Pd Pt Rh mix industrial cat refining tips ?

[Yggdrasil]

Hi sa dugay nga panahon kami adunay usa ka medyo komplikado nga problema nga naglingkod sa among refining workshop.
Solusyon nga adunay gibanabana nga:
34% Pd
9% Pt
2% Rh
ang uban mga base nga metal, kasagaran Fe, Co, Ni, pipila ka mga timailhan sa Pb, walay Ag o Au.
Ang mga metal anaa sa porma sa mga chloride sa AR nga solusyon nga gigamit. Tino nga adunay pipila ka nitric. Ang among tumong mao ang pagbawi sa gipadato nga tipik sa rhodium, labaw pa sa 50% sa masa mahimong talagsaon, tungod kay kami nagtrabaho uban sa daghan niini nga materyal.
Dugang pa, ang Pt ug Pd fractions dili kinahanglan nga super puro, ug ang mixed PtPd fraction mahimong igo. Nagbasa ako usa ka hugpong sa mga mantalaan, mga thread sa forum ...
Ug nakamugna ako usa ka plano sa DIY kung giunsa ang pag-atubang sa problema:
1. Ipagawas ang Pd nga adunay DMG - Rh enrichment solution, sa pH ca 3 kinahanglan nga dili daghan ang Ni co-precipitation, pero kung naa, dili kini dako nga problema.
2. buhian ang dili putli nga Pt nga adunay NH4Cl uban ang pipila ka bahin sa Rh isip kontaminant
3. nahabilin nga mga halangdon nga metal, semento sa usa ka butang (Zn, Fe?)
4. calcination sa dili putli nga ammonium hexachloroplatinate ug pagtunaw sa nahabilin nga metal nga espongha ngadto sa NaHSO4
- o leaching sa Rh uban sa H2SO4
- unsa nga paagi ang mas maayo?
o aduna bay mas maayo nga paagi kay niini?
5. halangdon nga mga metal nga gisemento sa leaching sa susama nga paagi sama sa ibabaw.
Wala akoy daghang kasinatian sa kini nga natad, apan ako adunay daghang praktikal nga kasinatian sa chemistry sa kinatibuk-an.
Tingali kulang ako usa ka punto o nasayop ako sa usa ka paagi ...
Ang akong pangutana mao:
mahimo ba kini?
Labing maayo nga pangutana:
unsa ang imong sugyot?
sa unsa nga paagi kini mahimo nga mas maayo / mas episyente? mahimo pa ba?
Salamat daan sa imong opinyon.


Google translate makes wonders

 

[Yggdrasil]

Hi
for a long time we have a rather complex problem sitting in our refining workshop. Solution containing approx.:
34% Pd
9% Pt
2% Rh
the rest are base metals, mostly Fe, Co, Ni, some traces of Pb, no Ag or Au.
Metals are in the form of chlorides in the AR solution used. Certainly some nitric is present.
Our goal is to recover the enriched fraction of rhodium, more than 50% by mass would be fantastic, as we work with a lot of this material. Furthermore, the Pt and Pd fractions do not need to be super pure, and the mixed PtPd fraction would be adequate.

I read a bunch of newspapers, forum threads... And came up with a DIY plan of how to deal with the problem:

1. Release Pd with DMG - Rh enrichment solution, at pH ca 3 there should not be much Ni co-precipitation, but if there is, this is not a big problem.
2. release impure Pt with NH4Cl along with some part of Rh as a contaminant
3. rest of noble metals, cement on something (Zn, Fe?)
4. calcination of impure ammonium hexachloroplatinate and melting the remaining metal sponge into NaHSO4 - or leaching of Rh with H2SO4 - which approach would be better? or is there a better approach than these?
5. noble metals cemented with leaching in a similar manner as above.

I don't have a lot of experience in this field, but I have a lot of practical experience in chemistry in general. Maybe I'm missing a point or I'm wrong in some way...
My question is: will it work?
Best question: what's your suggestion? how could this be done better / more efficiently? is it even possible?

Thank you in advance for your opinion.

And now in English

Please post in English. It is an international forum and English reach most members.

Regards Per-Ove

 

[Geo]

Just as we refine gold twice to improve quality, PGM's from the same process. The fastest process is to precipitate Pt with NH4Cl. Filter out Pt salt. Precipitate Pd by adding chlorine gas or other source. Precipitate Rh with cementation. All three will be contaminated. Reduce the salts in your preferred method. Refine a second time taking more care or using different precipitants.

 

[butcher]

Authur Kierski our well-known member is still having trouble with the new forum, I do not understand the problem but it may have something to do with translating his messages.

