Characterization and Extraction Techniques for Micro- and Nanoplastics in Environmental Matrices

Micro- and nanoplastics (MNPs) are persistent pollutants in the environment, difficult to detect and remove due to their small size, surface variability, and environmental complexity. This dissertation addresses two core challenges: understanding how submicron plastics degrade and developing a practical, low-input method for removing microplastics (MPs), including microfibers, from environmental matrices. Infrared photothermal heterodyne imaging (IR-PHI) was used to monitor UV-induced degradation of ~1000?nm polystyrene (PS) particles. Within 6 hours, oxidation products such as ketones, acids, and esters formed, accompanied by a measurable size reduction to 478?±?158?nm after 36 hours. Degradation followed a volumetric, rather than surface-limited, pattern. Based on observed rates, a complete degradation is projected in under 500 hours of peak sunlight. Building on this analytical foundation, a hexadecane-assisted aggregation method was developed to extract MPs from water without chemical coagulants or surface modification. The method performed consistently across various plastic types (PE, PP, PS, PET, PVC, PMMA) and particle sizes (125?µm–2?mm). Microfibers were also effectively removed. Aggregation succeeded in tap, river, lake, and wastewater, and was unaffected by pH, ionic strength, or turbidity. Mechanistic experiments confirmed that capillary bridge formation drove aggregation, requiring high interfacial tension (IFT =?50?mN/m), strong capillary force (Fc), and low capillary numbers (Ca =?0.01) to prevent bridge rupture. Favorable wetting of the plastic surface was also essential. No aggregation occurred in ethanol, and outcomes were inconsistent in ethylene glycol and air, underscoring the importance of interfacial interactions. Microscopy confirmed hexadecane bridges between irregularly shaped MPs. Together, these findings provide a high-resolution view of submicron plastic degradation and introduce a robust, field-relevant strategy for MP removal. Together, these findings bridge analytical insight and practical innovation, offering scalable tools to address plastic pollution across diverse and resource-constrained environments.