RU_KLO
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Manganese sulfate not crystallizing
Hi,
I have purchase (as bulk) Manganese Sulfate from a company that sells bulks chemicals. This comes in a pinkish fine powder.
I have made Manganse Sulfate from batteries (as Der Alte process) and purified as Nurd rage process (making 30% of the solution as Hydroxide, reacting
with main solution and filtering)
The solution is then crystallized, which game me the cristals.
But for bought Manganese Sulfate, I cannot get it cristallized and what I ve got now is a brown solution with a brown sludge.
The procees was (it was made 2 times, once with the salts as is was purchased, and once as purified with the nurd rage procees) both gave me the same
results.
200ml of dH2O was heated and some manganese sulfate was added till it is saturated at aprox 90°.
It was hot filtered and then it volume was reduced till aprox 50ml without boiling and helped with a fan.
the strong pink solution was left aproximately one week, and as days past the solution got brown with a brown sludge formed at the bottom.
in the nurd rage purification process: after the solution first cools down aprox 30% of it was treated with NaOH, the precipitate (white) was poured
into the remaining 70% solution. A pink solution was obtained. the residue in the filter paper was white with a thin layer of brown material (probably
oxidation)
1) Does manganese sulphate oxidizes with air?
(in my experience with battery extraction, it form cristalls and does not visible oxidate)
Whats wrong and how can i get cristalls or purify bought manganese sulfate?
thanks,
Go SAFE, because stupidity and bad Luck exist.
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Cathoderay
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I think you are a bit unclear.
Sounds like you have two problems, purification and crystallization, and also two different sources of raw material. I gets a bit confusing about what
you are referring to at each point.
Have you or have you not been able to do the NurdRage purification and crystallization successfully using the manganese sulfate from batteries?
How can you be sure that the contamination in the bought manganese sulfate is iron?
I have to assume that the brown sludge that appeared while you were waiting a week for it to crystallize was not due to a dust storm (Ha-ha!).
There are three forms of manganese hydroxide, Mn(OH)2 white, MnO(OH)2 and MnO(OH). The last two are brown-black. All three are insoluble or nearly so.
I don't know if an oxidized form would be created fast enough or under the conditions you described.
Unless the material would be effected by heating you should always be able to boil a solution down to the point of getting crystals. As the solution
cools more crystals should form.
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RU_KLO
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1) Have you or have you not been able to do the NurdRage purification and crystallization successfully using the manganese sulfate from batteries?
Yes I have.
2)How can you be sure that the contamination in the bought manganese sulfate is iron?
Im not sure if contamination is Iron. If contaminated, do not know what is the contamination. (I performed Nurd rage process, because was the only one
Ive found for purificationof manganese sulfate.
Direct cristallization of bought product did not work.
will try these: Unless the material would be effected by heating you should always be able to boil a solution down to the point of getting crystals.
As the solution cools more crystals should form.
(Did not do this earlier because I read that for the cristals to be "purer", they should come out from solution and not from dryness or less mother
liquor.)
Go SAFE, because stupidity and bad Luck exist.
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blogfast25
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Iron and manganese are very often found together and almost certainly in battery MnOx.
But ferric hydroxide and Mn can be separated quite easily. Nurdrage describes a procedure, IIRW...
[Edited on 10-3-2023 by blogfast25]
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Texium
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You mean the one he already said that he tried, multiple times in this thread?
@RU_KLO I had a similar experience years ago with some manganese sulfate that I bought on ebay. In my case, it appeared that MnO2 was the contaminant.
Industrially, manganese sulfate is made by reduction of MnO2 with SO2. The stuff that I got was brown and there was a lot of insoluble brown sludge
when added to water, as you described. It also had a strong odor of SO2 remaining when dissolved in water. I don't remember if I checked for iron. You
can see if there is iron contamination easily by adding ferrocyanide. If it is pure manganese, a white/tan precipitate should form, but if there is
iron you will clearly see prussian blue.
I had success with mine just by gravity filtering the solution through a couple coffee filters and then boiling down the filtrate. Crystals were slow
to form and remained very small, but they were a lovely pale pink.
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Cathoderay
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RU_KLO, it is true that boiling down will not help purify the substance, but you can crystallize it.
Again, crystallization and purification can be two separate things.
