palladium from nitrate solution

[necromancer]

now that's fast refining :shock: wonder what's in that guys under pants after taking off that fast.

 

[Marcel]

Just for the completeness, silver oxide can be reduced with H2O2, too.

Here is one link for those who are interested: EDIT: and to those, who do not read the answers below: Lou says, don't use this, because of possible steam explosions

http://goldrefiningforum.com/~goldrefi/phpBB3/viewtopic.php?f=50&t=19249

I tried it once with a few gramm, but sugar is cheaper to me. For many it is getting harder to buy H2O2.

Silver oxide will be reduced to silver simply by applying heat (+100°C). Did that the other day, worked like a charm.

Now it seems, that the photos are in the wrong order... :|

 

[Research135]

Hello all:
What alternatives are there to recover pure/impure platinum from nitrate solutions (palladium, platinum, silver, copper, nickel, zinc, traces of others), before recovering silver?. Order of metals given, approximate net values in $). Thanks.

 

[FrugalRefiner]

Welcome to the forum.

Hoke provides some guidance in her book. You'll find links to it in my signature line below.

Dave

 

[Research135]

Welcome to the forum.

Hoke provides some guidance in her book. You'll find links to it in my signature line below.

Dave

Thanks Dave.
I wish to completely avoid the silver chloride route.
I can get the palladium with DMG.
Maybe I can drop the silver as silver oxide, and then go for the platinum?. That would work.

Is there another way to get the platinum out from solution quantitatively, before the silver?

 

[Lou]

Resin.

 

[Research135]

Resin.

Thanks sir. Would you please ellaborate or post a link to that procedure?

Would sodium formate precipitate platinum selectively, or would the silver come down at the same time?.

Thanks in advance.

 

[Lou]

Silver will come down.


Probably easiest for you is to bring the pH up to 6.5, collect the Pd precipitate, rinse well with DI, acidify with HCl and then separate the Pd from silver chloride by rinsing with 2% w/v HCl solution until no more yellow rinses from the chloride filter cake.
Then you can cement it and save it until you have a few ounces worth to process.

 

[g_axelsson]

If you try to collect Pd at lower pH, will that break down the precipitate and oxidize the DMG?

At least that is what I suspect my first trial with DMG resulted in... The precipitate started to float and in a short while it dissolved again.



Göran

 

[Lou]

Assuredly so, Goran.

DMG really works best in solutions that are 0.5 M-3M in acid, preferably either nitric or in hydrochloric. DMG-Pd complex will dissolve in aqua regia or in HCl/Cl2.

Lou

 

[Research135]

Thanks for all the suggestions, but as I mentioned, I do not want to deal with silver chloride.

Is there a solvent selective for Pt(II) (preferred) or for Ag(I) (second choice) that will work with nitrate/nitric solutions?

 

[Lou]

Do you need to remove platinum (II) or palladium (II)?

Generally speaking, Pd is done with sulfides from chloride milieu, as nitrates will oxidize the s/x extraction agent so that's out.

What's the solution composition in g/L of these elements (inclusive of base metals)?

 

[Research135]

Original question:

Hello all:
What alternatives are there to recover pure/impure platinum from nitrate solutions (palladium, platinum, silver, copper, nickel, zinc, traces of others), before recovering silver?. Order of metals given, approximate net values in $). Thanks.

The solution is about 87% silver nitrate, 1.5% platinum nitrate, 0.5-4% palladium nitrate, balance other metals mainly copper.

g/L will depend on the dilution/concentration. I try to keep water to a minimum.

Thanks.

edit: both platinum and palladium are valence +2, I believe, in this case.

 

[g_axelsson]

I'm no expert as I haven't done any solutions like this yet, but with those concentrations I would scavenge the Pd with DMG first, then cement silver and Pt with copper and run that through a silver cell to get pure silver out. Last I would treat the slime from the cell to get the platinum and refine it with standard methods when I got enough.

