Silver refining with electrochemistry

[Swissgoldrefiner]

Hello,
I wounder if we can separate silver from copper in electrical cell.
For example, using CuSO4/H2SO4 electrolyte to move copper from anode into solution and then move it to the catode.
Leaving behind the silver which will fall down.
Actually i tryed it, it work more or less...but...
I think in some way the silver went into solution. Why i think that? My solution contain some NaCl that i added at begining, and after few minutes i saw the white precipitate of AgCl...
Is there maybe a specific voltage to apply? I think maybe voltage is too high(12V).

 

[Swissgoldrefiner]

Actually, some silver really precipitate and i was able to collect it...but i worries if some silver went into the solution.

 

[Elemental]

Swiss,

You can separate silver and copper using a electrolytic cell. I use this to refine my fine silver. What I do is have a silver anode and a stainless steel cathode. I pass approx 3.5 volts through it. A silver nitrate solution is used for the electrolyte. The pure silver crystallizes on the cathode, copper goes into solution and any other metals are captured in a cloth bag as a slime to be refined later. Please let me know if you have any questions.

Elemental

 

[Swissgoldrefiner]

You can separate silver and copper using a electrolytic cell. I use this to refine my fine silver. What I do is have a silver anode and a stainless steel cathode. I pass approx 3.5 volts through it

Hello Elemental,
Your anode is lets say high level of silver. Mine have only 4% lets say of silver. I will probably saturate fast the electrolyte with other base metal.
My aim is to do the opposit: send all base metal to the cathode and keep the silver in the bag.

Swiss

 

[Elemental]

Swiss,

I think the issue you're going to run into is that since silver uses a lower voltage than let's say copper, that you are going to see some loss due to the silver plating out with your other unwanted metals. I suppose if you just used a chloride as your electrolyte, you would see the silver precipitate out as silver chloride and drop out of solution (which it looks like you've seen). By having a sulfate in there, it makes the chemistry a bit more complex. It's an interesting concept through.

What you can do for a test is continue to run your cell, once you are complete, take a piece of the recovered cathode, rinse it really well, and dissolve a piece of it in HCL, if you get a white cloudy mixture or end up with a white precipitate, that would mean you likely have plated silver out in your cell.

I'll add that I'm a bit new to doing electro-refining, so if we can get someone with more experience to chime in, that would be great too. Ultimately though, you're trying something new, so experiment and let us know what you learn.

Elemental

 

[butcher]

Copper pipe silver soldered, silver contact points cut from bus bar, silver-plated copper bus bars, and bolts nuts...

The cell can be a large salad bowl.

The DC power supply can be a transformer and a bridge rectifier, (a capacitor could be used to smooth ripple but is not needed) fancier supplies you could add a voltage regulator and a couple of more capacitors these can be part of almost any electronic device or made from their scrap parts.
old computer power supply's can be wired or made to work.

A nonautomatic 12volt DC (14.5 volt DC) automotive battery charger (basically a step-down transformer (line voltage AC to about 15 volts AC), and a diode ( converting AC to DC current) works very well, making getting started easy.


Copper sulfate is highly concentrated as an electrolyte.
If you bag the silver/ copper in a sock with an anode (larger bar same material).
from the positive of your 12v battery charger's positive lead goes to a twelve-volt automotive headlamp the other side of that headlamp is jumpered to your anode the bagged material you wish to put into solution as ions, the cathode can be thin copper plate or foil (or stainless steel) connected to the negative lead of your DC power supply.

When the anode material is high in copper, the electrolyte is high copper most silver will stay in the anode bag, and fairly pure copper plates out.

After running large runs, the electrolyte can be crystallized through evaporation, you can recover the small amount or the rest of your silver from the bright blue crystal you are saving to reuse in the cell later or for some other purpose.

The lamp is useful to limit and regulate the current through the cell, it drops the voltage as it is a variable resistance being wired in series with the copper cell, the filament of the lamp changes resistance with heat or as the lamp glows.
The lamp is a visible indicator of the cell operation its current and voltage if it is working or there is a problem in the circuit.
The lamp protects your cell and the circuit from a shorted cell, (the shorted cell not being resistance to current any longer, would just ground out, or give full voltage to the lamp lighting it its brightest, the lamp limits the current of the cell or the load on your DC power supply...

copper sulfate can be bought (sewer pipe tree root killers).

Copper sulfate can be made from other copper salts or solutions, if you use copper waste solutions and you distill (safely understanding the dangers involved) you can convert copper nitrate into nitric acid and copper sulfate, or you can convert copper chloride into copper sulfate and hydrochloric acid, the very hot and concentrated copper sulfate remaining after the distilling process removed hot and is crystalized through cooling of the solution, the crystals reject impurities to the blue copper crystals if you add cut up pieces of copper to the solution you are distilling it helps drive the reaction forward if the copper is gold plated it is a bonus.

