# Metal core catalysts



## Yggdrasil (May 28, 2017)

Hi!
I could not find a topic to this subject, so I generated a new one.
If the mods have a better spot for this post, please do advice so it can be moved.

I came a cross a metal core catalyst.
During my readings on the big wide web  I came to the conclusion that it was most likely of Kanthal.
Since Kanthal is a Chrome, Iron and Aluminum alloy, I decided to try dissolving the matrix in HCL.
This would have the benefit of leaving the potential PGMs as metal and not in solution, 
as well as using cheap HCl.
But after prolonged leaching I still was left with a much more and voluminous residue than expected.
So I suspected that it might be another alloy which had some pacification issues.
This put me in a kind of squeeze since I didn't like the idea of sulfuric acid yet.
Sulfuric would maybe dissolve Rhodium if present. And nitric would attack Palladium and Platinum if present.
I'm not set up for proper roasting either yet, it is on its way  

It is comprised of a very fine fluffy grey sludge and some coarser gritty residue in a mix.
It seem that this residue will weigh in around 1 kg when dried.







I finally caved in, and extracted a couple of grams residue and added fresh HCl and a few milliliters nitric acid.
This is my first use of AR on a metal expected to react with AR.
So I expected a relative active reaction because of the fine powder and the concentration of acids.
But to my surprise there was no visible reaction at first, no bubbles and no fumes.
The reaction is at room temperature.
After a while the mixture turned brownish and then bright red, but still no bubbles and fumes  
HCL is 36% and fumes and the nitric is 65% and fumes as well.
I really expected both bubbles and fumes.




So now I will dry it completely and take a sample that is weighed and repeat this, then weigh it after.
With the respect to color of solution and stannous test, I suspect Platinum and not much Palladium.





There seem to be some precipitation of some kind too.
My plan now is to leach out as much as I get from the sample and then cement it out with copper.
Then leave the rest of the sludge in metallic form for later.
I'm not quite set up to do much PGMs yet. That was why the base metal leaching looked appealing.

Does anyone have a explanation why the AR didn't evolve neither smoke nor bubbles?
Micro bubbles?
It does the job though


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## g_axelsson (May 28, 2017)

It seems like the stainless steel is made up of a high aluminum and chrome alloy, 20% chrome and 5% aluminum to get high corrosion resistance. Probably a lot of the aluminum is already oxidized to form a protective surface. Then you have the wash coat of aluminum oxide that also adds to the insoluble part.

Ref : Development of Ferritic Stainless Steel Foil as Metal Support for Automotive Catalytic Converter (pdf)

Göran


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## Yggdrasil (May 28, 2017)

Ok, that makes sense.
Still I would have expected strong HCl to penetrate the layer, and it did in the beginning.
Some time after the reaction started it slowed down until it finally died down to nothing.

Will a passivization layer be the reason why the brown smokes and bubbles doesn't develop as I expected?
Aluminum passivization layer slows down the nitric in the AR so much that the fumes and bubbles are practically invisible?


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## Platdigger (May 28, 2017)

You say you may have one KG of residue, what was the beginning weight of the material you put in acid?
Also, if it did not cement back out, you could have put some pd into that first solute.


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## Yggdrasil (May 28, 2017)

Well, that is a bit embarrassing. 
It was not possible to get it separated properly during disassembly, it seemed soldered/brazed to the casing.
So I just ended putting the whole "shabang" into a PP bucket and added HCl, 
minus the casing and some bits of core sticking to it.
If I should guesstimate, I would guess I have the third left as residue.
So you think that the palladium may have oxidized and left itself accessible for the HCl?
There was a very faint greenish color from the stannous test, 
but it might just have been the dark green from the liquor itself.
And of course I haven't thrown away anything, 
my plan has always been to cement out from the initial leach as well.
I have appr 10-15l of dilute liquor left from that.


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## g_axelsson (May 28, 2017)

If the wet material is close to a kilo then the dried material can be a lot less. The density of the sludge should be quite telling, a kilo of stainless steel is just about 1/8 of a liter. If the sludge is even close to a liter then the density is close to water.

If there was very little NOx released then I would expect very little metal remained in the sludge. Maybe the AR broke up some metal complexes and released the water from it, making it more compact.

Göran


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## Yggdrasil (May 29, 2017)

Thanks Gøran.

The stannous test seems to indicate relatively strong concentration, doesn't it?
Or maybe false positive, I have no reference to the color of the liquor yet.
I will have exact weight on residues later and I will start test on a 5 gram batch 
to see how much is dissolved in AR.
I also have to find a way to see if there are anything left in the residues after AR.
Maybe sulfuric is the way here, or I may just save it up for later.


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## g_axelsson (May 29, 2017)

Since you dissolved a catalytic converter it's not unexpected to find palladium and platinum in solution. You might get some rhodium too, it should be insoluble in AR but if there is any rhodium oxide it might dissolve in HCl if I remember correctly. You better do a search on the forum than trust me on that.

