First gold recovery

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EurekaNach
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First gold recovery

Post by EurekaNach » November 9th, 2019, 9:26 pm

Hello guys I wanted to show you guys the gold I recovered from a batch of fingers and ask your opinion about the method I used and any tips on going from gold powder to a gold pebble.

I took a batch of 29 g of closely trimmed fingers from various sources and put them in some diluted nitric for a couple of days and then scraped off all of the gold with some tweezers, I then filtered it and let it soak in some clean diluted nitric overnight. After pouring the nitric it soaked in into the stock pot I prepared 200 ml of AR and dissolved the gold flakes in it, when it was done dissolving I heated it to around 50 °C and let it simmer for an hour.

https://imgur.com/Fp2OBKj
https://imgur.com/TlwuvVV

I then tried 3 things. 1) cementing with zinc , 2) adding Sodium Bisulfate, 3) Both. Zinc seemed to work best and Im not really sure what happened with option 3, I think i made some kind of zinc salt, so I cemented the rest with zinc and cleaned the precipitate with hot water, nitric, and water again.

https://imgur.com/m5Mvx5U

So I would like your opinions, I have learned a lot here in the forum and reading the recommended books but since its my first time I would love to hear you comments about what I might have done wrong.

PS:Im a Chemical Engineer and am pretty decent in the lab safety wise, all of this was done in a ventilated area (not my living space) with protective equipment. The images were too big, ill resize them tomorrow and attatch them as images

butcher
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Re: First gold recovery

Post by butcher » November 9th, 2019, 10:26 pm

Zinc will cement other base metals from solution with your gold solution, it is good for a recovery method to get gold out of solution but it is not that helpful in refining the gold.

My guess is you over-used nitric, and I do not see any description or process of removing the free nitric or nitrates from the aqua regia solution, in your description, the zinc used up free nitric and cemented your gold along with the other base metals in solution...

I cannot see much you have done wrong, you recovered your gold from solution. I do see several things you could do differently.
Nitric is fine if you can get and refine with it economically, there are other ways to recover the foils, they may not be as fast or may require a little more work...

You can also dissolve the gold foils without the troubles of aqua regia, or the use of nitric acid, using HCl and H2O2 or sodium hypochlorite as the oxidizer)...

Learning to use the aqua regia wisely and efficiently (limiting the nitric use), which you may already be practicing.
Removing free nitric acid, triple evaportation method with HCl additions, the addition of a gold button, sulfamic acid...

Dilution to precipitate silver or other insoluble chlorides, a few drops of sulfuric acid (or the sulfamic acid above) to precipitate lead as a sulfate, letting settle and decanting filtering the solution before attempting to precipitate the gold

Using a reagent that is selective for gold (like sodium Bisulfate).

Testing for gold in solution.

Re-refining and washing the gold.

I cannot say your doing anything wrong, but your skill and process can only improve by spending time studying the process and gaining more knowledge in the reactions and the process...

EurekaNach
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Re: First gold recovery

Post by EurekaNach » November 9th, 2019, 10:39 pm

butcher wrote:
November 9th, 2019, 10:26 pm

Nitric is fine if you can get and refine with it economically, there are other ways to recover the foils, they may not be as fast or may require a little more work...
In my country the sell of either HCL or sulphuric is heavily restricted, fortunately Nitric goes for around 2-3 usd per gallon and is not restricted

butcher
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Re: First gold recovery

Post by butcher » November 10th, 2019, 12:30 am

If you used aqua regia, you obviously have access to HCl.

You have a computer so there must be some DC batteries with sulfuric acid as the electrolyte someplace around you, or places that repair or recycle batteries...

Probably most of the people walking around town have some HCl hidden under their tee shirt (or in their breadbasket), those acids are so very common and used in so many areas in industry, they are probably more accessible to you than you know, although it may take some work ( and or education) to find a source or a workaround...

With some cases of refining, where we may need sulfuric acid, we can use substitutes for the sulfuric acid, like using sulfamic acid to remove free nitric acid and byproduct of that reaction the lead in solution will form an insoluble sulfate (eliminating the need for the few drops of sulfuric acid).

That confuses me that you can get nitric but you can not get the more common acids like HCl or sulfuric acid because they are restricted that just seems odd to me.

