E-waste copper-lead alloy cupellation

[Ayham Hafez]

Recently I did many tests on E-waste cupellation, my test samples was about 50:50 lead - copper alloys, I make cupollation in a small foundry furnace using waste oil flame from the top of the furnace so flame hit directly the alloy.

I noticed after the cupellation furnace be hot enough it only took 10 minutes to oxidize all lead (time calculated based on second alloy so furnace was hot), and if I make it 15 minutes all copper oxidized!

Unlike gold and silver cupellation, the copper bead looks similar like lead copper bead so I can't recognized when cupellation finished, I only try to recognize the white smoke of lead oxide but also copper oxide gives same smoke!


Tried to reduce the air blower as much as I can, but not successed, copper from 5 attempts fully oxidized twice, and for the rest attempts it a bit oxidized, am not talking about copper oxidization because of lead, I'm talking about red oxidized material that it's very eazy to recognize from lead-copper oxidize slag/matte.

How I can know when to stop cupellation and how to prevent copper from been oxidized very quickly?

 

[Yggdrasil]

Recently I did many tests on E-waste cupellation, my test samples was about 50:50 lead - copper alloys, I make cupollation in a small foundry furnace using waste oil flame from the top of the furnace so flame hit directly the alloy.

I noticed after the cupellation furnace be hot enough it only took 10 minutes to oxidize all lead (time calculated based on second alloy so furnace was hot), and if I make it 15 minutes all copper oxidized!

Unlike gold and silver cupellation, the copper bead looks similar like lead copper bead so I can't recognized when cupellation finished, I only try to recognize the white smoke of lead oxide but also copper oxide gives same smoke!


Tried to reduce the air blower as much as I can, but not successed, copper from 5 attempts fully oxidized twice, and for the rest attempts it a bit oxidized, am not talking about copper oxidization because of lead, I'm talking about red oxidized material that it's very eazy to recognize from lead-copper oxidize slag/matte.

How I can know when to stop cupellation and how to prevent copper from been oxidized very quickly?

This kind if negates the intention of cupellstion.
As the intent usually are to get rid of all base metals leaving only PMs.
The marker for when this is finished is the it "blicks" a small flash of the surface.
For Copper I do not know.

Additionally proper cupellation depends on plenty Oxygen and good heat control.
Something waste oil burners do not have.

Electric furnaces are the best for this.

 

[Ayham Hafez]

This kind if negates the intention of cupellstion.
As the intent usually are to get rid of all base metals leaving only PMs.
The marker for when this is finished is the it "blicks" a small flash of the surface.
For Copper I do not know.

Additionally proper cupellation depends on plenty Oxygen and good heat control.
Something waste oil burners do not have.

Electric furnaces are the best for this.

I will try to use natural gas flame instead of waste oil next test, but still need to know how recognize all lead been oxidized and avoid copper oxidization.

BTW I don't know which thread someone said waste oil flame is a reduction flame, no its not, even flame from wood is not a reduction flame.

 

[Yggdrasil]

I will try to use natural gas flame instead of waste oil next test, but still need to know how recognize all lead been oxidized and avoid copper oxidization.

BTW I don't know which thread someone said waste oil flame is a reduction flame, no its not, even flame from wood is not a reduction flame.

Most flames of Carbon rich material is reducing, you need to add enough air or Oxygen for them to be Oxidizing.

 

[Yggdrasil]

I will try to use natural gas flame instead of waste oil next test, but still need to know how recognize all lead been oxidized and avoid copper oxidization.

BTW I don't know which thread someone said waste oil flame is a reduction flame, no its not, even flame from wood is not a reduction flame.

Most flames of Carbon rich material is reducing, you need to add enough air or Oxygen for it to be Oxidizing.

 

[Ayham Hafez]

Most flames of Carbon rich material is reducing, you need to add enough air or Oxygen for them to be Oxidizing.

Theorly yes, but from my experienced the fuel carbon don't reduce anything, carbon of the fuel burnt and make CO2 gas before reduce anything even with very low air source.

 

[Yggdrasil]

Theorly yes, but from my experienced the fuel carbon don't reduce anything, carbon of the fuel burnt and make CO2 gas before reduce anything even with very low air source.

A reducing flame do not reduce anything, it consumes the Oxygen so it protects the "melt" from Oxydizing or soaking up Oxygen as with Pd and Ag.
For cupelling you need either an electric furnace or an oxidizing flame.

 

[Ayham Hafez]

A reducing flame do not reduce anything, it consumes the Oxygen so it protects the "melt" from Oxydizing or soaking up Oxygen as with Pd and Ag.
For cupelling you need either an electric furnace or an oxidizing flame.

I thought carbon from reducing flame itself reduce, thanks for this info.

Now I have oxidization flame, but still not know when to stop cupellation with copper, copper oxide will absorb or little amount of PM's so I have to stop cupellation once all lead oxidized.


