# acid combination in PGM leaching



## kjavanb123 (Jun 7, 2011)

All,

After reading some files on this subject, the following acid combination would dissolve more than 95% of Pt, Pd and Rh in one shot.

HCl + HNO3 + HClO4 + H2SO4 + HF ( 15ml , 5ml, 10ml, 5ml, 2ml ) accordingly. I can assume HF is used to remove the ceramic particles in the grind catalytic convertor, can HClO4 which is very expensive almost $80 per liter be replaced with H2O2? another word does any chemists here know if this following acid combination would dissolve most of the Pt, Pd, and Rh from the grind catalytic convertor;

10 parts HCl + 1 part H2O2 + 1 part H2SO4?

I have built an agitator, and will start my latest method of leaching a grinded catalytic convertor at 700rpm, 90c and for 2hrs just curios if that acid combination would dissolve all 3 PGMs at once.

Thanks
Kev


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## Joeforbes (Jun 7, 2011)

I've experimented with H2SO4 + HCL + HNO3 with ground up cat material, and it worked very well in removing most of the PGM material. I've also done experiments with HCL + Cl + dilute H2O2 and it worked well in removing the Pt and Pd, but a boil in H2SO4 showed me that it didn't do a very good job in removing the Rh. 

Hydrofluoric acid. It would dissolve the ceramic or alumina in the material, but not the metal. It seems like you would only be adding an unnecessary contamination to your solution by using it. If the material is ground, you wouldn't need to dissolve the unwanted material. Also, hydrofluoric acid is one of the most dangerous things we could encounter. Unless you have a very good containment system, I would not recommend using it. It will dissolve the glass in your beakers. 

"Perchloric acid is also dangerously corrosive and readily forms explosive mixtures." - http://en.wikipedia.org/wiki/Perchloric_acid

"On February 20, 1947, in Los Angeles California, 17 people were killed and 150 injured when a bath, consisting of over 1000 litres of 75% perchloric acid and 25% acetic anhydride by volume, exploded. The plant, 25 other buildings and 40 automobiles were obliterated and 250 nearby homes were damaged. " From the same wiki article. 

Perchloric acid is used as a powerful oxidizer.

Honestly, I really would not recommend trying the HCl + HNO3 + HClO4 + H2SO4 + HF Method. It is a disaster waiting to happen if you ask me...


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## goldsilverpro (Jun 7, 2011)

That is a very nasty mix and, since you would have to use it in large quantities, I would definitely shelve that idea and find something less dangerous. Perchloric acid and hydrofluoric acid are not something I would ever want in my refinery, not even just sitting on the shelf. I have used small quantities of both for lab use but that's another deal.


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## Lou (Jun 7, 2011)

Perchloric isn't too bad if it's not over 70%. It's the high test stuff that is obscenely dangerous. Anyway, the combination that you mentioned is what's used for etching valve metals like Ti, W, Hf, Nb, etc.


Gross overkill for converters.

Lou


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## kjavanb123 (Jun 8, 2011)

All,

I finally put my PGM leaching system to work here are the pictures.

the grinded catalytic convertor.



after Hcl addition at room temprature.



after H2O2 addition while heating it.



my leaching system to work 



After 2hrs and 11mins of agitation at tempratures over 80c with 2 liter hcl and 200ml of h2o2 this is final shot



Filtering this solution takes a long time, so i am gonna try to hook it up to a vaccume filter, also handmade, so it i can speed it up. more pics coming soon.


Regards,
Kev


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## Joeforbes (Jun 8, 2011)

Congrats! Glad to see it worked for you. :mrgreen: 

What concentration of H2O2 did you use?

Even with a vacuum filter, the ground up cat material doesn't filter very well.

I would recommend letting it settle over night, and siphoning the solution off the top, then vacuum filtering it. You could also use a wick filter. I'm no expert on them, but I've seen a lot of things about them on the forum and I'm sure a quick search would find it for you.


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## goldsilverpro (Jun 8, 2011)

How many of those large beakers have you broken so far?


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## Palladium (Jun 8, 2011)

I was wondering how he was heating that. Is that heated with direct flame?


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## goldsilverpro (Jun 8, 2011)

Palladium said:


> I was wondering how he was heating that. Is that heated with direct flame?



Sure looks like it to me. If so, it looks like a broken beaker just waiting to happen.


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## samuel-a (Jun 8, 2011)

I see two main flaws in your setup:
As mentioned, You are using direct heat.
2nd, your engine will degrade in time by the fumes, eventually come to a halt.

If it was me, i'de use a large volume vacuum erlenmeyer flask and seal the rotor shaft so that no fumes will come out of the top. you'll need smaller blades, but at 400 rpm, i don't think it will make much difference.
Then connect the vaccume nuzzle to a reflux.

