# Processing Crushed Substrate from an Auto Catalytic Converte



## kadriver (Jul 16, 2012)

I received this bag of crushed substrate with a batch of beads that I bought. It is a crushed up honeycomb from a single catalytic converter (I think).

For this material I chose to use hot concentrated aqua regia.

First, I put the crushed material into a clean, heavy pyrex coffee pot with a lid.


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## kadriver (Jul 16, 2012)

Outdoors, I then added 600ml HCl to the crushed material.

Followed by 100ml concentrated nitric acid.

I know this is not the correct formula for aqua regia, but I needed extra liquid to cover the crushed material.

Adding extra hydrochloric acid won't hurt.

Adding water to make up the difference would dilute the AR and I wanted to avoid that.


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## kadriver (Jul 16, 2012)

As soon as I added the nitric acid I snapped this picture.

There was an immediate reaction that produced this orange color in the reaction vessel - possibly platinum.


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## kadriver (Jul 16, 2012)

I added some heat to aide the reaction.

First photo is about an hour into the reation with medium low heat.

Second photo is about 3 hours after adding medium low heat.


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## BAMGOLD (Jul 16, 2012)

You have great picture posts! Keep it up!


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## kadriver (Jul 16, 2012)

The following day I added about 30ml more nitric acid and placed the vessel back on the heat.

I allowed it to cooked for 6 hours on medium low heat until no more fumes were being emitted.


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## kadriver (Jul 16, 2012)

A stannous chloride test gave inconclusive results - probably too much acid.

Tomorrow I will do a spot plate test with the acid neutralized so the test won't be affected by excess acid.

Added about 400ml distilled water and course filtered.


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## kadriver (Jul 16, 2012)

I plan to do another aqua regia extraction after I get back from vacation on the 27th of July.

I will put the aqua regia into the vessel before I leave and allow it to leach for the week that I am gone.

kadriver


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## kadriver (Aug 1, 2012)

Photo of the liquid after passing through a fine filter paper whatman #5.

This liquid does not look too promising judging by the color.

More to follow - kadriver


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## lazersteve (Aug 1, 2012)

I have tested many solutions with extremely high amounts of free nitric acid for Pt with stannous chloride and had great success. The swab should go immeadiately dark orange when the stannous is added.

The color of your solution doesn't look quite right to me either.

Steve


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## kadriver (Aug 1, 2012)

I did some more tests on this solution today.

The swab did turn a slight orange color indicating platinum - but not much.

The spot plate test;

left cavity: palladium standard test solution 100mg/100ml

Mid cavity: Sample of filtered solution unknown content

right cavity: platinum standard test solution 100mg/100ml

Looks like this crushed substrate contained very little PGMs based on the results I got with these tests.

kadriver


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## kurt (Aug 3, 2012)

kadriver - are you incinerating your cat ceramic substrate before acid processing? --- if not the carbon &/or oils may be tying up your PGMs

I just picked up 7 cats that I am working on - so far I have leached & preciped the after market cat & today I incinerated & put in the leach (HCL/clorox) the comb from a Honda Hot Dog.

How I processed the after market - first I poured some lacquer thinner through the comb as a solvent to wash out any oils & then used my tourch to incinerate by playing the tourch on each end of the comb as well as heating it around on the out side of the comb to burn "off" the lacquer thinner & burn "out" the carbon.

I then covered the comb with straight HCL - the idea here was to leach out the alumina that makes up the wash coat before leaching the PGMs. To my suprise the straight HCL leach also leached the PGMs (positive test for both Pd & Pt with stannous)

I then preciped this leach with zinc (the pic is the heaver PGM black that settled right away & there is still more of the finer PGM black settling in the larger volume of solution.

I then cut a small sample of the comb out - cut that in half & put one half in an AR leach & the other half in a HCL/Clorox leach --- after a couple hours I tested these samples & did not get a positive test for PGMs from ether sample - so aparently the straight HCL leached all the PGMs

There was some black sediment in the HCL leach - which I filtered out & is drying - I will be testing this to see if it is more PGMs or just carbon that didn't burn out when I incinerated

If your not incinerating - try it - I think you will find you get a cleaner more complete leach --- I use lacquer Thinner or acitone because they work as a solvent on any oils & burn off &/or evaporate off clean (meaning they don't creat a carbon residue of there own)

Anyway - have been following your threads on your process & want to say thanks for doing such an awesome job of posting your process.

Kurt


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## kurt (Aug 3, 2012)

Opps - forgot to post the pic of the PGM black preciped with zinc from the after market stright HCL leach

Kurt


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## kadriver (Aug 4, 2012)

Kurt;

I noticed much black carbon especially on the beads.

I do two filter passes - one course with four coffee filters, and then a fine with a whatman #5 through a vacuum.

The leach liquids come pretty clean after these two filterings.

I have never considered incinerating the substrate before leaching - sounds like a good idea to remove external dirt and oils.

I have learned that mechanical cleaning prior to any wet processes produces a better product and less work in the end.

