Separation and Purification Au,Pt,Pd,Ag,Rh,Os,Ir,Ru

[HAuCl4]

Those two threads are awesome and full of useful, hard to find, information.

Would you guys mind if I compile several of those threads, and other book, articles, etc. content into one coherent, step by step document to refine silver, gold, platinum and palladium in a straightforward and expedite (one day refining) manner? . Let's leave the "other" metals out as black residues for now.

It may take me a while to post a document ready to be commented/edited/etc by other members, but I feel it would be a worthwhile contribution to "get it all in one place". My only contribution would be to assemble the processes that have been shared by others, and even that may be re-assembled better if a reasonable "better way to do things" is pointed out.

I feel the need to ask permission, since some of the work and experienced steps shared by Lou, 4metals, Lazersteve, GSP and others, could be considered "proprietary". It has been made public in one way or another...but still...

Game?. :?:

 

[Oz]

I would be hesitant as there are some advantages to new people having to put this information together piece by piece themselves while learning on the forum. It slows them up just enough to learn safety as well as what “not” to do before they find out the hard way. Unless you are writing a book it is also hard to cover all the variables that occur based on the feedstock, each requiring a different approach.

Are you proposing writing a book based on the forum? I am unsure how involved you intended this to be, but appreciate your intent. Ultimately every word written here is the property of Noxx, the owner of the forum.

You asked so I know this is not your intent, but in the past we have had people lift/steal processes and procedures word for word and sell them as their own work, one guy was actually selling a rather complete copy of the forum on fleabay. Putting everything into a book format makes theft a bit too easy for someone using cut, copy, and paste and selling it as their own work on fleabay or elsewhere.

Just a couple thoughts.

 

[HAuCl4]

It would be a 4-5 page document of step-by-step procedures, posted publically for the original contributors to dissect/correct, etc.

Only if the original posters give their permission, and OK.

The thought of writing a book crossed my mind, but I have decided to pass because frankly I'm not qualified, and there are others better at this than me, with tons more practical experience, and it's other's people content. What I would be contributing of my own is really a minute portion, especially since there are "better ways" that I learned right here.

I'm compiling a document for myself anyway, and again, will not post unless everyone involved is OK. It'll take a while.

 

[Oz]

At 4-5 pages I would imagine you plan on outlining the procedures for these metals from a scrap jewelry feedstock perspective. I can see some value in that.

There are indeed several members more than qualified to write a book based on their own experience. In fact our own Goldsilverpro has http://goldrefiningforum.com/phpBB3/viewtopic.php?f=84&t=5810&hilit=book

 

[Lou]

I expressly grant my permission for anyone to use what I've said here for commercial gains so long as they agree to a.) indemnify and hold me harmless for any (mis)use of any procedure, methodology, technique, or idea I've outlined or espoused, b.) credit this forum and myself. What I state by PM is a different story--I'd rather have people NOT post that, forward it, or disclose it without my express written permission.


Time willing, I'll get all the photographs together for my book on techniques of purifying and assaying the platinum group--it focuses mainly on higher end scrap and relatively pure commercial feedstock, but I also will cover S/X on each of the PGMs. So far it is review-style and HEAVILY referenced (several hundred articles, technical pubs, patents). I really need to pare it down...who would want to read an 800 page treatise on the latest and greatest in processing PGMs? I'd really like to add an escrap and karat gold section, but karat gold books are a dime a dozen. Also, it is quite biased to my personal whims, which should be removed or at least moderated.

 

[HAuCl4]

On a better light: I think I will just compile the document for myself, and if anyone is interested they can look on the posts and threads of their interest and do the same. I don't want to ruffle any feathers.

 

[4metals]

I tend to agree with Oz on this issue, while I have no issue with someone compiling the procedures discussed here, the methods involved in these particular threads involve a higher degree of understanding of chemistry. Those members who wish to follow the threads and develop useful methods for their own circumstances usually have enough knowledge to follow the threads and ask questions when necessary.

By summarizing these threads you make it easier for the more casual refiners to just jump in and possibly hurt themselves. I do not think that would be wise.

Some of the discussions here have been put together, I believe by Palladium, (or is it Gold, or Platinum or all of the above?) but those discussions were not of this threads nature.

