Adsorption of lead(II) onto PE microplastics as a function of particle size: Influencing factors and adsorption mechanism

The adsorption of Pb ions, on high-density polyethylene (PE) microplastics (MPs) with the diameter of 48-500 mu m, was examined in this study. According to the Langmuir isotherm, MP of the smallest size, 48 mu m, had the greatest adsorption capacity of 0.38 mu mol g(-1). The mechanism of Pb ions adsorption onto PE MPs was chemical adsorption, in particular, hydrogen bonding and surface complexation. Pb adsorption onto PE particles was proceeded at a rapid rate, as predicted by the pseudo-second-order rate model (R-2 > 0.99). The PE 48 mu m had the maximum adsorption capacity of 0.44 mu mol g-1 (or 0.2 mol m(-2)) at pH 5. While humic acid can operate as a bridging agent, boosting heavy metal adsorption on the surface of PE MPs, fulvic acid has the reverse effect. The findings indicated that PE particles may serve as a carrier of heavy metals in the aquatic environment, posing perceived risks to the environment and public health.