Graphene is the sexy new wonder material that seems to have a million and one uses.
From thin flexible screens to solar cells that work when it’s raining, people are
finding all sorts of potential applications for this one-atom thick sheet of carbon.
Now scientists have added another trick to graphene’s repertoire; making seawater drinkable.
Desalination is not a new concept; Israel gets over a quarter of its fresh water from
the mediterranean sea.
But graphene could make the whole process much more efficient.
The main technique used for large scale desalination is called reverse osmosis.
Normal osmosis is where water flows across a semipermeable membrane to areas of higher
saltiness, if you were one of those kids that poured salt on snails, causing the snail to
shrivel up as the water leaves its body, you’ve seen it in action and also, dude, c’mon.
The reverse osmosis used for desalination, however, is when pressure is applied to saltwater
to force it in the directions it doesn’t normally flow, through special membranes to
areas of lower salinity, separating the H2O and telling the salt Na Na Na Na, hey hey
hey, goodbye…
Get it because sodium is…
NA.
Anyway, this all sounds great but it’s not perfect: water from desalination is very expensive,
costing anywhere from $1,000 to $2,500 per acre foot, which is about the amount of water
10 people use in a year.
Generally it’s cheaper to just use less water and recycle the water you do use, but
for some particularly dry places there’s no other option.
Part of the expense comes from pre-treating the water, but pumping the water through the
jelly-roll-like plastic membranes uses a lot of energy.
Computer models have predicted that if we could use super-thin graphene sheets instead
of these thicker membranes, the amount of energy needed for reverse osmosis could be
reduced anywhere from 15-46%.
Less energy used for pumping means less expensive water, and that could make a huge difference
to people in the world’s poorer and drier places.
Unfortunately reality doesn’t always cooperate with computer models, and making graphene
that can separate water from salt isn’t as straightforward as it appears.
Researchers found that when their graphene oxide membranes were submerged in water, they
swole a little bit.
They would still filter nanoparticles, organic molecules, and even larger salts but not the
common salts found in seawater, which are dangerous to drink because they just lead
to more dehydration.
That’s normal osmosis at work again.
But now new findings from the same group of researchers have figured out how to prevent
the swelling and control the pore size.
Now the dissolved salts and the water molecules they bind to can’t get through the pores,
but free water molecules can, and do so surprisingly fast, which is a good thing when you’re
trying to make fresh water as quickly as possible.
The researchers hope that their discovery can make desalination more affordable, which
would be a huge boon to poorer drought stricken countries who can’t afford to build billion-dollar
desalination plants.
With climate change threatening to make droughts even worse, graphene could do more than just
make flexible screens, it could help saves lives.
Oh graphene you’re my hero.
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Do you think desalination is the answer to solving drought or is the problem to huge
to make a dent in?
Let us know in the comments and don’t forget to subscribe while you’re down there.
If you’re worried that making graphene is still too expensive and hard to make to fulfill
it’s promises, good news!
Scientists accidentally found out how to make it cheaper, and Trace tells you about that
right here.
Thank you guys for watching Seeker.