Palladium explosion!

I was reprocessing solution, which contained Palladium. This is a process I have done many times before
I learned the process from this forum and the video’s I had purchased. I am not a chemist so please bare with me. The solution had already gone through gold refining with poor mans Aqua Regia and precipitated with SMB. But it still contained a significant amount of Palladium along with Chromium, Nickel, and some Copper. This process I do outside because of the Chlorine gas. I first put the solution in a large plastic bowl and add powdered chlorine (pool chemical) it boils and gives off a lot of gas. Occasionally I return to stir it, which makes more gas. It was during one if these stirrings that the explosion happened BOOM!!!!. As if I put a firecracker in it. I was splattered with solution on my arm luckily not in my face. Now I have done this many times before and nothing like this has ever happened, What did I do wrong??

I think powdered chlorine was a poor choice. Your going to hurt yourself buddy. Take a step back from this for awhile and do some more research. Your probably lucky you didn't go blind or worse.

Did you have any metals in it, that generate H₂ in HCl (I think all above hydrogen)? If so and if it still was acidic, this might have been a chlorine-hydrogen reaction. a blend of those two gases react violently as soon as it is exposed to UV light.

I think this is a valuable post and should make everyone conscious of always to expect a worst case scenario.

please be careful, safety first, i always wear my goggles at the least, i can do without a finger but i need both my eyes !!!

Sometimes we learn by our dumb mistakes . Thanks for the advice I won't be doing that again anytime soon. I did find this in the safety forum
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Post November 25th, 2008, 8:47 pm
Incompatabilities
Here is a brief list of things that are incompatible with each other:

Aqueous ammonia and free halogens.
This means NH3 and F2, Cl2, Br2, and I2.
In particular, the combination of ammonia and chlorine or ammonia and iodine. Both of those form highly reactive and highly unstable explosives, NCl3 and NI3 which can explode with the slightest agitation.

Many of the things we do with the chemistry of these metals, can form explosive compounds, or explosive gases.
More than one refinery lab, or chemistry lab, has blown up before, and sometimes from processes done many times before.

Trying recovery or refining without educating ourselves can make us dangerous, even with education, we can get complacent to the dangers involved, and get hurt, and sometimes we mix things without understanding all of the reactions going on, or set up a dangerous environment in the working area, this chemistry is dangerous, you never know where when your safety gear will protect you from an accident, sometimes when you least expect it to, accidents do not happen when we expect them to.

I am glad you were not hurt.

I am always very cautious when it comes to ammonia or ammonium compounds and metals, but these are not the only dangers.

I have had a solution in a five gallon pail, as the gases left the solution they would pop like small firecrackers, and in the dark I could see the small flashes of light from these small explosions, for me at the time it was quite interesting to watch.

Was any kind of alcohol (ethanol methanol etc.) added at any time - in particular DMG that was prepared with ethanol (or other alcohol) to test for &/or precipitate Pd

If so you may well have created metal salts known as fulminates - fulminates are highly pressure sensitive explosives - mercury fulminate is used to make the primers for bullets & other detonators - silver fulminate is so sensitive to pressure that it will explode when wet & under its own weight - fulminates of other metals can be formed as well

Fulminates are produced when alcohols are introduced to acids that have had metals dissolved in them

It is for this reason that I have posted warning in the past about preparing DMG with alcohols (ethanol in particular has been suggested to prepare DMG) when preparing DMG use NaOH

Kurt

Kert:

No alcohol was used in this process. But I will keep that in mind. Thanks for the information
Earl

In my search for a safer way to process my Palladium I seem to remember reading someplace that powdered Zinc will precipate PMG.s. I cannot use SMB because it is already in there (that’s how I remove the Au). My solution is a little different in that there is only Palladium (no other PMG’s present). But it does have Chromium. Nickel, copper, and some Iron along with the Palladium.
Where I got into trouble was trying to get the last little bit of Palladium out. There is always some left in solution and I don’t want to just throw it away! Now that I realize what a dangerous process this is I was wondering if at the end I added powdered Zinc wouldn’t that drop out all the remaining metals at one time (it is certainly safer than what I am presently trying to do)? I could than ship them off to a proper refinery and be done with it.
Earl
P.S. again thanks for you’re past advice (my printer has run out of ink printing from this forum)

Why not cement it out with copper instead of zinc? You won't get the other metals mixed with your palladium.

Dave

FrugalRefiner said:

Why not cement it out with copper instead of zinc? You won't get the other metals mixed with your palladium.

Dave

Click to expand...

