DETERMINATION OF MASS-TRANSFER RATES IN WETTED AND NON-WETTED MICROPOROUS MEMBRANES

The mass transfer resistance of microporous membranes placed between a gas and a liquid phase was studied for both wetted and non-wetted mem branes. It was found that the mass transfer coefficient can be describ ed according to the film model in which the porosity of the membrane a nd the tortuosity of the pores is incorporated. For the non-wetted mem branes (mean pore diameter of 0.1 mum), the Knudsen and continuum diff usion must be taken into account. No difference was observed in the va lues of the liquid-phase mass transfer coefficients between systems wi th and without a membrane at the gas-liquid interface, despite the dif ferent hydrodynamic situation at the interface. The influence of a che mical equilibrium reaction on the mass transfer through a wetted membr ane was analysed mathematically (two-film concept). With this model th e tortuosity factor of the membrane was calculated from experimentally determined fluxes.