I wonder about the voltage you are using. According to the research I have done, copper has an electrochemical potential of .34 and silver is .7. You said you use no more than 1.5 volts. Wouldn't that plate your silver out as well? I'm running 2 cells currently and my anode refining cell is at .4 volts and my winning cell cell is at 1.5. The winning cell is removing all metals within the range of 1.5 and lower. The nitric should in theory be able to be reused. There should also in theory be no gold or pgms as this is nitric solution only. Please be aware this is posed as a question only as this is my first run. Any corrections to my formulas would be greatly appreciated. Is my refining voltage too low? My blister copper contains all metal with rhodium as well. There is a nice layer of black powder on the bottom but my cell has been running for 3 weeks now and the anode is only slightly smaller. My cathode was made from wires and is now more than 1/2" thick. The cathode looks real purdy, when inspected under light it looks like bright and shiny copper with no trace of impurities.any thoughts would be appreciated as the the correct voltage to use. I am currently using 2 calibrated rectifiers built for this purpose. The voltage stays the same, always, but the amperage seems to increase as my cathode gets larger. According to my calcs, it should about 1 month per lb. Of blister copper. Like said, it has been 3 weeks and the cathode looks about the weight of 1 lb or more now. By the way, the amperage according to the digital meter started at .15 and is now up to .21 Thank you all for this awesome site and any clarifications or corrections in advance. Cheers.
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Electrochemistry Copper Nitrate Cell
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John the reduction copper in the half cell as i understand it when gaining an electron is 0.34 volt, but also would you not also have the copper anode oxidation voltage to consider, bringing up the voltage requirements of the cell, and as I understand it, it is the current that is important in determining how much copper is transferred from anode to the cathode in the cell, and surface are will play a big part in that figure.
What happens if you increase the current your running the cell?
It sounds like your getting a good solid plate of copper, if so this may be a way for us to sell our copper waste, if making the copper powder we generated into anodes was not too costly to melt.
Using copper nitrate waste in a copper cell and then possibly making nitric acid out of the copper nitrate solution when your finished with the project does sound like a good idea.
Laser Steve had a post about using graphite to remove copper from the copper nitrate solution, and then use the nitric in an silver cell.
John is there any way you could post a picture of the cell?
How did that purple powder come out, I do not think we ever heard the rest of the story on that project.
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=37&t=6361
I have been up too many hours my mind fell asleep but my finger are still typing, good night, let us know some more about this project.
What happens if you increase the current your running the cell?
It sounds like your getting a good solid plate of copper, if so this may be a way for us to sell our copper waste, if making the copper powder we generated into anodes was not too costly to melt.
Using copper nitrate waste in a copper cell and then possibly making nitric acid out of the copper nitrate solution when your finished with the project does sound like a good idea.
Laser Steve had a post about using graphite to remove copper from the copper nitrate solution, and then use the nitric in an silver cell.
John is there any way you could post a picture of the cell?
How did that purple powder come out, I do not think we ever heard the rest of the story on that project.
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=37&t=6361
I have been up too many hours my mind fell asleep but my finger are still typing, good night, let us know some more about this project.
