# Silver refining with electrochemistry



## Swissgoldrefiner (Dec 20, 2021)

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 (Dec 20, 2021)

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


----------



## Elemental (Dec 20, 2021)

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 (Dec 20, 2021)

Elemental said:


> 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 (Dec 20, 2021)

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 (Dec 20, 2021)

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 (Dec 20, 2021)

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 (Dec 20, 2021)

Elemental said:


> 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.
> 
> ...


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 (Dec 20, 2021)

nickvc said:


> 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 (Dec 20, 2021)

Elemental said:


> 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 (Dec 20, 2021)

butcher said:


> 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.
> 
> ...


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 (Dec 20, 2021)

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 (Dec 20, 2021)

Swissgoldrefiner said:


> 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 (Dec 20, 2021)

Swissgoldrefiner said:


> 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 (Dec 20, 2021)

FrugalRefiner said:


> 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 (Dec 20, 2021)

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 (Dec 20, 2021)

butcher said:


> 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 (Dec 20, 2021)

FrugalRefiner said:


> 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 (Dec 20, 2021)

orvi said:


> 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 (Dec 20, 2021)

Electrolytic copper refining cell


The principles behind a copper cell. Our purpose in refining copper is primarily to concentrate the precious metals we have collected in copper based bullion anodes. For years I used smelting techniques, which we have discussed in the smelting thread, to separate the metals, which can be...




goldrefiningforum.com


----------



## butcher (Dec 20, 2021)

Much of the silver if it is thicker in coating or contact points they can remain as pieces and flakes along with powders and salts of silver in the anode bag.

Silver sulfate is quite insoluble in water, temperature plays a minor role (so try not letting the cell overheat by trying to push too much current), the solubility of silver comes up to being quite soluble in strong or hot concentrated H2SO4 (the more free acid in the electrolyte the more the silver or its ions become soluble.

I find a raw Dc power supply works better than a filtered fancy lab supply or a computer supply which are basically switching power supplies switching high-frequency AC and then heavily filtering it for a very smooth DC output, a single diode battery charger has a pulsed DC coming on and off 60 times a second, this pulsed DC single diode rectified supply is helpful to the operation of the cell, a better option I have not tried yet is a supply that pulses a varying DC duty cycle with changing of currents with long positive polarity and with fast short negative polarity in the pulse stream.

The current density will work over a wide range or even cell voltages, much depending on the size of the cell and your operation.

When electrowinning copper they can use 8 to 10 times more power than they do electrorefining copper(2KW h/kg) for electrowinning, for copper refining cells power at around 0.25KW h/Kg.
Lower current where purity is a concern.

I am more focused on the recovery of silver and copper in these discussions, as old copper pipe bus bars and dirty motor contactor points are not a feedstock for refining, although the cathode copper from the cell can be used as an anode in a refining cell basically running it back into a copper cell with better electrolyte, I have no need for pure copper at this point I have enough electrical copper.


----------



## FrugalRefiner (Dec 20, 2021)

Swissgoldrefiner said:


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


Hmmm... I downloaded it back in 2014. I'm not finding a link now either, so I'll just attach it here. It was provided by Google because the copyright has expired. One of the best books I've read.

Well, the pdf is too large to attach. I have a smaller version that I found that someone did OCR on. It has a lot of OCR errors in it, but I hope it will be of use to you. I started with the digital versions, but I felt it was good enough to buy, so I found an old library copy being sold online. I think it was less than $10.00

Dave


----------



## kurtak (Dec 21, 2021)

Swissgoldrefiner said:


> 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.




Correct - a copper cell is run at MUCH lower volt/amp then a silver cell

Kurt


----------



## butcher (Dec 23, 2021)

What is this magic lamp?

Let us look at our copper cell.

In the cell voltage is not important we do not need to worry about it and just forget it while running the cell.
An electrolytic cell itself is a variable resistance to current flow, it will also vary in the voltage drop through the cell, depending on many different conditions the cell is operating under.

We will discuss voltage in setting up this discussion and the cell in our example here.

We are concerned about current flow (amperage) which is what does the work in our cell, our voltage is just along for the ride.

