
Graphene-based sieve turns seawater into drinking water (2017) - 11thEarlOfMar
https://www.bbc.com/news/science-environment-39482342
======
bariswheel
Graphene can do almost anything except exit the lab. I hope to see my
grandchildren see its benefits one day.

[https://www.reddit.com/r/askscience/comments/6tzy80/graphene...](https://www.reddit.com/r/askscience/comments/6tzy80/graphene_can_do_just_about_anything_except_leave/)

~~~
baldfat
I also have the feeling but people continue to state that it takes 15 years
for products to come out in the past. I just don't see how in our day and age
we see all the wonders of graphine promises and still sit here waiting for
some to start coming to fruition. It holds so much promise.

~~~
Haga
It's the fusion of material sciences.

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entee
One of the key questions for desalination is how good can it get. It turns out
that many desalination plants are probably close to the thermodynamic limit
[1, 2], which means that even with new technologies it's likely energy costs
aren't going to go down by an enormous amount. The Ars review suggests the
best we can do is a factor of 3-4x, which is nice, but if we're expecting this
to solve all our water needs we may have another thing coming. For reference,
the cost of water is as low as $25 per acre-foot [3] in CA, and the most
recent desalination plant in San Diego is on the order of $2000 per acre-foot
[4]. Even some of the other estimates in [3] suggest that the average cost of
water is something like $7-800 per acre-foot, which would put us right around
where the thermodynamic limit suggests the floor of desalinated water would
be.

Obviously this is great new tech and more water purification technologies are
always needed, but given the physical boundaries it's unlikely we'll be able
to use desalination as the only solution to water crises. We should still be
figuring out ways to be more efficient about water use.

[1] [https://arstechnica.com/science/2011/08/desalinization-is-
th...](https://arstechnica.com/science/2011/08/desalinization-is-this-as-good-
as-it-gets/)

[2]
[http://science.sciencemag.org/content/333/6043/712](http://science.sciencemag.org/content/333/6043/712)

[3]
[http://www.cpuc.ca.gov/uploadedFiles/CPUC_Public_Website/Con...](http://www.cpuc.ca.gov/uploadedFiles/CPUC_Public_Website/Content/About_Us/Organization/Divisions/Policy_and_Planning/PPD_Work/PPD_Work_Products_\(2014_forward\)/PPD%20-%20Production%20costs%20for%20new%20water.pdf)

[4] [https://www.mercurynews.com/2014/05/29/nations-largest-
ocean...](https://www.mercurynews.com/2014/05/29/nations-largest-ocean-
desalination-plant-goes-up-near-san-diego-future-of-the-california-coast/)

~~~
gizmo686
You are assuming that electricity is the only cost involved.

Based on the numbers in the article, the plant runs at 38-megawatts, consumes
100,000,000 gallons of sea-water a day, and produces 1 gallon of drinkable
water per 2 gallons of sea-water.

Assuming a cost of 15.2 cents/kwh [0] (california seems to be one of the most
expensive states), this comes out to an electricity bill of $451.70/acre-foot.
A non-trivial portion of the total cost, but there is plenty of room for cost
savings without reducing electricity usage.

Its also worth keeping in mind that Isreal exists, relies heavily on
desalination plants, and is an agricultural exporter so we know the situation
is solvable [1]

[0]
[https://www.npr.org/sections/money/2011/10/27/141766341/the-...](https://www.npr.org/sections/money/2011/10/27/141766341/the-
price-of-electricity-in-your-state)

[1] Although will likely involve less wasteful agricutlure.

~~~
mabbo
> Isreal exists, relies heavily on desalination plants, and is an agricultural
> exporter so we know the situation is solvable

Israel also has a lot of reclamation systems. Most of their sewage gets
filtered and the fresh water reused. In most of North America, we give minimal
safe treatment to sewage and then dump it back into our water sources.

That is a very expensive process, but cheaper than desalination usually. We
just need to get over the ick factor.

~~~
atoav
That is interesting to hear, I grew up in the alps, where water plays an
important role in my province (90% of the enery comes from water). You can
drink the water from the lakes etc.

The idea not to perfectly clean the sewage water you created, would sound
irresponsible to anybody living here, as the water cycle becomes very apparent
even to the craziest right wing nut when you live in the mountains.

~~~
ctdonath
Political slam unnecessary.

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Animats
_" 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)."_

Er, yes. All they have is an experimental membrane that won't pass salt. Lots
of those exist. Can you backwash it and get the salt out? It has to handle
concentrated brine in reverse. Plus whatever other crud is in the incoming
water. Most of the headaches of real desalinization plants revolve around
those issues. Fragile membranes are a big issue.

This is in _Nature Nanotechnology_ , not _Desalinization_ , which has a more
practical orientation.

~~~
JoeAltmaier
Its a matter of degree. If the membranes are cheap enough (the point of the
new material in fact) then they don't have to last as long.

