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j_sum1
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Recycling copper, working at scale. Suggestions.
I have a large canvas bag filled with approximately 20kg of copper scrap. Most of it is old house wiring insulated with badly perished rubber
insulation. This suff is thick, stiff, difficult to handle and contains many iron tacks. Also in the bag is a quantity of modern wires including small
grades, as well as plumbing scrap and offcuts.
I would love to turn this mess into a usable copper compound or copper metal. I am wondering about the most efficient (and cost-effective) method.
There are some constraints.
I do not have the ability to shred it into small pieces. I can whack it with some hand tools, but getting anything granulated is beyond my reach.
Burning is out of the question. I live in an urban area and let's say, clouds of rubber smoke will not go down well.
Peeling off the insulation is difficult. The rubber flakes off and does not come free in one piece.
Acid digestion methods at bucket scale will be ok, but I would want to be economical with acid (and peroxide).
Electrolysis would be my preferred method, but my starting material does not lend itself to that.
I am open to creative suggestions to process this stuff in a practical way.
Any ideas?
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Sulaiman
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I would call a scrap dealer and ask if they want the stuff as-is
you won't get a lot of cash,
but you avoid the hassle and potential hand/finger cuts.
Or
teach a kid some entrepreneurship 
Keep enough of the easy to strip wires for a little chemistry etc.
10 moles (635.46g) should last a chemistry lifetime.
Thick copper strands with pvc insulation intact will resist long term storage corrosion the best.
CAUTION : Hobby Chemist, not Professional or even Amateur
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RU_KLO
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hi,
1) how much it is volumetric? for example a 10 l bucket full? a 20L bucket full?
(just to imagine)
brainstroming:
removing the plastic coat:
1) via solvent (find the best and cheap solvent that do the work - here I cannot help)
2 via burning. As you mention you cannot do this, but maybe in a large tin can (with lid) or metal paint can (with lid) where you can attach a hose or
tube from one hole (chimney) of the "burning can" to a scrubber made with another 20L closed bucket (maybe filled with NaOH solution - I found that
NaOH is good at scrubbing different things.
I dont know if inside pressure of "burning can" is enough to get through, or you need to put a pump (maybe a vacum cleaner) in the other end of the
"scrubber" bucket
And for the metal, if you cant by selling "peeled" copper, I would go nitric acid.
Go SAFE, because stupidity and bad Luck exist.
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bnull
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Is it solid core or stranded wire?
Burning the insulation off is not a good idea. Depending on the city regulations, they fine you if some nosy neighbor lodges a complaint. And the
thing tends to char into a foul-smelling solid foam. I've seen it, I've been through it, it has happened to me.
For solid core, stick two knives at an angle into a piece of wood to make a wire stripper. It doesn't matter if the insulation is good or flaking off;
it gets stripped anyway. Put the wire between the knives (mind the fingers!) and pull it through. 1-2 meters sections are manageable. It is quite
boring but does the job.
If 10% hydrochloric acid is still OTC and cheap, use a PCB etchant to dissolve copper: hydrochloric acid with some copper sulfate. When it stops
working, just bubble air through the solution with an aquarium air pump. Cut the copper into pieces small enough to go inside one of those PP 5 L
bottles, add the solution and leave it alone for some time. By the time it gets deep brown, stick a hose from the air pump and bubble air for an hour
or so, or until the solution becomes bright green again.
You know one interesting use to copper wire? Removing manganese dioxide stains from glassware. Add some acid, drop some copper and swirl. The stains
gradually dissolve. I'm not exactly sure how it happens, except that somehow copper(i) is formed and reduces the dioxide to something soluble.
Quod scripsi, scripsi.
B. N. Ull
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averageaussie
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Just spitballing ideas here.
I'll have to agree with RU_KLO, nitric acid seems like the way to go, after you've stripped the wires. Solvent does seem to be a decent way to do it,
although a quick google search reveals that insulation is somewhat resistant to chemical attack (it also reveals this https://www.youtube.com/watch?v=NggoS-b3jEM though it might be worth it still)
dissolve them up, and reduce back down using aluminium foil to get copper... bits? flakes? its of a reasonable purity regardless.
copper isn't impossible to melt, but with a melting point of ~1000 c it isnt the easiest. certainly harder than aluminium. a charcoal forge will still
do it (https://www.instructables.com/Mini-Charcoal-Furnace/ this seems like a good furnace, but if just using a bunch of fire bricks would also
definitely work)
if you go down this route you could easily just skip the nitric acid step completely and just melt it in bulk.
if you dont have access to such high temperatures but do have access to a blowtorch or something, you can utilise the forging temperature of copper.
its about 900c - 740c (https://en.wikipedia.org/wiki/Forging_temperature) its basically the temperature it becomes soft and squishy without melting. just shove a bunch
of stripped copper wire in a copper pipe, heat it and whack it with a big hammer™ to make it one chunk.
another maybe possibility if you know what you're doing is the tammann and hüttig temperatures (https://en.wikipedia.org/wiki/Tammann_and_H%C3%BCttig_temper...) which apparently are the temperatures where stuff becomes sinterable (squish to
make one block) specifically the Hüttig temperature, which is calculated using the equation: 0.3 x melting temperature (kelvin). its pretty damn
simple and seems a bit too good to be true, especially considering how its only 134c for copper, but its still worth a shot.
