Characterization, permeation analysis and stability increasing of facilitated transport membranes through incorporation of bis(bipyridine) silver (II) peroxydisulfate

Bis(bipyridine) silver (II) peroxydisulfate (Ag(bipy)2S2O8) has been applied as an alternative salt in the preparation of polyethersulfone (PES)/polyethylene oxide (PEO) facilitated transport membranes aiming at postponing the reduction process of silver carrier agents. The geometrical structure, mechanical and permeation properties of membranes containing Ag(bipy)2S2O8 or AgBF4 salts were compared in the ethylene/ethane separation process.Formation of silver nanoparticles from [Ag(bipy)2]2+ cations was lower than from Ag+, which was detected by means of UV–Visible spectroscopy and transmission electron microscopy (TEM). The two positive charges of [Ag(bipy)2]2+ cations besides oxidative properties of S2O82− anions postponed the reduction time of active sites. Ag(bipy)2S2O8 incorporated membranes possessed higher permeation, selectivity durability, mechanical strength and stronger CO bond strength and lower pore size and surface roughness than that of membranes containing AgBF4 salt. Lower lattice energy and steric hindrance of AgBF4 salt resulted in homogeneous distribution of Ag+ cations and counter-ions. The maximum selectivity of 124 was obtained at the highest AgBF4 concentration (molar percent = 50%) and operational pressure (4 barg). On the other hand, the maximum ethylene selectivity after saturation step belonged to the membrane containing (Ag(bipy)2S2O8) salt, which was 115 at the same condition.