# extra rhodium



## arthur kierski (May 19, 2011)

as i need rh to make plating solution, i get some extra rh(0,26 grams per kilo -average) doing the following:after doing the normal leach with hcl-cl or ar,i take the almost spent cat powder and put it in an h2so4(60%) solution+0,1mole nacl and boil for1,30hour----add slowly water to the cold solution ,filtate and then cement the rh with iron or zinc-------

this action proves that there is more rh in cats then indicated by manufactures-----if i leach 100kilos of cats,i obtain 26 to 30grams extra rh----makes 15 plating solutions which pays for all the cats bought
i am passing this information and would like to ask if one knows another way of obtaining an extra rh from cats


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## kjavanb123 (May 19, 2011)

I crushed, then ball-milled the cats so they are like powder, i am going to dissolve them in 10HCL:1H2O2 solution at 80c and agitate it with 300rpm for 3 hrs. According to this Turkish univ article it should extract 95% of the Pt in it, I am pretty positive it will get most of the Pd, does Rh dissolve in Aqua Peroxide? or should i leach the remaining powder in sulfuric?

Thanks
Kev


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## arthur kierski (May 19, 2011)

Kjavand,i did the turkish method(10hcl:1h2o2)and got all all the pt and pd----the rh stayed in the powder-----the method is good for separating rh from pt and pd in mixed pgm powders,but not to obtain rh from cats-----
regards 
Arthur

ps :you get more but not all rh with ar leach or hcl-clorox leach------


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## kjavanb123 (May 20, 2011)

Arthur,

How long did you boil the remaining powder +Rh in sulfuric acid? Does temprature 80c and agitation rate of 300rpm apply for Rh recovery also? Thanks

Kev


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## arthur kierski (May 20, 2011)

kjavand, the powder is boiled for 2hours,but if the mixture becames too thick,you may boil for less time----1 to 1,30 hours-------yes ,it is advantageous to agitate the solution---it avoids that the powder get stuck in the botton of the becker---- do not forget to add the nacl(6 to 10grams per liter of sulfuric solution)----it does not work with kcl or nh4cl,.
please,if you do the experiment,do not forget to pass to me your yeald per kilo of powder
i need to compare the rh yealds to see if i am withdrawing all the rh from the spent powder
regards, 

temp 100 0r more centigrades 
Arthur


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## skippy (May 20, 2011)

I don't know the exact details on the procedure, but I've read that by fusing with 10:1 pyrosulfateowdered catalyst 
you get essentially total solubilization of the rhodium. It's done for analysis, and obviously it's not very practical for recovery, but it may be possible
to use it on a sample after your two leachings to see qualitatively whether there is significant Rhodium left .


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## kjavanb123 (May 20, 2011)

Arthur,

I will post pictures along with recovery data from my AP leach on 1100grams catalytic convertor, which weighed 1085grams after milling. Also what is the purpose of NaCl addition?

Thanks all,
Kev


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## arthur kierski (Jun 19, 2011)

as i described the method for extra rh from cats----i said that after carefully putting water to the solution and then filtering ,i obtained a green solution with the extra rh in it--------this green solution was cemented with iron and the rh cemented in the botton of the vessel----------------
i found that the rh in the botton of the vessel was contaminated with lead and silicates from the cats powder----this mixture is horrible to filtrate---------- had to decant and siphon out the precipitates
in other words: if you have a mixture ( of precipitated pb,rh, and silicates as a black powder),how would you separate these elements from the rh?

i incinerated these mixture and the black powder became reddish brown collor-----


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## kjavanb123 (Jun 19, 2011)

Arthur,

I went ahead and leached PGMs from powder catalytic converter, and filtering is a pain. Try wick filtering, just type in "wick filter" in search area and you will see a post about it with detail and everything.

Only downside about using h202 instead of hno3 is when cementing with zinc the solution turns black and you have let the solution sit for at least 24 hrs to settle before you can decant and dry the black powder. in aqua regia solution turned clear and you could see the black powder at the bottom of beaker, decant and let it dry and proceed.

I can't post pictures due to forum software issues.

Kev


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## skippy (Jun 19, 2011)

Arthur, I know what you mean, you start high temperature leaching and you get a lot of dissolved alumina, magnesia, ceria, and if you are right, silica too. I didn't think silica really had much of an aqueous acidic chemistry though. 

