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Fulmen
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It works, even if it's a bit slow. IIRC the initial reaction is slow, but increases a bit once you have copper in solution. But any air-powered
reaction will be slow, that's just the price to pay for free oxidizer. So what? Time is cheap if you don't have to monitor the reaction. I don't think
sulfuric acid and air will be any faster.
One benefit of this reaction is that it produces a dense copper carbonate powder of uniform composition, something that is impossible with direct
precipitation.
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clearly_not_atara
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You might be able to kickstart the reaction with ammonium persulfate like I suggested earlier. It's Cu(NH3)2(+) that gets oxidized by oxygen to
Cu(NH3)4(2+)
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Sulaiman
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I think that if you 'burn' the copper eg on a BBQ grill) to form an oxide layer it will dissolve in HCl much easier.
When the reaction slows, burn the copper again.
CAUTION : Hobby Chemist, not Professional or even Amateur
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Fulmen
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That should work, but I doubt it will be fast. And it will require more work and energy. For a small batch it's probably doable but for 20kg? Air
oxidation is slow, but it can be done with little effort and a small aquarium air pump. I've done this both with ammonia/CO2 and sulfuric acid, albeit
not on such quantities.
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pesco
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Chemicals pricing and availability depends on your location. In most places HCl is the cheapest mineral acid. Can be even cheaper, if you make it
yourself and you can easily do it in huge amounts for free or nearly free. Just pyrolyze some PVC, preferably uPVC or CPVC and you'll have gallons of
HCl.
From that pile of Cu I would select some somewhat clean pieces and
1) electrolyze in NaCl solution to obtain Cu2O or CuO. Best precursor to Cu salts.
2) melt some cables (purer) to get nice electrode for electrochemistry or cementation of Ag
Other bits, dirty, tiny wires, difficult to strip or mixed with Sn/Fe I would stick in sealed steel paint can or similar and pyrolyze. Gasses pass
through water to scrub HCl and then into the fire to neutralize. If the fire is HOT (500+ °C) and the gasses stay there for around 1-2 seconds then
all the nasties will get destroyed.
Once pyrolyzed and Cu exposed flood it with HCl.
PET bottles outside work very well. PET is UV stable and bottles wont disintegrate after a while spilling the content. I have PET bottles in full sun
for couple years and they seem to be still like new, just dirty  . I keep the
bottles inside old aquarium placed on its side. That way rain doesn't get into the bottles, even very strong wind wont knock them down and the
temperature get a bit higher when Sun is out speeding up reactions.
HCl works initially slow, but once some Cu dissolves the dissolution speeds up. If you place and aerator in the bottles then it is pretty fast.
Aquarium airpumps work great, they are cheap and need very little electricity. Wouldn't bother with peroxide, too expensive in these amounts and not
necessary, especially if you are not in a hurry.
Dissolution by HCl is not as fast as HNO3, but the later is nearly everywhere difficult to obtain and WAY more expensive than HCl.
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Fulmen
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HCl + nitrates should work as a substitute for nitric acid.
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pesco
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All acids attack copper. In a way
Even dilute cold sulfuric or acetic will do, however it will take a while.
Copper is readily oxidised by dissolved oxygen, either in liquid on moist air. Both come down to O2 in presence of H2O.
Once oxidized pretty much any acid will attack the oxide.
This is how patina is formed. By dissolving copper oxide by carbonic acid.
Long time ago, for shits ang giggles I poured some 10% vinegar in a bottle, put some coper wire in it. In couple months time it got deep blue.
HCl is much faster than most. Out of "common" acids only nitric and concentrated sulfuric are faster.
Once you have some CuCl2 in solution it works as a catalyst.
Cu + CuCl2 -> 2CuCl
4CuCl + 4HCl + O2 → 4CuCl2 + 2H2O
In effect HCl is pretty fast in dissolving copper as long as there is free oxygen dissolved in the mixture and just atmospheric O2 is
enough.
