Institute for Chemical and Bioengineering, ETH Zurich , 8093 Zurich, Switzerland.
Environ Sci Technol. 2014 Sep 16;48(18):10690-8. doi: 10.1021/es501655v. Epub 2014 Sep 8.
The heteroaggregation of engineered nanoparticles (ENPs) with natural colloids (NCs), which are ubiquitous in natural surface waters, is a crucial process affecting the environmental transport and fate of ENPs. Attachment efficiencies for heteroaggregation, α hetero, are required as input parameters in environmental fate models to predict ENP concentrations and contribute to ENP risk assessment. Here, we present a novel method for determining α hetero values by using a combination of laser diffraction measurements and aggregation modeling based on the Smoluchowski equation. Titanium dioxide nanoparticles (TiO2 NPs, 15 nm) were used to demonstrate this new approach together with larger silicon dioxide particles (SiO2, 0.5 μm) representing NCs. Heteroaggregation experiments were performed at different environmentally relevant solution conditions. At pH 5 the TiO2 NPs and the SiO2 particles are of opposite charge, resulting in α hetero values close to 1. At pH 8, where all particles are negatively charged, α hetero was strongly affected by the solution conditions, with α hetero ranging from <0.001 at low ionic strength to 1 at conditions with high NaCl or CaCl2 concentrations. The presence of humic acid stabilized the system against heteroaggregation.
工程纳米颗粒（ENPs）与天然胶体（NCs）的异质聚集，在天然地表水中普遍存在，是影响 ENPs 环境传输和归宿的关键过程。在环境归宿模型中，需要将异质聚集的附着效率（α hetero）作为输入参数，以预测 ENP 浓度并有助于进行 ENP 风险评估。在这里，我们提出了一种新的方法，通过使用激光衍射测量和基于斯莫鲁霍夫斯基方程的聚集建模相结合来确定α hetero 值。使用二氧化钛纳米颗粒（TiO2 NPs，15nm）与代表 NCs 的更大的二氧化硅颗粒（SiO2，0.5μm）一起演示了这种新方法。在不同的环境相关溶液条件下进行了异质聚集实验。在 pH 值为 5 时，TiO2 NPs 和 SiO2 颗粒带相反电荷，导致α hetero 值接近 1。在 pH 值为 8 时，所有颗粒均带负电荷，α hetero 受到溶液条件的强烈影响，在低盐度条件下，α hetero 值低至 0.001，而在高 NaCl 或 CaCl2 浓度条件下，α hetero 值高达 1。腐殖酸的存在稳定了系统，防止了异质聚集。
