# Precipitating PGMs from AR



## madelyn (Jun 11, 2015)

Apart from zinc, what else can I use to precipitate pgms from my Aqua regia? I tried alluminium and it works good and cheap, but there is always some extra metal that ends up with the pgms which I have no clue what it is. 
Wil copper work or even copper sulphate?
Any suggestions would help.

Also the pgms are from jewelry, so it contains platinum ,palladium and rhodium.


----------



## butcher (Jun 11, 2015)

Although several metals can be used to replace the more nobel metals from solution, aluminum in my mind would be a poor choice, aluminum can form a gellitinous solution, as aluminum displaces hydrogen from solution.
Zinc is a good choice as it is very reactive, does not form a gell and is easily washed from the cemented values.
Copper will work well to cement the values but is not as easily to wash from the values, and if some metalic copper remains you risk putting values back into solution while trying to remove the copper.
Cementing values with metals is normally a recovery proceedure.
Zinc in my opinion would be the best choice.
Zinc (like copper) is a very common metal , both used in the electrical industry, copper in buss bars, and zinc is used for electrical conduit fittings.

using a reactive metal like zinc will displace all metals below zinc in the rteactivity series, this means if your solution contains these metals zinc will also displace them, copper being much lower in the reactivity series will dislpace less of these base metals, but it also being less reactive is harder to wash the metal from the cemented metal...

Precipitation of the PGM's can also be done with chemical reagents, if the solutions are loaded enough with the PGM metals, to somewaht selectively precipitate them from solution.


----------



## madelyn (Jun 11, 2015)

Thanks for the proper post butcher.
It's just that I can optain copper much easier than zinc and I pay $55 for a 5kg zinc powder.
Copper I can buy for market price at any scrap yard.

What about copper or irion sulphate? 
I'm figuring this would actually work well or better?


----------



## Lou (Jun 11, 2015)

Those will do nothing for you.


If you want to use less zinc, partially neutralize the solution to pH 0.


FYI, 

http://www.lmine.com/mm5/merchant.mvc?Screen=PROD&Store_Code=LMS&Product_Code=18322-50&Category_Code=


----------



## kurtak (Jun 12, 2015)

Instead of buying copper from the scrap yard ask them about die cast - its much cheaper then copper

Pictures of die cast used for electrical conduit connectors :arrow: http://goldrefiningforum.com/phpBB3/viewtopic.php?f=48&t=17699&p=189086&hilit=diecast#p189086

Kurt


----------



## g_axelsson (Jun 12, 2015)

Diecast would cement copper and some other metals too, not only precious metals.

Göran


----------



## patnor1011 (Jun 12, 2015)

Zinc for free can be found in heavy duty batteries - casing.
Something like this: http://www.powerpak.com.au/catalog/battery-volt-pi-1142.html?osCsid=sk3eebppm9qfrm1aovrc5vqa61


----------



## Lou (Jun 12, 2015)

Of all the cemented stuff I've ever seen, that produced by lazersteve with his zinc turnings is far and away the best.


----------

