Ruan Jiahui, Yang Jiahui, Wang Xingyan, Liang Cuihua, Li Lihua, Zeng Yaqi, Wang Junhua, Li Yongtao, Huang Weilin, Chen Chengyu
College of Natural Resources and Environment, Guangdong Provincial Key Laboratory of Agricultural & Rural Pollution Abatement and Environmental Safety, South China Agricultural University, 483 Wushan Road, Guangzhou, Guangdong 510642, China.
Department of Environmental Sciences, Rutgers, The State University of New Jersey, 14 College Farm Road, New Brunswick, NJ 08901, USA.
J Hazard Mater. 2024 Aug 15;475:134857. doi: 10.1016/j.jhazmat.2024.134857. Epub 2024 Jun 12.
Interactions between positively charged amino-modified (APS) and negatively charged bare (BPS) polystyrene nanoplastics may cause heteroaggregation in aquatic environments. This study investigated the effects of particle concentration ratio, solution chemistry [electrolytes, pH, and natural organic matter (NOM)], and interaction sequence on their heteroaggregation kinetics. In the absence of electrolytes and NOM, the APS/BPS ratio for attaining maximum heteroaggregation rate (k) increased from APS/BPS= 3/7 to APS/BPS= 1/1 as pH increased from 4 to 10, indicating that electrostatic interactions dominated heteroaggregation. In the absence of NOM, k ranked APS/BPS= 2/3 > APS/BPS= 1/1 > APS/BPS= 3/2. Colloidal stability decreased linearly as pH increased from 4 to 8 at APS/BPS= 1/1, while diffusion-limited heteroaggregation persisted at pH 10. In NaCl solution, humic acid (HA) retarded heteroaggregation more effectively than sodium alginate (SA) via steric hindrance and weakening electrostatic interactions, following the modified Derjaguin-Landau-Verwey-Overbeek (MDLVO) theory. Compared with simultaneous interactions among APS, BPS, NaCl, and NOM, the NOM retardation effects on heteroaggregation weakened if delaying its interaction with others. In CaCl solution, the effects of NOM on heteroaggregation depended on counterbalance among charge screening, steric hindrance, and calcium bridging. These findings highlight the important role of heteroaggregation between oppositely charged nanoplastics on their fate and transport in aquatic environments.
带正电荷的氨基修饰聚苯乙烯纳米塑料（APS）与带负电荷的裸聚苯乙烯纳米塑料（BPS）之间的相互作用可能会导致它们在水生环境中发生异质聚集。本研究调查了颗粒浓度比、溶液化学性质（电解质、pH值和天然有机物（NOM））以及相互作用顺序对其异质聚集动力学的影响。在没有电解质和NOM的情况下，随着pH值从4增加到10，实现最大异质聚集速率（k）的APS/BPS比值从APS/BPS = 3/7增加到APS/BPS = 1/1，这表明静电相互作用主导了异质聚集。在没有NOM的情况下，k的排序为APS/BPS = 2/3 > APS/BPS = 1/1 > APS/BPS = 3/2。在APS/BPS = 1/1时，随着pH值从4增加到8，胶体稳定性呈线性下降，而在pH值为10时扩散限制的异质聚集持续存在。在NaCl溶液中，根据修正的Derjaguin-Landau-Verwey-Overbeek（MDLVO）理论，腐殖酸（HA）通过空间位阻和减弱静电相互作用比海藻酸钠（SA）更有效地抑制异质聚集。与APS、BPS、NaCl和NOM同时相互作用相比，如果延迟NOM与其他物质的相互作用，其对异质聚集的抑制作用会减弱。在CaCl溶液中，NOM对异质聚集的影响取决于电荷屏蔽、空间位阻和钙桥联之间的平衡。这些发现突出了带相反电荷的纳米塑料之间的异质聚集在其在水生环境中的归宿和迁移方面的重要作用。
