Titanium-oxide nanomaterials: synthesis, characterization, and selective photocatalysis

The side effects of some recent scientific advances challenge the well-being of our planet. Water contamination, one of these side effects, from industrial effluents is a major source of fresh water pollution. Semiconductor photocatalysis, which operates under ultraviolet or visible light irradiation, is a well proven approach to water de-contamination. Among the various available semiconductor photocatalysts, nanocrystalline titanium-oxides are unique in their activity, stability and biocompatibility. Consequently titanium-oxide mediated photocatalytic mineralization of organic pollutants in aqueous solution has become a well established research area. Titanium-oxides are mostly exploited as non-selective photocatalysts in degrading water contaminants, mainly organic compounds. However, selective degradation has the advantage of being able to allow the recovery of valuable desired compounds from waste water while degrading the rest. This thesis is about the synthesis, characterization and selective adsorption and degradation properties of titanium dioxide and potassium titanate nanostructures. A low-temperature sol-gel method followed by a pH controlled precipitation technique was adopted for the synthesis of titanium dioxide photocatalysts with tailored surface charge. Potassium titanate was derived by the alkali (KOH) treatment of titanium dioxide nanoparticles under near-ambient experimental conditions. These nanomaterials were tested for their selective adsorption and photocatalytic properties with a cationic and an anionic dye. The origin of the selective adsorption and photocatalytic ability of the synthesized titanium-oxide samples was found to be due to the synergistic effects of surface charge and crystallinity.