I am needing some guidance as to how I should continue my gold recovery process

[dteberian]

Hey there, everybody!

I am working with a ton of old PCBs and connectors that are gold plated, I have been working on recovering some gold, and I am making good progress. That being said, I need all the advice I can get, so I have decided to come here and ask the experts.

I have several methods that have worked (kind of):
1. Aqua regia - The classic, reliable method. The issue is that I can't really afford the amount of nitric acid that I would need to recover the amount of gold that I need to. I can make my own, using nitrate salts and concentrated sulfuric acid, but that is very time-consuming, and it often has problems.

2. Manually removing gold - This is the worst method, and it is not even close. If you want to end up injuring yourself, ruining gold, and having to use another method to make use of the stuff you manage to salvage via this method, this method is for you. I really do not like this method, and I would encourage others to avoid it.

3. Reverse electro-plating - This is the most interesting method to me right now. It has worked well, it has removed gold plating almost immediately, but I have not figured out how to use the gold powder that I get from this method. Could I melt that "mud" down into a small bead of gold, put it in hot sulfuric/nitric acid, and allow the acid to purify the gold by dissolving the base metals?

4. A weird method to remove the plating, using pretty common stuff - I have found that it is incredibly easy to remove all of the gold from a PCB by putting a glass dish on a hotplate, putting muriatic/hydrochloric acid and hydrogen peroxide into the dish, and heating it up. It ends up eating the adhesive that keeps the plating attached to the boards and pulls the gold off of them.


I am most interested in some advice as to how I can use the third method, but feel free to lead me toward another method if you think I should try something else. I am excited to see what you all come up with! Thanks, and God bless!

 

[Yggdrasil]

Hey there, everybody!

I am working with a ton of old PCBs and connectors that are gold plated, I have been working on recovering some gold, and I am making good progress. That being said, I need all the advice I can get, so I have decided to come here and ask the experts.

I have several methods that have worked (kind of):
1. Aqua regia - The classic, reliable method. The issue is that I can't really afford the amount of nitric acid that I would need to recover the amount of gold that I need to. I can make my own, using nitrate salts and concentrated sulfuric acid, but that is very time-consuming, and it often has problems.

2. Manually removing gold - This is the worst method, and it is not even close. If you want to end up injuring yourself, ruining gold, and having to use another method to make use of the stuff you manage to salvage via this method, this method is for you. I really do not like this method, and I would encourage others to avoid it.

3. Reverse electro-plating - This is the most interesting method to me right now. It has worked well, it has removed gold plating almost immediately, but I have not figured out how to use the gold powder that I get from this method. Could I melt that "mud" down into a small bead of gold, put it in hot sulfuric/nitric acid, and allow the acid to purify the gold by dissolving the base metals?

4. A weird method to remove the plating, using pretty common stuff - I have found that it is incredibly easy to remove all of the gold from a PCB by putting a glass dish on a hotplate, putting muriatic/hydrochloric acid and hydrogen peroxide into the dish, and heating it up. It ends up eating the adhesive that keeps the plating attached to the boards and pulls the gold off of them.


I am most interested in some advice as to how I can use the third method, but feel free to lead me toward another method if you think I should try something else. I am excited to see what you all come up with! Thanks, and God bless!

Point 1. For PCBs Aqua Regia is not a good solution anyway so save your Nitric.
Point 1.5 Better use AP or Cupric Chloride etching as it actually are.

Take the PCBs and cut away the plated items as fingers and such and then put them in a bucket and cover it with some HCl.
Then put in a small tube and start bubbling air through it.
This will create Cupric Chloride and it will etch the Copper away from under the Gold plating.
When the Cu are gone the foils are free and can be collected.
The foils are easily dissolved in HCl/bleach or better HCl/ pool chlorine.
AR will be an overkill in these settings.

How do you make your AR by the way?

Point 2. This is kind of "easy" but labour intensive, so not very good, most of the time.

Point 3. Do you mean the Sulfuric Cell?

Point 4. HCl and Peroxide will dissolve the Gold readily, which will then cement out on the base metals.

 

[dteberian]

Point 1. For PCBs Aqua Regia is not a good solution anyway so save your Nitric.
Point 1.5 Better use AP or Cupric Chloride etching as it actually are.

Take the PCBs and cut away the plated items as fingers and such and then put them in a bucket and cover it with some HCl.
Then put in a small tube and start bubbling air through it.
This will create Cupric Chloride and it will etch the Copper away from under the Gold plating.
When the Cu are gone the foils are free and can be collected.
The foils are easily dissolved in HCl/bleach or better HCl/ pool chlorine.
AR will be an overkill in these settings.

How do you make your AR by the way?

Point 2. This is kind of "easy" but labour intensive, so not very good, most of the time.

Point 3. Do you mean the Sulfuric Cell?

Point 4. HCl and Peroxide will dissolve the Gold readily, which will then cement out on the base metals.

Thank you for the advice, regarding cupric chloride. Is there a good way to cut the fingers away, or to bubble air into the bucket with PCBs?

How is it that HCl can dissolve gold foil when it cannot dissolve gold under normal circumstances (as far as I am aware)?

I used a sulfuric cell, but I don't know which portion of that point you are referring to, specifically. Could you explain what you are referring to? I apologize if I am missing something obvious.

What do you mean by "cement out"?



Regarding my process for creating AR, most of the work is from me making the nitric acid. I have a hotplate, I pour concentrated sulfuric acid into a beaker, put that beaker onto the hotplate, and add some nitrate salts whenever the acid is warm. I have distilled nitric acid using sulfuric acid and nitrate salts, but that is more complicated, and requires a lot more work.

 

[Yggdrasil]

Thank you for the advice, regarding cupric chloride. Is there a good way to cut the fingers away, or to bubble air into the bucket with PCBs?

How is it that HCl can dissolve gold foil when it cannot dissolve gold under normal circumstances (as far as I am aware)?

I used a sulfuric cell, but I don't know which portion of that point you are referring to, specifically. Could you explain what you are referring to? I apologize if I am missing something obvious.

What do you mean by "cement out"?



Regarding my process for creating AR, most of the work is from me making the nitric acid. I have a hotplate, I pour concentrated sulfuric acid into a beaker, put that beaker onto the hotplate, and add some nitrate salts whenever the acid is warm. I have distilled nitric acid using sulfuric acid and nitrate salts, but that is more complicated, and requires a lot more work.

HCl do not dissolve Gold alone it need an oxidizer as in AR where Nitric is the Oxidizer or in HCl/Bleach where Chlorine is the oxidizer or HCl/Peroxide where the Peroxide is the oxidizer.
Describe your Sulfuric cell please.
Any less noble metal will engage in a Ion exchange process where the noble metal readily goes out of solution replacing itself with the less noble metal.
The metal falling out in Silver solutions looks liker Cement hence the name.
Copper will only "Cement" out precious metals and Mercury.

Read this:
https://goldrefiningforum.com/threads/a-glossary-of-common-terms.23400/post-246408

 

[Martijn]

but I have not figured out how to use the gold powder that I get from this method.

You can siphon off the clear acid after a couple days, pour the black concentrated goo in a beaker with water while stirring. Brush, or spray rinse the lats bit out. Be carefull, sulfuric acid on glas is slippery.
Then boil that water to dissolve some base metals and salts. Let it cool and settle.
Decant and add HCl with an oxidizer like nitric or bleech to dissolve the gold. Melting at this point will not yield pure enough gold.
Proceed as usual to filter, precipitate, wash and then melt your refined gold.