Assessment of atomic force microscopy for characterization of PTFE membranes for membrane distillation (MD) process

The membrane distillation (MD) process is an emerging and under-developed technique, which is currently investigated for various applications, e.g. desalination and wastewater treatment. As specific membranes for MD are not yet commercially available, most of the applied membranes for MD experiments are those microfiltration membranes made of hydrophobic polymers. Characterization of such kinds of membranes is important in order to achieve a better and clearer understanding of their performance, which helps to fabricate specific membranes for the MD process. In this work, atomic force microscopy, which is a high-resolution technique and newly applied for characterization of MD membranes, has been used for the topographical study of different polytetrafluoroethylene membranes, which are typically recommended for various MD applications. The membranes were characterized for their pore size, pore size distribution, surface roughness, and nodule aggregate. Moreover, the other two important specifications, liquid entry pressure and surface hydrophobicity, were measured and compared. A sweeping gas MD experimental setup was used for solute rejection evaluation of the applied membranes by use of four different feed samples.