Zhang Yunhai, Chen Zihao, Shi Yuexiao, Ma Qing, Mao Haoran, Li Ying, Wang Hao, Zhang Yongjun
School of Environmental Science and Engineering, Nanjing Tech University, Nanjing 211816, People's Republic of China.
School of Environmental Science and Engineering, Nanjing Tech University, Nanjing 211816, People's Republic of China.
Sci Total Environ. 2023 May 20;874:162480. doi: 10.1016/j.scitotenv.2023.162480. Epub 2023 Feb 28.
The co-occurrence of microplastics (MPs) and organic contaminants in aquatic environment can complexify their environmental fate via sorption interactions, especially when the properties of MPs can even vary due to the aging effect. Thus, quantitatively clarifying the sorption mechanisms is required to understand their environmental impacts. This study selected popularly occurring carbamazepine (CBZ) and four types of MPs as model systems, including polyethylene, polyvinyl chloride, polyethylene terephthalate and polystyrene in their pristine and aged forms, to investigate the sorption isotherms, kinetics, and desorption. The variation of MPs during the aging process were analyzed with scanning electron microscopy, contact angle, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. It was found that the aging process elevated the sorption capacity and intensified the desorption hysteresis of CBZ on MPs via increasing the surface roughness, decreasing the particle size, and altering the surficial chemistry of all MPs. The extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory was innovatively applied hereby to calculate the interfacial free energies and revealed that the hydrophobic interaction was significantly lessened after aging for all MPs with the slightly enhanced van der Waals interaction. Then the total interfacial free energies were dropped down for all MPs, which resulted in their declined specific sorption capacity. This work reveals the sorption mechanisms of CBZ on pristine and aged MPs with XDLVO and provides a useful reference to study the sorption of other neutral organics onto MPs.
微塑料（MPs）与有机污染物在水生环境中的共存可通过吸附相互作用使其环境归宿复杂化，特别是当微塑料的性质甚至会因老化效应而发生变化时。因此，需要定量阐明吸附机制以了解它们对环境的影响。本研究选择普遍存在的卡马西平（CBZ）和四种类型的微塑料作为模型体系，包括原始形态和老化形态的聚乙烯、聚氯乙烯、聚对苯二甲酸乙二酯和聚苯乙烯，以研究吸附等温线、动力学和解吸情况。利用扫描电子显微镜、接触角、傅里叶变换红外光谱和X射线光电子能谱分析了微塑料在老化过程中的变化。研究发现，老化过程通过增加表面粗糙度、减小粒径以及改变所有微塑料的表面化学性质，提高了卡马西平在微塑料上的吸附能力并增强了解吸滞后现象。在此创新性地应用扩展的Derjaguin-Landau-Verwey-Overbeek（XDLVO）理论来计算界面自由能，结果表明，老化后所有微塑料的疏水相互作用显著减弱，范德华相互作用略有增强。然后所有微塑料的总界面自由能下降，导致其比吸附容量降低。这项工作揭示了卡马西平在原始和老化微塑料上的吸附机制，并为研究其他中性有机物在微塑料上的吸附提供了有用的参考。
