Nuclear Magnetic Resonance as Investigation Tool for Pollutant/Sorbent Interactions

Abstract

Molecular separation using membranes is widely considered as an energy-efficient alternative for conventional industrial separation techniques. For the preparation of such membranes sol-gel technology is highly suitable. Using sol-gel techniques thin (50–100 nm) amorphous nanoporous layers having pore sizes in the micropore (<2 nm) or fine mesoporous (<5 nm) region can be prepared on a porous substrate. These layered porous systems, usually in tubular form, can be used for nanofiltration, pervaporation and gas separation applications. The application window is dependent on the material properties, such as the pore size and pore size distribution, the interfacial properties of the pores, and the defect density. The success of this technology in actual industrial applications strongly depends on reproducible large scale production of the sol-gel membranes and on a sufficient stability of the membranes with respect to flux and selectivity. In addition the production cost of the full membrane system is an important aspect. Here, we will focus on the more chemical aspects in the membrane preparation. Main topics are synthesis and properties of the sols, the preparation of microporous thin films, and the search for membrane materials that have a high hydrothermal stability.