Behavior, mechanisms and hazardous changes of interactions with microplastics when heterogeneous pollutants coexist: Arsenic and thiram

Microplastics (MPs), as emerging pollutants, have attracted significant attention from researchers due to their inherent characteristics and the potential synergistic effects with other types of pollutants. Therefore, this study selected six types of MPs and used As and thiram degraded from tuzet as representative mixed pollutants to investigate the adsorption behavior, adsorption mechanisms and potential hazards. The adsorption processes of As and thiram on MPs both conform to pseudo-second-order kinetic model and Langmuir model. The adsorption processes primarily involve physical diffusion and chemical adsorption, with monolayer adsorption being the dominant mechanism. The adsorption processes are spontaneous endothermic processes. When As and thiram are adsorbed by MPs simultaneously, their adsorption processes are both competitive and synergistic. The adsorption performance of MPs depends on the combined effects of the characteristics of MPs, the characteristics of adsorbate, and external environment. The adsorption mechanisms primarily include hydrophobic interactions, electrostatic interactions, and other non-covalent interactions. After being adsorbed, As and thiram do not significantly increase the acute toxicity to the environment, but they pose a stronger potential hazard to human health. In summary, this study provides a theoretical basis for subsequent research on the toxicology of MPs, as well as their control and removal.