One approach to your problem might be to precipitate your silicate/silicate like mineral junk and the lead before you cement your Rhodium out. Maybe with careful neutralization - don't go too far or you will precipitate aluminum hydroxide, which is an awful mess. You can actually neutralize quite a bit before this happens. Also, I've actually had decent luck making the colloidal crap drop out with a bit of salt sometimes, so you might give that a whirl - it's certainly something easy enough to try. Was your filtered solution clear?


Back to your original line of thought. If you find you can decant, wick or filter your contaminated values out of the liquid easily enough I think you could get the silica out by attacking it with hot concentrated sodium hydroxide. Dissolve the silica, let the solution cool, and then add small amounts of H2O2 which will dissolve the lead. That's how I'd try to do it, but hopefully someone else has more details. I've never done it.


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## arthur kierski (Jun 19, 2011)

Skippy,thanks for your insights and experience-----i think that the material in the solution is silica,but i might be wrong and the solution is composed of alumina,ceria, magnesia and perhaps sillica-----anyhow it is very difficult to filtrate and as you asked ,the filtrated solution is not clear,but milky----------------------------------------------------------------------------------------------------------i added some nh4oh to the solution and it formed a white precipitate -------
i will try with salt and see if i am lucky as you were-----
thanks for you replies and i will pass any results that i obtain from these experience
Arthur


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## skippy (Jun 19, 2011)

I think I was just confused and thought you had precipitated the silica from a clear solution. Which wouldn't happen from an acidic solution unless you were using hydrofluoric acid. 
The milky suspended stuff that found its way into your liquid could easily be silica though.

I thought I would add for anybody who doesn't know that hot sodium hydroxide is very dangerous. That is to say, a stray drop spattering into your eye will blind you dangerous A face shield and goggles would be a very good idea. Hot concentrated sodium hydroxide is incompatible with glass, but a stainless pot should work.


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## Harold_V (Jun 20, 2011)

arthur kierski said:


> as i described the method for extra rh from cats----i said that after carefully putting water to the solution and then filtering ,i obtained a green solution with the extra rh in it--------this green solution was cemented with iron and the rh cemented in the botton of the vessel----------------
> i found that the rh in the botton of the vessel was contaminated with lead and silicates from the cats powder----this mixture is horrible to filtrate---------- had to decant and siphon out the precipitates
> in other words: if you have a mixture ( of precipitated pb,rh, and silicates as a black powder),how would you separate these elements from the rh?
> 
> i incinerated these mixture and the black powder became reddish brown collor-----


I would think that a wash in hot HCl would free the solids of iron, plus anything that makes filtration difficult. I'd actually boil, briefly, then take up the solution with water. Allow to settle, then siphon. Repeat with a water rinse. Eventually, the solids will filter without issue if you follow this routine, although you likely won't have need to filter until you've dissolved the values. 
Any traces of lead that may have made it through can be eliminated by adding a few drops of sulfuric acid to the solution after the values have been dissolved. It will be converted to lead sulfate and removed in filtration. 

Harold


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## arthur kierski (Jun 20, 2011)

Harold ,are you talking abou the redish brown powder that the mixture became after incineration?
or the powder cemented as a black powder mixture before incineration?
thanks for the reply
Arthur


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## Harold_V (Jun 21, 2011)

arthur kierski said:


> Harold ,are you talking abou the redish brown powder that the mixture became after incineration?
> or the powder cemented as a black powder mixture before incineration?
> thanks for the reply
> Arthur


Yes, after incineration, Arthur. I expect it will work. The iron (red powder) should dissolve with HCl, so you can remove it by siphoning once dissolved. Might be a good idea to post if you give it a try and let us know. If you have any palladium present, test the solution with stannous chloride after dissolution to insure that you haven't dissolved some palladium oxide. If so, send the solution to the stock pot. 

Harold


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## arthur kierski (Jun 21, 2011)

Harold,thanks for the reply------tomorrow i will have the results and will pass it to you 
Arthur


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## arthur kierski (Jun 23, 2011)

Harold, i boiled the red powder (resulted from the incineration) with hcl-----it took some time but the iron dissolved and the rh powder stayed in the botton of the beaker-------the solution became green and was tested for pd------no pd ----------------
thanks for the help, it worked well
regards, 
Arthur


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## Harold_V (Jun 25, 2011)

You're most welcome, Arthur. 

As readers likely know, I've promoted the washing of things with HCl on a routine basis. It's one of the tools in the arsenal (along with incineration) that is truly a "magic bullet".

Harold


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