Dave is correct here - any solutions that contained PMs that used chemicals to drop out the PMs (such as SMB used to drop gold etc.) should go to a stock pot that has copper in it in order to cement out any "trace" PMs that chemical precipitation did not get - that is standard procedure

you would be surprised at what is recovered in the stock pot

Kurt

I did not know that I guess I need to do more reading .Thank you for that information
Earl

I found this information about Cementing ? Now I'm off to Home Depot to see what I can find .Should this be done hot?
Earl
patnor1011 wrote:
No need to add smb, mainly when you already added too much of it. Skip smb go for evaporating and then cement values on copper. Cemented powder should be dried and incinerated. Then you may want to leach base metals out of it with warm HCl maybe with few drops of peroxide. Then cemented powders (what will be left of them) can be redissolved in AR. Forget about smb till you do all of this.

Jason,
Using copper to cement values will leave base metals and salts in solution, if kept acidic during the process will consume the oxidizer, yes you will most likely put more copper into solution as your gold cements out, and if done right, large clean copper buss bar, you will have basically little or no copper mixed with your impure gold, if you use copper in other forms, like thin copper metal or powders you may get more copper mixed with the gold as the copper metal may not get consumed, or the thin copper dissolves unevenly dropping pieces of metal off the sheet, where the thick bar of copper would not.

No need to use heat.

Cementation relies on the dissloved cations coming into contact with the copper. Stir the solution or swirl it around from time to time. Give it plenty of time to work.

Dave

I read what Hoke said about cementation (on page 60). She says you can use Zinc, Copper, or Iron to “cement out” other metals She describes the process as using Zinc and Iron as faster than Copper.
I tried all 3 metals to see the difference.
Zinc: this was the fastest only took about an hour I did a lot of stirring and all the Palladium settled out (stannous tested clear).
Copper: This was the slowest even after 12 hours (including adding HCL + heat) and it did not get much metal out.
Iron: worked almost as fast as Zinc lots of stirring, Heating and HCL added. It also removed all the Palladium .
My conclusion was that Iron is my best bet (cheep, fast)
I know from this stage I can run this powder (when washed and dryad) through pure HCL to remove all other metals accept Palladium and filter to get my pure Palladium.
You are never too old to learn.
Thanks for all the advice
Earl

One more thing I wanted to share .To dry this or any other precipitant I use a food dehydrator (29.95 at Walmart) It works great .

With Iron you will also get copper, tin and lead if any of those were in solution. With zinc you will get iron, copper, tin and lead plus any gold, silver, Pt, Pd. So your precipitation will be contaminated and will have to be refined again to get anything pure. Unless your solution had very little dissolved base metal, you still have some steps ahead of you.

Forgot to add that HCl alone will not dissolve all base metal. What was the material that was dissolved in The beginning?

Be sure to check your hcl wash for pd.
Finely divided pd will slowly dissolve in hcl.
At this point it would be better to use nitric and cement the pd with copper.
When cementing with copper from a solution of hcl it is very slow with out an oxidizer.

jeweler1

The way cementing works is the result of the reactivity metals have to acids so its based on the reactivity series - the more reactive they are to acids the high up on the series & the less reactive the lower on the series - so because the acids like to react more with the metals higher in the series when you put them in a solution that has metals lower in the series the acid will go to work on the metal higher in the series - but because the acid can only hold so much metal as the metal higher in the series goes into solution it has no choice but to drop out the metals below it (or lower)

so copper will cement out the metals below it which are gold, silver, & PGMs (as well as Hg & W) (there can be "some" drag down of metals higher but not much)

iron will cement out a long list of metals including the PMs & copper --- zinc will cement the PMs, copper & iron

So you want a stock pot with copper in it - solutions that had PMs in them & were precipitated with chemical you want to send to the stock pot (with copper) to cement "trace" PMs that didn't come down in the chemical precipitating --- this is strictly a "recovery" process for missed "trace" PMs that didn't come down in chemical precipitating --- PGMs cement very slowly

When the stock pot is done you then send it to the iron cementing stock pot to cement out copper & anything below iron --- you can then treat that solution which is now mostly iron with NaOH or lime to remove the iron & make the solution safe to dump

when cementing with iron (or cementing in general) if you have lead in the solution it will pasivate the iron (or copper) & prevent it from complete cementing --- you can remove the lead by adding sulfuric acid first (it doesn't take much sulfuric)

Here is a link to the reactivity series - http://en.wikipedia.org/wiki/Reactivity_series

Kurt