I remember reading on this forum ingenious way one of the members developed to produce copper acetate. It involved flask with acetic acid topped with
reflux column with copper bits packed into it and air supplied below. As acetic acid evaporates it passes, together with fresh air (Os),
through copper bits, then condensates above and drips down to the flask on the way dissolving copper already oxidises by Os.
[Edited on 6-12-2024 by pesco]
[Edited on 6-12-2024 by pesco]
[Edited on 6-12-2024 by pesco]
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teodor
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But why you don't consider persulfate as was suggested already. The price?
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Rainwater
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Monday, i put 1g of fine copper strands into 250ml of di water with 1g NaCl and an air bubbler.
Today, I have no copper metal left in the beaker. But a lite green percipitate i assume is copper carbonate
"You can't do that" - challenge accepted
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Fulmen
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@Rainwater: Well done, now you just have to repeat it 20'000 times :-)
@teodor: We're talking 20kg of copper here, have you calculated the amount of persulfate needed to dissolve that? It's not going to be cheap with any
available oxidizer (besides air). Basically you have the choice between expensive and slow.
We're not banging rocks together here. We know how to put a man back together.
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bnull
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@Rainwater: Try a more concentrated solution (1 g of NaCl in 10 mL of water, for example); the more chloride ions, the better. The precipitate is
apparently a mixture of basic copper carbonate and copper hydroxide.
I was reading a patent the other day but forgot to jot down the number. Searching for it today, I found one (US2046937, "Process for the preparation of copper compounds from metallic copper") that looks more interesting. It uses copper (ii) chloride
ammonium chloride. I'll test a variation of it, starting today.
Quod scripsi, scripsi.
B. N. Ull
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Rainwater
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Naa. I keep mine as metal and toss it in the mash as needed.
Just trying something as its the closest to an experiment ive been able to do in months.
"You can't do that" - challenge accepted
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DraconicAcid
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I'm honestly considering a career change. Despite my decades in an academic setting, and electrician's salary would be much nicer.
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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teodor
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Quote: Originally posted by Fulmen  |
@teodor: We're talking 20kg of copper here, have you calculated the amount of persulfate needed to dissolve that? It's not going to be cheap with any
available oxidizer (besides air). Basically you have the choice between expensive and slow. |
Yes, but for working at scale it probably could be formed in situ by electrolisys of (NH)4SO4 solution in H2SO4. If copper is present in the bath it
will be converted to CuSO4. I doubt you can make it more economical pumping air with electricity instead of oxidising with electricity.
Also with proper activation persulfate can conver many organic compounds to CO2, but I am not sure about the insulation.
[Edited on 8-12-2024 by teodor]
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Precipitates
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| Quote: Originally posted by Fulmen | | It's not going to be cheap with any available oxidizer (besides air). Basically you have the choice between expensive and slow.
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Bleach is pretty cheap.
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pesco
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| Quote: Originally posted by teodor |
Yes, but for working at scale it probably could be formed in situ by electrolisys of (NH)4SO4 solution in H2SO4. If copper is present in the bath it
will be converted to CuSO4. I doubt you can make it more economical pumping air with electricity instead of oxidising with electricity.
Also with proper activation persulfate can conver many organic compounds to CO2, but I am not sure about the insulation.
[Edited on 8-12-2024 by teodor] |
Don't know about the costs electricity in electrolysis vs pumping air.
Need to be calculated/tested by somebody with inclination and a bit of spare time
Point is that you don't have to pump air. It only speeds the reaction up. If you don't use airpumps then the oxygen will naturally diffuse into
solution and oxidize copper anyway. It will just take a bit longer. A bit longer doesn't mean years. It is literally "a bit" longer. Done it, seen it.
If you really want to have some fun with fiddling around and save (tiny amount of) money then rig up small device. A bit of a plastic shaft/tube with
two fans linked via string or threaded rod. The top fan will be turned by wind and it will "power" the bottom fan which, half submerged, will agitate
surface of the solution. That should be pretty much as efficient as air pump and no electricity involved.
Small aquarium airpumps have wattage of 2W to maybe 8W for pretty powerful one. Lets assume you have bigger one, 5W model, and you want to run it
24/7.
