Graphene-Based Sieve Turns Seawater Into Drinking Water (bbc.com)

An anonymous reader quotes a report from BBC: 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. Isolated and characterized by a University of Manchester-led team in 2004, graphene comprises a single layer of carbon atoms arranged in a hexagonal lattice. Its unusual properties, such as extraordinary tensile strength and electrical conductivity, have earmarked it as one of the most promising materials for future applications. But it has been difficult to produce large quantities of single-layer graphene using existing methods, such as chemical vapor deposition (CVD). Current production routes are also quite costly. On the other hand, said Dr Nair, "graphene oxide can be produced by simple oxidation in the lab." Graphene oxide membranes have already proven their worth in sieving out small nanoparticles, organic molecules and even large salts. But until now, they couldn't be used to filter out common salts, which require even smaller sieves. Previous work had shown that graphene oxide membranes became slightly swollen when immersed in water, allowing smaller salts to flow through the pores along with water molecules. Now, Dr Nair and colleagues demonstrated that placing walls made of epoxy resin (a substance used in coatings and glues) on either side of the graphene oxide membrane was sufficient to stop the expansion.

Comments

Re:I'm no chemistry expert, but...

[Mal-2]

I'm no chemistry expert, but isn't graphene oxide simply CO2?

Only the same way graphene is diamond.

Allotropes.

Re:yes but....

[Ol Olsoc]

"The biggest problem isn't removing the salt, it is what to do with all the excess salt that remains. If you dump it back into the ocean, it wipes out all sea life in a large radius. It is pretty devastating."

This is classic enviro bullshit.

And your response is typical reaction to an uninfomed person, making their statement magically said by all people concerned about the environment

You just claimed that if we suck in some seawater, separate the water from the minerals, and then return the minerals to the ocean again, that they magically turn toxic against the same species that have been spending their lives in it? Human desalination cannot change the amount of water or salt in the environment. "Excess salt" does not exist.

Okay lads, let's sit down and talk like adults, because you are both wrong.

One of the first things we have to look at is the amount of salt that might be returned to the ocean. So we have a desalinization plant. Until the plant is taking a significant amount of water out, extracting the salt, and returning the salt to the ocean, it is hardly going to be a blip in the percentage of salt. So that environut you're railing at is generally wrong. Because there is one hellava lot of water in the ocean.

note: because of local conditions, you would want to have a distributed return of the salt. You do not want to just dump it on the shoreline.

But before you go patting yourself on the back, it is possible to get so much salt that it affects what if anything can live in the water. Mono Lake is one example. It has become so salty that no fish live in it. Brine shrimp and algae are it. The salinity level has varied - topping out at alomst 100 framps per liter in the early 80s. We've stopped diverting so much water, and the salinity level is lowering now, the target is 70 grams per liter. The reason we'r eallowing the lake to replenish is that it is an important migratory pathway for a lot of birds. The Great Salt Lake in Utah, which is the remnant of Lake Bonneville is another hypersaline body of water, and ecologically similar to Lake Mono. The Dead Sea is another hypersaline area, and it's named dead sea for a reason. Not much can live there. A few types of bacteria. So you are completely wrong - It is highly possible to have excess salt.

So by spreading the return of the salt to the ocean over an area that avoids local hypersalinization, we'll not have much effect on the salinity of the oceans.