Modeling the adsorption mechanism of 3-tertiary-butyl-4-hydroxyanisole (3BHA) on polyethylene and polypropylene microplastics.

Abstract The Polyethylene (PE) and polypropylene (PP) microplastics (MPs), can act as carriers of the molecule 3-tertiary-butyl-4-hydroxyanisole (3BHA), which propose harmful impacts to aqueous ecosystems. Meanwhile, 3BHA has already been detected in several environments and human urine and serum samples. 3BHA is an antioxidant in foods, food packaging, cosmetics and pharmaceuticals. However, it raised concerns about its possible endocrine-disrupting effect in recent years. The interaction between two MPs and 3BHA could start in farmland and be maintained during transportation to the ocean. Herein, the adsorption behavior and mechanism of 3BHA by PE and PP MPs were investigated via molecular dynamics (MD) simulation, density functional theory (DFT), non-covalent interactions (NCI), the density of states (DOS) and frontier molecular orbital (FMO). Furthermore, the stability of 3BHA adsorbed complexes was investigated by adsorption-free energies (Δ Gads ), showing that the 3BHA has a significant interaction with the MPs studied, mainly with PP MP. Intermolecular van der Waals forces were one of the primary adsorption mechanisms of 3BHA by MPs, as evidenced by NCI calculations. It was demonstrated that the adsorption of the 3BHA in MPs decreases the energy gap of the HOMO and LUMO orbitals, as well as a slight shift in the HOMO and LUMO states in the TDOS analysis. In conclusion, this study about the mechanism of adsorption of the 3BHA in PE and PP MPs can provide new evidence and enhance our understanding of the environmental behavior of 3BHA in the environment.