(a)   Supercritical fluid Extraction –

Supercritical fluid extraction (SFE) is a separation process that uses a supercritical fluid as the solvent.

-        A supercritical fluid is a substance that is above its critical temperature and critical pressure. At this point, the fluid has the properties of both a gas and a liquid, making it an ideal solvent for extraction.

-        At critical point, The Rate of extraction is very High.

-        The most common supercritical fluid used in SFE is carbon dioxide (CO2).

-        CO2 is a good choice because it is non-toxic, non-flammable, and inexpensive. It also has a low critical temperature and pressure, making it easy to work with.

-        Critical temperature of CO2 is 30.980C, and critical Pressure is 73 atm.

Steps –

(i)              The sample to be extracted is placed in a pressure vessel.

(ii)            Supercritical fluid is pumped into the vessel until it reaches the desired pressure and temperature.

(iii)          The supercritical fluid dissolves the desired compound(s) from the sample.

(iv)           The supercritical fluid containing the extracted compound(s) is then removed from the vessel and passed through a separator.

(v)             The pressure is reduced in the separator, causing the supercritical fluid to return to its gaseous state.

(vi)           The extracted compound(s) are then collected from the separator.







Advantages –

-        High selectivity: SFE can be used to selectively extract specific compounds from a mixture without altering their chemical properties.

-        High yield: SFE can achieve high extraction efficiencies, resulting in high yields of the desired compounds.

-        Fast extraction times: SFE is a fast extraction technique, with extraction times typically on the order of minutes or hours.

-        Environmentally friendly: Supercritical fluids are generally non-toxic and non-flammable, and they can be easily recycled after use.

 

Disadvantages –

(i)     High capital costs: SFE equipment is expensive, which can make the process cost-prohibitive for some applications.

(ii)   High operating pressures: SFE requires high operating pressures, which can be challenging to work with.

(iii)  Limited range of solvents: Only a limited number of fluids can be used as supercritical solvents.

(iv)  Not suitable for all compounds: SFE is not suitable for extracting all types of compounds. For example, it is not well-suited for extracting compounds that are highly polar or have high molecular weights.

 

Applications -

(i)              Extraction of essential oils from plants

(ii)            Extraction of caffeine from coffee and tea

(iii)          Extraction of hops for brewing beer

(iv)           Extraction of natural food additives, such as vanillin and beta-carotene

(v)             Extraction of pharmaceuticals and other high-value compounds

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