Silver Slimes processing

[Gsracer]

So after running just about 250 troy ounces of silver through my silver cell, the anode basket slimes have reached the limit of my storage capacity. Im ready to process this material and wanted help on the process.

The feed stock was sterling and coin flatware from the 1800s to about the 1940s and candle sticks plates etc. No jewelry. This was melted poured into shot, dissolved with nitric, cemented on copper, poured into shot bars and run through a 2L cell. I did at times run the cementation till i got black powder.

I will say i don't think I'm ready to deal with PGM salts yet so my main goal will be recover the silver and if any present gold.

From my reading the slimes is mostly a mixture of silver oxide, and possibly PGMs and AU.

So the first thing i did was pick out any undissolved silver from all the filters rinse off the finely seperated slime into a beaker. I kept the solid silver separate for running back through the cell, there wasnt much solid silver anyway as i would always make it a point to remove the silver from the spent anode basket.

I was left with about 75 grams of wet finely dissolved powder after evaporation.

After this i took the anode filters which where devoid of solid silver and incinerated them, as the muslin cloth burned the silver nitrate residue solidified into metal. And so did the slimes apparently as i was left with about 149 grams of metal and powder.

What would be the best approach in order to process this for silver and gold if any shows up with stannous?

Thanks everyone

Pics of material.

 

[Lino1406]

Best to take XRF test - to see if it worths

 

[Gsracer]

that would of course be the best plan of action however an XRF is not available to me at this time.

Im mainly interested in the silver, i just dont want to drop any palladium with it as i think its possible that there is a bit in there. So cementing with copper is not an option.

I think im going to take a sample and dissolve it in nitric, as i understand look for yellow or brown for PGMs. If any present i will convert the silver to chloride. Then i guess drop everything else with copper and save for future refining. As i understand a stannous test would be inconclusive in a silver saturated solution.

 

[4metals]

Usually the slimes collected and melted into a bar is mostly silver. One easy method to concentrate the slimes is to dissolve the bar in nitric. This will make silver nitrate, good for use as electrolyte. Test the liquid with some Dimethylglyoxime to determine if it has Palladium dissolved as nitric will also dissolve the Palladium. The insolubles will be precious and their volume will (unfortunately) be greatly reduced from what you started with. Filter the solution for use as electrolyte or cement the silver back out on copper to reduce it to metal for casting into anodes in your cell.
When you collect enough of the filtered off solids they can be processed in aqua regia.

 

[Gsracer]

Thank you 4metals. As this post was from last year. I created a new thread where I continued the process recently here. Doing pretty much what you recommended.


https://goldrefiningforum.com/threads/is-there-any-thing-to-chase-in-these-slimes.30924/

 

[snoman701]

Usually the slimes collected and melted into a bar is mostly silver. One easy method to concentrate the slimes is to dissolve the bar in nitric. This will make silver nitrate, good for use as electrolyte. Test the liquid with some Dimethylglyoxime to determine if it has Palladium dissolved as nitric will also dissolve the Palladium. The insolubles will be precious and their volume will (unfortunately) be greatly reduced from what you started with. Filter the solution for use as electrolyte or cement the silver back out on copper to reduce it to metal for casting into anodes in your cell.
When you collect enough of the filtered off solids they can be processed in aqua regia.

Any suggestions on pre-treatment of the slimes prior to melting? Or just rinse really well then dump them in a crucible and go?

I did a few pounds of gold plated silver and need to recover the gold.

 

[Yggdrasil]

Any suggestions on pre-treatment of the slimes prior to melting? Or just rinse really well then dump them in a crucible and go?

I did a few pounds of gold plated silver and need to recover the gold.

I'd guess much of the slimes will be Silver so a good soak in dilute Nitric first may be wise.

 

[4metals]

I did a few pounds of gold plated silver and need to recover the gold.

For silver with gold, no appreciable Palladium just dry it and part it in nitric. The insolubles, mostly gold, are put into aqua regia for recovery.

 

[Amol Gupta]

For silver with gold, no appreciable Palladium just dry it and part it in nitric. The insolubles, mostly gold, are put into aqua regia for recovery.

What are the benefits of putting the insolubles in aqua regia over smelting....?
Smelting the same seems much easier(atleast with the recovery part of things).

 

[4metals]

Slimes are typically finely divided metals which dissolve easier due to the large surface area. Smelting will melt it into either shot or a bar and, just because of the basic physics, will take longer to react.

 

[Amol Gupta]

Slimes are typically finely divided metals which dissolve easier due to the large surface area. Smelting will melt it into either shot or a bar and, just because of the basic physics, will take longer to react.

Recovery and refining being two different aspects.
Assuming my slimes are fairly consistent (mainly gold) with no other PGM's my best guess is it will be wiser(and much more convenient offcourse) to just smelt the slimes and recovering the gold.
Processing it later if need be.

 

[Shark]

Actually, recovery is almost a failed refine in that it will need doing twice. Yes, it is sometimes seemingly unavoidable, but often the second refine can be avoided depending on what you need to accomplish. If your slimes are primarily gold, the one refine could well get you to the needed purity.

Saying that I was never happy unless it was a pure as I thought I could get it. Even going to multiply refines to please myself.

 

[nickvc]

I called the residues from the cell swines as they got everywhere no matter how hard I tried, I gather the method the old refiners used was boiling the slimes in an iron pot with dilute sulphuric to remove the silver and anything else that could dissolve in it , then onto simple refining with AR and no worries about silver chlorides .
With your material I would try dilute nitric with heat to remove the silver, which will be by far the largest portion, filter and rinse well and any material remaining pick your process of choice to dissolve the values , been very small particles virtually any process will work.