Arthur posted above:
Hi
for a long time, we have had a pretty complex problem sitting in our refining workshop. A solution containing approx.:
34% Pd
9% Pt
2% Rh
the rest are base metals, mostly Fe, Co, Ni, some traces of Pb, no Ag or Au.
Metals are in the form of chlorides in the AR solution used. Certainly some nitric is present.
Our goal is to recover the enriched fraction of rhodium, more than 50% by mass would be fantastic, as we work with a lot of this material. Furthermore, the Pt and Pd fractions do not need to be super pure, and the mixed PtPd fraction would be adequate.

I read a bunch of newspapers, forum threads... And came up with a DIY plan of how to deal with the problem:

1. Release Pd with DMG - Rh enrichment solution, at pH, ca 3 there should not be much Ni co-precipitation, but if there is, this is not a big problem.
2. release impure Pt with NH4Cl along with some part of Rh as a contaminant
3. rest of noble metals, cement on something (Zn, Fe?)
4. calcination of impure ammonium hexachloroplatinate and melting the remaining metal sponge into NaHSO4 - or leaching of Rh with H2SO4 - which approach would be better? or is there a better approach than these?
5. noble metals cemented with leaching in a similar manner as above.

I don't have a lot of experience in this field, but I have a lot of practical experience in chemistry in general. Maybe I'm missing a point or I'm wrong in some way...
My question is: will it work?
Best question: what's your suggestion? how could this be done better / more efficiently? is it even possible?

Thanks in advance for your opinion
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[orvi]

Just as we refine gold twice to improve quality, PGM's from the same process. The fastest process is to precipitate Pt with NH4Cl. Filter out Pt salt. Precipitate Pd by adding chlorine gas or other source. Precipitate Rh with cementation. All three will be contaminated. Reduce the salts in your preferred method. Refine a second time taking more care or using different precipitants.

I make small test runs (4) in the bigger testtubes now. Owner gets excited about this approach (because previously we observed no Rh leaching to nitric), but i am slowly loosing my "amazement" from beginning as we used the PtPdRh cemented mix, nitric only leached out portion of Pt and Pd, Rh left in precipitate.
I do not understand it, but now it also eaten up Rh... after only 16 hours at low heat ...broken XRF, some troll who add HCl to our nitric, i don´t know. More and more strange results.

As this experiment will be over, best chances are that i go with approach you suggest.
If some significant portion of Rh gets stuck in Pt NH4Cl drop, i will consider bromate hydrolysis to scavenge the Rh.
If Pd portion drag significant ammount of Rh... Hmmm... This will be more complicated

Overall, we wanted to base our preliminary research on initial findings, but now, reconsidering the results... Very likely we will come back from reinventing the wheel to standard approaches

 

[orvi]

"i would do the folowing---1-cement with copper--the powder from cementatio,dissolve with nitric,making a solution,with pd---the powder left use hcl+peroxide,the liquid will contain pt and the powder left is rh--now ,treat the solutions with the reagents like dmg for pd and the platinum solution with nh4cl--the rh ,purifies your way"

I had considered this approach and very similarly, I replicated this procedure one time, but obviously i have made some mistakes with precipitations - i lost practically more than 50% of Rh to the ammonium hexachloroplatinate and Pd(DMG)2 complex.

After this researching, one of my next attempts will be something like this, but this time more prepared, well educated about all the right parameters of each precipitation, and hopefully we get some usable outcome

 

[Yggdrasil]

Authur Kierski our well-known member is still having trouble with the new forum, I do not understand the problem but it may have something to do with translating his messages.

Arthur posted above:
Hi
for a long time, we have had a pretty complex problem sitting in our refining workshop. A solution containing approx.:
34% Pd
9% Pt
2% Rh
the rest are base metals, mostly Fe, Co, Ni, some traces of Pb, no Ag or Au.
Metals are in the form of chlorides in the AR solution used. Certainly some nitric is present.
Our goal is to recover the enriched fraction of rhodium, more than 50% by mass would be fantastic, as we work with a lot of this material. Furthermore, the Pt and Pd fractions do not need to be super pure, and the mixed PtPd fraction would be adequate.

I read a bunch of newspapers, forum threads... And came up with a DIY plan of how to deal with the problem:

1. Release Pd with DMG - Rh enrichment solution, at pH, ca 3 there should not be much Ni co-precipitation, but if there is, this is not a big problem.
2. release impure Pt with NH4Cl along with some part of Rh as a contaminant
3. rest of noble metals, cement on something (Zn, Fe?)
4. calcination of impure ammonium hexachloroplatinate and melting the remaining metal sponge into NaHSO4 - or leaching of Rh with H2SO4 - which approach would be better? or is there a better approach than these?
5. noble metals cemented with leaching in a similar manner as above.

