Calculation of effective pore diameters in porous filtration membranes with image analysis

In filtration/separation applications, porous membranes separate particles by a sieving mechanism determined by pore size of membrane and particle size. However, since pores in the membranes have irregular shape and vary in size, the definition of the pore size has been complex and sometimes, even confusing. In this work, we introduced a novel geometric parameter called effective pore diameter to characterize particle permeation performance in porous filtration membranes. The effective diameter of a pore is defined as the maximum diameter of a spherical particle which can pass through the pore in the membrane. We for the first time applied advanced image analysis techniques to automatically measure effective pore diameters and their distribution from scanning electronic microscopic image of the membrane using Euclidean distance transform (EDT). It is found that the effective pore diameter and its distribution are more accurate than the parameters previously used, to evaluate the membrane's filtration and separation performance and especially, particle permeation performance.