processing MLCC's - grey sludge

[alvaschein]

I guess I got it!
I cemented as mentioned before, filtered and dryed the black sludge. After this I added HCl to remove eventually remaining Zn. And ... yes ... in my 18 mm diameter testing tube I have now an 8 mm thick black layer of undissolved black powder. I think this is now the Pd (?).

Roy

 

[alvaschein]

Finally I got the Pd Black.
I took three very small sample and tried to dissolve them in hydrochloric acid, sulphuric acid and nitric acid. It only dissolved in nitric acid. The following test of this solution was Pd positive!

Well, yes, what a work. I have to go over the whole process again to see where is the most probable source of errors.

The yield was 0.2 g (mpfff, sorry had to hold my laughter). But anyway, it was fun.

Silver I didn't find, maybe I threw it away in the inicial steps, but plenty of metastannic acid - the ominous gray sludge that looked like jelly after having passed it through a centrifuge.

Roy

 

[Marcel]

This may be a bit off topic but the MLCC leaching is not an optimal way. You simply have to redo it many many times to be sure that you have not left anything behind.
I took a very old beaker with dried-in remains from several leaches and thought: "Hey let´s give it another try!"
Added plain water(!) to the dried-in solids and let it stand for a month.
After that I received an canary orange solution Pd positive and precipitated another 1.2 g of Pd. As I said, these were old wrenched out solids from leaching!
After that I took the dried remains added 1:1 borax and directly hit it with the torch.
At first there was noting spectacular happening, but under the scope I was able to see tiny silverish balls.
So I dissolved all in 5% sufuric acid, let it stand for some days and received a mass of tiny metal balls.
I put them under my torch again and out came 20g of Pd! ( I suppose mixed with some Au as well, but most must be Pd because I cannot even melt this button with my oxy torch.

I am telling this longwinded story just to say that leaching is not very effective - at least for me. I used hot HCl, dilute and 53% nitric, hot AP and what else to squeeze out the last drop of the 1 Kg MLCCs.
I think the problem is the decanting in this process. You never get all dissolved liquid out like that and you have to rinse with a lot of water.
Better try to use some funnel construction, where the liquid will leave downwards and you add water from top to wash the solids and the salts off.
Before, I ran into this "Hey! What is this sludge?" as well. I is most likely silverchloride mixed with fine Pd powder and some other useless ceramic stuff. But it is the wrong approach to try to get this fine sediment from the bottom to the top. Instead wash it out downwards. Just my two cents.

Ok, this is not state of the art recovery. I should have dissolved and precipitated the sludge instead of going this straight way. But I did this before and I spend a lot of chemicals, water, time and energy to get my first 9gs, then I found more than 20g in this damned sludge!
Since I had treated the solids so many times, there were no base metals left anymore, so I gave this way a try.
Maybe there is even other PMs involded than Pd because this sponge nugget will not melt with my oxy torch. But at least I got them all!

Looking for a buyer for my nugget btw....

 

[solar_plasma]

@Marcel

Very interesting post, Marcel! How much Pd did you get overall from 1kg?

 

[Marcel]

29.68g unrefined Pd from 1.25 Kg MLCCs.

 

[alvaschein]

Hi Marcel

Interesting post. But reading and re-reading I couldn't find the fil-rouge of your MLCC recovering process. It's not a critique but I would like to learn how the steps were (maybe others too).
When I was looking on my 0.2 g Pd out of 50 g MLCC's (yield 0.4%) I had to laugh considering the work I had to recover. Comparing to your 29.68 g Pd (yield 2.37%) I feel ashamed .
No a few questions to you:
- Would you be so glad to post step by step how your recovering process was?
- Did you you use a batch of mixed or equal size MLCC's?
- Did you crush the MLCC's before processing them?

Thanks in advance

Roy

 

[lysdexic]

Hi Marcel (Thank you one and all for this post, I'm sponging up information and trying to keep the cotton out of my ears and in my mouth)

I have been searching for info on the MLCC's and resisters and gathered tons of info on what to look for, but I'm only at a gathering and reading stage. I would like to ask something though and I HAVE NOT searched it. It's a safety question and not for my benefit so I hope it's okay. ...anyway:

Marcel was that red hot metal on a cement floor in the picture you posted? I'm sure it's common knowledge and the quantities are not large enough to make it a big risk but I feel I should share just in case anyone doesn't know and ends up in a sketchy situation. It's standard practice for those working with molten metals to work over a bed of sand. Concrete traps moisture and if the metal is hot enough or the charge of significant size it can vaporize the water which has no escape route so it makes one taking concrete with it. Even if there isn't enough heat for that to happen if working with any sizable charge of metal, crucible failure can be devastating. Sand is porous so explosion danger is minimized and splatter from crucible failure is also much less likely (and your metal will be easier to find).

