Adding gases to leeching liquids

[Yggdrasil]

Hi!

I came over a test done in dissolving the PGMs from auto-catalysts. I found the PDF somewhere here in the forum I believe.
They used a mix like this: H2(g)/HCL/H2SO4/H2O2.
What function will the gaseous hydrogen have in a mix like this?
Wouldn't it push the equilibrium the wrong way?
HCl(aq) + H₂O(l) + H₂(g)--> H₃O+ (aq) + Cl- (aq)+????
What effect has the addition of gases like Cl2, O2 and H2 to leeching liquids?
To what side do we want to push the equilibrium in order to obtain our target (Dissolving PMs)?

 

[Lou]

You don't want to leach aqueously unless you are a rockstar and have some money.

 

[Anonymous]

You don't want to leach aqueously unless you are a rockstar and have some money.

Priceless 8) 8)

Ygg - it's been mentioned plenty of times on here about these and how inefficient (and dangerous) it is to leech this stuff.

 

[Lou]

It requires a way to oxidize the C off the reduce the PdO and Rh2O3, then large investments in IX, instrumentation, filter presses, tankage, etc.

Sepramet is a good example of people doing it right.

 

[Yggdrasil]

Hi!
Thanks for the quick reply, but if you read my question again I think my actual question goes unanswered :wink:
What will adding H₂ accomplish in the described setting?
Adding the Cl₂ and O₂ was on my behalf to see if I could get a wider understanding for what goes on when adding gases to a mix [stt]fro[/stt] for dissolving PMs.

BR PoA

 

[Lou]

Generally speaking, adding oxidizers (O2 or Cl2) with a fuel (H2) accomplishes destruction of equipment and personnel. Put succinctly, BOOM.

As the PGMs are not reducing metals under virtually most circumstances, the presence of H2 matters not to equilibria in these systems, so your equation would have H2 on the other side as it isn't participating. It might only serve to reduce refractory and heck-to-dissolve Rh and Pd oxides and do a horrible job of doing it in aqueous environment: H2 isn't exactly as soluble as Cl2 let alone CO2. It'd have to be made in situ such as by adding Fe, for instance. Putting it in with a cylinder doesn't work well.

As for the only part that makes sense...Cl2 dissolved into HCl (made either from the oxidation of chloride to chlorine by any oxidant capable of doing the job; in practice that's what peroxide, chlorate, etc do). When you add Cl2 into solution from a steel cylinder, most of it doesn't dissolve.

Anyway, most operators use about 5-7M HCl, a sealed reactor and Cl2 under pressure. 60 C-120 C are usually the conditions employed. If you want to be super cheap on reagents, even sulfuric, water, sodium chloride and air/oxygen over pressure can be used.

Personally, I'd save a bunch of money, skip the autoclaves and use HCl/Br2. Much better at overcoming passivation phenomena and of course the bromine is much more easily recovered. Freechemist (RIP) got me hooked on that!

Question answered?

 

[Yggdrasil]

Thanks again Lou.

Yes question answered
But I'm still puzzled as why they put in the H₂ (g)
So I have to delve into my downloaded Pdfs to find out which University made the pdf in mention.
In all fairness if memory serves me right, it was in the preliminary these formulas were outlined.

BR PoA

PS! May I send you a PM regarding Rhodium?

 

[nickvc]

As Jon has pointed out messing with PGM salts is not good, for those who read this thread and are thinking of trying to wet refine cats I suggest looking up platinosis...

 

[Yggdrasil]

Thanks Nick.
Safety precautions are always important when dealing with potential harmful ingredients.
But then again if you are not to endeavor into new territories now and then, you will never learn or discover new ground/(Read knowledge)

All this work is supposed to be done in a smoke hood anyway, except for the incineration/melting/fusion parts that is.
Regarding economics of leaching vs fusion/smelting, the latter commands a complete different investment in equipment and one has to learn to crawl before running.
From where I am now, I can allow myself to spend a few bucks to get less than perfect leaching results in order to learn.

To my surprise the challenge seems to get my hands om some cats to leach.
I'll probably have to buy them at quite higher prices than I envisioned.

 

[Anonymous]

Thanks Nick.
Safety precautions are always important when dealing with potential harmful ingredients.
But then again if you are not to endeavor into new territories now and then, you will never learn or discover new ground/(Read knowledge)

All this work is supposed to be done in a smoke hood anyway, except for the incineration/melting/fusion parts that is.
Regarding economics of leaching vs fusion/smelting, the latter commands a complete different investment in equipment and one has to learn to crawl before running.
From where I am now, I can allow myself to spend a few bucks to get less than perfect leaching results in order to learn.

To my surprise the challenge seems to get my hands om some cats to leach.
I'll probably have to buy them at quite higher prices than I envisioned.

Whilst to some extent I understand your thinking, in another way I am afraid that I don't. Yes everything that we do has a risk attached to it and we manage those risks to the best of our ability, using the knowledge gained from other members and the forum resources.

Let's talk about risk though. There's a risk/reward trade off. Effectively to take a high risk there should be the possibility of a far higher gain. Knowingly taking the risk of long term disability (which incidentally can take years to manifest) when one has to pay high prices for the material and actually gain nothing financially doesn't appeal to me. I'm not trying to impose my way of thinking upon you I am merely explaining my own thinking on this topic and that's what reasoned debate is all about. If you were increasing the risk to triple the gain then yes I'd possibly take a slightly different view however in this case I have to say I don't see the benefit.

To put this into context, I'm certainly not risk averse. I am comfortable working with Cyanide. The unreasoned hysteria that sometimes manifests about the process is mainly the result of lack of knowledge, however in terms of the risk/reward analogy that I used previous it is a perfect example. Effectively not only can you process around ten times the product (if not more) per day, but you can also treat a far wider range of products than using other methods. That is the reward part. The risk part is manageable, with a defined process, proper safety procedures, and a well thought out process with the right equipment. It also involves far less waste liquids than other systems but that's a different story.So there are circumstances where added (or the perception of added) risk are acceptable, however I don't perceive this to be one.

Good luck with whatever you decide though, and thanks for taking the time to read this.

Jon