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Author Topic: Desalination with Renewable Energy  (Read 20 times)

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AGelbert

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Desalination with Renewable Energy
« on: April 03, 2017, 02:35:39 pm »


Graphene sieve turns seawater into drinking water    

April 3, 2017

A graphene membrane. Credit: The University of Manchester

Graphene-oxide membranes have attracted considerable attention as promising candidates for new filtration technologies. Now the much sought-after development of making membranes capable of sieving common salts has been achieved.

New research demonstrates the real-world potential of providing clean drinking water for millions of people who struggle to access adequate clean water sources.

The new findings from a group of scientists at The University of Manchester were published today in the journal Nature Nanotechnology. Previously graphene-oxide membranes have shown exciting potential for gas separation and water filtration.

Graphene-oxide membranes developed at the National Graphene Institute have already demonstrated the potential of filtering out small nanoparticles, organic molecules, and even large salts. Until now, however, they couldn't be used for sieving common salts used in desalination technologies, which require even smaller sieves.

Previous research at The University of Manchester found that if immersed in water, graphene-oxide membranes become slightly swollen and smaller salts flow through the membrane along with water, but larger ions or molecules are blocked.

The Manchester-based group have now further developed these graphene membranes and found a strategy to avoid the swelling of the membrane when exposed to water. The pore size in the membrane can be precisely controlled which can sieve common salts out of salty water and make it safe to drink.

As the effects of climate change continue to reduce modern city's water supplies, wealthy modern countries are also investing in desalination technologies. Following the severe floods in California major wealthy cities are also looking increasingly to alternative water solutions.

When the common salts are dissolved in water, they always form a 'shell' of water molecules around the salts molecules. This allows the tiny capillaries of the graphene-oxide membranes to block the salt from flowing along with the water. Water molecules are able to pass through the membrane barrier and flow anomalously fast which is ideal for application of these membranes for desalination.

Professor Rahul Nair, at The University of Manchester said: "Realisation of scalable membranes with uniform pore size down to atomic scale is a significant step forward and will open new possibilities for improving the efficiency of desalination technology.

"This is the first clear-cut experiment in this regime. We also demonstrate that there are realistic possibilities to scale up the described approach and mass produce graphene-based membranes with required sieve sizes."

Mr. Jijo Abraham and Dr. Vasu Siddeswara Kalangi were the joint-lead authors on the research paper: "The developed membranes are not only useful for desalination, but the atomic scale tunability of the pore size also opens new opportunity to fabricate membranes with on-demand filtration capable of filtering out ions according to their sizes." said Mr. Abraham.

By 2025 the UN expects that 14% of the world's population will encounter water scarcity. This technology has the potential to revolutionise water filtration across the world, in particular in countries which cannot afford large scale desalination plants.

It is hoped that graphene-oxide membrane systems can be built on smaller scales making this technology accessible to countries which do not have the financial infrastructure to fund large plants without compromising the yield of fresh water produced.

https://phys.org/news/2017-04-graphene-sieve-seawater.html


Agelbert NOTE:
PLEASE, spare me the, "but, but, you need fossil fuels to make graphene" argument. What you NEED is ENERGY. And there are MILLIONS of places on planet earth that you can HARVEST that (RENEWABLE) energy for an on location graphene factory that does not use ANY fossil fuels, EVER! 
Leges         Sine    Moribus     Vanae   
Faith,
if it has not works, is dead, being alone.

AGelbert

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Re: Desalination with Renewable Energy
« Reply #1 on: April 03, 2017, 10:13:00 pm »
Quote
https://phys.org/news/2017-04-graphene-sieve-seawater.html
Graphene sieve turns seawater into drinking water

Agelbert NOTE: PLEASE, spare me the, "but, but, you need fossil fuels to make graphene" argument. What you NEED is ENERGY. And there are MILLIONS of places on planet earth that you can HARVEST that (RENEWABLE) energy for an on location graphene factory that does not use ANY fossil fuels, EVER!

