Silver recovery cannister issues.

[Scorpster]

Ok, so almost 20 years ago I acquired a silver recovery cannister that was processing the output from a film processor. Every time silver prices went up I thought about how to process the contents myself. So about 2 years ago I bought a little electric melting furnace and tested out how simply heating the contents would convert the silver oxide into metallic silver. Testing seemed to go ok, but would have taken too long to process the whole 4 gal container. Fast forward to Xmas and I got a propane melting furnace. Now my issue is that the molten contents in the crucible doesn't seem to become fluid enough to allow the silver beads to fall to the bottom, and I've ended up with a black thick goo with silver suspended throughout. There was some pools of silver but I need to process most if it further. Now the volume of material has been reduced considerably, I assume the excess O2 has been expelled, but I tried both borax and soda ash fluxes but neither seemed to work well. So I'm looking for suggestions on how to proceed at this point. I have access to hydrochloric and sulphuric acids but neither seem to react very fast, I have also tried oxalic and formic acids with little results. I also tried using 2lbs of copper in the crucible to start to try and "inquart" the silver into the copper. Too much got stuck in the crucible so my return was poor. So I'm looking for suggestions on how to proceed. Should I do a weak HCL or oxalic acid solution and just give it time, or try some electrolysis method that doesn't involve nitric. Any suggestions would be appreciated.

 

[anarxi]

I think you need nitric acid to dissolve the silver stuck in the slag.

 

[Yggdrasil]

Ok, so almost 20 years ago I acquired a silver recovery cannister that was processing the output from a film processor. Every time silver prices went up I thought about how to process the contents myself. So about 2 years ago I bought a little electric melting furnace and tested out how simply heating the contents would convert the silver oxide into metallic silver. Testing seemed to go ok, but would have taken too long to process the whole 4 gal container. Fast forward to Xmas and I got a propane melting furnace. Now my issue is that the molten contents in the crucible doesn't seem to become fluid enough to allow the silver beads to fall to the bottom, and I've ended up with a black thick goo with silver suspended throughout. There was some pools of silver but I need to process most if it further. Now the volume of material has been reduced considerably, I assume the excess O2 has been expelled, but I tried both borax and soda ash fluxes but neither seemed to work well. So I'm looking for suggestions on how to proceed at this point. I have access to hydrochloric and sulphuric acids but neither seem to react very fast, I have also tried oxalic and formic acids with little results. I also tried using 2lbs of copper in the crucible to start to try and "inquart" the silver into the copper. Too much got stuck in the crucible so my return was poor. So I'm looking for suggestions on how to proceed. Should I do a weak HCL or oxalic acid solution and just give it time, or try some electrolysis method that doesn't involve nitric. Any suggestions would be appreciated.

Welcome to us.

 

[Yggdrasil]

Ok, so almost 20 years ago I acquired a silver recovery cannister that was processing the output from a film processor. Every time silver prices went up I thought about how to process the contents myself. So about 2 years ago I bought a little electric melting furnace and tested out how simply heating the contents would convert the silver oxide into metallic silver. Testing seemed to go ok, but would have taken too long to process the whole 4 gal container. Fast forward to Xmas and I got a propane melting furnace. Now my issue is that the molten contents in the crucible doesn't seem to become fluid enough to allow the silver beads to fall to the bottom, and I've ended up with a black thick goo with silver suspended throughout. There was some pools of silver but I need to process most if it further. Now the volume of material has been reduced considerably, I assume the excess O2 has been expelled, but I tried both borax and soda ash fluxes but neither seemed to work well. So I'm looking for suggestions on how to proceed at this point. I have access to hydrochloric and sulphuric acids but neither seem to react very fast, I have also tried oxalic and formic acids with little results. I also tried using 2lbs of copper in the crucible to start to try and "inquart" the silver into the copper. Too much got stuck in the crucible so my return was poor. So I'm looking for suggestions on how to proceed. Should I do a weak HCL or oxalic acid solution and just give it time, or try some electrolysis method that doesn't involve nitric. Any suggestions would be appreciated.

Is this the steel wool type of canister?
Then the Silver should be metallic.

Silver do not alloy with Iron so my guess would be tha simple
s/melting would do the trick.
Maybe add some flux to pick up the Iron.

You need more heat I think.

 

[kurtak]

So about 2 years ago I bought a little electric melting furnace and tested out how simply heating the contents would convert the silver oxide into metallic silver.

