Borax and Cryolite flux for MLCC's the best?

[924T]

In several different GRF threads that discuss smelting ceramic substrates (MLCC's, catalytic converters),
it was emphasized that chemical leaching would not achieve the same percentage of recovery of PGM's as smelting.

The 2 main ingredients for a flux for smelting MLCC's seem to be Borax and Cryolite, with Silver as the collector.

Will Borax and Cryolite alone (with Ag as collector) get the job done, and if so, what ratio of one to the other should I use?

Also, I've seen negatives about Carbon contaminating Pd, so wouldn't a graphite crucible be all wrong for
smelting MLCC's?

Wouldn't molten Cryolite attack a graphite crucible?

Thanks for any commentary/help on this, as I really do want to get the processes correct for pursuing Pd in MLCC's,
and it's appearing that smelting and then leaching is the optimum route to take.

Cheers,

Mike

 

[samuel-a]

Mike,

I have smelted a friend's MLCC's about a year and a half ego.. Since i couldn't find any reference in the literature, i came up with the following flux recepie:
The flux used was premixed 9:1 Borx(dec):fluorspar. The ratio of flux to mlcc's was 1:1.

The MLCC's were not crushed. I have placed the MLCC's in a graphite crucible and brought the gas furnace to about 800-900C. At this point the flux was slowly added via a makeshift auger until all of the calculated amount was added.
Using a steel rebar with a weldded half moon; 30-40 minuted later the flux would still be quite fluid and no capacitors had been felt on the bottom.
When done, the slag and metal was poured into an angle bar mold, welded shut on both ends. (see pic)

There's no need to use collector this way, there's enough metal already.
keep note, that this flux is highly acidic and react violantly with the ceramic substrate, so the first additions are done slowly.
The resulting rods were sent to Metalor for further refining.



Good luck

 

[924T]

samuel-a,

That's exactly what I was looking for----thanks for weighing in with a fast response!

Were you using actual Fluorspar from Iceland?

Your post is the first I've heard or seen of an 'angle mold' (thanks for taking the time and trouble to put
your picture in your post----this is a case of a picture is worth more than 1,000 words).

It looks substantially more cost effective than a cast iron 'cone' mold. Do you preheat the angle mold prior
to performing a pour, as you would have to with a graphite mold?

Cheers,

Mike

 

[samuel-a]

Yes, a picture in this case is indeed far better than i could have explained it.
I was looking for proper cone mold but were very expensive so i have to improvise. I too never seen this anywhere else.

The mold was seasoned with a layer of soot from a torch and pre-heated prior to pouring.

I have no idea where did the Fluorspar came from.

One more note to the process, once the first few additions of flux are done, the temp' was lifted and maintained at 1200C +- for 30-40 minutes.

After visual inspection of broken slag pieces, the slag should not hold any metal beads, or at least small amount of beads near where the metal button/rod.

There's a reason why you never seen this info before and I have kept this process to my self for too long. Hope you and others could make good use of it.

 

[kjavanb123]

Hi Samuel,

Please advise if the same flux formula can be used to extract metals from incinerated ashes??

Thanks
Kevin

 

[924T]

Sam,

I'm extremely grateful you not only took the time and trouble to respond to my post, but were generous enough
to share what turns out to be several innovations you came up with!

I had been gritting my teeth about having to drop $200 or more for a cone mold; I am definitely going to be
talking with a buddy of mine that welds, and try to duplicate your angle molds.

How did you go about calculating the size of your angle molds before you made them? That in itself is a bit
of a story within the story.

Do you mind sharing the dimensions of your angle molds? And what/how you preheat them?

Also, it's like you're reading my mind------I got on the forum tonight with the purpose of asking you
if you preheated the angle molds, and if you used any coating or release chemical-----and your answer
was already there! That's the kind of stuff that just keeps me pumped up about the GRF----innovation
everywhere, and experienced people that are willing to help the less experienced members out.

My pursuit of MLCC's has gotten me over the hump of not having a defined sense of purpose regarding the pursuit of
precious metals----I ordered in (and just received a few days ago) Hoke's book-----it's time for me to get serious about having some (safe) fun with all this, and the only way to be safe is to become informed, and then get some experience. I'm on page 25 now, having only scratched the surface of all that content.

I have 10 kg of MLCC's (no resistors in with them) waiting for me to get all the right glassware and chemicals in, and now, also, to get a Kerr MaxiMelt in. My plan is to experiment by running the process you've shown in your videos, lazersteve's
process, and now to also smelt and run the resulting rods through your and lazersteves's processes, and note
as many details as possible along the way, and then compare final results at the end (running 1 kg each time).
Fortunately, I have just enough MLCC's that if I really screw things up, I can get advice and analysis here on the GRF,
and then run the experiments a second time.

Cheers,

Mike

 

[samuel-a]

Dear Mike,

Sorry for the very late reply..... my time is extremely limited lately.
I'm glad i could help.

As for the mold, don't bother yourself with the size and volume, it really doesn't matter. Just produce the largest your work bench and budget allows you to. It will pay off one day.
Make sure wall thickness will not be thinner than 1/8", other wise you risk piercing it.

Do note, seperating Bi and Sb from Pd is no easy task.

Good luck.

Sam

 

[necromancer]

GNS - e-scrap yield list v1.0 (link fixed)

file not found, i think i have asked about this in another post a long while ago, thanks samuel-a

 

[samuel-a]

try now

 

[4metals]

I always liked to add soda ash as well. I noticed Samuels formula listed borax as (dec) is that in reference to decahydrate? I always used anhydrous borax as it does not foam up.

