nicholas.dougal - 15-8-2016 at 03:09
I know that deltah and aga and others spent a LONG time on trying to devise green ways to salvage gold from electronics and pcbs.
https://www.sciencedaily.com/releases/2016/01/160128122901.h...
These guys at the University of Saskatchewan claim to be able to strip only gold in 10-20 seconds using vinegar, an unnamed oxidant, another acid, and
zinc to precipitate the gold in the end. They say that if the acid were at 5% it would be regular vinegar, but don't actually say that they use it at
5%.
the video
https://www.youtube.com/watch?v=Wqql-5S8dm4
I researched the blue hot plate in the video. The right dial is speed of magnetic stirring. So they heat is off, the second hot plate has a "hot if
light is lit" light which is off. So the reaction takes place at room temperature.
Which brings me to my question.....
So zinc was used to precipitate the gold. If we assume that the white crystals at the bottom of the glass is Sodium Nitrate then.
So ZnAu if we follow this backwards we arrive at 2Au(NO3)3 + 3Zn -----> 2Au + 3ZnNO3
so they are using sodium nitrate in the reaction most likely before to form the gold nitrate.
I haven't had chemistry in a long time, so I'm wondering if they aren't using highly concentrated vinegar (C2H4O2).
in a combo with Sodium Nitrate(NaNO3), Hyrdrogen Peroxide (H202), Chloroacetic Acid(C2H3Cl02).
it would yield Gold, Table salt, water, and more vinegar.
I don't know if this all checks out, I know this is not a lot of information but I feel like it has to be attainable and would be ridiculously
helpful. The biggest point about this stuff is that it is sooo cheap and he says the by-products are the greenest things in the world next to water.
This process is so simple that they aren't going to publish a journal article or patent because everyone in the world could just do it at home. They
are actively seeking someone to by this information from them on a industrial scale.
The ingredients all are extremely cheap, and environmentally friendly, so it seems plausible.
j_sum1 - 15-8-2016 at 03:31
The originator of this idea on these boards was kadriver -- aka sreetips on youtube. you can look up the thread and channel.
There are two processes going on.
The first of these is dissolving the gold. Bleach and vinegar is sufficient to pull this off -- much to the surprise of many here. But this is
largely due to the excellent oxidation properties of hypochlorite. I guess other "unnamed" oxidants would also work.
The second process is precipitation of the gold with a reducing agent. There are many to choose between. Zinc would not be my first choice. Sodium
metabisulfite is readily available, environmentally friendly and cheap. But really, the precipitation side of things is not the nasty part of the
process -- it is the dissolving that is generally the ugly bit.
I don't have time to watch the video at the moment and so don't follow your reasoning on sodium nitrate. I ill get back to this though.
nicholas.dougal - 15-8-2016 at 03:33
thanks i read all the posts on the other thread but none of the methods they used could remove the gold in 10-20 seconds like in the video that's the
only reason i was asking. no one else i've found has tried to put actual work into making these green alternatives work.
j_sum1 - 15-8-2016 at 03:46
No one else was using high concentration acetic acid either.
My guess is 50%+ acetic acid plus strong hypochlorite plus a little something else to get past the passivation of the gold and/or increase reaction
rate.
Not diminishing what is shown (and I really should watch the video. Right now I am being distracted from work.) But from the description it does not
sound dissimilar to what was discussed here. This really is an area of chemistry that deserves some proper investigation
j_sum1 - 15-8-2016 at 05:57
Ok. I have had a read and a view now. If all is as it seems then this is really a very significant improvement on current processes. The fact that
it appears to be selective for Au is quite an achievement.
A couple of points.
1. They do not give any details (that I have been able to find) that reveal anything about the composition of the solution (other than it contains AA
and an oxidant and another acid.) This makes it difficult to verify.
2. With the paucity of actual real information supplied, it would be easy to produce a misleading video as well. I am not talking deliberately
deceptive or fraudulent here -- just an exaggeration of the efficiency. My skepticism prevents me from believing everything that I see.
3. I don't see any reference to any published papers here. Which means that it is probably an effort to raise the profile of the project (and hence
funding) while they iron out the wrinkles. I see an aim to scale up in size. But I wonder what other issues there are.
With those disclaimers out of the way, I have to admit that I am impressed. I wonder if we can deduce what might be in the mix. There are a lot of
good brains on this site and we might make some progress.
The solution does not dissolve copper. This is surprising because acetic acid by itself will.
They mention also that nickel cobalt and iron are left behind. (cite) Again this rules out a few things.
