Hao Lin, Ma Hongzhu, Xing Baoshan
School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'An, Shaanxi 710119, PR China.
School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'An, Shaanxi 710119, PR China.
Sci Total Environ. 2024 Sep 20;944:173962. doi: 10.1016/j.scitotenv.2024.173962. Epub 2024 Jun 12.
The vast application and deep integration of plastic commodity with our human lives raise a great concern about the ubiquitous microplastics (MPs) in nature, yet the environmental behavior of MPs remain unclear. As a main type and candidate of MPs, pristine polypropylene MPs (PP-MP-Pris), as well as the influence of ultraviolet (UV) irradiation on the degree of aging and surface characteristics, were characterized quantitatively by Fourier infrared spectroscopy, scanning electron microscopy, contact angle meter, automatic specific surface area and pore analyzer and laser particle analyzer, with natural aged PP-MPs (PP-MP-Age) as comparison. The carbonyl index (CI) of UV aged PP-MPs (PP-MP-U) was increased with extension of exposure time, while biofilm with abundant functional groups and the maximum CI value were the characteristics of PP-MP-Age. Moreover, the adsorption capacity of PP-MP-U for crystal violet (CV) was increased and reached the maximum after 30 days, while that of PP-MP-Age was weakened, probably due to the enhanced hydrophilicity and the shedding of calcium carbonate (CaCO) during the natural aging process, which was demonstrated by hydrochloric acid treatment, indicating the vital involvement of CaCO. Moreover, the better fitting to PSO kinetics and Freundlich isotherm models indicated that the multilayered and non-homogeneous surface adsorption was acted as the rate-controlling step. Furthermore, the positive values of ΔG, ΔH and ΔS indicated that the adsorption was a non-spontaneous, endothermic process with increased degree of the freedom on the interface of PP-MPs and CV solution. The presence of divalent salts inhibited CV adsorption, demonstrating that electrostatic attraction played a major role in CV capture. The hydrophobic interaction, micropore filling, hydrogen bonding, and π - π conjugation were possible involved. This study is of great significance for better understanding the complex pollution of MPs and its potential environmental risks in the future.
塑料商品在人类生活中的广泛应用和深度融合引发了人们对自然界中普遍存在的微塑料（MPs）的极大关注，然而微塑料的环境行为仍不清楚。作为微塑料的主要类型和候选物，通过傅里叶红外光谱、扫描电子显微镜、接触角测量仪、自动比表面积和孔隙分析仪以及激光粒度分析仪对原始聚丙烯微塑料（PP-MP-Pris）进行了定量表征，并与自然老化的PP-MPs（PP-MP-Age）进行比较，研究了紫外线（UV）辐照对其老化程度和表面特性的影响。UV老化的PP-MPs（PP-MP-U）的羰基指数（CI）随暴露时间的延长而增加，而具有丰富官能团和最大CI值的生物膜是PP-MP-Age的特征。此外，PP-MP-U对结晶紫（CV）的吸附能力增加，并在30天后达到最大值，而PP-MP-Age的吸附能力减弱，这可能是由于自然老化过程中亲水性增强和碳酸钙（CaCO）的脱落，盐酸处理证明了这一点，表明CaCO起到了重要作用。此外，对PSO动力学和Freundlich等温线模型的较好拟合表明，多层和非均匀表面吸附是速率控制步骤。此外，ΔG、ΔH和ΔS的正值表明吸附是一个非自发的吸热过程，PP-MPs与CV溶液界面的自由度增加。二价盐的存在抑制了CV的吸附，表明静电吸引在CV捕获中起主要作用。疏水相互作用、微孔填充、氢键和π-π共轭可能参与其中。这项研究对于更好地理解微塑料的复杂污染及其未来潜在的环境风险具有重要意义。
