# Silver from contacts



## goldandsilver123 (Aug 11, 2015)

Hello!!

I'm recovering silver from these contacts, but I'm having some trouble processing it.

Here's the photo from them:



These contacts are previously cut and just the part that has the silver part is digested.

I think there's iron and perhaps tungsten in some of them. The iron because it starts a red/brown sludge if it sits for too long. And tungsten because of a purple part that doesn't digest.

The way i'm digesting them is simply pouring nitric acid on the contacts on the SS container of the photo.

I was thinking in another way, first a HCl to dissolve most of the iron, then HCl with H2O2 to dissolve most of the copper, and if present the tungsten. The leftover silver be purified with HNO3.

*That seems good??

What do you guys recommend?*

The content of silver I recovered is about 25%.

Thanks!


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## MarcoP (Aug 12, 2015)

Iron and tungsten are both present is contact points, butcher posted very detailed info about it http://goldrefiningforum.com/phpBB3/viewtopic.php?f=50&t=20969&p=215987#p215987

Some contacts are welded and those may have Cadmium in the solder so you must be aware of all dangers and follow "Dealing with waste" in the library section http://goldrefiningforum.com/phpBB3/viewtopic.php?f=85&t=10539 (you had to in any case) to process your waste solution.


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## g_axelsson (Aug 12, 2015)

Going the copper chloride way will take quite some time on thick material as this. If you try it I recommend you put in a treatment with sodium hydroxide after the copper chloride step to turn any silver chloride into silver oxide, then incinerate to drive away any residual chlorides so it doesn't form silver chloride again when you go to the nitric acid step.

Personally I would go straight for nitric acid for speed and ease.

Göran


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## goldandsilver123 (Aug 12, 2015)

MarcoP Thanks for butcher's info! That is very helpfull, I will try to find what type are my contacts.


Göran:
Do you think silver will oxidize with the HCl + H2O2?

I'm already using straight nitric acid, but it forms a brown sludge (iron oxides) that filters very very slowly, even with vaccuum, here's some photos:

Besides the fact that it forms this sludge, it uses too much acid, 9kg of contacts I used almost 30 L of 63% nitric.

How would you solve this sludge problem? I only see removing the iron first with HCl.


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## goldsilverpro (Aug 12, 2015)

Your nitric usage is actually slightly less than what I would predict. It is best to dilute the nitric with distilled water to the equivalent of 50/50 for 70% nitric. Since you have only 63% nitric, I would use, by volume, about 57% nitric and 43% distilled water. Dilution will tend to make everything work more efficiently.


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## MarcoP (Aug 12, 2015)

For sure you have mixed contacts so the link was to show you which base metals you are likely to have. Nitric acid and iron forms iron nitrate, not oxide as you comment below your picture, thus the brownish color sludge.

To remove the sludge and all heavy metals (cadmium just to pick one) you must follow the "Dealing with waste" thread as noted above.

HCL alone will form a silver chloride layer passivating the silver metal from further attacks from acids, including nitric. This is why if you follow the HCl route you have to follow Göran advice, or tumble the contacts with steel nails and 10% sulfuric acid to get straight to silver metal.

Marco


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## justinhcase (Aug 12, 2015)

If you melted first with the right flux might it not take out a good amount of the problem element's before digestion.
go's as said Very well ventilated up a proper flue.


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## MarcoP (Aug 12, 2015)

Justin, since some contacts had solder on them wouldn't cadmium pose an high risk when smelting. I'm also going forward reading about smelting, for some feedstock is the best approach, what flux mixture would you use, borax, soda ash and some cryolite to drop the melting point?

Marco

Edit: spelling


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## justinhcase (Aug 12, 2015)

MarcoP said:


> Justin, since some contacts had solder on them wouldn't cadmium pose an high risk when smelting. I'm also going forward reading about smelting, for some feedstock is the best approach, what flux mixture would you use, borax, soda ash and some cryolite to drop the melting point?
> 
> Marco
> 
> Edit: spelling


Yes Not only Cadmium but nickle and a hole host of other oxide's and compound's would be very bad new's if inhaled.
But that has been the same as any smelting since it was invented.
Most people seem to make do with a traditional flue that takes all noxious fumes far away from people.
I would advise an Electrostatic precipitator


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## MarcoP (Aug 12, 2015)

Electrostatic precipitator, I love this toy! Thanks!

