palladium from nitrate solution

[lazersteve]

Thanks freehemist, that explains my experimental observations.

Steve

 

[kjavanb123]

Please advise this method is correct or not.

Drop the Pd and other contaminants from the Pd nitrate using zinc, wash with boiling water, decant, then drop HCL to the residue, heat, that would dissolve any other contaminants except Pd, decant, wash, decant, and finally for more purifcation of Pd residue, dissolve it in ammonia, drop it HCL and get the yellow salt.

Thanks
Kev

 

[lazersteve]

Please advise this method is correct or not.

Drop the Pd and other contaminants from the Pd nitrate using zinc, wash with boiling water, decant, then drop HCL to the residue, heat, that would dissolve any other contaminants except Pd, decant, wash, decant, and finally for more purifcation of Pd residue, dissolve it in ammonia, drop it HCL and get the yellow salt.
Kev

No.

From my observations and Freechemist's reply above I would take the Pd nitrate solution and add SMB in water to give the bright yellow Na2Pd(SO3)2x2H2O, containing about 31% Pd. Test your left over solution with DMG for traces of Pd, if present add to your PGM stock pot.

Dissolve the bright yellow Pd salt in excess ammonium hydroxide, filter and precipitate the canary yellow Pd ammonium chloride with HCl. This is the purified Pd salt we have made in the past. It gets converted to Pd metal via incineration or zinc in 5% HCl.

Steve

 

[kjavanb123]

Steve,
This is what happened when i tried using SMB with Pd nitrate solution from 4 combs.
1. I dissolved 54g of SMB in 100ml of hot water, and there is the Pd nitrate solution from dissolving the black powder from 4 combs in nitric.

2. After addition of 2 more 100ml + 54g SMB solution to the Pd nitrate solution it changed to color below.

3. After 4th SMB solution addition the Pd nitrate solution no longer fizzed so I stopped, checked the solution it still shows very positive for Pd with stannous.

4. The same solution sitting for half an hour.


what should i do now?

Thanks
Kev

 

[shyknee]

Something is not right with your SMB mine is all ways clear in solution (when mixed with water).
check your source

 

[kjavanb123]

Something is not right with your SMB mine is all ways clear in solution (when mixed with water).
check your source

Is your ratio of mixing SMB with water same as mine? 54g to 100ml of water?
Thanks
Kev

 

[lazersteve]

Kev,

If you have a relatively clean Pd nitrate ( ie: no other precious metals) solution you can use SMB to precipitate the Pd metal and refine it a second time for higher purity.

Correction.

I tried this yesterday and had mixed results. The result was a bright yellow powder that tested positive as a Pd salt, not a fine black powder as expected (Pd metal). I read the source literature again and noticed it said SO2 gas, not SMB so I figured the sodium ions worked to form a double salt with Pd instead of the metal as expected.

I added my SMB dry, perhaps if I had dissolved it in a little HCl first I would have had better results. I also noticed I did not get any precipitate even after the SMB fully dissolved, until I added additional water.

Steve

I'm at a loss to understand why you keep adding enormous amount of acids and precipitants to your solutions in an effort to get the proper reaction. Again, you must start small at every step until you know what you are doing. Learn how to repeat the reaction and get the same results every time before you scale up. In chemistry more does not equal better. Have you ever had a glass of sweet tea or coffee with too much sugar in it?

A few grams of Pd only requires a few mL of nitric acid to dissolve and only a few grams of SMB to precipitate. Any more of either reagent is not only wasteful, but alters the overall reactions.

Your problem with the Palladium Nitrate solution is that it is most likely too dilute. You should have tried boiling it down before you added that much SMB. Unfortunately, now you have a saturated solution of SMB with a tiny amount of Pd in it so evaporation is not an option. I would try freezing the solution to see if the Pd will precipitate out at lower temperatures. Odds are you are going to get some sulfates mixed with the yellow Pd salt when you do. There is an off chance you can add some water and get the bulk of the yellow Pd to precipitate.

If all else fails I think you already know how to use the zinc recovery method. Be careful adding the zinc to the acidic solution with SMB (free SO2) present. You will very likely form sulfides and/or hydrogen sulfide which is a very deadly gas. Hydrogen sulfide initially smells of rotten eggs until your sense of smell becomes dulled by it and then you no longer even know you are being exposed to this deadly gas until it kills you. The difference in concentration between the level at which you smell it at and the lethal dose is very small. With hydrogen sulfide, if you drop to one knee from exposure, you are most likely going to die from it. Please do not do this indoors or near animals, children, or in close proximity to any other occupied dwellings. Gentle heating of the saturated SMB solution may help to drive off the SO2 gas. Definitely do this before adding any base metals or acids to the solution.

