as a substitute for organic solvents in a range of industrial and laboratory processes. Carbon dioxide and water are the most commonly used supercritical fluids; they are often used for decaffeination and power generation, respectively.
Explanation:
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Abstract
The properties of the supercritical fluid near the critical point can be changed by varying the pressure and temperature, allowing selective and faster extraction. Supercritical fluids exhibit liquid-like density and gas – like viscosity & diffusion coefficients and can penetrate more into the solid matrix inaccessible to liquids due to negligible surface tension and viscosity. They are suitable as a substitute for organic solvents in a range of industrial and laboratory processes. These properties of supercritical fluids are well suited for the extraction of solutes, from various plants, fruits, flowers, seeds, leaves, which cannot be easily extracted using conventional extraction processes. In view of above mentioned advantages, supercritical fluid extraction is becoming increasingly popular in many industries such as petroleum, chemical, food, and perfumery. Supercritical fluids are also used for the extraction of metal ions from aqueous solutions and solid and liquid matrices.