Diffusion/Permeation through PTFE (Gore-Tex)

[michaelrs at ezzeus.vmsmail.ethz.ch]

Hi everybody,

	We are using a PTFE membrane covered sparger for aeration of a bioreactor. In
principle this should give bublefree sparging. Now we find that the mass
transfer (klA) is worse than ever. It is actually at 3 orders of magnitude
lower. We are running at 50 ml air/min, a stirrer speed 0f 500 rpm. We checked
all connections and found, that there must be some diffusion limitation. So in
contrast to the claimed increase in klA we have a dramatic loss. Now that
points us to question the diffusion or permeation coeeficient for air, oxygen
and nitrogen thru this membrane (about 1 mm PTFE, porous). And also if there is
a special pressure is required. Any ideas ? Anyone with related experience ?

	I would appreciate any kind of feedback, Thanx!

						Michael R Schuppenhauer
						ETH Zurich, Switzerland
						michaelrs at ezzeus.vmsmail.ethz.ch