Faster, cheaper desalination

A faster, cheaper way to transform seawater into fresh water has been developed by a University of Illinois research team. The invention could make fresh water cheaper and more plentiful for coastal nations, such as Saudi Arabia, when droughts are becoming more frequent around the world.

In the usual process of removing brine from ocean water, the fluid is pushed through a plastic membrane riddled with microscopic holes big enough to let water through but small enough to block the larger molecules of minerals such as salts. However, the membranes are relatively thick, requiring a lot of energy to force the water through, and the pores tend to clog, yielding only a trickle of potable water.

The Illinois group tested several materials and discovered that a sheet of molybdenum disulfide — molybdenum and sulfur — solved the problem.  Molybdenum attracts water, drawing water molecules into the sheet; sulfur repels water, squirting it out of the sheet’s far side, and the process is accomplished with less energy. Also, poking a hole in the sheet creates a nozzle-like shape because of the molecules’ geometry, which helps prevent clogs.