TiO₂-Based Photocatalysis for Plastic Degradation

Plastic pollution has become an environmental and social crisis, with plastic waste often bypassing proper disposal systems and accumulating in the environment. This crisis includes macroplastics (MaPs), microplastics (MPs), and nanoplastics (NPs), each impacting ecosystems and economic activities due to their resistance to natural degradation. Vulnerable populations are disproportionately affected, highlighting the social justice dimension of plastic pollution. Photocatalysis using TiO2 has shown promise for degrading plastic waste due to its high activity, low cost, and availability. Photocatalytic degradation of plastic waste follows two approaches: creating TiO2/plastic composites or dispersing plastic debris in aqueous TiO2 suspensions. Composites involve dissolving plastic in hot solvents and incorporating TiO2, which may generate MPs and NPs if incomplete degradation occurs. Dispersion of plastics in aqueous suspensions with TiO2 powders or films faces challenges due to limited interaction between plastics and the TiO2 surface. Despite these issues, research has identified conditions improving degradation efficiency, making this approach viable for wastewater treatment plants (WWTPs). Trends indicate that smaller MPs and NPs are more easily degraded when dispersed, while immobilizing photocatalysts in films or foams reduce efficiency, often due to the use of visible light for activation, which limits OH• availability (from H2O2 photolysis). TiO2 powders enhance MP degradation by ensuring effective interaction with OH•. Photocatalyst characteristics, such as high surface area, porosity, and crystallinity, are crucial for efficiency, particularly for larger MPs. TiO2 morphology, including innovative designs like TiO2 micromotors, further optimizes pollutant interaction and degradation.