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

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4metals

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These methods are to process concentrates and are usually not worth processing small quantities. The details have been left out for the Ruthenium and Osmium as these are really dangerous metals and should only be handled in closed reactors.

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

This is a general schematic for processing a concentrate of any combination of the above listed metals usually generated from anode slimes or slimes collected from cementation of waste acids holding values.

Roast the slimes to convert any PdO to metal to assure its place in the soluble fraction.

The concentrate is treated in aqua regia, this solubilizes the gold, platinum and palladium and leaves the other metals in insoluble form.

The solution basically contains HAuCl4, H2PtCl6, H2PdCl4. Drive off the NOx by classic boil down and successive 3X’s addition of HCl. Drop the gold with either Sulfur dioxide or Ferrous sulfate. It has been suggested that reducing the gold with Ferrous sulfate results in a more complete drop of the platinum in the following steps. Gold, with either precipitant, will have to be re-refined for high purity. Alternatively the gold can be extracted with Dibutyl carbitol and recovered with oxalic acid resulting in a high purity gold and leaving the Platinum and Palladium behind for recovery.

The Pt is dropped by treatment with Ammonium chloride to drop the insoluble (NH4)2PtCl6. These salts are washed with a solution of 15% ammonium chloride and dried. The salts are collected and further purified via bromate hydrolysis.

Pd is dropped with a solution of dimethylglyoxime dissolved in dimethyl sulfoxide. The yellow palladium glyoxime is filtered and washed with 60% alcohol and 10% HCl. The alcohol assists in the drying and the dry palladium glyoxime is dissolved in excess ammonium hydroxide until dissolved and generating a clear solution. The addition of HCl results in the precipitation of diaminopalladous chloride salt or “palladium yellow”

You have now completed the easy part, the following treatment is for the insolubles left behind in the aqua regia process.

The insolubles are smelted with lead carbonate, carbon, borax and soda ash. This forms a slag with silica, alumina and base metal impurities. The PM’s are dissolved in the lead. Separate the lead and the slag, remelt the lead and granulate it in nitric acid. Filter off the insolubles, Rh, Ru, Ir, and Os.

The silver and lead are in the Nitric acid, sulfuric acid is added to drop out the lead as insoluble lead sulfate. This is collected and converted to lead carbonate and recycled. Classically the silver is dropped as a chloride and smelted but cementation with copper yields an effective product for further electrolytic purification.

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.
 
Now thats a post 4metals 8) ,but im glad i dont handle enough Pgms to make it necessary im sure i would end in a right mess :lol:
 
Good information.

4Metals, What is the cost benefit to using DMG?

A note to those contemplating trying this with 'ores' and concentrates: Always assume Arsenic and probably Selenium are present and will become volatile when digested in AR. Native materials should always be digested in a sealed system with provisions to collect the fumes.
Even AP can volatilize Ruthenium in 'ores'. It's not an effective recovery technique but it's enough to make you very ill.
 
Alternatively the gold can be extracted with Dibutyl carbitol and recovered with oxalic acid resulting in a high purity gold and leaving the Platinum and Palladium behind for recovery.
Hi 4metals
How is this done
extracted with Dibutyl carbitol

do you precipitate the gold in AR with Dibutyl carbitol
also what do you mean recovered with oxalic acid
 
Irons,

The cost benefit to DMG is a question of scale. I always ran jewelry related materials so the Pd rarely exceeded 10% of the Pt content. DMG was quick and provided a way to store the Pd as Pd glyoxime until I had enough to purify fully. The alternative could have been sodium chlorate.

Goldie,

Methods of dibutyl carbitol extraction have been posted on this forum before. I'm not trying to be mean so don't take this the wrong way but these techniques require a pretty good grasp on the chemistry involved. The last thing I want to see is someone hurting themselves. If you are interested in solvent extraction, try it on small lots with known contents. Extraction is selective and does not carry over PGM's so subsequent PGM recovery is simplified. Read the posts about it and be careful.
 
4metals said:
Irons,

The cost benefit to DMG is a question of scale. I always ran jewelry related materials so the Pd rarely exceeded 10% of the Pt content. DMG was quick and provided a way to store the Pd as Pd glyoxime until I had enough to purify fully. The alternative could have been sodium chlorate.

Goldie,

Methods of dibutyl carbitol extraction have been posted on this forum before. I'm not trying to be mean so don't take this the wrong way but these techniques require a pretty good grasp on the chemistry involved. The last thing I want to see is someone hurting themselves. If you are interested in solvent extraction, try it on small lots with known contents. Extraction is selective and does not carry over PGM's so subsequent PGM recovery is simplified. Read the posts about it and be careful.