It is still worth noting that copper is a relatively soft metal, so you probably could just heat it to some arbitrary hot temperature and whack it
with a big hammer™ to fuse it together.
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Rainwater
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Just checked and its $4.35/lb for #1 copper. This is electrical wire
#2 is comming in @ 4.15/lb. This is plumbing copper.
The difference is #1 is typical 3 9's fine and plumbing is 97 or better.
When stripping, its best to do it when hot.
Use of a pvc heater will make easy work of the most cut resistant jacket.
Burning the copper or casting ingots will lessen its scrap value.
Fact being it is illegal to sell burnt copper wire without a signed statement from the local county fire chief in my state.(house fire situation).
As for chemical conversion, HCl + sunlight takes forever, until you hook up a solar panel.
"You can't do that" - challenge accepted
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DraconicAcid
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HCl + CuCl2 + air is significantly faster.
Edit -- corrupt formatting
[Edited on 26-11-2024 by j_sum1]
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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j_sum1
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These are all good suggestions. I have been doing some more thinking myself over the past couple of days. I will hopefully get some time to work on
this over the summer break.
I will do a bit of experimenting with solvents to see if I can soften, loosen or dissolve the insulation. Petrol is my cheapest and most
accessible bulk solvent so I will start there. Not expecting much, but you never know.
Another option may be pyrolysis. I have a discarded LPG tank that could possibly be converted to a retort. I do not have welding gear (and my
welding skills are crap), but I may be able to screw something in place of the tap and pass the gases through a scrubber.
Nitric acid just seems wasteful. However, most other acids are going to need some help.
I would actually prefer a nice copper compound as a product rather than copper metal. Sulfate is always useful. But oxide, chloride or carbonate
would be acceptable too.
My best thoughts so far are to strip the wires until they are exposed even if not fully clean. Then join together to make anode. Then electrorefine
in a solution of copper sulfate. The problem here is that the resultant copper won't necessarily be in the most useful form.
I have time. There is no rush. I have been hanging on to the bag for a decade already.
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RogueRose
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Liquid Nitrogen? Dry Ice & acetone bath? Cool the insulation & hit it with a hammer?
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averageaussie
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electrorefining like this? https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcQ-u8kJ...
or something else?
if you want copper metal -> copper compounds, acid might be a not bad idea, copper is pretty acid resistant though...
apparently concentrated HCl with oxidisers present can attack copper... seems like anecdotal evidence at best, likely someone added a nitrate salt to
HCl.
electrolysis in a sulfuric acid solution seems like your best bet.
if you can melt the copper down, you could maybe pour it from a height into a bucket of water to make copper shot, then use that (higher surface area)
in the electrolysis bath. dunno if thats gonna work though.
apparently, you can use a mix of acetic acid and hydrogen peroxide to attack metallic copper. can this make peracetic acid? apparently. is it worth a
shot? maybe. (https://crystalverse.com/copper-acetate-crystals/)
good luck.
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clearly_not_atara
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^Incredible formatting glitch. I think you borked the whole page.
I think you can leach copper with ammonium persulfate and then precipitate the Cu(NH3)4SO4 by adding alcohol.
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Precipitates
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Quote: Originally posted by j_sum1  | Then electrorefine in a solution of copper sulfate. The problem here is that the resultant copper won't necessarily be in the most useful form.
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20 kg of copper could make some big old copper sulphate crystals!
Useful? No. Nice ornament? Yes!
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j_sum1
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| Quote: Originally posted by Precipitates | | Quote: Originally posted by j_sum1 | Then electrorefine in a solution of copper sulfate. The problem here is that the resultant copper won't necessarily be in the most useful form.
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20 kg of copper could make some big old copper sulphate crystals!
Useful? No. Nice ornament? Yes! |
Electrorefining gives metallic copper -- in whatever form it deposits on to the cathode. In my experience it is dendritic, but by controlling surface
properties and current density, it is possible to have nice sheets or even a powder that sloughs off.
