Sciencemadness Discussion Board

Separating Gd, Ce, and Nd

elementcollector1 - 16-12-2017 at 09:28

Just finished my senior thesis paper on recycling neodymium magnets. The proposed method was electrolytic separation of the Nd from the transition metals, but upon analysis of the deposited metallic substance I ran into some interesting results.

It turns out the deposited metal consisted of a large portion of iron (about equal to what I started with), followed by roughly equivalent portions of cerium, gadolinium, and neodymium instead of just neodymium.

I can separate out the iron by selective precipitation, but what about these three elements? Rare earths are typically very chemically similar, so how do I get these three apart?

I'd imagine the first step would be to remove the Ce by oxidizing it to the +4 state and then complexing that away somehow, but I've no idea on the Gd.

Heavy Walter - 16-12-2017 at 09:48

Hi

Many years ago, I was planning to extract rare earths from a local ore.
Life had different plans for me and that remained as a dream.
I was planning to separate rare earths oxides with ion-exchange columns and fractional crystallization, as per these papers:
The separation of Rare Earths.
Journal of Chemical Education, Vol. 37, Number 12, December 1960, pp 629-633.
The Lighter Lanthanides.
Proc. fo the California Association of Chemistry Teachers.
Vol. 40,, Number 8, August 1963, pp 433-437.
Hope this helps.
Good luck!

kmno4 - 16-12-2017 at 14:22

Quote: Originally posted by elementcollector1  
(...)The proposed method was electrolytic separation of the Nd from the transition metals, but upon analysis of the deposited metallic substance I ran into some interesting results.

It turns out the deposited metal consisted of a large portion of iron (about equal to what I started with), followed by roughly equivalent portions of cerium, gadolinium, and neodymium instead of just neodymium.

It sounds interesting.
Any experimental details ?

j_sum1 - 16-12-2017 at 15:19

I don't remember the details but there is some current research using micro organisms to separate out RE ions quickly, efficiently and with low energy expenditure. It should not be too hard to find details. I probably read it on BBC news a couple of years ago if that helps.

elementcollector1 - 16-12-2017 at 19:43

Quote: Originally posted by kmno4  

It sounds interesting.
Any experimental details ?


Not much of note, considering it failed. Voltage was 1.5 V, current varied from 0 to 3 A (due to distance of electrodes), electrodes were a steel cathode and magnet-alloy anode, electrolyte was extremely acidic solution of 'magnet sulfate', and the final composition was about 70% iron, and 10% each of the rare earths.



Attachment: Lindh_J_EMSE399_FinalPaper.docx (1.2MB)
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Sulaiman - 18-12-2017 at 00:16

Quote: Originally posted by elementcollector1  
Just finished my senior thesis paper on recycling neodymium magnets. The proposed method was electrolytic separation of the Nd from the transition metals, but upon analysis of the deposited metallic substance I ran into some interesting results.

It turns out the deposited metal consisted of a large portion of iron (about equal to what I started with), followed by roughly equivalent portions of cerium, gadolinium, and neodymium instead of just neodymium.

I can separate out the iron by selective precipitation, but what about these three elements? Rare earths are typically very chemically similar, so how do I get these three apart?

I'd imagine the first step would be to remove the Ce by oxidizing it to the +4 state and then complexing that away somehow, but I've no idea on the Gd.


I can't help with the separation of the elements but I can give you a clue as to the cost effectiveness ;
some smart guy discovered that NdFeB magnets are ok to use Nd together with its almost inseperable cousins
- hence saving a fortune on the separation :P

The easiest way to succeed in separating Nd from magnets is to start with an early NdFeB magnet that used refined Nd, not the new chinese economy magnets.

All from vague memories of stuff I've read, not done.

P.S. given the present volume of NdFeB magnet production,
surely the most cost effective recycling would be to make the ingredients for more magnets,
massively simplifying separation requirements to just the removal of plating and binders (if any) ?

[Edited on 18-12-2017 by Sulaiman]

elementcollector1 - 27-3-2019 at 21:01

Quote: Originally posted by Sulaiman  

I can't help with the separation of the elements but I can give you a clue as to the cost effectiveness ;
some smart guy discovered that NdFeB magnets are ok to use Nd together with its almost inseperable cousins
- hence saving a fortune on the separation :P

The easiest way to succeed in separating Nd from magnets is to start with an early NdFeB magnet that used refined Nd, not the new chinese economy magnets.

All from vague memories of stuff I've read, not done.

P.S. given the present volume of NdFeB magnet production,
surely the most cost effective recycling would be to make the ingredients for more magnets,
massively simplifying separation requirements to just the removal of plating and binders (if any) ?

[Edited on 18-12-2017 by Sulaiman]


Bringing this back after digging out the solution in question from storage - I have the hydroxides precipitating out right now for selective precipitation to get rid of the iron, still considering next steps.

As for the most cost-effective method of recycling - true, but that wouldn't have given me the chance to do some hobby chemistry for my senior thesis. ;)

Per the commercial-scale process for separating rare earths, I know how to eliminate Ce - calcining the RE's to oxide and then reacting with pure HNO3 should see the CeO2 untouched, as apparently it doesn't react appreciably with nitric acid. That just leaves the separation of Nd and Gd.