When we set the current through the cell, the voltage drop through the cell is determined by the resistance of the cell, so the voltage will change with the cell's function or its electrochemical or physical properties or conditions.
Factors or conditions which are variable in our cell such as metal ion type and concentration spacing anode to cathode, surface area, pH, temperature, passivation of anode or cathode, and many more variable often play a role.

We choose the current we wish to have through our cell or its circuits, we choose this by determining our cell's cathode area.

A common copper tank house may run a cell at 270A/m squared to 300A/m2 which would be about 25amps per square foot (144 square inches), or about 0.176A/sq in ( 176 milliamps per square inch of cathode area).

Now let's look at our simple power supply and our "magic tool" in our circuit the light bulb in series.

Acting as an indicator of the health and operation of our cell, as a current limiter regulating the amperage or current through the circuit, current drawn from our power supply and limiting and being a major factor in regulating the current within our in our copper cell or with any other type of cell.
With a little math and Ohms law, we can set up any cell and its parameters. here I will discuss a simple setup that can be expanded upon, I will try to cover some of the math and explain it the best I can.

Let us say we have a cathode area of our cell at 6 inches square, and we plan on running it at 176 milliamps per square inch (or at 25 amps per square foot of cathode area), so we need a cathode current through our cell of one amp. we will choose a power supply and a series lamp which will do its magic.

Different incandescent lamps in series in our circuit will give us different currents depending or relative to the wattage of the lamp (the filament resistance at that temperature...).

Our lamp is a load dependant resistor, with a low current the lamp is cool and runs as a lower resistance in the circuit, as the load resistance changes or draws more current the lamp filament will heat up glowing brighter, this heated filament becomes a higher resistance regulating and limiting current to the load our copper cell.
The lamps resistance in series with our cell also drops voltage (dependant on resistance...) to our cell or regulates the voltage our cell sees, as it will drop the remaining voltage from our power supply,

The lamp's filaments resistance varies with its temperature, this resistance change also changes the lamp's voltage drop. keeping the voltage of the cell in the proper range for optimum operation.

The lamp limits the current we choose by our choice of lamp we use in series with our cell.

Let's go with a nonautomatic simple car battery charger putting out 14.5 volts DC.
volts x amps = watts
to choose our lamp 14.5volt dc power supply x 1 amp current limit through circuit = we get 14.5 watts, we will choose a 15-watt lamp, a small lamp from our trucks indicator, or a courtesy lamp from the car, this in series with our battery charger will limit the current through our circuit (and our cell to 1 amp maximum.
The copper cells' natural variable resistance will drop some voltage to the lamp (just as the lamp drops the majority of the voltage of the circuit), thus the lamp will not glow full brightness during operation, the lamp's light output will vary with the cells resistance or its function or current...
when the copper cell is shorted and no longer is a resistance in the circuit the lamp protects our power supply or its fuses, the lamp takes full voltage and glows its brightest pulling the maximum value of current of one amp in this case, giving us a visible indication of operation and of a problem in our circuit.


In our circuit of 14.5 volts, the lamp will drop more or less 9/10 of the voltage (13 to 13.5 volts). the copper cell will drop the rest of the voltage 1/10 ( 0.5 to 1.5 voltage drop perfect for our small cell).
Here the lamp's current and the cell's current are set to 1 amp, the resistance of the lamp here would be around 13 ohms, and our copper cells resistance would be 1.5 ohms, as we plate copper out of solution.

A 25-watt lamp would work for a 2 amp copper cell (12 square inches of exposed cathode area).
35-watt lamp for a 3 amp regulator to your cell.
For a copper cell with a cathode area of about 30 square inches use a 65-watt headlamp from your pickup truck with your car battery or its battery charger, limiting the current through your cell and its circuit to 5 amps...

A lamp's resistance to the flow of current (temperature dependant on how hot the filament glows), a cold filament will be a very low resistance cold and allow more current through your cell (up to its limiting range).
As the light glows heating the filament the resistance climbs drastically limiting the current flow through it and through your copper cell.

You do not need a fancy regulated power supply, you can build one a fancy as you like if you are handy and can learn what you study, or use some simple DC source, with a little understanding of OHMs law we can build a regulated circuit perfect for our use of recovery or refining copper or our other metals.


----------



## butcher (Dec 25, 2021)

How much copper will we deposit in an hour of operation with our simple copper cell with the magic lamp dropping the voltage of our 14.5-volt dc supply and regulating its current to 1 amp?

