Effect of UV-degraded microplastics on Dissolved Air Flotation (DAF) removal

Abstract

Microplastics (MPs) are ubiquitous environmental pollutants that cause significant effects on the aquatic ecosystem and human health, including challenging water treatment systems due to their small particle size and high environmental persistence. This study aims to investigate the effect of ultraviolet (UV) radiation on two types of MPs, polypropylene (PP) and polystyrene (PS), by using the dissolved air flotation (DAF) process. In this work, MPs in the size ranges (300-500 μm) were subjected to controlled UVC exposure to simulate environmental weathering. After 30 days of irradiation, the results show that the removal efficiency of aged PP increased to 40.67%, while the unaged PP was only 35.12%. Similarly, pristine PS had a removal efficiency of 14.66%, which substantially improved to 31.33% after UVC degradation. The increase in UV-aged MPs can be attributed to surface modifications, such as increased surface roughness and the formation of more oxygen-containing functional groups, which modified their interactions with air bubbles in the DAF process and hence affected their removal efficiency. These findings indicate that UV exposure significantly enhances the DAF process in removing MPs, providing a promising approach for improving MP mitigation in water treatment systems.