Sciencemadness Discussion Board

pgm extraction

BleepingAmazing - 18-8-2013 at 16:56

Hi i have been conducting an experiment with pgm's in catalytic converters. I took the one off my old car (80 cutlass) and it had pellets in that are ceramic coated in platinum, palladium and rhodium.

I removed pellets and ground them down super fine in a mortar and pestle. I took 1 ounce of ground material and placed it in a 500 ml beaker and added 200 ml of sulfuric acid(93%). Mixed thoroughly by swirling beaker. I then added 200 ml of distilled water. mixed thoroughly again.

Solution becomes extremely hot giving off vapors and immediately the solution turned a bluish grey color. I kept mixing with stir rod at this point. i did this for about 30 minutes.

With solution still hot i poured it off into a 2000 ml beaker and added ice. enough ice to reach the 1000 ml line.

I then added another 100 ml of both sulfuric acid and water to the original reaction vessel.. kept swirling and stirring it. All that is left in the reaction vessel now is fine white granules.

The jar i added ice too has cleared up some odd 3 hours later and dropped a bluish colored mud in the bottom.

So tell me if i am wrong here, but i am pretty sure the bluish substance is a mix of palladium and platinum? If so can i just pour off cleared up solution and dry the mud on a hot plate? If so is the palladium/platinum in a ready form for smelting?

To further add i went back and added another 100 ml of water and 100 ml of sulfuric acid again to the white ceramic residue left. Hours later my solution has turned a reddish brown?!?!? Rhodium perhaps?

Any input is welcome... Seems there is a major argument online that pgm's(platinum group metals) are insoluble in sulfuric acid... Well i must say that the ceramic never dissolved and even the pgm coating on a whole(unbroken) ceramic pellet gets dissolved leaving a white pellet.

elementcollector1 - 18-8-2013 at 17:07

I don't think you dissolved any PGM's - it takes the likes of aqua regia (nitric/hydrochloric acid) to dissolve them. Sulfuric acid alone won't cut it.
No clue what the blue-gray stuff was - undissolved sludge? See if it settles out after a while.

BleepingAmazing - 18-8-2013 at 17:18

Well i would agree with that statement but most of my minerals books say pgm's are soluble in hot concentrated sulfuric acid. That is what originally led me to believe this would work. water and concentrated sulfuric acid make an instant exothermic reaction giving off crazy amounts of heat for about an hour or so. I have tried dissolving many types of ceramic and failed with this solution. I have however dissolved a palladium ring in it. Palladium and rhodium are soluble for sure in it, but platinum is a bit more resistant... if i had a loose piece of pure platinum laying around i would give it a go...

BleepingAmazing - 18-8-2013 at 17:20

Oh yeah but hey if your right then those solid white pellets are pgm's!

bfesser - 18-8-2013 at 17:26

My input is that you should report weight in grams (<em><a href="http://en.wikipedia.org/wiki/International_System_of_Units" target="_blank">SI</a></em> <img src="../scipics/_wiki.png" />;) rather than ounces (antiquated, ambiguous, <a href="http://en.wikipedia.org/wiki/Imperial_units" target="_blank">imperial</a> <img src="../scipics/_wiki.png" />;).

[Edited on 19.8.13 by bfesser]

MrHomeScientist - 19-8-2013 at 05:59

Quote: Originally posted by BleepingAmazing  
Well i would agree with that statement but most of my minerals books say pgm's are soluble in hot concentrated sulfuric acid.

Generally when sources say "hot, concentrated' when referencing sulfuric acid, they mean "near boiling, nearly free of water." Conc. sulfuric is generally understood to be somewhere in the neighborhood of 98% acid, so if you added water then you probably didn't meet that criteria. I've never heard of using sulfuric acid in PGM recovery - as EC1 said, it's usually aqua regia.

=====================================

Funny that this would get posted - I actually was about to post a similar topic myself! I might be getting my hands on a catalytic converter, and was going to try my hand at recovery as well. I found a nice "beginner's guide" that I was going to base my procedure on (attached below). What it boils down to is this:

1) Grind catalytic converter material down to a coarse powder.
2) Incinerate material in a furnace to burn off road dirt and organic residues (if it isn't a brand new converter).
3) Treat material with HCl, followed by HNO<sub>3</sub> (separately!). This removes any base metals (this step might be unnecessary).
4) Treat material with aqua regia (3:1 HCl:HNO<sub>3</sub>;) to dissolve platinum and palladium. Rhodium remains insoluble. <b>(how would I separate this from undissolved ceramic?)</b>
5) Precipitate platinum from solution as the bright yellow ammonium hexachloroplatinate, using a saturated solution of NH<sub>4</sub>Cl.
6) Precipitate palladium from solution as the bright red ammonium hexachloropalladate, by adding a saturated solution of KClO<sub>3</sub> (my source recommends sodium chlorate, but I have the potassium salt and I can't imagine that would make a difference). Technially, it is the chlorine produced that causes this compound to form.
7) Calcine both the PGM salts in ceramic dishes to reduce them to their metals - driving off ammonium chloride. Ramp up the heat slowly to avoid vaporizing any metals.


