Mechanism of Photodegradation of Organic Pollutants in Seawater by TiO2-Based Photocatalysts and Improvement in Their Performance

The mechanism of photodegradation of organic pollutants in seawater by TiO2-based catalysts irradiated by visible light was first explored by adding holes and free radical traps. The results showed that the photogenerated holes formed by the catalyst played a key role in the degradation of organic pollutants, regardless of whether the photodegradation occurred in seawater or pure water. Considering that the Yb-TiO2-rGO catalyst has a strong adsorption for organics, the salt ion almost did not interfere with the adsorption of pollutants by Yb-TiO2-rGO. Therefore, the degradation performance of Yb-TiO2-rGO did not remarkably change in the two water systems. For P25-ZN with a weak adsorption capacity for organics, several salt ions in the seawater hindered the contact of pollutants with the catalyst surface. Thus, the degradation rate of P25-ZN for phenol was significantly reduced. After the solvothermal reduction treatment for catalysts using ethylene glycol (EG) as the solvent, the increase in the Ti3+ content in the catalyst improved the visible-light response and activity of the catalyst. In addition, a small amount of EG grafted on the catalyst surface promoted the photocatalytic reaction process on the catalyst surface, thereby effectively resisting the interference of salt ions.