Recovering silver and palladium from MLCC:s

This is a description of how I'm doing silver and palladium recovery from MLCC:s. It is based on various procedures here on the forum, put together in a mix that suits me with the limitations I have in my access to chemicals and the fact that I can't incinerate without a whole lot of work.

As I like to do some experimenting myself and not just follow a receipt that wouldn't suit my situation, I have read a lot about palladium recovery and refining during the winter. Then I put together a procedure that should work for me, given my circumstances. It might differ from common procedure and I'm in the middle of testing it out, but so far so good...

I started with a batch of 145g mixed MLCC:s and I wanted to recover silver and palladium powder for later refining. This is the steps I took. I'm not in a hurry so I can do one step, put it away for a while and then continue weeks later if so. Most steps are not time critical and even benefits from being left alone for some time to let the chemicals react to the end.

Any solutions that were filtered off were checked for values before proper disposal. Any reaction that gives off fumes were done outside. Safety precaution should always be in place when working with strong acids and bases, the pictures are taken outside of the plastic bin I normally use as a catch basin.

1. Soak the MLCC:s in hydrochloric acid to remove tin, lead and other base metals. As I didn't heat it I just left it in acid for several days before switching to new acid. Stopped it when it seemed there were no more reaction. Eventually many of the MLCC:s breaks up into separate metallic foils but it can take a week or longer.
2. Wash and decant the broken down MLCC:s with water to get the chlorides and HCl out, quite some foils in it.
3. Add NaOH to transform any AgCl that formed in the HCl treatment into Ag₂O. I don't know if this is necessary or even works.
4. Wash and decant off the NaOH solution
5. Add nitric acid to dissolve the silver, silver oxide and palladium. Some chlorides will remain but they get locked up in silver chloride that forms.
6. Filter off the dissolved values. I decanted and filtered. It was apparent that there were some silver chloride in the reaction vessel as the filter clogged up with silver chloride that turned purple.
7. add NaCl solution to the filtered tea colored solution, it precipitates the silver as white silver chloride. Stop when additional NaCl doesn't make any precipitation.
8. Decant and filter off the palladium solution, I reused the filter from above as it caught all silver chloride. Multiple washes was used to get most of the palladium out from the silver chloride.
9. Treat the silver chloride with NaOH and sugar to get silver powder.
10. Add zinc shavings to the palladium solution to cement out the palladium.
11. Decant off the liquid from the cemented palladium and then wash it with HCl to remove excess zinc and eventual base metals that the zinc precipitated.
... collect, dry and weigh the result. The fluids goes to the proper stockpot and the metal powders are put into respective storage beaker with other powders awaiting final refining when I have enough to do it.

Right now I'm at step 9 and 10.

Some pictures....

Step 5, leaching palladium out of MLCC:s


Step 7, NaCl added and the silver chloride drops to the bottom. The palladium solution is coloring it yellow.


Step 8, decanting the palladium solution from the silver chloride. Pour along a glass rod for better control of the liquid.


Step 8, after two washes. There is still some palladium mixed in with the silver chloride but it is getting paler. I think I made five washes totally.
The minute amount of palladium I didn't wash out will follow the silver until it is separated in the silver cell I'm going to build some day.

Between step 8 and 10, the filtered palladium solution, free from silver.


(Continued below)

Step 10, added zinc turnings. It was like a palladium lava lamp, small bits bobbing up and down. As I had a density gradient from the different washes, many pieces jumped up half ways to the surface and got stuck in the middle, just hovering. 8)


Step 10, almost done now. Just a little more zinc to add.


As this is my first run, there are a lot of things I will improve for the second run, things to note.
- Crushing speeds up the leaching process quite a bit. Maybe I'll try that on the next batch.
- I used too little nitric at first so I'm leaching the solids again and by the color it looks like I'm getting as much palladium in the second leach as the first.
- I'll try to get proper filter paper and a vacuum filtration unit, that ought to speed up filtering and washing the silver chloride.
- My homemade filter holder (a bent copper wire) was attacked by the fumes from the acid and shed some copper scale that dropped in among the palladium. Better make one out of plastic.

Harold, I actually took up Hooks book yesterday and read everything about precipitating palladium from solutions. All involved one or another chloride compound so it wouldn't work with my silver and palladium nitrate solution until after getting the silver out first. I just prefer my solution, collecting cemented metals for the time being.

Comments?

Göran

from step 10; you could have added FeS04 to participate the Pd from the nitrate solution; and then you can refine it from their.

