不同表面改性聚苯乙烯纳米粒子与天然胶体的异质聚集,Science of the Total Environment

这项研究调查了三种表面官能化的聚苯乙烯纳米粒子（PSNP），即带负电荷的未官能化纳米粒子（Bare-PS）和羧基化的纳米粒子（COOH-PS）和带正电荷的氨基官能化纳米粒子（NH 2）的杂聚-PS），带有两种模型天然胶体，分别是带正电的赤铁矿和带负电的高岭土。异质聚集是在恒定的天然胶体浓度和可变的NP /胶体浓度比下进行的。静电相互作用是驱动杂聚体形成的主要机制。在含有赤铁矿和Bare-PS / COOH-PS的二元体系中，随着PSNP浓度的增加，观察到电荷中和-电荷逆转机制。在NP /赤铁矿浓度比远小于或大于完全电荷中和点的情况下，主要的杂聚集体是稳定的，而完全电荷中和会诱导形成较大的次要杂聚体。在含有高岭土和NH 2的悬浮液中未观察到大的聚集体-PS，为高度带正电的NH 2-PS以极低的浓度逆转了高岭土的表面电荷。由于强烈的静电排斥作用，PSNP与具有相同电荷的天然胶体之间的异质聚集是不利的。在存在电解质的情况下，均聚和异聚均发生，当PSNPs浓度低时，赤铁矿的均聚起关键作用。Suwannee River天然有机物（SRNOM）的存在可以修饰纳米颗粒的表面电荷，从而影响二元悬浮液的杂聚行为。当SRNOM和电解质同时存在时，SRNOM是诱导还是阻碍二元体系的稳定性是NP /胶体浓度比，SRNOM浓度，电解质类型和离子强度的综合作用。2+也代表异类聚合。这些结果突出了表面修饰对NP的环境行为的关键作用，并将巩固我们对NP在水生环境中的命运和运输的理解。

"点击查看英文标题和摘要"

This study investigated heteroaggregation of three surface-functionalized polystyrene nanoparticles (PSNPs), i.e. negatively charged unfunctionalized nanoparticles (Bare-PS) and carboxylated nanoparticles (COOH-PS), and positively charged amino-functionalized nanoparticles (NH2-PS), with two model natural colloids, positively charged hematite and negatively charged kaolin, respectively. Heteroaggregation was conducted at a constant natural colloid concentration and variable NP/colloid concentration ratios. Electrostatic interaction was the main mechanism driving the formation of heteroaggregates. In binary systems containing hematite and Bare-PS/COOH-PS, a charge neutralization – charge inverse mechanism was observed with the increase of PSNP concentration. At NP/hemetite concentration ratios much smaller or larger than the full charge neutralization point, the primary heteroaggregates were stable, while full charge neutralization induced the formation of large secondary heteroaggregates. Large aggregates were not observed in suspensions containing kaolin and NH2-PS, as highly positively charged NH2-PS reversed surface charges of kaolin at extremely low concentrations. Heteroaggregation between PSNPs and natural colloids with the same charge is unfavorable due to strong electrostatic repulsion. In the presence of electrolytes, homoaggregation and heteroaggregation both occurred, and homoaggregation of hematite played a key role when the concentration of PSNPs was low. The presence of Suwannee River natural organic matter (SRNOM) could modify surface charges of nanoparticles, and thus affect heteroaggregation behaviors of the binary suspension. When SRNOM and electrolytes were both present, whether SRNOM inducing or hindering the stability of the binary system was a combined effect of NP/colloid concentration ratios, SRNOM concentrations, electrolyte types and ionic strength. Mechanisms extensively reported in homoaggregation such as steric hindrance and cation bridging effects between SRNOM and Ca2+ also stand for heteroaggregation. These results highlight the critical role of surface modification on the environmental behaviors of NPs, and will underpin our understanding of the fate and transport of NPs in the aquatic environment.