Adsorption Kinetics of Diflubenzuron by Mulch-derived Microplastic PE.

Polyethylene (PE) agricultural mulch is prone to embrittlement and decomposition into microplastics (MPs) in the environment. More and more studies have shown that MPs can absorb organic pollutants, which may affect their distribution and bioavailability. Pesticides such as diflubenzuron are widely used in field vegetables, which have potential environmental and personal safety risks. They may coexist with MPs in the environment for a long time, resulting in pollution to the ecosystem. Therefore, it is helpful to explore the adsorption behavior of diflubenzuron and PE microplastics from agricultural plastic mulching film for the risk assessment of co-exposure of pesticides and microplastics. In this study, a batch adsorption experiment was carried out to systematically study the adsorption process of diflubenzuron and PE microplastics, and the environmental factors affecting the adsorption capacity of microplastics were evaluated, and the adsorption mechanism was discussed. The results showed that diflubenzuron could be adsorbed by PE MPs and reached the equilibrium adsorption capacity of 84.89 µg/g in 80 min. The dosage of 10 g/L PE MPs will be determined as the most effective dosage for the adsorption of insecticide. Under the initial concentration of 1.0 mg/L of insecticide, the adsorption capacity of insecticide increases first and then becomes stable with the increase of pH value in the range of 3~6. In the salinity range of 0.05%~3.5%, high salt concentration is not conducive to the adsorption of PE MPs for diflubenzuron. The pseudo-second-order model is more suitable to describe the kinetic process of PE MPs adsorption on diflubenzuron, which indicates that the adsorption process involves mass transfer and intra-particle diffusion in addition to the adsorption on the surface. It is necessary to investigate the adsorption processes between other pesticides and MPs and their influencing factors. [ABSTRACT FROM AUTHOR]