Hafnium and zirconium

[Enthalpy]

Since I've had worries after thinking at the following, I make it public.

Three uneasy processes are known to separate Hf from Zr according to Wiki, for instance the fractional distillation of HfCl₄ and ZrCl₄. In addition, I propose to separate gaseous HfCl₄ from ZrCl₄ by centrifugation.

ZrCl₄ sublimates at 331°C=604K where HfCl₄ has 1.7atm vapour pressure. RT=5022J/mol there. A lower pressure improves a bit.

A tube of 2000MPa Maraging steel can rotate at 416m/s with 20% margin. Ti-Al6V4 and AA7075 would be good enough too, and graphite fibres much better.

Neglecting the isotopes, HfCl₄ weighs 87g per mole more than ZrCl₄: that's 29* easier than uranium enrichment. The kinetic energy differs by 7528J/mol or 1.50*RT, so after some 10 stages, the metals are pure.

Marc Schaefer, aka Enthalpy

[Sensei]

Do you have a sample to play with?

 

I would analyze compounds of these metals, to find one which is soluble in some solvent, while the other one is barely soluble.

Difference between properties of compounds which can be utilized during separation.

 

F.e. there is Zr(NO₃)₄ which can be prepared by using ZrCl₄ + N₂O₅

https://en.wikipedia.org/wiki/Zirconium_nitrate

Check if Hafnium also undergoes this reaction, and whether it's also soluble in water and ethanol, and in what concentrations.

If there is difference in concentration at which one is still soluble, other one not anymore, utilize this to separate them.

 

Edit: Just found "Differences in the solubility of the tetrachlorides in ethanol have been used for the separation of zirconium and hafnium."

https://www.inorganicventures.com/samples-containing-zirconium-or-hafnium

Edited June 17, 2016 by Sensei

[John Cuthber]

Do you have a sample to play with?

 

I would analyze compounds of these metals, to find one which is soluble in some solvent, while the other one is barely soluble.

Difference between properties of compounds which can be utilized during separation.

 

F.e. there is Zr(NO₃)₄ which can be prepared by using ZrCl₄ + N₂O₅

https://en.wikipedia.org/wiki/Zirconium_nitrate

Check if Hafnium also undergoes this reaction, and whether it's also soluble in water and ethanol, and in what concentrations.

If there is difference in concentration at which one is still soluble, other one not anymore, utilize this to separate them.

 

Edit: Just found "Differences in the solubility of the tetrachlorides in ethanol have been used for the separation of zirconium and hafnium."

https://www.inorganicventures.com/samples-containing-zirconium-or-hafnium

"I would analyze compounds of these metals, to find one which is soluble in some solvent, while the other one is barely soluble."

Thank you for making it clear that you do not know what you are talking about.

Did it really no occur to you that, if it was that easy, Enthalpy wouldn't have even raised the issue?

Why did you even post here?

Edited June 17, 2016 by John Cuthber

[Sensei]

"I would analyze compounds of these metals, to find one which is soluble in some solvent, while the other one is barely soluble."

Thank you for making it clear that you do not know what you are talking about.

Did it really no occur to you that, if it was that easy, Enthalpy wouldn't have even raised the issue?

Why did you even post here?

 

Why are you writing such nonsense (yet again, and again).. ?

Concentrate on talking about things that you know.

 

US patent for separating Zirconium and Hafnium using alcohol

https://www.google.com/patents/US2571237

 

"The column feed solution is prepared by dissolving the mixed zirconium-hafnium tetrachloride in an organic solution. The organic solvent maybe an alcohol, a ketone, an aldehyde, an organic acid or other similar solvent in which the tetrachloride will dissolve without decomposition of the tetrachloride or of the solvent. Representative solvents include methanol, glycerol, benzyl alcohol, acetone, acetaldehyde, acetic acid and nitrobenzene. Oxygen-containing organic solvents have been found to be preferable. The alcohols have been found to be most suitable in that they have less tendency to decompose than some of the other solvents, such as acetone, and they permit highly preferential separation. Both the monohydric and polyhydric alcohols may be used, but it is believed that the monohydric alcohol, methanol, is the most satisfactory solvent."

[John Cuthber]

You said.

"I would analyze compounds of these metals, to find one which is soluble in some solvent, while the other one is barely soluble."

 

Yet it is known that there are no such compounds (at least- not so far discovered)

 

And then you go on about a technique that relies on both compounds being soluble in a solvent.

 

So, having said you would do something that's well known to be, at least very nearly, impossible, and being called out on it, you pick out a patent on crude chromatography.