The normal way to dissolve rhodium is by salt fusion, peroxide fusion if I remember correct.

Palladium might be oxidized and in PdO form, then I think it might be insoluble too. I have heard different statements, some claiming it is insoluble in HCl or AR, some that it will dissolve in HCl. I don't know what is true.

This is nothing I have any experience from, so consider it as hints for further research and not as advice.

Silver and gold is easy, PGM:s are devious. :mrgreen: 

Göran


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## Topher_osAUrus (May 29, 2017)

g_axelsson said:


> Palladium might be oxidized and in PdO form, then I think it might be insoluble too. I have heard different statements, some claiming it is insoluble in HCl or AR, some that it will dissolve in HCl. I don't know what is true.
> 
> Göran



Mrs Hoke says when treating PdO HCl is the way to get it into solution, it is insoluble in nitric or AR, so they wont have effect upon it. 

She talks about it in the stock pot section, on methodology for treating slimes after roasting. Page 146 or 147, I believe.

Lou gave another method, I think HBr, but I could be mistaken on that.


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## Platdigger (May 29, 2017)

Even metalic pd will eventually go into hcl with just the oxygen absorbed from air.


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## g_axelsson (May 29, 2017)

Check this thread for stannous reactions.
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=41&t=5271&p=45030#p45030

Göran


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## Lou (May 29, 2017)

Best solvent system for cat cons is HBr/Br2.


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## Yggdrasil (May 30, 2017)

A small update.

I have now weighed the dried residue.
It ended up at 500g +/- (cheap kitchen scale) including what is used (5-8g) in the two test batches leaching now.
The cat it self was rather large so between 2/3 and 3/4 of the cat may have been dissolved in HCl.

When I have cemented out whatever Pd that has gone into the HCl liquor I can treat the liquor for disposal.

Just out of curiosity: 
Does anyone have a tip on how to treat a liquid containing at least chrome, iron and aluminum?
It could be nice to cement out the chrome at least, would aluminum shavings be OK for this?

Is it feasible to distill it to dryness and collect the azeotropic HCl?


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## Yggdrasil (May 30, 2017)

Thanks for the replies.



g_axelsson said:


> Check this thread for stannous reactions.
> http://goldrefiningforum.com/phpBB3/viewtopic.php?f=41&t=5271&p=45030#p45030
> 
> Göran



I regularly go to this section to check my stannous reactions  , 
haven't found much on how to test for Rhodium though, other than the small tip in this same link. 
Will it give a similar reaction for ordinary stannous test as the others?



Lou said:


> Best solvent system for cat cons is HBr/Br2.



I haven't found any details on how to do the HBr/Br2 here on the forum.
Is it because it is too complicated in method or equipment for most of us?
Where can I find details on this method?

BR Per-Ove


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## Yggdrasil (Jun 17, 2017)

Hi!
I have now (partially) processed appr 15grams of residue. Including some very fine light grey residue 
that slipped by the first siphoning. It is so fine that it sticks to the walls of the vessels.
The leach of this, is yellowish in color and test positive for Platinum with stannous.
I have used both AR and HCl/Cl for the leach, to test both methods.
The residue from this has been treated with conc sulfuric with no further progress.
Awaiting results from test of base residue to see what it is composed of.

But while I was wrapping up this small scale test, while I was trying to cement out the PGMs with Zink, 
to put it back to its metal form, I fell into a few rookie traps.

First I forgot to deNoxx, so when I heated the ppt in solution, 
it redissolved (Stunning how black it was  ).
Next I'm not sure what happened, since I ended up with floating (contaminants) 
which on closer inspection was floating PGMs, silver white in color.




I also notices that the beaker and stir rod was plated.
The cementing was very slow prior to this.

Then I added some more HCl and a dash Nitric and heated, to dissolve the "plating".
The plating loosened somewhat and the ppt turned to black again.
The solution are now yellowish brown in stead of red.

How will I get coarser ppt during cementing? Copper vs Zink. Powdered vs large surface?
Zink seemed to be the best with respect to post cement cleanup with HCl.

The use of Ammonium Chloride might be a better procedure but I wanted to drop all out of solution, 
which the cementing was supposed to do.

Besides it is easier for me to get most chems in industrial quantities and qualities.
So Ammonium Chloride is easy to get in 25Kg bags but hard in smaller quantities.


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## g_axelsson (Jun 17, 2017)

Yggdrasil said:


> Thanks for the replies.
> 
> 
> 
> ...


I thought I had answered this one already... but better late than never.

