# Graphene-based sieve desalination



## Basil (Feb 4, 2006)

http://www.bbc.co.uk/news/science-environment-39482342

Anyone know the difference between this and RO?


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## Dartskipper (Jan 16, 2015)

Interesting article, both for itself, and the questions it doesn't answer.

How do they drill the small holes? Do they use lasers?

Wasn't waste water passed through those large circular filters at the treatment works to produce potable water? Wouldn't that still be a more economical alternative to graphene filter technology?

There is a treatment works at the head of Galmpton Creek on the River Dart. An inspector would take samples from the outfall at low tide, and test it. If he was thirsty, he would also drink it.

Do scientists sometimes overlook a simple and obvious solution?


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## kewl dude (Jun 1, 2008)

re: Anyone know the difference between this and RO?

Doesn't seem to be any difference? This story describes the new membranes can only be made in a lab. 

Quote

"This is our first demonstration that we can control the spacing [of pores in the membrane] and that we can do desalination, which was not possible before. The next step is to compare this with the state-of-the-art material available on the market," said Dr Nair.

In a news and views article accompanying the study in Nature Nanotechnology, Ram Devanathan, from the Pacific Northwest National Laboratory in Richland, US, said more work needed to be done to produce graphene oxide membranes inexpensively at industrial scales. 

He added that scientists also needed to demonstrate the durability of the membranes under prolonged contact with seawater and ensure the membrane was resistant to "fouling" by salts and biological material (which requires existing barriers to be periodically cleaned or replaced).

Unquote

We have a desal plant nearby, billed as the Worlds Largest:

http://tinyurl.com/l7g6v5p

<https://en.wikipedia.org/wiki/Claude_%22Bud%22_Lewis_Carlsbad_Desalination_Plant>

Quote

The plant is expected to produce 50 million US gallons (190,000 m3) of water per day[30] (0.069 cubic kilometres per annum) with energy use of ~3.6[31] kWh for 1 m3 fresh water, or ~38 MW of average continuous power.[6][32] Another estimate has the plant requiring 40 MW to operate, and a cost of $49 million to $59 million a year.[1] It will provide about 7% of the potable water needs for the San Diego region.[4]

The San Diego County Water Authority signed a contract with the plant operator to purchase a minimum 48,000 acre-feet per year of water, but it can also demand up to a maximum of 56,000 acre-feet per year.[33][34] This is equivalent to 43 million gallons per day (mgd), or about 86% of the plant's output.

The cost of water from the plant will be $100 to $200 more per acre-foot than recycled water, $1,000 to $1,100 more than reservoir water, but $100 to $200 less than importing water from outside the county.[35] As of April 2015, San Diego County imports 90% of its water.[11] A conglomerate of California-based environmentalist groups, the Desal Response Group, claims that the plant will cost San Diego County $108 million a year.

Unquote

http://carlsbaddesal.com/

Is the desal plant URL, but it is off-line right now.

Greg Hayden


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## Engine Serang (Oct 15, 2012)

Probably a play to attract government grants for "research".
RO is a commercially available technology.


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## Duncan112 (Dec 28, 2006)

The only hope is that it would work at a lower pressure than RO, reducing power demand


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## Mad Landsman (Dec 1, 2005)

Is it just me, or is the current state of Graphene an answer looking for questions?


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## chadburn (Jun 2, 2008)

Engine Serang said:


> Probably a play to attract government grants for "research".
> RO is a commercially available technology.


Graphene is indeed the new wonder material, I thought that the people who initially developed the material were based on Teesside and as you have indicated will no doubt be looking for funding.
There will I am sure be a down side to the material (as with Carbon Fibre) but there is no mention of what it is yet.


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## Frank P (Mar 13, 2005)

chadburn said:


> Graphene is indeed the new wonder material, I thought that the people who initially developed the material were based on Teesside .


I understood that it was developed in Manchester........(Thumb)


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## david freeman (Jan 26, 2006)

iF on a cruise it now costs, and one has to be invited to see 'God' or the 'devil's enviroment. This kit as described, it it applied to desalination for boiler water treatment, on a modern day large steamship, or a large cruise liner? either for potable water, or genernal freshwater consumption? Or is the engine crew back to descaling evaporator coils at regular intervals, and what are the dangers to humans in low teperature water desalination plants? Does one have to have a complicated upstream chemical injection/water treatment plant??


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## Ron Stringer (Mar 15, 2005)

Frank P said:


> I understood that it was developed in Manchester........(Thumb)


At Manchester University to be more precise... 

http://www.graphene.manchester.ac.uk/explore/what-can-graphene-do/


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## TonyAllen (Aug 6, 2008)

I have had a salt water swimming pool for the last 20 years.and I take out the plateS once month to clean with COKE COLA,24 hours job done for £2


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## Varley (Oct 1, 2006)

david freeman said:


> iF on a cruise it now costs, and one has to be invited to see 'God' or the 'devil's enviroment. This kit as described, it it applied to desalination for boiler water treatment, on a modern day large steamship, or a large cruise liner? either for potable water, or genernal freshwater consumption? Or is the engine crew back to descaling evaporator coils at regular intervals, and what are the dangers to humans in low teperature water desalination plants? Does one have to have a complicated upstream chemical injection/water treatment plant??


In terms of efficiency surely the method used on a vessel is determined by the heat balance. I cannot imagine a steamship being so efficient elsewhere that an evaporator or two would not improve it. Likewise motorships of higher installed power. I think we were contemplating retrofitting evaporators on offshore tonnage of, then, operating at about 4 MW (50%). Tonnage of this sort of power was also target for RO plant - horses for courses. I suppose the better the membrane the less power it takes to run RO plant but Google is not forthcoming, we will need a real expert for this one.


