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Chemistry Alchemist
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Removal of Iron from Manganese
Ive just done a thermite reaction of MnO2 that also has Iron Oxide contaminated in, how do i clean away the Iron Metal from the Manganese metal with
out it destroying the Manganese?
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unionised
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First you get a time machine, then you go back to before you did the reaction and you dissolve the Mn and Fe oxides in acid. Then you recrystallise
the Mn salt to remove the Fe. Then you dissolve the pure Mn salt in water and re precipitate the Mn as the carbonate or hydroxide. You calcine that o
get the pure oxide and then you repeat the thermite reaction.
Hypothetically you could vacuum distil the metals but that's not very practical either.
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Chemistry Alchemist
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Would you be able to write it out as a equation if possible... ive tried to crystallize the chloride but i was unsure on what one crystallized
first...
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Megamarko94
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if there is no much iron... than its manganesse chloride because there is more of it also if it has slight pink color than its manganesse chloride...
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Chemistry Alchemist
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The solution was still really brown from the iron 3 chloride, but there were crystals at the bottom... Would they of been manganese chloride
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blogfast25
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Quote: Originally posted by Chemistry Alchemist  | | Ive just done a thermite reaction of MnO2 that also has Iron Oxide contaminated in, how do i clean away the Iron Metal from the Manganese metal with
out it destroying the Manganese? |
Hmmm... I thought you didn't have any aluminium? Also obtaining manganese metal from thermite is quite hard, I know this from personal experience.
Show us your metal.
The iron needs to be removed prior to the reduction reaction. Small amounts of Fe can be removed by recrystallising the MnCl2 or MnSO4, larger
quantities require more drastic measures like Nurdrage's method.
Also: try not to start too many separate but closely regards threads. This matter is closely related to your other manganese related thread...
[Edited on 26-8-2011 by blogfast25]
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Chemistry Alchemist
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I'll post a picture n it either tomorrow or the next day... Wen ever I get around to taking pictures of it...
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not_important
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Once you have the metal, electro-refining is the best route. A bit tricky, requires careful control of conditions, and is also the best way to get
high purity Mn metal.
When starting from Mn compounds you adjust the pH and add an oxidiser to convert Fe(II) to (FeIII) which precipitates out as the hydrated oxide at the
selected pH. If starting from MnO2 use the method I've posted here before - add enough con H2SO4 to make a thin paste of the MnO2, _slowly_ heat in a
ceramic container until you drive off excess H2SO4, then continue heating up to red heat - 700 C. After allowing the reaction mix to cool, extract
with warm water to get MnSO4. Iron compounds will have been converted to the oxides, ditto for several other metals that might be in there. If you
want something other than MnSO4, add aqueous NH3 to ppt out the hydroxide, if thermite is the target then bubble air through the solution during the
addition of NH3 and for some time afterwards, the Mn(OH)2 converts to Mn(III) hydrated oxide; wash, dry, roast in air.
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blogfast25
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| Quote: Originally posted by not_important |
[snip]
, if thermite is the target then bubble air through the solution during the addition of NH3 and for some time afterwards, the Mn(OH)2 converts to
Mn(III) hydrated oxide; wash, dry, roast in air.
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No need for the air, in my experience, bleach (hypochlorite) works instantly and completely. Filter, wash cake profusely with clean water, dry and
lightly calcine the MnO2.
But MnO2 thermites aren't easy at all. The main problem is that the BP of manganese metal is very close to the MP of alumina. And since as to get
decent separation of metal and slag you need to get above the MP of alumina, inevitably quite a bit of metal is simply evaporated. I've rarely
obtained yields of more than 30 %.
You also need CaF2 (or Cryolite) as a slag fluidiser/coolant (heat sink) to get decent metal. W/o a flux the MnO2/Al mixture tends to behave like a
flash powder. I'll see if I can post a photo of my manganese later on.
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not_important
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If you do use NaOCl, then don't use NH3 8-)
I prefer using ammonium salts because A) they tend not to bind to the ppts as strongly, B) they're easier to remove, C) for Mn they will complex other
d-block metals without grabbing the Mn. But for thermite use some sodium contamination isn't going to be harmful, it'll boil off and/or function as a
flux.
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blogfast25
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| Quote: Originally posted by not_important |
[snip]
C) for Mn they will complex other d-block metals without grabbing the Mn. But for thermite use some sodium contamination isn't going to be harmful,
it'll boil off and/or function as a flux.
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You mean complexing Zn2+ and Cu2+ as ammonia complexes? Are there any others?
