# Honeycomb in HCL-Clorox



## Rag and Bone (May 27, 2008)

I picked up some cat honeycomb. I plan on leaching it in hot HCl-Clorox.

What do I need to do before I begin the leach? If there is already a post on the subject please let me know. I can't seem to find anything detailed on honeycomb in HCl-Clorox. 

(I must say, PGMs don't hold the same allure of gold, despite their higher value)


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## lazersteve (May 27, 2008)

Rags,

I've processed only one honeycomb with HCl-Cl. I heated the honeycomb to red hot temperatures with MAPP gas before processing to remove the carbon. I'm not sure if it was really necessary though, since lots of black material floated off as soon as I added the HCl to the mix without any clorox. This may have been trapped carbon, I'm not really sure.

I processed a domestic honeycomb and the yields for one pass were very low. I would estimate less than 1/4 gram Pt and less than 1/8 gram Rh. I haven't got any final numbers yet since the Pt and Rh are still in unrefined forms. The honeycomb most likely has more on it and will need a second or even third run thru the HCl-Cl to get everything. 

The process did not yield any Pd. I'm not sure if that's because it all burned away with the MAPP gas treatment, or because it just didn't contain any Pd. I won't be heat treating the next one.

I'll post more later.

Steve


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## Buzz (May 28, 2008)

Steve,

According to the info published by Megan Rose, cats from diesels don't contain Pd, just Pt and Rh.
If that info is correct, maybe your cat came from a diesel?

Regards
Buzz


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## Irons (May 28, 2008)

The solubility of Chlorine decreases with increasing temperature to where it's almost zero at 100 Deg. Centigrade. Unless you heat under pressure to contain the Chlorine, it will boil off.


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## lazersteve (May 28, 2008)

Irons,

With this reaction I keep the solution at or below 60C. Granted the chlorine solubility is decreased, but with small additions of clorox directly into the vanes of the honeycomb, the chlorine is in close contact with the PGMs when it is generated. 

I'm also looking at adding sodium chloride to the mix to increase the total number of chlorine ions in the solution.

Remember as long as the chlorine is consumed when it is generated it doesn't have to remained dissolved into the solution matrix as free chlorine. In effect the chlorine gas is being generated in direct contact with the catalytic surface of the honeycomb. It then preferentially reacts with the PGMs due to it's lowered solubility in water. The water soluble chlorinated PGMs then become part of the solution matrix. With excess clorox the chlorine of course is wasted as off gases. 

Pressurizing the reaction vessel is a really good idea, but complicates the reaction from the home setup perspective. 

Steve


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## Irons (May 28, 2008)

Try some ground up cat in a 2 liter bottle with HCl/Cl. Leave at least 50% head room as a pressure buffer. The PETE is permeable to Hydrogen and it will escape through the walls. You can get an idea of the internal pressure by squeezing the bottle. You can safely get 2 atmospheres of pressure and it will make up for the lower temperature of operation.

I have not noticed much if any Chlorine odor, so the plastic must be retaining it well.

No acid or Chlorine loss makes for a more efficient operation.

You can feel the bottle and tell when the Chlorine is used-up and it's time to add more Bleach.

If you let it sit long enough, a negative pressure develops.

I noticed that sunlight really increases the activity, so be careful if the bottles get exposed as the pressure will build, even with the same temperature. This could be a good thing if monitored properly.


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## lazersteve (May 28, 2008)

Irons,

I read the previous post about using the coke bottle, but haven't given it a test run yet.

I'm not a soda drinker so I'll have to got to the store and pick up a 2-3 liter to test it out.

Sounds interesting.

Have you had any success with this method for Pt and Rh?

Steve


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## Rag and Bone (May 28, 2008)

My aerated AP reaction bucket has a sealed lid and builds up good pressure. The lid bulges out and gets "tight as a drum". I wonder if this amount of pressure would be effective?


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## Lino1406 (May 28, 2008)

From my experience, good sprinkling with
water will clean a good part of the dirt and carbon
2ndly, unground cat inclines to get blocked, so first
rinse should be quick.


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## Irons (May 28, 2008)

Rag and Bone said:


> My aerated AP reaction bucket has a sealed lid and builds up good pressure. The lid bulges out and gets "tight as a drum". I wonder if this amount of pressure would be effective?