Steve

 

[kjavanb123]

Steve,
Following your tips, i went ahead and heated the SMB saturated solution on a steam bath for few mins. Then slowly added small amount of zinc to it it turned dark as you can see from these pics.
The SMB saturated solution after SO2 emission using steam bath.


Same solution after zinc addition.


So i transfered it to a larger beaker, added 20% lye solution and as it turned out i had added too much zinc, then added boiling water, and 5% HCL and it looks like all the zinc removed and left is the black powder. which i will dissolve in nitric.
The black powder from processing 4 new honeycombs, i dissolved in minimal amount of nitric and steam bath to make sure it was saturated enough. then per your previous posts, i dissolved 4grams of SMB in few drops of HCL, then poured it in beaker containing Pd nitrate. lots of foaming and brown fumes, and this light brown color residue apperard which was gone to the bottom of beaker. I added total of 5 SMB HCL solution to the Pd nitrate, and filtered it. I am curios is this the right dark yellow Pd salt expected from SMB and nitrate solution?

Pd nitrate solution after addition of SMB HCL solution


SMB dissolved in small amount of HCL


Filtered residue and remaining Pd nitrate solution.


Please advise

Kev

 

[freechemist]

Reading through this whole thread again I see things which can go wrong and actually have gone wrong. I am sorry for not having given more detailed information together with my posted suggestions. Most important: palladium-refining, especially using nitrate solutions, has to be carefully planned and calculated as far as possible. Mixing palladium solutions, probably in fairly concentrated nitric acid with reducing agents like sodium-meta-bisulfite, even in small amounts, can become very dangerous through nearly explosive emission of toxic fumes (NOx) and foaming over and spilling of hot strongly acidic oxidizing and etching solution. In addition to this do not forget the palladium losses caused by such events.

Complex palladium sulfite salts, like the ones earlyer cited in my previous
post are formed only in nearly neutral solutions. That means, that most of all remaining acid has to be neutralized before addition of sulfite salts. This can best be done by adding carefully not too concentrated aqueous NaOH and controlling the pH-value. In the "Chemicals"-section I will post some more details about use of sulfite in palladium and gold-refining, as well as some details about the earlyer mentioned DMG in palladium-separation.

Regards, freechemist

 

[MarcoP]

If you have a relatively clean Pd nitrate ( ie: no other precious metals) solution you can use SMB to precipitate the Pd metal and refine it a second time for higher purity.

Steve

Correction.

I tried this yesterday and had mixed results. The result was a bright yellow powder that tested positive as a Pd salt, not a fine black powder as expected (Pd metal). I read the source literature again and noticed it said SO2 gas, not SMB so I figured the sodium ions worked to form a double salt with Pd instead of the metal as expected.

I added my SMB dry, perhaps if I had dissolved it in a little HCl first I would have had better results. I also noticed I did not get any precipitate even after the SMB fully dissolved, until I added additional water.

More to come....

Steve

Apologises to resume an old thread but after days of searching and coming up with unrelated or catalyst-about documents I felt not having much choice. I'm looking for the same literature, lazersteve could you point me to the right direction?
I'm trying to separate silver from palladium using SO2 to drop palladium and cementing silver with zinc or copper as already posted in the petrol gauge thread.

 

[necromancer]

you "may" find something here to help ??

http://goldrefiningforum.com/~goldrefi/phpBB3/viewtopic.php?f=51&t=18564

 

[MarcoP]

you "may" find something here to help ??

http://goldrefiningforum.com/~goldrefi/phpBB3/viewtopic.php?f=51&t=18564

That's the same topic where I learned about it, if you look up the petrol gauge thread, http://goldrefiningforum.com/phpBB3/viewtopic.php?f=34&t=20886&p=225959#p225959 , you'll understand why I still needing to learn about the subject.
Thanks if I didn't know about that thread it would surely helped to get started.

 

[necromancer]

you "may" find something here to help ??

http://goldrefiningforum.com/~goldrefi/phpBB3/viewtopic.php?f=51&t=18564

That's the same topic where I learned about it, if you look up the petrol gauge thread, http://goldrefiningforum.com/phpBB3/viewtopic.php?f=34&t=20886&p=225959#p225959 , you'll understand why I still needing to learn about the subject.
Thanks if I didn't know about that thread it would surely helped to get started.

yes, read them both, the link offered was a guess. maybe if you don't get a answer in a few days you can start a new thread on the subject :?:

 

[MarcoP]

Sure I could, on the mean time I get the right glassware and keep searching.

 

[kurtak]

Apologises to resume an old thread but after days of searching and coming up with unrelated or catalyst-about documents I felt not having much choice. I'm looking for the same literature, lazersteve could you point me to the right direction?
I'm trying to separate silver from palladium using SO2 to drop palladium and cementing silver with zinc or copper as already posted in the petrol gauge thread.

