海水环境因子对聚乙烯微塑料吸附锌离子行为的影响研究

聚乙烯（PE）微塑料是一种新型海洋污染物，易与海水中的锌离子（Zn2+）吸附产生复合生态毒性，危害海洋生态系统。不同海水环境因子对PE微塑料吸附Zn2+行为的影响不同，本文探究了Zn2+浓度、微塑料的投加量、盐度和pH等对3种不同目数的PE微塑料吸附Zn2+行为的影响，并对其吸附动力学和热力学进行了讨论。结果表明，3种不同目数的PE微塑料对Zn2+的最佳吸附时间均为4 h；吸附能力为30目<100目<500目，最大平衡吸附量分别为1.428 mg/g、1.454 mg/g和1.498 mg/g；盐度（0～10）对吸附量的抑制率为7%；吸附量随pH的增加而增加，3种目数PE微塑料的最佳投加量均为0.1 g。Freundlich模型为最佳等温吸附方程，3种目数PE微塑料的拟合相关系数R2均大于0.982（p < 0.01），说明存在多层化学吸附。准二级动力学方程为最佳吸附动力学方程，3种目数PE微塑料拟合相关系数 R2均大于0.991（p < 0.01），表明该吸附过程主要为化学吸附。吸附热力学 ?G < 0， ?H > 0，说明PE微塑料对Zn 2+的吸附为自发吸热过程。

Effect of different seawater environmental factors on zinc ion adsorption behavior by PE microplastics

Polyethylene (PE) microplastic is a new type of marine pollutant, which is easy to adsorb Zn2+ in seawater and can cause complex ecotoxicity to marine ecological health. However, environmental factors in different seawater have different effects on the adsorption behavior of Zn2+ by PE microplastic. The effects of concentration, dosage, salinity and pH on the adsorption behavior of Zn2+ were also investigated, and the adsorption kinetics and thermodynamics were discussed. The results showed that the optimal saturation time for Zn2+ adsorption on the three kinds of PE microplastics with different mesh numbers was 4 h, and the increasing adsorption capacities of different mesh numbers were in the order of 30 mesh < 100 mesh < 500 mesh. The maximum equilibrium adsorptions were 1.428 mg/g, 1.454 mg/g and 1.498 mg/g, respectively, and salinity played an inhibitory adsorption effect. The adsorption capacity increased as pH increases, and the optimal dosage was 0.1 g. Freundlich model was used to fit the best adsorption isotherm experiment; the fitting correlation coefficient ( R2) of the three kinds of PE microplastics with different mesh numbers were all > 0.982 ( p < 0.01), which indicated the existence of a multilayer chemisorption. The quasi second order adsorption kinetic model was used to fit the best kinetic experiment. The fitting correlation coefficient of the three kinds of PE microplastics with different mesh number was statistically significant ( R2 > 0.991; p < 0.01), indicating that the adsorption process was mainly chemisorption. In adsorption thermodynamics experiment, the ?G < 0 and ?H > 0 indicated that the adsorption process of PE microplastics for Zn 2+ was spontaneous and endothermic.