Through a glass brightly

A simple solar still using gold nanoparticles.

In time for your Thanksgiving dinner, just what the world was waiting for: the first fundamental breakthrough in distillation for 1200 years. (Via Clean Technica.)

Rice University solar nanoparticle still

This looks low-tech because you can´t see the important bit. (The Fresnel lens concentrator can presumably be replaced by a simple arrangement of parabolic reflectors.)

A team at Sake Rice University under Professor Naomi Halas, assisted by a rainbow team of graduate students including, I am informed, B. Samedi, S.A. Tan and B. L. Zebub (*), have developed a solar still using gold-coated nanoparticles. (Press release, research paper.) Moderately concentrated sunlight heats up the particles in seconds to 150 deg C. They quickly surround themselves with vapour bubbles that rise to the surface and pop, releasing the particle to sink and heat up again. The paper doesn´t say how the valuable gold particles are recovered for the next batch. Everything else is cheap glassware.

The technology can also be used for making steam to generate power, purify waste, etc, but on this blog, alcohol´s our thing. The setup can distil alcohol to 99%: at that Siberian nirvana, all the flavours are presumably lost. But perhaps it can be tuned to keep some of the desirable compounds, as in whisky ¨tails¨. You could of course also waste perfectly drinkable alcohol by putting it in your car.

A boom in backyard ¨sunshine¨ may be unlikely. Booze is cheap enough that few will be tempted on economic grounds. I do predict a niche market in solar-powered hooch, marketed to the kind of people who will pay $20,000 for speaker cable. Purified with gold! No peat bogs were harmed making this exclusive ¨Spirit of the Sun¨!

But if things continue on the current downhill trajectory, a cheap way of staying drunk all the time may be a handy ¨adaptation¨.


A 15th-century imagined European portrait of Abu Musa Jabir ibn Hayyan (Geber), 721-815? CE, Persian founder of chemistry and alchemy, and pioneer of the alembic.

Arab glass alembic, date not given, Corning Glass Museum

(*) The actual co-authors of the paper are listed as Oara Neumann, Alex Urban, Jared Day, Surbhi Lal, Peter Nordlander, and Naomi J. Halas. Ms. Lal and Mr. Urban are postdocs, Mr. Day and the lead author Ms. Neumann are graduate students. Peter Nordlander is another professor of physics at Rice, and Ms. Halas´ husband. Professor Halas put herself last – that´s what I call leadership. Congratulations all round.

Author: James Wimberley

James Wimberley (b. 1946, an Englishman raised in the Channel Islands. three adult children) is a former career international bureaucrat with the Council of Europe in Strasbourg. His main achievements there were the Lisbon Convention on recognition of qualifications and the Kosovo law on school education. He retired in 2006 to a little white house in Andalucia, His first wife Patricia Morris died in 2009 after a long illness. He remarried in 2011. to the former Brazilian TV actress Lu Mendonça. The cat overlords are now three. I suppose I've been invited to join real scholars on the list because my skills, acquired in a decade of technical assistance work in eastern Europe, include being able to ask faux-naïf questions like the exotic Persians and Chinese of eighteenth-century philosophical fiction. So I'm quite comfortable in the role of country-cousin blogger with a European perspective. The other specialised skill I learnt was making toasts with a moral in the course of drunken Caucasian banquets. I'm open to expenses-paid offers to retell Noah the great Armenian and Columbus, the orange, and university reform in Georgia. James Wimberley's occasional publications on the web

28 thoughts on “Through a glass brightly”

  1. A neat technology. Seems unlikely to do anything for the efficiency of large scale distillation and boiling, as that’s fairly efficient already, and the bubbles would equilibrate before they reached the surface if the setup weren’t small. But it might have some practical applications in small scale distilling and desalinization.

    1. Geometry? In parabolic trough CSP plants, the working fluid is in a narrowish cylindrical tube at the focus, so the surface-to-volume ratio inside can be quite high. You don´t need nanoparticles to get steam there, though. But they could raise efficiency.

      Neumann & Halas etc. state that for steam generation, 82% of the incoming solar energy gets transformed directly into steam, only 18% in heating the water. That is a step change in efficiency.

      1. I think it’s unlikely to work in parabolic trough systems; The reason this technique increases efficiency is that the nanoparticle created bubbles rapidly separate themselves from the bulk fluid, before they leak their heat back into it. This requires a fairly short, vertical path from the area being heated, to a separate space for the steam. You couldn’t use a “narrowish” cylindrical tube, it would hold the steam in contact with the unheated water, causing it to condense again, and all you’d have would be hot water.

