Polymeric Membranes

A membrane can be defined as an "interphase between two adjacent phases acting as a selective barrier, regulating the transport of substances between the two compartments" . Membrane technologies are widely recognized as advanced separation/concentration processes, which are ideally placed to aid process intensification, thanks to the possibility of exploiting the synergy between different membrane operations in an integrated system. Membrane processes are now widespread at the industrial level, a result of the advances in membrane performance connected to higher productivity, enhanced selectivity, and improved stability. Nowadays, membranes are prepared using a wide variety of techniques, mainly depending on the membrane material but also on the application. In this chapter, the most common membrane preparation methods are described, with peculiar focus on phase inversion (PI) or phase separation (PS), which is the foremost technique for preparing polymeric membranes. The thermodynamic principles of PI, the main factors affecting membrane morphology and properties as well as the peculiarities of hollow-fiber membranes preparation through PI, are examined. Furthermore, significant examples of membrane preparation for selected applications, spanning from classical pressure-driven processes, such as reverse osmosis (RO), nanofiltration (NF), ultrafiltration (UF), and microfiltration (MF), to more recent emerging processes, such as membrane contactors (MCs), are reported.