Harold has put together an excellent collection of methodology that he used in processing at his refinery. His descriptions were written to be easily understood by those with less chemical background and have helped many on this forum.

Ultimately what you do is up to you, but if you read some of the posts that are made here you can understand the benefit of having a member do his or her homework, or due diligence, before beginning to process the more challenging metals.

 

[nickvc]

HAuCl4 I don't think your ruffling any one who has been posting on this thread most of the members commenting understand what is been discussed but their concerns over new members who just leap into processes they don't understand I feel is well justified. Your knowledge of refining is well documented as are all the others commenting but read the threads from new members and I think you will see why there are reservations. I refined commercially for many years but my original comment on this post still stands, my actions concerning PGMs is going to be the same as ever , melt assay and trade to some one who knows their way round them and for the vast majority of the members that's the best and safest way.

 

[HAuCl4]

It's settled: It's better to not do what I proposed. Better men for the job to write a book or procedures that will hardly be used by anyone anyway. No harm done or intended either way.

Back to PGM: In page 205 Hoke quotes Wichers:

"A second precipitation of the dioxides suffices to effect complete removal of platinum". (After referring to the dioxides after the bromate hidrolysis in 2 lines!).

How do they put that stuff in solution again to repeat the bromate drop?.

How to assess the purity of the Platinum after going through all this?.

 

[HAuCl4]

One last question, before I go away from the computer for a while:

Let's say from a mainly gold solution with excess sodium chlorate, I recover both the palladium salts and the platinum salts together with ammonium chloride, before processing the gold.

I save the mixed salts till there is a large enough amount that merits processing.

What is the best plan forward if I want to produce very pure metals Pt and Pd?.

 

[HAuCl4]

After more reading...

1-Would a thorough wash with ammonia dissolve most of the palladium salts and silver chloride and leave the now relatively clean platinum salts as solids ready for the "bromate hydrolysis" process with the goal of pure platinum or would it be better to reduce to metal and re-dissolve, etc. before attempting the "bromate hydrolysis"?.

2-Is there a direct way to directly precipitate Pt with some other precipitant, after the "bromate hydrolysis" that avoids dropping the Pt with ammonium chloride before reduction to pure metal?.

3-What to do with the palladium+silver+other solution from 1 to get to pure palladium?. Reduction to metal, re-dissolve in A.R. and DMG to get very pure palladium or is there a way to avoid the cumbersome DMG and still get very pure palladium?.

Thanks for answers in advance.

 

[HAuCl4]

2-Is there a direct way to directly precipitate Pt with some other precipitant, after the "bromate hydrolysis" that avoids dropping the Pt with ammonium chloride before reduction to pure metal?.

Would it be a complete mistake to drop the Pt with copper after the bromate hydrolysis or the contamination to the final product would be too great?.

 

[HAuCl4]

Is there some process similar to the Platinum Bromate Hydrolysis, but to purify Palladium from other PGMs?.

Talking to myself like the lunatics?. :lol:

 

[4metals]

This procedure will clean up Palladium which have been collected as salt and reduced.

It is useful to separate Pd from Ag.


• Refining Palladium concentrates.

• Digest the impure palladium metal in 50% nitric / distilled water.

• Raise the pH to anywhere between 1 and 2 with NH4OH

• Filter the solution to remove any turbidity or sediment, which may be AgCl.

• Take a volume of solution equivalent to 500 grams of palladium.

• While stirring add NH4OH to a pH of 10 (Expect to add at least 1500 ml of NH4OH) Any Iron or Nickel will precipitate.

• Filter the solution of any turbidity or sediment.

• Acidify with HCl to pH 6.5 to 7. At this pH any AgCl will come out of solution.

• Filter the solution to remove any sediment.

• Continue to acidify with HCl to a pH of 3 where the precipitation of Palladium is essentially complete.

• Cool the batch and decant or pump off the liquid. Slurry the precipitate to a buchner funnel and rinse with a rinse liquid made with 10 ml of HCl per liter of DI water.

• Place all liquors into reclaim as there are always values which should be cemented and collected.

• Slurry the salt with 1000 ml of DI water into a heat-able vessel and add 9000 ml additional DI water.

• Add 100 ml HCl and 250 ml formic acid

• Heat solution to 65 C

• Slowly add 850 ml of 6.25N NaOH maintaining the temperature at 65-70 C

• Reduction is complete when the Pd drops to the bottom the solution becomes colorless and the pH will be between 7 – 8. some recoverable Pd remains in the liquids so save the liquids as before for cementation.

