Removing stones from scrap jewelry?

[FrugalRefiner]

This is what I was leaning towards. Which got me wondering about the process..
1. Leave the jewelry with stones in AR long enough until the stones can be removed. 2. Once stones are gone, clean the gold piece and Inquart and proceed as usual.
If the AR digests the jewelry enough for the stones to fall out, am I correct in thinking that the AR solution will now contain traces of gold along with other base metals? What am I supposed to do with this "contaminated" AR solution?

You don't necessarily have to pull the items out as soon as the stones are out. Some gold alloys will dissolve completely in AR. The problem alloys are usually those with a silver content over about 8 to 10 percent. If it dissolves, you're fine. If it doesn't, you can dissolve the silver chloride crust with thiosulfate or ammonia (be sure to reacidify the ammonia solution promptly). Then you can inquart any pieces that remain.

Yes, you will probably have both gold and base metals in solution. You precipitate the gold from the dirty solution with a selective reducing agent, knowing there will be a lot of contamination. Wash it properly, then re refine it a second time.

I was concerned that if I proceed to precipitating the gold, all the other base metals drop out as well, therefore leaving me with impure and brittle gold..

That's why we use the reducing agents we do. They're selective for gold. While there will be some contamination from the dirty solution, done correctly, the majority of the base metals will remain in solution.

Or is this "contaminated" AR solution something that goes into the stock pot and recovered later.

You add your solution to the stock pot only after you've removed as much of your values as possible.

There's much more to it than my simplified answers indicate, but hopefully they'll point you in the right direction. Keep studying Hoke. She provides all the details behind my brief summaries.

Dave

 

[browninkie]

Ooh, I didn't even think about refining a second time. Very good pointers~~ Thanks Dave.

I've been searching about sodium thiosulfate and it's ability to dissolve silver chloride, but I didn't find too many information regarding the silver recovery from the silver/thiosulfate solution. I read about a technique that involved a rotating silver drum with a negative cathode.. which sounds really complicated
I also read briefly about using steel wool to cement out the silver? This process seemed feasible but I couldn't find any info about the actual process.
Are these my only options of recovering the silver?
Or is there a simpler method of cementing out the silver from the solution??
Any additional sources or links regarding sodium thiosulfate would be really appreciated

 

[Palladium]

If your talking about agcl you can use the sodium hydroxide/sugar method, or hcl/zinc- aluminum foil method, or you could use iron and sulfuric acid. Their are many methods it's just according to where you coming from and where your going with it.

 

[browninkie]

Hey Palladium,
I was researching using AR to remove stones from jewelry and a common problem was that AgCl stops the process.
Therefore, people used either ammonium hydroxide or sodium thiosulfate to dissolve the AgCl crust before proceeding again with the AR.
Now, this is where I'm hitting a wall..
How am I supposed to recover the silver that was dissolved in the sodium thiosulfate solution?
People mentioned using steel wool to cement out the silver or this rotating SS drum cell contraption, however I couldn't find any detailed information about these processes and was hoping someone could point me to the right direction..

 

[4metals]

The silver contained in the thiosulfate is not as easy to recover as silver dissolved in ammonium hydroxide. If you are producing a lot of the thiosulfate it pays to set up a flow through steel wool canister system and smelt out the silver when the canister fills up.

If you are only processing a small amount, the ammonia used to clean up the gold encrusted with chlorides can be acidified with HCl to drop silver as a chloride. The silver chloride can be collected and when you have enough it can be reduced to silver method by any of the methods already outlined on the forum.

Ammonia tends to fume a lot, the genie in the bottle as I like to call it. The thiosulfate has no smell or fume. It's a trade-off. Small quantities, deal with the fume and recover the silver quickly. Larger quantities the thiosulfate method is more advantageous even though the recovery is more difficult.