What you might be referring to is Fractional Crystallization. If your air humidity to very high the solution may not evaporate very fast. Dry warm air
may help.
Any sludge you have should be able to be removed with filtering with paper with small enough pores. Filter paper with extra small pores is called
"Slow", because it is. If there is soluble contamination the filtering will not remove that.
NurdRage had a lot of iron contamination and slow crystallization wouldn't purify it well. He also had a good idea that the contamination was iron,
including soluble forms of iron. That may not be your case.
Texium has some good ideas about identifying the contamination. There are probably more analysis that you could do.
Manganese sulfate can crystallize as the monohydrate (pale pink), the pentahydrate (rose) or the tetrahydrate (pink). I'm not sure but it may depend
on the temperature. If I understand my reference book, the pentahydrate is most stable between 9 and 26 C, the tetrahydrate between 26 and 27 C and
the monohydrate between 57 and 117 C. The anhydrous form is reddish but you can't directly crystallize it from water.
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Jome
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I've done the "nurdrage process" several times (though using ceramic MnO2), and it very often turns brown. I think what is happening is that the
solution is remaining alkaline, precipitating fine particles of white Mn(OH)2 that are almost invisible as well as fine enough to pass through
glass-frit. These are then air-oxidized to brown MnO2. Perhaps SO2 could be bubbled through the solution to get rid of the brown.
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blogfast25
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Quote: Originally posted by Jome  | | I've done the "nurdrage process" several times (though using ceramic MnO2), and it very often turns brown. I think what is happening is that the
solution is remaining alkaline, precipitating fine particles of white Mn(OH)2 that are almost invisible as well as fine enough to pass through
glass-frit. These are then air-oxidized to brown MnO2. Perhaps SO2 could be bubbled through the solution to get rid of the brown.
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I've used the procedure (which is originally based on some Russian patent) several times, w/o the slightest problem, so I'm surprised you're reporting
frequent problems.
The solution should of course be as neutral as possible.
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blogfast25
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| Quote: Originally posted by Texium | You can see if there is iron contamination easily by adding ferrocyanide. If it is pure manganese, a white/tan precipitate should form, but if there
is iron you will clearly see prussian blue.
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For Fe +III concentrated thiocyanate (KSCN) is more sensitive, I think.
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Jome
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By the way, I forgot to add that presence of MnO2 could be checked by adding a pinch of ascorbic acid (vitamin C), the brown MnO2 disappears (reacts
within seconds to form a very pale pink Mn2⁺ solution), while Fe-oxides instead form colored solutions.
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Texium
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| Quote: Originally posted by blogfast25 | | Quote: Originally posted by Texium | You can see if there is iron contamination easily by adding ferrocyanide. If it is pure manganese, a white/tan precipitate should form, but if there
is iron you will clearly see prussian blue.
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For Fe +III concentrated thiocyanate (KSCN) is more sensitive, I think. |
Possibly so, though either should work sufficiently. I personally like the prussian blue test since the color is so different and
unmistakable. Ferrocyanide is sensitive to Fe(III) while ferricyanide is sensitive to Fe(II).
| Quote: Originally posted by Jome | | By the way, I forgot to add that presence of MnO2 could be checked by adding a pinch of ascorbic acid (vitamin C), the brown MnO2 disappears (reacts
within seconds to form a very pale pink Mn2⁺ solution), while Fe-oxides instead form colored solutions. |
It depends. If the MnO2 is present in the sample from the beginning, it might be tough calcined stuff that won't readily
react with ascorbic acid or other reducing agents.
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woelen
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If you add a drop, maybe two drops, of dilute H2SO4 to the solution, then it will not oxidize. At high pH, Mn(2+) is very air-sensitive and easily is
oxidized to hydrous Mn2O3, or hydrous MnO2. This is the brown sludge you observe. If you add a tiny amount of acid, such that the liquid is somewhat
acidic, then the Mn(2+) is quite stable in air. Just adding a drop of acid to e.g. 100 ml of solution is sufficient. Let it stand, so that all brown
insoluble matter sinks to the bottom and then decant the clear liquid, which should be nearly colorless (very pale pink). Let this liquid evaporate
slowly, and then I expect pale pink crystals.
Do not add too much acid, just a drop, maybe two drops.
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j_sum1
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It's always funny when woelen tells people to drop acid.
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