Synthesis of porous titanium dioxide membranes

Abstract

Until recently, the industrial membranes used for filtration, distillation, separation or extraction were manufactured from polymers. However, inorganic membranes are emerging as an alternative to polymeric membranes for applications due to their thermal, mechanical and chemical characteristics. The sol-gel process is the way to obtain an inorganic structure that becomes a porous ceramic layer after thermal treatment with controllable porosity. The sol-gel process involves low-temperature synthesis of an inorganic network by a chemical reaction in solution. The synthesis of this material was accomplished using a titanium isopropoxide, Ti(OC 3H 7) 4, as a precursor followed by peptization with nitric acid. The synthesis procedure strongly influenced the formation of the mesophase. The control of sol-gel transition and thermal decomposition allowed the synthesis of two forms of titanium dioxide — anatase and rutile. TiO 2 dioxide was chosen for study for its interesting properties and the interest in which it may bring to the domain of chemical and mechanical high resistance of inorganic membranes. Deposit thin layers were created with a sol prepared with the destabilization of a colloidal solution process. These results show the great potentiality of inorganic membranes and new applications to be taken into account, particulary wastewater treatement and gas separation. Crossflow microfiltration and ultrafiltration are becoming of increasing interest to produce drinking water. X-ray diffraction, thermogravimetric analysis, and infrared spectroscopy have been used to characterize the mesostructure formed at room temperature as well as calcined at different temperatures. The pore diameters, porous volume and surface area of the materials measured from N 2 adsorption–desorption isotherms indicate the variation according to temperature. Scanning electron microscopy is used to characterize membrane morphology, that is, the absence of cracks, the thickness and its homogeneity along the support. Some experimental results on the synthesis and characterization of inorganic membranes are presented.