Any pressure increase will increase the rate of reaction. You have to be careful, especially at first because the reaction rate can quickly get out of control. I don't allow the pressure to build up by limiting the concentration of the leach. Start out with straight HCl to get any base metals or contaminants that generate a lot of Hydrogen. Once it settles down, add a very small amount of bleach and watch. As long as there are tiny bubbles forming, the solution is saturated and adding more will just make the Chlorine boil off and increase the pressure. Chlorine will make the leach look cloudy, so that is a good indicator that it is still working.

Every system has its limits. Be careful. Keep a big container of cold water handy in case things look like they are going badly. Don't try to unscrew the cap. It will foam and spray you with acid when the pressure is released. Keep a big container of cold water handy so you can just drop the bottle in and slow things down. If it pops in the water, you can always recover the materials later. The cap tends to jam under pressure, so if you cant unscrew it easily, cool it down.

A warning about heating. PETE loses its strength rapidly as the temperature increases. If the bottom starts to push out, cool things down. I had a bottle give way last year while heating.
Spraying hot acid is not a safe pastime.

Don't be a stingy and try to use the bottle more than once and be sure to check for any scratches or other damage that might cause a point of failure.

Have fun and be safe.


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## Rag and Bone (May 28, 2008)

Irons,

You mentioned soaking in HCl to remove base metals. Won't Pd go into solution in straight HCl?


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## Irons (May 28, 2008)

Rag and Bone said:


> Irons,
> 
> You mentioned soaking in HCl to remove base metals. Won't Pd go into solution in straight HCl?



Once the base metals have finished dissolving you might get some. I pour it off and save it for the next batch. Any Pd that went into solution will precipitate out once you put it in contact with base metals in the next batch. The Pd might get moved around, but it's not lost. When the HCl is spent, it goes into the stock pot.

The only thing I throw away has been stripped of anything of value or that is toxic.

Everything but the squeal.


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## Rag and Bone (May 28, 2008)

Lino,

Is there a chance the water rinse would remove PGMs? Or are they more tightly bound to the substrate?


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## Lino1406 (May 28, 2008)

Negligent, but if so you
can right collect them. no?


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## Rag and Bone (May 29, 2008)

Sure. Nothing goes to waste.


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## skippy (Jun 3, 2008)

I wonder if it would be possible to very slowly add chlorox to the HCl through a capilary tube or something. Slow enough so the concentration of chlorine in the solution never exceeds the amount soluble at the given temp and pressure Put a tight lid on the reaction vessel that still allows pressure release and then just give it lots of time to react to make up for the low chlorine concentration. 

http://www.resistoflex.com/chlorine_graphs.htm
Looking at the graph there's still some chlorine in solution at say 90 degrees C. I don't know much about reaction kinetics, so I guess my question is would it be better to have the solution at a higher temperature with less concentration of Cl2, or at a lower temperature with higher concentration of Cl2.


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## Anonymous (Oct 8, 2008)

I've been lurking and studying here quite a bit as of late...Have been experimenting with Iron 2-litre Cat Honeycomb Cold process...HCL/Clorox...My question is how do you precip the material out of you solution??? Same as AR method Heat and add chems??? THx Rick


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## lazersteve (Oct 9, 2008)

When using HCl-Cl on cats, I suggest using zinc to precipitate all the dissolved PGMs together first, then redissolving the mixed PGMs with AR and then separate as usual.

The reason for this is the salt (NaCl) that is formed when HCl is reacted with clorox. This salt precipitates out when the solution is evaporated (required to concentrate the solution before precipitation). This is undesireable so use the zinc to pull the PGMs from the solutoin and redissolve with a small amount of AR to separate.

Steve


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## Anonymous (Oct 9, 2008)

As always your reply was direct and very interesting.. Thx so much for your rapid reply..If I might assess that your method employs the Zinc to the post filtered solution from the HCL/Clorox digestion..Heat it up to say 105-add Zinc at prill range and watch the precip. precip stops take off heat and filter the precip away..apply this filter cake precip to your normal AR solution of
HCL/Nitric follow procedure to re-digest into AR then boil off your Nitric and Precip with normal chems for the Pt Etc...???? Once again your insight in most valued cant wait to read further into this ...Thx Rick..


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## lazersteve (Oct 9, 2008)

Zinc Process Overview


Use the search function to find more information on using zinc.

Steve


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