Average 1kWh costs nowadays around £0.25 in UK.
1000/5 = 200 so on 1kWh you can run this pump for 200h
1 week = 24*7 = 168h
cost of electricity for 1 week = (168*£0.25)/200 = £0.21
A month of constant running such pump costs less than £1.
And hassle free, stick the airstone in, turn the pump on and forget about it for few weeks.
Not really worth messing about
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bnull
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At the time of my post above (14h08m), I dissolved about 1 gram of sodium chloride (table salt, nothing fancy) and 1 gram of copper (ii) sulfate
pentahydrate in the smallest quantity of reverse-osmosis water. Since I don't have ammonium chloride because it is restricted here (O_o), I used 2
grams of ammonium bicarbonate and about 6 mL of 15% HCl to neutralize the stuff. The solution was a weak green-blue on top of a white precipitate,
perhaps an anti-caking agent like silicon dioxide.
I cut about 50 cm of varnished copper wire from an old de-Gaussing coil. After burning off the insulation on a spirit lamp and removing the charred
residue with a wood sandpaper, I made it into a multi-turn loop and inserted it into the test tube in a way that most of it remained submerged. The
loop slipped to the bottom of the tube. I used used some expletives (bugger that, I won't fish it) and left the tube alone for about eight hours.
Later that night (0h32m):
Notice the three liquid phases. Green is relatively rich in oxygen, so most if not all of the copper is copper (ii). Brown has a considerable quantity
of copper (i) and is very poor in oxygen. A clear, transparent solution means that all the copper present is copper (i), with no oxygen whatsoever in
solution. The white stuff is apparently silicon dioxide. Most of the copper wire was gone. The distribution of the phases was affected by the
diffusion rate of oxygen through the solution. The relative size of the phases is about 8 green to 3 brown to 1 clear.
I attached another length of shiny copper wire to a small motor and used it as a stirrer to mix the three phases and dissolve more copper. The
solution became yellowish, as an unfiltered wheat beer (straw yellow). I added 10 drops of 15% HCl to a small section of the top phase without
disturbing the rest of the solution. It immediately turned brown. Today, two days later, the solution is a dark amber color with a greenish
precipitate of oxychloride or hydroxide or basic carbonate, or a mixture of the three.
The presence of ammonium cations indeed increases the rate at which copper dissolves. The patent may be right about a 50-fold increase after all .
On hindsight, I could have made ammonium chloride from table salt and ammonium bicarbonate and used the solution, which would need less HCl.
Quod scripsi, scripsi.
B. N. Ull
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Fulmen
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This looks slightly relevant: https://www.sciencedirect.com/science/article/pii/S266679082...
Seems like both chlorides, carbonates and sulfates are suitable candidates.
The carbonate process still has an ace up it's sleeve imho. It can be reduced to very pure CuO that's the perfect raw material for a number of other
copper compounds. But if this isn't a problem the chloride process looks like a very promising candidate.
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j_sum1
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Thanks for all the suggestions. I have not read through all of them yet. It looks like I have a few trial runs to set up in my lab. I hope to get
to that in the next couple of days.
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Dr.Bob
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You may have already seen this, but similar to what you are doing:
Also see http://www.sciencemadness.org/talk/viewthread.php?tid=160306...
"I have another idea: copper can be dissolved in ammonia solution with ammonium chloride (or even sodium chloride).
Resulting tetraammine copper(II) chloride should decompose when heated to copper(II) chloride and ammonia.
Dissolution in ammonia works better with "ammonia water" (24%), but diluted household grade ammonia also works, but more slowly, I once made
tetraammine copper perchlorate from 10% ammonia and lithium perchlorate. Thin copper wire (incompletely) dissolved in several hours. Edit: in 24
hours, actually.
What I'm not sure is whether decomposition will produce copper chloride or copper oxide and HCl."
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Sulaiman
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I like the idea of an air pump and bubbler, if only to circulate the liquid,
removing reaction products away from the copper , allowing the oxidising components to get to the copper.
The extra dissolved oxygen will of course help with the oxidation.
I would avoid bleach due to the sodium ions.
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