Do you know how much exactly lead needed to oxidize 1 kg of copper, friend of mine mentioned that 5 kg of lead oxidize 1kg of copper, do you have any idea?

 

[4metals]

Cupellation involves the lead being oxidized and the metals mixed in with the lead alloy are also oxidized. These oxides are absorbed into the bone ash cupel or the bone ash base of the furnace specifically designed for cupellation. The reason the precious metals separate out from the other metals in the molten lead is that they are noble metals and do not oxidize in that environment.

Copper is not a noble metal so it will be absorbed into the bone ash base of the furnace. But I assume the furnace has a bone ash base as what you describe and call cupellation requires this. But you never mention the cupel material. If this was a true cupellation, the copper would oxidize into the bone ash with the lead. And the ratio of lead to base metal needs to be much higher. A 50:50 lead copper bead processed in a proper assay furnace on a bone ash cupel wouldn't have enough lead to draw all of the copper into the cupel.

 

[Ayham Hafez]

Cupellation involves the lead being oxidized and the metals mixed in with the lead alloy are also oxidized. These oxides are absorbed into the bone ash cupel or the bone ash base of the furnace specifically designed for cupellation. The reason the precious metals separate out from the other metals in the molten lead is that they are noble metals and do not oxidize in that environment.

Copper is not a noble metal so it will be absorbed into the bone ash base of the furnace. But I assume the furnace has a bone ash base as what you describe and call cupellation requires this. But you never mention the cupel material. If this was a true cupellation, the copper would oxidize into the bone ash with the lead. And the ratio of lead to base metal needs to be much higher. A 50:50 lead copper bead processed in a proper assay furnace on a bone ash cupel wouldn't have enough lead to draw all of the copper into the cupel.

I used 50:50 dry cement Portland and calcium hydroxide, do you think I have to stop use calcium hydroxide to decrease the absorption ability?

 

[4metals]

You should try an experiment. Mix up a sample of lead to copper as 3:1 and run it in the furnace. If that doesn't draw the copper into the cupel blend completely, try lead to copper 4:1. If it gets to the point where too much lead is required then I would consider eliminating the CaOH. Where did you read about CaOH used in a blend for cupellation?

But the point is, if you get the right blend of copper to lead it will all go into the cupel. What do you accomplish? Unless there is gold in the mix that you haven't mentioned.

 

[Ayham Hafez]

You should try an experiment. Mix up a sample of lead to copper as 3:1 and run it in the furnace. If that doesn't draw the copper into the cupel blend completely, try lead to copper 4:1. If it gets to the point where too much lead is required then I would consider eliminating the CaOH. Where did you read about CaOH used in a blend for cupellation?

But the point is, if you get the right blend of copper to lead it will all go into the cupel. What do you accomplish? Unless there is gold in the mix that you haven't mentioned.

Regard CaOH, I read about it in GRF, they mentioned that its like bone ash.

I processed 50 kg of mixed telecom boards, I added 40% of ash weight Pb, PbO and PbSO4 after PCB's components pyrolizing, components weights was 28 kg, after pyrolizing I got 21 kg ash, after finished smelting I got about 10 kg copper-lead alloy, it was totally not magnetic, depends on my experience with same lead components, the total weight of lead is about 4.5 kg.

I melted the alloy into shots to make cupellation easier,and make 3 equal batches, first two batches I got 2 metallic pure copper-PM's alloy each one 550 grams, now parting in nitric and they gave me high good stannous test indication for palladium, the last batch the cupellation furnace was very hot, so after only 10 minutes I stopped it but only got material similar to the photo, all Copper oxidized.

First photo I added a piece of oxidized lead to show the difference.

 

[4metals]

One thing is apparent, you have to figure out how to get consistent temperature in your furnace so you can compare results under the same conditions and work up a method to get reproducible results.

Usually in a cupellation furnace for assays, it is important to heat the cupels before they are charged, I assume the same for a top fired flame furnace. If you charge a cold furnace, you will cause the charge to oxidize before it is molten. Usually the charge melts first then the air is supplied to drive the lead which provides oxygen to draw the oxides onto the cupel. Your system seems to be a hybrid so it is difficult to draw conclusions about your results.

There should be no oxidized lead remaining on the bed as that is easily absorbed into the bone ash and oxidized copper implies not enough lead was available to complete the reaction. In theory the copper Palladium 550 gram chunks should have absorbed into the bone ash leaving only Palladium on the surface if there was enough lead.

It would be interesting if you took a sample of your bone ash that has been exposed to the lead oxide and dissolve it to see if any values were taken into the cupel.

 

[Ayham Hafez]

One thing is apparent, you have to figure out how to get consistent temperature in your furnace so you can compare results under the same conditions and work up a method to get reproducible results.

Usually in a cupellation furnace for assays, it is important to heat the cupels before they are charged, I assume the same for a top fired flame furnace. If you charge a cold furnace, you will cause the charge to oxidize before it is molten. Usually the charge melts first then the air is supplied to drive the lead which provides oxygen to draw the oxides onto the cupel. Your system seems to be a hybrid so it is difficult to draw conclusions about your results.

