Electrolytic copper refining cell

[goldsilverpro]

A search for bone glue is depressing. I have found "hide glue" and "animal glue", which is hard to find, but not one supplier of bone glue. From the looks of it, it is a craftsman adhesive for making guitars and violins.

Try Electroplating supplies or Cabinetmaker's supplies. My Dad and Grandad were cabinetmakers in my hometown for a total of about 50 years. They always had an electric pot of hot bone glue over the workbench. Bone glue was used because it was strong and reliable, yet furniture glued with it could easily be taken apart without damaging anything. For plywood stuff, they used white or yellow glue. For fine furniture, bone glue. I don't think I've ever used it for copper plating but I have used iron-free molasses several times. I also saw urea of the long list I posted. For all of these additives, only "pinches" are used.

 

[Geo]

If even copper deposit is not necessary, are the buffers necessary? Any copper reclaimed was going to be melted and poured into molds anyway. I am not really interested in clean cathode copper sheets. I wouldn't mind it being lumpy or even granular.

 

[g_axelsson]

Note that the acid copper plating solutions are almost identical to the copper electrorefining solutions. Here's another article.

http://www.ct.ufrgs.br/ntcm/graduacao/ENG06631/5-b_copper.pdf

This is a good advice that I spotted in that article.

The copper anodes must have the correct size and geometry (i.e. flat plates larger than the starter sheets of aluminum, titanium, steel, or thin Cu foil for the cathodes to avoid heavy edge deposits)

It's well worth reading the full article, it also discusses copper winning.

Göran

 

[4metals]

If even copper deposit is not necessary, are the buffers necessary?

I don't think it really matters to commercial refiners what the copper looks like physically as it gets cast into some product anyway what is important is the ability for the cell to run continuously. Just like a silver cell produces silver all day the copper production goes consistently 24/7. The difference is it is impossible to not grow the silver in needles that must be knocked down into the cell to avoid a short. The leveling ability of the organics like bone glue allows the anodes to be closer to the cathodes as the growth does not cause a dendrite to form and short out the cell.

The beauty of this, and I think the necessity especially for a small cell, is you want to run continuously. If your cell produces a few ounces an hour, at the end of 24 hours it is beneficial to have 3 or so pounds of copper plated. Remember, the values we are concentrating in the slimes are in the 1 to 1.5% range, so if you only plate 3 pounds of copper, you only generate a concentrate with 14 to 21 grams of values (Au, Pt, Pd, Ag). So running continuously is a plus, and leveling makes that possible.

When you factor in all of the effort it is going to take to process your slimes, keep in mind that it is pretty much the same amount of work if you process one ounce of slimes or 1 pound of slimes. So I would vote to set up a cell to run continuously to accumulate the slimes generated from the collection of anode material available and know that with the leveling ability of the additives, it can run with little attention on my part.

 

[nickvc]

When you factor in all of the effort it is going to take to process your slimes, keep in mind that it is pretty much the same amount of work if you process one ounce of slimes or 1 pound of slimes. So I would vote to set up a cell to run continuously to accumulate the slimes generated from the collection of anode material available and know that with the leveling ability of the additives, it can run with little attention on my part.

Having worked with slimes from a silver cell this is certainly true they can be and are a pain to work with and seem to get everywhere,I'm looking forward to your hearing your method and see if your experiences match mine.

 

[4metals]

Nick,

Were the anodes bagged on the cells you worked with? If not they are all over the cell and truly are a bear to collect to process. But if you use anode bags, it seems to be contained in the bags. Cleaning the bags can be a chore but if done in a tank of rinse water it all does eventually settle out. If you use anode bags which run the length of the buss, they are easily emptied with a length of PVC pipe connected to a vacuum receiver by simply vacuuming up the sludge routinely. It settles in the solution drawn off and the electrolyte can be decanted shortly back to the bath. If decanting always decant into an anode bag just to be on the safe side, because, as Nick said, they seem to get everywhere and we try to minimize that. There are anode bags with a rubberized boot at the bottom, I believe the trade name is "crap trap", these are excellent for this process where you routinely vacuum out sludges and leave the bags in place.

When I processed anodes made strictly from jewelers sweeps, the slimes were roasted and ball milled then pretreated with Nitric and Distilled water, this took care of separating the silver (and rarely Pd) and the base metals from the slimes and made for easy filtration and the balance were processed in aqua regia without rinsing or incinerating.

When processing the slimes from e-waste it is different because we try to enhance filtration. The slimes are still roasted and milled but they are then treated in Hydrochloric to eliminate any tin, the bane of filtration if processed directly in Aqua Regia. They are then rinsed well and again roasted to eliminate any Hydrochloric, this allows nitric treatment to separate silver and palladium. After a good rinse and filtration, the remaining insolubles are digested in Aqua regia and refined normally.

The roasting and milling makes digestion much quicker and under no circumstances should your slimes be melted first. Melting just slows the process of digestion.