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## Basil (Feb 4, 2006)

> we will need a real expert for this one


Thank Heaven for that; when I first posed the question I thought someone would immediately say: "Obvious innit?"

I do recollect, in the sixties, being impressed by Bethlehem Steel LP evaporators cf the old Weirs jobs we'd been using before.
Just a minute - didn't Nicholas Parsons serve his engineering apprenticeship at Weirs?


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## Varley (Oct 1, 2006)

Should that have been the case, Basil, Google would have been forthcoming.

On the second that superlative engine is less unforthcoming:

After he had left school, his family contacted relatives in Scotland, who arranged a job for him on Clydebank near Glasgow, where he spent five years employed as an engineering apprentice at Drysdales, a maker of marine pumps.[6] While there, he also spent two six-month periods studying engineering at the University of Glasgow.[7] He never graduated, but finished his apprenticeship and gained sufficient qualifications to become a mechanical engineer. He was offered a position in the Merchant Navy during the Second World War, which he never took up due to illness.

(By 1959 they were a subsidiary of Weirs)

He is so teased on the game shows he hosts that one would have thought he served his time with Trevithick.


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## tsell (Apr 29, 2008)

Dartskipper said:


> Interesting article, both for itself, and the questions it doesn't answer.
> 
> How do they drill the small holes? Do they use lasers?
> 
> ...


G'day, Roy,

I just read your query above, regarding the 'small holes'.
I think a little bit of common sense is required here... the holes were already there and they built the material around them!!(Fly)

Taff


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## Satanic Mechanic (Feb 23, 2009)

Basil said:


> http://www.bbc.co.uk/news/science-environment-39482342
> 
> Anyone know the difference between this and RO?


There is a difference but it's a bit woolly - basically

RO membranes don't really act as strainers per say but as conduits for the diffusion of solvent. As the name suggests by using pressure to overcome the osmotic pressure reverses the flow of solvent and it will flow between the molecules of the membrane

These new ones act as strainers whereby the salt can't fit through the holes

Or sumfing like that


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## Dartskipper (Jan 16, 2015)

tsell said:


> G'day, Roy,
> 
> I just read your query above, regarding the 'small holes'.
> I think a little bit of common sense is required here... the holes were already there and they built the material around them!!(Fly)
> ...


A bit like the old trawler skipper grabbing a handful of holes and a ball of string to make a new net?


I understand now.(Jester)

Cheers(Thumb)


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## chadburn (Jun 2, 2008)

Satanic Mechanic said:


> There is a difference but it's a bit woolly - basically
> 
> RO membranes don't really act as strainers per say but as conduits for the diffusion of solvent. As the name suggests by using pressure to overcome the osmotic pressure reverses the flow of solvent and it will flow between the molecules of the membrane
> 
> ...


I understand that wear can take place around the holes causing an efficiency drop, to combat the wear they have to put a coating over the wonder material.


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## Duncan112 (Dec 28, 2006)

chadburn said:


> I understand that wear can take place around the holes causing an efficiency drop, to combat the wear they have to put a coating over the wonder material.


Nichrome coated Graphene - now there's a thought, a very tiny tig torch would be required.


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## chadburn (Jun 2, 2008)

At least there will be no temptation for people to put their fingers in the holes(Sad)
That's four and a half Pints please.


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## Duncan112 (Dec 28, 2006)

chadburn said:


> At least there will be no temptation for people to put their fingers in the holes(Sad)
> That's four and a half Pints please.


First thing I was told at sea was never use your finger to line up holes.

Sailed with a second who had lost the end of his finger - he said he phoned his wife to tell her and she replied "The whole finger?" response "Yes, but not all of it!!"


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## chadburn (Jun 2, 2008)

Nice one Duncan(Jester), the warning against 'hole poking' down the Engineroom was part of my induction chat with the new members of the Engineroom team.


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## Satanic Mechanic (Feb 23, 2009)

chadburn said:


> Nice one Duncan(Jester), the warning against 'hole poking' down the Engineroom was part of my induction chat with the new members of the Engineroom team.


I was always good with the general rule of thumb 'don't stick your finger where you wouldn't stick your cock' 

This also works in reverse


How cool is this I'm sending this from a plane half way across the Atlantic bound for Montreal


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## Basil (Feb 4, 2006)

Satanic Mechanic said:


> I was always good with the general rule of thumb 'don't stick your finger where you wouldn't stick your cock'
> 
> This also works in reverse
> 
> ...


Lest you should think that HM commissioned officers do not use engine room idiom, I recollect an RAF flight commander (of cadet officers) remarking, upon our return from leave, that he would hesitate to place the tip of his umbrella where we had probably placed our gentleman's prized possession.

"How cool is this" It is, in fact, very cool. When I last worked we used HF radio for long range oceanic air traffic control. This at a time when passengers, and cabin crew, who were prepared to pay, could use crystal clear satcom. I can assure you that HF was difficult and unreliable and unsuited to flying across the World at 600mph. Funny old thing, HF worked fine with Portishead and Stockholm.
The unreliability did work to my advantage once when a central African state tried to refuse us overflight clearance - presumably because the dash had gone to the wrong bank account.
ATC: "You are not cleared to enter our airspace!"
Bas: "Unreadable, say again!" 
Bas Thinks: 'We can't re-route and negotiate a crossing clearance with the country next door in the time available. Do they have radar and can they really get a fighter airborne in the middle of the night?' Answer to both: High prob NO.
Once in VHF contact:
Bas: "HF was unreadable, terribly sorry, do apologise, will speak to company and ensure that overflight fees are paid."
After leaving their airspace:
Bas: "Hey, company, FFS do not send anyone over ****** until this is sorted out!"


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