Quantitative microscopic study of surface characteristics of ultrafiltration membranes

Abstract

This paper presents the first high-resolution field emission scanning electron micrographs of the top skin layer of various ultrafiltration membranes at a low accelerating voltage. It was found that the fine structure on the top surface of PTHK, SKIP, ETNA 20A and MPS membranes was network-like. All the membrane surfaces observed were inhomogeneous, with wide variations in the size and shape of the pores, in surface roughness, and in appearance. The surface pore characteristics of the membranes have been determined quantitatively from the micrographs using image analysis. In most cases the pore density ranged from ca. 10 10–10 11 pores/cm 2 and the surface porosity was less than 10%. The pore spread factor (diameter for 20% greater than/diameter for 80% greater than) ranged from 2.2–6.6. The present results from field emission scanning electron micrographs compare reasonably with those obtained from transmission electron micrographs.