Again sorry I hope everyone understands my reason.

Doug aka Dex

 

[au-artifax]

Can you tell us exactly what steps you took in processing the MLCC's ?

that would really help in finding the cause.

The steps:
1. weighed batch of 50 g assorted MLCC's (dimensions +/- 0.8 x 0.8 x 2.0 mm)
2. put batch in beaker and added 320 ml HCl (that means 250 ml as 5 times the batch's weight plus 70 ml to compensate the difference of my 25% HCl to 32% HCl as described in the process)
3. let it boil for about 4-5 hours
4. let it settle over night
5. solution was divided into 3 sections (top down): purple solution (2" thick), grey sludge (0.5"-0.75" thick), metallic traces (visible only from the bottom view)
6. poured off only the purple solution, kept sludge and metals
7. added diluted aqua regia
8. let it boil for 3-4 hours
9. let it cool and settle over night
10. the solution was divided into two sections (top down): clear orange solution (2.5" thick), white(?) sludge (0.5" thick)
11. filtered solution
12. tested remainder for Ag --> negative --> to the waste
13. tested solution for Pd --> positive
14. added Zn to solution for cementing Pd

These were all the steps I took, ending up with this mysterious grey sludge...

Roy

? No filtering and rinsing after pouring off purple solution?! You still have waaay too much garbage in your mix to be throwing in the AR.

 

[necromancer]

great posts, but i am still trying to figure it out, any help would be great

please reply here:

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=49&t=20518&p=211572#p211572

thank you very much, i have another 2 KG to recover after i figure this out

 

[saadat68]

Hi I have 2 questions
In Sam's method we get all (or most) of silvers in precipitate in initial AR digestion
Can we refine silver with this process?
1- Wash all precipitate in first and second AR digestion with water
2- Add dilute sulfuric acid and some iron nails to precipitate and convert silver chloride to silver
3- incinerate them for rid of HCl and Cl and then digest them in nitric acid
4- cement silver with copper

----------------
In another method from goldrefiningwiki.com we have:

Washing in hydrochloric acid to remove the tin. Prolonged treatment could dissolve the ceramics too, freeing the internal metal electrodes.
Wash in water and then crush the ceramics to access the internal metal.
Dissolve silver, nickel and palladium with nitric acid.

How much time needed for socking MLCCs in HCl to remove tin ?
(I want to remove tin without breaking ceramics with HCl and produce AgCl)

 

[g_axelsson]

Just add acid and watch the reaction until it is finished. There is no fixed time, there are so many factors affecting the speed of a reaction. Heat, concentration, agitation, material, volumes.... who could tell.

Göran

 

[saadat68]

Just add acid and watch the reaction until it is finished. There is no fixed time, there are so many factors affecting the speed of a reaction. Heat, concentration, agitation, material, volumes.... who could tell.

Göran

Thanks
So one or two hours is enough.
Not several days
Right?
__________________

How much time and temperature needed for incineration to rid of HCl ?

 

[saadat68]

Just add acid and watch the reaction until it is finished. There is no fixed time, there are so many factors affecting the speed of a reaction. Heat, concentration, agitation, material, volumes.... who could tell.

Göran

Thanks
So one or two hours is enough.
Not several days
Right?
__________________

How much time and temperature needed for incineration to rid of HCl ?

I test it
I think maximum 5 hour is enough to remove tin without breaking mlccs

 

[saadat68]

Is palladium refining from MLCCs and chips dangerous like Pt ?
Do I must stay away from it ? Many of E-scraps have palladium!

If I drop palladium with DMG or cementation, Is it completely safe ? Even in chloride solution ?

 

[Raza shahid]

Hi gyz i am new here i am tryng to get pd salt from mlcc and follow gold n scarpe tutotial when i precipitate black pgm by putting zn or Al, but when i sm tryng to disolve tht pgm black powder in aquaregia it did not dissolve completely i heated 2 hours but blck powder still un disolve, any one can help me please, discribe the right way to dissolve