'Magic' potions for a greener environment

By mixing two solids, chemists can - as if by magic - create a liquid that is non-toxic and biodegradable: yet it can dissolve a range of materials. They have produced a series of such liquids that can be used to substitute the strong and corrosive acids traditionally used as solvents in many industrial chemical reactions.

Safer industrial metal coatings and shinier cars are just two of the possible spin-offs predicted to result from this research.

Mixing an ingredient of chicken feed (choline chloride) with a common fertiliser (urea) is all that it takes to make an ionic liquid. Changing the ingredients, or modifying the relative ratios of the mixture, can alter the physical properties of the liquid, such as its electrical conductivity. Electroplating, electropolishing and metal extraction are just some of the chemical processes that might be improved by substituting ionic liquids for the organic solvents used today.

The liquids can be used to dissolve a range of metals, polymers, sugars and salts and are in a class of their own when it comes to their solvent properties. They are non-volatile, so their use dramatically improves conditions for those who have to work with solvents. They remain liquid over a range of temperatures.

They dissolve compounds that could otherwise only be attacked by highly caustic or corrosive solvents. They can be produced and stored cheaply by selecting the right basic ingredients. And they are biodegradable.

The scientists at the University of Leicester in the English Midlands are working with a consortium of academic and commercial partners to develop the technologies on an industrial scale, and to test them by electroplating high-tech pieces of aircraft.

Project leader Dr Andrew Abbott is enthusiastic about the benefits it could bring. He said: "Finding ways to scale up the benefits of ionic liquids means that we may soon be able to use them in real-life industrial processes. They could make things cheaper, easier, safer and more environmentally friendly."

Commercial applications for the technology include improving the chromium plating process widely used to provide a safe, durable coating to equipment in almost every industry, from medical instruments to the kitchen sink. Although chromium provides the perfect non-reactive coating, the chemicals used to produce it generate highly toxic by-products. An ionic liquid based on a less toxic family of chromium salts could reduce the acidic and metal process vapours generated during the process.

The technology is also good news for the electropolishing industry that uses acids to dissolve a thin layer of a metal coating to give it a smooth, shiny surface. Polishing carries high costs - energy inefficiencies, unpleasant working conditions and high labour requirements. Using ionic liquids improves the working conditions and is 10 times more energy efficient.