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UK researchers create graphene-based sieve that can remove salt from seawater
- dijit 10y agoI hope this isn't Science being taken to a irrational extreme, as tends to happen with news and science. This has incredible potential not only for the developing world but also for sea travel and even the fact that we are running out of drinkable water in the west. Only 2.5% of the water on the planet is even potentially drinkable. If we were able to convert even 1%. Crazy.
- larsiusprime 10y agoThe question, as always, is how much energy it takes to do the filtering.
- daveguy 10y agoYup. Sieve implies that the only energy required is that necessary to pump the water to a level above the filter. I highly doubt that is the case. Surely you need some significant pressure differential. Even with pores the size of proteins (100x+ larger) you need pressure.
- larsiusprime 10y agoIndeed, and even if we live in a magical world where it was 100% free to run the filter, you need to manufacture the filter in the first place, and it will have to be replaced at some point, so there is ongoing energy expenditure no matter how you slice it.
- JoeAltmaier 10y agoIn any case, they have designed it for pressure. The article describes how pressure causes water atoms to line up, train fashion, and move water much much faster than without pressure.
- daveguy 10y agoright, the question is -- how much pressure is required? Is it the pressure generated by a 1 cm column of water (as is implied by sieve), or is it the pressure generated by a 1000 watt high pressure pump? The difference will determine whether they have groundbreaking technology or get a participation trophy. From the article it didn't seem like there was any sort of functional prototype.
- VygmraMGVl 10y agoWhat you're describing is Reverse Osmosis - pushing salt water through a water permeable, salt impermeable membrane. It requires very large pressures, on the order of 2-30 atmospheres of pressure. The membranes used are incredibly cheap, most of the cost of RO is the pumps and maintenance. IMO innovations on the membrane are pretty marginal to the cost of RO and are usually done for hype.
- ghaff 10y agoNote that reverse osmosis desalination through membranes already exists as the article notes. (Not sure what the current state of the art is as I haven't worked in this area for a long time.) The question in whether this has advantages to the desalination systems used today.
- SEJeff 10y agoGenerally speaking, the Aussies and Israelis have some of the top of the line Reverse Osmosis Purification Tech. I saw a ROPU (reverse osmosis purification unit) truck from the Army Corps of engineers when I was active duty US Army and that thing was unreal. You could ingest raw sewage into that thing and out would come drinkable, albeit not wonderful tasting, clean drinking water.
- callalex 10y agoThat only works when you have the luxury of burning massive quantities of oil on the taxpayers' dime.
- dijit 10y agoMy impression was that removing salt/saline from water is possible but it consumes a lot of energy to do so.
- M_Grey 10y agoI swear I've heard about this before... is this one of those stories that emerges about a technology that never seems to enter the market? That "super slick" coating for condiment container interiors is another that springs to mind.
- beatpanda 10y agoYes, it is. My understanding is that there are still barriers to producing enough graphene at a large enough scale to make many of its uses commercially viable. http://www.azonano.com/article.aspx?ArticleID=3677 http://www.azonano.com/article.aspx?ArticleID=3677
- MetallicCloud 10y agoThis is mentioned at the start of the article. They are using graphene oxide which is much easier to create at scale.
- johncolanduoni 10y agoProduction appears to be what they are improving here: > But it has been difficult to produce large quantities of single-layer graphene using existing methods, such as chemical vapour 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". > "In terms of scalability and the cost of the material, graphene oxide has a potential advantage over single-layered graphene."
- Keyframe 10y agoGraphene was re-discovered only in 2004. It takes time.
- Alex3917 10y agoFrom the discovery of new basic science to commercialization usually takes 30 - 40 years. We're not even halfway there yet. E.g. look at how long it took to develop digital cameras, flat screen TVs, etc.
- mrcactu5 10y agowe have experienced droughts in Puerto Rico. this could likely lower our water prices as well. http://www.noticel.com/noticia/177413/la-sequia-es-para-largo-asi-lo-predice-la-historia.html http://www.noticel.com/noticia/177413/la-sequia-es-para-larg...
- sirpros 10y agoAs many drought hot spots around the Globe. I hope this gets the traction it really deserves
- mgberlin 10y agotl;dr: A material was produced on a very small scale, which, with no regard to the energy required, might be able to remove 97% of the salinity. I.e. science-ey click-bait with a bullshit title.
