# Pellets vs Honeycombs Recovering the PGM's



## kadriver (Dec 26, 2011)

There are two types of metal bearing catalytic converters that I know of; those with pellets, and those with honeycombs.

I have seen two different processes used for each type.

The pellets were processed using dilute aqua regia in a reaction vessel over heat.

The honeycombs were leeched over a period of about 10 days or so using hydrochloric acid and bleach.

I know HCl/Cl leech works with the honeycombs, but can the HCl/Cl leech be used to get the Platinum Group Metals off of the pellets as well?

Also, can aqua regia be used to recover the metals from the honeycombs? 

It seems that the aqua regia would dissolve the material that the honeycombs are made of.

But it seems reasonable to be able to use the HCl/Cl leech process for the pellets.

Thank you - kadriver


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## samuel-a (Dec 27, 2011)

kadriver said:


> It seems that the aqua regia would dissolve the material that the honeycombs are made of.



I doubt it will, to any considerable extent.

Instead of both HCl/Cl & AR, You can also bubble air through the HCl+pellets/honeycombe for a week or so.
This is cheap and do not require your attention. Just make sure the bubbles are spread evenly through the bucket and is supplyed with sufficient amounts.


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## goldenchild (Dec 27, 2011)

I can confirm that neiter beads nor honeycomb will dissolve in AR. This is the way I was processing this material when I started getting into PMG's. Then I realized it was too much work for my taste. I'm sitting on about 50 pounds of beads and crushed combs if anyone is interested.


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## kadriver (Dec 27, 2011)

goldenchild said:


> I can confirm that neiter beads nor honeycomb will dissolve in AR. This is the way I was processing this material when I started getting into PMG's. Then I realized it was too much work for my taste. I'm sitting on about 50 pounds of beads and crushed combs if anyone is interested.



1. Is the material fresh, or has it been partially processed?

2. What is your asking price for the 50 pounds of material?

3. I live in South Carolina, what would be the approximate cost to ship it to me?

I am interested in aquiring this material. Please email me at [email protected] or PM me your response.



samuel-a said:


> Instead of both HCl/Cl & AR, You can also bubble air through the HCl+pellets/honeycombe for a week or so.
> This is cheap and do not require your attention. Just make sure the bubbles are spread evenly through the bucket and is supplyed with sufficient amounts.



samuel-a: thank you for your response, but I am a little confused - did you mean HCl/Cl+pellets/honeycombe in your quote above?

If yes, then what type of device would be suitable for evenly distributing the air bubbles? Can you post a picture of the air bubble device that you use?

Thanks for the insight that you have both provided.

kadriver


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## lazersteve (Dec 27, 2011)

You can process either type of cat material by either method equally well.

There are other types of cats out there also, the metal foil type is another you may run into. Beyond vehicle catalytic convertors there are numerous varieties of industrial catalytic materials that may or may not contain PGMs. 

Any leach solution that produces active chlorine in solution can be used to process the alumina/ceramic based cat material. My DVD Fundamentals of Platinum and Palladium demonstrates me processing this material via two separate routes. Either route shown on the DVD is equally effective. The differences in which leach you should choose comes down to equipment required, processing speed, reaction temperature, target metals, cat substrate, and waste management. Choose the oxidizer which most effectively attacks the target metal in the material you are processing and is least labor intensive. 

The cylindrical beads will decay* to a fine white powder if treated with strong oxidizing solutions and some heating. You can witness the breakdown of one of these beads on my DVD in the section where I test the leached bead for Pt with hot AR and the bead has begun to dissolve. The process is slow, but they do decay and eventually become soft and powder easily. This can lead to filtering problems when dealing with this type of bead.

Steve


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## kadriver (Dec 27, 2011)

Steve:

when leaching with HCl/Cl, is there a benefit to using dilute 50/50 HCl/H2O over full strength 31.45% hydrochloric acid?