Marco


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## Smack (Aug 12, 2015)

MarcoP said:


> Electrostatic precipitator, I love this toy! Thanks!
> 
> Marco



Pretty sure I put a link up a long time ago on one.


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## Palladium (Aug 13, 2015)

Chris is right. You're short on nitric. Over shoot the nitric and the brown will usually go back into solution. The brown usually happens when you have excess water and depleted nitric. I boil mine in straight 67℅ nitric on a simmer for 24-48 hours sometimes more. Leaching those things are a pain in the butt sometimes. Get a 5 gallon stainless pot also. It will be easier to handle and safer to pour from.


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## Geo (Aug 15, 2015)

You might try adding some ethylene glycol to the mix. It helps keeps the nitric in solution longer.


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## goldandsilver123 (Aug 17, 2015)

Hello!

Thanks everyone!


Taking what goldsilverpro and palladium said, I estimated around 35 L to 9 kg of contacts. So I added 1,6 L of water to the contacts, then 1,6 L of 63% nitric to a new smaller batch.

I tried a smaller batch, 400 g of contacts.








The corrosion proceeded very vigorously




When I saw very little reaction, I decanted off the liquid and transfered the remained solid to a beaker




Then I add 200 mL of 63% nitric, the reaction was very vigorously again, and when finished there was no chunk of anything, just a purple dust/sludgy but very little of that.


The filtration took long time, but much less than with the iron oxides. It proceed very fast at the beginning but it clogs the filter after some time with vacuum.


Anybody knows where I can find filtrations tips?



On other topic, I made the silver chloride, washed well with water and proceeded to reduce it with sodium hydroxide and table sugar. Everything went well!

I wanted to ask for advice on washing the silver powder, since when I melt it, I can smell the sugar!

Thanks again!






MarcoP:

We send every residue that we produce to a company to be treated, since it's small volumes, they take it for free. Thanks for the tips on how to treat it!


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## goldandsilver123 (Aug 17, 2015)

Leftover reaction:




Silver powder reduced with sugar and lye:


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## rickbb (Aug 17, 2015)

If you can smell sugar then you haven't washed it enough. Hot water washing should remove it.


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## Palladium (Aug 17, 2015)

https://youtu.be/BmZgunOWiSo


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## MarcoP (Aug 18, 2015)

Smack said:


> MarcoP said:
> 
> 
> > Electrostatic precipitator, I love this toy! Thanks!
> ...


I've looked all 42 pages of posts made by you but I couldn't find it. Do you think one, or a couple in series, household electrostatic precipitator will suffice?


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## goldandsilver123 (Aug 19, 2015)

I've been using this funnel:




But it clogs after some time, with or without vacuum.

I want to know, what's the next "level" of filtration:

Does a table top buchner funnel works better?

Any diferente filtering medium? (we are using filter paper or filter press mantle, filter press mantle works quicker but the filtrate is cloudy)

A small filter press?

Thanks!



Palladium said:


> https://youtu.be/BmZgunOWiSo



I've seen all the 28 minutes of the video, but I don't think I'm making anything different, the filter press mantle has pores even bigger than those paper towels.



rickbb said:


> If you can smell sugar then you haven't washed it enough. Hot water washing should remove it.



I'll work harder with the rinsings! Thanks!


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## Palladium (Aug 19, 2015)

How much material are you doing in a batch? Is this something that you will do everyday or is this a temporary thing and then no more?


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## goldandsilver123 (Aug 19, 2015)

Palladium said:


> How much material are you doing in a batch? Is this something that you will do everyday or is this a temporary thing and then no more?



I think we will do this monthly, around 10 kgs of contacts each batch.


