Moar press-release "OK, science"

[DCFusor]

Don't worry, this isn't going to reduce the price of gold anytime soon, if ever. But you'd never know by the title or most of the article if you didn't know what the real problem is.
http://phys.org/news/2013-05-gold-green-non-toxic-method.html

Ok, this junk (basically a sugar) will make gold in certain complex solutions fall out.

Whoopee - they say it could eliminate cyanide as a way to get gold into solution. Whaaa?

Nevermind, I'm just pitching my usual bitch about this kind of thing.

 

[pmbug]

As I read it, I thought to myself - hey this sounds like a fun, non-toxic science experiment for the kids - harvesting gold from scrap electronics. Then I read near the bottom of the article:

...
The supramolecular nanowires, each 1.3 nanometers in diameter, assemble spontaneously in a straw-like manner. In each wire, the gold ion is held together in the middle of four bromine atoms, while the potassium ion is surrounded by six water molecules; these ions are sandwiched in an alternating fashion by alpha-cyclodextrin rings. Around 4,000 wires are bundled parallel to each other and form individual needles that are visible under an electron microscope.
...

wat? Doesn't sound like it's going to be practical for home chemists playing with test tubes, beakers or bath tubs.

 

[DCFusor]

That's not really the problem - so the gold dust is tiny particles. There can still be lots of it - and I'm sure that most of us would like to have a pound here and there.
You can always melt that into a solid block later in the game, which is done no matter what the recovery procedure.

The problem is that this technique only works for gold already in solution as an alkaline metal/bromide/chloride. How do you go from a big pile of rocks, with a little metallic gold (the only form normally found in nature as gold compounds are unstable) - to there?

Crap, once you've got a solution of any gold compound, it's easy as pie to make the gold precipitate (often only heat, needed to melt it anyway into more useful form, is all that is required - and sometimes it's even easier than that). For example, to recover the gold from my electroplating solutions, all you need to do is heat them up (don't breathe the fumes!) - and if you want something other than powder, keep on heating till it melts.

That's what the cyanaide compounds do - dissolve the gold without dissolving the rock that isn't gold. This stuff doesn't do that - it merely makes the gold fall out of solution. There is no evidence (that I'm aware of) that this stuff dissolves anything, or that it would be selective to just gold if it did. All it does is take gold already in a particular kind of solution and make it precipitate. That was easy already, since gold compounds are unstable and "want" to break up into gold + whatever.

Getting the gold into solution is the problem, not getting it back out.
The two things that dissolve gold and little else are cyanides and the even worse (to some minds) mercury. Everything else that dissolves gold (aqua regia and similar) also eats the rock itself, which is expensive and non-separative.

In other words, as even this paper says, the experiment (making gold nanocubes) failed, and now he wants more money to use it anyway as an extraction process from solution. Thing is, that was never the problem - it was getting the gold into solution in the first place without a bunch of other junk/minerals, which is what the cyanide compounds accomplish. Obviously the author is hoping no one in the funding chain knows that.