Electrolytic cells and smelting

[Paul Allee]

Okay can we discuss the merits of this idea: e waste copper base with trace PMs run through a sulfate cell. Take the anode slimes and put them in a crucible with sterling scrap as a collector metal, and run it as an oxidizing smelt. That way the sulfides and some base metal goes into the slag and whatever silver and gold are incorporated into the silver. Then you run the silver through a nitrate cell, and collect those anode slimes and smelt them in with some karat scrap, so whatever gold is there is incorporated into the karat gold, and then run that through a chloride cell and THOSE slimes can be put back in with the e waste since they should only have silver and copper.

Assuming a safe lab and procedures and a skilled technician which I am not, wouldn't this scheme eliminate having to use wet chemistry on the slimes? I mean even if the material has to be run twice it seems easier than dealing with slimes.

Any thoughts??

 

[Alondro]

What sulfides? You state you're going to do this with e-waste. Where would sulfides even come from? You mean SULFATES. If you wash the slimes in distilled water, the vast majority of the sulfates (for e-waste, mainly copper and tin sulfate) will be gone. Remaining will be some lead sulfate, assuming you have e-waste from before the lead-free era, and trace amounts of other transition metal sulfates which are insoluble). If you heat them in an electric furnace (which I assume you'd be using since you plan of cupeling), they'll decompose and burn off as SO2 gas, leaving the base metal oxides mixed with the PM fine powder. This could be cupeled directly. Assuming you have enough powderered PMs, they'll melt into a button and the oxides will melt and wick away into the cupel. You can add a little collector metal to help the process, since the collector metal will melt at a fairly low temperature.

But there's no need to use sterling for a collector metal when bismuth works just as well as lead, but is vastly safer, and will oxidize and cupel away completely.

The slimes from e-waste, depending upon what you're using for starting material, may also have PGMs (platinum group metals). These will not be separated by the process you propose.

If you're just using gold plated pins and traces (melted into a bar for electrolysis), there's no need to add silver, because no other PM should be present other than gold. You'd only need to cupel away any sulfates left over in the slimes, using a little bismuth to help the process along.

If your e-waste has many mixed parts, you'll have slimes with many possible mixtures of metals and insoluble sulfate salts in them. This will require wet chemistry for proper separation and purification of all the metals. Again, depending upon the mix of e-waste, you could have rhenium, rhodium, tungsten, palladium, platinum, as well as gold and silver.

Properly classifying and sorting the e-waste for the first step will make processing it much simpler. You want to limit the number of metals as much as possible. The more metals present, the harder it will be to purify them.

 

[Paul Allee]

Thank you for the correction. Yeah I mean sulfates. I'm still learning the difference.
So in this particular hypothetical scenario I wouldn't necissarily want to cupel anything. I did mention that before on another thread though. This is a different idea.
The goal is processing slimes without wet chemistry.
The point of smelting with sterling would be to collect any gold and silver without acids, then refine the silver in a silver nitrate cell, then the resulting slimes smelted with gold so again you collect the PMs without having to process slimes.
In an electrolytic gold cell, the slimes woud probably have silver chloride left over, so smelting that back in with e waste copper would mean you could grab that silver in the copper and put it back to step one, the copper sulfate cell. Then just keep that going, copper slimes in with silver, silver slimes in with gold, gold slimes back to copper.
Is there a reason this wouldn't work?
I understand you wouldn't be parting PGMs but I don't want to mess with them really.

 

[Yggdrasil]

Thank you for the correction. Yeah I mean sulfates. I'm still learning the difference.
So in this particular hypothetical scenario I wouldn't necissarily want to cupel anything. I did mention that before on another thread though. This is a different idea.
The goal is processing slimes without wet chemistry.
The point of smelting with sterling would be to collect any gold and silver without acids, then refine the silver in a silver nitrate cell, then the resulting slimes smelted with gold so again you collect the PMs without having to process slimes.
In an electrolytic gold cell, the slimes woud probably have silver chloride left over, so smelting that back in with e waste copper would mean you could grab that silver in the copper and put it back to step one, the copper sulfate cell. Then just keep that going, copper slimes in with silver, silver slimes in with gold, gold slimes back to copper.
Is there a reason this wouldn't work?
I understand you wouldn't be parting PGMs but I don't want to mess with them really.

Since you are planning to run electrolytic cells you already are in the deep end.
They are for all practical purposes comprised of wet chemistry and acids.
Just gather the slimes, dissolve in HCl Peroxide or HCl Bleach and then drop with SMB or other precipitants, then Cement the PGMs on Copper and melt to a button.
Depending on which route you are choosing of course.

 

[Paul Allee]

Since you are planning to run electrolytic cells you already are in the deep end.
They are for all practical purposes comprised of wet chemistry and acids.
Just gather the slimes, dissolve in HCl Peroxide or HCl Bleach and then drop with SMB or other precipitants, then Cement the PGMs on Copper and melt to a button.
Depending on which route you are choosing of course.

