Because of the pore structure of the these adsorbents
with the macropores being much larger relative to the size of the
adsorbate molecules, the adsorbate is speculated to experience
film diffusion resistance not only on the external adsorbent surface
but also inside the large macropores, i.e., a film exists between the
bulk of the pore and the internal pore surface. Unlike external particle
film diffusion, internal film in macropores cannot be suffi-
ciently removed by external agitation