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Little_Ghost_again
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Have you kept the blue solution? and the white precipitate? Well done by the way
Dont ask me, I only know enough to be dangerous
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Little_Ghost_again
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I forgot to add for a fine mesh filter goto a tropical fish shop and ask for a nylon brine shrimp nupali net, they are around 5 micron I think
(maybe10)
Dont ask me, I only know enough to be dangerous
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kadriver
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I have some very fine mesh copper screen. I'll fashion a screen from that.
I saved the blue liquid and the precipitate. I'll do some experiments as I get some more time.
I received a large order today so it'll be a while before I can go forward.
Here is the gold from the fingers - success!
kadriver
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deltaH
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That's pretty kadriver and your yields are thoroughly consistent!
The way I see it, this process has three important sections:
Mineral acid-free 'fish and chips' gold refining process
(1) Base metal leaching: vinegar + salt + air bubbling + initial H2O2
(2) Gold foil dissolution: vinegar + salt + bleach
(3) Base metal recovery: ?
Comments:
* Step (1) has now been tried on small and larger scales thanks to the pioneering work of aga and kadriver. Step (2)
has only been tried on a small scale by aga and Step (3) is largely completely open.
* Step (3) is vitally important though. Without it, the process doesn't deal with its waste and is incomplete.
Also, part of the copper containing solution from step (3) could be recycled into step (1) so that peroxide is no longer needed, then this thing would
come full circle and you would have a reliable, low cost and safe complete process that could be used again and again.
Looking forward to someone continuing the research into this, i.e. scaling up of step (2) and development of step (3).
[Edited on 7-10-2015 by deltaH]
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Little_Ghost_again
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I cant afford the gold for step 2, but I can get enough copper to do step 1 and step 3, to be honest step 3 is what interests me the most. How to get
the base metals back, ok some can be reused to start the reaction next time but would also be good to be able to take some out. I will post pics of my
copper solution I got (no gold fingers) its darker than yours but then again I used alot of copper.
I didnt use Hydrogen Peroxide (didnt have any) but did heat it for a while at 50c and bubble air until it started to change colour, I then turned off
the heat, its cold here around 5c in the shed so its been slow but seems to work fine
Dont ask me, I only know enough to be dangerous
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aga
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I really want to see a whole process, so there's 3g of .999 Au winging it's way from Istanbul to see what will happen.
This will be solid gold, which might take ages to dissolve.
Would it be better to melt it and chuck it in a bucket of water to make shot ?
Does that even work with gold ?
There's no chance that i'm going to file 1g of metal into filings.
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deltaH
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For long dissolving times, the pH of the solution is going to be very important.. Too low and the chlorine will just come off in minutes and it
will be dead after that (not a problem for the foils because they dissolve so rapidly), too high and dissolution rate will be too slow or not at all.
My guess is that the sweet spot will be ~ pH 4.5-5.5.
Start with 200ml neat vinegar and add as much 0.5M solution sodium hydroxide solution so as to raise the pH to 4.5. Then add the required amount of
salt to obtain 2M NaCl solution (this will depend on your volume achieved). Then I'd say start with 50ml bleach and keep monitoring the pH, adding
neat vinegar with stirring to bring it back down and as close as possible to 4.5-5.5. Add 50ml bleach every few hours if it seems necessary to do so.
Keep monitoring pH and adjusting with neat vinegar.
The pH 4.5 - 5.5 value is my educated guess as based on the pourbaix diagrams at the beginning of this thread.
Remember bleach is basic, so it will raise your pH immediately when you add it. Also, the gold dissolution consumes acidity and so will also raise the
pH, albeit gradually. So check and correct immediately after adding bleach and then periodically as dissolution progresses (if it progresses).
Always stir rapidly when adding neat vinegar to a solution containing bleach or else the local highly acidic spots when it first hits will
evolve chlorine gas!
The acetic acid/sodium acetate buffer is particularly effective ~pH 4.5, so it should be well suited to this system.
[Edited on 7-10-2015 by deltaH]
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aga
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It'll be a 1g bar of solid gold, specifically this :
http://www.ebay.co.uk/itm/301586182892?_trksid=p2057872.m274...
Your show deltaH, so do as much calculating as you can in the time before the gold arrives.
When it arrives, there's dissolving to get done.
