Rick Miller
Member
GSP, maybe I didn't elaborate enough. I was just curious about the difference between ammonium thiosulfate and sodium thiosulfate in the pulling of silver from the paper.
My equipment consists of a large barrel (1 cubic meter), a pump of 1500 liters per hour (the performance can be controlled by a frequency regulator), a electrolyser with two rotating (150 revolutions per minute) stainless steel cathodes with a total active surface of 1 square meter, anodes made of graphite plates, a power supply unit that operates on a three-electrode circuit in potentiostatic mode. The maximum cathode current is 100 amps per 1 square meter, the current is set automatically depending on the silver content. I typed on cathodes up to 8 kg of silver (4 for each cathode). Oh, I forgot: the Cathodes rotating in a bath of 100 liters. This is my electrolytic cell. pump from the barrel 1000 liters in the bath to the cathode, from the bath by gravity to the eurocub (barrel) with bags of film or photo paper. Activation is due to the supply of fresh pump solution and due to the rotation of the cathodes. The sludge on the cathodes contains 98.5 % silver.goldsilverpro said:ION 47 said:Rick, good day! I process the x-ray film is not exposed, as well as the photo paper by the following method: I grind the material to a size of 2 cm by 2 cm, load the wicker bags, and fill (1 cubic meter) solution of sodium thiosulfate. The thiosulfate solution is taken from the bottom of the barrel and pumped through the electrolysis cell, then fall back into the barrel. And so on until there is no silver in the solution. Thiosulfate solution can be used repeatedly. Modes and techniques can be used in the series "J" from Kodak. I think you'll lose a lot less silver than by burning the photo paper. With respect, Yevgeny.Rick Miller said:I like it when you think out loud. Still sampling
That could work great, assuming there enough agitation of, or on, the cathode to reduce the formation of the black silver sulfide.
Does your electrolytic unit have a rotating cathode? If not, how do you do it?
Ammonium thiosulfate works faster than sodium thiosulfate, it is used to speed up the process of fixing photo prints (usually mixed with sodium thiosulfate) in developing machines. The ammonium thiosulfate will work, but with the correct electrolysis mode, the hydrogen pH will grow, it will smell like ammonia, ventilation is needed.Rick Miller said:GSP, maybe I didn't elaborate enough. I was just curious about the difference between ammonium thiosulfate and sodium thiosulfate in the pulling of silver from the paper.
Paper you need to chop, you can use like this: Rayson Shredder A506P, the density will be greater. You should try to pour as much paper to the silver content in the solution was 2-5 grams per literRick Miller said:Yevgeny, thanks for the input.... Also, my paper is in large rolls. I'm attempting to unroll it through a bath. I haven't had this much fun in a while.
I also use an Autonomous electrochemical AK-1 ( informationit available on the Internet), the cathode of which consists of a conductive porous material, the activation of the solution in it is due to the supply of a solution of 1000 liters per hour in the interelectrode space.goldsilverpro said:Rick Miller said:Yevgeny, thanks for the input. I have ordered ammonium thiosulfate to run a sample with. From my reading, it sounded better than sodium thiosulfate. What are your thoughts on the difference between the two? Also, my paper is in large rolls. I'm attempting to unroll it through a bath. I haven't had this much fun in a while.
Like i said before, it's success is based on cathode agitation. All of the many electrolytic systems that were once sold for this purpose had a rotating drum cathode, made of stainless steel. This would give a constant exchange providing fresh solution to the layer right next to the cathode metal, the cathode film. Without sufficient cathode film replacement, the thiosulfate will decompose and deposit a layer of sodium sulfide + a little silver sulfide, a stinking black slimy substance which falls off the cathode. That's why I asked Yevgeny what he was doing about the cathode situation. Maybe he has a trick up his sleeve. I am still interested in that. He probably is using a commercial unit with a rotating cathode, though. The number of amps you use could also be critical.
To make this work, you must do something about the cathode. Although I've never tried it, a flat sheet of stainless could be used for the cathode (and anode), and the output from a pump set to impinge directly on the cathode face. This might provide enough cathode agitation to prevent the sulfide formation. Even with the very best agitation, some silver sulfide will form and the silver will never be pure. I've seen it vary from about 80% (black stinking slime) to about 99% (hard white brittle metal). Any metal adhering to the cathode is brittle and can be removed by flexing the stainless sheet a bit.
In any case, the silver can be purified easily by melting it with about 1/3 to 1/2 it's volume of a flux mixture consisting of 3/4 anhydrous (preferably) borax and 1/4 soda ash. Several lengths of rebar long enough to protrude out of the crucible, so they can be easily removed, are added. some of the iron from the rebar combines with the sulfide and it becomes part of the slag. After 30, or so minutes, the rebar is removed, the melt poured into a cast iron mold, When everything becomes solid, the bar is dumped and immediately quenched, while still hot, in a trough of cool water. What slag remains is chipped off. Pure silver bar.
Rick, one more recommendation: do not keep photo paper under the influence of sunlight for a long time, ultraviolet light restores silver from salt, and thiosulfate will not be able to bind the complex with it, there will be losses, it will be necessary to use a bleaching solution, which is much more difficult.Rick Miller said:Thanks for the input, I have considered stripping with caustic. Even so far as drawing up ideas for an automatic unroller. After learning that 25 to 30 percent is lost in burning, may lean this way.
https://waste.ua/cooperation/2008/theses/vays.html The authors here point out that this equipment allows to maximalle preserve the components of the process solutions of photo printing. Operation of AK-1 in my shop showed: decomposition of thiosulfate is certainly present, but very small. The electrolysis current is set automatically depending on the set potential and the silver content in the solution. The greater the current density, the worse the thiosulfate is preserved, sulfur begins to sit on the anode, and sulfide on the cathode. I have now switched to using equipment with rotating cylindrical stainless steel cathodes. Each equipment has positive and negative properties.Platdigger said:For whatever reasons they claim:
"The AK-1 complex does not admit the cathode decomposition of thiosulfate and creates the conditions for repeated use of the fixing solutions in the photographic process."
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