Investigation of nanopores in nanofiltration membranes using slow positron beam techniques

The pore distribution of the commercial nanofiltration membranes Desal 5DL, Desal 51HL, N30F, NTR 7450 and NF‐PES‐10 were analyzed by positron annihilation spectroscopy using slow positron beam analysis. From the depth selective 3γ/2γ analysis a dense nanoporous filtration layer could be determined. From the depth selective lifetime analysis the size and distribution of the nanopores could be extracted. The measurements indicate the presence of 2 pore sizes in the samples with a radius of 1.25‐1.55 Å and 3.2‐3.95 Å. These experimental values are compared with the molecular weight cut‐off values of these membranes. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)