Used Sodium Thiosulfate disposal

This is essentially electroplating. Electroplating isn't hard to do, at least on the home experimentation level.

I have occasionally made my own electroplating setup at home. Just using a variable, regulated power supply, some wire and an old, plastic margarine container filled with a weak solution of muriatic acid you can easily electroplate the copper off a penny and deposit it onto a quarter. I once caught a wild hare and got the idea to plate copper onto my house key so it would be a different color than the others.

I did everything myself and determined what I needed to know empirically. I built my own regulated power supply with parts from Radio Shack. Schematics from the internet. I made the apparatus and got it working. To determine how much voltage/current to use, I adjusted the power supply until I could just barely see bubbles coming off the electrode then backed down a bit from there. I let it run over night. In the morning, I had a copper plated house key.

Silver recovery, although a little different, uses the same principles. Instead of making your own power supply, you could probably use the wall wart transformer from an old cell phone charger that you don't use anymore. It doesn't necessarily have to be regulated. Many wall warts are already regulated, however. It shouldn't be a problem if, instead of an adjustable power supply, you put a potentiometer in line. It's not the preferred way but it will still work. So what if you overload the transformer? You recycled it from being tossed in the garbage, anyway. Right? For the plating electrode, I would probably use a silver coin. If you could find silver foil, more's the better.

I see no reason why an enterprising person couldn't take what I just wrote and figure it out for himself.

I have done projects like this in the past and I will likely do similar projects in the future. I'm a natural tinkerer. These are things I like to do for fun.

I could probably create a project like this for $50, more or less, using materials from around the house.
I just felt that the time I would have spent building, testing and experimenting would be better served making photographs in the darkroom instead of tinkering in the garage. To each, his own. Decide on your personal circumstances and inclination.

In the end, I agree with John. It doesn't matter how you do it. Just do it.
You'll be doing a good thing for the environment. You'll be dumping money down the drain if you don't.

polyglot said:

Since you've done it, do you want to write an "adequate" set of instructions to go in my FAQ? Even if it's just a set of simple requirements (min/max electrode voltage, current limits, suitable electrode metals, stirring, etc) rather than instructions, that'd be a good start that a competent hacker could build something from.

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hi polyglot

get a copy of IPS ( introductory to physical science )
http://glencoe.mcgraw-hill.com/sites/0078617049/
its an 8th grade science text book.
the first experiment is plating silver out of a solution onto a copper wire.

it says EVERYTHING you need to know.

it isn't hard to do anything yourself but some people attempt, and fail
and then they dump their fixer in their back yard or down the drain because they don't
want to waste anymore time or money experimenting ...

Hello All,

Apologies for chiming in so late but the Silver Magnet works great and is easy to use. The paper test strips are a good purchase. The Silver Magnet gets the level down to where the silver no longer registers on the strips.

Neal Wydra

polyglot said:

Since you've done it, do you want to write an "adequate" set of instructions to go in my FAQ? Even if it's just a set of simple requirements...

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Hi, thanks, but probably not. It seems like a lot of work doing a thankless task. The requirements are not really that simple (Gerald listed most of the important parameters in post #60). And one would ideally go beyond this to get better control of silver - multi-stage fixers to get the silver concentrated in the first tank, while minimizing carryout loss to the wash water from the second (or even third) tank.

My intention was to dispell the notion that such information is commonly available on the Internet. Even in this thread, several people have implied that they COULD do it, yet as far as I can see they have not. (I'll bet a dollar that Worker 11811 [post #62] would turn his silver-quarter cathode black with sulfide in less than 2 minutes).

Very briefly, the main difficulty with fixer is that one needs a good supply of free silver ions near the cathode, and these tend to disappear quickly. If they're not there, the result will probably be production of silver sulfide. The main ways to prevent this are 1) increase agitation at the cathode, or 2) reduce the plating current. With good agitation, in a C-41 type fixer, with silver concentration above 1 gram per liter, you can probably safely run a current density of about 5 to 10 amps per square foot of cathode area.

Without agitation, I don't have any experience, but the Silver Magnet may be a good example. You could make some estimates from the specs. As a wild guess, I'd say the current density may be about 100 times lower than with a well-agitated system. The Silver Magnet seems like a fairly elegant design for a low-volume plug-n-play system.