Even the patent you cite shows that your original plan was daft where it says "The two metals, however, are so very similar in their chemical properties that it has been extremely difficult to separate the hafnium from the zirconium. "

 

So, if you want to show that I'm the one writing nonsense you have to show that you can do what you said you would.

 

You need to "analyze compounds of these metals, to find one which is soluble in some solvent, while the other one is barely soluble."

well, get on with trying to do so.

Find such compounds. (as far as I can tell from what's available on-line, the tetra chlorides of both metals are soluble in ethanol- so your reported separation doesn't count; I rather suspect it's an error. It's a pity they didn't include a reference so we could check.)

 

When you discover it's not possible, perhaps you will accept that I was right to say what I did.

In the mean tine you should "Concentrate on talking about things that you know."

Edited June 19, 2016 by John Cuthber

[Enthalpy]

Distillation at a lower pressure is often more selective. The distillator by sublimation I suggest there
http://www.scienceforums.net/topic/95971-distillation-by-sublimation/
may benefit to HfCl₄ and ZrCl₄.

[John Cuthber]

Distillation at a lower pressure is often more selective. The distillator by sublimation I suggest there

http://www.scienceforums.net/topic/95971-distillation-by-sublimation/

may benefit to HfCl₄ and ZrCl₄.

It has a much better chance than Sensei's idea that one can "analyze compounds of these metals, to find one which is soluble in some solvent, while the other one is barely soluble."

[Enthalpy]

Nb and Ta too are reportedly difficult to separate, so a centrifuge might help too.

A mole of Nb weighs 93g, Ta 181g, so TaCl₅ is 88g heavier than NbCl₅, 30* easier than uranium enrichment. Isotopes let that fluctuate by +-5g. After the centrifuge is built, it can optionally spend some time separating ³⁵Cl from ³⁷Cl to save time separating Nb from Ta. NbCl₅ melts at +205°C and boils at +248°C under 1atm, TaCl₅ at +216°C and +239°C (decomp).

A tube of 2000MPa Maraging steel rotating at 416m/s makes 7.7kJ/mol difference in the kinetic energy. At arbitrary +127°C=400K, that's 2.3RT, so the metals are pure in half a dozen steps, or 1 or 2 steps with tubes of graphite fibres.

The oxides mix is reduced, Cl₂ or HCl give the mix of pentachlorides, centrifuges separate the pentachlorides before reduction. No fluorine needed. I can't tell whether the process is globally advantageous.

Marc Schaefer, aka Enthalpy

[Enthalpy]

Centrifuges have an additional trick that I had not grasped. The contents drifts slowly downwards at the bigger radius and upwards at the centre. This second movement establishes a vertical composition gradient in addition to the radial gradient, letting the centrifugal force act several times on the composition within a single tube. Very astute. They don't tell it there
https://en.wikipedia.org/wiki/Zippe-type_centrifuge

So that's why the shape is a long cylinder, despite not being the strongest against centrifugal force.

Here Hf would separate from Zr in a single tube, Ta from Nb too. But with graphite composite, the vertical drift may not even be necessary, and this allows shapes that rotate even faster.

----------

Other processes achieved isotopic separation: gaseous diffusion, vortex, nozzles...
https://en.wikipedia.org/wiki/Isotope_separation#Practical_methods_of_separation
They look less interesting than centrifuges, but would separate the elements too.

[Enthalpy]

Rare earth ore provides them all, but it's reportedly difficult to separate Sc and Y from the lanthanides. Centrifuges could do it thanks to the well spread molar masses: 45g, 89g and for La (138g) 139g with at least 44g difference, 15* easier than for uranium.

Volatile compounds are rare. ScCl₃, YCl₃ and RCl₃ need some 1800K to boil under 1atm, so hopefully 1000K make a usable vapour pressure. Monoisotopic Cl brings a bit.

Aluminum, maraging and graphite-epoxy can't operate that hot, superalloys rotate slowly. But carbon-carbon could make the rotors, maybe with a thin hermetic metal liner. 2D tubes resist even at heat around 200MPa, varying a lot among the suppliers, so near-azimuthal winding shall exceed that. 2000kg/m³ let a tube rotate at 316m/s, so 1/2*Delta(m)*V²=0.26*RT at 1000K, needing around 27 steps.

More volatile compounds would reduce RT and enable faster maraging or graphite-epoxy. Salts of organic acids seem excellent, if finding data or measuring.

Marc Schaefer, aka Enthalpy