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Extracting palladium from nitric acid


#1

Hi I am wondering if there is anyone who knows how to get the
palladium out of the liquid that remains after extracting gold from
lemel in nitric acid.

I heard you can get the silver out with salt, but I am most
interested to get the palladium out, as my lemel contains alot of
white gold. What should you get out first the palladium or the
silver, and how do you get the palladioum out!?

Javier Ingunza


#2

Kirsten,

you may also try asking this question on a Yahoo! group dedicated to
precious metal recycling: GoldandPlatinumRecycling Very knowledgable
people there.

Andreas


#3

For l purposes only!

Leave refining to the refiners.

Assuming that you started with Aqua Regia gold solution, precipitated
gold with zinc, precipitated silver with solution of Sodium Chloride.
Now you have solution containing Platinum Group metals. Ammonium
Chloride will precipitate platinum our of solution. Palladium a bit
tricky. When you add Ammonium Chloride nothing will happen.

After that you nave to slow add Sodium Chloride crystal by crystal
and stir gently until precipitate forms.

Warning! This is not step-by-step instructions. Practice is far more
complicated than theory. Handling dangerous chemicals require
training and experience.

Leonid Surpin
www.studioarete.com


#4

Palladium is not soluble in nitric acid. If you have put your lemel
(filings) in nitric acid only the base metals and silver will
dissolve into solution the remaining. Palladium will however dissolve
in aqua regia but so will the gold, some platinum and iridium. You
can then easily remove the gold from the aqua regia leaving the other
metals in solution but recovering platinum group metals requires more
time and skill and is more dangerous than simple gold refining. Most
small refiners don’t even do it but save the PGM (platinum group
metals) containing solutions and send them to a specialized refiner
of PGM’s due to the cost and processes requirements. I suggest you
read Refining Precious Metal Wastes by C.M. Hoke as he describes the
processes involved in detail and provides step by step instructions.
Remember however that the book was written in 1940 and the safety
instructions in it are almost non existent and inadequate by modern
standards even when mentioned. So check with a trained chemist to
make sure you have a through understanding of the safety requirements
of the processes involved. The processes required involve not only
the use of corrosives and poisons but also involve potentially
explosive and flammable materials and reactions.

Jim

James Binnion
@James_Binnion
James Binnion Metal Arts


360-756-6550


#5

It has been pointed out to me that palladium is soluble in nitric
acid. My experience with it is that I do not see any evidence of
etching of 950Pd when immersed in a 50% nitric acid solution for
several minutes as we do that several times a week for rings that are
950Pd and sterling laminates or. One reference I just found on the
web says that palladium is soluble in nitric acid but more so in
fuming nitric acid which is a concentrated nitric acid and nitrogen
peroxide mixture and lists the fuming nitric acid as the method of
dissolving it. So it may be that it is soluble in nitric the way
platinum is in aqua regia i.e. slowly and to a limited degree but I
will leave that to a chemist. Also I went back and re-read the Hoke
refining text and he states that during refining of lemel or buttons
it is taken up in the aqua regia when alloyed with gold. So again in
the gold alloy it may be that it has limited solubility in the
nitric or takes a great deal of time or ? But I am fairly certain
that much of the Pd is still in your lemel along with any platinum or
iridium present.

James Binnion
@James_Binnion
James Binnion Metal Arts


360-756-6550


#6

My suggestion would be to remove the palladium electrochemically.
However this requires a significant knowledge of Oxidation-reduction
values and excellent equipment to maintain the proper voltages
necessary to plate out only one metal at a time. Something best left
to those who do this all the time.

Wayne