Hi butcher, the purple powder was gold as you mentioned, it turned out great. If memory serves, it was about 5 grams or so. I use your process on all my reclaimed powders know with exceptional results. Thank you very much for the thorough explanation. On the cells, I would love to post photos but dont know how yet. Can you help? The winning cell is working great, and no you don't need to remelt the copper for sale purposes. I am using sheet as cathodes that I ran through my rolling mill. The thickness is about 1/16" and 2" wide and 14" long. That's what I start with. The anode is superfine carbon graphite bar 3/4" thick and 4" wide and 14" long. BTW, I have tons of graphite, Anyone please PM me if interested. The cathode deposit is ultra fine copper crystal and my cathode after winning my first batch is now about 1/2" thick. No legs or stragglers. Just an increased thickness of my cathode. I could roll it through the mill and continuously accumulate pure copper that way. The voltage on this machine is higher than my refining cell. Voltage at the anode was a question you asked,that would be the refining cell of course. I assume the voltage is still .34 at both the anode and cathode. It seems to doing a great job although it's awful slow :x my goal is to run a series of 8 cells at the same time. It would take about 3 months and after completion I would need to replace the blister anodes. The sludge would be collected and refined and hopefully by combining all the sludge from the 8 cells, I would have a pretty good yield of PM's. :lol:
The electrolyte would of course be reused until completely spoiled by solubles. I am hoping to get at least 3 runs out of it. Once pregnant, the nickel and other solubles would be dropped. Not sure which method would use yet. I'm thinking I may be able to run this material through the winning cell but still need to do more research.thanks butcher, you are as always a great help.Jonn
The electrolyte would of course be reused until completely spoiled by solubles. I am hoping to get at least 3 runs out of it. Once pregnant, the nickel and other solubles would be dropped. Not sure which method would use yet. I'm thinking I may be able to run this material through the winning cell but still need to do more research.thanks butcher, you are as always a great help.Jonn
Hi butcher, sorry I misunderstood when you said if the copper powder is not too expensive to melt into anodes. I don't melt copper only into anodes. I selectively add gold and silver when I first cast the anodes to insure there is at least 97% copper. I plan on refining my silver and gold after the copper is removed, therefore eliminating a step. I don't need to boil in nitric first to eliminate copper. The cell does that for me. As for the reduction potential of the anode, the nitric actually reduces the anode, not the electricity. My electrolyte is at first saturated with copper, with a blister copper anode. The cathode and current cleans up the electrolyte a bit until there is Free nitric. The free nitric dissolves the copper blister anode. The Current deposits clean copper onto the cathode. The sludge falls and is collected once the anode is gone. The sludge is then refine with a minimum amount of acids. All in theory of course as this is my first run.
By the way, I removed the winning cell cathode grid this morning, it was almost 5/8" thick. I sent the cleaned electrolyte over to my finger dissolution bucket and added more pregnant copper electrolyte to my grid. Fingers are the only thing I boil in nitric. And that is my cell electrolyte.
From what I gather on from this forum, most folks boil in nitric first to remove impurities. I'm trying to replace that process with the electrorefining cell. I used to also boil in nitric first, but have accumulated too much solution. That is the reason im trying this way. Another bonus is that the cell puts off a bit of heat and some electrolyte evaporates. I simply add more from my stock pile and hope to reduce my volume and increase the strength at the same time. I hope it works. :roll: we will see.
By the way, I removed the winning cell cathode grid this morning, it was almost 5/8" thick. I sent the cleaned electrolyte over to my finger dissolution bucket and added more pregnant copper electrolyte to my grid. Fingers are the only thing I boil in nitric. And that is my cell electrolyte.
From what I gather on from this forum, most folks boil in nitric first to remove impurities. I'm trying to replace that process with the electrorefining cell. I used to also boil in nitric first, but have accumulated too much solution. That is the reason im trying this way. Another bonus is that the cell puts off a bit of heat and some electrolyte evaporates. I simply add more from my stock pile and hope to reduce my volume and increase the strength at the same time. I hope it works. :roll: we will see.
Jonn,
Since your electrolyte is fairly clean, copper nitrate used only on fingers, and your copper if fairly pure, may be the reason for the tight grain, and not the loose fluffy copper powder I have seen, the way I understand the current and surface area have a lot to do with how much copper moves from anode through solution to cathode, maybe increasing surface are of the cells, and running higher current, might speed things up some?
Are you sure you will not also have to figure in anode oxidation voltage?
I am not very good with computers, and a friend showed me how to post a picture, I done it then, but I am unsure if I can do it now, I will try here, with how I am doing it:
Reply to post to bring this page to type into.
At top of this page there are a bunch of boxes with funny letters and symbols.
Click on the box Img.
It puts two img on page with the curser between blinking.
Below you will see a square box Browse, click on it.
It will allow you to pick a picture out of your computer (you may have to find the file you have the picture in like my pictures), pick the picture, can also type in a note, in box below and click add the file.
If the picture shows up I still can do it, if not we both need help.
Since your electrolyte is fairly clean, copper nitrate used only on fingers, and your copper if fairly pure, may be the reason for the tight grain, and not the loose fluffy copper powder I have seen, the way I understand the current and surface area have a lot to do with how much copper moves from anode through solution to cathode, maybe increasing surface are of the cells, and running higher current, might speed things up some?
Are you sure you will not also have to figure in anode oxidation voltage?
I am not very good with computers, and a friend showed me how to post a picture, I done it then, but I am unsure if I can do it now, I will try here, with how I am doing it:
Reply to post to bring this page to type into.
At top of this page there are a bunch of boxes with funny letters and symbols.
Click on the box Img.
It puts two img on page with the curser between blinking.
Below you will see a square box Browse, click on it.
It will allow you to pick a picture out of your computer (you may have to find the file you have the picture in like my pictures), pick the picture, can also type in a note, in box below and click add the file.
If the picture shows up I still can do it, if not we both need help.
Attachments
Hi butcher, your picture showed up so I will also try to load photos. Yes the current and surface area have a lot to do with the speed of plating, I agree with that. As mine cathode grows in size the amperage increases which in turn hastens deposition. My voltage stays the same though. If I were to increase the voltage, the amps would also increase. But my deposit would be loose and fluffy, ( tried it). my machine controls voltage only and the amperage is automatically set by the surface area of the cathode. This is only my opinion so far but since the machines are digital and calibrated and built for plating I assume this to be correct. If I put the electrodes closer together my amperage would increase. If I use larger electrodes my amperage should increase. I am 4" apart now and fear that if I get any closer they may grow a crystal and short out the unit.your photo shows 2 cells, I am using only one with copper nitrate as the electrolyte. I definitely need to study more on this subject, that's for sure. Is that a salt bridge in between two cells? Would it plate both copper and iron at the same time? Looks like a good idea. I guess I still have a lot of reading to do. 
I will study further and report back. In the meantime let's see if I can snap photos and upload. Thanks again butcher , helpful as always and much appreciated. Jonn
I will study further and report back. In the meantime let's see if I can snap photos and upload. Thanks again butcher , helpful as always and much appreciated. Jonn
Geo
Well-known member
i am far from "in the know" about the cell and its operation but in my experience heat also factors in the amperage usage. cold electrolyte tends to use less amps than heated.this is not a fact, more like an observation on my part.
That makes a lot of sense Geo. I believe you are correct. Heat is energy. I hope I can keep my cells cool enough for safety reasons and also power consumption. I can't seem to get my photos to load. Maybe it's because I'm using a iPad. I wonder if theres an app. for that??
Electrolytic cells (plating cells or electro winning cells), and galvanic cells (voltaic cells) are very different, although they have similarities as well.
An electrolytic cell is like your refining cell using an external power source, (or a battery being charge by an external power source).
The galvanic or voltaic cell is the battery being discharged, like when using the battery to light a bulb.
Let us discuss a battery for a bit.
A battery can act as both of these, depending if it is discharging or charging,
In a battery (voltaic or galvanic cell), it can be somewhat confusing as polarity of the cell is reversed during discharge and charging conditions.
Cathode is an electrode that, in effect, oxidizes the anode, or absorbs the electrons.
During discharge, the positive electrode of the voltaic cell (battery) is the cathode.
When charging, that reverses and the negative electrode of the cell is the cathode.
Basically when,
Discharging the battery the cathode is the positive terminal, and the anode is the negative terminal.
When charging the (the battery becomes an electrolytic cell in a sense),
And the above reverses,
Cathode it’s the negative terminal and the anode is the positive terminal.
The battery, is just two dissimilar metals in an electrolyte (either acidic or caustic solution), the battery discharging the chemical reaction produces an electric current, and the chemical energy makes an electrical energy we can use, and when being charged the external electrical current applied from the charger is converted to chemical energy within our battery, so our induced electrical current results in a chemical reaction.
Negative terminal
When the battery is discharging the electrons are released at the negative terminal (Anode).
And when the battery is being charged Cations receives electrons from the cathode (negative terminal).
Positive terminal
When the battery is discharging, here the electrons are received by the positive terminal (cathode).
When the battery is being charged Anions release electrons to the Anode (positive terminal).
In essence you’re plating or electro-winning cell is very much just like the battery that being charged with an external source.
Edit to add:
I have always called the positive of a battery teminal the anode, this makes this discussion on batterys even more confusing for me when thinking of charging and discharging the cells of a battery.
