Silver Recovery PH

Anyone out there have experience in PH & silver recovery?

Seems to be conflicting information on what is an ideal PH.

I will be using a, electronic recovery unit, not steel wool.
Currently the solution will be from 4~5 PH.

We have recovery units in place for another machine and other fixer tanks.

Will an electronic unit collect silver @ 4.5 PH?

thanks, dw

hi dw

with the magnet ( electrolytic cell ) the target ph has to be about. 3

David, I was involved in large scale silver recovery for many years (a few metric tonnes per year). Your pH is fine for electrolytic recovery, we used to fit electrolytic units around the UK as well as use them ourselves. (We imported machines from the US).

Ian

thanks ian,
i was going by the target info usi tells me.
its good to know david has wiggle room.

john

I use Ryuji Suzuki's Neutral fixer, which my pH strips tell me is about pH 7. Can I simply add household vinegar to bring the pH closer to 4.5, or should I use something else? I also have Citric Acid and, of course, stop bath concentrate.

Acetic Acid buffers quite well at pH 4-5, which means you don't have to add precise amounts of vinegar and still end up in the ball park of your target pH. Citric Acid, on the other side, will readily pull the pH down to the point where the Thiosulfate disintegrates, and at this point any Silver Magnet like device will have difficulty collecting all the Silver in your liquid.

Just out of curiosity, what is silver recovery, and what is it useful for? Please excuse my naivety! Thank you!

silver recovery is removing the silver in the fixer ... ( to be refined, reused or whatever )
its useful because in a lot of places it isn't legal to dump
fixer full of silver ( more than 3- 5 parts per million ) down the
drain. it has the potential of causing trouble with your septic system
corroding your pipes, and causing trouble in some municipal sewer systems.
and it just isn't good juju to dump spent fix down the drain. granted
some say there are household chemicals that do just as much or worse things
this may be true, but again, as i said, in some places there are laws that tell you what you can and can't put in your drain
and used fixer often times is on the "no" list ..

jnanian said:

silver recovery is removing the silver in the fixer ... ( to be refined, reused or whatever )
its useful because in a lot of places it isn't legal to dump
fixer full of silver ( more than 3- 5 parts per million ) down the
drain. it has the potential of causing trouble with your septic system
corroding your pipes, and causing trouble in some municipal sewer systems.
and it just isn't good juju to dump spent fix down the drain. granted
some say there are household chemicals that do just as much or worse things
this may be true, but again, as i said, in some places there are laws that tell you what you can and can't put in your drain
and used fixer often times is on the "no" list ..

Click to expand...

jnanian, Thank you for the informational and quick response, I appreciate it! This is good to know even if your are like me, and only use fixer every once and a great while! I don't foresee myself going this route, however, the thought will rest in the back of my mind for now! Thanks again, and happy photography!

jnanian said:

hi dw

with the magnet ( electrolytic cell ) the target ph has to be about. 3

Click to expand...

Hi John, I don't think this pH value can be right. I don't believe the thiosulfate in fixer will hold up under such a low pH, although I've never actually tried destroying it in this manner. But there is photographic literature indicating that thiosulfate-based fixers should not be used at pH less than 4.0, for this reason.

The short answer to the question is, I think, that just about any pH will work fine for electrolytic recovery from a conventional (thiosulfate-based) fixer.

A little more complete answer is, that with pH around 4.5 or lower, the fixer is more likely to become degraded during the process as the pH falls slightly.

The majority of my electrolytic silver recovery from fixer has been with C-41 fixer, in the general pH range between 6 and 7, where it is done very successfully. I also have a bit of experience with B&W fixers in the general range of 4.5 to 5 which also worked well. Overall, I think the higher pH values are preferable, but not enough that it is worth making any adjustment.

thanks for the details mr bill.
i have a call into usi this week
and i will question the numbers i was given.
it did seem a bit low, but the numbers
you said ( 6-7 ) are also the range they
gave me for c-41 ... maybe i just wrote it down wrong ...

John, I'd agree with Mr Bill, Actually in commercial situations the fixer pH has never been an issue for silver recovery in my experience.

Once the silver has been recovered the pH needs to be adjusted for disposal, this is actually usually done by mixing with the spent developer. in most places you need permission or a license.

A note to David, usually after a commercial electrolytic silver recovery unit you need steel wool tailing units to reduce the silver level to the permitted 1-2ppm.

Ian

i just heard back from usi ... i wrote down what they told me wrong ..

SORRY FOR MISINFORMING YOU DAVID !

ian and mr bill thanks for setting me straight and correcting my misinformation !