NEED TO ELIMINATE LEAD

[EMRE]

Hello everyone,
I am trying to separate the lead and the silver from a smelted bar with these xrf ratios so I can ship it to a refinery.(about 175 ozt)

AG 52%
PT 13%
AU 1%
PB 16%

I do not have to separate the gold and the platinum. Do you recommend using dilute nitric to take out silver and lead, then cementing silver?

or, treating with slightly diluted sulfuric acid for silver first, then treating with nitric?

I would appreciate any input,
Thanks
emre

 

[nickvc]

Welcome to the forum.
I would suggest you take a known amount of a sample from your bar, 100 grams would be good, and dissolve it in distilled water and nitric mix using heat, do this under a fume hood, filter any solids and precipitate the lead by adding sulphamic acid, filter again to remove the lead. This will leave the silver in solution along with some platinum, you can now either cement the silver using copper and eventually the platinum or add Hcl or table salt to create silver chloride filter and then cement the platinum from the solution with copper using plenty of agitation.
Be aware that PGM salts are nasty and very toxic.

 

[snoman701]

Smelt it. You need a scrubber.


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[anachronism]

I know I'm a complete rookie when it comes to heating things up however wouldn't cupelling remove the lead leaving the other goodies behind?

 

[snoman701]

I know I'm a complete rookie when it comes to heating things up however wouldn't cupelling remove the lead leaving the other goodies behind?

Yes, but that's a big cupel (available) and you'd still need a scrubber.


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[4metals]

Part it in nitric and the silver and lead will dissolve. the Au and most of the Pt will remain insoluble. Then cement the silver with copper. Any Pt that came across on the digestion because of the high silver will be cemented with the silver if you cement with copper.

Then you can remelt the cemented silver metal which should have traces of Pt and the insolubles from the parting into a bar which will now be substantially lower in lead.

You may be right on the border line of effective nitric parting so try a sample. If it won't dissolve, you may have to increase the silver percentage for the nitric to work better. Try a sample.

 

[g_axelsson]

Welcome to the forum.
I would suggest you take a known amount of a sample from your bar, 100 grams would be good, and dissolve it in distilled water and nitric mix using heat, do this under a fume hood, filter any solids and precipitate the lead by adding sulphamic acid, filter again to remove the lead. This will leave the silver in solution along with some platinum, you can now either cement the silver using copper and eventually the platinum or add Hcl or table salt to create silver chloride filter and then cement the platinum from the solution with copper using plenty of agitation.
Be aware that PGM salts are nasty and very toxic.

The sulfates that is created by treating nitric acid with sulfamic acid will interfere with the silver and precipitate a lot as silver sulfate.
The two viable methods I can see is 4metals method with cementation on copper or cupellation suggested by Jon.

There are 18% unknowns not accounted for in the XRF. It might interfere with one or the other method. For example if there is tin in the bar then it will create a problem if you use nitric acid.

Göran

 

[snoman701]

Goran makes a good point on the percentages.

Have you assayed this with other methods? What is the source?

With that much lead, your xrf assay is not representative of the bar.


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[Palladium]

I'm interested to know the source.
Did he use lead as a collector?

 

[4metals]

Another option could be to smelt it with oxygen sparging at 175 ounces it is a small lot but the lead could be removed by this method and report to the slag leaving all of the other precious metals behind.

Still like to know what the other 18% is.

Cupellation would work but you would need to add a substantial quantity of lead. The biggest cupels I have used are Mabor cupels and at 10" diameter they can hold 14000 grams of lead.

http://www.lmine.com/mabor-magnesia-cupels-c-1_164_268/mabor-pc-cupel-production-size-10-p-4846.html

But at $96 each plus freight you will probably use 4 of them after lead additions. Will the penalty at the refiner be $400?

 

[EMRE]

I'm interested to know the source.
Did he use lead as a collector?

I am not sure about the source, we purchased it from a lady who inherited it from her father. it looked like pieces of charcoals before we smelted them. could be some sort of industrial by product. Must be from fifties our guess..

 

[EMRE]

Goran makes a good point on the percentages.

Have you assayed this with other methods? What is the source?

With that much lead, your xrf assay is not representative of the bar.


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I am not sure about the source, we purchased it from a lady who inherited it from her father. it looked like pieces of charcoals before we smelted them. could be some sort of industrial by product. Must be from fifties our guess..
we did not fire assay it.we settled on xrf results with the customer.

 

[EMRE]

Another option could be to smelt it with oxygen sparging at 175 ounces it is a small lot but the lead could be removed by this method and report to the slag leaving all of the other precious metals behind.

Still like to know what the other 18% is.

Cupellation would work but you would need to add a substantial quantity of lead. The biggest cupels I have used are Mabor cupels and at 10" diameter they can hold 14000 grams of lead.

http://www.lmine.com/mabor-magnesia-cupels-c-1_164_268/mabor-pc-cupel-production-size-10-p-4846.html

But at $96 each plus freight you will probably use 4 of them after lead additions. Will the penalty at the refiner be $400?

this may work but not sure.. we have a vcella furnace for fire assays 11"wide and 7" height. i could run it in few batches and try to extract the lead. here is the full breakdown of xrf;
Ag 52%
Pb 16%
Pt 13%
Cu 13%
Ni 5%
Au 1%
refinery penalty is around $6000.))))))) ( yes I did not misspell it)

 

[anachronism]

Refinery penalty or refinery charge?

 

[EMRE]

Refinery penalty or refinery charge?

all charges included.( lot is worth about22K )

 

[snoman701]

What is the refinery cutoff for nickel? Get rid of the lead and that could be your next problem.


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[EMRE]

What is the refinery cutoff for nickel? Get rid of the lead and that could be your next problem.


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not sure. we have been with the same refinery and subject never came up because we deal with karat gold bars most of the time..

 

[snoman701]

So you smelted the ore, why not just smelt the bar and blow off the lead then? I want to say nickel cutoff is around 12%, but I'm not sure.


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[EMRE]

So you smelted the ore, why not just smelt the bar and blow off the lead then? I want to say nickel cutoff is around 12%, but I'm not sure.


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not sure with what you mean "blowing off the lead" we are only equipped with two induction furnaces..

 

[anachronism]

You say the lot is worth $22k - but surely that is just based on your own readings correct or have the refinery assayed it themselves as well?