Given our ecclectic , uh.. Tastes and Membership, is anybody into chemistry? I’d like to ask a few questions about metals, acids and metals, glassware.
2 Likes
5 Likes
Sounds like @amal’s wheelhouse.
2 Likes
i wish i was that knowledgeable but unless it pertains to exactly what i’m working on, my knowledge in this area is extremely narrow.
1 Like
Yeah, that’s kind of nerd normal. Seems like a tendency to get mile deep knowledge, but only on the specific thing you’re focused on.
But you never know, one of us might titrate 
for a living.
4 Likes
I was once upon a time a chemist, I might be able to answer your question.
5 Likes
I have a technical diploma in applied chemical sciences, rarely have any use of it 
Happy to answer questions or perform experiments.
6 Likes
I’m trying to extract Platinum, Palladium, Rhodium from catalytic converters.
To date, I have smelted a converter using Copper as a collector metal, and am attempting to dissolve the copper away using a combination of Sulfuric Acid and Hydrogen Peroxide in water.
The problem I’m currently experiencing is that the exposed PGM seems to (suprise!) act as a very efficient catalyst and break down the Peroxide.
Question 1, Can you recommend an alternative method or oxidizer? The goals are cheap, locally available, does not dissolve palladium.
Question 2, Is there a better collector metal? Something easier to remove. Lead is a no go in acid, Zinc won’t survive smelting temperatures, etc.
I’m going to be needing to filter this out eventually and it’s fine fine fine powder. My limited understanding has lead me to believe I need a Buchner vaccum filtration funnel / flask, with ashless filter paper with very fine porosity.
Question 3, Is the Buchner my best choice for this?
Question 4, Where to buy it? Amazon has 1000ml kits for 60-70 dollars, but I’m working with gallons (yeah, yeah, don’t mix units 
) and would prefer a 5000ml setup, but they seem to be an amazing jump up in price.
1 Like
Rubbing my hands
I like your problem.
-
So for dissolving copper without a limitation on time all you need is sulfuric acid and aeration IME. Forcing air or oxygen through hot sulfuric acid dissolves the copper slowly but safely without using any destructive chemicals (i.e. hydrogen peroxide).
If you’re in need for a faster method I’d recommend ferric sulfate as the oxidizer in the sulfuric acid, ferric ions will cleanly dissolve the copper. It’s pretty easy to come by here and is cheap, you’ll need to confirm if the same is accurate where you live. -
There aren’t really better collector metals, just alternative methods like iron matte processing or a copper electrorefining cell. Iron matte uses iron/sulfur mixture to produce a matte that can be crushed and dissolved in milder acids, copper electrorefining turns the PGMs into an anode slime and reduces the amount of acid consumption; neither is either more efficient or productive.
-
Your Buchner Funnel is definitely the best choice for your powders, it’s the standard for fine chemical particulates for this reason.
-
Scaling is expensive, what I recommend is looking for a wholesaler or surplus supplier for laboratories and source glass components or large-scale polypropylene vacuum filter funnels through them.
Hope this helps.
5 Likes
Nerd. 
Damn, was really hoping for a silver bullet. Air bubbling and electro-winning were my top two alternatives, but so so slow.
A bunch of mostly BS theories have been suggested via Gemini, and it did come up with one option, but I’ve no way to evaluate whether it would work. Care to take a shot?
Basically replace the H2O2 with potassium monopersulfate, also known as non chlorinating pool shock. Good idea, or nasty chemical repurcussions?
2 Likes
Terrible idea if you want Palladium, lol, it’ll dissolve it.
To expand, you’re also going to be dealing with a lot of potassium salt contamination, and that’s one sticky mess I’d not meet ever again.
3 Likes
This is why I don’t blindly trust Gemini.
Thanks!
Also, just for fun, I’m also getting into casting (trying to), and I may soon have enough platinum to cast a Lucky 38 poker chip.
5 Likes
One last question about the economics of acid.
Would I be better off to:
- Muddle through with sulfuric and H202, and then process the resulting fines via Aqua Regia and selective precipitation.
- Skip selectively dissolving the copper, and go Nitric, then add Sulfuric to get Aqua Regia, followed by selective precipitation of the PGMs.
Operating under the assumption that this is an occasional thing. Just trying to figure out if the cost of Nitric is gonna be killer if it’s “wasted” on copper. FYI, my copper prill is 132 grams + 4 grams PGM.
1 Like
I’d muddle through unless you have a relatively open chequebook, nitric acid is extremely cost-prohibitive, using it to dissolve 97% base metal is extremely inefficient IMO.
As a best-for-value route you can go hydrochloric acid with a small amount of cupric chloride or ferric chloride; HCL is cheap, and air is free, it will also leave your PGM untouched. Only downside is the speed.
2 Likes
Are you able to get the cat out with your Sawzall before the owner hears it and shows up with a shotgun?
It’s Arkansas, for a beer the owner will cut it out for you.
3 Likes
Results are in.
I’ve got 52 grams of my original 136 gram prill left. I consumed 1 quart of liquid fire (95-98% sulfuric acid) 5 quarts of 3% hydrogen peroxide, and 1 gallon of 12% hydrogen peroxide.
Take a look at the copper and you’ll see it’s matte black. That’s a fine coating of Platinum Group Metals. Which is the problem. The peroxide can’t get to the copper before being destroyed (catalyzed) by the PGM.
During the process, as my jar got full, I’d let the fines settle, then siphon off the copper sulfate solution (saving for process back to copper), and the last bit I’d stir up and pour off to try and separate as much PGM as possible. That jar is currently settling and will be siphoned, diluted, repeat repeat repeat until I can get rid of the water and just have fine dry PGM powder.
Pretty obvious this isn’t viable, so I think I’ll try electrowinning next. FYI, that’s basically just reverse electroplating the copper onto something else, so that the PGM is left to fall to the bottom of the tank for later.
Anywho, FOR SCIENCE!!!
5 Likes
Ahh good ol Piranha Solution!
1 Like
Are you trying to do this commercially or just to get x amount as a one off? Purity?
We have a bunch of electroplating titanium drums at work. It’s an incredible process. Sulfuric will work with additives, as your electrolyte, we did it from battery scrap, but get prepared for low voltage high amp rectifiers. Up cycling!
1 Like
This works really well, can attest!