The entire thing should sit on a sand bath or at least have asbestos sheet underneath to evenly spread the heat.


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## skippy (Jun 8, 2011)

Kev,
Funny, to me it looks like your third picture has the most pgms in solution, with its nice orange color, and the last pic of the heated stirred 2hrs solution look less concentrated to me, but it could be just turbidity?
Anyhow I'd be interested in a picture of your settled solution, if you will.


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## kjavanb123 (Jun 9, 2011)

Thank u all for ur comments.

1. I have broken 2 beakers so far not due to heat shock, but they were dropped . But i just purchased an asbest filter to put in between heat and beaker.

2. Containing the fumes that come out is something i am worried about, I am gonna put the motor in a PVC back so it will be ok from the fumes.

3. The last picture is because I added 500ml HCL after 1hrs and 30mins into the agitation, but the filtered solution is more like the 3rd pic color. 

Also the H2O2 used here is 30% I guess I forgot what the label said 

Siphoning is the best method. I bought this used vaccume motor I am modifying it so it gets connected to funnel. I willl post more pics tommorow.

Thanks
Kev


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## kjavanb123 (Jun 12, 2011)

skippy said:


> Kev,
> Funny, to me it looks like your third picture has the most pgms in solution, with its nice orange color, and the last pic of the heated stirred 2hrs solution look less concentrated to me, but it could be just turbidity?
> Anyhow I'd be interested in a picture of your settled solution, if you will.



Here is a photo of some of the filtered solution. Color looks promising.

If only this software allows me to upload the pictures, i don't know how it works, I just can't figure it out, this is annoying. Some days it will let u upload, others it just keep asking the "Are you interested in refining" question and reload the page with no link to the photo. I just checked the IE error log, it mentions line 761 char 2 as syntax error. I hope this helps the web admin.

Regards,
Kev


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## Palladium (Jun 12, 2011)

I noticed that happening to me a few months ago. This may sound crazy but it fixed my problem. When you enter the answer to the question do you hit enter or point the mouse over the button and click submit? It is a Security question to stop spammer bots and i believe when you press enter on the keyboard it might show up to the security system as a response that was automatically generated by a bot. By moving the pointer and physically clicking the button you have passed the security check. Multilayer security blanket i guess. I don't know if that's your problem or not but i haven't had a problem since then. Come to think of it i only get a security question once in a blue moon now anyway.


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## samuel-a (Jun 12, 2011)

Hi Kev

If you still have upload problems, you can send your pic's to me, i'll host them for you.
[email protected]


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## samuel-a (Jun 13, 2011)

kjavanb123's picture






AP Filtered solution

(I only received one picture)


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## Barren Realms 007 (Jun 14, 2011)

Is that a plastic bag? That looks to be dangerous.


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## skippy (Jun 14, 2011)

Looks like a plastic PET bottle to me. They seem to work just fine for short to intermediate storage of most acid solutions, in my experience. Not so good for concentrated sulfuric acid though (ugh... also in my experience )


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## kjavanb123 (Jun 14, 2011)

Samuel,

Thanks for your posting my pic. It's a plastic bottle. It just used to temprarly keep the filtered solution.Also vaccume filtering the grinded catalytic converter is litterly impossible, i have hooked on a vaccume motor to bucket which a filter has been inserted on top of it, and nothing, not a single drop eventhough i got a huge suction on the top hole. So i guess decanting it and let it sit and decan would be the best option for filtering the solution from grinded catalytic converter.

Kev


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## Joeforbes (Jun 14, 2011)

kjavanb123 said:


> Samuel,
> 
> Thanks for your posting my pic. It's a plastic bottle. It just used to temprarly keep the filtered solution.Also vaccume filtering the grinded catalytic converter is litterly impossible, i have hooked on a vaccume motor to bucket which a filter has been inserted on top of it, and nothing, not a single drop eventhough i got a huge suction on the top hole. So i guess decanting it and let it sit and decan would be the best option for filtering the solution from grinded catalytic converter.
> 
> Kev



Wick filters work amazingly well for this purpose. They take a while to work, but all you have to do is set it up and forget about it.


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## kjavanb123 (Jun 14, 2011)

Is this the "wick filter" you are talking about?


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## jimdoc (Jun 14, 2011)

It is covered in this thread;
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=56&t=3393&p=97741&hilit=wick+filter#p97741

Jim


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## Joeforbes (Jun 14, 2011)

kjavanb123 said:


> Is this the "wick filter" you are talking about?



That would work well I'm sure, but I was thinking something more like this.


