TiO2-based Nanomaterials with Photocatalytic Properties for the Advanced Degradation of Xenobiotic Compounds from Water. A Literature Survey

In recent years, the photochemistry of nano-semiconductor particles has been one of the fastest growing research areas in the physical chemistry field. TiO2 is considered as the most thoroughly investigated semiconductor in the literature, due to its photocatalytic activity, excellent functionality, thermal stability, and non-toxicity. It seems to be the most promising for the photocatalytic destruction of organic pollutants. The challenge for scientific materials is to find a processing method in which the crystalline phase as well as the size and morphology of TiO2 nanocrystals can be controlled. The concept of the present paper consists of a comprehensive study regarding the level of knowledge in the synthesis of TiO2-based nanopowders and their application in the advanced degradation of aromatic nitrocompounds. The objectives are related to: critical analysis of the synthesis techniques of the TiO2-based nanopowders, underlining the importance of using the sol–gel method evaluation of the morphological and structural specific characterization of these techniques; and a comprehensive study of the operational parameters of the pollutant photocatalytic degradation. The relative simple sol–gel method is the most widely used, being considered as a versatile means of developing catalytic materials, as well as an important experimental tool in understanding their physical and chemical properties. In order to enhance TiO2 photocatalysis and to extend the response into the visible domain, titanium has been doped with metals, nonmetals, and ionic components. A recent literature survey concerning some transition metals-doping (Fe, Co, and Ni) of TiO2 nanopowders by the sol–gel method was also included.