- johncolanduoni 10y agoNot really, their whole purpose was to find a way to produce suitable membranes with something much easier and cheaper to produce than traditional graphene sheets (i.e. graphene oxide). The article not only puts adequate focus on that issue, but even ends in a cautionary note about the future work required.
- pthreads 10y agoSorry, but that is a very misleading tl;dr. I encourage other HN readers to actually read the article. I found it quite informative. Especially the use of graphene oxide instead of single-layer graphene.
- threeseed 10y ago1. This is the BBC. They aren't a clickbait site. 2. I count about 12 words you can fit into the title. How else can you adequately describe what the article was about ? Their choice seems completely reasonable. 3. The scale and energy required are irrelevant. The article wasn't describing a fully fledged product it was discussing a concept.
- sirpros 10y agoI could up vote your response a few more times if it was legal.
- mmaunder 10y agoReverse osmosis has been around for a long time and is used on boats everywhere for desalination. This sounds like a new membrane that requires less pressure and thus energy? I guess sieve sounded better?
- dreamcompiler 10y agoRO membranes are notoriously finicky and non-robust. They require a lot of maintenance and can be ruined by common chemicals like chlorine. A more robust desalination membrane would be a very good thing.
- ghaff 10y agoWhen I was involved in RO in the early eighties, that was exactly the issue. In the context of offshore drilling rigs, we just couldn't get the adherence to protocol around flushing and filtering that the units needed to work over a reasonable lifetime. We eventually gave up and went with an Alfa-Laval heat exchanger based approach.
- weaksauce 10y agoWhy wasn't the flushing automated? edit: I have worked on many RO systems and we always did auto flushing and I am not sure I ever saw anything other than that. It was pharma though.
- Gibbon1 10y agoLikely the issue is, with a large RO plant you hire people for the specific domain knowledge and develop a work culture around it. For a place like an oil rig none of this specific domain knowledge is central to the work at hand. So the technology isn't reliable in that context.
- weaksauce 10y agoI suppose it's probably something along those lines or the fact that the end product doesn't(to my knowledge) reflect the RO unit working correctly. With pharma they need RO to feed to WFI to use to make the drugs or do their research and it needs to work every day. Still seems like a simple RO system with a basic PLC would work fine on a ship to supply drinking water.
- JoeAltmaier 10y agoThe layering approach has much potential. In this case, graphene oxide layered with epoxy resin stabilizes the membrane and lets them control pore size. The next step, problems with contaminants (seawater) fouling the membrane, might be mitigated with more layers? Say a Teflon layer to aid in cleaning. Or an ionized layer to repel many particulates. I wish they'd said more about how they control pore size. How does the epoxy layer avoid covering the pores? Is it laid down before pores are etched or something? Fascinating subject.
- johncolanduoni 10y agoHave you read the paper? It's on arxiv: https://arxiv.org/pdf/1701.05519.pdf https://arxiv.org/pdf/1701.05519.pdf
- Cogito 10y agoThe paper is quite short and very readable (especially if you are just skimming and can skim over some of the details/jargon) but here [0] is a diagram (from the paper) that perhaps will help you understand what is going on. [0] http://imgur.com/a/LNWUz http://imgur.com/a/LNWUz [edit] To summarise, they prepared graphene oxide laminates using vacuum filtration, and then stored them at different relative humidities by changing the salt concentration of the storage liquid. The different relative humidities cause different layer spacing, which they measure with X-ray diffraction, and choose whichever layer spacing they want before adding the epoxy. The relevant quote from the paper: Thick (≈100 µm) GO laminates were prepared by vacuum filtration of aqueous GO solutions, as reported previously. The laminates were cut into rectangular strips (4 mm × 10 mm) and stored for one to two weeks at different relative humidities (RH), achieved using saturated salt solutions. The resulting interlayer spacing was measured by X-ray diffraction as shown in Fig. 1e and varied from ≈ 6.4 to 9.8 Å with RH changing from zero to 100%. GO laminates soaked in liquid water showed d ≈ 13.7 ± 0.3 Å. All these values agree with previous reports, where the changes in d were attributed to successive incorporation of water molecules into various sites between GO sheets. Individual GO strips with desirable d were then encapsulated and stacked together using Stycast epoxy as shown in Figs. 1b,c to increase the available cross-section for filtration to 1 mm (see Methods and supplementary Fig. S1). The stacked GO laminates, now embedded in the epoxy (Fig. 1c), are referred to as physically confined GO (PCGO) membranes because the epoxy mechanically restricts the laminate’s swelling upon exposure to RH or liquid water (Methods). The stacks were glued into a slot made in either metal or plastic plate (Fig. 1b). Two sides of these stacked PCGO membranes were then trimmed off to make sure that all the nanochannels are open (Fig. 1d) before carrying out permeation experiments, in which ions and water molecules permeates along the lamination direction as shown in Fig. 1a.
