Nanostructured materials in advanced membrane technology for separation processes

Abstract

Separation by selective transport through membranes is a dynamic and rapidly growing field. However, the existing of polymeric and inorganic membrane materials are inadequate in terms of sustaining the membrane performance for long term operation under high pressure and high concentration of impurities to be separated. These are some of the key issues to be addressed by scientist and engineers to fully exploit membrane technology in a broader perspective. Thus, to address the key issues, Mixed Matrix Membrane (MMM) has developed. MMM composed of homogeneously interpenetrating polymeric and inorganic particle matrices offers a viable and promising route that has been rapidly researched and is an attractive candidate for membrane-based separations processes. The combination of polymer and inorganic filler in MMM resulted in a synergistic effect in which the rigid adsorptive porous type inorganic phase provides superior separation properties, meanwhile the presence of flexible polymer enables the ideal membrane forming hence solving the problem of fragility inherent found in the inorganic membranes. In the fabrication of MMMs, the polymeric layer is normally tightly packed with nano-inorganic fillers such as zeolite, carbon molecular sieve as well as carbon nanotube to form a dense region of mixed matrix layer. These nanoporous materials possess the shape and size selective nature and hence allow molecular sieving discrimination by permitting smaller sized penetrates to diffuse at higher rate than that of larger sized. The practical utilization of MMMs for particular separation processes can only be achieved only if the intrinsic properties of the MMM is fully optimized. In this aspect, the selection of proper filler and adaption of modification to enhance the filler compatibility are crucial steps to be taken into consideration in order to facilitate and also bring a new insight into a wider application of MMMs.