Well, we need some figures to start.
Faraday's constant:
one coulomb = one amp flowing for one second.

A charge of electrons carries 1.60 x 10 -19 coulombs.
One mole of electrons contains Avogadro's constant, or 6.02 x10 23 electrons.

This means that one mole of electrons must carry
(6.02x10 23 x ( 1.60 x 10 -19 = 96320 coulombs
for the farady constant here we will use i mole electron flow =96500 coulombs in our calculations.
As the faraday constant.
Ok
in our circuit, we have copper II sulfate Cu 2+ and we are going to reduce these copper ions to metal, writing out the formula for our reaction we see:

Cu2+ + 2e---> Cu0(s)

Here we see we need to have 2 moles of electrons to reduce one mole of copper.
From our periodic chart of elements:
we see that a mole of copper = 63.5 grams of copper.
and we see from above:
one mole electrons = 96500 coulombs.


S in order to deposit one mole of copper (63.5 grams of metal), we need 2 moles of electrons (96500 coulombs for each mole of electrons).

Now understanding this we can calculate to see how much copper we deposit on our cathode with one amp of current running for one hour.

Cu2+ + 2e---> Cu0(s)
2 moles of electrons = 2e-= 2x96500C = 193000 coloumbs produce 63.5 grams of copper deposit.

Our example cell running at a current density of 1 amp of current flowing x 60 seconds x 60 minutes (one hour) gives us = 3600 coulombs of electron flow.

copper mass deposited on our cathode =
coulombs used/2 moles electrons (2x96500 coloumbs) x 1 mole of copper (63.5g),
or
3600/193000 x 63.5 grams = Cu solid =(0.18625) x 63.5g = 11.84 grams of copper.

14.5vDC supply <------- (lamp)-----+ Anode {CuSO4 ectrolyte } Cathode ------> negative supply

So with our 14.5-volt battery charger and the magic lamp a15 watt lamp in series with our cell, and a high copper content (silver plated) at our anode with our lamp regulating the cells current to one amp we will dissolve and deposit 11.8 grams of copper in an hour of operation (leaving us silver in our anode bag (sock).


----------



## shadybear (Dec 26, 2021)

I have a headache


----------



## Elemental (Dec 26, 2021)

It’s a great explanation on electro-chemistry and a simple way to build a cell. Thanks! @butcher posts are great for being accurate, concise, and straight to the heart of the topic.


----------



## butcher (Dec 27, 2021)

The electrolyte of copper sulfate.

While running this copper cell to recover copper and silver, we want to keep the silver from going into solution as ions, or becoming a salt of silver as much as possible.

Ag2SO4 has pretty low solubility in water, or very dilute sulfuric acid solutions, the salts of silver II sulfate becomes much more soluble in concentrated solutions of sulfuric, with temperature playing a heavy role in both solubilities.
So we do not want to have a high concentration of sulfuric or free acid in the cell, we do not want to drive the cell with too much current which would cause heating of the cell, concentrate solution (splitting water into gases), and can begin to change pH...

Running our cell with as high of concentrations of dissolved copper ions as we can, and as free of other metal ions as much as we can, with as low silver content in solution as we can, and with using mostly a very high feedstock of fairly high purity of copper in our anode sock (mostly silver plated electrical bus bars, silver soldered copper pipe... While eliminating other base metals from the anode as possible in order to keep the electrolyte as free of other metals as much as possible, High in copper concentration.

Some metals like lead, their salts are also fairly insoluble as sulfates in water.

Other metals like iron will dissolve easier in dilute sulfuric but can passivate in concentrated acid.

When cleaning up the cell, recovering the electrolyte for reuse we will concentrate the solution after filtering for insoluble's as much as possible.
Evaporating the already fairly concentrated blue copper sulfate solution drives off the water, any free acid concentrates, this makes any silver sulfate even more soluble in the more concentrated acidic solution.
Where copper becomes less soluble in the concentrated solution, while this solution after concentrated and kept hot is liquid (keeping or dissolving more silver in a solution of a very concentrated solution of bright blue copper salts also dissolved in this solution.
Once we cool or remove the heat the copper salts will begin to form crystals growing as they push silver and other metal ions from their bonds, our dissolved silver, and the insoluble silver sulfate is washed from the crystals as they are jarred, stored under some of their own liquid and a few drops of fresh H2SO4, saving our blue copper sulfate for another project or cell or as a lab reagent as the pretty blue copper crystals are fairly pure.

