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Recycle Rare Earths

recycle - 7-8-2012 at 00:25

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.

Arthur Dent - 7-8-2012 at 03:26

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]

Wizzard - 7-8-2012 at 05:06

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.

Wizzard - 7-8-2012 at 05:07

Double post.

[Edited on 8-7-2012 by Wizzard]

recycle - 7-8-2012 at 05:21

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.

blogfast25 - 7-8-2012 at 06:29

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.

DJF90 - 7-8-2012 at 07:30

Inorganic syntheses volume 2 has details on separating the rare earth elements.

Wizzard - 7-8-2012 at 10:36

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.

MR AZIDE - 7-8-2012 at 11:43

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]

recycle - 7-8-2012 at 16:30

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

blogfast25 - 8-8-2012 at 05:55

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.

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 Nd3+ 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.

Nicodem - 8-8-2012 at 08:20

Quote: Originally posted by blogfast25

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]

blogfast25 - 8-8-2012 at 12:01

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]

Gibberator - 8-8-2012 at 19:52

If you don't mind my asking but where did you acquire such a mix of metals?

recycle - 9-8-2012 at 19:12

Gibberator: From a machine that is cutting magnets.

Gibberator - 9-8-2012 at 20:42

I see! And how much of the metal slurry do you have, enough to share?

recycle - 10-8-2012 at 01:01

enough to share indeed .... but comes at small price..

[Edited on 10-8-2012 by recycle]

Wizzard - 10-8-2012 at 04:50

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.

blogfast25 - 10-8-2012 at 05:34

Quote: Originally posted by recycle

Gibberator: From a machine that is cutting magnets.

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...

Gibberator - 10-8-2012 at 09:05

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.

Wizzard - 10-8-2012 at 11:20

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?

blogfast25 - 10-8-2012 at 12:43

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]

Gibberator - 10-8-2012 at 13:59

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.

blogfast25 - 11-8-2012 at 05:57

Interesting data on these magnesium - RE double nitrates, here:

http://www.einstein.yu.edu/uploadedFiles/EJBM/26-31.pdf

blogfast25 - 11-8-2012 at 12:36

I attempted to synth some Nd2Mg3(NO3

12.24H2O 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…

DJF90 - 12-8-2012 at 00:28

I already provided a reference to the magnesium rare-earth nitrates up thread. I guess people were just too lazy to look up the reference so I guess I'll do the leg-work and provide the relevant pages.

In future it might be worth listening up and chasing these down for yourself. If you don't have access to these files then ask as required and I can provide them. Ignorance won't get you very far.

The added benefit of the Inorganic Syntheses series is (much like OrgSyn), the preparations are PEER REVIEWED.

Attachment: ISv2 p29-43.pdf (1.6MB)
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Attachment: ISv2 p44-51.pdf (827kB)
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Attachment: ISv2 p52-61.pdf (1.1MB)
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blogfast25 - 12-8-2012 at 12:29

Thanks DJF, but I cannot view these files: AR indicates there’s a ‘problem’.

Below, 1st crop, crap photo of the Nd2Mg3 double nitrate, a few gram:

The photo doesn’t really do it justice: crystals are typically a beautiful Nd lilac/violet and clear as you would expect a 24 hydrate to be.

More was synthesised this afternoon and both crops combined and are recrystallising now.

The trouble is drying them properly. After rinsing the first, still ice cold crop with a bit of iced water, I tried to get most of the water off with filter paper, then on a low setting hot plate but they melted immediately.

The next drop will be air dried at RT on filter paper then desiccated over CaCl2.

I’ll try a melting point reading after that (melting points for all the RE2Mg3 double nitrates are listed in the paper I linked to above.

recycle - 12-8-2012 at 16:50

I have run the elemental analysis on slurry that i have and it comes out with the following result:

wt%

Nd 19.02, Pr 5.10, Fe 50.7, B 0.73, Dy 3.23, Tb 0.02, Al 0.51, Cu 0.1, Co 1.14, Ti 0.1, Ga 0.05.

i guess there is a problem because the numbers do not add up to 100....it is possible that the slurry was not treated for the removal of water or another lubricants that comes from cutting....

the tools are cutting only ndfeb magnets so therefore there is no traces of Sm in this slurry ......

how can i download Handbooks Patnaik Handbook inorganic chemicals 2003 ? (any help??)

recycle - 12-8-2012 at 16:55

@ DJF90 : You have uploaded an empty pdf's...can you provide a references again please!

[Edited on 13-8-2012 by recycle]

blogfast25 - 13-8-2012 at 09:12

Quote: Originally posted by recycle

wt%

Nd 19.02, Pr 5.10, Fe 50.7, B 0.73, Dy 3.23, Tb 0.02, Al 0.51, Cu 0.1, Co 1.14, Ti 0.1, Ga 0.05.

So your main man is Nd. I say dissolve sludge in 37 % HCl, filter off insolubles and saturate the filtrate with K2SO4. Allow to stand overnight for maximum yield as insoluble RE/K double sulphates precipitate.

Filter and wash filter cake with acidified sat. K2SO4. Then convert RE/K double salts with strong ammonia to RE(OH)3 + soluble K sulphate and separate by filtration.