Well, what are the restrictions, What paper or document do you need? What politician do you have to pay in gold for a license or document? What do you have to do to qualify or to become registered to purchase and use these common mineral acids?


There are some workarounds or sometimes other ways of doing a recovery process using a different acid or processes, or of making a reagent that you need, and sometimes you can refine the gold with some other process, but you will find it difficult to go far recovering and refining gold without being able to get HCl or sulfuric acids...

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g_axelsson
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Re: First gold recovery

Post by g_axelsson » November 10th, 2019, 12:39 am

You don't need sulfuric acid to remove lead, any soluble sulfate will do, for example copper sulfate.

Sulfuric acid is easy to make by electrolysis of copper sulfate with a platinized titanium anode. Then hydrochloric acid can be made by mixing sulfuric acid with table salt and distilling off hydrochloric acid. It takes some time but for small amounts it's possible.

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EurekaNach
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Re: First gold recovery

Post by EurekaNach » November 10th, 2019, 1:16 am

butcher wrote:
November 10th, 2019, 12:30 am
That confuses me that you can get nitric but you can not get the more common acids like HCl or sulfuric acid because they are restricted that just seems odd to me.
They are restricted because both are used in the production of cocaine from coca leaves, and its not impossible to get, I would need to go to the police and fire departments and get an inspection get some certificates, a whole bunch of paperwork basically that Im currently working on. They do sell it clandestinely and I have the contact but the prices are significantly higher and im trying to minimize their use

EurekaNach
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Re: First gold recovery

Post by EurekaNach » November 10th, 2019, 1:18 am

g_axelsson wrote:
November 10th, 2019, 12:39 am
You don't need sulfuric acid to remove lead, any soluble sulfate will do, for example copper sulfate.

Sulfuric acid is easy to make by electrolysis of copper sulfate with a platinized titanium anode. Then hydrochloric acid can be made by mixing sulfuric acid with table salt and distilling off hydrochloric acid. It takes some time but for small amounts it's possible.

Göran
My current HCL was done this way with some leftover sulfuric a friend had

butcher
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Re: First gold recovery

Post by butcher » November 10th, 2019, 1:56 am

You may find some ways to do workarounds like using HNO3 and NaCl to dissolve gold, but they will have their own set of problems to overcome, it would be simpler if you can find a source of the acids or a product that uses the acid, or get the authorization to purchase it, especially the HCl.

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Re: First gold recovery

Post by Shark » November 10th, 2019, 2:36 pm

I then tried 3 things. 1) cementing with zinc , 2) adding Sodium Bisulfate, 3) Both. Zinc seemed to work best and Im not really sure what happened with option 3, I think i made some kind of zinc salt, so I cemented the rest with zinc and cleaned the precipitate with hot water, nitric, and water again.
That Sodium Bisulfate should have been Sodium Bisulfite or Sodium metabisufite.
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EurekaNach
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Re: First gold recovery

Post by EurekaNach » November 10th, 2019, 7:08 pm

Shark wrote:
November 10th, 2019, 2:36 pm
I then tried 3 things. 1) cementing with zinc , 2) adding Sodium Bisulfate, 3) Both. Zinc seemed to work best and Im not really sure what happened with option 3, I think i made some kind of zinc salt, so I cemented the rest with zinc and cleaned the precipitate with hot water, nitric, and water again.
That Sodium Bisulfate should have been Sodium Bisulfite or Sodium metabisufite.
It was, i wrote the wrong thing

Shark
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Re: First gold recovery

Post by Shark » November 10th, 2019, 7:55 pm

Then your on the right path. It really sounds tough in your country with the acid problems as well.

Best of luck.
No job is so simple that it cannot be done wrong.

"Learn from the mistakes of others. You can't live long enough to make them all yourself."
- Eleanor Roosevelt

EurekaNach
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Re: First gold recovery

Post by EurekaNach » November 11th, 2019, 6:01 pm

I have a question about using the busilfite, if it bubbles does it mean i have excess nitric?

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FrugalRefiner
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Re: First gold recovery

Post by FrugalRefiner » November 11th, 2019, 6:18 pm

Bisulfite bubbles when it reacts with HCl in your AR to produce SO2 gas. It is the SO2 that reduces the gold and causes it to precipitate.

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