# NEED TO ELIMINATE LEAD



## EMRE (Mar 1, 2018)

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


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## nickvc (Mar 1, 2018)

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.


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## snoman701 (Mar 1, 2018)

Smelt it. You need a scrubber. 


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## anachronism (Mar 1, 2018)

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?


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## snoman701 (Mar 1, 2018)

anachronism said:


> 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 (Mar 1, 2018)

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.


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## g_axelsson (Mar 1, 2018)

nickvc said:


> 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


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## snoman701 (Mar 1, 2018)

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 (Mar 1, 2018)

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


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## 4metals (Mar 2, 2018)

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?


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## EMRE (Mar 2, 2018)

Palladium said:


> 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..


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## EMRE (Mar 2, 2018)

snoman701 said:


> Goran makes a good point on the percentages.
> 
> Have you assayed this with other methods? What is the source?
> 
> ...


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.


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## EMRE (Mar 2, 2018)

4metals said:


> 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.
> 
> ...


 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)


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## anachronism (Mar 2, 2018)

Refinery penalty or refinery charge?


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## EMRE (Mar 2, 2018)

anachronism said:


> Refinery penalty or refinery charge?



all charges included.( lot is worth about22K )


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## snoman701 (Mar 2, 2018)

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


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## EMRE (Mar 2, 2018)

snoman701 said:


> What is the refinery cutoff for nickel? Get rid of the lead and that could be your next problem.
> 
> 
> Sent from my iPhone using Tapatalk



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..


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## snoman701 (Mar 2, 2018)

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 (Mar 2, 2018)

snoman701 said:


> 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.
> 
> 
> Sent from my iPhone using Tapatalk


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


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## anachronism (Mar 2, 2018)

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?


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## anachronism (Mar 2, 2018)

If I may be straight with you here. Your problem isn't the $6000 to do the job. Your problem is that you are basing your numbers on an XRF reading. Until you have a proper assay that confirms your estimates the alloy has only a notional value.

Then you're also in the trap that happens in the US where proper assays cost an arm and a leg. If I had that over here I could get an assay on that for under £100 assuming of course all the material was the same. At that point I could then go to 5 people and see who would give me the best payout up front based upon the assay results. 

If you can do the job for less than $6,000 yourself and you're 100% sure that your XRF is correct then do crack on. If you want a second opinion do feel free to send me 2g of representative material and I'll happily have the assays run for you at cost. At least then you'll know where you stand. 

Regards

Jon


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## snoman701 (Mar 2, 2018)

If you only have induction melters, you lack the capacity to effectively smelt off the lead. 

Lead has a low vapor temperature, so it "steams" off. Not something you want to play with if you aren't absolutely positive you have perfect ventilation, and that your ventilation is scrubbed prior to exhausting into the atmosphere.

Honestly, if you aren't set up to refine it already, or smelt it....sell it and take the hit.

You need a proper assay either way. If xrf, your sample needs to be free of lead. The xrf also needs to be better than a handheld model. The sensors in the handheld models do not have the spectral precision to differentiate between elements that have similar brehmstrung energies. Plus, the software making the interpretation also makes the assumption that you have precious metal, when in fact you may just have scrap.


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## EMRE (Mar 2, 2018)

anachronism said:


> 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?



Of course. i mentioned it on average just to show the ratio between the value of the bar and the fees,,


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## Palladium (Mar 3, 2018)

What are you calling a penalty? I think what you mean is they are willing to pay you for the pt, but they aren't willing to pay out on the gold and the silver. Are you basing the $6,000 dollar penalty on the basis of being paid for all metals?


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## nickvc (Mar 3, 2018)

I’m not sure if your saying the refinery is willing to pay $22000 or that it’s that less $6000, if the former don’t bother with any processing as the best figure I could come to was around $23000 assuming the readings are correct...


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## Palladium (Mar 3, 2018)

The way i understand it is he's saying the bar value is $28,000 the way he is valuing it which sounds like pay out on all metals. Then they are penalizing him $6,000 which would make the refineries offer at $22,000 which seems like the payout on the pt portion minus any other metals. That's my thinking anyway.


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## snoman701 (Mar 3, 2018)

Refineries regularly "penalize" you if your alloy falls outside of a standard category. For exsmple, cadmium in an alloy means that they can't just melt, pin, and report...they have to do an acid digestion. 

With lead, they will need to process the material prior to an assay. Lead causes stratification in the sample, so it's more difficult to sample a melt and it doesn't just fit right in to one of their standard material categories (karat scrap, 1-5% Au, dental, silver, etc) So it costs them a lot more to process.

So if he just melts it with borax, how much of the lead will report in the slags vs vaporize off??


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## EMRE (Mar 3, 2018)

Palladium said:


> What are you calling a penalty? I think what you mean is they are willing to pay you for the pt, but they aren't willing to pay out on the gold and the silver. Are you basing the $6,000 dollar penalty on the basis of being paid for all metals?




well,we get paid 98% of our PT on our regular platinum lots which is a very good rate ( PT must be >80%, even if it is less than 80% they take another 2%) . refineries do not want to deal with lead. this particular one wants to pay us 65% of it with $1000 lot charge. that adds up to roughly $6K. I hope I was able to explain better.


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## 4metals (Mar 3, 2018)

The explanation of the rates made me think of another option. Add about another 25% by weight as silver and part in nitric acid. A small percentage of the Platinum will dissolve with the silver but most will not. The Platinum and Gold will remain after parting. 