Thank you - kadriver


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## lazersteve (Dec 27, 2011)

Diluting saves zinc on the recovery side as the reaction is less acidic. It also saves acid in the leach process. 

Try both ways and see which one works best for you.

Steve


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## kadriver (Dec 27, 2011)

got it - thanks


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## goldenchild (Dec 27, 2011)

kadriver said:


> 1. Is the material fresh, or has it been partially processed?
> 
> 2. What is your asking price for the 50 pounds of material?
> 
> ...



1. This material has not been processed at all. It still has the carbon on the beads. I actullay sent a pound to Samuel a while back to compare his yeilds to mine and I think he will vouch that the yeilds are pretty good. 

2. I'll have to look at my records to see what I paid for the material. My asking price per pound will be fair in that I just want to make back what I spent on them. From what I remember I got a very good deal on all the material. I believe it was right before the fever hit.

3. Later on today I will do some research on shipping ie. exact material weights, types, box size, *etcetera* (Hi Harold) and also include pictures.


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## samuel-a (Dec 27, 2011)

Kev

I meant HCl (dilute)+air. Air bubble through the solution and the coverter materia.
This can be done in two 5 gallon buckets.

I can upload a sketch later today if you want.


As for the beads offered by goldenchiled, unfotunatly, i have no exact numbers at the moment.
I'll probably have them in few days if you guys want to wait and split the difference.


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## kadriver (Dec 27, 2011)

samuel:

Thank you, I would really appreciate a drawing of your bubbler rig.

I have made an offer to mario for his cat material - if you get some numbers from the material he forwarded to you, then that would be helpful to me.

Also, have you tried the zinc/dilute HCl method to turn the platinum powders to platinum metal as described in item 16 in the guided tour by lazersteve?

I am doing all the research I can before attempting to process any material.

Thank you - Kevin (kadriver)


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## samuel-a (Dec 28, 2011)

Hi Kev.

It is basically, the two buckets method.

I used a teflon tube and preforated it with a hot nail, since the tube is so rigid, i had to tie it down to some plastic cross/X that i found to keep it in place and positioned. The air supply is from a tiny compressor.

The solution is 50/50 HCl/water, but that's up to you, say, if you plan on leaching several batches with same solution, better use concentrated HCl.
Air contains about 21% oxygen.

4HCl + O2 = H20 + 4Cl


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## kadriver (Dec 28, 2011)

samuel:

Could I use pvc?

Where did you get the teflon tube?

Great drawing - I am going to use your design to do my first leach with.

I was wondering where you were getting your chlorine - now I see you get it by bubbling the air (21% - O2) through the hydrochloric acid.

Do you think I could still add bleach to hasten the process?

Do you use any sort of external heat such as a bucket band heater or maybe an aquarium heater?

Thank you! 

Kevin (kadriver)


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## samuel-a (Dec 28, 2011)

I really don't know how the pvc will perform.
I think i know what you are thinking, to stack them in a pvc pipe... that's clever.

Heat will drive off Cl2... Unless it's frozen out side, i see no reason to add any.

Leach time will probably be best around 5 days and yes adding chlorox will increase dissolution rate.
Though, the point being in this setup is not to attand to it too much as it self supporting, both by Cl creation and agitation.

My dad sells these tubes so i got it fir free from him. Teflon tubes are commercially availble, though not cheap.


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## skippy (Dec 28, 2011)

PVC will be fine, especially at a low temperature. PVC is good for wet chlorine up to 60C or so IIRC, at which point I think it loses mechanical properties. CPVC, which is more rigid softens at a higher temperature, but is way more expensive and not as available. I don't think PVC is good for AR type leaches, but I may be wrong. I think if your solution is cold you're likely going to miss out on a lot of rhodium that would go into solution at a higher temperature. On the other hand with your method Sam, if you warm it too much you'll start losing a lot of HCL out of your solution

If you use conc. HCl you'll end up blowing a lot of it out your column due to the high vapor pressure of HCL when concentrated. Half-half concentrated HCl to water is probably good. At that concentration the vapor pressure above HCl is very largely due to water so you can blow a lot of air through the solution and not lose HCL (not very much anyways) and just top up with water. Cool idea Sam.