They mention an oxidant. In the absence of better information I am going to suggest either hydrogen peroxide or sodium hypochlorite. However, both
of these have been used before and both react with other metals in acidic conditions.
The white powder circuating in the beaker in one portion of the video is perplexing. It is not sodium nitrate as you suggest since that is soluble.
I am reminded of trichloroisocynauric acid but that really is a stab in the dark. Besides TCCA is probably not the sort of chemical that one would
describe as "the next greenest solvent to water". Really I have no idea.
The presence of some chloride ions seems likely to attack the surface of the gold in the same way that it works in aqua regia.
It would be quite good if we could crack this one. Or at least get close enough to do some experimentation.
Is it really as selective as it appears? What could it be that leaves the other elements behind?
NEMO-Chemistry - 15-8-2016 at 16:57
What about Vitamin C? there has been some talk on Ascorbic acid, i have zero idea how this fits, except it would be a fit for another acid.
Maybe i am well off here but how does perchlorate as an acid fit (i can remember the name of the acid!!), but isnt it strong and yet only very
oxidising under certain conditions?
I was reading something else in a book a week or so ago, so i can go back and check WTF i am on about!
But Ascorbic Acid wouldnt surprise me.
PHILOU Zrealone - 16-8-2016 at 06:00
Some personal observations and comments after viewing the video:
The initial color of the reaction media seems to be initially yellow what argues in favor of some chlorine (hypochlorite, chlorite, chlorate) or
nitrite into the media.
Concentrated acetic acid will not work without an oxydiser --> TCCA, hypochlorite, chlorite, chlorate, H2O2, nitrite, nitrate, ...
Concentrated vinegar is not compatible with too concentrated hypochlorite, chlorite, chlorate or nitrite unless you have a triming effect maybe the
white powder is devoted to this!
HOCl, HOClO, HOClO2 and HONO are unstable if too concentrated and turns into toxic, corrosive and sometimes explosives gases.
Some extra comments:
1°) The selectivity is not proved at all...they only leave the electronic plates for 10 to 20 seconds into the media and since the gold seems to be
plated onto the surface, there is absolutelly no proof that the solution is non reactive to the underlayer metal...did they leave the plates in for 20
minutes...NO.
So the solution might be corrosive to Cu, Ni, ... aswel!
2°) The plate is OFF for the heating, but they use a glass watch above their beaker...and there seems to be little condensation ...
so:
-eather it is a hot solution,
-eather it is not as friendly/greenier a solution as one may think it is.
Why to use a glass watch?...it is only in the way and troublesome for the process to me!
Later in the video the last trial before aqua regia...they don't put the glass watch...
Sulaiman - 16-8-2016 at 06:47
I had a read of some of the papers by professor Stephen Foley
lots of platinum group work ... too complex
maybe a happy accident well observed ?
if the reaction proceeds by oxidation then I would expect gold to dissolve last,
could the acid be something kind of oxalic acid/ oxalate,
which can form intermediate metal complexes, specifically gold oxalate in this case ?
(feel free to flame me 
argyrium - 16-8-2016 at 10:02
A related patent here:http://rexresearch.com/foleygold/foleygold.html
"…….The disclosed extractant employs derivatives of dithiobiuret as a means to simultaneously extract gold and palladium from acidic solutions
containing chloride and base metal ions derived from leaching of ores, catalysts, anode slimes or other such materials containing precious metals.
…….."
dlog - 9-9-2016 at 04:16
Hello all
Search in libgen.io for "gold leaching" or id:1553889
GOLD LEACHING IN ORGANIC SOLVENTS: SIMPLE AND MILDE REACTION CONDITIONS FOR FAST GOLD DISSOLUTION
OR ID 1553895
A highly effective system for palladium dissolution under mild conditions - page 9
In the present work, a new method has been introduced for the dissolution of palladium under very mild
conditions. Palladium was quickly dissolved in some particular organic solvents including acetonitrile, ethyl acetate or acetic acid containing low
concentrations of hydrochloric acid, hydrogen peroxide and CaCl2. Among these three organic solvents, acetic acid showed the highest rate of palladium
dissolution. The rate of 1200 gm-2h-1 was measured at room temperature in acetic acid containing 0.5 M HCl, 0.2 M H2O2 and 0.2 M CaCl2 . The
dissolution rate significantly increased to 4500 g m-2 h-1 by raising the temperature up to 60 oC. The dissolved palladium was precipitated out using
Zn powder as a reducing agent. This new leaching method is highly promising to find industrial applications for recovery of palladium from both
primary and secondary sources like,PGM ores, spent catalysts, copper anode slime and jewelry scraps.