Microplastics have recently become a major environmental issue due to their ubiquitous distribution, uncontrolled environmental occurrences, small sizes and long lifetimes. Actual remediation methods include filtration, incineration and advanced oxidation processes such as ozonation, but those methods require high energy or generate unwanted by-products. Here we tested the degradation of fragmented, low-density polyethylene (LDPE) microplastic residues, by visible light-induced heterogeneous photocatalysis activated by zinc oxide nanorods. The reaction was monitored using Fourier-transform infrared spectroscopy, dynamic mechanical analyser and optical imaging. Results show a 30% increase of the carbonyl index of residues, and an increase of brittleness accompanied by a large number of wrinkles, cracks and cavities on the surface. The degree of oxidation was directly proportional to the catalyst surface area. A mechanism for polyethylene degradation is proposed.

Microplastics are persistent anthropogenic pollutants which have become a global concern owing to their widespread existence and unfamiliar threats to the environment and living organisms. This study demonstrates the degradation of fragmented microplastics particularly low-density polyethylene (LDPE) film in water, through visible light-induced plasmonic photocatalysts comprising of platinum nanoparticles deposited on zinc oxide (ZnO) nanorods (ZnO-Pt). The ZnO-Pt nanocomposite photocatalysts were observed to have better degradation kinetics for a model organic dye (methylene blue) compared to bare ZnO nanorods, attributed to the plasmonic effects leading to better interfacial exciton separation and improved hydroxyl radical activity along with a 78% increase in visible light absorption. These demonstrations of the plasmonically enhanced photocatalyst enabled it to effectively degrade microplastic fragments as confirmed following the changes in carbonyl and vinyl indices in infrared absorption. In addition, visual proof of physical surface damage of the LDPE film establishes the efficacy of using plasmonically enhanced nanocomposite photocatalytic materials to tackle the microplastic menace using just sunlight for a clean and green approach towards mitigation of microplastics in the ecosystem.

Plastic products are used in almost all aspects of our daily life. Due to their low cost, portability, durability, and resistance to degradation, these products are affecting the health of the environment and biota on a global scale. Thus, the removal and mineralization of microplastics is an important challenge in the 21st century. Advanced oxidation processes (AOPs) have recently been identified as a viable treatment technique for tackling recalcitrant organic molecules and polymers. However, information on kinetic degradation mechanisms and photocatalytic reactor design is insufficient. This review discusses the fundamentals of photocatalysis and photo-Fenton processes in addition to the photocatalytic degradation mechanisms. We also introduce different characterization techniques of the major microplastic pollutants such as PE, PP, PVC, PS, PMMA, and PA66. In addition, a detailed overview of the major existing photocatalytic plants and the scaling-up methods of photoreactors are discussed.