# Recovering Platinum From Copper & Silver



## benign01 (Sep 29, 2013)

Need a little help here please experts. I have what I can only call 20 kilos of "sand". The content analysed before melting on my xrf analyser seemed to be 56% silver, 40% copper and 4% Platinum. Not sure if xrfs are accurate when analysing such a sandy form. Is this correct?
After melting into a nugget the xrf is throwing up 89.5 % copper, 10% silver and 0.5% platinum. Very Weird. 

I didnt do this melt,because my electronic melt machine only reaches temps of 1100C, but I was told by the melter I did use that the Platinum would melt at a lower temp, due to its fine consistency. Its my belief that the Platinum after melting probably remained at the bottom of the crucible. This fine sand was silver in colour and yet I ended up with a nugget of copper colour and the silver seemed to just reduce???

So I thought about melting it in nitric but now I just read somewhere on this forum that such a low ratio of platinum to silver would mean the platinum would end up in the solution. Is that correct? What exact steps would I need to perform to recover this platinum and of course the silver.
Any answers would be greatly appreciated, but please tho I'm competent at melting ant using acids, I'm at a basic level
Thanks


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## benign01 (Sep 29, 2013)

21 Views and no reply! Can anyone give me some advice here please. What I need to do is to remove both the silver and the platinum from the copper and then from each other. I'd really appreciate any help.


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## pgms4me (Sep 29, 2013)

I cant give you a direct answer,because I dont know what the material came from. I am giving an opinion based on the information you provided. xrf machines sometimes favor percentages of surface materials over the core if they were made in layers. If the sand was a silver /platinum alloy surface coating with a copper center that could have explained your first reading. After melting the sand granuals,the copper would be mixed with the silver and platinum more uniformly ,therefore showing the change in copper percentage after melting. I am assuming they were not melted at higher than necessary tempereatures That may have vaporized some of them. Also if slowly cooled the platinum would settle to tthe bottom layer of the bead. If this happened you could get a different xrf reading looking at the top versus the bottom.
There is lots of information on the forum serach, as well as Hoke's about processing alloys containing those three metals.


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## FrugalRefiner (Sep 29, 2013)

benign01 said:


> Need a little help here please experts. I have what I can only call 20 kilos of "sand". The content analysed before melting on my xrf analyser seemed to be 56% silver, 40% copper and 4% Platinum. Not sure if xrfs are accurate when analysing such a sandy form. Is this correct?
> After melting into a nugget the xrf is throwing up 89.5 % copper, 10% silver and 0.5% platinum. Very Weird.


I was one of those 21 views. I didn't post because I don't know that I can answer some of your questions. Instead, I'll give you some thoughts and rely on others to correct me where I'm wrong.

I wouldn't rely on XRF results on something the consistency of sand. The after melt result is likely closer to correct.



> I didnt do this melt,because my electronic melt machine only reaches temps of 1100C, but I was told by the melter I did use that the Platinum would melt at a lower temp, due to its fine consistency. Its my belief that the Platinum after melting probably remained at the bottom of the crucible. This fine sand was silver in colour and yet I ended up with a nugget of copper colour and the silver seemed to just reduce???


Metals don't melt at lower temperatures because of a fine consistency. However, since you have a mix of metals, the platinum might just melt for you. The copper and silver will melt readily at those temperatures and they will act as solvents for the platinum. The melting temperature of the alloy would likely be below the melting point of pure platinum.

Why do you believe your platinum remained at the bottom of the crucible? The metals you've mentioned will easily alloy together. While the melt might not be completely homogenous, it is unlikely the platinum would simply sink to the bottom and remain there, assuming whoever melted it for you achieved a full melt.



> So I thought about melting it in nitric but now I just read somewhere on this forum that such a low ratio of platinum to silver would mean the platinum would end up in the solution. Is that correct? What exact steps would I need to perform to recover this platinum and of course the silver.


You do not "melt" metals in nitric. You melt metals with heat. You dissolve metals with acid. Yes, platinum will tend to follow the silver in going into solution. Maybe some of it. Maybe all of it.



> Any answers would be greatly appreciated, but please tho I'm competent at melting ant using acids, I'm at a basic level
> Thanks


If it were mine, I wouldn't start by melting a finely divided material into a lump. Metals dissolve more easily when they are finely divided. No need to waste fuel just to make the dissolution more difficult.

I would start with a few small scale experiments. Nitric acid would dissolve all the metals you've listed. The silver would be easy to precipitate as AgCl, leaving copper and platinum in solution. The platinum could be cemented on copper.

If the small scale test works, ramp it up a bit - not the whole batch yet - just a larger batch. If it continues to work, keep increasing batch sizes as you feel comfortable.

I don't know if those are the best suggestions, but you asked for _any_ advice.

Dave


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## benign01 (Sep 29, 2013)

Thanks for the replies. I'll give Dave's suggestion a go. Not sure about the plat cementing on copper process,but I'm sure there is an article somewhere on the forum. What would happen if once the metals have been dissolved if I then placed a lump of copper in the fluid. Wouldn't the silver then take the place of the copper lump ending up with silver seperated from the rest?


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## patnor1011 (Sep 29, 2013)

benign01 said:


> Thanks for the replies. I'll give Dave's suggestion a go. Not sure about the plat cementing on copper process,but I'm sure there is an article somewhere on the forum. What would happen if once the metals have been dissolved if I then placed a lump of copper in the fluid. Wouldn't the silver then take the place of the copper lump ending up with silver seperated from the rest?



Can you re-read?
Can you go through answer you just got again?


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## butcher (Sep 29, 2013)

"Sand" is this from jeweler bench, ore or what?

Silver content would be a factor of whether the platinum would go into solution with nitric acid.

With 10 times weight in silver the platinum should dissolve int the nitric acid.

I also believe XRF reading would be useless, an proper fire assay or wet chemical assay would be better to determine metal content. 

Without understanding the basics of recovery and refining, you may not understand the answer given to your questions, when you understand the basics, you do not need to ask the question, as it is easier to figure out the problem for yourself.
Study Hoke's book, and the forum, to gain a the knowledge needed.


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## Dan Dement (Sep 29, 2013)

Benign,

I might be able to shed a little light on some of your questions. First, most XRF machines use a Silicon Detecter to measure the readings. What happens is the XRF can only read elements above #14 which is Silicon. So you can't read Sand, Silicon, Sapphire, Zinc Oxide, Aluminum,and lots of other things in an XRF. I had a friend send me kilo's of bench sweeps which my XRF called 75% gold which was correct on the gold content but was greatly incorrect on the weight. What is not seen is everything under element 14 which could be 99%+ of the weight. On jewelers bench sweeps, most jewelers buff''s and polishing wheels are Zinc Oxide which is Corundum based which is silicon that an XRF will not see. So, your percentage's of the metals shown may be correct but the % of total weight is probably way off. I have been there and done the same exact thing!

On melting Platinum, 1100 Degrees is not close to the 1800C necessary to melt platinum. Now you certainly can suspend Platinum in melting with lesser melting metals. Of course, this can be a totally different issue with Stratification and metals settling as poured.Platinum is certainly a lot heavier than most and can settle to one end of a melted bar. So you might get a strong Pt reading on one end of the bar due to the settled Pt. 

I am no expert but understand the problems. Good Luck.

Dan


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