Direct production of a free-standing titanate and titania nanofiber membrane with selective permeability and cleaning performance

Abstract

Herein, we report the direct production of free-standing titanate and TiO₂ nanofiber membranes with selective permeability and cleaning performance. The membrane was prepared through the hydrothermal reactions among tetra-n-butyl titanate, graphene oxide and NaOH. Tetra-n-butyl titanate reacted with NaOH to form high-quality nanofibers with lateral dimensions below 100 nm and longitudinal dimensions of several tens of micrometres. Graphene oxide was condensed with the nanofibers and enabled the nanofibers to organize into a free-standing membrane with a diameter of 1 cm. Interestingly, the interlayer of the as-prepared membrane stood parallel and as closely packed nanofibers, totally different from the disorders of those prepared by the filtration method. Benefiting from the distinctive structure, the nanofiber membrane showed a selective permeability: water could cross it easily while organic dyes and bacteria were trapped for a long time (120 h for methylene blue and methyl orange and 24 h for rhodamine B and Bacillus coli). Furthermore, the membrane showed a high efficiency in the photodecomposition of the trapped dyes because it combined the photocatalytic activity, the porosity, and the capability of separating photogenerated electrons and holes. Consequently, the membrane possesses both the separation function and cleaning function and should find potential applications in membrane-based water purification.