Here is another guide that has the same overall process, but differs a bit on terminology. e.g. it calls the brick red precipitate ammonium hexachloropalladate rather than a chlorate salt like the attachment does. Theirs seems to make more sense, so I went with that name above.

Any comments on this method? Suggestions, things to avoid, etc.? I have no intention of making money off of this, I simply want to explore the process and get some palladium and rhodium for my collection!

Attachment: PGM Recovery from Catalytic Converters.pdf (282kB)
This file has been downloaded 852 times

BleepingAmazing - 19-8-2013 at 07:41

I am still experimenting as i read sulfuric acid should eat the ceramic and some base metals online. But what really caught my interest was old refining techniques using vitriol to refine silver?!?!? I am hoping that the bluish mud is residue left from the ceramic material and the base metals. i was hoping that i would be left with a mix of pgm's and other possible chemical resistant elements that i could separate by density as most vary greatly in density(but after the experiment above i dissolved palladium in the same solution and failed with ceramic{the ceramic made no residue}). If this is the case then it would be so much easier than reverting it to salts and back to metal form. i am guessing a lot here till i further study this... But i have plenty of material left to play with as a fellow backyard chemist has gotten more material and is helping now explore what is exactly happening and if it is a possible means of extraction with little to no loss. I honestly believe the old methods are the best! Everything older is absolutely better! My freezer from the 50's costs less to run than a 4 star energy one >.>....... But as far as the technique you shared. I have no clue if it even works... I tried refining gold and silver with techniques posted on the internet and failed massively on most of them. So there is a lot of disinformation out there on these subjects. But one thing i am sure is the bluish substance is first to go! But then there are also red and brown muds gathering after the buish substance was poured off and process restarted. I will keep ya posted on what i find out.

elementcollector1 - 19-8-2013 at 08:11

I would imagine rhodium can be attacked by something if it's finely divided - chlorine, maybe?
Wiki quote from the RhCl3 page:
Quote:
Anhydrous RhCl3 is prepared by reaction of chlorine with rhodium sponge at 200–300 °C


Old things are better, but they're often less efficient - a real step forward in research would be to use only organic, non-harmful compounds to dissolve/recover PGM's, instead of acids and such.

MrHomeScientist - A lot of jewelry is rhodium plated, and the stuff underneath is usually either base metal or sterling silver (this is plated to offset tarnish). Simply file a piece off, dissolve everything underneath, and there's your rhodium. Just a thought. (Also: Would you have the setup to melt the rhodium out? Likely not, considering its MP...)

blogfast25 - 19-8-2013 at 09:23

Quote: Originally posted by BleepingAmazing  

I removed pellets and ground them down super fine in a mortar and pestle. I took 1 ounce of ground material and placed it in a 500 ml beaker and added 200 ml of sulfuric acid(93%). Mixed thoroughly by swirling beaker. I then added 200 ml of distilled water. mixed thoroughly again.



At the risk of sounding facetious, NEVER add water to concentrated sulphuric acid, always do it the other way around: acid to water. Distilled water in your case is a waste of distillation: tap water would do fine.

50 % H2SO4 (or thereabouts) doesn't put a dent in PGMs. But it will also only very partially dissolve the ceramic matrix, I think.

The PGMs should remain in the insoluble residue, which could be treated one more time with conc. H2SO4. Whatever's left after that should then be treated with Aqua Regia to dissolve the PGMs.

[Edited on 19-8-2013 by blogfast25]

