Mischmetal Separation

[elementcollector1]

So, after a few months of heavy research, I came up with this:

Lanthanum (La)

 

To obtain Lanthanum, see the process for Cerium.

 

Cerium (Ce)

 

Metallic cerium is found in 50% or higherconcentrations in magnesium firestarters, known as “mischmetal” flints. To getthe cerium, you must first obtain a bunch of mischmetal parts. To heat it to just the righttemperature, I would suggest a Bunsen burner, which burns at about 900 degreesC, perfect for this application. Use a steel crucible, preferably with asupermagnet attached to it (so that the iron oxide draws to here). When the ceriumis liquid, and there is something floating on top, scoop it out and separateany iron oxide remaining. This should now be a mixture of lanthanum metal andmagnesium oxide. See Lanthanum above for the rest of the steps.

 

Mischmetal:MP 788-844 degrees C, non-eutectic, typically 50% cerium, 25% lanthanum, 4%praseodymium, 21% iron/magnesium oxide.

 

Lanthanum:MP 920 degrees C, D 6.162 g/cm^-3, mD 5.94 g/cm^-3

 

Cerium: MP 795 degrees C, D 6.770 g/cm^-3, mD 6.55 g/cm^-3

 

Praseodymium:MP 935 degrees C, D 6.77 g/cm^-3, mD 6.50 g/cm^-3

 

Iron Oxide: MP 1566 degrees C, D 5.242 g/cm^-3

 

MagnesiumOxide: MP 2852 degrees C, D 3.58 g/cm^-3

 

When molten mischmetal is heated to795-920 degrees C:

 

Lanthanum:solid, D 6.162 g/cm^-3

 

Cerium:liquid, D 6.55 g/cm^-3

 

Praseodymium: solid, D6.77 g/cm^-3

 

Iron Oxide: solid, D 5.242 g/cm^-3

 

MagnesiumOxide: solid, D 3.58 g/cm^-3

 

Therefore,when molten mischmetal is heated to below 920 degrees, but above 795 degrees, praseodymiumas a solid will sink to the bottom, whereas lanthanum and the two oxides willfloat on the top as solids, and cerium will stay molten.

 

 

Questions I have are:

 

-Is this process feasible?

 

-Are there any problems I might encounter while doing this (rapid oxidation, sudden reaction, etc.)?

 

-How do I separate the Lanthanum from the Magnesium Oxide?

 

 

All help and criticism is appreciated, constructive or not.

 

 

[John Cuthber]

The major problem is that it won't work.

For a start the magnet it mentions will lose its magnetism when heated. Also, it won't work through a steel crucible.

But that's not the real problem.

Imagine I'm living in Siberia.

It's 40 below zero here.

I have a mixture of two solids; ice and a little salt (say about 20%) salt.

 

I look up the melting points and find that one melts at 0 C and the other melts at 800 C

So, I figure, if I warm the mixture to a temperature between those two values, the ice will melt and the salt won't, so I can filter off the salt and separate them.

I'm going to be disappointed when I see that , at -10 or so, the whole lot has melted and the salt has dissolved in the water.

 

The same problem will happen with the mischmetal.

The Pr and La will dissolve in the Ce.

 

Also, the mixture will react rather quickly with air. They don't use this stuff for lighter flints for a joke; it's easy to set on fire.

 

Separating the lanthanides isn't easy. It's one of the more difficult challenges in preparative chemistry. If you could do it with a thermometer and a furnace they wouldn't resort to ion exchange chromatography when they did it commercially.

 

 

It is possible to get a fairly clean sample of cerium oxide from the lighter flints (and a mixture of the other lanthanides) if that's what you want for an element collection.

[elementcollector1]

I see. So, solubility is an issue to take into account...

Is there any known way I could get a higher concentration of Cerium metal in the mischmetal?

Also, is there anything I could use that is like mineral oil, but has a much higher BP to control the fire?

