Combined pollution risk of partially fluorinated microplastics: Strong interaction with organic arsenic revealed by quantum chemical calculations.

The fluorination degree of microplastics significantly influences their environmental behavior and combined pollution risks. This study employed quantum chemical calculations to explore the adsorption mechanisms of p-arsanilic acid (p-ASA) onto non-fluorinated polyethylene (PE), partially fluorinated polyvinylidene fluoride (PVDF), and perfluorinated polytetrafluoroethylene (PTFE) microplastics. PVDF displayed the strongest interaction energy (-43.1 kJ/mol) with p-ASA, higher than those of PE (-32.3 kJ/mol) and PTFE (-25.5 kJ/mol), indicating its greater potential for combined pollution risk. Energy decomposition analysis revealed that the enhanced adsorption capacity of PVDF originated from the synergistic effects of electrostatic and van der Waals (vdW) interactions, whereas PE and PTFE primarily relied on vdW interactions (> 93 %). The alternating H/F arrangement in PVDF induces a polarized surface with a broad electrostatic potential (ESP) range. In contrast, the chemically homogeneous surfaces of PTFE and PE exhibit narrow, near-neutral ESP distributions, limiting their electrostatic engagement with p-ASA. Moreover, fluorine atoms in PVDF serve as both hydrogen bond acceptors and vdW interaction sites, whereas those in PTFE participate only in vdW interactions. These findings provide molecular-level insights into the enhanced environmental risk of combined pollutants posed by partially fluorinated microplastics with organic arsenic.