1.D.229. The Electrically Tunable Polypyrrole Nano-Pore (ETP-NP) Family
Regulating ion transport behavior through pore size variation is important for membranes to meet the need for precise separation, but nanofiltration (NF) membranes with tunable pore size is desirable. A NF membrane with electrically tunable pores was fabricated by intercalating polypyrrole into reduced graphene oxide interlayers. As the potential switches from reduction to oxidation, the membrane pore size shrinks by 11%, resulting in a 16% increase in salt rejection. The membrane pore size expands/contracts at redox potentials due to the polypyrrole volume swelling/shrinking caused by the insertion/desertion of cations, respectively (Wu et al. 2023). In terms of the inserted cation, Na+ and K+ induce a larger pore-size stretching range for the membrane than Ca2+ due to greater binding energy and larger doping amount. Such an electrical response characteristic remained stable after multiple cycles and enabled application in ion selective separation; e.g., the Na+/Mg2+ separation factor in the reduced state is increased by 41% compared to that in the oxide state. This work provides electrically tunable nanochannels for high-precision separation applications such as valuable substance purification and resource recovery from wastewater (Wu et al. 2023).