More detailed rhodium test.
http://goldrefiningforum.com/~goldrefi/phpBB3/viewtopic.php?t=2007

Göran


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## Yggdrasil (Jun 17, 2017)

I didn't ask for stannous reactions this time, but rather the best way to cement the PGMs. And to show progress ;-) 

Sent fra min SM-G950F via Tapatalk


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## g_axelsson (Jun 17, 2017)

Yeah, I know, but there was an unanswered question in the thread. :wink: 

Cementing PGM:s have always been tricky and it is too far in between for me so I don't have mastered it yet enough to giving advice. I have had perfect drops with zinc when I ended up with an easily handled black powder and I have made palladium mirrors including across the surface when cementing on copper. I've even made crystals in the form of flakes that later fell apart when washing in water, it was so fragile.
The total of my black PGM powders is only 10 grams so far. When I get a decent amount I'll try to refine it.

Göran


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## Yggdrasil (Jun 17, 2017)

Thanks for the answer Gøran.

Hmm I always thought that it was enough to have a slightly acidic liquor and add whatever 
suited metal of ones choice and it would happen.
The result of finer or coarser the ppt would be, was a function of liquor concentration and metal form/type.
Would it be better with a large solid plate or powder for instance.
For [stt]Zink[/stt] Zinc the cleanup would be easy, on the other hand Copper might need another approach.
Especially when using powdered metal, one can assume that not all has been dissolved and it will need 
to be removed from the cement somehow.
I will update, when I have cleaned up this batch and received the result of the test (AAS I guess), 
done by another member.

One funny/interesting thing though.
When trying to strike down these floating bits of metal with the spray bottle.
I noticed some of the small specs apparently defying gravity by climbing the wall of the beaker, 
even when the spray was directed directly at them. 
It must be some kind of surface tension effect.
A slightly mesmerizing effect, causing me to add more water than needed :lol:

Edited for spelling:
Hope my misspelling are forgiven in time :wink:


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## Yggdrasil (Jul 12, 2017)

Hi!
Here is an update.
I have sent some powder for a XRF reading.
The result baffles me. :? It allegedly reads high in Pd.
But none of the tests I have done here seems to support that.
Oddly enough the Kanthal was leached in HCl, 
but when I put the dried powder in 36 percent HCl the solution turns orange in a short time. 
When adding Nitric it turns red, most likely because of increased concentration.
To check it I did two tests.
One strannous the other DMG in Isopropanol.
First test here in a 1ml spoon for clarity




Here I expected a green color if Pd was present.


Second here for DMG


If the content of Pd was here this should be a lot of yellow precipitation, should it not?
The pictures aren't entirely correct in the colors.
My stannous test is bright red and then turns almost black as old blood within a short time.
The DMG just breaks up the surface tension and flattens and thins the drop.

BR Per-Ove


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## Yggdrasil (Jul 31, 2017)

I will be offline most of the next month. 
Then I will go to Mindanao and visit my in-laws and what comes there of.

In case of anything interesting or out of the ordinary just PM me.
TapaTalk will inform me 

BR PoA


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## Yggdrasil (Aug 24, 2017)

Hi 
Back and refreshed now 
Interesting things has happened in the lab while away  
It seems that I have redissolved much of my powders by accident  

I have what I call a reaction chamber. 
Basically a polypropylene storage box with gasket on the lid.
To this I have added a aquarium air pump and a large outlet.
It function as my PM storage, storing my gold powder and PGM blacks in concentrated HCl.

But just before leaving for my vacation, I put in a beaker which was not finished leaching ( 500ml HCl and 20-25Ml HNO3)
During my 3 weeks of absence the NOx gases had been picked up by the HCl and redissolved much of my powders.

Brain glitch, quite clear mistake in hindsight.
But there was also a small beaker which contained some catalyst pieces which had been test fused in Sodium bisulfate, before transferred to AR. 
It obviously still had significant amount of Sodium bisulfate in it.
This beaker had soaked up a lot of extra liquid and overflowed.

Lesson learned, but no damage done :wink:
I was supposed to do a secondary refining anyway  

BR PoA


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## butcher (Aug 24, 2017)

Zinc not zink (That misspelling of the word bugs me, as I also have problems spelling zinc and nickel).

DMG will be beneficial here, in your testing tool box.


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## Yggdrasil (Aug 24, 2017)

Hmm. 
A long time ago and easy to do in my case ;-) 
So I had to look it up again  
I stand corrected and will edit when back in the house. 
In my language we write zinc either as Sink or Zink. 

Sent fra min SM-G950F via Tapatalk


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## Yggdrasil (Aug 24, 2017)

DMG are in my toolbox.
I use it with IsoPropanol as recommended by forum members.

In this case it does not give the expected result. 
IP or water give same result.

It works fine for Nickel though.

It is all in the thread with pictures and all.
And it have me quite puzzled, since the XRF says it has substantial amount of Pd.
But both Stannous and DMG give no indication of Pd.
Reread the thread and see the reactions.

BR PoA


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## butcher (Aug 24, 2017)

I would trust DMG over an XRF.
That is if Pd was actually in the acidic solution (and not still in metal, or oxide form...)


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