Interfacial sorption of 17β-E2 on nano-microplastics: effects of particle size, functional groups and hydrochemical conditions.

Nano-microplastics and 17β-E2 have been frequently detected as emerging high-concern pollutants in aquatic systems, and their interaction at the solid/liquid interface has become a research focus in environmental studies. The interfacial sorption kinetics and equilibrium characteristics of 17β-estradiol (17β-E2) on nano-polystyrene (Nano-PS) with different particle sizes and organic functional group modifications were systematically investigated in aqueous environments in this study. The interfacial interaction mechanism between Nano-PS particles and 17β-E2 was elucidated by utilizing SEM, FTIR, XPS and BET techniques. The experimental results demonstrated that the interfacial sorption kinetics of 17β-E2 on different Nano-PS were rapid, in accordance with the pseudo-first-order models. Both Langmuir and Freundlich models provided a nice description of 17β-E2 sorption equilibrium on Nano-PS, indicating that physical effects predominantly governed the interfacial interactions. Modification of Nano-PS by -OH and -NH resulted in increase in polarity, decrease in hydrophobicity and reduction in the sorption capacity for 17β-E2, suggesting that hydrophobic partitioning primarily controlled the interfacial interaction between Nano-PS and 17β-E2. Furthermore, the superior sorption capacity of PS100-OH relative to PS100-NH can primarily be attributed to the enhanced hydrogen bonding capability provided by the -OH group. The sorption capacity of 17β-E2 by the same Nano-PS was inversely proportional to the particle size, indicating that a smaller particle size possessed larger specific surface area, thereby providing more active sites and facilitating more pore filling. Low temperature promoted the sorption process and increased the sorption capacity. This study established a scientific foundation for better assessment of the environmental behavior arising from co-pollution of nano-microplastics and endocrine disruptors (EDCs).