An electrolytic cell is like your refining cell using an external power source, (or a battery being charge by an external power source).
The galvanic or voltaic cell is the battery being discharged, like when using the battery to light a bulb.
Let us discuss a battery for a bit.
A battery can act as both of these, depending if it is discharging or charging,
In a battery (voltaic or galvanic cell), it can be somewhat confusing as polarity of the cell is reversed during discharge and charging conditions.
Cathode is an electrode that, in effect, oxidizes the anode, or absorbs the electrons.
During discharge, the positive electrode of the voltaic cell (battery) is the cathode.
When charging, that reverses and the negative electrode of the cell is the cathode.
Basically when,
Discharging the battery the cathode is the positive terminal, and the anode is the negative terminal.
When charging the (the battery becomes an electrolytic cell in a sense),
And the above reverses,
Cathode it’s the negative terminal and the anode is the positive terminal.
The battery, is just two dissimilar metals in an electrolyte (either acidic or caustic solution), the battery discharging the chemical reaction produces an electric current, and the chemical energy makes an electrical energy we can use, and when being charged the external electrical current applied from the charger is converted to chemical energy within our battery, so our induced electrical current results in a chemical reaction.
Negative terminal
When the battery is discharging the electrons are released at the negative terminal (Anode).
And when the battery is being charged Cations receives electrons from the cathode (negative terminal).
Positive terminal
When the battery is discharging, here the electrons are received by the positive terminal (cathode).
When the battery is being charged Anions release electrons to the Anode (positive terminal).
In essence you’re plating or electro-winning cell is very much just like the battery that being charged with an external source.
Edit to add:
I have always called the positive of a battery teminal the anode, this makes this discussion on batterys even more confusing for me when thinking of charging and discharging the cells of a battery.
Thank you Butcher,that explains a lot. I must admit I'm a bit stubborn though. In spite of being told to turn up the voltage on refining cell, I did not. I have it running at .4 and went to inspect on it this evening. WOW, what a shock.....
I lifted my grid out of the electrolyte and was a bit upset to see that my anode has retained it's shape and size. My cathode has grown to over 1" in thickness. So I did what any curious cat would do, I touched the anode and boy was I surprised. It crumbled. It appears that if I shook it or disturbed it in any way, it would simply and completely fall apart. I have decided to get some rest now and look at it in the morning. My plan is to let it run again overnight and remove it tomorrow. I will place the anode over a tall form beaker and poke at it with a skewer made of glass. I am quite curious to see if there is any copper left in the core. The anode is multi colored in the crumbled side wall where I touched it . The colors observed were brown, grey, and black with spots of blood red. I am assuming the blood red is Iron (FE). I will post results after I poke at the anode tomorrow. Thanks.
I lifted my grid out of the electrolyte and was a bit upset to see that my anode has retained it's shape and size. My cathode has grown to over 1" in thickness. So I did what any curious cat would do, I touched the anode and boy was I surprised. It crumbled. It appears that if I shook it or disturbed it in any way, it would simply and completely fall apart. I have decided to get some rest now and look at it in the morning. My plan is to let it run again overnight and remove it tomorrow. I will place the anode over a tall form beaker and poke at it with a skewer made of glass. I am quite curious to see if there is any copper left in the core. The anode is multi colored in the crumbled side wall where I touched it . The colors observed were brown, grey, and black with spots of blood red. I am assuming the blood red is Iron (FE). I will post results after I poke at the anode tomorrow. Thanks.
Ok, so I removed the anode and placed it over a tall form beaker. I poked at it with a glass rod and was able to remove about 1/4" of sludge all the way around. I squirted the anode with water and exposed fresh copper which appeared to be etched or lightly sand blasted. I set the grid back into the electrolyte to complete the process. I'm thinking it may be another month or so until it is completely refined. I may have to remove the sludge again possibly. This was done 2 days ago and the blister anode is once again changing color to grey/ black. Will keep posting as I progress. Thank you.
