How to Recover silver from steel wool by yourself

[Mr Bill]

Where to start... (or continue?)...
A brief diversion into Brian's link to "regenerate fixer," etc., using zinc dust to remove silver. That was once used, I don't know how commonly, in the US to precipitate silver, etc. The big issue, in my view, is the zinc added to your effluent stream (it's probably preferable to put iron in there). But it also takes time to let it settle out, then substantially dry. (Yeah, I've spent time in rubber boots and my MSA mask, shoveling out the zinc sludge from large settling tanks, mid-1970s.) In the US today, if they knew you were dumping zinc they would probably regulate it in your sewering permit.

in any case one will not be able to, per the linked patent, successfully regenerate conventional C-41 fixer in this, or similar, manner. The main issue is buildup of iodide ion which drastically slows down the rate of fixation in conventional C-41 fixer (yeah, I've been there also, desilvering and regenerating C-41 fixer, several hundred gallons, as a trial). It's possible to reuse limited amounts, but all things considered it's probably preferable to, uh, do different things (too many angles to cover here, etc.).

Back to the case at hand, and Koraks' brief analysis of available silver... I did a brief "back of the envelope" reality check on "available silver." I concur that his numbers for photo PAPER are probably pretty close; they sorta agree with what we (where I used to work) used to recover, in very rough numbers. But... PAPER is not the issue here. However, he is guessing at the silver content of FILM as a factor of that in PAPER. I think his guess for FILM is too low, at least for the films of 20 years ago. Today's films may possibly be significantly lower due perhaps to use of things like so-called antenna dyes and 2-electron sensitization, etc. If I had to make a guess on silver content of current films, I'd guess somewhere between koraks' guess and double that number. (In the past, when I was involved in photolab work, we would actually measure the recoverable silver in our materials, then compare our actual physically recovered silver against this.) But in this case I'm just guessing. Anyway, it looks to me like a lot of silver is being "left on the table," so to speak.

But none of this is really relevant to the OP's original question.

 

[koraks]

I concur that his numbers for photo PAPER are probably pretty close

I can give a very firm guarantee that my numbers for paper are 'very close' The film number I guessed. It may be off, considerably. Note I assumed color film and not B&W film, which will have far more silver in it.

 

[Valerie]

I've heard of putting spent fixer out to evaporate and that silver is left behind. Is this true?

 

[koraks]

I've heard of putting spent fixer out to evaporate and that silver is left behind. Is this true?

Yes. Along with some organic stuff. But it works that way for sure. You end up with a black sediment which you can dry by evaporating off all moisture. If you then melt this at a fairly high temperature (a few hundred degrees C), much of the organic muck will oxidize/burn off and you're left with fairly pure silver.

 

[eli griggs]

I've heard of putting spent fixer out to evaporate and that silver is left behind. Is this true?

This is the method I recommend, as well as electrolysis which is well described im Brian's links.

If you do no have oxygen or acetylene tanks, or a propane oxygen setup, the portable MAPP gas torches will, in most cases, do a fine job, though it's more expensive than propane, and a ceramic fiber chicken wire kiln or "furnace" will more quickly burn away trash materials and melt silver.

 

[eli griggs]

https://pubs.usgs.gov/of/2004/1251/2004-1251.pdf

https://www.ijltemas.in/DigitalLibrary/Vol.7Issue7/80-87.pdf

https://patentimages.storage.googleapis.com/fb/1b/8e/88f98c7d0a243a/US5244777.pdf

US5958657A - Regeneration of spent fixer solution - Google Patents

A process for regenerating spent fixer solution which includes the steps of adding finely particulate zinc, such as zinc dust, to the solution to cause silver dissolved therein to precipitate and removing the precipitate from the solution hereby producing a regenerated fixer solution.

patents.google.com

Brian, thank you for putting these very pertinent links.; They are very good in explaining the basic processes.

 

[MingMingPhoto]

No, no metallic silver like that in a silver coin or spoon, but the collected sludge which is processed, melted down with heat, into a metallic silver.

I'm not sure which part exactly you're responding to

Simply put, the steel wool method & blow torch will give you crap purity that'll be difficult to sell, the electrolysis method gives good purity. In theory the difference shouldn't be there, but in reality you're going to trap all sorts of crud and dirt in your silver by blowtorching it off of steel wool. Keep in mind the steel wool itself will burn when blowtorched. You'll end up with silver with a crapload of iron oxide trapped in it. It'll be a mess, but by all means give it a try. Even if it's a failure in terms of purity, the silver will still be there.



And some other organic compounds. But it'll be easier to separate out the silver in a thermal process this way, essentially burning away all the organics that you'll also be left with.

alright, I see. Yes I think I'll still give it a try honestly and see first hand, I don't mind spendign the time and money to get the experince. I'll also try to wash off the steel wool first to reduce dirt

 

[reddesert]

Just a suggestion, if you're operating a minilab in an NYC storefront, don't blowtorch or smelt silver in the building. Take it far away and make sure you have a plan to clean up after it.

Part of the silver recovery guy's fee is covering the costs of doing this without creating an environmental nuisance and with the proper permits, etc. (I know he pays you, but his "fee" is that he gets to keep a significant fraction of the market value of the silver for the hassle.)

 

[_T_]

The cost of consumables in silver recovery will always be greater than the returns in refined silver for small operations. By that i mean small silver recovery operations. There’s no way that you’re going to produce enough silver waste as a photo lab for it to ever be profitable to refine the silver yourself.

The fact that you are receiving any money at all for the silver you sell to your contact means you’re getting an excellent deal. Most people have to pay to have their waste disposed of properly.