        You’d need, at a minimum, either a largish cylinder, with the water resting only on the bottom, and a considerable empty space above for steam to occupy, or better, a figure 8 shaped tube, water in the bottom, steam in the top. And even so, the steam quality would not be the best. Certainly not well suited to turbine systems.

        For large scale steam generation systems, this wouldn’t have any benefits, because the entire water flow is being transformed into steam in those systems, meaning segregating the steam from the feed water doesn’t enhance efficiency. Thermodynamics wouldn’t permit it to be more efficient than THAT.

        The chief benefit I can see from this, actually, is that it would permit steam generation using brackish or salt water, without any tendency towards scaling of the boiler, because the steam wouldn’t be generated at the boiler surface. Scale buildup is ruinous for the efficiency of boilers, you know.

        No, the primary use I see is small scale distillation. The question is whether it’s actually superior to reverse osmosis for that. Maybe from the perspective of maintenance, given the lack of scaling, and no concern about fouling membranes.

        The real question is how well they can recover the nanoparticles, since being able to segregate the steam from the water is only a benefit if you aren’t ultimately going to boil all the water, and you wouldn’t want the particles to be going away with the waste stream.

        Really neat, though.

        1. Yup. Commercial CSP parabolic trough collectors seem to have adopted mineral oil in preference to water as the working fluid, no doubt partly because of the condensation issue. Tower CSP uses steam, but at much higher temperatures, for which nanoparticles are irrelevant.

    2. distillation of fuel ethanol is not nearly efficient enough!
      Solar distillation could turn bio-fuels from an energy waste to an energy source – if it can be done at bulk scale.

      The efficiency comes because you don’t have to turn the sunlight into volts, transport it 100 miles, and convert it back to heat.

      Overall, I’m not sure how much of the energy the distillation phase of bio to ethanol chain consumes. But it is tempting to contemplate

      1. Googling quickly found me a paper that says this:
        ¨The US Department of Energy estimates that there are more than 40,000 distillation columns in North America, and that they consume about 40% of the total energy used to operate plants in the refining and bulk chemical industries.¨
        Distillation is a very big target for green technology.

  2. A friendly warning to non-chemist readers. 100% or 99% alcohol is deadly. Water and ethanol at atmospheric pressure form an azeotrope around 95%. You can do better than that if you add a third ingredient, but the most common is benzene, which is nasty stuff. Stick to the 190 proof super-hooch. It’s also deadly, but at least it is deadly in a familiar way.

    1. Just idle curiosity: Why is the azeotropic property relevant to (or a cause of) its toxicity?

      1. Leaving aside the fact that really high concentration alcohol will immediately kill surface cells in your mouth and throat as you drink it, and the fact that the lethal dose is so small in volume compared to alcohol in beer or wine, (Where it’s really difficult to drink enough to die of acute toxicity without throwing up first.), in order to reach 100% concentration in alcohol you have to resort to chemical processes which involve some nasty chemicals, and which will further poison the alcohol unless removed essentially completely. As Eb says, you don’t want benzene in your cocktail.

        Really, the allotrope is concentrated enough for purposes of human consumption. Getting the last few percent of water out is pointless unless you’re using the alcohol for industrial purposes.

    2. According to travel writer Paul Theroux, Siberian Russians drink 95% alcohol ¨sprt¨ because unlike regular girly vodka it won´t freeze up at your -30deg C winter picnic in the taiga. Doesn´t do much for their life expectancy though.

  3. As a chemist (although not one that uses solvents frequently), the assertion that 100% alcohol is much more dangerous than 95% struck me as odd. But after a bit of searching I think I understand the reasoning.

    Concentrations of alcohol higher than 96% are hard to achieve by distillation because water and alcohol form an azeotrope. One way to increase the concentration would be is, to extract the alcohol with benzene, which does not dissolve the water. Evaporate the benzene and you’re left with high purity alcohol, but with a significant benzene percentage, which you would not want to drink.

    Another method is to use a drying agent to remove the water, which does not necessarily add toxins to the alcohol. (I’d say not to try this at home but it’s rather pointless to turn 96% alcohol into 99% alcohol.) If you leave the alcohol exposed to the air, it will absorb water until the concentration is 96% again, though.

