Enhanced pervaporation performance of poly (dimethyl siloxane) membrane by incorporating titania microspheres with high silver ion loading

Facilitated transport membranes were fabricated by incorporating Ag+ loaded titania (TiO2) microspheres into poly (dimethyl siloxane) (PDMS) matrix for pervaporative desulfurization of model gasoline. The pristine monodispersed TiO2 microspheres with controllable particle size were synthesized via a modified sol–gel method. The surface of TiO2 microspheres was then coated with dopamine through bioadhesion-inspired strategy. Subsequently, the Ag+ ions were coordinated with dopamine to acquire Ag+/TiO2 microspheres. The composition and structure of Ag+/TiO2 and pristine TiO2 microspheres were characterized comprehensively by HR-TEM, PSDA, BET, ICP, XPS, FT-IR and TGA. The results indicated that Ag+ loading amount was dramatically increased with the mediation of dopamine. The structures of the membranes were probed by free volume characteristics analysis. And the facilitated transport function of Ag+ was verified by the pervaporation experiments of the membranes. The normalized permeation flux and enrichment factor of the membranes were simultaneously enhanced with the increase of Ag+/TiO2 microsphere weight fraction from 0.0 wt% to 5.0 wt%, which was mainly attributed to the interfered polymer chain packing through the inorganic particle incorporation and specific reversible chemical reaction between Ag+ and thiophene. When the weight fraction of Ag+/TiO2(0.01) microsphere reached 5.0 wt%, the membrane displayed an optimum desulfurization performance with permeation flux of 4.14 kg/(m2 h) (47.9% more than that of PDMS-TiO2 membrane) and enrichment factor of 8.56 (23.3% more than that of PDMS-TiO2 membrane). Moreover, after incorporating Ag+/TiO2 microspheres into PDMS matrix, the membranes showed improved stability as verified by TGA analysis and operating condition experiments. Obviously, the present study offers a novel approach to attach a large pool of functional groups/ions/molecules onto a variety of surface to acquire enhanced comprehensive performance of the membranes.