I just find strong, clean reasonably priced NH3 solution not so easy to find. The weaker ones are a rip off.
Photo: Manganese reguli from MnO2 aluminothermic reduction (compared to a 1 p coin). In the irregular shape of these nuggets lay clues: the melt never
got to settle well because of evaporating Mn.
[Edited on 26-8-2011 by blogfast25]
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not_important
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When I was doing this I had access to cheap slaked lime and lye with some NaCl content; both did fine for recovering & recycling the NH3 content
of the salts. Plus the pottery place I was buying my MnO2 at was sloppy and got dust from one material spread about and into others. As most of their
customers seemed to use MnO2 for heavy manganese with or without copper coloured glazes, a little iron, copper, or whatever, wasn't a problem for
those folks.
Cu and Zn are p-block, but yes - along with Cd they form fairly strong NH3 complexes. But a number of other transition metals, as well as Ca and Mg,
form weaker complexes that increase the solubility of otherwise low solubility compounds of them. I've posted the effect of ammonium slats on the
solubility of CaSO4 several times, pointing out that the Ca(NO3)2 + (NH4)2SO4 route to AN needs a bit more work to get a clean product.
All of the thermal routes to metallic Mn suck, and the electrolytic means aren't as simple as those for some other metals.
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blogfast25
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Quite a reputable book on pyrometallurgy (I forget which one right now) claims that metallic manganese (rarely needed, truth be told) is made by
aluminothermic reduction of Mn3O4, in open crucibles. Apparently once reaction gets going the crucible is then continuously topped with more oxide/Al
mixture and the crusible then gradually fills with liquid Mn. Hmmm...
An early lab method consisted in adding Mg powder (slowly!) to a molten KCl/anh. MnCl2 mixture. After reaction is complete, the crucible is then
heated to above the MP of Mn for some time, then cooled to RT. Chemically pure Mn resulted, or so it was claimed...
My pottery MnO2 contained about 25 % acid insolubles. Some silicates, I think...
[Edited on 26-8-2011 by blogfast25]
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Arthur Dent
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I had some Manganese Carbonate from the pottery store I bought a while ago and decided to test it out.
I remember Peach mentioning that his Manganese Carbonate purchased on eBay was full of crap, and very impure. So I wanted to check mine if it was
pure. First off it's the right color, a light tan, very fine powder with no signs of other impurities.
So I carefully and slowly added some concentrated hydrochloric acid to it, expecting to obtain a pink solution. Ugh! 
The resulting mixture bubbled a bit, resulting in a dark coffee-colored solution, more reminiscent of ferric chloride! Wow! Even the crud from carbon
zinc batteries has a lower iron content than that! I can't believe that this stuff contains so much iron! Or could it be something else? I really
don't see what, though.
I succesfully removed Ferric Chloride impurities from Manganese Chloride months ago, using the chemical process of Ferric Hydroxide precipitation
which resulted in a light pink solution, which yielded beautiful pink crystals unpon a long crystallization process. But this stuff I made this
morning is so dark that I don't know if the Ferric Hydroxide trick will work with this crap. And the HCl is technical grade so it's not the culprit.
I know I shouldn't expect reagent-grade purity from pottery store stuff, but come on! that's just plain wrong!
Robert
[Edited on 26-8-2011 by Arthur Dent]
--- Art is making something out of nothing and selling it. - Frank Zappa ---
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blogfast25
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| Quote: Originally posted by Arthur Dent | I know I shouldn't expect reagent-grade purity from pottery store stuff, but come on! that's just plain wrong!
Robert
[Edited on 26-8-2011 by Arthur Dent] |
Precisely because they don't specify any degree of purity they can get away with this legally. And because these impurities probably don't affect
performance in glazes the sellers will rarely face a justified complaint.
There is some high grade MnO2 available too on eBay, it's not all 'pottery crap'. I bought some quality MnO2 there and it was really quite pure.
Even quite large amounts of iron should be removable with the method you used though...
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unionised
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If you expose Mn++ to the air under alkaline conditions it oxidises so the oxides and carbonates are likley to contain Mn(III) and Mn(IV).
If you dissolve those in HCl you get mixed oxidation state complexes of Mn. Those complexes are dark green/ brown.
Their other characteristic is that they smell of chlorine because they are not stable.
Does the brown stuff you get smell of chlorine?
If it does then leaving it a while or heating it will help decolourise it.
