Membrane-based separations are becoming increasingly relevant for a number of applications owing to their low energy requirements and steady-state operation. Polymeric hollow-fiber membranes are amenable to large-scale fabrication and have large surface area/volume ratios, but they have a trade-off between their permeability and selectivity. Porous inorganic membranes have been shown to possess high permeability, tunable selectivity, and high resistance. Their applications are yet limited by the difficulty of fabrication on a technologically scalable platform. Ordered mesoporous silica materials are advantageous for a rapid diffusion of target molecules, and can be modified in a variety of ways, allowing for specific separations. We will describe the technologically scalable fabrication of mesoporous silica membranes on polymeric hollow fibers. These asymmetric mesoporous silica membranes are continuous over large areas and have a high gas flux. We then functionalize the mesopores using aziridine. Aziridine is polymerized in a silica framework and forms a hyperbranched aminosilica (HAS) membrane. In addition, the gas transport properties of aziridine-functionalized membranes are investigated. The HAS membrane shows counter-intuitive N2 selective permeation under dry conditions owing to the effects of a strong adsorption of CO2. However, the HAS membrane is CO2 selective under humid conditions, because water molecules allow the facilitated transport of CO2. On the other hand, silylated mesoporous membranes are evaluated for a pervaporative separation of aqueous organic solutions. The large increase in hydrophobicity of the membranes upon silylation allows an upgrading of the feed mixtures to permeate streams with considerably higher organic content. This selectivity is attributed to both the organophilic nature of the surface and the effective pore size of the silylated mesopores.

Functionalized mesoporous silica membranes on polymeric hollow fibers for separation applications

251st National Meeting (2016)

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