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## Iridium chaser (Mar 27, 2019)

Well,don't know if anybody's still here sometimes but if yes-than I'm not writing it in vain  
So I personally just took a simpler approach and just did all the needed processes with a 48-51% HF without diluting it and also without grinding the material!So what I got was initially a vigorous reaction and after that quite a long and dull dissolving of the honeycomb until the only thing that was left undissolved was a pile of PGMs sponge in a large plastic canister full of somehow green solution(why it's always green? :mrgreen: :? )..
Anyway being tired of waiting for all that stuff to dissolve I decided to clock up the HF and so first idea was to use HNO3,so I again poured HF,waited until the reaction calmed down a bit and added 68% HNO3..It was a disastrous miscalculation:first of all it was going nuts each time I added HNO3 but the main issue was that platinum metal not only escaped but created quite a mess all over the place because actually this gas,platinum hexafluoride is a remarkably strong oxidizer and fluorinating agent-it is actually even able to oxidize oxygen AT ROOM TEMPERATURE AND PRESSURE!Which it also by the way did..So I guess if you add all the rest of the acids in your list-you will most likely end up with a demolition of the compound where you will do this stuff,and by the way why you are going to get the reaction that fast?Just HF×H2O2 is actually enough!And if you really want a mess,do the following:find a crystalline solid anhydrous peroxomonosulfuric acid and combine it with HF-I mean dissolve anhydrous pure H2SO5 in anhydrous pure HF(remember:if temperature rises above +19.5°C-you are completely stuffed,even if you do it in a very good lab)-and apply THAT to the converter material:trust me-it will do wonders with it..


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## Yggdrasil (Mar 30, 2019)

I'm a bit on uncertain ground now, 
but will adding a strong oxidizer to HF create the conditions for hexafluorides?
In such a case can Pt and Rh be dissolved by the HF oxidizer mix?

The beauty of dissolving the ceramic or metallic substrate of cats, is that what you have left, 
is a concentrate of PGMs. 
It may or may not be economically viable, unsafe and so on , but it seems nice to treat a small batch of PGMs in stead of a whole bunch of honeycomb 

If the PGMs are converted to hexafluorides, won't it create a whole new set of challenges?


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## snoman701 (Mar 30, 2019)

Iridium chaser said:


> Well,don't know if anybody's still here sometimes but if yes-than I'm not writing it in vain
> So I personally just took a simpler approach and just did all the needed processes with a 48-51% HF without diluting it and also without grinding the material!So what I got was initially a vigorous reaction and after that quite a long and dull dissolving of the honeycomb until the only thing that was left undissolved was a pile of PGMs sponge in a large plastic canister full of somehow green solution(why it's always green? :mrgreen: :? )..
> Anyway being tired of waiting for all that stuff to dissolve I decided to clock up the HF and so first idea was to use HNO3,so I again poured HF,waited until the reaction calmed down a bit and added 68% HNO3..It was a disastrous miscalculation:first of all it was going nuts each time I added HNO3 but the main issue was that platinum metal not only escaped but created quite a mess all over the place because actually this gas,platinum hexafluoride is a remarkably strong oxidizer and fluorinating agent-it is actually even able to oxidize oxygen AT ROOM TEMPERATURE AND PRESSURE!Which it also by the way did..So I guess if you add all the rest of the acids in your list-you will most likely end up with a demolition of the compound where you will do this stuff,and by the way why you are going to get the reaction that fast?Just HF×H2O2 is actually enough!And if you really want a mess,do the following:find a crystalline solid anhydrous peroxomonosulfuric acid and combine it with HF-I mean dissolve anhydrous pure H2SO5 in anhydrous pure HF(remember:if temperature rises above +19.5°C-you are completely stuffed,even if you do it in a very good lab)-and apply THAT to the converter material:trust me-it will do wonders with it..



You responded to an 8 year old thread to add that? 

I'd seriously rather wet ash chips in an open vessel over a camp fire wearing flip flops and a tank top than process cat material by dissolving the honeycomb in HF.


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## Lou (Mar 31, 2019)

Moreover, depending on the cat:

1.) HF doesn’t dissolve them (it won’t dissolve alumina, cordierite yes).

Not depending on anything:
2.) HF is not an oxidizer under any circumstance.
3.) Nitric can’t oxidize fluoride to fluorine
4.) The least exotic way to make PtF6 is with F2 gas and fine Pt powder, not even any peroxysulfuric acid going to do it.


Holy nonsense thread resurrection.


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## Lino1406 (Apr 1, 2019)

Ressurection... that's good Lou. You couldn't say it better.


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## Yggdrasil (Apr 2, 2019)

I have a few comments here:

1. It was an unusual resurrection of a thread, but it is not uncommon to discover/rediscover threads to which, one has comments, it has happened a few times the last couple of weeks alone, even stranger than this one.