I don't have a lot of experience in this field, but I have a lot of practical experience in chemistry in general. Maybe I'm missing a point or I'm wrong in some way...
My question is: will it work?
Best question: what's your suggestion? how could this be done better / more efficiently? is it even possible?

Thanks in advance for your opinion
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Send feedback
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Hi Butcher.
What surprises me is that when these translation issues happen, the OPs don't seem to notice.
Is this some kind of forum software thing?
Or don't they reread what they posted after posting?
In retrospect I see that l should have added some additional text around the translations, sorry about that.
I really don't like posting long posts from my phone.

Regards Per-Ove

 

[Geo]

Have you tried reducing Pd with formic acid? I have not read that formic acid will reduce Rh. I have reduced formic acid for Pd and it seemed to do a good job. Once the metallic salts are reduced, there is no chance to mistake it for something else. It normally reduces to heavy, dark to black powder. If am not mistaken, the formic acid will reduce the Pd but not Rh, leaving it in solution.

 

[Geo]

Or, the Rh stays in salt form and can be dissolved with boiling water.

 

[goldandsilver123]

Why don't you try some purolite resin (9140 or 9200) to absorb just the PMs and when you have more mass you can try to separate them.

Have you tried reducing Pd with formic acid? I have not read that formic acid will reduce Rh. I have reduced formic acid for Pd and it seemed to do a good job. Once the metallic salts are reduced, there is no chance to mistake it for something else. It normally reduces to heavy, dark to black powder. If am not mistaken, the formic acid will reduce the Pd but not Rh, leaving it in solution.

Formic does reduce rhodium:
https://goldrefiningforum.com/threa...t-option-for-rhodium-chloride-solution.28847/

 

[orvi]

Why don't you try some purolite resin (9140 or 9200) to absorb just the PMs and when you have more mass you can try to separate them.


Formic does reduce rhodium:
https://goldrefiningforum.com/threa...t-option-for-rhodium-chloride-solution.28847/

good idea, i didn´t considered resins yet

 

[orvi]

Okay, idea with leaching platinum from high surface area PtRh blacks (from "inquartation" with Cu or Al) was given up. In all samples, rhodium tend to also slowly dissolve. Dissolution rate of platinum is higher, but it very quickly reach equilibrium in 65% nitric, and no more dissolves even after prolonged heating. PtRh black from Cu inquartation/dissolution is very active, does not settle over time, and rhodium is dissolved relatively quickly.
PtRh black from Al inquartation is very compact and easy to work with. But also here, Rh slowly dissolves into the solution.
Nitric acid used was p.a. grade 65%, and both procedures were conducted with exclusion of chlorides.

Next, I will focus on perfecting classic sequence of NH4Cl Pt drop, followed by NH4Cl/"Cl2" Pd drop (after Christmas ).
I will probably try to follow an article (listed below), where authors pointed out some good points in terms of temperatures, concentrations of HCl and NH4Cl ammounts and reaction times.

My aim is not to obtain the best yield of Pt salt, but to loose as little Rh as possible in the precipitated Pt ammonium salt. Some rational compromise

I read whole bunch of threads here on this classic sequence, but it seems to me that procedures vary from user to user in terms of concentration, precipitation temperature, HCl content, ammount of NH4Cl used and mostly by contact time of formed precipitate with mother liquor.
In many articles I read that contact time should be minimized due to unwanted "reversed hydrolysis" (precipitation of Pt salt reform HCl in the solution) of other PGM chlorocomplexes, which cause unwanted drag of other PGM salts with ammonium chloroplatinate.

Any suggestions are very appreciated.

 

[orvi]

So I am back. I was elaborating Pt NH4Cl drop on two samples of PGM solutions - one containing base metals (heavily polluted, up to 50%), the other was clean PtPdRh solution.

As in the accessible literature aren´t much information about exact procedures, i was just making it from the best assumptions i had. I tried to follow the article above, but it failed to deliver results which I could work with.

Denoxxing was done by two times boil down the solution to the viscous liquid (refilling with fresh 35% HCl after first boil-down). After HCl evaporation to temperature of 150°C, whole mixture started to form viscous semi-solid goo. As i realized it, i took it off hotplate and let it cool, then try to redissolve the formed precipitate, but it was too late, good portion of precipitate did not make it to the solution... Filtration was near impossible, so i stopped the experiment and started with fresh sample.