BleepingAmazing - 19-8-2013 at 09:25

Very interesting! I think just even changing the acids into a non toxic form would work just fine and possibly receive a usable byproduct. But any way i do have a oxy-acetylene torch setup i modified into an oven :). I would think that would do the trick but i would prefer to break down my base metals and keep the pgm's in metal forms and separate via solution by density. I now have in my reaction jar after over night a water clear solution and fine grains that are white, brown and silvery white with a little blue gray mud on top. Jar 2 (the pour off with oxidized elements suspended) has turned completely clear and left a blue gray mud. The white grains surely are ceramic in my opinion. I may be wrong. I am currently getting ready to pour off the liquid from jar 2 and experiment with my blue gray mud which i am guessing is either palladium or some base metal. I have no idea what it is... So i figure i will dry it and try to form a solid via heat in a crucible. If it puddles and fuses then i can take a density reading i guess. Also i redid the test above and this was my result. I think in the first round i didn't rinse the rubbing alcohol out the jar and it contaminated the solution giving me the reddish brown liquid (possibly iodine). First try was more of i don't care lets see what happens and just mixed w/e increments to see what the best reaction was. Second try was more technical taking exact measurements on everything... I do believe i have the platinum and rhodium separated and undissolved with the ceramic in the reaction jar. I also must say there is an awful lot of it. I would say about 15% by volume verses the ceramic. Now to find a way to dissolve the ceramic leaving the other pgm's unaffected. I am really hoping my grayish mud is palladium cause then i would only require one solution of around a density of 14-18 to separate the platinum and rhodium in metal form that won't react to them. Then i would save tons in the process and lose absolutely nothing but sulfuric acid and water! Either way just removing all the non pgm's without any loss would be a massive help and far better for my collection!

BleepingAmazing - 19-8-2013 at 09:32

I was also thinking if there is zinc, lead or copper in the base metals. my solution may be creating an electrical current as well. Still have to test that one?!?!?! maybe i can just collect the blue gray material via a conductive wire or something?!?!?! still a lot to explore here...

elementcollector1 - 19-8-2013 at 11:15

Your solution wouldn't be creating any electrical current of note, and certainly not enough to 'collect the material'. You're right that if there are two metals such as copper and zinc in there, it would create a battery... for about a second. Then the copper/zinc would dissolve, and there wouldn't be any ion flow.

BleepingAmazing - 19-8-2013 at 11:56

Well wouldn't that depend on amounts in solution and for how long the reaction lasted or what form the metals are in? I can tell you soon as the water is added it generates near boiling temperatures and gives rise to the blue gray material in solution instantly. it only takes a tiny amount of water to get the reaction going but mixing half and half seems to generate a better exchange and produces far more heat that lasts about 1-2 hours. Though by slowly adding water in increments the reaction would last far longer and produce a longer held electrical charge. What elements it does dissolve, it only does it quickly with the heat, otherwise it is a very lengthy process... Tomorrow i will have results on the blue mud after testing. I also read that stannous chloride is good for checking platinum content. But i am unsure if it would work in sulfuric acid as it does in aqua regia?

blogfast25 - 19-8-2013 at 12:51

Quote: Originally posted by BleepingAmazing  
I can tell you soon as the water is added it generates near boiling temperatures and gives rise to the blue gray material in solution instantly. it only takes a tiny amount of water to get the reaction going but mixing half and half seems to generate a better exchange and produces far more heat that lasts about 1-2 hours. Though by slowly adding water in increments the reaction would last far longer and produce a longer held electrical charge.


The addition of water to the acid (like I said for safety reasons you should really do it the other way around!) causes solvation enthalpy (heat) to be released. It's very significant: prepare a 50 % H2SO4 solution in water staring from RT and the resulting solution will be quit near 100 C.

But produce 'electrical charge'??? Explain?

BleepingAmazing - 19-8-2013 at 13:23

Just like a car battery... In theory even with the heat and the reaction there is the possibility of electrical discharge from the solution depending on what metals are in the solution. I would think the heat would amplify this effect given that the solution was properly loaded with the right metals even added possibly to try for a self sustaining electrolyte. That would bypass a lot of of need for electrical equipment if possible. not to mention the possibilities of instant electroplating or possibly selective electroplating for that matter. Who knows there is so many possible directions general chemistry or alchemy can go....... But as far as mixing the water and sulfuric acid, i find it more feasible to add the water to it. If something was to go wrong then i would be dropping water and not acid as i fled the area to reevaluate the situation. Also i tried it both ways and it does the same thing. But then there is always a risk of splatter too when pouring. so a flask may be more desirable for that. Any which way you look at it there is tons of possibilities and unknown dangers or breakthroughs still in chemistry. In my opinion if we think we know just about everything then we must start over...

blogfast25 - 19-8-2013 at 13:44

Quote: Originally posted by BleepingAmazing  
In theory even with the heat and the reaction there is the possibility of electrical discharge from the solution depending on what metals are in the solution.


‘In theory’? What theory? There is no theory that supports what you so vaguely describe here.
Quote: Originally posted by BleepingAmazing  
I would think the heat would amplify this effect given that the solution was properly loaded with the right metals even added possibly to try for a self sustaining electrolyte.