• Transfer the metal into a funnel and wash 3 or 4 times with warm DI water followed by washes with warm 2% w/v ammonium sulfate solution.

• This process produces a fine powder of high purity in excess of .999. This process was used to clean up palladium concentrates to make powder for the electronics industry as paste for the hybrid microelectronics manufacturers. High purity is related to feedstock. Highly contaminated feedstock will carry over impurities from insufficient rinsing.

 

[HAuCl4]

Thanks 4 metals!.

What's the expected purity of the Pt after bromate hydrolysis?.

How do you verify the purity of these metals Pt, Pd, before you deliver the refined product?.

 

[4metals]

Purity from both the bromate hydrolysis and the palladium refining process I posted can reach .9999 depending on your feedstock, and technique.

The only way to determine purity at that level is by ICP. But if you have enough metal on a consistent basis to apply these methods, you can afford to do an instrumental analysis.

 

[HAuCl4]

Thanks a lot 4metals. I have learned very much, from you especially, and others as well. This concludes my "search for better techniques and knowledge for the 4 main metals (pun)".

I hope one day I will land the material to refine in this fascinating field of PGMs and high purity Ag, Au, which field I had only scratched its surface previously.

 

[HAuCl4]

The insolubles filtered off are fused at 500 C with molten sodium bisulfate. This converts the Rhodium to water soluble Rh2(SO4)3 . The Ru, Os, and Ir are untouched. The sulfate cake is cooled and dissolved in water, the insolubles filtered off and the Rhodium is precipitated with NaOH and collected for further purification as quantities warrant.

The remaining insolubles are fused with sodium peroxide and sodium hydroxide at 500 C forming water soluble sodium hyperosmate and sodium ruthenate. The iridium is now Iridium dioxide.
The iridium dioxide is dissolved in aqua regia and precipitated as ammonium hexachloroiridiate with ammonium chloride. The salt is further purified by digestion in dilute ammonium sulfide which will precipitate impurities filtered and re-precipitated with ammonium chloride to reform the ammonium hexachloroiridiate. This can be reduced in hydrogen at 1000 C to pure metal.

What are the processes used industrially to re-purify to obtain high purity Rhodium and Iridium after they are in solution as sulfate for Rh, and as chloride for Ir?. What is the standard for high purity in these rare metals?.

As you can see I'm getting very little gold and silver to refine these days, and I'm confined to research and study!. :lol:

 

[Lou]

Dude, who do you work for? :mrgreen:


Ir and Rh are notoriously difficult to separate, and almost impossible if they're in the trivalent state. Ir is the most challenging of the platinum group metals to refine, and almost everything about Ir and Rh chemistry is strictly proprietary. Which means that no one will really give you the goods.

So, options on refining? 4metals listed the classical method for Ir but it's not terribly satisfactory--usually it's followed up with SSX. Fusion is about the only way to to get Ir into solution, although you can make Na2IrCl6 (and the same thing with Rh, but valence +3) by heating it in a fast stream of chlorine with NaCl matrix and then digesting it all in dilute HCl. You can get rid of some of the earlier base metals with hydrolytic separation (pH controlled).

Rhodium, oh rhodium--many ways here. Ammonium hexachlororhodate isn't nearly as insoluble as the hexachloroplatinates and " "palladate congeners. Furthermore, it's more prone to include base metals as it crystallizes. Typically, the ASHs (the nitrite salt) are one manner in which it's done, but again, solvent extraction works a charm. The big rider with rhodium is usually iridium, thankfully, one can oxidize Ir to (IV) in acidic milieu and selectively pull out the Rh and strip with dilute HCl. Or you can electrowin it.

I'm not surprised you haven't turned anything up in the literature.

I have some pure 3N5 Ir and pure Rh, if you want to try your hand at it. I can sell you an ounce of each and you can chase them through solution if you like...

 

[4metals]

Chloride,

I really haven't spent a lot of time with PM's other than Gold, Silver, Platinum, and Palladium. Now if I was well versed in Iridium and Rhodium as well I might have chosen the name 6metals.

At todays prices, I'd suggest you fork over $3330 to Lou and have at it. :lol: