Sciencemadness Discussion Board - Economical extraction of copper from PCBs

Economical extraction of copper from PCBs

Random - 10-9-2014 at 14:02

Been thinking about it for a while, removing the components and then soaking the PCBs in poor man aqua regia or just copper chloride etchant solution. They are said to contain like 20% copper so from like 5kg of recycled PCBs I would get a kilo of Cu. It would be dropped by Al and heavy metals would be precipitated into powders.

Would it be economical to make scrap copper that way? Only problem would be that it would be a powder.

I guess I could make more money by that than to scrap silver and gold from electronics.

[Edited on 10-9-2014 by Random]

Oscilllator - 10-9-2014 at 16:59

Just an idea: If you can buy it in bulk, it may well be cheaper to reduce the copper from solution using ascorbic acid. I understand it's fairly easy to reduce copper(II) to copper metal using ascorbic acid, and although it costs $15+/kg when you buy one or two kilos, I imagine the bulk discount would be quite large.
In the past, I have used a mixture of 37% HCl and KNO3 to dissolve scrap copper. This is extremely cheap and works quite well, however the copper is dissolved as copper(I) chloride, so if you want to reduce it using a metal you may want to buy a cheap air bubbler to oxidise the copper(I) to copper(II).

Bert - 10-9-2014 at 19:03

I believe this is done commercially by a hybrid process- First the boards are ground up, then various mechanical, magnetic and electrostatic separations of the powder are done until a much higher metal % concentrate is achieved. This concentrate is chemically treated and electrolytically refined...

franklyn - 10-9-2014 at 21:09

Entering " pcb copper extraction " into Google I got these hits

http://www.scielo.br/scielo.php?pid=S0104-66322009000400003&...

http://www.isca.in/IJES/Archive/v2i1/3.ISCA-RJEngS-2012-122....

Chemical means are mostly for recovery of metals as copper from waste leaching solutions which etch traces on printed circuit boards. This sort of enterprise does not show a profit but does defray the cost of disposal of what is otherwise toxic waste. Solids are sent to allocated land fill at some expense. Metal recycling from boards is best done mechanically. If excessive heat is applied the copper laminate separates ( it's called de-lamination ) from the epoxy , or uncommonly these days , phenolic board. Chopping boards into one centimeter squares and filling a metal container placed into an oven at medium heat will loosen the laminate so that further mechanical beating will separate the metals from the board substrate. A heap of copper and solder slag is itself waste and will only be purchased from you as such. Larger batch processing is more remunerative so taking a metal drum set over a fire can yield a more profitable recovery effort. The bath method you envision is best for recovery of precious metal as gold. What profit you will realize is entirely dependent on how you acquire the waste , free or at trivial cost it may be worth a try , otherwise this is best left to dedicated recyclers.
http://stores.ebay.com/Garland-Computer/_i.html?_nkw=scrap&a...

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Random - 11-9-2014 at 05:29

Things like electrostatic separation would be out of reach for me and burning is somewhat dangerous due to toxic fumes, I am also scared of dioxins and polychlorinated biphenyls, not sure if these are created during that "cooking" process. Now if I would dissolve them and electrolytically refine it instead of dropping with Al, would I get powder or solids? As someone above said powder could be treated just like metal slag and that couldn't be sold as scrap copper.

Ascorbic acid in bulk is still somewhat expensive considering the price of Al scrap in comparison by Cu by molar mass.
Now with introducing electricity there are new questions about profitability of the procedure.

Thing is I have access to these lower grade boards that contain more copper than gold strips or palladium MLCCs and there is nobody who would buy scrap PCBs like they do in america.

It would be also possible to drop copper as carbonate since copper salts aren't cheap either but I wouldn't know what to use it for in large amounts and nobody would buy it.

[Edited on 11-9-2014 by Random]

MrHomeScientist - 15-9-2014 at 07:08

I think ascorbic acid precipitation is a great idea. This supposedly yields a very fine, quite pure powder of Cu metal. You could always take the powder and melt it down into bars. I have a little micro propane furnace I bought off eBay that works great for small amounts.

Although come to think of it, I'm not sure how selective ascorbic acid is if you have lots of other dissolved metals too (solder, etc.). I suppose you could subject the precipitated powders to HCl to dissolve the tin, at least.

WGTR - 17-9-2014 at 10:06

It is going to be difficult to melt fine copper powder into solid copper, as an FYI. Copper powder oxidizes quickly in a non-reducing atmosphere, at room temperature even.

Instead of using ascorbic acid (which is more expensive than copper itself), it is possible to reduce copper at 200-300°C with waste alcohol/antifreeze/hydrogen vapors in an otherwise inert environment.

I have reduced small amounts of copper and nickel powder using hydrogen in a heated (with a propane torch) test tube. A gas bag full of hydrogen was attached to the rubber stopper, and the tube was flushed out with excess hydrogen before stoppering it. Both copper and nickel melt at high temperatures, however, much higher than can be achieved in borosilicate test tubes.

In the process of making various aldehydes, I have passed alcohol vapors through a borosilicate tube full of copper oxide "beads". The temperature was about 300°C. As the reaction proceeded the copper was reduced to sintered beads of copper. If the reaction proceeds above 400°C, this sintering effect becomes more pronounced to the extent that the beads are no longer catalytically active.

I have also reduced copper oxide in refluxing ethylene glycol. The glycol needs to be hot. At temperatures below reflux it is a slow/nonexistent process. The ethylene glycol can be distilled from old radiator fluid.

Little_Ghost_again - 17-9-2014 at 12:12

wouldnt H2So4 turn copper into copper sulphate? If so then solar panel and a copper pipe as Anode

, just keep added copper plate to the pipe

Or am I being stupid?

aga - 17-9-2014 at 13:06

Quote: Originally posted by Random

Would it be economical to make scrap copper that way?

The last time i had a production run of PCBs made, the PCB maker was using Ammonia to etch the boards.

That's what they said, so maybe not Just ammonia.

The deal was that they got the Etchant for free, so long as they gave it back after using it.

The Supplier obviously cycled out the Copper, sold it, and gave back fresh etchant.

Look up a local PCB manufacturer and ask them for a 1 litre sample of etchant amd analyse it.

The worst they can do is say No.

WGTR - 17-9-2014 at 13:06

Stupid is as stupid does (To quote Forrest Gump).

Enjoy:

http://www.youtube.com/watch?v=M2hjv6FS67g

aga - 17-9-2014 at 13:17

Quote: Originally posted by Little_Ghost_again

wouldnt H2So4 turn copper into copper sulphate? If so then solar panel and a copper pipe as Anode

, just keep added copper plate to the pipe

Or am I being stupid?

Nope.

Just need to find a way to make it Commercially workable an you'll be hailed as a Genius.

aga - 17-9-2014 at 13:19

Quote: Originally posted by WGTR

Stupid is as stupid does (To quote Forrest Gump).

Forrest Gump is my favourite US president of all time.