I mean that sounds simple enough, but nothing is that straightforward in practice. I've seen so much information here and other places saying that slimes are a real pain in the neck since colloids are like wet clay and get everywhere. And of course I watched sreetips go through so many steps to try to work over the silver cell slimes. I think it was you also who said that melting slimes into a dirty button will only complicate things. Also spending a lot of effort and reagents for a small amount of gold, the danger of platinosis, the risk of spills and contamination when under the hood makes me leary of doing that if I don't have to. I'm not intimidated by it, just seeing if there is a way to lessen it.

I know there is no easy button and I'm not trying to push my ignorance, but is there any merit to what I'm proposing? Just avoiding the mess and getting the material into a crucible and using a collector metal which you then use as an anode in a different cell, just recycling the slimes in order copper, silver, gold, and back to copper.

At the risk of overstating my case, if well sorted e waste is trace PMs and mostly copper, the slimes are some copper, some silver some gold and whatever insoluble junk. If most of the trash goes into the slag and the silver would collect the gold, the it would leave it in the silver slimes. Then use gold karat scrap to collect the gold from the silver slimes, leaving silver and whatever else in the gold cell slimes. Smelting that in with more e waste copper would just marginally increase the PM content and wind up in the slimes again, and come out as silver crystal in that cell.

Is this making sense? If I'm barking up the wrong tree let me know.

 

[Yggdrasil]

I mean that sounds simple enough, but nothing is that straightforward in practice. I've seen so much information here and other places saying that slimes are a real pain in the neck since colloids are like wet clay and get everywhere. And of course I watched sreetips go through so many steps to try to work over the silver cell slimes. I think it was you also who said that melting slimes into a dirty button will only complicate things. Also spending a lot of effort and reagents for a small amount of gold, the danger of platinosis, the risk of spills and contamination when under the hood makes me leary of doing that if I don't have to. I'm not intimidated by it, just seeing if there is a way to lessen it.

I know there is no easy button and I'm not trying to push my ignorance, but is there any merit to what I'm proposing? Just avoiding the mess and getting the material into a crucible and using a collector metal which you then use as an anode in a different cell, just recycling the slimes in order copper, silver, gold, and back to copper.

At the risk of overstating my case, if well sorted e waste is trace PMs and mostly copper, the slimes are some copper, some silver some gold and whatever insoluble junk. If most of the trash goes into the slag and the silver would collect the gold, the it would leave it in the silver slimes. Then use gold karat scrap to collect the gold from the silver slimes, leaving silver and whatever else in the gold cell slimes. Smelting that in with more e waste copper would just marginally increase the PM content and wind up in the slimes again, and come out as silver crystal in that cell.

Is this making sense? If I'm barking up the wrong tree let me know.

Slimes dissolves easy as it is very fine powders.
Melting it will give losses, every time you process a feedstock it will give some losses.
The amount depends on process efficiency lot size and so on.

The amount of slimes from a batch will not be much comparing to the material you run through your cell.

To me, your plan seem to be overcomplicated.

I have not seen all Sreetips videos, but I would follow his advice.

Edit to rephrase post.

 

[KKris]

Hello Everyone
I would like to continue this topic. Our e-waste smelting output is 95%+ copper. The typical composition of this billet is as follows.

Elements	%
Cu (%)	96.000​
Fe (%)	0.128​
Sn (%)	2.585​
Ni (%)	0.990​
Sb (%)	1.062​
Pb (%)	0.047​
Zn (%)	0.000​
As (%)	0.000​
Ir(%)	0.000​
Cr (%)	0.000​
Au (%)	0.020​
Ag (%)	0.157​
Pt (%)	0.000​
Pd (%)	0.001​

Now when we try to do electrolysis of this black copper, the slime is rich in tin and we are unable to recover gold, silver. Silver and tin are forming some weird mass and it takes multiple rounds of hcl washing to recover gold. Even then we are recovering 50%.
People have told me that we should achieve 98.5%. But i still have worry that with even 1.5% tin,the situation wont change much. Is there a better solution?

 

[Yggdrasil]

Hello Everyone
I would like to continue this topic. Our e-waste smelting output is 95%+ copper. The typical composition of this billet is as follows.

Elements	%
Cu (%)	96.000​
Fe (%)	0.128​
Sn (%)	2.585​
Ni (%)	0.990​
Sb (%)	1.062​
Pb (%)	0.047​
Zn (%)	0.000​
As (%)	0.000​
Ir(%)	0.000​
Cr (%)	0.000​
Au (%)	0.020​
Ag (%)	0.157​
Pt (%)	0.000​
Pd (%)	0.001​

Now when we try to do electrolysis of this black copper, the slime is rich in tin and we are unable to recover gold, silver. Silver and tin are forming some weird mass and it takes multiple rounds of hcl washing to recover gold. Even then we are recovering 50%.
People have told me that we should achieve 98.5%. But i still have worry that with even 1.5% tin,the situation wont change much. Is there a better solution?

What kind of cell do you run?
Copper Sulfate?

 

[KKris]

What kind of cell do you run?
Copper Sulfate?

