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Harmless
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Recycle Rare Earths
I have a several kgs slurry that contains rare earths. I am wondering if anyone knows how to extract rare earths from a oxidized slurry as a mixture
and not individual elements. The chemistry to pull out individual elements seems to be too complicated. If i can get out rare earths and other
elements in some proportion would be lovely.
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Arthur Dent
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There is a thread on this forum entitled "the trouble with Neodymium" that highlights pretty much all the info you want, including several processes
(and process attempts) to extract Nd and other metals of the genre. The most basic thing you want to do is to separate transition metals from rare
earth metals.
Robert
[Edited on 7-8-2012 by Arthur Dent]
--- Art is making something out of nothing and selling it. - Frank Zappa ---
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Wizzard
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What other oxides does the slurry contain? Might be best to use oxalic acid- It's salts of rare earths are insoluble, unlike it's other ionic
compounds. But then you're stuck with oxalates, no more oxides... But thermal decompostion is easy at this point.
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Wizzard
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Double post.
[Edited on 8-7-2012 by Wizzard]
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Harmless
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Arthur Dent
Thanks for referring me to the previous thread on the the trouble with Neodymium it seems okish but not quite the same. The mentioned thread mostly
deals with separation of individual elements and producing oxides. I want a robust and fast method of geting out the metallic product in a form of a
mixture which is quite different.
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blogfast25
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Quote: Originally posted by recycle  | | I want a robust and fast method of geting out the metallic product in a form of a mixture which is quite different. |
You are asking for a lot! Look up 'Mischmetal' for procedure, I think Wiki has a good entry.
Four easy [COUGH!!] steps:
1)Extract all REs and separate collectively from non-REs.
2)Convert to mixed RE chlorides.
3)Dehydrate mixed chlorides to anhydrous form.
4)Electolyse in a KCl eutectic mixture.
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DJF90
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Inorganic syntheses volume 2 has details on separating the rare earth elements.
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Wizzard
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You wont be able to simply extract the RE oxides from the mix  You're much better
off making salts of the whole mess, using their different properties to separate them, then making them back into oxides by electrochemistry or by
fire.
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MR AZIDE
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It is possible to separate a mixture of these metals soluble salts by , reacting with a citrate solution, whereby, as the M3+ radius ions of the
lanthanides decreases as the Atomic no increases so does the metals increasing ability to form citrate complexes increases.
( this Must be due to the increasing polarization effect, as the +3 charge is more ' concentrated' as the radius decreases. )
Under the conditions of eluting RE metals soluble salts mixture down a column of ion exchange resin using a citrate as the complexing ligand, each
different lanthanide ctrate complex can be recovered in order, due to each lanthanides increasing ability to form the citrate complexes..
Lutetium citrate complex would be the first, and in the proper conditions, the rest of the lanthanides should follow in order of their increasing
ability to form the citrate complex due to the ionic radii.
This is how they are separated in industry.
The metals can be isolated separated by reducing the chlorides, flourides and trioxides of the metals .
All this would require very exacting conditions..........is it outside the scope of the home experimenter.....???
It might help that some these metals form different coloured M3+ solutions. LA, Ce, Gd, Yb and Lu are all colourless. Nd is the only one thats red
violet it thats what youre after.
[Edited on 7-8-2012 by MR AZIDE]
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Harmless
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The slurry contains mainly Nd,Pr,B,DY,Tb,Al,Cu,Co,Ti, Fe and Ga...i am not only after Nd but all other rare earths...ion exchange for sure gives out
individual and most pure elements, but it is indeed outside my scope
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blogfast25
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| Quote: Originally posted by MR AZIDE |
The metals can be isolated separated by reducing the chlorides, flourides and trioxides of the metals .
Nd is the only one thats red violet it thats what youre after.
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It doesn’t appear to be possible to reduce the halides or oxides by means classical reductions. The oxides for instance cannot even be reduced by
means of aluminothermy and the fluorides can’t be reduced with magnesium. But Wiki does mention the reduction of cerium chloride or cerium fluoride
with calcium. Mostly they’re produced by electrolysis of anhydrous chlorides (mixed with an alkali metal chloride) I believe.
Re. the colour of Nd<sup>3+</sup> solutions, there’s quite a bit of data on this here forum. The colour seems to vary quite a lot: NdCl3
solutions have been reported by woelen to be yellow. I have a good purity sample of quite concentrated NdCl3 which also looks yellow.
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Nicodem
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| Quote: Originally posted by blogfast25 | It doesn’t appear to be possible to reduce the halides or oxides by means classical reductions. The oxides for instance cannot even be reduced by
means of aluminothermy and the fluorides can’t be reduced with magnesium. But Wiki does mention the reduction of cerium chloride or cerium fluoride
with calcium. Mostly they’re produced by electrolysis of anhydrous chlorides (mixed with an alkali metal chloride) I believe.
