Synthesis of Novel Bismuth-Based Catalysts for the Degradation of Microplastics in Aquatic Matrices

Microplastics are one of the most widely studied and concerning contaminants, as they are present in all environmental compartments, especially water bodies. Wastewater treatment plants are one of the most important pathways through which these pollutants enter the environment. Currently, novel techniques are being developed to eliminate microplastics from wastewater, including heterogeneous photocatalysis. In this study, two bismuth-based photocatalysts were synthesized using different methods: BiPO4 by the solvothermal method, and Bi2O3/TiO2 by the wet impregnation method. These were morphologically and structurally characterized. Both photocatalysts were then tested in laboratory-scale experiments to evaluate their effectiveness on the degradation of polypropylene microplastics under UV irradiation in ultrapure water. The effectiveness of the treatment was estimated by measuring the reduction in the area of each of the microplastics, and structural changes were assessed using infrared spectroscopy (FTIR). It was found that the BiPO4 catalyst was more effective when applying UV-B radiation, achieving a reduction in the area of microplastics of up to 10.81%, while the Bi2O3/TiO2 catalyst showed a higher efficiency when applying UV-A, achieving a reduction in the area of microplastics of up to 9.15%. The study of microplastics by ATR-FTIR revealed the appearance and modification of some absorption bands, which indicates incipient degradation. The application of both catalysts in real wastewater showed a reduction in the efficiency of the treatment; hence, further studies should be conducted to determine the influence of other variables in the photocatalytic process. In the current context of growing environmental concern, the development of new, easily synthesized catalysts represents a key strategy for reducing or eliminating MPs. This study presents significant advances in the formulation and evaluation of innovative catalysts, demonstrating their potential as effective and accessible tools for mitigating one of the most pressing global pollution challenges.