I haven't heard that copperas, FeSO₄, could precipitate palladium. On the contrary, copperas is used to precipitate gold from palladium containing liquids.

In http://goldrefiningforum.com/~goldrefi/phpBB3/viewtopic.php?f=37&t=1438

Harold_V said:

....
In your example, you'd have gold and palladium remaining to be recovered. Assuming you had a large percentage of gold, with a small amount of palladium, you'd selectively precipitate the gold, using one of many precipitants. I used SO2, and also copperas (ferrous sulfate). Each of them will precipitate only the gold, but you'd get considerable drag down of both palladium and copper, so the gold wouldn't end up pure, although very close.
....

Click to expand...

Do you have a reference of the contrary or is it that FeSO₄ could precipitate palladium from nitrate solutions?

By the way, in step 10 it isn't any longer a clean nitric solution, it is a weak aqua regia as I added an excess of NaCl to get the silver out of solution.

Göran

Found it!

http://www.goldrefiningforum.com/phpBB3/viewtopic.php?f=49&t=6026&p=87562#p87562

FeSO₄ is precipitating palladium from a nitric solution. So are SO₂ too, so SMB should also work.
If it works then I could drop the palladium first before going after the silver.

So.... after extracting and filtering the silver palladium leach from the MLCC:s I can do:
- Add SMB to drop palladium as metal
- Decant and filter
- add solid copper to extract silver and trace amounts of other precious metals

This is perfect, I don't have to mess around with silver chloride or palladium salts just to recover a concentrate.

Thanks!

Göran

I'm glad to help you out. I know that participating gold with SMB or Copperas in a chloride solution causes PGM's drag down. In a nitrate solution it can fully precipitate Pd.

The best way of recovery is to use efficient methods in recovering various metals;

You can crush the MLCC's which is time consuming but it will leach faster and have better yield results.

I first tend to use nitric 50/50 D. water to leach the base metals including Ag & Pd; after 2 or 3 leaches of fresh nitric solution; filter the solids out including the metastannic acid.

Drop out the Pd in the filtered nitrate solution with SMB or Copperas and; filter nitrate solution then recover the Ag with your preferred method.

Incinerate the solids including the metastannic acid; Then put the Incinerated solids in hot HCl; wash the solids a prepare boiling AR with a watch glass to leach Pt if it contains any.

After the recovery you can refine it or add it to your stock pot for later.

After stumbling upon this thread http://goldrefiningforum.com/~goldrefi/phpBB3/viewtopic.php?f=51&t=9058
I found out that upon addition of SMD in a Palladium nitrate solution it will participate a Complex Palladium salt; namely Na2Pd(SO3)2x2H2O. I guess you could try to participate metallic Palladium with copperas (in a Pd nitrate solution); maybe steve or freechemist has a input on this matter.

I wonder what the solubility of that salt is? I got a voluminous precipitate and a yellow salt crystallizing on the surface... and the solution still have some palladium nitrate judging from the color.

This is what I got when adding SMB to an acidic palladium and silver nitrate solution.

And this is the day after, it's compacted a bit.

I think I'll go back to my old way, this made a bigger mess than dealing with silver chloride. I know I will learn some new tricks recovering from this mess. :mrgreen:

What is the best way from here? Filtering off the precipitate and calcine it maybe?
I'll just treat the filtrate as before, creating silver chloride and get the silver from that, If there any values after that I'll just cement it with zinc.

Göran

I would say Keep adding SMB in small increments until no further participation.

filter the solution and rinse it with D.water; this salt is very insoluble and the water will only hold a very small amount of this salt. add the water you rinsed with to your stock pot. scavenge the remaining Pd with DMG from the primary nitrate solution.

after 3 hot D.water rinses with a gentle stir to insure proper washing of the salt.

freechemist's quote; "add excess aqueous ammonia, it dissolves giving a colorless solution, probably containing the complex cation [(NH3)4Pd]2+ and sulfite as anion. Boiling the salt in excess aqueous sulfuric acid - no halides, nor nitrates may be present! - it decomposes to metallic palladium, NaHSO4, SO2 and water."

Steve's qoute; "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."

I have presented 2 alternative methods that have been covered in the past.

If all fails; calcine and refine it from their.

and then you can start recovering the silver in the first nitrate solution.

Has anyone used FeSO4 "Copperas" to participate Pd metal from a nitrate solution?; it normally should not form a complex salt; since their is no possibility for a double displacement.

upon the addition of FeSO4 to a Palladium nitrate solution; Palladium precipitates (edit) as a metal or as a sulfate salt (PdSO4) .

