The role of chemical aging in microplastics and its impact on elimination of polyethylene microplastics by coagulation

Microplastic pollution has emerged as a potential threat to the environment. Exposure to microplastics presents a major emerging threat to ecosystems due to their potential adverse effects. Microplastics (MPs) are persistent environmental contaminants that readily enter and accumulate within the food chain due to their refractory nature and resistance to biodegradation. Their small size, ranging from the micrometer to the nanometer scale, renders them virtually impossible to eliminate once released into natural ecosystems. These characteristics contribute to their classification as emerging pollutants of global concern. Coagulation technology has been extensively employed for the treatment of microplastics in water; however, most research focuses on virgin (unaged) microplastics. In response to these challenges, this study is concerned with the impact of chemical aging on microplastics' properties and coagulation efficiency. Polyethylene (PE) microplastics, which are particularly difficult to settle in water, were selected as representative pollutants to investigate the conventional coagulation performance. Microplastics were incubated in 0.1 M HCl, 0.1 M NaOH, CH₃OH, 30% H₂O₂, 0.1M KMNO₄ and 0.1M Na₂S₂O₈ solutions at 5, 25, and 60°C for 7 14, and 28 days. The removal efficiency of pristine microplastics was 27%, while the range obtained for aged PE was 15.98 to 79.02%. The highest increase in efficiency was observed after incubation of PE in KMnO₄, while a decrease in coagulation efficiency was observed in the case of using methanol and hydrogen peroxide. The temperature and time of incubation significantly influenced the obtained results.