Membrane Materials

Abstract

The membrane itself represents the core of a membrane crystallizer. Although a quite large variety of membranes exists (depending on their different morphology, topology, mass and energy transport properties, selectivity, and separation mechanism), microporous hydrophobic membranes are usually required for membrane crystallization (MCr) operations. However, in principle, any surface is suitable for promoting a controlled heterogeneous nucleation phenomenon. According to the most traditional classification, synthetic membranes are divided into organic (polymeric) and inorganic membranes; within the same class, different properties are originated by dissimilar raw materials or preparation methods.At present, due to their easy processability on industrial scale and possibility to properly modulate their physico-chemical properties, polymeric membranes have attracted much more interest than inorganic ones. The most significant exception probably concerns the use of ceramic membranes in high-temperature separation and emulsification processes. Membrane PolymersThe selection of a polymeric material is preliminarily driven by the necessity to achieve a high chemical and thermal stability. Moreover, preparation methods and related characteristics of the resulting membranes critically limit the choice of materials. It is beyond the scope of this book to give details on such an extremely complex matter, and readers are referred to specific handbooks and literature papers in this field. 77 Membrane-Assisted Crystallization Technology Downloaded from www.worldscientific.com by NATIONAL UNIVERSITY OF SINGAPORE on 10/09/15. For personal use only.78 Membrane-Assisted Crystallization Technology MEMBRANES SYMMETRIC ASYMMETRIC HOMOGENEOUS DENSE FILM POROUS SPONGE-TYPE COMPOSITE INTEGRAL Porous skyn layer Dense skyn layer