Sciencemadness Discussion Board

Rare earth citrate production

Brain&Force - 20-5-2015 at 22:37

So I'm continuing to make different rare earth citrates - I've already gotten excellent results with holmium citrate, and gadolinium citrate is currently in progress. I do, however, have a few notes and questions regarding them.

Notes:

Both holmium and gadolinium citrate appear to be soluble in water. As I lack a balance I don't know exactly how much I'm using (bad science, I know) but I have reason to suspect they are only soluble in excess citric acid.

If not enough citric acid is used, the metal dissolves to form a precipitate. Among the metals they all seem to have a yellow precipitate. However, they are all at least 99.95% pure so the only source of iron possible is the file I use to powder them before reacting. Anyone know what this is? I want to try some other acid to see if the same thing happens but I can't think of one that'll dissolve the metal cleanly and is available with reasonable purity.

They tend to go syrupy before crystallizing, and my attempt to seed some holmium citrate doesn't seem to be working.

gatosgr - 21-5-2015 at 01:45

how do you make these citrates?

Volanschemia - 21-5-2015 at 01:46

By dissolving the metals in Citric Acid I would imagine...

gatosgr - 21-5-2015 at 01:57

these elements are not very reactive..

[Edited on 21-5-2015 by gatosgr]

diddi - 21-5-2015 at 05:04

LANTHANIDEZ are quite reactive. they dissolve readily in acids including citric acid. they must be stored in argon or prevent oxidation which can be quite rapid even at low temps

blogfast25 - 21-5-2015 at 06:06

Quote: Originally posted by gatosgr  
these elements are not very reactive..

[Edited on 21-5-2015 by gatosgr]



Hahahahha.

They're among the most reactive metals in the PT, matey. Quit spreading misinformation already!

Citrate buffers are used to separate the RE(III)'s by resin exchange columns. I have some juicy details for those interested.

[Edited on 21-5-2015 by blogfast25]

Brain&Force - 21-5-2015 at 09:50

Yeah, they were formed from dissolving the metal in a solution of citric acid. They actually tend to react pretty slowly compared to a metal like magnesium, instead dissolving about as fast as zinc. I've been powdering the samples with a file - I'm a little worried about Fe contamination as well, but it seems to be no problem.

I've actually run into a small problem with holmium - I'm finding it difficult to sand down the stringy pieces. The samarium I have is in the same form, but is nowhere near as hard as the holmium.
Quote: Originally posted by blogfast25  


Citrate buffers are used to separate the RE(III)'s by resin exchange columns. I have some juicy details for those interested.

[Edited on 21-5-2015 by blogfast25]


I want to hear this

blogfast25 - 21-5-2015 at 10:39

Quote: Originally posted by Brain&Force  

I want to hear this


Dowex-50 column, elution performed at 100 C, using pH = 3.28 ammonium citrate buffer. Heavy REs elute first.

(From Glenn T. Seaborg's 'The Trans-Uranium Elements, p. 154)

gatosgr - 21-5-2015 at 14:19

I meant gadolinium and holmium compared to the other rare earths... interpretering however you like again huh?:o

http://www.chemistryexplained.com/elements/C-K/Gadolinium.ht...


and your juicy details

https://www.google.com.ar/patents/US2897050?

[Edited on 21-5-2015 by gatosgr]

Brain&Force - 21-5-2015 at 16:14

It seemed that you said the rare earths as a whole were unreactive. Gadolinium, dysprosium and holmium are definitely air-stable and dissolve only slowly.

blogfast25 - 21-5-2015 at 16:18

Quote: Originally posted by gatosgr  
I meant gadolinium and holmium compared to the other rare earths... interpretering however you like again huh?


Avoid txtinglish and people might know what you're on about. There won't be any interpretational problems then.

Thanks for the patent.

[Edited on 22-5-2015 by blogfast25]

A citrate complex?

Brain&Force - 25-5-2015 at 11:47

So I made some dysprosium citrate and attempted to precipitate it with sodium carbonate, to get the carbonate to precipitate. That didn't work - instead I'm able to dissolve large amounts of sodium carbonate in the dysprosium citrate solution without any precipitate forming.

I have found a reference to a bis(citrato)lanthanum complex and I'm interested in finding out if I've made a dysprosium analog myself. But as for producing a rare earth oxide/hydroxide/carbonate I guess I'll just attempt to pyrolyze the citrate.

Brain&Force - 26-5-2015 at 13:47

So I downloaded the paper and I think a buffer formed, rather than a stable citrato complex. The citrato complexes of lanthanum are only stable in acidic solution (pH 3 at most) according to the paper I linked, and the dissolution of sodium carbonate seems to be insufficiently basic to induce precipitation of the Dy and Ho ions.

blogfast25 - 26-5-2015 at 14:28

Quote: Originally posted by Brain&Force  
So I made some dysprosium citrate and attempted to precipitate it with sodium carbonate, to get the carbonate to precipitate. That didn't work - instead I'm able to dissolve large amounts of sodium carbonate in the dysprosium citrate solution without any precipitate forming.

I have found a reference to a bis(citrato)lanthanum complex and I'm interested in finding out if I've made a dysprosium analog myself. But as for producing a rare earth oxide/hydroxide/carbonate I guess I'll just attempt to pyrolyze the citrate.


I bet potassium oxalate would break the complex.