Rh and Pd extraction and separation

[derik 234]

Hi dear, I read some of your topics on the forum about handling rhodium and palladium and respectfully I would like to know if you could instruct me. I have approximately 20 kg of scrap from galvanic processes plated with Rh and Pd in the final layer, and the lower ones are copper and tin and the piece is solid brass alloy 70% Cu and 30% Zn. I will send you photos of brass wires in this same alloy plated with these noble metals, Rh and Pd. My intention is to produce a Rh° and Pd° powder of acceptable purity.
I have reagents, equipment, ovens and structure.
I know it's a lot to ask, but would you be my mentor in this endeavor?

 

[4metals]

How much tin is involved? Is the wire a brass wire which is plated either with Rhodium or with Palladium and the wires are mixed?

 

[derik 234]

How much tin is involved? Is the wire a brass wire which is plated either with Rhodium or with Palladium and the wires are mixed?

Considering only an ultra-thin flash layer of tin at around 2% representative of the total weight, copper will be in thicker plating layers and in the alloy. They are 70% Cu and 30% Zn brass wires, coated with Rh and Pd, mixed.

 

[4metals]

So to be clear the brass base material is a wire which is copper plated followed either by Rhodium plating or Palladium plating and then a flash top coat of tin? Presumably the tin aids in solder ability?

If the tin is in fact the top layer of plating but I want to be sure before proceeding

 

[SeRKaN PGM HuNTeR]

Copper and brass (zinc alloy) will be dissolved using sulfuric acid, copper and zinc can be precipitated by adding ammonium and calcium-based compounds for copper and zinc from the solution, ammonia-based solvents can be used to purify rhodium and palladium in the following steps.

Regards

 

[derik 234]

So to be clear the brass base material is a wire which is copper plated followed either by Rhodium plating or Palladium plating and then a flash top coat of tin? Presumably the tin aids in solder ability?

If the tin is in fact the top layer of plating but I want to be sure before proceeding

I value your dedication to the steps, they are brass wires in the 70% Cu and 30% Zn alloy that initially receive 2 thick layers of Copper, the first to level the surface and the second to give shine, the tin is the third layer and comes in as a small layer of flash, followed by the final layers of Pd and/or Rh and sometimes both are mixed.

 

[derik 234]

Copper and brass (zinc alloy) will be dissolved using sulfuric acid, copper and zinc can be precipitated by adding ammonium and calcium-based compounds for copper and zinc from the solution, ammonia-based solvents can be used to purify rhodium and palladium in the following steps.

Regards

Exactly it is an alloy, it proposes to dissolve everything in sulfuric attack, perhaps at a hot temperature of 60°C and continue precipitating aminocymplexes.
Going in aggressively with H2SO4 seems functional to me but not very efficient, the last layers are the ones of interest, the less they favor mixing between base, semi-noble and noble metals, the less difficult it will be to purify.

 

[4metals]

My concern about the tin is filtration if it is too high a concentration in your acid. If the last layer would have been tin it was a no brainer, but without other options I would with the thought that cold aqua regia will not attack the Rhodium and you should effectively dissolve everything else. The insoluble in this case would be the Rhodium. If you were to melt it all together and then react it it is possible you will have finely divided Rhodium which has a greater probability of dissolving in the aqua regia.

One could argue you could use nitric in which the Palladium is soluble and the Rhodium is not as well. In that case using Dimethylglyoxime to recover the Palladium would be my first suggestion unless there is a lot of Palladium in which case it becomes cost prohibitive.

It is entirely possible you may be able to melt the Rhodium foils or sell them as a powder (by grinding them) without further treatment (or expense)

 

[Yggdrasil]

How about trying a small batch with hot Copper Chloride aka AP and see if one can reach both the Tin, Copper and Zinc in one go.
Maybe they need to be squished/flattened a bit first.
Hot HCl with plenty bubbling may do the trick.
Or maybe not.

Take 100g or so and test.

 

[derik 234]

My concern about the tin is filtration if it is too high a concentration in your acid. If the last layer would have been tin it was a no brainer, but without other options I would with the thought that cold aqua regia will not attack the Rhodium and you should effectively dissolve everything else. The insoluble in this case would be the Rhodium. If you were to melt it all together and then react it it is possible you will have finely divided Rhodium which has a greater probability of dissolving in the aqua regia.

One could argue you could use nitric in which the Palladium is soluble and the Rhodium is not as well. In that case using Dimethylglyoxime to recover the Palladium would be my first suggestion unless there is a lot of Palladium in which case it becomes cost prohibitive.

It is entirely possible you may be able to melt the Rhodium foils or sell them as a powder (by grinding them) without further treatment (or expense)

These are important points, especially in the amount and concentration of acid to be used, a very common mistake that makes what is no longer easy very complicated quickly. Hydrometallurgical routes must be very considered, DMG in AR is a good option for Pd cost-benefit must be really analyzed, I do not intend to merge all the material initially I think about taking it easy.

