ABSTRACT

Atomic force microscopy (AFM) is an extremely versatile tool for the membrane technologist. This powerful imaging device allows the topographical study of membrane surfaces both in air and process relevant aqueous environments. This chapter presents systematic studies of microfiltration, ultrafiltration and nanofiltration membranes in air and liquid. The chapter describes how accurate images of membrane surfaces are produced and how these can provide quantitative data on pore size distributions and surface morphology. However, AFM is not only an imaging technique. Measurements in electrolyte solutions can provide quantitative information on the surface charge properties of membranes. Furthermore, the instrument can directly quantify the forces of interaction between a membrane surface and a pertinent colloidal particle. Such a colloid probe AFM technique allows direct quantification of surface adhesion. Hence, AFM may be used to quantify the three parameters that most influence membrane separation performance: pore size distribution, membrane surface electrical properties and membrane adhesion (fouling). In each case AFM has substantial advantages over competing methods. AFM is a new technology and the range of its applications is growing rapidly. The chapter ends with a discussion of the future prospects of AFM and some of the potential applications within membrane science. AFM is fast becoming essential for the research and development of membrane separation processes.