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To: Kellis91789

I find it intriguing as well. It’s going to be expensive for a long time, whereas using a couple of carbon wires and 1.2Volts is already cheap.

Desalination: Energy Hog No More?

Copyright Burj Khalifa.

Porifera Inc. – Innovation: Carbon Nanotubes

Desalination has long been the domain of arid, energy-rich states like those in the Persian Gulf thanks to its high-energy footprint. But as populations have boomed, as climate change makes water supplies more uncertain, and as clean water regulations are tightening on industry, more governments and businesses have been looking to desalination.

Efficiency and reallocation are much cheaper and sustainable options for obtaining new water supplies for municipalities. Water reuse in cities is also up and coming, as I will discuss in a future column. But the market to clean industrial wastewater of all kinds is booming.

For all these reasons, innovation in desalination has been continuing apace. At the Blue Tech Forum in San Francisco yesterday, Tyler Algeo, a research analyst at BlueTech Research, said that patents for desalination technologies in 2010 were double the number filed in 2005. Desalination energy inputs have been reduced more than 50 percent in the past decade.

Many entities are interested in these technology breakthroughs, said Algeo: large water technology corporations, venture capital firms, Fortune 500 companies, research groups, consulting engineering practices, and government agencies.

In addition to the Middle East, Australia, Algeria, and Spain now have major desalination programs, he said.

The Forum selected three companies with various approaches to desalination: carbon nanotubes, radial deionization, and biomimetic aquaporin membranes. Today I report highlights from the company that is innovating with carbon nanotubes. Look for the other two technologies in subsequent days.

Porifera Inc. is a two-year-old company based in Hayward, Calif. Vice president of business development, Jeffrey Mendelssohn, said it has achieved a breakthrough in forward osmosis membranes by using carbon nanotubes.

Reverse osmosis is a common filtration technology that uses a pump to push water through a filter. It can be energy intensive, which is why a lot of innovation is happening in forward osmosis.

Forward osmosis uses the thermodynamic law of entropy to separate solids from a fluid. Using a vessel separated into two compartments by a membrane filter, you put a dirty liquid on one side and clean water on the other. The water passes through the membrane until the percentage of solids on both sides is the same.

“Forward osmosis works better in high fouling environments [severely contaminated water] much better than pressure-driven membrane processes [reverse osmosis] because particulate matter in high fouling environments will scrunch up against the membrane under pressure and cause membrane performance to fail,” said Mendelssohn.

Porifera’s membrane isn’t just for desal, although Mendelssohn claims that it can perform salt rejection 10 times better than existing forward-osmosis processes. The company claims it has superior permeability, durability, and selectivity for water purification to other membranes. This innovation was reported in Science magazine in 2006 and was discovered at the Lawrence Livermore National Laboratory by a group of scientists led by Porifera’s principal R&D team.

From its website:

Carbon nanotubes are seamless, atomically smooth carbon “straws” whose diameters range from less than a nanometer to tens of nanometers (a water molecule is ~0.3nm). Water flows through these unique pores 1,000 times faster than through any other pore of similar diameter. Moreover, gases also flow through the nanotubes pores more than 100 times faster than through any other nanometer scale pore. This reduction in flow resistance manifests itself in large enhancements of the membrane permeability and in drastic reduction of viscous losses.

Other applications include dewatering and water treatment of all kinds.

Markets include the Department of Defense, said Mendelssohn, which needs portable on-site desalination to reduce the number of water and fuel resupply convoys in Afghanistan.

The developing world is also a potent marketplace. Dubai’s famous Burj Khalifa skyscraper has no wastewater service, said Mendelssohn, like many newly developed areas of the city. Instead, tanker trucks remove sewage regularly. By installing an on-site water treatment and reuse facility, Porifera could reduce those truck trips by 90 percent, said Mendelssohn.

On the domestic market, the company could clean water from oil and gas hydrofracking at half the cost of current forward osmosis systems and also recycle the water for reuse onsite, said Mendelssohn.

Commercial elements will begin shipping in July, he said.

39 posted on 06/11/2012 10:57:18 AM PDT by Kevmo (SUCINOFRAGOPWIASS: Shut Up, CINOs; Free Republic Aint a GOP Website. It's A Socon Site.)
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To: Kevmo
Forward osmosis uses the thermodynamic law of entropy to separate solids from a fluid. Using a vessel separated into two compartments by a membrane filter, you put a dirty liquid on one side and clean water on the other. The water passes through the membrane until the percentage of solids on both sides is the same.