 

[browninkie]

Thank you very much 4metals~ just the answer I was searching for.
Early on, I decided not to use ammoninium hydroxide because of its fulminating properties with metal salts. :shock:
However, the process you mentioned looks good so I'll keep reading about safely handling NH4OH.
Thanks once again~~

 

[4metals]

Never store ammoniacal solutions with silver in them, always acidify them with HCl, this will drop the silver chloride and eliminate the potential problem of forming silver fulminates (which are explosive)

Many years back I had a client in the west who was a bucket refiner, he had buckets everywhere, some with solution and some with crust. Thank God this happened on a weekend but one of those crusty dry buckets was ammonia and silver which blew the wall of his refinery out of the building. No one was hurt, or even close by, but that was 100% luck. Storing silver in ammoniacal solutions is a bad practice. After the silver chloride dissolves, decant the solution and add HCl and you will never have a bucket that goes boom in the night.

 

[butcher]

Also keep the ammonium waste solutions separate, and treat it separately from the other waste you produce (acidic waste of metal solutions), where mixing of the two can again form a dangerous solution or situation, during the process or in treatment of these wastes.

 

[luca]

Dear Sirs.

FIOA INTERNATIONAL Have made a machine for this purpose:

http://www.fioainternational.com/en/macchinari-per-orafi-goldsmith-machines/decastonatura-chimica-pietre-preziose-chemical-precious-stones-removal/scastonatura-chimica-pietre-preziose/

 

[luca]

This is what I was leaning towards. Which got me wondering about the process..
1. Leave the jewelry with stones in AR long enough until the stones can be removed. 2. Once stones are gone, clean the gold piece and Inquart and proceed as usual.
If the AR digests the jewelry enough for the stones to fall out, am I correct in thinking that the AR solution will now contain traces of gold along with other base metals? What am I supposed to do with this "contaminated" AR solution?

You don't necessarily have to pull the items out as soon as the stones are out. Some gold alloys will dissolve completely in AR. The problem alloys are usually those with a silver content over about 8 to 10 percent. If it dissolves, you're fine. If it doesn't, you can dissolve the silver chloride crust with thiosulfate or ammonia (be sure to reacidify the ammonia solution promptly). Then you can inquart any pieces that remain.

Yes, you will probably have both gold and base metals in solution. You precipitate the gold from the dirty solution with a selective reducing agent, knowing there will be a lot of contamination. Wash it properly, then re refine it a second time.

I was concerned that if I proceed to precipitating the gold, all the other base metals drop out as well, therefore leaving me with impure and brittle gold..

That's why we use the reducing agents we do. They're selective for gold. While there will be some contamination from the dirty solution, done correctly, the majority of the base metals will remain in solution.

Or is this "contaminated" AR solution something that goes into the stock pot and recovered later.

You add your solution to the stock pot only after you've removed as much of your values as possible.

There's much more to it than my simplified answers indicate, but hopefully they'll point you in the right direction. Keep studying Hoke. She provides all the details behind my brief summaries.

Dave

Here is the solution:

http://www.fioainternational.com/en/macchinari-per-orafi-goldsmith-machines/decastonatura-chimica-pietre-preziose-chemical-precious-stones-removal/scastonatura-chimica-pietre-preziose/

 

[g_axelsson]

Dear Sirs.

FIOA INTERNATIONAL Have made a machine for this purpose:

http://www.fioainternational.com/en/macchinari-per-orafi-goldsmith-machines/decastonatura-chimica-pietre-preziose-chemical-precious-stones-removal/scastonatura-chimica-pietre-preziose/

Interesting, what principle is it based on? Which chemistry? Mechanical?

Göran

 

[kurtak]

looks like a fume hood with standard glassware in it to me :lol:

How much $$$$ do they want for this "Stone Removal Machine" :roll:

Kurt

 

[4metals]

I believe Mr Luca is an employee of the manufacturer, just my guess. If you are Mr Luca we invite you to post your wares for refining in the Refiners section in Miscellaneous. No other manufacturer has done that to date and it is a shame because that is where it belongs and I for one would like to see it there.

 

[luca]

Dear Mr 4metals, i am new on this gold refining forum and i was just thinking that it can be useful for people interested in gemstone removal to learn more about this machine and technology.
Anyhow i understand the rule, if we are allowed to post equipments and machinery only in the refiners section in miscellaneous, i will follow your instructions.

