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'[EE]:Silver extraction'
2002\05\01@044813 by Reelf Monsees

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I'm thinking about retrieving silver electrolytically from ordinary
photographic fix (i.e. ammonium thiosulphate solution).
It is possible, that's a fact. But I've got no informations about the
electrodes, the voltage, the current, the mode (constant current or
constant voltage etc.) and other basic things.
Does anybody on this list has some informations about this ?

regards,
   Reelf Monsees

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2002\05\01@053846 by Alan B. Pearce

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>I'm thinking about retrieving silver electrolytically from ordinary
>photographic fix (i.e. ammonium thiosulphate solution).
>It is possible, that's a fact. But I've got no informations about the
>electrodes, the voltage, the current, the mode (constant current or
>constant voltage etc.) and other basic things.
>Does anybody on this list has some informations about this ?

My father used to do this, extracting silver from the solutions of the
photographic shop where he worked. I do not know where he got the
information and equipment from, but it went something like this.

The solution was in a plastic container, about the size of a 10 litre paint
pail. This then had a stainless steel disc lowered into it, which had been
cut and twisted so it was like a single turn corkscrew. This disc was on a
shaft that was motor driven using a small ac driven motor. The silver
collected on the disc, and because the disc is stainless, was easily broken
off the disc to remove it. Rotation of the disc both stirred the solution to
enhance the collection of silver, and caused the silver to deposit more
evenly, which I believe helped to remove current "hot spots" from causing
localised heating of the solution.

I assume the other electrode was also stainless steel, but cannot recall it.
However doing a web search produced information that seemed to suggest
carbon or maybe iron (which would get eaten away and replace the silver in
the solution). I do not know what level of current was used either.

After removing the silver from the disc electrode he would then heat it and
skim the surface to remove impurities in the time honoured way.


Hope this helps you.

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2002\05\01@064954 by Reelf Monsees

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Hi Alan,
yes, that's some helpful information to start with !
Hope someone comes up with some voltages and currents ...
regards,
    Reelf

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2002\05\01@072331 by Jinx

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> Hope someone comes up with some voltages and currents ...

Current is the more important factor, not voltage, although some
consideration must be given to the electrodes' and the silver's
relative positions in the electrochemical series. As Alan says his
father used stainless steel electrodes with silver then you can
take it that method will work for you too

An electroplating bath may have 2.5VDC across it, measured
as amps per sq cm. That assumes an E.P. solution optimised
chemically for good throwing (ie deposition efficiency) power

4g of silver is deposited by 1 amp-hour. What you'll need to do
is use a PSU set to 2.5V and adjust the current for whatever it
is you want across the solution to deposit the silver content you
estimate is in the photographic solution in a reasonable time

The actual amount of power going into your solution will depend
on the separation of the electrodes and thus the resistance of
the liquid between them, as well as impurities that impede the
deposition process. Using a copper electrode may help, as the
copper will replace the silver that comes out of solution, so
keeping the conductivity of the solution up

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2002\05\01@074032 by Alan B. Pearce

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>Using a copper electrode may help, as the copper will
>replace the silver that comes out of solution, so
>keeping the conductivity of the solution up

Presumably part of the reason for reclaiming the silver is to allow the
depleted chemicals to be disposed of in a safe manner. I doubt that changing
the silver salt to a copper salt will allow the resultant to be classed as
environmentally safe, as copper poisoning is also a problem.

I am not involved in chemistry so cannot point you to better possibilities,
but will be following this thread with interest also.

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2002\05\01@075314 by Russell McMahon

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> Presumably part of the reason for reclaiming the silver is to allow the
> depleted chemicals to be disposed of in a safe manner.

Good point.
We're off and running again and don't really know what the real user
requirement is.
All together now .. "tell us what you want and we'll give you what you need
..." (or try to anyway).

WHY are you trying to reclaim the silver?
What are ALL the objectives.
ie is it the value of the recovered silver, the desire to reuse / extend the
chemicals, reduction of toxicity of the fluid or some or none of these?


       Russell McMahon

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2002\05\01@081153 by Alan B. Pearce

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>> Presumably part of the reason for reclaiming the silver is to allow the
>> depleted chemicals to be disposed of in a safe manner.

>Good point.
>We're off and running again .........
>All together now .. "tell us what you want .....

>WHY are you trying to reclaim the silver?
>What are ALL the objectives.
>ie is it the value of the recovered silver, the desire to reuse / extend
the
>chemicals, reduction of toxicity of the fluid or some or none of these?

