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



## sathyashrayan (Dec 24, 2018)

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.


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## IdahoMole (Dec 24, 2018)

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


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## snoman701 (Dec 24, 2018)

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


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## rickzeien (Dec 24, 2018)

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 (Dec 24, 2018)

Require

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## Shark (Dec 24, 2018)

rickzeien said:


> If pyrolysis is done first could the low melting temperature metals be "sweated out" first?
> 
> Tin/449.5 F
> Lead/621.4 F
> ...



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


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## FrugalRefiner (Dec 24, 2018)

rickzeien said:


> 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


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## rickzeien (Dec 24, 2018)

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 (Dec 24, 2018)

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


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## rickzeien (Dec 24, 2018)

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 (Dec 24, 2018)

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.


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## snoman701 (Dec 24, 2018)

rickzeien said:


> https://www.midwesttechnology.com/bay-state-graphite-crucible-bottom-pour-9-1-4h-x-7-1-2-dia/
> 
> 
> Sent from my LG-H872 using Tapatalk



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 (Dec 24, 2018)

Geo said:


> 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 (Dec 24, 2018)

snoman701 said:


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


I had not considered scale when contemplating the process. 

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## Geo (Dec 24, 2018)

rickzeien said:


> Geo said:
> 
> 
> > 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.
> ...


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.


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## sathyashrayan (Dec 24, 2018)

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.


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## anachronism (Dec 26, 2018)

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


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## Platdigger (Dec 26, 2018)

Especially with tin at near 10 dollars per pound right?


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## anachronism (Dec 26, 2018)

Platdigger said:


> Especially with tin at near 10 dollars per pound right?



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


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## 4metals (Dec 26, 2018)

> 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.


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## anachronism (Dec 27, 2018)

4metals said:


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



Thanks 4metals. Still sucky though! 8) 8) 

Some of the older material is genuinely laden in either/both of those metals though so it does "bite."


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## niks neims (Dec 27, 2018)

4metals said:


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



Hey man, I have one of the greatest respects for you in GRF, and I believe that, due to your experience, you are our best chance to gain any truthful information about any large-scale refining operations possible back-office. But I have very, very hard time believing that the large scale refineries do not try their best to make a profit from each and every gram of metal (material) they get their hands...
I mean come on! The volume of material they work through... and in a field packed with top of the line scientists, engineers and inventors... the stakes are high enough for them to be motivated to squeeze all of the possible value out... I bet, even here, someone much smarter than me, could theorize how to get max value out of material like that - what about bathing PCB in good old NaOH - u get aluminium, tin, zinc all in one quick move...? And nickel - isn`t nickel magnetic, why can`t it be mechanically seperated? Especially if your end product is not "refined metal" per se, but some value-added product - like aluminium powder for example? 
For somewhat trace values - like tantalum in capacitors - the "story" about selling slag to second-stage refiners make sense, but for the big ones - Tin & Nickel - it sounds more like plausible excuse - "this metal is too hard to get out" so you aren`t getting paid on it... Even if it gets sold to second-stage refinery, unless it`s significantly worse than raw ore, they are getting paid handsomely on it... And only reason that the client doesn`t see any of this money is just because they have snuck one past us...

By the way... what happens to all of the fiberglass (glassy slag?) from FR-4? Can`t be landfill...


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## rickzeien (Dec 27, 2018)

"By the way... what happens to all of the fiberglass (glassy slag?) from FR-4? Can`t be landfill..."

What is FR-4? And why can't it be landfills? Wouldn't the fiberglass just burn off in the smelting process. 

Why isn't the slag sold as road base or other aggregate as other mills like steel mills do?

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## niks neims (Dec 27, 2018)

rickzeien said:


> "By the way... what happens to all of the fiberglass (glassy slag?) from FR-4? Can`t be landfill..."
> 
> What is FR-4? And why can't it be landfills? Wouldn't the fiberglass just burn off in the smelting process.
> 
> ...



https://en.wikipedia.org/wiki/FR-4

it is my understanding it`s the base material for most PCBs today - basically just fiberglass cloth, with epoxy, with poisonous flame retardants added...


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## rickzeien (Dec 27, 2018)

Looks like the often discussed pyrolysis/incineration done properly is the way to begin followed by the smelting process also outlined in this forum is the best practice. 

