光老化对不同粒径聚苯乙烯微塑料吸附Cu(Ⅱ)的影响

为评估老化作用和粒径等因素对微塑料（MPs）吸附重金属的影响,对紫外光老化作用下3种不同粒径聚苯乙烯（PS:1、50和100 μm）吸附Cu（Ⅱ）的行为进行了系统研究.结果表明,紫外光老化显著改变了PS的表面形貌和理化性质,1 μm粒径PS的老化程度最强.PS对Cu（Ⅱ）的吸附动力学符合伪二阶动力学模型,而Freundlich模型更好地拟合了PS对Cu（Ⅱ）的等温吸附实验数据,表明PS对Cu（Ⅱ）的吸附过程发生在其非均匀表面,吸附行为为多层吸附；Freundlich模型参数n值均小于1,表明PS对Cu（Ⅱ）的吸附行为为强度较高的物理吸附；不同粒径PS对Cu（Ⅱ）的理论最大吸附量依次为:1 μm> 50 μm> 100 μm,说明粒径是影响PS吸附污染物的重要因素,而老化作用增强了同一粒径PS对Cu（Ⅱ）的吸附能力.对不同环境条件下PS吸附Cu（Ⅱ）的研究结果表明,PS对Cu（Ⅱ）的吸附能力随环境pH升高而增强,而盐度升高则产生相反的效果,表面络合和电性吸附是PS吸附Cu（Ⅱ）的主要机制.研究可为全面了解环境中MPs对重金属的吸附行为提供重要科学依据.

Effect of Photoaging on Adsorption of Cu(Ⅱ) by Polystyrene Microplastics with Different Particle Sizes

In order to evaluate the effect of aging and particle size on the adsorption of heavy metals by microplastics, the adsorption behavior of Cu(Ⅱ) by three different particle sizes of polystyrene (PS; 1, 50, and 100 μm) under UV irradiation was systematically studied. The results demonstrated that UV aging significantly changed the surface morphology and physicochemical properties of PS, and 1 μm PS had the strongest aging degree. The adsorption kinetics of PS on Cu(Ⅱ) conformed to the pseudo-second-order kinetic model, and the Freundlich model was more suitable for the experimental data of isothermal adsorption of Cu(Ⅱ) by PS. These results indicated that the adsorption of Cu(Ⅱ) by PS occurred on the non-uniform surface of PS, and the adsorption behavior was multilayer adsorption. Parameter "n" of the Freundlich model was less than 1, indicating that the adsorption behavior of PS on Cu(Ⅱ) was a higher intensity physical adsorption behavior. The order of theoretical maximum adsorption capacity of different particle sizes PS for Cu(Ⅱ) was as follows:1 μm > 50 μm > 100 μm, indicating that the size of PS was an important influence factor for the adsorption capacity of PS to pollutants. For the same particle size PS, aging enhanced its adsorption capacity for Cu(Ⅱ). The results on the adsorption of Cu(Ⅱ) by PS under different environmental conditions indicated that the adsorption capacity of PS for Cu (II) increased with the increase in pH, whereas an increase in salinity had the opposite effect. Surface complexation and electrical adsorption were the main mechanisms of adsorption of Cu(Ⅱ) by PS. This study provides an important scientific basis for understanding the adsorption behavior of microplastics to heavy metals in the environment.