Nanophotocatalysis for Degradation of Organic Contaminants

Abstract

The continuous introduction of pollutants into the environment presents new challenges for their total removal and promotes the development of novel strategies with high efficiencies. Photocatalysis can be defined as a photoinduced reaction which is accelerated by the presence of a catalyst. Semiconductor nanomaterial-based photocatalysis is recognized as a promising alternative to the conventional methods for pollutant removal owing to its low cost, non-toxicity, reusability, and high stability. Nano-materials used for photocatalysis show many advantages compared to bulk materials due to their unique properties, such as increased surface area and particular quantum effects. Nanophotocatalysts can be classified as metal oxide-based (TiO2, ZnO, Fe2O3) or metal free-based (graphitic carbon nitride (g-C3N4), CdS, ZnS). Their wide or narrow band gap energies determine if the nanophotocatalysts require high or low energy UV light for their photocatalytic reactions. In this chapter, the most common pollutants and the importance of their removal from the environment have been discussed. Moreover, the principles of photocatalysis along with different variables like the structure of the catalyst, the pH, the amount of the catalyst, and the intensity of the light that affect the photocatalysis of these pollutants have also been mentioned comprehensively. The most commonly applied nanomaterials for this purpose with their advantages and disadvantages are presented. Different strategies adopted for extending the photocatalytic active region to the visible light have also been offered including metal/non-metal doping, photosensitive materials, combination with other nanoparticles, and composite formation.