There should be no oxidized lead remaining on the bed as that is easily absorbed into the bone ash and oxidized copper implies not enough lead was available to complete the reaction. In theory the copper Palladium 550 gram chunks should have absorbed into the bone ash leaving only Palladium on the surface if there was enough lead.

It would be interesting if you took a sample of your bone ash that has been exposed to the lead oxide and dissolve it to see if any values were taken into the cupel.

I'm willing to smelt the cupellation slags with adding carbon to get lead and Copper alloy again, will also add some more pure lead, since slags about 4 kg, then will try to make cupellation again with preheating as suggested and with reducing the air blower to minimum

 

[Alondro]

It sounds like you're trying to purify copper using cupelling. Why?

Cupelling is only used to recover precious metals. It has never been used to purify copper, because it WILL oxidize.

Electrolysis is the MOST effective and efficient way to purify copper. Every major refiner uses electrolysis, and it's not difficult to set up. If you're using a sulfate electrolytic cell, you don't even have to worry about lead sulfate because it's insoluble! It's simplicity itself to separate the lead and copper this way.

 

[Ayham Hafez]

It sounds like you're trying to purify copper using cupelling. Why?

Cupelling is only used to recover precious metals. It has never been used to purify copper, because it WILL oxidize.

Electrolysis is the MOST effective and efficient way to purify copper. Every major refiner uses electrolysis, and it's not difficult to set up. If you're using a sulfate electrolytic cell, you don't even have to worry about lead sulfate because it's insoluble! It's simplicity itself to separate the lead and copper this way.

No, I just want to oxidize lead used as a collector metal while E-waste smelting, so need to avoid oxidizing copper only lead, now I'm trying to treat the issue,will make update after finish

 

[Yggdrasil]

No, I just want to oxidize lead used as a collector metal while E-waste smelting, so need to avoid oxidizing copper only lead, now I'm trying to treat the issue,will make update after finish

I'm not sure that is possible.
It depends on which temperature the Copper start oxidizing, if that is higher than the cupelling temperature.
If not it is not possible.
Then you have the interaction among the metals themselves and their respective oxides.

 

[snoman701]

Traditionally in the fire assay, you would scorify that, utilizing a borax slag to absorb the copper oxide. Then once you have removed enough copper through scorification, you can then cupel to leave just precious metals remaining. You may have to add lead after scorfication. On a larger scale, you would be utilizing a retort furnace.

 

[g_axelsson]

One point of a more academic nature...

A flame from a carbon based fuel can be either reducing, neutral or oxidizing depending on the amount of oxygen that is used. Carbon doesn't go directly to carbon dioxide in one step. If you have an oxygen starved flame it will produce carbon monoxide, CO, and that is fully capable to reduce many metal oxides down to pure metal.
One major example is old blast furnaces producing iron where the coal is placed in the bottom and the gases going up through the ore reduces the iron oxide down to metallic iron.

A common way to remove impurities like iron and lead from raw copper is to do an oxygen sparging. First the copper is molten in large crucibles. Then pipes with oxygen or air are pushed down under the surface of the molten raw copper and oxygen is blown into the melt. By carefully monitoring the slag or metal, a raw Copper-nickel alloy can be produced.
Iron, led, tin, zinc... and so on will be oxidized and absorbed into the slag while more precious metals are left in the copper melt. Nickel is so close to copper so it's impossible to remove the nickel that way. The next step to get a clean copper product is electrolysis where the nickel comes out as nickel sulphate and precious metals ends up in the anode slime.

At least that's the theory that I've read.

Göran

 

[Ayham Hafez]

I did the following:

Smelt all lead oxide with copper oxides collected from the cupellation attempts, material was 22 kg, I added 1 kg sugar and some borax and soda ash, I got 10.5 kg of metal shots, then make cupellation for them in three equal batches, I used lpg with minimum air source, the issue was the high temperature of the cupellation furnace, copper can be oxidized easily with high temperature in cupellation process so the solution is to control the temperature and use a reduction flame during the cupellation process.

If I want to reduce the copper content by use an oxidizing flame, will PM's be lost in the oxidized copper, answer is yes, I did an experiment for some oxidized copper from the cupellation by parting it using nitric and at the end I got silver,gold and palladium!


I think the easiest way to get +99% copper from e-waste smelting is to use lead oxide and lead sulphate then make cupollation to reduce the lead content. Lead sulphate and oxide will push most of base metals into slags, but don't do that with tin, soda ash can take care of the tin.


Now I wonder if Copper electrolysis cell will be effected if I use copper-lead alloy about 50:50 , if lead is not soluble in copper sulphate electrolysis cell, that mean I can shortage the process and don't make cupellation, just melt lead-copper alloy into anodes and use it in copper electrolysis cell.