    To make things more confusing, alcohol used as a solvent contains 5% benzene etc (denatured alcohol) so that it cannot be used to get drunk.

    1. “To make things more confusing, alcohol used as a solvent contains 5% benzene etc (denatured alcohol) so that it cannot be used to get drunk.”

      So it cannot safely be used to get drunk. Stupid people die of it every year anyway. It’s denatured to get a different tax status, the poison being added serving no other useful purpose.

      1. This is something that always struck me as odd from a public health perspective. Why don’t we require denatured alcohol to contain an emetic and/or something unbearably bitter, so people are physically unable to drink it? Just putting some flavourless poison in it is only going to stop informed drinkers, but they’re not the real problem – you’re just making the stuff even more lethal to alcoholics, people with learning disabilities, or even someone who is from a different enough culture that they don’t understand the ‘POISON’ label on the bottle.

        1. It’s got to be something that evaporates, as it’s used for cleaning, that kind of limits the options.

  4. I haven’t read the paper, but from your explanation it sounds like the nanoparticles don’t leave the stillpot, in which case no recovery is required.

    1. Unless you’re distilling distilled water, (Kind of pointless, unless you’re generating steam for power or heat transfer…) eventually you end up with a residue that has to be dumped.

      1. I made precisely this point to Profesor Halas in the FYI email notifying her of the post. I suggested iron cores for the gold nanoshells, allowing magnetic recovery. She replies: ¨We have several strategies for this, so we don’t anticipate it being a problem.¨ I read this as caginess for commercial reasons – recovery would be a critical part of a patent. Good luck to them.

        1. One of Prof. Halas’s competitors, Vicki Colvin (also at Rice), has published a method for making magnetite nanoparticles on a stovetop, starting with rust, lye, and vegetable oil. I would take her at her word when she says that recovery could be accomplished without undue hardship.

  5. Placing your name last has recently become en vogue for claiming principle investigator status. This is most prominent in the really large collaborations at places like CERN.

    1. From what I’ve heard, name order conventions in academia (and also who gets named in the first place) are a horrible mess that varies from subfield to subfield. It’s problematic for e.g. job applications, when you have people from different areas trying to assess the strength of a candidate based on their publications, without understanding the conventions in use. At any rate though, for individual teams, it is not a free choice, in that they will get criticised if they don’t follow the rules of the area/journal they are publishing in. The ‘name of head of lab goes last’ convention is quite common.

      Pure mathematics, unsurprisingly, has the simplest convention: alphabetical order, and all authors are considered to have contributed equally.

      1. It´s certainly good practice to let graduate students take proper credit in publications. Is it universal?

        One thing that struck me in the interdisciplinary Halas team was its ethnic diversity and gender balance. Having women as team leaders in science makes a difference to the next generation.

        1. It is the near-universal convention in the physical sciences that the PI goes last, and the lead author is generally the grad student or postdoc who actually carried out the experiments. Second through (N-1)th authors can be assigned in order of precedence or alphabetically.

          1. This was my point, the position of Halas on the author list is meaningless as a measure of leadership.

          2. I would dispute the assertion that this is recent — it’s been the case for as long as I’ve been in the field…

          3. I´m pleased to hear this. It looks as if my attribution of exceptional leadership on these grounds was misplaced, Professor Halas was just following a good convention. Her leadership was in the work itself.

          4. I’m glad to hear your anecdotal evidence of a particular field is contrary to someone else’s in another field.

      2. Colin: It’s the same in economics: alphabetical. But economists never assume contributions are equal: the convention instead seems to be that people call or email their friends to find out who did what. And the same method, personal contact, is used to make sure that co-authors who shirk aren’t likely to be invited to co-author again (or not much). In other words, economists, true to form, use markets, and market signals–and. again true to form, they tend to assume the market signals embody near-perfect information even when there’s no particular reason to think that.

        Yes, it causes misunderstanding in hires (e.g. in a public policy department, where economics is one field among many from which applicants come), though over time a bunch of professors in mixed fields tend to figure out one another’s conventions reasonably well I think.

  6. I am forced to point out that whatever ibn Hayyan’s claims to have founded chemistry, he has no claim to have founded alchemy. There was a fairly rich alchemical tradition in Greco-Roman times, including Zosimos of Panopolis who seems to be the first alchemical writer on record.

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