Surfactant-mediated transport of polyvinyl chloride nanoplastics in porous media: Influence of natural organic matter, natural inorganic ligands and electrolytes

This study investigates the transport behavior of polyvinyl chloride nanoplastics (PVC-NPs) in porous media under surfactant-mediated conditions through a combination of column experiments, numerical simulations, and extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) interaction energy analysis. The effects of different surfactant types, ionic species, ionic strength, humic acid (HA), and phosphate were examined. Results indicate that surfactants enhance the transport of PVC-NPs, with anionic surfactants exhibiting a stronger enhancement effect than cationic ones. Generally, the addition of cations inhibited PVC-NPs transport, with divalent Ca 2+ exhibiting a stronger inhibitory effect than monovalent Na + . Interestingly, at low ionic strengths, Na + had a stronger inhibitory effect than Ca 2+ . In the presence of anionic surfactants, higher Na + concentrations promoted PVC-NPs transport. In contrast, both HA and phosphate inhibited PVC-NPs transport under cationic surfactants, with the degree of inhibition positively correlated with their concentrations. However, under anionic surfactants, high concentrations of HA inhibited PVC-NPs transport, while lower concentrations had no significant impact. Phosphate, under anionic surfactant conditions, initially inhibited but subsequently promoted PVC-NPs transport. This study provides a comprehensive understanding of the natural transport and transformation mechanisms of PVC-NPs in the environment under surfactant influence, offering a solid data foundation and theoretical framework for accurately assessing the potential ecological and human health risks posed by nanomaterials.