Influence of the strongly anisotropic cross-section morphology of a novel polyethersulfone microfiltration membrane on filtration performance

Polyethersulfone (PES) microfiltration membranes with remarkably improved filtration performance were recently developed. Subtle changes in the conditions of the phase separation process lead to a very pronounced anisotropic (“hour glass”-like) cross-section morphology of these novel membranes named DuraPES®. Furthermore, due to macromolecular additives, the membranes are permanently hydrophilic. The properties and performance of the DuraPES® membranes are compared to other membranes available on the market, such as AMC Accupor, Osmonics Micron PES, Pall Supor, Sartorius Sartopore, and Millipore Express. Parameters investigated are on the one hand focussed on membrane structure such as pore morphology (from SEM), volume porosity, trans-membrane pore size distribution, contact angles and wetting with water, and trans-membrane streaming potential. On the other hand, membrane performance is evaluated with respect to water permeability, the filtration of a protein solution and the correlated fouling, as well as other filtration tests with more complex feed solutions. Up to >10 times higher filtrate fluxes are observed for the DuraPES® membranes as compared to the other membranes having the same nominal pore size. However, such higher performance is only achieved with the macroporous surface upstream to the feed. The overall analysis of all data shows that the significant advantages of DuraPES® membranes resulted from their special surface and pore morphology.