After that I would think ... But not certain... The slag could be marketed as aggregate or further processing.

https://documentcloud.adobe.com/link/track?uri=urn%3Aaaid%3Ascds%3AUS%3Af3a2bf2a-de26-44b3-bcbc-319cf8654056

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## Shark (Dec 27, 2018)

One could hammer mill the boards then run on a shaker table like Mount Baker Mining has done. 

https://www.youtube.com/watch?v=Sbr1LK2NKZ4&t=83s

(I have no affiliation with them) It seems like a reasonable alternative, but might need more research.


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## rickzeien (Dec 27, 2018)

Looks like it does well isolating the metal but we are still left with non metal fractions. 

How would we dispose of this safely at what cost? (Would be the largest fraction by far)

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## sathyashrayan (Dec 27, 2018)

Shark said:


> One could hammer mill the boards then run on a shaker table like Mount Baker Mining has done.
> 
> https://www.youtube.com/watch?v=Sbr1LK2NKZ4&t=83s
> 
> (I have no affiliation with them) It seems like a reasonable alternative, but might need more research.



mbmmllc shaker table is a wonderful concept that is simple and very cost effective.
But..
Air separated e-waste has dust collection bag. According to one of a machine vendor those dust is toxic. Per 1000 Kg around 50kg of dust gets collected. Disposing with ETP is unclear in case of mbmmllc.
Another thing is Air is all around compared to water.

(I am neither associated nor hate mbmmllc. Just sharing my thought.)


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## Shark (Dec 27, 2018)

rickzeien said:


> Looks like it does well isolating the metal but we are still left with non metal fractions.
> 
> How would we dispose of this safely at what cost? (Would be the largest fraction by far)
> 
> Sent from my LG-H872 using Tapatalk



Just thinking out loud here, but I wonder if it could be used as a filler in concrete? Maybe some other type building material. Would it make a fiberglass roofing material? Filler in asphalt for road paving?

I am pretty sure that if one can filter the dust from an air type separator, they do it with a hammer mill. I worked in a cotton mill (cloth factory) years ago and the dust was controlled by super fine mists of water. Our cloths would stay dry, but it always felt damp in there and it had the extra benefit of helping to keep the place cool.


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## 4metals (Dec 27, 2018)

I think that it probably could be used as a filler in concrete or some other similar application. Interesting fact is that in the USA the EPA would require TCLP testing for RCRA metals before approving its use. Ever wonder why this type smelting and incineration isn't done in the US anymore? Other countries do not have the same standards as the US so we cannot compete.


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## Shark (Dec 27, 2018)

A few years back there was a company that found they could repave roads using old tires as the filler instead of new asphalt. The cost was about one third that of the old standards but the EPA put a stop to it. The metal in the tire belts were cited as the reason. I think that recycling will never become an accepted standard until it can be at a lower cost than the production of new materials. So many places still charge for recycling things like waste oil, tires or some batteries, even though they resell them.


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## rickzeien (Dec 27, 2018)

I think for me pyrolysis then incinerate to reduce the organic fraction. Done properly with an afterburner and a NOX scrubber would be the way to go. 

Other than that I think the sorting and select processing then selling the remainder. That way the largest fraction of waste goes to the buyer. 



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## Geo (Dec 27, 2018)

Shark said:


> One could hammer mill the boards then run on a shaker table like Mount Baker Mining has done.
> 
> https://www.youtube.com/watch?v=Sbr1LK2NKZ4&t=83s
> 
> (I have no affiliation with them) It seems like a reasonable alternative, but might need more research.



I received a fifty pound sample of concentrates from "high grade" printed circuit boards. I wanted to leech the base metal out with HCl and cast the remainder into anode bars for some test runs. Of the fifty pound sample, 12 pounds was removed with a magnet and HCl. Nearly 15 pounds was bits of PCB fiberglass material and other bits of plastic and non-metallic's. That leaves 23 pounds of potential, recoverable metal. I am expecting to have a percentage of that being other non-magnetic and non-metallic material. I may have 20 pounds of usable material when I'm finished.


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## anachronism (Dec 27, 2018)

Jeff have you got a pic of the original boards?


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## Geo (Dec 27, 2018)

It came from some guys on the group. I have some pics in my messenger but I would have to dig them out. It looked like telecom boards. Gold plated traces but it had what looked like aluminum or zinc boxes that also looked gold plated or anodized. It would have been much simpler to have processed them without grinding them up but now it's just a mess. It's two brothers, Eric and Chris. Big pot moguls in Co. Met them through Sonny.


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