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Author: Subject: CuSO4 to H2SO4 problems
LostLandgull
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[*] posted on 21-2-2015 at 18:06
CuSO4 to H2SO4 problems


I have recently been trying to convert copper sulfate to sulphuric acid electrolyticly, but I only have carbon electrodes, which corrode incredibly fast. They corrode so fast that they are not an economically viable electrode. I don't want to spend lots of money on platinum electrodes, however I have heard that gold and gold plated metals will also work without corroding.

Does anyone know if gold or gold plated metals will work for this process?
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[*] posted on 21-2-2015 at 19:51


I have had good success with a piece of lead -- a strip used as flashing for roofing tiles.
It quickly builds up a PbO2 layer that stays put. No contamination to speak of. No significant anode erosion. Easy.
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blogfast25
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[*] posted on 22-2-2015 at 05:19


Quote: Originally posted by LostLandgull  
I have recently been trying to convert copper sulfate to sulphuric acid electrolyticly, [...]


What's the reaction that's supposed to take place?




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LostLandgull
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[*] posted on 22-2-2015 at 10:16


Because its done through electrolysis, there are multiple things occuring at once and therefore no linear equation for the reaction. What I know is happening is that at the cathode the copper sulphate bond is being broken, and at the anode the oxygen/hydrogen bond is being broken. The sulphate ions bond to the hydrogen ions creating the sulphuric acid, the copper is deposited onto the copper electrode, and the leftover oxygen is released as O2
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blogfast25
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[*] posted on 22-2-2015 at 10:21


Quote: Originally posted by LostLandgull  
Because its done through electrolysis, there are multiple things occuring at once and therefore no linear equation for the reaction. What I know is happening is that at the cathode the copper sulphate bond is being broken, and at the anode the oxygen/hydrogen bond is being broken. The sulphate ions bond to the hydrogen ions creating the sulphuric acid, the copper is deposited onto the copper electrode, and the leftover oxygen is released as O2


There is no 'copper sulphate' bond: copper sulphate in aqueous solution is (almost) completely dissociated to Cu ions and sulphate ions.

Even without a 'linear equation' [sic] you need to understand what happens at the electrodes. You clearly don't.


[Edited on 22-2-2015 by blogfast25]




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AJKOER
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[*] posted on 28-2-2015 at 08:51


For those suffering with CuSO4 to H2SO4 electrolysis related woes and not fond of the metal Lead or desiring even trace impurities of such in your acid, may I dare suggest turn your Copper sulfate into CuCl2 (perhaps adding NaCl to aqueous CuSO4 and then freezing out the Na2SO4, which will produce a not entirely pure aqueous CuCl2). Proceed to add SO2 and to quote from Wikipedia (link: http://en.m.wikipedia.org/wiki/Copper(II)_chloride ):

"CuCl2 reacts with several metals to produce copper metal or copper(I) chloride with oxidation of the other metal. To convert copper(II) chloride to copper(I) derivatives, it can be convenient to reduce an aqueous solution with sulfur dioxide as the reductant:

2 CuCl2 + SO2 + 2 H2O → 2 CuCl + 2 HCl + H2SO4 "

where one gets not just Sulfuric acid, but a good measure of Hydrochloric acid (which, being more volatile, can be separated out if so desired). I would avoid forming concentrated HCl here as it dissolves CuCl forming a complex.

What I like about this path is how a mole of CuCl2, a mole of water and a half a mole of SO2 is turned into 1.5 moles of acid, without impacting your light bill. Well, at least on paper, as I have not as of yet verified the suggested procedure.

[Edited on 28-2-2015 by AJKOER]
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Sulaiman
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[*] posted on 28-2-2015 at 09:26


Would manganese dioxide electrodes help?
https://www.youtube.com/watch?v=nvMVlhBmv7M
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[*] posted on 28-2-2015 at 13:02


This a Beginners question, which is one reason Blogfast25 isn't being too helpful.

(there is a Beginners Topic, which is where your question belongs)

I tried this early on, and failed to get any useful uncontaminated H2SO4.

In reverse, it is an easy way to make a good qty of CuSO4 from H2SO4 + copper electrodes, although be sure to limit your voltage to about 5volts, otherwise the electrodes disappear very fast.




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[*] posted on 28-2-2015 at 13:17


Quote: Originally posted by aga  
otherwise the electrodes disappear very fast

Isn't that the goal?
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aga
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[*] posted on 28-2-2015 at 13:22


Disappearing into CuSO4, yes.

Going all black and falling to bits before all the Cu has reacted, no.

Edit:

Thinking about it for a second, it would seem more sensible in any electrolysis where an electrode is also a reactant, it'd make more sense to continually feed the electrode into the reactor.

That way it really wouldn't matter so much how fast it reacted.

In a static design, you can end up with the electrode breaking in half, effectively cutting it out of the circuit.

[Edited on 28-2-2015 by aga]




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