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Author: Subject: how to dissolve ferrite?
alvis220
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[*] posted on 26-5-2009 at 01:38
how to dissolve ferrite?


I have collected some 7 kilos of varios ferrite cores and black magnets from old electronics and have readed that they mainly contain zinc manganese barium iron strontium. I'm interested to leach out these compounds except iron. So far i tryed to dissolve in conc and 40% sulfuric acid with practically no results after of week submerging the color of sollution doesnot changes, only what can be seen is one of ferrite cores covered vith thin rust like cover, but it also stoped soon and no bubbling or rust droping is observed. sorry i m russian with very bad english
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not_important
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[*] posted on 26-5-2009 at 02:50


As these are rather dense crystalline material, you will first need to convert them to fine powder, otherwise reactions will be too slow. There's no good way to dissolve some of the metals without dissolving everything.

After that you could try:

A) Refluxing with 20% hydrochloric acid, which should dissolve everything. After that you will have the problem of separating the desired elements.

or
B) Heating with strong sulfuric acid for an extended time, then diluting somewhat to leave a precipitate containing SrSO4 and BaSO4, plus a solution of the other metals. The sulfates can be converted to carbonates by repeated boiling with fresh measures of strong aqueous Na2CO3. then the carbonates can be dissolved in HCl.

or
C) Fuse with NaHSO4, with results similar to B) as molten acid-sulfates function as a very active form of H2SO4.

The separation of Fe, Mn, and Zn is not too difficult, Sr & Ba are harder to separate cleanly. I am not sure it is worth the effort and reagents needed to effect solution and separation of these mostly common metals, though.
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Hydragyrum
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[*] posted on 26-5-2009 at 06:30


Sometimes oxides which don't dissolve in acid (or only dissolve slowly) will dissolve in NaOH solution. Examples are V2O5, As2O3, and so on. I can't say that I know it will work, but you can try it and see.



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bfesser
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[*] posted on 26-5-2009 at 11:28


Since you have so much material, it might be a bit wasteful to just rely on different precipitation properties, etc. to separate the metals once dissolved. Have you considered cation exchange column chromatography with an ion exchange resin? One can obtain cheap resin as surplus, online, or from certain water softeners (not mixed bed). Just charge it, elute it in fractions, and use one of the lit. quantative cation tests to decide which fractions to combine.
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roamingnome
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[*] posted on 26-5-2009 at 17:22


http://adsabs.harvard.edu/abs/2001GeoJI.145..740V

Selective dissolution of magnetic iron oxides in the acid-ammonium oxalate/ferrous iron extraction

something about the oxalate/ oxalic acid. There are various references with oxalic acid, may be helpful...



[Edited on 27-5-2009 by roamingnome]
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JohnWW
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[*] posted on 26-5-2009 at 18:16


Ferrites, particularly of heavy metals, are similar to magnetite, Fe3O4. This substance can be formed on mild steel as "passivating", a form of corrosion protection. Magnetite and ferrites are resistant to corrosion by acids, due to their dense crystal structures in which there is some Fe-Fe bonding. However, strong alkalis may attack them better.
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[*] posted on 27-5-2009 at 11:34


If I wanted to dissolve these things for analysis I'd try fusing with KHSO4.
For recyling, I wouldn't bother; I can get Fe, Zn, Mn, Ba, and Sr elsewhere more easilly.
I guess a blast furnace would recover the Fe and Mn fairly well.
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not_important
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[*] posted on 27-5-2009 at 19:53


Alkalies don't attack the common ferrites except under pretty extreme conditions, enough to convert the iron to ferrate and the manganese to permanganate. Acids are the better choice for dissolution, for smelting treatment similar to that used with taconite would likely be useful.
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