Gas Permeation through the Porous Membrane Prepared from Synthetic Water-Swelling Fluoromica

Abstract

Porous membranes were prepared from fine particles of synthetic water-swelling fluoromica. The pore structure of membrane was studied by scanning electron microscopy and mercury penetration method. Permeability was determined for several gases under different pressures, and discussed in connection with the pore structure. Four kinds of pores, i.e. 7×10⁴, 2×10⁴, 3×10² and under 4nm as the maximum diameters were observed in the membrane. Permeation properties were represented well by the intermediate state equation between Knudsen and viscous flow. The hydraulic radius of the membrane, estimated by introducing experimental factors of He to the intermediate state equation, was 150nm. Separability of He/Ar decreased at high pressures owing to collision between different gas molecules (Present-de Bethunes' effect) and viscous flow. The separation factors which were determined by experiment agreed with the one predicted from the Present-de Bethunes' equation, assuming the pore radius is 80nm.