Nano-Elements of Nature: Water

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Though it covers over 70% of the Earth’s surface, only a small fraction of water, less than 3%, is suitable for human use; not only that, but a large portion of this small fraction is hardly accessible to humans, being enclosed in ice reservoirs far in the Poles.

With the steady growth of human population and the accelerated effect of climate change, the challenge of securing sufficient supplies of freshwater is to become more and more compelling in the coming decades. Nanotechnology offers a brighter scenario though, for it represents a means for providing Man with cheap access to the huge unused amounts of salty waters.

A research team led by Jongyoon Han, Associate Professor of Biological Engineering at Massachusetts Institute of Technology (MIT), has innovated a nanotechnology water desalination system that works on the ion* levels. The core mechanism of this system relies on the polarization of ion concentrations. Salty water passes through a channel lined with nano-structured membrane that polarizes salt ions; salts are diverted into a branched brine channel leaving another for salt-free water. Han states this mechanism “moves not only salts, but also any charged colloids in the water source, such as cells or bacteria, thereby fundamentally eliminating the potential for membrane fouling and clogging. This can significantly reduce the complexity and cost of direct seawater desalination”.

It is claimed that in this single-step operation, 99% of the salt contained in seawater is removed; however, it cannot remove non-ionized organic compounds. Hence, to obtain drinkable water, we should further use conventional methods such as charcoal absorption for removing neutral compounds. This technology can be applied to produce small scale, portable desalination systems operated by batteries. However, the team currently aims to build a scaled-up version of the current unit device in order to reach a meaningful flow rate (100 mL/min).

*An Ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge.

References

nanotech-now.com
sigmascan.org
nanowerk.com

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