What I have read on the forum is that low level of platinum alloyed with silver could be dissolved with nitric acid. How about the anode slime? Is that fine enough to be dissolved in nitric alone or could the silver be dissolved with nitric while leaving most of the platinum undissolved?
Anyhow, the anode slime would contain a lot higher level of platinum than the original solution and platinum is a lot easier to work with when concentrated.

But my best advice is that when it comes to PGM:s Lou is the master here. If you follow his advice you can't go wrong. 8)

Göran

 

[Research135]

Thanks Göran. I will investigate the "resin" suggestion by Lou. The other processes suggested are too time consuming, except the DMG treatment for palladium which is fast and simple.

 

[Research135]

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.

Hello. Do you have a chart like this, that also includes gold and the PGMs?. Thanks.

 

[solar_plasma]

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.

Hello. Do you have a chart like this, that also includes gold and the PGMs?. Thanks.

Read once more, what Butcher has told: "the range they do so can vary widely". Even though you find some charts, they will only be true in an accurately similar setting regarding concentrations, pH, ORP, temperature, contaminants and interfering ions, complexing agents and other compounds.

Page 20, Eh-pH Diagrams will give you an impression of a few facettes. (Au, Pt, Pd and most other metals are also included, pages 32, 198, 190) The concentration in those diagrams is set to 10^-10 mole/kg or in my words: next to nothing. With concentrations of up to about 1 mole/kg things may be completely different.

If I find something closer to your case, I will post it here.

edit: german wikipedia (Hydroxide) tells that AgOH precipitates between pH 8,3-11,3. But as I said before, this can vary several pH'es up or down or becoming something completely different depending on the other influences, so you can't use this.

 

[butcher]

Many metals are also Amphoteric, they can preciipitate at one range of pH on the basic side and dissolve again as the solution becomes even more basic.
Separation of base metals using pH could be difficult at the very least least (depending on the metals involved) up to impossible as many of the metals overlap in their solubilitys at certain pH ranges.

 

[kurtak]

The resin Lou is taking about is on the order of this product :arrow: http://goldrefiningforum.com/phpBB3/viewtopic.php?f=84&t=16948

Also concerning PH adjustment :arrow: http://goldrefiningforum.com/phpBB3/viewtopic.php?f=51&t=9058&p=226093&hilit=palladium+nitrate#p226025 read from this post down the next 7 or 8 post

Kurt

 

[Research135]

The resin Lou is taking about is on the order of this product :arrow: http://goldrefiningforum.com/phpBB3/viewtopic.php?f=84&t=16948

Also concerning PH adjustment :arrow: http://goldrefiningforum.com/phpBB3/viewtopic.php?f=51&t=9058&p=226093&hilit=palladium+nitrate#p226025 read from this post down the next 7 or 8 post

Kurt

Thanks a lot to all.
edit to add:
I'm finding it hard to login to the forum. It looks like a problem on the forum's server side.

FWIW, and I'm not recommending the procedure to anyone, since it is tedious and difficult, and not quantitative in its separations, this is a brief summary of how we process it currently:

1-Work with very concentrated, hot solutions, with very little excess nitric acid to begin with.
2-Add DMG dissolved in concentrated KOH. We watch the pH to always stay below 7. We drip extra KOH, if needed, to bring pH to almost 7.
3-Filter the Pd-DMG precipitate. Washing precipitate with plain water.
4-Add nitric acid to the filtrate to pH 0-1.
5-We add K2SO4 to the solution, and keep the heat on till most of the Ag2SO4 crystallizes/precipitates.
6-Filter the Ag2SO4.
7-Bring pH to 6 again and add concentrated potassium formate to drop the platinum black. Filter.
8-Cement with Cu the nitrate solution, and then recycle the nitrates to make nitric acid again.

I was hoping there was a magic ingredient to drop the platinum quantitatively that worked on platinum like DMG works on palladium.

The resin route seems too involved and expensive for all but the largest operations. Or that's my uninformed opinion.