Department of Chemistry , University of Iowa , Iowa City , Iowa 52242 , United States.
Langmuir. 2018 Mar 6;34(9):3136-3145. doi: 10.1021/acs.langmuir.8b00300. Epub 2018 Feb 21.
TiO nanoparticles are some of the most widely used metal oxide nanomaterials mainly because of their diverse industrial applications. Increasing usage of these nanoparticles raises concerns about the potential adverse effects on the environment. Humic acid is a ubiquitous component of the natural organic matter in the environment that is known to get adsorbed onto nanoparticle surfaces. In this study, adsorption of humic acid on TiO nanoparticles of two different sizes (5 and 22 nm) is studied at different environmentally relevant pH values using attenuated total reflectance Fourier transformation infrared spectroscopy. These vibrational spectra provide insights into the nature of the adsorption process (extent of adsorption and reversibility) as a function of pH as well as information about the bonding to the surface. Additionally, the impact of humic acid adsorption on surface charge and agglomeration has been investigated. Interestingly, the results show that the humic acid adsorption is strongly pH-dependent and that adsorption of humic acid on TiO nanoparticles alters the extent of agglomeration and modifies the zeta potential and surface charges depending on the pH, thus potentially increasing the bioavailability of TiO nanoparticles in the environment.
TiO 纳米颗粒是最广泛使用的金属氧化物纳米材料之一，主要是因为它们具有多种工业应用。这些纳米颗粒的使用量不断增加，引起了人们对其对环境潜在不利影响的关注。腐殖酸是环境中天然有机物的普遍成分，已知会被吸附到纳米颗粒表面上。在这项研究中，使用衰减全反射傅里叶变换红外光谱法研究了腐殖酸在两种不同大小（5nm 和 22nm）的 TiO 纳米颗粒上的吸附，其环境相关 pH 值不同。这些振动光谱提供了有关吸附过程（吸附程度和可逆性）的信息，其作为 pH 的函数以及关于与表面结合的信息。此外，还研究了腐殖酸吸附对表面电荷和团聚的影响。有趣的是，结果表明腐殖酸的吸附强烈依赖于 pH 值，腐殖酸在 TiO 纳米颗粒上的吸附改变了团聚的程度，并根据 pH 值改变了动电电势和表面电荷，从而可能增加环境中 TiO 纳米颗粒的生物利用度。
