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Cyanide Destruction & Gold Recovery (3 replies and 2 comments)
If I may offer you a better and safer suggestion for deplating computer fingers?
Simple HCl with the addition of air from a fish tank bubbler, will cause the base metal (copper) to oxidize and dissolve, thus leaving the gold to sink or float.
Once all the fingers are clean, pour off the HCl and gold into a coffee filter (4 or 5 filters to make sure it dont break through) Rinse the gold flakes really well.
Now use a spray bottle with water and rinse the gold into a beaker. Let settle.
Siphon off the water, or as much as you can. Now add HCL to just over the gold flakes by 1/4".
Here is the dangerous part......
Now add common household bleach to the HCl and gold.
This will cause a very STRONG odor and will take your breath away and this will cause foaming. Never have more bleach than HCl.
You will now see that the solution has turned immediaely gold... or possible orange depending on the concentration of gold.
Swirl the solution around until all the gold has dissolved. It may take a few minutes. If you notice the dissolving has ceased, but you still have gold flakes, slowly pour in a little more bleach. AGAIN, this will cause a strong smell and foaming.
Once all the gold has dissolved..... Pour gold solution through more clean coffee filters. Repeat this step 3 or 4 times. You will see the liquid getting clearer and clearer.
After the filtration put the air hose back in the solution and leave for about 24 hours. You cant skip this step. The chlorine will hold the gold in suspension, so the air bubbling in it will cause the chlorine to bubble out.
Now you can use your favorite method to drop the gold out of solution.
I use SMB (Sodium Metabisulfite)
Thanks for your suggestion. I will follow it next time. Now I need to recover the gold from the cyanide solution. I have written about the metals present in the gold cyanide solution in my question. I want to destroy sodium cyanide and hydrogen peroxide present in the solution using SMB and recover gold with sodium hydrosulfite. I want to know how to proceed about it. What quantity of SMB will be used ? Is oxygen and heat also necessary in this process or we can do without them also. Do we need to add some more chemicals to the solution to complete the process?
Thanks & Regards
Auman pretty much nailed it! For fingers he has given you the easiest solution to processing these. If it were some other type of materials then i might recommend cyanide.
May i ask how many lbs of fingers you processed? What type of fingers?
How did you arrive at the 100 grams in solution number?
It was 40 lbs. Previously I used aqua regia method. That’s why I know the correct recovery. I got 2.5 grams of gold per lb with aqua regia method. This time I thought of recovering gold with sodium cyanide because in short future, we are likely to get gold plated connectors. And I have seen many people removing gold from the connectors with cyanide method. They add copper sulfate solution to the gold cyanide solution and then add sulpphuric acid to that to recover gold.
I need to recover the gold from the cyanide solution now. I have written about the metals present in the gold cyanide solution in my question. I want to destroy sodium cyanide and hydrogen peroxide present in the solution using SMB and recover gold with sodium hydrosulfite. I want to know how to proceed about it. What quantity of SMB will be used ? Is oxygen and heat also necessary in this process or we can do without them also. Do we need to add some more chemicals to the solution to complete the process?
Thanks & Regards
As a matter of fact after you get the foils from the ap process ( This is what hcl with air is nick named) you can dissolve the foils with hcl and additions of the 36% H2O2 you have instead of Hcl/bleach. Heat the solution up to about 180 degs F and let cool to break down the H2O2. Then you can drop with Sodium formate, Smb, Ferrous Sulphate (Copperas), Sulfur dioxide gas, or what ever you favorite precipitate may be. The gold that comes from the foils is almost pure as it is so about the only thing you need to do to get it past .995 is after you precipitate it and wash it with water once or twice is do do a couple of washes in Hcl then water again to help remove any copper contaminates that may have been dragged down in the precipitation.
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We have a gold cyanide solution of 30 liters. We removed gold from gold fingers. We used 500 grams of commercial grade sodium cyanide and 1.5 liters of hydrogen peroxide of 36%. This solution contains 100 grams of gold around 5 grams of iron and 5 grams of solder. We want to use copper sulphate, sodium metabisulfite for cyanide and hydrogen peroxide destruction. And sodium hydro sulfite for gold recovery from the solution. How do we proceed about it. Is oxygen and high temperature necessary in this process or we can do without them also. We are sure about the gold quantity in the gold cyanide solution because we previously recovered gold through aqua regia method from the same material. We are focussing on this because we have a big lot of High Grade gold plated connectors. Gold is plated on brass pins in the connectors.
Thanks!