Saerynide
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MnO2 and Batteries
I opened a few fresh D cells to get the carbon rods, so now Im left with a ton of electrolyte mix. I decided not to waste it and I washed out the mix
to remove all the zinc and ammonium chloride.
Now, how would I get the amorphous carbon out of the MnO2? Does it float in water? So far, as Ive been trying to rinse out dissolved salts, some
greyish/black powder floats to the top everytime. I assumed that was the carbon and have been pouring it off. Can anyone tell me if Im on the right
track?
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BromicAcid
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Well, MnO2 has a density of 5.03 g/ml so you should be able to seperate it from the carbon black based on the different densitys like when ore is
being refined. I myself have taken apart lantern batteries to get the graphite rods. I decided that I didn't want to waste the manganese
dioxide so I filtered it and washed it with water. I really didn't mind the carbon impurities because I use it as a catalyst for the
decomposition of H2O2 so I just use as is.
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Saerynide
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Im thinking about trying the MnO2 + Al thermite reaction. I suppose I could us KMnO4, but that is so much more expensive than batteries 
Edit: I just read that it has a density of 1.7-1.9. So, if I add salt to water til it has a density of about 2 something, the carbon black will
float while the MnO2 still sinks. Then I can rinse the MnO2 clean of salt later. Would that work?
Btw, is it the MnO2 that stains everthing, or is it the carbon black, or both?
[Edited on 19-3-2004 by Saerynide]
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Organikum
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Its lampblack - a form of carbon black which stains everything and makes the batteries a pest. They contain up to no MnO2 - they are Bunsen-elements
Zn/C. The more expensive alkaline species contains MnO2 but not in its most active form mostly - its a mixture of different active MnO2 subspecies.
But it should be possible to activate the MnO2 in alectrolytic cell or with KMnO4.
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Saerynide
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They seem to claim that it has MnO2.
So almost all the stuff is carbon?  How will there be enough MnO2 for the
battery reactions?
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vulture
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Being a solid, MnO2 has an activity of one and thus not much is required to keep the potential.
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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Saerynide
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Hmph. So much for all that time spent trying to get the carbon out 
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Magpie
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Would it be possible to separate the carbon from the MnO2 by burning the carbon, i.e., place the mix in an oven of sufficient temperature.
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BromicAcid
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MnO2 is an oxidizing agent, C is a fuel, therefore reaction.
2MnO2 + C ---> 2MnO + CO2
But I don't think anyone would raise it to a temp to steal that other oxygen from Mn.
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unionised
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The last couple of zinc/carbon batteries I pulled apart contained MnO2 (at least, they contained something that oxidised HCl to Cl2).
As I bought them for the zinc and the carbon, I took them apart without using them to supply any current. The MnO2 must get used up to some degree
during use of the batteries, but there is still Mn there.
You could disolve the MnO/ MnO2 in acid filter off the carbon black and reprecipitate it with bleach to get fairly clean MnO2
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