Jiangsu Provincial Key Laboratory of Materials Cycling and Pollution Control, School of Environment, Nanjing Normal University, Nanjing, 210023, China; Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application, School of Geography Science, Nanjing Normal University, Nanjing, 210023, China.
Jiangsu Provincial Key Laboratory of Materials Cycling and Pollution Control, School of Environment, Nanjing Normal University, Nanjing, 210023, China.
Chemosphere. 2021 Feb;265:129133. doi: 10.1016/j.chemosphere.2020.129133. Epub 2020 Nov 28.
Microplastics are a kind of new organic pollutant in the environment. In this study, the adsorption of tetracyclines (TCs), including tetracycline hydrochloride (TC), chlortetracycline hydrochloride (CTC) and oxytetracycline hydrochloride (OTC) onto polyethylene (PE) microplastics in aqueous solutions were investigated. The mechanism of the adsorption behavior was preliminarily explored by adsorption kinetics, isotherms, and thermodynamics, in combination with scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). In addition, molecular dynamics (MD) simulation was applied to investigate the adsorption processes of TCs on PE at a molecular level. It was found that the adsorption behaviors of TCs reached an equilibrium state within 30 h. The experimental data showed that adsorption capacities of TCs onto PE were as follows: OTC (64.40 ± 2.38 μg/g)>CTC (63.36 ± 4.92 μg/g)>TC (53.52 ± 3.43 μg/g). TC sorption onto PE increased with pH, peaking at around pH 6 and then decreased. The increase of ionic strength in the solution led to the reduced adsorption capacity of TC onto PE. The results indicated that the experimental data were well fitted by the pseudo-second-order model and the Freundlich isotherm model, indicating both monolayer and multilayer coverage of TCs onto the surface of PE. The results of MD simulation showed that PE can effectively adsorb the TCs molecule mainly through non-bond interactions, and PE exhibited the highest affinity for CTC and OTC, followed by TC.
微塑料是环境中一种新型的有机污染物。在这项研究中，研究了四环素（TCs），包括盐酸四环素（TC）、盐酸金霉素（CTC）和盐酸土霉素（OTC）在水溶液中对聚乙烯（PE）微塑料的吸附。通过吸附动力学、等温线和热力学，结合扫描电子显微镜（SEM）、傅里叶变换红外光谱（FTIR）和 X 射线光电子能谱（XPS），初步探讨了吸附行为的机理。此外，还应用分子动力学（MD）模拟从分子水平上研究了 TCs 在 PE 上的吸附过程。结果表明，TCs 的吸附行为在 30 小时内达到平衡状态。实验数据表明，TCs 对 PE 的吸附容量如下：OTC（64.40±2.38μg/g）>CTC（63.36±4.92μg/g）>TC（53.52±3.43μg/g）。TC 在 PE 上的吸附随 pH 值的增加而增加，在 pH 值约为 6 时达到峰值，然后降低。溶液中离子强度的增加导致 TC 对 PE 的吸附容量降低。结果表明，实验数据与准二级动力学模型和 Freundlich 等温线模型拟合良好，表明 TCs 以单层和多层覆盖的方式吸附到 PE 表面。MD 模拟的结果表明，PE 可以通过非键相互作用有效地吸附 TCs 分子，并且 PE 对 CTC 和 OTC 的亲和力最高，其次是 TC。