Once cooled the copper crystals are more difficult to dissolve back into the water, for this reason, we have to learn to use heat and the facts of the salts solubility of different temperatures when working with these projects, it just makes things go much more smoothly.

Upon diluting the remaining highly concentrated acidic solution (we washed from our solid copper sulfate blue crystals) the white silver sulfate ( or yellow if less dilute and allowed to sit longer) silver salts precipitate in the diluted less concentrated acidic solution.

Recovering cathode copper, Blue copper sulfate crystals, and silver as metal with some silver salts, with as little waste generated as possible during the processes, leaving us with less waste to deal with.


----------



## butcher (Dec 27, 2021)

Gold can also be recovered from a copper cell, very similar to how we can recover silver.

If we are dealing with 98% copper and attempting at recovering a tiny bit of gold silver or PGM's

It seems to me we should not think about being in the gold business.

But put our focus more on our copper business instead.

Besides, we are going to need tons of copper if we are all going to be riding around inside those tiny little electric "smart bicycles" with no mining of metals to make the needed batteries (we can make our own cells) for more pedal power up the hills.


----------



## Swissgoldrefiner (Dec 27, 2021)

butcher said:


> In the cell voltage is not important we do not need to worry about it and just forget it while running the cell.


I totally disagree with you about that. With voltage, you can setup almost which metal you remove and which you dont move.
The rest about the amp looks a mess too! In electronics, you never choose the amp, the best you do is chosing the max amp. 
You decide the voltage and the resistance of a circuit and the amp comes from U=R*I
The resistance is depending of the concentration of the electrolyte solution, off curse the area of your anode and cathode and voltage. 
With same area as you suggest, if you put the anode and cathode 10 cm from each other or 50 cm of each other you will not have same current. 

How i do with my experiment? I use multimetre...i try to see the current during the process and i try to check the resistance between my anode and cathode.


----------



## Swissgoldrefiner (Dec 27, 2021)

butcher said:


> The lamp limits the current we choose by our choice of lamp we use in series with our cell.


This lamp methode is interessting methode, but cant be used in large scale. Our aim is to make it workable in large scale. Dont forget, if you use a lamp, you loose some part of the electricity, so you pay more for your refining.


----------



## Swissgoldrefiner (Dec 27, 2021)

butcher said:


> Ag2SO4 has pretty low solubility in water


Desagree again, at least wiki desagree: 8.3 g/L at 25°C. 
What make this selective is the voltage and i am testing it. You never consider the E° of element...in my opinion, if you stay under 0.8 [V] you dont move any Silver into solution. The voltage that you need for copper is 0.3 [V].
What i will test is choosing as high as possible current with limited voltage around 0.3 [V].

Will let you know if it works.


----------



## butcher (Dec 27, 2021)

If you understand the electricity and its reactivity in an electrolytic cell or basically any circuit works then you will understand my post.

If you do not understand it, you can do the research and experiment for yourself to see that what I stated are facts and how electricity works...


----------



## butcher (Dec 27, 2021)

What I suggest will work with a large-scale copper recovery or refining operation, sure we may choose a different method of regulating current through the cell choosing a different DC source besides using an automotive lamp but the principles are the same.

I believe you misunderstand the wiki and the stated solubility of the silver salts. which have a low solubility compared to copper ions in solution, with the cell here as described, we are not running it at a potential to put silver into solution (or we are not forcing the electrons to move from the silvers atoms at the anode, we keep the cells parameters to keep as much silver or other metals out of solution as ions as possible) in our design here, we have set up the electrical conditions to pull electrons from the copper atoms (preferentially over the silver atoms), our goal here is to move copper ions (not the silver ions) so we set our parameters so that we do not dissolve or plate out silver as much as we possibly can with our lamp helping us with this trick.

Yes, we will get some silver in the cell electrolyte, we also recover that silver as I have explained above.

You cannot measure the internal resistance of the cell, measure its current, or measure its voltage directly with meters...

