Sunshine instead of moonshine

Researchers in the US have demonstrated a remarkably efficient new way to distil alcohol from water – using light. The method needs less energy than conventional thermal distillation and produces a more concentrated distillate. While the new method is unlikely to displace conventional distillation in industry, the researchers say, it could find niche applications in separation and purification processes.

Naomi Halas and co-workers at Rice University in Houston laced a mixture of water and ethanol with gold–silica nanoparticles and shone laser light on the suspension from above. When light hits a nanoparticle it both absorbs photons, becoming warmer, and scatters photons, which can be picked up by its neighbours, increasing their temperature. In this way light energy becomes trapped close to the surface, causing local heating and driving off the more volatile of the two components – in this case ethanol.

This article provides a link to coverage by Chemistry World