Definition of a Green Solvents: A green solvent is the solvent that makes a product or process have the least environmental impact over its entire life cycle.

Green solvents are environmentally friendly solvents, or biosolvents, which are derived from the processing of agricultural crops.  Green solvents were developed as a more environmentally friendly alternative to petrochemical solvents. 

Examples of Green Solvents | Green Chemistry

A classic example is water, which is a very green solvent for consumer products such as toilet bowl cleaner but is not a green solvent for the manufacture of polytetrafluoroethylene. For the production of that polymer, the use of water as solvent requires the addition of perfluorinated surfactants which are highly persistent.

Instead, supercritical carbon dioxide seems to be the greenest solvent for that application because it performs well without any surfactant.

Ethyl lactate, for example, is a green solvent derived from processing corn. Ethyl lactate is the ester of lactic acid. Lactate ester solvents are commonly used solvents in the paints and coatings industry and have numerous attractive advantages including being 100% biodegradable, easy to recycle, noncorrosive, noncarcinogenic, and nonozone-depleting. Ethyl lactate is a particularly attractive solvent for the coatings industry as a result of its high solvency power, high boiling point, low vapor pressure, and low surface tension. It is a desirable coating for wood, polystyrene, and metals and also acts as a very effective paint stripper and graffiti remover. Ethyl lactate has replaced solvents such as toluene, acetone, and xylene, resulting in a much safer workplace. Other applications of ethyl lactate include being an excellent cleaner for the polyurethane industry. Ethyl lactate has a high solvency power, which means it is able to dissolve a wide range of polyurethane resins. The excellent cleaning power of ethyl lactate also means it can be used to clean a variety of metal surfaces, efficiently removing greases, oils, adhesives, and solid fuels. The use of ethyl lactate is highly valuable, as it has eliminated the use of chlorinated solvents.

Green solvents usually are used in the enzyme-assisted extraction methodology, which are the solvents with lowest toxicity such as acetone, ethanol, methanol, 2-propanol, ethyl acetate, isopropyl acetate, methyl ethyl ketone, 1-butanol, and tert-butanol.

 A solvent might be green for one application (because it results in less environmental harm than any other solvent that could be used for that application) and yet not be a green solvent for a different application.

Examples of Green Solvents : Water, PEG, Deep eutectic solvent, Ethyl lactate,
 Ionic liquid, supercritical carbon dioxide, FC-72

In summary, no solvent can be declared to be a "green solvent" unless the declaration is limited to a specific application

Read more: Green chemistry Examples  || 12 Principles of Green Chemistry 

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