With clean water access becoming an issue of major concern for many of the world’s peoples, we are seeing more investment in water desalination (salt removal) and purification technologies and systems. While current desalination technology (using ‘reverse osmosis’ filtering) can effectively remove salt from water, the process is slow and does not remove some pollutants and microbial pathogens.
Now comes a nano-technology solution from the engineers at MIT in the form of a super-tiny, ion channel polarization (ICP) system–so small that hundreds could fit on one’s thumbnail…
Engineers at MIT–lead by Jongyoon Han–have recently developed a promising nano-tech system for separating charged salt ions from water, and which also separates out unicellular contaminants. But more challenges remain.
In an ICP system, sea water is sent through a tiny channel that is forked at one end, and which has an electrical potential applied to it–repelling the charged ions in the water (the NA+ and Cl – ions) and forcing them to separate from the water and into a separate channel.
- This 4 mm-by-4 mm wafer (insert) may one day help researchers create portable desalination devices that could provide fresh drinking water during emergencies.
The innovative system has also been tested for its ability to filter/separate out potential pathogens in the form of microbes (bacteria, etc.), using red blood cells (RBCs) that contain a fluorescent protein used for tracking cellular movement. The ICP system successfully separated the RBCs out of the water stream (as determined by the lack of fluorescence in the water).
But other challenges and drawbacks remain: the system does not yet remove all pollutants (charcoal filtering would still be necessary), and smaller pathogens might possibly make it through undetected (note: filtering water through a matrix of titanium dioxide [TiO2] nano-particles shows promise for water purification).
Further, the envisioned, portable device has yet to be built, as currently, the desalination system exists only on a small disc and would need to be scaled up considerably to provide appreciable amounts of clean water.
- Seawater Diagram showing concentrations of various salt ions in seawater: Cl− 55%, Na+ 30.6%, SO2−4 7.7%, Mg2+ 3.7%, Ca2+ 1.2%, K+ 1.1%, Other 0.7%
Some critics doubt whether the device is superior to traditional reverse osmosis filtering systems (in which pressure is applied to sea water, forcing the ions through a one-way membrane) in removing salt and thus making ‘potable’ drinkable water. However, this criticism can be addressed as the system is scaled up and water purity analyses are conducted.
The engineers at MIT, reporting in the journal Nature Nanotechnology (March, 2010), see the future, scaled-up version becoming a life-saving gadget in areas hit hard by drought (forcing people to flee towards coastal regions), which climate change forecasts predict will occur at greater frequency in the coming years.
Nanotechnology involves the manufacturing of devices that control matter at the atomic or molecular level. Huge advances in nanotech have been achieved in the past decade, making it one of the most investment-intensive, new industries to emerge in the 21st Century.
More information about this nanotech development can be found here.
Nanotech diagram: Credit: Mark A. Shannon, Nature Nanotechnology, 5, Advance Online Publication (April 2010); (inset) Sung Jae Kim/MIT.
bottom diagram: Seawater Diagram showing concentrations of various salt ions in seawater; derivative work: Tcncv (talk), Sea_salt-e_hg.svg: Hannes Grobe, Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany; SVG version by Stefan Majewsky, Creative Commons Attribution-Share Alike 2.5 Generic license.