# Rhodium plating solutions



## autumnwillow (May 24, 2016)

I have a lot of rhodium plating solutions from Degussa Umicore and Metallor.
It is contaminated with some dust, silver and copper.
I can remove the dust with simple filtration but how do I go about precipitating the copper and silver selectively?

The process of refining Rhodium thru boiling concentrated sulfuric acid is just too dangerous for my wooden epoxy coated fume hood.
A member here has mentioned that Rhodium can be dissolved in AR. How do you go about precipitating it?

Maybe I could try dissolving a few grams in less than 20ml of concentrated sulfuric.


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## nickvc (May 24, 2016)

Lou is your man for this, are you sure you have copper and silver dissolved in the solution because normally the Rh is deposited by plating onto the objects so unless you reversed the process I can't see how you can have them in solution.


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## autumnwillow (May 25, 2016)

nickvc said:


> Lou is your man for this, are you sure you have copper and silver dissolved in the solution because normally the Rh is deposited by plating onto the objects so unless you reversed the process I can't see how you can have them in solution.



Yes. We usually do reverse [stt]plating[/stt] polarity and sometimes forget to switch the + and - back.

HCL maybe? NaHS?

I am willing to sell them but if I can re-condition the baths that would be better.


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## goldsilverpro (May 25, 2016)

A large refinery I worked for used magnesium powder to cement the rhodium out of plating solutions. Ended up with a nice Rh sponge.


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## alexxx (May 25, 2016)

Can't you cement everything on zinc first and than run the solids in nitric to get rid of Cu & Ag ?


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## Lou (May 25, 2016)

Easiest just to add lye or ammonia until pH 7.5, give it a good boil, filter the Rh hydroxide and re-use.

Chris is right, Mg is best for Rh cementation (after pH adjustment!!!)--zinc won't get it all.

Lou


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## autumnwillow (May 25, 2016)

I'm a bit confused.

Will Mg drop silver and copper too? If it does, do I just digest in nitric to get rid of silver and copper?
Increasing the pH to 7.5 will also drop copper and silver hydroxide right?

Any hazards when handling Rhodium? Is it like Platinum? Or is this metal safer than Pt?


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