Solvent-extraction desalination unveiled at MIT

Yet another desalination innovation is on its way from the Massachusetts Institute of Technology (MIT) – researchers have developed a membrane-free, solvent-extraction method to remove salt from seawater that works at low temperatures.

Although significant advances have been made in membrane desalination in recent years, Prof Gang Chen and MIT colleagues Cambridge, have gone a step further and removed the need for a membrane entirely, according to a report in the Royal Society of Chemistry’s Chemistry World.

Prof Chen explains how his team used decanoic acid as a solvent to mix with the water: “Upon slight heating, our solvent dissolves the water out, leaving salts and impurities behind. Then, upon cooling, the mixture separates into two layers by gravity, releasing pure water. Unlike reverse osmosis, this method does not use expensive membranes and unlike evaporation processes, does not need heating to high temperatures.”

The process was shown to be effective at temperatures as low as 40°C and the recovered water met salinity standards set by the World Health Organisation and the US Environmental Protection Agency.

Chen believes that the work opens up a new field of research in desalination. ‘Being a simple, inexpensive process, directional solvent extraction also bears tremendous commercial potential in the desalination of seawater, clean-up of industrial wastewater, treatment of water produced from oil and gas wells and other such uses,’ he concludes.