A new approach to water desalination

Published on Jul  2, 2012

The availability of fresh water is dwindling in many parts of the world, a problem that is expected to grow with populations. One promising source of potable water is the world’s virtually limitless supply of seawater, but so far desalination technology has been too expensive for widespread use.

 

Now, MIT researchers have come up with a new approach using a different kind of filtration material: sheets of graphene, a one-atom-thick form of the element carbon, which they say can be far more efficient and possibly less expensive than existing desalination systems.

Read more at MIT News: http://web.mit.edu/newsoffice/2012/gr…

 

Nanotechnology key to new Desalination System

(Nanowerk News) The scarcity of fresh water is an  increasingly serious problem around the world due to growing populations and  diminishing supplies of fresh water. Desalination could help alleviate these  shortages, but it has traditionally been an extremely expensive process.

The demand for water is so great that the worldwide desalination  market is expected to reach an astonishing $87.8 billion by 2016, even though  only about 1 percent of the world’s drinking water is produced by desalination.  There is a huge need for technologies that could reduce this cost.

To help meet this need, the Innovation Fund, the University of  Chicago’s venture philanthropic proof-of-concept fund, awarded Heinrich Jaeger, the William J. Friedman and Alicia Townsend  Professor of Physics at the University of Chicago, $65,000 in its third round of  funding at the end of 2011 to establish the commercial feasibility of a  nanoparticle desalination system that Jaeger invented.

A  grant from the University of Chicago’s Innovation Fund will help Heinrich  Jaeger, PhD, establish the commercial feasibility of a nanoparticle desalination  system.

“In order for desalination to become a real solution to the  growing water scarcity problem, new technologies will be required to reduce the  major cost components of the process,” says Sean Sheridan, an assistant director  at UChicagoTech, which administers the Innovation Fund. “Professor Jaeger’s  nanofiltration technology represents a promising step towards achieving this  goal.”

The high cost of traditional desalination is driven by the price  of energy for high-pressure systems and the capital cost of high-pressure pumps  and seals. Today, recovery of capital and electric power add up to as much as  73% of the cost of desalinated water.

“Our system has the potential to cut these costs by using an  ultrathin self-assembled nanoparticle membrane,” Jaeger says. “Due to its  extreme thinness and excellent permeability characteristics, this nanofiltration  membrane can be used for a wide range of nanofiltration processes at low  pressures, including desalination.”

The nanofiltration membrane was developed by Jaeger and Xiao-Min  Lin, scientist at Argonne’s Center for Nanoscale Materials, together with  University of Chicago postdocs Jinbo He, Edward Barry and Sean McBride. At about  30 nanometers, it is the world’s thinnest and has unique features that may turn  out to make the crucial difference with this technology. The size, shape and  chemical structure of the membrane’s pores can be systematically tuned to  optimize its filtration properties. As a result, it allows 100 times more flow  at the same pressure. In addition, the self-assembly process used to fabricate  it reduces costs.

UChicagoTech’s role

Jaeger has a close working relationship with UChicagoTech, which  is committed to supporting University faculty as they work to translate bench  science to commercial applications. He regularly updates the office on his new  ideas and research results. After he approached UChicagoTech with his initial  data about the nanofiltration system, UChicagoTech helped him to develop a  business proposal and present the opportunity to the Innovation Fund.  UChicagoTech also filed an international patent application at the end of 2012  to protect the technology.

“The Innovation Fund award has been extremely helpful by giving  us not only financial support to further develop this technology in a timely  manner but also by connecting us with a highly supportive group of industry  experts and entrepreneurs,” Jaeger says.

The award is helping to optimize the low-pressure ion  rejection/permeation characteristics for the product; develop and test a system  that is environmentally friendly, compatible with drinking water standards, and  scalable for the production of large volumes of water; and design an assembly  process that is compatible with existing commercial filtration systems.

Initially, Jaeger intends to target small, distributed or mobile  water treatment systems. After being proven on a small scale, the technology  could attract additional funding and be developed for larger systems.

