# your way



## arthur kierski (May 24, 2008)

i e-mailed some members of the forum and had no replies yet--------------the question is:i precipitated 5,9grams of black powder from a leach of one and a half fiat cat(1680grams of substrate)---i eliminated the excess iron with h2so4(10%)----------------------------------------------
the black powder is 5,9grams of pgm +perhaps some lead(in the 5,9grams)
i would like to know YOUR WAY to separate the 3pmgs

thanks for all replies----Arthur Kierski


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## ChucknC (May 24, 2008)

What leaching method are you using? By using H2SO4, it would be safe to say that almost all the black powder could be lead sulphate. The method used would confirm or disprove this.

By all I can find, Rh is insoluble in most leaches available to small guys. I've read some people claim they have reocovered Rh using AR, but Rh forms RhO inthe presence of nitric, an insoluble material. Now Iridium is somewhat soluble in Ar. It does precipitate as a black powder.

Chuck


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## Lou (May 24, 2008)

Iridium is even less soluble in AR than rhodium.


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## arthur kierski (May 24, 2008)

in resume ----forget cats ok?
the question is:if you have a black powder containing pgm and perhaps lead;what is your way of separating the pgm from each other?


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## Irons (May 25, 2008)

ChucknC said:


> What leaching method are you using? By using H2SO4, it would be safe to say that almost all the black powder could be lead sulphate. The method used would confirm or disprove this.
> 
> By all I can find, Rh is insoluble in most leaches available to small guys. I've read some people claim they have reocovered Rh using AR, but Rh forms RhO inthe presence of nitric, an insoluble material. Now Iridium is somewhat soluble in Ar. It does precipitate as a black powder.
> 
> Chuck



Lead Sulfate forms white feathery crystals and very little Lead will dissolve in H2SO4.


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## lazersteve (May 25, 2008)

Arthur,

Hoke also has a process for separating Pt and Pd from Rh and Ir using incineration and AR. Read the chapter on the stock pot to see this information. Like some of the others some of the Rh and Ir follow the Pt and Pd.

Alternately, dissolve the Pd with nitric then go after the Rh with sodium or potassium pyrosulphate via fusion reaction. The Rh forms a soluble salt, and the Pt remains as a black powder.

I've had success extracting PGMs from cats using very dilute hot AR, hot HCl-Cl, and 60% H2SO4+ 0.1 M NaCl at 135C.(Ref: M.H.H. Mahmoud)

Another method of PGM recovery is sodium peroxide fusion to remove the honeycomb substrate (nearly quantitative yields). I have not tested this one yet. (Ref: Kallman and Maul, Talanta, 30, 1, 21-39, 1983)

Additional means of separating the dissolved PGMs include selective extractions using resins or phase separation with organic compounds (G.P. Demopoulos and E. Benguerel) 

Lastly, treating the honeycomb with chlorine gas mixed with SO2 at 550C will volatize Pd and Pt as the chlorides which condense between 200-300C. Increasing the reaction temperature to 1000C will volatize the RhCl3 which condenses at 800C. (ref: E-Tek Inc)

Steve


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## markqf1 (May 25, 2008)

Mmm, ... well lets see here.
A magnet would probably remove alot of the undesirables.
And if you made up some hot AR, it's supposed to dissolve all of the pgm's but the Rh(at least in auto catalysts). According to "the book", NH4Cl should drop the pt but not the pd. For it, use NaClO3.

Mark


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