You also need Energy to make the water cross the membrane, because you are reversing Entropy, (there is more Entropy in seawater, a mixture of water and chemicals, than there is in pure water here and a bunch of chemicals there).  In the desalination efforts currently up and running, that Energy is input by applying pressure to the seawater with electricity-power pistons.  The cost of the Energy to do this makes desalination plants in Australia (Brisbane and Sydney) too expensive, white elephants - used only during extreme long-term droughts.

So the third world is never going to get fresh water this way.

The Palloy reading comprehension difficulties, AGAIN. This new desalination filter will NOT require PRESSURE, either osmotic or otherwise. THAT MEANS that there will be ZERO energy REQUIRED for the separation of the major part of the ions from the H2O.

If you had a grasp of biosphere math, enzymatic catalysts in nature and all the various shortcuts the biosphere uses to avoid the STUPID and inefficient HEAT, BEAT and TREAT method humans prefer due to a preference for brute force approaches (as if THAT ruinously energy intensive approach is "IT" in thermodynamics - it's actually the WORST approach!), I would discuss this issue with you.

But since you are routinely deliberately obtuse and selective in the way you measure the COST of energy invested to run processes in civilization and energy returned from those investments (UNETHICALLY DENYING the Social cost of Carbon CONTINUOUSLY), I have nothing but pity for your inflated self confidence in these matters.

You do not have the remotest idea of what you are talking about. Have a nice deluded, ARROGANT, CLOSED MINDED, DAY.
Leges         Sine    Moribus     Vanae   
Faith,
if it has not works, is dead, being alone.

AGelbert

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Re: Desalination with Renewable Energy
« Reply #2 on: April 04, 2017, 05:16:20 pm »
So you are going to undo Entropy without using Energy?  That will be a first for the Universe.

If you built a seawall in a cove with high tidal differences, you could use the pressure of the water against the wall at high tide to push it through desalinating membranes.

Of course, you still would have pumping to do since the fresh water you would be collecting would be below sea level.  You probably could do the pumping with windmills though.  In fact, you could use windmills to pump seawater through desalinating membranes directly.

RE


Thank you, RE, for trying to inject some reality into Palloy's selective thermodynamics fun and games. You see, Palloy is about as objective on these matters of energy in general (AND FOSSIL FUELS IN PARTICULAR) as Putin. Palloy thinks fossil fuels are IT. Of course he pretends to "like" renewable if they, uh, would "only" be as "efficient" as those GLORIOUSLY "energy dense" fossil fuels. It's like talking to a wall. He never stops his wishful thinking about that crap called fossil fuels. His concepts of scientific terms like entropy and thermodynamics and maybe brownean movement and molecular diffusion, etc. are so twisted to defend polluting fuels and ALWAYS find fault with ANY Renewable Energy, that he continues to come up with fascinating bits of erudite sounding irrelevance to try to persuade the uneducated that isn't full of S H I T.

He COMPLETELY missed the point of the graphene filter. Yeah, it takes a LOT of energy to make graphene. BUT, the filter itself will EASILY separate Na and Cl  ions associated with water molecules by gravity alone. Old Palloy likes big factories and scaled up monstrocities that he can point to as being "more efficient". ::)

These graphene filters will be distributed to individuals and will probably NEVER be part of some big desalination facility, although that option is available. And entropy doesn't have beans to do with all this because a solar powered water pump can easily dump sea water into a graphene filter. Gravity will, alas for Palloy, defeat part of all that entropy that poor Palloy is obsessing about (deliberately on purpose, of course   ). The forces inside a graphing filter take care of other entropy caused energy gradient factors by dislodgling the normal charge on a clump of sea water by their whiplashing (graphene isn't perfectly flat - it has a modified chair structure like graphite, but more ordered) around of positive and negative charges in the graphene structure. It's AMAZING STUFF!        

But thanks again for showing how CFS can be applied to the graphene filter to overcome any minor problems. If Palloy wants to make entropy mountains out of gravity assist molehills, that's his problem. I think he takes his talking points from Pruitt and/or Putin.   
Leges         Sine    Moribus     Vanae   
Faith,
if it has not works, is dead, being alone.

 

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