9kuuby9 said:

participated .

Click to expand...

par·tic·i·pate (pär-ts-pt)
v. par·tic·i·pat·ed, par·tic·i·pat·ing, par·tic·i·pates
v.intr.
1. To take part in something: participated in the festivities.
2. To share in something: If only I could participate in your good fortune.
v.tr. Archaic
To partake of.
[Latin participre, participt-, from particeps, particip-, partaker : pars, part-, part; see part + capere, to take; see kap- in Indo-European roots.]
par·tici·pative adj.
par·tici·pator n.

:lol:

scm

squarecoinman said:

9kuuby9 said:

participated .

Click to expand...

par·tic·i·pate (pär-ts-pt)
v. par·tic·i·pat·ed, par·tic·i·pat·ing, par·tic·i·pates
v.intr.
1. To take part in something: participated in the festivities.
2. To share in something: If only I could participate in your good fortune.
v.tr. Archaic
To partake of.
[Latin participre, participt-, from particeps, particip-, partaker : pars, part-, part; see part + capere, to take; see kap- in Indo-European roots.]
par·tici·pative adj.
par·tici·pator n.

:lol:

scm

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oh I made a catastrophic error! :mrgreen:

If you precipitate something it isn't participating any longer. :lol:

I had to go on a business trip for a couple of days so the yellow palladium salt was left standing. During the week it compacted even more, forming a cake at the bottom and the yellow complex salt also made a crust on the inside of my beaker. The cake at the bottom seems to break down to a dark brown mud that doesn't dissolve in water but easily filters off. The crust I broke down with a glass rod and collected in the bottom of the beaker with the help of a spray bottle. Storing that for later processing.
To the rest of the now clear yellow solution containing silver nitrate and dissolved palladium salt I added zinc, taking everything back to metal and then I will wash it and dissolve it again in nitric and treat it as the first batch.

For future reference I add a link to the post where Freechemist gives a way to get palladium from the complex salt.
http://goldrefiningforum.com/~goldrefi/phpBB3/viewtopic.php?f=51&t=9058#p87626
I will try that when I have a possibility to boil sulfuric acid.

I wish I had done some more research before doing this procedure, then I could have avoided this mess. I feel just like a noob right now. :mrgreen:
... I'm taking the scenic route to palladium.

Göran

Good observation Göran; "Good judgment comes from experience, and a lot of that comes from bad judgment."

I will try to use Copperas to precipitate Pd from a nitrate solution and see how it goes

It all sounds a bit complicated to me.
As it has been said, finechrush the material first, then your results will be better. I use a large hammer and a steel pot for that.
Add HCL to remove BMs.
From there dissolve either with HCl+Cl or HAP (hot AP).
Drop Pd with copper.
Treat the remaining solids with nitric. Let it soak for a long time (f.i. 1week), because the fine powder needs very long to fully dissolve the PMs.

well I use a iron pestle and mortar; but frankly it's really slow.

I can imagine if you work with a steel pot and a hammer that a lot off MLLC's start flying around when you are crushing them. and also use a breathing mask while doing so; because they release a very fine dust.

Maybe some has found a more efficient way of crushing MLCC's?

I thought of a cheap little kitchen grinder for 10€ from Kloppenburg. Anyone who knows how long this will be durable to the hard ceramics? I think someone of you talked about that, was it you, Marcel?

solar_plasma said:

I thought of a cheap little kitchen grinder for 10€ from Kloppenburg. Anyone who knows how long this will be durable to the hard ceramics? I think someone of you talked about that, was it you, Marcel?

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maybe 15min. of continuous grinding? ; they are made from ceramics and Zirconium dioxide so thin metal blades wear off pretty fast...

Something like this would normally work fine;http://www.benl.ebay.be/itm/110998457104?ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2649

I don't know if they sell them in Germany? but these are made by a hobbys't in the US; so normally they are not sold.

Some pieces of iron or SS and a welder would accomplish it.

solar_plasma said:

I thought of a cheap little kitchen grinder for 10€ from Kloppenburg. Anyone who knows how long this will be durable to the hard ceramics? I think someone of you talked about that, was it you, Marcel?

Click to expand...

I've tried to use a blender from the thrift store lasted about 200g then the blades were worn down. mortar is really hard too. I think a hammer mill or ball mill would work the best.

Eric

This never failed me. (your hands can but recovery is fast)