Green aspects


The recent interest surrounding ILs in regards to Green Chemistry and the associated development of new solvents and alternative technologies has largely been a result of their negligible vapour pressure which inhibits evaporation into the air and allows simple recycling and reuse.
The missing vapour pressure has very important advantages compared to other volatile organic chemicals (VOCs). Therefore ionic liquids are not flammable and not explosive and a long range distribution via air can not be expected.1,4,12

The principles of Green Chemistry encompass a new attitude toward industrial practices and chemical syntheses where gaseous, liquid or solid wastes are not treated as inevitable byproducts of the chemical manufacturing chemistry . Instead, the new approach involves steps to decrease or eliminate the hazards in the system and eliminate the waste before it is produced.4
Thus, the potential of ILs to provide a nonvolatile solvent system has become a practical target for reducing waste and hazards by eliminating traditional volatile organic solvents.

But is this already sufficient for safe industrial chemicals of tomorrow?

Despite the excitement, chemists are cautious about too much hype about ionic liquids' greenness:1

"Before we can say that ionic liquids are green, we have to look at their entire life cycle. People are calling ionic liquids green because they are not volatile, but we have to look at how they are made all the way through to recycling and disposal"
Robin Rogers, director of the Center for Green Manufacturing at the University of Alabama in Tuscaloosa.

Environmental issues need to be takled, before ionic liquids can be used routinely.

  • In fact VOCs are used to manufacture ionic liquids, and the ionic liquids themselves are made from species that, before their combination, are VOCs. However, already in 2001 there had been advances in the solventless synthesis of ionic liquids, for instance Rajender Varma and Vasudevan Namboodiri at EPA's National Risk Laboratory in Cincinnati, OH, prepared the 1-alkyl-3-methylimidazolium halides in open containers in a microwave oven without any solvents.

  • Researchers also need to find better ways to recycle ionic liquids.
    Many processes for cleaning up ionic liquids involve washing with water or VOCs.
    "This needs more work, we don't want to create a secondary waste "
    Robin Rogers, first major US meeting on ionic liquids, held in 2001 at the American Chemical Society meeting in San Diego
    For example, in 2001 Notre Dame researcher Joan Brennecke succesfully removed dissolved organic compounds from ionic liquids using supercritical CO2, while Roger and Davis clean the ionic liquids in their contaminated metal process by heating under a vacuum.1

And what about toxicological and eco-toxicological effects of ionic liquids?

let's have a look at ILs' Toxicology...Continue...


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