Seperating gold from other metals

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M

MonteDorado

Member
Joined
Jul 28, 2018
Messages
9
So I have about 7 kilos of gold that is 85%+ purity. This gold has silver, platinum, rhodium, iridium, palladium, etc. I want to seperate the gold, purify it, and then precipitate the silver and pgms. I don't care about purifying the platinum, silver, etc. I just want the gold pure and the pgms and silver I can just ship out to the refinery. What would be the best way of going about this? I currently have oxalic acid 99.6%, sodium borohydride 98%, sodium metabisulfite 98.6%+, nitric acid 67.2%, sulfuric acid 98%, hydrochloric acid 32%, acetone 99.5%. Anything missing, let me know. I have plenty of lab glass and lab equipment. So, again, to summarize, I want pure gold, and to precipitate all else (any purity).

Thanks so much for all the help!

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jimdoc said:
You should just sell it to someone who pays for the other metals also.
Click to expand...
I know that, but I have a particular circumstance that requires me to do this.

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I should probably also mention I have 99.9% pure zinc shot and 99.9% pure tin shot.

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A first step would be dissolving the gold and palladium in cold aqua regia what would leave AgCl, and most rhodium, iridium platinum as solids.
 
Lino1406 said:
A first step would be dissolving the gold and palladium in cold aqua regia what would leave AgCl, and most rhodium, iridium platinum as solids.
Click to expand...
So if I use the aqua regia at room temp (or would i have to keep it a certain temp?) on the gold, only gold and palladium would be dissolved? AgCl, rhodium, platinum, iridium, would stay solid? After that, filter, precipitate gold, filter, then precipitate palladium, then dispose of ar?

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If you use cold AR as Lino said it will dissolve gold palladium and base metals but as dissolving will create heat the chances are you will dissolve some of the PGMs so once all the gold has dissolved filter your solution neutralize any excess nitric using sulfamic and precipitate your gold using smb. Decant the solution off and rinse your gold powders with water adding the rinses to your starting solution, a good long soak in Hcl would be no bad idea again rinsing the powder off using water and add to the rest of the solution.
To recover the any PGMs simply add a copper bar and use an air bubbler to keep the solution moving, the values should form as a black powder, testing with stannous should tell you if you have any values left in solution.
The solids and any silver chloride will be in your initial filter so convert any silver chloride by the method of your choice and add the cemented black powders once the silver and solids have been filtered and rinsed and melt.
Bear in mind that you will be creating some fairly toxic solutions with PGMs in solution so use extreme care and all this has to be done under a fume hood and any waste solutions will need to be properly treated to make them safe to dispose of, all of which is fully covered here on the forum.
 
nickvc said:
If you use cold AR as Lino said it will dissolve gold palladium and base metals but as dissolving will create heat the chances are you will dissolve some of the PGMs so once all the gold has dissolved filter your solution neutralize any excess nitric using sulfamic and precipitate your gold using smb. Decant the solution off and rinse your gold powders with water adding the rinses to your starting solution, a good long soak in Hcl would be no bad idea again rinsing the powder off using water and add to the rest of the solution.
To recover the any PGMs simply add a copper bar and use an air bubbler to keep the solution moving, the values should form as a black powder, testing with stannous should tell you if you have any values left in solution.
The solids and any silver chloride will be in your initial filter so convert any silver chloride by the method of your choice and add the cemented black powders once the silver and solids have been filtered and rinsed and melt.
Bear in mind that you will be creating some fairly toxic solutions with PGMs in solution so use extreme care and all this has to be done under a fume hood and any waste solutions will need to be properly treated to make them safe to dispose of, all of which is fully covered here on the forum.
Click to expand...
Wow! Thank you for such a detailed response! By sulfamic do you mean sulfuric? Also, would it be fine to use a stir bar instead of an air bubbler?

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No sulfamic acId will work on the nitric to convert it to sulphuric allowing easier precipitation of your gold, also if you have any lead in solution it will drop it out as lead sulphate which can be filtered off.
A stir bar will be fine so long as it moves the solution around, if it doesn’t you will find the PGMs will coat your copper bar and stop it cementing any more PGMs out of solution, it can take some time to collect it all so patience is the key.
Once you have your silver and PGMs maybe contact Lou to sell it.
 
nickvc said:
No sulfamic acId will work on the nitric to convert it to sulphuric allowing easier precipitation of your gold, also if you have any lead in solution it will drop it out as lead sulphate which can be filtered off.
A stir bar will be fine so long as it moves the solution around, if it doesn’t you will find the PGMs will coat your copper bar and stop it cementing any more PGMs out of solution, it can take some time to collect it all so patience is the key.
Once you have your silver and PGMs maybe contact Lou to sell it.
Click to expand...
Great info! How much sulfamic should I add?

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You can usually see it working as it fizzes as you add it to a warm or hot solution when a further addition stops working as in it fizzes stop.
If you add too much the sulphuric produced will destroy your filter paper...
 
nickvc said:
You can usually see it working as it fizzes as you add it to a warm or hot solution when a further addition stops working as in it fizzes stop.
If you add too much the sulphuric produced will destroy your filter paper...
Click to expand...
So I add in small increments until the fizzing stops?

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Yes add in small increments preferably while your solution is still hot and before you filter it, overdo the sulfamic and your filter paper is history, do not ask me how I know :shock:
 
Wait a minute... 85% gold but how much is silver? If silver is close to 15% then you would probably get a problem with passivation from a silver chloride crust.

Before running a large batch you should do a couple of smaller tests to get a feeling of what works and not.

If you have too much silver then inquartation is the way to go. You don't need too much silver initially if you make it in smaller batches, the silver is easily recovered with cementation and can be reused in the next batch. Most of the PGM:s will probably follow the silver. Rhodium and iridium might follow the gold.
The gold can be either just melted afterwards if it is pure enough, or easily refined with aqua regia to get it really pure and remove trace PGM:s.

Göran
 
g_axelsson said:
Wait a minute... 85% gold but how much is silver? If silver is close to 15% then you would probably get a problem with passivation from a silver chloride crust.

Before running a large batch you should do a couple of smaller tests to get a feeling of what works and not.

If you have too much silver then inquartation is the way to go. You don't need too much silver initially if you make it in smaller batches, the silver is easily recovered with cementation and can be reused in the next batch. Most of the PGM:s will probably follow the silver. Rhodium and iridium might follow the gold.
The gold can be either just melted afterwards if it is pure enough, or easily refined with aqua regia to get it really pure and remove trace PGM:s.

Göran
Click to expand...
They are actually pretty high in platinum, I will try to find sample of assay so I can post here now

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I got mixed up withanother batch about the platinum. I understand this can't speak for all of the material, but it's an idea, so yeah it looks like it would be better to inquart everything.
e2b22d23145e6ffe8656ba86ca6ea9f3.jpg


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Yeah, 12% silver would definitely give you problem with aqua regia.

It's all in the details, another lot high in platinum would probably react different compared to a lot with one high in copper.

Here is the image link again, clickable, the board software have problem with pictures on https links. (just a technical observation)
https://uploads.tapatalk-cdn.com/20180802/e2b22d23145e6ffe8656ba86ca6ea9f3.jpg

Göran
 

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