Chapter 11: Smart Polymeric Membranes with Magnetic Nanoparticles for Switchable Separation

This chapter provides an overview on the topic of magneto-responsive membranes for switchable mass separation. The combination of concepts, materials and methods in the field of filtration membranes with the application of magnetic materials and magnetic fields is described. Combining organic polymer-based membranes with inorganic magnetic nanoparticles is the most efficient approach to obtain “smart” membranes that can show large and reversible changes in barrier and surface properties upon activation with static or alternating magnetic fields of different frequencies. Two general approaches can be distinguished: (i) addressing secondary interactions during membrane separation such as concentration polarization or fouling, or (ii) focussing on intrinsic membrane barrier properties. Until now, the most progress toward switchable separations has been achieved by membranes that change effective pore size in the micro- or ultrafiltration range, either via reversible deformations induced by static or low frequency magnetic fields or via the synergistic combination of magneto-heating by stimulation with high frequency alternating magnetic fields and thermo-responsive hydrogels as building blocks for mixed matrix composite membranes. This pioneering work will trigger much more research and development toward real applications, e.g., in bioseparations and/or for bioanalytical or biomedical applications, wherever the option of remote-controlled switching of separation selectivity is of interest.