The reason you are having a problem is because the silver is in the form of a sulfide & not an oxide

If it was an oxide of silver then simply heating it in a furnace would drive off the oxygen atom & reduce it to silver - you wouldn't even need any flux

Because what you have is a silver sulfide complex in order to reduce it to actual silver you ether have to reduce it chemically - or by metal ion exchange --- both of these methods are done by way of smelting

Chemical smelting uses a flux that includes potassium nitrate as "one" of it flux ingredients - I have never used this method so can't speak to the details of this method

metal ion exchange smelting uses iron (along with flux) in the smelt to reduce the silver sulfide to silver by exchanging the sulfur ions in the silver sulfide to iron sulfide which is then slagged off in the flux (borax & soda ash) leaving you with actual silver

For more details about this method read these threads ---------

https://goldrefiningforum.com/threads/metals-from-picture-fixer-solutions.12404/

https://goldrefiningforum.com/threa...e-precipitated-from-kagcn2.34250/#post-368853

I bought a little electric melting furnace

Do not use that furnace to smelt your silver sulfides - the graphite crucibles WIL NOT hold up to the flux used for smelting silver sulfides - the flux will eat through those crucibles & not only destroy the crucible in the first smelt but also destroy the heating coils in the furnace

You need a gas fired furnace & good quality crucibles - they make gas fired furnaces that you can buy for right at the same price of those junk (IMO) electric furnaces - those electric furnaces work fine for melting "pure" metals - but NOT for smelting with flux's

Kurt

 

[kurtak]

I think you need nitric acid to dissolve the silver stuck in the slag.

No - & that is because there is little to no actual silver in his slag - rather it is silver sulfide & nitric will do NOTHING as nitric does not dissolve silver sulfide

What he needs to do is re-smelt it using some potassium nitrate in the (re) smelt to chemically reduce the silver sulfide the actual silver - or - (re) smelt it & put some iron (rebar or nails) in the re-smelt to reduce the silver sulfide to actual silver by way of metal (iron) ion exchange - which is the way I would go with it

and I've ended up with a black thick goo

That black goo is in fact silver sulfide - so re-smelting with iron (& flux) with reduce it to actual silver

Read the two links I provided you with - they will get you on the right track - make sure to read what GSP & Harold posted in that first link/thread

Kurt

 

[kurtak]

picture of smelting silver sulfides (with iron) & results

Kurt

 

[anarxi]

No - & that is because there is little to no actual silver in his slag - rather it is silver sulfide & nitric will do NOTHING as nitric does not dissolve silver sulfide

What he needs to do is re-smelt it using some potassium nitrate in the (re) smelt to chemically reduce the silver sulfide the actual silver - or - (re) smelt it & put some iron (rebar or nails) in the re-smelt to reduce the silver sulfide to actual silver by way of metal (iron) ion exchange - which is the way I would go with it

That black goo is in fact silver sulfide - so re-smelting with iron (& flux) with reduce it to actual silver

Read the two links I provided you with - they will get you on the right track - make sure to read what GSP & Harold posted in that first link/thread

Kurt

it's not really clear what he had there
was it sulfide or maybe sulfite.
what was the starting material?
but, i read about silver balls and puddles, so i suggested the nitric acid route.

 

[kurtak]

it's not really clear what he had there
was it sulfide or maybe sulfite.

Actually it was very clear what Scorpster has - he posted it in the first sentence of his post

Ok, so almost 20 years ago I acquired a silver recovery cannister that was processing the output from a film processor

The silver recovery cannister he is talking about is made for the recovery of silver from (the old) black & white picture fixer solutions used in developing black & white pictures

Those fixer solutions are made of silver dissolved in thiosulfate - so a solution of silver sulfate

Those cannisters are used to recover the dissolved silver from the sulfate solution by way of cementation

Somewhat like cementing silver from a nitrate solution with copper - except copper does not work in this case because copper does not work with a sulfate solution - but iron does

So the cannister is packed full of steel wool - so when you fill the cannister with the silver sulfate (fixer) solution the steel wool cements the silver out of solution - BUT - it does not cement the silver as actual silver - but rather cements it out as silver sulfide

That silver sulfide - recovered from solution by cementing with iron (steel wool) needs to be further reduced to get to your actual silver - that is done by smelting

As I said in my first post yesterday there are two different smelting methods to reduce the silver sulfide to actual silver

One is to chemically reduce it using potassium nitrate as "part" of the flux make up in the smelt - as I also said yesterday I have never used this method so can not speak to the details of this method

The other method is using metal ion exchange in the smelt to reduce the sulfide to actual silver

Here is how that works - you are starting with silver ions that are complexed with sulfur ions - so you need to remove the sulfur ion from the silver sulfide in order to reduce it to actual silver - but - in order to do that it needs another metal that is higher on the reactive series in order to give that sulfur ion a place to go - & in this case iron is what works because the sulfur will react with the iron at HIGH TEMPS

In other words - just like the ion exchange that takes place when cementing silver from a silver nitrate solution with copper - is what happens in the crucible of this high temp smelt - the high temp drives the reaction causing the sulfur ion to react with iron (it actually goes to work at dissolving the iron) which in turn reduces the silver sulfide to actual silver while at the same time creating iron sulfide - which is then carried off by the borax/soda ash flux - resulting in a pool of actual molten silver in the bottom of the bottom crucible

The smelt is then poured to a cone mold so that the silver can settle to the bottom of the cone mold with the slag on top of the silver & when it all cools down it is removed from the mold & the slag is knocked off the silver

This is what Scorpster needs to do if he wants to recover his silver

Kurt