- USANEEDSHELP 10y agoHow safe is graphene for human consumption?
- desireco42 10y agoThis is all fine, but if it isn't inert and if it 'leaks' graphene, it can be super toxic as well. I don't want to pu-pu it, but it is legitimate concern.
- adrianratnapala 10y agoI didn't know that graphene was toxic. I should stop licking my pencils. And from what little chemistry I know, I though graphene oxide was rather inert.
- krastanov 10y agoThe naive (very hand-wavy) explanation for the toxicity of graphene (nanotubes to be specific, not sheets in general) is not chemistry, rather the nanotubes physically rupturing cell organelles. Same with asbestos: small rigid particles that cut everything else in pieces.
- desireco42 10y ago:) You can continue licking your pencils.
- twobyfour 10y agoGraphene != graphite
- edent 10y agoFor future reference, the phrase is "to pooh-pooh" - see https://en.wiktionary.org/wiki/pooh-pooh https://en.wiktionary.org/wiki/pooh-pooh
- desireco42 10y agoThank you, I genuinely appreciate your comment, obviously English is my second language.
- edent 10y ago
- 35bge57dtjku 10y agoWhat stops this from getting clogged?
- Neliquat 10y agoStandard filters catch most particulate matter, this is able to remove dissolved impurities afterward.
- Xophmeister 10y agoThis is somewhat OT, but I've noticed a trend -- although I can't say how recent -- of headlines of the form "British [X] do [Amazing Thing]", particularly (but not necessarily) from the BBC. I note that the HN headline has been changed to "UK researchers" (IIRC, it said "British Scientists" earlier) and this BBC article doesn't actually use this phrase in their headline, but it appears prominently in the tagline. This may be because I'm restricted to English language articles, but I don't see, for example, "Spanish researchers do [Amazing Thing]". Even in English, I don't regularly see "US/Australian/NZ/Canadian/South African/etc. [X] do [Amazing Thing]"; even though I'm sure plenty of amazing things have been done by these folks. I understand that the popular press is directed towards the masses, but is the nationality/allegiance of [X] really so important? More so than their discovery/invention/whatever? I'm British and, in a time when populist nationalism is causing all kinds of problems, I'm not sure this rhetoric is helpful. Just be proud of the achievement. How about just: "[Amazing Thing]"? Or, if you want to associate it with people, to make it more personal and less "stark" (perhaps to sell it better): "Humanity achieves [Amazing Thing]".
- martinald 10y agoIs this a different headline on BBC.com? On BBC.co.uk the headline is what you say, [amazing thing?]
- louhike 10y agoYes, it is [amazing thing?] on bbc.com. But the point might be that the HN title should the same than the BBC one.
- olalonde 10y agoI'm not seeing "British" anywhere in the article though it does say "UK-based team". I agree that highlighting the nationalities or country of residence of researchers is distracting at best and that your comment is OT for HN.
- fooballs99 10y ago> in a time when populist nationalism is causing all kinds of problems (I realize this forum will be almost overwhelmingly in favor of the above statement, but thought I would respond anyway to give an alternative viewpoint from outside). What problems? Is it really causing problems, or is it just that you are politically opposed to it? The lack of nationalism I would say has caused far more problems over the last few decades (Mass clashing of cultures, rise of terrorism, global multi-nationals exploiting workers, not paying taxes etc, moving democracy and accountability further and further away from people). If a family member achieved something you would naturally feel more "proud" than if it was a person in the world picked at random. For some people, their nationality is important to them - an extended family of shared identity, culture, experiences and values. I would much much rather use a local taxi company, which will benefit my local community, friends, family, than use some faceless global thing like Uber, which will benefit some rich people in another country. Further, competition is good. It's the way we achieve things. If a team of scientists in [other_country] see this news, they will likely be spurred on. This is why things like the space race worked so well.