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I guess Kirk-Othmer could be the place where to find the reference, but I'm not in the mood to check. However, a negligent search gave FR2052082 (aka
US3721549, GB1269029 ... the nationalized versions differ a bit) where metal oxides are reduced in an inductively coupled furnace in a solution of
calcium in CaF2. The patent abstracts claims the method applies to lanthanides as well (and just about any metal), but the patent
application itself mainly focuses on titanium, uranium and zirconium.
A more bizarre reduction method is that of hydrogen reduction of cyanide complexes of lanthanides at 700-1300 °C, which is described in GB1394842
(aka US3909247).
[Edited on 8/8/2012 by Nicodem]
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
Read the The ScienceMadness Guidelines!
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blogfast25
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Very interesting. Doesn't sound like a currently industrially applied method though...
Here's a full version of US 3721549:
http://www.google.com/patents/US3721549?printsec=abstract#v=...
[Edited on 8-8-2012 by blogfast25]
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Gibberator
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If you don't mind my asking but where did you acquire such a mix of metals?
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Harmless
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Gibberator: From a machine that is cutting magnets.
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Gibberator
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I see! And how much of the metal slurry do you have, enough to share? 
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Harmless
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enough to share indeed .... but comes at small price..
[Edited on 10-8-2012 by recycle]
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Wizzard
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I'd surely like to take a crack at it, being an element collector, even a small sample containing all those RE elements would be nice.
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blogfast25
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As far as I know, only 2 types of RE magnets are in use today: NdFeB and SmCo, so that would limit the composition of the slurry somewhat. Isolating
the REs from non-RE's shouldn't be too difficult. But separating Nd from Sm is not easy...
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Gibberator
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I have to agree with Blogfast. I haven't heard of any rare earth magnets containing Praseodymium, Dysprosium, or Terbium, so that would limit it to
only Neodymium and Samarium, that is unless you work at some secret government laboratory  In any case if you have several kilos of the mix then I don't see why not try it at least, but I can tell you right now that if you
actually want pure samples of Neodymium and Samarium salts then just using magnets is probably the best way to go, unless you like hundreds of
fractional recrystallizations.
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Wizzard
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I second the notion that the sample, if used for cutting magnets, would likely contain whatever other materials are being used (Iron, Cobalt, Boron;
other housing material)... but only Sm/Nd as a present REEs.
Nd, Fe, B Neo Magnets
Sm, Co Samarium Cobalt Mags
Al, Ni, Co Alnico Magnets
Pr, Dy, Tb - Traces in Sm and Nd magnets, only as impurities.
Cu - Present from electroplated coatings? My best guess.
Ti, Ga as trace? Unsure why they would be in there. Perhaps the tools used to cut the samples?
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blogfast25
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I guess if you wanted to recover some value of what I understand is essentially a waste/by-product, then working up the material until it is RE only,
would leave you with something of commercial value, like mixed Nd/Sm sulphates or oxides. I think the very poorly soluble potassium/RE double
sulphates would do the trick very well to get rid of the non-RE junk...
Even the solid part of the slurry (presumably mostly metal particles, including REs) would have value to a metal processor who knows what he's doing.
[Edited on 10-8-2012 by blogfast25]
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Gibberator
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I may have stumbled upon something that would make this extraction a lot easier. In the thread The trouble with Neodymium they talk
about double salts of Neodymium sulfates and alkali sulfates which are insoluble to precipitate Neodymium out of solution, well I found this in The
Handbook of Inorganic Chemicals by Patnaik, 2003
"Rare earth salt solution is then treated with magnesium nitrate. The double salts of samarium, europium, and gadolinium nitrate crystallize out."
The rare earths could be precipitated out as the oxalates, calcined to the oxides, dissolved in either sulfuric or nitric acid and one at a time be
precipitated out as their double salts.
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blogfast25
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Interesting data on these magnesium - RE double nitrates, here:
http://www.einstein.yu.edu/uploadedFiles/EJBM/26-31.pdf
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blogfast25
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I attempted to synth some Nd<sub>2</sub>Mg<sub>3</sub>(NO<sub>3</sub><sub>12</sub>.24H<sub>2</sub>O from Nd2(CO3)3, nitric acid 70 %, Epsom Salt and strong ammonia
this afternoon and eventually succeeded (I think!) The trouble is that this stuff is extremely water soluble (> 100 g solute / 100 ml water at
least) and solubility-temperature dependence is fairly flat too (I’m guessing), so crystallising isn’t easy. More tomorrow…
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