Bismuth oxyhalides as novel adsorptive photocatalysts for water remediation by concentrate and destroy approach

Environmental pollution has become a hot issue in today's world. It is mainly caused by toxic chemicals released in the air, water, and soil, leading to the destruction of biodiversity and the degradation of human health. Pollution levels increase day by day, needing fast and efficient solutions. In the last decades, the scientific community has proposed essential solutions for the depollution of the various matrices employing different approaches. Advanced oxidation processes (AOPs) offer important perspectives in this regard. Photocatalytic degradation has a special place, operating under ambient conditions and degrading many pollutants without the addition of chemical oxidants [1, 2]. However, photocatalytic processes are less effective when used to treat trace concentrations of pollutants in a large volume of contaminated matrices due to: 1) large reactor size (necessity of particular reactor configuration, with consequent increase of the costs), 2) limited light penetration, 3) high energy cost, and 4) difficulties in recycling and reusing the photocatalysts. To facilitate the degradation of traces of pollutants, sophisticated carbon/TiO2 nanotubes composites have been proposed [3, 4] that combine high adsorption capacity and photoreactivity. In the present study, we report our recent results in the use of BiOX (X = Cl, I, and Br) as novel adsorptive photocatalysts able to concentrate on their surface different classes of pollutants (polyphenols, drugs, dyes, etc.) also in the dark and degrade them quantitatively after exposure to solar light irradiation. We thank Velux Stiftung Foundation for the financial support through project 1381 "SUNFLOAT – Water decontamination by sunlight-driven floating photocatalytic systems". [1] R. Djellabi, R. Giannantonio, E. Falletta, C. L. Bianchi, Curr. Opin. Chem. Eng., 1, 2021, 100696. [2] G. Ren, H. Han, Y. Wang, S. Liu, J. Zhao, X. Meng, Z. Li, Recent Advances of Photocatalytic Application in Water Treatment: A Review, Nanomaterials, 11(7), 2021, 1804. [3] W. Liu, Z. Cai, X. Zhao, T. Wang, F. Li, D. Zhao, High-Capacity and Photoregenerable Composite Material for Efficient Adsorption and Degradation of Phenanthrene in Water, Environ. Sci. Technol., 50, 2016, 20. [4] F. Li, Z. Wei, K. He, L. Blaney, X. Cheng, T. Xu, W. Liu, D. Zhao, A concentrate-and-destroy technique for degradation of perfluorooctanoic acid in water using a new adsorptive photocatalyst, Water Research, 185, 2020. 116219