Mr Bill said:

My intention was to dispell the notion that such information is commonly available on the Internet. Even in this thread, several people have implied that they COULD do it, yet as far as I can see they have not. (I'll bet a dollar that Worker 11811 [post #62] would turn his silver-quarter cathode black with sulfide in less than 2 minutes).

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Agreed. There is a certain amount of experimentation and care needed to carry out a project like this. Yes, that is one of the things you have to watch out for and, if it happens, take steps to counter.

However, I am a natural experimenter and tinkerer. Even as a kid, I used to take things apart just to find out how they worked. As an adult, it became my job.

If one is not willing to put in the time and effort to figure out how to do a thing like this he would be better off not doing it. Better he should just buy a Silver Magnet and be done with it. The Silver Magnet is a good product which works as advertised. Even I, as a experimenter, decided it was better to buy than to tinker.

Just for information, I do consider agitation to be important, even using the Silver Magnet. About once per day, I will go check on progress. I unplug the transformer, pull it out of the solution and let it drain then stir the liquid in the container before putting it back in and turning it on.

Read the instructions that come with the Silver Magnet. They do discuss this. There is a chart that details the color of the material that is plated out and what that means. It describes the continuum of light gray color to charcoal colored. It tells you know to know when the process is under way or when it is nearing completion.

I find that the Silver Magnet works well and, with occasional stirring, it works even better. If I was going to suggest an improvement to the product, I would say that the next update to the instruction book should mention this. Use an old, non-metal spoon or utensil to stir the solution once every day or so.

Worker 11811 said:

Just for information, I do consider agitation to be important

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I did graduate work in electrochemical engineering and worked on several electrolytic silver recovery projects while at Kodak. Silver plating is very much a diffusion controlled process; the electrolyte at the cathode surface becomes depleted of silver ions and fresh solution must be brought into contact with the cathode surface. Without agitation, your plating current must be limited; even with agitation, as the solution silver content drops, the plating current must be limited.

To really investigate the plating rate of process you need to look at a number of variables: silver concentration, pH, cathode surface and area, and agitation and you need to monitor the process by measuring the cathode potential with a reference electrode and high input impedance electrometer.

Mr Bill said:

(I'll bet a dollar that Worker 11811 [post #62] would turn his silver-quarter cathode black with sulfide in less than 2 minutes).

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Yup, the conditions for good silver plating require operating the cell at a high silver concentration; electrolytic silver recovery must operate at much lower silver concentrations. Therefor the cathode current density requirements are far different.

This conversation is making me think about a different tack. Recently I've been playing with soaking regular developing paper in KN03 to make a sort of weak printing out paper. With all that silver dissolved in the used fixer, I wonder if there is some way to use it directly instead of trying to recover it as a solid metal. Something along the lines of coating a paper with sodium chloride and potassium nitrate and then soaking it in the used fixer to re-use the silver for photographic purposes ( I do realize there is a nonsensical aspect to this thought... the fixer is for removing the unconverted silver from paper in the first place... I want to put it back onto the paper for re-use instead! )

Prof_Pixel said:

I did graduate work in electrochemical engineering and worked on several electrolytic silver recovery projects while at Kodak.

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Cool; I have no formal education on these areas, rather the school of "hard knocks" and "screwing around." Where I worked, our best sources of information were SPSE papers by Kodak people, especially Austin Cooley, who we considered like the Greek god of silver recovery.

At the place where I worked, I concocted a scheme for a multi-stage continuous flow system for bleach-fix; as you feed used blix in one end, desilvered blix comes out the other end. The only operator intervention needed was about 20 minutes per day to knock off the silver. (You can probably appreciate what it takes to get 50 lb of silver per day out of several thousand gallons of blix, which we did for a couple peak weeks every year.)

To really investigate the plating rate of process you need to look at a number of variables: silver concentration, pH, cathode surface and area, and agitation and you need to monitor the process by measuring the cathode potential with a reference electrode and high input impedance electrometer.

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We tried several "silver controllers" way back (probably 1980s?), and were never very satisfied. They had to be somehow calibrated with the user's specific fixer, or perhaps used same as the filling solution in a reference cell. At any rate, we found manual operation more reliable, using operator judgement.

I wish I'd had a better understanding of things back in those days, but I didn't have either the discipline or the interest to learn the fundamentals.