Also, I am convinced that incineration is very important to most refining processes. 

Thank you for the input - kadriver


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## rusty (Aug 4, 2012)

Here's my jar of blacks, with more to be added soon.

Aug 05/12 added more black powder to my jar, this is from the milled cats I had sitting in AR for over a year and half. Now that most of the zinc has been washed out the powder settles out quickly.


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## kadriver (Aug 21, 2012)

I transfered the AR leach of the crushed cat substrate to a 2 liter beaker.

Then I repeated the stannous chloride test.

The test shows the presence of some PGMs.

I plan to evaporate this solution down to syrup and drive off the nitric as per Steve's DVD "Fundamentals of Pt & Pd"

kadriver


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## kadriver (Aug 22, 2012)

Rusty:

Nice photos of your black powder - keep us posted on your progress.

Today I was able to evaporate the liquid down from just under 1100ml to just under 600ml.

Started the evaporation at 4pm and concluded at 2am next day - 10 hours total.

The color has darkened nicely. I'll do another stannous test and post the results.

I plan to evap down to syrup and then rehydrate with HCl to drive off excess nitric as per Steve's DVD.

kadriver


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## kadriver (Aug 23, 2012)

I was able to further reduce the liquid to just below 400ml today.

A yellowish colored solid began to form on top of the liquid, and on the bottom of the beaker.

I do not know what this material is - I am trying to rid the solution of excess nitric acid by evaporation.

This took about 8 hours on medium heat to get to this point.

I added a little HCl and there was some fuming, but I did not see any brown fumes.

I'll continue evaporation tomorrow.


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## kadriver (Aug 23, 2012)

I also did another stannous test at this concentration.

The liquid was syrupy about like maple syrup.

The test showed that there is a little palladium in this solution.

kadriver


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## kadriver (Sep 3, 2012)

Since I am familiar with cementing the blacks with zinc, I am thinking of using this process for this batch of AR dissolved PGMs; evap, rehydrate with HCl to expell nitric, then dilute with water and add zinc shavings (and more HCl if necessary) to get the mixed black powders.

I went back and checked this post:

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=51&t=12516

It was my first failed attemp to recover PGMs from some catalytic converter beads - the container slipped and broke in my catch container.

I had forgotten that I have already done the procedure to get the mixed black powders from that failed attempt.

Once recovered and washed with tap water to neutral pH, I will add this black powder to my collection of black powders recovered from HCl/Cl leaches and just go from there.

More pictures to follow.

kadriver


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## kadriver (Sep 3, 2012)

I would very much like to know what that yellowish colored solid formation is on the bottom of that beaker - salt?

It is obviously something that is formed as the solution becomes highly concentrated by evaporation - but is it valuable?

I would also like to know if that solid material will impact my plan to rid the excess nitric in this solution by evaporation and rehydration with HCl.

I seem to remember this same yellowish solid formation in the container on my last attempt to evaporate an AR solution that contained Pt & Pd.

Should I filter the solid material out of the solution before I proceed?

If anyone could provide some insight before I continue, it would be greatly appreciated.

kadriver


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## lazersteve (Sep 4, 2012)

Filter out a sample of the yellow solid, rinse well, hydrate with HCl and test it with stannous chloride and DMG. 

If the yellow powder contains values, these two tests should reveal them.

Steve


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## kadriver (Sep 4, 2012)

Thanks Steve, I'll do the test as you described.

kadriver


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## kadriver (Sep 5, 2012)

Today I evaporated the solution down some more.

When I added some hydrochloric acid to rehydrate there were much brown fumes.

The yellow solid material dissolved each time I added the HCl.

I repeated the evaporations 3 times, rehydrating with HCl and expelling brown fumes each time.

This is as far as I got with this today. 

I believe that there is more nitric to be expelled, so tomorrow I will continue the evaporation prcess on this solution.

When I get no more brown fumes being expelled (indicating that all the nitric has been expelled) then I will rehydrate with water and cement with zinc shavings to recover the black PGM powders.


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## Oz (Sep 5, 2012)

kadriver said:


> I believe that there is more nitric to be expelled, so tomorrow I will continue the evaporation prcess on this solution. When I get no more brown fumes being expelled (indicating that all the nitric has been expelled) then I will rehydrate with water and cement with zinc shavings to recover the black PGM powders.


Maybe I missed something, but if you plan on cementing this with zinc, why bother removing the nitric? You could adjust the pH up a bit to conserve on zinc when cementing.


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## kadriver (Sep 5, 2012)

Oz:

I was thinking that with all that nitric in the solution (130ml nitric acid added in the beginning) that any black powders that cemented out would be dissolved by the aqua regia solution.

That was my reason for first evaporating to remove excess nitric. 

kadriver


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## RaoOvious (Sep 6, 2012)

No cementing with zinc from AR wont put them back except you wod have to use some extra zinc(better if Ph raised) and its far comforting than denoxxing(  )..


