Degradation of Microplastics by Zinc Oxide Nanoparticles Synthesized Using Piper longum Leaf Extract

Background: The environmental hazards posed by microplastics have drawn considerable concern due to their buildup in ecosystems. Microplastics accumulate in human saliva, skin, and hair. Developing effective technology for managing and degrading microplastics remains a substantial challenge. In a concerted attempt to save the ecology, this study explores the photocatalytic breakdown of common microplastics like polystyrene (PS) microspheres and polyethylene (PE) using green-synthesized zinc oxide nanoparticles (ZnO NPs) under UV light exposure. Aim: To synthesize and characterize zinc oxide nanoparticles prepared using the extract of the leaves of Piper longum and qualitatively assess the photocatalytic degradation potential of the nanoparticles under light microscopy. Material and Methods: A fresh extract of P. longum leaves was used as a reducing agent to synthesize zinc oxide nanoparticles. Fourier transform infrared (FTIR) analysis, X-ray diffraction (XRD) analysis, UV-Vis spectra analysis, and scanning electron microscopy (SEM) analysis were performed to characterize the nanoparticles. Microplastics were isolated from the saliva of 50 healthy patients and were purified and filtered. In a six-well microtiter plate, 0.5 μg of varying concentrations of nanoparticles were added. After fixing with 15% formaldehyde, microplastics were subjected to UV irradiation for 2 hours with different concentrations of ZnO nanoparticles (25, 50, 75, and 100 µg). Custom photoreactors activated the photocatalysts to degrade the microplastic pollutants. The six-well microtiter plate was viewed under 40x magnification in a light microscope to observe microplastic morphology after 24 hours of degradation. Results: The FTIR spectrum showed distinct peaks at 890.51 cm⁻¹, indicating the involvement of C-N in-plane vibrations of amino acids. XRD analysis revealed three distinct diffraction peaks at 31.68°, 34.39°, and 36.33°, corresponding to the hexagonal wurtzite structure of ZnO nanoparticles. The synthesized ZnO nanoparticles ranged from 50 to 90 nm in size, viewed at 100x magnification on SEM. The highest degradation of microplastics was observed at a ZnO NP concentration of 100 µL, with the ZnO NPs 50-90 nm in size. Conclusion: Zinc oxide nanoparticles synthesized using Piper longum leaf extract effectively degrade microplastics, with the highest degradation observed at a 100 µL concentration of ZnO nanoparticles and optimal degradation occurring at a concentration of 75 µL.