Silver bearing scrap

Hello everyone,

I was shown this material today to consider a toll refining deal.


Since I barely work with silver-bearing scrap, I have some questions:

- Does the analysis seem legit?
- Is it worth to recover the silver, on a toll refining basis?
- I was thinking about using heated dilute nitric to dissolve the scrap and cement the silver out with copper. From my knowledge, either this or the chloride way, and I don't like the chloride way that much
Is there any other option?

Thanks in advance to anyone that can weigh in on this !!

Winged

Keep in mind that it takes 4 times more nitric (67% - 70% nitric) to dissolve base metals then to dissolve silver

1 gallon of 67% - 70% will dissolve "about" 8 pounds of silver but only "about" 2 pounds of base metals

So on a toll refine you need to be sure to factor that in to the cost of the refining because an alloy at 50% base metal you are going to use MORE nitric

That also means you will have more waste to deal with

The process it's self is the same --- dissolve the metal (with nitric) then cement the silver with copper --- no need to go the chloride method

The XRF read out should be "ball park" true (plus/minus)

You can test that to confirm --- take a sample (say 100 grams) dissolve it - cement it with copper - wash the acid out - dry the cemented silver - put the dry silver on your scale - it should be in the ball park of 48 grams

Kurt

Kurt, might this be a case where it would be a good idea to first smelt the material to slag off most of the zinc and copper before processing the remaining material?

Dave

That's braze.

Since it doesn't have Cd, best ran in a retort furnace to get it up to 80%+ Ag, then sell as is.

what I think you should do first : grind peace of material and test it on that part or test it on the cut side,
to make sure it is not silver plated german brass ,

ssabovic said:

what I think you should do first : grind peace of material and test it on that part or test it on the cut side,
to make sure it is not silver plated german brass ,

Click to expand...

Good point.

I was also going to ask if you were sure this is all the way through, or just the surface. 8)

FrugalRefiner said:

Kurt, might this be a case where it would be a good idea to first smelt the material to slag off most of the zinc and copper before processing the remaining material?

Dave

Click to expand...

To "slag off" that much base metal you would need to use a VERY oxidizing flux which would be VERY hard on crucibles

If you used PbO you would then have to cupel the lead dore

I guess it would depend on cost of nitric compared to smelting cost - as long as you can get the nitric reasonable/cheap nitric is the way to go

Kurt

snoman701 said:

That's braze.

Since it doesn't have Cd, best ran in a retort furnace to get it up to 80%+ Ag, then sell as is.

Click to expand...

IF - you have a retort furnace

Kurt

kurtak said:

FrugalRefiner said:

Kurt, might this be a case where it would be a good idea to first smelt the material to slag off most of the zinc and copper before processing the remaining material?

Dave

Click to expand...

To "slag off" that much base metal you would need to use a VERY oxidizing flux which would be VERY hard on crucibles

If you used PbO you would then have to cupel the lead dore

I guess it would depend on cost of nitric compared to smelting cost - as long as you can get the nitric reasonable/cheap nitric is the way to go

Kurt

Click to expand...

If you have an induction furnace and an oxyfuel torch, all you have to do is keep your flux donut so that the peak of molten metal pops through it. Then aim an oxygen jet right at it while molten. The induction furnace offers constant movement to the molecules, the oxygen speeds up oxide formation, and the flux, which can be as simple as borax, or a balanced flux of borax, soda ash, silica sand, absorbs the oxides.

It goes pretty fast for the zinc. The copper takes a little longer. Minimal losses of silver.

snoman701 said:

If you have an induction furnace and an oxyfuel torch, all you have to do is keep your flux donut so that the peak of molten metal pops through it. Then aim an oxygen jet right at it while molten. The induction furnace offers constant movement to the molecules, the oxygen speeds up oxide formation, and the flux, which can be as simple as borax, or a balanced flux of borax, soda ash, silica sand, absorbs the oxides.

It goes pretty fast for the zinc. The copper takes a little longer. Minimal losses of silver.

Click to expand...

Yes - but (kind off like you suggestion for a retort furnace) - IF - you have an induction furnace

most members - if they have a furnace - it's likely a standard propane furnace

So - to oxidize the base metals so they go of in the slag you would need a VERY oxidizing flux which is VERY hard on crucibles - also - for the flux to be effective at oxidizing the base metals the metal would need to be "ground" to a fine powder & mixed in well with the flux

OR --- with large pieces of metal - you can blow oxygen into the pool of molten metal at the bottom of crucible with a HIGH temp pipe (they make them in high temp carbon or glass just for smelting) the oxygen will oxidize the base metals so they go off in the slag - but again the oxygen at high temps is hard on crucibles

Yes - the zinc will go off before the copper as a result of the reactivity series (more reactive/less reactive)

Bottom line - nitric acid is the way to go - the question of whether it is worth it or not is a question of what you have to pay for your nitric

If you can get your nitric for $2.50 a gallon (as I did before shutting down) then it's most certainly worth it --- if you have to pay the $50 to $70 a liter (that so many report having to pay) not worth it

There's more then one way to skin a cat - the question is --- "is it worth it &/or are you set up to do it"

Kurt

Why does everyone forget breakdown cell?
At least near all of zinc and manganese is gone!

Lou said:

Why does everyone forget breakdown cell?
At least near all of zinc and manganese is gone!

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Many just don't understand enough to try them. Being one of those myself I would really like to learn more about them and how they work.

As kurtak said, provided you can get nitric cheap that would be the fastest and easiest way to go. That scrap being flat and thin is too perfect to molest it IMO. That is, if it's indeed what the XRF reads of course.