The photocatalytic degradation of oxytetracycline using 2D and 3D Bi5O7I and BiOCl under visible light irradiation - Optimization of the reaction parameters

Bismuth oxyhalides are a group of efficient photocatalysts to achieve the complete degradation of organic pollutants in water under UV-A/visible light irradiation. In this work, BiOCl and Bi5O7I were synthesized through different procedures to obtain 2D (nanoneedles) and 3D (microspheres and nanoflakes) structures. The structural, chemical and optical properties of the materials were characterized as well as their photocatalytic activity to degrade the antibiotic oxytetracycline under visible light irradiation. Bi5O7I nanoflakes completely degraded oxytetracycline within 300 min of UV-A/visible light irradiation while BiOCl materials achieved only 80% of removal. The pH, initial concentration of oxytetracycline and the catalyst dosage were optimized using the BoxBehnken design of experiments. At pH of 9, irrespective of dosage and initial concentration of oxytetracycline, the complete degradation was achieved after < 10 min of irradiation, with an initial rate constant of 0.36 min-1. Under the optimal reaction conditions, Bi5O7I nanoflakes demonstrated to efficiently remove the target pollutant in tap water through three consecutive reaction cycles, displaying the potential of this material to be tested in upscaled systems.