More gibberish. What are we to understand by a ‘self sustaining electrolyte’? Please explain in known terms.
Quote: Originally posted by BleepingAmazing  
That would bypass a lot of of need for electrical equipment if possible. not to mention the possibilities of instant electroplating or possibly selective electroplating for that matter. Who knows there is so many possible directions general chemistry or alchemy can go


Alchemy? This is a SCIENCE forum. Alchemy is the historical precursor to chemistry, it’s the latter we practice here.
Quote: Originally posted by BleepingAmazing  
....... But as far as mixing the water and sulfuric acid, i find it more feasible to add the water to it. If something was to go wrong then i would be dropping water and not acid as i fled the area to reevaluate the situation.


Well, have it your way and go against decades of good practice: you’re far more likely to have to flee the area the way you do it. See e.g.:

http://antoine.frostburg.edu/chem/senese/101/safety/faq/alwa...
Quote: Originally posted by BleepingAmazing  
In my opinion if we think we know just about everything then we must start over...


Maybe but that doesn’t mean well established science has to be ditched each time someone tries to recover PGMs from a car catalyst and is getting confusing results.


[Edited on 19-8-2013 by blogfast25]

BleepingAmazing - 19-8-2013 at 19:03

I sense some attitude and frustration on your end with my uneducated and ever so improper manner in the usage of terminology and chemicals.

In theory?

"In theory" it could be possible to produce a electrolyte(battery solution) that has it's own energy source. No outside electrical source via anode and cathode. I think your living cells are good enough basis for my theoretical thought, right?

I suppose that is more gibberish though in your minds eye...



Alchemy is not just a fundamental precursor to what you believe is science. Philosophy and exploration of our environments and selves is still the very same as it was in the past. Mind you there are many forms of alchemy... I never stated which and will leave you to assume which to keep some sort of riddle going.


Well if i mix a tiny bit of acid into a solution of water then my acid is no longer nearly as concentrated as before. I will continue to do things the way i have been as i want the greater amounts of heat with greater concentrations and have a reaction vessel that can withstand it. As far as adding the water to the acid, i do use extreme caution as an accident could become a living a nightmare. I guess i could of added in some safety issues but you ever so eloquently covered that for me. Thanks


Well established science? Please by all means define just what you "believe" that to be!!!??? I use that statement on pretty much everything i do. If i could only count the amount of times man has failed at one thing only to learn another.....


Also for your information there is a known industrial process for refining pgm's with sulfuric acid in a kiln. I am also glad you wasn't Edison's teacher as i may not have lights at the moment. In other words thanks for the words of "encouragement and thought" added to my experiment and if my personal research is to um fallible for your thought process and or nature. Then by all means don't read it... It isn't like i forced you too... Blah, any way my money, my experiments and my life. If i seem to be to reckless and a danger to others then by all means let the moderator delete my thread and if that is the case then i must of misread the top left of the page that says "The art and science of "amateur" experimentalism". Back to my pointless research that is just more gibberish i guess.

elementcollector1 - 19-8-2013 at 21:36

I sense some attitude and frustration on your end that we disagree with you.

A chemical battery without electrodes technically is more gibberish, as that's not how electricity works. The electrodes are vital to the application: Remove them and nothing happens.

The problem with adding the water is that the enthalpy of solvation (discussed earlier) will cause the water to boil occasionally, splashing sulfuric acid around. Not fun. Use 98% acid in a (Ceramic?) crucible, and heat strongly for several hours - this might dissolve the PGM's.

But why try so hard when you can just add some nitric acid and have a makeshift aqua regia? Then you'd be able to dissolve them at room temperature - you could even leave the stuff overnight if you wanted to.

We are trying to help, and I actually do want to see you achieve this. I would also prefer that we discuss things calmly, to avoid yet another thread pruning.

froot - 19-8-2013 at 23:16

You probably have insoluble values in both vessels and all you've achieved at this point is pulled the base metals and possibly some ceramic substrate into solution.
If I were you I'd combine both solutions again, let it settle for a day or so and then decant the liquid off to access the precipitate. Once decanted mobilise the precipitate by adding some water and neutralise by adding NaOH solution dropwise. Settle and decant.

Once done follow MrHomeScientist's advice above.


BleepingAmazing - 20-8-2013 at 04:46

Elementcollector1

It isn't gibberish as the exothermic reaction has the possibility of sustaining a pyroelectric reaction. Provided other things are added to the solution.


froot

It is not an experiment if i follow known procedures. I am experimenting.... I have had great success with refining silver and gold with different procedures that are not found on the internet or in books.

I am officially done with this post and will keep my "research" to myself. Make a new thread and post your known procedures and keep telling yourself it is an experiment. Good luck to you all in your "experiments" or should i say lab projects.

*deletes account and says good riddance*

bfesser - 20-8-2013 at 05:11

BleepingAmazing, it is unwise to post your distaste of the scientific method on a science forum and expect a friendly response. [thread closed]