Heterogeneous Photocatalysis: Use in Water Treatment and Involvement in Atmospheric Chemistry

Heterogeneous photocatalysis (HP) involves redox reactions initiated by the optical excitation of a semiconductor. This chapter considers the role of HP in the environment with two viewpoints. First, HP is at the basis of a new technology for water treatment, and a study of the destruction of some organic micropollutants is presented. Second, the importance of HP in tropospheric chemistry needs to be assessed, and laboratory studies in this direction are included. Isolated Titanium dioxide (TiO₂) is a less abundant component; however, since titanium is the seventh element in the Earth's crust, this dioxide can be encountered as an impurity in other oxides or can form titanates, especially ilmenite (FeTiO₃), which is a semiconductor. Consequently, HP phenomena susceptible to occur on these semiconducting particles cannot be a priori neglected in atmospheric chemistry. The disappearance of naphthalene (NPH), previously adsorbed onto TiO₂ in the dark, was also determined in a dry-air-filled static reactor as a function of the irradiation time.