refining silver, palladium and platinum from same solution.

[user 72133]

Hi I have a question, i wanna dissolve some relay contacts (silver palladium alloy) in nitric acid . My question is next : to recover silver and palladium is good to drop first silver from solution with sodium chloride dissolved in little water and after check the solution for platinum with ammonium chloride and in final after filtration of silver chloride and platinum if is present to put in solution some concentrated HCl acid to make aqua regia and after neutralise the nitric with urea and in the final step to add aluminium ? IT IS GOOD TO RECOVER THE PALLADIUM IN THIS WAY WITH ALLUMINIUM?(I don't have acces to zinc and dimerhylglioxime) THE PALLADIUM WILL DROP WITH ALLUMINIUM?

if you only have silver platinum and palladium you could do it like this.
What I would change is instead of using urea to remove the nitric, evaporate the solution by adding hydrochloric acid little by little until a syrup is formed. Then you could precipitate the palladium with dropwise diluted sodium chlorate.
Aluminum would precipitate all metals, but if you only have palladium left, that's fine.

 

[Wonka]

Do you have to us aluminum? Doesn’t the ammonia form it into crystals? Then you filter and heat at 600c before refining?

 

[Yggdrasil]

Do you have to us aluminum? Doesn’t the ammonia form it into crystals? Then you filter and heat at 600c before refining?

It all depends on what you have in the solution.
Aluminum will drop all metals including base metals.
If the solution is pure that is ok.
If one need to separate the PGMs it is necessary to perform some kind of separation step.

 

[Wonka]

I e been thinking about that. Couldn’t you do AR. Drop the gold. Then drop the silver. Boil at 180C then add a little more AR and then drop the platinum/ pladdium?

 

[Yggdrasil]

I e been thinking about that. Couldn’t you do AR. Drop the gold. Then drop the silver. Boil at 180C then add a little more AR and then drop the platinum/ pladdium?

There is no Silver in AR.
You can’t boil AR at 180C since it is over the boiling point.
Where did you get that temperature from?

 

[Wonka]

There is no Silver in AR.
You can’t boil AR at 180C since it is over the boiling point.
Where did you get that temperature fro

 

[billgold]

The person was asking about silver palladium contacts. You cannot use AR on them as the silver will passivate the rest of the metals. Nor would they contain any gold. However, much of the contacts mass is likely to be base metals - not pure silver palladium alloy.

The best and most economical process to follow would depend on the various metal ratios - as well as the mass of material to be processed.

 

[kurtak]

The person was asking about silver palladium contacts. You cannot use AR on them as the silver will passivate the rest of the metals.

The OP (Original Poster) was not planning to dissolve the Ag/Pd contacts with AR - he was going to use Nitric to do that

He was going to use AR later in "his" process (after the nitric dissolve) & that is the part I don't get because there should be no need for AR at all as the nitric alone should dissolve both the Ag & Pd - so there should be no metals to dissolve that require AR

He did mention Pt (which sounded more like he was guessing about rather then actually knowing about)

So - IF (the BIG IF) the points were actually an alloy of Ag/Pd/Pt just what would happen in processing them would depend on the percentage of each of those metals - especially the % of the Pt

If the Pt was very high nitric would likely not even work - & AR would likely have difficulty due to the silver (just like gold/silver alloys) so would likely need to alloy with other metals to allow ether nitric to work - or AR to work

On the other hand - if the Pt was very low then the nitric would dissolve the Ag & Pd as well as likely at least some of the Pt (due to the silver in the alloy)

So - that would result in a solution with Ag & Pd as well as maybe some Pt dissolved in it --- any Pt that did not dissolve in the nitric would then end up as fine dust that could then be filtered/settled out - meaning - that fine dust would then be the only thing needing AR treatment --- that AR treatment is a process separate from the original nitric dissolve

After the (assumed) fine Pt dust if settled/filtered out - you then have a solution of Ag/Pd with maybe some Pt

So the next step is to drop out the Ag as AgCl - then wash out (very well) the still dissolved Pd (& maybe Pt) from the AgCl

The Pd (& maybe Pt) can then be recovered form that solution by refiners choice (DMG - cementing - or other chemical processes used in PGM chemistry)

In other words - in this case - the only place AR would be needed would be on the solids remaining after the nitric (which should already be filtered from the solution) meaning the treatment of those solids are a process of it's own - not part of the original nitric dissolve

Once the solids are filtered from the nitric solution there should be no need for AR in the process of the separation of the metals from that solution as it only takes salt &/or HCl to separate the Ag from the PGMs

That leave just a PGM solution - once the PGMs are recovered from that PGM solution (by refiners choice) they can be re-refined if the refiner so chooses --- but again that is a process of it's own & not part of separating the metals from the original nitric dissolve

Kurt

 

[Abdoulapapatte]

Pourquoi parlez-vous de la dénoxing comme d'un neutralisant ???
La destruction du nitrique et des NOx n'est PAS une étape de neutralisation, c'est une étape de décomposition/destruction.
La neutralisation pousse le pH à 7 de haut en bas et ne fera pas grand-chose sur le nitrique ou le NOx.
Cela créera cependant des hydroxydes qui pourraient rendre votre raffinage encore plus difficile.

can you teach us brother, I don't understand, I denoxinize nitric with urea or sulfamic after the acids lose their power

 

[Yggdrasil]

peux-tu nous apprendre mon frère, je ne comprends pas, je dénoxine le nitrique avec de l'urée ou du sulfamique après que les acides perdent leur pouvoir

English please

 

[Yggdrasil]

can you teach us brother, I don't understand, I denoxinize nitric with urea or sulfamic after the acids lose their power

The best is to not overuse the Nitric.
Next is to use Sulfamic acid, but it has to be done hot. Appr 90C and in small increments with a lot of headroom.

If you use Urea, be aware that Urea is caustic and will neutralize the acid if one use too much.
If the pH get too high, the SMB will not work.

 

[Abdoulapapatte]

of corse i understand , and i don't like smb , because gaz is not specially toxic but no good for eyes and other , so i using feso4 and he is more selective

 

[Abdoulapapatte]

je would like to try with oxalic acide , for gold i can have 999.9 without electrolyse but . for palladium i never try to have 999, maybe i will teste in few time