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## kadriver (Sep 6, 2012)

I have never cemented PGMs from an AR solution with zinc - this will be my first attemp at doing this.

The only experience I have is based on hydrochloric acid and bleach (HCl/Cl) leach.

With this type of leach (HCl/Cl), there is no nitric.

You just add the zinc to the HCl/Cl leach liquid (after raising pH a little) and the black powders cement out nicely.

What I am starting to see (after two posts from other members) is that I can cement with zinc from an AR solution without having to remove excess nitric acid first - there is NO NEED to get rid of the excess nitric.

I am going to try this experiment today and I'll post some pictures - thanks to both or you for this guidance.

kadriver


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## kadriver (Sep 8, 2012)

I re-hydrated the AR solution with distilled water - after spending hours dehydrating the solution to denoxx I learned that denoxxing is not necessary - still learning here.


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## kadriver (Sep 8, 2012)

After adding distilled water to rehydrate, I filtered the liquid through a Whatman #5 fine filter paper - took about 3 hours to get it all through the filter.

After cleaning the beaker, I transfered the filtered liquid back into the beaker to precipitate the PGMs with zinc shavings.


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## kadriver (Sep 8, 2012)

I moved everything outside and put on my protective clothing and mask.

I added some sodium carbonate to increase the pH - the reaction was very mild.

I expected it to be much greater.


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## kadriver (Sep 8, 2012)

Then I added zinc and observed the reaction - very tepid compared to the HCl/Cl solutions.

I had to add some hydrochloric acid to get all the sodium carbonate to dissolve.

Later, I added more hydrochloric acid to get all the zinc shavings to react.


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## kadriver (Sep 8, 2012)

Ultimately I ended up with some more black powders from this extraction.

I had to pick out a few pieces of zinc that did not dissolve completely.

I'll wash and add to my collection of black powders for further refining.

Now I have the experience of getting the black powders from an AR solution.

Thanks for looking.

kadriver


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## lazersteve (Sep 8, 2012)

Great work again Kevin.

As a side note:

Denoxxing *is necessary* for the final refining stage of the PGMs, but not for the recovery stage regardless of which method you initially leach the converters with. If you have a concentrated solution of mixed PGMs that you are going to precipitate first Pt, then Pd from using ammonium chloride (for Pt) and a chlorine source (for Pd) you must denoxx.

Use zinc (or other base metal like iron) to collect the mixed PGMs from very dilute solutions regardless of how the PGMs got into solution. If you know the dilute solution if free of Pt then you can use DMG to scavenge the traces of Pd and save your zinc for solutions of mixed PGMs with relatively high value of dissolved PGMs. 

Steve


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## RaoOvious (Sep 8, 2012)

good work kevin...


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## kadriver (Sep 10, 2012)

I wish I would have known this when I decided to evaporate and denoxx this solution - but now I am all the wiser.




lazersteve said:


> As a side note:
> 
> Denoxxing *is necessary* for the final refining stage of the PGMs, but not for the recovery stage regardless of which method you initially leach the converters with. If you have a concentrated solution of mixed PGMs that you are going to precipitate first Pt, then Pd from using ammonium chloride (for Pt) and a chlorine source (for Pd) you must denoxx.
> 
> Steve



If this is true (and I believe it is) then would it be possilbe to use ammonium chloride to precipitate platinum from an HCl/Cl leach, then sodium chlorate to precipitate palladium from same, after filtering the HCl/Cl leach and heating it to drive off excess chlorine?

There should be no nitric in this HCl/Cl leach.

Once the dirt and excess chlorine is removed, it seems like this solution would be nearly identical to a denoxxed AR solution containing PGMs.

also:



lazersteve said:


> If you know the dilute solution if free of Pt then you can use DMG to scavenge the traces of Pd and save your zinc for solutions of mixed PGMs with relatively high value of dissolved PGMs.
> 
> Steve



I think it may have already been said, but just to clarify - can the palladium DMG precipitate scavenged from dilute Pd solutions be added to the brick red palladium powder (in the same container) and both be dissolved with ammonia at the same time?

This information is all very helpful - thank you.

kadriver


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## lazersteve (Sep 10, 2012)

Yes the two PGM salts can be combined.

With mixed PGMs in HCl-Cl you most likely have a diluted solution due to the high dilution of the reagents (31% HCl and 5-10% Sodium hypochlorite). This will require you to evaporate down just to get rid of the excess water. After evaporating to a level that is appropriate for precipitation, you will invariably encounter large deposits of sodium chloride and other salts. These salts tend to trap values and are not easy to rinse clean.


Steve


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## RaoOvious (Sep 10, 2012)

Other than the obvious reasons cited by steve,evaporating such volumes of HCL/CL leaches are even worse than denoxxing, time consuming and unwise,so best way is to scavenge values from big chunk leach volumes and then go ahead from blacks...


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## kadriver (Sep 11, 2012)

Excellent - it all makes sense - thank you for the insight.

kadriver


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