Pervaporation and membrane distillation technology in biorefinery

A membrane can be defined as a selective barrier which separates two phases, regulating the transport of various chemical species between the two compartments. Specifically, it is possible to distinguish homogeneous or heterogeneous membranes, with symmetric or asymmetric structure or again they may be positive or negative superficial charges, etc. Therefore the term "membrane" includes several types of membrane materials and membrane morphologies. Today, membrane processes are employed in a wide range of applications thanks to their advantageous separation/concentration/fractionation properties, and to the possibility of exploiting the synergy between different membrane operations in an integrated system. Recently, much research has been devoted to biorefinery, defined as the sustainable transformation of biomass into a spectrum of bio-based products (food, feed, materials, and chemicals) and bioenergy (biofuels, energy, and heat). In this context, membrane technology represents an optimal solution thanks to its important advantages as low energy consumption, low processing operations, and high separation efficiency. Indeed, membranes can be successfully applied in biorefinery for several separation processes such as microfiltration, ultrafiltration, nanofiltration, pervaporation (PV), and membrane distillation (MD). In this chapter the attention will be focused on PV and MD processes. In particular, a general overview of PV and MD processes will be treated and their applications in biorefinery will be discussed in detail.