Yes. Copper Sulphate Cell

 

[Yggdrasil]

Yes. Copper Sulphate Cell

Then I'd collect the slimes and leach them in HCl to remove any Tin residue.

After that is done you can dissolve the slimes in HCl/Peroxide or HCl/(Bleach or pool Chlorine)
This will eliminate the risk of Metastannic acid.
Then drop the Gold as your favorite method SMB, Iron Sulfate, Ascorbic acid or what ever.
I don't think there is enough Pd to chase it.
Let it drop in the stock pot.

Edit to add:
Forgot the Silver.
The Silver will be in the residue and needs to be separated from the slimes.
After filtering.
Take the filtrate and dissolve in Nitric and then cement on Copper, the Tin should have been removed with the first HCl leach.

 

[KKris]

Then I'd collect the slimes and leach them in HCl to remove any Tin residue.

After that is done you can dissolve the slimes in HCl/Peroxide or HCl/(Bleach or pool Chlorine)
This will eliminate the risk of Metastannic acid.
Then drop the Gold as your favorite method SMB, Iron Sulfate, Ascorbic acid or what ever.
I don't think there is enough Pd to chase it.
Let it drop in the stock pot.

Edit to add:
Forgot the Silver.
The Silver will be in the residue and needs to be separated from the slimes.
After filtering.
Take the filtrate and dissolve in Nitric and then cement on Copper, the Tin should have been removed with the first HCl leach.

Thank you. Is there any temperature and concentration of HCl to be followed during leaching with HCl?

 

[Yggdrasil]

Thank you. Is there any temperature and concentration of HCl to be followed during leaching with HCl?

Nothing spesial that I'm aware of.
Warmer is faster but also gives more offgassing.

 

[KKris]

Nothing spesial that I'm aware of.
Warmer is faster but also gives more offgassing.

@Yggdrasil Thank you. But i was wondering why you specifically asked me if we run a sulphate cell. Is it to understand in what form is the tin? Earlier, when we had not run the electrolysis, we were dissolving the billets from smelting in Sulfuric+ Nitric acid mixture. We were ending up with residue with a lot of tin. Metastannic acid was causing a problem in recovery. In fact we still have that material with us where gold and silver is stuck in a complex with tin. Does HCl leaching help there also? We were only leaching it directly in aqua regia after roasting without results.

 

[Yggdrasil]

@Yggdrasil Thank you. But i was wondering why you specifically asked me if we run a sulphate cell. Is it to understand in what form is the tin? Earlier, when we had not run the electrolysis, we were dissolving the billets from smelting in Sulfuric+ Nitric acid mixture. We were ending up with residue with a lot of tin. Metastannic acid was causing a problem in recovery. In fact we still have that material with us where gold and silver is stuck in a complex with tin. Does HCl leaching help there also? We were only leaching it directly in aqua regia after roasting without results.

The reason was to check if you had Metastannic acid.
No HCl will not normally fix Metastannic acid.
But if you dry and roast it to a red glow it will transform to a Tin Oxide and that will dissolve in HCl.

 

[4metals]

Hello Everyone
I would like to continue this topic. Our e-waste smelting output is 95%+ copper. The typical composition of this billet is as follows.

Elements	%
Cu (%)	96.000​
Fe (%)	0.128​
Sn (%)	2.585​
Ni (%)	0.990​
Sb (%)	1.062​
Pb (%)	0.047​
Zn (%)	0.000​
As (%)	0.000​
Ir(%)	0.000​
Cr (%)	0.000​
Au (%)	0.020​
Ag (%)	0.157​
Pt (%)	0.000​
Pd (%)	0.001​

Now when we try to do electrolysis of this black copper, the slime is rich in tin and we are unable to recover gold, silver. Silver and tin are forming some weird mass and it takes multiple rounds of hcl washing to recover gold. Even then we are recovering 50%.
People have told me that we should achieve 98.5%. But i still have worry that with even 1.5% tin,the situation wont change much. Is there a better solution?

What process do you use to recover the copper based billet in this form? It seems to me that oxygen sparging the molten copper will effectively remove the majority of the remaining tin into the slags with no risk of losing any PM's. Removing the tin and antimony from the bullion should clear up the issue. My assumption is the boards have an exceptional amount of solder to begin the smelting process and more sparging, or sparging with just oxygen will be necessary.

 

[Alondro]

What process do you use to recover the copper based billet in this form? It seems to me that oxygen sparging the molten copper will effectively remove the majority of the remaining tin into the slags with no risk of losing any PM's. Removing the tin and antimony from the bullion should clear up the issue. My assumption is the boards have an exceptional amount of solder to begin the smelting process and more sparging, or sparging with just oxygen will be necessary.

I'm glad I've been waiting to smelt chips! All these little tidbits coming up are helping me avoid pitfalls when I do start. The chips will have a LOT of tin, both from solder dots and tin-plated brass legs.

So I need to make adjustments to the typical flux recipe to both oxidize the elemental silicon AND the tin.

I'll have to look up how to do this sparging procedure with my smelting setup.