Off topic (or maybe not). Look up the artwork "Seizure" by Roger Hiorns
I am liking the idea of HCl and air. HCl is my cheapest acid per mole of H+. I have a spare aquarium bubbler. I think I can find a way to tame
stray HCl vapours. I will do some trial runs, but this might be a winner.
(OTOH, locally available hardware store HCl is typically contaminated with Ti -- of all things. And distilling several litres might not be a fun
thing.)
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Sulaiman
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| Quote: Originally posted by j_sum1 | ...I would actually prefer a nice copper compound as a product rather than copper metal. Sulfate is always useful. But oxide, chloride or carbonate
would be acceptable too.
My best thoughts so far are to strip the wires until they are exposed even if not fully clean. Then join together to make anode. Then electrorefine
in a solution of copper sulfate. The problem here is that the resultant copper won't necessarily be in the most useful form.
I have time. There is no rush. I have been hanging on to the bag for a decade already. |
your copper has
probably survived a decade of poor storage posing little risk during that period.
All soluble copper salts are potential biohazards.
It is a lot easier to produce copper compounds from pure copper than it is to produce pure copper from copper compounds.
Copper can be used as an electrode or wire.
Solvent compatibility is a significant factor in materials choice for electrical insulation.
Unless you wash in solvent many times, your pure copper will have a plastic film coating.
Just a few thoughts
CAUTION : Hobby Chemist, not Professional or even Amateur
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Rainwater
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The jacket on the wire will probably an THHN or THWN. Both of these are a two layer nylon outter jacket surrounding a PVC jacket. Chemical compatible
with petro and resistant to most solvents at room temperature.
Best bet will be a good flat knife, cut resistance gloves, and some heat.
Heating the wire up to about 80-100c will make the insulation very easy to remove
"You can't do that" - challenge accepted
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j_sum1
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The bulk of the wire has ancient rubber insulation more than 70 years old. The rubber is cracked and perished. The copoer itself is partly oxidised.
The old wire is twin single core with about 2mm diameter. That is thick enough to make flexing difficult. It also means there is quite a bit of copper
there - which is why I hung on to it. I added my own wiring scrap to the pile over the years. And there was some more modern wiring in the house as
well, which is why it is a tangled mix.
Yeah, I could get a couple of bucks for it as scrap. But there seemed some aesthetic value in recycling it myself if I can.
Making something out of scrap is the first goal.
Clearing the garage is the second.
Purity and making money are not big considerations. OTOH, I don't want to spend hundreds on nitric acid. Doing it cheaply seems like a better way to
go.
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bnull
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| Quote: Originally posted by averageaussie | | apparently concentrated HCl with oxidisers present can attack copper... seems like anecdotal evidence at best, likely someone added a nitrate salt to
HCl. |
10% HCl does it pretty well. I never had any issues with the watery stuff from the hardware store. As for the anecdotal part, put NaCl brine or HCl in
a test tube and add solid copper sulfate. When it has dissolved, drop some copper wire or scraps and leave the test tube alone for one hour. Then
examine the copper and the solution, which will be deep brown.
Adding a nitrate would a very bad idea: NO2 is given off, whether you can smell it or not, and it gets worse with heating. First hand
experience.
The crux of the biscuit here is the combination of the oxidising properties of copper(ii) chloride with the formation of chloride complexes
([CuCln](n+1)- perhaps, I forgot how much is n). It goes like
this:$$Cu(s)+CuCl_2(aq) \rightarrow 2CuCl(aq)$$ for the dissolution of metallic copper, and $$4CuCl(aq)+4HCl(aq)+O_2(g) \rightarrow
4CuCl_2(aq)+2H_2O(l)$$ for the regeneration with air. You can even use an alkaline chloride (table salt, for example) in the first reaction (there
must be an excess of chloride ions, no matter who supplies them) and reserve the hydrochloric acid to dissolve the newly formed copper hydroxide after
the regeneration.
Ullman's Encyclopedia of Industrial Chemistry, chapter on copper compounds, section on copper(i) chloride: | Quote: | | The copper(I) chloride solution is produced, for example, by mixing a copper(II) chloride solution with metallic copper in the presence of
hydrochloric acid or sodium chloride. The colorless to brown solution is stable only in the absence of air |
because air oxidises Cu(i) to Cu(ii).
An example of process:Make a copper(ii) chloride or sulfate solution with extra chloride ions. If you have a way to contain the
vapors of hydrochloric acid, use it. If not, sodium or potassium chloride will do, and you can save hydrochloric acid for the regeneration;
Add copper. Since the insulation in the old ones is cracked, beat them a few times with a stick to remove most of the flakes. The ones that can
be stripped should be stripped.
Leave the solution alone for some time. Check in each day to see what color it is. If deep brown, it's time for regeneration.