But we can use one or more of these types of meters to do some measurements and calculate the values of the cell using Ohms law, and see what is going on inside the cell by measuring the external circuit and calculating the unknown values within our cell.


----------



## butcher (Dec 27, 2021)

The solubility of pentahydrate copper sulfate in water at 20 degrees centigrade is around 32g/100ml or 320 grams per liter.

The silver sulfates solubility at around 25 degrees centigrade is around 0.83 g/ml or 8.3g/liter.

Also, that with running the electrolytic cell at a lower potential as we have discussed, or not forcing electrons from the silver at the anode, we have put less silver into solutions as ions.

That, and with our highly concentrated copper electrolyte, we do not leave much room for silver ions.

With our copper (at the anode and with copper metal reduced at the cathode) in this solution, which tends to displace silver ions from solution (converting the ions to atoms or insoluble silver metal powder through a displacement type of chemical reaction (helping to lower silver ion content in our electrolyte solution.

Ag2SO4 (aq) + Cu (s) --> 2Ag (s) + CuSO4 (aq)

Our ideal would be for this to happen in our anode bag before the silver ions leave the anode area, where the copper atoms give up electrons to the silver ions as fast as they are formed in the anode compartment or anodes vacinity.

If you happen to be using city water, or have any chloride in the electrolyte solution that also will pull silver ions from the solution (although that is not our goal here in our discussion)...

Here we are discussing more of a metal recovery operation for these metals, but a refining type operation would be almost the same but with tighter parameters.


----------



## olawlor (Dec 27, 2021)

Swissgoldrefiner said:


> ... In electronics, you never choose the amp, the best you do is chosing the max amp.
> You decide the voltage and the resistance of a circuit and the amp comes from U=R*I


I do electrolysis with a little lab power supply (to be specific, this one: https://www.amazon.com/gp/product/B077GVMP5X/ )
Like most lab power supplies, it runs in one of two modes:
Constant Current (CC): limits the current delivered (A)
Constant Voltage (CV): limits the voltage delivered (V)

Both values are displayed on the front panel at the same time, which is handy for debugging the cell. For example, a short circuit (due to a dendrite forming) will show up as CC mode, voltage nearly zero. An open circuit (due to the anode dissolving off, or a wire coming loose) will show up as CV mode, with amps zero. 

For electrolytic metal purification (at least for copper, silver, and iron cells), I normally run the supply in constant current (CC) mode, based on the area of the cathode and anode metals. The cell voltage varies with the solution temperature and concentration, which will vary during a run. As butcher points out, the number of amp-hours through the cell is directly related to the amount of metal you deposit (and the current efficiency, which is normally high for precious metals).

With warm concentrated electrolyte and good cell geometry, I've seen the voltage run below 0.1 volt for copper, below E°, which surprised me! I think this indicates the metal-electrolyte-metal "battery" gives a zero net voltage when the cathode and anode are the same metal. I have needed much higher voltages when electrowinning, such as a few volts needed to recover iron from iron oxides, because then the magnetite-electrolyte-iron "battery" gives a net voltage we need to fight back to recover actual metal.


----------



## Elemental (Jan 18, 2022)

Electro-plating & electro-refining of metals; : Watt, Alexander : Free Download, Borrow, and Streaming : Internet Archive


Book digitized by Google from the library of Harvard University and uploaded to the Internet Archive by user tpb.



archive.org





Another link to Watt's book on Electroplating and Electrorefining.


----------



## FrugalRefiner (Jan 18, 2022)

Yes! That's the version I tried to find. Thanks for providing the link.

Dave


----------



## popslab (Dec 4, 2022)

butcher said:


> 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.
> 
> ...


Thank you for tour answer i have been experimenting with this and did what swissgoldrefiner did and got the same results. I was ready to attempt with copper sulfate but really not sure on concentration of the electrolyte. Any suggestions?


----------



## Yggdrasil (Dec 4, 2022)

popplaysgold said:


> Thank you for tour answer i have been experimenting with this and did what swissgoldrefiner did and got the same results. I was ready to attempt with copper sulfate but really not sure on concentration of the electrolyte. Any suggestions?


Read the book they refer to, it should be there.


----------



## popslab (Dec 4, 2022)

Yggdrasil said:


> Read the book they refer to, it should be there.


Yep found it 
Just ordered on Amazon 
Thanks


----------

