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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.
Sure, but the Water Seer can turn air into drinkable water!
No. But it's not graphene either. Graphene oxide has been around since the 1850s. Graphene (isolated planes of graphite). The first single-layers of graphene were grown in small amounts in the 1970s, but it wasn't really until the 2000s that sizeable amounts produced by macroscopic means were achieved.
This article is playing on graphene hype to try to play up graphene oxide, which is a more mundane substance. Don't get me wrong, it's neat and has uses (due to how planar its membranes are), but it doesn't have the properties of graphene itself. And it's been used in this particular application (desalination membranes) since the 1960s. Lockheed has had them on the market since 2013.
Kneel Before Christ!
Desalination of seawater by reverse osmosis is an old hat. The main challenge from an energy POV is the high pressure differential (and the flow, of course) needed. This won't change much with a new membrane.
Of course, a new membrane might have other desirable properties (cost, robustness, whatever), so every new option is a Good Thing, but the abstract suggests that graphene is something new here. It isn't. Just one more tool in an old chest.
From what I've read in the marine world, there's no cure for clogging, just ways to minimize it. Multi-stage sea strainers cheaply and/or easily replaced and cleaned to get the water as de-gunked as possible before it hits the really good membrane. And enough water storage that you don't have to run your water maker in poor quality harbor or shallows water.