2. Since there has been no to few comments/discussions to an acid/chemical that is, after all, widely and commonly used in various industries, it is not unexpected that its use, pop up from time to time. 
In my eyes it would be more fruitful to openly discuss its use and dangers, then silently overlook it and hope it dies away.

Regarding Lou's answer to Iridium Chaser.

Maybe we should have a thread that discusses how to dissolve/treat "support" structures like alumina, cordierite and other metallic and ceramic bases?
The metallic ones has been widely discussed in many threads, but I guess there will always be more 

I can not see where HF was called an oxidizer, at least not directly, so can you please point me in the right direction?

Will HF not create PtF6 in any circumstances, even when subjected to strong oxidizers?

The methods and chemistries surrounding PGMs are shrouded with warnings, secrets and patents I guess.
I'm not trying to understate the dangers but invite to guidance and discussions rather than slaps on the hand.
Maybe we should discuss more openly the methods that are not locked down by patents and such.

We did after all, do a similar thing a couple of years back, when we opened up for more discussions regarding the use of cyanides and its derivates.


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## snoman701 (Apr 2, 2019)

Yggdrasil said:


> The methods and chemistries surrounding PGMs are shrouded with warnings, secrets and patents I guess.
> I'm not trying to understate the dangers but invite to guidance and discussions rather than slaps on the hand.
> Maybe we should discuss more openly the methods that are not locked down by patents and such.
> 
> We did after all, do a similar thing a couple of years back, when we opened up for more discussions regarding the use of cyanides and its derivates.



I think that the difference between gold and silver refining, vs the pgm's, is in the amount of understanding of the risks one is undertaking.

Gold and silver, in almost any solution (even cyanides), are remarkably safe to human life (in comparison), should you have a spill, if you were following the rules for that chemical. 

People are less willing to help you go down the rabbit hole in reference to the pgm's, because the risks you face very well could put you on a trail that is a shortcut to the morgue...even with you practicing standard lab hygiene. They have very special rules. 

Kurtak was pretty forthcoming that he did a substantial amount of work to try to process cats via hydro-metallurgical methods. He's no dummy. He was doing his pilot work in a professional setting. I have known others who have tried to do it as well...even got to help one of them clean up all their waste after they got sick (unrelated)...and he was definitely no dummy. Both said that by the time you take in to account the waste, it's not feasible. 

Lou has said that using modern technology, it is possible, but it's no small investment in analytics, equipment or talented manpower.

So as long as you are putting Platinum into solution with a halogen, it's a major health risk. 

The methods and chemistry surrounding pgm's aren't all that shrouded. The patents are available online. 
Most books or journal articles are available at any university library. Gilchrist is available. There have been plenty of discussions as to how to process cats. I've managed to put together a theoretical working knowledge of how to get PGM's off substrates and concentrated, simply through readings posted to this group and a very small amount of related correspondence. BUT...I've also put in a heck of a lot of reading to get to that point. And here's the key...I still am not in a place where I have the health and safety infrastructure to do it. Oh, I can be set up to do it literally in two weeks...but I'll be poisoning myself, my family, and god forbid if something were to happen to me, whoever should have to clean up my lab. 

What no one has done, is condense how to process cats profitably in to a thread. And there are two major reasons. One is health, and it's HUGE. 

So I guess that's my opinion as to why it's not discussed as freely. By the time you do your homework, you either scare yourself off, or you recognize how dangerous it is, and you are very concerned about who you share with....but I assure you, if you've done your homework, can show that you have done your homework...and have actually put it together... the people who do it LOVE to share their experiences and learn from you and have real conversations about it. It's just not broken down to condensed steps and posted on a public forum.


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## Yggdrasil (Apr 2, 2019)

Fair enough Snoman, I still feel that we may all benefit to be more open.
Both towards health issues and methods, some will go down the rabbit hole anyway. 
So it may well serve us all better if they have the possibility to gather as much safety and process information as possible on the way down the hole ;-)
We still need to stress the dangers! 
Do anyone have good links and such to the safety issues bye the way?


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## anachronism (Apr 3, 2019)

Another thing Ygg.

When the health risks are pointed out to many people they just shrug their shoulders and assume that it won't happen to them. They assume it's hype, or some conspiracy to prevent them from achieving mythical riches that are secretly found by "the elite." 

It's ironic that the guys who shout the loudest about the risks from pgms are the guys who are both experienced and comfortable working with cyanides. Given most see cyanides as truly lethal, what does that tell you? 

Jon


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## Platz (May 4, 2019)

I'm still a bit baffled why anyone would try leaching cats, the recovery of the Pgm's will never be great (it's highly likely some of the Rh will be rhodium oxide and wont leach unless you add bromide :wink: ) It also creates 2 waste streams which both need to be disposed of and I have never been able to find a way to successfully filter the ground up core quickly, it takes days.


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