I liked 2 parts borax, 1 part soda ash and 1/4 part fluorspar. Equal volume to what you are melting.

And yes it does eat crucibles.

I always preferred to grind the ceramic to a powder before melting so it mixes better and reacts faster. Less melt time equals less attack on the crucibles.

I would try without any collector first, see what size bar you can get, then do a re-melt of the slags using a flux of 1 part borax, 1 part soda ash and 1/8 part fluorspar. You can add some silver to this to see if you pick up any more values by using a collector, I never needed a collector.

But remelting the slags even without a collector is common, collects the loose beads.

 

[Irons]

It took me a while to find a good source of Cryolite. It turns out that Cryolite is used in some ceramic glazes. It was a pure white powder, not the dirty natural material. Good stuff. Check with your local ceramics supply house.

 

[4metals]

source of cryolite

http://www.washingtonmills.com/products/cryolite/

 

[Irons]

source of cryolite

http://www.washingtonmills.com/products/cryolite/

Sheffield Pottery http://www.sheffield-pottery.com

..has 5 pounds of Cryolite for 12 DollarsUS.

 

[4metals]

Sorry, I got carried away, Washington Mills only sells 50 pound bags.

Remember, even 12 pounds is enough to eat crucibles quickly, be conservative.

 

[924T]

Irons and 4metals,

I was going to inquire as to the appetite of Cryolite for Graphite, and you were way ahead of me!

Lmine has a 50 lb. bag of Cryolite for $58.99 http://www.lmine.com/category/flux_components.html,
but I don't know if it's the natural stuff or the white kind.

I'll definitely be starting out with a smaller quantity, like the 5 lbs. Irons mentioned.

I was also going to inquire about remelting the slag, and you were ahead of that one, too.

I did find a picture of melted Borax (forgot to bookmark it), which saved asking the question of whether
it's transparent or not------------in the picture I saw, the poured-and-cooling Borax looked yellowish------
is that what I should be expecting to see when I've finally melted some?

Lmine also has anhydrous Borax, 55 lbs., for $54.20 (same link as above). Is that a pretty competitive price?

Cheers,

Mike

 

[4metals]

Cryolite is sodium hexaflouroaluminate it is a synthetic compound made to mimic the natural Kryolite which is mined in Greenland. Natural Kryolite is usually a grey to reddish grey powder (I have seen it more grey and more red so it varies) Cryolite is white.

Looking at the Legend website I do not see Cryolite but I do see fluorspar which is calcium diflouride.

In my experience, Cryolite is far more effective at dissolving alumina substrate materials (ceramic) than flourspar. They both eat crucibles, fluorspar is used as a thinning agent for flux, cryolite is for dissolving ceramic materials in a melt.

Years ago I used to dissolve the gold off of granulated ceramic substrates and save the stripped substrates to send them to a large smelter in upstate NY. They would melt 4 drums of substrates at a time in huge furnaces and add borax and a secret ingredient which they never spoke of and melted for about 12 hours. I think they only melted that long so I would fall asleep waiting but that's another story. Anyway when it came time to pour, out came lots of liquid slag and only the last bit was metal. Everything was liquid for the pour.

Since then I have melted ceramics instead of the acid process and recovered all of the mixed metals which went into the refining circuit. Much less acid used that way!

As far as pricing goes for anhydrous borax, that seems fair but depending on where Rock Island is, freight may be an issue.

 

[Irons]

The Cryolite from Sheffield is a pure white powder, about 200 mesh with no lumps. It's as nice as you could ask for and blends perfectly.

4Metals is right. A little bit goes a long way. 5 pounds will last most people a long time.

 

[kjavanb123]

Today I tried formula mentioned in this post, here is the scope,

60g mixed MLCCs and SMD resistors.
2 part borax
1 part sodaash
1/4 cryolite

Mixed them well and dropped MLCCs into graphite crucible, added the flux on top,and let it melt in my cupola furnace for 20 minutes, during of which I took the crucible out and swirled it for better mixing. I poured into angeled iron mold and here are the result


I am thinking I should have left the crucible longer inside the furnace but it seemes to produced two large beans of alloyed metal.

Thanks
Kevin

 

[4metals]

Melts like this require a long stay in the furnace. Usually after a time in the furnace some of the slags are dipped out and poured over a flat surface for inspection to determine how long it is taking for the metals to begin to join together and sink to the bottom. When you reach that point you pour off the top half of the pool of slag and continue to add new fluxed material.

This is where 2 things are very important. 1. is to use anhydrous borax so it does not swell up as it releases its water, and 2. is to use a scrap / flux mix that is thoroughly dry.

When you pour off the slags inspect them to make sure they are glassy and free of beads. This is repeated until there is a decent pool of molten metal in the crucible. When you pour the entire melt, the metal is the last to come out and it is of a much different appearance than the slags while pouring.

It is common to have a slag remelt day where all of the slags are re-melted until liquid and given time for all of the remaining beads to settle out before pouring.

If you are processing a consistent stream of scrap, the mixture is fluxed in bulk and it is easier once you determine the time for slagging off and the addition rates. Then it is just a repetitive thing, pour flux off, new mix in, in timed cycles.

 

[Irons]

I've found that, when processing an unfamiliar material, to do a small test batch, and like 4 metals said, see how long it takes for the material to give up the values. It's better than making a mess with the whole batch and trying to figure out how to clean it up. Trying to recover everything on the first pass may not be economical, so pouring off half the flux and adding new material is a good idea. I plan to have a dedicated Ball Mill, just for blending the flux with the ground material to give a homogenous charge. Right now, I do it by hand and the results aren't always even, plus, it's time that could be applied best elsewhere.