~~~
Animats
Claims of "it's much cheaper" from something that isn't even at pilot plant
stage yet are usually suspicious. There are many articles on early-stage
desalination membranes.

From 2010: [1] NanoH20. That actually worked. LG Chem bought the company and
they sell reverse osmosis cartridges using the technology. In the end, it was
about a 20% improvement.[4]

From 2012: [2] Contact membrane. That worked, but doesn't seem to have reached
production. Inventor developed other interesting membrane separation systems,
mostly for non-seawater applications.

From 2018: [3] Improved membrane production process. No product on the market
yet.

Actual progress tends to be in the form of improvements in the 10-20% range.
20% gets you a startup company win.

[1]
[https://www.greentechmedia.com/articles/read/nanoh2o](https://www.greentechmedia.com/articles/read/nanoh2o)

[2] [https://www.scientificamerican.com/article/desalination-
memb...](https://www.scientificamerican.com/article/desalination-membrane-
tech/)

[3] [https://today.uconn.edu/2018/08/new-findings-may-lead-sea-
ch...](https://today.uconn.edu/2018/08/new-findings-may-lead-sea-change-
desalination-technology/)

[4] [http://www.lgwatersolutions.com/en/product/seawater-
ro](http://www.lgwatersolutions.com/en/product/seawater-ro)

------
omosubi
Not to rain on the parade, but is there any example of graphene being used at
scale to do anything? I feel like I've heard about graphene for the last 20
years and how it's going to be a miracle material, but we have little to show
for it besides some nice lab results

~~~
whoisjuan
No because that’s exactly what haven’t been solved: mass production / scale.

And it seems that the progress in that area is pretty slow and anemic.

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gumby
This is a component -- what's the device model? The energy cost of crossing
that gradient will continually increase (you could use gravity, but you still
have to clean the briny side).

The of course brine disposal is a problem.

Don't get me wrong -- I love this work -- but it's just part of the solution.

For a lot of people in poor, hot regions a simple evaporator of concrete with
a glass top is surprisingly effective, both cap ex and op ex (both pretty low,
though they assume a tiny cost of labor).

~~~
lsh
you're the first only commenter to mention the waste products from
desalination:

[https://news.ycombinator.com/item?id=18911969](https://news.ycombinator.com/item?id=18911969)

[https://www.youtube.com/watch?v=qZ5ut_4zKug](https://www.youtube.com/watch?v=qZ5ut_4zKug)

------
QuamStiver
What is it about every HYS in the Science section that attracts the population
control nutters? We all add one to the total. Those screaming for our numbers
to be reduced fail to notice a small part of the solution to the problem every
time they look in the mirror.

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Jakob
Does anyone have a solution by now on what to do with the millions of tons of
salt which are produced by desalinating water?

I read that right now the salt is just dumped somewhere being a huge burden
for flora and fauna.

~~~
mxuribe
Store it in salt domes for use on U.S. roads for the inevitable ice age-level
snow removal that we will have to contend with. Seriously though, i would
guess that this remaining salt is likely not suitable for food
preparation...but can't it be used for salting roads in winter? Or, perhaps,
maybe in molten salt reactors/energy storage systems?

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snazz
Might want to attach the (2017) label, although I hadn’t heard of it until
now.

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chrisweekly
What _can 't_ graphene do?

~~~
HillaryBriss
i must be missing something. the story says they had to:

1\. put epoxy resin on each side of the graphene membrane to prevent swelling
when exposed to water (which is important because if the graphene swells, then
it allows sodium chloride to pass).

2\. "drill" 1 nanometer (or smaller) holes into this membrane

so, what role does the graphene really play here? i mean, as long as you can
drill tiny holes into it -- could the filter be made out of other material?

~~~
peeters
The part about drilling holes was for context, explaining why the alternative
(single-layer graphene) was currently impractical. In the case of graphene
oxide, which this article is about, the challenge was the swelling, the
solution to which seems to be the key discovery in this article.

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salty_biscuits
Osmotic pressure is still a thing and semipermiable membranes already exist.
Will be intersting to see what the actual benefits are compared to what
already exists.

~~~
thatcat
Good point, these graphene membranes would be useful if they were chemical
resistant or stronger. So that the membranes could be backwashed and
chemically cleaned more easily.

~~~
Mangalor
Graphene is incredibly strong.

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SunnyS
I have heard about graphene being some kind of holy water in the last decade
quite a few times. Sadly, it seems only possible to recreate amazing results
lab wise.

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wolfi1
Has there been any progress on it? Seems to be just a lab experiment

~~~
OJFord
This is a comment on graphene as much as it is this particular application!

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AltmousGadfly
Seriously this was news 5 years ago.

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bkmeneguello
Taokey?

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Amendeson530
Excellent news I need a desalinator for my boat and this should bring down
there ridiculess costs, can't wait to see the production model. This will
revolutionize fresh water production for many dry third world countries and
make a lot of revenue for Britain

