Photocatalyst Based on TiO₂ and Its Application for Environmental Remediation: A Challenge to Sustainable Development

This is an overview of the photocatalyst TiO2 which gets activated under UV rays. Its use in wastewater management is discussed. TiO2 is a semiconductor that uses the transient nature of electrons and holes to produce radicals such as OH• and HO2• to degrade organic pollutants, inorganic pollutants, and pathogens, particularly into carbon dioxide, water, and oxides of organic compounds, respectively. The oxides are recycled back into the biogeochemical cycle. TiO2 differs in its structure such as anatase, brookite, and rutile, and hence its properties. Besides this, there are several methods of its preparation that can be obtained through natural sources or synthetic preparation. To enhance the outcome of wastewater treatment, TiO2 is doped or modified with certain elements. These include nonmetal Dopants such as porous minerals, carbon materials (fiber, graphene, activated carbon), polymer materials (PLC, PE), nitrogen, etc., and metals such as precious metals (Ag, Pt), ions (Fe3+, Mo5+). Composite modifications are also done. The formation of hetero junctions is one such method that enhances the activity of TiO2 to increase the photo response in the visible and infrared regions. Co-doping is also done such as N and Co-doped TiO2 . Certain parameters which affect the efficiency of TiO2 .> are discussed briefly along with the limitations it has. The degradation rates of some doped TiO2 acting on methylene blue and Rhoda mine B are recorded and a case study on the degradation of butachlor using Degussa-25 is discussed briefly. While degradation, a new byproduct, i.e., carboxylic ions (such as acetate and formate) was also found but later on, after undergoing photoKolbe’s reaction, CO2 was formed along with regenerated TiO2 . Here, peroxide ions played a major role in degradation as due to the presence of common salt, there was a competition to occupy the active holes of TiO2 . Hence, OH• became non-selective.