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.

Automated summary

The mechanism of organic pollutant degradation in seawater by TiO2-based catalysts under visible light irradiation was investigated for the first time. The presence of different catalysts resulted in significant differences in the degradation performance of organic pollutants in seawater and pure water, with salt ions on the catalyst surface having a major impact on the degradation of organic pollutants. The visible-light response and activity of the catalyst were enhanced by the increase in Ti3+ content in the catalyst, and the presence of a small amount of EG grafted on the catalyst surface effectively resisted interference from salt ions.