 

[nickvc]

I did my silver refining in a large 25-30 litre stainless steel cooking pot, I connected the negative directly to the pot and put the anode bars into a large plastic colander with a filter cloth all across it and connected the positive to that with a silver probe attached which needed to be replaced every so often.
I ran well over 100 kilos of sterling through the cell which was usually gold plated jewellery and I kept the silver content high by adding extra nitric to the electrolyte to dissolve more silver once I could see the start of a colour change, I only changed the electrolyte once and the cell ran all week only been switched off at the weekend.
I only rinsed the filter cloth once the residues, slimes, had built up direct into a plastic bucket and left them to settle for a few days before decanting the liquid off and transferring the slimes to a beaker for further treatment, they still got everywhere !

 

[4metals]

Silver slimes are different, they have a lot of silver in them often in chunks or large scales (kind of like high priced fish scales). With Thum cell slimes, I like to remove the entire anode cloth after draining down the electrolyte so the bag can dry out a bit. Then I fish out the big silver chunks of undissolved anode material and rinse it with a squeeze bottle right into the bag, then roll up the filter material and toss the lot into an incinerator to burn the bag. Then the powder is milled and sifted and it starts with the nitric treatment.

With a Thum cell it is tough to recycle the anode bag and they're cheap enough. It is impossible to suck the slime out of the bag as the anodes are lying right on it.

 

[nickvc]

Yep silver slimes are full of silver and all I did was dissolve the silver with nitric, filter and then go after the gold, are the slimes from a copper cell easier to treat ?
I have absolutely no idea having never run one but I will watch this thread with interest to see how to treat them and how the cell works in recovering the values.

 

[4metals]

Slimes from a copper cell are no more difficult than a silver cell, the trick is not melting them, roasting and milling them, and knowing what they are made up of. Then you just go about selecting the chemistry to pick it apart.

 

[Irons]

I wonder if Gelatin could be used instead of Bone Glue. The rendering process is pretty much the same, except that Gelatin is purified to a higher degree.

 

[Lou]

I have used gelatin and gotten the same effect.

It's the collagen as does the leveling/smoothing effect, so far as I know.

Lou

 

[4metals]

All of the classic literature gives levels of bone glue but I have heard of gelatin being used (as Lou has just confirmed) but never had any details as to concentrations.

A few years back I had to get rid of an old friend, a horse I had owned and ridden for a very long time, Guyreba. I have always thought of him every time I see bright shiny copper plating!

 

[Shark]

I finally got some things done and tried a very small copper cell. Not much for production but it made for a good boost in my morale as for having a working version. It is all in a 1/2 liter measuring cup.

 

[Shark]

Any suggestions as to how much gelatin to use? My little cell is now forming a sponge type build up on the anode. It started when it seemed to heat up (around 150°F) then turned the solution more of a green color than blue. At the same time it seemed to slow down considerably.

Also the sponge is very loose and falls free very easily. Could it be to much nickel build up in the solution?

 

[Irons]

The fused clay doesn't really seem like it's going to do the job. Either I can't get the form right or the mix right. I am using fire clay and sodium silicate.

I think you may have trouble with the Sodium Silicate. My experience is that the Crucible will turn to a liquid at Copper Melting temperature. Fire the Crucible first and see how it reacts.

 

[g_axelsson]

I finally got some things done and tried a very small copper cell. Not much for production but it made for a good boost in my moral as for having a working version. It is all in a 1/2 liter measuring cup.

It's a start, but that power supply isn't suitable for electrolysis. The best supplies are made with voltage control as well as maximum current limits.
Too high a voltage and you will start breaking down water as well as the acid used. It's called secondary or parasitic electrode processes if my memory serves me. The gas makes for a more spongy surface. The gas that is produced could also form an explosion hazard as it is often hydrogen and oxygen in a perfect mix. Do this in a well ventilated area or outside.

Did you measure the current? The best surface is formed within a current window, not too high or too low current density. In your setup the backside of the cathode doesn't add too much to the current drawn so I would just disregard it when calculating the current density.

It's always fun to build your first cell, the only way now is to improve the results.

I haven't dabbled with copper cells in 20 years, but I basically started like you did, making a copper powder that would fall off if it got too thick. Last time I made a copper cell I managed to make a large solid copper blob at the end of a wire. It looked like a upside down coppery cauliflower.

Göran

 

[Shark]

Thanks Göran, your explanation just rang a bell for me. I was getting ready to set up a slightly larger cell but had planned to use the cathode and anode in the wrong order. I will be holding off a bit on the new cell until I can look at the whole project a bit closer, including the use of my power supply. I think I can make it work for the small cells, but going much bigger I will need to re think it.

After using the set up as pictured above I added a small filter bag to the set up and actually captured some of the slimes. Those are being processed now.

 

[Shark]

Having re weighed the anode and adding a filter bag, I ran the anode again for a couple of hours. I removed 76.4 grams from it and processed the slime's from that amount. My digital scales won't weigh it and I am to tired to dig out my powder scales since my reloading supplies are all put away, but here is the tiny button of gold.



After processing the slime's I still have what seems to be a decent amount of pgms of some type. The remains would not go into solution using cold AR, but went in quite well when heated. I used stannous to test and received a very dark, blackish result. Heating the solution to near boiling for 20 minutes still gave a very dark test result. I didn't think to dilute a few drops and retest it. After trying to drop gold again using SMB with no precipitate at all I dropped it with copper and put it away until a later date.

 

[Shark]

Once again, I thought this had been posted before.....