Doesn't sound very useful, diluting the dirty liquid. Why use a filter at all, just add clean water to the dirty. Diluting isn't separating anything.

42 posted on 06/11/2012 1:31:12 PM PDT by Toddsterpatriot (Math is hard. Harder if you're stupid.)
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To: Kellis91789

Nanoporous graphene could outperform best commercial water desalination techniques
June 22, 2012 by Lisa Zyga

(Top left) Hydrogenated and (top right) hydroxylated graphene pores. (Bottom) Side view of the simulated nanoporous graphene filtering salt ions and producing potable water. Image credit: Cohen-Tanugi and Grossman. ©2012 American Chemical Society
( -- Although oceans and seas contain about 97% of Earth’s water, currently only a fraction of a percent of the world’s potable water supply comes from desalinated salt water. In order to increase our use of salt water, desalination techniques must become more energy-efficient and less expensive to be sustainable. In a new study, two materials scientists from MIT have shown in simulations that nanoporous graphene can filter salt from water at a rate that is 2-3 orders of magnitude faster than today’s best commercial desalination technology, reverse osmosis (RO). The researchers predict that graphene’s superior water permeability could lead to desalination techniques that require less energy and use smaller modules than RO technology, at a cost that will depend on future improvements in graphene fabrication methods.

Water permeability of various desalination techniques. The graphene nanopores can reject salt ions with a water permeability 2-3 orders of magnitude higher than commercial reverse osmosis (RO) techniques. Image credit: Cohen-Tanugi and Grossman. ©2012 American Chemical Society
“Because those carbon atoms at the pore edge would be quite reactive without passivation, in one way or another under realistic experimental conditions they will likely have some form of chemical functionalization,” Grossman said. “This can be controlled to some extent, so we wanted to explore the two limits of hydrophobic vs. hydrophilic edge chemistries. If we had no functional groups (just bare carbon) then within a short time water molecules would dissociate at the pore edge and likely either hydrogenate or hydroxylate those carbons.”

The scientists compared the two chemistries, along with different pore sizes, of nanoporous graphene in their simulations by running saltwater with a salinity of 72 g/L over the membranes, which is about twice the salinity of average seawater (about 35 g/L).
They found that, although the largest nanopores could filter water at the highest rate, large nanopores allowed some salt ions to pass through. The simulations identified an intermediate range of nanopore diameters where the nanopores were large enough to allow the passage of water molecules but small enough to restrict salt ions.
The simulations also showed that the hydroxylated graphene significantly enhances the water permeability, which the scientists attribute to the hydrophilic nature of the hydroxyl groups. Since, in contrast, the hydrogenated pores are hydrophobic, water molecules can flow through only when in a limited number of highly ordered configurations. But hydrophilic groups allow water molecules to have a greater number of hydrogen-bonding configurations inside the pores, and this lack of restrictions increases the water flux.
Overall, the results show that nanoporous graphene can theoretically outperform RO membranes in terms of water permeability, which is expressed in liters of output per square centimeter of membrane per day and per unit of applied pressure. Whereas high-flux RO has a water permeability of a few tenths, the simulations showed that nanoporous graphene’s water permeability ranged from 39 to 66 for pore configurations that exhibited full salt rejection (23.1 Å2 hydrogenated pores and 16.3 Å2 hydroxylated pores). Graphene with the largest hydroxylated pores reached 129, but allowed some passage of salt ions.
The scientists explain that there are two main challenges facing the use of nanoporous graphene for desalination purposes. One is achieving a narrow pore size distribution, although rapid experimental progress in synthesizing highly ordered porous graphene suggests that this may soon be feasible. The other challenge is mechanical stability under applied pressure, which could be achieved using a thin-film support layer such as that used in RO materials.
“Computationally, we're looking at a range of other potentially new ways to engineer membranes for desalination and decontamination,” Grossman said. “Experimentally, we are currently fabricating nanoporous membranes and hope to test their desalination performance in the coming months.”
More information: David Cohen-Tanugi and Jeffrey C. Grossman. “Water Desalination across Nanoporous Graphene.” Nano Letters. DOI: 10.1021/nl3012853
Journal reference:Nano Letters
Copyright 2012

47 posted on 06/22/2012 6:00:03 PM PDT by Kevmo (SUCINOFRAGOPWIASS: Shut Up, CINOs; Free Republic Aint a GOP Website. It's A Socon Site.)
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