Dry water – a.k.a. hydrophobic fumed silica/water – touted as CO2 absorbent, emulsion transporter | The American Ceramic Society

Dry water – a.k.a. hydrophobic fumed silica/water – touted as CO2 absorbent, emulsion transporter

“Dry water.” Credit: ACS.

The American Chemical Society today distributed a story that came out of one of its meetings regarding the use of “dry water” powder as a medium for absorbing CO2, enhancing certain chemical reactions and storing emulsions. Although the story is interesting, it’s not exactly clear to me if the CO2 angle, which is the one being played up, is really news. But, here is the scoop anyway.

The background to this is that Andrew Cooper and his group at the University of Liverpool have been playing around with uses for dry water for several years. Dry water is really just tiny water droplets that have been given a coating of hydrophobic fumed silica, except that it sort of looks like fine sand or sugar. What goes on with the creation of dry water is akin to the phenomenon one sees if a water droplet fall onto powdered mud: The water droplet balls up and has a visible coating of the dust.

Making dry water (DW) is apparently simple enough. It basically requires putting a mixture of water and hydrophobic fumed silica (19:1, by mass) in an ordinary blender.

Back in 2008, Cooper and his researchers gained some notoriety because they successfully demonstrated that DW could be used to store methane (in the form of methane gas hydrate) in a powder form if kept at low temperatures (-70°C) or under pressure.

The thinking of Cooper and others in his group at the time was that since the DW/methane gas hydrate combo can be easily made, it could be used to store and transport large amounts of methane for use, for example, in cars. They said that in 30 minutes a liter of methane gas could be stored in just 6 grams of DW.

But, even then, they also described the use of DW as an absorbent for CO2.

Cooper et al. also published an update on DW in late 2009, describing a method of making the DW perform as a gas separator and be recyclable by including a gelling agent.

So, the thrust of today’s story is that Cooper argues that DW is being overlooked as a piece of solving the CO2 accumulation problem. According to the ACS release, “Cooper and coworkers found that dry water absorbed over three times as much carbon dioxide as ordinary, uncombined water and silica in the same space of time. This ability to absorb large amounts of carbon dioxide gas as a hydrate could make it useful in helping to reduce global warming, the scientists suggested.”

But, like I said, I am not sure what the news is here.

Perhaps its more newsworthy that Cooper also described two new applications for DW:

  • To speed up catalyzed reactions between hydrogen gas and maleic acid to produce succinic acid, eliminating the need to stir the mixture; and
  • To transform simple emulsions into a dry powder, making it safer and easier for manufacturers to store and transport potentially hazardous materials.

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