聚苯乙烯微（纳）塑料是环境中最常见的微（纳）塑料之一，较大的比表面积及强疏水性使其成为水环境中污染物的运输载体。三氯生在水环境中被广泛检出，易于吸附在疏水性颗粒表面，产生耦合生态风险。针对微（纳）塑料对疏水性药物吸附行为和影响因素不清、吸附机制不明等问题，本文选择不同粒径不同官能团聚苯乙烯纳米塑料（PSNPs），表征其表面特性，研究其对三氯生的吸附过程，探究不同环境条件对吸附的影响，并分析相关机理。通过材料表征实验分析了PSNPs的表面特性，发现PSNPs小球形状均一，表面光滑无褶皱，具有较强的疏水性，且表面带有负电荷，比表面积随着粒径的减小而逐渐升高，表面不存在孔结构。通过吸附动力学实验和吸附等温实验，研究了不同粒径和不同官能团聚苯乙烯纳米塑料对三氯生的吸附行为。三氯生在PSNPs上的吸附动力学符合伪二级动力学模型，并且外传质过程吸附效率最高。三氯生在PSNPs上的吸附等温线符合Freundlich模型，表明聚苯乙烯纳米塑料表面吸附位点分布不匀。进一步分析PSNPs吸附三氯生的粒径效应和官能团效应，发现PSNPs的吸附能力随粒径增大而减弱：PSNPs-50 nm（5.06 L/g）>PSNPs-100 nm（2.50 L/g）>PSNPs-200 nm（2.08 L/g）>PSNPs-500 nm（1.99 L/g）>PSNPs-900 nm（1.50 L/g）；同粒径PSNPs吸附能力，含有官能团的强于不含官能团的：PS-COOH-NPs（4.73 L/g）>PS-NH2-NPs（3.84 L/g）>PSNPs-500 nm。导致PSNPs吸附三氯生的粒径效应和官能团效应的主要原因分别是比表面积差异和氢键强度差异。探究了pH、盐度和溶解性有机质等条件对PSNPs吸附三氯生的影响。发现随着pH升高，PSNPs对三氯生的吸附量逐渐下降，表明中性条件下PSNPs吸附的主要为分子态三氯生。随着盐度增加，PSNPs对三氯生的吸附量先下降后升高，主要由于PSNPs聚集和三氯生的“盐析效应”；PS-COOH-NPs和PS-NH2-NPs对三氯生的吸附量逐渐降低，主要由于钠离子对氢键的静电屏蔽效应。溶解性有机质对PSNPs-50 nm吸附三氯生影响显著：吸附量呈现先降低后升高的趋势，推测是腐殖酸与三氯生在PSNPs上的竞争吸附及其引起的二次吸附所致。PSNPs对三氯生的吸附机制主要为疏水相互作用、π-π相互作用和氢键作用。
Polystyrene micro(nano)plastic is one of the three most common micro(nano)plastics in the environment. Its large specific surface area and strong hydrophobicity make it a transport carrier for pollutants in the water environment. Triclosan is widely detected in the water environment and can easily adsorb on the surface of hydrophobic particles such as micro(nano)plastics, resulting in coupled ecological risks. Most of the current research focuses on microplastics, and there are still few studies on the adsorption of pollutants by nanoplastics. In this paper, polystyrene nanoplastics (PSNPs) with different particle sizes and different functional groups were selected to characterize their surface properties, to study their adsorption behaviors for triclosan, to investigate the effect of different environmental conditions on adsorption and analyze the related mechanism.Material characterization experiments were carried out to analyze the surface characteristics of PSNPs. PSNPs are small spheres of uniform shapes with negative charges on their surface, and the specific surface area increases gradually with the decrease of particle size, and there is no pore structure on the surface.Adsorption kinetic experiments and adsorption isotherm experiments were carried out to study the adsorption behavior of triclosan on polystyrene nanoplastics with different particle sizes and different functional groups. The adsorption kinetics of triclosan on PSNPs followed the pseudo-second-order kinetic model, and the adsorption efficiency was the highest during the external mass transfer process. The adsorption isotherms of triclosan on PSNPs fit the Linear model and the Freundlich model, indicating that the adsorption sites on the surface of polystyrene nanoplastics are unevenly distributed. The particle size effect and functional group effect on PSNPs adsorption of triclosan were further analyzed. For PSNPs with different particle sizes, the smaller the particle size, the stronger the adsorption capacity: PSNPs-50 nm (5.06 L/g)>PSNPs-100 nm (2.50 L/g)>PSNPs-200 nm (2.08 L/g)>PSNPs-500 nm (1.99 L/g)>PSNPs-900 nm (1.50 L/g); the adsorption capacity of functionalized PSNPs is stronger than that of PSNPs without functional groups of the same particle size: PS-COOH-NPs (4.73 L/g)>PS-NH2-NPs (3.84 L/g)>PSNPs-500 nm. The particle size effect and functional group effect of PSNPs adsorption of triclosan were mainly due to the difference in specific surface area and the difference in hydrogen bond strength, respectively.To explore the effects of environmental conditions (pH, salinity and dissolved organic matter) on the adsorption of triclosan to PSNPs. With the increase of pH, the adsorption percentage of triclosan by PSNPs gradually decreased, indicating that the adsorption of PSNPs is mainly molecules triclosan. With the increase of salinity, the adsorption of triclosan by PSNPs with different particle sizes first decreased and then increased, mainly due to the aggregation of PSNPs and the "salting-out effect" of triclosan. The adsorption of triclosan by PS-COOH-NPs and PS-NH2-NPs gradually decreased, mainly due to the electrostatic shielding effect of sodium ions on hydrogen bonds. Dissolved organic matter had a significant effect on the adsorption of triclosan on PSNPs-50 nm: the adsorption amount showed a trend of first decreasing and then increasing, mainly due to the competitive adsorption of humic acid and triclosan on PSNPs and the secondary adsorption caused by organic matter encapsulated polystyrene nanoplastics. The adsorption mechanisms of PSNPs for triclosan were mainly hydrophobic interaction, π-π interaction and hydrogen bonding.
