Battery-powered desalination

Scientists said recently they had made a nanotech device to strip salt from seawater, paving the way to small-scale or even battery-powered desalination for drought-hit regions and disaster zones.

Conventional desalination works by forcing water through a membrane to remove molecules of salt.

But this process is an energy-gobbler and the membrane is prone to clogging, which means that desalination plants are inevitably big, expensive, fixed pieces of kit.

The new gadget has been given a proof-of-principle test at Massachusetts Institute of Technology (MIT).

It works through so-called ion concentration polarisation, which occurs when a current of charged ions is passed through an ion-selective membrane. The idea is to create a force that moves charged ions and particles in the water away from the membrane.

When the water passes through the system, salt ions — as well as cells, viruses and micro-organisms — get pushed to the side. This saltier water is then drawn off, leaving only desalted water to pass through the main microchannel.

The tiny device had a recovery rate of 50 per cent, meaning that half of the water used at the start was desalinated. Ninety nine per cent of the salt in this water was removed.

Energy efficiency was similar to or better than state-of-the-art, large-scale desalination plants.

“Rather than competing with larger desalination plants, the methods could be used to make small- or medium-scale systems, with the possibility of battery-powered operation,” their paper, published by the journal Nature Nanotechnology, suggests. — AFP

Courtesy: The Hindu


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