Sorption Behavior\nof Trace Organic Chemicals on Carboxylated\nPolystyrene Nanoplastics

Nanoplastics possess unique characteristics (e.g., high\nsurface\narea/volume ratio) that enhance the adsorption of organic chemicals\nonto their surface. Their occurrence raises human health and ecotoxicological\nconcerns, as pollutants bound to nanoplastics can have a larger effect\nthan they would on their own. This study assessed the sorption of\nplant protection products (glyphosate and methyl parathion), an antidepressant\n(fluoxetine), a perfluorochemical (perfluorooctanoic acid [PFOA]),\nand a polycyclic aromatic hydrocarbon (phenanthrene) onto commercially\navailable carboxylated polystyrene (PS) nanoplastics (NPs, 500 and\n20 nm). Based on the calculated sorption coefficients (<i>K</i><sub>d</sub>, L/kg), the sequence of chemicals displaying the highest\nto lowest affinity toward PSNPs is fluoxetine > phenanthrene >\nmethyl\nparathion > PFOA > glyphosate, with 20 nm PS showing a higher\npotential\nto sorb organic chemicals. Cationic (fluoxetine) and hydrophobic (phenanthrene)\nsubstances were more amenable to sorption, whereas negatively charged\nand more hydrophilic ones (i.e., PFOA and glyphosate) showed poor\nsorption. pH influenced sorption for all target chemicals except phenanthrene.\nSorption capacity was further reduced in water spiked with natural\norganic matter and in tertiary-treated wastewater effluent. Overall,\nour work enhances the understanding of how representative organic\nchemicals sorb onto nanoplastics and provides quantitative information\n(i.e., <i>K</i><sub>d</sub>) on future simulations of nanoplastics’\nfate and transport.