This time, when starting the sequence of denoxxing boil-down, I added 2,4 molar equivalent of NaCl (to PGMs present) to the solution, which prevent the salts from decomposing at elevated temperature. It worked as expected, and I was able to stripp all the HCl present, forming crispy red-brown solid at the end of denoxxing step.
The formed solid readily dissolved in water without leftover solids.
For experiment, I was using 2g of dissolved PGMs containing roughly 51% Pd 42% Pt and around 2,5% Rh.

I diluted the solution to total volume of 10 mL, then according to the article heat it up to 60°C (best temperature I figure from their graphs in terms of purity and recovery intended) and measure NH4Cl saturated solution in a way that final concentration of free NH4Cl does not cross 0,5 M (molar) - also get this number from the table in the publication, showing that after 0,5M mark, complexes tend to be less soluble in general for all PGMs. I used around 0,75 grams, from which 0,47g was calculated stechiometry, 0,31 was excessive. Given the solubilities of Pd and Rh NH4 complexes, this excess in theory should not bother them to coprecipitate... (well, I was clearly wrong).
According to the article, i did not mix the precipitated powder too long, so after few minutes i filtered it and wash it with 150g/L NH4Cl as was mentioned in the article (used 10 mL + 2 mL of it).

Only to find out that dropped ammonoplatinate is only 93,6% Pt. Also contained around 4% Pd and 2% Rh...
Mother liquor contained in terms of PGMs only 1% Pt.

After it was done, I realized few mistakes and misconceptions i did and have.
When using the NaCl method for denoxxing, there is no way to form partially hydrated PGM complexes, which authors of article mentioned to be beneficial for the precipitation. Also, maybe I should not use excess NH4Cl and dont rely on theoretical values of solubility.

My questions to you, more skilled PGM refiners, are:

1. when dropping (NH4)2(PtCl6), how much NH4Cl (stechiometry) do you use when refining platinum from the mixtures containing lot of PdRh ? Should I use stechiometric ammount or excess... less than stechiometry ? My aim is some rational compromise between purity and recovery, so the process is of any use. Say when 90% of Pt will drop with minimal other PGM, i would be happy. What do you suggest ?

2. how long you routinely stirr the suspension of formed solid ammonoplatinate ? in the article, folks wrote that contact time between suspension and mother liquor should be kept minimum. But it was more likely for their case, taking the advantage of slow reverse hydrolysis of PGM complexes, when HCl is formed during the drop.

3. what temperature you use to precipitate NH4 Pt salt from solution ? also, it was heavily discussed in scientific literature, but no practical implications can be found on real world material examples - like mine canister of dissolved PGMs.

4. does sodium content (not negligible) inevitably present from using NaCl for proper denoxxing and driving off HCl mess the whole process ? I mean if it could mess up the solubilities of PGM salts, as the solution will be more saturated with chlorides. Could it be done this way with NaCl content or I should abbandon it and try to proceed in another way ?

5. I used rough concentration of 85g Pt / L for the drop of ammonoplatinate. Considering there is also other PGMs which could coprecipitate more likely if it was more concentrated. Do you think the solution should be more diluted when dropping Pt from such excess of other PGMs ?

I will be very happy if you could shed some light into this problem. I know that maybe I am asking for secret informations as the refining of PGMs is well hidden from the ordinary small refiners as I am - but I tried any information will help.
Thank you
Orvi

 

[goldandsilver123]

With your denoxxed solution of Pt, Pd and Rh, I would raise the pH to 10 with a mixture of sodium hypochlorite and sodium hydroxide. You need to keep the solution really oxidizing. Pd and Rh will ppt as hydroxides, the filtrate will render you pure platinum >99.9%.

The Pd and Rh can be recovered from the hydroxides.

My experience is that ppt with NH4Cl will always drag Rh. And I see on Pt from other refineries Rh and Ir contamination on their "pure 99,99% "platinum products

 

[orvi]

With your denoxxed solution of Pt, Pd and Rh, I would raise the pH to 10 with a mixture of sodium hypochlorite and sodium hydroxide. You need to keep the solution really oxidizing. Pd and Rh will ppt as hydroxides, the filtrate will render you pure platinum >99.9%.

The Pd and Rh can be recovered from the hydroxides.

