Advanced TiO₂-based catalysts for polypropylene degradation in aquatic media

Area of Science:

• Environmental Science
• Materials Science
• Catalysis

Background:

• Plastic pollution, particularly microplastics (MPs), poses a significant environmental threat, with millions of tons released annually.
• Wastewater treatment plants are a major pathway for MPs entering the environment, lacking effective degradation methods.
• Polypropylene (PP) is a prevalent microplastic pollutant, contributing to widespread environmental contamination.

Purpose of the Study:

• To synthesize and evaluate novel catalysts for the degradation of polypropylene microplastics (PP-MPs).
• To assess the efficiency of UV irradiation in conjunction with different catalysts for PP-MP degradation.
• To investigate the ecotoxicity of degraded PP-MPs and the influence of catalyst composition on toxicity.

Main Methods:

• Synthesis of three catalysts: ZnO/TiO2, CeO2/TiO2, and ZnO-CeO2/TiO2 using the incipient wetness impregnation technique.
• Testing catalyst performance under UV-A and UV-B irradiation for the degradation of PP particles in wastewater and ultrapure water.
• Conducting toxicity assays using Phaeodactylum tricornutum to evaluate the environmental impact of degraded PP-MPs.

Main Results:

• A degradation of 6.6 ± 1.6% of MP area was achieved in wastewater, slightly lower than 8.4 ± 1.0% in ultrapure water.
• The ZnO-CeO2/TiO2 catalyst demonstrated lower growth inhibition in toxicity assays compared to ZnO/TiO2.
• ZnO/TiO2 catalyst exhibited toxicity levels comparable to UV-aged PP-MPs without any catalyst.

Conclusions:

• The developed catalysts show potential for degrading polypropylene microplastics, although efficiency is slightly reduced in real wastewater matrices.
• Catalyst composition significantly influences the ecotoxicity of degraded microplastics, with ZnO-CeO2/TiO2 offering a less toxic outcome.
• This research highlights the importance of catalyst design in mitigating the environmental risks associated with microplastic degradation.