 

[derik 234]

How about trying a small batch with hot Copper Chloride aka AP and see if one can reach both the Tin, Copper and Zinc in one go.
Maybe they need to be squished/flattened a bit first.
Hot HCl with plenty bubbling may do the trick.
Or maybe not.

Take 100g or so and test.

I will carry out this test and report it here, I will take a sample under moderate heating without O2 and we will see if a precipitate appears, it may work

 

[Yggdrasil]

I will carry out this test and report it here, I will take a sample under moderate heating without O2 and we will see if a precipitate appears, it may work

The bubbling and thus O₂ is what enables the formation of Copper Chloride which in turn is the active component.
HCl alone will only remove the Tin it has access to.
For this to be effective the wires may need to be cut in smaller pieces.

Lets see what the test say.

Nothing should precipitate by the way only dissolve.
So what should be left is the PMs

 

[anarxi]

Exactly it is an alloy, it proposes to dissolve everything in sulfuric attack, perhaps at a hot temperature of 60°C and continue precipitating aminocymplexes.
Going in aggressively with H2SO4 seems functional to me but not very efficient, the last layers are the ones of interest, the less they favor mixing between base, semi-noble and noble metals, the less difficult it will be to purify.

In concentrated hot (50-90 degrees) sulfuric acid, copper and brass do not dissolve, but are passivated.
This is how silver removal occurs.
but palladium can also be removed in this way.
Immerse the wires in sulfuric acid, heat them and add nitric acid little by little.
palladium will dissolve.
the base will remain untouched
then pour in this solution
into clean distilled water (dilute it) and put aluminum there.
add some hydrochloric acid.
All palladium will precipitate in the form of black particles
there will be about 800 samples of palladium.

 

[4metals]

All palladium will precipitate in the form of black particles
there will be about 800 samples of palladium.

This statement is unclear, are you referring to purity? What does 800 samples mean?

 

[anarxi]

This statement is unclear, are you referring to purity? What does 800 s

This statement is unclear, are you referring to purity? What does 800 samples mean?

purity of palladium.
The translator translated this incorrectly...

 

[SeRKaN PGM HuNTeR]

800 can be expressed ppm, 1000 ppm is equal to one gram.

 

[Yggdrasil]

800 can be expressed ppm, 1000 ppm is equal to one gram.

It is a measure without nomination so unless you say it is in grams meters or apples it do not say much.
It is just 0.1% of something.
1000 parts per million.
1000 is one thousands of a million.

 

[derik 234]

Hi dears, initially, I started the experiment by taking part of the rhodium-plated wires that I believe have a Palladium bath underneath, I cut them and weighed 100 grams of these plated wires. I placed them in a packer and added hydrochloric acid P.A. Initially, I did not inject oxygen. After a few minutes, I installed a pump that will inject the oxygen, as shown in the following video, you can follow the reaction.

 

[derik 234]

Hi dears, initially, I started the experiment by taking part of the rhodium-plated wires that I believe have a Palladium bath underneath, I cut them and weighed 100 grams of these plated wires. I placed them in a packer and added hydrochloric acid P.A. Initially, I did not inject oxygen. After a few minutes, I installed a pump that will inject the oxygen, as shown in the following video, you can follow the reaction.

Hi dears, I'm continuing with the experiment. After only four days, we noticed that the RH and Pd-plated wires immersed in HCl P.A are undergoing a very gradual attack and a change in color is noticeable. We noticed silver particles, some in suspension and others in the background. I think it could be undissolved Rh. If I add drops of concentrated H2O2, I will have a flow of toxic gases and an exothermic reaction. However, a fume hood, gloves and gas masks are useful for this. However, will I have Rh solubilization, even if in minimal percentages? If this happens, could I precipitate and separate the Rh from the Pd with a good percentage? These small blue pieces are from the hose that fell into the beaker. Disregard them.

 

[derik 234]

Hi dears, following the Hcl p.a attack with O² injected, I noticed that the attack was being very slow as the days went by, so I added drops of H2O2 v.200 and quickly noticed an increase in the silver particles that are insoluble in Hcl p.a. with concentrated H2O2, with I filtered all the dissolved threads and washed them until acid neutralized, separating the mixture a little like the one in the photo. What remains is this blackened chloride solution where we have a lot of palladium. I thought about drying these particles and melting them at 550°C with NaHSO4 or KHSO4 for a few hours in the hope of dissolving them and precipitating a Rh hydroxide, washing until neutralized and dissolving in H2SO4, repeating until an acceptable purity and perhaps then reducing to Rh powder. contaminated. When they can, if the masters want to guide me, this is a great store of knowledge, I intend to help the group with a donation.