Regenerate the etchant. If you used hydrochloric acid in the beginning, simply stick a hose from the aquarium air pump to the bottom of the
solution. It goes from deep brown to bright green, when it's time to leave it alone again to dissolve more copper. If you used an alkaline chloride,
stick the air hose the same way as before, and when it becomes bright green turn off the pump and add hydrochloric acid to dissolve the hydroxide and
oxychloride and whatever else that precipitated.
You can leave it unattended for however long you want because there is no risk of foaming or hydrogen gas or production of a corrosive spray. No
electricity is used except during regeneration, which is so simple that you can do it while reading a book, as long as you can see the color change.
Quod scripsi, scripsi.
B. N. Ull
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Sir_Gawain
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By my calculations it would take about 50 L of HCl, or 15 L of sulfuric acid, to dissolve all the copper (assuming about 15kg of pure metal present).
Where I live, that’s about 100 USD of acid, but you may not access to that much acid at a reasonable price.
Put the acid and copper into a large container and add an air pump. I don’t know how long it will take, but it should eventually dissolve. Copper
sulfate would be easier to crystallize out than copper chloride, but sulfuric acid is harder to get. I suppose you could precipitate with sodium
carbonate, but I can’t imagine filtering that much blue sludge.
“Alchemy is trying to turn things yellow; chemistry is trying to avoid things turning yellow.” -Tom deP.
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Texium
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If you have access to relatively concentrated hydrogen peroxide (~10% should be fine, 30% would be better but not required) you can speed up the
reaction with HCl quite significantly. I even made a significant amount of copper chloride back in the day using HCl and 3% peroxide, but the
resulting solution was very dilute and took a long time to evaporate, so I wouldn’t recommend that for large scale work. Bubbling air through is
certainly more economical, but also significantly slower.
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charley1957
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I stripped the insulation from a LOT of copper wire by drilling a hole through a 2 X 4 piece of lumber just larger than the wire, maybe an inch from
the edge. Then take a drywall screw and screw it into the lumber from the edge such that the tip of the screw emerges into the hole you drilled.
Then insert your wire into the hole and draw it through, adjusting the drywall screw until you get a good stripping action. The 2 X 4 lumber is best
secured to something solid. You will probably need to do some preparatory stripping to get this to work, or it’s possible this same technique might
work on two-conductor sheathed wire, called Romex here in the US. I saw this on YouTube and I couldn’t believe how well it worked, and why I waited
so long to try it. Once I saw how well it worked I had it all done in just an hour or so, and I had a LOT of wire. Give it a whirl, doesn’t take
much time and if it doesn’t work for you, it hasn’t cost you anything but a little time.
You can’t claim you drank all day if you didn’t start early in the morning.
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Fulmen
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There is another process that uses ammonia, CO2 and air to leech copper. It forms a highly soluble ammonia-carbonate complex using air as the oxidant.
Once saturated the liquid is boiled down to produce basic copper carbonate, the ammonia can be captured and reused. A simpler recipe is to use a
mixture of ammonia and ammonium carbonate and just discard the ammonia.
We're not banging rocks together here. We know how to put a man back together.
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Sir_Gawain
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| Quote: Originally posted by Fulmen | | There is another process that uses ammonia, CO2 and air to leech copper. It forms a highly soluble ammonia-carbonate complex using air as the oxidant.
Once saturated the liquid is boiled down to produce basic copper carbonate, the ammonia can be captured and reused. A simpler recipe is to use a
mixture of ammonia and ammonium carbonate and just discard the ammonia. |
I don’t think this will work very well. I’ve tried it before, and the reaction is extremely slow.
“Alchemy is trying to turn things yellow; chemistry is trying to avoid things turning yellow.” -Tom deP.
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averageaussie
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Thank you for explaining that to me Bnull, that clears things up a lot.
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Dr.Bob
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Anything other than just recycling the metal is going to lose value compared to just recycling it. I end up collecting lots of metal scrap each year
or so, and end up taking a pile of metals to the junk yard each year, I have gotten over $100 for a few bags of copper wire (insulated and not very
clean), and over $200 for a large pile of steel and stainless. I could see using a few kilos for chemistry, but trying to recycle it via acid,
solvents or other means would cost more than the wires value, plus be an environmental diaster. Most scrap yards and recyclers have special equipent
to more easily recycle it.
[Edited on 27-11-2024 by Dr.Bob]
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j_sum1
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Scrap prices locally are feeble. I am likely to get about $20 for my bag if I take it in. Principally because it is not clean.
OTOH, If I buy $20 of HCl and invest some time, I should be able to get a reasonable stockpile of a copper compound. I will need to do some math to
work out how much of my scrap I will use up.
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