Gold nanoparticles for moonshiners
Heating with nanoparticles will separate alcohol from water
ChemPort.Ru based on Chemistry World: Move over moonshine, here comes sunshineA new method of heating liquid mixtures can reduce the energy costs required for the distillation of substances.
It was found that laser irradiation of gold nanoparticles in an ethanol/water mixture allows for selective evaporation of ethanol without forcing the entire liquid mixture to boil.
The method works if the laser radiation is replaced by irradiation with ordinary sunlight. The researchers suggest that the new technology may be useful for use in the field.
During the usual distillation process, liquid mixtures are heated, and the separation of components is carried out based on the difference in boiling temperatures – at the beginning of distillation, vapors above the liquid are enriched with a lighter boiling substance (if the mixture of liquids is not an azeotropic mixture), cooling and condensation of vapors allows separating the light boiling component from the reaction mixture. As Rice University Professor Naomi J. Halas notes, distillation is an exceptionally energy-intensive process. Thus, in the production of bioethanol, 75-80% of the total energy that is spent on obtaining biofuels is spent on distillation.
To reduce energy costs, Halas and her colleagues decided to use nanoparticles. A decade ago, Halas was the first to report a process based on the fact that nanoparticles with a metal shell can absorb light with a certain wavelength, as a result of which they intensively heat the area around them. In 2012, chemists from Rice University showed that sunlight illumination of aqueous solutions containing 100-nanometer nanoparticles with silicon oxide nuclei and a shell of gold can lead to the generation of steam.
In the new work, a similar technique was tried on water-ethanol mixtures. Using a light guide, the researchers illuminated water-ethanol mixtures containing the already mentioned nanoparticles with a near-IR laser with a power of 15 watts. After a few minutes, the nanoparticles warmed up, and their heating led to the evaporation of ethanol, the vapors of which were selected and condensed. According to Halas, large nanoparticles did not get into ethanol vapors even in trace concentrations. The developed technique also makes it possible to prevent the formation of azeotrope, a common problem that complicates the separation of water–alcohol mixtures and necessitates the use of desiccants to bind water. The researchers tested the "nano-race" on mixtures with different ratios of ethanol and water, and in all cases the selected ethanol fraction turned out to be cleaner than the fraction that can be obtained using traditional distillation.
Figure from the article by Neumann et al. Nanoparticle-Mediated, Light-Induced Phase Separations (Nano Lett. 2015) – VM
The researchers have not carried out calculations that make it possible to clearly demonstrate how much more economical the new technique is in its energy requirements compared to traditional distillation, but Halas claims that sunlight can be used for nano-racing, which will replace a power plant. Moreover, the replacement of two–layer gold-containing particles with carbon particles will help to reduce the cost of the new distillation method even more.
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25.11.2015