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[kjavanb123]

Thanks Kjavan.
Interesting that this method hasn't been covered more.
How are the losses comparing to the Lye Sugar or Iron Sulphuric method?

Hi

As long as zinc is mixed well with silver chloride then losses should be zero.

Best
KJ

 

[Yggdrasil]

Dave:
I have to admit, that I did not search for the method specifically.
One of the reasons for that is the I didn't even know it existed.
Hence my comment:

Interesting that this method hasn't been covered more.

But then again on "all" discussions here on the forum, the options outlined has almost all been: Lye-Sugar, Iron-Sulphuric or direct smelting.
And the first page of the 400 results has either nothing to do with AgCl or points to this thread, so even if the results are plentyful they don't necesssary produce anything meaningfull, unless you know what you are looking for in the first place.
So I'm still curious why, is it cost or something else?

Kjavan:
The DMG process for Pd is that as useful for Chlorides as well as Nitrates?

 

[kjavanb123]

Kjavan:
The DMG process for Pd is that as useful for Chlorides as well as Nitrates?

Hi

I dont understand your question, please elaborate.

Regards
KJ

 

[Yggdrasil]

You use it for Palladim nitrate, will it be as effective if you have Palladium Chloride?

 

[kjavanb123]

You use it for Palladim nitrate, will it be as effective if you have Palladium Chloride?

Yes DMG solution will percipitate Pd as yellow DMG salt from nitrate as well as chlroide solutions at ph 1-2.

But due to its high prices, it is usually used for analytical purposes.

Regards
KJ

 

[Yggdrasil]

Thanks for the information.

 

[anachronism]

Sodium Formate is also really good for precipitating Pd. As is Ascorbic acid.

Then again as you pointed out Ygg- since it's not "covered and established" some people consider it not worthy of discussion because they would rather discuss the established methods they used to use "back in the day" when were actually refining. Basically because they don't understand the newer methods having no experience of them.

Kevin

Good call on the Zinc. I've not tried it but heck I am going to give it a go. What's the worst that could happen.... :lol: :lol:

Thanks

Jon

 

[Yggdrasil]

I hadn't heard about the Sodium Formate path.
There was a procedure where the PGM salts were boiled in formic acid instead of calcining.
I really can't remeber just where I saw it at the moment.
This is a simplified way of the same?

I remember asking a general question to the forum a few years back, about methods of precipitating PMs,
I think that one boiled down and faded out ;-)

 

[anachronism]

Sodium Formate in water produces Formic acid with a pH of around 3.75 and shares similarities in the chemistry with that of metallic cyanides insofar as the pH determines the content of the ions in the water.

If you raise the pH to 6 then the amount of Formate ions as opposed to Formic acid increases dramatically.

The same analogy applies with metallic Cyanides because at pH7 most of the free cyanide is present as HCN in solution whereas at pH 11 most of the free cyanide is present as CN- (Hence why a higher pH provides a lot more safety)

You can drop out PGMs with a pH 3.75 solution of formic acid but it works much more rapidly at pH 6 as the concentration of Formate present is far higher. The Formate is the active ingredient.

I'm sure Lou will correct my Chemistry if I have missed something important (or completely fluffed it) but that is my layman's understanding of the situation.

Jon

 

[Yggdrasil]

Thaks again my friend!
Spoken so a noob can understand it
My regular supplier don't have it though, Formic acid on the other hand is easy.
Well I'll cross that bridge if I need to, somwhere down the road :wink:

 

[Lou]

Sodium Formate in water produces Formic acid with a pH of around 3.75 and shares similarities in the chemistry with that of metallic cyanides insofar as the pH determines the content of the ions in the water.

If you raise the pH to 6 then the amount of Formate ions as opposed to Formic acid increases dramatically.

The same analogy applies with metallic Cyanides because at pH7 most of the free cyanide is present as HCN in solution whereas at pH 11 most of the free cyanide is present as CN- (Hence why a higher pH provides a lot more safety)

You can drop out PGMs with a pH 3.75 solution of formic acid but it works much more rapidly at pH 6 as the concentration of Formate present is far higher. The Formate is the active ingredient.

