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MIT team invents efficient shockwave-based process for desalination of water.

November 30, 2019


As the availability of clean, potable water
becomes an increasingly urgent issue in many parts of the world, researchers are searching
for new ways to treat salty, brackish or contaminated water to make it usable. Now a team at MIT
has come up with an innovative approach that, unlike most traditional desalination systems,
does not separate ions or water molecules with filters, which can become clogged, or
boiling, which consumes great amounts of energy. Instead, the system uses an electrically driven
shockwave within a stream of flowing water, which pushes salty water to one side of the
flow and fresh water to the other, allowing easy separation of the two streams. According to the researchers, this approach
is a fundamentally new and different separation system. Unlike most other approaches to desalination
or water purification, this one performs a “membraneless separation” of ions and
particles. Membranes in traditional desalination systems,
such as those that use reverse osmosis or electrodialysis, are “selective barriers”. They allow molecules of water to pass through,
but block the larger sodium and chlorine atoms of salt. Compared to conventional electrodialysis,
“This process looks similar, but it’s fundamentally different,” In the new process, called shock electrodialysis,
water flows through a porous material —in this case, made of tiny glass particles, called
a frit — with membranes or electrodes sandwiching the porous material on each side. When an
electric current flows through the system, the salty water divides into regions where
the salt concentration is either depleted or enriched. When that current is increased
to a certain point, it generates a shockwave between these two zones, sharply dividing
the streams and allowing the fresh and salty regions to be separated by a simple physical
barrier at the center of the flow. Even though the system can use membranes on
each side of the porous material, the water flows across those membranes, not through
them. That means they are not as vulnerable to fouling — a buildup of filtered material
— or to degradation due to water pressure, as happens with conventional membrane-based
desalination, including conventional electrodialysis. The underlying phenomenon of generating a
shockwave of salt concentration was discovered a few years ago by the Stanford University. But that finding, which involved experiments
with a tiny microfluidic device and no flowing water, was not used to remove salt from the
water. The new system, by contrast, is a continuous
process, using water flowing through cheap porous media, that should be relatively easy
to scale up for desalination or water purification. One possible application would be in cleaning
the vast amounts of wastewater generated by hydraulic fracturing, or fracking

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2 Comments

  • Reply Zoltan Korda April 6, 2017 at 9:29 pm

    Well, my suggestion is that we make efficient and quick use of this method, because large banks and corporations are buying up huge swaths of land with water aquifers and buying spring water companies because of their belief that water is severely undervalued and under-priced. These companies include Chase, Deutsche Bank, etc. I need not explain that these people, in all probability, do not believe that potable water is a human right, in that they are the same companies who charge huge interest rates on credit cards. I am spreading this information to anyone who will listen because it is my belief that it will take a world-wide resistance in order to stop this disturbing trend. You can read the article if you google the following: "The New 'Water Barons': Wall Street Mega Banks Are Buying Up The World's Water". In fact, these corporations believe that water should be triple, even quadrupled to its existing price.

  • Reply djchinatown November 18, 2018 at 7:20 pm

    Very interesting. Is this being used now?

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