[Edited on 13-8-2012 by blogfast25]

[Edited on 13-8-2012 by blogfast25]

recycle - 13-8-2012 at 17:33

blogfast25 : Thanks for nice steps

to recover Nd.... (i guess that Pr will dissolve too ??), but HOW ABOUT Dy.....

no my main elements are Nd, Pr and Dy and i want to isolate them in a mixture....ignoring Dy and Pr is no go .....

i am aware of this paper; Journal of Alloys and Compounds; vol. 408 - 412; (2006); p. 1382 - 1385, where;

The hydrothermal treatment of used Nd-Fe-B sintered permanent magnet was investigated in order to recover the rare- earth resources efficiently. Commercially available Ni-coated Nd2Fe14B sintered magnet was hydrothermally treated under the op- timum conditions at 110 .deg.C for 6 h in the mixed aqueous solution of hydrochloric acid (3.0 mol/dm3) and oxalic acid (0.2 mol/ dm3). As a result, more than 99percent of Nd metal contained in the magnet was collected as solid precipitate of Nd 2(C2O4)3*xH2O with the purity as high as 99.8percent.

The challenge is to collected all the above elements out from oxidized slurry in a particular mixture

blogfast25 - 14-8-2012 at 04:26

@ recycle:

Firstly, bugger that paper: 3 M HCl (roughly 10 w%) is nothing, no wonder it takes six f*cking hours, might as well try lemon juice! 37 w% HCl is about 12 M (mol/L), about 4 times faster. Also having oxalic acid in there risks precipitating other oxalates (most ionic oxalates are highly insoluble), such as Fe. Their method is useless rubbish. And their claim of purity only works if the magnets contain no other REs, as the ‘method’ [cough!] does not distinguish between one and the next RE.

Hot 12 M HCl however WILL dissolve the LOT, in a matter of perhaps 2 hours tops, including ALL REs and even that bit of Ti. Insoluble residue will be mainly a small amount of B (from NdFeB). Then precipitate all REs as potassium double sulphates, convert to mixed hydroxides. Trust me I’M NOT IGNORING Pr, Dy: their oxides will be mixed in with the Nd (and any other RE that might be lurking there!) oxide.

Separating the REs effectively is such a specialist job I wouldn’t even begin to think about it. This mixed oxide will have commercial value, though, make no question about it…

[Edited on 14-8-2012 by blogfast25]

[Edited on 14-8-2012 by blogfast25]

elementcollector1 - 14-8-2012 at 12:31

No, it works. I've separated neodymium from iron using the oxalate method because iron formed a trioxalatoferro complex when enough oxalic acid was added, thus staying in solution while the rare earth oxides precipitated out.
As for separating Praseodymium and Neodymium, I believe it was discussed extensively in 'the trouble with neodymium', but I don't recall if they reached any solid conclusion.

blogfast25 - 15-8-2012 at 05:19

Quote: Originally posted by elementcollector1

No, it works. I've separated neodymium from iron using the oxalate method because iron formed a trioxalatoferro complex [note: trisoxalato ferric, not ferro, BF] when enough oxalic acid was added, thus staying in solution while the rare earth oxides [oxalates, not oxides, BF] precipitated out.
As for separating Praseodymium and Neodymium, I believe it was discussed extensively in 'the trouble with neodymium', but I don't recall if they reached any solid conclusion.

Not only is the amount of oxalic acid discussed in that paper ridiculously small, there is also no mention of oxidising the Fe2+ to Fe3+, needed for the separation based on trisoxalate ferric complex. Trust me, it was me who introduced that method on 'The trouble with neodymium'.

It was also me who thought I'd found some praseodymium in magnet Nd but the whole thing ended up inconclusive.

[Edited on 15-8-2012 by blogfast25]

recycle - 15-8-2012 at 16:49

@ blogfast25

Look depends on the year when the magnet was manufactured. initially magnets did not have any Pr inside unless they were made for specific applications. recently (several years ago) they have started to put some Pr in magnets in order to reduce the price.

Especially if the magnet was from hard disk drive it will be difficult to find inside any Pr. I hope this helps to explain you why there was no Pr in your magnet.

blogfast25 - 18-8-2012 at 06:43

Hmmm... the spot FOB for praseodymium appears slightly higher than for neodymium. No great savings there. Small amounts of Pr don't affect NdFeB performance it would seem. That would be a motive to use contaminated Nd. I'm guessing here.

Also I didn't say there wasn't any Pr in my magnets (back then): I said it was inconclusive. W/o XRF it's really hard to detect small amounts of one RE in the matrix of another.

[Edited on 18-8-2012 by blogfast25]

watson.fawkes - 18-8-2012 at 09:52

Quote: Originally posted by blogfast25

Small amounts of Pr don't affect NdFeB performance it would seem. That would be a motive to use contaminated Nd. I'm guessing here.

I would guess that it's not so much contamination as a mixed-element ore body that's being exploited, and that the refiner is spending less money on a complete RE separation process. Cheaper cost of goods sold, adequate performance for a certain class of product; sounds like a win overall.

DJF90 - 19-8-2012 at 16:12

Sorry about that, been busy all week. It appears as if CutePDF was having a spazwank, so I've split the file using another program. Find the two segments attached (and in working order!)

Attachment: Segment 001 of ISv2 rare earths.pdf (1.3MB)
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Attachment: Segment 002 of ISv2 rare earths.pdf (1.3MB)
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blogfast25 - 20-8-2012 at 07:32

Thanks DJF, these work fine.