Photoaging of Microplastics in the Presence of Minerals

This work investigated the photoaging behaviors of polyethylene (PE) and polypropylene (PP) microplastics in the presence of natural minerals, using a simulated intertidal environment as a model. The results showed that UV radiation promoted microplastics oxidation and generated oxygen-containing polar groups. Due to the lower dissociation energy of tertiary carbon atoms in the polymer backbone, the degree of photo-oxidation of PP was higher than that of PE (e.g., the carbonyl indices in the UV+clay group were 7.70 and 0.54, respectively). Furthermore, natural minerals adsorbed onto microplastics surfaces to form a mineral-plastic composite layer, in particular, clay minerals specifically acted as the primary promoter of oxidation, whereas the effect of sand was less dramatic. This indicates that microplastics degradation in realistic mineral-rich coastal environments is more severe than in bulk water. This study revealed the accelerated aging mechanism driven by environmental minerals, providing theoretical support for the scientific management of plastic pollution in complex marine systems.