Marco

Due to the silver in the nitrate you will need to use DMG to "first" drop out your Pd

The problem being (at least as I understand it from the research I have done) is that I order to drop Pd from a nitrate solution (with other then DMG) is that you need to change the PH of the solution from acidic to very near neutral before the PD will drop out --- so the problem is that in adjusting the solution from acidic to near neutral you will drop the silver out as a complex of silver (not elemental silver)

Edit to add ; - in other words - as long as the nitrate solution is acidic the Pd will just go back into solution as fast as it tries to precipitate with reagents other then DMG

Edit to add ; - Chloride (acidic) solutions are another story - which is why SO2 will precip Pd (at least in part) from an AR solution

Kurt

 

[MarcoP]

Thanks Kurt for the clarification. I just wanted to avoid the silver chloride route and the use of ammonia but it seems the there is no other easy way around.

As learned, DMG is a scavenger and should not be used to recover palladium, but instead it should be used to test the presence or precipitate traces of palladium. Here I'm only trying to follow the best practices possible, most of the times reading all different methods can easily get someone confused.

So unless I use silver metal to cement palladium with heat, time, stirring and patient (IF it will ever work due the tiny electronegativity difference of 0.3) ...I have to go the silver chloride method and cement palladium on zinc/copper.
Anyway I'll keep searching about this argument before going ahead.

 

[solar_plasma]

so the problem is that in adjusting the solution from acidic to near neutral you will drop the silver out as a complex of silver (not elemental silver)

Wouldn't the precipitation of AgOH start at a pH of 8,3? Even though I learned that the pH range of hydroxide precipitation might be influenced by a lot of variables and is one of the poorest ways to part different metals, 8,3 seems to be far enough from acidic to near neutral and the only thing needed is, that the silver won't precipitate. Though I wouldn't bet my ... and choose the safest way with known results.

 

[kurtak]

so the problem is that in adjusting the solution from acidic to near neutral you will drop the silver out as a complex of silver (not elemental silver)

Wouldn't the precipitation of AgOH start at a pH of 8,3? Even though I learned that the pH range of hydroxide precipitation might be influenced by a lot of variables and is one of the poorest ways to part different metals, 8,3 seems to be far enough from acidic to near neutral and the only thing needed is, that the silver won't precipitate. Though I wouldn't bet my ... and choose the safest way with known results.

Solar

here is a picture of some silver precipitated by NaOH with the PH adjusted to near neutral (with NaOH) but still acidic

My 2 to 10 PH paper (sitting on top of the beaker) is telling me the PH is between 4 & 6

so I used a piece of my 5.5 to 8.0 range paper (sitting by beaker) & its telling me more like 6.2 maybe 6.4

The silver nitrate came from dissolving Ag crystals from my silver cell to make more electrolyte - when I dissolved the silver it was of course 50/50 nitric/water - not all the silver dissolved (which left some very fine silver sediment in the bottom of the beaker) so after I siphoned most the Ag nitrate for my electrolyte there was still some remaining in the beaker which was then diluted about another 50% when I washed the beaker walls down with my wash bottle - so it was normal 50/50 Ag nitrate diluted about another 50%

So at near neutral but still acidic the silver does precip - at least when NaOH is used to ajust the PH

Edit to say; - you have to look close to the left hand side the PH paper on top of the beaker to see the slight red (acidic) test of the 2 to 10 paper

 

[butcher]

Although metals do precipitate as hydroxides the range they do so can vary widely, it is not that they get to a certain pH and then just drop out of solution.

My guess here is when you bring the pH up closer to neutral (pH 6 to 7) some of the silver will precipitate as an hydroxide of silver, but much more when you get into the pH of around 9, all the way up to around pH 12 where the silver hydroxide will be the least soluble as a hydroxide.

 

[g_axelsson]

I haven't done any more experiments with precipitating Pd from nitric solution since that thread referenced above. I came to the conclusion that the precipitation was not good enough (but that could depend on pH) and going the silver chloride route was easiest. To put things in perspective, I'm not going to chase a few grams of a metal worth about 2.5% of palladium when I can recover that part later on from the wastes. My main focus is palladium and that is easiest to recover with zinc from the dilute solution after precipitating the silver with chloride and denoxing the palladium solution (evaporation to get rid of excess acid once and acidifying it with dilute HCl).
This process suits me well and that is what I'm going to use next time.

For treatment of silver chloride I usually treat it with NaOH to turn it into oxide / hydroxide, then dissolving it in nitric acid and cementing it with copper. Any leftovers of silver chloride is caught in filters and ends up in my burn pile for later processing.

Göran