I ordered 3 so one can go into an aqua regia solution for comparison.
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deltaH
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A 1g 'bar' can probably be cut with scissors into slithers 
[Edited on 7-10-2015 by deltaH]
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aga
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Oh ! so i got to Work as well now ?
Careful : this bitch ain't no ho.
Go with solid bar. Processing a 24kt ring as part of a pile of (indivually) untested gold scrap would be equivalent.
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deltaH
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If it was a big bar, I'd say drill it to get turnings, but 1g is going to be a thick foil and gold is soft after all, but I hear you, it's closer to
bulk gold processing.
As for the amounts, for 1g, you probably won't need more than 50ml neat vinegar and 50ml bleach to start with (notwithstanding the required amount of
sodium hydroxide and NaCl).
Don't start with larger volumes, a dilute solution of gold might make you problems with reducing it or using it for other applications later on.
Besides, your volume will grow as you add the base and keep correcting the pH with additional vinegar.
[Edited on 7-10-2015 by deltaH]
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deltaH
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To make this a fair test for a comparison to aqua regia, we should match up the concentration of chloride in both. That way we will compare on
oxidising ability alone. What recipe will you be using for the aqua regia?
The oxidation potential of 1M HClO solution at pH 4.5 is ~1.4V or about the same as chlorine gas. I'd say this is very comparable to aqua regia and so
expect similar dissolution rates.
[Edited on 7-10-2015 by deltaH]
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gdflp
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How are you planning on measuring the pH? One problem you might run into is that it is difficult to measure the pH of an oxidizing solution like this
because the hypochlorite can "bleach" (destroy the dye molecule) the indicator being used to measure the pH, be it universal indicator paper or
something else, rendering it impossible to get an accurate reading. A pH meter might be necessary to get an accurate reading, or the use of a more
chemically resistant indicator.
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aga
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A digital pH meter is on hand.
I'll use that rather than keep dropping stuff onto some UI paper.
Good point though gdflp - any pH indicator can be destroyed by the reaction it's supposed to be indicating (including a digital
reading one).
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kadriver
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Quote: Originally posted by aga  | I really want to see a whole process, so there's 3g of .999 Au winging it's way from Istanbul to see what will happen.
This will be solid gold, which might take ages to dissolve.
Would it be better to melt it and chuck it in a bucket of water to make shot ?
Does that even work with gold ?
There's no chance that i'm going to file 1g of metal into filings. |
If you melt the 3g of pure gold and pour it in a METAL container of cold tap water it will flatten out and present more surface area to the acid, and
dissolve quicker.
Be careful not to get the gold too hot when you melt it, let it cool a second or two before you pour the molten gold into the water. If you pour it
while it's real hot it will make a loud pop and bust up into tiny gains smaller than sand. No problem, but it could cause you to lose some of the
metal because it will be so small.
Then take the flakes of gold from the tap water, and put in a 250ml beaker with a watch glass. Next add about 100ml HCl. Place on LOW heat (under no
circumstances should you boil it) and add concentrated nitric acid a drop at a time until all the gold dissolves - should only take about 1 or two ml
of nitric.
Once it's all dissolved, filter out any solids making sure to rinse the filter free of color. Return the clear filtered chloroauric acid to the beaker
and place it inside a Corning ware dish in case you get a boil over. Add a spoon of sodium meta bisulfite
And watch the gold precipitate almost immediately. Test the solution with stannous chloride! If positive then add some more SMB until all the gold
comes down and the stannous test is negative.
Wait for the gold powder to settle then decant the barren liquid by siphoning with a small tube or use a transfer pipette, then rinse the gold powder
with some HCl and decant after settling. You can dry the gold powder over low heat while it's still in the beaker.
You will be left with about three grams of brown powder that is pure gold. You can then try to dissolve as per step two from deltaH.
I could have sold you 3g of pure gold powder in a nice little glass vial for about $40 per gram - let me know if you need some gold in the future.
kadriver
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kadriver
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I wish you would have checked with me. I could have poured the shot/flakes for you at $40 per gram then shipped as a gift with no duty to the UK.
Here is a gold bar that I just finished;
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kadriver
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| Quote: Originally posted by deltaH | To make this a fair test for a comparison to aqua regia, we should match up the concentration of chloride in both. That way we will compare on
oxidising ability alone. What recipe will you be using for the aqua regia?
