本研究采用X射线光电子能谱(XPS)来分析经历降解过程的塑料样品,目的是了解相关的化学过程并揭示碎裂机理。两种型号塑料,即聚苯乙烯(PS)和聚乙烯(PE),在人工紫外线辐射触发的风化之前和之后进行选择和分析,在模拟环境水动力条件下,在淡水和海水中不同的时间间隔。本研究的目的是识别和量化可能证明发生水解和氧化反应的化学基团。它们是环境中退化过程的基础,确定大塑性碎片。还通过拉曼和FT-IR光谱分析了人工风化的塑料样品。XPS揭示了表面化学随风化的变化,涉及化学部分的增加(羟基,羰基,和羧基官能团),这可能与导致大塑性破碎的降解过程相关。另一方面,拉曼光谱和FT-IR光谱证明了塑料风化过程中没有显著的改性,这证实了研究塑料表面的重要性,它代表了暴露于降解剂的材料的第一部分,从而揭示了XPS研究为此目的的力量。将实验风化颗粒的XPS数据与从真实海洋环境中收集的微塑料上获得的数据进行比较,以研究发生的降解过程。
The present
study employs X-ray photoelectron spectroscopy (XPS) to analyze plastic samples subjected to degradation processes with the aim to gain insight on the relevant chemical processes and disclose fragmentation mechanisms. Two model plastics, namely polystyrene (PS) and polyethylene (PE), are selected and analyzed before and after artificial UV radiation-triggered weathering, under simulated environmental hydrodynamic conditions, in fresh and marine water for different time intervals. The object of the
study is to identify and quantify chemical groups possibly evidencing the occurrence of hydrolysis and oxidation reactions, which are the basis of degradation processes in the environment, determining macroplastic fragmentation. Artificially weathered plastic samples are analyzed also by Raman and FT-IR spectroscopy. Changes in surface chemistry with weathering are revealed by XPS, involving the increase in chemical moieties (hydroxyl, carbonyl, and carboxyl functionalities) which can be correlated with the degradation processes responsible for macroplastic fragmentation. On the other hand, the absence of significant modifications upon plastics weathering evidenced by Raman and FT-IR spectroscopy confirms the importance of investigating plastics surface, which represents the very first part of the materials exposed to degradation agents, thus revealing the power of XPS studies for this purpose. The XPS data on experimentally weathered particles are compared with ones obtained on microplastics collected from real marine environment for investigating the occurring degradation processes.