Copper stripping cell success (sort of)

[gotgoldfever]

I used Steve's ap process to strip some boards. The remaining liquor was dark green, almost black. I diluted 250 ml of this solution with 250 ml of water in a beaker. I then made a carbon cathode and anode by taking 4 .7 mm pencil leads and wrapping one end with fine copper wire then tinning the windings with solder. I then soldered these to wires, suspended them in the solution, and ran the wires to a 3 amp DC power supply. When I turned it on the copper started plating out on the anode immediately. I got a nice large glob of copper from top to bottom, I lifted it out and it washed right off with a spray bottle into another beaker. The down side is that it totally ate the cathode and the graphite floated to the top of the solution. Chlorine gas was liberated in the process. I wish I could have taken pictures but one of my kids has absconded with my camera and I can't find it. So I have a couple of questions for the experts:
- Is this process rejuvenating my hcl?
- Is there a better material I could use for my cathode?
- This stripped copper is in a form that can be easily melted and sold as scrap right?

 

[OMG]

First things first, I'm no expert, but I'm learning.

I've done the same thing as you before. I don't have many carbon "electrodes" left, they get destroyed pretty quickly. Titanium apparently will not degrade. I am going to try it out. The titanium I ordered should be here on Monday. I'll let you know how it holds up.
This is not rejuvenating your HCl (well very little). When you used HCl to dissolve the copper, the copper became copper chloride. Then using the electrolysis you separated the copper from the chlorine and got copper on the cathode and chlorine coming off the anode. So all the chlorine that came out escaped... except for maybe a little bit that got dissolved back into the solution before it could escape. For the little bit that got dissolved, it would most likely form HCl and HOCl (hydrochloric and hypochlorous acid) - it actually depends on the pH and temperature of the solution as to how much Cl2 can get absorbed and what form it takes. It also depends on what else is in the solution. But you probably didn't dissolve much.
On your third question.. from what I've read on here, the copper in that state is pretty much garbage.

 

[Harold_V]

On your third question.. from what I've read on here, the copper in that state is pretty much garbage.

In this instance, the recovered copper may well be pure enough to melt---but the cost of fluxing and melting may well negate any profit one may hope for.

Harold

 

[Oz]

I’ve been thinking about this for some time. Steve has a great PDF on his site relating to balancing the AP solution geared towards people stripping boards for manufacture that gives a lot of insight. Ultimately though you end up with a saturated copper solution. Which by the way can be a good thing because it assures you have all the dissolved gold out of solution as a black powder.

It would still be nice to be able to remove some of the copper in an elemental form to rejuvenate the solution instead of using steel to plate it out and have to start from square one again. I would love to find a way to do this to be able to reduce waste.

Rereading your post are you sure you have no dissolved Au in solution before you started with your eletrolic cell experiment?

 

[Anonymous]

I have been studying and working on this for a while, you need a much lower voltage like .5 and larger surface area, way larger than pencil lead.

What I have got so far, treat the chlorides with sulfuric, boil off the hcl and capture to reclaim (I have not perfected this, yet) I think bubbling through water may work, not sure, then plate out the copper using a lead anode and ss cathode. You get oxygen evolved and regenerate the sulfuric.

I do not have enough materials to make enough cells in series to lower the voltage in each one to .5 volt yet, that is were I am at. I wish I could get power supply that was 1 volt and 5 amps. Then I would just have to have the materials for 2 cells.

Low voltage is one of the main keys to get the copper to plate solid.

 

[Platdigger]

Goldfever, what was the color of the solution when you finished?

So, looks like maybe lead would be a better material for the cathode then.

What was the voltage of your power supply?
Randy

 

[gotgoldfever]

Rereading your post are you sure you have no dissolved Au in solution before you started with your eletrolic cell experiment?

I used stannous solution on it. I did not get any purple but it did go clear. I am still not so confident in the stannous solution. Are there some pictures somewhere of a positive stannous test?

Goldfever, what was the color of the solution when you finished?

The color did not change noticeably, I think there was still lots of copper in there when my cathode was used up.

What was the voltage of your power supply?

13.8 V

 

[lazersteve]

You can find a photo of the stannous test positive results in the General Reactions List under Stannous chloride.

The General Reactions List can be found in the guided tour link in my signature.

Steve

 

[Art Corbit]

James,

I have made my own resistors to cut the voltage down on something like this. All it takes is a cup or two of water and a break in the anode lead for each cup. use glass so it doesn't short. You can adjust the voltage by adding salt to reaise it and fresh water to lower it. A couple of nails work fine for the anode and cathode in the cups. DC doesn't travel very good through clear water.

Art

 

[Anonymous]

Art, thanks, I was going to use a resistor also, because they are cheap. But the waste the voltage dropped as heat. Need to be efficient to break even.

Jim

 

[Scott2357]

I think the low voltage high current approach will work best, however that's just my thinking since I haven't actually tried it.

Has anybody done any speed/efficiency tests with a cell at differnt voltages and currents?

James,

I see in an earlier post you mention 1 volt 5 amps. Do you, or anyone else for that matter, know what voltage/current is optimal. Designing a supply for 1.2v with up to about 5-10 amps shouldn't be too hard. Below 1.2v is more difficult but 1.2-12v is all about the same. To save on construction cost, you could use the battery charger as input and just regulate to desired voltage/current.

When the time comes for me to crank up a cell project, I'll probably modify the charger itself to output what I need. It's much quicker and cheaper than adding new circuitry.

 

[Anonymous]

Scott, from what I have been able to find low voltage, solution content, and current density per surface area are key.

I have so many irons in the fire (sorry Irons) that I have not really been able to work on anything.

I am however convinced that convertying the Nitrates and Chlorides to Sulfates is the way to go. You can with the right glass ware get all of the acids back this way.