Question

Why are the film resistances to mass transfer on either side of the membrane for gas permeation often negligible?

Answer 1

This is because when gas diffusing into the liquid is not very soluble then the film resistance to mass transfer becomes negligible.

We know from text book that overall mass transfer coefficient is given by :

1/Ky = 1/ky + m/kx

Where Ky is the overall mass transfer coefficient, And ky and kx are the locally applicable gas and liquid mass transfer coefficients

and m is the slope of the line connecting the equilibrium composition with the bulk composition.

So if gas diffusing is not very soluble in liquid, 1/ky becomes negligible.

and overall coeeficient

= 1/Ky ~ m/kx