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StringJunky

Graphene-based sieve turns seawater into drinking water

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This is pretty cool and could help solve a major problem for many.

 

 

A UK-based team of researchers has created a graphene-based sieve capable of removing salt from seawater.

The sought-after development could aid the millions of people without ready access to clean drinking water.
The promising graphene oxide sieve could be highly efficient at filtering salts, and will now be tested against existing desalination membranes.
It has previously been difficult to manufacture graphene-based barriers on an industrial scale.
Reporting their results in the journal Nature Nanotechnology, scientists from the University of Manchester, led by Dr Rahul Nair, shows how they solved some of the challenges by using a chemical derivative called graphene oxide. Read more (BBC News)
Edited by StringJunky

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Is graphene actually used for anything?

 

All the reports I see say things like "could be used" or "indications suggest"

There's plenty of information on the chemical properties showing "promise"

and "if this could be scaled up"

Here we have another report of "could be" being touted as a final solution.

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Is graphene actually used for anything?

 

All the reports I see say things like "could be used" or "indications suggest"

There's plenty of information on the chemical properties showing "promise"

and "if this could be scaled up"

Here we have another report of "could be" being touted as a final solution.

I didn't see that BBC report as counting any chickens. The rewards for a successful outcome are nevertheless extremely high. Can you give an example where the difficulties are being downplayed -in this report?

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The difficulty seems to be in flow rate (not precisely mentioned) and also on the overwhelming saturation of graphene oxide membranes with the high salt and biological material content of seawater. A pre-filter for biological material could be used but what about the salts excluded from the final clean water? How easy would it be to get rid of the excess salts?

 

I am very encouraged by the results and this presents hope for water management for people living next to significant bodies of water.

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Taken directly from the paper:

 

The salt rejection properties of our GOGr membranes were further investigated using

forward osmosis, where we employed concentrated sugar (3 M) and
NaCl (0.1 M) solutions as the draw and feed solutions, respectively
(Supplementary Section 7). ..
are the concentration of NaCl at the draw and
feed sides, respectively. Our analysis yielded ≈97% salt rejection
for the GOGr membranes with a water ux of ≈0.5 l m2 h–1
.
Even though the ux is lower than 510 l m–2h–1 typical for
forward osmosis, we believe this characteristic can be signicantly
improved by decreasing the membrane thickness to 1 µm or less
(Supplementary Section 7). Such thicknesses are readily achievable
for GO laminates and can result in uxes >5 l m–2h–1

 

IMO, we now have a good solution for desalination of water using a relatively cheap material (graphene) but the flow rates depend on single salt solutions in controlled experiments where the flow rate achieved is approximately 5 litres per metre squared per hour. You can use thousands of graphene oxide membranes simultaneously to get a reasonable flow rate. However, the amounts of different salts and biological materials would need a pre-filter that would slow down the flow rate. Is it possible to give an impoverished coastal town with sufficient clean water for their drinking needs? I don't know - I am not an engineer or a materials scientist. However, I am sure there are such people on the forum who can chip in on this important matter.
Salty_ocean_6.jpg
.

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I really hope it can be made to work - I'm just tired of seeing announcements of things that

can't be done - or are never done - as if they already exist. Anyone can come up

with ideas that "might" work. I just wish those never made it into newsrooms.

 

Graphene seems to collect these - hence I asked if graphene is actually

used for anything right now?

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Being fair fred, it is quite new. I would imagine that when people learnt about semi conductors and electron holes they might have though... "what's the point?".... Computers were promised to all and people thought "So what, who cares, who needs a computer..?"... and now almost everyone has one in their pocket... but it takes time, many decades even for the potential of something new to be realised.

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Sure you're right DrP

I don't doubt it's great we have this "new" material to experiment with

and it's properties are very interesting.

I just dont want to waste my time reading about what might be possible one day.

I'd much rather it stayed out of the general press until at least a prototype was produced.

 

There's an interesting editorial in the magazine for the med-tech show in Coventry (UK)

that touches on this - pointing out the pharmaceutical industry hates to say too much too

soon because they don't want to have to publish "sorry it doesn't work in after all" papers afterwards.

 

Perhaps the rest of us could learn a little from them.

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OK Fred - I was at a coatings show last year where they were reporting large increases in performance from anti rust primers from the addition of modest amounts graphene powder added to the formulations. They were trying to convince people to take samples for testing in their own products. I said I would test some out, for completely different purposes, but then it turned out they wanted about £1000 for a sample... so I did not bother, lol.

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OK Fred - I was at a coatings show last year where they were reporting large increases in performance from anti rust primers from the addition of modest amounts graphene powder added to the formulations. They were trying to convince people to take samples for testing in their own products. I said I would test some out, for completely different purposes, but then it turned out they wanted about £1000 for a sample... so I did not bother, lol.

The price can't be helping, for a lot people, to experiment empirically (suck-it-and-see) with it and explore its possibilities.

Edited by StringJunky

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Hopefully it is not the only game in town

 

http://www.jta.org/2017/04/04/news-opinion/israel-middle-east/israeli-firm-to-provide-drinking-water-from-the-air-for-india-and-vietnam

 

I am not sure how much of an impact this technology is having...

The model you are suggesting is a water generator that filters and then condenses the water directly from the air. It seems great for isolated villages or small companies but I see the production rate of water unlikely to serve small towns or cities unless it becomes a popular trend, and the technology is rolled out through distributors on a worldwide scale. But, if solar energy can be used to power the device it looks suitable for small scale use in a sustainable manner.

 

 

Water Gen devices use thin plastic leaves to condensed water from warm, humid air. The company says that its largest unit can produce 825 gallons of water per day for only 10 cents a gallon (mostly in energy costs).

 

In India, Water Gen is to deploy its technology to supply drinking water to remote villages in India with solar power from Vikar Solar. The Vietnam project is to generate tens of thousands of liters of water a day for the people of Hanoi. Water Gen also said in a statement that it plans to build a factory to produce technology for sale in the region.

http://www.jta.org/2017/04/04/news-opinion/israel-middle-east/israeli-firm-to-provide-drinking-water-from-the-air-for-india-and-vietnam

Edited by jimmydasaint

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