If it doesn't then it's probably got Fe in it. You can extract that from a solution in HCl with ether
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blogfast25
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| Quote: Originally posted by unionised | If you dissolve those in HCl you get mixed oxidation state complexes of Mn. Those complexes are dark green/ brown.
Their other characteristic is that they smell of chlorine because they are not stable.
Does the brown stuff you get smell of chlorine?
If it does then leaving it a while or heating it will help decolourise it.
If it doesn't then it's probably got Fe in it. You can extract that from a solution in HCl with ether |
My experience is that Mn3+ in the presence of chloride breaks down incredibly quickly:
Mn3+ + Cl- === > Mn2+ + 1/2 Cl2
In fact, from what I observed, it appears that Mn3+ in conjuction with Cl- forms a very dark coloured, semi-covalent compound, MnCl3, which is even
more unstable in water than MnCl4. The decomposition of MnCl3 is accompanied by great evolution of heat and proceeds very quickly.
Cheaper would be extraction of FeCl3 with acetone, in which it is greatly soluble. But I'm not sure about MnCl2's solubility in acetone.
[Edited on 27-8-2011 by blogfast25]
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m1tanker78
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Robert, even a tiny bit of iron impurity will yield an apparent impressive quantity of fluff when precipitated as hydroxide. I guess one should be
thankful that iron is the main impurity? Easy to clean up in this case. 
Tank
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Bezaleel
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You say that FeCl3 will be extracted by the ether, while MnCl2 will remain in solution? Sounds like a handy extraction method.
| Quote: Originally posted by blogfast25 |
(...)
Cheaper would be extraction of FeCl3 with acetone, in which it is greatly soluble. But I'm not sure about MnCl2's solubility in acetone.
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My experience is that MnCl2 also has an appreciable solubility in acetone. However, if you crystallise the MnCl2 contaminated with FeCl3, the FeCl3
will crystallise in the latter part of the crystallisation proces, meaning that it will reside on the outside of the MnCl2 crystals. You can quickly
rince with acetone to remove the FeCl3. Since the soubility of FeCl3 in acetone is high, only use a small amount of acetone.
Another method of removing the iron from the manganese is by simply boiling off the water. Thereby the FeCl3 will largely decompose and, the remaining
Fe2O3 can be filtered off after redissolving the product. This will remove about 90% of the Fe, is my experience.
Besides, a small amount of an emerald green substance is formed as a very finely divided by product, which I believe to be MnO. I believe this despite
its unusually high stability.
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not_important
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Ah, but with ether you can extract from aqueous solution, while with acetone you need to work with the solids, which generally trap some of the
material to be extracted.
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AJKOER
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Many have mentioned a path using sulfates, however, not mentioned is the enormous difference in solubility of the corresponding sulfate salts.
In fact, Ferric sulfate is 8 times more soluble at 20 C than the MnSO4.
Use this to your advantage in separating the Fe from the Mn.
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blogfast25
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| Quote: Originally posted by not_important | Ah, but with ether you can extract from aqueous solution, while with acetone you need to work with the solids, which generally trap some of the
material to be extracted.
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Good point.
AJKOER:
The methods described above were presented precisely because separating Mn and Fe based on solubilities alone is very difficult.
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Chemistry Alchemist
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and if you were working with the solubility method, wouldn't you need to have a good amount of the stuff to get a good precipitate? ive been working
with small amounts, not enough to separate via solubility... i think ill go with the Acetone method or the Crystallize MnCl2 out of solution method
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Arthur Dent
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After many-a-months in the dessicator, my solution of MnCl<sub>2</sub> is almost completely crystallized, so I decided to harvest my
Manganese Chloride crystals which have grown to rather respectacle sizes, from 1 to 3 cm each!
I opened the dessicator and upon the rush of air, promptly emitted a puff of suffocating white HCl smoke...
The crystals have been deposited on a paper towel to dry a bit, but I'm wondering if these are hygroscopic and will absorb water from the air, Or I
could just let them to dry out in the air for a while.
Also, they still smell of chlorine a bit, so I thought to wash them with some solvent. Is there a solvent in which MnCl<sub>2</sub> is
insoluble? I have 99% isopropanol, anhydrous methanol and 99% acetone in stock...
Robert
--- Art is making something out of nothing and selling it. - Frank Zappa ---
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blogfast25
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Yummy crystals, Robert! I would just let then dry in air now... MnCl2 isn't hygroscopic at all, in my experience. Chlorine will evaporate (it's
couldn't in your dessicator). Everything will be fine: halleluyah! 
Are they really that red or is that camera bias?
[Edited on 26-9-2011 by blogfast25]
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