Hi Butcher. I've been doing more research on the electrorefining of copper and found a book that says: the voltage of copper at the cathode for deposition is +.34 volts and the voltage at the anode to strip is -.34 volts, in theory the cell can run at 0 volts. That's not going to give any current or account for any losses, so the cell should be set to .34 volts. That gives a pure and clean deposit. My cell is set at .40 . Free nitric should be in the range of 10%. my deposit is slow to be certain but my cathode is super bright and hard without any loose powder or impurities. I bought the book. It's quite interesting.it is ; The handbook on material and energy balance calculations in material processing. That's the title. It's some technical reading, almost like learning another language. But very worthwhile do you know if running multiple electrodes changes anything as far as the rate of deposit?? If my cell is running 3 electrodes and shows a proper voltage and current, would that be 3 times faster in mole transfer or simply faster because of quantity? Anyone please feel free to comment as I'm always open to learning. I did start another cell with 3 anodes and four cathodes placed in circular fashion. 3 anodes in a circle with 3 cathodes in between and one cathode dead center. This is my second refining cell and I will post results. Thank you.
do you know if running multiple electrodes changes anything as far as the rate of deposit?? If my cell is running 3 electrodes and shows a proper voltage and current, would that be 3 times faster in mole transfer or simply faster because of quantity? Anyone please feel free to comment as I'm always open to learning. I did start another cell with 3 anodes and four cathodes placed in circular fashion. 3 anodes in a circle with 3 cathodes in between and one cathode dead center. This is my second refining cell and I will post results. Thank you.I would think oxidation and reduction would total 0.68 volts, this will also not count for resistance of the cell the power supply would have to overcome, so I would try around 1.5 volts and see how it worked you can make adjustments as needed.
The larger surface area (or multiple electrodes), would increase production from surface area, you would also most likely see a higher current draw from your power supply, (less cell resistance also I would expect).
This is not from experience just my theory, your results may differ.
Look again at the cells in the picture above the one on the right side, notice the voltages add up to .78 volts needed from the battery to dissolve the anode (into solution and plate onto cathode (from solution), (the picture represents a divided cell with a salt bridge but the principle is the same).
The larger surface area (or multiple electrodes), would increase production from surface area, you would also most likely see a higher current draw from your power supply, (less cell resistance also I would expect).
This is not from experience just my theory, your results may differ.
Look again at the cells in the picture above the one on the right side, notice the voltages add up to .78 volts needed from the battery to dissolve the anode (into solution and plate onto cathode (from solution), (the picture represents a divided cell with a salt bridge but the principle is the same).
Hi Butcher, you are correct. The plating voltage for FE is -.44 and copper de-plate is -.34 which equals a negative -.78
In the galvanic cell the de-plating of FE is a positive +.44 and the plating onto copper is a positive +.34 which is a cell potential of positive +.78
Now, to deplate copper, as in your diagram, you need a negative -.34 volts....
To plate copper, as in your diagram, you need a positive +.34 volts
A quick math question? What is -.34 + +.34 ? Is it not zero?
My second cell is now running at .2 volts and it is actually plating quicker. This is the one with 3 anodes and four cathodes. I initially started it out at .4 but the deposits were loose and falling of the cathodes.
My second cell also has a higher amperage. So, I turned the voltage down, which decreased the amperage to the same amperage as my first cell. I am now getting a strong deposit.
By the way, the formation of hydrogen is commenced at 1.8 volts. I would strongly recommend for anyone to NEVER run a cell at or above 1.8. Hydrogen in the presence of Oxygen is immediately EXPLOSIVE.
Its the formula NASA uses for their shuttles. If that can propel a shuttle into space, I'm certain it could also propel a garage or lab into your neighbors yard or far beyond
So, is my math correct? Please advise.... Thank you.
In the galvanic cell the de-plating of FE is a positive +.44 and the plating onto copper is a positive +.34 which is a cell potential of positive +.78
Now, to deplate copper, as in your diagram, you need a negative -.34 volts....
To plate copper, as in your diagram, you need a positive +.34 volts
A quick math question? What is -.34 + +.34 ? Is it not zero?
My second cell is now running at .2 volts and it is actually plating quicker. This is the one with 3 anodes and four cathodes. I initially started it out at .4 but the deposits were loose and falling of the cathodes.
My second cell also has a higher amperage. So, I turned the voltage down, which decreased the amperage to the same amperage as my first cell. I am now getting a strong deposit.
