Silver Recovery

[removed account4]

h the town seems to have no problem with us dumping some fix in the sink. "

i have never heard this in my life. i lived in / near / outside of boston for 15 years and currently live 50 miles away, ...

as for your silver recovery solution, you might thnk about a trickle tank. it it gravity fed, painless, and will remove
a large amount of the silver in your waste stream.

 

[seezee]

If you're in central Oklahoma, there are several silver recovery services in OKC. I called the first one to pop up in a Google search & they said they'd give me a ring when their driver was in my town.

 

[anfenglin]

Hello everybody!

I desilver my spent fix using Sodium Dithionite H2S2O4 in a 5 liter bottle, the precipitation is sometimes black, sometimes more brownish but mostly gray. I use about 40ml of Dithionite in 5 l of spent fix (Ilford Rapid Fixer and now Adox Adofix), I then shake the bottle and wait a day or two, then shake again to loosen the precipitation on the inner walls, then I wait another day until everything has sunk to the bottom, then I can decant the watery bit.

I know I end up with silver sulfide, my question is, assuming I want to get the silver and get rid of the sulfur, how would I manage that? Just heat it up? Melt it together with something? How do I get the silver out?

Also, I'd like to know what happens on a chemical level, so Ag+ + H2S2O4 = AgS something.
Can anyone help please?
Thanks!

 

[AgX]

Why do you do so, for retaining the silver or for sparing the environment? In case of the latter just bringing it to the hazardous waste collection would be more appropriate as then desilvering would be done more effectively.
Keep in mind that for the "silver" in your refinement state you would not get best prices anyway. If the refinery accepts it at all.

 

[anfenglin]

I do it because it is the best possible way of getting rid of fixer for me. Taking the car to bring the canister to the disposal yard across town to then have it burned is the stupid and wasteful way imo.
I don't care about how pure the silver is I get, I want to experiment and I want to know what happens chemically.
Maybe I can make something from it and maybe I'll learn something along the way.
I like trying new stuff.
That's why.

 

[AgX]

In my county it is prohibited to let spent fixer down the drain, be it desilvered or not. I transport my stuff by bike.

 

[anfenglin]

*sigh* I don't care about that, I want to know the chemistry.

 

[fdonadio]

*sigh* I don't care about that, I want to know the chemistry.

I am still reading it... Judging by the abstract, this study should explain everything you want to know:

http://www.scielo.org.mx/pdf/jmcs/v56n2/v56n2a13.pdf

 

[AgX]

I am surprised by the high revovery rates.
But still the question of Anfenglin of what to do with the Silverdithionite is unanswered. He wants to use it.

 

[removed account4]

why don't you just make a trickle tank and be done with it.
you won't end up with any nasty chemical you need a fume hood to
burn off impurities, and you can put it through the tank as many times as you need
to, in order to extract as much of the silver as you need to.
to extract the silver out of spent fixer with some nasty chemical
to get an even nastier chemical to deal with, because you don't want to dispose of it the way
your county, town, city, state wants you to makes me wonder what the laws/rules are about dumping
the compound you made down the drain - dithionite --- yuck...

 

[anfenglin]

I am still reading it... Judging by the abstract, this study should explain everything you want to know:

http://www.scielo.org.mx/pdf/jmcs/v56n2/v56n2a13.pdf

Thanks for that!
I am now wondering where the Cyanide is supposed to be coming from.
From the Ammonium Thiosulfate maybe?
But that is not mentioned in the paper.

 

[removed account4]

the cyanide is part of the refining, plating or mining process
they use arsenic, cyanide, and a handful of other nasty / dangerous
chemicals in the industry.

 

[fdonadio]

I am now wondering where the Cyanide is supposed to be coming from.

the cyanide is part of the refining, plating or mining process

Potassium (and maybe Sodium) Cyanide can be used as a fixer for wet plate (collodion).

I've heard there's people using it to this day. Crazy, eh?

 

[removed account4]

Potassium (and maybe Sodium) Cyanide can be used as a fixer for wet plate (collodion).

I've heard there's people using it to this day. Crazy, eh?

sure is ! ( KCn )

 

[anfenglin]

Well, I have as a starting point, the chemicals Ag (aq), Ammonium Thiosulfate, Acetic Acid and Sodium sulfite from the Adox Adofix, I am not sure which reagent they use in the Ilford Rapid Fixer I used before that, maybe Sodium thiosulfate NA2S2O3 which is very similar to dithionite but uses one less O.
Then in comes the Sodium Dithionite Na2S2O4 and everything reacts. I know the Ag sort of replaces the Na but I am not sure how. All I know is that the silver reacts with sulfur (and maybe others) to insoluble compunds and I am left with harmless chemicals that are by far not as bad as other stuff people pour down the drain like left over oil in the garage, all those cleaning agents to clear drains etc.
The point is, I am getting rid of the silver that is floating around in the spent fixing solution and I even end up with something that maybe even can be used for something.

 

[AgX]

Thanks for that!
I am now wondering where the Cyanide is supposed to be coming from.
From the Ammonium Thiosulfate maybe?
But that is not mentioned in the paper.

That paper is not specifically aimed at photographic lab work, though in text the case of the silver-thiosulfate complex is considered too.