Many thanks and Best Regards

I believe Mr Luca is an employee of the manufacturer, just my guess. If you are Mr Luca we invite you to post your wares for refining in the Refiners section in Miscellaneous. No other manufacturer has done that to date and it is a shame because that is where it belongs and I for one would like to see it there.

 

[luca]

Dear Sir,

Chemically the system uses aqua regia to dissolve the gold parts holding gemstones, and once the stones are removed it is possible to recovery fine gold by precipitation as well as wash out the stones covered with silver chloride.
The unit is compact, including one or two etching reactors, vacuum filtration section and gold precipitation section with magnetic stirrer.
All is controlled by the switchboard (heaters, vacuum etc) and the fumes are washed directly in the hood thanks to a recycling tank connected to a proper fumes recovery area in the hood itself.
For further info you can contact the company.

Best Regards

Dear Sirs.

FIOA INTERNATIONAL Have made a machine for this purpose:

http://www.fioainternational.com/en/macchinari-per-orafi-goldsmith-machines/decastonatura-chimica-pietre-preziose-chemical-precious-stones-removal/scastonatura-chimica-pietre-preziose/

Interesting, what principle is it based on? Which chemistry? Mechanical?

Göran

 

[4metals]

Thank you Mr. Luca

I think links to your different equipment in the refiners section would be useful.

You are also more than welcome to respond to any posts with your expertise and reference any equipment but we would appreciate the commercial type links to advertisement or equipment you manufacture be in the refiners section.

 

[g_axelsson]

Dear Sir,

Chemically the system uses aqua regia to dissolve the gold parts holding gemstones, and once the stones are removed it is possible to recovery fine gold by precipitation as well as wash out the stones covered with silver chloride.
The unit is compact, including one or two etching reactors, vacuum filtration section and gold precipitation section with magnetic stirrer.
All is controlled by the switchboard (heaters, vacuum etc) and the fumes are washed directly in the hood thanks to a recycling tank connected to a proper fumes recovery area in the hood itself.
For further info you can contact the company.

Best Regards

Thank you for your answer.

I'm a bit disappointed though, it seems to be nothing else but a fancy digester and some plumbing for moving liquids. I was hoping for a novel approach to dealing with high silver content gold alloys, some way to break down the passivising silver chloride covering.

Regards, Göran

 

[4metals]

Goran,

I was hoping for a novel approach to dealing with high silver content gold alloys, some way to break down the passivating silver chloride covering.

Filter the acid containing the silver chloride coated metal, I prefer to do a coarse filtration through a plastic screen so the loose silver chloride will pass through leaving only the chunks of silver chloride coated gold and the stones in the screen.

A lot, if not all, of the stones will have been dislodged so select a mesh that will not allow the smallest of the diamonds, those pesky little 1 pointers, to fall through.

Now tumble everything in the screen in a saturated solution of sodium thiosulfate. This will dissolve the silver chloride and leave you with a shiny gold surface where the silver chloride has stopped the work of the aqua regia. Small rock tumblers work well or a plastic wide mouth jar sitting on a pair of rollers.

If the chlorides are heavy it may require one or two tumbles to complete the process. This process has no smell and it need not be done in a hood.

Pass the solution through the screen again and rinse well. The gold will be a bright yellow if it is done. The stones will be loose and clean, just requiring a good rinse. If the gold still has stones set in it they can often be mechanically removed as they are likely loose. If required the gold can be put back in aqua regia for further digestion.

Most prefer to spend some time to remove any loose stones mechanically and melt the gold into a button. Commercial refiners use an XRF to find the gold content and pay on that plus the gold that comes out of the aqua regia.

Since the gold coated over so severely, it is easiest if you want to recover it completely to inquart the button in silver and do a nitric dissolve.

The silver chlorides that fell through the screen on the first coarse filtration can be filtered out and collected and reduced with caustic and sugar to produce a metallic silver with a minor percentage of gold when assayed. Easily cleaned up in a silver cell.

(edited to add the last paragraph.)

 

[justinhcase]

In my little cell all you have is a very fine cell slime and stone's.
I just feel through the filter paper for the stone's and put all the left over's in my next inquartation.
I always ware glove's and just wash them back into the paper when I am finished.
I will have to try a small screen before the filter instead.