Wednesday, May 1, 2013

Process Wednesday: decantation

From "Organometallics in Process Chemistry" [1], a comment on decanting in a chapter on removing metals on scale:
Decantation, also known as siphoning, can be used in place of filtration to separate the process stream from solid metal particles. Decanting is useful for gross separations, as in the case of removing water from Raney nickel, but it can be impractical to perform on scale. Decanting requires time to allow metal to settle below the suction (siphon) inlet. Fine metal particles can be difficult to remove and when present in large amounts, can plug filtration equipment. In addition, the remaining metal particles must be thoroughly cleaned from the reactor. Decantation also leaves behind some of the product rich process stream; additional solvent, followed by decantation, would be required to improve product recovery thus increasing cycle time and batch volume. 
Well, there goes that idea about tipping the reactor on its side to pour out some supernatant...

[A long time ago, I was subject to a senior chemist suggesting that we use decanting as a viable technique for separating the product stream from a heavy metal oxidant. I must have looked at him as if he had 3 heads...]

[Doesn't "decantation" sound like some sort of anti-witchcraft technique?]

1. Bien, J.T.; Lane, G.C.; Oberholzer, M.R. "Removal of Metals from Process Streams: Methodologies and Applications." Topics in Organometallic Chemistry 20046, 263-283.


  1. Yes it does. As in the opposite of incantation.

  2. They should be able to design something that separates particles by centrifugal force. That is commonly used in plasmapheresis to separate blood cells from plasma. I imagine that it could be scaled up pretty easily.

    1. For a several hundred liter tank?

    2. Stewie Griffin