 

[removed account4]

and I am left with harmless chemicals that are by far not as bad as other stuff people pour down the drain like left over oil in the garage, all those cleaning agents to clear drains etc.

before you pour it down the drain claiming it is less harmful than these other things,
i would make sure from your local officials that they don't mind you dumping dithionite down your drain.
where i live, people don't dump waste oil in their woods or down their drains, and " cleaning agents "
are taken to the waste depot as well. a lot of people use enzymes to clean their drains/biosludge not nasty stuff.
besides, large sewer systems can eat a lot of things in the drain, but maybe not dithionite.. and if you are on septic
i hope you don't have a well, or animals, a garden or a local stream &c without knowing with dithionite actually does...

 

[anfenglin]

Oh no, I live in a big city and the people from the waste water treatment place tell me that there is such a lot of water in the system that (inofficially) it is absolutely ok to pour used developer down the drain.
The dilution is so enormous that the amount of developer reaching the processing plant is not measureable.
I mainly use Caffenol and sometimes Rodinal, that is chemically related to Paracetamol and that end up in the canals very often.
I don't know about dithionite but I know that Sodium Dithionite is not very stable as it is. When it gets warmer and / or in contact with moisture it starts oxidizing very quickly and can even start burning.
In water it quickly reacts to Sulfoxylic acid while taking on water but that in turn quickly becomes thiosulfate, especially when in soapy climate.

Dithionite is also used as a bleaching agent in "Fleckensalzen", a powder that is used for getting rid of stains in clothing.
So, basically, it is allowed in the waste water treatment facilities and the sewer system.

 

[removed account4]

go caffenol !!
good to read you know what you are getting yourself into.
all too often there are people who have absolutely no idea about anything
and they ask for instructions about making silver nitrate in their kitchen, for example ...
or they do their color processing and chrome processing on the kitchen counter
where they prepare dinner &c, or they are dumping
cyanide fixer in their back yard ... or claiming selenium is harmless because trace amounts
are found in multi vitamins ...
one never knows who on the internets they are talking with ...

 

[anfenglin]

Hmm yeah, maybe I should have started with that.
Well, it is sort of making it up as I go along, I am learning as I go along, I want to know what is happening and what I can do with the stuff I have.
As soon as I started developing my own film or as I started shooting almost exclusively medium format I ended up with a lot of waste products.
In the beginning I only used Rodinal which, as you know, is diluted pretty strongly, so I ended up with 1 liter of waste after just two films.
I had so much waste and I was starting to think if there is a better alternative to always having to ride my bike or the tram all the way across town to the place that would take the exhausted developer and fixer.
I quickly learned that they incinerate all of the special waste and I thought, that's no good.
So, after having a chat with a few water engineers I started dumping the spent developer down the drain. As I said, in the big city over here that doesn't matter.
Nowadays I use Caffenol for 97% of all films so that gets dumped down the drain of course. Waching soda, vitamin c and coffee are of course allowed in the sewer.

Of course, pouring fixer with free silver ions down the drain is out of the question, so I started looking for options to get rid of the fixer without having to carrying it around, especially since I collect it in a 5L container.
Transporting that in my backpack on my bike is unthinkable.
So I came upon the option of the sodium dithionite, that is a solution for now because it works now. Maybe in a few months time I'll find something else that works better.
For now I am desilvering and the pouring the rest down the drain. I know an engineer in a different forum, he uses the same method.
I am really interested what happens chemically and what the precipite is. It shimmers and glistens, my guess is, that that is the silver. But what is the other stuff?
Elemental silver mixed in with other compounds? Silver compounds like silver sulfite only? Others?

 

[CMoore]

I put my Fix into a 5 gallon bucket and let most of the water evaporate. Then i toss it in a One Liter bottle and bring it to our local College.
They have a Film/Darkroom program and take the fix. I just started doing this a few months ago.
Is there a school near you.?
They will be happy to take your fix.
good luck

 

[AgX]

There are no school darkrooms in Germany any more.
But we have municipal special-waste collecting offers. There are even special codes for photographic baths to ease collecting and recycling.

 

[CMoore]

There are no school darkrooms in Germany any more.

Christ,,,,,that is a Staggering/Sobering comment.
I am not doubting your word....just kind of shocked, but.....you are positive about that.?
Was that by Law/Design, or did the schools just not have any student interest in it.?
That is very surprising to me. It sounds much more like a mistake my own usa would make.......

 

[AgX]

In general the darkroom situation is very different in Germany from that in the US.

 

[fdonadio]

I am really interested what happens chemically and what the precipite is. It shimmers and glistens, my guess is, that that is the silver. But what is the other stuff?
Elemental silver mixed in with other compounds? Silver compounds like silver sulfite only? Others?

In your case, I am not sure what you're getting in that precipitate.

From the paper I linked to above, I understand they get metallic silver as a precipitate, with some thiosulfate and sulfite in solution. It would've easy to decant of filter that and reclaim the silver.

The paper clearly states that all dithionite gets oxidized to sulfite, so there's no problem with introducing "toxic" dithionite in the sewers.

It also seems to suggest that temperature control and stirring are essential for getting the desired results.

I believe a skilled chemist could go further and separate the sulfite and thiosulfate...

Cheers,
Flavio