Edited September 25, 2011 by elementcollector1

[John Cuthber]

In principle, if you dissolve the mixed metals in excess hydrochloric acid and add hydrogen peroxide to oxidise the iron to ferric chloride, then extract the solution with ether (which will remove the iron as "HFeCl4").

 

Then add a solution of sodium hydroxide and hydrogen peroxide slowly. The peroxide will oxidise the Ce(III) to Ce(IV) and the sodium hydroxide will ppt the Ce(Iv) as CeO2. H2O

Until all the Ce has been precipitated, practically all the other lanthanides will stay in solution.

 

It's messy, but you should, with care and practice, be able to get a fairly pure sample of CeO2. H2O that way.

 

You can then add more sodium hydroxide solution and precipitate the other lanthanides.

 

Adding oil will just add fuel to the fire.

I don't think you can melt these metals in air. They might not actually catch fire, but the oxidation will make it impractical.

Edited September 25, 2011 by John Cuthber

[elementcollector1]

Thanks! I can actually use this.

[John Cuthber]

Good luck. If you haven't tried this sort of thing before you will probably make a mess of it.

Still, at least you probably won't burn the house down.

[insane_alien]

still best to have some form of extinguisher handy when playing with hot things though. handy if(when) you drop something thats at around 1000*C

[elementcollector1]

On a side note, would a displacement reaction be possible, with say, Lithium?

 

Li + CeCl2 -> LiCl + Ce?

 

Probably not, but the reactivity series seems to support me.

Also, random question: Would the above reaction work with MgCl to create Mg?

[elementcollector1]

Will any ether work, or does it have to be a specific ether?

Failing that, is there any substitute? I heard YT2095 managed to make CeO2, and he mentioned he only had the basic acids on him at the time. Though I may have misread that. http://www.sciencefo...rom-mischmetal/

Oh, and if possible John Cuthber, can you give me a few specific measurements for the solutions? "X grams of NaOH dissolved in X mL of H2O2 solution", and so on?

EDIT: Something I found on Wikipedia, and I would opt for method 2:

 

The two oxidation states of cerium differ enormously in basicity: cerium(III) is a strong base, comparable to the other trivalent lanthanides, but cerium(IV) is weak. This difference has always allowed cerium to be by far the most readily isolated and purified of all the lanthanides, otherwise a notoriously difficult group of elements to separate. A wide range of procedures have been devised over the years to exploit the difference. Among the better ones:

Leaching the mixed hydroxides with dilute nitric acid: the trivalent lanthanides dissolve in cerium-free condition, and tetravalent cerium remains in the insoluble residue as a concentrate to be further purified by other means. A variation on this uses hydrochloric acid and the calcined oxides from bastnasite, but the separation is less sharp.

 

Precipitating cerium from a nitrate or chloride solution using potassium permanganate and sodium carbonate in a 1:4 molar ratio

 

Boiling rare-earth nitrate solutions with potassium bromate and marble chips.

 

What would this precipitate the cerium as, for method #2?

Edited November 26, 2011 by elementcollector1

[John Cuthber]

The precipitate would be CeO2- probably hydrated to some degree.

The answer to your question about " can you give me a few specific measurements for the solutions? "X grams of NaOH dissolved in X mL of H2O2 solution", and so on?" is that I'm sorry, but I can't. I'd have to experiment to find out.

[elementcollector1]

That's fine. Trial-and-error can work too.

[elementcollector1]

Quick update, I found a sample of what *might* be cerium oxide (anhydrous?) as a polishing powder from back when I was a mineral collector. Is there any way I can prove that this is indeed CeO₂?

[elementcollector1]

Well, trial-and-error worked! I got cerium oxide (definite tan color), probably with still a few iron impurities. Quick question for later: Cerium metal production seems to favor the anhydrous chloride (for best effect). Could the hydrated version still produce cerium metal, or would be something else?

 

Also, lanthanum chloride and magnesium chloride are probably still in solution. How should I separate these two?

Edited December 29, 2011 by elementcollector1