High Performance Nanocomposite Cation Exchange Membrane: Effects of Functionalized Silica-Coated Magnetic Nanoparticles

Nanocomposite cation exchange membranes (CEMs) were prepared by adding various amounts of functionalized silica-coated magnetite nanoparticles to the sulfonated polyethersulfone (sPES) polymeric matrix. The particles were synthesized first by the co-precipitation method (M0). Different surface modifications were then carried out on them by grafting three functional groups of mercaptopropyl, propylsulfonic acid, and sulfonic acid to yield functionalized particles of M1, (M2, ion exchange capacity (IEC)= 3.09 meq.g-1), and (M3, IEC= 2.88 meq.g-1), respectively. The SEM images of nanocomposite membranes verified a uniform dispersion of the nanoparticles in the membrane matrix. The nanoparticles provided more ion exchange groups and regulated water content of the membrane, and consequently enhanced its transport properties, IEC, and conductivity. The maximum values of IEC and conductivity of nanocomposite membranes were 1.8 meq.g-1 and 0.274 S.cm-1 corresponded to the membranes having 3 and 2 wt% of M2 nanoparticles, respectively. The maximum ion conductivity of nanocomposite membrane was about 2 times higher than that of sPES membrane. The nanocomposite membranes containing functionalized silica-coated magnetic nanoparticles showed superior IEC, water uptake, membrane conductivity, and transport number compared to those values for the membranes containing corresponded functionalized silica nanoparticles.