My experience is that ppt with NH4Cl will always drag Rh. And I see on Pt from other refineries Rh and Ir contamination on their "pure 99,99% "platinum products

As high as pH 10 ? Interesting. I always read that it is extremely pH sensitive, any kind of "hydrolysis" type reaction with PGM. Most of the guys getting it to the pH 7.5 - 9.
When you are saying that you could go as high as 10, that would simplify the proces by order of magnitude.
Thanks for the advice

 

[Abdoulapapatte]

hello orvi little question what do you think about the use of potassium persulfate know that it melts at 180.
and it dissolves the rhodium if it can help you
I hope you have managed to improve your process in the meantime.
I think you should have no more problems with pd and pt and have good racial %.
what are your best pt pd and rh ration that you have measured in solid (powder mud, until now?)
courage you are on the right track. it's good what you do if you want i give you an answer in mp.
for me the closest to my way of doing is geo,
you should also know that after the Nh4Cl episode and the release of platinum,
yes we can use chlorate, I didn't know that there was a risk of splashing, technically potassium chlorate produces a purer salt theoretically, then by evacuating the remaining liquid with hcl we can recover the rhodium

 

[orvi]

hello orvi little question what do you think about the use of potassium persulfate know that it melts at 180.
and it dissolves the rhodium if it can help you
I hope you have managed to improve your process in the meantime.
I think you should have no more problems with pd and pt and have good racial %.
what are your best pt pd and rh ration that you have measured in solid (powder mud, until now?)
courage you are on the right track. it's good what you do if you want i give you an answer in mp.
for me the closest to my way of doing is geo,
you should also know that after the Nh4Cl episode and the release of platinum,
yes we can use chlorate, I didn't know that there was a risk of splashing, technically potassium chlorate produces a purer salt theoretically, then by evacuating the remaining liquid with hcl we can recover the rhodium

Thanks for the support, but we did not manage to separate it and needed to pass the bulk metal further. Sad, but life goes on
What I learned is fact, that with simple textbook separations, you can´t do it with that low percentage of metal you are aiming to salvage. At least, I cannot do it.
Every time I´ve attempted to follow some published procedures, it gives me poor resolutions and bad separations. Things aren´t 100% efficient and basically, you are just producing enriched fractions at least, i was producing enriched fractions.

It will be possible to go with two-step rafination, for the first pass, enrich the Pt and Pd above 93-95% with NH4Cl or KCl method, and then refine the Pt and Pd to squeeze the last traces of Rh out (best with hydrolysis for Pt). Create enriched mix of PtPdRh, and if it is not on the sellable side, go one more time.
But this procedure will be labor intensive, and with my current health issues, not possible

 

[Abdoulapapatte]

don't feel defeated at 2 minutes of victory

 

[Yggdrasil]

ne vous sentez pas vaincu à 2 minutes de la victoire

Kan ikkje du være så snill å skrive på engelsk?

 

[Abdoulapapatte]

hi orvi

I would like to recommend these videos, they are very high quality and illustrate your situation perfectly.

You start with plain water, so before the first step you either concentrate your solution and boil it.

You evacuate the water in vapor and you concentrate your concentrations of pgms. then when the solution is ultra concentrated, and quite dark, you dilute by adding hcl to eradicate hno3, you evaporate, you concentrate and you put back hcl a second time.

,1) if now you have 100 liters, add zinc, added with zinc (or cu) and precipitate the pgms

hno3+hcl from dissolving pgms------> boil-----> evaporate ( pgms concentration)-----> add hcl

-----> boil and insert the solution again then you get to this stage, note all the tips in the video.



2) after applying the platinum sponge ----> reduction in its metallic form by ammonium formate



3)Then separation of palladium:



3.1) add ammonium chloride again in small quantities, add also

kclo3 (potassium chlorate or NaClO3 (sodium chlorate works better). -----> boil

the red concentrate-----> red precipitate will be palladium , the rest of the highly concentrated liquid will be rhodium .

3.2 rinse with HCL or with a 10% ammonium chloride solution (pd salt will not dissolve)

4 turn the palladium sponge into metal:



dilute palladium precipitate with water ------> boil ------> ammonium formate----> Pd metal

5) precipitation of rhodium in its metal form :



THE OLD ZINC TECHNIQUE ------> will not dissolve in aqua regia

6) another observation

to refine rhodium easily it is necessary to prepare it (make it etchable):

two videos not to be underestimated :

https://www.youtube.com/watch?v=Bd8Ou4WGNXk&t=486s
https://www.youtube.com/watch?v=2gzzCDHtvzE&t=6s (precipitation with alcohol)



I hope that it helped you, I wonder if the stoichiometry is really important, I know well that Nh4cl can precipitate platinum and palladium at different precipitation times

1)platinum -----> precipitates-----------time-----> palladium precipitates

bye