An overview of different separators/membranes used in microbial electrochemical technologies

A relatively new area for fundamental and practical research in the field of energy is bioelectrochemical systems, or microbial electrochemical technology (MET), operating with organic activities of exoelectrogens. Its main benefit is its adaptability to valorize any type of waste (solid, liquid, and gaseous) to produce a variety of products (electricity, biofuel, biogas, platform chemicals) sustainably. A significant component of MET is separators. Ions between the anode and cathode can move more easily with the help of separators. Proton exchange membrane (PEM) such as Nafion or sulfonated poly-(ether-ether-ketone), which is a type of nonfluorinated membrane, often divides into two regions—an anode compartment with an anaerobic region, and an aerated cathode region, which allows for quick passage of ion through it. However, different issues with PEM are now emerging due to the expensive membrane, oxygen, and substrate crossing, and the transfer of ions other than the selective ones. To enable effective electron transmission and avoid cross-contamination between the two chambers, the separators used in MET must possess some qualities, including excellent ion selectivity, low electrical resistance, and good mechanical stability. Separators such as glass fibers, porous membranes, salt bridges, ion-exchange membranes, and others are now considered the potential alternative. These membranes assert that they are less expensive than conventional PEM, yet they can perform much more effectively. Although there are still difficulties in the actual implementation, the improvements in membrane structure and components Improvements in separator structures and components have offered new opportunities to bypass these constraints. This chapter specifically focuses on explaining an overview of different separators or membranes used in METs, the current research related to them, and the future development and scaling-up possibilities for these separators.