Fusionfire
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Centrifugal concentration
As centrifuges can separate isotopes, it occurred to me that high yield strength (so high RPM) corrosion-resistant centrifuges (ceramic, stainless
steel or titanium) should make short work of "difficult" processes such as separating azeotropic mixtures, e.g. 68% HNO<sub>3</sub> or
methanol - ethanol and concentrating e.g. 30% H<sub>2</sub>O<sub>2</sub>.
Does anyone have any experience to share in the context of using centrifuges an amateur science setting?
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watson.fawkes
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Quote: Originally posted by Fusionfire  | | As centrifuges can separate isotopes, it occurred to me that high yield strength (so high RPM) corrosion-resistant centrifuges (ceramic, stainless
steel or titanium) should make short work of "difficult" processes such as separating azeotropic mixtures, e.g. 68% HNO<sub>3</sub> or
methanol - ethanol and concentrating e.g. 30% H<sub>2</sub>O<sub>2</sub>. |
The
molecules containing the isotopes are all of the same chemical species and are free to move with respect to each other. With azeotropic mixtures, you
have intermolecular forces that would have to be overcome. These forces are relatively large in comparison. The difference in centrifuge forces
between isotope-varied molecules has to overcome diffusion velocities from collisions in the molecules. To use a centrifuge for azeotrope separation
you'd have to overcome both diffusion and the intermolecular forces. Although there would likely be some measurable effect, separation yields would
appear to be lower than for isotope separation, and that's only a fraction of a percent per pass.
This technique might be a way to measure some physical constants about solvation; that seems perfectly feasible and indeed interesting. But it's
unlikely to yield a practical separation method.
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Fusionfire
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| Quote: Originally posted by watson.fawkes | | Quote: Originally posted by Fusionfire | | As centrifuges can separate isotopes, it occurred to me that high yield strength (so high RPM) corrosion-resistant centrifuges (ceramic, stainless
steel or titanium) should make short work of "difficult" processes such as separating azeotropic mixtures, e.g. 68% HNO<sub>3</sub> or
methanol - ethanol and concentrating e.g. 30% H<sub>2</sub>O<sub>2</sub>. |
The
molecules containing the isotopes are all of the same chemical species and are free to move with respect to each other. With azeotropic mixtures, you
have intermolecular forces that would have to be overcome. These forces are relatively large in comparison. The difference in centrifuge forces
between isotope-varied molecules has to overcome diffusion velocities from collisions in the molecules. To use a centrifuge for azeotrope separation
you'd have to overcome both diffusion and the intermolecular forces. Although there would likely be some measurable effect, separation yields would
appear to be lower than for isotope separation, and that's only a fraction of a percent per pass.
This technique might be a way to measure some physical constants about solvation; that seems perfectly feasible and indeed interesting. But it's
unlikely to yield a practical separation method. |
What if you heated the azeotropic mixtures to increase the mobility (random KE) of the molecules relative to the intermolecular bond energies?
For example consider the following thought experiment: if you had a solid state alloy (e.g. copper/zinc brass) and put it in a linear accelerator, the
acceleration you'd have to get to physically separate the components would be very, very high. If instead you melted the alloy or even vaporised it,
the accelerations you'd need would become lower.
However are we agreed that this process will definitely work on non-azeotropic mixtures, e.g. of 30%
H<sub>2</sub>O<sub>2</sub> and water?
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watson.fawkes
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| Quote: Originally posted by Fusionfire | What if you heated the azeotropic mixtures to increase the mobility (random KE) of the molecules relative to the intermolecular bond energies?
[...]
However are we agreed that this process will definitely work on non-azeotropic mixtures, e.g. of 30%
H<sub>2</sub>O<sub>2</sub> and water? |
So, you want to increase the thermal velocity,
yet keep the intermolecular forces the same, and keep the centrifugal forces the same, and you expect that to have better separation?
H2O and H2O2 mutually solvate each other. How does an non-azeotropic mixture of these two change anything?
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Fusionfire
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| Quote: Originally posted by watson.fawkes | | Quote: Originally posted by Fusionfire | What if you heated the azeotropic mixtures to increase the mobility (random KE) of the molecules relative to the intermolecular bond energies?
[...]
However are we agreed that this process will definitely work on non-azeotropic mixtures, e.g. of 30%
H<sub>2</sub>O<sub>2</sub> and water? |
So, you want to increase the thermal velocity,
yet keep the intermolecular forces the same, and keep the centrifugal forces the same, and you expect that to have better separation?
|
Where did I say heating it will not keep the intermolecular forces the same?
I'm saying that the energy to separate MeOH and EtOH molecules can either come from random thermal energy or work via centrifugal forces. Once
intermolecular forces between MeOH of EtOH have been overcome by either means, centrifugal forces will keep them apart.
| Quote: |
H2O and H2O2 mutually solvate each other. How does an non-azeotropic mixture of these two change anything?
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Because you seemed to be homing into the difficulty of separating azeotropic mixtures by centrifuge specifically. Sorry if I misunderstood you.
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watson.fawkes
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| Quote: Originally posted by Fusionfire | | I'm saying that the energy to separate MeOH and EtOH molecules can either come from random thermal energy or work via centrifugal forces. Once
intermolecular forces between MeOH of EtOH have been overcome by either means, centrifugal forces will keep them apart.
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No, that's not how it works. Thermal energy works against the gradient of centrifugal force
with respect to separation. Increasing temperature changes the characteristic residence time of a collision/contact event, lowering it, but it
simultaneously raises the rate of such contacts. So while higher temperatures cause more molecular separations, it also causes more molecular
contacts.
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elementcollector1
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^Reported.
Elements Collected:52/87
Latest Acquired: Cl
Next in Line: Nd
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Texium
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Thread Moved
20-11-2023 at 12:39 |
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