# My Sick Electrolysis Unit



## mda20 (Nov 20, 2012)

Hi,
Good Day everybody. I need your help to solve my problem.
I use an electrolysis unit to recover silver from used fixer. This machine is rotating system. I estimate the solution before starting.

My problem is that I get less quantity of silver than Expecting.

For instance, estimate paper says there is about 5gm/l. But what I get is about 2 or 3 gram.

If anyone can help me to know what is wrong with this machine.

My best regards.


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## butcher (Nov 20, 2012)

I am not going to be much help here, but I would think this is silver being reclaimed by contact with a base metal Iron from a solution of dissolve silver (thiosulfate?), (a metal replacement chemical reaction), the iron would dissolve and go into solution as the silver cements out on the iron, several factors come to mind pH of the solution, concentration of the silver in the solution, conditions of the solution (contamination) and conditions of the metal used to plate out the silver, if the iron is being oxidized or passivated it would not work as well, also how well the elemental metal came into contact with the silver, flow rate , silver content of the solution, and other factors as mechanical problems with the unit.

This is a gold refining forum, I am not sure if anyone here can answer your question about this particular problem, someone else here may have some experience with these machines.

You would probably get more help contacting the manufacturer of these recovery units or reading documents online like Kodak or other who would deal with these units.


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## sena (Nov 20, 2012)

do a sample test , with a 1 litre solution test with your estimate paper , drop it with copper . you will know the percentage of silver in the solution , may be GSP would help you ....
thanks


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## goldsilverpro (Nov 20, 2012)

What color is the deposit on the drum? White or black or both? If black, your current might be too high for the amount of silver present. Is there any black sludge on the bottom of the tank that has fallen off the cathode? If so, it likely contains silver. At this point, based on the Kodak estimating papers, how much silver is in the solution?

I might mention that most people only plate until they get the silver down to a certain low level. They then remove all of the rest of the silver or, "polish" it, with a steel wool canister. 

The silver is in the solution as a negative complex ion, which is repelled by the negative cathode. The only part of the solution that silver is deposited from is the cathode film, which is the solution actually touching the stainless cathode. As the silver in the cathode film plates out, it must be replenished. If it isn't, the thiosulfate will decompose and create black sulfide compounds at the cathode, such as silver sulfide. Since the silver ion is attracted to the anode and not the cathode, the only way to replenish the silver in the cathode film is by mechanical agitation. This is created by the rotating cathode. At some point, though, as the silver plates out, there won't be enough silver in the solution to adequately replenish the cathode film. At that point, you have to slow the deposition down. As the silver gets lower and lower in the solution, you will have to progressively lower the current in order to get a decent deposit. All in all, you'll probably never be able to plate out 100% of the silver. The longer you try to plate out that last bit, the more black stuff you will create. This isn't a batch process.

If I've confused you, please ask questions


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## mda20 (Nov 21, 2012)

Thank you butcher and sena for your kind reply.

Thank you GSP for Your explanation. 

The deposit color is white in the beginning. Then milky and brown. I follow this process:
- I start with high current. In this case deposit color is white. 
- After an hour I reduce the current. When the color go to brown I reduce the currency again and again.
- I try not to make it black.

But I do not use the unit continously. The first step is about 3 hours then I switch off the unit. I come on the evening or on the next day to complete the process, 3 more hours. Mostly I spend 5 days to process 50 lts. This because of my duty time.

My unit features;
- Rotating cathode.
- Indian manufactured.
- Capacity is 50 Lts.

Regards


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## butcher (Nov 21, 2012)

mda20, 
I am sure glad we have GSP here to help you out as I had a whole different process in mind, and was no help at all.
I also edited your post to change the word currency to current, just to avoid confusion.


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## mda20 (Nov 21, 2012)

Thank you butcher very much.


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## mda20 (Nov 24, 2012)

I have been waiting for a reply from GSV and other experience member but no response. If my problem is not understood, I will try to make it more clear. 

I think the answer of these questions may help:
- How can I know that the currency connection is good and there is no fault? ( because there is some rust on the wall of the unit).
- Is the black material collected on rotating cathode is silver? ( this happens with high current).
- Is my processing plan is correct?

I am still waiting for your help becuase I know there many experience people here.

Regards,


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## butcher (Nov 24, 2012)

mda20,
You should wait for response from GSP.
I would think shutting down the unit without cleaning it would cause some trouble?
From what GSP described, if I am understanding it the black is not good the high current is breaking down the thiosulfate to form silver sulfide.

