Baalousha Mohammed, Manciulea Adriana, Cumberland Susan, Kendall Kevin, Lead Jamie R
School of Geography, Earth, and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom.
Environ Toxicol Chem. 2008 Sep;27(9):1875-82. doi: 10.1897/07-559.1.
The interactions between unpurified manufactured nanoparticles (NPs; iron oxide NPs, approximately 7 nm) and standard Suwannee River humic acid (SRHA) were investigated under a range of environmentally relevant conditions. At low pH, approximately 35% of the total iron was in the dissolved phase (< 1 kDa), present from the initial synthesis, whereas at pH more than 4, this concentration was negligible because of the formation of new particles via hydrolysis. Dynamic light scattering results indicated that extensive aggregation of NPs began at approximately pH 5 to 6 and reached a maximum at approximately pH 8.5, whereas with added SRHA, aggregation was shifted to lower pH values of 4 to 5 and was affected by SRHA concentration. Aggregation could be explained mainly by charge neutralization. Further, more detailed investigations by flow field-flow fractionation and transmission-electron microscopy were performed under a more restricted set of conditions (pH 2-6) to examine the aggregation process. Results indicated the formation of SRHA surface coating on iron oxide NPs of approximately 1 nm and the increase in thickness of this coating with the increase of SRHA concentration. Iron oxide NPs were shown to form increasingly large aggregates with increases in both pH (from 2 to 6) and SRHA concentration (from 0 to 25 mg/L). The structure and aggregation mechanism of these aggregates were found to be both pH and SRHA concentration dependent, with open, porous aggregates in the absence of SRHA and compact aggregates in the presence of SRHA.
在一系列与环境相关的条件下，研究了未纯化的人造纳米颗粒（NPs；氧化铁纳米颗粒，约7纳米）与标准的苏万尼河腐殖酸（SRHA）之间的相互作用。在低pH值下，约35%的总铁处于溶解相（<1 kDa），这是初始合成时就存在的，而在pH值大于4时，由于水解形成新颗粒，该浓度可忽略不计。动态光散射结果表明，纳米颗粒的大量聚集在pH值约为5至6时开始，并在pH值约为8.5时达到最大值，而添加SRHA后，聚集转移到较低的pH值4至5，并且受SRHA浓度影响。聚集主要可以通过电荷中和来解释。此外，在更受限的条件（pH值2 - 6）下，通过流场-流分级和透射电子显微镜进行了更详细的研究，以检查聚集过程。结果表明，在约1纳米的氧化铁纳米颗粒上形成了SRHA表面涂层，并且该涂层的厚度随着SRHA浓度的增加而增加。随着pH值（从2到6）和SRHA浓度（从0到25毫克/升）的增加，氧化铁纳米颗粒显示出形成越来越大的聚集体。发现这些聚集体的结构和聚集机制既依赖于pH值，也依赖于SRHA浓度，在没有SRHA的情况下形成开放、多孔的聚集体，在有SRHA的情况下形成致密的聚集体。
