Budhiraja Vaibhav, Urh Anja, Horvat Petra, Krzan Andrej
Department of Polymer Chemistry and Technology, National Institute of Chemistry, Hajdrihova 19, 1000 Ljubljana, Slovenia.
Polymers (Basel). 2022 Jun 30;14(13):2674. doi: 10.3390/polym14132674.
Microplastics (MPs) are persistent tiny pieces of plastic material in the environment that are capable of adsorbing environmental organic pollutants from their surroundings. The interaction of MPs with organic pollutants alters their environmental behavior, i.e., their adsorption, degradation and toxicity, etc. Polyethylene (PE) is the most widely used plastic material. The environmental weathering of PE results in changes to its surface chemistry, making the polymer a much better vector for organic pollutants than virgin PE. In this study, a laboratory-accelerated weathering experiment was carried out with a virgin PE film and an oxidatively degradable PE (OXO-PE) film, i.e., PE modified by the addition of a pro-oxidant catalyst. The degradation of PE and OXO-PE was assessed through Fourier transform infra-red (FTIR) spectroscopy and their wettability was measured by contact angle (CA) measurements. Their thermal properties and morphology were studied using thermogravimetric analyses (TGA) and scanning electron microscopy (SEM), respectively. Further, the adsorption of two model organic pollutants onto weathered and virgin PE was analyzed. Triclosan (TCS) and methylparaben (MeP) were chosen as model organic pollutants for the adsorption experiment due to their frequent use in the cosmetics industry, their uncontrolled release into the environment and their toxicity. The adsorption of both model pollutants onto PE and OXO-PE MP was analyzed by using gas chromatography with a flame ionization detector (GC-FID). The adsorption of MeP onto OXO-PE was higher than onto PE MPs. However, TCS showed insignificant adsorption onto PE and OXO-PE. When both pollutants were present simultaneously, the adsorption of TCS onto both PE and OXO-PE was significantly influenced by the presence of MeP. This result demonstrates that the adsorption behavior of one pollutant can be significantly altered by the presence of another pollutant. Both the effect of weathering on the adsorption of organic pollutants as well as the interaction between organic pollutants adsorbing onto MPs is highly relevant to actual MP pollution in the environment, where MPs are exposed to weathering conditions and mixtures of organic pollutants.
微塑料（MPs）是环境中持续存在的微小塑料碎片，能够从周围环境中吸附环境有机污染物。微塑料与有机污染物的相互作用会改变它们的环境行为，即吸附、降解和毒性等。聚乙烯（PE）是使用最广泛的塑料材料。PE的环境老化会导致其表面化学性质发生变化，使这种聚合物成为比原始PE更好的有机污染物载体。在本研究中，对原始PE薄膜和可氧化降解PE（OXO-PE）薄膜进行了实验室加速老化实验，即通过添加促氧化催化剂改性的PE。通过傅里叶变换红外（FTIR）光谱评估PE和OXO-PE的降解情况，并通过接触角（CA）测量来测定它们的润湿性。分别使用热重分析（TGA）和扫描电子显微镜（SEM）研究了它们的热性能和形态。此外，还分析了两种模型有机污染物在老化和原始PE上的吸附情况。由于三氯生（TCS）和对羟基苯甲酸甲酯（MeP）在化妆品行业中经常使用、不受控制地释放到环境中以及具有毒性，因此选择它们作为吸附实验的模型有机污染物。使用带有火焰离子化检测器（GC-FID）的气相色谱法分析了两种模型污染物在PE和OXO-PE微塑料上的吸附情况。MeP在OXO-PE上的吸附高于在PE微塑料上的吸附。然而，TCS在PE和OXO-PE上的吸附不显著。当两种污染物同时存在时，MeP的存在对TCS在PE和OXO-PE上的吸附有显著影响。这一结果表明，一种污染物的吸附行为会因另一种污染物的存在而发生显著改变。老化对有机污染物吸附的影响以及吸附在微塑料上的有机污染物之间的相互作用，都与环境中实际的微塑料污染高度相关，在这种环境中，微塑料会暴露于老化条件和有机污染物混合物中。
