Researchers led by Jongyoon Han at the Massachusetts Institute of Technology have developed a nanotechnology device able to extract salt from seawater, paving the way for small-scale desalination for drought regions and disaster zones.

Conventional desalination works by forcing water through a membrane to remove molecules of salt. This process requires a lot of energy and maintenance of the membrane. As a result, conventional desalination plants are big and expensive.

The new nanotechnology device works by a process called "ion concentration polarisation". A current of charged ions is passed through an ion-selective membrane. This creates a force which moves charged ions and particles in the water away from the membrane. Salt ions and any impurities get pushed to the side. This saltier water is then drawn off, leaving only de-salinated water.

The energy efficiency of the process is comparable to a large-scale desalination plant but small to medium scale, and even battery-power, desalination devices are feasible.

The costs of scaling up the process have not yet been determined but overheads should be lower than in conventional plants because gravity, rather than pumps, can be used to feed the water and because there is less of a problem with membrane fouling.