I Do not know if these would help but these can be found:

http://www.google.co.in/patents/US5277775
http://www.google.co.in/patents/US5277775?printsec=abstract#v=onepage&q&f=false
http://www.google.com/patents/US6254782?printsec=abstract#v=onepage&q&f=false
http://infohouse.p2ric.org/ref/01/00048.htm
http://www.google.com/patents/US4280884?printsec=abstract#v=onepage&q&f=false
http://www.google.com/patents/US4131455?printsec=abstract#v=onepage&q&f=false
http://motion.kodak.com/motion/uploadedFiles/US_plugins_acrobat_en_motion_support_processing_h243_1209.pdf
http://www.bing.com/search?q=patients+kodak+electroless+silver+thiosulfate+recovery&qs=n&form=QBRE&pq=patients+kodak+electroless+silver+thiosulfate+recovery&sc=0-45&sp=-1&sk=


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## goldsilverpro (Nov 24, 2012)

Any black solids produced anywhere in the system will contain silver as silver sulfide. They are most likely produced from too much current and/or too little silver in solution. These are not easily processed chemically and I wouldn't even attempt to try it. They should be dried and then melted in a crucible furnace using about an equal amount of about a 2/1 mix of anhydrous borax/anhydrous soda ash. Put into the crucible several pieces of rebar long enough to stick up out of the crucible so you can remove them easily by hand with gloves. The iron will combine with the sulfur in the silver sulfide and release the silver as metal.

Earlier, you said that you only got about half of what the estimating papers indicated. Did you base this on the yield or by difference using the estimating papers? I asked you what the estimating papers read at the end and got no answer. The difference in the readings should give you an idea of how much total has been deposited, in the white cathode deposit and in the black sludge.


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## butcher (Nov 24, 2012)

- How can I know that the current or the connection is good and there is no fault? 

Does the unit have an ammeter, and or a voltmeter? If not an ammeter can be added in series with the cell, the volt meter parallel with the cell, electrical connection can be checked with an ohmmeter, voltages checked with a voltmeter.

say we have a voltmeter measuring voltage, and an ammeter we can calculate the resistance of the cell using Ohm's law, or if we know two values we can calculate the third value.

some formula's of Ohms law 
E=volts (electromotive force)
I=amps (current flow)
R=Ohms (resistance)
P=Watts (power or heat)

E/I=R
E/R=I
IxR=E
P/I=E
P/E=I
IxE=P


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## mda20 (Nov 25, 2012)

Thank you butcher for your answers and for the links.

Thank you GSP too.



goldsilverpro said:


> Any black solids produced anywhere in the system will contain silver as silver sulfide.



This make me wonder if the black solid that sometimes precipitates in the bottom of the container before processing is also silver sulfide



goldsilverpro said:


> Earlier, you said that you only got about half of what the estimating papers indicated. Did you base this on the yield or by difference using the estimating papers?



I base this on the yield.



goldsilverpro said:


> I asked you what the estimating papers read at the end and got no answer.



I use estimate paper just before starting but I do not repeat the reading.


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## goldsilverpro (Nov 25, 2012)

There's quite a bit of good info in this Kodak brochure.
http://www.kodak.com/eknec/documents/03/0900688a800f8103/J215ENG.pdf


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## mda20 (Nov 26, 2012)

Thank you GSP for this link. It is very useful.

I would be please if you tell me about that black solid that sometimes precipitates in bottom of the container if it is silver or not and how to deal with it.


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## butcher (Nov 26, 2012)

Quoting GSP's post above:

Any black solids produced anywhere in the system will contain silver as silver sulfide. They are most likely produced from too much current and/or too little silver in solution. These are not easily processed chemically and I wouldn't even attempt to try it. They should be dried and then melted in a crucible furnace using about an equal amount of about a 2/1 mix of anhydrous borax/anhydrous soda ash. Put into the crucible several pieces of rebar long enough to stick up out of the crucible so you can remove them easily by hand with gloves. The iron will combine with the sulfur in the silver sulfide and release the silver as metal.


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## mda20 (Nov 26, 2012)

Thanks dear butcher.

My question is about unprocessed fixer solution. Here is my previous post.



mda20 said:


> goldsilverpro said:
> 
> 
> > Any black solids produced anywhere in the system will contain silver as silver sulfide.
> ...


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## butcher (Nov 26, 2012)

silver thiosulfate would be soluble, I think the black sludge would be a silver sulfate or a sulfide.


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## goldsilverpro (Nov 26, 2012)

If it were me, I would collect any solids, whether before or after, dry them and melt them, using borax. soda ash, and rebar.


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## mda20 (Nov 27, 2012)

Thank you butcher.
Thank you GSP.

I will colloect it, dry and melt it with borax. soda ash as GSP said.


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