The oxidation potential of 1M HClO solution at pH 4.5 is ~1.4V or about the same as chlorine gas. I'd say this is very comparable to aqua regia and so
expect similar dissolution rates.
[Edited on 7-10-2015 by deltaH] |
It is best NOT to premix the Aqua regia. Prefixing guaratees that there will be excess nitric that causes problems when you go to precipitate the
gold.
Instead add just HCl, cover, place on low heat, and add concentrated nitric a drop at a time until all the gold dissolves. With 1 gram I would add
only 20 or 30ml HCl. Then just drops of HNO3.
Also, if you have any, add about three or four drops of H2SO4 just before you filter the chloroauric acid solution as a precaution to precipitate out
any lead as lead sulfate. It can then be filtered out. It doesn't hurt a thing, but lead, even in trace amounts, will ruin the ductility of the gold.
Hope this helps.
kadriver
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kadriver
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| Quote: Originally posted by deltaH | That's pretty kadriver and your yields are thoroughly consistent!
The way I see it, this process has three important sections:
Mineral acid-free 'fish and chips' gold refining process
(1) Base metal leaching: vinegar + salt + air bubbling + initial H2O2
(2) Gold foil dissolution: vinegar + salt + bleach
(3) Base metal recovery: ?
Comments:
* Step (1) has now been tried on small and larger scales thanks to the pioneering work of aga and kadriver. Step (2)
has only been tried on a small scale by aga and Step (3) is largely completely open.
* Step (3) is vitally important though. Without it, the process doesn't deal with its waste and is incomplete.
Also, part of the copper containing solution from step (3) could be recycled into step (1) so that peroxide is no longer needed, then this thing would
come full circle and you would have a reliable, low cost and safe complete process that could be used again and again.
Looking forward to someone continuing the research into this, i.e. scaling up of step (2) and development of step (3).
[Edited on 7-10-2015 by deltaH] |
How about 2a; precipitating the pure gold powder?
There are several choices. I prefer sodium meta bisulfite. It is sold at the hardware store as "Stump Out" stump remover by BONIDE. Stump out by
spectracide is NOT sodium meta bisulfite, it is potassium nitrate! So be sure it's stump out by BONIDE.
Another good one is copperas (ferrous sulfate) it is also sold at gardening shops and the hardware store. To use I pour about 200ml of the green
powdered ferrous sulfate into a 600ml beaker, then fill with tap water to about 500ml and stir over low heat until dissolved.
It will look orange in color, I add about 10ml of hydrochloric acid to turn it green. I set up a filter station with a ring stand and filter the
dissolved ferrous sulfate directly into the clean chloroauric acid solution. The gold precipitates quickly and cleanly.
Ferrous sulfate produces no noxious fumes, but SMB make lots of sulfur dioxide gas and must be done in a fume hood.
kadriver
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kadriver
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Another though; using gold powder vs gold shot will more closely match gold foils as the foils are just microns in thickness where as the gold
flakes/shot could be several millimeters thick.
kadriver
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Little_Ghost_again
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Out of interest do you know what happens to the rest of the board after they cut the fingers off and sell on ebay?
Dont ask me, I only know enough to be dangerous
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kadriver
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Some of the chips have traces of gold. They can be removed and the gold recovered and refined, but it takes a lot of them to get any gold.
The actual boards have copper and nickel, only the connection points, the "fingers" are gold plated.
I don't know what happens to them once the fingers are trimmed off.
kadriver
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deltaH
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| Quote: Originally posted by kadriver | | Quote: Originally posted by deltaH | To make this a fair test for a comparison to aqua regia, we should match up the concentration of chloride in both. That way we will compare on
oxidising ability alone. What recipe will you be using for the aqua regia?
The oxidation potential of 1M HClO solution at pH 4.5 is ~1.4V or about the same as chlorine gas. I'd say this is very comparable to aqua regia and so
expect similar dissolution rates.
[Edited on 7-10-2015 by deltaH] |
It is best NOT to premix the Aqua regia. Prefixing guaratees that there will be excess nitric that causes problems when you go to precipitate the
gold.
Instead add just HCl, cover, place on low heat, and add concentrated nitric a drop at a time until all the gold dissolves. With 1 gram I would add
only 20 or 30ml HCl. Then just drops of HNO3.