By the way, the formation of hydrogen is commenced at 1.8 volts. I would strongly recommend for anyone to NEVER run a cell at or above 1.8. Hydrogen in the presence of Oxygen is immediately EXPLOSIVE.
Its the formula NASA uses for their shuttles. If that can propel a shuttle into space, I'm certain it could also propel a garage or lab into your neighbors yard or far beyond
So, is my math correct? Please advise.... Thank you.
Notice in this document they use about 2 volts to electrolyticly refine copper.
http://electrochem.cwru.edu/encycl/art-m02-metals.htm
Here around 2 to 2.3 volts.
http://www.saimm.co.za/Journal/v109n06p343.pdf
I ain’t no math wiz, (-0.34) + (+0.34) = 0.68 volts, but you have much more you need to consider, the cells resistance to this voltage, look up cells over potential.
It is when the current is too high that you gas off hydrogen (splitting water in the cell).
Current can be regulated, I use an old truck head lamp in series with the cell.
http://electrochem.cwru.edu/encycl/art-m02-metals.htm
Here around 2 to 2.3 volts.
http://www.saimm.co.za/Journal/v109n06p343.pdf
I ain’t no math wiz, (-0.34) + (+0.34) = 0.68 volts, but you have much more you need to consider, the cells resistance to this voltage, look up cells over potential.
It is when the current is too high that you gas off hydrogen (splitting water in the cell).
Current can be regulated, I use an old truck head lamp in series with the cell.
http://www.uctm.edu/departments/MCMT/BG/E-library/Extractive_Metallurgy_of_Copper_-_G._W._DAVENPORT.pdf
check out this book.
check out this book.
Hi butcher, the first link you sent me says next to fig. 6
" the voltage is -.28 v. "
Am I missing something? The second link is in regards to winning copper. My winning cell voltage was higher than my refining cell. I completed the winning process so I am using my rectifier for my second refining cell.
" the voltage is -.28 v. "
Am I missing something? The second link is in regards to winning copper. My winning cell voltage was higher than my refining cell. I completed the winning process so I am using my rectifier for my second refining cell.
Butcher, I owe you an apology. I just reread my last posts and I'm afraid I just sounded downright rude. I didn't mean mean it that way so, I'm sorry. The third link you sent me on page 328 says " the electrical potential needed for electrowinning is 2 volts as compared to 0.3 volts for electrorefining.
I think this has to do with the anode, the copper being in solution, heat and losses. Also, the winning process is ran at 300 A/M2. I have noticed that this is about 100 amps more than the first link you sent dealing with refining. I am left to assume that during the winning process there is not much concern with the solidity of the copper.?? I need to read the whole thing because I feel as though I missed something. Thank again.
I think this has to do with the anode, the copper being in solution, heat and losses. Also, the winning process is ran at 300 A/M2. I have noticed that this is about 100 amps more than the first link you sent dealing with refining. I am left to assume that during the winning process there is not much concern with the solidity of the copper.?? I need to read the whole thing because I feel as though I missed something. Thank again.
Jonn,
No apology needed at all.
I have to admit I have never studied copper refining or electro winning, I have studied battery's and electrolysis for years, I was using that as my basis for the oxidation and reduction values, I cannot say for sure what the best voltage parameters would be, or the current density for your cell, I can possibly help some with principles or theory.
I do find it strange that the refining cells would run at such a low voltage, although these cells industrially are very large, also I believe the surface area of electrodes are so large, and so close together, and amperage also seems very high, this may be different than a home setup, could you post a picture of your cells?
You have peaked my interest in this some, I will try to spare a little time to read more about this subject.
No apology needed at all.
I have to admit I have never studied copper refining or electro winning, I have studied battery's and electrolysis for years, I was using that as my basis for the oxidation and reduction values, I cannot say for sure what the best voltage parameters would be, or the current density for your cell, I can possibly help some with principles or theory.
I do find it strange that the refining cells would run at such a low voltage, although these cells industrially are very large, also I believe the surface area of electrodes are so large, and so close together, and amperage also seems very high, this may be different than a home setup, could you post a picture of your cells?
You have peaked my interest in this some, I will try to spare a little time to read more about this subject.