“The potential of this technology to establish a new class of  nanofiltration devices is an exciting prospect,” Jaeger says. “Many purification  processes in a wide range of industries depend on nanofiltration and could  benefit greatly from highly specialized and tunable parameters in a low-pressure  technology. UChicagoTech’s help has been indispensible.”

Source: By Greg Borzo, University of Chicago

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Chemists work to desalt the ocean for drinking water, 1 nanoliter at a time

(Nanowerk News) By creating a small electrical field  that removes salts from seawater, chemists at The University of Texas at Austin  and the University of Marburg in Germany have introduced a new method for the  desalination of seawater that consumes less energy and is dramatically simpler  than conventional techniques. The new method requires so little energy that it  can run on a store-bought battery.

The process evades the problems confronting current desalination  methods by eliminating the need for a membrane and by separating salt from water  at a microscale.

The technique, called electrochemically mediated seawater  desalination, was described last week in the journal Angewandte Chemie (“Electrochemically Mediated Seawater  Desalination”). The research team was led by Richard Crooks of The  University of Texas at Austin and Ulrich Tallarek of the University of Marburg.  It’s patent-pending and is in commercial development by startup company Okeanos  Technologies.

The  left panel shows the salt (which is tagged with a fluorescent tracer) flowing  upward after a voltage is applied by an electrode (the dark rectangle) jutting  into the channel at just the point where it branches. In the right panel no  voltage is being applied. (Image: Kyle Knust)

“The availability of water for drinking and crop irrigation is  one of the most basic requirements for maintaining and improving human health,”  said Crooks, the Robert A. Welch Chair in Chemistry in the College of Natural  Sciences. “Seawater desalination is one way to address this need, but most  current methods for desalinating water rely on expensive and easily contaminated  membranes. The membrane-free method we’ve developed still needs to be refined  and scaled up, but if we can succeed at that, then one day it might be possible  to provide fresh water on a massive scale using a simple, even portable,  system.”

This new method holds particular promise for the water-stressed  areas in which about a third of the planet’s inhabitants live. Many of these  regions have access to abundant seawater but not to the energy infrastructure or  money necessary to desalt water using conventional technology. As a result,  millions of deaths per year in these regions are attributed to water-related  causes.

“People are dying because of a lack of freshwater,” said Tony  Frudakis, founder and CEO of Okeanos Technologies. “And they’ll continue to do  so until there is some kind of breakthrough, and that is what we are hoping our  technology will represent.”

To achieve desalination, the researchers apply a small voltage  (3.0 volts) to a plastic chip filled with seawater. The chip contains a  microchannel with two branches. At the junction of the channel an embedded  electrode neutralizes some of the chloride ions in seawater to create an “ion  depletion zone” that increases the local electric field compared with the rest  of the channel. This change in the electric field is sufficient to redirect  salts into one branch, allowing desalinated water to pass through the other  branch.

“The neutralization reaction occurring at the electrode is key  to removing the salts in seawater,” said Kyle Knust, a graduate student in  Crooks’ lab and first author on the paper.

Like a troll at the foot of the bridge, the ion depletion zone  prevents salt from passing through, resulting in the production of freshwater.

Thus far Crooks and his colleagues have achieved 25 percent  desalination. Although drinking water requires 99 percent desalination, they are  confident that goal can be achieved.

“This was a proof of principle,” said Knust. “We’ve made  comparable performance improvements while developing other applications based on  the formation of an ion depletion zone. That suggests that 99 percent  desalination is not beyond our reach.”

The other major challenge is to scale up the process. Right now  the microchannels, about the size of a human hair, produce about 40 nanoliters  of desalted water per minute. To make this technique practical for individual or  communal use, a device would have to produce liters of water per day. The  authors are confident that this can be achieved as well.

If these engineering challenges are surmounted, they foresee a  future in which the technology is deployed at different scales to meet different  needs.

“You could build a disaster relief array or a municipal-scale  unit,” said Frudakis. “Okeanos has even contemplated building a small system  that would look like a Coke machine and would operate in a standalone fashion to  produce enough water for a small village.”

Source: McGill University

Read more: http://www.nanowerk.com/news2/newsid=31072.php#ixzz2XZnuQSxT