I'm sure Lou will correct my Chemistry if I have missed something important (or completely fluffed it) but that is my layman's understanding of the situation.

Jon

This is true, but in many cases, it is best to have a slow release of the formate ions, if you wish to have the highest quality metal product that filters, rinses and assays the best.

OFten times it is best to boil the Pd (or even Pt/Rh) with formic acid and urea (which slowly hydrolyzes to NH3/CO2) and makes a buffered ammonium - formate reduction medium. This produces compact, granular metal products of higher purity.

For most people's purposes, just using sodium formate, which is actually a basic salt and getting the pH in the 4-6 range will be sufficient.

 

[anachronism]

Thanks

In all fairness I only started learning about this thanks to a video by Owltech where he was taking a silver Nitrate/Pd Nitrate solution to pH6, hydrating the Pd Nitrate which dropped as solid. Then filtering and leaving behind pure Silver Nitrate solution. Then converting the remaining solid to Pd Chloride solution whilst leaving the remaining Silver behind in the filter as Silver Chloride (not a lot.)

Then using a pH 6 with formic Acid and heat to drop the Pd.

It turns out that it's easier to get Sodium Formate over here than Formic acid and I just started reading around the topic and voila the chemistry is there.

 

[Lou]

That hydrolytic procedure is a common one, especially with cleaning up cell electrolyte. It can be operated in reverse of course, precipitating AgCl, filtering, and then forming the hydrous oxide before redissolving in sulfuric, fuming, forming the Pd sulfito complex and decomposing in sulfuric to Pd metal.

Also bear in mind that UHP silver nitrate is made by using a small amount of formate to free it of PGM. Pd usually comes down first at low pH.

Keep in mind you can make formic in situ with the addition of a stronger acid (it is itself a weakly basic salt).

One thing to point out is formic and its salts on heating with strong acids, particularly sulfuric, release carbon monoxide! Have a care and make sure to check the hood draft and put a detector!

All in all, much safer than hydrazine. Slower but safer.

 

[rickbb]

Good call on the Zinc. I've not tried it but heck I am going to give it a go. What's the worst that could happen.... :lol: :lol:

Actually using zinc powder was one of the very first methods to recover silver. 100's of years old.

It was first used on depleted photo fixers. Adding zinc powder up to 10% over the expected yield will drop mostly pure silver. IF done correctly, not correctly and you have excess zinc in your silver drop.

When continuous electrolytic recovery units were developed it put the zinc powder method out to pasture. The yield in purity and savings in HCL costs plus all that washing labor and disposal of zinc chloride waste made it a no brainer.

On small scale it's probably a good method to use. But, I'll still use the sugar lye method, I'm used to it and does not leave a metal in an acid solution to drop and dispose of.

 

[anachronism]

I put my money where my mouth is and tried a batch of MLCC that I know to have a yield of 5.57% Pd.

I want to say firstly that I have done this as a one off to learn and understand the process as I am not wanting to deal with PGM however I felt it was a lacking my my knowledge base but it allowed me to learn new processes and precipitation with sodium Formate which in fact has a lot of other uses including denoxxing.

I also liked the fact that it involves full conversion of the salts to metals within one container. Naturally I used my fume cabinet and full PPE but here is the Palladium metal in the filter (130mm filter) and the waste solution after conversion and settling.

Excuse the piece of detritus on the Pd- that's been removed 8) 8)

 

[anachronism]

The Pd precipitated is extremely fine. Can anyone suggest whether Citric acid would be a good flocculant for Pd particles?

Jon

 

[Lou]

I would not say citric would work. Usually more boiling is indicated.

 

[anachronism]

I would not say citric would work. Usually more boiling is indicated.

Gotcha- will give that a go.

 

[kurtak]

VERY nice Jon

Kurt

 

[anachronism]

Thanks Kurt

One point to note.

I know we spend a lot of time saying that XRF readings cannot be relied upon in many circumstances. I XRFed the raw MLCC and it came back with 5.55% this is why I sent a sample for assay. I simply didn't believe the result.

The result came back near as dammit the same.