Department of Chemical & Environmental Engineering, University of California, Riverside, CA 92521, United States.
J Colloid Interface Sci. 2012 Mar 1;369(1):16-22. doi: 10.1016/j.jcis.2011.12.019. Epub 2011 Dec 17.
In this study, a microscope-based technique was utilized to understand the fundamental mechanisms involved in deposition of TiO(2) nanoparticles (TNPs). Transport and deposition studies were conducted in a parallel plate (PP) flow chamber with TNP labeled with fluorescein isothiocyanate (FITC) for visualization. Attachment of FITC-labeled TNPs on surfaces is a function of a combination of parameters, including ionic strength (IS), pH and flowrate. Significantly higher deposition rates were observed at pH 5 versus pH 7. This is attributed to the conditions being chemically favorable for deposition at pH 5 as compared to pH 7, as predicted by DLVO theory. Additionally, deposition rates at pH 5 were reduced with IS below 10 mM due to the decrease in range of electrostatic attractive forces. Above 10 mM, aggregate size increased, resulting in higher deposition rates. At pH 7, no deposition was observed below 10 mM and above this concentration, deposition increased with IS. The impact of flowrate was also observed, with decreasing flowrate leading to greater deposition due to the reduction in drag force acting on the aggregate (regardless of pH). Comparisons between experimental and theoretical approximations indicate that non-DLVO type forces also play a significant role. This combination of observations suggest that the deposition of these model nanoparticles on glass surfaces was controlled by a combination of DLVO and non-DLVO-type forces, shear rate, aggregation state, and gravitational force acting on TNPs.
在这项研究中，我们采用基于显微镜的技术来了解 TiO(2)纳米颗粒（TNPs）沉积涉及的基本机制。在带有荧光素异硫氰酸酯（FITC）标记的 TNPs 用于可视化的平行板（PP）流动室中进行了输送和沉积研究。FITC 标记的 TNPs 附着在表面上是一系列参数的组合的函数，包括离子强度（IS）、pH 值和流速。与 pH 值为 7 相比，在 pH 值为 5 时观察到明显更高的沉积速率。这归因于与 pH 值为 7 相比，在 pH 值为 5 时的条件有利于化学沉积，这与 DLVO 理论预测的一致。此外，在 IS 低于 10 mM 时，由于静电吸引力范围减小，在 pH 值为 5 时沉积速率降低。在 10 mM 以上时，由于聚集物尺寸增加，导致沉积速率增加。在 pH 值为 7 时，在低于 10 mM 的情况下观察不到沉积，而在高于该浓度时，随着 IS 的增加，沉积增加。还观察到流速的影响，由于作用于聚集物的阻力减小（与 pH 值无关），流速降低导致沉积增加。实验与理论近似值的比较表明，非-DLVO 类型的力也起着重要作用。这些观察结果的组合表明，这些模型纳米颗粒在玻璃表面上的沉积受到 DLVO 和非-DLVO 类型力、剪切速率、聚集状态以及作用于 TNPs 的重力的组合控制。