Well I was just trying to make the point that using copper to replace the
silver may not be the best when trying to hand on the chemicals after
reclaiming the silver, whatever the original reason for silver reclaim was.
From my web search as a result of the original request, it rapidly became
clear that much of the problem is silver contamination of waste water
systems, where silver is regarded as a heavy metal with poison properties
being regarded as similar in magnitude to cadmium and the like, hence it
requires processing to get rid of the silver.

Replacing this with copper may produce a similar problem, which may eat up
any profit from selling the silver itself, as the copper solution may still
need treating.

I suspect using a carbon electrode may be the best, but then you may get
ammonia fumes given off, so do it in a well ventilated area.

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2002\05\01@081416 by Jinx

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> > Presumably part of the reason for reclaiming the silver is
> > to allow the depleted chemicals to be disposed of in a
> > safe manner

> Good point.

Well yes, except you've have to get pretty pernickety and
determine what level of silver is remaining in solution. What
about the rest of the crud even after the silver has been
removed ? I wouldn't drink it. Whatever the constitution of
the liquid I wouldn't feel right pouring down the drain and
would try to dispose of it via the council etc

If it's to recover some metal then it's hardly worth the effort
commercially - silver is cheap. And you can't guarantee that
the metal deposited is going to be of usable purity, particularly
as photographic solution is not EP solution. Chance is that
the deposition will be quite poor and need refining. Options
for that include treatment with conc sulphuric, hydrochloric or
nitric acids to get the silver salt (assuming you can put up with
all the other rubbish in the deposition also being salted), then
taking that salt and re-electroplating it or fusing or smelting it

If this doesn't work out for you perhaps try a jeweller or EP
company to see if they can help you out

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2002\05\01@082616 by Russell McMahon

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> >All together now .. "tell us what you want .....

> >WHY are you trying to reclaim the silver?
> >What are ALL the objectives.
> >ie is it the value of the recovered silver, the desire to reuse / extend
> the
> >chemicals, reduction of toxicity of the fluid or some or none of these?

> Well I was just trying to make the point that using copper to replace the
> silver may not be the best when trying to hand on the chemicals after
> reclaiming the silver, whatever the original reason for silver reclaim
was.

Yes. Understood. As I said, good point.
I in turn was just noting that we have all largely assumed that the
extracted silver was the target of the exercise when it may well not be. It
MAY even be intended to extend the solution life (which is also achieved by
adding the ammonium salt to "silver poisoned" solutions I understand). If
regeneration of the solution was the aim then adding copper or carbon or
most anything else would probably defeat the purpose.

So, while silver extraction is probably the aim. 'taint necessarily so.
What, then, are all the original aims?



           RM

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2002\05\01@092627 by Olin Lathrop

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> Replacing this with copper may produce a similar problem, which may eat up
> any profit from selling the silver itself, as the copper solution may
still
> need treating.

What about using iron, since it's not toxic and even cheaper than copper?


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2002\05\02@164515 by Jinx

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Reelf, where are you mate ? Dying to know why you
want to get silver out of photographic fix

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2002\05\03@031942 by Reelf Monsees

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Hi,
well, just to get the silver from the fluid, first for it's value,
second : I can't dispose the stuff on the local refuse dump when the
silver is above a certain level. Below that level, I may dispose it there for free, otherwise it's  toxic waste and very expensive to get rid of. So, I thought of taking out the silver ....

regards,
   Reelf

Jinx schrieb:
>
> Reelf, where are you mate ? Dying to know why you
> want to get silver out of photographic fix
>
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2002\05\03@053842 by Jinx

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> So, I thought of taking out the silver ....

And why not. It's worth trying - hope the list has helped

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2002\05\03@110720 by Sean H. Breheny

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Ever since this thread started I have been wondering: why would fix contain
silver? It is some Thiosulfate compound, right? (I think someone said
Ammonium Thiosulfate). Certainly the pure stuff doesn't contain silver.
Does it react with the photographic chemicals (which contain silver) to
form a silver compound and that is what you are trying to extract silver from?

Thanks,

Sean

At 08:22 AM 5/3/02 +0200, you wrote:
>Hi,
>well, just to get the silver from the fluid, first for it's value,
>second : I can't dispose the stuff on the local refuse dump when the
>silver is above a certain level. Below that level, I may dispose it
>there for free, otherwise it's  toxic waste and very expensive to get
>rid of. So, I thought of taking out the silver ....
>
>regards,
>     Reelf

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2002\05\03@121857 by Dale Botkin

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Which made me think for a moment...  I wouldn't think there would be any
silver in the fixer, at least not more than trace amounts.  Should all be
off in the developer, maybe some in the stop bath.  Do they still use
(very) dilute acetic acid for that?