And do it outdoors. It smells like the oxidized funk of something you wouldn't want to meet in a dark alley.
 
I try and keep away from DMG, it's too expensive. Under the right circumstances, it's definitely a very selective precipitant. Unfortunately, the voluminous precipitate it makes with Pd is quite likely to drag down other impurities in solution. I suppose if you're doing small amounts of Pd it's worth the money...


Good work leaving the oxides of Os and Ru out of it--many are ill equipped to deal with them. That and the metals are so very rarely encountered (especially osmium; ruthenium is used as a hardener in some jewelery platinum alloys).
 
Lou said:
I try and keep away from DMG, it's too expensive. Under the right circumstances, it's definitely a very selective precipitant. Unfortunately, the voluminous precipitate it makes with Pd is quite likely to drag down other impurities in solution. I suppose if you're doing small amounts of Pd it's worth the money...
My opinion is that it is an excellent indicator, but using it for recovery of palladium borders on the ridiculous. Not only is the volume excessive, the resulting solid material is akin to working with grease. However, it really shines when you have doubts about the results of a stannous test. I routinely used a combination of ferrous sulfate, DMG and stannous chloride when testing mixed elements. Quite a common occurrence when refining jeweler's wastes.

Harold
 
Note caution:
The details have been left out for the Ruthenium and Osmium as these are really dangerous metals and should only be handled in closed reactors.

$Metals :thanks for going through that, we know you are a busy man.
 
butcher said:
Note caution:
The details have been left out for the Ruthenium and Osmium as these are really dangerous metals and should only be handled in closed reactors.

$Metals :thanks for going through that, we know you are a busy man.

..and Ruthenium Tetroxide detonates at 109 Deg. C. I was near a fume hood when some Ruthenium Tetroxide we were distilling detonated. It wrecked the hood and contaminated the lab. It was a very expensive accident. That was my first introduction to Ruthenium poisoning.
 
Hello all,
I have an ore that will wait until who-knows-when-if ever for any attempt at progress.

I have two assay reports that differ and will wait ( forego the expense ) before getting any more.
Our member Richard36 says Fe Pd Ru Ir almost no Au or Silver
a hand held ? Niton ? ?xrf analyser says 96% Fe 2.7% Ir

PGMs appear to me to be too hard to recover for any expectation of profit at this point if ever
If anyone wants some to play with i can pay the freight.
 
can someone let me know if i can use potassium chlorate to precipitate palladium

and or if there are any drawbacks if it is usable .or special procedure

thanks
 
It works, but not nearly as well as sodium chlorate. You're better of using sodium hypochlorite (bleach) in lieu of KClO3.
 
thanks Lou

what shall i do to dispose of the potassium chlorate about 300grams or so

and I don't want to build a rocket or smoke up the neighborhood ? :|
 
Lou said:
It works, but not nearly as well as sodium chlorate. You're better of using sodium hypochlorite (bleach) in lieu of KClO3.

I'd also like to add that calcium hypochlorite (dry bleaching powder) also works as does most any source of chlorine gas.

Steve
 
I wouldn't get rid of it! You can make a solution of KClO3 in hot water and add this solution to gold that is sitting in HCl, it'll put the gold into solution right quick!

Then you can reduce with bisulfite or all the usual suspects insofar as reducing agents go.
 
thanks Lou
I will have to try this
everyone hates to wait.

humm :?: :?: would it put palladium that is siting in HCl into solution faster :?:
 
4metals said:
The salts are collected and further purified via bromate hydrolysis.

Would you please ellaborate on this re-purification?.

After this "bromate drop", what is the best way to get the pure platinum out of solution and then reduced to metal with minimal losses?. Fire or formic acid?.

How to assay the purity of the platinum and palladium final product?. Can one expect 999+ or maybe 9999+ Platinum?. How about Palladium fineness?.

Let's assume the other PGM metals are just kept together as mixed powders in very small quantities, if any, and just focus on the Pt and Pd, that were mainly dropped from a gold chloride solution with ammonium chloride, and sodium chlorate, before dropping the gold.

In summary the "feed" for re-purification are the colored salts of platinum and palladium, separate or mixed, containing traces of other PGMs. And the goal is high purity Pt and Pd, with minimal losses and hassle.

Thanks 4metals, Lou, others, in advance.
 
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