9 ms·
Graphene-based sieve turns seawater into drinking water (2017)
- salty_biscuits 8y agoOsmotic 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.
- snazz 8y agoMight want to attach the (2017) label, although I hadn’t heard of it until now.
- entee 8y agoOne 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-this-as-good-as-it-gets/ https://arstechnica.com/science/2011/08/desalinization-is-th... [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/Content/About_Us/Organization/Divisions/Policy_and_Planning/PPD_Work/PPD_Work_Products_(2014_forward)/PPD%20-%20Production%20costs%20for%20new%20water.pdf http://www.cpuc.ca.gov/uploadedFiles/CPUC_Public_Website/Con... [4] https://www.mercurynews.com/2014/05/29/nations-largest-ocean-desalination-plant-goes-up-near-san-diego-future-of-the-california-coast/ https://www.mercurynews.com/2014/05/29/nations-largest-ocean...
- BariumBlue 8y agoI think the calculus should get a bit better with cheap renewables - desalinating only when more energy is produced than can be reasonably used. I think if we can find a bunch of things that can effectively use excess power but aren't time sensitive, it'll also make renewables much more attractive.
- thinkcontext 8y agoThe lower the capacity factor of the plant the longer it will take to recover the capital cost of building it. Whether this is economic depends on the ratio of energy cost to capital cost. Do you know what that ratio is?
- pishpash 8y ago> only when more energy is produced than can be reasonably used But when would that ever happen. They'd just get used up in e.g. mining $coins.
- raz32dust 8y agoThis is assuming the current energy costs though, right? If we can get cheaper energy, say via fusion, it could go down.
- entee 8y agoFor sure! But cheap energy is hard :( I'm cheering for Solar, renewables and Nuclear Fission to become cheaper and more widespread. Fusion... well it would be nice, but given that it's never been demonstrated in a form suitable for commercialization, it's hard to hold out for that.
- est31 8y agoWith renewables due to changing weather and demand, prices for electricity at international markets are falling regularly, sometimes even becoming negative (keeping the frequency is must), only to rise again when there is more demand than supply. Desalination plants have the advantage that, as long as you have overcapacities compared to the average needs around, they can be turned on when energy is cheap and off when it's expensive. While they are operating, they would fill reservoirs that would provide a continuous supply of water. There might be a thermodynamic limit onto how much energy you need to desalinate water, but the limits of harvesting renewable energy are far from being reached. We might make the sahara green, in this very century.
- chrisweekly 8y agoWhat can't graphene do?
- 90minuteAPI 8y agoMake it out of the lab.
- robotresearcher 8y agoSalty
- HillaryBriss 8y agoi 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?
- maccio92 8y agoright but that's the point - graphene is pretty much the only material so far we've been able to drill holes that size in to
- peeters 8y agoThe 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.
- logfromblammo 8y agoGraphyne. Cyclohexane rings connected by poly-yne chains of equal length. Allows for a somewhat tunable pore size, with no "drilling" necessary. Graph-di-yne and graph-tri-yne are nearest the appropriate pore size for water. A series of graphyne filters with larger pore sizes would likely be needed to clear out particulates and larger ions, so that the final purification step proceeds at a reasonable flow rate. https://arxiv.org/abs/1312.3179 https://arxiv.org/abs/1312.3179 Similar problem as graphene, in that it has not only never been outside of the lab, but also never been outside of the computer model.
- gumby 8y agoThis 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 8y agoyou'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
- bkmeneguello 8y agoTaokey?
- omosubi 8y agoNot 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 8y agoNo 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.
- hawski 8y agoDoes graphene coated heatsink count? I don't know, I'm asking. https://www.pine64.org/?product=rockpro64-slim-profile-graphene-heatsink https://www.pine64.org/?product=rockpro64-slim-profile-graph...
- bariswheel 8y agoGraphene 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_can_do_just_about_anything_except_leave/ https://www.reddit.com/r/askscience/comments/6tzy80/graphene...
- biglenny 8y agoI could not have put it better
- epai 8y agoThe sieve is made out of Graphene-oxide, not pure Graphene, so should be easier to produce.
- baldfat 8y agoI 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 8y agoIt's the fusion of material sciences.
- Animats 8y ago"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 8y agoIts 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 8y agoClaims 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-membrane-tech/ https://www.scientificamerican.com/article/desalination-memb... [3] https://today.uconn.edu/2018/08/new-findings-may-lead-sea-change-desalination-technology/ https://today.uconn.edu/2018/08/new-findings-may-lead-sea-ch... [4] http://www.lgwatersolutions.com/en/product/seawater-ro http://www.lgwatersolutions.com/en/product/seawater-ro
- wolfi1 8y agoHas there been any progress on it? Seems to be just a lab experiment
- OJFord 8y agoThis is a comment on graphene as much as it is this particular application!
- Amendeson530 8y agoExcellent 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
- QuamStiver 8y agoWhat 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.
- AltmousGadfly 8y agoSeriously this was news 5 years ago.
- Jakob 8y agoDoes 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.
- iamphilrae 8y agoMy guess it is dumped back into the sea which will cause a seriously high salt concentrations close to the dumping site. However it’s net effect on salivation levels in the oceans overall will be neutral since all the fresh water produced will likely end up back in the sea.
- mxuribe 8y agoStore 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?
- SunnyS 8y agoI 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.