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## Palladium (Aug 20, 2015)

You need to gravity feed your filtering. You could move up to a table top Buchner but it more than likely to still clog with the fine dust that can come from running them things. Table tops are expensive and so are the papers for it. If you were running larger solutions I would use a air assisted diaphragm pump and a filter sock inside a housing unit. You can push 100 psi through it with no problem, about $800. Frankly I would get me 4- 5 gallon pots and use four bounty filter set ups and roll with it. Trust me I have more than my fair share of what works and don't work when it comes to rednecking some silver. That still leaves you with the washing of the cemented silver which with a table top makes life easy so I would go with gravity stage 1 and vacuum for stage 2.


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## Palladium (Aug 20, 2015)

Skip the cemented silver part I see your using chloride. That makes things tricker. In order to use that method you need a perfectly clear solution or it is going to contaminate your final product. Looks like you might have to stick with a tabletop Buchner funnel and just slow filtering. Personally for me the silver cell is easier than the chloride method.


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## goldenchild (Aug 20, 2015)

What happened to good old settling and decanting? Maybe your operation requires everything to be done very quickly I don't know but you will greatly reduce your filtering woes if you let the solution settle for 12-48 hours and then proceed.


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## goldandsilver123 (Aug 31, 2015)

Palladium said:


> You need to gravity feed your filtering. You could move up to a table top Buchner but it more than likely to still clog with the fine dust that can come from running them things. Table tops are expensive and so are the papers for it. If you were running larger solutions I would use a air assisted diaphragm pump and a filter sock inside a housing unit. You can push 100 psi through it with no problem, about $800. Frankly I would get me 4- 5 gallon pots and use four bounty filter set ups and roll with it. Trust me I have more than my fair share of what works and don't work when it comes to rednecking some silver. That still leaves you with the washing of the cemented silver which with a table top makes life easy so I would go with gravity stage 1 and vacuum for stage 2.



Thanks Palladium! A diaphragm pump with a filter sock is what we are looking for! =)
I've been working with the chloride method for a long time now, and I have nothing to complain, I reduce it with sugar, and measuring with AA I constantly get 99,99% purity. (I know that AA is not the best analytical method, but it's always 99,99+%, expect when the processing silver has palladium).




goldenchild said:


> What happened to good old settling and decanting? Maybe your operation requires everything to be done very quickly I don't know but you will greatly reduce your filtering woes if you let the solution settle for 12-48 hours and then proceed.



We have to refine quickly because we are told to do so, but with the solution clogging the filter, we already let it settle for 2-3 days, taking just the clear liquid and it still clogs the filter. I think Palladium gave a good option!


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## 4metals (Aug 31, 2015)

> measuring with AA I constantly get 99,99% purity. (I know that AA is not the best analytical method, but it's always 99,99+%,



Are you running the AA for silver to come up with .9999? Refined metals are measured by difference on an instrument, meaning you run the suspected impurities on the AA and subtract their concentration from 100%. The error in the volumetric glassware can exceed your tolerances when measuring high concentrations.


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## goldandsilver123 (Sep 1, 2015)

4metals said:


> > measuring with AA I constantly get 99,99% purity. (I know that AA is not the best analytical method, but it's always 99,99+%,
> 
> 
> 
> Are you running the AA for silver to come up with .9999? Refined metals are measured by difference on an instrument, meaning you run the suspected impurities on the AA and subtract their concentration from 100%. The error in the volumetric glassware can exceed your tolerances when measuring high concentrations.



Sure, I think I expressed myself wrong, we analyze the impurities, mainly Cu, Pb, Pd, Zn, Fe, Cd, Ni!


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## edsikes (Sep 2, 2015)

i love running contacts, i dont get them in anywhere near that quantity though...


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## matts800 (Dec 17, 2015)

I have about 150 lbs of contacts like these - but all of them still have the copper bus bar still attached. Is there a company that will refine them for me and pay more than the scrap yard?


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## g_axelsson (Dec 17, 2015)

It all depends on what the scrap yard will pay. 8) 

Göran


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## kurtak (Dec 17, 2015)

Pm sent

Kurt


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