Drinking water from the sea: Electrochemically mediated seawater desalination in microfluidic systems

Jun 27, 2013

(Phys.org) —A new method for the desalination of sea water has been reported by a team of American and German researchers in the journal Angewandte Chemie. In contrast to conventional methods, this technique consumes little energy and is very simple. This electrochemically mediated seawater desalination is based on a system of microchannels and a bipolar electrode.

The United Nations estimates that one-third of the global population already lives in -stressed areas; this figure is expected to double by 2025. Salt water, on the other hand, is not in short supply. A seemingly obvious solution would be to desalinate seawater; however, this is not so easy. Processes like and subsequent of the water require enormous amounts of energy. Reverse osmosis additionally requires expensive, delicate membranes that are easily fouled, and the water must undergo complex pre-treatment steps.

Developed with the support of the U.S. Department of Energy by Richard M. Crooks (The University of Texas at Austin), Prof. Ulrich Tallarek (University of Marburg, Germany), and their colleagues, the new works without membranes or large amounts of energy. The researchers force the water through a system of two microchannels that are about 22 µm wide, an auxiliary channel and a branched working channel, flowing on to the outlets. The two channels are electrically connected through a bipolar . The auxiliary channel is connected to a voltage source, the working channel is grounded, and a potential difference of 3.0 V is established between the two channels.

The structure of the channel system is critical: The electrode juts into the branch point of the working channel. Because of the voltage, some of the negatively charged in the seawater are oxidized to neutral chlorine at one end of the bipolar electrode. In the narrow channel system, this creates a zone that has a lower number of negatively charged ions, which results in an electric field gradient that directs the positively charged ions in the seawater into the branching channel. Physics requires the electroneutrality within the microchannels to be maintained, so the anions follow the positive ions into the branched channel. The water flowing through the branch is thus enriched with ions, while the water continuing through the main working channel is partially desalinated.

The amount of energy required for this new technique is so low that the system can operate with a simple battery. In contrast to reverse osmosis, it is only necessary to remove sand and sediment from the seawater. No further treatment, disinfection, or addition of chemicals is needed. A simple parallel arrangement of many microchannel systems should allow for an increase in water throughput.

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More information: Crooks, R. Electrochemically Mediated Seawater Desalination, Angewandte Chemie International Edition. dx.doi.org/10.1002/anie.201302577

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MR166
2.7 / 5 (7) Jun 27, 2013
This could be a game changer in many parts of the world.
jscroft
2.3 / 5 (6) Jun 27, 2013
Good Lord, you could build this into a frigging drinking straw!

Also worth pointing out that making fresh water is a critical energy sink aboard steam-powered warships. That's been a major factor in the replacement of steam plants with diesel & gas turbine engines, both of which are otherwise far less fuel-efficient than steam. This development could tip the balance back again.

A game-changer no matter how you look at it.
antialias_physorg
3.7 / 5 (6) Jun 27, 2013
Yep, this looks pretty neat. No moving parts, no membranes...as long as you can keep the channels from clogging this should be good.

(Large scale desalination still is tricky, as you have to dump the now hypersalinated water byproduct somewhere - usually not far from where you gathered the water to start your process. Water turnover isn't infinitely large - even in the ocean - so you tend to salinat your "reservoir" which eventually makes your process less effective. But I'm pretty sure a solution for that detail is far easier than waht they have achieved here)
TheGhostofOtto1923
1 / 5 (3) Jun 27, 2013
Yep, this looks pretty neat. No moving parts, no membranes...as long as you can keep the channels from clogging this should be good.

(Large scale desalination still is tricky, as you have to dump the now hypersalinated water byproduct somewhere - usually not far from where you gathered the water to start your process. Water turnover isn't infinitely large - even in the ocean - so you tend to salinat your "reservoir" which eventually makes your process less effective. But I'm pretty sure a solution for that detail is far easier than waht they have achieved here)
As desalination has been in use for a long time, a little research tells us about how salt brine is a commodity which can be processed and sold and also yield additional energy.
http://www.usbr.g...t089.pdf

-I am sorry but I am going to have to start downrating you for laziness.
Bob_Kob
2.4 / 5 (5) Jun 29, 2013
-I am sorry but I am going to have to start downrating you for laziness.


Heaven forbid anyone who didn't read a 50 page document on desalination before replying to this article.
TheGhostofOtto1923
1 / 5 (3) Jun 30, 2013
-I am sorry but I am going to have to start downrating you for laziness.


Heaven forbid anyone who didn't read a 50 page document on desalination before replying to this article.
Oh sorry bob it took me only 5 min to scan the table of contents and find that the process produces energy from brine, and that salt is sold for money.

Sorry you dont reed so good.
jscroft
1 / 5 (3) Jul 03, 2013
Scott! Good Lord, man, why are you such an unrepentant creep?