Next cement the silver on copper. The copper will drop the silver and any Pt that dissolved. Now you guys are saying that I'm repeating myself and to this point I am but..... do not mix the cemented silver with the parted Pt and Au, that will lower the % of Pt and get you the lower rate. Ship them a button of Gold and Platinum, and a separate bar of the cemented silver to get the higher rates because the purity is higher.


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## g_axelsson (Mar 3, 2018)

Do you really need to add extra silver? The amount of silver + copper + lead is 81%, platinum + nickel + gold is 19%. I put nickel in the hard to dissolve column as it sometimes is hard to dissolve in nitric acid as a solid metal, but in this alloy it will probably be easily dissolved.

The drawback of dissolving / cementing is to treat all the acid waste afterwards. But $6000 pays for a lot of waste hauling.
... and the Big Freaking Red Cloud of NOx released while dissolving the metal. An acid proof fume hood with scrubbing is recommended.

Göran


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## EMRE (Mar 4, 2018)

g_axelsson said:


> Do you really need to add extra silver? The amount of silver + copper + lead is 81%, platinum + nickel + gold is 19%. I put nickel in the hard to dissolve column as it sometimes is hard to dissolve in nitric acid as a solid metal, but in this alloy it will probably be easily dissolved.
> 
> The drawback of dissolving / cementing is to treat all the acid waste afterwards. But $6000 pays for a lot of waste hauling.
> ... and the Big Freaking Red Cloud of NOx released while dissolving the metal. An acid proof fume hood with scrubbing is recommended.
> ...


we are equipped with polypropylene fume hood and caustic scrubbers..should not be a problem. running a test run with 100dwt to see the result..

thanks


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## EMRE (Mar 4, 2018)

4metals said:


> The explanation of the rates made me think of another option. Add about another 25% by weight as silver and part in nitric acid. A small percentage of the Platinum will dissolve with the silver but most will not. The Platinum and Gold will remain after parting.
> 
> Next cement the silver on copper. The copper will drop the silver and any Pt that dissolved. Now you guys are saying that I'm repeating myself and to this point I am but..... do not mix the cemented silver with the parted Pt and Au, that will lower the % of Pt and get you the lower rate. Ship them a button of Gold and Platinum, and a separate bar of the cemented silver to get the higher rates because the purity is higher.



do you think %50 Ag is not rich enough for nitric to work properly that I should add more? My other question is I am not sure how much Pt would dissolve with it? if it is only few dwt i could live with that. if i ship the silver with very little pt in it I would not get paid on it for sure because refineries has minimum deductions,( 0.25ozt of any secondary metal). if more Pt dissolves, I will have to reduce it with ammonium chrolide..


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## snoman701 (Mar 4, 2018)

Why not ship with just enough + Pt so that you get paid on it? You should always adjust your melt so you have enough in it to get paid on it.


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## 4metals (Mar 4, 2018)

It's hard to say how much Platinum will pass into the nitric acid with the silver, it's not supposed to be soluble in nitric acid but the silver affects its solubility. I have never heard any hard fast numbers as there are likely a lot of different parameters that can influence the quantity digested. From the old assayers books the rule of thumb is if there is 10 times the quantity of Silver over Platinum, some of the Platinum will dissolve with the silver. It isn't ounces but it can be pennyweights. 

Adding Platinum to get up the concentration is a theory that can backfire on you. Sure you may get it above the concentration threshold and make it payable but then the minimum Platinum deduction, often 1 ounce, will kick in so it can cost you in the long run. 

Out of curiosity, does your XRF read the same on the top of the bar and the bottom? That is a huge problem melting higher temperature melting metals with low temperature melting metals. Usually a lot of copper is added to make it homogeneous.


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## EMRE (Mar 4, 2018)

4metals said:


> It's hard to say how much Platinum will pass into the nitric acid with the silver, it's not supposed to be soluble in nitric acid but the silver affects its solubility. I have never heard any hard fast numbers as there are likely a lot of different parameters that can influence the quantity digested. From the old assayers books the rule of thumb is if there is 10 times the quantity of Silver over Platinum, some of the Platinum will dissolve with the silver. It isn't ounces but it can be pennyweights.
> 
> Adding Platinum to get up the concentration is a theory that can backfire on you. Sure you may get it above the concentration threshold and make it payable but then the minimum Platinum deduction, often 1 ounce, will kick in so it can cost you in the long run.
> 
> Out of curiosity, does your XRF read the same on the top of the bar and the bottom? That is a huge problem melting higher temperature melting metals with low temperature melting metals. Usually a lot of copper is added to make it homogeneous.



i drilled the bar from ten different location and gathered the dill dust in a plastic bag and took the xrf readings. I never read the top and the bottom of it. I am sure though the top will read lead heavy. i will check it tomorrow at the office and post the results here. i plan on decimating the bar to almost dust with large press drill to speed up the digestion process and efficiency anyways.
Regards


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## EMRE (Mar 4, 2018)

snoman701 said:


> Why not ship with just enough + Pt so that you get paid on it? You should always adjust your melt so you have enough in it to get paid on it.
> 
> 
> Sent from my iPhone using Tapatalk



we have 50ozt of PT,PD scrapt jewelry waiting to be shipped for this process to be done. we will do so.))))


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## Richard NL (Apr 30, 2018)

4metals said:


> It's hard to say how much Platinum will pass into the nitric acid with the silver, it's not supposed to be soluble in nitric acid but the silver affects its solubility. I have never heard any hard fast numbers as there are likely a lot of different parameters that can influence the quantity digested.


 https://archive.org/stream/bub_gb_sok6AAAAMAAJ#page/n8/mode/1up 
Same one on scribd.com https://www.scribd.com/document/377664093/Platinum-Silver-Alloys

Richard,


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