Abstract
Anatase-based photoactive thin layers and membranes with an ordered mesoporosity resulting from mesophase templating were synthesized for coupling membrane separation and photocatalyzed reaction. A sol-gel method was developed to prepare a nanocrystalline anatase hydrosol at low temperature. Mesostructured thin layers and membranes were produced using this hydrosol and triblock copolymers (poly(ethylene oxide)-poly(propylene oxide)- poly(ethylene oxide)). These amphiphilic molecules give rise to templating mesophases by self-assembly process. Two different mesostructures were obtained: an initially 2D hexagonal structure (crystallographic type p6mm) corresponding to a close-packed arrangement of cylindrical micelles and then of cylindrical pores; a cubic mesostructure (crystallographic type Fm3m) with spherical pores resulting from a micellar cubic mesophase. The removal of the templating mesophases at low temperature (150°C) is possible using the photocatalytic properties of the anatase layers. Thus, such layers could be deposited on low thermal stability substrates. Mixed oxide (TiO2/SiO2) and doped mesostructured films were also prepared. Doping would be an opportunity to shift the photoactivity in the visible light range. The photocatalytic activity of the various thin layers and membranes was investigated. These experiments showed a high photocatalytic efficiency. Preliminary experiments of coupling separation/degradation were performed with an aqueous solution of organic dye (methylen blue). The membranes were also characterized with liquid and gas permeation measurements.