See my post on killing two birds with a stone for more ideas.

 

[nickvc]

Running copper electrolytic cells is one of the oldest technologies around so there is plenty of information as to how to run one successfully, in fact at one point the copper refiners in the US produced a large percentage of the silver there and quite an amount of gold.

 

[Swissgoldrefiner]

Swiss,

I think the issue you're going to run into is that since silver uses a lower voltage than let's say copper, that you are going to see some loss due to the silver plating out with your other unwanted metals. I suppose if you just used a chloride as your electrolyte, you would see the silver precipitate out as silver chloride and drop out of solution (which it looks like you've seen). By having a sulfate in there, it makes the chemistry a bit more complex. It's an interesting concept through.

What you can do for a test is continue to run your cell, once you are complete, take a piece of the recovered cathode, rinse it really well, and dissolve a piece of it in HCL, if you get a white cloudy mixture or end up with a white precipitate, that would mean you likely have plated silver out in your cell.

I'll add that I'm a bit new to doing electro-refining, so if we can get someone with more experience to chime in, that would be great too. Ultimately though, you're trying something new, so experiment and let us know what you learn.

Elemental

Dear,
As say nickvs this methode is very old methode, but may be hard to manage....will let you know if i am able to manage it.

 

[Swissgoldrefiner]

Running copper electrolytic cells is one of the oldest technologies around so there is plenty of information as to how to run one successfully, in fact at one point the copper refiners in the US produced a large percentage of the silver there and quite an amount of gold.

Do you have any link or experience on it? I know it's how they do recover some silver gold, palladium...but it s one thing knowing they do it and another making it works.
If you have any link with detail, voltage, concentration of electrolyte, etc...or any experimental, let me know.

 

[Swissgoldrefiner]

since silver uses a lower voltage than let's say copper

Are you sure about that?? E° of Ag is 0.80 where the E° of Cu is 0.34...
In my opinion, copper will move with lower voltage than silver.

 

[Swissgoldrefiner]

Copper pipe silver soldered, silver contact points cut from bus bar, silver-plated copper bus bars, and bolts nuts...

The cell can be a large salad bowl.

The DC power supply can be a transformer and a bridge rectifier, (a capacitor could be used to smooth ripple but is not needed) fancier supplies you could add a voltage regulator and a couple of more capacitors these can be part of almost any electronic device or made from their scrap parts.
old computer power supply's can be wired or made to work.

A nonautomatic 12volt DC (14.5 volt DC) automotive battery charger (basically a step-down transformer (line voltage AC to about 15 volts AC), and a diode ( converting AC to DC current) works very well, making getting started easy.


Copper sulfate is highly concentrated as an electrolyte.
If you bag the silver/ copper in a sock with an anode (larger bar same material).
from the positive of your 12v battery charger's positive lead goes to a twelve-volt automotive headlamp the other side of that headlamp is jumpered to your anode the bagged material you wish to put into solution as ions, the cathode can be thin copper plate or foil (or stainless steel) connected to the negative lead of your DC power supply.

When the anode material is high in copper, the electrolyte is high copper most silver will stay in the anode bag, and fairly pure copper plates out.

After running large runs, the electrolyte can be crystallized through evaporation, you can recover the small amount or the rest of your silver from the bright blue crystal you are saving to reuse in the cell later or for some other purpose.

The lamp is useful to limit and regulate the current through the cell, it drops the voltage as it is a variable resistance being wired in series with the copper cell, the filament of the lamp changes resistance with heat or as the lamp glows.
The lamp is a visible indicator of the cell operation its current and voltage if it is working or there is a problem in the circuit.
The lamp protects your cell and the circuit from a shorted cell, (the shorted cell not being resistance to current any longer, would just ground out, or give full voltage to the lamp lighting it its brightest, the lamp limits the current of the cell or the load on your DC power supply...

copper sulfate can be bought (sewer pipe tree root killers).

Copper sulfate can be made from other copper salts or solutions, if you use copper waste solutions and you distill (safely understanding the dangers involved) you can convert copper nitrate into nitric acid and copper sulfate, or you can convert copper chloride into copper sulfate and hydrochloric acid, the very hot and concentrated copper sulfate remaining after the distilling process removed hot and is crystalized through cooling of the solution, the crystals reject impurities to the blue copper crystals if you add cut up pieces of copper to the solution you are distilling it helps drive the reaction forward if the copper is gold plated it is a bonus.

See my post on killing two birds with a stone for more ideas.

First i dont get the point with the lamp...better using multimeter..to monitor the voltage, etc...
Second problem is anode in my case fall down in the electrolyte, so crystalisation is not worthy.
I have some patent from a friend, i am trying to check them to find how they do...but most patent are in a way that impossible to reproduce without many many tryal.
Will let you know if i have better result...if you have any link, it's well come too.

