# Platinum and Gold Refining



## marhaba01 (Sep 16, 2022)

Hello All,

We have a small refinery setup for gold and silver refining. 

We have received a batch of 10 kgs metal. The content is 4500 gms of platinum. 5000 gms is gold. 500 gms is silver. This is in bar form. We want to process it. Is there any specific process to be followed since it has a higher content of platinum? Which metal is likely to be recovered first? Gold or Platinum. We are aware of the aqua regia process in which both gold and silver are recovered. We are using the aqua regia process on a regular basis. However this batch has a higher content of platinum, hence the question. Any guidance/suggestion will help a lot. 

Thanks in advance.


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## orvi (Sep 16, 2022)

marhaba01 said:


> Hello All,
> 
> We have a small refinery setup for gold and silver refining.
> 
> ...


Dissolving 10kg ingot of AuPt in AR will took ages  I will re-melt the bar and pour shot from it, then proceed to digestion. Finer the better, best would be very thin cornflake or run the melt through atomizer.

Gold can be relatively selectively dropped apart from platinum using ferrous sulfate. SO2 is also relatively selective, but as I heard, it tend to drag more Pt with it. Any additional SMB or SO2 will reduce Pt(IV) in solution to Pt(II).

Bulk of the Pt, you can precipitate as chloroplatinate to get quite pure salt. Rest you will cement and re-refine  Altough I do not know what purity you are aiming for... If the bar is already just AuPtAg, majority of Ag will precipitate during dissolution/dilution stage of the ingot, so you will be left with essentially pure PtAu solution. And when you drop the gold, then practically only Pt remains in solution. So maybe candidate for formate or hydrazine reduction, as you obviate the necessity of creating the ammonium salt - which is problematic/tedious to incinerate in large quantities.


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## kadriver (Sep 23, 2022)

orvi said:


> Gold can be relatively selectively dropped apart from platinum using ferrous sulfate. SO2 is also relatively selective, but as I heard, it tend to drag more Pt with it. Any additional SMB or SO2 will reduce Pt(IV) in solution to Pt(II).


How about boiling oxalic acid to remove the gold and leave the platinum in solution?


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## orvi (Sep 25, 2022)

kadriver said:


> How about boiling oxalic acid to remove the gold and leave the platinum in solution?


I do not have experience with oxalic and PGMs. For me, SO2, formate or FeSO4 are sufficient, so I didn´t tried exploring further  But I think somebody certainly does.


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## zachy (Sep 26, 2022)

marhaba01 said:


> Hello All,
> 
> We have a small refinery setup for gold and silver refining.
> 
> ...


You must granulate all the bars so that this remains as an alloy powder. This is achieved using a granulator, which is nothing more than making a jet of water collide with the jet of molten metal in a container with a conical bottom, then you attack this powder. with aqua regia in a reactor, in this step the silver remains at the bottom as silver chloride, you filter it and trap all the silver chloride, make sure there is no excess nitric acid, evaporate the excess nitric acid or eliminate it with sulfamic acid, then you start by first precipitating the gold with metabisulfite, or ferrous sulfate, then you heat the mother liquor that contains platinum in solution until it boils with hydrochloric acid and add a little H2O2, THEN YOU COOL AND PRECIPITATE THE PLATINUM WITH AMMONIUM CHLORIDE . FILTERS AND YOU ALREADY HAVE THE THREE SEPARATE METALS.


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