- matt4077 10y agoBack at university I dreamt of creating bacteria to do desalination, powered by the sun. All the necessary components exist–in fact, a seemingly endless number of genes code for channels and transports that selectively target the charged ions (Na^2+, Cl- mostly, but also Potassium and Magnesium). It's partially the legacy of life having arisen in saltwater, and many biological processes are controlled with ion concentration gradients. Signal transmission along a nerve? -> Ions. Want to get all this water out of here? -> Transport the salt across the membrane, and the water follows voluntarily.
- pluteoid 10y agoThis is interesting to think about. As I'm sure you've considered, bacteria and other living cells exist in a state of highly regulated homeostasis. In bacteria, things like charged ion concentrations are maintained internally by various physiological mechanisms (chiefly the membrane-bound transport channels you describe) at specific concentrations with little variation. Salinity concentrations are generally the same as the surrounding seawater (marine bacteria are usually osmoconformers, as opposed to more sophisticated osmoregulators like fish), and the transport mechanisms exist as adaptations to maintain this state. So while some aquatic bacteria can exist at a wide range of external salt concentrations (they are "euryhaline"), I don't know of any bacteria that have adaptated to actively concentrate salt internally above the salinity of typical seawater. Beyond a certain not-very-useful threshold, this would disrupt too many metabolic pathways and kill the bacterium. So I don't see how a concentrate-in-the-bacteria-then-filter-them-out approach to industrial desalination would work. You might be thinking about brine pool extremophile bacteria / archaea, but again, they are just well-adapted when it comes to expelling salt or resisting salt intake, not actively concentrating it internally. However, if you could embed euryhaline bacteria into some kind of impermeable membrane in a controlled orientation, and engineer them to express the right kind of one-way channels on opposite sides of the cell... there are some big bioengineering obstacles to doing this, but it's an interesting idea. It would basically be a sped-up version of the double reverse osmosis desalination approach already widely used, potentially more efficient and available to be powered more easily by sustainable / free energy sources. I'm just typing as I think there, so maybe there's been work in this area already.
- BrendanD 10y agoSeeing as we are unable or unwilling to deal with the present micro and nano-particles resulting from decades of plastic use and disposal, I worry about the environmental effects of graphene.
- CalRobert 10y agoCan anyone with experience in the topic comment with regards to graphene decomposition? A few things I've found: https://en.wikipedia.org/wiki/Graphene https://en.wikipedia.org/wiki/Graphene "10 µm few-layered graphene flakes were able to pierce cell membranes in solution" http://www.kurzweilai.net/graphenes-negative-environmental-impacts http://www.kurzweilai.net/graphenes-negative-environmental-i... "In groundwater, which typically has a higher degree of hardness and a lower concentration of natural organic matter, the graphene oxide nanoparticles tended to become less stable and eventually settle out or be removed in subsurface environments. In surface waters, where there is more organic material and less hardness, the nanoparticles remained stable and moved farther, especially in the subsurface layers of the water bodies." (also http://online.liebertpub.com/doi/abs/10.1089/ees.2013.0392 http://online.liebertpub.com/doi/abs/10.1089/ees.2013.0392)
- Neliquat 10y agoAbspestos 2.0 Funny enough, its not actually banned in the USA, just a liability nightmare. I ocasionally still see brake pads with the stuff. I suspect graphine, and other 'nano' materials will be similar in practice.
- BrendanD 10y agoThat would be _malpractice_.
- sp332 10y agoIs there a reason this wouldn't be subject to the same physics that requires a lot of energy to desalinate water by other means? Thermodynamics puts a limit on how efficiently you can reduce entropy like that.
- Nomentatus 10y agoI wouldn't say "a lot" in economic terms: "The theoretical absolute minimum amount of energy required by natural osmosis to desalinate average seawater is approximately 1 kilowatt-hour per cubic meter (kwh/m3) of water produced, or 3.8 kilowatt-hours per thousand gallons (kwh/kgal)." https://www.amtaorg.com/wp-content/uploads/7_MembraneDesalinationPowerUsagePutInPerspective.pdf https://www.amtaorg.com/wp-content/uploads/7_MembraneDesalin...