Organic, carbonacous material in my "ore".

[SamTheChemist]

I am a Ph.D. chemist and yet I am fairly new to the PM recovery game. I have acquired about three kilgrams of what I think is high content (maybe 4 wt% Pt, maybe a small about of Pd as well) recovered catalyst. However, the material has a lot of carbon in it. I am able to make the recovery in small amounts once the material is dissolved, but I am worried that the aqua regia I plan to use will form something hazardous (like a fulminate, or an organic nitrate) with the organic material stuck to it. Is there any way to (inexpensively) burn off the carbon without losing volatile salts? Or I am I overthinking the problem and should I expect graphitic/charcoal/carbonaceous material in general to be inert to nitration by aqua regia? I have a glass filter with which I can filter off any undissolved solids.

 

[dtectr]

incineration @ red heat (approx. 700*)

 

[Lou]

Woah, there. Slow down on the chemospeak. You're not nitrating anything (I hope!).

It's very simple, as said above, incinerate. I do catalysts like these in a quartz tube with a slow stream of oxygen. Same way you do resin. It's far safer to just use air and start slow enough to bake all the organic solvents off of it.

 

[SamTheChemist]

Thank you gentlemen but I think the solvents are already gone. I'm worried about the carbon black or whatever it is. I actually have a quartz tube, oxygen, and a tube furnace which goes up to 1100C, and a fume hood in my lab. Will 700C be enough to blow off all the carbon, in the presence of pure oxygen under those conditions?

 

[samuel-a]

Thank you gentlemen but I think the solvents are already gone. I'm worried about the carbon black or whatever it is. I actually have a quartz tube, oxygen, and a tube furnace which goes up to 1100C, and a fume hood in my lab. Will 700C be enough to blow off all the carbon, in the presence of pure oxygen under those conditions?

Yes.
You have a near pefect setup i'll say...

Iv'e been heating such material in open alumina crucible at 800C with gentel stream of air.
In some cases there are a lot of (refactory) oxides left, probably from the original catalyst product...

edit: clarification

 

[SamTheChemist]

Thank you Gentlemen. I will split the difference and go pure oxygen at 750C. The quartz tube I have is a custom job with tapered joints on it. I have other such tubes, that are not customize. I may sac one to see if the quartz itself will withstand the rigors of having this material in direct contact with it ( have a scarred up one available, without joints. (I do not as yet have an alumina boat or a sleeve, that I can insert in the tube, but it may not be necessary. I will send a picture of the custom setup in my fume hood when I get that far.

One other thing, since we're on the saftey channel here (and moderators--I will repeat these warning in separate topics if you like). I do know that there is a method for reducing the platinum salts used to isolate platinum from other metals. The process involves the using the same reactor, but 300C in a hydrogen environment. It is a fact that hydrogen will, at or above 300C, reduce silica at its surface to form silane (SiH4), which combusts violently with air on contact. I am half-tempted to try it, because I am able to trap silane with little effort in a special solution at a trap at the other end of the furnace, but I suspect that many people here aren't aware of that chemistry (most chemists aren't either, trust me), nor are they quailified to handle it. I am also unaware whether normal borosilicate (pyrex) glass suffers the same disadvantage. It may not, in which case my reduction steps to the native metal may become trivial, and may be a more publicly viable alternative. But I am unwilling to let anyone else try first.

OK, two other things. I also have a procedure for quickly isolating all the palladium from solution containing both palladium and platinum with the use of pure carbon monoxide (CO), something I am actually long qualified to safely handle, especially with the facilities I have here (my own lab). I cannot stress the dangers of anyone here trying something like what I'm proposing independantly in a non-professional, non-laboratory situation. So, ethically I cannot give the particulars of the method here. Carbon monoxide is especially hazardous because of the spectre of forming Nickel tetracarbonyl [Ni(CO)4], a colorless, odorless gas, which is just as acutely, (and even more chronically) dangerous than pure carbon monoxide itself.

 

[Palladium]

Yeah!!! That's way above my pay grade. Welcome to the forum.
You and Lou should get along just fine. He's your man for them kind of questions.

 

[freechemist]

Hi SamTheChemist,

As a now retired chemist having worked for years in PM recovery and refining, safety-issues are of great importance to me. Thus let me comment a few topics in your safety-related posting.
You say: "I do know that there is a method for reducing the platinum salts used to isolate platinum from other metals. The process involves the using the same reactor, but 300C in a hydrogen environment."
As far as I know this reduction starts with already pure (refined) Pt-salt, that means, that other metals than Pt have been eliminated in the foregoing chemical refining steps. The reduction itself uses hydrogen gas, highly diluted with nitrogen to a concentration of only a few percent hydrogen (about 3%). At my active times there was a company, Prior Engineereing, which had an apparatus called "Calcimat" in their sales-program for this kind of reduction.
Further:"It is a fact that hydrogen will, at or above 300C, reduce silica at its surface to form silane (SiH4), which combusts violently with air on contact."
IMHO this reaction occurs, if ever, not to a significant extent and thus poses no impact on safety to be worried about. Think only of the forensically important "Marsh-probe", where gaseous AsH3 is generated, together with a lot of hydrogen, which then is decomposed thermally in a glass tube, to deposit a mirror of elemental As. SiH4 decomposes thermally into the elements, H2 and Si, at temperatures above 420oC, which evidently would lead to false results under conditions of the "Marsh-probe".
Further:"OK, two other things. I also have a procedure for quickly isolating all the palladium from solution containing both palladium and platinum with the use of pure carbon monoxide (CO), something I am actually long qualified to safely handle, especially with the facilities I have here (my own lab). I cannot stress the dangers of anyone here trying something like what I'm proposing independantly in a non-professional, non-laboratory situation. So, ethically I cannot give the particulars of the method here. Carbon monoxide is especially hazardous because of the spectre of forming Nickel tetracarbonyl [Ni(CO)4], a colorless, odorless gas, which is just as acutely, (and even more chronically) dangerous than pure carbon monoxide itself."
Nickel tetracarbonyl never forms under conditions of wet-chemical recovery/refining reactions and thus imposes no additional risk on using carbon monoxide (CO). The same thing CO does, namely reduce dissolved Pt and/or Pd to the metal does formic acid (HCOOH), which is cheaper and more easy to handle, than CO compressed in steel-cylinders. And finally, if your ethical concerns are really genuine, you shoudn't have mentioned the CO-procedure on this place, IMHO.

freechemist

 

[butcher]

Thank you freechemist, we needed the clarification.