地膜微塑料的降解特征及其对菲的吸附研究

Degradation of Microplastics Generation from Different Types of Mulch Films and Their Adsorption to Phenanthrene

在环境风化下,塑料材料会形成更小尺寸的微塑料,其中农业领域的污染具有重要意义并日益引起社会关注。塑料地膜被认为是农业土壤微塑料污染的主要来源。然而,很少有人了解塑料地膜形成微塑料的机制和对其他污染物的吸附。在这项研究中,在模拟紫外线和热氧照射下,对土壤中地膜(PVC、PP、PET)微塑料的降解规律以及其对有机污染物菲的吸附进行探讨。结果表明:塑料薄膜降解后,黄度指数变大,其中紫外降解处理下的PVC变化最明显;塑料表面形貌发生显著变化,含氧官能团吸收强度增加。菲在3种降解微塑料表面的吸附量为:PP>PVC>PET,在不同的土壤环境中对菲的吸附存在差异,无机盐离子体系>淡水体系>有机相体系;分别用Langmuir和Freundlich模型拟合吸附等温线数据,结果显示Freundlich模型拟合度更高;准二级模型能更好地描述吸附动力学,微塑料作为吸附剂的吸附机制是化学吸附,还包括通过吸附剂和吸附物之间共享或交换电子的价力。

Under environmental weathering,plastic materials will form smaller microplastics,of which pollution in the agricultural field is of great significance and has attracted more and more social concern.Plastic mulch is considered to be the main source of microplastic pollution in agricultural soil.However,little is known about the mechanism by which plastic mulch forms microplastics and the adsorption of other pollutants.In this study,the degradation laws of mulch(PVC,PP,PET)microplastics in soil and their adsorption to typical organic pollutants phenanthrene were investigated under simulated ultraviolet and thermal oxygen irradiation.The results showed that after the plastic film was degraded,the yellowness index increased,and the PVC under UV degradation treatment had the most obvious change.The surface morphology of the plastic changed significantly,and the absorption strength of oxygen-containing functional groups increased.The adsorption amount of phenanthrene on the surface of three degraded microplastics was:PP>PVC>PET.There were differences in the adsorption of phenanthrene in different soil environments.Inorganic salt ion system>water system>organic phase system;Langmuir and Freundlich models were used respectively.Fitting the adsorption isotherm data,the results showed that the Freundlich model had a better fit;the pseudo-second-order model could better describe the adsorption kinetics,in which the adsorption mechanism of microplastics as adsorbents was chemisorption,and also included the adsorption of microplastics and valence force of sharing or exchanging electrons between adsorbates.