Dale
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On Fri, 3 May 2002, Sean H. Breheny wrote:

> Ever since this thread started I have been wondering: why would fix contain
> silver? It is some Thiosulfate compound, right? (I think someone said
> Ammonium Thiosulfate). Certainly the pure stuff doesn't contain silver.
> Does it react with the photographic chemicals (which contain silver) to
> form a silver compound and that is what you are trying to extract silver from?

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2002\05\03@135734 by Ian Hooper

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I used to work in the imaging department of a mid-size offset printing firm.
I can avow that there is a lot of silver dissolved in used fixer.  Developer
serves to convert the exposed silver halide in the film emulsion to a more
metallic form which appears as an opaque image. The remaining "un-exposed"
silver halide must be removed from the emulsion by means of the fixer, or it
will eventually oxidize and become opaque also. An example of this is seen
in old prints that have gone "brown" due to incomplete fixing/washing.

"Stop bath" is usually just a mildly acid solution (i.e. acetic) which
counteracts the alkaline developer.

Unfortunately I can't remember the name of the Ag recovery unit we were
using at the shop, but I do know that we collected up to a pound or two or
silver out of the unit every month. Mind you, that is from many thousands of
metres of 18" wide litho film.I do recall that it was low-volatge and had a
stainless steel "collector"

cheers,

ian

GeminiDatatech Inc.


{Original Message removed}

2002\05\03@135832 by Paul Hutchinson

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The silver does end up in the fixer, bleach-fix, and stabilizer or wash
waters.

This FAQ @ Kodak has a bunch of good info on this topic.
http://www.kodak.com/cluster/global/en/service/faqs/faq5024.shtml

Here's a good 20 page pamphlet also from Kodak.
"Environmental Guidelines for Amateur Photographers"
http://www.kodak.com/US/en/corp/environment/kes/pubs/pdfs/J300.pdf

This search finds a bunch of companies that sell silver recovery equipment
some for amateur photographers.
http://www.google.com/search?hl=en&as_qdr=all&q=+photo+%22silver+recovery%22


And, yes, stop bath is usually still a 1% to 2% acetic acid solution.


Paul

> {Original Message removed}

2002\05\03@165126 by Jinx

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> silver is above a certain level. Below that level, I may dispose it
> there for free, otherwise it's  toxic waste and very expensive to get
> rid of. So, I thought of taking out the silver ....

Just a thought - spray it around Brandon's place at dead of night.
He'll think he's hit pay-dirt. But you didn't hear it from me, right ?

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2002\05\03@174958 by Olin Lathrop

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> Ever since this thread started I have been wondering: why would fix
contain
> silver? It is some Thiosulfate compound, right? (I think someone said
> Ammonium Thiosulfate). Certainly the pure stuff doesn't contain silver.
> Does it react with the photographic chemicals (which contain silver) to
> form a silver compound and that is what you are trying to extract silver
from?

Yes.  Some newer processes use polymers, but the basic standard old
fashioned photographic process uses silver halide as the light sensitive
agent.  That's why it's called the "wet silver" process.  The black in black
and white prints is actually oxidized silver.  The silver is removed from
the light areas by the fixer.  All the silver is removed in the color
process because only the color dyes are left.


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2002\05\03@175009 by Olin Lathrop

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> Which made me think for a moment...  I wouldn't think there would be any
> silver in the fixer, at least not more than trace amounts.  Should all be
> off in the developer, maybe some in the stop bath.  Do they still use
> (very) dilute acetic acid for that?

The developer transforms the exposed silver halide to silver oxide (?), but
does not remove any.  The stop bath only stops the developing action because
it is an acid (usually dilute acetic acid) and the developer is an alkaline.
The fixer removes all the silver that is not used in the final result.


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2002\05\18@130942 by Brandon Fosdick

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Jinx wrote:
>
> > silver is above a certain level. Below that level, I may dispose it
> > there for free, otherwise it's  toxic waste and very expensive to get
> > rid of. So, I thought of taking out the silver ....
>
> Just a thought - spray it around Brandon's place at dead of night.
> He'll think he's hit pay-dirt. But you didn't hear it from me, right ?

So this is what I get for not checking my mail in a while. I'll be keeping an
eye on you Jinx.

As for the silver, there's really no need to spray it around, just leave it in a
bucket by the front door. :)

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2002\05\20@140424 by Jinx

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> As for the silver, there's really no need to spray it around, just
> leave it in a bucket by the front door. :)

Absolutely. Hey, and if you're lucky and I'm in the mood I
might even leave you a pail of "liquid gold" too

eeuuuhttp://www.......

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