 

[butcher]

You can use the lamp with or without meters to get a visual view of both current and voltage the lamp is a visual indicator just like your meters are.
the lamp in series drops voltage within the range of the copper cell, the filament of the lamp acts as a variable current regulator, you can choose different wattage lamps for different voltage drops or currents, it also protects your power supply if your cell short circuits and the indicates the shorts in cell.

 

[orvi]

First i dont get the point with the lamp...better using multimeter..to monitor the voltage, etc...
Second problem is anode in my case fall down in the electrolyte, so crystalisation is not worthy.
I have some patent from a friend, i am trying to check them to find how they do...but most patent are in a way that impossible to reproduce without many many tryal.
Will let you know if i have better result...if you have any link, it's well come too.

It is advisable to use regulated power supply, or cheap adjustable constant current constant voltage DCDC converter from Aliexpress for experimenting in lower quantity. They could be obtained for several USD, and operate around 8A max. (without burning it down). Just plug in some ATX PC power supply or any suitable power supply, adjust the thing to your needs and let it go. Usually they will go as low as 1,2 volts.
And when you figure out the necessary voltage and current density, just purchase/make the suitable high current power supply for production.

For the anode "fall off", you will need to create anode basket, if you want clean electrolyte without particles drossing off the anode.
With impure crystals at the bottom, you could conveniently do classic crystalization: you will heat the crystals in mother liquor to boiling, adding just enough water to create saturated solution, filter the particles on classic filter paper (while still boiling hot), and then let it cool and crystallize. From the clean mother liquor, you could let water to evaporate to scavenge even more.

 

[FrugalRefiner]

Do you have any link or experience on it? I know it's how they do recover some silver gold, palladium...but it s one thing knowing they do it and another making it works.
If you have any link with detail, voltage, concentration of electrolyte, etc...or any experimental, let me know.

Google The Electroplating and Electrorefining Manual. It's an old book, but full of information. It's a free download. Electrorefining of copper hasn't changed much.

Dave

 

[orvi]

Google The Electroplating and Electrorefining Manual. It's an old book, but full of information. It's a free download. Electrorefining of copper hasn't changed much.

Dave

Agree. With that variables you operate with, aside of additives which help to grow even and well crystallized deposits... No. It is still the same. Every copper wire was once originated in electrolytic cell.
Here where I live, major factory for processing raw copper produced some gold and silver from anode slimes. Back in 50-60s. Copper ore sulfides concentrates contained also some gold and silver, and after smelt, it ended up in raw metal.
Commies times they did not bothered about optimizing the process back in the day, more than 80% of precious metals ended in the wires all across the country. Older copper wire you found, more silver and gold it contain. Some of them assayed nearly 0,01-0,02% gold, but bulk was lower. I was doing a calculation, if the refining of this stuff is anywhere near economical, back in the day. Even with electricity cost excluded, it wasn´t (no surprise).

 

[butcher]

The copper has been sitting a few years and shows oxidation not as pretty as when it first comes out of the cell, the recovered silver looks the same as it did when it first went into the jar.
The camera doesn't do the colors well, the copper has a greenish hue of some copper oxidation due to air and the environment, the silver is a gray color powder.

 

[Swissgoldrefiner]

You can use the lamp with or without meters to get a visual view of both current and voltage the lamp is a visual indicator just like your meters are.
the lamp in series drops voltage within the range of the copper cell, the filament of the lamp acts as a variable current regulator, you can choose different wattage lamps for different voltage drops or currents, it also protects your power supply if your cell short circuits and the indicates the shorts in cell.

Ah ok, i see now what you mean...It's good idea. However, i would like to find the right voltage and apply it with precision.

 

[Swissgoldrefiner]

Google The Electroplating and Electrorefining Manual. It's an old book, but full of information. It's a free download. Electrorefining of copper hasn't changed much.

Dave

Nice, i will google it, it looks intereresting! Could you maybe leave a link? I am finding different kind of books.

 

[Swissgoldrefiner]

Agree. With that variables you operate with, aside of additives which help to grow even and well crystallized deposits... No. It is still the same. Every copper wire was once originated in electrolytic cell.
Here where I live, major factory for processing raw copper produced some gold and silver from anode slimes. Back in 50-60s. Copper ore sulfides concentrates contained also some gold and silver, and after smelt, it ended up in raw metal.
Commies times they did not bothered about optimizing the process back in the day, more than 80% of precious metals ended in the wires all across the country. Older copper wire you found, more silver and gold it contain. Some of them assayed nearly 0,01-0,02% gold, but bulk was lower. I was doing a calculation, if the refining of this stuff is anywhere near economical, back in the day. Even with electricity cost excluded, it wasn´t (no surprise).

Fun fact about the wire and containing PM.

 

[butcher]

https://goldrefiningforum.com/threads/electrolytic-copper-refining-cell.24397/