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## lazersteve (Dec 28, 2011)

Sam, 

Although your equation (4 HCl +O2 = H2O + 4Cl) appears right at first glance, in practice it does not occur at standard temperatures and pressure. The reason is due to the electro-potential of O2 ( 1.23V) with respect to that of chlorine (Cl2 = 1.36V). The O2 is the weaker oxidizer and therefore cannot promote the oxidation of HCl to chlorine even in highly acidic environment of HCl.

Think of the oxidizers in much the same way as the activity series of metals. It takes a higher reactivity metal to reduce a metal from solution. The oxidizing agents work in a similar heirarchy of reactivities.

Perhaps one of our formally educated chemist could expand on this further.

Steve


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## lazersteve (Dec 28, 2011)

I'll post a list of oxidizers and there reactivities when I get home.

Steve


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## samuel-a (Dec 28, 2011)

lazersteve said:


> Sam,
> 
> Although your equation appears right at first glance, in practice it does not occur at standard temperatures and pressure. The reason is due to the electro-potential of O2 ( 1.23V) with respect to that of chlorine (Cl2 = 1.36V). The O2 is the weaker oxidizer and therefore cannot promote the oxidation of HCl to chlorine even in highly acidic environment of HCl.
> 
> ...



Yes Steve. I can see your point. 
I'm truly eberessed for not thinking before writing.

For those who read and un sure, For example:
F2 or clortates/hypoclorites will oxidize Cl- ions
F2 + 2HCl = 2HF + Cl2

But O2, Br2, I2 will not.


Even though, i'm in agreement with you, i think there's more to it then just the reaction of HCl and O2 since in aq. solution, we are dealing with ions and not pure chemicals. As you said, maybe a chemist can help out here.

So, i'm assuming in that case, that the free O2 scrubbed through the solution is the one who oxidize the Pt and Pd to the respective oxides that in turn are replaced by Cl- and then the chloro-acids.

Tell me what you think Steve. After all, this leach work, and works well.

p.s. - Wiki has a complete table of these:
Standard electrode potential


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## lazersteve (Dec 28, 2011)

Sam,

I would have to assume since you are treating catalytic convertors with this reaction that the catalytic activity of the Pt and Pd are assisting in the reaction. 

It's even possible that straight HCl will give the results you are seeing. I say this because O2 is not all that soluble in water ( about 6.04 milliliters (mL) of oxygen per liter of water at STP ) and even the Pd, which is more reactive than Pt towards O2, must typically be heated to combine with O2.

I'd venture to say the reaction you are seeing is independent of O2 and more dependent upon HCl catalytically/chemically reacting with Pd and Pt and/or their oxides inside of the used homeycomb. Lets not forget that most used honeycombs off of cars already have NOx as a contamination which we all know forms HNO3 with water and therby some unknown dilution of AR with HCl. You can likely see the same results you are getting by bubbling any inert gas such as argon from a lab bottle through the HCl in the presence of honeycomb or pellets pulled from an automobile.

Perhaps the water you are using is the culprit, I know my water out of the tap reeks of chlorine lately.

Still looking for book with the table.

Steve


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## kadriver (Jan 2, 2012)

lazersteve said:


> There are other types of cats out there also, the metal foil type is another you may run into.



I have already encountered two metal foil cats right off the bat! Evidently, the platinum is on a stainless steel substrate (rather than ceramic).

I don't have any experience processing even one ceramic cat, let alone a more difficult metal foil type cat.

If anyone has any experience with these metal foil type cats, then I would be very interested in hearing about it.

From what I can gather, there are not many here on the forum who have experience recovering PGMs from these metal foil type cats.

Thanks - kadriver


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