Also, if you have any, add about three or four drops of H2SO4 just before you filter the chloroauric acid solution as a precaution to precipitate out
any lead as lead sulfate. It can then be filtered out. It doesn't hurt a thing, but lead, even in trace amounts, will ruin the ductility of the gold.
Hope this helps.
kadriver |
That's a good point about adding in the nitric acid as required and thanks.
Back to matching chloride concentrations, aga, if you're using 37% HCl, that a 12M solution of chloride ions, which means you will
need a 12M solution of NaCl, that's 701g/l... NOT POSSIBLE 
The best you can do is half that i.t.o the solubility of the NaCl in pure water, probably much lower in pure vinegar (the 5-10% acetic acid would make
the salt less soluble).
[DON'T be tempted to use ammonium chloride, it will kill you!
[Edited on 8-10-2015 by deltaH]
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deltaH
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| Quote: Originally posted by kadriver | | Quote: Originally posted by deltaH | That's pretty kadriver and your yields are thoroughly consistent!
The way I see it, this process has three important sections:
Mineral acid-free 'fish and chips' gold refining process
(1) Base metal leaching: vinegar + salt + air bubbling + initial H2O2
(2) Gold foil dissolution: vinegar + salt + bleach
(3) Base metal recovery: ?
Comments:
* Step (1) has now been tried on small and larger scales thanks to the pioneering work of aga and kadriver. Step (2)
has only been tried on a small scale by aga and Step (3) is largely completely open.
* Step (3) is vitally important though. Without it, the process doesn't deal with its waste and is incomplete.
Also, part of the copper containing solution from step (3) could be recycled into step (1) so that peroxide is no longer needed, then this thing would
come full circle and you would have a reliable, low cost and safe complete process that could be used again and again.
Looking forward to someone continuing the research into this, i.e. scaling up of step (2) and development of step (3).
[Edited on 7-10-2015 by deltaH] |
How about 2a; precipitating the pure gold powder?
There are several choices. I prefer sodium meta bisulfite. It is sold at the hardware store as "Stump Out" stump remover by BONIDE. Stump out by
spectracide is NOT sodium meta bisulfite, it is potassium nitrate! So be sure it's stump out by BONIDE.
Another good one is copperas (ferrous sulfate) it is also sold at gardening shops and the hardware store. To use I pour about 200ml of the green
powdered ferrous sulfate into a 600ml beaker, then fill with tap water to about 500ml and stir over low heat until dissolved.
It will look orange in color, I add about 10ml of hydrochloric acid to turn it green. I set up a filter station with a ring stand and filter the
dissolved ferrous sulfate directly into the clean chloroauric acid solution. The gold precipitates quickly and cleanly.
Ferrous sulfate produces no noxious fumes, but SMB make lots of sulfur dioxide gas and must be done in a fume hood.
kadriver |
Another good point, yes the reducing agent does indeed warrant some thought.
The whole idea with the fish and chips process is to use benign and also environmentally benign, cheap OTC reagents.
Nothing too wrong with the ferrous sulphate nor sodium metabisulfite, but... there's always a but ... I would favour an even more benign and environmentally friendly reducing agent.
In that sense, I am thinking a non-toxic organic agent is better. Something like ascorbic acid (vitamin C)? It's cheap, you can chuck it down the
drain with no impact on the environment and it's completely non-toxic and benign to the user working with it.
Can you share your experience with us on this kadriver? Can it be used?
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deltaH
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| Quote: Originally posted by kadriver | Another though; using gold powder vs gold shot will more closely match gold foils as the foils are just microns in thickness where as the gold
flakes/shot could be several millimeters thick.
kadriver |
I think aga wants a 'show stopper' of sorts, i.e. to see if this can match aqua regia head-to-head in the really tough dissolution...
bulk gold pieces.
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Little_Ghost_again
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I know everyone is chasing gold, BUT there is alot of copper compared to gold in pcb's, while the spot price isnt fabulous I have spotted another
outlet with good returns.
I would be very interested in buying the scrap boards with gold already recovered and the copper left in place , I figure they have to be cheaper by a long way. If you look carefully there are places copper is worth more than
gold, then look at the copper process used here, do you have a rough idea of mesh size from the copper powder you recover?
Dont ask me, I only know enough to be dangerous
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