Chapter 8 - MD Membrane Characterization

Abstract

The characterization techniques of membrane distillation (MD) membranes are physical methods, which are related to membrane permeation such as liquid and gas flow tests permitting to obtain various permeation related parameters and the techniques permitting to obtain directly the morphological and structural properties of the membranes including scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), and atomic force microscopy (AFM) among others. These techniques must be considered as mutually complementary rather than competitive to better understand morphology and performance-related parameters. The characterization technique in relation to membrane permeation should be chosen in such a way that the characterization method and the final application of the membrane are similar. The MD separation performance is directly associated with the overall membrane morphology. Therefore, the successful application of MD may be aided by a good knowledge of the different membrane parameters. An important factor governing the permeability and separation factor of MD membranes is pore size and its distribution. In the membrane literature, there are several well-established techniques to determine the pore size of flat sheet, capillary, and hollow fiber membranes. Most of the techniques are explained in details. In MD process only vapor is transported through the membrane pores. Therefore, this technique is suitable to determine the pore size of the membranes used in MD.