E-waste copper recovery and getting rid of nickel and tin (soldering)

[sathyashrayan]

What will happens to the nickel and tin (soldering) that comes along the PCB grinding, segregating and melting stage? During electrolysis to purify the copper will the nickel and tin gets along the cathode from anode and that will make the copper impure?

I just joined the forum and I am searching for a answer in the older thread. But finding a Perl out of a sea is not an easy task.

 

[IdahoMole]

Welcome to the forum.
I have never done it myself but what I understand from reading is that most metals are fluxed out during the smelting process leaving copper contaminated with PM's ready for further separation in a copper cell.
This is a good place to start.
https://goldrefiningforum.com/phpBB3/viewtopic.php?f=85&t=25592&hilit=smelting+flux

Jason

 

[snoman701]

The tin is fluxed out in smelting and the nickel is recovered from the electrolyte in copper refining.


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[rickzeien]

If pyrolysis is done first could the low melting temperature metals be "sweated out" first?

Tin/449.5 F
Lead/621.4 F
Zinc/787.2 F

I am not sure what other deleterious metals are present but I think pyrolysis rewired temperatures approaching 900 F

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[rickzeien]

Require

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[Shark]

If pyrolysis is done first could the low melting temperature metals be "sweated out" first?

Tin/449.5 F
Lead/621.4 F
Zinc/787.2 F

I am not sure what other deleterious metals are present but I think pyrolysis rewired temperatures approaching 900 F

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An interesting approach, and I would be curious to see how that would work out as well.

 

[FrugalRefiner]

If pyrolysis is done first could the low melting temperature metals be "sweated out" first?

Tin/449.5 F
Lead/621.4 F
Zinc/787.2 F

As Harold pointed out many times, molten metals are good solvents for other metals, so "sweating" them out (liquation) only works in a few circumstances, where the metals that are not melted are also not soluble/alloyable with those that melt.

Consider that when circuit boards are wave soldered, some of the gold plating on the boards dissolves into the solder bath.

Dave

 

[rickzeien]

The typical reflow temperature range for Pb-Free (Sn/Ag) solder is 240-250°Cwith 40-80 seconds over 220°C. It should be noted that the recommended Sn/Pb reflow temperature range are less critical, and that minor deviations in temperature of equipment and components generally do not create soldering problems.

Maybe holding a lower temperature prior to pyrolysis would leave the majority of PMs intact.

Pouring off the low temp metals using a bottom pouring crucible (link below) before increasing to pyrolysis temperature.

Full disclosure: I am not a metallurgist. I just play one on the internet : )

Has anyone used the sand bath method of depopulating boards and did this remove the solders etc.

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[rickzeien]

https://www.midwesttechnology.com/bay-state-graphite-crucible-bottom-pour-9-1-4h-x-7-1-2-dia/


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[rickzeien]

The first paragraph was information I found regarding desoldering and repair of wave soldering. I neglected to provide a link or to give credit. Sorry

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[Geo]

There is a technique called "wicking" but the flux used coats the metal first and the solder is bonded to the substrate on a molecular level. So, it can't just be heated and separated as the solder becomes part of the substrate. Copper is a transitional metal and alloys easily with other metals.

 

[snoman701]

https://www.midwesttechnology.com/bay-state-graphite-crucible-bottom-pour-9-1-4h-x-7-1-2-dia/


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I think this neglects the scale by which recovery from circuit boards is ran at.

It's my understanding that some of these smelters sample a 40,000 lb load using a front loader. The rest of it is just shoved into the rotary kiln.

Redirecting tin lead solder would just confuse their assay as it would be yet another material stream.




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[rickzeien]

There is a technique called "wicking" but the flux used coats the metal first and the solder is bonded to the substrate on a molecular level. So, it can't just be heated and separated as the solder becomes part of the substrate. Copper is a transitional metal and alloys easily with other metals.

I guess the gold that is plated to the copper would go with it also correct?

This is why I love this forum. The combined knowledge saves a lot of trial and error. (Emphisis on the error)

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[rickzeien]

https://www.midwesttechnology.com/bay-state-graphite-crucible-bottom-pour-9-1-4h-x-7-1-2-dia/


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I think this neglects the scale by which recovery from circuit boards is ran at.

It's my understanding that some of these smelters sample a 40,000 lb load using a front loader. The rest of it is just shoved into the rotary kiln.

Redirecting tin lead solder would just confuse their assay as it would be yet another material stream.




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I had not considered scale when contemplating the process.

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[Geo]

There is a technique called "wicking" but the flux used coats the metal first and the solder is bonded to the substrate on a molecular level. So, it can't just be heated and separated as the solder becomes part of the substrate. Copper is a transitional metal and alloys easily with other metals.

I guess the gold that is plated to the copper would go with it also correct?

This is why I love this forum. The combined knowledge saves a lot of trial and error. (Emphisis on the error)

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This is why a barrier metal (nickel) is used between gold and copper. All gold plated material that you see on electronics has a nickel layer between the gold and copper substrate. The nickel layer is selective because a masking material is used when plating the different metals on the board. Each metal is selectively plated in the places where it is needed and the masking is removed between each step.

 

[sathyashrayan]

Thanks to IdahoMole,snoman701,rickzeien,Shark , FrugalRefiner, Geo,snoman701 and everyone who is going to contribute to the thread. It was very helpful. I am not a metallurgist. I play around internet. As a start-up Idea which is going to be based in India I made some ground works on e-waste recycling. Some doubts keeps coming again and again during copper electrolysis. So using flux during melting we can get copper and PM seperated and could be further processed with anode - cathode. The link provided by IdahoMole was very helpful on the melting part.

This answers encouraging me to go for a silver membership in future.

Hope I could answer the question raised by investors.

 

[anachronism]

One of the biggest gripes I have with refineries is their flat refusal to pay out for Nickel and Tin.

 

[Platdigger]

Especially with tin at near 10 dollars per pound right?

 

[anachronism]

Especially with tin at near 10 dollars per pound right?

Exactly but they don't pay on it- they keep it themselves.

 

[4metals]

Exactly but they don't pay on it- they keep it themselves.

If they are smelting the material, as many do, the expense of recovering an oxide of the metal encased in glassy slags may greatly exceed the value. Even with tin at $10 a pound that's only 68¢ a troy ounce. Nickel at 64¢ and zinc at 8¢.

The tin, and nickel, and zinc form oxides that will slag off when smelted with the proper flux. The copper forms an oxide that decomposes and returns the copper to the molten pool as metallic copper. So the slag may be rich (relatively speaking) in tin, nickel or zinc but it is usually sold off as a waste to a base metal refiner and paid on, if concentrated enough, and if it covers the refining fee's (if lucky) at a fraction of it's already low value.

So I don't think your refiners getting rich on the base metals, and they're paying on the copper they refine, along with the PM's.